Palladium catalytic systems for reforming in cyclic flow reactors.

Abstract

Palladium-based catalytic systems for the reforming of hydrocarbons are provided, as well as methods for using such catalytic systems. The catalytic systems can be deposited or otherwise coated on surfaces or structures, such as monoliths, to improve activity and / or structural stability. It has been found that for palladium-based catalytic systems, loss of catalytic activity for reforming over time can be reduced or minimized by operating the reactor / reaction cycle such that a portion of the reaction environment containing the palladium-based catalytic system is not exposed to oxidizing conditions at temperatures between 600°C and 900°C. Optionally, the reactor can also be operated / reaction cycle can also be designed such that the peak temperature of the portion of the reaction environment containing the palladium-based catalytic system during the reforming cycle is 1300°C or less.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to a palladium-based catalyst system for use in hydrocarbon reforming in high temperature environments. [Background technology]

[0002] BACKGROUND OF THEINVENTION A countercurrent reactor is an example of a reactor type that is beneficial for use in processes with cyclic reaction conditions. For example, due to the endothermic nature of the reforming reaction, additional heat needs to be consistently introduced into the reforming reaction environment. A countercurrent reactor can provide an efficient way to introduce heat into the reaction environment. After a portion of the reaction cycle is used for reforming or another endothermic reaction, a second portion of the reaction cycle can be used for combustion or another exothermic reaction to add heat to the reaction environment in preparation for the next reforming step. U.S. Pat. No. 7,815,873 and U.S. Pat. No. 8,754,276 provide examples of using a countercurrent reactor to carry out various endothermic processes in a cyclic reaction environment.

[0003] Endothermic reactions such as reforming can also benefit from having a significant amount of available catalytic surface area. Ceramic monolith structures are an example of a type of structure that can provide high available surface area. One option is to use a monolith that corresponds to a packed array of cells or channels through which reactant gases pass. A washcoat is added to such a monolith to provide catalytic activity.

[0004] Although counter-current reactors provide an efficient method for introducing heat into the reaction environment, the peak temperatures encountered within the reforming environment of a counter-current reactor tend to be higher than those of a conventional steam methane reformer. These higher temperatures can reduce catalyst activity over time, although at least some of the mechanisms leading to such activity loss are not fully characterized. It would be beneficial to have a system and method for conducting reforming reactions in a counter-current reactor environment that can reduce, minimize, or mitigate changes in catalyst activity over time.

[0005] US Patent Application Publication No. 2020 / 0030778 describes a monolith structure for use in hydrocarbon reforming, where the monolith structure is composed of a mixture of one or more dopant metal oxides and one or more structural oxides. The dopant metals and structural oxides are selected based on the relative Gibbs free energy values ​​of the dopant metal oxides and the structural oxides. NiO and Al2O3 are described as examples of suitable combinations of dopant metal oxides and structural oxides to form the monolith structure. Summary of the Invention

[0006] Summary of the Invention In various embodiments, a method for reforming hydrocarbons is provided. The method includes exposing a reactant stream comprising reformable hydrocarbons to a catalyst system in a reaction zone of a reactor to form a product stream comprising H2. The reaction zone includes a catalyst system supported on one or more surfaces of a support structure. The catalyst system includes Pd in ​​at least a portion of the reaction zone. The method further includes reacting a mixture comprising a fuel and 0.1 vol% or more O2 under combustion conditions in a combustion zone of the reactor, and heating one or more surfaces in the reaction zone to a regeneration surface temperature of 1000°C to 1300°C. In various embodiments, a minimum temperature in at least a portion of the reaction zone at the end of the exposure is 900°C or greater and / or a minimum temperature in at least a portion of the reaction zone at the start of the reaction can be 900°C or greater. [Brief description of the drawings]

[0007] [Figure 1] An example of the operation of a counter-flow reactor is given below. [Diagram 2] An example of a counter-flow reactor is shown. [Diagram 3] 1 shows an example of a catalyst system deposited on the surface of a honeycomb monolith. [Figure 4] 1 shows an example of a temperature profile for carrying out steam reforming in a counterflow reactor. [Diagram 5] 1 shows flame ionization detection (FID) results of the output flow from reforming a methane stream in the presence of a Ni-based catalyst. [Figure 6] 1 shows FID results of the output flow from reforming a methane stream in the presence of a lower amount of Ni-based catalyst. [Figure 7] 1 shows the FID results of the output flow from reforming a methane stream in the presence of a Rh-based catalyst. [Figure 8] 1 shows the FID results of the output flow from reforming a methane stream in the presence of a Pd-based catalyst. [Figure 9] 1 shows the conversion of methane during reforming under cyclic reforming conditions in the presence of various catalyst systems. [Figure 10] 1 shows the thermal conductivity results of exposing a Pd-containing catalyst system to an O2-containing gas stream at various temperatures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Detailed Description of the Embodiments All numerical values ​​within the detailed description and claims herein are modified by the value indicated as "about" or "approximately" to account for experimental error and variations that would be expected by one of ordinary skill in the art.

[0009] (overview) In various embodiments, palladium-based catalyst systems are provided for the reforming of hydrocarbons, along with methods for using such catalyst systems. The catalyst systems can be deposited or otherwise coated on surfaces or structures, such as monoliths, to improve activity and / or structural stability. It has been found that for palladium-based catalyst systems, loss of catalytic activity over time for reforming can be reduced or minimized by operating the reactor / reaction cycle such that a portion of the reaction environment containing the palladium-based catalyst system is not exposed to oxidizing conditions at temperatures between 600°C and 900°C. Optionally, the reactor can also be operated / reaction cycle can also be designed such that the peak temperature of the portion of the reaction environment containing the palladium-based catalyst system during the reforming cycle is 1300°C or less.

[0010] It is noted that oxidation of Pd may occur below 600°C, and that the Pd in ​​the catalyst system may be present in oxide form before starting the cyclic reforming process. When the temperature of the Pd-containing portion of the catalyst system is below 600°C, the Pd-containing portion of the catalyst system may be heated in the presence of a reducing and / or inert environment back to a temperature above 900°C before exposing the Pd-containing portion of the catalyst system to an oxidizing environment. It is noted that the Pd-containing catalyst system may also be referred to as a palladium-based catalyst system. It is further noted that the Pd-containing / palladium-based catalyst system does not require that Pd be distributed throughout the catalyst system. For example, a first portion of the catalyst system may contain Pd, while a second portion of the catalyst system intended for operation at a lower temperature may have a lower concentration of Pd or may be substantially free of Pd.

[0011] Without being bound to any particular theory, it has been discovered that a portion of the loss of reforming activity of a catalytic system in a direct heat transfer, cyclic flow reaction environment can be attributed to the volatilization of the catalytic metals at the relatively high temperatures present in such an environment. Such metals can be volatilized in oxide or metallic form. Once the metal is volatilized, the flow within the reaction environment can carry the metal to different locations within the reaction environment and / or completely remove the metal from the reaction environment. This can result in a loss of catalytic activity (due to transport of the catalyst to portions of the reaction environment that operate at lower temperatures). Furthermore, such loss of metals can also potentially reduce the stability of the catalytic system over time.

[0012] It has further been discovered that the use of a palladium-based catalyst system can reduce or minimize the difficulties associated with catalyst volatility when the palladium-based catalyst system is paired with an appropriate reforming reaction cycle. In various embodiments, a reforming reaction cycle can be used such that in at least a portion of the reaction zone in the reactor containing the palladium-based catalyst system, a temperature profile is maintained in which the palladium-based catalyst system is exposed to oxidizing conditions at a temperature of 900°C or higher, such as up to 1300°C. In other words, at the beginning of the exposure to oxidizing conditions, the minimum temperature of the portion of the reaction zone containing the Pd-containing catalyst system can be 900°C or higher. Additionally or alternatively, during and / or at the end of the exposure to oxidizing conditions, the peak or maximum temperature of the portion of the reaction zone containing the Pd-containing catalyst can be 1300°C or lower. Exposure to oxidizing conditions can occur, for example, when a fuel reacts with oxygen in or near the reaction zone to provide heat for the next reforming step of the reforming reaction cycle. In some embodiments, even further stability can be achieved by maintaining the Pd-containing portion of the catalyst system when exposed to oxidizing conditions at temperatures of 950° C. or higher, or 1000° C. or higher, such as up to 1300° C. Oxidation of Pd in ​​a palladium-based catalyst system can be reduced, minimized, or avoided by maintaining the temperature of at least one region at 900° C. or higher when fuel is reacted with oxygen near the palladium-based catalyst system (and / or when oxidizing conditions are otherwise present).

[0013] At temperatures above 900°C, Pd is resistant to conversion to the oxide form. However, at temperatures above 900°C, the volatility of the oxide form of Pd is substantially greater than that of metallic Pd. By reducing, minimizing, or eliminating the exposure of Pd to oxidizing conditions at temperatures below 900°C during the reforming cycle, Pd in ​​a palladium-based catalyst system can maintain the metallic state throughout the reforming cycle. Due to the substantially lower volatility of metallic Pd at temperatures between 900°C and 1300°C, any loss of catalytic activity due to catalyst volatility is thereby reduced or minimized, and difficulties associated with volatilization of Pd oxides at high temperatures can be avoided. At temperatures above 1300°C, Pd may begin to become increasingly volatile even without exposure to an oxidizing environment. Without being bound to any particular theory, it is noted that the melting point of Pd is about 1550°C. At temperatures above 1300° C., the volatility of Pd metal is believed to increase sufficiently to reduce or minimize the benefit of the volatility difference between Pd metal and oxides of Pd.

[0014] In this discussion, the catalyst system is defined to include at least a catalytic metal (either in metallic or oxidic state) and at least one metal oxide support layer. In at least a portion of the reaction zone, the catalyst system can include Pd. Optionally, other catalytic metals (metallic and / or oxidic forms) can also be present in at least a portion of the reaction zone and / or in other portions of the reaction zone. In some embodiments, the catalyst and the metal oxide support layer can be simultaneously coated onto the monolith, such as in the form of a washcoat layer on the support. In such embodiments, the catalyst can be mixed with the metal oxide support layer. Alternatively, the catalyst and the metal oxide support layer can be deposited sequentially, with the support layer being deposited first, followed by the catalyst. In some optional embodiments, the metal oxide support layer can correspond to a thermally stable metal oxide support layer, such as a metal oxide support layer that is thermally phase stable at temperatures between 800° C. and 1600° C. Optionally, an intermediate tie layer can be applied to at least a portion of the monolith or other structure prior to depositing the catalyst system. The catalyst system may be beneficial for use in a cyclic reaction environment, such as a counter-flow reactor or other type of reactor operated using opposite flows and different times within the reaction cycle. The reaction conditions in a cyclic reaction environment may also be subject to fluctuations in temperature and / or pressure during the reaction cycle.

[0015] To use the catalyst system in a cyclic reaction environment, the catalyst system can be typically coated or otherwise supported on a structure or surface that is present in the reaction environment during a polymerization process cycle. For example, the catalyst system can be applied as a washcoat on the surface of one or more monoliths or other structures disposed in the reactor. Such monoliths or other structures can include a large number of channels or cells per unit surface area to substantially increase the amount of structural surface area that can be coated with the catalyst system. In some embodiments, the catalyst system can be deposited on a monolith or other structure comprised of a low surface area material that is phase stable under high temperature reforming conditions. In such embodiments, the catalyst system and monolith or other structure can be annealed at a temperature equal to or higher than the processing temperature prior to use. This can provide additional structural stability to the catalyst system, resulting in an unexpected increase in the amount of time that the catalyst system can substantially retain a desired level of reforming activity.

[0016] 3 shows an example of a portion of a monolith 300, including a catalyst system 310 deposited (or otherwise coated) on the surface of the monolith 300. In the example shown in FIG. 3, the portion of the monolith corresponds to a regular pattern of square cells that allow reactive gases (such as a reformed feed gas flow) to pass through the cells. In other embodiments, any convenient type of cell shape can be used, such as circular or hexagonal cells. The catalyst system 310 corresponds to a layer including a catalyst 312 and a metal oxide support 314 coated on the surface of the cells of the monolith.

[0017] In some embodiments, the catalyst system can correspond to one or more catalysts in a single zone, with at least one of the catalysts corresponding to Pd. In other embodiments, the catalyst system can correspond to multiple catalyst zones, with a catalyst corresponding to Pd being present in at least one of the catalyst zones. Optionally, in such embodiments, at least one catalyst zone can include a different catalyst than the catalyst in a second catalyst zone.

[0018] Reforming of hydrocarbons to form synthesis gas is a potentially desirable route to reduce or minimize the CO2 emissions associated with hydrocarbon fuels. Reforming can convert hydrocarbon fuels to H2, a fuel with no CO2 emissions, and CO or CO2. By separating H2 from carbon oxides at a single location, some of the difficulties associated with preventing CO2 emissions can be reduced or minimized. However, due to the high temperatures required for hydrocarbon reforming, balancing efficient hydrocarbon reforming with energy consumption and operational life of the equipment remains a challenge.

[0019] One option to improve the energy efficiency of the reforming process can be to use a reaction system such as a counter-current reactor or another type of reaction system where the flow passes through the reactor in opposite directions during the reforming and regeneration (heating) steps. Counter-current reactors (and other similar types of reactors) can provide several types of advantages. First, the use of multiple steps with different flows during the reaction cycle allows for heating to the reaction zone where reforming occurs by performing combustion in or near the reaction zone. This can reduce or minimize heat losses while attempting to add heat to the reaction zone. The use of flows in opposite directions can provide further advantages with regard to developing a desired temperature profile in the reaction zone. Although a counter-current reactor is used herein as an example of this type of system, it is understood that a counter-current reactor is an example of a reactor that can provide such advantages.

[0020] (Reforming catalyst and metal oxide support layer) In various embodiments, one option for adding a reforming catalyst to a monolith can be to coat the monolith with a mixture of the catalyst (optionally in oxide form) and the metal oxide support layer. For example, a powder of the catalyst oxide and the metal oxide support layer can be used to form a washcoat that is then applied to the monolith (or other structure). This can result in a catalyst system in which the catalyst is mixed into / dispersed throughout the metal oxide support layer, as opposed to the catalyst being deposited on top of the metal oxide support layer. In other words, at least a portion of the catalyst system can correspond to a mixture of the catalyst and the support layer. In other embodiments, any convenient method can be used to deposit or otherwise coat the catalyst system on a monolith or other structure. The weight of the catalyst system on the monolith (or other structure) can correspond to 0.1% to 10% by weight, or 0.5% to 10% by weight, or 2.0% to 10% by weight, or 0.1% to 6.0% by weight, or 0.5% to 6.0% by weight, or 2.0% to 6.0% by weight of the total weight of the catalyst system plus monolith.

