Hydrogen production and apparatus

Abstract

A method for production of pressurised hydrogen, the method comprising: providing a catalyst for conversion of ammonia to hydrogen and nitrogen; contacting a pressurised reaction stream comprising ammonia with the catalyst to convert at least a portion of the ammonia into hydrogen in a reaction zone; and obtaining a hydrogen product stream comprising pressurised hydrogen by selectively driving hydrogen from the reaction zone through a hydrogen-selective membrane under a pressure differential between a reaction-side pressure of the reaction stream and a product-side pressure of the hydrogen product stream; wherein the product-side pressure is at least 30 bar a.; and apparatus therefor.

Description

[0001] P5500PC00

[0002] HYDROGEN PRODUCTION AND APPARATUS

[0003] TECHNICAL FIELD

[0004] This invention relates to the production of pressurised hydrogen. In particular, though not exclusively, this invention relates to methods of producing pressurised hydrogen, and to reactors for use in such methods.

[0005] BACKGROUND

[0006] The global transition to sustainability has generated significant interest in a hydrogen economy because hydrogen has the potential to serve as a clean fuel and / or a clean chemical feedstock. The widespread adoption of hydrogen in this way has, however, faced critical logistical challenges. Hydrogen is gaseous at atmospheric temperatures and pressures, and storage of useful quantities of hydrogen typically requires it to be stored at high pressure. In addition, hydrogen is a highly flammable gas, requiring robust safety measures and gas-tight equipment to be utilised throughout a hydrogen supply chain. A common method of hydrogen production is centralised production in large-scale hydrogen production facilities, which then requires feasible methods of distributing hydrogen to its point-of-use and / or point-of-sale to the end user. Current methods for transporting hydrogen from a centralised hydrogen-production facility to a point of use rely on either low-pressure pipelines, which are costly and require extensive infrastructure, or high-pressure cylinders that are transported by vehicle, which are inefficient because these cylinders are heavy and carry only limited amounts of hydrogen, requiring multiple trips to meet demand. For instance, a typical hydrogen refuelling station for commercial fleets needs 1,500 kg of hydrogen daily. Traditional methods, such as transporting compressed hydrogen at 250 or 500 bar by tube trailer, require frequent and costly tube trailer journeys. Liquid hydrogen, through its high density requires fewer trailer journeys, but incurs high cryogenic costs.

[0007] One alternative is on-site production of hydrogen using methods such as electrolysis, followed by pressurising the hydrogen up to useful storage pressures. For instance, at current refuelling stations, hydrogen is produced by electrolysis at up to around 30 bar and is then compressed to over 350 bar a, or even over 700 bar a for some applications. In addition to electrolysis, another process that has been used to generate hydrogen is ammonia cracking, which is a chemical process whereby ammonia is split into hydrogen and nitrogen, using an appropriate catalyst. The reaction follows the equation:

[0008] 2

[0009]

[0010] M.Hj 3J?2 + JVaP5500PC00

[0011] This splitting is reversible, meaning the products (hydrogen and nitrogen) can recombine to form ammonia. The equilibrium position of the reaction depends on factors including temperature and pressure. In the forward direction, as can be seen in the scheme above, the reaction starts with two molecules of gas (2 NH3molecules) and splitting provides four molecules of gas (3 H2molecules and 1 N2molecule). Low pressure favours the splitting of two molecules to four molecules, and high pressure pushes the equilibrium in the reverse direction to the two molecules of ammonia, so ammonia cracking is therefore typically conducted at low pressure. For instance, WO 2023 / 137197 A2 discloses using an ammonia cracking membrane reactor to generate hydrogen at pressures of up to about 5 bar g; US 2020 / 0269208 Al discloses using an ammonia cracking membrane reactor, where the working fluid (i.e. ammonia) pressure is between approximately 1 to 5 bar, meaning the hydrogen is generated at a pressure below 5 bar; and US 2024 / 0327209 Al discloses using an ammonia cracking membrane reactor that makes use of a feedstock of ammonia in pressurised tanks, which typically have a pressure of up to about 10 bar, meaning the hydrogen is generated at a pressure below 10 bar.

[0012] Pressurisation of hydrogen up to more useful pressures requires passing the hydrogen through specialist hydrogen-specific (particularly gas-tight and ignition source free) compression equipment, such as the specialist Maximator Max hydrogen compressor. Such compression equipment must able to get the hydrogen to the desired pressures reliably without risk of leaks and / or ignition sources such as errant sparking and / or heat build-up. The complexity of this compression equipment requires frequent maintenance. While the costs of installing and maintaining such compression equipment may be feasible at large-scale central hydrogen-production hubs, it is much less economically feasible to install, run and maintain such compression equipment at a distributed network of start / stop point-of-use sites.

[0013] These limitations hinder the feasibility of establishing a reliable and distributed hydrogen supply chain, thereby slowing the adoption of hydrogen as a stock for applications such as fuel for transportation. The present invention seeks to addresses one or more of the above challenges.

[0014] SUMMARY OF THE INVENTION

[0015] From a first aspect, the invention provides a method for production of pressurised hydrogen, the method comprising: providing a catalyst for conversion of ammonia to hydrogen and nitrogen; contacting a pressurised reaction stream comprising ammonia with the catalyst to convert at least a portion of the ammonia into hydrogen in a reaction zone; and obtaining a hydrogen product stream comprising pressurised hydrogen by selectively driving hydrogen from the reaction zone through a hydrogen-selective membrane under a pressure differential between a reaction-side pressure of the reaction stream and a product-P5500PC00

[0016] side pressure of the hydrogen product stream; wherein the product-side pressure is at least 30 bar a.

[0017] Where hydrogen has been driven from the reaction zone, and particularly the catalyst, the equilibrium position of remaining ammonia in contact with the catalyst favours generation of further hydrogen.

[0018] Thus, when ammonia cracking is conducted at high pressures with hydrogen selectively driven through a hydrogen-selective membrane, then the overall reaction process can be forced to generate hydrogen. However, as set out in the introduction above, a high-pressure method of operation runs contrary to perceived wisdom with seemingly little benefit.

[0019] It has now been found that an unexpected advantage is that by cracking a pressurised reaction stream comprising ammonia and selectively driving resulting hydrogen through a hydrogen-selective membrane, the hydrogen can be obtained such that it is already at high pressure. Generating pressurised hydrogen this way can be less energy-intensive and operationally more straightforward than the alternative of generating hydrogen at low pressure and subsequently compressing the hydrogen up to higher pressure.

[0020] For example, energy-intensive hydrogen gas compression equipment may be replaced with liquid ammonia compression equipment, which may be done using conventional liquid pumps. This may, for example, reduce costs and improve reliability.

[0021] Another advantage is that ammonia is easier to transport and store than hydrogen, which may, for example, make supply chain logistics lower cost, more straightforward, safer, and more environmentally friendly. For instance, ammonia can be transported at high density in a more convenient manner than transportation of hydrogen, with lower-cost trailers, reducing logistics costs and overall lowering pressurised hydrogen prices.

[0022] It is also noted that ammonia cracking creates hydrogen and nitrogen, without the reaction generating the greenhouse gas carbon dioxide.

[0023] Pressure

[0024] Pressure determinations are well known in the art, for example based on pressure sensor measurements and / or pressure calculations.

[0025] The product-side pressure is a pressure on a downstream side of the hydrogen selective membrane (also referred to as a permeate side). It may be determined in any suitable way.

[0026] For example, a product-side pressure may be determined at or near a permeate side surface of the hydrogen-selective membrane.P5500PC00

[0027] Suitably, a product-side pressure may be determined at a hydrogen store, such as for example a collection vessel, for the hydrogen product stream. Thus, the pressure differential may advantageously drive hydrogen from the reaction zone, through the hydrogen selective membrane to a hydrogen store.

[0028] Advantageously, the product-side pressure may be at least about 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500 or 550 bar a. Suitably, the product-side pressure may be up to about 2000, 1500, 1000, 900, 800, 700, or 600 bar a. Suitably, the product-side pressure may be a value in the range of about 35 to about 2000, about 40 to about 1500, about 50 to about 1000, about 60 to about 900, about 70 to about 800, about 80 to about 700, about 80 to about 600, about 90 to about 550, about 100 to about 500, about 150 to about 450, about 200 to about 400, or about 250 to about 350 bar a. Suitably, the product-side pressure may be about 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 700, 800, 900, 1000, 1500, or 2000 bar a.

[0029] Advantageously, the product-side pressure may be at least about 450 bar a. Hydrogen pressures of at least about 450 bar a may be particularly useful for certain purposes, such as vehicle fuel.

