Dry reforming catalyst system

Abstract

Dry reforming catalyst, methods of making the catalysts, and methods of dry reforming over the catalyst are described. A preferred catalyst comprises a core comprising SiC and Al-Si alloy, less than (5) wt% oxygen; an intennediate coating disposed over the core, the intermediate coating comprising at least 50% of Al-Si alloy; and disposed over the intermediate coating, a coating comprising Ni or Ni-alloy supported on an oxide comprising Mg and Ca. In the intermediate layer, Ni is preferably in the range of (5) to 25 wt% Ni.

Description

[0001] Dry Reforming Catalyst System

[0002] Related Applications: This application claims the priority benefit of US Provisional Patent Application Ser. No. 63 / 462,682 filed 18 November 2022.

[0003] Government Rights Clause: This invention was made with Government support under contracts DE- SC0015800 and DE-SC0013114 awarded by the U.S. Department of Energy. The Government has certain rights in this invention.

[0004] Introduction

[0005] A promising process technology for the reduction of greenhouse gas emissions is in chemicals production using the Dry Reforming of Methane (DRM reaction), in which CO2 and CH4 convert catalytically to form synthesis gas (CO and Hydrogen “syngas ” is a precursor to many useful chemicals and fuels). The reaction is highly endothermic and substantial amounts of steam are required to avoid formation of solid surface site carbon in practical industrial reactors. Surface coking reduces catalyst effectiveness, on-stream time, and concomitant fast deactivation rates lead to frequent catalyst replacement. Commercialization of this important reaction approach to reducing greenhouse gas emissions has been limited due to a lack of a practical catalyst system that can run unaffected by coke formation for long run lengths (months to years) on industrial scale catalyst pellets.

[0006] One resource to produce syngas via DRM is biogas feedstock, a combination of CH4 and CO2 (which is natural by-product of anaerobic digestion, AD). AD systems are part of waste-water treatment plants and used to decompose food waste or animal manure. Landfills produce significant amounts of biogas as part of the natural destruction of organic matter. A practical system to convert this low value biogas stream to a higher value product (synthesis gas) has great commercial value. Sources of biogas are often distributed, and a simple compact tubular conversion technology would have commercial benefit to avoid transmission of biogas for central processing or reduce purification costs to separate CO2 from CH4 for subsequent methane addition to natural gas pipelines.

[0007] It is understood that the feed gas may comprise methane and carbon dioxide as captured together or separately and then mixed from sources beyond traditional biogas sites. The feedstock may comprise carbon dioxide as collected from direct air capture systems, industrial flue gas, or other sources. The technology may be considered compact as enabled by larger tube diameters due to the improved heat transfer resulting in fewer tubes, lower costs, and a smaller footprint for a multi-tubular reactor system.

[0008] Further, in a carbon-constrained economy, the capture and utilization of emitted CO2 from industrial and biological processes present a compelling means of reducing atmospheric CO2. Reforming processes that utilize CO2 to produce syngas streams with the appropriate carbon to hydrogen ratios for synthesis processes to make feedstock chemicals (Fischer Tropsch liquids and waxes (FTS), methanol (MeOH), di-methyl ether (DME), among others) are both economically and ecologically advantaged in the marketplace.

[0009] For the DRM reaction, it is theorized that different active catalyst sites contribute to the conversion of CH i and CO? and hence, different rates of deactivation are possible, including those that are resultant from coke formation.

[0010] Dchirni ct al (2017) uses microkinctic modeling for DRM to teach that methane absorbs and activates on Nickel catalyst sites for the DRM reaction. CO2 adsorbs on a site before dissociating to CO* and 0* . The paper discusses that the surface coverage of CO2 on Ni is low, and CO2 may adsorb first on a support site (for their reported single active metal catalyst). The paper also teaches that the main cause of carbon formation is the surface coverage of CO* which can decompose to surface carbon.

[0011] Jun, et al., (2011) describe a reaction mechanism for dry reforming on a Ni-based catalyst. Exemplar kinetics developed for the inventive catalysts were partially based on the mechanism described by Jun and co-workers. The authors note that the use of carbon dioxide in the feed increases the rate of deactivation due to carbon deposition. Their tests were conducted with a steam to carbon ratio between 2 and 4 to avoid coke formation favored by lower steam to carbon ratios.

[0012] Liu, et al., (2019) report that the addition of Co active metal with Ni acts to improve a DRM catalyst resistance to carbon formation for tests conducted at 1 atm, 700 °C, 1:1 CH4to CO2ratio, and no steam in the feed mixture. During a 3-hour test, there was no reported loss of conversion but during subsequent TGA of spent catalysts whisker carbon formation was observed. The measured CO2conversion was higher than CEL conversion due to the RWGS reaction. For the reported feed flowrate, conversions and weight of catalyst noted in the cited reference (100 mg powder), the DRM catalyst productivity was 32.5 g / g / h.

[0013] Tanios, et al., (2017) report that the bimetallic DRM catalyst of Co-Ni is more resistant to carbon formation. Tests with 100 mg of powder catalyst were tested for 2 hours at 1 atm without added steam and 700 C. Methane was near 90% and CO2 conversion near 85%. Even with the short test duration (2 hours) there was carbon fonnation although noted as somewhat reduced with the addition of Co to the Ni catalyst. The calculated DRM catalyst productivity was about 27.7 g / g / h.

[0014] Wehinger, et al., (2016) show atmospheric data for the dry reforming reaction of a 10-micron Ni- based catalyst coated on the exterior of roughly 1 mm diameter dense alumina spheres as tested between 635 °C and 850 °C wall temperature. The feed mixture did not contain steam. As shown in Figure 15A and 15B of the reference, the images suggest shows solid carbon formation in tire last third of the reactor length and preferential carbon formation in the outer annular region rather than the center of the catalyst bed. Kang, et al., (2011) used a core-shell type Ni-catalyst coated on the exterior of alumina nanoparticles and tested the material under DRM conditions at 1 atm. The catalysts consisted of a 2 nanometer (nm) thick coating of a Ni catalyst around about a 50 nm diameter alumina nanoparticle. The nanoparticle catalyst was distributed within a quartz wool where 100 mg of Ni-nanoparticles were placed within a reactor volume consisting of an 8 mm tube diameter and a 0.5-m tube length. The highly dispersed packing of nanoparticles is needed to avoid a substantial pressure drop otherwise created by very small particles (2 nanometer). Further this dispersed packing configuration would be unlikely to result in cold spots. Solid carbon was measured after testing between 700 and 800 °C for 150 hours with an aluminabased catalyst support material, but no carbon formation was noted for the highly dispersed nanoparticles using an MgO-based support. The amount of carbon deposited is higher at lower temperatures but measurable under reported test conditions.

[0015] Cho, et al., (2020) tested an Ni-based SMR catalyst as an eggshell around a porous pellet. The authors report a reduction in the amount of coke formed, but carbon still formed after 6 hours as tested under atmospheric conditions and a Steam to Carbon of 0.5.

[0016] Latsiou, et aL, (2022) coat aNi-based catalyst as an eggshell on a gamma-alumina porous extrudate catalyst and tested under DRM conditions. Carbon deposition occurred on tire Ni surface but was reduced by the placement of the eggshell catalyst.

[0017] Summary of the Invention

[0018] In a first aspect, the invention provides a catalyst capable of catalyzing dry reforming, comprising: a core comprising SiC and / or a core coated with an Al-Si alloy; an oxide-supported Ni orNi alloy disposed on the exterior of the catalyst. The catalyst is characterizable by one or any combination of the properties described herein, for example: when CH, and COz in a 1: 1 ratio are passed into a tube reactor having an inner diameter of 0.019-m (or, alternatively, at least three times the mass average diameter of the catalyst pellets) containing a catalyst zone of 10 cm3in the central region of a tube furnace of packed bed pellet catalyst, where the temperature of the wall of the tube reactor is held at 850 °C; wherein a feedstream consisting of CH4, H2O, and CO2 , at a CH4 / CO2 = 1 and a steam to carbon ratio of 0.5 at 20 bar(gauge) and a flow rate of 1500 GHSV (based on volume of catalyst chamber) and converting at least 10% or at least 20% or 10 to 25% CO2 for at least 100 hrs or at least 200 hrs without regeneration and having a decrease in CO2 conversion of 1% or less without regenerating the catalyst over this time; and converting at least 30, at least 40, or at least 50, or 30 to 50g CH4 per g Ni per hour and / or converting at least 20, at least 30, or at least 35, or 20 to 40g CO2 per g Ni per hour. Note that ‘'characterizable” means that the catalyst can be characterized by testing under these conditions, but tire scope of the invention is not limited by these test conditions. Preferably, no observable carbon is deposited on the carbon during the characterization testing.

