Process, reactor, and system for cracking ammonia

Abstract

A process for cracking ammonia (NH3) to produce hydrogen (H2), comprising feeding an ammonia gas input stream 4 to an ammonia cracking reactor 2 to crack the ammonia gas 4 to generate a hydrogen containing gas stream 8, wherein the cracking reactor 2 comprises one or more reaction tubes 6 containing ammonia cracking catalyst and one or more burners 12 for combusting a mixture of an oxidant-containing gas 18 and a fuel 10 in a fuel combustion zone 14 surrounding the one or more reaction tubes 6 to provide heat energy to support the cracking of ammonia, wherein the oxidant-containing gas 18 is pre-heated to at least 300°C prior to being fed to the one or more burners 12. Further defined are an ammonia cracking reactor for implementing the process, and a system comprising the reactor and a purification unit, wherein the purification unit is configured to generate a purified hydrogen stream and a waste gas stream which is directed to the combustion zone of the ammonia cracking reactor to at least partially fuel the reactor. The oxidant-containing gas may be air, oxygen-enriched air or oxygen, and may be pre-heated by a heat-exchanger within a flue duct of the reactor.

Description

Field The present specification relates to a process, a reactor, and a system for producing hydrogen gas by catalytically cracking ammonia. Background There is renewed interest in using hydrogen as a green, carbon free, fuel in a variety of industrial settings. Hydrogen may be combusted to produce heat energy or electricity. Alternatively, hydrogen may be used to produce electrochemical energy in, for example, a fuel cell. Ammonia has received interest as a possible compound to enable the storage and transport of hydrogen. Liquid ammonia has a higher hydrogen density than liquid hydrogen and may be transported using existing infrastructure which is already in use for this purpose, such as that used for the transportation of ammonia in the agrochemical fertiliser industry. Once the liquid ammonia has been transported it may be combusted directly or converted to hydrogen by the process of cracking. The catalytic cracking of ammonia into hydrogen and nitrogen has been known for many years. The reaction may be depicted as follows: 2NH3^N2 + 3H2 The ammonia cracking reaction is endothermic and may usefully be achieved by passing ammonia over a suitable catalyst in heated catalyst-containing reaction tubes disposed in a furnace. Such furnaces are known, for example, for the steam reforming of natural gas or naphtha feedstocks. In industrial processes used for the catalytic cracking of ammonia, the gas produced by the ammonia cracking reaction is purified to produce a purified hydrogen stream and a waste gas stream. There remains a need for improved processes for the catalytic cracking of ammonia. Summary One issue to consider for an ammonia cracking process is safety. NH3 slip in the flue gas following combustion can lead to ammonium nitrate formation, a compound which can cause a detonation risk. Another issue to consider for an ammonia cracking process is environmental emissions such as N2O. In this regard, N2O emissions are generated in the flue gas following combustion which can require costly N2O abatement solutions to be installed to prevent this greenhouse gas from emitting into the atmosphere. Another issue to consider for an ammonia cracking process is a desire to increase hydrogen production for a given quantity of ammonia input to the process. Yet another issue to consider for an ammonia cracking process is a desire to decrease capital and / or operating costs. In accordance with the present specifications, the aforementioned problems have been addressed by providing a process for cracking ammonia to produce hydrogen, the process comprising: feeding an ammonia gas input stream to an ammonia cracking reactor to crack the ammonia gas input stream to generate a hydrogen containing gas stream, wherein the ammonia cracking reactor comprises one or more reaction tubes containing ammonia