[0030] The method selectively drives hydrogen from the reaction zone through the hydrogenselective membrane under a pressure differential between a reaction-side pressure of the reaction stream and a product-side pressure of the hydrogen product stream. Typically, the reaction-side pressure may be higher than the product-side pressure. Conveniently, high pressure hydrogen may be obtained from the pressurised reaction stream with no further pressurisation steps. Suitably, the product-side pressure may be derived from the reactionside pressure.

[0031] The reaction-side pressure is a pressure on an upstream side of the hydrogen selective membrane (also referred to as a retentate side). It may be determined in any suitable way. For example, a reaction-side pressure may be determined at or near a retentate side surface of the hydrogen-selective membrane.

[0032] Conveniently, a reaction-side pressure may be determined in the reaction zone.

[0033] Suitably, a reaction-side pressure may be determined at a reaction stream source, such as a source vessel, inlet or pump from which the reaction stream originates. Thus, the pressure differential may advantageously act from the reaction stream source, to drive hydrogen from the reaction zone through the selective membrane, to the product stream, and optionally to a hydrogen store.

[0034] Advantageously, the reaction-side pressure may be a pressure that maintains the productside pressure. Suitably, the reaction-side pressure may be a pressure that drives sufficientP5500PC00

[0035] hydrogen across the hydrogen-selective membrane to maintain the product-side pressure. Conveniently, the product-side pressure may be maintained by the reaction-side pressure and / or the product-side pressure may be maintained by the pressurised reaction stream.

[0036] Suitably, the reaction-side pressure may be at least about 4 / 3 times the product-side pressure. In other words, the reaction-side pressure may be at least about 133.33% of the product-side pressure. Advantageously, the reaction-side pressure may be at least about 135%, 140%, 145%, 150%, 155%, 160%, 170%, 180%, 190%, 200%, 250%, 300%, 400%, 500%, 750%, 1000%, 1500%, 2000%, or 5000% of the product-side pressure. Suitably, the reaction-side pressure may be up to about 10000%, 8000%, or 6000% of the product-side pressure.

[0037] The reaction-side pressure and product-side pressure may be in accordance with any given entry in the following table:

[0038] Product-side Reaction-side pressure: at least about [value below]% of the pressure at least product-side pressure

[0039] about (bar a)

[0040] 30 133 135 140 145 150 155 160 170 180 190 35 133 135 140 145 150 155 160 170 180 190 40 133 135 140 145 150 155 160 170 180 190 50 133 135 140 145 150 155 160 170 180 190 60 133 135 140 145 150 155 160 170 180 190 70 133 135 140 145 150 155 160 170 180 190 80 133 135 140 145 150 155 160 170 180 190 90 133 135 140 145 150 155 160 170 180 190 100 133 135 140 145 150 155 160 170 180 190 150 133 135 140 145 150 155 160 170 180 190 200 133 135 140 145 150 155 160 170 180 190 250 133 135 140 145 150 155 160 170 180 190 300 133 135 140 145 150 155 160 170 180 190 350 133 135 140 145 150 155 160 170 180 190 400 133 135 140 145 150 155 160 170 180 190 450 133 135 140 145 150 155 160 170 180 190 500 133 135 140 145 150 155 160 170 180 190 550 133 135 140 145 150 155 160 170 180 190 600 133 135 140 145 150 155 160 170 180 190 700 133 135 140 145 150 155 160 170 180 190 800 133 135 140 145 150 155 160 170 180 190 900 133 135 140 145 150 155 160 170 180 190

[0041]

[0042] P5500PC00

[0043] 1000 133 135 140 145 150 155 160 170 180 190 1500 133 135 140 145 150 155 160 170 180 190 2000 133 135 140 145 150 155 160 170 180 190 30 200 250 300 400 500 750 1000 1500 2000 5000 35 200 250 300 400 500 750 1000 1500 2000 5000 40 200 250 300 400 500 750 1000 1500 2000 5000 50 200 250 300 400 500 750 1000 1500 2000 5000 60 200 250 300 400 500 750 1000 1500 2000 5000 70 200 250 300 400 500 750 1000 1500 2000 5000 80 200 250 300 400 500 750 1000 1500 2000 5000 90 200 250 300 400 500 750 1000 1500 2000 5000 100 200 250 300 400 500 750 1000 1500 2000 5000 150 200 250 300 400 500 750 1000 1500 2000 5000 200 200 250 300 400 500 750 1000 1500 2000 5000 250 200 250 300 400 500 750 1000 1500 2000 5000 300 200 250 300 400 500 750 1000 1500 2000 5000 350 200 250 300 400 500 750 1000 1500 2000 5000 400 200 250 300 400 500 750 1000 1500 2000 5000 450 200 250 300 400 500 750 1000 1500 2000 5000 500 200 250 300 400 500 750 1000 1500 2000 5000 550 200 250 300 400 500 750 1000 1500 2000 5000 600 200 250 300 400 500 750 1000 1500 2000 5000 700 200 250 300 400 500 750 1000 1500 2000 5000 800 200 250 300 400 500 750 1000 1500 2000 5000 900 200 250 300 400 500 750 1000 1500 2000 5000 1000 200 250 300 400 500 750 1000 1500 2000 5000 1500 200 250 300 400 500 750 1000 1500 2000 5000 2000 200 250 300 400 500 750 1000 1500 2000 5000

[0044]

[0045] Conveniently, the reaction-side pressure may be at least about 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 bar a higher than the product-side pressure. Suitably, the reaction-side pressure may be up to about 5000, 3000, or 1500 bar a higher than the product-side pressure.

[0046] Any reference herein to a pressure of 'at least' a set value, may include cases where the pressure maintains a constant value that is above the set value, and may include cases where the pressure fluctuates and maintains values that are above the set value throughout the fluctuation.P5500PC00

[0047] As used herein, "pressure" refers to total pressure unless "partial pressure" is recited. Total pressure is straightforward to measure and control. However, in principle, a partial pressure of hydrogen may drive hydrogen through the membrane.

[0048] Suitably, the method may comprise driving hydrogen from the reaction zone through the hydrogen-selective membrane under a hydrogen partial pressure differential between a reaction-side hydrogen partial pressure of the reaction stream and a product-side hydrogen partial pressure of the hydrogen product stream, wherein the hydrogen pressure differential may be at least about 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 bar a. Suitably, the hydrogen pressure differential may be up to about 5000, 3000, or 1500 bar a. Suitably, the hydrogen pressure differential may be about 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 3000, or 5000 bar a. In some cases, the hydrogen pressure differential may be in a range of about 1 to about 5000, about 5 to about 3000, about 10 to about 1500, about 20 to about 1000, about 30 to about 900, about 40 to about 800, about 50 to about 700, about 60 to about 600, about 70 to about 500, about 80 to about 400, about 90 to about 300, or 100 to about 200, bar a. Suitably, the reaction-side hydrogen partial pressure may be higher than the product-side hydrogen partial pressure.

[0049] Determination of partial pressures is also well known in the art, for example based on pressure sensors and suitable pressure calculations.

[0050] The product-side hydrogen partial pressure is a partial pressure on a downstream side of the hydrogen selective membrane (also referred to as a permeate side). It may be determined in any suitable way.

[0051] For example, a product-side hydrogen partial pressure may be determined at or near a permeate surface of the hydrogen-selective membrane.

[0052] Suitably, a product-side hydrogen partial pressure may be determined at a hydrogen store, such as for example a collection vessel, for the hydrogen product stream.

[0053] Thus, the hydrogen partial pressure differential may advantageously drive hydrogen from the reaction zone, through the hydrogen selective membrane to a hydrogen store.

[0054] The reaction-side hydrogen partial pressure is a pressure on an upstream side of the hydrogen selective membrane (also referred to as a retentate side). It may be determined in any suitable way.

[0055] For example, a reaction-side hydrogen partial pressure may be determined at or near a retentate surface of the hydrogen-selective membrane.P5500PC00

[0056] Conveniently, a reaction-side hydrogen partial pressure may be determined in the reaction zone.

[0057] Advantageously, the reaction-side hydrogen partial pressure may be a pressure that maintains the product-side hydrogen partial pressure. Suitably, the reaction-side hydrogen partial pressure may be a pressure that drives sufficient hydrogen across the hydrogenselective membrane to maintain the product-side hydrogen partial pressure. Conveniently, the product-side hydrogen partial pressure may be maintained by the reaction-side hydrogen partial pressure and / or the product-side hydrogen partial pressure may be maintained by the pressurised reaction stream.