[0021] In some embodiments, the catalyst system can include a thermally stable metal oxide support layer. A thermally stable metal oxide support layer corresponds to a metal oxide that is thermally stable with respect to structural phase change at temperatures between 800° C. and 1600° C. In some embodiments, such a thermally stable metal oxide support layer has a surface area of ​​20 m 2 The thermally stable metal oxide coating can be formed by coating the surface (e.g., using a washcoat) with a metal oxide powder having a density of 0.5 m / g or less. For example, the metal oxide powder used to form the thermally stable metal oxide coating can be 0.5 m / g or less. 2 / g~20m 2 / g, or 1.0m 2 / g~20m 2 / g, or 5.0m 2 / g~20m 2The catalyst may have a surface area of ​​1000° C. / g. In various embodiments, the catalyst may be annealed at a temperature of 1000° C. or higher, or 1100° C. or higher, or 1200° C. or higher, or 1300° C. or higher, such as up to 1500° C., or even higher. This temperature may be substantially equal to or higher than the peak temperature to which the catalyst is exposed during the reforming process cycle. In some embodiments, the annealing temperature may be between 1000° C. and 1300° C. An annealing temperature substantially similar to the peak temperature may correspond to an annealing temperature that is 0° C. to 50° C. different from the peak temperature.

[0022] As an example of a thermally stable metal oxide support layer, alumina has various phases such as α-Al2O3, γ-Al2O3, and θ-Al2O3. Metal powder of α-Al2O3 is typically 20 ml. 2 In contrast, the γ-Al2O3 and θ-Al2O3 phases have higher surface areas, and metal powders for use in γ-Al2O3 and / or θ-Al2O3 washcoat solutions can have surface areas of up to 20 m 2 / g. Conventionally, phases such as θ-alumina and γ-alumina are considered superior support structures for deposited catalysts, as their larger surface area per gram makes more catalytically active sites available than α-alumina. However, phases such as γ-Al2O3 and θ-Al2O3 are not thermally phase stable at temperatures between 800°C and 1600°C. At such high temperatures, phases such as γ-Al2O3 and θ-Al2O3 undergo phase transitions to more stable phases. For example, at high temperatures, γ-Al2O3 first transforms to Δ-Al2O3 at approximately 750°C, which then transforms to θ-Al2O3 at approximately 950°C, and then θ-Al2O3 transforms to α-Al2O3 while exposed to further high temperatures of 1000°C to 1100°C. Therefore, α-Al2O3 is a thermostable version of Al2O3 at temperatures between 800℃ and 1600℃.

[0023] Without being bound to any particular theory, it is believed that such phase changes during exposure to high temperatures may contribute to the decomposition of the catalyst and / or the structure supporting the catalyst. In contrast, by using a support that is phase stable at high annealing temperatures and then annealing the catalyst (including the support) at high annealing temperatures, the resulting catalyst can maintain substantially its initial catalytic activity level for an extended period of time. It is noted that the initial catalytic activity achieved by depositing a catalyst on a monolith formed from a phase-stable, low surface area per gram material may be lower than depositing the catalyst on a similar monolith formed from a material having a higher surface area per gram. However, it has been discovered that this initial activity advantage for higher surface area materials is rapidly lost during exposure to cyclic high temperature reforming conditions.

[0024] By way of further example, and without being bound to any particular theory, γ-Al2O3 is a transition alumina that can be considered a defect oxyhydroxide with a spinel-related crystal structure. Previous academic studies have suggested that γ-Al2O3 is formulated as an alumina spinel, with the defect sites being Al 8 / 3 □ 1 / 3 O4, where □ represents an open cationic site. 2.5 □ 0.5 O 3.5 (OH) 0.5Such γ-Al2O3 is thermally unstable compared to α-Al2O3. θ-Al2O3 is more crystalline and has a lower surface area and hydroxide content compared to γ-Al2O3, but θ-Al2O3 also contains defect sites (i.e., open cation sites and is thermally unstable compared to α-Al2O3). Thus, both γ- and θ-Al2O3 have defect sites (□) that can react with multivalent cations (or metal oxides). Both Rh(O) and Ni(O) can react to produce denser phases, and Rh and Ni may not be chemically accessible for catalytic reactions compared to their oxide or metallic states. Even in the absence of reactions with Rh or Ni, γ- and θ-Al2O3 are thermodynamically unstable compared to α-Al2O3 under high temperature conditions.

[0025] It has been discovered that using thermally stable metal oxides in catalytic systems in combination with annealing the catalytic system on a monolith at high temperatures can provide unexpected activity and structural stability benefits over extended periods of time. Without being bound to any particular theory, it is believed that when catalytic systems including non-thermally stable metal oxides are used as coatings for monoliths, exposure of such catalytic systems to cyclic high temperature reforming environments can cause structural decomposition of the catalytic system. It is believed that this structural decomposition of the catalytic system can contribute to a reduction in available catalytic sites, possibly due to the catalyst becoming embedded within the decomposed structure and / or additional sintering or agglomeration of the catalyst as the non-thermally stable metal oxides in the catalytic system are converted to lower surface area phases. This structural decomposition can be observed, for example, by examining the catalytic system on a monolith after exposure to cyclic high temperature reaction environments. In conventional catalytic systems, the catalytic system is easily chipped away from the underlying structure after exposure to cyclic high temperature reaction environments. Furthermore, a substantial decrease in activity can be observed.

[0026] In contrast, when using a catalytic system that includes a thermally stable metal oxide, the activity of the catalyst in the catalytic system can unexpectedly be maintained for extended operating times with little or no loss of activity. Furthermore, after exposure to a cyclic high temperature reforming environment, the catalytic system can unexpectedly remain strongly attached or coated on the underlying monolith or other structure. It should be noted that because thermally stable metal oxides typically have a relatively low surface area, the initial catalytic activity may be lower than that of a conventional system. This would initially reduce the number of available catalytic sites. However, because thermally stable metal oxides do not undergo a phase transition when exposed to heat, the catalytic activity of the catalytic system that includes the thermally stable metal oxide can be maintained. Due to the rapid deactivation of the conventional catalyst or catalytic system, the activity of the conventional catalytic system can rapidly fall below that of a catalytic system that uses a thermally stable metal oxide.

[0027] The catalyst system can be applied to the monolith or other structure, for example, by applying the catalyst system as a washcoat suspension. To form the washcoat suspension, the catalyst system can be added to water to form an aqueous suspension having 10% to 50% solids by weight. For example, the aqueous suspension can include 10% to 50% solids by weight, or 15% to 40% by weight, or 10% to 30% by weight. Optionally, an acid or base can be added to the aqueous suspension to reduce or increase the pH, respectively, to change the particle size distribution of the alumina catalyst and / or binder particles. For example, acetic acid or another organic acid can be added to achieve a pH of 3 to 4. The suspension can then be ball milled (or otherwise processed) to achieve a desired particle size of the catalyst particles, such as a particle size of 0.5 μm to 5 μm. After milling, the suspension can be stirred until the time of use to ensure that the particles are substantially uniformly distributed in the solution.

[0028] The washcoat suspension can then be applied to the monolith structure to provide the desired amount of catalyst (such as nickel or rhodium) on the monolith surface. As an example, in one embodiment, a washcoat thickness of 10 microns was achieved by forming a washcoat corresponding to 10% by weight of the monolith structure. Any convenient type of monolith structure can be used to provide a substantial surface area for supporting catalyst particles. The washcoat can be applied to the monolith to form cells having an inner surface coated with the catalyst. One option for applying the washcoat can be to dip or otherwise submerge the monolith in the washcoat suspension.

[0029] After clearing the cell channels of excess washcoat, the catalyst system coated on the monolith can be optionally dried. Drying can correspond to heating at 100° C. to 200° C. for 0.5 hours to 24 hours. After any optional drying, calcination can be performed. In some embodiments, calcination can correspond to heating at 200° C. to 800° C. for 0.5 hours to 24 hours.

[0030] In other aspects, a high temperature calcination step can be used such that the calcination temperature for the catalytic system coated on the monolith is substantially equal to or greater than the peak temperature to which the monolith is exposed during the cyclic high temperature reforming reaction. For monoliths in the high temperature zone, this can correspond to calcining the catalytic system coated on the monolith at a temperature of 900° C. or more, or 1000° C. or more, or 1200° C. or more, or 1300° C. or more, for example up to 1500° C. or even higher. Note that if multiple catalytic zones are present, the calcination of the monoliths in the different catalytic zones may be different.

[0031] It has been unexpectedly discovered that performing a calcination at a temperature equal to or higher than the peak temperature during a cyclic high temperature reforming process can unexpectedly allow for improved activity of the catalyst system and / or adhesion of the catalyst system to the underlying monolith. Without being bound to any particular theory, it is believed that exposing the monolith and deposited catalyst system to high temperatures prior to exposing the catalyst to the cyclic reaction environment facilitates the formation of a stable interface between the catalyst system and the monolith. This stable interface can then have improved resistance to the high temperature oxidizing and / or reducing environments during the reforming process, resulting in improved stability for maintaining the catalyst system on the surface of the monolith.

[0032] In various embodiments, at least a portion of the catalyst system can have Pd as the catalyst (or as at least a portion of the catalyst). During operation, this region or zone can be maintained at a temperature between 900° C. and 1300° C. when the catalyst is exposed to oxidizing conditions. Because oxidizing conditions are used to provide heat to the reaction cycle, in some embodiments, maintaining a temperature between 900° C. and 1300° C. can correspond to having at least one region containing Pd as a catalyst at a temperature of 900° C. or higher starting the regeneration step of the reaction cycle, and then having a temperature of 1300° C. or lower at the end of the regeneration step, since the oxidizing conditions are used to provide heat to the reaction cycle.

[0033] It should be noted that even if some of the Pd in ​​the reaction zone begins in the form of palladium oxide, such Pd can be readily converted to metallic Pd. This can be accomplished, for example, using an initial activation step in the presence of H2. Another option can be to simply conduct one or more reforming cycles as long as at least some H2 is present in the portion of the reaction zone that contains Pd. Since Pd resists oxidation at temperatures between 900°C and 1300°C, once Pd is converted to the metallic form, it can remain substantially metallic during the conduct of cyclic reforming reactions under conditions in which Pd is exposed to oxidizing conditions between 900°C and 1300°C.

[0034] In some embodiments, a catalytic system can be used in which Pd and another catalytic metal are used. In other embodiments, multiple regions or zones of the catalyst can be used, with a first region or zone containing a Pd-containing catalyst, while one or more other zones can be selected to have a different catalyst, possibly corresponding to a catalyst that does not contain Pd. In embodiments in which the catalyst contains a metal other than Pd and / or some of the catalysts do not contain Pd, suitable catalytic metals can include, but are not limited to, Ni, Co, Fe, Rh, Ru, Pt, Ir, Cu, Ag, Au, Zr, Cr, Ti, V, Mo, Nb, and combinations thereof. The catalytic metals can be selected based on the type of catalytic activity desired. Such catalytic metals can be used in the catalyst in the form of metal oxides. In some embodiments, Ni, Rh, Ru, Pt, Ir, Cu, Co, or combinations thereof can be suitable catalytic metals in combination with Pd and / or in regions or zones in which catalysts other than Pd are used for reforming hydrocarbons in the presence of H2O and / or CO2 to make hydrogen. The weight of the catalytic metal oxide in the catalyst system can range from 0.1 wt.% to 70 wt.%, or 1.0 wt.% to 60 wt.%, or 2.0 wt.% to 50 wt.%, based on the total weight of the catalyst system. In some embodiments where the catalytic metal is a precious metal or corresponds to a precious metal, the weight of the catalytic metal oxide in the catalyst system can range from 0.1 wt.% to 10 wt.%, or 0.2 wt.% to 7.0 wt.%, or 0.5 wt.% to 4 wt.%.

[0035] The catalytic metals can be selected to provide long-term stable performance in a particular temperature zone of the catalytic bed. This allows for stable methane conversion, phase stability with the metal oxide support, and reduced or minimized sintering of the catalytic metal. As an example including three catalytic zones, the catalytic system in the highest temperature catalytic zone (e.g., 900-1300°C), which is exposed to the highest temperatures and some of the most severe temperature fluctuations, can be composed of Pd as the catalytic metal and Al2O3 as the metal oxide support. This catalytic system can be formed, for example, by using a mixture of Pd and Al2O3 as a washcoat on an α-Al2O3 monolith. In such an example, the catalytic system in the medium temperature catalytic zone (e.g., 600-1150°C) can be composed of Ni and Rh as the catalytic metal (NiO and Rh2O3 as the catalytic metal oxides) and Al2O3 as the metal oxide support. To form this catalytic system, NiO and Rh2O3 as the catalytic materials and 、 A mixture with Al2O3 (optionally but preferably α-Al2O3) as the metal oxide support material can be washcoated onto a monolith containing 95 wt% α-Al2O3, 4 wt% SiO2, and 1 wt% TiO2. In such an example, the catalyst system in the low temperature catalytic zone (e.g., 400-1050°C) can be composed of Rh as the catalytic metal (Rh2O3 as the catalytic metal oxide) and α-Al2O3 as the metal oxide support. To form this catalyst system, a mixture of Rh2O3 and α-Al2O3 as the catalytic materials can be washcoated onto a monolith containing 93 wt% α-Al2O3, 5 wt% SiO2, and 2 wt% MgO.

[0036] In various embodiments, suitable metals for the metal oxide support layer in the catalytic system include, but are not limited to, Al, Si, Mg, Ca, Sr, Ba, K, Na, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Co, Y, La, Ce, and combinations thereof. The metal (or metals) for the metal oxide support can be selected such that the metal oxide support is not substantially converted to metallic form under the reducing conditions present in the cyclic reaction environment. As an example, when the catalytic metal oxide is NiO, one choice for the metal oxide support is Al2O3, preferably α-Al2O3. Another example of a suitable metal oxide support, optionally combined with NiO as the catalytic metal oxide, is a mixture of Al2O3 with SiO2, MgO, and / or TiO2. In such an example, SiO2 can combine with Al2O3 to form a mullite phase that can increase resistance to thermal shock and / or mechanical failure. Additionally or alternatively, in such examples, MgO and / or TiO2 may be added. The weight of the metal oxide support in the catalyst bed may range from 1.0 wt% to 40 wt%, or 2.0 wt% to 30 wt%, or 3.0 wt% to 20 wt%, based on the total weight of the monolith in the catalyst bed.

