Cleaning of fuel gases containing CO2

Description

1 / 17 Cleaning of fuel gases containing CO2 TECHNICAL FIELD

[0001] The present invention relates to a process for cleaning a CO2-rich gas feed, in particular for removing sulfur-containing impurities and, optionally, oxygen (O2). BACKGROUND

[0002] Carbon dioxide (CO2) is commercially available in different grades. Typically, food-grade or beverage-grade CO2 has a purity of 99.9%. However, for processes involving the catalytic conversion of CO2 into other chemicals (e.g., energy conversion into X), impurities such as sulfur-containing compounds in the CO2 stream can contaminate the synthesis catalyst, even when present at concentrations of 0.00001% (100 ppbV) or even lower. Oxygen (O2) will rarely be a contaminant to the catalyst, but its ability to oxidize catalyst materials can lead to structural damage in the catalyst, resulting in mechanical or catalytic degradation if present at higher concentrations, for example, greater than 100 ppm.

[0003] Despite the high purity of certain CO2 sources, it has been found that further purification is necessary to avoid catalyst contamination or downstream synthesis catalyst degradation.

[0004] Sulfur compounds are well known as contaminants for catalysts, reacting with the active material in catalysts and rendering them catalytically inactive. For some catalysts, oxygen (O2) is also a critical substance that leads to catalyst degradation, and for example, the Cu-based methanol catalyst is prone to oxidation by oxygen and therefore high concentrations of oxygen present in CO2 feed gases. Petition 870250087370, dated 09 / 26 / 2025, page 8 / 40 2 / 17 (or H2) for a methanol plant needs to be removed at a position upstream of the methanol catalyst.

[0005] Catalyst / absorbent systems developed to remove sulfur impurities from CO2 have also proven sensitive to relatively high oxygen concentrations, and a solution has been developed to remove O2 from CO2 gas before it enters the sulfur removal process.

[0006] Systems and processes for purifying CO2 streams are known, for example, EP2457636, CN112999843, US2007028764, US200702877, US2022333015 and CN112957872. SUMMARY

[0007] The present inventors have discovered that sulfur cleaning of CO2 feeds is necessary and can be carried out after the addition of 2% H2 via adsorption onto a metal-promoted protective material, to such an extent that the CO2 stream subsequently contains <10 ppbV of sulfur. It has also been discovered that any oxygen in the CO2 feed can influence the sulfur capacity and mechanical integrity of a protective material.

[0008] Thus, in a first aspect, the present invention relates to a process for cleaning a CO2-rich gas feed, said CO2-rich gas feed comprising at least 80% by weight of CO2 and one or more sulfur-containing impurities; wherein said process comprises the step of: - Passing a CO2-rich gas feed along with a hydrogen-rich feed over a shielding material and adsorbing one or more sulfur-containing compounds onto said shielding material, in order to provide a clean CO2-rich gas stream.

[0009] A process for the production of a synthesis gas stream is also provided, wherein the said process comprises Petition 870250087370, dated 09 / 26 / 2025, page 9 / 40 3 / 17 completes the process described above and also includes: - to provide at least a portion of the aforementioned CO2-rich gas stream cleaned up from the process described above; - To provide a second hydrogen-rich feed, optionally obtained from the water electrolysis process in one or more electrolysis units; - react the aforementioned portion of the clean CO2-rich gas stream with the second hydrogen-rich feed, to provide at least one synthesis gas stream.

[0010] A process for producing a synthetic fuel stream is also provided, said process comprising the process described above and further comprising the step of converting said at least one synthesis gas stream into at least one synthetic fuel stream, preferably a MeOH (methanol) stream, a DME (dimethyl ether) stream or a synthetic fuel stream, wherein the synthetic fuel may be aviation fuel, gasoline, diesel or similar.

[0011] Additional aspects are presented in the following descriptive text, figures and claims. CAPTIONS

[0012] Figure 1 shows a simple layout of one embodiment of the invention's process.

[0013] Figure 2 shows a layout for the production of a synthesis gas stream.

[0014] Figure 3 shows another layout of the CO2 gas purification process.

[0015] Figure 4 shows the data for Example II. DETAILED DESCRIPTION

[0016] Unless otherwise indicated, any gas content percentages are in %, ppm (parts per million) or ppb (parts per billion). Petition 870250087370, dated 09 / 26 / 2025, page 10 / 40 4 / 17 (100g) by volume. All feeds are preheated as needed. Unless otherwise indicated, concentrations are given on a dry basis, i.e., without taking into account the water present.