[0058] Suitably, the hydrogen product stream may consist essentially of, or consist of, hydrogen. When the hydrogen product stream consists essentially of, or consists of, hydrogen, the product-side hydrogen partial pressure may be equivalent to the product-side pressure. Conveniently, in such cases, the reaction-side hydrogen partial pressure may be higher than the product-side pressure. Advantageously, the reaction-side hydrogen partial pressure may be a pressure that maintains the product-side pressure. Suitably, the reaction-side hydrogen partial pressure may be a pressure that drives sufficient hydrogen across the hydrogen-selective membrane to maintain the product-side pressure. Conveniently, the product-side pressure may be maintained by the reaction-side hydrogen partial pressure. Suitably, the product-side pressure may be maintained by the pressurised reaction stream.

[0059] The reaction-side hydrogen partial pressure and product-side hydrogen partial pressure may be in accordance with any given entry in the following table:

[0060] Product-side Reaction-side hydrogen partial pressure: [value below] bar a higher hydrogen partial than the product-side hydrogen partial pressure

[0061] pressure at least

[0062] about (bar a)

[0063] 30 1 5 10 20 30 40 50 60 70 80 90 35 1 5 10 20 30 40 50 60 70 80 90 40 1 5 10 20 30 40 50 60 70 80 90 50 1 5 10 20 30 40 50 60 70 80 90 60 1 5 10 20 30 40 50 60 70 80 90 70 1 5 10 20 30 40 50 60 70 80 90 80 1 5 10 20 30 40 50 60 70 80 90 90 1 5 10 20 30 40 50 60 70 80 90 100 1 5 10 20 30 40 50 60 70 80 90 150 1 5 10 20 30 40 50 60 70 80 90 200 1 5 10 20 30 40 50 60 70 80 90

[0064]

[0065] P5500PC00

[0066] 250 1 5 10 20 30 40 50 60 70 80 90 300 1 5 10 20 30 40 50 60 70 80 90 350 1 5 10 20 30 40 50 60 70 80 90 400 1 5 10 20 30 40 50 60 70 80 90 450 1 5 10 20 30 40 50 60 70 80 90 500 1 5 10 20 30 40 50 60 70 80 90 550 1 5 10 20 30 40 50 60 70 80 90 600 1 5 10 20 30 40 50 60 70 80 90 700 1 5 10 20 30 40 50 60 70 80 90 800 1 5 10 20 30 40 50 60 70 80 90 900 1 5 10 20 30 40 50 60 70 80 90 1000 1 5 10 20 30 40 50 60 70 80 90 1500 1 5 10 20 30 40 50 60 70 80 90 2000 1 5 10 20 30 40 50 60 70 80 90 30 100 200 300 400 500 600 700 800 900 1000 35 200 250 300 400 500 750 1000 1500 2000 5000 40 200 250 300 400 500 750 1000 1500 2000 5000 50 200 250 300 400 500 750 1000 1500 2000 5000 60 200 250 300 400 500 750 1000 1500 2000 5000 70 200 250 300 400 500 750 1000 1500 2000 5000 80 200 250 300 400 500 750 1000 1500 2000 5000 90 200 250 300 400 500 750 1000 1500 2000 5000 100 200 250 300 400 500 750 1000 1500 2000 5000 150 200 250 300 400 500 750 1000 1500 2000 5000 200 200 250 300 400 500 750 1000 1500 2000 5000 250 200 250 300 400 500 750 1000 1500 2000 5000 300 200 250 300 400 500 750 1000 1500 2000 5000 350 200 250 300 400 500 750 1000 1500 2000 5000 400 200 250 300 400 500 750 1000 1500 2000 5000 450 200 250 300 400 500 750 1000 1500 2000 5000 500 200 250 300 400 500 750 1000 1500 2000 5000 550 200 250 300 400 500 750 1000 1500 2000 5000 600 200 250 300 400 500 750 1000 1500 2000 5000 700 200 250 300 400 500 750 1000 1500 2000 5000 800 200 250 300 400 500 750 1000 1500 2000 5000 900 200 250 300 400 500 750 1000 1500 2000 5000 1000 200 250 300 400 500 750 1000 1500 2000 5000 1500 200 250 300 400 500 750 1000 1500 2000 5000

[0067]

[0068] P5500PC00

[0069] 2000 200 250 300 400 500 750 1000 1500 2000 5000

[0070]

[0071] Conveniently, the invention can provide for storing the hydrogen product stream under a storage pressure, wherein the storage pressure can be derived from the reaction-side pressure. Optionally, the storage pressure may be the product-side pressure.

[0072] Advantageously, the storage pressure may be at least about 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500 or 550 bar a and / or up to about 1000, 900, 800, 700, or 600 bar a. Conveniently, the storage pressure may be about 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 700, 800, 900, or 1000 bar a. Hydrogen can be stored at such storage pressures without compressing low pressure hydrogen to such storage pressures, as the storage pressure can be derived from the reaction-side pressure, such as the pressure of the pressurised reaction stream.

[0073] In many embodiments, it is not necessary to know a specific value of the reaction-side pressure, or the reaction-side hydrogen partial pressure. For instance, where the productside pressure may be maintained at a suitable pressure, the reaction-side pressure and / or reaction-side hydrogen partial pressure may be regarded as inherently also at a suitable pressure.

[0074] Conveniently, the reaction-side hydrogen partial pressure can be calculated based on a calculation model. Such models are known, for example in automotive exhaust catalytic aftertreatment systems. Suitably, a model may be constructed for any given ammonia cracking arrangement.

[0075] Hydrogen-selective membranes

[0076] Advantageously, the hydrogen-selective membrane may be curved, with a concave surface in communication with the reaction stream. Suitably, a convex surface may be in communication with the hydrogen product stream. Advantageously, the hydrogen-selective membrane may be cylindrical or spherical. Suitably, the hydrogen-selective membrane may be cylindrical.

[0077] Suitably, the concave surface of the hydrogen-selective membrane may be in contact with the reaction-side pressure and the convex surface may be in contact with the product-side pressure. An advantage of having a higher rection-side pressure exerted on a concave surface of the hydrogen-selective membrane is that the hydrogen-selective membrane is pushed outwards. Suitably, the hydrogen-selective membrane may be under tensile stress, as opposed to compressive stress, from the reaction-side pressure. If the reaction-side pressure was instead applied to a convex surface the hydrogen-selective membrane might need reinforcement against collapse. An advantage of having the concave surface in contactP5500PC00

[0078] with the pressurised reaction stream, and / or reaction-side pressure, is that the hydrogenselective membrane does not need reinforcement against collapse and can therefore be made from thin material.

[0079] Architectural configuration and inversion

[0080] Optionally, the hydrogen-selective membrane may be configured such that the reaction-side pressure produces a tensile stress within the membrane. This configuration contrasts with conventional membrane reactor arrangements in which the membrane is exposed to compressive loading resulting from higher pressure on a convex side.

[0081] In many conventional membrane reactor configurations for hydrogen production, the hydrogen-selective membrane is arranged such that the membrane experiences compressive forces on a convex side, due to higher pressure of a reaction stream on an outside surface of the membrane relative to an inside surface. Such configurations often require additional structural reinforcement to prevent mechanical collapse of the membrane.

[0082] In contrast, the membrane reactor of the present invention may optionally be effectively inverted relative to such conventional configurations. In particular, the pressurised reaction stream may be located on a concave side of the hydrogen-selective membrane, while the hydrogen product stream may be located on a convex side of the membrane. As a result, the reaction-side pressure may act to place the hydrogen-selective membrane under tensile stress rather than compressive stress.

[0083] This inverted pressure configuration may provide several advantages. First, the membrane can be manufactured with reduced thickness because the risk of structural collapse is reduced when the membrane is subjected primarily to tensile loading. Second, a thinner membrane reduces the diffusion path length for hydrogen permeation, thereby increasing hydrogen flux across the membrane. Third, the configuration enables operation at significantly higher reaction pressures than are typically feasible in conventional membrane reactor configurations.

[0084] The inverted architecture therefore enables efficient production of pressurised hydrogen directly from a pressurised ammonia reaction stream while avoiding the need for downstream hydrogen compression.

[0085] An advantage of using a thin hydrogen-selective membrane is the decreased path length that hydrogen traverses through the hydrogen-selective membrane. A decreased path length can increase the rate at which hydrogen can cross the membrane. Advantages of having the concave surface in contact with the reaction stream, and / or reaction-side pressure, is that the reaction-side pressure can provide both: (a) a driving force for drivingP5500PC00

[0086] hydrogen through the hydrogen-selective membrane and (b) means for the hydrogenseparation membrane to comprise thin material.

