Methane reformer for producing hydrogen and hydrocarbon fuels

Abstract

The present disclosure is directed to systems and methods for reforming methane into hydrogen and hydrocarbon fuels. In an example embodiment, the methane reformer integrates a photocatalytic steam methane reforming (P-SMR) system followed by a photocatalytic dry methane reforming (P-DMR) system.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 63 / 054,163, filed July 20, 2020, the entire contents of which are incorporated by reference herein.

[0002] Background of the disclosure Field of Disclosure

[0002] The present disclosure is directed to systems and methods for reforming methane into hydrogen and hydrocarbon fuels. In an example embodiment, the methane reformer integrates a photocatalytic steam methane reforming (P-SMR) system with a subsequent photocatalytic dry methane reforming (P-DMR) system. [Background technology]

[0003] Technical background

[0003] A conventional Steam Methane Reforming (SMR) system, such as that shown in FIG. 1, can be used to produce synthesis gas (hydrogen and carbon monoxide) from, for example, methane (natural gas) according to the following equilibrium: CH4+H2O⇔CO+3H2 (Formula 1) Conventional SMRs have several shortcomings. For example, they are sensitive to sulfur that may be present in pipeline quality gas and require desulfurization (i.e., a combination of a hydrodesulfurization (HDS) catalyst and a ZnO adsorbent bed). Furthermore, conventional SMRs are heat-intensive endothermic reactors and hydrogen production is limited due to the conversion limitations associated with near cracking temperatures. This limitation is overcome by the use of high and low temperature water gas shift reactors (WGS) installed in series. Furthermore, the high temperature operation of SMRs produces significant amounts of greenhouse carbon monoxide (CO), thus necessitating the installation of a WGS reactor.

[0004]

[0004] Furthermore, conventional SMRs typically have two carbon dioxide (CO2) exhaust streams that require CO2 removal. The first CO2 exhaust stream is derived from natural gas and uses air as fuel to power the SMR reactor. This produces lean CO2 and nitrogen oxides (NO X ) and sulfur oxide (SO X ) from the flue gas stream. Methods for capturing and utilizing the CO2 from the flue gas stream are complex and expensive. A second CO2 exhaust stream is produced as part of the process gas and contains concentrated CO2 that is easier to capture or utilize. The amount of CO2 released to the atmosphere from both of these streams makes conventional SMRs a large source of greenhouse gas emissions. In plants that include equipment for capturing CO2 from these streams, the capital expenditure for such equipment is a significant portion of the overall plant cost.

[0005]

[0005] One of the conventional methods used to remove CO2 is a combined absorber-regenerator system using hot potash or amine-based liquid absorbents, such as monoethanolamine (MEA) or activated methyldiethanolamine (aMDEA). Not only does this system require high pressure (near 400 psi(g) when the liquid enters the absorber) and high temperature (near 200°C in the regenerator reboiler), but the amine-based liquids used in the system can be corrosive in nature. These limitations require expensive and costly materials, i.e., the entire tower must be made of stainless steel, or injection of passivating agents such as vanadium pentoxide (V2O5) and continuous iron monitoring. Foaming is another common problem. Excessive foaming can carry over to downstream systems with adverse effects. Finally, solution chemistry must be analyzed at regular intervals to maintain the required absorption rate and address system losses.

[0006]

[0006] Conventional SMR designs also require a fully functional burner management system (BMS) to ensure safe ignition and light-off of the burners operated with gas / liquid fuels. The BMS system has a critical step before the tolerance for burner ignition becomes an issue. This sequence traditionally involves purging the furnace to eliminate any combustibles (if any) by running the blower or ID fan at near full speed. After this purging sequence is completed, a tightness test is performed to ensure that there are no leaks in the fuel circuit, followed by a trial ignition, and then the main burners are ignited and the system is pressurized based on a pre-determined or operationally required sequence. As can be seen, this is a complex system with excessive bootstrapping. Moreover, any leak in the fuel system will render the entire sequence useless. Moreover, raising or lowering the furnace requires a lot of time and effort. A commercial reformer with almost 100 burners requires manual operation every time the pressure is increased or decreased. A combination of shutoff and regulating valves (ie, control valves) ensures precise control and, if necessary, fail-safe shutdown, but requires constant vigilance from control panel and field personnel. Summary of the Invention [Problem to be solved by the invention]

[0007]