cracking catalyst and one or more burners for combusting a mixture of an oxidant-containing gas (e.g., air, oxygen enriched air, or oxygen) and a fuel in a fuel combustion zone surrounding the one or more reaction tubes to provide heat energy to support the cracking of ammonia in the one or more reaction tubes, and wherein the oxidant-containing gas is pre-heated to a temperature of at least 300°C (optionally at least 325°C, 350°C, 375°C, 400°C, 450°C, or 500°C) prior to being fed to the one or more burners. A key feature of the method is pre-heating of the oxidant-containing gas in an ammonia cracking process. The following advantages are found from raising the oxidant-containing gas pre-heat temperature in an ammonia cracking process: • There is a significant reduction in primary N2O emissions generated in the flue gas following combustion which results in lower N2O emissions and / or a smaller / lower cost N2O abatement solution being required. • There is a significant reduction in levels of NH3 slip in the flue gas following combustion which reduces the likelihood of ammonium nitrate formation, a compound which can cause a detonation risk. • There is a reduction in the proportion of ammonia, cracked gas, or hydrogen product that is required to be diverted to fuel. This feature, along with the reduction in ammonia slip from the ammonia cracking reactor, results in an increase in hydrogen production for a given quantity of ammonia. The present specification also provides an ammonia cracking reactor for implementing the process as described herein, the ammonia cracking reactor comprising: one or more reaction tubes containing ammonia cracking catalyst; one or more burners for combusting a mixture of an oxidant-containing gas and a fuel in a fuel combustion zone surrounding the one or more reaction tubes to provide heat energy to support the cracking of ammonia in the one or more reaction tubes; a flue duct, downstream of the fuel combustion zone, through which combustion gases are passed; and one or more heat exchangers within the flue duct configured to pre-heat the oxidantcontaining gas to a temperature of at least 300°C, 325°C, 350°C, 375°C, 400°C, 450°C, or 500°C prior to being fed to the one or more burners. The oxidant-containing gas can be pre-heated by a first heat exchanger within the flue duct of the ammonia cracking reactor and may be further pre-heated by at least one further heat exchanger provided within the flue duct of the ammonia cracking reactor. The at least one further heat exchanger can be provided within the flue duct of the ammonia cracking reactor at a location closer to a furnace exit of the ammonia cracking reactor than the first heat exchanger in order to ensure higher pre-heating temperatures are achieved. In this regard, combustion air (oxidant-containing gas) is heated in a combustion air pre-heater, which may be located as the final heat exchanger within the flue gas duct of the ammonia cracking flowsheet. For a single air-preheater, the upper temperature limit can be in the region of 380°C before the temperature approach across the heat exchanger is too small. To further raise the pre-heat temperature of the combustion air, a second combustion air preheater can be installed in the duct closer to the exit from the cracker furnace. This second pre-heater can make use of higher flue gas temperatures nearer the exit of the cracker furnace to further raise the temperature of the combustion air. The present specification also provides a system for the catalytic cracking of ammonia to produce hydrogen, the system comprising: an ammonia cracking reactor as described herein to crack an ammonia gas input stream to generate a hydrogen containing gas stream; and a purification unit to increase the hydrogen content of the hydrogen containing gas stream, wherein the purification unit is configured to generate a purified hydrogen gas stream and a waste gas stream, and wherein the system is configured to direct the waste gas stream from the purification unit to the combustion zone of the ammonia cracking reactor