Catalyst support materials containing silicon carbide, catalysts comprising such support materials, and reaction methods using the catalysts

Abstract

A catalyst having a core and a catalytically active layer (C) containing, for example, Ni attached to the core, the core comprising a composite (A) of SiC grains and a protective matrix of one or more metal oxides (such as alumina) in the voids between the SiC grains, the density of the core being >60% of the theoretical density. Also provided is a catalyst support and a method for manufacturing a catalyst core, the catalyst support comprising a composite of SiC grains and a protective matrix of one or more metal oxides in the voids between the SiC grains. The catalyst can be used in Fischer-Tropsch synthesis or steam methane reforming.

Description

[0001] Statement Regarding Federally Sponsored Research or Development

[0002] This invention was made in part under government support by grant number DE-SC0013114 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

[0003] Cross-Reference to Related Applications

[0004] This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 681,652, filed on June 6, 2019, entitled “CATALYST SUPPORT MATERIALS, CATALYST SUPPORTS, CATALYSTS AND REACTION METHODS USING CATALYSTS”. The entire disclosure of the foregoing provisional patent application is incorporated herein by reference. Background of the Invention

[0005] Although there may be various catalyst support materials, catalyst supports (also referred to herein as catalyst cores), catalysts, methods of producing the foregoing, and reaction methods using catalysts, it is believed that no one prior to the inventors has made or used the invention as described herein. Brief Description of the Drawings

[0006] Although the specification concludes with claims particularly pointing out and distinctly claiming the invention, it is believed that the invention will be better understood from a detailed description of some embodiments of the invention when read in conjunction with the drawings. Like numerals are used in the drawings to identify like elements unless the context otherwise indicates. Additionally, some of the figures may have been simplified by omitting some elements in order to more clearly show other elements. Such omissions do not necessarily indicate the presence or absence of a particular element in any exemplary embodiment, except as may be expressly noted in the corresponding detailed description.

[0007] Figure 1 SEM cross-sectional images of the catalyst of the present invention at low magnification (left) and high magnification (right) are provided, showing the interface between the core and the outer layer. The material was treated in air at 1250 °C and contains an Al-Si outer layer.

[0008] Figure 2 Cross-sectional SEM images of the material of the present invention coated with BSAS (A) and co-treated with BSAS (B) and heat-treated at high temperature to convert BSAS into a protective coating are provided. BSAS is the white material.

[0009] Figure 3Cross-sectional SEM images of the inventive material coated with a mixture of Al2O3 (introduced in the form of a mixture of Al and Al2O3 in the slurry at a volume ratio of 25% to 75%) are provided.

[0010] Figure 4 Cross-sectional SEM images of a sealed coated SiC / Al2O3 composite nuclear pellet are provided. (A) refers to the coating containing Al2O3 mixed with a CAS glass former, (B) refers to the Al2O3 coating, and (C) is the core of the material.

[0011] Figure 5 Cross-sectional SEM images of a SiC / Al2O3 composite nuclear pellet that has been coated with a first interfacial layer of alumina and then an outer layer of a Ni-containing catalytically active material are provided.

[0012] Figure 6 Photographs showing the antioxidant properties of the inventive catalyst in a steam-containing and high-temperature environment are provided. Figure 6 A is a photograph of as-received commercial SiC pellets before (left) and after (right) exposure to 25% steam in air at 900 °C for 44 hours, while Figure 6 B shows photographs of the inventive catalyst support before (left) and after (right) exposure to the same conditions and time.

[0013] Figure 7 Results of the weight gain over time of a representative sample of the inventive material at 900 °C under conditions of 50% steam in synthesis gas (3% hydrogen in nitrogen) are provided.

[0014] Figure 8 (A to D) provides graphs showing the mass fraction of the nth hydrocarbon relative to the carbon number for α ranging from 0.8 to 0.99. As α increases, the mass fraction of the heavy hydrocarbons increases significantly.

[0015] Figure 9 A graph showing the effect of pellet porosity and temperature on the normalized static packed bed radial conduction coefficient is provided.

[0016] Figure 10 Graphs of the effective packed bed thermal conductivity for both a commercial SMR catalyst and the inventive catalyst at 1970 h -1 (superficial velocity 0.52 m / s) are provided.

[0017] Figure 11 Graphs comparing the experimental data of the steady-state thermal conductivities (k r ) of a commercial SMR catalyst and the inventive catalyst support (k s ) are presented. r The (k

[0018] Figure 12 Provided is a graph of the reactor outer wall temperature versus the axial distance at an applied average heat flux of 33.17 kW / m 2 , showing that the enhanced thermal conductivity from the catalyst of the present invention reduces the maximum wall temperature by 13 °C.

[0019] Figure 13 Compared is the relationship of the wall temperature and the gas temperature versus the axial distance for commercial and the present invention catalyst packed beds at a space velocity of 1970 h -1 .

[0020] Figure 14 Shown is the effect of the increase in GHSV for the catalyst of the present invention on dry methane escape, showing that using the catalyst of the present invention as a support allows a 36% higher GHSV for comparable dry escape.

[0021] Figure 15 Provided is a graph of the heat flux curve for comparable dry methane escape. For the same wall temperature and escape, the material of the present invention absorbs 33% more heat.

[0022] Figure 16 Provided is a graphical representation of the equilibrium conversion of methane at a temperature range of 650 °C to 900 °C, a pressure of 1 to 20 absolute bar, and a steam to carbon (S / C) ratio of 3.

[0023] Figure 17 Shown is the catalytic performance of the catalyst support of the present invention under steam methane reforming conditions, where Option A has an external porous layer impregnated with SMR-active metal ions followed by calcination, and where Option B has an active catalyst layer directly deposited on the outside of the catalyst support material of the present invention.

[0024] Figure 18 Shown is the effect of a space velocity study on the catalyst support material of the present invention under steam methane reforming conditions, where Option A has an external porous layer impregnated with SMR-active metal ions followed by calcination, and where Option B has an active catalyst layer directly deposited on the outside of the catalyst support material of the present invention.

[0025] Figure 19 Shown is the performance stability during steam methane reforming conditions, where Option A has an external porous layer impregnated with SMR-active metal ions followed by calcination, and where Option B has an active catalyst layer directly deposited on the outside of the catalyst support material of the present invention.

[0026] Figure 20 Shown is the packed bed thermal conductivity (normalized to the value of dense SiC as a reference) of commercial SMR materials, different generations of the catalyst of the present invention, and dense SiC at 530 °C and 830 °C.

[0027] The accompanying drawings are intended to illustrate rather than limit the scope of the present invention. Embodiments of the present invention may be implemented in ways that are not necessarily depicted in the accompanying drawings. Thus, the accompanying drawings are only intended to assist in the explanation of the present invention. Accordingly, the present invention is not limited to the exact arrangements shown in the accompanying drawings. Detailed Description

[0028] The following detailed description describes examples of embodiments of the present disclosure only for the purpose of enabling a person of ordinary skill in the relevant art to make and use the embodiments of the present disclosure. Thus, the detailed description and illustration of these embodiments are purely illustrative in nature and are in no way intended to limit the scope of the present invention or its protection.

[0029] Embodiments of the present disclosure provide catalysts that include a silicon carbide (SiC)-based core (also referred to in the art as a catalyst support) and one or more catalytically active materials (e.g., one or more metals) attached thereto (e.g., forming a shell on the core within a porous catalyst support layer). Embodiments of the present disclosure also provide SiC-based cores for manufacturing catalysts, particularly core-shell catalysts. To protect the SiC-based core during subsequent use in catalytic reactions, especially from oxidation and corrosion under high-temperature conditions in the presence of H2O (e.g., as steam), one or more protective materials are used in combination with the SiC-based core. In some embodiments, the density of the catalyst core is ≥60% of the theoretical density and includes a composite of SiC grains (or sub-particles) and a protective matrix of one or more metal oxides (e.g., alumina) in the voids between the SiC grains. In other embodiments, the SiC-based core is protected by one or more interfacial layers located between the SiC core and the external catalytically active layer. The interfacial layer may include, for example, dense alumina (e.g., ≥80%, ≥90% or ≥95% of the theoretical density) or another protective material such as barium strontium aluminosilicate ("BSAS"). In still further embodiments, the interfacial layer (also referred to herein as the "third layer") may be applied on a composite SiC / oxide (e.g., SiC / Al2O3) core.

[0030] The catalytically active material can be attached to the core in any of a variety of ways known to those skilled in the art or developed hereafter, such as being disposed on the surface (including the inner surface) of a porous catalyst support material in the form of spots, dots, nanoclusters, etc., which is typical for obtaining a high surface area active catalyst of a dispersed catalytic metal on an oxide support. In some embodiments, one or more interfacial layers (e.g., a layer including α-alumina) are provided between one or more catalytically active materials loaded on a porous catalyst support and an internal medium solid particle core composed of silicon carbide (SiC). One embodiment of the interfacial layer is a substantially dense Al2O3 layer applied around the outside of the catalyst support (i.e., the core), which separates the SiC core from a porous catalyst layer composed of a porous oxide and having an active catalyst metal dispersed therein.

[0031] Accordingly, the catalysts of the present disclosure are defined by a combination of at least two, three, and in some cases four (or more) layers. The first layer is defined by a core having a theoretical density of ≥60%, the core being composed of SiC, which may also contain other components such as Al and / or Si, and oxides of Al and Si (in particular, alumina) dispersed therein. The outer second layer is catalytically active for the target reaction and is generally composed of a porous oxide support having at least one active catalyst metal disposed therein, such as in the form of nanoclusters, spots, dots, etc. A third interfacial layer and in some cases a fourth non-porous gas-tight protective coating ("fourth layer") are located between the first two layers. The interfacial layer can be, for example, one or more substantially dense α-alumina layers that protect or passivate the first layer (i.e., the SiC surface) from steam corrosion. The fourth layer can be a highly dense (≥90%, ≥95%, or about 100% of the theoretical value) non-porous sealing coating that is gas-tight and prevents oxidation of the SiC in the core at high temperatures in a steam-containing environment. The third layer and in some cases the fourth layer also serve to anchor or support the attachment of the coated catalyst or the second layer to obtain a long working life. It is undesirable for the second or outer layer composed of a porous catalyst support to delaminate, break off, spall, or otherwise be lost from the structural surface, the support having an active metal disposed therein. Moreover, any or all of the layers can include, be mixed with, coated with, or doped with a high emissivity material, or be surface processed to modify to increase the overall emissivity of the support.

[0032] In yet another alternative embodiment, particularly when the core includes a protective matrix such as alumina within the voids between SiC grains, a porous interfacial layer can be provided between the first and second layers. For example, as further described herein, a semi-transparent porous layer of alumina can be used to increase the emissivity of the catalyst.

[0033] In some embodiments, the catalyst core comprises a composite of SiC grains or sub - grains and a metal oxide surrounding the SiC grains and, in some cases, a protective matrix of residual metal. A grain is defined as a discrete microcrystal of SiC and other components having a size in the range of 0.01 to 100 microns. In the catalyst structure of the present invention, the SiC grains of the first layer (i.e., the core) are compressed during manufacture to produce a larger and compressed unified pellet or other desired shape, as further described herein. The catalyst pellet typically has a characteristic size or hydraulic diameter of about 1 mm to 50 mm. In some embodiments, the density of the catalyst core is from about 60% to 100% of the theoretical density, or from about 60% to about 90% of the theoretical density, or from about 65% to about 80% of the theoretical density. The role of the protective matrix is to prevent steam and, in some cases, oxygen from reaching the SiC in the core (i.e., the first layer) of the pellet under reaction conditions. In one embodiment, the protective matrix is composed of alumina. In alternative embodiments, the protective matrix barrier layer is composed of alumina, titanium dioxide, silica, zirconia, or a combination of two or more of the foregoing. The protective matrix not only protects the SiC grains from corrosive oxidation, it also serves as an intergranular phase that binds the SiC grains together to form the core. The result is a composite catalyst core that is ≥60% theoretically dense, as opposed to a more porous (<60% theoretically dense) conventional SiC catalyst core.

[0034] As noted above, in some embodiments, the protective matrix comprises Al2O3. In still further embodiments, the protective matrix comprises Al2O3 and one or more oxides of silica and / or a combination of aluminum and silicon, such as mullite (Al6Si2O 13 )). Similarly, in other embodiments, the protective matrix comprises alumina and titanium dioxide, zirconia, and / or one or more oxides of a combination of zirconia, aluminum, and / or titanium. Also as noted above, in some embodiments, the catalyst core (i.e., the first layer) is densified to some extent, e.g., the actual density is between about 60% and about 100% of the theoretical density, from about 60% to about 95% of the theoretical density, from about 60% to about 90% of the theoretical density, from about 65% to about 90% of the theoretical density, or from about 65% to about 80% of the theoretical density. Even at 60% of the theoretical density, the cores of the present disclosure have a higher density than commercially available SiC catalyst cores, which are typically porous.

[0035] In the second layer, on the other hand, the active catalytic metal is dispersed within a porous carrier (i.e., on its inner and outer surfaces) having a porosity (also known as void volume) in the range from about 40% to about 80%. An optional third interfacial layer that may be disposed between the first and second layers is composed of a dense material, where the density of the third layer is from about 80% to 100% of the theoretical value. The third layer, which serves as a passivation layer to protect the underlying first SiC layer, may be composed of, for example, alumina, silica, titania, zirconia, or other materials that can form a substantially dense layer on the core. The third layer is substantially inert to unwanted reactions and serves to assist in the attachment of the second layer composed of the porous carrier and the active catalytic metal disposed therein.

[0036] When used in combination with the third layer, the fourth hermetic protective coating presents a denser and more sealed protective coating to enhance stability in corrosive gases (which, for nuclear materials, includes steam) and in highly oxidizing environments at high temperatures. The fourth layer may be a hermetic (≥90% or ≥95% theoretical density) protective coating that includes Al2O3 in combination with a glass former such as alkaline earth metal aluminosilicate glass, alkaline earth metal aluminoborosilicate glass, and lanthanide aluminosilicate glass.

[0037] Embodiments of the present disclosure also include a method of manufacturing a catalyst core (i.e., a carrier) by mixing SiC and Al (or Al - Si alloy) powders with one or more additives such as a binder, a plasticizer, and / or a lubricant. Thereafter, the mixture is formed into pellets (or other desired shapes), such as by dry pressing or extrusion, and then calcined (e.g., in ambient air) to form a densified catalyst core containing SiC within a protective matrix of Al2O3.

[0038] The catalyst carriers and catalysts of the present disclosure can be manufactured in any of a variety of shapes, including those known to those skilled in the art and those developed hereafter. Suitable shapes include, for example, spheres, cylinders, pellets, beads, lobed cylinders (e.g., bi - lobed, tri - lobed, quad - lobed, etc.), saddles, wheels, rings, Pall rings, Raschig rings, ribbed or grooved cylinders, notched cubes, grooved pyramids, daisy - shaped and star - shaped pellets. Alternatively, the catalysts of the present disclosure can be manufactured as monolithic structures. The catalyst carriers can be formed into the desired shape and size, for example, by extrusion, pressing, or molding. It will be understood that although parts of the description herein specifically refer to pellets, it should be understood that the description will apply equally to any other catalyst shape unless the context otherwise indicates.

[0039] The catalysts of the present disclosure can be used in any of a variety of reactor types and configurations, including those known to those skilled in the art and those developed hereafter. For example, the catalysts of the present disclosure can be used in fixed bed reactors (also known as packed bed reactors), fluidized bed reactors, mid-channel reactors, milli-channel reactors, micro-channel reactors, membrane reactors, ebullated bed reactors, chromatographic reactors, and moving bed reactors. The catalysts of the present disclosure are particularly useful in fixed bed (i.e., packed bed) reactors, where free-flowing catalyst is loaded into a reaction chamber having various cross-sectional shapes (such as cylindrical, rectangular, square, or other shapes). The free-flowing catalyst conforms to the shape of the reaction chamber and is fixed in place for reaction operation. During operation, the catalyst is substantially fixed in place within one or more reaction chambers, rather than moving as in the case of a fluidized bed reactor.

[0040] The catalyst cores of the present disclosure can be used with any of a variety of catalytically active materials attached thereto (either directly or using one or more interfacial layers), including those known to those skilled in the art and those developed hereafter. Suitable catalytically active materials include, for example, metals such as Ni, Co, Ru, Rh, Pd, Ir, Pt, Os, and Re. Additional suitable catalytically active materials include Au, Ag, Cu, Fe, Mn, Mg, V, Mo, and Cr.

[0041] Additional embodiments of the present disclosure include reaction methods using the catalysts described herein. These reaction methods include, for example, steam methane reforming, acetylation, addition reactions, alkylation, dealkylation, hydrodealkylation, reductive alkylation, amination, aromatization, arylation, autothermal reforming, carbonylation, decarbonylation, reductive carbonylation, carboxylation, reductive carboxylation, reductive coupling, condensation, cracking, hydrocracking, cyclization, cyclo-oligomerization, dehalogenation, dimerization, epoxidation, esterification, Fischer-Tropsch, halogenation, hydrohalogenation, homologation, hydration, dehydration, hydrogenation, dehydrogenation, hydrocarboxylation, hydroformylation, hydrogenolysis, hydro-metallation, hydrosilylation, hydrolysis, hydrotreating, hydrodesulfurization / hydrodenitrogenation (HDS / HDN), isomerization, methanation, methanol synthesis, methylation, demethylation, metathesis, nitration, oxidation, partial oxidation, polymerization, reduction, steam and carbon dioxide reforming, sulfonation, telomerization, transesterification, trimerization, water gas shift (WGS), and reverse water gas shift (RWGS).

[0042] As further described herein, the catalyst cores and catalysts according to various embodiments of the present disclosure exhibit several advantageous properties and characteristics.

[0043] Composition and Fabrication of ≥60% Theoretically Dense SiC-Based Catalyst Nuclei

[0044] Nickel-based catalysts have traditionally been used in steam methane reforming ("SMR") reactions and other types of catalytic reforming processes. Typically, nickel (the catalytically active material) is arranged or dispersed in the form of small nanoclusters (with an average diameter of 5 to 100 nm) on a catalyst support with a high internal surface area (10 to 1500 m 2 / g) composed of porous ceramics (e.g., alumina, ceria, titania, magnesia, silica, composites, mixtures, etc.). This type of catalyst system has also been used in catalytic dry reforming (DR) or combined steam and dry reforming (CSR), oxidative steam reforming (OSR), autothermal reforming (ATR), oxidative dehydrogenation (ODR), and catalytic partial oxidation (CPOX), and in some cases, other elements are added that are beneficial for suppressing coke formation and / or increasing the reaction rate and / or improving the catalyst thermal stability under high-temperature operation using steam.

[0045] In addition to Ni, other metals such as Co, Ru, Rh, Pd, Ir, and Pt are also used as the main active catalyst metals or as promoters or stabilizers when combined with Ni. High-temperature processes (above 600 °C) are more likely to include one or more platinum group metals ("PGM": Ru, Rh, Pd, Ir, Os, and Pt) used in combination with Ni as the main catalytically active material or as a promoter or stabilizer. Industrially, due to its sufficient activity, low cost, and availability, Ni is the preferred active metal for producing hydrogen by SMR of natural gas. Nickel is not the most active catalyst for SMR, but industrial fixed-bed reactors are usually limited by the equilibrium reaction. Moreover, due to the relatively low effective thermal conductivity of commercially available fixed-bed catalysts, the heat supply required for endothermic reactions in industrial fixed-bed reactors (e.g., for SMR) is slow.

[0046] For conventional SMR catalysts and catalysts for other types of reforming, the active metal is almost always deposited on another material that acts as a support or a high-surface-area support. Table 1 below provides a non-exhaustive summary of some of the catalyst systems commonly used in the above technologies. As indicated in Table 1, an alumina support is commonly used, but compositions of other porous supports can also be used, which contain the active metal arranged therein. For example, Ni supported on a porous alumina support is commonly used to catalyze industrial SMR using natural gas or biogas feedstocks. In some cases, small amounts of other elements are added to, for example, increase the catalyst's tolerance to coke formation and enhance the catalyst stability caused by high-temperature operation in a high-steam environment. In Table 1, ATR refers to the autothermal reforming reaction. CPOX refers to the catalytic partial oxidation reaction. DR refers to the dry reforming reaction. OSR refers to the oxidative steam reforming reaction. SMR refers to the steam methane reforming reaction.