[0007] Therefore, there remains a need for an effective system for methane reforming that does not suffer from the drawbacks of conventional SMR systems currently in use. [Means for solving the problem]

[0008] Disclosure Summary

[0008] One aspect of the present disclosure provides a system for recovering synthesis gas (i.e., hydrogen and carbon monoxide) from a methane feedstock. Such a system includes: a first stage including a photocatalytic steam methane reformer configured to produce at least a carbon dioxide stream and a hydrogen stream from a methane feed; a second stage adjacently downstream from the first stage, the second stage including a photocatalytic dry methane reformer configured to produce synthesis gas from a second methane feedstock and the carbon dioxide stream produced in the first stage; Includes.

[0009]

[0009] The system of the present disclosure can be used in a process for preparing zero-emission hydrogen in addition to low-emission or zero-emission products such as methanol or dimethyl ether (DME). Accordingly, another aspect of the present disclosure provides a process for converting a methane feedstock into synthesis gas. Such a process includes: providing a methane feedstock to a first stage comprising a photocatalytic steam methane reformer as described herein to obtain at least a carbon dioxide stream and a hydrogen stream; supplying said carbon dioxide stream to a second stage comprising a photocatalytic dry methane reformer as described herein to produce synthesis gas; Includes.

[0010]

[0010] Another aspect of the present disclosure provides a method for preparing a hydrocarbon fuel, such as methanol or dimethyl ether, from a methane feedstock. Such a method includes: providing a methane feedstock to a first stage comprising a photocatalytic steam methane reformer as described herein to obtain at least a carbon dioxide stream and a hydrogen stream; supplying the carbon dioxide stream to a second stage comprising a photocatalytic dry methane reformer as described herein to produce synthesis gas; feeding the synthesis gas to a third stage comprising a reactor to obtain methanol or dimethyl ether; Includes.

[0011]

[0011] Other objects, features, and advantages of the present disclosure will become apparent from the following detailed description. However, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description, it should be understood that the detailed description and examples, while illustrating specific embodiments of the present disclosure, are given by way of example only.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of the disclosed systems and methods, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments of the present disclosure, and together with the description, serve to explain the principles and operation of the present disclosure. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a process flow diagram illustrating a conventional SMR system. [Diagram 2]

[0014] FIG. 1 is a process flow diagram illustrating a methane reformer system for producing synthesis gas according to a first example embodiment. [Diagram 3]

[0015] FIG. 2 is a process flow diagram illustrating a methane reformer system for producing synthesis gas according to a second example embodiment. [Figure 4]

[0016] FIG. 1 is a schematic diagram illustrating a method for producing syngas according to an example embodiment. [Diagram 5]

[0017] FIG. 11 is a process flow diagram illustrating a methane reformer system for producing hydrogen and methanol according to a third example embodiment. [Figure 6]

[0018] FIG. 11 is a process flow diagram illustrating a methane reformer system having an Organic Rankine Cycle (ORC) unit for producing hydrogen and methanol according to a fourth example embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Detailed Description

[0019] Example methods and systems are described herein. Any example embodiment or feature described herein should not necessarily be construed as preferred or advantageous over other embodiments or features. The example embodiments described herein are not meant to be limiting. It will be readily understood that certain aspects of the disclosed systems and methods can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[0015]

[0020] Given the present disclosure, the systems and methods described herein can be configured by one of ordinary skill in the art to meet desired requirements. In general, the disclosed systems, methods, and devices provide improved photocatalytic reaction systems and processes. In particular, the present invention provides an improved powered SMR reactor, photocatalytic steam methane reformer (P-SMR), that does not burn hydrocarbon fuels, but instead uses electricity to produce hydrogen and CO2 (as a process by-product). This CO2 is then utilized in a second powered reactor, photocatalytic dry methane reformer (P-DMR), to form synthesis gas (or syngas). This synthesis gas can be sent to a synthesis reactor to produce liquid fuels, such as methanol or dimethyl ether. As a result, in certain embodiments, the system uses less natural gas than conventional methods, does not release CO2 to the environment, and can use renewable electricity for operation. In certain embodiments, the disclosed systems and methods can be advantageously used to produce alternative commercially advantageous materials, such as methanol or dimethyl ether. The systems and methods of the present disclosure, in some embodiments, eliminate the capital costs and operational complexities associated with BMS and CO2 capture equipment in conventional plants. In some embodiments, waste heat generated in one part of the system (e.g., in the reactor cooling jacket) can be advantageously utilized elsewhere in the system to increase the operating efficiency of the overall system.

