Catalyst and process for methane dehydrogenation

Abstract

This application relates to a methane dehydrogenation process in which a methane feedstock is subjected to a novel SiO2 catalyst under dehydrogenation conditions to produce hydrogen, ethylene, aromatics, or any mixture thereof. In another embodiment, this application relates to a novel catalyst for methane dehydrogenation. The catalyst comprises amorphous particles of SiO2. The amorphous particles have a nominal particle size of about 5 nm to 1 cm. The amorphous particles of SiO2 have sufficient Lewis acidity to activate one or more C-H bonds in methane and produce one or more methyl radicals when the catalyst is subjected to methane dehydrogenation conditions. In another embodiment, this application relates to a method for making a novel catalyst for methane dehydrogenation.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 63 / 427,319, filed November 22, 2022, and U.S. Non-Provisional Application No. 18 / 221,806, filed July 13, 2023, the contents of which are incorporated herein in their entireties.

[0002] Field of Disclosure This application relates to a fused silica catalyst and a process for methane dehydrogenation using the catalyst. [Background technology]

[0003] background Natural gas is an efficient, abundant, and versatile energy source, primarily composed of methane (CH4). Natural gas is one of the traditional fuels with the lowest emissions from combustion, producing lower CO2 emissions than heavier hydrocarbon fuels, such as coal and oil. Natural gas is also a major source of raw material for hydrogen production. Traditionally, hydrogen has been produced by the steam methane reforming (SMR) process. Unfortunately, even when achieving the highest achievable H2 yield from methane, SMR also produces significant amounts of CO2 as a by-product (H2:CO2 = 4:1). To reduce CO2 emissions, carbon capture and sequestration (CCS) is often combined with SMR, which adds complexity and expense to the process.

[0004] To date, the use of methane for hydrogen production accounts for only a small fraction of its total consumption. Natural gas is still primarily used for its calorific value during combustion to produce both CO2 and HO, but its chemical value has yet to be fully exploited. Today, feedstock chemicals (olefins, aromatics, etc.) are primarily produced from crude oil, a process that is complex, expensive, and polluting. A small portion of feedstock chemicals, such as olefins, are currently converted from methane via intermediate syngas pathways, but even this indirect conversion is complex, carbon-intensive, and expensive.

[0005] Direct conversion of methane by oxidation reactions has been attempted, for example, the oxidative coupling of methane to ethylene (OCM) and the partial oxidation of methane to methanol and formaldehyde (SOM). Unfortunately, overoxidation often results in low selectivity.

[0006] Methane dehydrogenation, also known as methane cracking, methane pyrolysis, or methane cracking, has been attempted to (1) produce hydrogen with "low carbon" efficiency and (2) produce feedstock chemicals from methane without going through synthesis gas. Unfortunately, many of these efforts, such as those using Mo / zeolite-based bifunctional catalysts, have failed due to, for example, an inability to achieve high selectivity to alternative chemicals to coke and / or other inefficiencies.

[0007] It would be desirable to develop new methods and catalysts for converting methane to feedstock chemicals. It would be even more desirable if such new methods and catalysts could directly convert methane to useful products. It would also be even more desirable if such new methods and catalysts could provide high selectivity to one or more desired chemicals. Summary of the Invention

[0008] In some embodiments, the technology described herein relates to a catalyst for methane dehydrogenation, the catalyst comprising amorphous particles of SiO, the amorphous particles having a nominal particle size of from about 5 nm to about 1 cm, and the amorphous particles of SiO having sufficient Lewis acidity to activate C-H bonds in methane to produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0009] In some aspects, the technology described herein relates to a methane dehydrogenation process comprising subjecting a methane feedstock to a catalyst under dehydrogenation conditions and producing hydrogen, alkanes, alkenes, aromatics, or any mixture thereof, wherein the catalyst comprises amorphous particles of SiO, the amorphous particles having a nominal particle size of from about 5 nm to about 1 cm, and the amorphous particles of SiO have sufficient Lewis acidity to activate C-H bonds in methane and produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0010] Further features of the disclosed systems and methods, and advantages offered thereby, are described in more detail below with reference to specific exemplary embodiments that are illustrated in the accompanying drawings. [Brief explanation of the drawings]

[0011] To facilitate a better understanding of the present invention, reference is now made to the accompanying drawings, which should not be construed as limiting the invention, but are intended only to illustrate various aspects and embodiments of the invention.

[0012] [Figure 1] FIG. 1 shows a typical process for producing a catalyst.

[0013] [Figure 2] FIG. 2 shows a typical process for producing the catalyst.

[0014] [Figure 3] FIG. 3 shows a typical process for producing the catalyst.

[0015] [Figure 4] FIG. 4 shows a typical process for producing the catalyst.

[0016] [Figure 5] FIG. 5 shows a representative process for preparing the catalyst.

[0017] [Figure 6] FIG. 6 shows a representative process for preparing the catalyst. DETAILED DESCRIPTION OF THE INVENTION

[0018] To illustrate various features of the present invention, exemplary embodiments of the present invention will now be described. The embodiments described herein are not intended to limit the scope of the invention, but rather to provide examples of the components, uses, and operation of the present invention.