[0087] Advantageously, the hydrogen-selective membrane may be about 1 to about 500 pm in thickness. Optionally, the hydrogen-selective membrane may be at least about 2, 5, 10, 20, 50, 100, 150 or 200 pm in thickness and / or up to about 450, 400, 350, 340, 330, 320, 310, 300 pm in thickness. Optionally, the hydrogen-selective membrane may be about 2 to about 450 pm, about 5 to about 400, about 10 to about 350, about 20 to about 340, about 50 to about 330, about 100 to about 330, about 150 to about 320, about 150 to about 310, or about 200 to about 300 pm in thickness.

[0088] Hydrogen-selective membranes are known in the art and the choice of hydrogen-selective membrane is not particularly limited. Suitably, the hydrogen-selective membrane may allow hydrogen to pass through while resisting passage of ammonia and nitrogen. Suitably, the hydrogen-selective membrane may allow hydrogen to pass through while substantially blocking passage of other substances in the reaction stream, in particular ammonia and nitrogen.

[0089] The reaction stream may comprise, consist essentially of, or consist of, ammonia. In some cases, the reaction stream may comprise ammonia and further components, such as additives and / or impurities. A common impurity in commercially available ammonia is water. Advantageously, the hydrogen-selective membrane may allow hydrogen to pass through while substantially blocking passage of ammonia, nitrogen and water. Another common impurity in commercially available ammonia is oil. Advantageously, the hydrogenselective membrane may allow hydrogen to pass through while substantially blocking passage of ammonia, nitrogen, water, and oil. In certain cases, the hydrogen-selective membrane may allow only hydrogen to pass through. Advantageously, a reactor that tolerates impure ammonia can allow for a further reduction in cost of the ammonia feedstock material.

[0090] Advantageously, the hydrogen-selective membrane may comprise, consist essentially of, or consist of a metallic membrane. Metallic membranes may offer good hydrogen selectivity while also remaining operational at elevated temperatures that may be required for catalytic cracking of ammonia. For example, the hydrogen-selective membrane may comprise, consist essentially of, or consist of palladium or a palladium alloy. Palladium membranes may provide for high hydrogen permeability, excellent selectivity, and mechanical stability at elevated pressures and temperatures. Palladium is known to offer a particularly useful mechanism for separating hydrogen from a hot gas mixture, at high purity levels, whereby gaseous hydrogen can dissolve into palladium, diffuse through the palladium, and desorb as gaseous hydrogen. In this way, hydrogen can pass through a retentate surface to a permeate surface of a palladium hydrogen-selective membrane, while other materials suchP5500PC00

[0091] as ammonia and nitrogen can be blocked from passing through the palladium hydrogenselective membrane. When a palladium or palladium alloy material is used, the hydrogenselective membrane may advantageously be brought to a temperature above 300 °C.

[0092] Palladium and palladium alloys can be permeable to hydrogen and no other gases, particularly when heated above 300 °C.

[0093] Hydrogen product stream

[0094] Advantageously, the hydrogen product stream may be obtained at a rate of between about 1 and about 1000 kg / h of hydrogen. Suitably, the hydrogen product stream may be obtained at a rate of at least about 1, 5, 10, 20, 30, 40, 50, 100, 150, 200, 300, or 400 kg / h of hydrogen, and / or the hydrogen product stream may be obtained at a rate of up to about 600, 700, 800, or 900 kg / h hydrogen. For instance, the hydrogen product stream may be obtained at a rate of between about 10 and about 900 kg / h, between about 50 and about 800 kg / h, between about 150 and about 700 kg / h, or between about 200 and about 600 kg / h of hydrogen.

[0095] The hydrogen product stream may comprise a hydrogen purity of at least about 99 wt%. For instance, the hydrogen purity may be at least about 99.9 wt%, 99.99 wt%, or 99.999 wt%.

[0096] A technique that may be used in membrane reactors to help draw the equilibrium towards reaction products is to forcibly remove the product coming through the membrane with a sweep gas. A sweep gas is a gas other than the product coming through the membrane. In the current context, a sweep gas would be a gas other than hydrogen, that is passed along the permeate side of the hydrogen-selective membrane, in order to sweep hydrogen away from the hydrogen-selective membrane and thereby reduce the hydrogen partial-pressure on the permeate side of the hydrogen-selective membrane. An advantage of the present invention is that a high reaction-side pressure may be used to obtain a hydrogen product stream without the need for a sweep gas. A further advantage is that the hydrogen does not become diluted by a sweep gas. Thus, suitably, a sweep gas is not used in the hydrogen product stream.

[0097] Catalyst

[0098] Catalysts for conversion of ammonia into hydrogen and nitrogen are known in the art. Such catalysts may be termed ammonia cracking catalysts. The choice of catalyst is not particularly limited, and may be any catalyst capable of converting ammonia to hydrogen and nitrogen. The catalyst may comprise, consist essentially of, or consist of, a metallic catalyst and / or a metal salt catalyst. The catalyst may comprise, consist essentially of, or consist of, a metallic catalyst selected from the list comprising: ruthenium, nickel, cobalt, and / or iron; and / or a metal salt catalyst that comprises a metal amide. Suitably, theP5500PC00

[0099] metallic catalyst may comprise, consist essentially of, or consist of, ruthenium on alumina, nickel on alumina, cobalt on alumina, and / or iron on alumina. Suitably, the metal amide may comprise lithium amide.

[0100] Ammonia cracking catalysts are typically operated at elevated temperature to facilitate ammonia cracking. For any given catalyst, typical operating temperatures are known in the art. Suitably, when in use, the catalyst will be above the temperature required to overcome an activation energy for conversion of ammonia to hydrogen. Suitably, when in use, the catalyst may be at a catalyst temperature between about 300 and about 1200 °C, such as between about 350 and about 1000 °C. For instance, if the catalyst comprises ruthenium the catalyst temperature may be between about 370 and about 550 °C, if the catalyst comprises iron the catalyst temperature may be between about 600 and about 750 °C, and if the catalyst comprises nickel the catalyst temperature may be between about 850 and about 950 °C. If the catalyst comprises lithium amide, the catalyst temperature may be between about 300 and 600 °C.

[0101] Suitably, the temperature and pressure in the reaction stream may be above the critical point for ammonia. For instance, the ammonia in the reaction stream may be supercritical ammonia. Maintaining ammonia above its critical point while it is in contact with the catalyst in the reaction zone, may be advantageous. Advantages include:

[0102] • enhanced mass transfer: supercritical ammonia exhibits high diffusivity and solvation properties, improving reactant transport to the catalyst;

[0103] • increased reaction kinetics: higher reaction rates due to improved heat and mass transfer efficiency; and

[0104] • compact reactor design: higher efficiency allows for a smaller, more modular system for hydrogen generation.

[0105] In principle, the reaction zone can be taken as any zone in which ammonia in the reaction stream is converted to hydrogen.

[0106] Suitably, the reaction zone can be a zone defined by the catalyst. For example, the reaction zone may be taken as a zone surrounding the catalyst up to a distance of about 100 mm, suitably up to a distance of about 50 mm, or even up to a distance of about 10 mm.

[0107] Conveniently, the reaction zone may simply be taken as a reaction vessel or other structure in which the catalyst is held.

[0108] Optionally, the reaction zone may be defined as a space between the catalyst and the hydrogen selective membrane.P5500PC00

[0109] In certain configurations, a catalyst bed can comprise the catalyst and a catalyst support material. The catalyst can be supported on a catalyst support material. Suitably, the catalyst can be coated on the catalyst support material. Suitably, the catalyst, catalyst support material and / or catalyst bed can be porous. Porosity can enhance the surface area of catalyst available to the reaction stream, and enhance conversion of ammonia to hydrogen and nitrogen.

[0110] The catalyst support material can provide a three-dimensional structure of the catalyst bed, which can define the flow path for the reaction stream and / or provide structural integrity to the catalyst. Advantageously, the catalyst support material can comprise a gyroid, woven mesh, lattice, foam, or sintered structure.

[0111] A gyroid structure can provide a flow path that increases residence time of the reaction stream within the catalyst bed. Suitably, a catalyst support material comprising a gyroid structure can be generated using three-dimensional printing. Conveniently, the catalyst bed can be generated using three-dimensional printing.