[0047] Table 1

[0048]

[0049]

[0050] Silicon carbide (SiC) is a material that has been studied as a catalyst support for reforming reactions. SiC is attractive because the base material exhibits a high thermal conductivity, which is desirable for improving heat transfer in reactors. For example, at room temperature, the thermal conductivity of dense alumina is about 25 W / m-K, dropping to about 10 W / m-K at 530 °C and further to about 7 W / m-K at 830 °C. On the other hand, bulk (dense, non-semiconductor grade) SiC has a thermal conductivity of about 130 W / m-K at room temperature (dropping to about 60 W / m-K at 530 °C and further to about 38 W / m-K at 830 °C). When used as a catalyst support, the higher thermal conductivity of SiC compared to alumina is advantageous. SiC also exhibits a high level of inertness in side reactions (including carbon formation), tolerance to acid and base environments, mechanical hardness, and other characteristics favorable for a catalyst support. However, for applications that require exposure to oxygen and / or steam at high reaction temperatures, SiC is not an ideal catalyst support or core because this degrades the material by forming SiO2 (which forms volatile SiO-(OH) species in the presence of steam).

[0051] Thus, despite having some favorable properties, unprotected SiC lacks sufficient stability in oxygen (e.g., air) and / or H2O (e.g., steam) environments at high temperatures. Under these conditions, the surface of SiC will oxidize to SiO2, which further corrodes to form gaseous Si(OH)4 in the presence of steam or steam plus oxygen. Over time, this phenomenon continues until all of the SiC is oxidized. This results in the weakening or degradation of the SiC structure, leading to failure of the material or catalyst system. This is the main failure mechanism of SiC and is the main reason why it has not been industrially applied as a catalyst support in reactions that require high temperatures and the presence of oxygen (e.g., as air) or water (e.g., as steam), despite its excellent thermal properties. In addition, when SiC transforms to SiO2, the thermal properties of the material change significantly. The thermal conductivity of silica is much lower than the SiC value, and thus the formation of SiO2 also reduces the thermal conductivity of the material.

[0052] Due to these issues, applying catalytically active materials directly to unprotected SiC substrates (e.g., foams, monoliths, pellets, etc.) will result in oxidation rates that lead to unacceptably short catalyst lifetimes for steam methane reforming catalysts as well as catalysts for many other reactions. If the SiC surface is to be used in high-temperature oxidation or hydrothermal reactions involving steam, it must be protected or passivated. Thus, the use of SiC as a catalyst support in reforming and related reactions is generally limited to depositing an external porous layer such as alumina onto commercial SiC (α or β) and then impregnating the porous alumina layer with a catalytically active metal such as Ni. Alternatively, the addition of Ni and the porous layer (e.g., alumina) can be done in a single step. Coating an outer surface of the SiC core with a porous ceramic catalyst support layer such as alumina will slow the rate of entry of steam and oxygen into the underlying SiC during catalyst use. However, a slight delay in corrosion will not provide a commercially acceptable lifetime for industrial methane reforming catalysts.

[0053] The catalyst cores of the present disclosure advantageously utilize SiC, taking advantage of its beneficial thermal properties while protecting the SiC core from oxidation and corrosion in order to significantly increase the catalyst service life. In one embodiment, the SiC core comprises a composite of SiC and alumina (and optionally silica). The alumina is present as a protective matrix around the SiC grains within the composite core. In alternative embodiments (or in addition to the protective alumina matrix around the SiC grains within the core), a shell coating of dense alumina extends over the exterior of the SiC core. (It will be understood that, as further described herein, an outer coating such as alumina (including porous alumina) can also be provided over a SiC / Al2O3 composite core that is ≥60% theoretically dense.)

[0054] In a first embodiment, aluminum (e.g., as a powder, including as a powder of an Al - Si alloy) is combined with SiC (e.g., as a powder) before forming a core pellet or other desired shape, such as by pressing or extrusion. The mixture may contain various additives, such as one or more binders, plasticizers, lubricants, processing aids, etc. During pressing or extrusion (or other pellet / nucleus formation process), the aluminum undergoes plastic deformation to flow around the SiC grains. Then, during a subsequent heat treatment (i.e., calcination) in the presence of oxygen, the aluminum melts and rearranges into the voids between the SiC grains and is converted to alumina by oxygen at a high temperature (e.g., a processing temperature of about 850 °C or higher). The aluminum scavenges oxygen from the heat treatment atmosphere, not only preventing oxidation of the SiC grains but also converting most of the aluminum to protective alumina. The alumina, along with any unoxidized aluminum that will be trapped in the matrix, provides coverage and protection to the SiC grains from steam and oxygen erosion during catalyst use. At the specified heat treatment temperature, when the heat treatment temperature exceeds the melting point of aluminum (660 °C), the aluminum that has not formed an alloy with other materials in the system becomes liquid during a high - pressure pressing process or a high - temperature heat treatment process. The portion of the aluminum that remains pure will melt and may flow into the gaps between and around the SiC grains, making the aluminum more accessible to oxygen for forming an alumina matrix. In the final structure, the aluminum added to the SiC will be transformed into alumina, with a portion of the aluminum being considered to form an alloy with other materials, thereby providing a stable protective matrix around the SiC grains without forming an internal liquid film within the core during catalyst use (e.g., during high - temperature methane steam reforming). It is also believed that some of the formed alumina will be exposed on the surface of the core, providing further protection to the core. When Si is used in combination with Al (e.g., as an Al - Si alloy powder), it is believed that some Si will be trapped in the alumina matrix, and some Si will oxidize and react with the alumina to form mullite (Al6Si4O 13 ).

[0055] By providing an internal protective alumina matrix around the SiC grains of the catalyst core, embodiments of the present disclosure largely retain the favorable thermal properties of SiC while protecting SiC from oxidation and corrosion. The addition of the alumina internal protective (or barrier - layer) matrix can extend the commercial life of the catalyst by limiting the oxidation and corrosion of the dense SiC core, thereby obtaining a longer and commercially acceptable catalyst life. In one embodiment, the life of the catalyst ranges from 6 months to 5 years. In another embodiment, the life of the catalyst ranges from 6 months to 30 months before replacement is required within an industrial reforming tube. Such an extended catalyst life can be achieved at an industrial pressure of 20 bar, an S:C ratio of 3, a gas hourly space velocity (“GHSV”) of 2000 h -1 , and a reaction temperature exceeding 800 °C.

[0056] In some cases, SiC powder is mixed with an Al - Si alloy (e.g., an alloy containing up to about 25% Si, between about 5% and about 20% Si, between about 10% and about 15% Si, or between about 11% and about 13% Si) instead of using pure or substantially pure Al. Additionally, the Si in the alloy is used to lower the melting temperature of the metal component and / or improve the wettability of the molten metal. In one embodiment, a eutectic or near - eutectic alloy of Al and Si with a melting point less than 600 °C is used.

[0057] Alternatively, pure or substantially pure Al and Si powder can be combined with SiC instead of an Al - Si alloy. Also, other aluminum alloys or even other metals or metal alloys with a melting temperature below 1400 °C (with or instead of Al or Al - Si) are contemplated.

[0058] For reactions with high energy requirements (e.g., strongly endothermic or exothermic reactions), the high thermal conductivity of SiC facilitates the radial driving of heat into an endothermic reaction chamber or, if SiC is arranged in a thermally efficient form, the radial removal of heat from an exothermic reaction chamber, as described herein with respect to the pellet or particulate catalyst structures of the present disclosure. The catalysts described herein will also unexpectedly provide advantages for autothermal reactions. The higher effective thermal conductivity of the catalysts of the present disclosure will reduce the local axial thermal gradient within a tubular reactor due to the strong exothermic portion of the combined autothermal reaction by increasing axial conduction and heat transfer. Through axial conduction within the catalyst bed, heat is more effectively transferred to the endothermic reaction within the combined autothermal reaction. Although for an autothermal reaction, the overall or total reaction energy or heat is balanced, the local rate of heat release of the exothermic reaction typically exceeds the local reaction rate of the endothermic reaction. This results in the formation of local hot spots. The catalysts of the present disclosure reduce the number of hot spots at the front of the reaction channel and improve the overall process efficiency by giving more time and a higher temperature for the slower endothermic reaction to reach a higher degree of reaction at the end of the reaction tube.

[0059] The alumina protective matrix of the catalyst core of the present disclosure can be produced, for example, from a composition containing aluminum dispersed in SiC by plastically deforming the aluminum (e.g., during pellet formation) to flow around the SiC grains and then forming an alumina protective barrier layer around the SiC grains through an oxidative heat treatment process. Optionally, silicon can be included, such as by using an Al - Si alloy dispersed in SiC powder and / or by adding Si powder together with Al powder.

[0060] In a specific embodiment, SiC powder is mixed with aluminum and optionally silicon powder or sub-particles (these terms are used interchangeably). The mixture is then pressed under high pressure or load, or alternatively extruded into pellets (or other desired shapes), and then calcined to form a bonded (i.e., fused) structure where the grains adhere together and do not easily disperse. As a test of the bonded structure, if the pressed pellets are dropped from a height of one meter, they do not break or fracture into the original grain arrangement. As further explained herein, the pellets can be calcined before or after coating with a catalytically active material or other coating (e.g., an interfacial layer). In ambient air, the pellet calcination temperature can vary, for example, between 850 °C and 1450 °C, with a duration between about 0.5 and 24 hours, or between about 900 °C and about 1000 °C for at least two hours. As further noted herein, in some embodiments, multiple heat treatment steps can be employed at various temperatures and under various conditions. The result is a SiC / Al2O3 composite core (e.g., a pellet) composed of angular SiC grains bonded together through intergranular Al2O3.

[0061] Before calcination, the pellets (or other shapes) are composed of silicon carbide (SiC) powder and aluminum-silicon (Al-Si) powder - the latter as a mixture of Al and Si powders or as an Al and Si powder alloy. In a specific embodiment, SiC powders of different particle sizes are blended with the Al-Si powder. Two or more different particle size grades of SiC powder can be used to optimize particle packing within the green body (e.g., the pellet). For example, a coarse fraction of SiC (e.g., with an average diameter of about 30 to about 70 microns) can be blended with a smaller amount of a fine fraction of SiC (e.g., with an average diameter of about 15 to about 30 microns), where the fine fraction is used to fill the large voids between the coarse fraction. The powder blend is further mixed with various additives such as one or more organic binders (polyvinyl alcohol, polyvinyl butyral (“PVB”), ethyl or methyl cellulose, etc.) and / or one or more plasticizers (e.g., butyl benzyl phthalate (“BBP”), ethylene glycol, polyethylene glycol, etc.). These additives allow the processing of the fine powder (e.g., by pan drying, milling and sieving, or by spray drying) to form larger agglomerated powders that are more easily fed into a dry pressing operation (or other pellet forming equipment). Additionally, to assist the pressing operation, lubricants such as zinc stearate, stearic acid, and / or carbon powders such as graphite can be added to the agglomerated powder to simplify the dry pressing operation.

[0062] Although dry pressing can be used to form the catalyst core (e.g., as a pellet), various other methods can be used to form the core, such as extrusion, wet pressing, slip casting, isostatic pressing, injection molding, and other common ceramic forming methods, provided that the method applies sufficient pressure to achieve the target density (≥60% of the theoretical density of the blended SiC / Al powder) in the green state and causes plastic deformation of the aluminum.

[0063] Although the pressed or extruded pellets can be calcined after pellet formation, in an alternative embodiment, the pellets can be further subjected to a pre-calcination high-temperature heat treatment in a substantially oxygen-depleted environment before calcination. When used, the pre-calcination heat treatment step may cause the aluminum (or aluminum alloy) particles to sinter (e.g., at temperatures above about 400 °C) and further melt and coalesce (e.g., at temperatures above about 550 °C), thereby allowing rearrangement of the microstructure. This liquid phase can also further slow down or prevent the oxidation of SiC during subsequent heat treatment in air or an oxygen-containing environment at temperatures above 500 °C by preventing the diffusion of oxygen or steam (gases) into the structure. Thus, the pre-calcination heat treatment can be carried out at the same or a different temperature as the calcination temperature, particularly at a lower temperature. However, generally, the pellets will be calcined after pellet formation (i.e., without pre-calcination heat treatment) at a temperature of 850 °C to 1450 °C or 900 to 1000 °C for a period sufficient to convert the aluminum into an alumina matrix around the SiC grains. The calcination is carried out in an oxygen-containing environment, such as oxygen, air, steam, or dilutions of the foregoing with nitrogen, argon, hydrogen, and / or another carrier gas. In one embodiment, the pellets containing SiC and Al (or Al-Si) are calcined in ambient air without controlling the amount of oxygen in the calcination environment, thereby reducing costs.

[0064] Nucleation Example - SiC Grains in a Protective Matrix of One or More Metal Oxides

[0065] 180 g of 400 grit SiC (average diameter of about 40 microns), 45 g of 1200 grit SiC (average diameter of about 15 microns), and 21 g of Al-Si alloy powder (Valimet eutectic alloy 4047 (11%-13% Si), grade S-2, average diameter of 2 microns) were combined and transferred to a powder mixer where they were kept mixed. Separately, 3.5 g of PVB was dissolved in 50 g of isopropyl alcohol by heating. Then the PVB in the IPA solution was sprayed onto the powder under continuous mixing. Then the uniformly wetted powder was spread out in a shallow bed and dried at 120 °C until completely dry. 4 wt% of stearic acid and 4 wt% of graphite carbon (KS-6) were added to the powder. These powders were added dry, but isopropyl alcohol was added to wet the mixture. The mixture was dried again before pressing. Then the dry powder blend was dry pressed into pellets in a laboratory scale press. Pressing was done in a manual or automatic pellet press and the pressure could be applied uniaxially or isostatically.

[0066] The above examples can be varied by changing the type and amount of the coarse and fine SiC fractions used. In some embodiments, the coarse SiC can be selected from SiC having a grit size of 230 (average diameter of about 70 microns) to 600 (average diameter of about 30 microns), while the fine SiC can be selected from SiC having a grit size of 600 (average diameter of about 30 microns) to 1200 (average diameter of about 15 microns). The weight percentage of coarse SiC in the mixed SiC powder can vary between 50% and 100%, while the weight percentage of fine SiC can vary from 0% and 50%. For the Al-Si alloy powder, Valimet eutectic alloy 4047 (11%-13% Si) can be used, where the particle size is in the median size range of 2 to 50 microns. Specific examples include grades S-2, S-5, S-8, S-10, S-15, S-20, and S-25 of the Al-Si eutectic alloy 4047 powder from Valimet. Other Al-Si alloys can be used, such as those having up to about 25% Si (on a molar basis). The volume of Al-Si (or Al when no alloy is used) in the mixture can vary between about 2.5% and about 80% of the volume of SiC, between about 5% and about 50% of the volume of SiC, between about 5% and about 30% of the volume of SiC, between about 10% and about 30% of the volume of SiC, or between about 10% and about 25% of the volume of SiC. When other oxides are used to form metals instead of or in addition to Al or Al-Si alloy, a similar total amount of the oxide-forming metal in the mixture is used (e.g., 2.5%-80% of the volume of SiC, 5%-50% of the volume of SiC, 5%-30% of the volume of SiC, 10%-30% of the volume of SiC, or 10%-25% of the volume of SiC).

[0067] The volume of the combined PVB and BBP can vary between 1% and 15% (based on the total formulation before pellet formation), while the weight percentages of stearic acid and carbon can each vary between 0% and 15%. Finally, the volume ratio of BBP to PVB can vary between 0% and 50%. A summary of these variations is shown in Table 2 below, where the amounts of SiC and Al - Si are reported as volume % of the total amount of SiC and Al - Si powders, and the amounts of PVP, BBP, stearic acid, and carbon are similarly reported as % of the SiC and Al - Si powders. Figure 5 SEM images of catalyst particles having a SiC / Al2O3 core produced in the above - described manner, together with an outer catalytically active layer and an additional interfacial (i.e., third) alumina layer between the SiC / Al2O3 core and the outer catalytically active layer, are depicted.

[0068] Table 2

[0069]

[0070] Example of Alumina Interface / Third Layer Deposition by Al-Coating Deposition

[0071] As previously mentioned, some embodiments of the catalysts of the present disclosure include one or more interfaces (i.e., third layers) coated on the core. A catalyst core comprising SiC and Al2O3 is coated with one or more of these interfaces (i.e., third layers) to further protect the SiC component from oxidation when exposed to an oxidizing environment at high temperatures. Under such conditions, on unprotected SiC, a slowly growing silica scale develops. This scale acts as a barrier to further diffusion of oxygen into the core of the particle and thus prevents further erosion of the substrate. However, the main drawback of the resulting silica scale is its volatility (e.g., formation of Si(OH)4) and its susceptibility to corrosion in the presence of alkali metal salts (e.g., formation of Na2SO4), which limits its applicability for the intended purpose. To mitigate this, the protective "third layer" coating acts as a barrier between the atmosphere and the SiC surface. In some embodiments, each of the one or more interface layers comprises alumina, silica, titania, zirconia, or a mixture or oxide of two or more of the foregoing (e.g., mullite).

[0072] In some embodiments, the density of the one or more interface layers is ≥80%, ≥90%, or ≥95% of the theoretical density. In some specific embodiments, the density of the one or more interface layers is greater than the density of the core.

[0073] As another example, an outer layer of aluminum or an aluminum alloy containing other transition metals or a metal mixture and a metal oxide can be applied as a thin coating on the surface of a carrier material to form an interface layer, which is converted into a substantially dense oxide layer after calcination.

[0074] The particle size of the metal and / or metal oxide used to form one or more interface layers in this system can be controlled within a specific range. For example, the particle size can be controlled such that the size of substantially most of the particles falls within about 2 microns. The range of particle sizes can vary from less than 1 micron to as high as 20 microns.

[0075] An example of this method is a thin aluminum coating applied to the surface of the core. The coating can be applied by a variety of methods, including but not limited to: dip coating, spraying, spin coating, or vacuum infiltration, manually or by an automated process. The coating slurry used can vary from a completely organic solvent and binder system to an aqueous solvent system with a polymer binder, or a combination thereof. The coating material can vary from a pure alumina material to alumina mixed with other metals, metal oxides, or non-metals. Moreover, the interface coating can be applied to a pre-calcined carrier material or to the core shape formed as disclosed below. After calcination, any metal (e.g., aluminum) in the coating is converted to alumina.

[0076] In this particular example, an entirely organic-based coating medium was employed. Table 3 discloses the composition of the coating slurry for the third layer coating. Examples of the range of successful coating formulations are listed, but should not be construed as a limitation on potential coating systems.

[0077] Table 3

[0078]

[0079] The slurry is deposited onto the pre-calcined or pre-uncalcined material core disclosed herein. In this example, the coating is deposited onto the core manually or alternatively using an automated spraying device by an organic-based aerosol spraying method. In both methods, depending on the thickness required for the final coating, the spraying is done in one step or by several repeated coatings with intermediate drying cycles. The drying cycles can be at different temperatures from 60°C to 150°C. Once dried, the coated pellets are calcined at temperatures ranging from 800°C to 1500°C, but preferably between 1000°C and 1300°C, and even more preferably between 1250°C and 1350°C. The result is a substantially dense (≥80% of the theoretical value) alumina interface layer, which also contains a small amount of mullite (due to the use of an Al-Si alloy). An example of an aluminum-derived coating applied using manual spraying and converted to an alumina layer is shown in Figure 1

[0080] Example of BSAS "Third Layer" Protective Coating Obtained by Aerosol Deposition of Glass-Forming Agents

[0081] As previously discussed, a method for protecting the core of the catalyst support material of the present disclosure involves treating SiC in the presence of other elements such as aluminum or a mixture or alloy of aluminum and silicon as previously described. This provides excellent antioxidant protection for SiC in high-vapor environments under high-temperature conditions.