[0017] A clean CO2 stream is defined as the output stream of the CO2 cleaning process in which at least 95% of the combined sulfur-containing impurities in the feed are removed or the sum of the sulfur-containing impurities in the clean CO2 stream is less than 500 ppb (parts per billion by volume), preferably less than 100 ppb and, most preferably, less than 50 ppb.

[0018] The sum of sulfur contained in the clean CO2 stream should be understood as sulfur equivalents, that is, 100 ppb of SO2 corresponds to 100 ppb of sulfur, while 100 ppb of CS2 corresponds to 200 ppb of sulfur.

[0019] Similarly, a clean CO2 stream is defined as the output stream of the CO2 cleaning process in which at least 95% of the oxygen from the feed is removed or the O2 concentration in the clean CO2 stream is less than 200 ppm, preferably less than 100 ppm and, most preferably, less than 50 ppm.

[0020] Synthesis gas is used as a reference for a synthesis gas, a gaseous mixture composed of hydrogen, carbon monoxide, carbon dioxide, and typically water, as steam and methane. It is called synthesis gas because it is the feed to a downstream catalytic synthesis, which leads to the desired product. In some applications, the downstream feed from said purification may be mixed with hydrogen and used as synthesis gas, for example, for the synthesis of methanol. In other applications, the clean gas, after mixing with hydrogen and optionally steam, may need to be converted in a reverse water-gas exchange (RWGS) reactor or in a combined RWGS and methanation reactor for Petition 870250087370, dated 09 / 26 / 2025, page 11 / 40 5 / 17 to form the final synthesis gas for the synthesis of the final product.

[0021] The proposed solution ensures that the feed gases for any downstream conversion into synthesis gas and synthesis for chemicals such as MeOH, DME, FT (Fischer Tropsch) synthetic fuels, TIGAS-based gasoline, etc., will not present problems regarding sulfur and oxygen contamination of the downstream synthesis catalyst. This will ensure that the operation can be carried out over time and will allow for a catalyst lifespan as expected with respect to industrial catalysts.

[0022] In a first aspect, therefore, a process is provided for cleaning a gas feed rich in CO2.

[0023] The CO2-rich gas feed supplied to the process appropriately comprises at least 90% by weight of CO2, such as at least 95% by weight of CO2, such as at least 99.0% by weight of CO2, preferably at least 99.5% by weight of CO2, more preferably at least 99.9% by weight of CO2. The CO2-rich gas feed therefore already has high purity prior to the process of the present invention.

[0024] Appropriately, CO2-rich gas feed is derived from a renewable source, such as: - combustion or gasification of lignocellulosic biomass, such as wood products, algae, grasses, forest residues and / or agricultural residues; - combustion or gasification of municipal waste, in particular its organic component, where municipal waste is defined as a raw material containing materials from items discarded by the public, such as mixed municipal waste, as defined in EU Directive 2018 / 2001 (RED II), Annex IX, Part A; - Microbial conversion of renewable nitrogen-rich raw materials, such as manure or sewage sludge; Petition 870250087370, dated 09 / 26 / 2025, page 12 / 40 6 / 17 - fermentation of hydrocarbon-rich (sugar) feed streams such as corn, sugar cane and beet.

[0025] CO2-rich gas feed can also be obtained by direct air capture processes, metallurgical processes, cement production or fossil fuel combustion.

[0026] The CO2 concentration in most of the gas streams mentioned above can typically be too low for further chemical processing, requiring a concentration step to increase the CO2 concentration to the desired value as mentioned above.

[0027] The CO2-rich gas feed comprises one or more sulfur-containing impurities. The one or more sulfur-containing impurities present in the CO2-rich gas feed may be selected from organosulfur compounds such as thiols, sulfides, disulfides, sulfones, sulfoxides and thioketones, CS2, COS, SO3, SO2 and H2S, preferably H2S and SO2, most preferably SO2. The total SO2 content in the CO2-rich gas feed is from 0.1 to 50 ppm SO2, such as from 0.2 to 10 ppm SO2, such as from 1 to 10 ppm SO2, such as from 0.5 to 5 ppm SO2, such as from 1 to 5 ppm SO2.