[0019] In another aspect, the invention provides a catalyst pellet capable of catalyzing dry reforming, comprising: a core comprising SiC and Al-Si alloy and comprising less than 5 wt% oxygen, preferably less than 2 wt% oxygen; an intermediate coating disposed over the core, the intennediate coating comprising at least 50% or 70% or at least 90 or 95 wt% of Al-Si alloy; and disposed over the intennediate coating, a coating comprising Ni orNi-alloy supported on an oxide comprising Mg and Ca. In the intermediate layer, Ni is preferably in the range of 5 to 25 wt% Ni, or 5 to 20%, or 10 to 15%; in some embodiments the intermediate layer consists essentially of Mg, Ca, Ni and O; in some embodiments the Mg / Ca weight ratio in the range of 0.1 to 10. Preferably, the catalyst is be further characterizable by one or any combination of the properties described herein

[0020] In any of the inventive aspects, the catalyst may further comprise one or any combination of the following: further comprising an Al or Al alloy coating over the core comprising SiC; having an average thickness of alloy coating at least 5 pm, or at least 100 pm, 200 pm or a range of about 20 to 100 pm; wherein the core further comprises Al-Si; mass ratio of SiC / Al-Si in the range of 5 : 1 to 4 / 6; or at most 4: 1 or at most 3: l or at most 7 / 10; or at least 1:1 or at least 1.5 or at least 1.7; or about 2: 1; wherein the catalyst comprises a Ni - based catalyst; and / or having an average thickness of exterior catalyst coating at least 5 pm, or at least 10 pm, or in the range from 5 to 400 pm, 10 to 300 pm, 50 to 350 pm. Note that thickness is measured by SEM of a cross-section of a catalyst, and average calculated from at least 5 representative areas of the cross-section.

[0021] In a further aspect, the invention provides a method of making a catalyst, comprising: combining SiC powder and Al-Si powder; adding binder and compressing into a pellet; coating the pellet with alloy pow der, preferably via an aerosol, calcining to form a calcined pellet; coating the calcined pellet with a Ni-based DRM catalyst; and calcining to result in an exterior catalyst coating.

[0022] The method optionally further comprises one or any combination of: wherein the green pellet has a volume of 0.05 to 1 cc. 0.07 to 0.3 cc; alloy powder is aluminum alloy, preferably Al-Si alloy; wherein the alloy comprises 5-25 mass% Si, 5-20%, 8-17%, 10-15%; wherein the calcining to form a calcined pellet is conducted at a temperature of at least 1200 C, 1300 C, 1350 to 1450 C in air; ramping down 2-10 °C, 3- 8 °C; average thickness of alloy coating at least 50 pm, or at least 100 pm, 200 pm; mass ratio of SiC / Al- Si in the range of 5: 1 to 4 / 6; or at most 4: 1 or at most 3: 1 or at most 7 / 10; or at least 1: 1 or at least 1.5 or at least 1.7; or about 2: 1; wherein the DRM catalyst comprises a Ni-based catalyst; wherein the catalyst is applied as a slurry'; slurry comprises binders; w'herein the resulting coated pellets are calcined; preferably calcined in air at 550 to 800; 600 to 750 C to result in an exterior catalyst coating; wherein the SiC core comprises 15 to 30 volume percent SiC; having an average thickness of exterior catalyst coating at least 5 pm, or at least 10 pm, or in the range from 5 to 400 pm, 10 to 300 pm, 50 to 350 pm.

[0023] Tire invention also includes a catalyst made by any of the methods described here.

[0024] In another aspect, the invention provides a method of reforming, comprising: passing CH4 and CO2 at a pressure of at least 5 barg and a feed Steam:C ratio less than or equal to 1.0 or less than or equal to 0.7 into a reaction chamber comprising a dry reforming catalyst comprising a core comprising SiC; a Ni or Ni alloy disposed on the exterior of the catalyst; reacting the CH4 and CO2 in contact with the catalyst at a temperature of at least 800 °C (at a wall of the reaction chamber) and converting at least 10% or at least 20% or 10 to 25% CO2 for at least 100 hrs or at least 200 hrs without regeneration and having a decrease in CO2 conversion of 1% or less without regenerating the catalyst; and converting at least 30, at least 40, or at least 50, or 30 to 50g CH4 per g Ni per hour and / or converting at least 20, at least 30, or at least 35, or 20 to 40g CO2 per g Ni per hour. Preferably, no observable carbon is deposited on the carbon during this method.

[0025] In a further aspect, the invention provides a method of reforming, comprising: passing a gas stream comprising CH4and CO2 into a reaction chamber comprising a catalyst; reaction chamber comprises a catalyst capable of catalyzing dry reforming, comprising a SiC core and Ni or Ni alloy disposed on tire exterior of the catalyst; reacting the CH4 and CO2 at atemperature of at least 750 °C; wherein the gas stream entering the reaction chamber has a steam: carbon ratio [steam to carbon ratio is the molar ratio of water to moles of carbon from all sources] of 1.4 or less; wherein CH4 conversion is at least 28%.

[0026] The method of reforming optionally further comprises one or any combination of: the method operating continuously at a pressure of 10 bar(gauge) for at least 5 hours or at least 10 hours without regenerating the catalyst and wherein the coke is not formed on the catalyst; a ratio of CH4 and CO2 in the gas stream at least 0.2, 0.5, 1.0, 1.2; or in range from 0.2 to 2; preheating the gas stream prior to entering the reaction chamber; reacting the CH4 and CO2 at a temperature of at least 775, 800, 825, in the range of 775 to 900, 800 to 850 °C; wherein the temperature refers to the temperature at a wall of the reaction chamber and wherein temperature in the center of the reaction chamber at a distance to the wall measured perpendicular to flow has a temperature in the range of about 125 to 25 °C or 75 to 25 °C lower than the wall temperature; steam:carbon ratio 1.2 or less, 1.0 or less, 0.8 or less, the lower limit may be 0 or 0.2 or more, 0.5 or more, 0.8 or more, 1.0 or more, or 1.2 or more; wherein CH4 conversion is at least 28% or at least 40% or at least 60% or at least 70% or in the range of 30 to 65% or 40 to 60%; wherein CO2 conversion is at least 10% or at least 20% or at least 40% or at least 50% or in the range of 30 to 65% or 10 to 70%; wherein CH4 conversion at steady state remains constant at any of the levels mentioned above and changes by 10% or less for at least 5 hours or at least 10 hours or at least 50 hours or at least 100 hours without regenerating or replacing the catalyst; wherein CO? conversion at steady state remains constant at any of the levels mentioned above and changes by 10% or less for at least 5 hours or at least 10 hours or at least 50 hours or at least 100 hours without regenerating or replacing the catalyst; wherein the catalyst shows no whiskers or amorphous fonns of carbon after operation at any of the conditions described herein.

[0027] The invention also provides a refonning system, comprising any of the apparatus, reactants, catalysts and / or conditions described herein.

[0028] The catalyst of the present invention comprises a SiC core. Materials referred to herein as “HeatPath™” comprise a SiC core and have properties of very high thermal conductivity and catalytic effectiveness and may include (but are not limited to) any of the core materials mentioned in US 20210245139 (incorporated herein as if reproduced in full below).

[0029] HeatPath™ pellets coated with a thin Ni-based DRM catalyst create a superior catalyst structure for reducing carbon formation, thus enabling a long-lived commercial DRM process to convert biogas to syngas (CO and H2). The highly conductive catalyst (pellet core that is substantially dense to catalyst and fluid, coupled with an external active catalyst coating) reduces thermal gradients at 1) the wall of the reactor (lower temperature needed to drive the reaction), 2) the center of the endothermic tubular reactor, and 3) eliminates cold spots inside an individual catalyst pellet.

[0030] The wall temperature required to drive heat into the endothermic reaction is lower for equal conversion due to the ease of thermal conduction heat transfer through the HeatPath™ pellets. The gradient across the tubular reactor bed in the radial direction is reduced by using the higher thermal conductivity of the superior HeatPath™ catalyst structure. The temperature cold spot at tire center of the tubular reactor is less severe than found if a conventional pellet with a lower thermal conductivity were used.

[0031] The internal HeatPath™ pellet is substantially dense from fluids and hence is not filled with catalyst nor reacting or product gases. In contrast, the interior of a porous catalyst pellet under endothermic reaction conditions is cooler than the exterior of the pellet. For catalyst-coated HeatPath™ pellets, the “cold core” inside a pellet is eliminated by blocking access of the catalyst and gases to the pellet interior, replacing it with the HeatPath™ structure. The interior of the pellet if not fully dense would allow gas diffusion and reactions which preferentially favor the fonnation of carbon monoxide and its subsequent conversion to tire unwanted solid carbon.