[0016]

[0021] As previously discussed, the present disclosure provides a system for recovering synthesis gas (i.e., hydrogen and carbon monoxide) from a methane feedstock. In particular, as shown in FIG. 2, the system of the present disclosure includes a first stage (30) configured to produce at least a carbon dioxide stream and a hydrogen stream from a methane feedstock. The first stage includes a photocatalytic steam methane reformer (P-SMR) (37). The P-SMR (37) is configured to contact the methane feedstock with steam in the presence of a first plasmonic photocatalyst to form a first reaction product stream comprising hydrogen and carbon monoxide.

[0017]

[0022] In one embodiment, as shown in Figure 3, the first stage (30) includes a photocatalytic steam methane reformer (37) and a water gas shift (WGS) reactor (42). The WSG reactor (42) is configured to contact the first reaction product stream with water to form a water gas shift stream comprising hydrogen and carbon dioxide.

[0018]

[0023] In some embodiments, the first stage (30) may further include a separation unit configured to separate carbon dioxide from the water-gas shift stream to obtain a carbon dioxide stream and a hydrogen stream. As shown in Figures 2 and 3, in some embodiments, the separation unit may include a pressure swing adsorption (PSA) hydrogen purification unit (40) and / or a CO2 absorption unit (41). It should be noted that while Figures 2 and 3 show a feedback CO2 stream from the CO2 absorption unit (41), such a stream is optional and need not be utilized in some embodiments. Similarly, other components and streams shown may be omitted in some embodiments, depending on the particular application and / or scale of the system implemented.

[0019]

[0024] As shown in FIGS. 2 and 3, in one embodiment, the first stage (30) can optionally include one or more of a water / sludge knockout vessel (31), feed discharges HX-1 and / or HX-2 (32 and / or 33), a trim heater / cooler (e.g., electric) (34), a desulfurizer (35), a steam generator (36), a water heater (38), and a chiller (39).

[0020]

[0025] One of the drawbacks of conventional methods is the heat loss from the SMR. Conventional SMR processes are only about 50% efficient, meaning half of the power delivered is lost as heat exhausted through the walls of the SMR. Furthermore, in conventional designs, a significant amount of heat is lost during condensation of the gas. The inventors have determined that heat can be recovered using an Organic Rankine Cycle (ORC). At a suitable scale, the ORC cycle can achieve efficiency rates as high as 40%. Energy Efficiency can be gained, thus making this an attractive option for increasing the energy efficiency of the process from 45% to as high as about 70%. Thus, in an embodiment, the first system (30) of the present disclosure can further include an organic Rankine cycle (ORC) configured to generate electricity within the system using the process waste heat. In larger systems, the available heat can be of even higher grade. For example, in an embodiment, the system can further include a steam turbine configured to generate electrical power on-site.

[0021]

[0026] A more detailed description of one embodiment utilizing an ORC unit for on-site power generation is shown in the process flow diagram of FIG. 6. The system of FIG. 6 produces hydrogen and methanol and utilizes an ORC unit for efficiency improvement. As shown, the system includes an ORC unit and its evaporator in parallel with a P-SMR reactor. In particular, the ORC unit utilizes waste heat from a fluid cooling system (e.g., cooling jacket or reservoir) associated with the P-SMR reactor to generate electricity. Such electricity can then be used to power auxiliary electrical components associated with the system, such as control electronics, pumps, sensors, or other electrically powered components. This can reduce the required electrical input to be obtained by conventional grid generation or another external means, such as locally or remotely generated renewable (e.g., solar or wind) generation.

[0022]

[0027] As mentioned, the aforementioned fluid cooling system for in-situ power generation may be in the form of a cooling jacket or reservoir associated with the P-SMR reactor. For example, each individual reactor cell may be surrounded by a fluid jacket through which a cooling fluid (e.g., water) moves. For example, the cooling fluid may be pumped or otherwise moved through the cooling jacket to remove heat generated by the reactor cells surrounded by the cooling jacket. In the case of annular reactor cells, the fluid cooling system may additionally or alternatively include an internal cooling jacket or reservoir in a central portion of the reactor cell, such that the internal cooling jacket itself is surrounded by the annular reactor cell. Other configurations of fluid cooling systems for use with ORC are possible and are intended to be within the scope of the present disclosure. For example, a cooling system that removes heat from two or more reactor cells or a cooling system associated with a multi-cell reactor (or multi-reactor reformer) may additionally or alternatively provide waste heat for in-situ power generation by the ORC unit.