[0037] In various embodiments, the metal oxide support layer (e.g., a thermally stable metal oxide support layer) can correspond to at least one oxide selected from corundum, stabilized zirconia, perovskite, pyrochlore, spinel, hibonite, zeolite, and mixtures thereof. The weight of the metal oxide support can range from 1.0% to 40% by weight, or 2.0% to 30% by weight, or 3.0% to 20% by weight, based on the total weight of the monolith + catalyst system.

[0038] One category of metal oxide support layers can correspond to conventional flame retardant oxides commonly used to form supported catalysts. For example, metal oxide supports include α-Al2O3, LaAlO3, LaAl 11 O 18, MgO, CaO, ZrO2, TiO2, CeO2, Y2O3, La2O3, SiO2, Na2O, K2O, and mixtures thereof. This genus is defined herein as the "corundum" genus of oxides, although many of the oxides in this genus do not have a corundum lattice structure. For example, CeO2 and MgO can both have a halite crystal structure. α-Al2O3 consists essentially of a tight arrangement of oxygen ions in hexagonal close packing, with Al filling two-thirds of the available octahedral sites. 3+ LaAlO3 (often abbreviated as LAO) is an optically transparent ceramic oxide with a distorted perovskite structure. 11 O 18 can be formed by the solid-state reaction of LaAlO3 and α-Al2O3. The catalytic metal can be trapped between the plate-like crystal structures, so that LaAl 11 O 18 Plate-like crystals of are particularly useful as metal oxide supports, suppressing sintering of small catalytic metals in the active material washcoated onto the monoliths of the catalyst bed. Further examples of oxides from the Corundum family include, based on the weight of the metal oxide support, i) 95 wt. % α-Al2O3 and 5 wt. % SiO2; ii) 93 wt. % α-Al2O3, 5 wt. % SiO2 and 2 wt. % MgO; iii) 94 wt. % α-Al2O3, 4 wt. % SiO2, 2 wt. % MgO and 1 wt. % Na2O; iv) 95 wt. % α-Al2O3, 4 wt. % SiO2 and 1 wt. % TiO2; v) 7 wt. % vi) 5 wt.% CaO and 95 wt.% α-Al2O3; vii) 5 wt.% MgO, 5 wt.% CeO2 and 90 wt.% α-Al2O3; viii) 20 wt.% ZrO2 and 80 wt.% CeO2, ix) 5 wt.% CeO2, 20 wt.% ZrO2 and 75 wt.% α-Al2O3, and x) 6 wt.% La2O3 and 94 wt.% α-Al2O3.

[0039] Another category of metal oxides for the metal oxide support layer corresponds to stabilized zirconia. In this discussion, stabilized zirconia as a metal oxide support is defined as an oxide comprising zirconia (ZrO2, zirconium oxide) and at least one additional oxide corresponding to Y2O3, CaO, MgO, HfO2, CeO2, SiO2, Sc2O3, La2O3, Al2O3, and mixtures thereof. Pure ZrO2 undergoes a phase transformation from a monoclinic (stable at room temperature) to a tetragonal (at about 1173 °C) and then a cubic (at about 2370 °C) structure. When making a metal oxide support from pure zirconia, it transforms from a tetragonal structure to a monoclinic structure, resulting in volume expansion, which may lead to fracture at low temperatures. To alleviate this problem, pure ZrO2 can be stabilized to a cubic polymorph over a wide range of temperatures. This is because the Zr in the crystal lattice 4+ Some of the ions (with an ionic radius of 0.082 nm) are 3+ This can be achieved by replacing the doped zirconia with slightly larger ions such as ions (ionic radius of 0.096 nm) and / or ions from other added oxides. The resulting doped zirconia material is called stabilized zirconia. In the present invention, the weight of the additive oxide in the stabilized zirconia can range from 5 wt% to 70 wt%, or 6 wt% to 60 wt%, or 7 wt% to 50 wt%, based on the total weight of the stabilized zirconia composition. The preferred stabilized zirconia is yttria (YO) stabilized zirconia, often abbreviated as YSZ. YSZ is a metal oxide support in which the cubic crystal structure of zirconia is stabilized at room temperature by adding yttria in an amount of 10 wt% to 30 wt% based on the total weight of the YSZ. Other examples of stabilized zirconia as metal oxide supports include, but are not limited to, i) 10 wt% Sc2O3 stabilized zirconia (ScSZ), ii) 6 wt% Sc2O3 and 1 wt% Al2O3 stabilized zirconia (ScAlSZ), iii) 65 wt% CeO2 stabilized zirconia (CSZ), and iv) 30 wt% CeO2 and 20 wt% Al2O3 stabilized zirconia (CeAlSZ).

[0040] Yet another category of metal oxides for the metal oxide support layer corresponds to perovskites. Perovskites as metal oxide supports are based on a cubic perovskite structure of the general formula (ABO3). The "A" and "B" sites can be doped with a number of metal cations, within size constraints. This allows the properties of the metal oxide support to be tailored to achieve various objectives. The A site cations are larger than the B site cations. The ideal cubic structure has the B site cations in 6-fold coordination surrounded by anion octahedra and the A site cations in 12-fold cuboctahedral coordination. The relative ion size requirements for stability of the cubic structure are so strict that slight buckling and distortion can produce several low symmetry distorted versions in which the coordination number of the A site cations, the B site cations, or both, is reduced. Thus, the doped perovskite structure can be represented as the following chemical formula: A x A' 1-x B y B' 1-y O 3-n wherein A or A' is an element selected from La, Sr, Ba, Ca, Zr, and Y, wherein B or B' is an element selected from Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ga, Zr, Y, and Zn, wherein both x and y are numbers independently selected in the range of 0.0 to 1.0, and wherein n is a number in the range of 0.0 to 0.5. Examples of perovskite structures for metal oxide support layers include SrTiO3, CaTiO3, YAlO3, LaMnO3, LaCoO3, and the like. 0.4 Ni 0.6 O3(LCN), Sr 0.65 La 0.35 TiO3(SLT), BaZr 0.8 Y 0.2 O3 (BZY), La 0.8 Sr 0.2 MnO3(LSM), La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O3(LSCF),Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2O3 (BSCF), La 0.6 Sr 0.4 Co 0.8 Cr 0.2 O3 (LSCC), La 0.6 Sr 0.4 Co 0.8 Mn 0.2 O3 (LSCM), La 0.8 Sr 0.2 FeO3(LSF), and Y 0.1 Ba 0.9 CoO3(YBC), but is not limited to this.

[0041] Yet another category of metal oxides for the metal oxide support layer corresponds to pyrochlore. Pyrochlore as a metal oxide support is based on the mineral pyrochlore crystal structure of general formula A2B2O7, where the "A" and "B" species are generally rare earth or transition metal species. The pyrochlore structure is a superstructure derivative of the simple fluorite structure. Thus, similar to perovskites, doped pyrochlore structures can be represented as the following chemical formula: A x A' 2-x B y B' 2-y O 7-n where A or A' is an element selected from La, Sr, Ba, Ca, Gd, Bi, Dy, Tl, Cd, and Y, B or B' is an element selected from Zr, Ti, Cr, Mn, Fe, Co, Ni, Ru, Mo, and Re, both x and y are numbers independently selected in the range of 0.0 to 2.0, and n is a number in the range of 0.0 to 0.5. Examples of pyrochlore structures for metal oxide support layers include La2Zr2O7, Gd 1.9 Ca 0.1 Ti2O 6.9 , Bi2Ru2O7, Dy2Ti2O7, Y2Mo2O7, Tl2Ru2O7, and Cd2Re2O7.

[0042] Yet another category of metal oxides for the metal oxide support layer corresponds to spinels. Spinels as metal oxide supports are based on a spinel structure of the general formula AB2O4, in which the O anions are arranged in a cubic close-packed lattice, and the cations "A" and "B" occupy some or all of the octahedral and tetrahedral sites within the lattice. The charges of A and B in the prototypical spinel structure are +2 and +3, respectively, with A being the most highly charged cation. 2+ B 3+ 2O 2- 4, but other combinations incorporating divalent, trivalent, or tetravalent cations are possible, such as Mg, Zn, Fe, Mn, Al, Cr, Ti, and Si. A and B can also be used to synthesize magnetite, the most abundant member of the spinel group, Fe3O4 (Fe 2+ Fe 3+ 2O 2- As in the case of (as in 4), it can be the same metal with different valences. Thus, the spinel structure can be represented as the following chemical formula: AB2O4, where A is an element selected from Mg, Be, Zn, Fe, Ni, Co, Mn, Cu, Ti, Si, and mixtures thereof, and B is an element selected from the group including Al, Mg, Fe, Mn, Cr, Co, V, and mixtures thereof. Examples of spinel structures of metal oxide supports include MgAl2O4, BeAl2O4, ZnAl2O4, FeAl2O4, NiAl2O4, MnAl2O4, (Mg,Fe)Al2O4, CuFe2O4, (Fe,Mn,Zn)(Fe,Mn)2O4, MnFe2O4, MgFe2O4, NiFe2O4, TiFe2O4, (Zn,Fe)Fe2O4, FeCr2O4, NiCr2O4, MgCr2O4, ZnCr2O4, Mn 1.5 Co 1.5 O4, FeV2O4, MgV2O4, (Mg,Fe)2SiO4, and BeMgAl4O8.

[0043] Yet another category of metal oxides for the metal oxide support layer corresponds to hibonite. Hibonite as a metal oxide support has the general formula AB 12 O 19where "A" is an element selected from a mixture of Mg, Ca, Sr, Ba, Fe, Ni, Co, La, Ce, and Y, and "B" is an element selected from Al, Si, Ti, Zr, Hf, Mg, Ca, and mixtures thereof. Examples of hibonite structures for metal oxide supports include CaAl 12 O 19 , (Ca, Ce) (Al, Ti, Mg) 12 O 19 , (Ca, Ce, La)(Al, Ti, Mg) 12 O 19 , and (Fe, Mg)Al 12 O 19 These include, but are not limited to, hibonite (Ca, Ce) (Al, Ti, Mg) because catalytic metals can be trapped between the platelet crystal structures. 12 O 19 The platelet crystals of can be useful as metal oxide supports, which can inhibit sintering of small catalytic metal particles in the active material washcoated onto the monoliths of the catalyst bed.

[0044] Yet another category of metal oxides for the metal oxide support layer corresponds to zeolites. In this discussion, zeolites as metal oxide supports refer to aluminosilicate materials composed of Si, Al, O, H, and optionally further containing metals such as Na, Ca, K, Mg, Ti, Sn, Zn, and mixtures thereof, which are members of a family of microporous solids known as molecular sieves. The term "molecular sieve" refers to the specific property of these materials to selectively sort molecules based primarily on a size exclusion process. This is due to a highly regular pore structure of molecular dimensions. The maximum size of a molecule or ionic species that can enter the pores of a zeolite is controlled by the dimensions of the channel. These are conventionally defined by the ring size of the opening, for example, the term "8-ring" refers to a closed loop built from eight tetrahedrally coordinated silicon (or aluminum) atoms and eight oxygen atoms. These rings are not always perfectly symmetrical due to various causes, including distortions caused by the bonds between the units required to generate the overall structure, or the coordination of some of the oxygen atoms of the rings to cations within the structure. Zeolites as metal oxide supports in the present invention include over 245 unique zeolite frameworks that are industrially produced on a large scale and over 40 naturally occurring zeolite frameworks. Some examples of zeolites that can be used as metal oxide supports include USY zeolite, L zeolite, mordenite, ferrierite, beta zeolite, ZSM-5, MCM-68, and mixtures thereof. Certain zeolite frameworks are known to be structurally stable up to about 750°C, making them particularly useful for metal oxide supports of active materials for the low temperature catalytic zone of the RFR. The stable micropores of the zeolite provide extensive surface area for catalytic metal dispersion. Other examples of zeolites as metal oxide supports include various types of faujasites. These include faujasite-Na, faujasite-Mg, and faujasite-Ca. All faujasites have the same basic formula (Na2, Ca, Mg) by varying the amounts of sodium, magnesium, and calcium.3.5 [Al7Si 17 O 48 ] 32 (H2O) are shared. Faujasite, like other zeolites, is synthesized from an alumina source such as sodium aluminum and a silica source such as sodium silicate. Other aluminosilicates such as kaolin are also used. The components are dissolved in a basic environment such as aqueous sodium hydroxide and crystallized at 70-300 °C. After crystallization, faujasite is in its sodium form and can be ion-exchanged with ammonium to improve stability. The ammonium ions are later removed by calcination, leaving the zeolite in its acidic form. Depending on the silica-to-alumina ratio of their framework, synthetic faujasite zeolites are divided into X and Y zeolites. In X zeolites, the silica-to-alumina ratio is 2-3, while in Y zeolites it is 3 or more. The negative charge of the framework is balanced by the positive charge of cations in non-framework positions. Such zeolites have ion-exchange, catalytic, and adsorption properties. The stability of the zeolite increases with the silica-to-alumina ratio of the framework. It is also influenced by the type and amount of cations located at non-framework sites. For catalytic cracking, Y zeolites are often used in rare earth hydrogen exchanged form. By using thermal, hydrothermal, or chemical methods, a portion of the alumina can be removed from the Y zeolite framework resulting in high silica Y zeolites. Such zeolites are used in cracking and hydrolysis catalysts. Complete delamination results in faujasite-silica. Yet another example of a zeolite that can be used as the metal oxide support layer is of the formula (Ca,Na2,K2,Mg)Al2Si4O 12 Chabazite has a cation content of 0.05% and a molecular weight of 0.05%. Recognized varieties include chabazite-Ca, chabazite-K, chabazite-Na, and chabazite-Sr, depending on the prominence of the cations represented. Chabazite typically crystallizes in the triclinic system with rhomboidal crystals.

[0045] (Structure (monolith) for supporting catalytic systems) One purpose of using a monolith or another support structure in a reforming environment is to increase the available surface area for holding the deposited catalyst / catalyst system. To accomplish this, some monoliths correspond to structures having a large number of cells or passages that allow gas flow through the monolith. Since each individual cell provides a surface area for deposition of catalyst, the inclusion of a large number of cells or passages per unit area can substantially increase the available surface area for the catalyst.

[0046] In general, monoliths or other structures used to support catalysts / catalyst systems can be formed from materials represented by formula (PQ), where P can be at least one metal selected from the group consisting of Al, Si, Mg, Ca, Sr, Ba, K, Na, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Co, Y, La, Ce, and mixtures thereof. Q is an oxide. Thus, the monolith material (PQ) is a metal oxide.

[0047] In some preferred embodiments, the metal oxide can correspond to aluminum oxide (also known as alumina), Al2O3. The preferred Al2O3 in the present invention is α-Al2O3. Although α-Al2O3 is the preferred crystalline phase, another phase containing sodium oxide (Na2O), which is sometimes an unavoidable impurity in α-Al2O3, namely Na2O(Al2O3) 11 Or NaAl5O8 may also be present.