[0032] Two modes of carbon fonnation are common and can occur in parallel the DRM reaction.

[0033] • Boudouard reaction: 2 CO -> CO2+ C(s); forms coke, favored at lower temperatures typically between 500 and 700 °C (due to cold spots in a reactor) and at higher total pressure and higher partial pressure of CO Cracking reaction: CH4 - C(s) + 2 H2; forms coke, favored at higher temperatures (hot walls)

[0034] These coking reactions occur in parallel with the primary reactions for the DRM reactor:

[0035] • DRM reaction: 2 CO + 2 H2; equilibrium limited favored at high T and low P

[0036] • SMR reaction: CH4 + H2O - CO + 3 H2; competes with DRM, equilibrium limited

[0037] • Water Gas Shift, WGS : CO + H2O = CO2+ H2

[0038] • Reverse Water Gas Shift, RWGS: CO2 + H2= CO + H2O

[0039] Coke formed from the Boudouard pathway (CO + CO = C(s) + CO2) is sensitive to temperature, wherein this reaction is more thermodynamically favored at lower temperatures. Reducing the magnitude of the cold spot or endotherm within a reactor by using the HeatPath™ catalyst structure creates a net higher temperature on active catalyst sites and thereby acts to reduce solid carbon fonnation.

[0040] Reduced cold spots at the center of the reactor and eliminated at the core of a pellet reduce the likelihood of carbon formation via the Boudouard reaction. Cooler wall temperatures reduce the likelihood of methane cracking which also forms solid carbon to block active catalyst sites. Tire HeatPath™ catalyst provides multiple benefits for stable operation with reduced carbon formation in a practical industrial tubular reactor.

[0041] HeatPath™ reduces carbon formation through a combination of variables - including an improved heat transfer structure, excluded internal pellet porosity to avoid a cold pellet core, and a catalyst composition that is sufficient for limiting carbon formation when operated with thermal control.

[0042] Brief Description of the Drawings

[0043] Fig. 1 A schematic of the test stand to collect data with the HeatPath catalyst for DRM.

[0044] Fig. 2 The product ratio of H2 / CO as a function of reactor temperature at 1500 hr-1 GHSV, 1: 1 CHuCCT, and S:C ratio near 1 .5 for either 10 barg (open symbol) or 20 barg (closed symbol).

[0045] Fig. 3 Tire product ratio of CO2 / CO as a function of reactor temperature at 1500 hr-1 GHSV, 1 : 1 CO2:CH4, and S:C ratio near 1.5 for either 10 barg (open symbol) or 20 barg (closed symbol).

[0046] Fig. 4 Hie conversion of CH4or CO2 as a function of feed S:C ratio at 20 barg, 850 C, 1: 1 CO2:CH4, and 1500 hr-1 GHSV.

[0047] Fig. 5 HeatPath stability shown as the reactant or product specie % vs time on stream in hours for various SteanrCarbon feed ratios at 850 C, 20 barg, Feed CH4 CO2 ratio=l, and 1500 hr-1 GHSV. No coke was observed on the spent catalyst tablets after 465 total hours of operation including S:C=0.3.

[0048] Fig. 6 Full Pellet stability shown as the reactant or product specie % vs time on stream for SteanrCarbon feed ratios of 1.5 and 0.5 at 850 C, 20 barg, Feed CFtyCCh ratio=l, and 1500 hr-1 GHSV. Fig. 7 shows SEM images with EDS analysis of Carbon observed inside the Full Pellet with Catalyst 1 after testing for 75 hours at S:C=0.5, 850 °C, 1500 hr-1 GHSV, 20 barg.

[0049] Fig. shows 8 SEM images with EDS analysis of Carbon inside the HeatPath pellet with Catalyst 1 after testing for 200 hours at S:C=0.3, 850 C, 1500 hr-1 GHSV, 20 barg.

[0050] Fig. 9 HeatPath stability shown as the reactant or product specie % vs time on stream in hours for various Steam:Carbon feed ratios at 850 °C, 20 barg, Feed CHyCCE ratio=l, and 1500 hr-1 GHSV. No coke was observed on the spent catalyst tablets after 302 total hours of operation including S:C=0.5.

[0051] Fig. 10 Full Pellet stability shown as the reactant or product species % vs time on stream for Steam:Carbon feed ratios of 1.5 and 0.5 at 850 °C, 20 barg, Feed CHyCCE ration I . and 1500 hr-1 GHSV.

[0052] Fig. 11 Methane (circle) and CO2 (triangle) conversion versus operating pressure (from 12 to 20 barg) for S:C=1 and CHyCCE for a HeatPath catalyst coated with a PGM catalyst (Catalyst 3) at either 5000 (closed) or 12,000 (open) GHSV in hr1.

[0053] Fig. 12 Equilibrium conversion of CO2 or CH4 at 10 or 20 barg as a function of S:C.

[0054] Fig. 13 Equilibrium conversion of CO2 or CH4 as a function of temperature for Steam: Carbon of 0.3 or 1.5. Fig. 14 Relative CO concentration from the inside of the pellet to the edge as a function of reactor length for the full Pellet as tested at S:C=0.5, 850 °C wall, 1500 hr-1 GHSV, CH4:CO2=1, and 20 barg.

[0055] Fig. 15 Calculated reactor bed temperature as a function of length for the full pellet tested at S:C=0.5, 850 C wall, 1500 hr-1 GHSV, CH4:CO2=1, and 20 barg.

[0056] Fig. 16 Carbon activity for the Boudouard coke formation reaction using the formula provided by Karabelchtchikova calculated inside the full pellet as tested at S:C=0.5, 850 C wall, 1500 hr-1 GHSV, CH4:CC>2=1, and 20 barg. The curves are at equidistant locations within the pellet with the edge of the pellet is the lowest curve and does not exceed 1. Carbon activity near the center of the pellet is the top curve and exceeds 1 near the front, and again near the middle region of the reactor length.

[0057] Fig. 17 Temperature profile comparison for the HeatPath (thick, circle) and full pellet (thin) along the reactor length predicted using the Catalyst 1 reaction kinetics for the comparison test conditions at S:C=0.5, 20 barg, 1500 hr1GHSV, and CH4 CO2M .

[0058] Additional Descriptions of the Invention

[0059] Catalyst supports and catalysts of the present disclosure can be fabricated in any of a variety of shapes, including those known to those skilled in the art as well as those hereafter developed. Suitable shapes include, for example, spheres, cylinders, pellets, beads, lobed cylinders (e.g., bilobe, trilobe, tetralobe, etc.), saddles, wheels, rings, pall rings, Raschig rings, ribbed or grooved cylinders, notched cubes, grooved pyramids, daisy-shaped, and star-shaped pellets. Alternatively, the catalysts of the present disclosure can be fabricated as monolithic structures. The catalyst supports can be formed into the desired

[0060] 8

[0061] SUBSTITUTE SHEET (RULE 26) shape and size by, for example, extrusion, pressing, or molding. It will be understood that, although portions of the description herein refers explicitly to pellets, it will be understood that, unless the context indicates otherwise, that description will apply equally to any other catalyst shapes. In some cases, catalyst pellets typically have a characteristic dimension or hydraulic diameter of about 1 mm to 50 mm. In some embodiments, the density of the catalyst core is from about 60% to 100% of theoretical density, or from about 60% to about 90% of theoretical density, or from about 65% to about 80% of theoretical density.

[0062] Catalysts of the present disclosure can be employed in any of a wide variety of reactor types and configurations, including those known to those skilled in the art as well as those hereafter developed. For example, catalysts of the present disclosure can be employed in fixed bed reactors (also referred to as packed bed reactors), fluidized bed reactors, microchannel reactors, membrane reactors, ebullating bed reactors, chromatographic reactors, and moving bed reactors. The catalysts of the present disclosure are particularly useful for fixed bed (i.e., packed bed) reactors, wherein a free-flowing catalyst is loaded within a reaction chamber of various cross-sectional shapes such as cylindrical, rectangular, square, or other shape. The free- flowing catalyst conforms to the shape of the reaction chamber and is fixed in place for reaction operation. During operation, the catalyst is preferably fixed in position within the reaction chamber(s), rather than moving as in the case of a fluidized bed reactor.