[0019] Furthermore, the described features, advantages, and characteristics of the embodiments may be combined in any suitable manner. Those skilled in the art will recognize that various embodiments may be practiced without one or more of the specific features or advantages of an embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments.

[0020] The flowcharts and block diagrams in the figures illustrate the structure, functionality, and operation of possible implementations of systems, methods, and products according to various embodiments of the present invention. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be performed substantially concurrently, or the blocks may sometimes be performed in the reverse order, depending upon the method and product involved.

[0021] Advantageously, the present system and method solve one or more, if not all, of the aforementioned problems and further problems. For example, this process can convert natural gas into high-value hydrocarbons and produce hydrogen as a carbon-free fuel without significant carbon dioxide emissions. Regarding the catalyst, one embodiment describes a novel catalyst for methane dehydrogenation, for example, comprising modified amorphous SiO particles doped with an Fe component. The catalyst particle size can range from a few nanometers to a few centimeters, and the Fe additive, which can take various forms, can be present in various weight percentages. The Fe additive activates C-H bonds in methane to generate methyl radicals during methane dehydrogenation. The amorphous particles can have a nominal diameter of about 5 nanometers to about 1 centimeter, preferably about 50 nanometers to about 1 millimeter. The amorphous SiO particles can contain silanol groups (—SiOH) with sufficient Lewis acidity to activate C-H bonds in methane and generate methyl radicals when the catalyst is subjected to methane dehydrogenation conditions. The Fe additive may be in the form of, but is not limited to, Fe, Fe2O3, FeO, Fe3O4, Fe(NO3)3, FeSO4, FeCl3, and FeS. The weight percentage of such Fe additives may vary, but is typically from about 0.01% to about 25%, preferably from about 0.025% to about 5%.

[0022] New catalysts and processes for producing catalysts The present invention relates to a novel catalyst and a method for methane dehydrogenation using the novel catalyst. The novel catalyst is generally a non-metallic derivative of fused silica (also known as fused quartz or quartz glass) as a catalyst. Products include hydrogen, olefins, alkanes, alkenes, aromatics, and coke, among which hydrogen, ethylene, benzene, and naphthalene can be the major products depending on the conditions selected. Advantageously, these non-metallic oxide catalysts do not require the active component to be a metal.

[0023] Fused silica is a glass composed of pure silica (silicon dioxide, SiO2) in an amorphous form. It can be produced in any convenient manner. For example, it can be produced by melting (fusing) high-purity silica sand composed of crystalline quartz, or by burning SiCl4 in a flame. Fused silica typically has a very low surface area (1 m²) due to the melting temperatures (approximately 1650°C) it is subjected to during production. 2 / g) and often has relatively low porosity or no pores at all. As described below, due to its high processing temperatures and chemical inertness under many conditions, fused silica can be made into many useful forms, such as reaction tubes, quartz frits, and / or quartz wool.

[0024] It has been found that the activity of new catalysts for methane dehydrogenation is often inversely correlated with the particle size of the fused silica under many reaction conditions, i.e., activity can be increased after the fused silica is subjected to a size reduction process, typically by means such as, but not limited to, crushing, milling, cutting, hot melt extrusion, or any combination thereof.

[0025] The catalyst typically comprises amorphous particles of SiO2. The size of the amorphous particles can vary depending on the desired application of the catalyst, the desired product, and the reaction conditions. Typically, the amorphous particles have a nominal diameter of about 5 nm to about 1 cm, preferably about 50 nm to about 1 mm.

[0026] The catalyst may be prepared by any convenient process, provided that the resulting particles contain silanol groups with sufficient Lewis acidity to activate C-H bonds in methane and generate methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0027] In some embodiments, the process includes reducing the size of the fused silica. The size reduction can be accomplished in any convenient manner. However, in some embodiments, it is desirable for the size reduction to increase the silanol-to-siloxane ratio in the catalyst. Useful size reduction techniques can include, for example, crushing, milling, cutting, hot melt extrusion, or any combination thereof. After size reduction, if desired, the reduced fused silica can be sieved to select the desired particle size. The sieve size can vary depending on the desired application of the catalyst, reaction conditions, desired products, and other factors. In some embodiments, the sieved size can be about 20 to about 40 mesh.

[0028] Metals are not required in the fused silica catalysts described herein, and it may be preferred that the fused silica catalyst be non-metallic or at least substantially metal-free. For example, the catalyst may contain less than about 15 ppm, or less than about 10 ppm, or less than about 8 ppm of metals, such as iron, as analyzed by inductively coupled plasma spectroscopy. Thus, the catalysts herein preferably contain active sites that are non-metallic. In some embodiments, the amorphous SiO2 particles in the catalyst contain multiple non-hydrogen-bonded silanol groups. This multiple non-hydrogen-bonded silanol groups can help the catalyst have sufficient Lewis basicity, as described above. The amount of non-hydrogen-bonded silanols can vary from catalyst to catalyst. In some embodiments, at least a portion of the silanols comprise non-hydrogen-bonded silanols. In other embodiments, the majority of the silanols can comprise non-hydrogen-bonded silanols.

