Hydrogen production using membrane reactors

Abstract

A system and method for producing hydrogen includes supplying a hydrocarbon and steam to an outer region of a tubular membrane within a vessel. The method includes steam reforming the hydrocarbon within the vessel over a reforming catalyst to produce hydrogen and carbon dioxide. The method includes diffusing hydrogen through the tubular membrane into a bore of the tubular membrane, the tubular membrane being hydrogen-selective.

Description

[Technical Field]

[0001] [Priority claim] This application claims priority to U.S. Patent Application No. 16 / 905,802, filed June 18, 2020, the entire contents of which are incorporated herein by reference.

[0002] [Technical field] The present disclosure relates to reforming hydrocarbons to produce hydrogen. [Background technology]

[0003] [background] Natural hydrogen is generally not found on Earth. Therefore, hydrogen is commercially produced. Hydrogen can be produced from fossil fuels. Hydrogen can be produced by coal gasification, biomass gasification, water electrolysis, or reforming or partial oxidation of natural gas or other hydrocarbons. Produced hydrogen can be a feedstock for chemical processes, such as fuel cells, ammonia production, aromatization, hydrodesulfurization, and hydrocarbon hydrogenation or hydrocracking.

[0004] Reforming natural gas is the most common method for producing hydrogen. Reforming natural gas to produce hydrogen can include steam reforming of natural gas. Bulk hydrogen is typically produced by steam reforming of natural gas (methane). Conventional steam reforming involves heating natural gas (e.g., between 700°C and 1100°C) in the presence of steam and a nickel catalyst. This endothermic reaction produces carbon monoxide and hydrogen. The carbon monoxide gas can be further converted to hydrogen by a water-gas shift reaction. Summary of the Invention

[0005] One aspect relates to a method for producing hydrogen, comprising supplying hydrocarbons and steam to a region outside a tubular membrane within a vessel. The method includes steam reforming the hydrocarbons within the vessel over a reforming catalyst to produce hydrogen and carbon dioxide. The method includes diffusing hydrogen through the tubular membrane into a bore of the tubular membrane, the tubular membrane being hydrogen-selective. The method includes providing heat for the steam reforming with an electric resistance heater disposed within the vessel, with a reforming catalyst disposed in the electric resistance heater and on the interior surface of the vessel wall.

[0006] Another aspect relates to a hydrogen production system including a vessel having an inlet for receiving hydrocarbons. The system includes a reforming catalyst that converts the hydrocarbons into a product gas comprising hydrogen and carbon dioxide, the reforming catalyst being disposed on an interior surface of a wall of the vessel and disposed in a plurality of resistance heaters within the vessel. The system includes a plurality of resistance heaters that heat the reforming catalyst and the hydrocarbons. The production system includes a tubular membrane that is hydrogen-selective and is disposed within the vessel to separate hydrogen from the product gas into a bore of the tubular membrane. The system includes a conduit collection header that receives hydrogen from the bore of the tubular membrane.

[0007] Yet another embodiment is a catalytic membrane reactor for producing hydrogen. The reactor includes a vessel having an inlet for receiving hydrocarbons. The reactor contains a reforming catalyst within the vessel and converts the hydrocarbons into a product gas comprising hydrogen and carbon dioxide. The reactor includes a plurality of electric resistance heaters for heating the reforming catalyst and for providing heat to a fluid within the vessel. The reactor includes a plurality of cylindrical membranes within the vessel, the plurality of cylindrical membranes being hydrogen-selective and separating a permeate (comprising hydrogen) from the product gas via the permeate diffusing through the wall of each cylindrical membrane to reach the bore of each cylindrical membrane. Each cylindrical membrane bore is coupled to a conduit collection header, which receives the permeate from each bore.

[0008] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view of a catalytic membrane reactor.

[0010] [Figure 2] FIG. 1 is a schematic side view of an electrically heated catalytic membrane reactor with the vessel wall in cross section.

[0011] [Figure 3] FIG. 1 is a schematic cross-sectional plan view of a catalytic membrane reactor.

[0012] [Figure 4] FIG. 4 is a side perspective view of one embodiment of the catalytic membrane reactor of FIG. 3.

[0013] [Figure 5] This is a method for producing hydrogen using a catalytic membrane reactor. DETAILED DESCRIPTION OF THE INVENTION

[0014] Large-scale methods for producing hydrogen typically involve steam methane reforming (SMR) of natural gas at high temperatures (e.g., 800°C-900°C) and pressures (e.g., 15-30 atm) using nickel-based catalysts in alloy tubes within a furnace. Providing heat for this reforming reaction (which is highly endothermic) can be problematic, leading to reduced efficiency. Steam generation is sometimes integrated with the furnace to increase thermal efficiency. Conventional SMRs are typically optimized for large-scale hydrogen production and generally do not scale down effectively for small-scale hydrogen production.

[0015] The rate of endothermic SMR reactions is often limited by external heat transfer to the reactor, which is why conventional industrial steam methane reforming catalyst tubes are typically installed inside large box furnaces burning hydrocarbon fuels. Such furnaces often consume at least one-third of the feedstock (e.g., natural gas), making the process inefficient and resulting in relatively large amounts of carbon dioxide emissions. Furthermore, the efficiency of large-scale industrial SMR processes depends on converting waste heat from the furnace exhaust into steam for use elsewhere in the plant or facility. Scaling down to applications that do not utilize the waste heat generated is therefore inefficient. In this case, the waste heat is often dissipated through active cooling, which consumes even more energy.

[0016] In contrast, some embodiments of the present disclosure are directed to catalytic membrane reactors with hydrogen-selective membranes for hydrogen production. These membranes can facilitate increasing both the yield and recovery of hydrogen from equilibrium-limited reactions, such as steam methane reforming. Heat supply for the endothermic reforming reaction can be achieved with electric heaters built into the reactor and in close proximity to the reforming catalyst. These internal electric heaters may be in contact with the reforming catalyst that drives the reforming reaction. This membrane reactor can operate at lower temperatures and be more compact than conventional SMR systems. The use of hydrogen-selective membranes can facilitate the production of pure hydrogen and a concentrated, retrievable carbon dioxide stream suitable for utilization or sequestration.

[0017] 1 is a schematic perspective view of a catalytic membrane reactor 100 including a vessel 102 and a hydrogen-selective tubular membrane 104 disposed within the vessel 102. The vessel 102 may be a cylindrical or tubular vessel. The vessel 102 may be oriented horizontally (as depicted) or vertically.

[0018] In operation, hydrocarbons 106 and steam 108 are fed into the vessel 102. The hydrocarbons 106 are steam reformed within the vessel 102 to produce hydrogen and carbon dioxide (CO) within the vessel 102. Steam reforming may involve the water gas shift (WGS) reaction of carbon monoxide (CO) to CO. The steam reforming reaction occurs in a region within the vessel 102 that is external to the tubular membrane 104. This region may be referred to as the reaction space, and is the retentate side of the tubular membrane 104.

[0019] As the steam reforming reaction occurs and hydrogen is produced, the hydrogen diffuses 110 (permeates) through the wall of the tubular membrane 104 and into the bore of the tubular membrane 104. The wall of the tubular membrane 104 is the membrane, i.e., the membrane material (e.g., a palladium alloy). The bore is the interior space of the tubular membrane 104 and is sometimes referred to as the lumen. The bore of the tubular membrane 104 is the permeate side of the tubular membrane 104.

[0020] A hydrogen-rich permeate 112 exits the bore of the tubular membrane 104 and exits the reactor 100. The permeate 112 may be, for example, at least 90 mole percent (mol%) hydrogen. A carbon dioxide (CO2)-rich retentate 114 exits the reactor 100 from the region (reaction space) of the vessel 102 around and outside the tubular membrane 104. The CO2-rich retentate 114 on a dry basis may generally contain less than 10 mol% of a combination of hydrogen and CO. The CO2-rich retentate 114 may generally contain unreacted water vapor. The CO2-rich retentate 114 may generally be at least 90 mol% CO2 (dry basis), which makes the retentate 114 ready for further compression, in some cases for geological sequestration or enhanced oil recovery (EOR), or further purification so that the CO2 can be used as a feedstock for another process. The CO2-rich retentate 114 may be subjected to steam (water) removal before compression or further purification.