[0063] The catalysts may be made from powders. A powder blend can be mixed with various additives, such as one or more organic binders (polyvinyl alcohol, polyvinyl butyral (“PVB”, ethyl or methylcellulose, and the like), and / or one or more plasticizers (e.g., butyl benzyl phthalate (“BBP”), ethylene glycol, polyethyl glycol, and the like). These additives allow the fine powders to be processed (e.g., via pan drying, crushing and sieve separation, or by spray drying) to form larger agglomerated powders that are more easily fed into a dry pressing operation (or other pellet forming equipment). Further, to aid in the pressing operation, lubricants, such as zinc stearate, steric acid, and / or carbon powders such as graphite can be added to the agglomerated powder to ease the dry pressing operation.

[0064] While dry pressing can be used to form the catalyst cores (e.g., as pellets), various other methods can be used to form the cores such as extrusion, wet pressing, slip casting, isostatic pressing, injection molding, and other common ceramic forming approaches, provided that the process applies sufficient pressure to achieve the targeted density in the green state (>60% of the theoretical density of the blended SiC / Al powders) and cause plastic deformation of the aluminum.

[0065] While the pressed or extruded pellets can be subjected to calcination following pellet formation, in an alternative embodiment the pellets can be further subjected to a pre-calcination high temperature heat treatment in a substantially oxygen-deficient environment before being subjected to calcination. When used, the pre -calcination heat treatment step may cause the aluminum (or aluminum alloy) particles to sinter (e.g., at temperatures above about 400° C.) and further melt and coalesce (e.g., at temperatures above about

[0066] 9

[0067] SUBSTITUTE SHEET (RULE 26) 550° C.) allowing for rearrangement of the microstructure. This liquid phase may also further slow or prevent the oxidation of the SiC during subsequent heat treatment at temperatures above 500 °C in air or oxygen-containing environments by preventing oxygen or steam (gas) diffusion into the structure. Thus, a pre -calcination heat treatment can be performed at a temperature which is the same as, or different from, the calcination temperature, particularly one that is lower. Typically, however, the pellets will be calcined following pellet formation (i.e., no pre-calcination heat treatment), at a temperature of 850 to 1450° C., or 900 to 1000° C., for a period of time sufficient to convert the aluminum into an alumina matrix around the SiC grains. Calcination is performed in an oxygen-contaming environment, such as oxygen, air, steam, or dilutions of the foregoing with nitrogen, argon, hydrogen and / or another carrier gas. In one embodiment, the pellets comprising SiC and Al (or Al — Si) are calcined in ambient air, without having to control the amount of oxygen in the calcination environment, thereby reducing costs.

[0068] Examples

[0069] The results of the experiments below demonstrate superior and unexpected properties of the inventive catalyst, method and system (apparatus plus reactants, products and / or conditions) as tested over a coated HeatPath™ pellet.

[0070] Example 1

[0071] A fixed bed reactor made of Incoloy 800 had an inner diameter of 0.01905-m and a catalyst zone length of 0.0351-m. Hollow AI2O3 tablets (5mm length, 5mm outer diameter, 2.5mm inner diameter) were packed upstream of the 10 cm3catalyst reactor volume. Downstream of the catalyst an additional 10 cm3of hollow AI2O3 tablets were packed and followed by a modest amount (between 1 to 5 cm3) of AI2O3 wool supported by a Ni wire coil to maintain axial position within the reactor. The total reactor volume in the catalyst section was about 10 cm3.

[0072] An equal feed mixture of CO2 and CH4 were used for most tests. Flows were fed using calibrated AliCat Scientific mass flow controllers and mixed upstream of the catalyst bed. A water stream was metered by a high-pressure piston water pump and then vaporized by a single zone vaporizer and a super heater chamber. The produced steam joined with the mixed CO2 and CH4 feed stream. The mixed gases were preheated by the single zone vaporizer and super heater chamber and fed in a downflow manner to the fixed bed reactor.

[0073] The HeatPath™ core pellet was a cylindrical tablet of approximately 0.006-m in diameter by 0.004- m in height. The material comprised about 64wt% SiC and 36wt% of Al-Si. The SiC powders were 400 grit (80wt%) and 1200 grit (20wt%) blend and 99.2+% purity as received from Panadyne. The spherical Aluminum silicon passivated powders were 3.8-micron average diameter of 11.73wt% Si and 87.9+wt%

[0074] 10

[0075] SUBSTITUTE SHEET (RULE 26) Al purity as received from Valimet. The core was created by mixing the powders and slowly incorporating a PVB, BBP, and ethanol binder solution using an Eirich mixer. The powder was dried in air before adding steric acid (3.7wt% relative to dry powder total) and carbon lubricants (3.7wt% relative to dry powder total). Pellets were then pressed using a Korsch press until a pellet density between about 70 and 72% of theoretical (in the green state) was achieved for a tablet size of approximately 6 mm in diameter by 4 mm in height. The pellets were then cleaned for sharp edges by tumbling and abrading edges, cleaned with compressed air and coated with an Aluminum suspension (AlumiLok) to approximately 5 weight percent.

[0076] The protective alumina (AlumiLok) coating is derived from an Aluminum-Silicon alloy powder, which is deposited on the as-pressed SiC / Al composite core, using aerosol deposition under ambient temperature and pressure. In this example, the core tablets are tumbled in an oblate “panning'’ vessel to create a cascading action. Hie coating could alternatively be performed on pellets on a moving conveyor or in a fluidized bed to achieve similar coating effects.

[0077] To prepare an AlumiLok coating suspension, 100 grams of an Al-Si alloy powder (Valimet S-2, 1 l-13wt% Si) with a D50 of 3.5 microns was added to a 1 -liter Nalgene container, in which a solution of 300 grams methyl acetate, 72.5 grams alpha terpineol and 27.5 grams screen printing vehicle (V006A, Heraeus) was prepared.

[0078] The Nalgene vessel was then placed on rotating rack and ball milled for 8 hours at 25 RPM. After the milling operation, the suspension was decanted from the mill into a reservoir. Using an aerosol nozzle, the suspension was deposited on as-pressed SiC / Al tablets, as described below.

[0079] Tablets (300 g, about 6 mm diameter by 4 mm height) were loaded into a tablet coater (BYC-600, Jiawanshun) with a 60 cm diameter vessel, turning at a rotation rate of 20 RPM for about 0.5h. This operation serves to remove asperities and high-radius-of-curvature features from the tablets. Residue from the polishing process was removed from the chamber prior to coating.

[0080] The protective coating was applied using a tablet coater (BY-200, Jiawanshun) with a 20 cm diameter vessel, turning at a rotation rate of 20 RPM. Coating was aerosol deposited in 10-15 second intervals, alternating with 40-50 second intervals of warm, dry air flow. Between the drying step and subsequent coating steps, the tablets were allowed 15-20 seconds to equilibrate. Coating -dryingequilibration was performed in iterations of 5 cycles, with intermediate weighing to assess the deposited coat weight. As needed, additional coating-drying-equilibration cycles were performed to achieve a deposition target of 0.04 grams of alloy per tablet. It is noted that thinner or thicker coatings might be achieved without significantly altering the approach or resulting structures.

[0081] The pellets with a protective coating were calcined at 1400C and maintained at a dwell temperature for 3 hours. The ramp rates were fixed at about 3C per min while ramping up and approximately 5C per min while ramping down in temperature. The active catalyst material comprised a Ni-based catalyst that was coated on the exterior of a HeatPath™ core pellet. Catalyst 1 was synthesized and is described by the formula 12wt%Ni / A12O3 + MgO + CaO. The catalyst powder was prepared by forming a 94.5wt% A12O3 + 4.5wt% CaO + 1.0wt%MgO oxide support powder with a d90 particle size less than 5 microns and a BET surface area of greater than 10 m2 / g. The oxide support powder was then mixed and dispersed with a diluted nickel solution and calcined at 600 degrees Celsius before sieving through a 500-micron mesh.

[0082] The powder material was mixed with a dissolved polyvinyl alcohol and deionized water to form a slurry of about 25 wt% solids. The slurry was roll milled with the addition of shiny7binders (1.5wt%) consisting of boehmite (Sasol 18N4-80) and PVA, DOW ECOsurf EH-9 surfactant (2wt%), ethylene glycol as a wetting agent (lwt%), polymer innovations DF002 defoamer (~0.5wt%) and acetic acid (0.5wt%) as a viscosity modifier. The mixture was milled with ZDC media until the suspension was homogeneous and powder particle size was reduced to less than an average of about 5 microns.

[0083] The slurry was coated on HeatPath™core pellets using a spray coating technique where the suspension was sprayed with a hand spray (Paasche 0.75mm head double action - internal mix - siphon feed system millennium airbrush set) while the pellets were shaken in a fine mesh sieve strainer. Tire coated pellets were sprayed several times with periodic drying at about 100C to 120C between coats. Once target loading was achieved, the catalyst coated pellets were calcined to 650C in air. The resulting coating was measured to have about an average 60-micron average coating thickness with an average loading (with respect to the HeatPath™core pellet) of 2.63 weight percent for data presented in Examples 2 and 3.