[0082] In this example, two additional methods for protecting the SiC core from oxidation are presented, one method using barium strontium aluminum silicate (BSAS) as a second phase in a SiC-based composite core, and another method using a protective BSAS coating around the Si-C core. Figure 2 Examples of materials obtained by these two methods are depicted. The white layer in these SEM images is BSAS.

[0083] Although BSAS has been used to demonstrate this concept, potential glass formers that can be similarly used in these coatings are polycrystalline solids prepared by the prereaction of glass-forming oxides, such as CaO-SiO2-Al2O3, or MgO-SiO2-Al2O3, SrO-SiO2-Al2O3, or BaO-SiO2-Al2O3. Other suitable glasses can include binary mixtures of alkaline earth metal elements in the glass former (such as BSAS itself), addition of rare earth elements substituting for alkaline earth metal elements in the formulation, or addition of small amounts of B2O3 or TiO2 as glass modifiers. Generally, alkaline earth metal aluminosilicates, modified with rare earth elements, borosilicate variants of alkaline earth metal aluminosilicates, or TiO2-modified variants of any of these formulations will be sufficient to provide a hermetic airtight coating. Additionally, such glass coatings can include second crystalline ceramic phase additives, such as alumina, titania, zirconia mullite, or other common oxide ceramics, to alter the thermal expansion of the layer during heat treatment and its densification behavior. In such composite coatings, the content of the crystalline oxide phase can be up to 40 volume percent of the coating solids.

[0084] In the first example, BSAS is coated onto granular SiC either before or after sintering (i.e., heat treatment) of the granular Si. If applied after firing the SiC, the BSAS coating is then heat treated. The heat treatment of the coating results in the formation of a substantially dense protective layer on the core material. The BSAS coating protects the SiC core from oxidation and corrosion during use.

[0085] Alternatively, BSAS is added to the SiC powder and the two powders are granulated together. This method is similar to the method described previously for the manufacture of SiC / Al2O3 composite nuclei. The granulated powder is then heat-treated in air (e.g., at a temperature above 1000 °C). During this treatment, BSAS melts to form a glassy complex that flows around the SiC and coats it during the process, thereby encapsulating the SiC and preventing oxidation. The production of SiC / BSAS composites by dry-pressing and heat-treating a mixture of precursor powders as shown is a unique and previously undisclosed method of obtaining composite materials. Figure 2 Examples of materials obtained by these two methods are shown. The white layer in these SEM images is BSAS.

[0086] Example of Alumina "Third Layer" Interface Coating Made of (Al + Al2O3)

[0087] In this example, a completely organic-based method is used. The specific composition of the coating slurry is disclosed in Table 4, which provides the exact reagents used in the formulation and the ranges that these components can have. The slurry can optionally be formulated with an aqueous medium. In this example, a combination of aluminum metal and alumina is used in the coating slurry. The aluminum metal and alumina can be mixed at the given ratios as shown in Table 4 such that the ratio between Al and Al2O3 varies between 2.5% and 50% by volume.

[0088] Similar to the previous example, the slurry is deposited onto the pre-calcined or pre-uncalcined core material of the present disclosure and dried. The coated core (e.g., pellets) is then calcined at a temperature ranging from 800 °C to 1500 °C, but preferably between 1000 °C and 1400 °C, and even more preferably between 1250 °C and 1350 °C. The resulting material is a core with a uniform and substantially dense alumina layer around the core, as Figure 3 seen.

[0089] Table 4

[0090]

[0091] Examples of Multilayer Protective Coatings:

[0092] In this example, the catalyst core of the present invention is coated with a multi-layer coating, the multi-layer coating including a highly dense (sealing) protective coating (fourth layer) and an underlying interfacial layer (third layer). The method produces an interfacial layer that is 70%-90% dense, and then an additional protective coating is deposited, the protective coating including a coating of alumina powder that contains a small amount of added glass-forming agent, hereinafter referred to as (Al2O3 + glass-forming agent). After firing at 1000 °C - 1400 °C, the multi-layer structure produces a sealing coating on the core.

[0093] For the interface layer, a layer of aluminum metal powder with a thickness of 10 - 40 microns is deposited on the surface of the core using the method of "depositing alumina 'third layer' by Al - coating deposition". In one embodiment, the coating is heated in air at 1000°C - 1400°C to produce an alumina coating that is 70% - 90% dense. After this heat treatment, a powder coating of (Al2O3 + glass - forming agent) with a thickness of 20 - 80 microns is applied by dip - coating, spray deposition, etc. Then the deposited coating is fired in air at 1000°C - 1400°C to produce a sealed protective coating.

[0094] In a second embodiment, before depositing a powder coating of (Al2O3 + glass - forming agent) with a thickness of 20 - 80 microns by dip - coating, spray deposition, etc., the initial aluminum - derived layer is dried but not heat - treated. Then the two deposited coatings are fired in air at 1000°C - 1400°C to produce a sealed coating.

[0095] (Al2O3 + glass - forming agent) formulations consist of (75% - 99%) commercial alumina powder, and the balance (1 - 25 wt%) is a glass - phase - forming material. The melting of the glass - forming agent effectively allows for an increase in the density of the coating, better adhesion to the underlying surface, and compliance of the coating during heat treatment to allow for the achievement of a sealed coating.

[0096] Suitable candidates for the glass - forming agent include precursor blends prepared by the pre - reaction of glass - forming oxides, such as CaO - SiO2 - Al2O3 ("CAS") or MgO - SiO2 - Al2O3 ("MAS"), SrO - SiO2 - Al2O3, or BaO - SiO2 - Al2O3. Other suitable glasses include mixed alkaline - earth metal aluminosilicates (e.g., BSAS), alkaline - earth metal aluminosilicates doped with rare - earth elements, or B2O3 - or TiO2 - modified alkaline - earth metal aluminosilicates.

[0097] In the current example, eutectic formulations of the CaO - Al2O3 - SiO2 and MgO - Al2O3 - SiO2 families are added to the alumina coating in the form of pre - reacted oxide mixtures. The glass - phase - forming agent and Al2O3 powder are mixed in an aqueous solution in an appropriate ratio.

[0098] To synthesize the glass - phase - forming agent precursor (Table 5), eutectic CAS and MAS compositions (based on the various oxides in the final formulation) are co - blended from calcium nitrate or magnesium nitrate, colloidal silica (SiO2), and boehmite (AlOOH) in water, then dried at 150°C and crushed to form a powder. Then the precursor powder is calcined at 1000°C to pre - react the oxides and reduce the surface area of the powder to between 8 and 12m 2between / g.

[0099] Table 5

[0100]

[0101] Then, the glass former powder is blended with alumina and suitable polymeric additives (dispersants, plasticizers, and binders) in an aqueous suspension, as listed in Table 6. Commercially available alumina and synthesized CAS or MAS, or other glass formers, are mixed in various proportions. Although the aqueous suspension is shown in Table 6, an organic solvent-based system can also be used.

[0102] The coating application process is preferably accomplished by a dip coating process, but can also be accomplished by a spray deposition process and other coating processes known to those skilled in the art. The coating thickness is controlled by these processes and can vary from 20 to over 80 μm. The coated pellets are heat-treated in air at a temperature between 1000 °C and 1500 °C, but preferably between 1200 °C and 1400 °C. Cross-sectional SEM micrographs of the sealed coated pellets are shown in Figure 4 in.

[0103] Table 6

[0104]

[0105] As described in more detail in the next section, the catalytically active material can be applied to the SiC / Al-Si core produced in the above manner either before or after the heat treatment (i.e., calcination) of the composite core. The resulting core / shell catalyst consists of at least two different layers and functions. The first layer consists of a SiC core with a high thermal conductivity and a high total normal emissivity, which serves to improve the radial or axial heat transfer within the reactor vessel. An optional third layer is a protective or barrier layer of alumina, which serves to minimize the ingress of corrosive vapors into the underlying SiC core and thereby extend the useful catalyst life. In some cases, this optional layer may be desirable in order to completely passivate the underlying SiC in addition to (or instead of) the alumina formed around the grains within the core. The optional third barrier layer preferably consists of a continuous dense alumina layer, where the density is between 80% and 100% of the theoretical value. This optional layer can be formed by applying an aluminum coating (e.g., as a slurry) and then heat-treating in an oxygen environment (e.g., ambient air) to convert the aluminum into a dense alumina coating. The second layer is the outer layer of the catalytically active material. In some embodiments, this second layer consists of two sub-layers: an inert but porous high-surface area support; and a catalytically active metal disposed within the porous high-surface area support to catalyze the desired reaction.

[0106] In some embodiments, the first layer is defined by an average pellet diameter ranging from 50 to 50,000 microns, preferably in the range from 200 to 15,000 microns average diameter. The third region is defined by an average thickness ranging from 0.3 to 50 microns, where the density is greater than 80% of the theoretical value. The second region or active catalyst coating is defined by an average thickness range from 5 microns to 200 microns, preferably in the range of 10 to 100 microns thickness.

[0107] Method of Coating a Catalyst Support Material

[0108] The nature of many industrial processes requires the use of the catalyst in its granular form instead of the powder catalyst. By doing so, the difficulties associated with the powder, such as handling, metering, and accurate measurement, are avoided. In some processes such as SMR, due to the process conditions involved, namely, high pressure, steam and flow conditions, and the associated excessive and thus uneconomical pressure drop across a small powder bed, the use of powder catalyst is not possible. Under these conditions, the powder catalyst further tends to be blown downstream of the reactor and into the product stream, which is undesirable.

[0109] By granulating the powder, the pressure drop is reduced and the processability and ease of use are significantly improved, avoiding the problems associated with the use of powder in industrial processes. Industrial processes such as SMR, catalytic partial oxidation, and dry reforming use granular catalysts in the reactor. For example, in SMR, the active metal (Ni) is impregnated into granular high-surface-area alumina.

[0110] In the present disclosure, the catalyst comprises a carrier material (i.e., the core) of high thermal conductivity and emissivity composed of pre-sintered α and β silicon carbide pellets having a protective outer coating (e.g., dense alumina or BSAS) or a composite of SiC / Al2O3 (with Si added). The powder is first granulated by dry pressing or extrusion and then heat-treated in an oxygen environment. Thereafter, the pellets are coated with a catalytically active layer, thereby providing a core / shell catalyst. The coating methods and options are further described herein.

[0111] To protect nuclear SiC from oxidation under high steam and temperature conditions, several methods can be employed. First, SiC can be mixed with a metal such as Al - Si powder that aids in its protection. After pressing, the aluminum plastically deforms to flow around the SiC particles, thereby forming an oxide phase around the SiC grains during subsequent oxidative heat treatment. Second, a mixture of barium strontium aluminosilicate (BSAS) can be added to the SiC powder and granulated before dry - pressing into pellets. The pellets are then heat - treated in air at temperatures ranging from above 1000 °C to 1500 °C. During this treatment, BSAS reacts to form a glassy complex that melts, flows around the SiC grains, and coats them. BSAS has good protective properties. Third, BSAS (or another protective layer such as dense alumina) can be coated onto granular SiC (pure or as a SiC / Al2O3 composite) either before or after firing the nuclear material. Heat - treating this coating at 1000 °C to 1500 °C results in the formation of a protective BSAS coating on the nuclear material. The BSAS coating ensures protection of the nucleus from oxidation. In Figure 2 Examples of the last two methods of protecting the nucleus are provided in

[0112] In the present disclosure, the high - thermal - conductivity materials of the present invention are processed with the various options discussed earlier, such as: (1) commercially available granular SiC materials can be coated with a protective outer layer such as BSAS, (2) BSAS can be added to commercially available SiC and granulated before heat - treatment, (3) a mixture of Al and Si can be incorporated into commercially available SiC powder, granulated, pelletized (or otherwise formed) and then heat - treated. In these options, the resulting pellets are further coated with an outer layer of a catalytically active material or a carrier layer (i.e., an interfacial layer) of a catalytically active material, resulting in the formation of a core - shell catalyst. The outer layer can be applied either after the catalyst carrier (i.e., the core) has been heat - treated or before heat - treatment (i.e., applied to the "green" core material). In either case, the deposited outer layer is typically heat - treated at different temperatures to cause the deposited outer layer to adhere to the core carrier material. The size of the deposited layer varies, with an average layer thickness ranging from 10 μm to 200 μm. It is this layer that is impregnated with catalytic metals for various catalytic applications (unless the catalytically active material is incorporated into the outer layer deposited on the core).

[0113] In some embodiments, the outer layer is deposited from a slurry containing a selected material onto granular high - thermal - conductivity catalyst carrier material that has not yet been heat - treated (i.e., is still green). In other embodiments, the deposition of the outer layer is done on a core that has already been heat - treated. In both cases, the deposited outer layer is heat - treated at different temperatures in the range from 600 °C to 1500 °C or from 850 °C to 1450 °C.

[0114] One or more outer layers of the catalysts disclosed herein can be applied to the SiC / Al-Si composite core in a variety of ways, including spraying or dip coating. In spraying, the materials of the outer layer are sprayed onto the pellets in the form of an organic or aqueous slurry. In dip coating, the granular particles are immersed in an organic or aqueous slurry containing the materials of the outer layer. Examples of the catalyst carrier cores of the present invention are shown in Figure 5 the SEM image of, where the outer layer containing the Ni catalytically active layer (shown as C) has been deposited onto the SiC / Al2O3 composite core (A), with an intermediate alumina interface layer (B).

[0115] As noted above, the catalysts described herein are core-shell type and are prepared by physically depositing an outer layer onto a SiC / Al-Si solid core. The outer shell can be an interface layer subsequently impregnated with a catalytically active material or a layer deposited with a catalytically active material already incorporated therein (e.g., an oxide porous catalyst phase).

[0116] In one embodiment, the pressed pellets are coated with an organic or aqueous slurry containing a second material in the form of a metal or an oxide. The slurry is composed of known transition metal and metal oxide catalyst carrier materials. In one embodiment, the slurry contains a nanoscale suspension of Ni particles (or other PGM particles) synthesized by the polyol process. After coating, the slurry is dried so that a solid coating remains on the surface. For slurry-based catalyst coatings, a calcination step is common to oxidize the binders and other carbon-based materials used in the formation of the slurry. The catalyst calcination step also serves to bond the catalyst coating to the surface. The materials are generally divided into two categories: (1) loaded catalyst powders, and (2) catalyst carrier powders. The former refers to catalyst carrier powders that already contain an active catalyst, while the latter refers to carrier powders without an active metal but impregnated with an active catalyst metal after forming a composite coating. The active catalyst layer can be added to or coated on the pressed pellets as a complete catalyst including the active metal disposed on the entire high-surface-area carrier or as only the high-surface-area carrier without adding or coating the active metal onto the pressed pellets. In the latter case, the active metal is impregnated into the porous carrier layer already coated on the pellets in a second step.

[0117] The coating slurry can be prepared, for example, by adding the desired powder material to an organic medium such as, but not limited to, ethyl cellulose, polyvinyl alcohol, or α-terpineol. The powder material can be selected from the following non-exhaustive list: in particular, aluminum-silicon, alumina doped with zirconia-ceria, alumina, ceria doped with zirconia, alumina-silica mixture, γ-alumina, α-alumina, magnesia-promoted alumina, calcia-promoted alumina, sodium-promoted zirconium-cerium oxide, cerium oxide, titanium dioxide-promoted silica. These materials will form a coating on the core, which supports the catalytically active material incorporated in the slurry or can be impregnated with the catalytically active material after heat treatment. The above oxides can be applied in the form of dispersed nanoclusters, spots, dots, etc., with or without the following catalytically active metals disposed therein: in particular, nickel, platinum, rhodium, ruthenium, cobalt, rhenium, iridium. Elements known to act as promoters or inhibitors of coke formation can be added optionally.

[0118] The so-dried coating is calcined on the pellets by slowly raising the temperature to the target temperature and holding at that temperature for about at least 1 hour. The catalyst calcination temperature can be in the range from about 300 °C to about 800 °C. The oxygen environment (e.g., ambient air) of the calcination process will cause any binder used in the catalyst slurry formation to burn off. After the catalyst calcination step, the catalyst coating will fuse to the underlying ≥60% theoretically dense SiC core, and the catalyst coating will retain porosity and be substantially free of organic binders.

[0119] If the applied coating does not include the catalytically active material, the final step in manufacturing the core-shell catalyst is to infiltrate (i.e., impregnate) the layer with active catalyst metal ions. The metal ions under consideration are dissolved in a medium preferably water, but can also be organic. The pellets are immersed in the medium, and thereafter the ions impregnate the porous outer layer. After a defined time, for example, in the range from about five minutes to about four hours, the metal-ion-impregnated support material is drained from the solution and dried, for example, at 120 °C for a period between 30 and 60 minutes or longer. Finally, the support material is calcined in air at different target temperatures in order to, for example, remove the binder (e.g., residual organics).

[0120] The Catalyst Structure of the Present Invention and Its Support Defined by Its Oxidation Resistance

[0121] When applications involve exposure to oxidative environments and high temperatures typical of many chemical reactions, including but not limited to steam methane reforming, silicon carbide (SiC) and SiC-based composites require protective coatings. Under these conditions, SiC undergoes simultaneous oxidation and volatilization in steam. SiC is oxidized upon exposure to oxygen at high temperatures by the following:

[0122] SiC + H2O(g) → SiO2 + CO(g) + 3H2(g)

[0123] The oxidation of SiC is limited by the mass transfer of oxygen to the core of the material. Thus, the oxidation will be non-uniform, slowing towards the core of the material. It has also been determined that the undesirable oxidation of SiC is enhanced in the presence of water compared to dry feed mixtures at high temperatures. This oxidation is due to the significant solubility of SiO2 in water, which changes the rate in favor of the formation of the undesirable SiO2. In the presence of water, the reaction after the volatilization of SiC is as follows:

[0124] SiO2 + H2O → Si(OH)4(g)

[0125] During the catalysis of chemical reactions, the potential oxidation of SiC catalyst supports is particularly problematic because the underlying layer beneath the catalyst coating may become weak, such that the catalyst coated on top of the weak underlying layer may be lost due to spalling and delamination. The loss of the catalyst is manifested as catalyst deactivation during the operation of the chemical reactor, which thus reduces the efficiency. In addition, spalling introduces fines within the packed bed reactor, which may block some of the gas paths, resulting in an increase in pressure drop and a reduction in the process or reaction efficiency.

[0126] As previously described herein, catalyst supports according to embodiments of the present disclosure can be manufactured by premixing SiC with Al (and optionally Si, particularly by using an Al-Si alloy), pressing into dense pellets, and then further fusing by heating at high temperature in an oxygen environment. Compared to conventional porous SiC, the resulting material (SiC / Al2O3) has an increased density and has excellent oxidation resistance characteristics. Experiments studying the oxidation behavior of SiC in the composite of the resulting SiC and alumina pressed pellets have revealed that such a composite material, unlike bare SiC which is easily oxidized in air and steam atmospheres at high temperatures, is highly tolerant to oxidation and subsequent volatilization, as shown by the low weight gain under such conditions seen below.

[0127] The tolerance of pellets with layers 1 and 2 to oxidation and volatilization was tested by heating the material in an environment of 25% steam in air at a temperature of 900 °C. Before conducting the aging test, the material tested in steam at 900 °C was first processed or heat-treated at a temperature of 1250 °C for one hour. For this test, the heating rate to 1250 °C was 3 °C / min and the cooling rate was 5 °C / min. Similarly, the oxidation behavior of materials (coated or uncoated) processed at different temperatures from 1050 °C to 1450 °C in an environment of 50% steam in synthesis gas (3% hydrogen, the remainder nitrogen) has been studied. These reactions have been studied for different time periods. Figure 6 A and 6B are photographs depicting the sample results from these studies, and Figure 7 is a graph of the weight gain of the samples during the study. InFigure 6 In the photograph of B, after a period of 44 hours in 25% steam in an air environment at 900 °C, there was no visible material change (no weight gain and no color change). In contrast, under the same conditions, commercial SiC pellets ( Figure 6 A) were completely oxidized, as seen from Figure 6 the white color in the unprotected SiC pellets in A. Figure 7 It shows how a significant weight gain occurs over time and the importance of protecting SiC when used in a high-temperature environment with steam required for industrial methane reforming catalysts.