[0021] In embodiments, a sweep gas (e.g., steam or nitrogen) is supplied to the bore of the tubular membrane 104 and flows through the bore, moving permeate (hydrogen) from the bore and out of the reactor 100. This movement of hydrogen may maintain or increase the driving force for hydrogen permeation through the wall of the tubular membrane 104 from the region outside the tubular membrane 104 (the reaction space) to the bore. In some embodiments, the sweep gas may be supplied and flow countercurrently to the hydrocarbon 106 and steam 108 feeds. Thus, in these embodiments, the permeate 112 may exit the reactor 100 at an end (the hydrocarbon feed end) opposite the end at which the retentate 114 exits.

[0022] Heat for the reforming reaction within the vessel 102 may be provided by an electric resistance heater (not shown) disposed within the vessel 102. The resistance heater within the vessel 102 may be referred to as an internal heater. In some embodiments, the resistance heater is an electric cartridge heater.

[0023] Heat for the reforming reaction may also be provided by a heat source external to the vessel 102. For example, electric heater(s) (not shown) may be disposed on the exterior surface of the vessel 102. In another example, the vessel 102 may be disposed in a furnace and receive heat from the furnace as an external heat source.

[0024] Exemplary operating temperatures for reactor 100 at which the reforming reaction can occur are below 600° C., or up to about 550° C. The operating pressure in the reaction space within vessel 102 can be, for example, in the range of 10 bar (1 MPa) to 50 bar (5 MPa), or in the range of 30 bar (3 MPa) to 40 bar (4 MPa), or at least 15 bar (1.5 MPa), or at least 25 bar (2.5 MPa).

[0025] A reforming catalyst (not shown) for steam reforming hydrocarbons 106 is disposed within vessel 102. The reforming catalyst may be disposed in contact with an internal resistance heater, such that the internal resistance heater (e.g., a cartridge heater) can quickly, easily, and directly heat the reforming catalyst to promote and advance the reforming reaction.

[0026] A reforming catalyst may additionally be disposed on the inner surface 116 of the wall of the vessel 102. In certain embodiments, the reforming catalyst is not in contact with the tubular membrane 104. The reforming catalyst may include a catalyst that promotes the WGS reaction of CO to CO.

[0027] The WGS reaction may occur in parallel with the steam reforming to convert the produced CO to CO. In practice, the steam reforming and WGS reactions may include: [1] CH + H2O⇔3H2 + CO and [2] CO + H2O⇔CO2 + H2, which result in the overall reaction [3] CH4 + 2H2O⇔4H2 + CO2.

[0028] 2 is a diagram of an electrically heated catalytic membrane reactor 200 with the vessel wall depicted in cross section. The reactor 200 may be a reformer that converts hydrocarbons into hydrogen and carbon dioxide. The catalytic membrane reactor 200 contains both an electric resistance heater 202 and a hydrogen-selective tubular membrane 204 within a vessel 206.

[0029] Electric resistance heaters 202 may be interspersed within the vessel 206. A reforming catalyst may be disposed on (in contact with) the resistance heaters 202, as described below. The resistance heaters 202 may supply heat directly to the reforming catalyst within the vessel 206. Heat may also be transferred by conduction and convection from the heaters 202 to the fluid contents of the region outside the tubular membrane 204 within the vessel 206. The resistance heaters 202 may heat the reforming catalyst disposed thereon to, for example, at least 550°C, at least 600°C, at least 700°C, or at least 800°C. The resistance heaters 202 may facilitate an operating temperature of the reactor 200 of at least 550°C or at least 600°C.

[0030] Two electric resistance heaters 202 are depicted in Figure 2. While these two internal heaters are depicted as electric resistance heaters, the internal heaters may instead each be a heater that relies on a heat transfer medium (heat transfer fluid). For example, the internal heaters may instead be conduits through which a heat transfer medium (e.g., molten salt) is recirculated.

[0031] In the illustrated embodiment, the electric resistance heaters 202 are generally cylindrical. The resistance heaters 202 may each be an electric resistance wire heater. The resistance heaters 202 may also be, for example, electric cartridge heaters, electric tubular heaters, etc.

[0032] A cartridge heater is a heating element typically having a cylindrical shape. The cartridge heater (heating element) may include a metallic outer casing (e.g., stainless steel) sheath. The cartridge heater (heating element) may include an insulator and a metallic wire coil (as a heater). The heater wire coil may be a metal alloy, such as a nickel-chromium alloy. During operation, an alternating current flows through the resistive wire coil within the cartridge heater, generating resistive heating by the wire coil. This thermal energy is transferred by conduction from the wire to the metal sheath and then to its surroundings. The cartridge heater may heat the reforming catalyst 212 disposed in contact with the cartridge heater to at least 700°C or at least 800°C. The cartridge heater may provide a reactor operating temperature of 800°C or higher, or at least 550°C or at least 600°C. During operation, the operating temperature of the reactor 200 may range from 450°C to 650°C, or may be less than 700°C, less than 600°C, or less than 550°C.

[0033] The tubular membranes 204 may be characterized or labeled as cylindrical membranes, hollow fiber membranes, etc. The walls of the tubular membranes 204 are the membrane, i.e., the membrane material. The bore 205 of each tubular membrane 204 is a cylindrical cavity (lumen) inside the tubular membrane 204 and is defined by the walls (membrane or membrane material) of the tubular membrane 204. The material of the hydrogen-selective tubular membranes 204 may be, for example, a palladium alloy. The membrane may be a thin film of a palladium alloy supported on a tubular porous substrate made of a metal or metal oxide. During operation, hydrogen can pass through the wall of the tubular membrane 204 and enter the bore 205 (internal cavity or lumen) of the tubular membrane 204. The bore 205 of the tubular membrane 204 is the permeate side of the membrane 204. Permeate hydrogen may be recovered from the bore 205 as product. The volume of the vessel 206 outside the tubular membrane 204 is the retentate side of the tubular membrane 204. The produced carbon dioxide may be vented from the vessel 206 through the retentate side.

[0034] As shown, vessel 206 houses tubular membrane 204 and resistance heater 202. Vessel 206 may be, for example, stainless steel. Vessel 206 may be a cylindrical vessel. Vessel 206 may have a vertical orientation (as depicted) or a horizontal orientation. Wall 208 of vessel 206 is depicted in cross section. In the depicted embodiment, outer surface 210 of vessel wall 208 is the exterior surface of vessel 206, and therefore, in this embodiment, the exterior surface of reactor 200.

[0035] Six hydrogen-selective tubular membranes 204 are depicted. Three tubular membranes 204 are in the upper portion of the vessel 206. Three tubular membranes 204 are in the lower portion of the vessel. In this embodiment, one end of each tubular membrane 204 is capped, and the other end exits permeated hydrogen for collection. The capped ends may generally be in the center or mid-portion of the vessel 206, relative to the vertical or longitudinal length of the vessel 206.

[0036] The tubular membranes 204 may be positioned adjacent to the resistance heater 204 and / or adjacent to the wall 208 of the vessel 206. In one embodiment, the tubular membranes 204 share a longitudinal axis with each other and with the vessel 206, as depicted. In the case of a vertical vessel 206, the vertical central axis of each tubular membrane 204 may be parallel to (along) the vertical central axis of the vessel 206. In the case of a horizontal vessel 206, the horizontal central axis of each tubular membrane 204 may be parallel to (along) the horizontal central axis of the vessel 206.

[0037] In embodiments, the upper tubular membrane 204 may be positionally paired with the lower tubular membrane 204. In particular, the two tubular membranes 204 may be axially arranged or aligned (vertically in the case of a vertical vessel 206) as a pair. Such a pair may generally run the majority of the longitudinal length of the vessel 206. The membranes 204 may also be staggered (zigzag) so that the pairs are not axially aligned. This may benefit retentate mixing and increase hydrogen mass transfer to the membranes. The membranes 204 may also be of different lengths relative to each other. Each heater 202 may also be configured with an upper and lower heater axially aligned as a pair or in a staggered manner. This may provide greater flexibility in controlling the temperature inside the reactor 200. In some embodiments, the heat output of the heater 202 may also be nonlinear along its length. For example, less heat input may be implemented toward the outlet of the reactor vessel 206, where more exothermic WGS reactions occur and fewer endothermic reforming reactions occur.