[0028] CO2-rich gas feed may also contain water. However, high water concentrations may limit / inhibit the absorption of sulfur compounds in the shielding material, and limiting the water concentration will provide more efficient operation of the shielding system. Therefore, it is appropriate that the total H2O content in the combined feed of CO2-rich gas feed and hydrogen-rich feed, after mixing said feeds, is not greater than 10% by volume, preferably not greater than 5.0% by volume, preferably not greater than 1.0% by volume, for example, approximately 0.5% by volume.

[0029] Gas feed rich in CO2 can - in certain cases Petition 870250087370, dated 09 / 26 / 2025, page 13 / 40 7 / 17 - contain oxygen (O2). Oxygen can also contaminate, poison, or lead to the degradation of downstream catalysts and protective material; therefore, any oxygen present in CO2-rich feed gas should be frequently reduced or eliminated. The total O2 content in CO2-rich feed gas is 50 to 10,000 ppm O2, as well as 50 to 5,000 ppm O2, as well as 100 to 3,000 ppm O2.

[0030] Generally, the process comprises the step of: passing a CO2-rich gas feed together with a hydrogen-rich feed over a protective material and adsorbing one or more sulfur-containing compounds onto said protective material, to provide a clean CO2-rich gas stream.

[0031] In one embodiment, the CO2-rich gas feed additionally comprises oxygen (O2), and the process comprises the additional step of: - Passing the CO2-rich gas feed along with said hydrogen-rich feed over an active catalyst in the hydrogenation of oxygen and reducing the oxygen in the CO2 / H2 gas mixture, to provide a first CO2-rich gas stream, before the step of passing the CO2-rich gas feed over the protective material to absorb one or more sulfur-containing impurities, to provide a clean CO2-rich gas stream.

[0032] The CO2-rich feed gas to be cleaned may first be mixed with a hydrogen-rich feed, which acts as a reducing agent for one or more sulfur-containing impurities and, optionally, for oxygen, in the CO2-rich feed gas. The hydrogen-rich feed for the process comprises at least 90% by weight of hydrogen, such as at least 95% by weight of hydrogen, such as at least 98% by weight of Petition 870250087370, dated 09 / 26 / 2025, page 14 / 40 8 / 17 hydrogen.

[0033] In one embodiment, hydrogen is suitably added in such a way that the total H2 content in the combined feed of the CO2-rich gas feed and the hydrogen-rich feed, after mixing said feeds, is from 0.2 to 10% by volume of H2 as well as from 0.5 to 3% by volume of H2. The advantage of this embodiment is that the addition of H2 is controlled, so as to limit undesirable side reactions, for example, the formation of methanol. The addition of hydrogen must always be sufficient to achieve the excess H2 in the product gas exiting the shielding material.

[0034] In one embodiment, hydrogen is suitably added such that the H2O2 molar ratio is greater than 2 in the combined feed of the CO2-rich gas feed and the hydrogen-rich feed, after mixing said feeds, and the clean CO2 exiting the CO2 purification system contains 0.2 to 10% by volume of H2, as well as 0.5 to 3% by volume of H2. The advantage of this embodiment is that the addition of H2 is controlled so as to limit undesirable side reactions, for example, the formation of methanol, while maintaining a sufficient surplus of H2 to ensure a high degree of hydrogenation of any oxygen and sulfur impurities. Furthermore, with this embodiment, the total gas flow is kept to a minimum, thus providing the smallest possible reactor and equipment size.

[0035] In another embodiment of the invention, hydrogen is added to the CO2-rich gas feed in an amount that corresponds to the feed composition for the downstream process for the production of synthesis gas, methanol, synthetic fuels, and other chemicals. As an example, for methanol production, the feed composition for the methanol process will be around 12% w / w H2 and 88% w / w CO2. This corresponds to a ratio Petition 870250087370, dated 09 / 26 / 2025, page 15 / 40 9 / 17 of 3 moles of H2 per mole of CO2. The advantage of this method is that H2 and CO2 can be mixed and, preferably, compressed before cleaning with CO2. The CO2 cleaning process can be located downstream of the final compression stage or between intermediate compression stages, whichever is more suitable in terms of cost, water concentration, risk of carbonate formation in the protective material, and risk of formation of unwanted byproducts such as water and methanol. Another advantage of this method is that any O2 present in the H2-rich feed will also be hydrogenated. The H2 from the water electrolysis can contain varying amounts of O2, depending on the operation of the electrolyzer.