[0023]

[0028] In an alternative embodiment, no on-site power generation is performed in the disclosed system. For example, the water gas shift reactor is exothermic in nature, and integration of process heat facilitates heating water for steam generation in the waste heat boiler. The main steam generator / waste heat boiler uses the hot SMR outlet stream to cool the process gas to the inlet temperature of the high temperature shift converter (HTSC). The shift conversion effectively reduces CO to traces (less than 1%, e.g., about 0.2%) by conversion to CO2. The shift reactor outlet stream is dried (to remove excess water) and compressed to 10 bar (145 psi(g)). In an example embodiment, the P-SMR of the present disclosure has a maximum inlet pressure of about 100 psi(g). In an embodiment, the gas is further compressed (to about 10 bar (i.e., 145 psi(g)) before being sent to a unit for separating hydrogen.

[0024]

[0029] Figure 5 is a process flow diagram illustrating a methane reformer system for producing hydrogen and methanol according to a third example embodiment. The system of Figure 5 is similar to that shown in Figure 6, except that the system of Figure 5 does not generate in-situ power, but instead simply circulates a coolant (e.g., water) through the cooling jacket of the P-SMR reactor after removing the generated heat. As shown, one or more cooling fans, reservoirs, and / or pumps can be used to circulate the coolant through the cooling jacket.

[0025]

[0030] The system of the present disclosure also includes a second stage (50) adjacent downstream from the first stage (30) that includes a photocatalytic dry methane reformer (P-DMR) (51) configured to produce synthesis gas from the second methane feedstock and the carbon dioxide stream produced in the first stage (30).

[0026]

[0031] In one embodiment, as shown in FIG. 4, the system of the present disclosure further includes a third stage adjacent downstream from the second stage (50), the third stage including a synthesis reactor configured to produce methanol or dimethyl ether from the synthesis gas produced in the second stage.

[0027]

[0032] An example reaction carried out in the second and third stages to obtain, for example, methanol is as follows: Step 1 - Dry Methane Reforming (DMR): 3CO2+3CH4→6CO+6H2 (formula 2) Step 2 - Water Gas Shift (WGS): 2CO+2H2O→2CO2+2H2 (Formula 3) Sum of steps 1 and 2: CO2+3CH4+2H2O→4CO+8H2 (Formula 4) Step 3-Methanol synthesis: 4CO+8H2→4CH3OH (Formula 5) Sum of steps 1, 2, and 3: CO2+3CH4+2H2O→4CH3OH (Formula 6)

[0028]

[0033] As previously described in Equation 2 (Step 1), the output from the P-DMR reactor is synthesis gas or synthetic gas, which is a mixture of CO and H2. Synthesis gas is the starting feedstock for many hydrocarbon fuels, such as methanol and dimethyl ether. The technology for converting synthesis gas to hydrocarbon fuels is mature and industrial and would be apparent to one skilled in the art.

[0029]

[0034] The synthesis gas from the second stage (50) generally comprises carbon monoxide and hydrogen in a ratio of about 1:1. In one embodiment, a hydrogen stream is fed to the synthesis reactor in the third stage such that the ratio of carbon monoxide and hydrogen in the synthesis reactor is about 1:2 (e.g., as shown in Equation 5). The hydrogen stream can be fed directly to the synthesis reactor or can be premixed with the synthesis gas stream before being introduced into the synthesis reactor. In one embodiment, the hydrogen stream introduced into the synthesis reactor is obtained in the first stage (30), such as from a PSA hydrogen purification unit (40).

[0030]

[0035] In an alternative embodiment, a shift reactor can be added adjacent to and downstream from the P-DMR (51) during the second stage (50), the shift reactor configured to produce a hydrogen stream that is fed to the synthesis reactor. This process is illustrated by Equations 3 and 4:

[0031]

[0036] In another embodiment, the second stage (50) includes a hydrogen separation membrane adjacent to and downstream from the P-DMR (51) and configured to produce a hydrogen stream that is fed to the synthesis reactor.