[0038] The area (space, volume) around (outside) the tubular membrane 204 may be the reforming reaction space within the vessel 206. As shown, this area (reforming reaction space) outside the tubular membrane 204 is the retentate side of the tubular membrane 204. This area (reforming reaction space) may generally include most or all of the volume within the vessel (the interior volume defined by the vessel wall 208) around the outside of the tubular membrane 204, the outside of the resistive heater 202, and any internal features (e.g., piping) within the vessel 206.

[0039] The vessel 206 may have a head (not shown). The vessel 206 may have a head at the top of the vessel and a head at the bottom of the vessel. The head may be, for example, a flat plate. The plate may be welded to the vessel wall 208, or the plate may be bolted (with an intervening gasket) to the vessel wall 208. In another example, the head is an oval-shaped head (see, for example, FIG. 3) welded to the vessel wall 208.

[0040] Vessel 206 may be a pressure vessel. The pressure vessel may be designed and constructed (e.g., have an appropriate wall thickness) to undergo an internal pressure up to a predetermined pressure (design pressure) greater than ambient (atmospheric) pressure. The pressure vessel may be suitable for holding materials up to the design pressure. During operation, the operating pressure within the pressure vessel may generally be maintained below the design pressure. The pressure vessel may be constructed in accordance with an official standard or code, such as the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPVC) or the European Union (EU) Pressure Equipment Directive (PED).

[0041] The reforming catalyst 212 (e.g., nickel, such as supported nickel) may be disposed on (in contact with) the resistive heater 202. Thus, the resistive heater 202 may heat the catalyst 212 more directly, including through conduction through the contact and with less thermal resistance, since the contact reduces the thermal resistance. Conversely, a space or gap between the catalyst (e.g., a structured catalyst) and the heat source (e.g., a resistive heater) may significantly increase the heat transfer resistance.

[0042] The reforming catalyst 212 may be, for example, a nickel-based catalyst or a noble metal-based catalyst. Noble metal-based catalysts may be more active at lower temperatures. In some embodiments, the catalyst 212 as a pelletized catalyst may be packed inside the membrane reactor 206 around the heater 202 and the membrane 204 (the catalyst 212 may contact the membrane 204).

[0043] The reforming catalyst 212 may also be disposed on (in contact with) the inner surface 214 of the vessel wall 208. The reforming catalyst 212 may be coated on the resistive heater 202 and on the vessel wall 208. In some embodiments, the reforming catalyst 212 does not contact the tubular membrane 204. In some embodiments, the reforming catalyst 212 may be disposed on the resistive heater 202 and on the vessel wall 208 in a structured form (e.g., a metal foam). The structured form may be, for example, a catalyst or a coated catalyst disposed on a metal foam, mesh, or monolith. The reforming catalyst 212 on the surface of the resistive heater 202 and on the inner surface 214 of the vessel wall 208 may be in the form of pellets, granules, metal foam (or disposed on a metal foam), washcoat, or the like. Metal foam is generally a cellular structure (a structure consisting of small compartments) made of solid metal with pores. The pores may account for, for example, 5-25% by volume of the metal foam. The pores may be closed (closed cell foam) or interconnected (open cell foam).

[0044] In embodiments, the catalyst 212 generally does not directly contact the membrane 204 to avoid passivating or scratching the surface of the membrane 204 material by the catalyst 212, thereby promoting a longer life of the membrane 204 material (e.g., a palladium alloy). The gap between the catalyst 212 and the membrane 204 may be relatively small (short), e.g., 1-5 millimeters, to facilitate or promote diffusion of hydrogen (produced by the reforming reaction) through the tubular membrane 204 from the reaction space into the bore 205 of the tubular membrane 204.

[0045] In some embodiments, instead of or in addition to the reforming catalyst 212 disposed directly on the surface of the resistive heater 202 and the inner surface 214 of the vessel wall 208, a packed catalyst reforming catalyst 212 (e.g., pelletized catalyst) may be packed into the vessel 206. Such a packed catalyst may contact the tubular membrane 204 in some embodiments.

[0046] The reforming catalyst 212 may provide WGS. However, in some embodiments, the catalyst 212 may include a layered catalyst having a steam reforming catalyst and a WGS reaction catalyst. In this case, the WGS catalyst may be, for example, nickel-based or precious metal-based. With this layered catalyst (e.g., by placing the WGS catalyst toward the outlet region of the membrane reactor), WGS has a higher equilibrium conversion (and is a mildly exothermic reaction). CH4 + H2O = CO + 3H2 and CO + H2O = CO2 + H2, resulting in an overall reaction of CH4 + 2H2O = CO2 + 4H2.

[0047] The steam reforming reaction (including any WGS reaction) occurs in the region (reaction space) described above. References to the steam reforming reaction in the embodiments can be understood to include the conversion of CO to CO.

[0048] The vessel wall 208 may optionally be heated by an electric heater 216 disposed on (in contact with) the exterior surface 210 of the vessel wall 208 or by burning fuel (e.g., via a furnace) as an external heat source. The external electric heater 216 (if utilized) or furnace (if utilized) may heat the vessel wall 208, which conducts heat directly to the reforming catalyst 212 disposed on the interior surface 214 of the vessel wall 208. Heat may also be transferred by conduction and convection to the fluid contents (e.g., hydrocarbons, steam, product gas, etc.) in a region 218 (within the vessel 206) outside the tubular membrane 204. As previously mentioned, this region 218 may be or provide the reaction space for the reforming reaction and is the retentate side of the tubular membrane 204.

[0049] The external electric heater 216 may be, for example, an electric band heater, an electric strip heater, an electric plate heater, etc. The band heater may be a ring-shaped heater that is clamped around a cylindrical object, such as the cylindrical vessel 206. Heat transfer from the band heater to the vessel 206 generally occurs via conduction. The band heater is an external heater that may be clamped around the outer diameter of the vessel 206 and heats the vessel 206. The band heater may include ceramic or mineral insulation to reduce heat loss to the environment.

[0050] The vessel 206 may have insulation disposed on the exterior surface 210 of the vessel wall 208. The insulation can reduce heat transfer from the vessel 206 to the environment, thereby conserving heat within the vessel 206. The insulation can also provide protection for personnel.

[0051] In operation of the catalytic reforming reactor 200, the vessel 206 is provided with a feed 220 (e.g., via a conduit) to a region 218 (space) outside the tubular membrane 204. During operation, the region 218 is generally at a higher pressure than the bore 205 of the tubular membrane 204. The feed 220 may include steam and hydrocarbons. The hydrocarbons react with the steam in the region 218 over the reforming catalyst 212. This reaction may be steam reforming of the hydrocarbons.

[0052] Feed 220 may typically be a feed gas or steam, but may also include a liquid (or supercritical fluid). To provide feed 220 to vessel 206, a feed conduit may deliver feed 220 to vessel 206 (e.g., to a nozzle on feed vessel 206).

[0053] Feed 220 may be a mixture of steam and hydrocarbons. The ratio of hydrocarbons to steam may be, for example, a typical steam-to-carbon molar ratio in the range of 1 to 6, 1 to 5, or 2.5 to 3.5. The mixture may be pressurized (greater than atmospheric pressure). In some embodiments, the steam and hydrocarbons may be provided separately to vessel 206 (e.g., via two respective conduits).

[0054] In certain feasible embodiments, baffles may be employed in vessel 206 to promote mixing of the steam and hydrocarbons. However, baffles may generally be avoided in embodiments. In some cases, baffles may not be easily installed due to, for example, space limitations. Also, the relatively close location of reactor internal components (e.g., tubular membrane 204, resistance heater 202, etc.) relative to one another may result in flow disturbances in the steam and hydrocarbon mixture without the use of baffles.

[0055] The hydrocarbons in the feed 220 may include, for example, natural gas, methane, liquefied petroleum gas (LPG), or a C1-C10 mixture, or any combination thereof. LPG may include, for example, propane and butane. The hydrocarbons in the feed 220 and steam react in region 218 over the reforming catalyst 212 to generate a product gas including hydrogen and carbon dioxide.