[0048] Optionally, the monolith or structural material (PQ) can be α-Al2O3 containing at least one additive oxide selected from the group consisting of SiO2, MgO, CaO, TiO2, Na2O, K2O, and mixtures thereof. The weight of the additive oxide in the monolith material composition can range from 0.1 wt% to 15 wt%, or 1.0 wt% to 10 wt%, or 2.0 wt% to 8.0 wt%, based on the total weight of the monolith material composition. As non-limiting illustrative examples, the monolith material (PQ) can be i) 95 wt% α-Al2O3 and 5 wt% SiO2, ii) 93 wt% α-Al2O3, 5 wt% SiO2 and 2 wt% MgO, iii) 93 wt% α-Al2O3, 4 wt% SiO2, 2 wt% MgO and 1 wt% Na2O, and iv) 95 wt% α-Al2O3, 4 wt% SiO2 and 1 wt% TiO2.

[0049] In other embodiments, the monolith material (PQ) can be partially or substantially composed of non-alumina-based oxides. As non-limiting illustrative examples, the monolith material (PQ) can be silica (SiO2), magnesia (MgO), ceria (CeO2), titania (TiO2), zirconia (ZrO2), cordierite (2MgO 2Al2O32SiO2), mullite (3Al2O32SiO2), aluminum titanate (Al2TiO5), magnesium aluminate (MgAl2O4), calcium stabilized zirconia (CaO-ZrO2), magnesium stabilized zirconia (MgO-ZrO2), yttria stabilized zirconia (Y2O3-ZrO2), yttria (Y2O3), barium zirconate (BaZrO3), strontium zirconate (SrZrO3), and mixtures thereof. Further examples of potential monolith materials include SiC, Si3N4, yttrium stabilized zirconia, and Al2TiO5 ceramics. Note that SiC and Si3N4 do not conform to the (PQ) structural formula.

[0050] In some embodiments, the monolith material (PQ) can further include auxiliary components. Such auxiliary components can facilitate easy extrusion and can accommodate additional structural components within the monolith material composition. For example, the monolith material composition can further include one or more silicates containing a metal selected from the group consisting of Al, Si, Ca, Mg, K, Na, Y, Zr, Hf, Ti, Cr, Mn, Fe, Ni, Co, and mixtures thereof. One example is bentonite, an aluminum phyllosilicate clay composed primarily of montmorillonite. Different types of bentonite are named after their respective dominant elements, such as potassium (K), sodium (Na), calcium (Ca), and aluminum (Al). For example, the chemical formula of sodium bentonite is Al2H2Na2O 13 Si4. Some hydroxyl ions (OH-) may be present in silicates, but under high temperature calcination and firing conditions, such hydroxyl groups may be converted to oxide forms. Yet another example is a silicate with the formula Mg3SiO 10 Talc is a clay mineral composed of hydrated magnesium silicate of (OH)2. The nature of basal truncation and non-uniform flat fracture allows it to be foliated into two-dimensional plate morphology that is beneficial for the extrusion of monolithic materials.

[0051] In various aspects, the monolith or other structure for providing a surface for a reforming catalyst system can be prepared by conventional ceramic powder manufacturing and processing techniques, such as, but not limited to, mixing, grinding, degassing, kneading, pressing, extruding, casting, drying, calcining, and sintering. The starting materials can correspond to suitable ceramic powders and organic binder powders in suitable volumetric ratios. The specific process steps can be controlled or adjusted to obtain the desired particle size and porosity ranges, and performance characteristics, by including various manufacturing, property tuning, and processing additives and agents, as is generally known in the art. For example, two or more types of oxide powders can be mixed in the presence of an organic binder and one or more suitable solvents for a time sufficient to substantially disperse the powders in one another. As another example, precursors of the oxides present in the monolith can be dissolved in water in the desired ratio, spray dried, and calcined to create a mixed powder. Such precursors include, but are not limited to, chlorides, sulfates, nitrates, and mixtures thereof. The calcined powders can be further mixed in the presence of an organic binder and a suitable solvent to create a mixed "dough". The mixed "dough" of material can then be placed in a die or form, extruded, dried, or otherwise formed into the desired shape. The resulting "green body" can then be sintered at a temperature in the range of about 1200° C. to 1700° C. for at least 10 minutes, such as 10 minutes to 10 hours, or optionally 10 minutes to 48 hours, or even longer.

[0052] The sintering operation may be carried out under ambient pressure or vacuum in an oxidizing, reducing, or inert atmosphere. For example, the oxidizing atmosphere may be air or oxygen, the inert atmosphere may be argon, and the reducing atmosphere may be hydrogen, CO / CO2, or H2 / H2O mixtures. The sintered body is then typically cooled to ambient conditions. The cooling rate may also be controlled to provide a desired set of grain and pore structures and performance characteristics in a particular component.

[0053] In some embodiments, the monolith material (PQ) can further comprise an intermediate bonding layer. The intermediate bonding layer can be applied to the monolith surface prior to washcoating active material comprising a metal oxide support and a catalytic metal. The intermediate bonding layer provides better adhesion to the washcoated active material. The intermediate bonding layer can comprise a metal oxide, (M) x O y where (M) is at least one metal selected from the group consisting of Al, Si, Mg, Ca, Sr, Ba, K, Na, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Co, Y, La, Ce, and mixtures thereof. Aluminum oxide (also known as alumina), Al2O3, is the preferred metal oxide for the bond layer. As an example of a method for forming the intermediate bond layer, the selected metal oxide (M) x O y can be dispersed in a solution to form a slurry. The slurry can then be washcoated onto the monolith. The selected metal oxide (M) x O y The washcoated monolith is dried and sintered at a temperature in the range of 1100° C. to 1600° C. to create an intermediate bonding layer.

[0054] It has been discovered that limiting the maximum porosity of the final sintered body tends to effectively limit the interconnectivity of the pore spaces with other pore spaces, even if not in practice, to a degree that increases or maximizes the volumetric heat capacity of the sintered body. The porosity range of the monolith or other structure may depend on the desired final component performance characteristics, but is within a range defined by one or more minimum porosity values ​​and one or more maximum porosity values, or any set of values ​​not explicitly recited between the minimum and maximum values. Examples of suitable porosity values ​​are 0 vol% to 20 vol% porosity, or 0 vol% to 15 vol%, or 0 vol% to 10 vol%, or 0 vol% to 5 vol%.

[0055] The sintered monoliths and / or other shaped ceramic structures can have any convenient shape suitable for use as a surface for receiving a catalyst or catalytic system. An example of a monolith can be an extruded honeycomb monolith. A honeycomb monolith can be an extruded structure that includes many (e.g., multiple, meaning two or more) small gas passages or conduits arranged in parallel with thin walls between them. A small reactor can include a single monolith, a large reactor can include multiple monoliths, and an even larger reactor can be substantially filled with an arrangement of multiple honeycomb monoliths. Each monolith can be formed by extruding a monolith block having a shaped (e.g., square, triangular, or hexagonal) cross section and stacking such blocks on top of, behind, and beside each other in two or three dimensions. Monoliths can be attractive as reactor internals because they offer high heat transfer capabilities with minimal pressure drop.

[0056] In some embodiments, the honeycomb monolith can be characterized as having an open frontal area (or geometric void volume) of 25% to 55% and a conduit density of between 50 to 2000 pores or cells per square inch (CPSI), or between 100 to 900 cells per square inch, or between 100 to 600 cells per square inch. For example, in one embodiment, the conduits can have a diameter / characteristic cell side length of only a few millimeters, such as on the order of about 1 millimeter. Reactor media components, such as monoliths or alternative bed media, can have an average wetted surface area per unit volume of 50 ft based on the volume of the first reactor used to transport the reactants. -1 ~3000ft -1 (Approx. 0.16km -1 ~about 10km -1 ), or 100ft -1 ~2500ft -1 (about 0.32km -1 ~about 8.2km -1 ), or 200ft -1 ~2000ft -1 (Approx. 0.65km -1 ~about 6.5km -1) range of packing. These relatively high surface area per unit volume values ​​can help achieve relatively fast changes in temperature through the reactor, as generally illustrated by the relatively steep slopes in the exemplary temperature gradient profile graphs shown in FIG. 1(a) or FIG. 1(b).

[0057] The reactor media components also have high volumetric heat transfer coefficients (e.g., 0.02 cal / cm 3 s℃ or above, or 0.05cal / cm 3 s℃ or higher, or 0.10cal / cal / cm 3 s °C or higher), channels with low resistance to flow (low pressure drop), channels with an operating temperature range consistent with the maximum temperature encountered during regeneration, channels with high resistance to thermal shock, and / or channels with high bulk heat capacity (e.g., 0.10 cal / cm 3 s℃ or above, or 0.20cal / cm 3 s °C or higher). As with the high surface area values, these relatively high volumetric heat transfer coefficient values ​​and / or other properties can aid in achieving a relatively fast change in temperature through the reactor, as generally illustrated by the relatively steep slopes of exemplary temperature gradient profile graphs such as Figures 1(a) and 1(b) of Figure 1. The values ​​quoted are average values ​​based on the volume of the reactor used to transport the reactants.

[0058] In various embodiments, an adequate heat transfer rate can be characterized by a heat transfer parameter, ΔTHT, less than 500° C., or less than 100° C., or less than 50° C. As used herein, the parameter ΔTHT is the ratio of the bed average volumetric heat transfer rate required for recovery to the volumetric heat transfer coefficient hv of the bed. A volumetric heat transfer rate (e.g., cal / cm) sufficient for recovery is 3The gas flow rate (e.g., g / sec) can be calculated as the product of the gas heat capacity (e.g., cal / g °C) and the desired end-to-end temperature change (excluding any reaction, e.g., °C), and then this amount is multiplied by the volume (e.g., cm) of the reactor (or part of the reactor) traversed by the gas. 3 The volumetric heat transfer coefficient of the bed, hv, is typically expressed as an area-based coefficient (e.g., cal / cm 2 s °C) and the specific surface area for heat transfer (av, e.g., cm 2 / cm 3 ) and is often referred to as the wetted area of ​​the packing.

[0059] (Multi-zone catalytic system) In some embodiments, the reforming can be further improved by using multiple catalysts in the catalyst system. In such embodiments, different regions of the reaction zone can include different catalysts. Due to the nature of the counterflow reactor, a temperature profile can be created in the reactor such that some reaction zones are at higher temperatures and other zones are at lower temperatures. By using a catalyst system that includes multiple catalysts, a catalyst in a reaction zone can be selected to improve the activity of the temperature in that reaction zone based on the temperature profile.

[0060] FIG. 4 shows an example of a temperature profile obtained during steam reconstitution of a methane feed in a 12-inch (approximately 30 cm) pilot-scale counterflow reactor. The pilot-scale reactor contains multiple catalyst zones, with a first (hotter) zone containing a nickel-based catalyst and a second (cooler) zone containing a rhodium-based catalyst. For the pilot reactor used to generate the temperature profile of FIG. 4, the reforming zone of the reactor corresponds to 4-12 inches of the reactor. The portion of the reactor from 0-4 inches corresponds to the inlet end of the reactor for the regeneration gas stream. A location of approximately 4 inches within the reactor corresponds to the location where combustion of the regeneration gas occurs. As shown in FIG. 4, the temperature profile at the end of the regeneration step is at a higher temperature than the temperature profile at the end of the reforming step. This is due to the cycle of consuming heat during reforming and then replenishing heat during regeneration. However, the overall shape of the temperature profile is similar after both the reforming and regeneration steps. It is believed that the general shape of the temperature profile is also present at the intermediate times.

[0061] Based on the example temperature profile shown in Figure 4, during operation of a counter-flow reactor for reforming, certain zones within the reactor will be at higher temperatures and other zones within the reactor will be at intermediate or lower temperatures. Because the locations of the high, medium and low temperature zones are relatively stable during the reaction cycle, it has been found that further advantage can be gained by using a catalyst with improved activity for the temperature classes within a given zone of the reactor.

[0062] When multiple catalytic zones are used in a reactor, any convenient number of zones can be used. Thus, when multiple catalytic zones are present, the number of catalytic zones can range from 2 zones to 10 zones, or from 2 zones to 6 zones, or from 3 zones to 10 zones, or from 3 zones to 6 zones. Of course, it is also possible to have a single catalytic zone, so in some embodiments, the number of catalytic zones can range from 1 zone to 10 zones, or from 1 zone to 6 zones.

[0063] The temperature profile of FIG. 4 can be used to illustrate the concept of using multiple catalytic zones. One way to organize catalytic zones having a temperature profile similar to that of FIG. 4 can be to use two zones corresponding to a high temperature catalytic zone and a low temperature catalytic zone. For example, for a reactor used to generate the temperature profile of FIG. 4, inches 4-6 (or inches 4-7) of the reactor can correspond to the high temperature zone, and inches 6-12 (or inches 7-12) of the reactor can correspond to the low temperature zone. Another option can be to use three zones having a high temperature, a medium temperature, and a low temperature zone. For example, for a reactor used to generate the temperature profile of FIG. 4, inches 4-6 can correspond to the high temperature zone, inches 6-9 can correspond to the medium temperature zone, and inches 9-12 can correspond to the low temperature zone. Still other options for organizing a reactor into two zones, three zones, four zones, or any other convenient number of zones are also available depending on the desired catalyst system and temperature profile of the reactor.

[0064] In some embodiments, when different catalyst systems are used in different zones, the zones can be characterized based on the peak temperatures in the different zones. For example, the peak temperature in a first zone can be 100° C. or more, or 200° C. or more, or 300° C. or more, such as up to 700° C. or even more, higher than the peak temperature in a second zone. The peak temperature in a zone refers to the location in the zone that has the highest average temperature at the end of the regeneration step. The average temperature at the end of the regeneration cycle can be calculated based on averaging the temperatures at the end of the regeneration step over 10 full cycles.

[0065] (Process Example - Countercurrent Reforming and Regeneration) In various embodiments, the reforming of hydrocarbons can be carried out under steam reforming conditions in the presence of H2O, dry reforming conditions in the presence of CO2, or under conditions where both H2O and CO2 are present in the reaction environment. As a general overview of operations during reforming in a swing reactor, such as a counterflow reactor, a regeneration step or part of the reaction cycle can be used to provide heat to the reactor. Reformation can then occur in the reactor during the reforming step or part of the cycle, with the reforming reaction consuming the heat provided during the reactor regeneration step. During reactor regeneration, fuel and oxidant are introduced into the reactor at the regeneration end of the reactor. The beds and / or monoliths in the regeneration section of the reactor can absorb heat but typically do not contain a catalyst for reforming. As the fuel and oxidant pass through the regeneration section, heat is transferred from the regeneration section to the fuel and oxidant. Combustion does not occur immediately, but instead the location of combustion is controlled to occur in the middle of the reactor. The flow of reactants continues during the regeneration step, providing further transfer of heat generated from combustion to the reforming end of the reactor.