[0128] To further quantify the weight gain, the pellets to be tested were weighed and first dried at a temperature of 150 °C. The dried pellets were loaded onto an alumina ceramic boat and then slid into the hot zone of a one-inch nickel-Inconel tube. Synthetic gas (3% H2 in N2) was passed through the pellets, and the tube was heated to 900 °C at a rate of 3 °C / min. Once the furnace temperature reached above 300 °C, water (pumped using an HPLC pump) was introduced into the tube. The water passed through a vaporization zone maintained at 500 °C, which turned the water into steam. The introduced water made the partial pressure of steam 50% of the total gaseous compounds. The test duration started when the furnace reached 900 °C. At the end of the timed test, the furnace was cooled at 5 °C / min. When the furnace temperature reached approximately 300 °C, the water was turned off. When the furnace had cooled substantially below 100 °C, the pellets were unloaded and their weight was immediately recorded. The cumulative weight gain of the SiC and alumina composite pellets of the present invention was less than 1% weight gain within 300 hours, and more preferably, when tested at 900 °C in a mixture of 50% steam in synthetic gas, the protected pellets of the present invention will have a weight gain of less than 0.1% within 300 hours. Similar results will be obtained by testing catalyst particles (i.e., cores coated with a catalytically active layer).

[0129] As previously discussed herein, a compacted green body is first formed using a mixture of SiC and aluminum grains. The aluminum is dispersed within the green body and plastically deforms around the SiC grains under a high-pressure compaction operation. The grains are defined by substantially micron-sized SiC particles (ranging from 0.1 micron to 50 microns), which are mixed with aluminum particles (from 0.1 micron to 50 microns) and then densified to form a green body, such as produced by using a high-pressure granulation press. When the green body composed of SiC and aluminum is subjected to an initial heat treatment process, the aluminum preferentially reacts with oxygen (in the form of air, oxygen, and / or steam) to form a protective scale composed of alumina around the exposed or gas-diffusion accessible (excluding solid-state diffusion) surface area of the SiC grains of the green body. The most preferred form of the protective scale is the α-alumina phase. In one embodiment, the protective scale includes a combination of alumina phases. The phases of alumina are controlled by selecting the heat treatment conditions (mainly temperature). Above about 900 °C, α-alumina becomes favorable, and the oxides formed at lower temperatures are further transformed into a substantially dense α-alumina phase. In some embodiments, the protective scale is composed of α-alumina and has an average thickness ranging from about 0.3 to 3 microns. The formation of the protective alumina scale occurs at a high temperature above about 850 °C, such as by calcining at 900 °C to 1000 °C for 2 to 20 hours.

[0130] The formation of a substantially dense alumina layer that protects the internal compacted SiC grains will reduce the oxidation or degradation of the SiC grains and extend the catalyst life. The resulting catalyst core material will show a weight gain of less than 1% within 300 hours, and more preferably, when tested in a mixture of 50% steam in synthesis gas at 900 °C, the protected green body of the present invention will have a weight gain of less than 0.1% within 300 hours. Similar results will be obtained by testing the catalyst particles (i.e., the core coated with a catalytically active layer).

[0131] The resulting catalyst, such as produced after forming the protective alumina barrier layer and subsequent coating with an active catalyst, will exhibit an activity loss of less than 1% during a run time between 100 and 1000 hours during the methane steam reforming reaction operation. The catalyst is resistant to oxidation corrosion of the underlying high-thermal conductivity SiC core due to its protective internal barrier layer, and thus the expected catalyst life before replacement is at least two years. During the two-year life period, in-situ regeneration cycles may be required to improve the catalyst performance, but the catalyst remains effective for operation and hydrogen production. The operating conditions of the catalyst are 20 bar, a steam-to-carbon ratio of at least 3, a GHSV of at least 2000 h -1 , and a tube wall temperature of at least 850 °C, where the methane conversion exceeds 50% and / or the equilibrium approach temperature is closer to at least 50 °C.

[0132] In another embodiment, the catalyst according to the present disclosure will match the extended life of the steam methane reforming tubes. As the tube life increases, the maintenance and plant downtime corresponding to tube replacement are matched to the catalyst life and catalyst replacement cycle. The end result is that the methane steam reforming unit operates with increased uptime. In one embodiment, by using the catalyst of the present invention, the uptime of the methane reforming unit is greater than 0.95 and more preferably greater than 0.98, and in the most preferred embodiment, the uptime of the unit exceeds 0.99. An uptime of greater than about 0.99 corresponds to a turnaround time or downtime of one week without hydrogen production during an operating cycle of at least about two years. During the one-week turnaround time, both the reaction tubes and the catalyst of the present invention contained therein are replaced to maximize the desired productivity or uptime of the methane steam reforming unit (defined by the operating rate or the proportion of time the unit produces product). For example, a commercial hydrogen plant producing at least 10 MM standard cubic feet of hydrogen per day using the catalyst of the present disclosure operates continuously for 12 months, where continuous operation includes intermediate catalyst regeneration cycles lasting less than 48 hours but not a complete plant shutdown (such as would be required for tube replacement).

[0133] Improved Selective Oxidation Reaction Using the Disclosed Catalyst

[0134] The selective or partial oxidation reaction combines a small molar volume of oxygen (added in the form of pure oxygen, air, or diluted to some extent with an inert gas) with a hydrocarbon reactant that can be in the gas or liquid phase. The oxygen reacts with the reactant hydrocarbon on a solid catalyst to preferentially produce high-value products. A small fraction of the oxygen may combine with the reactant and / or the desired product to form undesired deep complete oxidation or combustion products. These reactions are exothermic for the desired partial or selective oxidation reaction, and the reaction energy is less than the heat released when oxygen molecules form complete combustion products. When heat is released from any series-parallel reaction, the temperature increases, and the reaction rate towards the undesired deep oxidation reaction increases. Therefore, it is advantageous to reduce the temperature increase on the catalyst during these reactions in order to achieve a higher selectivity to the target or desired partial or selective oxidation product.

[0135] An example selective oxidation reaction is the production of maleic anhydride from n-butane over a commercial VPO (vanadium-phosphorus-oxygen) catalyst. As described by Hofmann and Turek (2017), the gas-solid reaction mechanism is series-parallel, where deep oxidation products can form in parallel and in series with the production of the desired product, maleic anhydride. The selectivity is highly sensitive to the reactor temperature, and heat removal through the catalyst particle bed is an important parameter for efficient production.

[0136] Hofmann and Turek compared for 4800 h -1Performance of 1.5 mm and 3 mm catalyst bed thicknesses at a GHSV of, a reaction temperature of 420 °C, and an initial n-butane concentration of 1.4%. At a reaction diameter of 1.5 mm (tested as VPO catalyst particles packed in a microchannel slit or chamber) and an average catalyst particle diameter of about 400 microns, at a n-butane conversion of about 60%, the selectivity to maleic anhydride was about 65%. At a higher n-butane conversion of about 95%, the selectivity to maleic anhydride decreased to about 55%. The decrease in selectivity with increasing conversion is the result of a change in the partial pressure within the catalyst bed, which favors the deep oxidation reaction pathway.

[0137] For the same catalyst particle size and reaction conditions, at a larger channel slit or gap or diameter of 3 mm, the selectivity decreased to about 45% at a conversion of about 95%, while the selectivity was 55% at the same conversion in a 1.5 mm slit. Compared to the 1.5 mm slit, the lower selectivity at the same conversion and GHSV for the larger 3 mm slit is the result of an increase in temperature within the catalyst particle bed packed in the 3 mm reactor gap.

[0138] In the 1.5 mm slit reactor, the measured reactor temperature was substantially isothermal. In this case, the 3-mm slit reactor was experimentally shown to have a hot spot and a thermal gradient of about 10 °C over the 3-mm reactor heat transfer distance, where the n-butane feed concentration was 1.4 vol%. For a higher n-butane feed concentration of 4.5 vol%, for the 3-mm packed bed slit reactor, the hot spot increased to 15 °C. This type of hot spot formation and the decrease in product selectivity for selective oxidation reactions are common. Generally, the GHSV is reduced to reduce the local heat generation rate and maintain good selectivity.

[0139] In one embodiment, the use of the SiC-based catalyst of the present disclosure will allow an increase in GHSV of about 0.1% to 10% while maintaining equivalent selectivity for equivalent tube diameter, feed composition, temperature, pressure, catalyst composition, and average catalyst particle size.

[0140] The catalysts of the present disclosure are capable of giving a fixed bed or particulate catalyst a relatively high effective thermal conductivity. When the measured range of effective thermal conductivities is applied to selective oxidation reactions, at the same WHSV, feed composition, temperature, pressure, and active catalyst composition, the expected increase in selectivity for the desired partial or selective oxidation reaction will be about 0.1% to about 10% higher. WHSV (weight hourly space velocity) is defined as the weight of the feed per hour divided by the weight of the catalyst contained in the active layer or shell coated around the SiC core of the disclosed catalyst.

[0141] In another embodiment, the catalysts of the present disclosure can be applied to selective liquid phase oxidation reactions. Liquid phase reactions generally operate at much longer residence times and lower catalyst WHSV. The mass diffusivity of reactants in the liquid phase reaction medium is approximately three orders of magnitude lower than the gas phase mass diffusivity, and thus the eggshell (i.e., core-shell) form of the catalysts of the present disclosure will provide an advantage for efficient catalyst use during liquid phase selective oxidation reactions. Liquid phase oxidation is also highly exothermic, and some reactions can operate near explosive conditions. Heat removal is crucial for safe operation and maintaining high selectivity to the target selective oxidation product. Due to its higher effective thermal conductivity, the catalysts of the present disclosure will remove heat more effectively than conventional fixed bed pellets. It is expected that when operating at the same WHSV, feed concentration, temperature, pressure, and catalyst composition, the selectivity to the high-value selective oxidation product will increase by from about 0.5% to 15% compared to conventional fixed bed catalysts. The temperature for liquid phase selective oxidation on a fixed bed particulate catalyst is typically controlled by operating at low WHSV to minimize heat generation and hot spots, while maximizing the desired product selectivity. The selectivity of liquid phase selective oxidation reactions is usually very high because the WHSV is very low. It is expected that using the catalysts of the present disclosure will enable an increase in the reaction WHSV without adversely affecting product selectivity. In one embodiment, the WHSV of the liquid phase selective oxidation reaction productivity will increase by a factor of 1.2 while maintaining the same selectivity. In an alternative embodiment, when operating at similar hydrocarbon and oxidant feed rates, diluent composition, temperature, and pressure, the WHSV and reaction productivity will increase from 1.05 to 1.3 while maintaining the same selectivity compared to a catalyst of the same composition.

[0142] Catalyst Containing SiC-Supported Catalyst That Can Be Loaded In-Situ Without Loading Process or Reactor Modification

[0143] Steam methane reforming (SMR) is used industrially to produce hydrogen and is a highly endothermic process (ΔHr = -206 kJ / mol). The process operates at high pressures (up to 40 bar) and high temperatures (up to 950 °C reaction temperature or 1050 °C tube temperature) in order to ensure high methane conversion due to the thermodynamic equilibrium limitations of the reaction at high temperature and pressure.

[0144] To maintain high temperatures and provide the necessary energy to drive strongly endothermic reactions, heat is provided around the outside of a series of parallel reactor tubes containing an active catalyst. Several techniques have been devised to heat the reactor. Methods for providing heat for endothermic reactions include convective heat transfer, radiative heat transfer, and direct combustion or burners. Compact reformers are also an area of active development for enhancing heat transfer and reducing the size and cost of industrial hydrogen production from methane reforming. Most industrial methane reformers provide heat through an integrated natural gas burner. The reactor furnace contains a box-shaped radiant section that houses the burner and a convective section designed to recover waste heat from the flue gas leaving the radiant section.

[0145] Catalysts for steam methane reforming are typically made of Ni deposited on a high-surface area support, mainly high-surface area porous alumina. Alternative metals such as cobalt and noble metals also show high activity but have not been widely adopted due to cost. The nickel surface area is the main factor controlling catalyst activity, but the total hydrogen productivity is mainly limited by heat transfer rather than catalyst activity.

[0146] For use in industrial reformers, a typical Ni / Al2O3 catalyst is formed into cylindrical pellets less than about 10 cm in length (usually 1 to 5 cm in length) and less than 10 cm in diameter (usually 0.5 to 3 cm in diameter). To ensure maximum contact of methane with the Ni particles and reduce the likelihood of increased pressure drop, radial holes are formed throughout the cylindrical pellets. These catalyst pellets are loaded into reactor tubes, which are typically about 0.1 m in diameter and up to about 10 m in length.

[0147] Loading catalyst pellets into an industrial SMR reactor tube is not a simple process. A typical 10-m tubular reactor is loaded with catalyst from the top, and the pellets fall under gravity. Inherently, the pellets are subject to large impacts as they tumble during loading from a high fixed height. Companies have designed loading methods aimed at minimizing such mechanical shock. These methods include: (1) using supersacks and attached socks that ensure a gradual loading of the pellets and minimize the maximum free-fall distance; (2) the Unidense method of loading catalyst pellets using proprietary Unidense equipment; and (3) other vibration techniques can be used to densify the catalyst packing in stages along the tube length while minimizing the mechanical stress on the catalyst pellets. Dense packing is preferred to minimize the non-uniformity of the pressure drop between the many parallel tubes that make up an industrial methane reforming unit. Uneven flow distribution between the tubes will affect performance and catalyst life because those tubes receiving less flow will be less able to utilize the heat provided by the external burners and will thereby create hot spots on the metal tube walls. Hot spots reduce the reactor tube life. Ultimately, reducing the breakage of the catalyst due to collisions, attrition, and abrasion, and denser packing to minimize the uneven flow distribution are desirable and beneficial to the catalyst.

[0148] The catalysts of the present disclosure not only have favorable thermal properties, but they are designed to be free-flowing and can thus be used in current SMR reactor tubes without any modification to the existing equipment or to the existing catalyst loading and packing densification tools. The catalysts of the present disclosure can be loaded in-situ after installation of the original tubes or replacement tubes. In an alternative embodiment, the catalysts of the present disclosure can be loaded into a separate facility during a plant turnaround and transported with the replacement reactor tubes. This embodiment will minimize the need for on-site dedicated catalyst loading equipment and can allow for a high utilization rate of the catalyst loading equipment from a dedicated facility.

[0149] Given the free-flowing nature of the catalysts of the present disclosure, they will follow conformal loading characteristics. If the catalyst must be replaced at a frequency greater than the tube replacement frequency, the catalyst can be more easily filled around the tube deformation. Industrial methane reforming tubes operating at high temperature and pressure will deform over time due to mechanical creep during operation. Due to the conformal and free-flowing nature of the catalysts of the present disclosure, tubes that may no longer be completely symmetric can still be relatively easily reloaded. By allowing the replacement of the catalyst before the end of the useful life of the industrial reforming tube or allowing the replacement of the catalyst simultaneously with a new reactor tube, the conformal filling property of the catalysts of the present disclosure will reduce the total cost of plant operation.

[0150] The catalysts of the present disclosure are made of densified (≥60% of theoretical density) SiC cores with excellent mechanical properties. The crush strength and vibration resistance of the SiC-based catalyst pellets are improved compared to those of traditional porous alumina pellets. The disclosed catalysts will provide initial performance close to that expected after catalyst loading and longer catalyst life by reducing crack formation, catalyst breakage, and fines formation after catalyst loading.

[0151] The disclosed catalyst support materials have been mechanically studied to determine how they will withstand typical loading processes used in industrial reforming tubes. These mechanical studies were developed using standard ASTM methods and involved radial crush testing, which involves subjecting the pellets to a radial load to study how much force is required to crush the pellets. Table 7 summarizes the mechanical properties of the catalyst cores of the disclosed supports compared to commercial catalysts. The results show that the materials are competitive and will not require any special modification to current reactor loading methods.

[0152] Table 7.

[0153] Properties Generation 1 Generations 2 and 3 Generation 4 Generation 5 Commercial Density (% of Theoretical Value) 45 69 >70 >70 45 Oxidation Resistance (% Weight Increase) 0.4-6 0.2-0.4 0.9 1 Not Applicable Radial Crushing Strength (N / mm) 71-89 53-125 120 >125 44

[0154] The crush strength of the disclosed catalyst supports exceeds that of commercial catalysts by at least a factor of 2 and, in one embodiment, from 2 to 5 times. The crush strength of the disclosed catalysts exceeds 50 N / mm and is in the range of 50 to 150 N / mm, where the crush strength of commercial reforming catalysts is 44 N / mm. The crush strength of the disclosed catalysts and commercial catalysts was carried out according to the established ASTM International test protocol (ASTM D6175-03(2013)).

[0155] In Table 7, "Generation 1" is a commercially available porous SiC catalyst support coated with BSAS. The porous SiC catalyst support is not dense enough (i.e., less than 60% of theoretical density). "Generations 2 and 3" are composite cores containing SiC / BSAS, and "Generations 4 and 5" are composite cores containing SiC / Al2O3 with slightly different amounts of lubricant added during processing.

[0156] Catalyst for Fischer-Tropsch Reaction

[0157] Fischer-Tropsch synthesis (FTS) (see Equations 1 and 2 below) is a method for converting non-petroleum carbon sources including coal, coalbed methane, and biomass into liquid fuels and chemicals. These sources are first converted into fuel and chemicals by FTS before synthesis gas, also known as syngas (CO and H2), is produced by technologies such as steam reforming or gasification. Two classes of products are obtained by FTS: non-oxidized products such as gasoline, diesel, and light olefins, and oxidized hydrocarbons such as methanol, ethanol, and mixed higher alcohols.

[0158] (2n + 1)H₂ + nCO = C n H 2n + 2 + nH₂O (Equation 1)

[0159] 2nH₂ + nCO = C n H 2n + nH₂O (Equation 2)

[0160] Due to the role of FTS in converting non - petroleum carbon sources via syngas, and because of the decreasing crude oil reserves and the rapid growth of global demand for liquid fuels, FTS has attracted much renewed attention in recent years.

[0161] The key to the success of FTS is the catalyst that plays an active role in converting syngas into products. Catalysts with high activity, selectivity, and stability are the main research directions in current FTS research. Typical active metals for FTS are Fe, Co, and Ru. Usually, these metals are deposited on supports such as, in particular, Al₂O₃, SiO₂, TiO₂. FTS is an exothermic reaction, releasing heat to the surrounding environment. As a result, excessive heat on the catalyst surface will lead to hot spots, which may damage the performance (activity and selectivity) of the catalyst. For it to be effective, this heat must be dissipated from the catalyst surface relatively quickly. Therefore, a catalyst support system that can discharge heat from the reaction surface to the outside of the tube is highly desirable. Thus, in addition to the catalyst having activity, selectivity, and stability, its ability to effectively discharge heat from the reaction surface and thus prevent the development of hot spots makes it a more effective catalyst. The increase in efficiency can lead to an increase in activity or selectivity.

[0162] The catalyst support (i.e., the core) of the present disclosure (a high - effective thermal conductivity support material) provides an improved support for FTS catalysts. Compared with the low thermal conductivity of current FTS supports, the high thermal conductivity will enhance the heat dissipation from the reaction surface. This will result in avoiding hot hot spots and thus leading to a more effective FTS catalyst.

[0163] The Fischer - Tropsch reaction combines carbon monoxide and hydrogen (syngas) on a cobalt - or iron - based catalyst at high pressure and temperature to achieve a chain - forming reaction that produces synthetic crude. The product mixture is a hydrocarbon mixture from C1 (methane gas) to C 100 and higher (solid waxes). Subsequently, the synthetic crude can be refined and upgraded to produce a unique product mixture: gasoline, diesel, jet fuel, and wax.

[0164] It is desired to convert as much of the syngas as possible into carbon fractions with more than five carbon atoms to minimize the amount of unwanted light gases (mainly methane). High carbon efficiency is desired and is characterized by a chain growth α. α is the chain growth parameter in the Anderson-Shultz-Flory distribution (see Equation 3 below), where F n is the mass fraction of hydrocarbons with n carbon atoms (e.g., for octane n = 8, C8H 18 ).