[0112] Gyroid structure

[0113] A catalyst support material comprising a gyroid structure may provide a continuous three-dimensional network of flow passages with high surface area and uniform distribution of catalyst. The gyroid geometry can promote enhanced mixing and turbulent micro-scale flow, thereby improving mass transfer between ammonia and catalytic sites. The continuous curvature of the gyroid structure can also improve mechanical strength while maintaining high porosity. In addition, gyroid structures are well suited to additive manufacturing techniques, allowing precise control over pore size, wall thickness, and overall catalyst bed geometry.

[0114] Woven mesh structure

[0115] A catalyst support material comprising a woven mesh structure may provide a high surfacearea conductive matrix suitable for catalyst deposition. The interwoven filaments define multiple interconnected flow channels which can promote uniform gas distribution and reduce pressure drop across the catalyst bed. Where the mesh is formed from electrically conductive materials such as FeCrAI alloys, the structure may also be capable of resistive (Joule) heating, enabling rapid and uniform heating of the catalyst bed while minimising thermal gradients. The woven geometry can further provide mechanical flexibility that accommodates thermal expansion during operation.

[0116] Lattice structureP5500PC00

[0117] A catalyst support material comprising a lattice structure may provide a mechanically robust framework that supports catalyst coatings while maintaining controlled porosity. The lattice architecture allows the geometry of flow passages to be engineered to optimise residence time and mass transfer within the reaction zone. Lattice structures may be produced by additive manufacturing processes, enabling precise tailoring of cell geometry, strut thickness, and catalyst distribution. This may improve catalyst utilisation and allow reactor designs with high structural integrity at elevated temperatures and pressures.

[0118] Foam structure

[0119] A catalyst support material comprising a foam structure may provide a highly porous network with a large internal surface area for catalyst deposition. The tortuous pore network of the foam can promote enhanced contact between the reaction stream and catalytic surfaces, improving conversion efficiency. Foam materials may also exhibit good thermal conductivity and thermal buffering, helping to maintain uniform temperature distribution within the catalyst bed. The open-cell foam geometry can also reduce localised hotspots by promoting convective heat transfer through the catalyst bed.

[0120] Sintered structure

[0121] A catalyst support material comprising a sintered structure may provide a mechanically stable porous matrix formed by bonding particles or fibres at elevated temperature.

[0122] Sintered structures can provide controlled pore size distributions and high structural strength, allowing operation at elevated pressures and temperatures. The interconnected porosity may facilitate uniform distribution of the reaction stream across the catalyst bed, improving catalyst utilisation and reaction efficiency. Additionally, sintered structures may offer improved resistance to catalyst attrition and mechanical degradation during long-term operation.

[0123] Advantageously, the catalyst support material can be capable of Joule heating. Joule heating is known in the art. Joule heating refers to heating up the catalyst support material using electric current. An advantage of Joule heating is that it can be controlled to ensure temperature uniformity along the length of the catalyst bed, avoiding hot or cold spots that could reduce efficiency or create mechanical stresses. The catalyst support material can comprise, consist essentially of, or consist of, any material capable of Joule heating.

[0124] Generally, for Joule heating, the catalyst support material can comprise, consist essentially of, or consist of, any material that generates heat when electric current is passed through. Suitably, the catalyst support material can comprise, consist essentially of, or consist of, SiC, FeCrAI, or MoSi2. Advantageously, the catalyst support material can comprise, consist essentially of, or consist of, SiC. SiC, or silicon carbide, can provide high thermal conductivity, mechanical strength, and resistance to corrosion from ammonia and hydrogen.P5500PC00

[0125] In one embodiment, the catalyst support material comprises, consists essentially of, or consists of, SiC comprising a gyroid structure. Advantageously, SiC comprising a gyroid structure can be generated using three-dimensional printing.

[0126] Advantageously, the method may be run as a continuous process. In some cases, the method may be stopped and started, for instance, as required by demand.

[0127] Suitably, the method may comprise obtaining a residual stream from the reaction zone. Advantageously, the residual stream may comprise less than 25 ppm ammonia. An ammonia content below 25 ppm may allow for the output from the membrane reactor to be vented to atmosphere. Additionally or alternatively, a residual stream may be recycled to the reaction stream.

[0128] In some embodiments of the invention, the method may be carried out in a membrane reactor as described anywhere herein.

[0129] Membrane reactor

[0130] A second aspect of the invention provides a membrane reactor comprising: a feed vessel comprising a catalyst bed comprising a catalyst for conversion of ammonia to hydrogen and nitrogen; a hydrogen collection vessel for collecting hydrogen at a pressure of at least 30 bar a; and a hydrogen-selective membrane separating the feed vessel and the hydrogen collection vessel for selective removal of hydrogen.

[0131] Suitably, the feed vessel may comprise a feed vessel inlet and a feed vessel outlet.

[0132] Optionally, the hydrogen collection vessel may comprise a hydrogen outlet.

[0133] Suitably, the catalyst bed, catalyst and hydrogen selective membrane may each independently be as described anywhere herein, for example in respect of the first aspect hereinabove.

[0134] Advantageously, the feed vessel may define a reaction zone for conversion of ammonia to hydrogen and nitrogen.

[0135] Advantageously, the feed vessel may be contained within the hydrogen collection vessel. In this configuration, the reaction-side pressure may provide a driving force that pushes the hydrogen outward through the hydrogen-selective membrane into the hydrogen collection vessel. The feed vessel may be a tubular feed vessel and the hydrogen collection vessel may be a tubular hydrogen collection vessel coaxial with the tubular feed vessel. In some embodiments, the feed vessel is a tubular feed vessel and the hydrogen collection vessel is a tubular hydrogen collection vessel coaxial with the tubular feed vessel, and the tubular feed vessel is contained within the tubular hydrogen collection vessel.P5500PC00

[0136] Suitably, the feed vessel may be substantially defined by a feed vessel pressure casing wherein at least a portion of the feed vessel pressure casing comprises the hydrogenselective membrane. The feed vessel pressure casing may separate the feed vessel from the hydrogen collection vessel, and a portion of the pressure casing may be the hydrogenselective membrane. Alternatively, the feed vessel may be substantially defined by the hydrogen-selective membrane. The hydrogen-selective membrane may be the entirety of the barrier between the feed vessel and the hydrogen collection vessel.

[0137] Advantageously, the hydrogen-selective membrane may encapsulate the catalyst bed.

[0138] In certain configurations, the catalyst bed may fill the feed vessel. Suitably, the catalyst bed may fill a cross-sectional portion of the feed vessel. For example, the flow path of the reaction stream may not avoid passing through the catalyst bed. In other configurations, the catalyst bed may fill a portion of a cross-sectional portion of the feed vessel. For example, the catalyst bed may have a hollow core.

[0139] Suitably, a surface of the catalyst bed may be in contact with, or in proximity to, a surface of the hydrogen-selective membrane. Suitably, a surface of the catalyst bed is in proximity to a surface of the hydrogen-selective membrane such that hydrogen evolving from the surface of the catalyst bed contacts the surface of the hydrogen-selective membrane.

[0140] Suitably, a surface of the catalyst bed may be in contact with, or may have a gap of up to about 20000, 15000, or 8000 pm from, a surface of the hydrogen-selective membrane. Suitably, a surface of the catalyst bed may have a gap of up to about 7000, 6000, 5000, 4000, 3000, 2000, 1000, 500, 250, or 100 pm from a surface of the hydrogen-selective membrane. Advantageously, contact, or proximity, of a surface of the catalyst bed with a surface of the hydrogen-selective membrane may provide for a minimal path for the hydrogen from the point of generation on the catalyst to the point of separation on the retentate surface of the hydrogen-selective membrane. Minimising the distance between the location of hydrogen generation on the catalyst surface and the hydrogen-selective membrane may reduce the diffusion path length for hydrogen within the reaction zone. Rapid removal of hydrogen from the catalyst surface may reduce the likelihood of reverse reaction between hydrogen and nitrogen to reform ammonia. In addition, reducing the diffusion path length may increase the effective hydrogen flux across the membrane and thereby improve overall reactor efficiency.

[0141] The feed vessel may be elongate. Suitably, the feed vessel may have an aspect ratio above about 5. Advantageously, the feed vessel may have an aspect ratio above about 10, 15, 20, 30, 40, 50, 60, 80, 100, 150, 200, 250, 500 or 1000. In such configurations, the reaction stream may be provided at one end of the feed vessel and passed through to the other end. Advantageously, such configurations may be used to increase conversion to hydrogen. As the reaction stream passes down the feed vessel hydrogen may continually be generatedP5500PC00

[0142] and removed. Advantageously, a feed vessel having such aspect ratios may increase the residence time of ammonia on the catalyst bed while simultaneously minimising the residence time of hydrogen on the catalyst bed.