[0036] One or more sulfur-containing compounds adsorbed onto the shielding material are typically selected from COS, SO2, and H2S, preferably SO2. The shielding material is suitably active in absorbing SO2 and H2S, preferably a Cu-Zn-Al shielding material. In the presence of H2, the shielding material is able to catalytically reduce the SO2 present in the H2S-rich CO2 feed, which is adsorbed onto the shielding much more efficiently than SO2. The shielding is also able to react the oxygen content in the CO2 feed stream with hydrogen to form water.

[0037] The process provides a clean CO2-rich gas stream. This clean CO2-rich stream typically comprises: - less than 500 ppb, preferably less than 100 ppb, preferably less than 50 ppb of sulfur and more preferably less than 25 ppb of sulfur, - less than 200 ppmV O2, less than 100 ppmV O2, less than 50 ppmV O2. The protective material used in the invention process is suitably located within a reactor vessel, said reactor vessel being arranged to receive the feed. Petition 870250087370, dated 09 / 26 / 2025, page 16 / 40 10 / 17 of CO2-rich gas and hydrogen-rich feed, optionally in mixture.

[0038] The protective material preferably has a chemical composition of 25 to 60% w / w Cu, 15 to 70% w / w Zn and, optionally, 2 to 10% w / w Al. It may also contain small amounts of K and C. The elements will be found in the reduced or oxidized state.

[0039] The CO2 cleaning process is typically operated in the pressure range of 1 to 100 bar (100 kPa to 10000 kPa), preferably 1 to 50 bar (100 kPa to 5000 kPa), depending on the pressure of the CO2 feed stream and the pressure of the downstream conversion process.

[0040] To provide the best balance between high catalytic / adsorption efficiency and low tendency to carbonate formation and evolution of undesirable side reactions, such as the formation of water and methanol, the CO2 cleaning process is typically operated in the temperature range of 120 to 250°C. A pressure in the range of 1 to 90 bar (100 kPa to 9000 kPa) is also typical.

[0041] In one aspect, more than 95% of one or more sulfur-containing impurities are retained in the protective material or the total concentration of sulfur-containing impurities in the clean CO2-rich gas stream is < 500 ppb, such as < 100 ppb, such as < 50 ppb.

[0042] As noted above, the clean CO2-rich gas stream is sufficiently pure that the contamination of the catalyst from downstream processes is significantly reduced. The invention, therefore, provides a process for the production of a synthesis gas stream, said process comprising the process as described above and which further comprises: - to provide at least a portion of the CO2-rich gas stream as clean from the process described here; Petition 870250087370, dated 09 / 26 / 2025, page 17 / 40 11 / 17 - To provide a second hydrogen-rich feed, optionally obtained from the water electrolysis process in one or more electrolysis units; - react part of the clean CO2-rich gas feed with the second hydrogen-rich feed, to provide at least one synthesis gas stream.

[0043] In this process, the step of reacting part of the clean CO2-rich feed stream with the second hydrogen-rich feed, to provide at least one synthesis gas stream, can be carried out in the presence of an active catalyst in the reverse water-gas shift.

[0044] An integrated process can also occur, in which CO2 cleaning, synthesis gas production, and subsequent downstream syntheses take place. Therefore, a process for producing a synthetic fuel stream is presented, comprising providing at least one synthesis gas stream, as described in this invention, and further comprising the step of converting said at least one synthesis gas stream into at least one synthetic fuel stream, preferably a MeOH stream, a DME stream, or a synthetic fuel stream, preferably wherein said synthetic fuels are aviation fuel, gasoline, or diesel. In one aspect, the process of converting said at least one synthesis gas stream into at least one synthetic fuel stream is a Fisher-Tropsch process, which provides a synthetic fuel stream.In another aspect, the process of converting said at least one synthesis gas stream into at least one synthetic fuel stream is a TIGAS process, which provides a synthetic fuel stream. Specific modalities Petition 870250087370, dated 09 / 26 / 2025, page 18 / 40 12 / 17

[0045] Figure 1 shows a simple layout of one embodiment of the invention's process. A CO2-rich gas feed 1 is mixed with a hydrogen-rich feed 2 and passed over a protective material 10 in the reactor vessel 100. Sulfur-containing compounds are adsorbed onto the protective material 10 and a clean CO2-rich gas stream 50 is released.