[0056] The generated hydrogen is removed from region 218 (reaction space). For example, the generated hydrogen diffuses (permeates) through membrane 204 and enters bore 205 of each tubular membrane 204. Bore 205 is the permeate and low-pressure side of tubular membrane 204. Permeate 222 (hydrogen-rich) with the diffused generated hydrogen may exit bore 205 to collection header 224 (described below) for distribution or further processing. Permeate 222 may be, for example, at least 90 mol % hydrogen. The collection header may be a single conduit or multiple conduits. As described below, if a sweep gas is used to displace hydrogen from bore 205, permeate 222 may be at least 90 mol % hydrogen on a sweep gas-free basis. Thus, if the sweep gas is water vapor, permeate 222 may be at least 90 mol % hydrogen on a dry basis.

[0057] The retentate 226 (rich in carbon dioxide) with evolved carbon dioxide may exit under pressure from region 218 for discharge from vessel 206. Again, region 218 is on the retentate side of tubular membrane 204, which may facilitate capture of carbon dioxide. In the illustrated example, retentate 226 is discharged from the bottom of vessel 206. Retentate 226 may be discharged from vessel 206 via a conduit. Retentate 226 may be discharged through a nozzle associated with vessel 206 and through a conduit connected to the nozzle. Retentate 226 may have, for example, at least 90 mol % carbon dioxide on a dry basis.

[0058] A sweep gas 228 (such as water vapor or nitrogen) may be utilized to increase the driving force for hydrogen permeation through the membrane 204. The sweep gas 228 may be fed into the bore 205 (membrane lumen). The sweep gas 228 may move the permeate (hydrogen) out of the bore 205 for collection.

[0059] In some cases, a tube 230 within the membrane 204 (within the bore 205) may be utilized for the sweep gas 228. The sweep gas 228 may flow countercurrently to the reactant (feed gas 220) flow direction to obtain a greater driving force for hydrogen permeation.

[0060] The tube 230 may be referred to as an inner tube or an insertion tube. The tube 230 may be concentrically disposed within the bore 205 (lumen) of the tubular membrane 204. Thus, there may be an annulus between the tube 230 and the wall (membrane) of the tubular membrane 204.

[0061] The sweep gas 228 may be supplied to the vessel 206 via one or more conduits. The sweep gas 228 feed may be split (within the vessel 206 or external to the vessel 206) via a manifold, a feed header (e.g., with an exhaust subheader), or multiple conduits as inputs to each tubular membrane 204.

[0062] In the example of FIG. 2 , the sweep gas 228 for the three upper tubular membranes 204 is introduced into tube 230. Thus, the sweep gas 228 exits tube 230 at the cap end (plugged end) of the tubular membrane 204 and flows upward through the annulus. The sweep gas 228 moves the permeate (hydrogen) through the annulus (through the three upper membranes 204) countercurrently to the flow of the reactant (feed gas 220). The permeate 222 discharged from vessel 206 to collection header 224 may include the sweep gas 228. The permeate 222 may flow to collection header 224 via a conduit (and a nozzle in vessel 206) connecting vessel 206 (and the annulus in bore 205) to collection header 228.

[0063] A sweep gas 228 for the three lower tubular membranes 204 is introduced into the annulus. For the three lower tubular membranes 204, the sweep gas 228 drives the permeate (hydrogen) through the annulus countercurrent to the flow of reactant (feed gas 220) to the vessel 206. Flowing the sweep gas 228 through the annulus countercurrent to the flow of retentate (as shown) generally increases the driving force for hydrogen permeation through the membranes 204. The sweep gas 228 and permeate enter tubes 230 at the cap end portions of the tubular membranes 204. Thus, the permeate 222 discharged from the vessel 206 to the collection header 224 contains the sweep gas 228. The permeate 222 (containing the sweep gas 228 and evolved hydrogen) exits the three lower membranes 204 through respective tubes 230 at the bottom of the vessel 206. The conduit may direct the permeate 222 to a conduit collection header 224 .

[0064] The presence of the sweep gas 228 discharged in the permeate 222 reduces the proportion of hydrogen in the permeate 212. However, in general, the sweep gas 228, as water vapor, may be easily removed from the permeate 212 to provide relatively pure hydrogen downstream. For example, the water vapor may be condensed in a heat exchanger and removed as liquid water.

[0065] The reactor 200 system may include a control system 232 that facilitates or directs the operation of the reactor 200 system, such as supplying or discharging streams (including flow rates), controlling heaters 202, 216, and controlling the operating temperature and pressure of the reactor 200. The control system 232 may include a processor and memory that stores code (e.g., logic, instructions, etc.) executed by the processor to perform calculations and direct the operation of the reactor 200 system. The processor (hardware processor) may be one or more processors, each having one or more cores. The processor(s) may include a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), a controller card, a circuit board, or other electrical circuitry. The memory may include volatile memory (e.g., cache or random access memory), non-volatile memory (e.g., a hard drive, solid-state drive, or read-only memory), and firmware. Control system 232 may include a desktop computer, a laptop computer, a computer server, a programmable logic controller (PLC), a distributed computing system (DSC), a controller, an actuator, or a control card. Control system 232 may be communicatively coupled to a remote computing system that performs calculations and provides instructions. Control system 232 may receive user input or remote computing input that specifies set points for controllers or other control components within the reactor 200 system. In some embodiments, control system 232 may calculate or otherwise determine the set points for the controllers.

[0066] Reactor operating temperature control via electrical heating may be implemented via the control system 232 or controller. Lower operating temperatures and the use of fewer electric heaters (compared to furnace heating) may allow for less expensive materials of construction (e.g., 300 series stainless steel) for membrane reactor systems. Electric heating may provide more precise temperature control, making it more advantageous for preventing reactor components from exceeding their design temperature or maximum operating temperature limits. Electric heating may be more efficient (especially if the electricity is obtained from a renewable resource) because energy is not wasted by venting hot flue gases, as in conventional SMR implementations. In some embodiments, renewable energy sources (e.g., solar, wind, etc.) can be utilized to reduce the cost of electricity supplied to the internal resistance heater 202 (and external heater 216, if employed). Supplying heat directly to the interior of the reactor (via an internal resistance heater) generally reduces conduction losses compared to external heating, such as via an external furnace. Thus, electrically heated reactors may be well suited to carrying out endothermic reactions (such as steam methane reforming) that utilize large energy inputs to provide the heat of reaction.

[0067] 3 is a schematic cross-sectional plan view of a catalytic membrane reactor 300 for steam reforming hydrocarbons to produce hydrogen and carbon dioxide. Reactor 300 includes a cylindrical vessel 302. Vessel 302 may be a vertical vessel or a horizontal vessel.

[0068] The reactor 300 includes a hydrogen-selective tubular membrane 304. The tubular membrane 304 is disposed within a vessel 302. The membrane material of the tubular membrane may be, for example, a palladium alloy.

[0069] Nine tubular membranes 304 are depicted. In some embodiments, two tubular membranes 304 may be axially aligned, one above the other (with their capped ends adjacent). See, e.g., FIG. 2. Thus, in those embodiments, reactor 300 includes 18 tubular membranes 304.

[0070] In embodiments, the tubular membranes 304 share a longitudinal axis with each other and with the vessel 302, as shown. In a vertical vessel 302, the vertical central axis of each tubular membrane 304 may be parallel to the vertical central axis of the vessel 302. In a horizontal vessel 302, the horizontal central axis of each tubular membrane 304 may be parallel to the horizontal central axis of the vessel 302.

[0071] The reactor 300 includes an internal heater 306, which is an electric resistance heater disposed within the vessel 302. The resistance heaters 306 may be interspersed within the vessel 302, including being spaced apart relative to one another and / or to the respective tubular membranes 304. The resistance heaters 306 may be, for example, electric cartridge heaters. In an embodiment, the resistance heaters 306 may generally heat a majority of the longitudinal length of the vessel 306. The reactor 300 may include more tubular membranes 304 and more heaters 306, and / or the membranes 304 and heaters 306 may be positioned closer together (than shown) to enhance performance.