[0143] Where the feed vessel is elongate, the catalyst and / or reaction zone may also typically be elongate. Suitably, the catalyst and / or reaction zone may be elongate and the hydrogenselective membrane may be arranged alongside the length dimension of the catalyst and / or reaction zone. Advantageously, the catalyst and / or reaction zone may have an aspect ratio above about 5, such as above about 10, 15, 20, 30, 40, 50, 60, 80, 100, 150, 200, 250, 500 or 1000. In such configurations, the reaction stream may be provided at one end of the catalyst and / or reaction zone and passed through to the other end. Advantageously, such configurations may be used to increase conversion to hydrogen. As the reaction stream passes down the catalyst, hydrogen may continually be generated and removed.

[0144] Advantageously, a catalyst having such aspect ratios may increase the residence time of ammonia on the catalyst while simultaneously minimising the residence time of hydrogen on the catalyst.

[0145] The volume of the feed vessel is not particularly limited. For example, the feed vessel may have a volume between about 1 litre and about 5000 litres. Suitably, the feed vessel may have a volume of at least about 2, 5, 10, 50, 100, 250, 500, 1000, or 2000 litres and / or up to about 4500, 4000, 3800, 3600, 3400, 3200, 2800, or 2500 litres. For instance, the feed vessel may have a volume of between about 2 and about 2500, about 5 and about 4000, about 10 and about 3800, about 50 and about 3600, about 100 and about 3400, about 250 and about 3200, about 500 and about 3000, about 1000 and about 2800, about 2000 and about 2500 litres.

[0146] The feed vessel may be a tubular feed vessel comprising a diameter of at least about 1 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, or 18 mm, and / or up to about 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 150 mm. The feed vessel may be a tubular feed vessel comprising a diameter of between about 1 mm and about 150 mm, about 2 mm and 100 mm, about 4 mm and about 90mm, about 6 mm and about 80 mm, about 8 mm and about 70 mm, about 10 mm and about 60 mm, about 12 mm and about 50 mm, about 14 mm and about 40 mm, about 16 mm and about 30 mm, and about 18 mm and about 20 mm. Advantageously, a small diameter tubular feed vessel may mean a small diameter catalyst bed, which may mean the hydrogen is produced in proximity to the hydrogen-selective membrane, aiding rapid removal of hydrogen from the catalyst bed.

[0147] Suitably, the hydrogen collection vessel may not comprise means for supplying a sweep gas. For instance, the hydrogen collection vessel may not comprise an inlet, such as a sweep gas inlet.P5500PC00

[0148] In an example, the feed vessel may: be a tubular feed vessel, be defined by the hydrogenselective membrane; be contained within the tubular hydrogen collection vessel; be coaxial with the tubular hydrogen collection vessel; have a diameter of between about 8 mm and about 70 mm; and have an aspect ratio of above about 5.

[0149] In an example, the membrane reactor comprises: a tubular feed vessel comprising a catalyst bed comprising a catalyst for conversion of ammonia to hydrogen and nitrogen; a hydrogen collection vessel for collecting hydrogen at a pressure of at least 30 bar a, wherein the hydrogen collection vessel encases the tubular feed vessel; a hydrogenselective membrane separating the feed vessel from the hydrogen collection vessel for selective removal of hydrogen.

[0150] In certain embodiments, the membrane reactor may be provided with at least one pump configured to provide the pressurised reaction stream. This may be via a feed vessel inlet. Advantageously, the pump may be a liquid compression pump. The type of liquid compression pump is not particularly limited and suitable pumps may include reciprocating pumps, rotary pumps, screw pumps, and centrifugal pumps.

[0151] Advantageously, the membrane reactor may comprise a pressure control module. This may be configured to provide for adaptive pressure control, whereby the pressure control module dynamically adjusts the pressure differential to account for variations in flow rate, temperature and ammonia concentration. Adaptive pressure control may be implemented through, for example, backpressure regulators, flow control valves, and controlled pump flow rates.

[0152] Conveniently, the membrane reactor may comprise multiple feed vessels within a single hydrogen collection vessel.

[0153] Advantageously, a hydrogen generation system may comprise multiple membrane reactors, suitably arranged in parallel.

[0154] Of course, the membrane reactor may suitably be operated according to a method as described or defined in aspect or embodiment. Optionally, methods according to aspects or embodiments herein may comprise feeding the pressurised reaction stream into the feed vessel and obtaining the hydrogen product stream in the collection vessel, the reactor providing the catalyst and hydrogen selective membrane.

[0155] Thus, the feed vessel may contain a pressurised reaction stream comprising ammonia, and the hydrogen collection vessel may contain a hydrogen product stream comprising pressurised hydrogen, wherein the hydrogen-selective membrane is under a pressure differential between a reaction-side pressure of the reaction stream and a product-side pressure of the hydrogen product stream, wherein the pressure differential is set to driveP5500PC00

[0156] hydrogen from the reaction stream through the hydrogen-selective membrane to obtain the hydrogen product stream; wherein the product-side pressure is at least about 30 bar a.

[0157] According to a third aspect, the invention provides a hydrogen generation station comprising a membrane reactor according to the second aspect. Suitably, the hydrogen generation station may be a hydrogen refuelling station for fuelling hydrogen-powered vehicles, such as automobiles, trains, aircraft, boats, and / or ships. Suitably, the hydrogen generation station may be an industrial hydrogen supply. An industrial hydrogen supply may serve industries such as glass manufacturing and food processing. Suitably, the hydrogen generation station may be a distributed energy system such as a decentralised hydrogen production system for energy storage and / or fuel cell systems.

[0158] Some aspects and embodiments of the invention are not confined to specific levels of high pressure.

[0159] According to a fourth aspect the invention provides a method for production of pressurised hydrogen, the method comprising: providing a catalyst for conversion of ammonia to hydrogen and nitrogen; contacting a pressurised reaction stream comprising ammonia with the catalyst to convert at least a portion of the ammonia into hydrogen in a reaction zone; and obtaining a hydrogen product stream comprising pressurised hydrogen by selectively driving hydrogen from the reaction zone through a hydrogen-selective membrane under a pressure differential between a reaction-side pressure of the reaction stream and a productside pressure of the hydrogen product stream. Optional features of the fourth aspect may be as described in respect of the first aspect of the invention.

[0160] Throughout the description and clauses of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, integers or steps. Moreover the singular encompasses the plural unless the context otherwise requires: in particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0161] Optional features of each aspect of the invention may be as described in connection with any of the other aspects. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the clauses and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination, unless such features are incompatible.

[0162] BRIEF DESCRIPTION OF THE DRAWINGSP5500PC00

[0163] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0164] Figure 1 is a schematic representation of a cross-section of a Joule heated membrane reactor according to an aspect of the invention, and

[0165] Figure 2 is a schematic representation of a cross-section taken along line A-A' of Figure 1. DETAILED DESCRIPTION

[0166] Figure 1 shows a schematic representation of a membrane reactor 2 according to an embodiment of the invention.

[0167] The membrane reactor 2 comprises a feed vessel 18 and a hydrogen collection vessel 24. The feed vessel 18 comprises a feed vessel inlet 20, a feed vessel outlet 22, and a catalyst bed 4 comprising a catalyst 6 and a catalyst support material 8. The catalyst bed 4 substantially fills the feed vessel 20. The catalyst 6 defines a reaction zone 7.

[0168] The feed vessel outlet 22 is fitted with a feed vessel outlet valve 36. The feed vessel outlet valve 36 can suitably be a pressure regulating / shutoff valve, selected to maintain the reaction stream 12 at the reaction-side pressure within the feed vessel 18.

[0169] The hydrogen collection vessel 24 has a hydrogen outlet 26 fitted with a hydrogen outlet valve 38. The hydrogen outlet valve 38 can suitably be a pressure regulating / shutoff valve, selected to maintain the hydrogen product stream 14 at a product-side pressure within the hydrogen collection vessel 18.

[0170] The feed vessel outlet valve 36 and hydrogen outlet valve 38 can be electronic back pressure regulator / shutoff valves.

[0171] The membrane reactor 2 also comprises a hydrogen-selective membrane 10 that separates the feed vessel 18 from the hydrogen collection vessel 24.

[0172] A pressure casing 28 encloses the membrane reactor 2 and thereby also encloses the hydrogen collection vessel 24.