[0029] Without wishing to be bound by any particular theory, the observed surprising and unexpected catalytic activity may be due to the relatively low ≡Si-OH / ≡Si-O-Si≡ (silanol to siloxane) ratio in large fused silica particles due to their low geometric surface area. Mechanical particle size reduction increases the ≡Si-OH / ≡Si-O-Si≡ ratio by forcing some ≡Si-O-Si≡ to open and convert to ≡Si-OH. Some, most, or even nearly all of the newly formed ≡Si-OH groups after size reduction can be characterized by Raman and / or IR spectroscopy as non-hydrogen-bonded silanol groups ("nearly free surface" silanol groups).

[0030] Without wishing to be bound by any particular theory, such non-hydrogen bonded silanol groups may have sufficient Lewis acidity to activate C-H bonds in methane molecules to generate methyl radicals, which in turn generate hydrogen, hydrocarbons, and carbon on the surface and in the gas phase through radical chain propagation and termination.

[0031] Fused silica catalysts differ from traditional Mo / zeolite catalysts. Methane cracking over Mo / zeolite catalysts follows a bifunctional pathway in which methane is activated and bound to ethylene by Mo carbide species, followed by aromatization of ethylene at Brønsted acid sites in the zeolite. In contrast, fused silica catalysts follow a radical reaction pathway in which C—H bonds are activated in the presence of fused silica to produce methyl radicals, followed by chain propagation and termination. These two catalysts also generally operate at different temperatures. Mo / zeolite catalysts can be operated at temperatures below about 700°C, while fused silica typically requires higher temperatures, up to 1100°C or higher.

[0032] Method and process for non-oxidative conversion of hydrocarbons to hydrogen using novel catalysts The catalysts described above can be used in processes for the non-oxidative conversion of hydrocarbons, such as natural gas, to produce, for example, hydrogen and potentially other products. The process generally involves contacting a hydrocarbon, such as natural gas, with the catalysts described above and / or a mixture of catalysts containing one of the catalysts described above. The contacting is typically carried out under conditions that convert the hydrocarbon to hydrogen. The process can also produce light hydrocarbon products, such as ethylene, benzene, naphthalene, or any mixture thereof.

[0033] A methane dehydrogenation process typically involves subjecting a methane feedstock to a catalyst under dehydrogenation conditions. The catalyst comprises amorphous particles of SiO. The amorphous particles have a nominal diameter of about 5 nm to about 1 cm, preferably about 50 nm to about 1 mm. The amorphous SiO particles have sufficient Lewis acidity to activate C-H bonds in methane and generate methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0034] Typically, hydrogen, ethylene, aromatics, or any mixture thereof, are produced. Aromatics may include aromatic compounds such as benzene, naphthalene, or any mixture thereof. If desired, the hydrogen and / or other products may be separated in any convenient manner.

[0035] Dehydrogenation conditions can vary widely depending on the equipment, the composition of the methane feedstock, the specific catalyst composition, and other factors. Useful conditions in some embodiments can include temperatures of at least about 800°C to about 1200°C, and / or residence times of about 0.05 to about 100, or about 0.05 to about 10 seconds, or about 1 to about 7 seconds.

[0036] The methane content in the methane feedstock can vary, but in some embodiments, the methane feedstock can contain at least about 70%, or at least about 90% methane. The methane feedstock can contain other components in amounts that do not significantly interfere with the process or the desired products. In some cases, the methane feedstock can further contain nitrogen.

[0037] Methane conversion and products produced may also vary depending on conditions, equipment, feedstock, specific catalyst composition, and other factors. In some embodiments, methane conversion may be at least about 15%. In some embodiments, the process produces a mixture comprising hydrogen, ethylene, and aromatics, or a mixture of aromatics.

[0038] Various methods and processes are possible for producing the new catalysts.

[0039] Figure 1 illustrates a process for producing the catalyst described and referenced further above. The catalyst produced by the process of Figure 1 is referred to as Catalyst A. To prepare Catalyst A, a specific grade of silica gel (a type of material made from silicon dioxide) is heated in the presence of air at a temperature of 900°C for 1 hour in operation 105. This process, called calcination, serves to convert the silica gel to the desired catalytic form.

[0040] FIG. 2 illustrates a process for producing the catalyst further described and referenced above. The catalyst produced by the process of FIG. 2 is referred to as Catalyst B. In operation 205, industrial-grade silica gel is subjected to a high temperature of 1650°C for six hours under a nitrogen atmosphere. This process, called calcination, serves to convert the silica gel to the desired catalytic form. After calcination, in operation 210, the material is subjected to ball milling (a grinding process using balls) and sieving to obtain particles within a size range of 20 to 40 mesh. Ball milling can be used to achieve a more uniform particle size distribution and reduce the particle size of the material. In some embodiments, the calcined material is placed in a container with grinding balls, and the container is rotated to begin the milling process. As a result of ball milling, the calcined material is further broken down into smaller particles. Following the ball milling step, in operation 215, the material is sieved to separate particles based on particle size. In this case, sieving is performed to obtain particles within the desired size range of about 20 to about 40 mesh. Sieving serves to select and separate particles that fall within a specified size range, ensuring that the final catalyst material meets the desired particle size requirements.