[0165] F n = n(1 - α) 2 α n-1 (Equation 3)

[0166] Figure 8A -D presents the relationship of the mass fraction of the nth hydrocarbon relative to the carbon number for α ranging from 0.8 to 0.99. As α increases, the mass fraction of the heavy hydrocarbons increases significantly. When α approaches the value of 1, the resulting hydrocarbon product consists of very long chain hydrocarbons that are essentially solid wax. In practical systems, an α value of 0.95 is very good and minimizes the amount of light gases produced with a methane slip or selectivity of less than 5 mol%. An α value less than 0.8 is considered poor and indicates a methane slip of greater than 10 mol%. Note that the light gas (less than carbon number 5) composition may deviate from (exceed) the weight fractions predicted by the conventional Anderson-Schultz-Flory distribution.

[0167] Chain formation reactions are favored at lower temperatures (Equation 4 below), while higher temperatures favor light gas production, mainly methane (Equation 5 below). The Fischer-Tropsch reaction is highly exothermic; heat must be removed from the chemical reactor during operation to avoid thermal runaway and control the selectivity to the desired products.

[0168] CO + 2H2 = (-CH2-) + H2O ΔH r_298K = -152 kJ / mol (Equation 4)

[0169] CO + 3H2 = CH4 + H2O ΔH r_298k = -206 kJ / mol (Equation 5)

[0170] The chain formation reaction is slightly less exothermic than methane formation and thus hot spots within the catalyst tend to further enhance the unwanted methane formation through a negative feedback loop. In some cases, thermal runaway may occur if poor heat removal and high internal temperatures promote a high degree of methanation reaction.

[0171] Fixed catalyst bed designs are common for cobalt-based catalysts. Typical operating conditions range from 190°C to 240°C and pressures range from 10 to 40 bar. The reaction tubes are typically cooled by generating steam as water flows around and between the tubes to remove the reaction energy at the edges of each tube filled with catalyst. When the temperature within the catalyst bed or particles increases by 10°C or more, the molar selectivity for methane formation increases by 5% or more, while α decreases by 0.05 or more. It is desirable to minimize exotherm or hot spots within the catalyst bed to less than 10°C and more preferably less than 5°C.

[0172] One option to reduce catalyst hot spots is to decrease the tube diameter that houses the particulate or fixed bed catalyst. An actual tube diameter of about 1 to 2.5 inches can be reduced to about 0.5 to 0.75 inches, but this will adversely affect the economics of the overall process. To achieve a given capacity or production rate, a greater number of tubes increases more metal (higher cost) and greater complexity of having more tubes within a larger vessel. It is desirable to reduce hot spots within the fixed bed catalyst without decreasing the reactor tube diameter.

[0173] The catalysts of the present disclosure have two features that actively reduce hot spots and provide better reaction performance for reactors filled with Fischer-Tropsch catalysts. The first advantage is a higher effective thermal conductivity within the fixed bed. The improved radial heat transfer removes more exothermic heat and reduces hot spots within the catalyst bed. The improved axial and radial heat transfer reduces or eliminates large thermal gradients, thereby reducing the total number of hot spots. Fewer hot spots thus increase the reaction α and reduce the amount of unwanted methane. A higher reaction α is preferred because the value of the wax produced is high and, depending on current market drivers, the wax can be hydrocracked into valuable jet fuel or different fuel blends.

[0174] It is expected that the Fischer-Tropsch catalysts produced by a thin catalyst layer on top of the disclosed SiC-based core will result in a 2°C to 8°C reduction in exotherm or hot spots compared to conventional Fischer-Tropsch catalysts when operated under the same conditions. When operated under similar conditions, with the corresponding conventional catalyst, the resulting methane molar selectivity will decrease by 2% or more and may decrease in the range from 2% to 5%. For tube diameters between about 0.75 and 2.5 inches, a GHSV of from about 500 to 5000 h -1 −1, for a cobalt-based catalyst at a starting temperature between about 200°C and 240°C and for an iron-based catalyst at a starting temperature between about 300 and 350°C, at pressures between about 10 and 40 absolute bar and a hydrogen to carbon monoxide feed ratio between about 1.9 and 2.5, the product α is at least 0.02 higher and higher in the range from 0.02 to 0.08.

[0175] A second advantageous feature of the disclosed catalyst for the Fischer-Tropsch reaction is the local control of the hydrogen to carbon monoxide ratio. From the reaction equation, a syngas feed ratio (H2 / CO ratio) close to 2 is favorable for the desired chain formation reaction, while a syngas ratio close to 3 is favorable for the undesired methane formation. Inside the catalyst pores, hydrogen is lighter and diffuses to the internal active catalyst sites more rapidly than carbon monoxide. As the hydrogen to carbon monoxide ratio gets closer to three, methane formation inside the catalyst is favored. The increase in methane formation inside the catalyst particles has two negative characteristics - more undesired methane is formed and more heat is released inside the particles, which serves to further shift the reaction away from the desired chain formation reaction and thus form even more methane.

[0176] The use of eggshell catalysts has been described in the Fischer-Tropsch prior art, where the active catalyst is impregnated in a thin ring or shell around the outside of a porous catalyst pellet. The role of the eggshell catalyst is to reduce the number of active catalyst sites where the local syngas ratio is greater than 2 and typically greater than about 2.5 to 3.

[0177] The catalyst structure of the present disclosure employs a densified (≥60% of the theoretical density) catalyst core instead of a porous core, and thus the center of the catalyst pellet cannot be filled with unreacted hydrogen nor retain storage of the formed liquid or wax products. The internal storage of liquid or wax inside the catalyst particles makes catalyst regeneration more challenging. Unreacted hydrogen retained in the porous core of the catalyst pellet may back-diffuse to the inner edge of the eggshell catalyst, and thus increase the local ratio of hydrogen to carbon monoxide and in turn increase the undesired methane selectivity.

[0178] Due to the solid core, the disclosed catalyst described herein has hydrogen and carbon monoxide diffusing only from the outside of the catalyst particle surface, and the diffusion distance within the catalyst coating outside the densified pellet remains small, i.e., from 10 to 100 microns. It is expected that with the disclosed catalyst, the selectivity for the desired chain formation reaction will increase, and when operated under similar conditions, the alpha value will be higher by 0.02 to 0.08 than that of conventional catalyst pellets, while the methane selectivity will be lower by 2% to 5% than that of conventional catalysts. The expected performance improvement of lower methane selectivity and higher alpha represents a significant improvement in the economics of the overall Fischer-Tropsch process.

[0179] The disclosed Fischer-Tropsch catalysts according to the present disclosure can be used in conventional gas-to-liquid plants. Prior to entering a fixed-bed Fischer-Tropsch reactor, methane or natural gas is steam reformed to produce synthesis gas, followed by processing steps to reduce the temperature and remove some hydrogen (to adjust the synthesis gas ratio to near 2 to 3). The disclosed Fischer-Tropsch catalysts can also be used in non-conventional gas-to-liquid plants, including those using biogas or bio-derived synthesis gas, which is formed by a gasification process using waste or biomass feedstock materials. The synthesis gas production process can include partial oxidation, autothermal reforming, or conventional reforming to form a carbon monoxide and hydrogen synthesis gas feed mixture prior to the Fischer process utilizing the disclosed catalysts.

[0180] Catalyst for the Production of Benzene, Toluene, and Xylene (BTX)

[0181] Benzene, toluene, and xylene (commonly referred to as "BTX") are important petrochemical compounds and are among the most abundantly produced chemicals in the world. BTX is defined by a product mixture containing benzene, toluene, and / or xylene. BTX chemicals are important raw materials for the production of automotive products, textiles, plastics, solvents, and many other common industrial products. BTX is mainly produced by the endothermic catalytic reforming of naphtha refined from petroleum, particularly naphtha obtained by distilling crude oil. Biobased methods for producing BTX chemicals are under development but face similar challenges as those present in conventional naphtha reforming, including thermally limited production rates and strong catalyst deactivation exacerbated by cold spots. The catalysts produced according to the present disclosure will be effective not only in conventional BTX production using naphtha feedstocks but also in biobased methods.

[0182] For example, a typical catalytic reforming system for producing BTX from naphtha includes multiple reactors operating in series (e.g., 3 or 4). Since the catalytic reaction is endothermic, heaters are typically provided upstream of the first reactor and between the reactors to heat (and reheat) the gas mixture. Electrical heaters are also provided along the reaction tubes to supply the additional energy required for the endothermic reaction. The reactors are typically filled with a catalyst made of Pt deposited on chlorinated Al2O3. The base catalyst has been improved over the years by adding various elements that extend the catalyst life and reduce deactivation. The reaction is carried out at temperatures up to 550 °C and pressure levels up to 40 bar.

[0183] Various reactions occur in a catalytic reforming reactor. For the production of BTX, the dehydrogenation cyclization of paraffins to aromatic compounds and the aromatization of paraffins result in the formation of BTX compounds. These reactions are endothermic and are characterized by consuming heat as heat is supplied to the catalyst from the outside. For this reason, the heaters on the outside of the reactor tube walls must maintain a high heat generation rate to maintain a sufficient heat flux through the reactor walls to drive the reactions. Gas-gas heat exchangers placed between the reactors are also used to supply heat from one reactor stage to the cooled effluent gas mixture to preheat the reactants before entering the next reactor in series. The thermal conductivity characteristics of the porous alumina catalyst pellets are low and thus the heat transfer efficiency of radial heat transfer is limited by current catalyst technology.

[0184] The catalyst core of the present disclosure having a high effective thermal conductivity is advantageously used as a naphtha reforming catalyst to produce BTX. The use of the disclosed catalyst support technology will result in improved heat transfer from the reactor tube walls to the active catalyst sites across the reactor radius and thus result in higher BTX productivity.

[0185] Fixed-bed reactors used in semi-regenerative reactor designs for the catalytic reforming of naphthalene to form BTX typically include additional reactor beds (e.g., 3 main reactors and a spare used during regeneration) to maintain continuous and stable production. The reactions are prone to coke formation and require a regeneration cycle for each fixed bed every 6 to 24 months. As carbon accumulates between regeneration cycles, the performance will slowly decline. The catalyst can only be regenerated 3 to 4 times before it must be replaced.

[0186] The disclosed catalyst of the present disclosure will improve the radial heat supply from the tube walls to the endothermic reactions occurring within the catalyst. As more heat is supplied to the reactor, the BTX productivity can be increased by reducing cold spots. The reduction of cold spots (higher thermal gradients) within the reactor also reduces the deactivation rate, including carbon formation. The lower deactivation rate increases the production capacity between reactor regeneration cycles and increases the time between regeneration cycles, thus extending the total catalyst life. Turaga and Ramanathan reported that the productivity or maximum catalyst activity for the reforming of naphtha to BTX is in the temperature range of 733 - 798 K (460 °C - 525 °C), and the deactivation increases in the temperature range of 755 to 773 °K (482 °C - 500 °C). Therefore, the disclosed catalyst of the present disclosure having a higher effective thermal conductivity will result in fewer cold spots and thus a lower deactivation rate.

[0187] Maintaining the temperature above 500 °C across the entire reactor radius reduces the deactivation rate and can be achieved by using the disclosed catalysts with high effective thermal conductivities of the present disclosure. In one embodiment, the catalysts of the present disclosure can simplify the configuration of a naphtha reformer. Existing naphtha reformers can be retrofitted to increase capacity, where the inventive method based on using the disclosed catalysts can be based on only two fixed-bed reactors instead of three or four. The first primary fixed-bed reactor operates with improved radial heat supply as enabled by the disclosed catalysts to reduce the internal catalyst thermal gradient to maintain productivity and minimize deactivation, including coking. Reactor operation can be switched between only two reactors to allow one fixed-bed reactor to be regenerated while maintaining the production capacity of the second fixed-bed reactor. In one embodiment, a four-reactor bed naphtha reformer can be retrofitted into two 2-reactor naphtha units, thereby increasing the overall plant production capacity of BTX.

[0188] Another major type of naphtha reforming to BTX is the continuous catalytic reformer, where during operation, a portion of the catalyst is removed from the reactor bed and flows to a regeneration reactor before being added back to the top of the original catalyst bed. For this type of process, the free-flowing nature of the disclosed catalysts and their improved effective thermal conductivities will serve to reduce deactivation and increase the time between regeneration cycles.

[0189] Examples of various types of naphtha reformers have been described in the prior art and include continuous catalytic reforming reactors (CCR) or continuous recycle processes used by producers or catalyst suppliers: Axens, Criterion Catalyst Co, Exxon Mobil, Indian Petrochemicals Corp, IMP (Instituto Mexicano del Petroleo), and UOP. Examples of semi-regenerative reactors for naphtha reformers used by producers or catalyst suppliers include: Axens, Criterion Catalyst Co, Exxon Mobil (enhanced reforming process), BP (Ultraforming process), Chevron (platinum-rhenium reforming process), BASF (Magnaforming process developed by Engelhard), Air Products and Chemicals (Houdry reforming process), Indian Petrochemicals Corp, IMP (Instituto Mexicano del Petroleo), and UOP.

[0190] BTX can also be produced from biomass rather than crude oil. One method being developed by Anellotech is to produce BTX from biomass-derived fast pyrolysis oil over a zeolite catalyst in a single-stage catalytic fluidized bed reactor. The catalyst is continuously regenerated in a slipstream. Virent has also developed the BioForming process for producing BTX from biomass feedstocks and has co-produced jet fuel and gasoline. Other researchers [5] are developing production methods for bio-BTX from biomass feedstocks, including crude glycerol. The reaction remains endothermic, and improved heat supply, as provided by the catalysts of the present disclosure, will increase efficiency. The production of bio-BTX still faces the challenge of co-producing carbon or solid coke that coats the catalyst and limits production efficiency.

[0191] It is expected that compared to conventional catalysts defined by catalyst composition, feed WHSV (grams of feed per gram of catalyst per hour), and equivalent feed composition, the use of the catalysts of the present disclosure can extend the time between catalyst regenerations by 1 to 12 months.

[0192] Catalyst Containing SiC-Supported Catalyst That Can Provide a Longer Tube Life

[0193] The high thermal conductivity catalyst support produced by the disclosed catalyst system as described herein enables significant energy reduction for highly endothermic reactions such as steam methane reforming or dry or CO2 reforming of methane. The disclosed catalysts also reduce wall temperature, thus simplifying metallurgy or extending tube life. Alternatively and additionally, such catalysts can increase reactor productivity or throughput.

[0194] A recognized problem in steam methane reforming is the need for high operating temperatures (800 °C - 950 °C) and high operating pressures (up to about 40 atmospheres) to overcome the fundamental thermodynamic limitations on the reaction conversion and selectivity of producing hydrogen from methane. These conditions also require allowing for downstream syngas purification by pressure swing adsorption or other reactors such as Fischer-Tropsch synthesis. To drive heat into the endothermic reaction, the metal walls containing conventional particulate or fixed bed catalysts must operate at very high temperatures generated by external burners. Combustion near the outer surface of the tubes results in high wall temperatures, which are required to drive sufficient energy into the tubes and through the particulate catalyst to match the energy consumption requirements of the strongly endothermic reaction.

[0195] The highly endothermic methane reforming reaction is shown in Equation 6 below. The highly endothermic dry reforming reaction is shown in Equation 7. The water-gas shift reaction, which occurs in parallel and follows thermodynamic limits with temperature variation, is shown in Equation 8. The combustion of the methane reaction provides energy for the endothermic reaction and is shown in Equation 9.

[0196] CH4 + H2O = CO + 3H2 ΔHr_0 = 206 kJ / mol (Equation 6)

[0197] CH4 + CO2 = 2CO + 2H2 ΔHr_0 = 247 kJ / mol (Equation 7)

[0198] CO + H2O = CO2 + H2 ΔHr_0 = -41 kJ / mol (Equation 8)

[0199] CH4 + 2O2 = CO2 + 2H2O ΔHr_0 = -803 kJ / mol (Equation 9)

[0200] The high wall temperature combined with the high internal pressure generates significant thermo-mechanical stresses on the reactor tubes. Extremely expensive high-chromium and high-nickel alloys are centrifugally cast to meet the operating design requirements. However, even these tubes are subjected to the combined action of heat and pressure, which accelerates grain growth, precipitation, and the formation of grain boundary voids (due to microstructural coarsening). The tube operating conditions are fully in the metallurgical creep regime, which limits the actual life of these expensive components. In industrial service, it is not uncommon for the tube life to be approximately 1 year.

[0201] Through the Larson-Miller relationship (Ref API 530), tube failures depend largely on the operating temperature. Since the tube life is very sensitive to the absolute operating temperature of the tube, operating at a wall temperature significantly higher than the design value may lead to a rapid increase in the number of tube failures. A 20°C increase in the tube metal temperature will shorten the tube life by more than 50% (Reference, Boumaza, World Academy of Science, Engineering and Technology International Journal of Chemical and Molecular Engineering, Volume 4, Issue 11, 2010).

[0202] As described herein, catalysts and catalyst supports composed of a high thermal conductivity carrier material increase the effective thermal conductivity of the catalyst particle bed. Since the effective thermal conductivity of the catalyst bed is increased due to the disclosed catalyst system, the wall temperature required to achieve equivalent performance is reduced. More heat is removed from the tube wall and enters the catalyst bed and the reactant gas. This effect in turn reduces the heat required to be generated by the reactor burner, thus significantly reducing the maximum operating temperature and also reducing fuel consumption. The lower fuel feed rate increases the carbon efficiency of hydrogen production and in turn reduces the production cost. By reducing the operating temperature of the metal reactor wall, the tube life can be significantly increased, resulting in less tube maintenance, higher plant operating rates, and longer replacement intervals during reactor operation. It is expected that when operating with conventional reforming catalysts, by using the disclosed catalysts, the tube life can be increased by 3 to 18 months compared to the existing tube life of about 12 months. When operating with the disclosed high effective thermal conductivity catalyst system, the expected tube service life of a steam methane reforming unit ranges from 15 to 30 months.

[0203] In addition, the lower operating temperature can provide other advantages in system design, allowing for tubes with thinner walls, tubes of less expensive alloys, or more conventional manufacturing processes, which will also contribute to reducing the capital cost.

[0204] Catalyst Containing SiC-Supported Catalyst That Can Reduce the Metal Wall Temperature

[0205] As described herein, catalysts and catalyst supports composed of a high thermal conductivity carrier (i.e., core) provide improved heat transfer in a packed bed even when maintaining a geometry and bed packing density similar to conventional materials. The effective bed thermal conductivity is determined experimentally using the experimental procedures and equipment described in the example entitled "Reduced Wall Temperature and Increased Hydrogen Production in Steam Methane Reforming Using the Disclosed Catalysts" provided later in this document. As described in this example, the expected wall temperature when using the disclosed catalyst system can be 10°C to 30°C lower than the wall temperature required for conventional methane reforming catalysts, while providing equal hydrogen productivity.

[0206] The relationship between the material thermal conductivity and the bed conductivity is a function of several non-trivial non-linear relationships:

[0207] k 有效 =F(T,P,ρ p ,k p ,k g ,ε n,p ε b ,φ p ,d p ,h p ,d 管 ,U,Re,Pe)

[0208] where T is the pellet and gas temperature, P is the gas pressure, ρ p is the density of the catalyst pellets, φ p is the partial pellet porosity, k p is the thermal conductivity of the catalyst pellets, ε n,p is the total normal emissivity at the surface of the catalyst pellets, d p is the diameter of the pellets, h p is the height of the pellets, d 管 is the diameter of the reactor bed, U is the superficial gas velocity (Darcy), k g is the thermal conductivity of the interstitial gas, ε b average bed porosity, Re is the Reynolds number of the superficial gas with respect to d p and Pe is the Péclet number of the superficial gas with respect to d p .