[0173] A liquid pump 34 is in fluid communication with the feed vessel inlet 20. If required, an additional heater (not shown) can be arranged between the pump 34 and the feed vessel inlet 20, to pre-heat the ammonia before it contacts the catalyst bed.

[0174] The reaction stream 12 is in a pressure-controlled environment when located between the liquid pump 34 and the feed vessel outlet valve 36.

[0175] The membrane reactor 2 and, accordingly, the feed vessel 18 and hydrogen collection vessel 24, are elongate. The break lines in Figure 1 show that the length of the elongateP5500PC00

[0176] membrane reactor 2 can extend to any suitable length. The feed vessel inlet 20 and feed vessel outlet 22 are positioned at either end of the elongate feed vessel 18. Such a configuration provides for a flow path for the reaction stream 12 through the feed vessel 18 and, accordingly, through the catalyst bed 4.

[0177] The catalyst bed 4 of membrane reactor 2 is capable of Joule heating. As such, the catalyst bed 4 is connected to an electrical supply 30 by electrically conductive wires 32. The type of electrical supply 30 is not particularly limited, and can be a direct current or alternating current source.

[0178] Further structural information can be seen in Figure 2, which is a cross-section of membrane reactor 2 taken across line A-A' as shown in Figure 1. In Figure 2, it can be seen that the feed vessel 18 is a tubular feed vessel 18 and the hydrogen collection vessel 24 is a tubular hydrogen collection vessel 24 that is coaxial with the tubular feed vessel 18 and wherein the tubular feed vessel 18 is contained within the tubular hydrogen collection vessel 24.

[0179] From Figures 1 and 2, it can be seen that the hydrogen-selective membrane 10 defines the feed vessel 18.

[0180] In use, the feed vessel 18 is at the reaction-side pressure and the hydrogen collection vessel 24 is at the product-side pressure. The reaction-side pressure is higher than the product-side pressure such that a pressure differential exists across the tubular hydrogenselective membrane 10. It can be seen in Figures 1 and 2 that the pressure differential pushes outward on the tubular hydrogen-selective membrane 10 and as such the hydrogenselective membrane 10 does not need to be reinforced against compressive forces.

[0181] The catalyst support material 8 is heated through Joule heating by the electrical supply 30 to a temperature suitable for the catalyst to crack ammonia to hydrogen and nitrogen.

[0182] A reaction stream 12 comprising ammonia is supplied to liquid pump 34 which increases the pressure of the reaction stream 12 to a pressure generated by the pump 34. When the reaction stream 12 comes into contact with the heated catalyst bed. The pressure generated by the pump 34 should be sufficient such that the reaction stream 12 is at a reaction-side pressure.

[0183] Suitably, the temperature and pressure within the feed vessel 18 are such that the ammonia is above its critical point.

[0184] It can be seen from Figure 1 that the reaction stream 12 transits the catalyst 6 I reaction zone 7 from the feed vessel inlet 20 to the feed vessel outlet 22. As the reaction stream 12 transits the reaction zone 7, ammonia will catalytically crack into hydrogen and nitrogen inP5500PC00

[0185] the reaction zone 7. At the reaction-side pressure, the hydrogen and nitrogen would likely recombine to form ammonia, except that through the pressure differential across the hydrogen-selective membrane 10, hydrogen is selectively removed from the reaction zone 7, and driven to the hydrogen collection vessel 24. As such, the reaction stream 12 becomes depleted in ammonia and depleted in hydrogen, and enriched in nitrogen, as it transits the reaction zone 7. As the reaction stream 12 moves further through the reaction zone 7, the removal of hydrogen through the hydrogen-selective membrane 10 allows for the equilibrium position of the ammonia cracking reaction to replenish the hydrogen through further catalytic cracking of ammonia into nitrogen and further hydrogen. Even though the equilibrium position in general may not favour hydrogen, by continuously removing hydrogen as it is generated, along the length of the reaction zone 7, the process as a whole can be forced to high conversion levels. By the time the reaction stream 12 reaches the feed vessel outlet 22, the reaction stream will be depleted in ammonia and enriched in nitrogen. Certain parameters of the membrane reactor 2, such as length of the membrane reactor 2 or pressure differential across the hydrogen-selective membrane 10, can be selected such that the reaction stream 12 is substantially devoid of ammonia by the time it reaches the feed vessel outlet 22.

[0186] As the hydrogen transits the hydrogen-selective membrane 10, the hydrogen is collected in the hydrogen collection vessel 24 as a hydrogen product stream 14. The hydrogen pressure in the hydrogen collection vessel 24 is maintained at the product-side pressure. In other words, the hydrogen product stream 14 is maintained at the product-side pressure. The hydrogen outlet valve 38 allows hydrogen to be released at the product-side pressure, such that the hydrogen collection vessel 24 does not significantly exceed the product-side pressure. As hydrogen passes from the feed vessel 18 into the hydrogen collection vessel 24, the hydrogen pressure in the hydrogen collection vessel 24 would otherwise increase, except for hydrogen being output through the hydrogen outlet valve 38. For instance, when the membrane reactor 2 is operating at a steady state, hydrogen outlet valve 38 may be open to an extent that maintains an output of hydrogen that maintains the hydrogen product stream 14 at the product-side pressure.

[0187] The skilled person can readily ensure a suitable reaction-side pressure for driving hydrogen through the hydrogen-selective membrane 10. Hydrogen transport through the membrane 10 is governed by Sieverts' Law, which describes the hydrogen flux as proportional to the square root of the hydrogen partial pressure difference across the membrane 10. In general, if the reaction-side pressure is at a pressure that provides a hydrogen partial pressure that is higher than the product-side pressure, the product-side pressure can be maintained or raised. If the product-side pressure drops below a pre-determined cutoff, when the hydrogen outlet valve 38 is shut off, the reaction-side pressure is not high enough and should be raised. For instance, if the hydrogen outlet valve 38 is shut off and theP5500PC00

[0188] product-side pressure does not increase above a pre-determined cutoff, there is not sufficient reaction-side hydrogen partial pressure to drive hydrogen through the membrane and reaction-side pressure should be raised.

[0189] Example product-side pressures and reaction-side pressures, for a reaction where substantially full conversion of ammonia to hydrogen and nitrogen is occurring, are provided in the table below:

[0190] Product-side Reaction-side pressure (bar a) for a differential hydrogen partial Pressure (bar a) pressure of 1, 10, 50, 100, or 1000 bar a

[0191] 1 10 50 100 1000 1 2.67 14.67 68 134.67 1334.67 10 14.67 26.67 80 146.67 1346.67 50 68 80 133.33 200 1400 100 134.67 146.67 200 266.67 1466.67 500 668 680 733.33 800 2000 1000 1334.67 1346.67 1400 1466.67 2666.67

[0192]

[0193] From a non-operational state, the feed vessel 18 and hydrogen collection vessel 24 should be brought up to pressure in a way that does not damage the hydrogen-selective membrane 10. In one embodiment, this can be performed by having a small amount of high-pressure hydrogen stored downstream, potentially isolated and stored from a previous operation, as well as a small amount of high-pressure nitrogen, also potentially isolated and stored during a previous operation. For start-up pressurisation of the membrane reactor 2, nitrogen would be fed into the feed vessel inlet 20 and / or feed vessel outlet 22 to bring the feed vessel 18 up to pressure. Simultaneously, hydrogen would be fed into the hydrogen outlet valve 36 to bring the hydrogen collection vessel 24 up to pressure. Pressure ramping of both the feed vessel 18 and hydrogen collection vessel 24 would be controlled to ensure the pressure differential across the hydrogen-selective membrane 10 is maintained within a range that does not damage the hydrogen-selective membrane 10. Once the feed vessel 18 is in a nitrogen atmosphere (i.e. any other gases have been purged) the catalyst bed 4 can be brough up to operational temperature in the nitrogen atmosphere. Once the target pressures and temperatures have been obtained, ammonia can be introduced to the feed vessel 18. Ammonia will start converting as soon as it enters the catalyst bed 4.

[0194] Depressurisation of the membrane reactor 2 would be conducted by a similarly controlled simultaneous reduction in pressure of both the feed vessel 18 and the hydrogen collection vessel 24.

[0195] Example 1P5500PC00

[0196] This example describes a membrane reactor 2 designed to produce 5 kg / h of pure hydrogen. The membrane reactor 2 integrates a 20-micron Pd / AI2O3hydrogen-selective membrane 10, a 3D-printed catalyst bed 4 enclosed by the membrane 10, and a 316L stainless steel pressure vessel 28 that captures the permeated hydrogen. The membrane reactor 2 operates with a 50 bar a hydrogen partial pressure difference, enabling hydrogen delivery at 30 bar a permeate pressure. The modular design allows for scalability by adding additional membrane reactors 2.