[0046] Figure 2 shows a layout for the production of a synthesis gas stream. Reactor vessel 100, CO2-rich feed gas 1, hydrogen-rich feed gas 2, and clean CO2-rich feed gas 50 are as shown in Figure 1. Subsequently, a second hydrogen-rich feed 202 reacts with the clean CO2-rich feed gas 50 in a synthesis gas section 300 to provide at least one synthesis gas stream 301.

[0047] Figure 3 shows one embodiment for the layout of the CO2 gas purification process. The CO2 gas feed 1, comprising O2 and one or more sulfur impurities, is mixed with a quantity of H2-rich gas 2. The mixed gas is sent to a compressor 5, where the pressure is increased. The high-pressure feed gas 6 is then preheated in a heat exchanger 7, and the heated feed gas 9 is sent to the oxygen hydrogenation reactor 11, in which an oxygen hydrogenation catalyst 12 is installed and hydrogenates O2 into H2O. The substantially O2-free CO2 gas stream 17 is then cooled in the heat exchanger 18, such that the feed gas 20 to the sulfur removal reactor 22 reaches the ideal temperature. In the reactor, a protective material 10 is installed, removing sulfur impurities.The gaseous effluent from the sulfur removal reactor 26 is substantially free of oxygen and sulfur impurities and can be further processed into synthesis gas and other products. Petition 870250087370, dated 09 / 26 / 2025, page 19 / 40 13 / 17 EXAMPLES

[0048] Experiments were conducted in a laboratory fixed-bed reactor under isothermal conditions to test the SO2 removal efficiency of the shielding material. The fixed-bed reactor is placed in an electrically heated furnace and heated to the desired operating temperature. Two internal thermocouples measure the inlet and outlet temperatures in the catalytic bed. The furnace is equipped with external thermocouples that control the temperature zones in the furnace. These zones are controlled by readings from internal thermocouples to obtain isothermal reaction conditions in the fixed bed.

[0049] The protective material is placed on the SilcoNert 2000™-lined stainless steel reactor on a grid, and the reactor is aligned to be in the center of the electric furnace. Feed gases are mixed from gas cylinders using mass flow controllers that control the feed of individual gases. These include nitrogen (N2), hydrogen (H2), carbon dioxide (CO2), and 15 or 100 ppmV of sulfur dioxide in methane (SO2 in CH4). Liquid water is supplied via a pump, passing through an evaporator and mixed with the feed gas upstream of the fixed-bed reactor.

[0050] The shielding material used is a coprecipitated shielding material based on Cu / ZnO / alumina. In the individual test, where the shielding material can be separated into several fractions (beds), the total weight of the shielding material and the number of fractions / beds are provided. Each fraction will normally have the same size. The shielding material was ground and sieved before loading into a particle fraction between 600 μm and 1000 μm of the original material size, to achieve an ideal size in the laboratory reactor. Before measuring the removal of SO2 from the CO2 feed gas, the shielding material was reduced by 2% H2 to N2 at 220°C and 3 barg Petition 870250087370, dated 09 / 26 / 2025, page 20 / 40 14 / 17 (300 kPa above local atmospheric pressure).

[0051] Table 1 lists the different tests performed with SO2 in the CO2 feed gas and the output analyses provided are after 200 hours with continuous SO2 dosing. Table 1 Test Load TP Input Composition Output Flow S-GC No. Grams / No. of beds °C Barg H2, % by vol CO2, % by vol H2O, % by vol CH4, % by vol SO2, ppmVv Nl / h SO2 ppbVv 1a 1b 1c 1.0 / 1 220 5 2 0 0 98N2 1.0 50 <100 220 5 70 24 0 7 1.0 51 <100 250 5 70 24 0 7 1.0 51 <100 2 3.0 / 6 220 35 5 88 0 7 1.1 40 <100 3 1.2 / 2 150 5 2.6 90 0 8 1.2 39 <50 4 1.2 / 2 150 7 2.5 89 0 9 1.3 40 <50 5a 5b 1.2 / 2 150 180 7 7 2.5 2.5 88 88 1 1 9 9 1.3 1.3 40 40 60 2 (<50) 6 4.3 / 6 180 7 2.5 88 1 9 1.3 40 6 (<50) 7 5.4 / 7 180 7 2.5 88 1 9 1.3 40 <50 8 5.4 / 7 200 7 2.5 88 1 9 1.3 40 <50 9 5.4 / 7 220 7 2.5 88 1 9 8.8 40 <dl (60h)