[0032]

[0037] The choice of hydrogen separation technology is directly determined by its end use. Emerging gas separation technologies include membrane separation, which has the advantages of flexible and simple operation, compact structure, low energy consumption, and environmental friendliness. The performance of membrane materials is the most important factor for determining the H2 separation and purification effect of membranes. Commonly used membrane materials mainly include metal and polymer membranes, and new membrane materials, such as nanomaterial membranes, CMSM, and MOF membranes, can show favorable separation performance. 99%+ purity cannot be obtained in single membrane type systems. In addition, membrane systems are highly susceptible to water condensation, because this forms a barrier on the surface of the membrane and reduces the permeation rate. Although the effect of amine vapor on the membrane is negligible, the possibility of foaming and carryover requires further unit operations such as the use of heaters and coalescing filters in conventional SMR systems. In the case of carryover of liquid MEA / MDEA, the only choice may be to shut down the equipment and replace the membrane.

[0033]

[0038] In contrast to conventional SMR systems, the disclosed system can utilize hydrogen separation membranes without the above drawbacks. For example, in one embodiment, the hydrogen separation membrane used in the disclosed system is a pressure swing adsorption (PSA) hydrogen unit. The PSA separation effect is mainly determined by the type of adsorbent and the technological process used. H2 is very different from most gas molecules such as CO2, CO, and CH4 in terms of capacitance, making it very suitable for PSA separation and purification. In one example, purity as high as 99% can be achieved.

[0034]

[0039] As previously mentioned, the systems of the present disclosure include a photocatalytic steam methane reformer (P-SMR). For example, such a P-SMR may: Housing and; at least one reactor cell disposed within the housing, the at least one reactor cell including an enclosure and a first plasmonic photocatalyst on a first catalyst support disposed within the at least one enclosure, the enclosure being optically transparent, the at least one reactor cell including at least one input for a methane feedstock to enter the at least one cell and at least one output for a first reaction product stream to exit the at least one cell; at least one light source, wherein use of the at least one light source causes the reactor cell to form a first reaction product stream from the methane feed material; and may include.

[0035]

[0040] Similarly, the disclosed system may include a photocatalytic dry methane reformer (P-DMR). For example, such a P-DMR may include: Housing and; at least one reactor cell disposed within the housing, the at least one reactor cell including an enclosure and a second plasmonic photocatalyst on a second catalyst support disposed within the at least one enclosure, the enclosure being optically transparent, the at least one reactor cell including one or more inputs for a second methane feedstock and a carbon dioxide stream to enter the at least one cell, and at least one output for a syngas to exit the at least one cell; at least one light source, wherein use of the at least one light source causes the reactor cell to form a synthesis gas from the second methane feedstock and the carbon dioxide stream; and may include.

[0036]

[0041] Further examples of suitable P-SMRs and P-DMRs are described in WO 2019 / 005777, WO 2019 / 005779, WO 2020 / 146799, WO 2020 / 146813, and WO 2018 / 231398, each of which is incorporated by reference herein.

[0037]

[0042] The reactor cells of the P-SMR and P-DMR of the present disclosure require one or more plasmonic photocatalysts, including a catalyst that couples to the plasmonic material, such as by physical, electronic, thermal, or optical coupling. Without wishing to be bound by theory, it is believed that the plasmonic material acts as an optical antenna that can absorb light due to a unique interaction between the light and the plasmonic material, resulting in the generation of a strong electric field on and near the plasmonic material (i.e., as a result of collective oscillation of electrons in the plasmonic material). This strong electric field on and near the plasmonic material allows for coupling between the catalyst and the plasmonic material, even when the catalyst and the plasmonic material are separated by distances of up to about 20 nm or more.

[0038]

[0043] In general, the plasmonic material may be any metal, metal alloy, metalloid element, or alloy thereof. In some embodiments, the plasmonic material of the present disclosure is selected from gold, gold alloy, silver, silver alloy, copper, copper alloy, aluminum, or aluminum alloy. In the present disclosure, the term "alloy" is intended to cover all possible combinations of metals. For example, the alloy may be a binary alloy such as AuAg, AuPd, AuCu, AgPd, AgCu, or may be a ternary alloy, or even a quaternary alloy. In some embodiments, the plasmonic material of the present disclosure is aluminum, copper, silver, or gold.