[0072] The width of the gap between the internal heater 306 and the membrane 304 may be determined, for example, based on the expected operating conditions (e.g., feed flow rate and composition, reactor operating temperature, etc.) so that the reaction rate (e.g., hydrogen production) is balanced by the rate of hydrogen diffusion through the membrane 304. This rate of hydrogen diffusion can be affected by the thickness of the gas diffusion boundary layer.

[0073] The catalytic membrane reactor 300 includes a reforming catalyst 308 (e.g., a nickel-based catalyst) disposed on the exterior surface of an electric resistance heater 306 and on the interior surface of the wall of the vessel 302. The reforming catalyst may be in the form of a coating or structured as described with respect to FIG.

[0074] Reticulated metal foam and washcoated catalysts generally have significantly greater thermal conductivity than conventional steam reforming catalysts composed of nickel deposited on a pelleted metal oxide support. A metal foam catalyst 308 attached directly to the resistance heater 306, or a catalyst 308 washcoated onto the resistance heater 306, increases heat transfer to the catalyst. This can also result in more uniform heating of the reactor, reducing the presence of cold spots and promoting more effective utilization of the catalyst 308 and membrane 304. The presence of foam in the reaction space also increases turbulence, thereby promoting hydrogen mass transfer to the surface of the membrane 304. A resistance heater 306 within the vessel 302 of the reactor 300 can facilitate more precise control of temperature, which can be beneficial for optimizing or improving reactor performance, including, for example, when supply conditions change in response to hydrogen demand. Having the catalyst 308 in direct contact with the internal resistance heater 306 to provide efficient heat transfer may be a beneficial aspect of the reactor 300. Interposing an internal resistance heater 306 between the membranes 304 may generally provide heat directly at a useful location for carrying out the endothermic steam reforming reaction.

[0075] In some embodiments, instead of or in addition to the resistive heater 306 and the reforming catalyst 308 disposed directly on the walls of the vessel 302, a packed catalyst reforming catalyst 308 (e.g., pelleted catalyst) may be packed within the vessel 302. Such packed catalyst may, in some instances, contact the tubular membrane 304. Additionally, the reforming catalyst 308 may provide WGS. The catalyst 308 may include a layered catalyst having a steam reforming catalyst and a WGS reaction catalyst.

[0076] During operation, the resistance heater 302 heats the catalyst 308 disposed in contact with (or adjacent to) the resistance heater 302. The reactor 302 may also include an external electric heater (e.g., a band heater) disposed on the exterior surface of the vessel 302 to heat the walls of the vessel 302 and, in turn, heat the catalyst 308 disposed on the interior surface of the walls of the vessel 302.

[0077] During operation, hydrocarbons and steam are supplied to vessel 306. The hydrocarbons and steam are converted to hydrogen and carbon dioxide in a steam reforming reaction over reforming catalyst 308. The hydrocarbons react with steam over reforming catalyst 308 to produce hydrogen and carbon dioxide. Heat for the endothermic steam reforming reaction may be provided by an internal electric resistance heater 306 or an external electric heater. The fluid contents within vessel 302 may receive heat by conduction and convection. The operating temperature of reactor 300 within vessel 302 may be in the range of 450°C to 650°C. The operating temperature of reactor 300 may be less than 800°C, less than 750°C, less than 700°C, less than 600°C, or less than 550°C. The operating pressure may be, for example, in the range of 10 bar (1 MPa) to 50 bar (5 MPa).

[0078] The steam reforming reaction may occur in the reaction space outside the tubular membranes 304. Thus, product gases including hydrogen and carbon dioxide may be produced in this volumetric region of the vessel, which is the reaction space. This region, or reforming reaction space, may include the space (volume) between each tubular membrane 304 and the space between each internal resistance heater 306. This reforming reaction space region may generally further include the space between the tubular membranes 304 and the internal resistance heater 302, the space between the tubular membranes 304 and the vessel 302 wall, and the space between the internal resistance heater 306 and the vessel 302 wall.

[0079] Hydrogen produced by the steam reforming reaction diffuses from the product gas (within the reaction space) through the membrane material of the tubular membrane 304 and into the bore 310 (lumen) of the tubular membrane 304. The bore 310 is the permeate side of the tubular membrane. The permeate containing the permeated hydrogen may be discharged from the bore 310 (and from the vessel 302) to, for example, a header (conduit) that directs the discharged permeate for recovery as product. The concentration of hydrogen in the discharged permeate may be, for example, at least 90 mol% (e.g., dry basis). The discharged permeate may be treated to remove the water vapor (water) if a steam sweep gas is used to drive the permeate from the bore. The discharged permeate may also be treated (e.g., purified) to provide more purified hydrogen.

[0080] In pilot plant examples, a single tubular membrane reactor provided greater than 90% conversion of methane to hydrogen at reactor operating temperatures ranging from 500°C to 575°C (e.g., about 550°C). Adding a second membrane in series within the same reactor (downstream of the first membrane) can provide near 100% conversion of methane to hydrogen (e.g., at least 98%, at least 99%, or at least 99.5% conversion). This is also beneficial in providing further purification of carbon dioxide in the retentate by extracting nearly all remaining hydrogen from the product gas.

[0081] As previously mentioned, a sweep gas may be provided to bore 310 to facilitate the movement of permeated hydrogen out of bore 310 (and out of vessel 302). The sweep gas moving permeated hydrogen out of bore 310 may maintain or increase the driving force for permeation (diffusion) of the produced hydrogen from the product gas in the reaction space through the membrane and into bore 310. The flow of the sweep gas in moving the permeate (primarily hydrogen) may be countercurrent to the introduction of hydrocarbons and water vapor into the reaction space in vessel 302. The permeate moved with the sweep gas may be discharged from bore 310 to a collection header. In some embodiments, the sweep gas (e.g., nitrogen or water vapor) may be easily separated from the permeate or permeate hydrogen.

[0082] In one embodiment, an inner tube 312 (eg, similar to tube 230 in FIG. 2) in bore 310 facilitates the guidance and flow of the sweep gas (and associated movement of permeate) within the bore.

[0083] The region (reaction space) outside the tubular membrane 304 is the retentate side of the tubular membrane 304. Carbon dioxide generated in the steam reforming reaction may be discharged from the reaction space to the vessel 302 as retentate.

[0084] 4 shows an embodiment of a reactor 300 having a vessel 302 as a vertical vessel with an oval head. A feed nozzle 400 at the top of the vessel 302 is an inlet for a feed gas as a mixture of hydrocarbons and steam. A retentate nozzle 402 at the bottom of the vessel 302 is an outlet for retentate (primarily carbon dioxide) to leave the vessel 302.

[0085] The permeate nozzle 404 provided at the top (top) of the vessel 302 is an outlet for discharging the permeate (mainly hydrogen) from the vessel 302 through the membrane 304 at the top of the vessel 302. The permeate nozzle 404 provided at the top of the vessel 302 is an outlet for discharging the permeate (mainly hydrogen) from the vessel 302 through the membrane 304 at the bottom of the vessel 302. The permeate discharged from both nozzles 402 may be sent via conduits to a conduit collection header.

[0086] Although one permeate (hydrogen) nozzle 402 is depicted at the top and one permeate (hydrogen) nozzle 404 is depicted at the bottom, there may be multiple permeate (hydrogen) nozzles 402 at the top and bottom. Such may depend on the routing of the permeate exiting the bores of each of the tubular membranes within vessel 302. In one example, vessel 302 includes a respective permeate nozzle 402 for each tubular membrane. Thus, in that example, and with the number of tubular membranes shown in FIG. 2, there are nine permeate nozzles 402 at the top of vessel 302 and nine permeate nozzles 402 at the bottom of vessel 302.

[0087] For coupling to their respective external conduits, nozzles 400, 402, 404 may be flanged (as shown), each may have a threaded connection, etc. Additionally, there may be additional nozzles in vessel 302 for the introduction of sweep gas, for instrumentation (e.g., pressure sensors or gauges, temperature sensors or gauges, etc.), etc.