to at least partially fuel the ammonia cracking reactor. Accordingly, the process may comprise the step of purifying the hydrogen containing gas stream from the ammonia cracking reactor using a purification unit to increase the hydrogen content of the hydrogen containing gas stream, wherein the purification unit generates a purified hydrogen gas stream and a waste gas stream, and the waste gas stream from the purification unit is directed to the combustion zone of the ammonia cracking reactor to at least partially fuel the main ammonia cracking reactor. In this regard, ammonia cracking is an endothermic reaction and requires a significant addition of energy to maintain the reaction temperature, typically in the range of 500 - 800°C. A typical ammonia cracking flowsheet sees the decomposition of the ammonia into hydrogen and nitrogen, followed by a separation stage. Hydrogen is produced at the required purity levels, and a tail gas containing N2, unrecovered H2, and unreacted ammonia is also produced. This tail gas or waste gas stream can be used as fuel for the cracking reactor, undergoing combustion to provide energy to maintain the reaction temperature for a portion of the ammonia. However, there may typically be insufficient energy within this tail gas fuel to provide the energy to crack all the ammonia in the feed, and top-up fuel, such as source ammonia gas, cracked gas, or hydrogen product may be required. In this case, the mixed fuel is fed into the combustion side of the fired ammonia cracker, as is a stream of combustion air, and the combustion of ammonia and hydrogen within the mixed fuel stream produces heat which drives the endothermic reaction and raises the temperature of the process gas to the required exit temperature (e.g., around 700°C). By pre-heating the oxidant-containing gas used by the burners, less ammonia and / or hydrogen is required to be added to the tail gas fuel mixture thus increasing the amount of hydrogen product for a given quantity of ammonia. Advantageously, using the pre-heated oxidant-containing gas, most of the fuel (at least by volume) is provided by the waste gas stream from the purification unit (e.g., at least 50%, 60%, 70%, 80%, 90%, 95%, or 100% by volume). Furthermore, there is reduced requirement to add ammonia from the source ammonia input to the system. For example, the fuel fed to the one or more burners may have no more than 50 mol%, 40 mol%, 30 mol%, or 20 mol% of ammonia from the ammonia gas input stream prior to the ammonia cracking reactor. Further still, advantageously, the present methodology reduces the requirement to utilized hydrogen product to fuel the ammonia cracking reactor. For example, the fuel fed to the one or more burners may have: no more than 50 mol%, 40 mol%, 30 mol%, or 20 mol% H2; at least 0 mol %, 5 mol%, 10 mol%, or 15 mol% H2; or a H2 content within a range defined by any combination of the aforementioned upper and lower limits, e.g., in a range 15 to 20 mol % H2. Advantageously, a ratio of oxidant-containing gas flow rate to fuel flow rate (by volume) provided to the one or more burners lies in a range 1: 0.60 to 1: 0.70, optionally in a range 1: 0.62 to 1: 0.70, 1: 0.65 to 1 : 0.70, or 1: 0.68 to 1 : 0.70. Oxidant-containing gas flow rates are based on a standard air composition. A particular preferred composition is a ratio of oxidant-containing gas (air) flow rate to fuel flow rate of 1: 0.693. In light of the above, it will be appreciated that the process, reactor, and system of the present specification reduces emissions, improves safety, increases hydrogen productions yields, and can decrease costs. Brief Description of the Drawings For a better understanding of the present invention and to show how the same may be carried into effect, certain embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 shows a schematic diagram of an ammonia cracking reactor; Figure 2 shows a schematic diagram of an ammonia cracking reactor with pre-heating of oxidantcontaining gas fed to the burners of the ammonia cracking reactor; Figure 3 shows a schematic