[0084] The HeatPath™ catalyst was loaded in the reactor by inserting a coiled nickel wire near to the center of the reactor Inconel tube. A small amount of AI2O3 wool was pressed into the top of the tube to rest on the coil followed by 10 cm3of alumina hollow tablets, 10 cm3of catalyst coated HeatPath pellets (described above), and finally 10 cm3of additional alumina hollow tablets. Tire tube structure was qualified by testing the reactor without HeatPath pellets to ensure no reaction took place and was visually inspected for material loss or shifting after ‘tapping’ the catalyst loaded reactor tube. The tube was inspected for bypass by ensuring there was no visible light through the bottom of the loaded reactor.

[0085] Tire reactor tube was held between two Thermcraft ceramic refactory heat elements with a setpoint of 850C or an alternative value based on tire reported experimental conditions. The catalyst section of the reactor was in the central region of the 0.61-m long tube furnace as estimated by a placement of 0.29-m from the top of the furnace. The reactor wall temperature was held constant during the run by a temperature controller which functioned based on a K-type thermocouple tied with a high temperature stable wire to the outer reactor wall. The reactor was pressurized using an AliCat Scientific back pressure controller which operates based on a set point and solenoid valve system and can electronically open and shut the valve to generate the necessary reactor operating pressure based off the set point. The controller compensated for flow to maintain the set point pressure automatically.

[0086] The effluent gas stream was measured for flowrate AliCat mass flow meter and product mole fractions were measured by an SRI GC using a I 'CD column with readings taken every 20 minutes.

[0087] The schematic of the stand is represented in Figure 1.

[0088] Methane conversion is defined by (mass flowrate of methane into the reactor - mass flowrate of methane out of the reactor) divided by the mass flowrate of methane into the reactor. CO? conversion is defined by (mass flowrate of CO2 in - mass flowrate of CO2 out) divided by the mass flowrate of CO2 in. A small tracer of nitrogen was added to account for the carbon mass balance given the change in moles during reaction.

[0089] The startup procedure after assembling the loaded reactor tube in the stand included heating up in N2 flowing at 200 seem to 250C at 1 ,5C per min ramp rate. The vaporizer / preheater was started when the reactor achieved 250C temperature and set to operate at 500C. Steam was introduced corresponding to a GHSV = 1500 hr1and S:C = 2.5. Heating was continued in nitrogen and steam up to an 800C reactor temperature at a rate of about 0.7C per min. S:C is defined throughout by the inlet molar flowrate of steam divided by the sum of the inlet molar flowrates of CO2 and CH4.

[0090] The catalyst activation procedure was initiated when 800C reactor temperature was reached. The N2 flow was reduced to 100 seem and CH4 was introduced at 40 seem. The pressure controller was set to a target absolute pressure of 10-barg (or higher pressure as specified for the experiment) and the reactor was slowly pressurized to condition over several hours. Once at pressure, flow conditions were set to achieve the target reported inlet flow rates for CO2, CH4, N2 (tracer), and H2O.

[0091] At the conclusion of testing, the catalyst shutdown procedure was to immediately shut off H2O and CH4 while simultaneously starting N2 at 200 seem. The vaporizer heating was turned off after feeds were stopped. The reactor was immediately cooled to 400C at 10C per min target rate followed by further cooling to room temperature at about 5C per min. The N2 gas remained flowing as the system was slowly depressurized to atmospheric conditions after the temperature returned to room temperature.

[0092] Example 2

[0093] A series of DRM catalytic reaction experiments using the inventive HeatPath™ catalyst were conducted with Catalyst 1 and the test apparatus as described in Example 1 .

[0094] The key gas phase reactions are as noted below (equations 1-4) with two potential carbon forming reactions (equations 5-6).

[0095] (1) Dry Reforming of Methane, DRM: CH4 + CO2 = 2 CO + 2 H2

[0096] (2) Steam Methane Reforming, SMR: CH4+ H2O = CO + 3 H2 (3) Water Gas Shift, WGS: CO + H2O = CO2+ H2

[0097] (4) Reverse Water Gas Shift, RWGS: CO2+ H2= CO + H2O

[0098] (5) Methane Cracking: CH4 = C(s) + 2 H?

[0099] (6) Boudouard: CO + CO = C(s) + CO2

[0100] GHSV is calculated as the total standard volumetric flowrate defined at 1 bara and 25 °C condition of the total gas inlet stream including steam, methane, CO2, and tracer (in Liter / hour) divided by the reactor superficial volume that contains the HeatPath™ pellet catalyst (about 0.01 L).

[0101] Pressure is established at the reactor exit with negligible pressure loss as measured over the reactor bed during reaction conditions as operated at a high absolute pressure between about 10 and 20 barg. Temperature is measured at the reactor wall. A small amount of nitrogen was added to act as a tracer to assess change in moles and calculate reactant mass conversions. The HeatPath™ pellets were coated with 0.2535 grams of active catalyst as contained within the about 10 cm3reactor volume for a total loading density of about 25.35 kg / m3.

[0102] Perfonnance is described in Table 2.1 where the HeatPath results for Catalyst 1 is presented for S:C near or about 1.5 for GHSV at 2450 or 1500 hr-1, feed ratio of CH4:CO2 of 0.87 or 1, pressure at 10 or 20 barg, and temperature from 775 to 850 C. Results are shown as conversion of CH4or CO? along with the product ratio based on effluent concentration of H2 / CO or CO2 / CO. Catalyst productivity in grams of CH4, CO2, or total CH4plus CO2feed converted per gram of catalyst per hour.

[0103] The total catalyst productivity for conditions tested in Table 2.1 ranges from about 3.4 to 12.6 g / g / h. At 850 C, the Steam to carbon (S:C) was varied from 1.5 down to 0.3 at 20 barg and a GHSV of 1500 hr- 1. Performance is presented in Table 2.2. The total catalyst productivity ranges from about 10 to 15.5 g / g / h.

[0104] In Figure 2, the product ratio of H2 to CO are shown as a function of reactor temperature at 10 or 20 barg, 1: 1 CHpCOz, and a S:C near 1.5. Figure 3 shows the product ratio of CO2to CO under the same conditions. Figure 4 plots tire conversion of CH4and CO2as a function of S:C ratio at 850 C, 1500 hr-1 GHSV, CH4:CO2=1, and 20 barg. The conversion functions follow a second-order polynomial form, where the CH4conversion equals (=) -18.973 * (S:C)2+ 89.228 * (S:C) -14.447. The functional dependency for CO2conversion equals (=) 10.691 * (S:C)2-3 3.582 * (S:C) + 46.796.

[0105] Table 2.1 HeatPath™ Catalyst Test Conditions and Performance for Catalyst 1 at temperatures from 775 C to 850 C

[0106] Table 2.2 HeatPath Catalyst Performance for Catalyst 1 at various Steam:Carbon Ratios at 850 C, 20 barg, and 1500 hr- 1 GHSV

[0107] The HeatPath tests included 0.2535 grams of catalyst in about 10 cm3reactor volume for a loading density about 25.35 kg / m3. The comparison full pellet tests made from pellets pressed using Catalyst 1 to the same pellet dimension as the HeatPath tests. Tire loaded pellets contained 9.63 grams of catalyst packed within the same 10 cm3 reactor volume for a loading density of about 963 kg / m3. For tests with equal GHSV, the HeatPath has only about 2.63% of total catalyst by weight as tested with the equivalent size full pellets.

[0108] The time on stream plots for HeatPath are shown in Figure 5 and for the companion foil pellet tests are shown in Figure 6. The full pellet tests show a clear loss of performance at S:C=0.5 with an increase in methane concentration and a decrease in CO concentration exiting the reactor as a function of time on stream (TOS). Coke was observed inside tire foil pellets after 140 total hours of operation.

[0109] Example 3 The composition of Catalyst 1 was based on a 12wt.%Ni doped AEOs-CaO-MgO catalyst powder as described in Example 1. The catalyst was coated on a HeatPath pellet and tested in the apparatus described in Example 2 with a catalyst loading density of 25.35 kg / m3.

[0110] Pellets of equal geometry as the HeatPath pellets prepared using the method described in Example 1, were tested under equal conditions. The catalyst loading density of the Traditional or full pellets w as about 963 kg / m3 within the same reactor tube and test stand apparatus. Results were comparable under the same test conditions as HeatPath.