[0197] The catalyst bed 4 is enclosed by a tubular Pd / AI2O3membrane 10, meaning the cracked hydrogen is in close proximity to the membrane 10 for rapid permeation. The catalyst bed 4 consists of a 3D-printed silicon carbide (SiC) gyroidal structure catalyst support material 8 impregnated with a ruthenium-based catalyst 6. The Pd / AI2O3membrane 10 (20-micron palladium layer supported on a porous alumina substrate) forms the boundary between the feed vessel 18 and the hydrogen collection vessel 24.

[0198] The pressure casing 28 encloses the Pd / AI2O3membrane 10, with a 5 mm radial gap between the membrane 10 outer surface and the pressure casing 28 wall inner surface. This defines the hydrogen collection vessel 24, which captures the permeated hydrogen and directs it through outlet port 26.

[0199] The pressure in the hydrogen collection vessel 24 is maintained at 30 bar a. The pressure in the feed vessel 18 is maintained at a pressure of 107 bar a, which provides a hydrogen partial pressure in the feed vessel 18 of 80 bar a, giving a hydrogen partial pressure difference of 50 bar a across the hydrogen-selective membrane 10.

[0200] The catalyst bed 4 is maintained at a temperature of 600 °C.

[0201] For a 50 bar a hydrogen partial pressure difference, the flux is: 1.2mol / m2 / s. The total membrane 10 area required is 0.578 m2. The feed vessel 18 has an internal diameter of 50 mm and the feed vessel 18 length is 3.68 m. The ammonia flow rate is 28.34 kg / h. The production rate of hydrogen is 5 kg / h, equivalent to 2,500 mol / h hydrogen or 0.694 mol / s hydrogen, and the hydrogen is obtained in high purity.

Claims

P5500PC00CLAIMS1. A method for production of pressurised hydrogen, the method comprising:providing a catalyst for conversion of ammonia to hydrogen and nitrogen;contacting a pressurised reaction stream comprising ammonia with the catalyst to convert at least a portion of the ammonia into hydrogen in a reaction zone; and obtaining a hydrogen product stream comprising pressurised hydrogen by selectively driving hydrogen from the reaction zone through a hydrogen-selective membrane under a pressure differential between a reaction-side pressure of the reaction stream and a product-side pressure of the hydrogen product stream; wherein the productside pressure is at least 30 bar a.

2. A method according to claim 1, wherein the product-side pressure is at least about 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 700, 800, 900, 1000, 1500, or 2000 bar a.

3. A method according to claim 1 or 2, wherein the reaction-side pressure is at least about 4 / 3 times the product-side pressure.

4. A method according to any preceding claim, wherein the reaction-side pressure is at least about 135%, 140%, 145%, 150%, 155%, 160%, 170%, 180%, 190%, 200%, 250%, 300%, 400%, 500%, 750%, 1000%, 1500%, 2000%, or 5000% of the product-side pressure.

5. A method according to any preceding claim, wherein the reaction-side pressure is at least about 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 bar a higher than the product-side pressure.

6. A method according to any preceding claim, comprising driving hydrogen from the reaction zone through the hydrogen-selective membrane under a hydrogen partial pressure differential between a reaction-side hydrogen partial pressure of the reaction stream and a product-side hydrogen partial pressure of the hydrogen product stream, wherein the hydrogen pressure differential is at least about 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 bar a.

7. A method according to any preceding claim, comprising storing the hydrogen product stream under a storage pressure, wherein the storage pressure is derived from the reaction-side pressure.P5500PC008. A method according to claim 7, wherein the storage pressure is at least about 35, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 700, 800, 900, 1000, 1500 or 2000 bar a.

9. A method according to any preceding claim, wherein the hydrogen-selective membrane is curved, with a concave surface in communication with the pressurised reaction stream.

10. A method according to any preceding claim, wherein the hydrogen-selective membrane is about 1 to about 500 pm in thickness.

11. A method according to any preceding claim, wherein the hydrogen-selective membrane comprises palladium or a palladium alloy.

12. A method according to any preceding claim, wherein the hydrogen product stream is obtained at a rate of between about 1 and about 1000 kg / h of hydrogen.

13. A method according to any preceding claim, wherein the hydrogen product stream comprises a hydrogen purity of at least about 99 wt%.

14. A method according to any preceding claim, with the proviso that a sweep gas is not used in the hydrogen product stream.

15. A method according to any preceding claim, wherein the catalyst comprises a metallic catalyst selected from the list comprising: ruthenium, nickel, cobalt, and / or iron; and / or a metal salt catalyst that comprises a metal amide.

16. A method according to any preceding claim, wherein the catalyst is at a temperature between about 300 and about 1200 °C.

17. A method according to any preceding claim, wherein the catalyst is contained in a catalyst bed comprising a catalyst support material.

18. A membrane reactor according to claim 17, wherein the catalyst support material comprises a gyroid, woven mesh, lattice, foam, or sintered structure.

19. A method according to claim 17 or claim 18, wherein the catalyst support material is capable of Joule heating.

20. A method according to any one of claim 17 to 19, wherein the catalyst support material comprises SiC, FeCrAI, or MoSi2.P5500PC0021. A membrane reactor comprising:a feed vessel comprising a catalyst bed comprising a catalyst for conversion of ammonia to hydrogen and nitrogen;a hydrogen collection vessel for collecting hydrogen at a pressure of at least 30 bar a; anda hydrogen-selective membrane separating the feed vessel and the hydrogen collection vessel for selective removal of hydrogen.

22. A membrane reactor according to claim 21, wherein the catalyst or catalyst bed is as defined in any of claims 15 to 20 and / or the hydrogen-selective membrane is as defined in claim 10 or 11.

23. A membrane reactor according to claim 21 or claim 22, wherein the feed vessel is contained within the hydrogen collection vessel.

24. A membrane reactor according to any one of claims 21 to 23, wherein the feed vessel is a tubular feed vessel and the hydrogen collection vessel is a tubular hydrogen collection vessel coaxial with the tubular feed vessel.

25. A membrane reactor according to any one of claims 21 to 24, wherein the feed vessel is substantially defined by a feed vessel pressure casing and wherein at least a portion of the feed vessel pressure casing comprises the hydrogen-selective membrane.

26. A membrane reactor according to any one of claims 21 to 25, wherein the feed vessel is substantially defined by the hydrogen-selective membrane.

27. A membrane reactor according to any one of claims 21 to 26, wherein a surface of the catalyst bed is in contact with, or has a gap of up to about 20000, 15000, or 8000 pm from, a surface of the hydrogen-selective membrane.

28. A membrane reactor according to any one of claims 21 to 27, wherein the feed vessel has an aspect ratio above about 5.

29. A membrane reactor according to any one of claims 21 to 28, wherein the feed vessel has a volume between about 1 litre and about 5000 litres.

30. A membrane reactor according to any one of claims 21 to 29, wherein the feed vessel is a tubular feed vessel comprising a diameter of between about 1 mm and about 150 mm.P5500PC0031. A membrane reactor according to any one of claims 21 to 30 operated with a method according to any one of claims 1 to 20.

32. A method according to any one of claims 1 to 20 comprising providing a membrane reactor according to any one of claims 21 to 30, feeding the pressurised reaction stream into the feed vessel and obtaining the hydrogen product stream in the collection vessel, the reactor providing the catalyst and hydrogen selective membrane.

33. A hydrogen generation station comprising one or more membrane reactors according to any one of claims 21 to 31.

34. A hydrogen generation station according to claim 33, wherein the hydrogen generation station is a hydrogen refuelling station for fuelling hydrogen-powered vehicles, an industrial hydrogen supply, or a distributed energy system.

35. A method for production of pressurised hydrogen, the method comprising:providing a catalyst for conversion of ammonia to hydrogen and nitrogen;contacting a pressurised reaction stream comprising ammonia with the catalyst to convert at least a portion of the ammonia into hydrogen in a reaction zone; and obtaining a hydrogen product stream comprising pressurised hydrogen by selectively driving hydrogen from the reaction zone through a hydrogen-selective membrane under a pressure differential between a reaction-side pressure of the reaction stream and a product-side pressure of the hydrogen product stream.

36. A method according to claim 35, comprising the features of any one of claims 2 to 20.

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