diagram of an ammonia cracking reactor with more than one heat exchanger for pre-heating of oxidant-containing gas fed to the burners of the ammonia cracking reactor; and Figure 4 shows a schematic diagram of an ammonia cracking reactor system with a hydrogen purification unit producing a purified hydrogen gas stream and a waste gas stream, the waste gas stream being recycled and used as combustion fuel in the ammonia cracking reactor with the preheated oxidant-containing gas. In all figures, like reference numerals are used for like parts. A list of the references is provided below: Reference Item 2 Ammonia Cracking Reactor 4 NH3Gas 6 Catalyst Containing Reaction Tubes 8 Cracked Gas 10 Fuel 12 Gas Burners 14 Combustion Zone 16, 16a, 16b Flue Gas Duct Heat Exchangers 18 Oxidant-containing gas (e.g., air, oxygen enriched air, or oxygen) 20 Pre-heated oxidant-containing gas 22 Purifier (e.g., Pressure Swing Adsorption Unit) 24 Purified Hydrogen Gas Stream 26 Waste Gas Stream (e.g., off-gas waste <20% Hz) 28 Waste Gas Stream Fuel Duct Detailed Description Figure 1 shows an example of a fired ammonia cracking reactor 2. Fired ammonia cracking reactors 2 are known and may comprise a fuel combustion zone 14 having a radiant section comprising one or more burners 12 to which one or more fuel streams 10 and an oxidant-containing feed gas, such as air, oxygen enriched air, or oxygen, are fed. The radiant section may comprise one or more catalyst containing reaction tubes 6 through which the ammonia stream 4 is passed and cracked to produce a hydrogen containing cracked gas stream 8. Combustion of one or more fuel streams 10 in the one or more burners 12 of the fuel combustion zone, creates heat energy (e.g., radiant heat) for heating the one or more catalyst containing reaction tubes 6. There may be tens or hundreds of catalystcontaining reaction tubes 6 in the radiant section. If desired, downstream of the radiant section, hot flue gas from the combustion of the one or more fuel streams may be used for steam generation, superheating, or process heating via a heat exchanger 16. Figure 2 shows a schematic diagram of an ammonia cracking reactor with pre-heating of oxidantcontaining gas for the burners. In many respects the ammonia cracking reactor is similar to that shown in Figure 1. Ammonia input gas 4 is provided into reaction tubes 6 which have ammonia cracking catalyst disposed therein to crack the ammonia and produce a hydrogen containing cracked gas 8. Fuel gas 10 is provided to burners 12 for combustion of the fuel gas in a combustion zone 14 surrounding the reaction tubes 6. In this configuration, flue gas from the combustion is used to preheat oxidant-containing gas 18 via one or more heat exchangers 16. The pre-heated oxidantcontaining gas 20 is then fed to the burners 12 with the fuel gas 10. Figure 3 shows a variant of the configuration of Figure 2 in which more than one heat exchanger 16a, 16b is provided in the flue duct of the ammonia cracking reactor to achieve higher pre-heat temperatures for the oxidant-containing gas. One or more of the heat exchangers can be provided closer to the exit of the reactor furnace to achieve higher pre-heat temperatures for the oxidantcontaining gas. Figure 4 shows another variant in which the cracked gas 8 can be passed to a purifier 22 such as a pressure swing adsorption unit. The purifier 22 generates a purified hydrogen gas stream 24 and a waste gas stream 26 which comprises a mixture of nitrogen and residual ammonia and nitrogen (e.g., off-gas waste <20% Hz). The waste gas 26 can be recycled via a waste gas stream fuel duct 28 and used as fuel 10 for combustion in the combustion zone of the reactor. Advantageously, a majority (e.g., at least 50%, 60%, 70%, 80%, 90%, 95%, or 100%) of the fuel (by volume) fed to the burners 12 is provided by the recycled waste gas 26. As described in the summary section, the following advantages are found from raising the air pre-heat temperature in an ammonia cracking process: • There is a significant reduction in primary N2O emissions generated