[0066] After a sufficient time has elapsed, the combustion reaction is stopped. Optionally, any remaining combustion products and / or reactants can be purged. The reforming step or portion of the reaction cycle can then begin. The reactants for reforming can be introduced into the reforming end of the reactor, thus effectively flowing counter-current to the flow during regeneration. The bed and / or monolith in the reforming section of the reactor can include a catalyst for reforming. In various aspects, at least a portion of the catalyst can correspond to a catalyst formed from a ceramic composition as described herein. When reforming occurs, heat introduced into the reforming zone during combustion can be consumed by endothermic reforming reactions. After leaving the reforming zone, the reformed products (and unreacted reactants) are no longer exposed to the reforming catalyst. As the reformed products pass through the regeneration zone, heat can be transferred from the products to the regeneration zone. After a sufficient period of time, the reforming process can be stopped, the remaining reformed products can optionally be withdrawn or purged from the reactor, and the cycle can begin again with the regeneration step.

[0067] The reforming reactions carried out in the reactor can correspond to the reforming of methane and / or other hydrocarbons using steam reforming, in the presence of HO, using dry reforming, in the presence of CO, or using "bi" reforming in the presence of both HO and CO. Examples of stoichiometries for steam, dry, and "bi" reforming of methane are shown in equations (1)-(3) below. (1) Dry reforming: CH4 + CO2 = 2CO + 2H2 (2) Steam reforming: CH4 + H2O = CO + 3H2 (3) Bi Reforming: 3CH4+2H2O+CO2=4CO+8H2

[0068] As shown in equations (1)-(3), dry reforming can produce lower H2 to CO ratios than steam reforming. Reforming reactions carried out with steam alone can generally produce H2 to CO ratios of about 3, such as 2.5 to 3.5. In contrast, reforming reactions carried out in the presence of CO2 can produce much lower ratios, in some cases approaching H2 to CO ratios of about 1.0 or even lower. By using a combination of CO2 and H2O during reforming, the reforming reaction can potentially be controlled to produce a wide variety of H2 to CO ratios in the resulting syngas.

[0069] It should be noted that the ratio of H2 to CO in the syngas may also depend on the water gas shift equilibrium. Although the above stoichiometries indicate a ratio of about 1 or about 3 for dry reforming and steam reforming, respectively, the equilibrium amounts of H2 and CO in the syngas may differ from the reaction stoichiometry. The equilibrium amounts may be determined based on the water gas shift equilibrium, which relates the concentrations of H2, CO, CO2, and H2O based on the reaction (4)H2O+CO<=>H2+CO2

[0070] Most reforming catalysts, such as rhodium and / or nickel, can also function as water-gas shift catalysts. Thus, if the reaction environment for producing H2 and CO also contains H2O and / or CO2, the initial stoichiometry from the reforming reaction can be altered based on the water-gas shift equilibrium. This equilibrium is also temperature dependent, with higher temperatures favoring the production of CO and H2O. Note that higher temperatures can also improve the rate at which equilibrium is reached. As a result, the ability to perform reforming reactions at high temperatures can potentially provide several advantages. For example, instead of performing steam reforming in an environment with excess H2O, CO2 can be added to the reaction environment. This can allow both a reduction in the ratio of H2 to CO produced based on the dry reforming stoichiometry and a reduction in the ratio of H2 to CO produced based on the water-gas shift equilibrium. Alternatively, if a higher H2 to CO ratio is desired, CO2 can be removed from the environment and the ratio of H2O to CH4 (or other hydrocarbons) can be controlled to produce the desired type of synthesis gas. This can potentially allow for the production of synthesis gas having H2 to CO ratios of 0.1 to 15, or 0.1 to 3.0, or 0.5 to 5.0, or 1.0 to 10, by selecting the appropriate amounts of feed components.

[0071] The reforming reactions shown in equations (1)-(3) are endothermic reactions. One of the challenges in commercial scale reforming can be providing heat to carry out the reforming reactions in an efficient manner while reducing or minimizing the introduction of additional components into the desired synthesis gas product. Cyclic reaction systems, such as counter-flow reactor systems, can provide heat in a desired manner by having a cycle that includes a reforming step and a regeneration step. During the regeneration step, combustion can be carried out in a selected area of ​​the reactor. The gas flow during regeneration can help transfer this heat from the combustion zone towards additional parts of the reforming zone in the reactor. The reforming step in the cycle can be a separate step, thereby reducing or minimizing the incorporation of products from combustion into the reactants and / or the incorporation of products from reforming. The reforming step can consume heat, which can reduce the temperature of the reforming zone. Once the products from reforming pass through the reactor, the reformed products can pass through a second zone lacking reforming or water gas shift catalyst. This allows the reaction products to be cooled before exiting the reactor. The heat transferred from the reformed products to the reactor can then be used to raise the temperature of the reactants for a subsequent combustion or regeneration step.

[0072] One common source of methane is natural gas. In some applications, natural gas, including associated hydrocarbons and impurity gases, can be used as a feedstock for the reforming reaction. The natural gas supplied can also be sweetened and / or dehydrated. Natural gas generally contains various concentrations of associated gases, such as ethane and other alkanes, preferably at lower concentrations than methane. The natural gas supplied can contain impurities, such as H2S and nitrogen. More generally, the hydrocarbon feed for reforming can contain any convenient combination of methane and / or other hydrocarbons. Optionally, the reforming feed can also contain some hydrocarbon compounds, such as alcohols or mercaptans, that are similar to hydrocarbons but contain one or more heteroatoms different from carbon and hydrogen. In some embodiments, the additional components present in the feed can correspond to impurities, such as sulfur, that can be adsorbed to the catalytic monolith during the reduction cycle (such as the reforming cycle). Such impurities can be oxidized in the next cycle to form sulfur oxides, which can then be reduced to release additional sulfur-containing components (or other impurity-containing components) to the reaction environment.

[0073] In some embodiments, the feed for reforming contains 5 wt. % or more, or 10 wt. % or more, or 15 wt. % or more, or 20 wt. % or more, for example up to 50 wt. %, or even higher, of C hydrocarbons such as ethane or propane, based on the total weight of the hydrocarbons in the feed for reforming. 2+The feed for reforming may include compounds. It is noted that nitrogen and / or other gases that are non-reactive in a combustion environment, such as H2O and CO2, may also be present in the feed for reforming. In embodiments where the reformer corresponds to an on-board reforming environment, such non-reactive products may be optionally introduced into the feed, for example, based on exhaust gas recycle to the reformer. Additionally or alternatively, the feed for reforming may include 40% by weight or more, or 60% by weight or more, or 80% by weight or more, or 95% by weight or more, such as having a feed that is substantially composed of methane (98% by weight or more). In embodiments where the reforming corresponds to steam reforming, the molar ratio of steam molecules to carbon atoms in the feed may be between 0.3 and 4.0. It is noted that methane has one carbon atom per molecule and ethane has two carbon atoms per molecule. In embodiments where the reforming corresponds to dry reforming, the molar ratio of CO2 molecules to carbon atoms in the feed may be between 0.05 and 3.0.

[0074] Within the reforming zone of a counter-flow reactor, the temperature can vary across the zone due to the nature of how heat is added to the reactor and / or the kinetics of the reforming reaction. The hottest part of the zone can typically be found near the middle of the reactor. This middle part is sometimes referred to as the mixing zone where combustion is initiated during regeneration. If the monolith with the reforming catalyst extends into the mixing zone, at least a portion of the mixing zone can correspond to a portion of the reforming zone. As a result, the location where combustion is initiated during regeneration can typically be closer to the end of the reforming zone in the reactor. Moving from the center of the reactor to the end of the reactor, the temperature can decrease. As a result, the temperature at the beginning of the reforming zone (end of the reactor) can be lower than the temperature at the end of the reforming zone (middle of the reactor).

[0075] As the reforming reactions occur, the temperature in the reforming zone can decrease. The rate at which the temperature decreases can be related to the kinetic factors of the amount of hydrocarbons available for reforming and / or the temperature at a given location in the reforming zone. As the reforming feed moves through the reforming zone, the reactants in the feed can be consumed, which can reduce the amount of reforming that occurs at downstream locations. However, the increase in temperature of the reforming zone as the reactants move across the reforming zone can result in an increase in the reaction rate.

[0076] In some embodiments, at about 500° C., the reaction rate for reforming can be sufficiently reduced so that little or no additional reforming occurs. As a result, in some embodiments where the reforming reaction proceeds, the beginning of the reforming zone can cool enough to effectively stop the reforming reaction in a portion of the reforming zone. This can move the location in the reactor where reforming begins to a location that is further downstream relative to the beginning of the reforming zone. If a sufficient portion of the reforming zone has a temperature below 500° C., or below 600° C., the reforming step in the reaction cycle can be stopped to allow regeneration. Alternatively, the reforming portion of the reaction cycle can be stopped based on the amount of heat introduced into the reactor during regeneration, based on the amount of reaction time, so that the amount of heat consumed during reforming (plus heat lost to the environment) is approximately balanced by the amount of heat added during regeneration. After the reforming process is stopped, the synthesis gas product remaining in the reactor can be optionally recovered before starting the regeneration step of the reaction cycle.

[0077] In other embodiments, the condition for switching from reforming to regeneration can be based on the temperature in the region where Pd is at least part of the catalytic system. In such embodiments, the reforming step can be stopped so that the minimum temperature of the region where Pd is at least part of the catalytic system is 900° C. or higher, or 950° C. or higher, or 1000° C. or higher, such as up to 1200° C., or even higher in some cases. In this type of embodiment, the region where Pd is at least part of the catalytic system is maintained at a temperature of 900° C. or higher when the region is exposed to oxidizing conditions. Note that in some embodiments, one region containing Pd in ​​the catalytic system can be maintained at 900° C. or higher (such as up to 1300° C.) and a second region can also contain Pd, but allow the temperature of the second region to fall below 900° C. when the second region is exposed to the regeneration process (and / or other oxidizing conditions). In other embodiments, all regions containing Pd in ​​the catalytic system can be maintained at 900° C. (and up to 1300° C.) when the region is exposed to the regeneration process / oxidizing conditions.

[0078] The regeneration process can then begin. During regeneration, fuel, such as methane, natural gas, or H2, and oxygen, can be introduced into the reactor and burned. Where the fuel and oxidant are mixed can be controlled in any convenient manner, such as by introducing the fuel and oxidant through separate channels. The non-reforming end of the reactor can be kept at a lower temperature by delaying combustion during regeneration until the reactants reach the center portion of the reactor. This can also result in a temperature peak in the middle portion of the reactor. The temperature peak can be located in a portion of the reactor that also contains the reforming catalyst. During the regeneration cycle, the temperature in the reforming reactor can be raised sufficiently to allow reforming during the reforming portion of the cycle. This can result in a peak temperature in the reactor of 1100° C. or higher, or 1200° C. or higher, or 1300° C. or higher, or potentially even higher. In some embodiments, in the region where Pd is part of the catalyst system, the peak temperature can be between 1100° C. and 1300° C.

[0079] The relative time lengths and reactant flow rates of the reforming and regeneration sections of the process cycle can be selected to balance the heat provided during reforming with the heat consumed during reforming. For example, one option can be to select a reforming step having a similar length as the regeneration step. Based on the flow rates of hydrocarbons, H2O, and / or CO2 during the reforming step, the endothermic demand for the reforming reaction can be determined. This heat demand can then be used to calculate the flow rate of the combustion reactants during the regeneration step. Of course, in other embodiments, the heat balance between reforming and regeneration can be determined in other ways, for example, by determining the desired flow rates of the reactants and then selecting the cycle length such that the heat provided by reforming balances the heat consumed during reforming.

[0080] In addition to providing heat, the reactor regeneration step during the reaction cycle can also enable coke removal from the catalyst in the reforming zone. In various embodiments, one or more types of catalyst regeneration can potentially occur during the regeneration step. One type of catalyst regeneration can correspond to the removal of coke from the catalyst. During reforming, some of the hydrocarbons introduced into the reforming zone can form coke instead of forming CO or CO2. This coke can potentially block access to catalytic sites (such as metal sites) of the catalyst. In some embodiments, the reforming rate can be increased in parts of the reforming zone exposed to higher temperatures, such as parts of the reforming zone exposed to temperatures of 800°C or higher, or 900°C or higher, or 1000°C or higher. During the regeneration step, oxygen can be present as the temperature of the reforming zone increases. At the temperatures achieved during regeneration, at least a portion of the coke produced during reforming can be removed as CO or CO2.

[0081] Due to the variation in temperature throughout the reactor, several options can be used to characterize the temperature in the reactor and / or in the reforming zone of the reactor. One option for characterizing the temperature can be based on the average bed or monolith temperature in the reforming zone. In a practical setting, the presence of a measuring device such as a thermocouple is necessary to determine the temperature in the reactor. Rather than trying to measure the temperature in the reforming zone, the average (bed or monolith) temperature in the reforming zone can be defined based on the average of the temperature at the beginning of the reforming zone and the temperature at the end of the reforming zone. Another option can be to characterize the peak temperature in the reforming zone after the regeneration step of the reaction cycle. In general, the peak temperature may occur at or near the end of the reforming zone and may depend on where combustion is initiated in the reactor. Yet another option can be to characterize the difference in temperature at a given location in the reaction zone at different times in the reaction cycle. For example, the temperature difference between the temperature at the end of the regeneration step and the temperature at the end of the reforming step can be determined. Such temperature differentials may be characterized at the location of peak temperature within the reactor, at the entrance to the reforming zone, at the exit from the reforming zone, or at any other convenient location.

[0082] In various embodiments, the reaction conditions for reforming hydrocarbons can include one or more of the following: an average temperature in the reforming zone ranging from 400° C. to 1200° C. (or higher); a peak temperature in the reforming zone ranging from 800° C. to 1500° C.; a temperature difference at the location of the peak temperature between the end of the regeneration step and the end of the subsequent reforming step of 25° C. or more, or 50° C. or more, or 100° C. or more, or 200° C. or more, e.g., up to 800° C. or even higher; the temperature difference at the inlet of the reforming zone between the end of the regeneration step and the end of the subsequent reforming step is 25°C or more, or 50°C or more, or 100°C or more, or 200°C or more, for example up to 800°C or even higher; and / or the temperature difference at the outlet of the reforming zone between the end of the regeneration step and the end of the subsequent reforming step is 25°C or more, or 50°C or more, or 100°C or more, or 200°C or more, for example up to 800°C or even higher. Additionally or alternatively, at least one region comprising Pd as part of the catalyst system may be maintained at a temperature of between 900°C and 1300°C.