[0041] FIG. 3 illustrates a process for producing the catalyst described and referenced further above. The catalyst produced by the process of FIG. 3 is referred to as Catalyst C. In operation 305, Catalyst C is prepared by dissolving iron(III) acetylacetonate (an iron-containing compound) in ethanol and mixing it with silica gel. The purpose of this step is to prepare a solution of iron compounds, which is later mixed with silica gel to incorporate iron into the catalyst. In operation 310, 115 grams of silica gel may be mixed with the solution. Next, in operation 315, in at least some embodiments, the mixture is dried. The mixture of iron(III) acetylacetonate solution and silica gel is typically dried by exposing the mixture to air at a controlled temperature. Drying removes the solvent (ethanol) from the mixture, leaving a solid material. This step is used to remove residual liquid and ensure the stability of the catalyst. In operation 320, the dried mixture is subjected to calcination, which involves heating the material at a high temperature of 900° C. for approximately one hour. This heat treatment process induces chemical and structural changes in the material to form the final catalyst structure and activate the desired catalytic properties. The high temperature promotes the reaction and conversion, resulting in the desired properties of Catalyst C. The presence of iron in the catalyst (Catalyst C) affects performance. Iron, a transition metal, can act as a catalyst itself or modify the catalytic properties of the silica gel matrix. The addition of iron enhances certain reactions and / or improves the selectivity and efficiency of the catalyst in the process.

[0042] FIG. 4 illustrates a process for producing the catalyst further referenced and described above. The catalyst produced by the process of FIG. 4 is referred to as Catalyst D. In 405, 9.5 mmol of ferrocene (containing iron) is dissolved in 5 mL of toluene. Ferrocene is an iron-containing compound that dissolves in toluene to form a solution. Dissolving ferrocene in toluene prepares a solution of iron compounds, which is later mixed with quartz sand to incorporate iron into the catalyst. In operation 410, the toluene solution of ferrocene is combined with quartz sand, a type of crystalline silica material. The mixing process ensures that the iron compounds are substantially uniformly distributed within the quartz sand matrix. Incorporating iron into the quartz sand can modify or enhance the properties and behavior of the catalyst. In one embodiment, 250 grams of quartz sand is mixed with the Fe solution in an uncovered 250 mL beaker at 50° C. in a fume hood until the toluene evaporates and the mixture reaches a homogeneous form. In operation 415, the mixture of ferrocene solution and quartz sand is typically dried by exposing it to air at a controlled temperature. For example, the mixture can be dried in air at 15°C for 72 hours. Drying removes the solvent (toluene) from the mixture, leaving a solid material. This removes residual liquid and ensures catalyst stability. In operation 420, the mixture is calcined at a high temperature of 1100°C for 1 hour. The dried mixture is subjected to calcination. In this case, the mixture is heated to a temperature of 1100°C for 1 hour. Calcination induces chemical reactions and structural changes in the materials, resulting in the formation of the final catalyst structure and activation of the desired catalytic properties. The high temperature promotes reactions and conversions and ensures the catalyst has the desired properties. The presence of iron in catalyst D imparts certain properties to the catalyst. Iron, a transition metal, can act as a catalyst itself and / or modify the catalytic properties of the quartz sand. The addition of iron enhances certain reactions and / or improves the selectivity and efficiency of the catalyst in certain chemical processes. The exact effect of iron on the properties and behavior of the catalyst often depends on the specific reaction and the conditions to which the catalyst is exposed.

[0043] FIG. 5 illustrates a process for producing the catalyst described further above. The catalyst produced by the process of FIG. 5 is referred to as Catalyst E. In operation 505, a mixture of 1 mmol of iron(III) acetate and 10 grams of quartz wool (a type of fibrous quartz material) with a nominal diameter of 4 μm is ball milled in N2 at 400 rpm for 12 hours. A catalyst containing iron compounds and a quartz wool matrix is ​​formed. The specific composition and ratio of iron(III) acetate to quartz wool determine the concentration of iron in the catalyst and its distribution within the quartz wool structure. Ball milling promotes mixing, dispersion, and particle size reduction. Ball milling also helps achieve a more uniform distribution of iron within the quartz wool matrix, which may result in improved catalytic properties. In operation 510, the mixture is melted in nitrogen at 1650°C for 5 hours to achieve a substantially uniform and solidified structure. The high temperature causes the materials to fuse together, resulting in chemical interaction and transformation. In operation 515, the resulting material is again subjected to ball milling and sieving to obtain a desired particle size of about 20 to about 40 mesh. The material resulting from the melting, ball milling, and sieving steps is identified as Catalyst E. The specific properties and catalytic behavior of Catalyst E may be influenced by the combination of iron(III) acetate with the quartz wool matrix, the structural changes induced by melting at high temperatures, and the fine particle size distribution obtained by ball milling and sieving.