in the flue gas following combustion which results in lower N2O emissions and / or a smaller / lower cost N2O abatement solution being required. • There is a significant reduction in levels of NH3 slip in the flue gas following combustion which reduces the likelihood of ammonium nitrate formation, a compound which can cause detonation risk. • There is a reduction in the proportion of ammonia or cracked gas that is required to be diverted to fuel. This feature, along with the reduction in ammonia slip from the ammonia cracking reactor, results in an increase in hydrogen production for a given quantity of ammonia. While a minimum oxidant-containing gas pre-heat temperature of 300°C is required, there are several advantages to increasing the pre-heat temperature to a minimum of 350°C, and potentially up to 500°C depending on the chosen materials of construction. It is noted that increasing the combustion air temperature may have a disadvantage of reducing the steam superheating capacity within the flue duct of the ammonia cracking reactor, and as a result reduce the electrical power generation within the flowsheet. However, depending on the requirements from the flowsheet it may be advantageous to increase hydrogen recovery and minimise emissions at the expense of an increase in net import of electricity (required to power rotating equipment). Furthermore, there is a slight increase in NOx emissions associated with a higher air combustion temperature. However, SCR (selective catalytic reduction) catalysts are a well-known technology for handling any slight increase in NOx to ensure that external emissions are not unduly affected. The ammonia cracking catalyst in the catalyst containing reaction tubes may be any ammonia cracking catalyst. For instance, nickel catalysts and / or ruthenium catalysts may be used. Preferred catalysts are nickel catalysts. The catalyst may comprise 3 to 30% by weight nickel, preferably 8 to 20% by weight nickel, expressed as NiO, on a suitable refractory support, such as alumina or a metal aluminate. The catalyst may be in the form of pelleted shaped units, which may comprise one or more through holes, or may be provided as a wash coat on a structured metal or ceramic catalyst. A particularly preferred catalyst is KATALCOR™ 27-200MQ available from Johnson Matthey PLC, which comprises 16 wt% nickel, expressed as NiO, on a cylindrical pellet formed from a high surface area calcium aluminate support. The input ammonia stream may be heated prior to being supplied to the fired ammonia cracking reactor. Accordingly, the process of the invention may comprise the step of heating the input ammonia stream. The input ammonia stream may be heated to a temperature of greater than 350 °C, greater than 400 °C, greater than 450 °C, greater than 500 °C, or greater than 550 °C. The input ammonia stream may be heated to a temperature of less than 1000 °C, less than 950 °C, less than 850 °C, less than 750 °C, or less than 700 °C. The input ammonia stream may be heated to a temperature of from 350 °C to 1000 °C, from 400 °C to 950 °C, from 450 °C to 850 °C, or from 500 °C to 750 °C, such as from 550 °C to 700 °C. The temperature of the hydrogen containing stream exiting the one or more catalyst containing reaction tubeswill influence the equilibrium position of the cracking reaction, and may be in the range of 500 to 950°C. Where nickel catalysts are used in the one or more catalyst containing reaction tubes, the temperature of the hydrogen containing stream exiting the one or more catalyst containing reaction tubes may preferably be greater than about 700°C. The pressure inlet to the one or more catalyst containing reaction tubes will be set by the flowsheet design and may be in the range 1 to 100 bar absolute, preferably 10 to 90 bar absolute, such as 31 to 51 bar absolute. The hydrogen containing stream from the reactor can be fed to one or more purification units to increase the hydrogen content of the hydrogen containing stream to produce an enriched hydrogen stream and a tail gas stream. An example of a purification