[0039]

[0044] In general, the catalytic material that binds to the plasmonic material can be any compound capable of catalyzing the required reaction (i.e., the first catalyst that binds to the plasmonic material can be any compound capable of catalyzing the SMR reaction (e.g., even if it is not bound to the plasmonic material)). In some embodiments, the catalyst of the present disclosure can be any metal or metalloid element, as well as any alloy, oxide, phosphide, nitride, or combination thereof of the above elements. For example, the first catalyst and / or the second catalyst of the present disclosure can independently comprise catalytically active iron, nickel, cobalt, platinum, palladium, rhodium, ruthenium, or any combination thereof. The catalyst of the present disclosure can comprise any alloy, oxide, phosphide, or nitride of catalytically active iron, nickel, cobalt, platinum, palladium, rhodium, or ruthenium. In some embodiments, the catalyst of the present disclosure comprises catalytically active iron or nickel.

[0040]

[0045] Examples of suitable plasmonic photocatalysts are given in D.F. Swearer et al., "Heterometallic antenna-reactor complexes for photocatalysis," Proc. Natl. Acad. Sci. USA 113, 8916-8920, 2016; Linan Zhou et al. "Quantifying hot carrier and thermal contributions in plasmonic photocatalysis," Science, 69-72, 05 Oct 2018; Linan Zhou et al., "Light-driven methane dry reforming with single atomic site antenna-reactor plasmonic photocatalysts," Nature Energy, 5, 61-70, 2020, each of which is incorporated herein by reference.

[0041]

[0046] As previously mentioned, the disclosed system may be used in a process for producing zero-emission hydrogen along with another low or zero-emission product, such as methanol or dimethyl ether (DME).

[0042]

[0047] For example, another aspect of the present disclosure provides a method for converting a methane feedstock into synthesis gas, the method comprising: providing a methane feedstock to a first stage comprising a photocatalytic steam methane reformer as described herein to obtain at least a carbon dioxide stream and a hydrogen stream; supplying said carbon dioxide stream to a second stage comprising a photocatalytic dry methane reformer as described herein to produce synthesis gas; Includes.

[0043]

[0048] In such a method, for example, in a first stage, a methane feedstock is provided to a photocatalytic steam methane reformer to form a first reaction product stream comprising hydrogen and carbon monoxide; and then, the first reaction product stream and water are provided to a water gas shift reactor to form a water gas shift stream comprising hydrogen and carbon dioxide. In particular, in the photocatalytic steam methane reformer, the methane feedstock is distributed among a plurality of reactor cells disposed within a housing of the photocatalytic steam methane reformer, each reactor cell including an optically transparent enclosure and a first plasmonic photocatalyst on a first catalyst support disposed within the optically transparent enclosure. This is followed by illuminating the interior of the housing of the photocatalytic steam methane reformer with at least one light source to convert the methane feedstock in the plurality of reactor cells into a first reaction product stream comprising hydrogen and carbon monoxide; and accumulating the first reaction product stream from the plurality of reactor cells.

[0044]

[0049] In certain embodiments of the disclosed process, the water-gas shift stream comprising hydrogen and carbon dioxide is fed to a separation unit to obtain a carbon dioxide stream and a hydrogen stream.

[0045]

[0050] Finally, in a second stage, the method of the present disclosure comprises: distributing, in the photocatalytic dry methane reformer, the carbon dioxide stream and the second methane feedstock to a plurality of reactor cells disposed within a housing of the photocatalytic dry methane reformer, each reactor cell including an optically transparent enclosure and a second plasmonic photocatalyst on a second catalyst support disposed within the optically transparent enclosure; converting carbon dioxide and methane into synthesis gas in the plurality of reactor cells by illuminating an interior of a housing of the photocatalytic dry methane reformer with at least one light source; accumulating synthesis gas from the plurality of reactor cells; Includes.

[0046]

[0051] Another aspect of the present disclosure includes a process for preparing methanol or dimethyl ether from a methane feedstock, in which synthesis gas from a second stage is fed to a third stage comprising a synthesis reactor to obtain methanol or dimethyl ether.

[0047]

[0052] In one embodiment, a hydrogen stream is provided to the synthesis reactor in the third stage such that the ratio of carbon monoxide to hydrogen in the synthesis reactor is about 1:2.