[0044] FIG. 6 illustrates a process for producing the catalyst further described above. The catalyst produced by the process of FIG. 6 is referred to as Catalyst F. Catalyst F is prepared using a sol-gel method, which involves mixing 40 grams of tetraethoxysilane (TEOS), 1 gram of Pluronic P123, 1 mmol of iron(III) acetylacetonate, and 3 mL of ethanol into 20 grams of nitric acid (16 wt %). In operation 610, the mixture is stirred at 60°C for 24 hours. Stirring ensures thorough mixing and interaction between the components. The elevated temperature promotes chemical reactions and the formation of a uniform gel-like material. In operation 615, the mixture is aged for 72 hours to undergo further chemical transformations and structural changes. During this time, the gel-like material matures to achieve the desired properties and structure for effective catalytic performance. In operation 620, the resulting gel is dried in an oven at 120°C for 2 hours to remove excess water from the gel and solidify the material. This operation serves to remove the solvent (in this case, ethanol) and stabilize the gel structure, converting it into a solid material. After stirring, aging, and drying, the gel-like material is treated in air at a temperature of 550 °C for 6 hours. This calcination promotes further chemical reactions and structural transformations within the material, removes residual organic components, induces crystallization, and / or enhances the catalytic activity of the material. The material resulting from the stirring, aging, drying, and calcination steps is identified as Catalyst F. Catalyst F is the final product obtained by the sol-gel method and subsequent heat treatment. The composition, structure, and thermal history of Catalyst F are tailored to make this catalyst suitable for the desired catalytic reaction.

[0045] The catalysts described above can be used in processes for the nonoxidative conversion of hydrocarbons, such as natural gas, to produce, for example, hydrogen and potentially other products. The process generally involves contacting a hydrocarbon, such as natural gas, with the catalysts described above and / or a mixture of catalysts comprising at least one of the catalysts described above. The contacting is typically carried out under conditions that convert the hydrocarbon to hydrogen. The process can also produce light hydrocarbon products, such as ethylene, benzene, naphthalene, or any mixture thereof.

[0046] A methane dehydrogenation process typically involves subjecting a methane feedstock to a catalyst under dehydrogenation conditions. The catalyst comprises amorphous particles of SiO. The amorphous particles have a nominal diameter of about 5 nm to about 1 cm, preferably about 50 nm to about 1 mm. The amorphous SiO particles have sufficient Lewis acidity to activate C-H bonds in methane and generate methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0047] Typically, hydrogen, ethylene, aromatics, or any mixture thereof, are produced. Aromatics may include aromatic compounds such as benzene, naphthalene, or any mixture thereof. If desired, the hydrogen and / or other products may be separated in any convenient manner.

[0048] Dehydrogenation conditions can vary widely depending on the equipment, the composition of the methane feedstock, the specific catalyst composition, and other factors. Useful conditions in some embodiments can include temperatures of at least about 800°C to about 1200°C, and / or residence times of about 0.05 to about 100, or about 0.05 to about 10 seconds, or about 1 to about 7 seconds.

[0049] The methane content in the methane feedstock can vary, but in some embodiments, the methane feedstock can contain at least about 70%, or at least about 90% methane. The methane feedstock can contain other components in amounts that do not significantly interfere with the process or the desired products. In some cases, the methane feedstock can further contain nitrogen.

[0050] Methane conversion and products produced may also vary depending on conditions, equipment, feedstock, specific catalyst composition, and other factors. In some embodiments, methane conversion may be at least about 15%. In some embodiments, the process produces a mixture comprising hydrogen, ethylene, and aromatics, or a mixture of aromatics.

[0051] In one embodiment, 1.0 g of commercially available quartz wool with a nominal diameter of 9 μm is loosely packed into a quartz tube with an inner diameter of 0.35 inches. The catalyst bed volume is 12.6 mL. This test run is designated R046.

[0052] In another embodiment, 1.0 g of commercially available quartz wool with a nominal diameter of 9 μm is tightly packed into a quartz tube with an inner diameter of 0.35 inches. The catalyst bed volume is 3.7 mL. This test run is designated R047.

[0053] In another experiment, 1.1 g of commercially available quartz wool with a nominal diameter of 9 μm was ball milled in a roller jar with yttria-stabilized zirconia balls at 25 rpm for 72 hours. The fine powder was compressed and sieved to 20 / 40 mesh size and placed in a quartz tube with an inner diameter of 0.35 inches. The catalyst bed was undiluted and had a volume of 2.2 mL. This test run is designated R048.

[0054] In another embodiment, 1.0 g of commercially available quartz wool with a nominal diameter of 4 μm is tightly packed into a quartz tube with an inner diameter of 0.35 inches. The catalyst bed volume is 3.9 mL. This test run is designated R050.