[0111] Test conditions and results are described in Table 3.1. Each condition was held at least 20 hours and up to 100 hours for some conditions. Catalyst efficiency is calculated as the converted grams of CH4, CCE, or combined CI I4+ CO2 per gram of catalyst per hour. Results are shown in Table 3.2

[0112] Table 3.1 Comparison of HeatPath versus Full Pellet for Catalyst 1

[0113] Table 3.2 Catalyst efficiency in g / g / h converted comparing HeatPath and Full Traditional Pellets under identical conditions for Catalyst 1

[0114] Table 3,3 Relative Catalyst Efficiency as tested on HeatPath and in a Full Pellet

[0115] The ratio of catalyst mass loaded between the Full traditional pellet (9.63 grams) and the HeatPath (0.2535 grams) is about 38, meaning that is there is about 38 times less catalyst loaded in the reactor for HeatPath experiments conducted with equal inlet gas flowrates.

[0116] The ratio of total catalyst efficiency in g / g / h at a S:C equal to 1.5 is also about 38 suggesting that the HeatPath coating has a 100% effectiveness, and that the effectiveness of the full traditional pellet is about 2.63%. At the lower S:C of 0.5, the ratio of catalyst efficiency (in g / g / h) is 27.23 for HeatPath versus the full pellet whereas the amount of catalyst in the full pellet is 38-times HeatPath.

[0117] This result suggests that the full pellet effectiveness at S:C=0.5 is closer to 3.67% and a higher catalyst coating thickness or corresponding loading density for HeatPath can be obtained. In the Tables and throughout, the “g / g / h” refers to the grams of the total composite catalyst coating (the mass of AI2O3 plus CaO plus MgO plus Ni). For the catalyst with a 12% by weight Nickel, then the site-specific catalyst productivity in grams of CO2plus CH4converted per gram of Nickel per hour would take the table values and divide by 0.12 for a Ni mass basis. For the HeatPath operated at a S:C of 0.5 and 1500 GHSV, the reported catalyst total productivity of 13.07 g / g_total catalyst / hour in Table 3.2 would equate to about 108.9 grams of total CO2 plus CH4converted per gram of Nickel per hour.

[0118] HeatPath has a thin catalyst coating and thereby substantially less active catalyst per unit reactor volume. The impact of reduced catalyst is not substantial due to the low catalyst effectiveness of the traditional or full pellet under the DRM conditions. Tire HeatPath catalyst has an advantage of less propensity for coke formation. After 465 hours of operation time, the HeatPath catalyst did not coke, whereas the full pellet formed undesired solid carbon as shown in Figure 7.

[0119] The full pellets made from the same catalyst composition as the coated HeatPath pellet show substantial amounts of carbon deposits at the center of the pellet (r=0, Point 3 of Fig 3.1) and the mid-point of the pellet (r=R / 2, Point 2 of Fig 7), while very little carbon is seen at the edge of the pellet (r=R, Point lof Fig 7). The HeatPath coated pellets, with a catalyst thickness of about 60 microns, show negligible amounts of carbon formed as seen in Figure 8.

[0120] Carbon observed in the crack and the AlumiLok layer of Figure 8 is due to the ingress of mounting epoxy prior to the epoxy solidification. Tire pellets, as shown in Figure 7 and Figure 8 were submerged in an epoxy resin and hardener mixture which is hardened at room temperature overnight. The external region of a porous or semi porous structure, as observed with the catalyst and Alumilok layers on HeatPath in Figure 3.2 will have liquidous epoxy infiltrate in the large pores in each layer prior to solidifying. It is clear that epoxy has not infiltrated the full pellet since the outermost region (Point 1 in Figure 7) does not show carbon in about the outermost 100 microns.

[0121] Tire fonnation of coke or solid carbon on the inside of the full pellet results primarily from the Boudouard reaction, where 2CO = CO2 + C(s). Uris reaction is favored at lower temperatures, especially in about a range of about 500 °C to about 700 C and when CO has the highest partial pressure. The CO partial pressure is higher as the system operating pressure increases and when the conversion of CH4 and CO2 are higher.

[0122] Tire reported reaction temperature is 850 °C for the data in Example 3 and ranges from 775 to 850 C for the data in Example 2. As the reactions are highly endothennic and heat is transferred via the flowing gas to the solid catalyst particles, cold spots inside the reactor and catalyst pellets are formed as the reaction progresses. Deep inside pellets, the reactants diffuse toward the center of the pellet and products diffuse outward. The local residence time for conversion of CH4 and CO2 increases inside the pellet which increases the local concentration of the CO product. The combined effect of a local cold spot and the higher local CO concentration inside the catalyst pellet contributes to the initiation of solid carbon fonnation via the Boudouard reaction. As the solid carbon fonns, active sites are blocked and the overall activity decreases.

[0123] HeatPath offers an advantage to keep the local temperature at the catalyst higher due to the higher thermal conductivity of the pellet, and to simultaneously block interior sites to catalyst infdtration or gas permeation outside the outermost region of the pellet, which keeps the local CO concentration in catalystcontaining regions lower. The combined effect reduces the propensity for coke formation when using exemplar catalysts made from Nickel or other active materials for the dry reforming of methane.

[0124] Example 4

[0125] A second catalyst composition (Catalyst 2) was a Ni-based catalyst of 12wt%Ni / MgO. The catalyst was formed by initially calcining Magnesium Carbonate at 1100 °C in air to yield tire MgO support powder. The powder was then sieved through a 500-micron mesh. The sieved support MgO powder was wetted with a dilute nickel solution using aerosol dispersion, while being agitated in a high dispersion mixer. The solution was applied using aerosol deposition onto the powder while mixing slowly with intennittent drying at 120 °C until the entire nickel solution was dispersed onto the MgO support powder. The resulting powder was then dried overnight between 100 °C and 120 °C, sieved through a 500-micron mesh, and calcined at 800 degrees °C. The material was again sieved at 500-micron mesh.

[0126] Catalyst 2 was coated on 20 grams of HeatPath pellets using the same approach as described in Example 1. A catalyst loading of 2.97 weight percent was yielded and the coated pellets were tested in the apparatus described in Example 2 with a catalyst loading density of 44.05 kg / m3. Catalyst pellets of 6 mm diameter with a similar but slightly shorter height (2.5 mm vs 4 mm height as described in Example 2) as the HeatPath pellets were prepared by dry pressing the Catalyst 2 powder and then fired at 600 degrees Celsius for 2 hours. Tire full pellets were tested and compared with the same catalyst as coated on HeatPath. Hie catalyst loading density of the Traditional or full pellets was about 1149 kg / m3 and results compared under the same test conditions as HeatPath.

[0127] As seen in Figure 9, the HeatPath Catalyst 2 took a surprisingly long time to stabilize, with steadily improving performance with TOS under both test conditions. At S:C=0.5 after more than 50 hours, the CH4outlet specie concentration continues dropping, showing that conversion performance is steadily improving.

[0128] In Figure 10 by contrast, the Full catalyst pellet specie concentration for methane at S:C=0.5 is steadily rising indicating a reduction in methane conversion from catalyst deactivation. Carbon is anticipated in this catalyst as likely to be found more heavily concentrated at the interior of the pellet.

[0129] Table 4. 1 Baseline performance comparison between Catalyst 1 and Catalyst 2 on HeatPath as tested under similar conditions with CH4:CO2= 1, Temperature = 850 C, Pressure = 20 barg, GHSV=1500 hr-1, and

[0130] S:C=1.5

[0131] Table 4,2 Comparison of HeatPath versus Full Pellet for Catalyst 2

[0132] Table 4.3 Catalyst efficiency in g / g / h converted comparing HeatPath and Full Traditional Pellets under identical test conditions for Catalyst 2

[0133] Table 4.4 Relative Catalyst Efficiency as tested on HeatPath and in a Full Pellet

[0134] Tire full pellet has substantially more catalyst within the same reactor volume (1149 kg / m3 vs 44.05 kg / m3 as loaded in the same about 10 cm3 reactor tube volume). With about 26x more catalyst for the full pellet vs the HeatPath pellet tests, the loss in efficiency in g / g / h was modest. For Catalyst 2 at the current coating thickness with 26x less catalyst per volume, the ratio of g / g / h for the HeatPath versus the full pellet at S:C=0.5 was about 2 lx as seen in Table 4.4. That is to say, the full pellet has an effective catalyst usage greater than the thickness of the HeatPath coating in Example 4 by a factor of about 26 / 21.14 or about 25%. Tire issue of reduced catalyst weight per reactor volume is small due to the low overall effectiveness factor for this conventional pellet and could be overcome with a slight increase in HeaPath coating thickness. Hie advantage of the HeatPath catalyst is the minimization or avoidance of carbon formation which allows for extended operation and a more practical catalyst system to implement commercially. Example 5

[0135] A third catalyst composition (Catalyst 3) was PGM-based and tested under DRM conditions as coated on HeatPath pellets. The catalyst composition was 0.75 wt% Rh, 0.7 wt% Pt on a CcCh-ZrCh-AbOs. A catalyst coating density of about 50 kg / m3 was tested in device described in Example 1. The coating thickness was about 40 microns.