[0209] Although very complex, these relationships can be broken down into core elements:

[0210] k 有效 = k p,o + k 对流 + k 辐射

[0211] where k p,o is the static pellet conductivity, including the effects of porosity and grain boundary interactions. k 对流 is the result of convective effects, thermal diffusion, turbulent conduction, and other gas-pellet interactions within the porous bed. k 辐射 is directly related to the emissivity of the pellet surface and the temperature of the pellets. For the same pellets and reactor geometry, the effects of convection are approximately the same. Although radiation effects deviate from changes in the material emissivity, they can largely be ignored for comparison purposes. Additionally, for the materials studied, the surface emissivity is within 10% - 15%. Therefore, the increase in conductivity is directly related to the static pellet conductivity. This can be clearly seen in Figure 11 , as further described in the text associated with it herein. Over a wide temperature range, the total effective radial conductivity is always separated by the same value (which is the static pellet conductivity k r,o ).

[0212] Simplified models, numerical simulations, and experimental methods are used to calculate the static radial bed conductivity for representative geometries. The effects of pellet porosity and temperature in a static packed bed are in Figure 9Shown in. The decrease in thermal conductivity is driven by the pellet porosity until the porosity reaches 40%. At this porosity level, the loss of internal pellet heat conduction is offset by the conduction of the gas and the emissivity of the pellet surface. The model ignores the surface effect of high porosity on emissivity. The porosity fraction and the densification fraction add up to one. Therefore, material composition, porosity, grain boundaries, and surface emissivity are the key means to control the bed conductivity.

[0213] Therefore, by replacing the conventional catalyst with a material of high thermal conductivity (i.e., replacing the porous Ni - Al2O3 composite with a catalytic coating on a densified support including SiC), the thermal conductivity of the catalyst is enhanced. Under steady - state conditions, the heat transfer capacity of the bed is increased by about 4 times, and there is an additional increase from about 1.5 to 3.5 at the expected system flow rates of 2000 to 5000 GHSV representing the methane reforming reaction at high temperatures (see Figure 10 , Figure 11 and Table 8).

[0214] Table 8.

[0215]

[0216] The increase in the effective radial thermal conductivity more effectively transfers heat from the wall of the high - temperature reactor tube to the catalyst bed and the reactant gas, which more effectively drives the endothermic reaction. The heat required to complete the reaction remains unchanged, but with the peak temperature reduced, the heat loss is reduced, thus reducing the energy input in the form of the feed rates of fuel and oxygen (or air).

[0217] The thermal gradient between the tube wall and the center of the catalyst particle bed is reduced, which allows a reduced tube wall temperature to produce the same amount of hydrogen. Alternatively, the tube wall can be maintained at the same temperature as the conventional catalyst with a correspondingly similar tube life, while increasing the hydrogen production or productivity in the range of 5% to 40% compared to the conventional catalyst. The tube life can be significantly increased, tubes with thinner walls, tubes using cheaper alloys, or more conventional manufacturing processes can be used, all of which will result in a significant reduction in the system capital cost.

[0218] Example Demonstrating the Improvement of SMR Using the Disclosed Catalyst

[0219] Reduced Wall Temperature and Increased Hydrogen Production in Steam Methane Reforming Using the Catalyst of the Present Invention

[0220] Steam methane reforming (SMR), or reforming, is an important industrial reaction for the production of hydrogen. Hydrogen is commonly used in refinery applications to upgrade crude to commercial fuels, metal processing, lipid hydrogenation, and many other diverse fields. Hydrogen is produced by adding steam to methane (the main component of natural gas) and reacting it over a nickel-based catalyst at high temperature and pressure. The SMR reaction is strongly endothermic and requires a large amount of energy (e.g., heat) to drive the reaction to produce hydrogen:

[0221] CH4 + H2O = CO + 3H2 (ΔHr 298K = 206 kJ / mol)

[0222] CO + H2O = CO2 + H2 (ΔHr 298K = -41 kJ / mol)

[0223] Industrial methane reformers utilize burner technology to burn natural gas outside a parallel tube array (100 cm is a typical diameter) filled with catalyst pellets or catalyst particles. The heat or energy released by the exothermic combustion reaction is conducted through the tube walls and then subsequently transferred into and through the packed bed or fixed bed reactor. This radial heat conduction through the catalyst particles drives the endothermic reforming reaction. Energy is also provided and dispersed by gas convection: the gas is heated when it contacts the inner surface of the tube walls and then dissipates heat as the gas flows in a tortuous path around the catalyst particles.

[0224] Improving heat transfer through the fixed bed by using the higher effective thermal conductivity catalyst of the present disclosure of the present invention drives more energy into the reforming reaction and thus requires a lower wall temperature to achieve the same performance. Reducing the peak wall temperature on the reforming tubes can serve to increase the lifespan and reduce the failure rate, which increases the operating rate of the hydrogen plant. Lao et al. reported in 2016 that a 20 °C reduction in wall temperature doubled the expected tube lifespan. The replacement cost of high-nickel alloy SMR tubes and the associated plant downtime increase the capital and operating costs of hydrogen production. The lower wall temperature in the industrial burner also reduces the operating cost due to the need for less fuel.

[0225] At equal wall temperatures, compared to conventional commercial SMR catalysts, using the higher effective thermal conductivity catalyst of the present disclosure of the present invention increases the overall reactor productivity because more hydrogen is produced per equal reactor volume.

[0226] As previously discussed herein, the catalyst of the present disclosure relies on a central core of high thermal conductivity SiC, which has been passivated by an inner matrix of alumina or / and an outer coating of dense alumina, BSAS, or other protective materials, and is coated with an effective layer of a high surface area catalyst support having catalytically active metal (e.g., Ni) for methane reforming.

[0227] Data was collected to measure the effective thermal conductivity of the catalyst of the present invention and compared with a conventional methane reforming catalyst. Specifically, data was collected at 500 °C and 800 °C in the range of GHSV (h -1 ). Under steady-state conditions, the effective thermal conductivity of the catalyst of the present invention is approximately five times that of a conventional SMR catalyst (4.8 W / m-K versus 1.0 W / m-K at 800 °C). As the GHSV increases (higher flow rate), the total effective thermal conductivity of the catalyst further increases due to thermal dispersion and convective heat transfer.

[0228] Figure 10 Experimental data of the effective thermal conductivity of a commercial SMR catalyst with and without an active catalyst layer and the catalyst of the present invention as a function of temperature are provided for comparison. At a GHSV of about 1970 h -1 and a temperature of 800 °C, the total effective thermal conductivity of the catalyst of the present invention is 13.1 W / m-K and that of a conventional reforming catalyst is 9.6 W / m-K, largely due to an increase in the effective thermal conductivity of the catalyst of the present invention by about 36%. These respective effective thermal conductivity values are used to evaluate the reactor performance of the catalyst system of the present invention relative to a conventional industrial reforming catalyst. The addition of the catalyst support coating and its active metal has little effect on the effective thermal conductivity of the entire catalyst system of the present invention. Figure 11 A comparison of experimental data of the effective thermal conductivity of a commercial SMR catalyst and the catalyst of the present invention at 500 °C and 800 °C under steady-state conditions is presented.

[0229] Modeling Results Support the High Thermal Conductivity Property of the Support Material of the Present Invention

[0230] Experiments have shown that the catalyst support of the present invention has superior pellet thermal conductivity compared to a commercial alumina-based steam methane reforming catalyst, as Figure 11 shown (the catalyst of the present invention (circles) compared to a commercial catalyst (squares)). The pellet thermal conductivity (k s : for the catalyst of the present invention) varies from 6.3 W / m-K at a temperature of 500 °C to 4.5 W / m-K at 900 °C, while the thermal conductivity (k s : commercial) of the commercial SMR catalyst remains almost constant at 1.0 W / m-K over the temperature range.

[0231] These experimentally determined values enable the determination of steady-state packed-bed thermal characteristics using an improved Zehner, Bauer, Schlünder (ZBS) model, as Figure 11 shown, (k r,o : HP, solid line for the catalyst of the present invention and k r,o: Com, commercial dotted line). Compared with commercial catalysts, the catalyst of the present invention maintains the consistent advantage of a packed bed thermal conductivity of 1.25 - 2.00 W / m-K.

[0232] Using commercially available geometries and reactor operating conditions for comparison, the effective radial thermal conductivity characteristics of the catalyst of the present invention are also enhanced compared with the effective radial thermal conductivity characteristics of commercial materials under flow conditions. Figure 10 Graphs of the packed bed thermal conductivity of commercial and the catalyst of the present invention are provided. Under gas flow conditions of 1970 h -1 (superficial velocity 0.52 m / s), steam-to-carbon (S / C) ratio of 2.7, inlet gas temperature of 580 °C, pressure of 30.65 (absolute) bar, and reactor diameter of 152.4 mm (external, 127 mm internal) and length of 10.0 meters, compared with commercial SMR catalysts, using the catalyst of the present invention, the effective radial thermal conductivity is increased by more than 35%.

[0233] The increased thermal conductivity of the catalyst of the present invention has an impact on other reactor characteristics such as the tube wall temperature. Figure 12 and Figure 13 Graphs of the reactor outer wall temperature and the internal reactor temperature versus the axial distance are provided under an applied average heat flux of 33.17 kW / m 2 . For a fixed reactor heat flux, the increase in the bed conductivity of the catalyst of the present invention results in:

[0234] 1. The tube wall temperature is increased by 13 °C.

[0235] 2. The equilibrium distance is reduced, i.e., 4.0 meters (using the catalyst of the present invention), compared with commercial SMR catalysts (9.0 m).

[0236] Literature shows that a 20 °C reduction in the tube wall temperature doubles the life of the reactor tube. Compared with commercial SMR catalysts, the catalyst of the present invention provides a 13 °C tube wall temperature advantage, which will increase the tube life by 65% compared with commercial SMR catalysts.

[0237] Fitting the tube wall temperature curve obtained from commercial operation to the fixed bed of the catalyst of the present invention results in a lower methane escape of 0.6 vol.% at 1970 h -1 . The tube wall heat curve of commercial catalysts results in 8.0 vol.% methane escape, and when replaced with the catalyst of the present invention, it results in 7.4 vol.% methane escape ( Figure 14 ), which confirms the superior characteristics introduced by the catalyst of the present invention.

[0238] Figure 15The data presented show that, under a constant tube wall temperature profile, increasing the gas hourly space velocity (GHSV) of the reactant gas, the catalyst of the present invention results in an increase in production. After the GHSV is increased to 3110 h -1 thereafter, the use of the catalyst of the present invention results in only 8.0 vol.% methane slip. This increase in GHSV represents a 36% increase over the commercial catalyst. For the same wall temperature and slip, the catalyst of the present invention absorbs 33% more heat.

[0239] Table 9 summarizes the increased enhancements provided by using the catalyst of the present invention compared to commercial SMR technology.

[0240] Table 9

[0241]

[0242]

[0243] Nuclear-Shell SMR Catalyst Defined by Catalyst Utilization

[0244] The main catalyst used in the steam reforming of methane is Ni metal deposited on alumina (Ni / Al2O3). Current industrial catalysts are prepared by impregnating Ni ions in solution onto porous alumina or by related methods. A typical industrial catalyst is a cylindrical pellet approximately 0.5 x 0.5 inches (L x OD) in size, with up to four internal holes (or more). The Ni content in the catalyst is any value between about 10% and 20 wt% (average of about 12 wt%). The catalyst also contains lesser amounts of other elements compared to Ni. This is a single pellet catalyst without a shell or inner shell, and the Ni is dispersed throughout the pellet structure. The typical weight of such a cylindrical pellet is 2.9 grams, but it can vary based on the size of the pellet used. Using an average of about 12% and the weight of the above cylinder, the average amount of Ni per pellet is about 0.35 grams. However, due to mass and heat transfer limitations, this total weight of Ni per pellet is not effective.

[0245] A core-shell material consists of a core material onto which another material is deposited to form a shell. These materials are typically designed for a specific purpose. There are multiple purposes for designing core-shell materials. One reason for forming the shell is to combine two materials and thus create two different properties within the same material. Another reason is to utilize the material properties brought about by a specific design and geometry, and finally to generate a set of properties that are not present in the individual materials alone. For example, in Fe3O4 / SiO2 core-shell materials, the properties of the core such as magnetic susceptibility can be the properties in a system where magnetic separation is desired, while the unique luminescent optical properties of SiO2 are utilized. The properties of the core and shell can be designed to achieve an optimal synergistic effect. Core-shell materials provide research opportunities in almost all scientific fields, especially including nanotechnology, catalysis, optics, electronics, medicine, catalysis, materials, biotechnology, and energy storage.

[0246] Most core-shell materials have been synthesized at the nano- or micro-scale level. The synthetic methods for preparing these structures involve chemical or physical methods. Chemical methods involve chemical synthesis or cation exchange processes. Chemical synthesis involves first synthesizing the core material and then growing the shell on top of the core. Cation exchange relies on synthesizing the core and then generating the shell from the core itself through cation exchange of lattice elements with ions in solution. Physical methods are few, and most of the reported physical methods involve depositing gaseous components onto a substrate. For reforming applications, Ni / SiO2, Ni / Al2O3, Ni / CeO2, and Ni / TiO2 catalysts have been designed and their activities in acetic acid reforming have been studied. Among the catalysts studied, Ni / Al2O3 showed the best activity, which was attributed to the small and narrow Ni nanoparticle size at the core. Core-shell Ni / SiO2 catalysts have also been used for reforming biogas.

[0247] The catalyst of the present invention disclosed herein is a core-shell structure prepared by physically depositing an oxide porous catalyst phase on a composite solid core. In some embodiments, the core includes a protective matrix of SiC and alumina. The catalytically active shell can be deposited, for example, by spraying and depositing a selected metal or metal oxide from an aqueous or organic medium. In alternative embodiments, in addition to spraying or depositing, the catalyst shell or coating can be deposited by other means known in the art.

[0248] In a typical method, the compacted pellets disclosed herein are coated with a slurry of catalyst carrier powder, with or without an active catalyst material in the slurry. If the slurry does not include an active catalyst material, then after forming the coating, the catalyst carrier layer is subsequently impregnated with the active catalyst material.

[0249] The coating slurry is prepared by adding a powder material to an organic medium such as but not limited to ethyl cellulose and α-terpineol. The powder materials for loading the active catalyst on the pellet core can be selected from the following non-exhaustive list: in particular, aluminum-silicon, alumina doped with zirconia-ceria, alumina, ceria doped with zirconia, alumina-silica mixture, γ-alumina, α-alumina, magnesium-promoted alumina, calcium-promoted alumina, sodium-promoted zirconium-cerium oxide, cerium oxide, titanium dioxide-promoted silica. The above oxides can be applied with or without one or more of the following metals (or other catalytically active materials): in particular, nickel, platinum, rhodium, ruthenium, cobalt, rhenium, iridium. Elements known to act as promoters or inhibitors of coke formation can be added optionally.

[0250] On a laboratory scale, the so-pressed (green) catalyst pellets are weighed and placed on a stainless-steel filter. The coating slurry is transferred to a special glass container which is connected to a slurry spraying system for manual deposition. The coating of the porous outer layer is manually applied to the pellets by manually spraying the pellets with the above slurry. The pellets are continuously agitated on the filter to ensure uniform coating. Then the coated pellets are dried at a temperature between 70 °C and 120 °C for a period between 30 and 60 minutes. After drying, the final weight is taken to determine how much porous material has been deposited on the pellets in the form of a coating. The uncalcined coated pellets are calcined by slowly raising the temperature to the target temperature and holding at that temperature for at least about one hour. Another method of applying the outer coating is by dip coating. The calcination temperature of the active catalyst layer can range from about 300 °C to about 800 °C.

[0251] As a final step of the core-shell, the catalyst material of the present invention containing only the carrier material shell without the active catalyst is infiltrated with the active catalyst metal ions into this layer. The metal ions under consideration are dissolved in a medium preferably water, but can also be organic. The pellets are immersed in the medium such that the metal ions impregnate the porous layer. After a period sufficient to achieve the desired loading, the metal-ion-infiltrated carrier material is removed from the solution and dried between 70 °C and 120 °C (for example, for a period between 30 and 60 minutes, or sometimes longer). Finally, the coated and impregnated pellets are calcined in air.

[0252] For the intended applications in steam reforming, this method of coating a high thermal conductivity core with a porous outer layer (also known as a shell or eggshell) is unique compared to the current practice of methane steam reforming discussed earlier. In some embodiments, the shell has a controllable thickness that ranges from about 10 microns to about 200 microns, or between about 50 and about 100 microns. For each gram of catalyst, the amount of material required to achieve a 50-micron thickness is about 0.05 grams. By replacing a conventional steam reforming catalyst with the disclosed catalyst and assuming that each pellet of the disclosed catalyst has the same weight as a typical industrial SMR catalyst (e.g., 2.9 grams), a 50-micron shell on that pellet will form the outer shell using about 0.145 grams of material. Depositing a catalyst that already has about 12% Ni active metal or impregnating the shell with the target Ni weight of about 12% will add about 0.02 grams of Ni to each catalyst pellet. This represents an absolute reduction of about 94% in the Ni metal weight per pellet, or a reduction in the range of about 80% to 95%. If the reaction has no mass or heat transfer limitations, then a 94% absolute reduction in the amount of catalyst metal will reduce the overall reaction rate or productivity. However, since conventional methane reforming pellets are strongly limited by mass and heat transfer, only a very small fraction of the Ni (about 10% or less) effectively contributes to the overall reaction rate of a conventional reforming catalyst pellet.

[0253] The porosity of the outer layer is also important and has been studied as a design principle. Adding a porosity-maintaining element to the slurry results in a layer with improved porosity. The increased porosity is important for the application of the materials of the present invention in catalysis and also serves to increase the diffusion of reactants within the coating, thereby further enhancing the effective utilization of the active catalyst contained therein. Additives that result in improved outer layer porosity can include, among others, lanthanum carbonate, magnesium carbonate, and graphitic carbon. Figure 5 A cross-sectional SEM image of the catalyst according to the present disclosure is depicted, including the outer layer deposited onto the core. The left image shows the unaltered outer layer, while the right image shows the effect of changing the composition to enhance the outer layer porosity.

[0254] Although the amount of active nickel is reduced on an absolute basis on the catalyst pellets of the present invention disclosed herein, the relevant effectiveness factor of the eggshell coating disclosed herein is significantly higher than that of conventional methane reforming pellets. At a much higher effectiveness factor, even with a reduced absolute mass of the catalytically active material, the net activity of the catalysts of the present invention will be comparable to that of conventional catalysts. In one embodiment, the volumetric activity of a fixed-bed reactor composed of the catalysts of the present invention will be within 80% of the activity of a conventional methane reforming catalyst. In an alternative embodiment, the activity of the catalysts of the present invention on a reactor volume basis will be comparable to that of a conventional methane reforming catalyst. In a preferred embodiment, the volumetric activity of the catalysts of the present invention is in the range of from about 1.0 to 1.3 times the volumetric activity of a conventional methane reforming catalyst.

[0255] The reaction occurs inside the catalyst pellets and is limited by mass transfer and heat transfer. As the endothermic reaction proceeds inside the pellets, it cools down and the net catalyst activity of this thermodynamically limited reaction decreases. Preferably, a catalyst is provided in the eggshell layer for the steam methane reforming reaction so that the active metal catalyst can be used highly effectively, while also effectively driving heat into the catalytic shell coating without the need to transfer heat deep into the cold pellets.

[0256] A classical effectiveness factor analysis is carried out to evaluate the effectiveness of the catalyst according to the present disclosure, where the relationship between the effectiveness factor and the Thiele modulus is known in the art. It has been reported that the effectiveness factor of a conventional steam methane reforming reaction is between about 1% and 10%. That is, in a conventional methane reforming pellet, more than 90% of the active catalyst metal is ineffective for the desired steam methane reforming reaction.

[0257] Due to mass diffusion limitations and poor internal heat transfer within conventional catalyst pellets, the effectiveness factor (the ratio of the actual or apparent reaction rate to the intrinsic reaction rate) of conventional SMR catalysts is low. As the reaction proceeds, the internal volume of the catalyst pellets cools down, which further slows down the apparent reaction rate beyond the mass transfer limit. Adris reported a commercial effectiveness factor for methane consumption of about 0.008. Lao also reported an effectiveness factor of 0.1 for a commercial steam methane reformer, where the effectiveness factor increased due to the use of internal pellet pores and other shape modifications to reduce the internal pellet mass transfer resistance.