[0088] 5 illustrates a method 500 for producing hydrogen using a catalytic membrane reactor via steam reforming. The catalytic membrane reactor includes a vessel containing a hydrogen-selective tubular membrane and an internal electrical resistance heater. The vessel may be, for example, a cylindrical pressure vessel. Multiple hydrogen-selective tubular membranes may reside within the vessel.

[0089] At block 502, the method includes supplying hydrocarbons and steam into a vessel to a region within the vessel outside the tubular membrane. This region within the vessel may be characterized as a reaction space and a retentate side of the tubular membrane. The hydrocarbons may include natural gas, methane, LPG, or a mixture of C1-C10 hydrocarbons, or any combination thereof.

[0090] At block 504, the method includes steam reforming hydrocarbons in the vessel over steam and a reforming catalyst (e.g., a nickel-based catalyst) in the vessel to generate hydrogen and carbon dioxide. Steam reforming converts steam and hydrocarbons into hydrogen and carbon dioxide. Steam reforming may generally involve reacting hydrocarbons with steam over a reforming catalyst. In an embodiment, the reforming catalyst is not in contact with the tubular membrane or membranes.

[0091] At block 506, the method includes diffusing the generated hydrogen through the tubular membrane into the bore of the tubular membrane. As noted, the tubular membrane is hydrogen-selective. The bore is the permeate side of the tubular membrane. If there are multiple tubular membranes in the vessel, the generated hydrogen diffuses (permeates) through the membrane material into the bore of each of the multiple tubular membranes. There may be multiple tubular membranes in the reactor vessel, each tubular membrane being hydrogen-selective and having a respective hole on the permeate side of each tubular membrane.

[0092] At block 508, the method includes discharging the permeate (having hydrogen) from the bore of the tubular membrane and from the reactor. Discharging the hydrogen may include discharging the hydrogen from the bore of the tubular membrane as permeate to a conduit for collection of hydrogen or hydrogen-rich permeate. The hydrogen content of the permeate on a dry basis may be at least 85 mol%, at least 90 mol%, or at least 95 mol%.

[0093] The method may include supplying a sweep gas (e.g., steam or nitrogen) to the bore to drive hydrogen (permeate) from the bore with the sweep gas, thereby increasing the driving force for hydrogen permeation through the tubular membrane from a region outside the tubular membrane to the bore. The sweep gas driving the hydrogen may flow countercurrently to the flow of hydrocarbons and steam into the vessel.

[0094] At block 508, the method also includes discharging the retentate (having the produced carbon dioxide) from the reaction space (retentate side) outside the tubular membrane(s). The retentate is generally rich in carbon dioxide. The retentate may have at least 90 mol% carbon dioxide on a dry basis. The method may also include discharging the carbon dioxide as a retentate from the vessel from a region outside the tubular membrane. This region may generally be the reaction space within the vessel and the retentate side of the tubular membrane.

[0095] At block 510, the method includes providing heat for steam reforming using an electric resistance heater (e.g., an electric cartridge heater) disposed within the vessel. A reforming catalyst is disposed in contact with the electric resistance heater and in contact with the inner surface of the reactor vessel wall. Supplying heat generally includes heating the reforming catalyst disposed in contact with the electric resistance heater via the electric resistance heater. Supplying heat may include heating the hydrocarbons in the vessel via heat conduction and convection from the electric resistance heater. The method may include heating the vessel wall and the reforming catalyst disposed in contact with the inner surface of the vessel wall via a heat source external to the vessel. The external heat source may be an external electric heater (e.g., a band heater) disposed in contact with the outer surface of the vessel wall. The method may include providing heat for steam reforming via electric heater(s) disposed in contact with the outer surface of the vessel wall.

[0096] This example catalytic membrane reactor may combine unit operations through process intensification and address distributed hydrogen production. The membrane reactor can be made efficient through structured catalysts and electrical heating. An internal resistance heater can provide heat directly to the catalyst (e.g., metal foam or washcoat catalyst) within the reactor, reducing the thermal resistance to heat transfer by contacting the resistance heater with the catalyst.

[0097] This technology facilitates the production of relatively pure streams of hydrogen and carbon dioxide (e.g., greater than 95 mol% of each) produced in a single unit operation, which may save both capital and operating costs compared to conventional systems. Hydrogen-selective membranes installed in series within the reactor may further increase both methane conversion and hydrogen recovery. Increased hydrogen recovery may further purify the CO2 in the retentate stream.

[0098] Conventional SMR processes are generally inefficient when scaled down. In contrast, the present embodiments can be efficient with a smaller footprint. Hydrogen produced in large-scale, centralized conventional SMR plants can be relatively inexpensive. However, transporting and storing hydrogen is generally expensive due to hydrogen's low density and the use of specialized trucks (tube trailers) and specialized tanks (high-pressure carbon fiber reinforced vessels).

[0099] Some of the present embodiments may facilitate the production of hydrogen where needed from liquid hydrocarbon feedstocks, where transportation is cheaper than hydrogen transportation. Some embodiments may be compact systems for on-site generation of hydrogen from hydrocarbon feedstocks. One application is on-site hydrogen generation at fueling stations using feedstocks that include liquid fuels. Some embodiments may produce reasonably pure hydrogen on-site for mobility applications. Applications may include portable hydrogen generators in some embodiments.

[0100] Exemplary membrane reactors (which reform hydrocarbon feedstocks) can be heated without generating carbon dioxide for heating. The CO2 generated in the reforming reaction can be relatively pure and under pressure. Embodiments produce hydrogen from hydrocarbons while simultaneously extracting and capturing CO2, which can reduce CO2 emissions and the facility's CO2 footprint. The concentrated, pressurized CO2 stream resulting from membrane reactor embodiments can facilitate CO2 extraction and capture, such as for sequestration, enhanced oil recovery (EOR), or use as a feedstock.

[0101] Although this discussion focuses on steam reforming, membrane reactors can be configured for hydrocarbon reforming reactions using air, oxygen, steam, or carbon dioxide. Additionally, certain configurations of membrane reactors may be utilized to hydrogenate or dehydrogenate hydrocarbons over a catalyst. In another example, a membrane reactor may be used for endothermic ammonia decomposition over a catalyst to form a mixture of hydrogen and nitrogen.

[0102] One embodiment is a method for producing hydrogen, comprising supplying hydrocarbons and steam to a region outside a tubular membrane within a vessel (e.g., a cylindrical pressure vessel) and steam reforming the hydrocarbons within the vessel over a reforming catalyst to produce hydrogen and carbon dioxide. The hydrocarbons may include, for example, natural gas, methane, liquefied petroleum gas (LPG), or a mixture of C1-C10 hydrocarbons, or any combination thereof. The region outside the tubular membrane may be a reaction space within the vessel and a retentate side of the tubular membrane. In some embodiments, the reforming catalyst is not in contact with the tubular membrane. The method includes diffusing hydrogen through the tubular membrane (hydrogen-selective) into a bore of the tubular membrane and discharging hydrogen from the bore (e.g., the permeate side of the tubular membrane) as permeate (e.g., at least 90 mol % hydrogen on a dry basis) to a conduit for hydrogen collection. The method may also include discharging carbon dioxide from the vessel as retentate (e.g., at least 90 mol % carbon dioxide on a dry basis). The method may include supplying a sweep gas (e.g., steam or nitrogen) to the bore and increasing the driving force for hydrogen permeation through the tubular membrane from a region outside the tubular membrane to the bore by moving hydrogen from the bore with the sweep gas. In embodiments, the sweep gas driving the hydrogen flows countercurrently to the flow of the hydrocarbon and steam into the vessel. Multiple tubular membranes may be present in the vessel, each bore being hydrogen-selective and on the permeate side of the respective tubular membrane.

[0103] The method includes providing heat for steam reforming using an electric resistance heater (e.g., an electric cartridge heater) disposed within the vessel. A reforming catalyst may be disposed in contact with the electric resistance heater and in contact with an inner surface of a wall of the vessel. Providing heat may include heating the reforming catalyst disposed in contact with the electric resistance heater via the electric resistance heater. Providing heat may include heating the hydrocarbons via thermal conduction and convection from the electric resistance heater. The method may include providing heat for steam reforming via an electric heater disposed on an outer surface of the wall of the vessel. The method may include heating the wall of the vessel and the reforming catalyst disposed in contact with the inner surface of the wall of the vessel via a heat source external to the vessel. In an embodiment, the heat source may be an electric heater disposed on the outer surface of the wall of the vessel.