[0052] Sulfur feed and outlet gas concentration were measured on the Agilent 7890A GC system equipped with an OI 5380 pulsed flame photometric detector (PFPD). Except in experiments 1 and 2, where an Agilent 8355, S was used with a chemiluminescence detector S, which showed a detection limit above 100 ppbV. For tests No. 5b and 6, the SO2 outlet analyses in Table 1 are estimated based on a sulfur equilibrium, since no SO2 was measured below the SO2 detection limit at 50 ppbV. These results are shown in italics. EXAMPLE (II) Petition 870250087370, dated 09 / 26 / 2025, p. 21 / 40 15 / 17

[0053] The hydrogenation activity of O2 was investigated using the Topsoe's O2Xtract™ hydrogenation catalyst, which comprises Pd and Pt as active components. Hydrogenation activity was measured in a CO2 feed gas containing 2.5% by volume of H2, 2000 ppm of O2, and 0 or 10 ppm of SO2. The catalyst space velocity was 180,000 Nm³ / h / m³ and the temperature ranged from 50 to 350°C. O2 concentrations were measured at the catalyst inlet and outlet with a designated O2-in-CO2 sensor, and O2 conversion by hydrogenation was based on these concentrations. The conversions as a function of catalyst temperature are shown in Figure 4. It is evident that the hydrogenation catalyst is very active in O2 hydrogenation, but also that the catalyst activity is significantly impaired by the presence of SO2.To operate the O2 hydrogenation catalyst without risk of sulfur contamination, the temperature must be above 200°C and preferably closer to or above 250-350°C. EXAMPLE III

[0054] In a process layout as depicted in Figure 3, the CO2 feed gas is mixed with H2 in an amount corresponding to 3 mol of H2 per mol of CO2 after purification of the CO2 gas, making the mixed gas suitable for methanol production in a downstream synthesis plant.

[0055] The CO2 feed gas contains 1% by volume of O2 and 5 ppm of SO2. The CO2 feed gas is mixed with all the H2 feed and compressed to 90 barg (9000 kPa above local atmospheric pressure) and preheated to 185°C in a designated heat exchanger, i.e., heat exchanger 7 in Figure 3 is divided into a feed gas preheater with its own heat source, such as steam or electricity, and a feed / effluent heat exchanger, connecting the cold side of heat exchanger 7 with the ex Petition 870250087370, dated 09 / 26 / 2025, page 22 / 40 16 / 17 hot heat exchanger 18.

[0056] The feed gas at 185°C is then preheated to 300°C in the feed / effluent heat exchanger through heat exchange with the hot gas outlet from the O2 hydrogenation reactor 11. At this temperature, the O2 hydrogenation catalyst is active and is not contaminated by SO2 present in the mixed gas. The O2 hydrogenation reaction is highly exothermic and increases the temperature from 35°C to 335°C, largely compensating for the temperature approach in the feed / effluent heat exchanger. To control the reactor inlet temperature, 15 to 20% of the hot gas from the O2 hydrogenation reactor 17 is diverted from the feed / effluent heat exchanger. The hot gas from the reactor is cooled to 195°C in the feed / effluent heat exchanger and mixed with the diverted hot gas, resulting in a mixing temperature of 220°C for the downstream shielding material 10, well within the ideal temperature range for this process. SO2 is hydrogenated into H2S and captured at the Cu and Zn sites of the protective material.The clean process gas can then be directed to the methanol synthesis plant at a temperature well suited for the methanol converter.

[0057] It is also an option to divert a fraction of the cold gas to the feed / effluent heat exchanger instead of diverting hot gas as described above.