[0048]

[0053] Various example embodiments described herein can be used to provide one or more benefits, such as benefits related to low-emission chemical production. In one example use case, methane obtained from dairy farms, landfills, or oil well site flare gases can be used to produce low / zero emission hydrogen from the methane without significant carbon emissions to the atmosphere. By processing the CO2 exhaust stream of the P-SMR immediately adjacent and downstream of the P-DMR reactor, the exhaust CO2 and methane (both strong greenhouse gases) can be processed into other "green" products, such as methanol or DME. In an embodiment, the disclosed method is a lower cost, less complex, and more environmentally friendly alternative to conventional SMR plants, ammonia plants, and methanol plants in oil refineries. The disclosed system and method can be used, for example, as a source of hydrogen fuel for distributed on-site production of hydrogen in fuel cell vehicle applications.

[0049]

[0054] The above detailed description sets forth various features and functions of the disclosed systems, apparatus, and methods with reference to the accompanying figures. Various aspects and embodiments have been disclosed herein. Other aspects and embodiments will become apparent. The various aspects and embodiments disclosed herein are merely illustrative and are not intended to be limiting.

[0050]

[0055] Certain embodiments of the invention are described herein, including the best mode known to the inventors for carrying out the invention. Of course, variations on these described embodiments will become apparent to those of skill in the art upon reading the foregoing description. The inventors expect such variations to be employed by those of skill in the art as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, this invention includes any combination of the above-described elements in all possible modifications thereof unless otherwise specifically indicated herein or otherwise clearly contradicted by the context.

[0051]

[0056] It is understood that the examples and embodiments described herein are for illustrative purposes only, and that various modifications or variations in light thereof will be suggested by those skilled in the art and are to be included within the spirit and scope of this application and the scope of the appended claims. All publications, patents, and patent applications cited herein are hereby incorporated by reference for all purposes.

Claims

1. 1. A system for recovering synthesis gas from a methane feedstock comprising: a first stage comprising: a photocatalytic steam methane reformer configured for contacting the methane feedstock with steam to form a first reaction product stream comprising hydrogen and carbon monoxide; a water-gas shift reactor configured for contacting the first reaction product stream with water to form a water-gas shift stream comprising hydrogen and carbon dioxide; and a separation unit configured for separating carbon dioxide from the water-gas shift stream to obtain a carbon dioxide stream and a hydrogen stream; a second stage adjacently downstream from the first stage, the second stage including a photocatalytic dry methane reformer configured to produce the synthesis gas from a second methane feedstock and the carbon dioxide stream produced in the first stage; Including, the system.

2. 10. The system of claim 1, wherein the photocatalytic steam methane reformer is further configured for contacting the methane feed material with steam in the presence of a first plasmonic photocatalyst.

3. The system described in claim 2, wherein the first plasmonic photocatalyst includes a first catalyst that binds to a plasmonic material.

4. The system described in claim 3, wherein the first catalyst comprises iron, nickel, cobalt, platinum, palladium, rhodium, or ruthenium, and the plasmonic material is aluminum, copper, silver, or gold.

5. The photocatalytic steam methane reformer comprises: Housing; at least one reactor cell disposed within the housing, the at least one reactor cell including an enclosure and the first plasmonic photocatalyst on a first catalyst support disposed within the at least one enclosure, the enclosure being optically transparent and including at least one input for the methane feedstock to enter the at least one cell and at least one output for the first reaction product stream to exit the at least one cell; at least one light source, wherein utilization of the at least one light source causes the reactor cell to form the first reaction product stream from the methane feedstock; a cooling system configured to remove heat from the photocatalytic steam methane reformer for in-situ power generation; The system according to any one of claims 2 to 4, comprising:

6. A system described in any one of claims 1 to 5, wherein the separation unit includes a pressure swing adsorption (PSA) hydrogen purification unit.

7. The system of any one of claims 1 to 6, wherein the first system comprises an organic Rankine cycle to generate electricity within the system using process waste heat.

8. 8. The system of claim 7, wherein utilizing an organic Rankine cycle to generate electricity comprises providing waste heat generated by a cooling system.

9. The photocatalytic dry methane reforming apparatus comprises: Housing; at least one reactor cell disposed within the housing, the at least one reactor cell including an enclosure and a second plasmonic photocatalyst on a second catalyst support disposed within the at least one enclosure, the enclosure being optically transparent and including one or more inputs for the second methane feedstock and the carbon dioxide stream to enter the at least one cell, and at least one output for the syngas to exit the at least one cell; at least one light source, wherein use of the at least one light source causes the reactor cell to form the synthesis gas from the second methane feedstock and the carbon dioxide stream; and The system according to any one of claims 1 to 8, comprising:

10. The system of claim 9 , wherein the second plasmonic photocatalyst comprises a second catalyst that binds to a plasmonic material.