unit is a pressure swing adsorption (PSA) unit, to increase the H2 content by separating H2 from the other components. The tail gas stream can be recycled and combusted as fuel in the combustion zone of the main reactor. It may be preferred that prior to feeding the hydrogen containing stream to the one or more purification units that the hydrogen containing streams are fed to a steam generation unit and / or a heat recovery zone. As will be understood by the skilled person the steam generation unit and / or the heat recovery zone may be used to recover low or medium grade heat. The enriched hydrogen stream after purification may comprise 70 mol% or more H2,75 mol% or more H2, 80 mol% or more H2,85 mol% H2 or more, or 90 mol% H2 or more. The enriched hydrogen stream may comprise up to 100 mol% or less H2. For example, the enriched hydrogen stream may comprise from 70 mol% to 100 mol% H2, from 75 mol% to 100 mol% H2, from 80 mol% to 100 mol% H2, from 85 mol% to 100 mol% H2, or from 90 mol% to 100 mol% H2. Preferably, the enriched hydrogen stream may comprise greater than 90 mol% H2, greater than 95 mol% H2, greater than 98 mol% H2, or greater than 99 mol% H2. More preferably, the enriched hydrogen stream may comprise greater than 99.9% mol% H2, greater than 99.95 mol% H2, or about 100 mol% H2. Most preferably, the enriched hydrogen containing stream may comprise greater than 99.95 mol% H2 or about 100 mol% H2. Case Study The following case study reports the pre-abatement NzO emissions and NH3 slip in flue gas, along with NHj addition fuel requirements, for an ammonia cracking flowsheet where the fuel is PSA tail gas with additional NH3 and the combustion air pre-heat temperature is set to 250, 300 and 350°C. For an ammonia cracker processing 42.2 TPH ammonia through the cracker, with the fired cracker using PSA tail gas and a variable NH3 fuel (which was set to achieve an ammonia slip of 1.31 mol% in all cases), the combustion air pre-heat temperature had the following impact on NH3 fuel requirements, NH3 slip in flue gas, and hydrogen recovery (emissions are reported on a dry basis, with a reference O2 of 3%): Air Pre-Heat (°C) NH3 as Fuel (TPH) NH3 slip in flue gas (ppmv) Hydrogen Recovery (%) 250 7.57 154 74.33 300 7.21 <1 74.87 350 6.86 <1 75.40 Additionally, there was a reduction in N2O emissions at higher temperatures as shown below (emissions are reported on a dry basis, with a reference O2 of 3%): Air Pre-Heat (°C) Primary N2O emissions (ppmv) 250 185 300 82 350 59 Accordingly, it has thus been found that a minimum pre-heat temperature of 300°C is required for the combustion air to ensure full fuel conversion and to generate lower N2O emissions. As N2O is a greenhouse gas, lower emissions ensure a greener process. NH3 slip is also reduced which reduces the likelihood of ammonium nitrate formation, a compound which can cause detonation risk, thus improving the safety of the system. Furthermore, there is a reduction in the proportion of ammonia gas that is required to be diverted to fuel. This feature, along with the reduction in ammonia slip from the ammonia cracking reactor, results in an increased hydrogen recovery of the process. While this invention has been particularly shown and described with reference to certain examples, it will be understood to those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A process for cracking ammonia to produce hydrogen, the process comprising:feeding an ammonia gas input stream to an ammonia cracking reactor to crack the ammonia gas input stream to generate a hydrogen containing gas stream,wherein the ammonia cracking reactor comprises one or more reaction tubes containing ammonia cracking catalyst and one or more burners for combusting a mixture of an oxidant-containing gas and a fuel in a fuel combustion zone surrounding the one or more reaction tubes to provide heat energy to support the cracking of ammonia in the one or more reaction tubes,wherein the oxidant-containing gas is pre-heated to a temperature of at least 300°C prior to being fed to the one or more burners.