[0055] A comparison of catalytic tests for methane dehydrogenation is summarized in Table 1.

[0056] [Table 1]

[0057] First, a comparison of R046 and R047 shows that the methane conversion rate of the coarse quartz wool sample increases with increasing residence time, but the reaction rate of methane conversion is essentially the same for both test runs. As shown in a comparison of R048 with R046 and R047, after ball milling the same type of coarse quartz wool into a fine powder, the reaction rate is nearly seven times higher than that of the raw coarse quartz wool. For the fine quartz wool sample, shown as R050, the reaction rate is nearly three times higher than that of both the coarse quartz wools, R046 and R047. These results demonstrate that quartz wool, a type of fused silica, is active for methane dehydrogenation. This activity can be enhanced by reducing its particle size, which may increase the number of non-hydrogen-bonded silanol groups, as mentioned above.

[0058] In another embodiment, 3.50 g of commercially available quartz wool with a nominal diameter of 9 μm was ball milled with yttria-stabilized zirconia balls in a roller jar at 25 rpm for 72 hours. The fine powder was compressed and sieved to a 20 / 40 mesh size before being placed in a quartz tube with an inner diameter of 0.35 inches. The catalyst was undiluted and had a volume of 7.0 mL. This test run is designated R054.

[0059] The test run is conducted at ambient pressure in a feed gas containing 90% CH4 / 10% N2 at a total flow rate of 120 mL / min at a temperature of 1080°C. The test run duration is 911 minutes. The overall conversion of methane during the test run is 21.0%. The overall mass balance is 101.43% and the mass balance of converted CH4 is 101.35%, respectively. Steady state is reached after the test run is performed for 256 minutes. The product selectivities (by weight) at steady state are shown in Table 2. The main products are hydrogen, ethylene, and aromatics.

[0060] [Table 2]

[0061] In some embodiments, the technology described herein relates to a catalyst for methane dehydrogenation, the catalyst comprising amorphous particles of SiO, the amorphous particles having a nominal particle size of 5 nm to 1 cm in diameter, and the amorphous particles of SiO having sufficient Lewis acidity to activate C-H bonds in methane to produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0062] In some aspects, the technology described herein relates to metal-free catalysts.

[0063] In some embodiments, the technology described herein relates to catalysts in which amorphous particles of SiO2 contain multiple non-hydrogen-bonded silanol groups.

[0064] In some aspects, the technology described herein relates to catalysts comprising less than about 10 ppm of iron impurity as analyzed by inductively coupled plasma spectroscopy.

[0065] In some embodiments, the technology described herein relates to a catalyst in which the amorphous particles of SiO2 contain multiple non-hydrogen-bonded silanol groups and have less than about 10 ppm of Group VIII metal impurities as analyzed by inductively coupled plasma spectroscopy.

[0066] In some aspects, the technology described herein relates to catalysts produced by a process that includes size reduction of fused silica.

[0067] In some aspects, the technology described herein relates to catalysts where reducing the size of the fused silica comprises increasing the silanol to siloxane ratio.

[0068] In some aspects, the technology described herein relates to catalysts where reducing the size of the fused silica comprises crushing, milling, cutting, hot melt extrusion, or any combination thereof.

[0069] In some aspects, the technology described herein relates to catalysts in which at least a portion of the silanols include silanols that are not hydrogen bonded.

[0070] In some aspects, the technology described herein relates to catalysts in which a majority of the silanols comprise silanols that are not hydrogen bonded.

[0071] In some embodiments, the technology described herein relates to catalysts that further include sieving the reduced fused silica to a size of about 5 nm to about 1 cm.

[0072] In some aspects, the technology described herein relates to a methane dehydrogenation process comprising subjecting a methane feedstock to a catalyst under dehydrogenation conditions and producing hydrogen, alkanes, alkenes, aromatics, or any mixture thereof, wherein the catalyst comprises amorphous particles of SiO, the amorphous particles having a nominal particle size of from about 5 nm to about 1 cm, and the amorphous particles of SiO have sufficient Lewis acidity to activate C-H bonds in methane and produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0073] In some aspects, the technology described herein relates to processes in which the aromatics include benzene, naphthalene, or any mixture thereof.

[0074] In some aspects, the technology described herein relates to a process further comprising separating the hydrogen.

[0075] In some embodiments, the technology described herein relates to processes wherein the dehydrogenation conditions include a temperature of at least about 800°C up to about 1200°C.

[0076] In some embodiments, the technology described herein relates to processes wherein the dehydrogenation conditions include a residence time of about 0.05 to about 100 seconds.

[0077] In some embodiments, the technology described herein relates to processes in which the methane feedstock comprises at least about 70%, or at least about 90% methane.

[0078] In some aspects, the technology described herein relates to processes where the methane feedstock further comprises nitrogen.

[0079] In some embodiments, the technology described herein relates to processes in which the methane conversion is at least about 15%.

[0080] In some aspects, the technology described herein relates to processes for producing a mixture comprising hydrogen, ethylene, and aromatics, or a mixture of aromatics.