[0136] The catalyst was very active for SMR at high temperatures (850 °C) and S:C equal to 1, but relatively poor at converting CO2. The catalyst was tested for a total cumulative 550 hours with a steam to carbon of about 1. There was no observation of carbon formation. Data is shown in Table 5.1 with varying total pressure from about 12 to 20 barg and GHSV of either 5000 or 12000 hr1. The conversion of CH4 or CO2 as a function of reactor pressure from 12 to 20 bar is shown in Figure 11 .

[0137] Table 5.1 DRM performance data for Catalyst 3 at S:C = 1, 850 C, GHSV from 5000 to 12000 hr-1 and pressure from 12 to 20 bare,

[0138] Example 6

[0139] To define the target operating window for HeatPath, an equilibrium analysis evaluated the impact of S:C ratio and wall temperature at 10 and 20 barg (Figures 12 and 13). Based on thermodynamics, lower operating values of S:C will result in higher CO2utilization. At a S:C of 0.3 with a temperature of 875 °C, the theoretical CO2 conversion is nearly 70% at 10 barg. If the DRM product output is the feed for a Fischer Tropsch system (FTS), an exemplar single-pass system would benefit from a HeatPath DRM and a HeatPath FTS operated a pressure between about 10 and 20 barg. If the pressure of the DRM is slightly higher than the pressure of the downstream FTS, then a syngas compressor is avoided.

[0140] Example 7

[0141] Kinetics were fit using the data collected for Catalyst 1 using a LHHW form for reactions 1 through 4.

[0142] Key reactions are defined below.

[0143] 1. CH4 + H2O = CO + 3H2

[0144] 2. CH4 + 2 H2O = CO2+ 4H2

[0145] 3. CO + H2O = CO2 + H2

[0146] 4. CH4 + CO2= 2 CO + 2 H2

[0147] 5. CO + CO = CO2 + C(s)

[0148] 21

[0149] SUBSTITUTE SHEET (RULE 26) Carbon activity for reaction 5 is estimated using a temperature dependent reference (Karabelchtchikova, 2007). It is known that carbon activity can depend on the surface form of solid carbon and this method is an estimate. In general, the higher the carbon activity, the greater the likelihood for solid carbon formation.

[0150] Carbon activity, ac = Pressure * (y_CO2 / y_CO2) * exp(20530.65 / Temperature (in K) - 20.98)

[0151] The rate expressions are defined below. rl= kl (PCH4 PH20 - PH23Pco / Keql) / PH22'5 / (1+ Kcm PCH + KH20 PH20 + Kco2 Pco2)2r2= k2 (PCH4 PH202- PH24Pco2 / Keq2) / Pn23'5 / (1+ KCH4 PCH4 + KHZO PH20 + Kco2 Pco2)2r3= k3 (Pco PH20 - PH2 Pco2 / Keq3) / PH2 / (1+ KCH4 PCH4 + KH20 PH20 + Kco2 Pco2)2r4= k4 (PCH4 Pco2 - PHI2Pco2 / Keq4) / (1+ KCH PCH4 + KH20 PH20 + Kco2 Pco2)2

[0152] Reaction rate energies follow a traditional Arrhenius form, where ki=ki0 exp(-EAi / R / T) while the adsorption energies follow a format of Ki=KiO exp(DHi / R / T). The activation energy (Eai) for the four reactions respectively are as follows: 231, 221, 60.5, and 231 kJ / mol. The adsorption energy for methane, water, and CO2 are 17.6, -18.9, -17.1 kJ / mol respectively. The values of ki’s in units for reaction rates in mol / s are as follows: 3.66el2, 3.54el2, 3.35el2, 6.48el2. The values of Ki's in units of inverse bar are 7.75, 0.89, and 4.73. The rate expressions evaluated using these constants and partial pressures with units of bar results in reaction rates having units of mol / kg_cat / s. To obtain the rate in units of mol / m3 / s, the calculated rate is multiplied by the bulk catalyst density with units of kg cat / m3.

[0153] Using kinetics fit with 10 and 20-barg data for the HeatPath Catalyst 1, the full DRM pellet geometry was investigated. An estimate of the internal specie relative concentration as a function of internal radius (r / R) was made and revealed a surprising concentrating effect of CO near the center of the pellet relative to the edge of the pellet. CO is a precursor to coke via reaction 5. As the CO partial pressure increases, the propensity for coke formation rises. A pore diffusion model as available in the DETCHEM PBR packed bed reactor model suite was used to calculate performance, bed temperature, and internal pellet specie concentration as a function of pore diameter, pellet radius, tortuosity, and chemical kinetics. For the modeling work, an internal catalyst average pore diameter of 1 micron was used with a tortuosity factor of 5 and a porosity of 10%.

[0154] The calculated carbon activity is consistent with the observed locations of carbon formation as measured using SEM EDS on the tested catalysts. The relative concentration of CO at the center to edge of the pellet as a function of reactor length for the full pellet is shown in Figure 14. The corresponding reactor bed temperature as a function of reactor length is shown in Figure 15 based on the HeatPath pellet thermal conductivity about 8.81 W / m-K at the DRM reaction temperature . The predicted carbon activity for the full pellet at various radial positions inside the full pellet is shown in Figure 16. Underthe same test conditions of 850 C wall, 1500 hr-1 GHSV, S:C=0.5, CH4:CO2=1, and 20 barg, the predicted bed temperature for the HeatPath and Full Pellet experiments are shown in Figure 17.

[0155] References:

[0156] Cho, E., Yu, Y , Kim, Y., Phan, T., Park, D., Ko, C., Egg-shell -type Ni supported on MgA12O4 pellets as catalyst for steam methane reforming: enhanced coke-resistance and pellet stability, 2020, Cataly sis Today, 352, 157-165.

[0157] Dehimi, L, Benguerba, Y., Virginie, M., Hijazi, El., Microkinetic modelling of methane dry reforming over Ni / A12O3 catalyst, International Journal of Hydrogen Energy, 2017, 42(30), 18930-18940.

[0158] Herrera Delgado, K., Maier, L., Tischer, S., Zellner, Z., Stotz, H., Deutschmann, O., Surface Reaction Kinetics of Steam- and CO2-Reforming as Well as Oxidation of Methane over Nickel-Based Catalysts, Catalysts, 2015, 871-904.

[0159] Jun, H., Park, M., Baek, S., Bae, J., Ha, K., Jun, K., Kinetics modeling for the mixed reforming of methane over Ni-CeO2 / MgA12O4 catalyst, Journal of Natural Gas Chemistry, 2011, 20(1), 9-17.

[0160] Karabelchtchikova, O., PhD thesis from Worchester Polytechnic Institute, Fundamentals of Mass Transfer in Gas Carburizing, 2007.

[0161] Kang, K., Kim, H., Shim, I., Kwak, H., Catalytic test of supported Ni catalyst with core / shell structure for dry reforming of methane, Fuel Processing Technology, 2011, 92, 1236-1243.

[0162] Latsiou, A., Bereketidou, O., Charisiou, N., Georgiadis, A., Avraam, D., Goula, M., Synthesis and Mathematical Modelling of the Preparation Process ofNickel-Alumina Catalysts with Egg-shell Structures for Syngas Production via Reforming of Clean Model Biogas, Catalysts, 2022, 12, 274, doi: 10.3390 / catall2030274.

[0163] Liu, A., Praserthdam, S., Phatanasri, S., Investigation on the increased stability of the Ni-Co bimetallic catalysts for the carbon dioxide reforming of methane, Catalysis Today, 2020, 358(1), 37-44.

[0164] Tanios, C., Bsaibes, S., Gennequin, C., Labaki, M., Cazier, F., Billet, S., Tidahy, H., Nsouli, B., Aboukais, A., Abi-Aad, E., Syngas production by the CO2 reforming of CH4 over Ni-Co-Mg-Al catalysts obtained from hydrotalcite precursors, International Journal ofHydrogen Energy, 2017, 42(17), 12818-12828.

[0165] Wehinger, G., Kraume, M., Berg, V., Korup, P., Mette, K., Schlogl, R., Behrens, M., Hom, R., Investigating Dry Refonning of Methane with Spatial Reactor Profiles and Particle Resolved CFD Simulations, AIChE J., 2016, 62(12), 4436-4452.