[0258] The Thiele modulus (φ) is shown in Equation 10 below. The effectiveness factor (ε) is shown in Equation 11 below.

[0259]

[0260]

[0261] where R is the radius of the pellet or the diffusion distance for mass transfer within the catalyst coating. The reaction rate constant is k1. The effective diffusion coefficient (D 有效 ) is the gas diffusion within the porous catalyst divided by the tortuosity factor, and for most catalyst systems, the tortuosity factor is typically about 3. The analytical equation for the effectiveness factor as shown in Equation 11 is for a first-order reaction, but this equation has been readily shown in the literature to be robust and works reasonably well for zero-order to second-order rate equations.

[0262] For a methane reforming reaction operating at about 20 absolute bar and about 850 °C, the molecular diffusion coefficient can be calculated using the Chapman-Enskog theory of mass diffusion, and for water (steam) it is approximately 0.143 cm2 / s and for methane is about 0.495 cm 2 / s. When the mean free path of the molecules is within one-third of the pore diameter where diffusion occurs, molecular diffusion is disrupted. Under the reaction conditions, the mean free paths of steam and methane are 0.03 and 0.01 microns, respectively. For catalysts with pore diameters less than about 0.1 micron, Knudsen rather than molecular diffusion should be considered the main mode of mass transfer within the catalyst pores. The Knudsen diffusion coefficients of the two reactants are about 0.05 cm 2 / s, or about 2 to 3 times slower than molecular diffusion.

[0263] As shown by the SEM photographs of the catalysts and their manufacturing methods according to the present disclosure, the voids (i.e., pores) within the catalyst coating are greater than about 1 micron and diffusion occurs readily therein by a molecular mechanism. To account for the effectiveness factor of the catalysts of the present invention, the diffusion coefficient of the slowest reactant (steam) in the molecular diffusion mode is estimated to be 0.143 cm 2 / s.

[0264] Conventional methane reforming catalyst pellets have been compressed to form the desired shape, and the diffusion of the reactants is considered to be in the Knudsen regime. The diffusion coefficient of the gaseous reactants through the conventional methane reforming pellets is about 0.05 cm 2 / s.

[0265] When the effect of tortuosity is added, such as a tortuous path for mass transfer rather than a straight diffusion path, through the catalyst layer or pellet to enable the reactants to reach the active catalyst sites disposed therein, the actual or effective diffusion coefficient of the catalysts of the present invention is estimated to be 0.0477 cm 2 / s, and for commercial SMR catalysts, the effective diffusion coefficient is estimated to be 0.0167 cm 2 / s.

[0266] By using the selected catalyst coating of the catalysts of the present disclosure designed with larger pores, the diffusion of the reactants through the catalyst thickness occurs mainly by the more favorable molecular rather than the slower Knudsen diffusion present in conventional methane reforming pellets.

[0267] The value of k1 or the reaction rate constant (in s -1 units) has been estimated to be about 34.3 s -1。For the catalysts of the present disclosure, the effective distance or R in the Thiele modulus equation was evaluated and compared with conventional SMR catalysts. Table 10 calculates the effectiveness factor of the catalysts of the present disclosure with coating thicknesses up to about 200 microns. In all cases, the effectiveness factor is high, indicating that the actual reaction rate is very close to the intrinsic reaction rate of methane steam reforming. For a 200-micron coating, the effectiveness factor is about 0.98, while for a 50-micron coating thickness, the effectiveness factor is about 0.999. Thus, for the methane steam reforming reaction, the effectiveness factor of the catalysts of the present invention is greater than about 0.90, and in a preferred embodiment greater than about 0.95, and in the most preferred embodiment from about 0.99 to 0.9999.

[0268] Table 10

[0269] Catalyst Thickness (μm) 50 100 200 <![CDATA[Effective diffusion coefficient (m 2 / s)]]> <![CDATA[4.67x 10 -6 > <![CDATA[4.67x 10 -6 > <![CDATA[4.67x 10 -6 > <![CDATA[Rate constant, k1 (seconds -1 )]]> 34.3 34.3 34.3 Thiele Modulus (Unitless) 0.14 0.27 0.54 Effectiveness Factor 0.999 0.995 0.981

[0270] For conventional methane steam reformers, using the same calculation methods and conditions, within the practical range of catalyst pellet sizes, the calculated effectiveness factors are shown in Table 11. As proposed in the literature, the effectiveness factors of conventional catalysts are very low. For 1 / 2-inch catalyst pellets (without internal pores), the effectiveness factor is about 0.051. For an effective diffusion distance of about 1 / 4 inch, the effectiveness factor of conventional methane reforming catalysts is about 0.1. Even when using very small catalyst pellets such as those with a diameter of about 1 mm, the effectiveness factor only rises to about 0.5. These very small pellets with a diameter of about 1 mm will have a very high pressure drop in the full-length reactor and are not commercially viable.

[0271] Table 11

[0272] Catalyst Thickness (μm) 1000 6350 12800 30000 Catalyst Thickness (m) <![CDATA[1.00x 10 -3 > <![CDATA[6.35x 10 -3 > <![CDATA[1.28x 10 -2 > <![CDATA[3.00x 10 -2 > Catalyst Size (inches) 0.04 0.250 0.50 1.18 <![CDATA[Effective diffusion coefficient (m 2 / s)]]> <![CDATA[1.67x 10 -6 > <![CDATA[1.67x 10 -6 > <![CDATA[1.67x 10 -6 > <![CDATA[1.67x 10 -6 > <![CDATA[Rate constant, k1 (seconds 1 )]]> <![CDATA[3.43x 10 -1 > <![CDATA[3.43x 10 -1 > <![CDATA[3.43x 10 -1 > <![CDATA[3.43x 10 -1 > Thiele Modulus (Unitless) 4.53 28.79 58.04 136.04 Effectiveness Factor 0.516 0.101 0.051 0.022

[0273] Thus, the catalysts described herein provide a significantly higher effectiveness factor than conventional methane steam reforming catalysts. The catalysts of the present invention will have an effectiveness factor greater than about 0.9, while commercial methane reforming catalysts operate at an effectiveness factor of about 0.1 and less than about 0.2. In other words, the effectiveness factor of the catalysts of the present invention is between 9 and 10 times greater than that of conventional methane steam reforming pellets. In the catalysts of the present invention, the amount of active nickel (or other metal) sites per volume can be reduced by approximately about 9 to 10 times while maintaining the same or similar volumetric reactor activity as conventional methane steam reforming catalysts.

[0274] Nuclear-Shell SMR Catalyst Defined by Performance

[0275] The industrial production of hydrogen is achieved through steam methane reforming (SMR), which is the main component of natural gas. In steam reforming, methane reacts with steam at high temperature in the presence of a catalyst to produce hydrogen and carbon monoxide. The resulting CO further reacts with steam to produce more hydrogen and carbon dioxide:

[0276] CH4 + H2O = CO + 3H2 (ΔHr 298K = +206 kJ / mol) (1)

[0277] CO + H2O = CO2 + H2 (ΔHr 298K = -41 kJ / mol) (2)

[0278] The following overall reaction is provided:

[0279] CH4 + 2H2O = CO2 + 4H2, (ΔHr 298K = +165 kJ / mol) (3)

[0280] This reaction is catalyzed by a specific catalyst. In the absence of a catalyst, the reaction would require extremely high temperatures. The steam reforming of methane is catalyzed by metals such as nickel (Ni), cobalt (Co), ruthenium (Ru), rhodium (Rh), palladium (Pd), iridium (Ir), and platinum (Pt). Ni is the most widely used catalyst for SMR.

[0281] Examples of the catalyst cores disclosed herein include high thermal conductivity composites of SiC / Al2O3. These materials are mixed, pressed into pellets, optionally coated in a subsequent step, and then fired in an oxygen environment (e.g., ambient air). The resulting material, which has been confirmed to have high thermal properties, is then impregnated with SMR active metal ions or coated with a slurry containing the active metal and fired. The impregnated metal or coated catalyst slurry is from the above SMR active metals. These metals are supported on different carriers from the following non-exclusive list: in particular, aluminum-silicon, alumina doped with zirconia-ceria, alumina, ceria doped with zirconia, alumina-silica mixture, γ-alumina, α-alumina, magnesia-promoted alumina, calcia-promoted alumina, sodium-promoted zirconium-cerium oxide, ceria, titania-promoted silica.

[0282] The coated catalyst operates with a high effectiveness factor, e.g., greater than 0.9, while conventional reforming pellets operate with a low effectiveness factor, typically less than about 0.2 and, in some embodiments, from about 0.05 to about 0.1. Due to the much higher effectiveness factor of the carrier material of the present invention, the net activity of the coated catalyst with a net reduction in nickel mass will remain similar to that of a conventional pellet with nickel dispersed throughout.

[0283] SMR is an endothermic equilibrium-controlled reaction, i.e., as the reaction proceeds, the volume expands with the increase in moles. This means that in order to drive the reaction to a meaningful hydrogen production level, the temperature must be increased, especially when the pressure is raised. Figure 16 It has been shown that as the temperature increases, the conversion rate increases as a monotonically increasing function. The conversion rate decreases with the increase in pressure. Industrial reactors operate at temperatures between 850 °C and 950 °C and pressures between 20 and 40 absolute bars. High-pressure conditions are necessary to meet downstream processing conditions, such as avoiding expensive and dangerous hydrogen compression, while also achieving a high conversion rate to overcome equilibrium constraints. To maintain a methane conversion rate above 80%, the average catalyst bed temperature must be kept high (above about 850 °C at about 20 bar). Moreover, due to the equilibrium nature of SMR, a comparison of the performance of the active catalyst is meaningfully carried out at 1 absolute bar and lower temperatures where the reaction kinetics play a greater role than at high pressures and temperatures.

[0284] The performance of the catalyst support material of the present invention or the catalysts disclosed herein has been experimentally evaluated through laboratory and pilot-scale reaction tests, in which the SMR catalyst is deposited as an outer coating (i.e., a shell) around a SiC core. In the laboratory, the reaction is carried out by loading a specific volume of pellets into a 1 / 2-inch Inconel Ni-alloy tube at high temperature. An electric heating furnace is used to provide heat in the laboratory. The reaction conditions for the laboratory-scale tests are shown in Table 12. The recorded temperature is the tube surface temperature outside the catalyst bed. Before entering the reactor, methane encounters vaporized steam in a vaporization chamber maintained at 500 °C.

[0285] Table 12

[0286]

[0287] Weigh the catalyst-coated pellets and load them into a one-inch nickel-inconel alloy tube reactor supported at both ends by inert alumina media. The reactant inlet side contains significantly more inert material than the outlet side. Load the reactor into an electric heating furnace. Introduce a reducing gas (hydrogen or a mixture of hydrogen and nitrogen) stream into the reactor while heating to 650 °C at 3 °C / min and conduct reduction therein for a minimum period of 2 h. By flowing a pure hydrogen gas stream at 100 sccm and then water starts to react. The water passes through the heating zone and evaporates it into steam. After another 15 min, methane is introduced, and after another 15 min, hydrogen is removed. Control the steam-to-methane content to 3 and monitor the reaction progress using gas chromatography (GC) in the temperature range of 650 °C to 850 °C. At 850 °C, monitor the lifetime performance of the catalyst using GC by periodic sampling. When the methane signal cannot be detected by GC, a methane conversion of 100% is achieved, and when the methane signal is recorded as 1% by calibrated GC, a decrease of even 1% is achieved due to loss of activity.

[0288] The tested catalysts were prepared by coating an SMR catalyst onto the high thermal conductivity core of the present disclosure of the present invention. Similarly, a porous support material was coated onto the catalyst core of the present invention, and thereafter an SMR active metal was impregnated onto the porous support layer. For example, catalyst A was prepared by spraying 0.21 g of a catalyst containing 1.5% noble metal supported on a cerium-zirconium oxide support onto 10 g of the disclosed catalyst support. In this study, 10.2 g of catalyst A (or approximately 7.5 cm 3 ) was loaded into the reactor. Catalyst B was prepared by infiltrating Ni 2+ ions (converted to 0.46 g of Ni metal) into an outer layer of 0.8 g deposited on 20 g of the disclosed core, corresponding to 36.5% Ni in the outer layer. Additionally, Mg 2+ ions (converted to 0.05 g of MgO) were added to this outer layer. In this example, 17.3 g of catalyst B (or approximately 15 cm 3 ) was loaded into the reactor. The coating thickness of these catalysts is any value between 25 and 100 μm.

[0289] Figure 17 Graphical results of the low-pressure testing of the above catalysts are shown. These catalysts all showed equilibrium conversion at the tested temperatures and conditions. For example, equilibrium performance was obtained at a space velocity from 3000 to 9000 h -1 . These catalysts have been tested at different space velocities, as Figure 18 can be seen.

[0290] Industrially, at a space velocity from approximately 2,000 to 3,000 h -1Commercial hydrogen production via SMR has been achieved at a space velocity of. The lifetime activity of some of these materials was evaluated over a period of 600 hours with no signs of degradation, carbon formation, pressure build-up, or metal dusting. The catalyst lifetime is shown in Figure 19 . These results reveal that the catalyst supported on the catalyst support material of the present invention can be loaded with an outer coating of a reforming catalyst deposited or impregnated in the form of a catalyst slurry onto a pre-deposited porous coating and can maintain high activity for at least 600 hours.

[0291] As Figure 18 seen, Catalyst A (1.5% PGM-coated catalyst) shows 100% close to equilibrium at 650 °C, 1 absolute bar, 3:1 steam:carbon, and a GHSV of 3,000 h -1 and a WHSV of 1.5 h -1 . Catalyst B (1.5% PGM-impregnated catalyst) shows 92% close to equilibrium at a GHSV of 3,000 h -1 and a WHSV of 0.1 h -1 .

[0292] Catalyst A (1.5% PGM catalyst) shows greater than 95% close to equilibrium at a GHSV of 9000 h -1 and a WHSV of 1,787,000 h -1 and a temperature of 850 °C, while Catalyst B shows greater than 90% close to equilibrium under the same conditions.

[0293] (1) Lower OPEX Reactor Cost Provided by the SiC-Based Catalyst Support Nucleus Disclosed Herein and (2) Higher Production Rate

[0294] SMR is the main route for industrial hydrogen production and is an equilibrium-controlled, highly endothermic reaction. Industrially, SMR reactors operate at high temperatures (850 °C to 950 °C) and high pressure conditions (20 to 40 bar). The high operating pressure is usually a result of the pressure requirements of downstream processes and high temperatures are needed to overcome the thermodynamic limitations and achieve high methane conversion (>70%).

[0295] The SMR reaction typically takes place on a catalyst that is arranged as a tightly packed bed of originally loose particles within a fixed-bed tubular reactor placed in a reactor box. The tubes are arranged in an array at a fixed distance from each other, and natural gas burners are scattered between them to provide heat. Heat from the burners (at temperatures of 1100 °C and higher) is radiated through the reactor tube walls and the fixed bed to the surface of the catalyst sites where the endothermic reforming of methane with steam occurs. The endothermic nature of the reaction means that the catalyst surface temperature continuously decreases, which can lead to cold spots. The heat reduction resulting from the endothermic reaction is offset by an increased heat flux from the reactor walls. The increased heat flux increases the energy demand for the burners. The result of this increased utility is increased natural gas usage and operating costs.

[0296] Compared to current SMR catalysts, the catalysts of the present disclosure have been shown to have the property of high thermal conductivity (see Figure 20 ). Table 13 provides a comparison of the effective thermal conductivity of a conventional packed bed and that of the packed bed of the present invention at a feed pressure of 20 absolute bar, showing the effect of the wall temperature. When the thermal conductivities of the catalyst of the present invention and commercial SMR catalyst materials of the present disclosure are used in a reactor performance prediction model (as described in detail previously herein), the results show that the increase in the thermal conductivity of the material of the present invention results in a reduction in the tube wall temperature of up to 30 °C, and for similar methane conversion / hydrogen yield compared to commercial catalysts, a representative case is a reduction of 13 °C. This phenomenon (entirely due to the increased thermal conductivity) has several benefits, two of which are as follows.

[0297] Table 13

[0298]

[0299]

[0300] First, if the tube wall temperature does not decrease but remains at a set constant temperature, the catalyst support material of the present invention results in a higher outlet temperature and a higher methane conversion / hydrogen yield. This improved performance is the extent of the increase in the feed flow rate without reducing the baseline conversion (the conversion of the commercial catalyst under similar conditions). The increased feed flow rate leads to an increase in productivity and is attractive to hydrogen producers with limited plant capacity.

[0301] Secondly, the increase in the reactor tube outlet temperature due to the use of the materials of the present invention means that the reactor tube wall temperature can be reduced by a similar amount and still maintain the original heat flux on the reactor tube without loss of methane conversion. The 30 °C reduction in the tube wall temperature is the result of a reduction in the natural gas burner temperature of up to 125 °C. A burner operating at a reduced temperature has the effect of consuming less natural gas and thus reducing the operating expenses (OPEX) associated with the natural gas burner fuel. The reduction is to a burner temperature of 1100 °C by 30 °C.

[0302] Based on the detailed description herein, the key advantages of the catalyst according to the present disclosure are summarized:

[0303] Compared with commercial SMR catalysts, at the same GHSV, temperature, pressure, and feed composition, the tube wall metal temperature is reduced by 5 °C to 30 °C.

[0304] Compared with commercial SMR catalysts having the same temperature, pressure, and feed composition, at the same conversion, the feed flow rate and the corresponding hydrogen production are increased by 1% to 30%.

[0305] The lower tube wall temperature results in lower operating costs for hydrogen production. As reported by Zolotech, a 30 - 50°F (16 °C to 28 °C) reduction in the tube wall temperature results in a fuel savings of 1.5 to 2.5 BTU / scf, which corresponds to an OPEX savings of $200,000 to $350,000 per year for a 100 million SCFD reformer. When compared with conventional methane reforming catalysts in a similar plant design, the catalysts of the present disclosure reduce the SMR OPEX by at least 2.5 BTU / scf and are in the range of 1 to approximately 3 BTU / scf.

[0306] As enabled by the catalysts of the present disclosure, a 30 °C reduction in the tube wall temperature in combination with conformal catalyst packing will facilitate the easy integration of the catalyst into existing reactor tubes or existing tube and plant designs. This technology is different from structured catalysts, which are difficult to integrate into existing plant tubes and reactor designs. Kumar et al. reported in 2015 that a 20 °C reduction in the tube wall temperature would increase the tube life by 50%. They also reported that compared to a 1% reduction in the energy cost portion of the plant OPEX, it results in a savings of $600,000 per year for a 100 million SCFD hydrogen plant. A 30 °C reduction in the tube wall temperature reduces the energy cost of hydrogen production from approximately 0.25% to approximately 1%.

[0307] Rostrup-Nielsen and Sehested reported in 2003 that in the absence of steam output, the energy consumption for hydrogen production by SMR was 300 BTU / scf. The reduction of the tube wall temperature thus reduces the OPEX for hydrogen production by methane reforming using the disclosed catalyst by up to about 1% or in the range from about 0.1% to about 1%. The total thermal efficiency of a methane reforming unit including waste heat recovery is about 95%. A reduction of about 1% in the operating cost is very important for hydrogen production and is an additional saving in addition to reducing the cost of tube replacement and the associated unit downtime during tube turnover (such as maintenance and tube replacement cycles).

[0308] As described in the John Zinc Combustion Handbook, when operating at high temperatures and pressures, the SMR tubes are in a creep state and close to the mechanical limit of the material properties. Tube failures can pose safety hazards and fires to the unit, which also reduces the uptime. The disclosed catalyst allows for a lower wall temperature and thus keeps the tube wall operating temperature away from the mechanical limit of performance to reduce tube rupture, breakage, and unit shutdown. The disclosed catalyst can extend the tube life by 3 to 12 months and can enable the unit to operate safely with fewer tube breakages and unit fires.