[0104] Another embodiment is a hydrogen production system including a vessel having an inlet for receiving hydrocarbons. The system includes a reforming catalyst for converting the hydrocarbons into a product gas comprising hydrogen and carbon dioxide, the reforming catalyst being disposed in contact with the inner surface of the vessel wall and in contact with a plurality of resistance heaters within the vessel. A plurality of resistance heaters (e.g., electric cartridge heaters) within the vessel heat the reforming catalyst and the hydrocarbons within the vessel. A hydrogen-selective tubular membrane (e.g., palladium or a palladium alloy) is disposed within the vessel to separate hydrogen from the product gas into a bore of the tubular membrane. The system includes a conduit collection header for receiving hydrogen from the bore of the tubular membrane. A conduit may connect the bore to the conduit collection header. The vessel may have a reaction space for steam reforming the hydrocarbons, the reaction space being outside the tubular membrane on the retentate side, the bore being on the permeate side of the tubular membrane, and hydrogen diffusing from the product gas through the wall of the tubular membrane into the bore. The conduit may supply nitrogen or steam as a sweep gas to the bore. In embodiments, an inner tube concentric with the bore may facilitate the flow of a sweep gas within the bore to move hydrogen from the bore toward a conduit collection header. The inner tube may facilitate the flow of a sweep gas to move hydrogen countercurrently to the flow of hydrocarbons and water vapor into the vessel. Furthermore, the vessel, reforming catalyst, multiple electric heaters, and tubular membrane may be components of a catalytic membrane reactor. Finally, an electric heater (e.g., an electric band heater) may be disposed on the exterior surface of the vessel wall.

[0105] Yet another embodiment is a catalytic membrane reactor for hydrogen production. The reactor includes a vessel having an inlet for receiving a hydrocarbon; a reforming catalyst (e.g., nickel or nickel-based) within the vessel for converting the hydrocarbon to a product gas containing hydrogen and carbon dioxide; a plurality of electric resistance heaters (e.g., electric cartridge heaters) for heating the reforming catalyst and supplying heat to a fluid within the vessel; and a plurality of hydrogen-selective cylindrical membranes (e.g., each palladium or palladium alloy) for separating a permeate, primarily hydrogen, from the product gas via the permeate diffusing through the wall of each cylindrical membrane into the bore of each cylindrical membrane. A region within the reactor vessel may be a reaction space for steam reforming the hydrocarbon, the region being exterior to the plurality of cylindrical membranes (e.g., tubular membranes), the bore of each cylindrical membrane being the permeate side of the cylindrical membrane, and the region exterior to the plurality of cylindrical membranes being the retentate side of the plurality of cylindrical membranes. The bore of each cylindrical membrane is coupled to a conduit collection header, which receives the permeate from each bore. In embodiments, an inner tube concentrically disposed within the bore of each cylindrical membrane may facilitate the flow of a sweep gas to move permeate from the bore. The reactor may include an electric heater disposed on the exterior surface of the vessel wall to heat the vessel and to provide heat to the fluid within the vessel. The exterior electric heater may heat the reforming catalyst, including any reforming catalyst, disposed on the interior surface of the vessel wall.

[0106] The reforming catalyst may be disposed in contact with a plurality of electric resistance heaters within the vessel. The reforming catalyst may be disposed in contact with the inner surface of the vessel wall. In embodiments, the reforming catalyst is not in contact with a plurality of cylindrical membranes. The reforming catalyst may be packed inside the vessel. In that case, the reforming catalyst packed inside the vessel may be in contact with a plurality of cylindrical membranes. For any reforming catalyst packed inside the vessel, the packed reforming catalyst may include pelletized catalyst.

[0107] A number of embodiments have been described. Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the disclosure.

Claims

1. 1. A method for producing hydrogen, comprising: supplying hydrocarbons and water vapor to a region outside a hydrogen-selective tubular membrane in a vessel, the hydrogen-selective tubular membrane comprising a plurality of hydrogen-selective tubular membrane units within the vessel, each hydrogen-selective tubular membrane unit being hydrogen-selective and having a respective bore on a permeate side of each hydrogen-selective tubular membrane unit, each pair of hydrogen-selective tubular membrane units sharing a longitudinal axis aligned with a central axis of the vessel, each hydrogen-selective tubular membrane unit of the pair of hydrogen-selective tubular membrane units including a capped end, and the capped ends of the hydrogen-selective tubular membrane units of the pair of hydrogen-selective tubular membrane units being arranged adjacent; steam reforming the hydrocarbons in the vessel over a reforming catalyst to produce hydrogen and carbon dioxide; diffusing the hydrogen through the hydrogen-selective tubular membrane into a bore of the hydrogen-selective tubular membrane; providing heat for the steam reforming with an electric resistance heater disposed within the vessel, the reforming catalyst being disposed in the electric resistance heater and on an interior surface of a wall of the vessel. method.

2. discharging the hydrogen from the bore as a permeate to a conduit for recovery of the hydrogen. The method of claim 1.

3. Discharging the carbon dioxide from the vessel as a retentate. The method of claim 2.

4. the permeate comprising at least 90 mole percent hydrogen on a dry basis and the retentate comprising at least 90 mole percent carbon dioxide on a dry basis; The method of claim 3.

5. the step of providing heat includes heating the hydrocarbon via thermal conduction and convection from the electrical resistance heater; The method of claim 1.

6. the electric resistance heater comprises an electric cartridge heater; The method of claim 1.

7. the region outside the hydrogen-selective tubular membrane is a reaction space within the vessel and a retentate side of the hydrogen-selective tubular membrane; the bore of the hydrogen-selective tubular membrane is on the permeate side of the tubular membrane; the reforming catalyst is not in contact with the hydrogen-selective tubular membrane; The method of claim 1.

8. supplying a sweep gas to the bore of the hydrogen-selective tubular membrane; displacing the hydrogen from the bore with the sweep gas; increasing the driving force for hydrogen permeation through the hydrogen-selective tubular membrane from the outer region of the hydrogen-selective tubular membrane to the bore by moving the hydrogen from the bore with the sweep gas. The method of claim 1.

9. the sweep gas driving the hydrogen flows countercurrently to the flow of the hydrocarbon and the water vapor into the vessel; The method of claim 8.

10. providing heat for the steam reforming via an electric heater disposed on an exterior surface of the wall of the vessel; The method of claim 1.

11. heating the wall of the vessel and the reforming catalyst disposed on the inner surface of the wall of the vessel via a heat source external to the vessel; The method of claim 1.

12. the heat source comprises an electric heater disposed on the exterior surface of the wall of the vessel; The method of claim 11.

13. 1. A system for producing hydrogen, comprising: a vessel having an inlet for receiving the hydrocarbon; a reforming catalyst disposed on an interior surface of a wall of the vessel for converting the hydrocarbons into a product gas comprising hydrogen and carbon dioxide, the reforming catalyst being disposed on a plurality of resistive heaters within the vessel and on the interior wall of the vessel; a plurality of resistance heaters for heating the reforming catalyst and the hydrocarbons; a plurality of electric heaters disposed on the exterior surface of the wall of the vessel; a plurality of hydrogen-selective tubular membranes disposed within the vessel, the plurality of tubular membranes separating the hydrogen from the product gas and directing the hydrogen to respective bores of the plurality of tubular membranes, the plurality of tubular membranes being disposed within the vessel in pairs, each of the pairs of tubular membranes sharing a longitudinal axis aligned with a central axis of the vessel, each tubular membrane of the pair of tubular membranes including a capped end and disposed such that the capped ends of the tubular membranes of the pair of tubular membranes are adjacent; a conduit collection header configured to receive the hydrogen from the bore of the tubular membrane; system.

14. the plurality of resistive heaters include electric cartridge heaters; The system of claim 13.

15. the electric heater comprises an electric band heater; The system of claim 13.

16. a catalytic membrane reactor comprising the vessel, the reforming catalyst, the plurality of electric heaters, and the tubular membrane, wherein the tubular membrane comprises palladium or a palladium alloy; The system of claim 13.