Claims

What is claimed:

1. A catalyst pellet capable of catalyzing dry reforming, comprising: a core comprising SiC and Al-Si alloy and comprising less than 5 wt% oxygen, or less than 2 wt% oxygen; an intermediate coating disposed over the core, the intermediate coating comprising at least 50% or 70% or at least 90 or 95 wt% of Al-Si alloy; and disposed over the intermediate coating, a coating comprising Ni or Ni-alloy supported on an oxide comprising Mg and Ca.

2. A catalyst capable of catalyzing dry refonning, comprising: a core comprising SiC and / or a core coated with an Al-Si alloy; an oxide-supported Ni or Ni alloy disposed on the exterior of the catalyst; and characterizable by one or any combination of the properties described herein, for example: when CH4 and CO2 in a 1: 1 ratio are passed into a tube reactor having an inner diameter of 0.019-m (or, alternatively, at least three times the mass average diameter of the catalyst pellets) containing a catalyst zone of 10 cm3in the central region of a tube furnace of packed bed pellet catalyst, where the temperature of the wall of the tube reactor is held at 850 °C; wherein a feedstream consisting of CH4, H2O, and CO2 , at a CH4 / CO2 = 1 and a steam to carbon ratio of 0.5 at 20 bar(gauge) and a flow rate of 1500 GHSV (based on volume of catalyst chamber) and converting at least 10% or at least 20% or 10 to 25% CO2 for at least 100 hrs or at least 200 hrs without regeneration and having a decrease in CO2 conversion of 1% or less without regenerating the catalyst over this time; and converting at least 30, at least 40, or at least 50, or 30 to 50g CH4 per g Ni per hour and / or converting at least 20, at least 30, or at least 35, or 20 to 40g CO2 per g Ni per hour.

3. The catalyst of claim 2 further characterizable by the absence of observable carbon is deposited on the carbon during the characterization testing.

4. The catalyst of any of the above claims further comprising an Al or Al alloy coating over the core comprising SiC.

5. The catalyst of any of the above claims having an average thickness of Ni or Ni alloy coating of at least 5 pm, or at least 100 pm, or at least 200 pm or having a range of 20 to 100 pm.

6. The catalyst of any of the above claims wherein in the intermediate layer, Ni is in the range of 5 to 25 wt% Ni, and wherein the intermediate layer comprises Mg / Ca in a weight ratio in the range of 0.1 to 10.

7. Tire catalyst of claim 6 having a mass ratio of SiC / Al-Si in the range of 5: 1 to 4 / 6; or at most 4: 1 or at most 3: l or at most 7 / 10; or at least 1: 1 or at least 1.5 or at least 1.7; or about 2: 1.

8. The catalyst of any of claims 3-7 wherein the exterior catalyst coating has an average thickness of at least 5 pm, or at least 10 pm, or in the range from 5 to 400 pm, 10 to 300 pm, 50 to 350 pm.

9. A method of making a catalyst, comprising: combining SiC powder and Al-Si powder; adding binder and compressing into a pellet: coating pellet with alloy powder, preferably via an aerosol, calcining to form a calcined pellet; coating the calcined pellet with a Ni-based catalyst; and calcining the calcined pellet with a Ni-based catalyst coating to result in an exterior catalyst coating.

10. The method of claim 9 wherein the compressed pellet, prior to calcining has a volume of 0.05 to 1 cc. 0.07 to 0.3 cc.

11. Tire method of any of claims 9-10 wherein the calcining to form a calcined pellet is conducted at a temperature of at least 1200 °C, 1300 °C, 1350 to 1450 °C in air.

12. The method of claim 11 comprising ramping down at a rate of 2-10 °C, 3-8 °C per minute.

13. The method of any of claims 9-12 wherein the alloy powder coating has an average thickness of at least 50 pm, or at least 100 pm, or at least 200 pm.

14. The method of any of claims 9-13 wherein the mass ratio of SiC / Al-Si is in the range of 5: 1 to 4 / 6; or at most 4: 1 or at most 3: 1 or at most 7 / 10; or at least 1: 1 or at least 1.5 or at least 1.7; or about 2: 1.

15. The method of any of claims 9-14 wherein the alloy powder is aluminum alloy.

16. The method of claim 15 wherein the aluminum alloy is a Al-Si alloy.

17. The method of claim 16 wherein the alloy comprises 5-25 mass% Si, 5-20 mass% Si, 8-17 mass% Si, or 10-15% mass% Si.

18. The method of any of claims 9-17 wherein the catalyst comprises a Ni-based catalyst catalyst applied as a slurry.

19. The method of any of claims 9-18 wherein the step of calcining the calcined pellet with a Ni-based catalyst coating is conducted in air at 550 to 800 °C; or 600 to 750 °C.

20. The method of any of claims 9-19 wherein the pellet from the step of adding binder and compressing into a pellet results in a pellet comprising 15 to 30 volume percent SiC.

21. The method of any of claims 9-20 results in an exterior catalyst coating having an average thickness of at least 5 pm, or at least 10 pm, or in the range from 5 to 400 pm, 10 to 300 pm, 50 to 350 pm.

22. A catalyst made by any of the methods described herein.

23. A method of reforming, comprising: passing CH and CO2 at a pressure of at least 5 barg and a feed Steam:C ratio less than or equal to 1 .0 or less than or equal to 0.7 into a reaction chamber comprising a dry reforming catalyst comprising a core comprising SiC; a Ni or Ni alloy disposed on the exterior of the catalyst; reacting the CH4 and CO2 in contact with the catalyst at a temperature of at least 800 °C at a wall of the reaction chamber and converting at least 10% or at least 20% or 10 to 25% CO2 for at least 100 hrs or at least 200 hrs without regeneration and having a decrease in CO2 conversion of 1% or less without regenerating the catalyst; and converting at least 30, at least 40, or at least 50, or 30 to 50g CH4 per g Ni per hour and / or converting at least 20, at least 30, or at least 35, or 20 to 40g CO2 per g Ni per hour.

24. The method of claim 23 wherein no observable carbon is deposited on the carbon.

25. A method of reforming, comprising: passing a gas stream comprising CH4 and CO2 into a reaction chamber comprising a catalyst; reaction chamber comprises a catalyst capable of catalyzing dry reforming, comprising a SiC core and Ni or Ni alloy disposed on the exterior of the catalyst;reacting the CH4 and CO2 at a temperature of at least 750 °C; wherein the gas stream entering the reaction chamber has a steanrcarbon ratio of 1.4 or less; wherein CH4conversion is at least 28%.

26. The method of claim 25 operating continuously at a pressure of 10 bar(gauge) for at least 5 hours or at least 10 hours without regenerating the catalyst and wherein the coke is not formed on the catalyst.

27. The method of claim 25 or 26 wherein the ratio of CFT and CO2 in the gas stream is at least 0.2, 0.5, 1.0, 1.2; or in range from 0.2 to 2.

28. The method of any of claims 25-27 comprising preheating the gas stream prior to entering the reaction chamber.

29. The method of any of claims 25-28 comprising reacting the CH4 and CO2 at a temperature of at least 775 °C, or at least 800 °C, or at least 825 °C, or in the range of 775 to 900 °C, or 800 to 850 °C.

30. The method of any of claims 25-29 wherein the temperature refers to the temperature at a wall of the reaction chamber and wherein temperature in the center of the reaction chamber at a distance to the wall measured perpendicular to flow has a temperature in the range of about 125 to 25 °C or 75 to 25 °C lower than the wall temperature.

31. The method of any of claims 25-30 having a steanrcarbon ratio 1.2 or less, 1.0 or less, 0.8 or less, the lower limit may be 0 or 0.2 or more, 0.5 or more, 0.8 or more, 1.0 or more, or 1.2 or more.

32. The method of any of claims 25-30 wherein CH4 conversion is at least 28% or at least 40% or at least 60% or at least 70% or in the range of 30 to 65% or 40 to 60%.

33. The method of any of claims 25-30 wherein CO2 conversion is at least 10% or at least 20% or at least 40% or at least 50% or in the range of 30 to 65% or 10 to 70%.

34. The method of any of claims 25-33 wherein CH4conversion at steady state remains constant at any of the levels mentioned above and changes by 10% or less for at least 5 hours or at least 10 hours or at least 50 hours or at least 100 hours without regenerating or replacing the catalyst.

35. The method of any of claims 25-34 wherein CO? conversion at steady state remains constant at any of the levels mentioned above and changes by 10% or less for at least 5 hours or at least 10 hours or at least 50 hours or at least 100 hours without regenerating or replacing the catalyst.

36. The method of any of claims 25-35 wherein the catalyst shows no whiskers or amorphous forms of carbon after operation.

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