[0081] In some aspects, the technology described herein relates to processes wherein the alkane comprises ethane, propane, butane, pentane, or any mixture thereof.

[0082] In some embodiments, the technology described herein relates to processes in which the alkene comprises ethylene, propylene, butene, pentene, an unsaturated C2-C5 hydrocarbon, or any mixture thereof.

[0083] In some aspects, the technology described herein relates to processes in which the aromatics include other polynuclear aromatic compounds.

[0084] While embodiments of the present invention have been described herein in terms of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that the utility of the present invention is not limited thereto, and that embodiments of the present invention may also be beneficially implemented in other related environments for similar purposes. Accordingly, the present invention should not be limited by the above-described embodiments, methods, and examples, but rather by all embodiments that fall within the scope and spirit of the invention as claimed.

[0085] Furthermore, it is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The terms "a" or "an," as used herein, are defined as one or more. The term "plurality," as used herein, is defined as two or more. The term "another," as used herein, is defined as at least a second or more. The terms "including" and / or "having," as used herein, are defined as comprising (i.e., open language). The term "coupled," as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. The term "providing," as used herein, is defined in its broadest sense as bringing into / coming into physical existence, making available, and / or supplying to someone or something, for example, as a whole or in parts, at one time or over a period of time.

[0086] The present invention has been described in various embodiments with reference to the accompanying drawings. However, it will be apparent that various modifications and changes may be made to the invention and additional embodiments may be implemented without departing from the broader scope of the invention as set forth in the claims that follow. Accordingly, the present invention and the drawings should be regarded in an illustrative rather than a restrictive sense.

[0087] The present invention is not limited with respect to the specific embodiments described herein, which are intended as illustrative of various aspects. Many modifications and variations can be made without departing from its spirit and scope. Functionally equivalent systems, processes, and apparatuses falling within the scope of the invention, in addition to those enumerated herein, may be apparent from the exemplary descriptions herein. Such modifications and variations are also intended to be included within the scope of the appended claims. The present invention is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such exemplary claims are entitled.

[0088] The foregoing description of exemplary embodiments provides non-limiting representative examples with reference to numerical values ​​to specifically illustrate the features and teachings of various aspects of the present invention. It should be recognized from the description of the embodiments that the described embodiments can be implemented alone or in combination with other embodiments. Those skilled in the art will be able to learn and understand the various described aspects of the present invention upon reviewing the description of the embodiments. The description of the embodiments should facilitate understanding of the present invention to the extent that other implementations not specifically included but within the knowledge of those skilled in the art upon reading the description of the embodiments will be understood to be consistent with the application of the present invention.

[0089] Embodiment 1. A catalyst for methane dehydrogenation, comprising:

[0090] containing a plurality of amorphous particles of SiO2,

[0091] The amorphous particles have a nominal diameter of about 5 nm to about 1 cm, and

[0092] A catalyst, wherein the amorphous particles have sufficient Lewis acidity to activate multiple C-H bonds in methane to produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0093] 2. The catalyst of embodiment 1, which is metal-free.

[0094] 3. The catalyst of embodiment 1, wherein the amorphous particles of SiO2 comprise a plurality of non-hydrogen-bonded silanol groups.

[0095] 4. The catalyst of embodiment 1, comprising less than about 10 ppm of iron impurity as analyzed by inductively coupled plasma spectroscopy.

[0096] 5. The catalyst of embodiment 1, wherein the amorphous particles of SiO2 contain a plurality of non-hydrogen-bonded silanol groups and have less than about 10 ppm of Group VIII metal impurities as analyzed by inductively coupled plasma spectroscopy.

[0097] 6. The catalyst of embodiment 1, produced by a process comprising size reducing a plurality of fused silica particles.

[0098] 7. The catalyst of embodiment 6, wherein reducing the size of the fused silica comprises increasing the silanol to siloxane ratio.

[0099] 8. The catalyst of embodiment 6, wherein reducing the size of the fused silica comprises at least crushing, milling, cutting, hot melt extrusion, or any combination thereof.

[0100] 9. The catalyst of embodiment 7, wherein at least a portion of the silanols comprise non-hydrogen bonded silanols.

[0101] 10. The catalyst of embodiment 9, wherein a majority of the silanols comprise non-hydrogen bonded silanols.

[0102] 11. The catalyst of embodiment 6, further comprising sieving the reduced fused silica to a size of from about 5 nm to about 1 cm.

[0103] 12. A methane dehydrogenation process comprising:

[0104] subjecting a methane feedstock to a catalyst under dehydrogenating conditions; producing hydrogen, one or more alkanes, one or more alkenes, one or more alkynes, one or more aromatics, or any mixture thereof; Including,

[0105] the catalyst comprises a plurality of amorphous particles of SiO2;

[0106] The amorphous particles have a nominal diameter of about 5 nm to about 1 cm;

[0107] A process wherein the amorphous particles have sufficient Lewis acidity to activate C-H bonds in methane and produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

[0108] 13. The process of embodiment 12, wherein the aromatic substance comprises benzene, naphthalene, or any mixture thereof.