2. A process according to claim 1,wherein the oxidant-containing gas is pre-heated to a temperature of at least 325°C, 350°C, 375°C, 400°C, 450°C, or 500°C prior to being fed to the one or more burners.

3. A process according to claim 1 or 2,wherein the oxidant-containing gas is air, oxygen enriched air, or oxygen.

4. A process according to any preceding claim,wherein the oxidant-containing gas is pre-heated by a first heat exchanger within a flue duct of the ammonia cracking reactor.

5. A process according to claim 4,wherein the oxidant-containing gas is further pre-heated by at least one further heat exchanger provided within the flue duct of the ammonia cracking reactor.

6. A process according to claim 5,wherein the at least one further heat exchanger is provided within the flue duct of the ammonia cracking reactor at a location closer to a furnace exit of the ammonia cracking reactor than the first heat exchanger.

7. A process according to any preceding claim,further comprising the step of purifying the hydrogen containing gas stream from the ammonia cracking reactor using a purification unit to increase the hydrogen content of the hydrogen containing gas stream,wherein the purification unit generates a purified hydrogen gas stream and a waste gas stream, and the waste gas stream from the purification unit is directed to the combustion zone of the ammonia cracking reactor to at least partially fuel the main ammonia cracking reactor.

8. A process according to claim 7,wherein at least 50%, 60%, 70%, 80%, 90%, 95%, or 100% by volume of the fuel fed to the one or more burners is provided by the waste gas stream from the purification unit.

9. A process according to any preceding claim,wherein the fuel fed to the one or more burners has no more than 50 mol%, 40 mol%, 30 mol%, or 20 mol% H2.

10. A process according to any preceding claim,wherein the fuel fed to the one or more burners has no more than 50 mol%, 40 mol%, 30 mol%, or 20 mol% of ammonia from the ammonia gas input stream prior to the ammonia cracking reactor.

11. A process according to any preceding claim,wherein a flow rate ratio of oxidant-containing gas flow rate to fuel flow rate provided to the one or more burners lies in a range 1: 0.60 to 1: 0.70, optionally in a range 1: 0.62 to 1: 0.70,1: 0.65 to 1: 0.70, or 1 : 0.68 to 1 : 0.70.

12. An ammonia cracking reactor for implementing the process according to any preceding claim, the ammonia cracking reactor comprising:one or more reaction tubes containing ammonia cracking catalyst;one or more burners for combusting a mixture of an oxidant-containing gas and a fuel in a fuel combustion zone surrounding the one or more reaction tubes to provide heat energy to support the cracking of ammonia in the one or more reaction tubes;a flue duct, downstream of the fuel combustion zone, through which combustion gases are passed; andone or more heat exchangers within the flue duct configured to pre-heat the oxidantcontaining gas to a temperature of at least 300°C, 325°C, 350°C, 375°C, 400°C, 450°C, or 500°C prior to being fed to the one or more burners.

13. A system for the catalytic cracking of ammonia to produce hydrogen, the system comprising:an ammonia cracking reactor according to claim 12 to crack an ammonia gas input stream to generate a hydrogen containing gas stream; anda purification unit to increase the hydrogen content of the hydrogen containing gas stream,wherein the purification unit is configured to generate a purified hydrogen gas stream and a waste gas stream, and wherein the system is configured to direct the waste gas stream from the purification unit to the combustion zone of the ammonia cracking reactor to at least partially fuel the ammonia cracking reactor.Application No: GB2313146.9Examiner:Dr Danielle MerrikinClaims searched: 1-13Date of search: 29 February 2024Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X 1-13 WO 2022 / 189560 Al (TOPSOE AS); See whole document, in particular page 3 lines 3-17, page 7 lines 28-34, page 10 lines 31-34, page 11 lines 1-2, page 13 lines 18-25, page 14 lines 1-5, page 19 lines 31-34 and page 20 lines 1-7. X 1-13 EP 4201875 Al (AIR LIQUIDE); See whole document, in particular paragraphs [0008], [0013], and [0018], X,E 1-4, 7, 10, 12, and 13 GB 2620828 A (JOHNSON MATTHEY PLC); See whole document, in particular page 2 lines 12-26 and 30-31, page 4 lines 22-31, page 6 lines 35-37, page 7 lines 15-16, page 8 lines 17-19, page 9 lines 1-13, page 10 lines 8-17, and page 13 lines 4-6, and Claims 5, 7, 8, and 14. X,E 1-4, 7, 12, and 13 WO 2023 / 245201 A2 (KELLOGG BROWN &ROOT LLC); See whole document, in particular paragraphs [0009], [0017], [0034]-[0036], and [0074] v A 1-13 WO 2022 / 265649 Al (AIR PROD &CHEM); See whole document, in particular paragraphs [0015], [0022], [0024], [0030], [0059], and [0061]Categories:X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if P Document published on or after the declared priority date but combined with one or more other documents of same category. before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:International Classification:Subclass Subgroup Valid From C01B 0003 / 04 01 / 01 / 2006 BOU 0019 / 24 01 / 01 / 2006 C01B 0003 / 50 01 / 01 / 2006

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