17. the vessel contains a reaction space for steam reforming of the hydrocarbon, the reaction space being outside the tubular membrane and on the retentate side of the tubular membrane, the bore being on the permeate side of the tubular membrane, and the hydrogen diffusing from the product gas through the wall of the tubular membrane into the bore; The system of claim 13.

18. a conduit connecting the bore to the conduit collection header; The system of claim 13.

19. a conduit for supplying nitrogen or water vapor as a sweep gas to the bore; The system of claim 13.

20. a concentric inner tube within the bore that facilitates the flow of a sweep gas within the bore that moves hydrogen from the bore toward the conduit collection header; The system of claim 13.

21. a concentric inner tube within said bore for facilitating the flow of a sweep gas that drives hydrogen countercurrently to the flow of said hydrocarbons and water vapor into said vessel; The system of claim 13.

22. 1. A catalytic membrane reactor for producing hydrogen, comprising: a vessel having an inlet for receiving the hydrocarbon; a reforming catalyst in said vessel for converting said hydrocarbons into a product gas comprising hydrogen and carbon dioxide; a plurality of electric heaters disposed on an exterior surface of the vessel wall; a plurality of electric resistance heaters for heating the reforming catalyst and supplying heat to the fluid in the vessel, each of the plurality of electric resistance heaters having a longitudinal axis offset from and parallel to the longitudinal axis of each of the plurality of cylindrical membranes; a plurality of cylindrical membranes that are hydrogen-selective, separating the permeate containing hydrogen from the product gas via the permeate diffusing through the wall of each cylindrical membrane into the bore of each cylindrical membrane; wherein the bore of each cylindrical membrane is connected to a conduit collecting header configured to receive the permeate from each bore; The plurality of cylindrical membranes are arranged in pairs within the vessel, each pair of cylindrical membranes sharing an axis aligned with a longitudinal axis of the vessel, each cylindrical membrane of the pair of cylindrical membranes including a capped end, and the cylindrical membranes of the pair of cylindrical membranes are arranged such that the capped ends are adjacent to each other. Catalytic membrane reactor.

23. the plurality of electric resistance heaters include electric cartridge heaters; 23. The catalytic membrane reactor of claim 22.

24. the reforming catalyst comprises nickel; 23. The catalytic membrane reactor of claim 22.

25. the plurality of cylindrical membranes comprising palladium or a palladium alloy; 23. The catalytic membrane reactor of claim 22.

26. a region serving as a reaction space for steam reforming the hydrocarbon is provided within the vessel, the region being outside the plurality of cylindrical membranes, the bore of each cylindrical membrane being on the permeate side of the cylindrical membrane, and the region outside the plurality of cylindrical membranes being on the retentate side of the cylindrical membranes; 23. The catalytic membrane reactor of claim 22.

27. a concentric inner tube within the bore of each cylindrical membrane for facilitating the flow of a sweep gas to move the permeate out of the bore; 23. The catalytic membrane reactor of claim 22.

28. the reforming catalyst is disposed on the plurality of electric resistance heaters within the vessel; 23. The catalytic membrane reactor of claim 22.

29. The reforming catalyst is disposed on the inner surface of the vessel wall.

29. The catalytic membrane reactor of claim 28.

30. an electric heater disposed on an outer surface of the wall of the vessel to heat the reforming catalyst disposed on the inner surface of the wall of the vessel and to supply heat to the fluid within the vessel; 30. The catalytic membrane reactor of claim 29.

31. the reforming catalyst is not in contact with the plurality of cylindrical membranes; 30. The catalytic membrane reactor of claim 29.

32. The reforming catalyst is filled in the container.

32. The catalytic membrane reactor of claim 31.

33. the reforming catalyst packed in the container is in contact with the plurality of cylindrical membranes; 33. The catalytic membrane reactor of claim 32.

34. The reforming catalyst packed in the container includes a pelletized catalyst.

33. The catalytic membrane reactor of claim 32.

35. 1. A system for producing hydrogen, comprising: a vessel having an inlet for receiving the hydrocarbon; a reforming catalyst disposed on an interior surface of a wall of the vessel for converting the hydrocarbons into a product gas comprising hydrogen and carbon dioxide, the reforming catalyst being disposed on a plurality of resistive heaters within the vessel and on the interior wall of the vessel; a plurality of resistance heaters for heating the reforming catalyst and the hydrocarbons; a plurality of electric heaters disposed on the exterior surface of the wall of the vessel; a plurality of hydrogen-selective tubular membranes disposed within the vessel, the plurality of tubular membranes separating the hydrogen from the product gas and directing the hydrogen to respective bores of the plurality of tubular membranes; a conduit collection header configured to receive the hydrogen from the bore of the tubular membrane; a conduit supplying nitrogen or water vapor as a sweep gas to the bore of each of the plurality of tubular membranes, the conduit including an inner tube concentrically disposed within the bore to facilitate flow of the sweep gas within the bore to move hydrogen from the bore toward the conduit collection header; system.

36. the plurality of resistive heaters include electric cartridge heaters, and the electric heater includes an electric band heater; 36. The system of claim 35.

37. a catalytic membrane reactor comprising the vessel, the reforming catalyst, the plurality of electric heaters, and the tubular membrane, wherein the tubular membrane comprises palladium or a palladium alloy; 36. The system of claim 35.

38. the vessel contains a reaction space for steam reforming of the hydrocarbon, the reaction space being outside the tubular membrane and on the retentate side of the tubular membrane, the bore being on the permeate side of the tubular membrane, and the hydrogen diffusing from the product gas through the wall of the tubular membrane into the bore; 36. The system of claim 35.

39. the driven hydrogen is in a countercurrent direction to the flow of the hydrocarbon and water vapor into the vessel; 36. The system of claim 35.

40. 1. A catalytic membrane reactor for producing hydrogen, comprising: a vessel having an inlet for receiving the hydrocarbon; a reforming catalyst in said vessel for converting said hydrocarbons into a product gas comprising hydrogen and carbon dioxide; a plurality of electric heaters disposed on an exterior surface of the vessel wall; a plurality of electric resistance heaters for heating the reforming catalyst and supplying heat to the fluid in the vessel, each of the plurality of electric resistance heaters having a longitudinal axis offset from and parallel to the longitudinal axis of each of the plurality of cylindrical membranes; a plurality of hydrogen-selective cylindrical membranes, the plurality of cylindrical membranes separating the permeate comprising hydrogen from the product gas via the permeate diffusing through a wall of each cylindrical membrane into a bore of each cylindrical membrane, the bore of each cylindrical membrane being connected to a conduit collection header configured to receive the permeate from each bore; an inner tube concentrically disposed within the bore of each of the cylindrical membranes to facilitate the flow of a sweep gas that moves the permeate from the bore of each of the cylindrical membranes toward the conduit collection header; Catalytic membrane reactor.

41. the plurality of electric resistance heaters include electric cartridge heaters; 41. The catalytic membrane reactor of claim 40.

42. the reforming catalyst comprises nickel; 41. The catalytic membrane reactor of claim 40.

43. the plurality of cylindrical membranes comprising palladium or a palladium alloy; 41. The catalytic membrane reactor of claim 40.

44. a region serving as a reaction space for steam reforming the hydrocarbon is provided within the vessel, the region being outside the plurality of cylindrical membranes, the bore of each cylindrical membrane being on the permeate side of the cylindrical membrane, and the region outside the plurality of cylindrical membranes being on the retentate side of the cylindrical membranes; 41. The catalytic membrane reactor of claim 40.

45. the reforming catalyst is disposed on at least one of the plurality of electric resistance heaters within the vessel and an interior surface of a wall of the vessel; 41. The catalytic membrane reactor of claim 40.

46. an electric heater disposed on an outer surface of the wall of the vessel to heat the reforming catalyst disposed on the inner surface of the wall of the vessel and to supply heat to the fluid within the vessel; 46. ​​The catalytic membrane reactor of claim 45.

47. the driven hydrogen is in a countercurrent direction to the flow of the hydrocarbon and water vapor into the vessel; 39. The system of claim 38.

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