[0309] Catalysts and Catalyst Nuclei Containing SiC Improve the Effective Packed Bed Conductivity by Changing the Solid Loading, Thermal Conductivity, and Emissivity Figure 10

[0310] As previously discussed herein, the disclosed catalyst and catalyst core (i.e., catalyst support) are composed of a high thermal conductivity composite of SiC / Al2O3, which provides improved heat transfer in a packed bed. Additionally, compared to conventional commercial catalysts, these catalysts and catalyst cores provide a higher total normal emissivity and thus provide improved heat transfer in a packed bed when operating in a high-temperature environment. Even when maintaining a geometry and bed packing density similar to that of conventional catalysts, an improved effective packed bed thermal conductivity is achieved due to the conductivity and emissivity of the catalyst and catalyst core.

[0311] Using the experimental procedures and equipment described previously herein, the effective bed thermal conductivity was determined experimentally. As previously pointed out, compared to the wall temperature required when using conventional methane reforming catalysts, the expected reactor tube wall temperature when using the disclosed catalyst system can be reduced by 10°C to 30°C while providing an equal hydrogen production rate.

[0312] One criterion for calculating the effective packed bed thermal conductivity from various geometries and bed properties is the ZBS (Zehner, Bauer, and Schlunder) model. The ZBS model includes a representative cylindrical unit cell composed of catalyst pellets and a fluid medium and accounts for the geometric interactions between other pellets and the solid / fluid domain. The model adjusts the effective conductivity based on the conductivities of the fluid and pellet solid, the emissivity of the pellet solid, the porosity of the packed bed (i.e., void fraction) (geometric effect), shape correction, deformation parameters, pressure, and gas kinetic variations based on the mean free path of gas molecules.

[0313] In previous examples herein, the effect of increased pellet thermal conductivity was studied separately. At lower temperatures, the effect of radiative heat transfer is minimized or negligible. However, at the temperatures used during steam methane reforming and other catalytic reactions, radiative heat transfer is the primary means. Radiation plays a major role because it is proportional to the cube of the temperature. The ZBS model can account for the effects of emissivity and conductivity.

[0314] Using measured and calculated parameters, the effective packed bed thermal conductivity is determined for a range of variations in total normal emissivity and pellet thermal conductivity. A fixed packed bed geometry is used, corresponding to the experimental measurement results discussed in the example above titled "Reduced Wall Temperature and Increased Hydrogen Production in Steam Methane Reforming Using the Catalyst of the Present Invention". The packed bed model is maintained at a fixed temperature of 800 °C, at ambient pressure, where the bed porosity is 0.40, under nitrogen.

[0315] The effect of total normal emissivity varies exponentially at lower pellet thermal conductivities and linearly at higher pellet conductivities. For reference, measured and calculated parameters for the catalyst core of the present disclosure and a commercial catalyst are provided. The novel core of the present disclosure achieves its enhanced effective packed bed thermal conductivity by improving its pellet thermal conductivity and its increased total normal emissivity. However, an increase in either parameter increases the total effective conductivity.

[0316] In one embodiment of the catalyst of the present disclosure, a SiC-based core (e.g., SiC in a protective alumina matrix) is coated with a thin, translucent layer of porous alumina in order to increase the emissivity of the catalyst produced therefrom. The total normal emissivity of SiC at high temperatures is very high, but it can be increased using other types of coatings, dopants, or base metals. These base metals are typically oxidized from mildly to severely and include, but are not limited to, iron, steel, stainless steel, nickel, titanium, nichrome, etc. SiC is not the only ceramic that can be used to increase emissivity. Other ceramics include carbide coatings, iron oxide, silicon nitride, zirconia, MgO, ZrC, etc. Additionally, high-emissivity glass can be used. BSAS can also be used to increase the emissivity of the support while also protecting the core SiC material from its environment (as further described herein). Other glass coatings, base coatings, or ceramic coatings can be used, such as aluminosilicate, borosilicate, Vycor glass, Pyrex glass, various carbide materials, CaO stabilized with Zr / Fe / Cr oxides, carborundum, and unstabilized zirconia.

[0317] Accordingly, by replacing a conventional catalyst with a material having a high thermal conductivity and a high total normal emissivity (i.e., replacing a porous Ni—Al2O3 composite catalyst with a catalyst comprising a catalytic coating on a dense core containing SiC), the thermal conductivity of the catalyst is enhanced, and the heat transfer capacity of the bed under steady-state conditions is increased by about 5-fold, and the constant offset is increased by about 1.5 to 3.5 at an expected system flow rate of 2000 to 5000 GHSV representative of the methane reforming reaction at high temperature due to the effects of thermal dispersion and pressure turbulent conduction (see Figure 11 and Figure 11 ).

[0318] The increase in the effective radial thermal conductivity more effectively transfers heat from the wall of the high-temperature reactor tube to the catalyst bed and the reactant gas, thus more effectively driving the endothermic reaction. The amount of heat required to complete the reaction has not changed, but as the peak temperature decreases, the heat loss decreases, thus reducing the energy input in the form of the feed rates of fuel and oxygen (or air).

[0319] The thermal gradient between the tube wall and the center of the catalyst particle bed is reduced, which allows for a reduced tube wall temperature to produce an equivalent amount of hydrogen. Alternatively, the tube wall can be maintained at the same temperature as a conventional catalyst with a correspondingly similar tube life while increasing the production or productivity of hydrogen by a range of 5% to 30% compared to a conventional catalyst. The tube life can be significantly increased, tubes with thinner walls can be used, tubes using less expensive alloys, or more conventional manufacturing processes, all of which will result in a significant reduction in system capital costs.

[0320] The various embodiments of the catalyst core (i.e., catalyst support) and the catalyst according to the present disclosure, and the various types and classes of reactions in which the catalysts of the present disclosure can be used, have been described in detail above. However, it will be understood that the components, features, and configurations, and the methods of making the catalyst core and the catalyst and their methods of use are not limited to the specific embodiments described herein.

[0321] By way of example, any of the various catalyst cores described herein and the catalysts employing such cores can be used with any of a wide variety of catalytic reactions and processes, including but not limited to: acetylation, addition reactions, alkylation, dealkylation, hydrodealkylation, reductive alkylation, amination, aromatization, arylation, autothermal reforming, carbonylation, decarbonylation, reductive carbonylation, carboxylation, reductive carboxylation, reductive coupling, condensation, cracking, hydrocracking, cyclization, cyclo-oligomerization, dehalogenation, dimerization, epoxidation, esterification, Fischer-Tropsch, halogenation, hydrohalogenation, homologation, hydration, dehydration, hydrogenation, dehydrogenation, hydrocarboxylation, hydroformylation, hydrogenolysis, hydrometallation, hydrosilylation, hydrolysis, hydrotreating, hydrodesulfurization / hydrodenitrogenation (HDS / HDN), isomerization, methanation, methanol synthesis, methylation, demethylation, metathesis, nitration, oxidation, partial oxidation, polymerization, reduction, steam and carbon dioxide reforming, sulfonation, telomerization, transesterification, trimerization, water gas shift (WGS) and reverse water gas shift (RWGS).

Claims

1. A catalyst, comprising: (a) A core, the core comprising a composite of SiC grains and a protective matrix of one or more metal oxides in the voids between the SiC grains, the density of the core being ≥ 60% of the theoretical density; and (b) A catalytically active layer attached to the core, wherein the catalyst further comprises an interface layer between the core and the catalytically active layer, the interface layer comprising a dense coating covering the core, wherein the density of the interface layer is from 80% to 100% of the theoretical density.

2. The catalyst according to claim 1, wherein, The one or more metal oxides are selected from the group consisting of: alumina, titanium dioxide, and silica.

3. The catalyst according to claim 2, wherein, The protective matrix comprises Al2O3.

4. The catalyst according to claim 3, wherein, The protective matrix further comprises one or more additional metal oxides selected from the group consisting of: silica and mixed oxides of aluminum and silicon.

5. The catalyst according to claim 4, wherein, The mixed oxide of aluminum and silicon comprises Al6Si2O 13 .

6. The catalyst according to claim 3, wherein, The protective matrix further comprises one or more additional metal oxides selected from the group consisting of: titanium dioxide and mixed oxides of aluminum and titanium.

7. The catalyst according to any one of claims 1-6, wherein, Based on the relative amounts in the starting materials, the volume ratio of the metal in the metal oxide protective matrix in the core to SiC is between 0.05 and 0.

50.

8. The catalyst according to any one of claims 1-6, wherein, Based on the relative amounts in the starting materials, the volume ratio of the metal in the metal oxide protective matrix in the core to SiC is between 0.025 and 0.

80.

9. The catalyst according to claim 3, wherein, Based on the relative amounts in the starting materials, the volume ratio of aluminum in the core to SiC is between 0.05 and 0.

50.

10. The catalyst according to claim 4, wherein, Based on the relative amounts in the starting materials, the volume ratio of aluminum and silicon in the protective matrix in the core to SiC is between 0.05 and 0.

50.

11. The catalyst according to any one of claims 1-6, 9 and 10, wherein, The density of the core is 60% to 90% of the theoretical density.

12. The catalyst according to any one of claims 1-6, 9 and 10, wherein, The density of the core is 60% to 95% of the theoretical density.

13. The catalyst according to any one of claims 1-6, 9 and 10, wherein, The catalytically active layer comprises one or more catalytically active metals.

14. The catalyst according to claim 13, wherein, The one or more catalytically active metals are selected from the group consisting of: Ni, Co, Ru, Rh, Pd, Ir, Pt, Os, Re, Au, Ag, Cu, Fe, Mn, Mg, V, Mo, and Cr.

15. The catalyst according to any one of claims 1-6, 9 and 10, wherein, The catalytically active layer comprises nickel.

16. The catalyst according to any one of claims 1-6, 9 and 10, wherein, The catalytically active layer includes a porous coating on the core and catalytically active material disposed on the inner and outer surfaces of the porous coating.

17. The catalyst according to claim 13, wherein, The catalytically active layer further includes a porous coating on the core, wherein the one or more catalytically active metals are disposed on the inner and outer surfaces of the porous coating.

18. The catalyst according to claim 16, wherein, The porous coating includes a porous oxide shell on the core.

19. The catalyst according to claim 16, wherein, The porous coating includes a porous alumina shell.

20. The catalyst according to claim 17, wherein, The porous coating has a porosity of 40% to 80%.

21. The catalyst according to claim 1, wherein, The density of the interface layer is ≥ 90% of the theoretical density.

22. The catalyst according to claim 1 or 21, wherein, The interface layer includes alumina, silica, titanium dioxide, or barium strontium aluminosilicate.

23. The catalyst according to claim 22, wherein, The interface layer includes α-alumina.

24. The catalyst according to any one of claims 1-6, 9 and 10, wherein the interfacial layer comprises alumina.

25. The catalyst according to claim 24, wherein, The interface layer includes a dense alumina coating covering the core, wherein the density of the interface layer is ≥ 90% of the theoretical density.

26. The catalyst according to claim 24, wherein, The interface layer includes a dense alumina coating covering the core, wherein the density of the interface layer is from 80% to 90% of the theoretical density.

27. The catalyst according to any one of claims 1-6, 9 and 10, which further comprises an airtight sealing protective coating located between the catalytic active layer and the core.

28. The catalyst according to claim 27, wherein, The hermetic sealing protective coating comprises Al2O3 combined with at least one glass former.

29. The catalyst according to claim 28, wherein, The at least one glass former is selected from the group consisting of alkaline earth metal aluminosilicate glass, alkaline earth metal aluminoborosilicate glass, and lanthanide aluminosilicate glass.

30. The catalyst according to claim 28, wherein, The at least one glass former is selected from the group consisting of CaO—SiO2—Al2O3, MgO—SiO2—Al2O3, SrO—SiO2—Al2O3, BaO—SiO2—Al2O3, mixed alkaline earth metal aluminosilicate, alkaline earth metal aluminosilicate doped with rare earth elements, B2O3-modified alkaline earth metal aluminosilicate, and / or TiO2-modified alkaline earth metal aluminosilicate.

31. The catalyst according to claim 28, wherein, The at least one glass former is selected from the group consisting of CaO—SiO2—Al2O3 and MgO—SiO2—Al2O3.

32. The catalyst according to claim 1 or 21, which further comprises an airtight sealing protective coating located between the catalytic active layer and the interfacial layer.

33. The catalyst according to claim 32, wherein, The hermetic sealing protective coating comprises at least one glass former selected from the group consisting of alkaline earth metal aluminosilicate glass, alkaline earth metal aluminoborosilicate glass, and lanthanide aluminosilicate glass.

34. The catalyst according to claim 33, wherein, The at least one glass former is selected from the group consisting of CaO—SiO2—Al2O3, MgO—SiO2—Al2O3, SrO—SiO2—Al2O3, BaO—SiO2—Al2O3, mixed alkaline earth metal aluminosilicate, alkaline earth metal aluminosilicate doped with rare earth elements, B2O3-modified alkaline earth metal aluminosilicate, and / or TiO2-modified alkaline earth metal aluminosilicate.

35. The catalyst according to claim 34, wherein, The at least one glass former is selected from the group consisting of CaO—SiO2—Al2O3 and MgO—SiO2—Al2O3.

36. The catalyst according to any one of claims 33-35, wherein, The hermetic sealing protective coating further comprises Al2O3.

37. The catalyst according to any one of claims 1-6, 9 and 10, wherein, The catalyst has an effectiveness factor greater than 0.9 in the steam methane reforming reaction.

38. The catalyst according to any one of claims 1-6, wherein, Based on the relative amounts in the starting materials, the volume ratio of the metal in the metal oxide protective matrix in the core to SiC is between 0.05 and 0.

30.

39. The catalyst according to any one of claims 1-6, wherein, Based on the relative amounts in the starting materials, the volume ratio of the metal in the metal oxide protective matrix in the core to SiC is between 0.10 and 0.

25.

40. The catalyst according to any one of claims 1-6, 9, and 10, wherein, The density of the core is 65% to 80% of the theoretical density.

41. A catalyst support comprising a composite of SiC grains and a protective matrix of one or more metal oxides in the voids between the SiC grains, the density of the core being ≥ 60% of the theoretical density, the catalyst support further comprising a porous coating on the support, the porous coating being adapted to be impregnated with a catalytically active material, the catalyst support further comprising an interface layer between the support and the porous coating, the interface layer comprising a dense coating covering the core, wherein the density of the interface layer is from 80% to 100% of the theoretical density.

42. The catalyst support according to claim 41, wherein, The one or more metal oxides are selected from the group consisting of alumina, titanium dioxide, and silica.

43. The catalyst support according to claim 42, wherein, The protective matrix comprises Al2O3.

44. The catalyst support according to any one of claims 41-43, wherein, Based on the relative amounts in the starting materials, the volume ratio of the metal in the metal oxide protective matrix to SiC is between 0.05 and 0.

30.

45. The catalyst support according to any one of claims 41-43, wherein, The density of the support is 65% to 80% of the theoretical density.

46. The catalyst support according to claim 41, wherein, The density of the interface layer is ≥ 90% of the theoretical density.

47. The catalyst support according to claim 41 or 46, wherein, The interface layer comprises alumina, silica, titanium dioxide, or barium strontium aluminosilicate.

48. The catalyst support according to any one of claims 41-43 and 46, further comprising a gastight sealing protective coating between the porous coating and the interface layer.

49. The catalyst support according to claim 48, wherein, The hermetic sealing protective coating comprises Al2O3 combined with at least one glass former.

50. A method of manufacturing a catalyst core comprising a composite of SiC grains and a protective matrix of one or more metal oxides in the voids between the SiC grains, the method comprising the following steps: (a) Combining SiC powder and one or more metal powders to form a mixture; (b) Forming the mixture under compression into a predetermined shape; And (c) Heat the predetermined shape in an oxygen-containing atmosphere such that at least a portion of the metal is converted into one or more corresponding metal oxides; wherein the density of the catalyst core is ≥ 60% of the theoretical density.

51. The method according to claim 50, wherein, The one or more metal powders include Al and / or Al-Si alloy.

52. The method according to claim 50, wherein, In step (a), combine the SiC powder with an Al-Si alloy containing up to 25% Si.

53. The method according to any one of claims 50 - 52, wherein, Before the compressing step, combine the SiC powder and the one or more metal powders with one or more additives selected from the group consisting of binders, plasticizers, lubricants, and processing aids.

54. The method according to any one of claims 50 - 52, wherein, The step of forming the mixture into a predetermined shape includes dry pressing, extrusion, wet pressing, slip casting, isostatic pressing, or injection molding.

55. The method according to claim 54, wherein, The step of forming the mixture into a predetermined shape includes dry pressing, extrusion, or wet pressing.

56. The method according to any one of claims 50 - 52, wherein, The compressing applies sufficient pressure to the mixture to provide a density of ≥ 60% of the theoretical density in the green state, thereby plastically deforming the one or more metal powders such that the metal flows around the SiC grains, and thereafter, during the heating step, forming a metal oxide protective barrier layer around the SiC grains.

57. The method according to any one of claims 50 - 52, wherein, The heating step includes heating the predetermined shape in an oxygen-containing atmosphere at a temperature between 850 °C and 1450 °C for between 0.5 and 24 hours.

58. The method according to claim 57, wherein, The oxygen-containing atmosphere includes ambient air.

59. The method according to any one of claims 50 - 52, wherein, The predetermined shape is selected from the group consisting of spheres, cylinders, pellets, beads, lobed cylinders, saddles, wheels, rings, ribbed or grooved cylinders, notched cubes, and grooved pyramids.

60. The method according to any one of claims 50 - 52, wherein, The predetermined shape includes cylindrical pellets.

61. The method according to any one of claims 50 - 52, wherein, The volume ratio of the one or more metal powders to the SiC powder used in step (a) is between 0.05 and 0.

30.

62. The method according to any one of claims 50 - 52, wherein, The predetermined shape is selected from the group consisting of daisy-shaped pellets and star-shaped pellets.

63. The method according to any one of claims 50 - 52, wherein, The predetermined shape is selected from the group consisting of Pall rings and Raschig rings.

64. A method for Fischer - Tropsch synthesis of hydrocarbons, the method comprising: (a) Generate synthesis gas from a feedstock, the synthesis gas comprising CO and H2; (b) Feed the synthesis gas into a fixed-bed reactor containing the catalyst according to any one of claims 1-36 and 38-40, wherein the catalytically active layer comprises one or more catalytically active metals suitable for Fischer-Tropsch synthesis; and (c) React the synthesis gas in the fixed-bed reactor over the catalyst to produce a hydrocarbon product mixture.

65. The method according to claim 64, wherein, The catalytically active metal is selected from the group consisting of Fe, Co, and Ru.

66. The method according to claim 64 or 65, wherein, The synthesis gas reacts in the fixed-bed reactor at a pressure of 10 to 40 bar and a temperature of 190 °C to 240 °C.

67. The method according to claim 64 or 65, wherein, The synthesis gas reacts in the fixed-bed reactor at a pressure of 10 to 40 bar and a temperature of 300 °C to 350 °C.

68. A method for steam methane reforming, the method comprising: (a) Methane and steam are fed into a plurality of fixed-bed reactor tubes filled with the catalyst as described in any one of claims 1-36 and 38-40, wherein the catalytically active layer comprises one or more catalytically active metals suitable for steam methane reforming; and (c) Reacting the methane and steam in the reactor tubes over the catalyst to produce hydrogen.

69. The method according to claim 68, wherein, The catalytically active metal is selected from the group consisting of: Ni, Co, Ru, Rh, Pd, Ir, and Pt.

70. The method according to claim 68 or 69, wherein, The methane and steam react in the reactor tubes at a temperature of 500 °C to 900 °C.

71. The method according to claim 68 or 69, wherein The catalyst has an effectiveness factor greater than 0.

9.

72. The method according to claim 68 or 69, wherein During the operation of the methane steam reforming reaction, within an operating time between 100 and 1000 hours, the catalyst exhibits an activity loss of less than 1%.

73. A method for carrying out a catalytic reaction, the method comprising: (a) One or more reactants are fed into a reactor containing the catalyst as described in any one of claims 1-36 and 38-40, wherein the catalytically active layer comprises one or more catalytically active metals suitable for catalyzing the reaction; and (b) Reacting the one or more reactants in the reactor over the catalyst to produce a product.

74. The method according to claim 73, wherein The product comprises BTX.

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