[0083] With respect to the average reforming zone temperature, in various embodiments, the average temperature of the reforming zone can be 500°C to 1500°C, or 400°C to 1200°C, or 800°C to 1200°C, or 400°C to 900°C, or 600°C to 1100°C, or 500°C to 1000°C. In some embodiments where the entire catalyst system includes Pd, the average temperature of the reforming zone can be 900°C to 1200°C. Additionally or alternatively, with respect to the peak temperature of the reforming zone (likely corresponding to a location within the reforming zone proximate to a location for combustion of the regenerated reactant), the peak temperature can be 1000°C to 1400°C, or 1200°C to 1500°C, or 1200°C to 1400°C, or 1000°C to 1300°C, or 1100°C to 1300°C.

[0084] Additionally or alternatively, reaction conditions for reforming hydrocarbons include a pressure of 0 psig to 1500 psig (10.3 MPa), or 0 psig to 1000 psig (6.9 MPa), or 0 psig to 550 psig (3.8 MPa), and a 1000 hour -1 ~50,000hr -1 The gas hourly space velocity of the reforming reactants may include the gas hourly space velocity of the reforming reactants per unit time. The space velocity corresponds to the volume of reactants relative to the volume of the monolith per unit time. The volume of the monolith is defined as the volume of the monolith as if it were a solid cylinder.

[0085] In some embodiments, the advantage of operating the reforming reaction at high temperatures may be the ability to convert substantially all of the methane and / or other hydrocarbons in the reforming feed. For example, for reforming processes in which water is present in the reforming reaction environment (i.e., steam reforming or dual reforming), the reaction conditions may be suitable for conversion of 10% to 100% by weight, or 20% to 80% by weight, or 50% to 100% by weight, or 80% to 100% by weight, or 10% to 98% by weight, or 50% to 98% by weight of the methane in the reforming feed. Additionally or alternatively, the reaction conditions may be suitable for conversion of 10% to 100% by weight, or 20% to 80% by weight, or 50% to 100% by weight, or 80% to 100% by weight, or 10% to 98% by weight, or 50% to 98% by weight of the hydrocarbons in the reforming feed.

[0086] In other embodiments, for reforming processes in which carbon dioxide is present in the reforming reaction environment (i.e., cyclic reforming or dual reforming), the reaction conditions may be suitable for conversion of 10% to 100%, or 20% to 80%, or 50% to 100%, or 80% to 100%, or 10% to 98%, or 50% to 98% by weight of the methane in the reforming feed. Additionally or alternatively, the reaction conditions may be suitable for conversion of 10% to 100%, or 20% to 80%, or 50% to 100%, or 80% to 100%, or 10% to 98%, or 50% to 98% by weight of the hydrocarbons in the reforming feed.

[0087] In some alternative embodiments, the reforming reaction can be carried out under dry reforming conditions, where the reforming is carried out with CO2 as a reagent, but the amount of H2O in the reaction environment is reduced or minimized. In such alternative embodiments, the objective of the reforming reaction can be to produce a synthesis gas with an H2 to CO ratio of 1.0 or less. In some embodiments, the temperature during reforming can correspond to the temperature range described for steam reforming. Optionally, in some embodiments, the dry reforming reaction can be carried out at a lower temperature of 500°C to 700°C, or 500°C to 600°C. In such embodiments, the H2 to CO ratio can be 0.3 to 1.0, or 0.3 to 0.7, or 0.5 to 1.0. Carrying out the dry reforming reaction under these conditions can also lead to substantial coke generation, which may require removal during regeneration to maintain catalyst activity.

[0088] (Example of a counterflow reactor configuration) For endothermic reactions operated at high temperatures, such as hydrocarbon reforming, a counter-flow reactor can provide a suitable reaction environment to provide heat for the endothermic reaction.

[0089] In a counter-current reactor, the heat required for the endothermic reaction can be provided by generating a hot hot bubble in the center of the reactor. A two-stage process can then be used in which heat is (a) added to the reactor bed or monolith via in-situ combustion and then (b) removed in-situ from the bed via an endothermic process such as reforming, pyrolysis, or steam cracking. This type of configuration can provide the ability to consistently manage and limit the hot bubble in a reactor region that can withstand such conditions for extended periods of time. The counter-current reactor system can allow the primary endothermic and regenerative processes to be carried out substantially continuously.

[0090] The countercurrent reactor system may include a first and a second reactor oriented in series with each other relative to a common flow path, and optionally, but preferably, oriented along a common axis. The common axis may be horizontal, vertical, or otherwise. During the regeneration step, the reactants (e.g., fuel and oxygen) may combine or mix in the reaction zone and combust in situ therein, creating a high temperature zone or hot bubble in the middle of the reactor system. The hot bubble may correspond to a temperature that is at least about the initial temperature for the endothermic reaction. Typically, the temperature of the hot bubble may be higher than the initial temperature for the endothermic reaction, since the temperature decreases as heat is transferred from the hot bubble in the middle of the reactor toward the end of the reactor. In some embodiments, the mixing may be enhanced by a reactant mixer that mixes the reactants to facilitate substantially complete combustion / reaction at the desired location, the mixer being optionally disposed between the first and second reactors. The combustion process may be carried out for a period of sufficient length that the flow of the first and second reactants through the first reactor also serves to transfer a substantial portion (if desired) of the heat (e.g., hot gas bubbles) generated by the reaction at least partially into and through the second reactor, but preferably over less than the entire path of the second reactor to avoid wasting heat and overheating the second reactor. Flue gas may be exhausted through the second reactor, but preferably the majority of the heat is retained within the second reactor. The amount of heat transferred to the second reactor during the regeneration step may also be limited or determined by the desired exposure time or space velocity that the hydrocarbon feed gas has in the endothermic reaction environment.

[0091] After regenerating or heating the second reactor medium (such as the phase-stabilized monolith described herein), in the next / reverse step or cycle, the endothermic reactant methane (and / or natural gas and / or another hydrocarbon) can be fed or flowed into the second reactor from a direction opposite to the direction of flow during the heating step. For example, in a reforming process, methane (and / or natural gas and / or another hydrocarbon) can be fed or flowed through the second reactor. The methane can contact the hot second reactor and mixer medium in the thermal bubble region to transfer heat to the methane for reaction energy.

[0092] For some embodiments, the basic two-stage asymmetric cycle of a countercurrent regenerative bed reactor system is shown in FIG. 1 (a) and FIG. 1 (b) in terms of a reactor system having two zones / reactors: a first or recuperator / quenching zone (7) and a second or reaction zone (1). Both the reaction zone (1) and the recuperator zone (7) can include regenerative monoliths and / or other regenerative structures. As used herein, regenerative monoliths or other regenerative structures include materials that are effective for storing and transferring heat as well as for carrying out chemical reactions. The regenerative monoliths and / or other structures can correspond to any convenient type of material suitable for storing heat, transferring heat, and catalyzing reactions. Exemplary structures include bedding or packing materials, ceramic beads or spheres, ceramic honeycomb materials, ceramic tubes, extruded monoliths, and the like, provided they maintain integrity, functionality, and can withstand prolonged exposure to temperatures in excess of 1200°C, or in excess of 1400°C, or in excess of 1600°C, which may allow for some operating margin.

[0093] For ease of explanation of Figure 1, the reactor will be described herein with reference to a reforming reaction, it being understood that other convenient types of endothermic reactions can generally be carried out using a countercurrent reactor such as the reactor shown in Figure 1.

[0094] As shown in FIG. 1(a) of FIG. 1, at the start of the "react" step of the cycle, the secondary end 5 of the reaction zone 1 (also referred to herein as the second reactor) can be at a higher temperature compared to the primary end 3 of the reaction zone 1, and at least a portion of the recuperator or quench zone 7 (including the first end 9) (also referred to herein as the first reactor) can be at a lower temperature than the reaction zone 1, resulting in a quenching effect on the resulting product. In embodiments where the reactor is used to perform reverse flow reforming, a methane-containing reactant source (or other hydrocarbon-containing reactant source) can be introduced into the primary end 3 of the reforming or reaction zone 1 via conduit 15. In various embodiments, the hydrocarbon-containing reactant feed can also contain H2O, CO2, or a combination thereof.

[0095] The feed stream from inlet 15 can absorb heat from reaction zone 1 and endothermically react to produce the desired synthesis gas product. As this step progresses, a shift in temperature profile 2 can be created based on the heat transfer characteristics of the system, as indicated by the arrows. If the ceramic catalyst monolith / other catalyst structure is designed with appropriate heat transfer capabilities, this profile can have a relatively sharp temperature gradient, which can move across reaction zone 1 as the reforming step progresses. In some embodiments, a sharper temperature gradient profile can provide improved control over reaction conditions. In embodiments where another type of endothermic reaction is performed, a similar shift in temperature profile can occur, such that a temperature gradient moves across reaction zone 1 as the reaction step progresses.

[0096] The effluent from the reforming reaction, which may include unreacted feed components (hydrocarbons, H2O, CO2) as well as syngas components, may leave the reaction zone 1 through the secondary end 5 at a high temperature, pass through the recuperator reactor 7, enter through the second end 11, and exit at the first end 9. The recuperator 7 may initially be at a lower temperature than the reaction zone 1. As the products from the reforming reaction (and optionally unreacted feed) pass through the recuperator zone 7, the gas may be quenched or cooled at the first end 9 to a temperature substantially close to the temperature of the recuperator zone, which in some embodiments may be at approximately the same temperature as the regenerator feed introduced into the recuperator 7 via conduit 19 during the second step of the cycle. As the reforming effluent cools in the recuperator zone 7, a temperature gradient 4 may be created within the regenerator bed of the zone, which may move across the recuperator zone 7 during this step. The quenching can heat the recuperator 7, which can be cooled again in a second step to provide another quenching service later and prevent the gradual growth in size and location of the thermal bubble through the quench reactor 7. After quenching, the reaction gas can exit the recuperator at 9 via conduit 17 and can be processed for separation and recovery of the various components.

[0097] The second step of the cycle, referred to as the regeneration step, can then begin with the reintroduction of the first and second regeneration reactants via conduit 19. The first and second reactants can pass separately through the hot recuperator 7 towards a second end 11 of the recuperator 7, where they can be combined for exothermic reaction or combustion in or near a central region 13 of the reactor system.

[0098] An example of the regeneration step is shown in FIG. 1(b) of FIG. 1. Regeneration can involve transferring recovered sensed heat from the recuperator zone 7 to the reaction zone 1 to thermally regenerate the reaction bed 1 for the next reaction cycle. Regeneration gas / reactants can enter the recuperator zone 7, such as via conduit 19, and flow through the recuperator zone 7 to the reaction zone 1. In doing so, as shown by the arrows in the exemplary graph of FIG. 1(b), temperature gradients 6 and 8 can move across the bed in a similar but opposite direction to the graph of temperature gradients generated during the reaction cycle of FIG. 1(a) of FIG. 1. Fuel and oxidant reactants can be combusted in a region proximate the interface 13 of the recuperator zone 7 and the reaction zone 1. The heat recovered from the recuperator zone along with the heat of combustion can be transferred to the reaction zone to thermally regenerate the regenerated reaction monolith and / or bed 1 located therein.

[0099] In some embodiments, some of the conduits in the channel may transport a mixture of the first and second reactants, due at least in part to some mixing at the first end (17) of the first reactor. However, the number of conduits carrying the combustible mixture of the first and second reactants may be sufficiently small so that the majority of the stoichiometrically reactable reactants do not react until they have exited the second end of the first reactor. The axial location of the onset of combustion or exothermic reactions in those conduits transporting the mixture of reactants may be controlled by a combination of temperature, time, and fluid dynamics. Fuel and oxygen typically require temperature- and mixture-dependent autoignition times to combust. Nevertheless, some reactions may occur within the axial portion of the conduits transporting the mixture of reactants. However, this reaction may be tolerated because the number of channels with such reactions may be small enough so that there is only an acceptable or irrelevant level of effect on the overall heat balance in the reactor. The design details of a particular reactor system may be selected to avoid mixing of the reactants in the conduits as much as reasonably possible.

[0100] FIG. 2 illustrates another exemplary reactor system that may be suitable for some applications for controlling and delaying the combustion of fuel and oxidant to achieve efficient regenerative heat. FIG. 2 illustrates a single reactor system operating in a regenerative cycle. The reactor system may be considered to include two reactor zones. The recuperator 27 may be the zone where quenching primarily occurs and provides a substantially isolated flow path or channel for transporting both quenching reactant gases to the reactor medium without incurring combustion until the gas reaches adjacent to or within the reactor core 13 of FIG. 1. The reformer 2 may be the reactor where regenerative heating and methane (and / or hydrocarbon) reforming primarily occurs and may be considered the second reactor for purposes of this specification. Although the first and second reactors of the reactor system are identified as separate and distinct reactors, it is understood that the first and second reactors may be manufactured, provided, or otherwise combined into a common single reactor bed, whereby the reactor system may be described as including only a single reactor integrating both cycles within the reactor. The terms "first reactor" and "second reactor" may simply refer to the respective zones within a reactor system whereby each step, such as regeneration, reforming, quenching, etc., takes place and do not require that separate components be utilized for the two reactors. However, various embodiments may include reactor systems in which the recuperator reactor includes conduits and channels as described herein and the reformer reactor may have conduits as well. Additionally or alternatively, some embodiments may include a reformer reactor bed in a different arrangement than the recuperator reactor bed and may even include different materials than the recuperator reactor bed.

[0101] As previously discussed, the first reactor or recuperator 27 may include various gas conduits 28 for separately channeling two or more gases after entering a first end 29 of the recuperator 27 through a regenerative bed disposed therein. The first gas 30 may enter a first end of the plurality of flow conduits 28. In addition to providing flow paths, the conduits 28 may also include effective flow barriers (e.g., effectively acting as conduit walls, etc.) to prevent cross-flow or mixing between the first and second reactants and to keep the majority of the reactants effectively separated from each other until mixing is permitted. As previously discussed, each of the first and second channels may include multiple channels or flow paths. The first reactor may also include multiple substantially parallel flow segments, each including a separated first and second channel.