[0109] 14. The process of embodiment 12, further comprising separating hydrogen from the catalyst.

[0110] 15. The process of embodiment 12, wherein the dehydrogenation conditions comprise a temperature of at least about 800°C up to about 1200°C.

[0111] 16. The process of embodiment 12, wherein the dehydrogenation conditions comprise a residence time of from about 0.05 to about 100 seconds.

[0112] 17. The process of embodiment 12, wherein the methane feedstock comprises at least about 70% methane.

[0113] 18. The process of embodiment 17, wherein the methane feedstock further comprises nitrogen.

[0114] 19. The process of embodiment 12, wherein the methane conversion is at least 15%.

[0115] 20. The process of embodiment 12, wherein a mixture comprising hydrogen, ethylene, acetylene, and aromatics or a mixture of aromatics is produced.

[0116] 21. The process of embodiment 12, wherein the alkane comprises ethane, propane, butane, pentane, or any mixture thereof.

[0117] 22. The process of embodiment 12, wherein the alkene comprises ethylene, propylene, butene, pentene, an unsaturated C2-C5 hydrocarbon, or any mixture thereof.

[0118] 23. The process of embodiment 12, wherein the alkyne comprises acetylene, propyne, or any mixture thereof.

[0119] 24. The process of embodiment 13, wherein the aromatic material further comprises other polynuclear aromatic compounds.

Claims

1. 1. A catalyst for methane dehydrogenation, comprising: comprising a plurality of amorphous particles of SiO2; the amorphous particles have a nominal diameter of about 5 nm to about 1 cm; and A catalyst, wherein the amorphous particles have sufficient Lewis acidity to activate multiple C—H bonds in methane to produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

2. 10. The catalyst of claim 1, which is metal-free.

3. SiO ２ 2. The catalyst of claim 1, wherein said amorphous particles of include a plurality of non-hydrogen bonded silanol groups.

4. 10. The catalyst of claim 1, comprising less than about 10 ppm of iron impurity as analyzed by inductively coupled plasma spectroscopy.

5. SiO ２ 2. The catalyst of claim 1, wherein said amorphous particles of said catalyst comprise a plurality of non-hydrogen bonded silanol groups and have less than about 10 ppm of Group VIII metal impurities as analyzed by inductively coupled plasma spectroscopy.

6. 10. The catalyst of claim 1 produced by a process comprising size reducing a plurality of fused silica particles.

7. 7. The catalyst of claim 6, wherein reducing the size of the fused silica comprises increasing the silanol to siloxane ratio.

8. 7. The catalyst of claim 6, wherein reducing the size of the fused silica comprises at least crushing, milling, cutting, hot melt extrusion, or any combination thereof.

9. 8. The catalyst of claim 7, wherein at least a portion of the silanols comprise non-hydrogen bonded silanols.

10. 10. The catalyst of claim 9, wherein a majority of the silanols comprise non-hydrogen bonded silanols.

11. 7. The catalyst of claim 6, further comprising sieving the reduced fused silica to a size of about 5 nm to about 1 cm.

12. 1. A methane dehydrogenation process comprising: subjecting a methane feedstock to a catalyst under dehydrogenating conditions; producing hydrogen, one or more alkanes, one or more alkenes, one or more alkynes, one or more aromatics, or any mixture thereof; Including, The catalyst is SiO ２ a plurality of amorphous particles of the amorphous particles have a nominal diameter of about 5 nm to about 1 cm; wherein the amorphous particles have sufficient Lewis acidity to activate C—H bonds in methane and produce methyl radicals when the catalyst is subjected to methane dehydrogenation conditions.

13. 13. The process of claim 12, wherein the aromatic material comprises benzene, naphthalene, or any mixture thereof.

14. 13. The process of claim 12, further comprising separating hydrogen from the catalyst.

15. 13. The process of claim 12, wherein the dehydrogenation conditions include a temperature of at least about 800°C up to about 1200°C.

16. 13. The process of claim 12, wherein the dehydrogenation conditions comprise a residence time of from about 0.05 to about 100 seconds.

17. 13. The process of claim 12, wherein the methane feedstock comprises at least about 70% methane.

18. 20. The process of claim 17, wherein the methane feedstock further comprises nitrogen.

19. 13. The process of claim 12, wherein the methane conversion is at least 15%.

20. 13. The process of claim 12, which produces a mixture comprising hydrogen, ethylene, acetylene, and aromatics, or a mixture of aromatics.

21. 13. The process of claim 12, wherein the alkane comprises ethane, propane, butane, pentane, or any mixture thereof.

22. The alkene is ethylene, propylene, butene, pentene, unsaturated C ２ ~C ５ 13. The process of claim 12, wherein the mixture comprises a hydrocarbon, or any mixture thereof.

23. 13. The process of claim 12, wherein the alkyne comprises acetylene, propyne, or any mixture thereof.

24. 14. The process of claim 13, wherein the aromatic material further comprises other polynuclear aromatic compounds.

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