11. The system of claim 10 , wherein the second catalyst comprises iron, nickel, cobalt, platinum, rhodium, or ruthenium, and the plasmonic material is aluminum, copper, silver, or gold.

12. 12. The system of claim 1, further comprising a third stage immediately downstream from the second stage, the third stage comprising a synthesis reactor configured to produce methanol or dimethyl ether from the synthesis gas produced in the second stage.

13. 13. The system of claim 12, wherein a hydrogen stream is provided to the synthesis reactor in the third stage such that the molar ratio of carbon monoxide to hydrogen in the synthesis reactor is 1:

2.

14. The system of claim 13 , wherein the hydrogen stream is obtained in the first stage.

15. 13. The system of claim 12, wherein the second stage includes a shift reactor downstream adjacent to the photocatalytic dry methane reformer, the shift reactor configured to produce the hydrogen stream, and the hydrogen stream obtained in the second stage is supplied to the synthesis reactor in the third stage such that a molar ratio of carbon monoxide and hydrogen in the synthesis reactor is 1:

2.

16. 13. The system of claim 12, wherein the second stage includes a hydrogen separation membrane adjacent to and downstream from the photocatalytic dry methane reformer, the hydrogen separation membrane configured to produce the hydrogen stream, and the hydrogen stream obtained in the second stage is supplied to the synthesis reactor in the third stage such that a molar ratio of carbon monoxide and hydrogen in the synthesis reactor is 1:

2.

17. 1. A method for converting a methane feedstock into synthesis gas, comprising: supplying the methane feed to a first stage comprising a photocatalytic steam methane reformer to form a first reaction product stream comprising hydrogen and carbon monoxide; providing the first reaction product stream and water to a water-gas shift reactor to form a water-gas shift stream comprising hydrogen and carbon dioxide; providing the water-gas shift stream to a separation unit to obtain at least a carbon dioxide stream and a hydrogen stream; supplying the carbon dioxide stream to a second stage comprising a photocatalytic dry methane reformer to produce the synthesis gas; A method comprising:

18. The method comprising: distributing, in the photocatalytic steam methane reformer, the methane feedstock among a plurality of reactor cells disposed within a housing of the photocatalytic steam methane reformer, each reactor cell including an optically transparent enclosure and a first plasmonic photocatalyst on a first catalyst support disposed within the optically transparent enclosure; illuminating the first plasmonic photocatalyst on the first catalyst support of each of the plurality of reactor cells with at least one light source to convert the methane feedstock in the plurality of reactor cells into the first reaction product stream comprising hydrogen and carbon monoxide; accumulating the first reaction product stream from the plurality of reactor cells; 20. The method of claim 17, further comprising:

19. 20. The method of claim 17, wherein the separation unit comprises a pressure swing adsorption (PSA) hydrogen purification unit.

20. distributing, in the photocatalytic dry methane reformer, the carbon dioxide stream and a second methane feedstock among a plurality of reactor cells disposed within a housing of the photocatalytic dry methane reformer, each reactor cell including an optically transparent enclosure and a second plasmonic photocatalyst on a second catalyst support disposed within the optically transparent enclosure; illuminating the second plasmonic photocatalyst on the second catalyst support of each of the plurality of reactor cells with at least one light source to convert carbon dioxide and methane from the carbon dioxide stream to the synthesis gas in the plurality of reactor cells; accumulating the synthesis gas from the plurality of reactor cells; The method of any one of claims 17 to 19, further comprising:

21. 1. A process for preparing methanol or dimethyl ether from a methane feedstock comprising: providing the methane feed to a first stage comprising a photocatalytic steam methane reformer to obtain at least a carbon dioxide stream and a hydrogen stream; supplying the carbon dioxide stream to a second stage comprising a photocatalytic dry methane reformer to produce synthesis gas; feeding the synthesis gas and the hydrogen stream to a third stage comprising a synthesis reactor to obtain methanol or dimethyl ether; A method comprising:

22. 22. The method of claim 21, wherein a hydrogen flow is provided to the synthesis reactor in the third stage such that the molar ratio of carbon monoxide to hydrogen in the reactor is 1:2.

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