[0102] In some embodiments, the recoverer may be constructed from one or more extruded honeycomb monoliths, as described above. Each monolith may provide a flow path (e.g., a flow channel) for one of the first or second reactants. Each channel preferably includes multiple conduits. Alternatively, the monolith may include one or more channels for each reactant with one or more channels or groups of conduits dedicated to flowing one or more streams of the reactant, while the remaining portion of the conduits flows one or more streams of the other reactant. At the interface between the channels, multiple conduits may transport the mixture of the first and second reactants, although it is recognized that the number of conduits is proportionally small.

[0103] In alternative embodiments, reactor media other than monoliths may be used, for example, the channel conduits / flow paths may include more tortuous paths (e.g., convoluted, complex, serpentine, and / or twisted but not straight or tubular), including, but not limited to, labyrinths, multiplicity of flow paths, conduits, tubes, slots, and / or pore structures having channels through portions of the reactor, and may include barrier portions along the outer surfaces of the segments or within the subsegments that are substantially effectively impermeable to gases, and / or other means suitable for preventing cross-flow between the reactant gases and for maintaining the first and second reactant gases substantially separated from each other during axial passage through the recuperator 27. Such other types of reactor media may be suitable, so long as at least a portion of such media may be formed by sintering the ceramic catalyst compositions described herein and subsequently exposing such media to reducing conditions to activate the catalyst. In such embodiments, the complex flow paths may result in longer effective flow paths, increased surface area, and improved heat transfer. Such designs may be preferred for reactor embodiments having a relatively short axial length through the reactor. Longer axial reactor lengths may experience increased pressure drop through the reactor. In such embodiments, however, the porous and / or permeable media may include, for example, at least one of a packed bed, a tile arrangement, a permeable solid media, a substantially honeycomb-type structure, a fibrous arrangement, and a mesh-type lattice structure.

[0104] In some embodiments, the counter-current reactor may include some type of device or method for directing the flow stream of one of the reactants into a selected portion of the conduit. In the exemplary embodiment of FIG. 2, the gas distributor 31 may direct the second gas stream 32 into a second gas flow channel that is substantially isolated from or not in fluid communication with the first gas channel, shown here as channel 33. As a result, at least a portion of the gas stream 33 may be kept separated from the gas stream 30 during the axial passage through the recuperator 27. In some embodiments, the regenerative bed and / or monolith in the recuperator zone may include a channel having a gas or fluid barrier that separates the first reactant channel from the second reactant channel. Thus, both of the at least two reactive gases passing through the channel means may pass completely through the regenerative bed to quench the regenerative bed and absorb heat into the reactive gases before combining to react with each other in the combustion zone.

[0105] In various embodiments, the gases (including fluids) 30 and 32 can each include a component that reacts with a component in the other reactant 30 and 32 to produce an exothermic reaction when combined. For example, each of the first and second reactants can include one of a fuel gas and an oxidant gas, which combusts or burns when combined with the other of the fuel and oxidant. By keeping the reactants substantially separated, the location of heat release that occurs due to exothermic reactions can be controlled. In some embodiments, "substantially separated" can be defined to mean that at least 50%, or at least 75%, or at least 90% of the reactants having a minimum or limiting stoichiometrically reactable amount of reactant between the first and second reactant streams are not consumed by reaction by the time these gases complete their axial passage through the recuperator 27. In this way, the majority of the first reactant 30 can remain separated from the majority of the second reactant 32, and the majority of the heat release from the reaction of the mixed reactants 30 and 32 can occur after the reactants begin to exit the recuperator 27. The reactants can be gases, although optionally some reactants can include liquids, mixtures, or gas phases.

[0106] The percent reaction of these regenerative streams refers to the percent of reaction possible based on the stoichiometry of the entire feed. For example, if gas 30 contains 100 volumes of air (80 volumes of N2 and 20 volumes of O2) and gas 32 contains 10 volumes of hydrogen, the maximum stoichiometric reaction is to burn 10 volumes of hydrogen (H2) with 5 volumes of oxygen (O2) to make 10 volumes of H2O. In this case, if 10 volumes of hydrogen were actually burned in the regenerator zone (27), this would represent 100% reaction of the regenerative stream. Nevertheless, in this example, there is residual unreacted oxygen because unreacted oxygen was present in an amount that exceeded the stoichiometric requirement. Thus, in this example, hydrogen is the stoichiometrically limiting component. Using this definition, less than 50% reaction of the regenerative stream, or less than 25% reaction, or less than 10% reaction may occur during the axial passage through the regenerator (27).

[0107] In various embodiments, channels 28 and 33 can comprise ceramic (including zirconia), alumina, or other refractory materials capable of withstanding temperatures in excess of 1200° C., or 1400° C., or 1600° C. Additionally or alternatively, channels 28 and 33 can be 50 ft -1 ~3000ft -1 , or 100ft -1 ~2500ft -1 , or 200ft -1 ~2000ft -1 The wetted area may be between.

[0108] Briefly referring again to FIG. 1, the reactor system can include a first reactor 7 including a first end 9 and a second end 11, and a second reactor 1 including a primary end 3 and a secondary end 5. The embodiments shown in FIGS. 1 and 2 are merely exemplary, provided for illustrative purposes only, and are not intended to represent a comprehensive embodiment. When referring to an "end" of a reactor, it simply refers to a distal portion of the reactor relative to the axial midpoint of the reactor. Thus, when gas enters or leaves an "end" of a reactor, e.g., end 9, it simply means that the gas can enter or leave at any of a variety of points along the axis between the respective end faces of the reactor and the midpoint of the reactor, but more preferably closer to the end faces than the midpoint. Thus, one or both of the first and second reactant gases can enter at the respective end faces, while the other is supplied to the respective end of the reactor via slots or ports in the exterior surface around or around the circumference of the respective end of the reactor.

[0109] Example 1 - Activity for reforming at high temperatures The following example demonstrates that Pd-based catalyst systems can provide suitable reforming activity under high temperature conditions. In this example, the catalyst system was tested by supporting the catalytic metal on particles of a thermally stable oxide layer. The particles were then placed in a quartz reactor and exposed to methane flow under steam reforming conditions. The weight hourly space velocity of methane relative to the catalyst particles was approximately 2.0 h -1The volumetric ratio of water to methane was about 2.0. The exposure was performed at atmospheric pressure (about 100 kPa-a). No monolith was used. After exposing the methane flow to the catalyst, a flame ionization detector (FID) was used to detect any unreacted methane.

[0110] The first catalyst system corresponded to NiO supported on NiAl2O4. The second catalyst system corresponded to Rh supported on α-Al2O3. The third catalyst system corresponded to Pd on α-Al2O3.

[0111] For the first catalyst system (NiO / NiAl2O4), 12.5 mg of catalyst was placed in a quartz reactor. The catalyst system was initially exposed to a hydrogen flow at 900°C to activate the catalyst. The activated catalyst system was then exposed to a methane flow under steam reforming conditions at 900°C. The FID results of the exhaust from the reactor are shown in Figure 5. As shown in Figure 5, a small amount of methane was detected in the reactor exhaust. This corresponded to approximately 96% conversion of the methane exposed to the catalyst.

[0112] In the second run, 5.2 mg of the first catalyst system was placed in a quartz reactor and activated using hydrogen. This smaller amount of activated first catalyst system was then exposed to methane flow under steam reforming conditions at 900° C. As shown in FIG. 6, a significant portion of the methane remained unreacted after exposure to the smaller portion of the first catalyst system. This corresponded to approximately 11% conversion of the methane exposed to the catalyst.

[0113] For the second catalyst system (Rh / α-Al2O3, 4.0 wt% Rh with respect to the weight of the catalyst system), 14.7 mg of the catalyst system was placed in a quartz reactor. Because rhodium catalysts are typically used at lower temperatures, the second catalyst system was exposed to methane flow under steam reforming conditions at 550 °C. As shown in Figure 7, only a small amount of unreacted methane was detected by FID. This corresponded to approximately 96% conversion of the methane exposed to the second catalyst system.

[0114] For the third catalyst system (Pd / α-Al2O3, 5.0 wt% Pd relative to the weight of the catalyst system), 5.5 mg of the catalyst system was placed in a quartz reactor. The catalyst system was initially exposed to a hydrogen flow at 900°C to ensure that the Pd was in metallic form (to activate the catalyst). The activated catalyst system was then exposed to a methane flow under steam reforming conditions at 900°C. Figure 8 shows the FID results corresponding to substantially no unreacted methane exiting the reactor. This demonstrates that Pd at high temperatures (e.g., above 900°C) can provide suitable reforming activity for use as a reforming catalyst.

[0115] Example 2 - Stability of Pd in ​​an oxidizing environment at 900°C to 1300°C To illustrate the resistance of Pd to oxidation at temperatures above 900°C, a catalyst system corresponding to 5.0 wt% Pd supported on alumina was placed in a flow cell. The Pd-containing catalyst system was exposed to a flow of 5.0 vol% O2 in He carrier gas. The catalyst system was first exposed to the gas flow at 1050°C for 60 minutes. The temperature was then ramped down to a temperature of about 100°C over a period of about 2 hours.

[0116] During exposure of the catalytic system to the gas stream, the output from the flow cell was analyzed using a thermal conductivity detector (TCD). The TCD allowed for detection of oxygen loss based on changes in the conductivity of the output gas flow. Since the alumina in the catalytic system is stable against further oxidation, the loss of oxygen from the output gas stream corresponds to the amount of O2 consumed by the oxidation of Pd.

[0117] FIG. 10 shows the results of exposing a Pd-containing catalyst system to a gas flow. In FIG. 10, the horizontal axis corresponds to the exposure time of the catalyst system to the gas flow. Data line 1010 corresponds to the temperature of the catalyst system during exposure to the gas flow. Data line 1020 represents the TCD signal. Note that for O2 in helium, consumption of O2 results in a decrease in the conductivity of the gas flow. To simplify the illustration of FIG. 10, data line 1020 corresponds to the TCD signal multiplied by -1 so that the location of maximum O2 consumption (and therefore maximum Pd oxidation) corresponds to the peak in FIG. 10.

[0118] As shown in FIG. 10, in the initial exposure at 1050° C., there is minimal change in the TCD signal during the initial hours of exposure time. This indicates resistance of Pd to oxidation at temperatures above 900° C., as little or no O2 consumption is occurring. After the first hour, the temperature was reduced. As shown in FIG. 10, there is a small shoulder peak in the TCD signal near 900° C., followed by a large peak. Due to the conditions of gas exposure used to generate the data in FIG. 10, maximum oxidation occurred at about 540° C. This peak location may vary depending on the reaction conditions. However, the onset of substantial oxidation at temperatures below 900° C. is a consistent feature for exposure of Pd to O2, independent of the specific gas flow conditions. As shown in FIG. 10, O2 consumption ceases at a temperature of about 400° C.

[0119] The resistance of Pd to oxidation at temperatures above 900°C is unexpected. Conventionally, the oxidation of metals in the presence of O2 is expected to increase as temperature increases. Furthermore, some oxidation is expected to occur as an equilibrium process even when the metal form has higher stability. However, as shown in Figure 10, Pd is unexpectedly resistant to oxidation at temperatures above 900°C. Based on this unexpected resistance, the volatility of Pd-containing catalyst systems can be unexpectedly reduced by avoiding exposure of Pd-containing catalyst systems to oxidizing conditions at temperatures between 600°C and 900°C. Avoiding the loss of Pd due to catalyst volatility can substantially extend the operational life of Pd-containing catalyst systems.

[0120] Examples 3A, 3B, and 3C - Catalyst Systems with Different Starting Alumina Phases This and subsequent examples demonstrate the advantages of using a thermally stable oxide support layer as part of a catalyst system. The monoliths used to support the catalyst system described in this example corresponded to monoliths having 400 cpsi (cells per square inch) and either 35% or 52% open frontal area.

[0121] Three different types of catalyst system washcoat formulations were used to prepare multi-zone catalyst systems for hydrocarbon reforming. In this example, a multi-zone catalyst system with two catalyst zones was used. The first zone (higher temperature) corresponded to a Ni-containing catalyst and the second zone (lower temperature) corresponded to a Rh-containing catalyst. Two monoliths were used to fill the desired catalyst bed volume in each zone of the pilot-scale reactor, so each catalyst system corresponded to a total of four monoliths.

[0122] For Example 3A, the first two monoliths with Ni-containing catalyst systems were prepared using NiO as the catalytic metal and α-Al2O3 as the oxide support layer. The molar ratio of Al to Ni in the catalyst system was about 1.5:1. This type of catalyst system can produce NiAl2O4 after exposure to cyclic high temperature reforming conditions. Sufficient washcoat was applied so that the weight of the NiO / α-Al2O3 catalyst system was about 5 wt% of the total weight of the washcoated monolith. For Example 3A, the second two monoliths with Rh-containing catalyst systems were also prepared using α-alumina as the oxide support layer. The Rh / Al2O3 catalyst system contained approximately 4.0 wt% Rh based on the weight of the catalyst system. Sufficient washcoat was applied so that the weight of the Rh2O3 / α-Al2O3 catalyst system was about 4 wt% of the total weight of the washcoated monolith.

[0123] For Examples 3B and 3C, instead of using a catalyst system consisting of a phase stable material, a washcoat containing a higher surface area material was deposited on the monolith, and thus the washcoat used in Examples 3B and 3C did not include a thermally stable metal oxide support layer.

[0124] In Example 3B, the catalyst system of the first two washcoats corresponds to θ-Al2O3 doped with 30% Ni with 4 wt% La as catalyst, which was formed at 1200°C. This type of composition can be referred to as 30%Ni-4%-La-θ-Al2O3. This catalyst system corresponds to a molar ratio of Al:Ni of 3.7:1. It should be noted that this ratio has a significant amount of excess Al compared to the stoichiometric ratio of NiAl2O4. After depositing the washcoats, the first two monoliths of Example 3B were calcined at 500°C. For the second two monoliths of Example 3B, a washcoat of 5% Rh on 4%-La-γ-Al2O3 was washcoated onto the alumina-rich monolith. It should be noted that the second two washcoats contained γ-Al2O3 instead of θ-Al2O3 of the first two washcoats. After the washcoat was deposited, the second two monoliths of Example 3B were fired at 500°C.

[0125] In Example 3C, the first two washcoats and the second two washcoats were prepared in a manner similar to Example 3B, but the calcination temperature of the first two monoliths was different: in Example 3C, a calcination temperature of 1200° C. was used after the washcoats were applied (compared to the 500° C. used for calcination in Example 3B).

[0126] Example 4 - Modification with monoliths having different starting alumina phases The washcoated monoliths described in Examples 3A, 3B, and 3C were used in a pilot-scale reactor to investigate the change in catalytic activity over time and to determine the structural stability of the washcoated monoliths. The monoliths were used to perform steam reforming on a methane feed under cyclic high temperature conditions. The reaction conditions included a regeneration step and a reforming step. During the regeneration step, air was used to provide a source of oxygen for the combustion of the hydrocarbon fuel. The amount of air was sufficient to provide 10% excess O2 relative to the amount of hydrocarbon fuel used for heating. The regeneration step during each cycle was performed at a pressure of about 150 psig (about 1.0 MPa-g) for about 15 seconds. The combustion during the regeneration step was performed to provide a temperature profile similar to that shown in FIG. 4, but with a target peak temperature of 1150° C. at the end of the regeneration step / beginning of the reforming step. The reforming step during each cycle was performed at a pressure of 300 psig (about 2.1 MPa-g) for about 15 seconds with methane as the reforming hydrocarbon. The molar ratio of H2O to CH4 in the reforming step feed was 1.3.

[0127] Figure 9 shows the average conversion of methane during the reforming step (right plot) when the process is carried out over a period of 4 to 6 weeks. Due to the effects of cooling in the reactor towards the end of the reforming step during a single cycle, the conversion at the end of the reforming step in each cycle is somewhat lower. This is shown by the difference in conversion between averaging the first 10 seconds of each reforming step (left plot in Figure 9) and averaging the first 15 seconds of each reforming step (right plot in Figure 9). Note that shorter reforming steps can be used if it is desirable to maintain a higher overall conversion over the entire length of the reforming step.

[0128] As shown in the right plot of FIG. 9, both Example 3B and Example 3C initially provided higher conversion than Example 3A. This is consistent with the expected effect of using a higher surface area phase of alumina as the support for Examples 3B and 3C. However, as shown in the right plot of FIG. 9, the activity for conversion of the catalysts of Examples 3B and 3C is not stable. Although the data is noisy, it is clear that the conversion activity of the catalyst of Example 3C begins to decline almost immediately after the start of the run. This decline in activity continues until about 300 hours of cycling. At that point, the reaction in Example 3C was stopped because a rapid loss of activity had occurred. Example 3B has a more gradual decline in catalyst activity, but Example 3B also suffers from a substantial decline in activity that began well before the 400 hour run time. Between 400 and 800 hours, another set of cycling reforming conditions not plotted in FIG. 7 was used, but a similar decline in activity over time was observed. At 800 hours, the process conditions were restored to the initial reforming conditions. By 800 hours, decomposition of the catalyst appeared to stabilize, albeit at a significantly lower activity level than the catalyst of Example 3 A. Again, this loss of activity is believed to be due to decomposition of the catalyst system on the monolith within the reactor, resulting in a loss of available surface area for exposing the methane feed to the catalyst.

[0129] In contrast to Examples 3B and 3C, the right plot of Figure 9 shows that the catalyst system of Example 3A maintained similar activity over the entire length of the process run. Without being bound to any particular theory, this is believed to be due to Example 3A corresponding to a) a monolith made from materials that are phase stable under cyclic high temperature reforming conditions, and b) a monolith that includes an oxide support layer, such that any interaction between the catalytic metal (such as Ni) and the oxide material (such as Al2O3) occurs at the oxide support layer and does not affect the structural integrity of the underlying monolith or other support structure.

[0130] The left plot in Figure 9 shows similar results. Again, Example 3C initially shows higher activity than Example 3A, but the activity of Example 3C begins to decline almost immediately. Examples 3A and 3B initially had similar activity, but only Example 3A maintained its activity. As shown in both plots in Figure 9, Example 3A maintained essentially the same activity at a run length of 750 hours.

[0131] To further characterize the results of cyclic reforming of the catalyst system and monolith from Example 3A, at the end of the run, the peak temperature in the reactor was cooled to 1000° C. while maintaining alternating oxidation and reduction cycles. The reactor was then cooled to room temperature using N2 flow. After cooling, additional characterization was then performed.

[0132] After cooling, it was initially noted that for the first and second monoliths of Example 3A, the catalyst system was difficult to remove from the underlying monolith. Due to structural destruction, it is typically relatively easy to separate a catalyst or catalyst system from a monolith if the catalyst or catalyst system does not contain a thermally stable metal oxide. However, it was unexpectedly discovered that the use of a thermally stable support metal oxide for the catalyst system allows the catalyst system to maintain strong adhesion to the monolith after long-term exposure to a cyclic high-temperature reforming environment.

[0133] After removal, the catalyst systems from Example 3A were characterized using X-ray diffraction (XRD). The XRD spectra showed that all catalyst systems were in a stable phase. For the first monolith, the catalyst system was primarily in a reduced state. This was indicated based on the presence of substantial peaks of Ni and α-Al2O3 while little NiAl2O4 was present. The catalyst system for the second monolith was more oxidized with a mixture of Ni, NiO, α-Al2O3, and NiAl2O4 present. The XRD spectra of the third and fourth monoliths were similar to each other, both showing primarily Rh and α-Al2O3. Additional microscopic and elemental analyses of the catalyst systems were consistent with the XRD spectra.

[0134] Additional Embodiments Embodiment 1. 1. A method for reforming hydrocarbons in a cyclic reaction environment, comprising: exposing a reactant stream comprising reformable hydrocarbons to a catalyst system in a reaction zone within a reactor to form a product stream comprising H, the reaction zone comprising the catalyst system supported on one or more surfaces of a support structure, the catalyst system comprising Pd in ​​at least a portion of the reaction zone; and reacting a mixture comprising a fuel and 0.1 vol.% or more of O in a combustion zone within the reactor under combustion conditions to heat one or more surfaces within the reaction zone to a regeneration surface temperature of 1000° C. to 1300° C., wherein a minimum temperature of at least a portion of the reaction zone at the end of the exposure is 900° C. or greater, or a minimum temperature of at least a portion of the reaction zone at the start of the reaction is 900° C. or greater, or a combination thereof.

[0135] Embodiment 2. 2. The method of embodiment 1, wherein a minimum temperature of at least a portion of the reaction zone at the end of the exposure is greater than or equal to 900° C., or a minimum temperature of at least a portion of the reaction zone at the start of the reaction is greater than or equal to 950° C., or a combination thereof.

[0136] Embodiment 3. The method of any of the preceding embodiments, wherein the peak temperature of at least a portion of the reaction zone at the start of the exposure is less than or equal to 1300° C., or the peak temperature of at least a portion of the reaction zone at the end of the reaction is less than or equal to 1300° C., or a combination thereof.

[0137] Embodiment 4. The method of any of the preceding embodiments, wherein the direction of flow of the reactant streams in the reaction zone is opposite to the direction of flow of the mixture.

[0138] Embodiment 5. The method of any of the previous embodiments, wherein the catalyst system comprises Ni, Rh, Ru, Pt, Cu, Ir, or combinations thereof in the second portion of the reaction zone.

[0139] Embodiment 6. The method of any of the above embodiments, wherein the at least a portion of the reaction zone comprises the one or more surfaces within the reaction zone.

[0140] Embodiment 7. The method of any of the previous embodiments, wherein the catalyst system further comprises a metal oxide support layer, the metal oxide support layer comprising stabilized zirconia, perovskite, pyrochlore, spinel, hibonite, zeolite, corundum group oxide, or a combination thereof.

[0141] Embodiment 8. 8. The method of embodiment 7, wherein the metal oxide support layer is thermally phase stable at 800°C to 1600°C.

[0142] EMBODIMENT 9. 9. The method of claim 7 or 8, wherein a) the catalyst system in at least a portion of the reaction zone further comprises Ni, Rh, Ru, Pt, Cu, Ir, or a combination thereof; b) at least a portion of the catalyst system comprises a mixture of the catalyst and the metal oxide support layer; or c) a combination of a) and b).

[0143] EMBODIMENT 10. 10. The method of any of claims 7-9, wherein i) the metal oxide support layer comprises α-Al2O3, yttria stabilized zirconia (YSZ), perovskite, or a combination thereof; ii) the metal oxide support layer comprises 80 wt% or more α-Al2O3, based on the weight of the metal oxide support layer; or iii) a combination of i) and ii).

[0144] Embodiment 11. 11. The method of any one of embodiments 7-10, further comprising an intermediate bonding layer comprising a metal oxide, a first surface of the intermediate bonding layer contacting at least a portion of the one or more surfaces of the support structure, and the catalyst system being supported on the surface of the support structure by being at least partially supported on a second surface of the intermediate bonding layer, the intermediate bonding layer optionally comprising α-Al2O3.

[0145] Embodiment 12. 5. The method of any of the previous embodiments, wherein the support structure comprises a monolith having a cell density of 50 cells per square inch to 900 cells per square inch, or the support structure comprises 80 wt. % or more Al2O3, or a combination thereof.

[0146] Embodiment 13. % or more 0.1 vol.% O2 under combustion conditions in the combustion zone of the reactor to heat the one or more surfaces in the reaction zone to a regenerative surface temperature of 1000° C. to 1300° C. after said exposing of the second portion of the reactant stream. The method of any of the above embodiments, further comprising: exposing a second portion of the reactant stream comprising the reformable hydrocarbon to the catalyst system in a reaction zone of the reactor after said reacting to form a product stream comprising H2; and reacting a second portion of the mixture comprising a fuel and 0.1 vol.% or more O2 under combustion conditions in the combustion zone of the reactor after said exposing of the second portion of the reactant stream to heat the one or more surfaces in the reaction zone to a regenerative surface temperature of 1000° C. to 1300° C., wherein a minimum temperature in the at least a portion of the reaction zone at the end of said exposing of the second portion of the reactant stream is 900° C. or more, or a minimum temperature in the at least a portion of the reaction zone at the start of the reacting of the second portion of the mixture is 900° C. or more, or a combination thereof.

[0147] Embodiment 14. 5. The method of any of the previous embodiments, wherein the catalyst system comprises 0.1 wt.% to 10 wt.% Pd based on the weight of the catalyst system, or the catalyst system comprises 0.5 wt.% to 6.0 wt.% Pd based on the weight of the catalyst system.

[0148] EMBODIMENT 15. 2. The method of claim 1, wherein the catalyst system comprises a catalyst system that has been calcined at a temperature between 900° C. and 1500° C. prior to the reaction.

[0149] Although the present invention has been described and illustrated with reference to specific embodiments, those skilled in the art will recognize that the invention accommodates variations not necessarily exemplified herein, and for this reason, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.

Claims

1. A method for reforming hydrocarbons in a cyclic reaction environment, comprising exposing a reactant stream containing reformable hydrocarbons to a catalyst system in a reaction zone within a reactor to form a H ２ forming a product stream comprising Pd in ​​at least a portion of the reaction zone, the catalyst system being supported on one or more surfaces of a support structure, the catalyst system comprising Pd in ​​at least a portion of the reaction zone; and ２ and heating one or more surfaces within a reaction zone to a regeneration surface temperature of 1000° C. to 1300° C., wherein a minimum temperature of at least a portion of the reaction zone at the end of the exposure is 900° C. or greater, or a minimum temperature of at least a portion of the reaction zone at the start of the reaction is 900° C. or greater, or a combination thereof.

2. 2. The method of claim 1, wherein a minimum temperature of at least a portion of the reaction zone at the end of the exposure is greater than or equal to 900° C., or a minimum temperature of at least a portion of the reaction zone at the start of the reaction is greater than or equal to 950° C., or a combination thereof.

3. 13. The method of any preceding claim, wherein the peak temperature of at least a portion of the reaction zone at the start of the exposure is less than or equal to 1300° C., or the peak temperature of at least a portion of the reaction zone at the end of the reaction is less than or equal to 1300° C., or a combination thereof.

4. 10. The method of any preceding claim, wherein the direction of flow of the reactant streams in the reaction zone is opposite to the direction of flow of the mixture.

5. 13. The method of any preceding claim, wherein the catalyst system comprises Ni, Rh, Ru, Pt, Cu, Ir, or combinations thereof in the second portion of the reaction zone.

6. 2. The method of any preceding claim, wherein said at least a portion of said reaction zone comprises said one or more surfaces within said reaction zone.

7. 2. The method of any preceding claim, wherein the catalyst system further comprises a metal oxide support layer, the metal oxide support layer comprising stabilized zirconia, perovskite, pyrochlore, spinel, hibonite, zeolite, corundum group oxide, or a combination thereof.

8. The method of claim 7, wherein the metal oxide support layer is thermally phase stable from 800°C to 1600°C.

9. 9. The method of claim 7 or 8, wherein a) the catalyst system in said at least a portion of said reaction zone further comprises Ni, Rh, Ru, Pt, Cu, Ir, or a combination thereof; b) at least a portion of said catalyst system comprises a mixture of said catalyst and said metal oxide support layer; or c) a combination of a) and b).

10. i) the metal oxide support layer is α-Al ２ O ３ , yttria stabilized zirconia (YSZ), perovskite, or a combination thereof, or ii) the metal oxide support layer comprises 80 wt. % or more of α-Al, based on the weight of the metal oxide support layer. ２ O ３ or iii) a combination of i) and ii).

11. and an intermediate bonding layer comprising a metal oxide, a first surface of the intermediate bonding layer contacting at least a portion of the one or more surfaces of the support structure, the catalyst system being supported on the surface of the support structure by being at least partially supported on a second surface of the intermediate bonding layer, and the intermediate bonding layer optionally comprising an α-Al ２ O ３ The method according to any one of claims 7 to 10, comprising:

12. The support structure comprises a monolith having a cell density of 50 cells per square inch to 900 cells per square inch, or the support structure comprises 80 wt. % or more Al ２ O ３ 5. The method of any of the preceding claims, comprising or a combination thereof.

13. After the reaction, a second portion of the reactant stream containing the reformable hydrocarbon is exposed to the catalyst system in a reaction zone within the reactor to produce H ２ and forming a product stream comprising fuel and at least 0.1 vol. % O under combustion conditions in the combustion zone of the reactor after said exposing said second portion of said reactant stream. ２ and heating the one or more surfaces in the reaction zone to a regeneration surface temperature of from 1000° C. to 1300° C., wherein a minimum temperature in the at least a portion of the reaction zone at the end of the exposure of the second portion of the reactant flow is 900° C. or greater, or a minimum temperature in the at least a portion of the reaction zone at the start of the reaction of the second portion of the mixture is 900° C. or greater, or a combination thereof.

14. 13. The method of any preceding claim, wherein the catalyst system comprises 0.1 wt% to 10 wt% Pd based on the weight of the catalyst system, or wherein the catalyst system comprises 0.5 wt% to 6.0 wt% Pd based on the weight of the catalyst system.

15. A method according to any preceding claim, wherein the catalyst system comprises a catalyst system that has been calcined at a temperature of from 900°C to 1500°C prior to the reaction.

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