[0058] Typically, feed / effluent heat exchangers are designed with a minimum temperature approach of 10 to 20°C to provide a more economical and efficient heat exchanger. If the CO2 feed contains 0.2% by volume of O2, the adiabatic temperature rise in the O2 hydrogenation reactor in this example will be 7°C, which is lower than normal design rules. The heat exchange surface can be increased to decrease the design temperature approach, or a small support heater can be used. Petition 870250087370, dated 09 / 26 / 2025, page 23 / 40 A 17 / 17 filter is installed to increase the temperature by the required 3 to 13°C. In principle, a quantity of O2 could also be added to the CO2 gas, providing more hydrogenation reaction and therefore released heat, but this option may be very expensive relative to H2 consumption, and the extra water formed will reduce the capacity of the protective material and the conversion efficiency at the downstream methanol plant.

[0059] An alternative solution could also be to perform the hydrogenation of O2 and the removal of sulfur before adding the total amount of hydrogen, i.e., with 3% by volume of H2, which is still sufficient for the hydrogenation of O2 and sulfur. Due to the smaller gas volume, the adiabatic temperature increase is now 21°C and a feed / effluent heat exchanger will operate efficiently without modifications.

[0060] For high O2 concentrations in feed streams rich in CO2 and H2, the water vapor formed can be advantageously removed at a position upstream of the shielding material and the synthesis plant. Water removal can be achieved by cooling the gas mixture to a temperature below the dew point of water to condense and extract a fraction of the water in liquid form.

[0061] The present invention has been described with reference to various aspects and figures. However, a person skilled in the art is able to select and combine various aspects within the scope of the invention, which is defined by the appended claims. All documents referenced herein are incorporated by reference. Petition 870250087370, dated 09 / 26 / 2025, page 24 / 40

Claims

1 / 5 CLAIMS 1. Process for cleaning a CO2-rich gas feed (1), said CO2-rich gas feed (1) comprising at least 80% by weight of CO2 and one or more sulfur-containing impurities; characterized in that said process comprises the step of: - passing the CO2-rich gas feed (1) together with a hydrogen-rich feed (2) over a protective material (10) and adsorbing one or more sulfur-containing compounds onto said protective material (10), to provide a clean CO2-rich gas stream (50).

2. Process according to claim 1, characterized in that the CO2-rich gas feed (1) comprises at least 90% by weight of CO2, such as at least 95.0% by weight of CO2, preferably at least 99% by weight of CO2, more preferably at least 99.5% by weight of CO2.

3. Process according to any of the preceding claims, characterized in that one or more sulfur-containing impurities in said CO2-rich gas feed (1) are selected from organosulfur compounds such as thiols, sulfides, disulfides, sulfones, sulfoxides and thioketones, COS, SO3, SO2 and H2S, preferably H2S and SO2, most preferably SO2.

4. Process according to any of the preceding claims, characterized in that the protective material (10) is active in reducing SO2 to H2S and in adsorbing H2S, preferably being a Cu-Zn-Al protective material.

5. Process according to any of the preceding claims, characterized in that the protective material (10) is located inside a reactor vessel (100), said reactor vessel (100) being arranged to receive said CO2-rich gas feed (1) and said hydrogen-rich feed (2), optionally in mixture.

6. Process according to any of the preceding claims, characterized in that the sulfur-containing impurity is SO2 and the concentration of SO2 in the CO2-rich gas feed (1) is from 0.1 to 50 ppm of SO2, such as from 1 to 10 ppm of SO2, such as from 1 to 5 ppm of SO2.

7. Process according to any of the preceding claims, characterized in that the CO2-rich gas feed (1) and / or the hydrogen-rich feed (2) additionally comprise oxygen (O2), and wherein the process comprises the further step of: - passing the CO2-rich gas feed (1) together with said hydrogen-rich feed (2) over a catalyst (12) active in hydrogenating oxygen and reducing oxygen in the CO2 / H2 gas mixture, to provide a first oxygen-free CO2-rich gas stream, before the step of passing the first oxygen-free CO2-rich gas feed over the protective material (10) to absorb one or more sulfur-containing impurities, to provide a clean CO2-rich gas stream.

8. Process according to any of the preceding claims, characterized in that the total O2 content in the CO2-rich gas feed (1) is from 50 to 10,000 ppm O2, such as from 50 to 5,000 ppm O2, such as from 100 to 3,000 ppm O2.

9. Process according to any of the preceding claims, characterized in that more than 95% of the O2 is converted in the active catalyst in the hydrogenation of oxygen or the total concentration of O2 in the clean CO2-rich gas stream is < 200 ppm, such as < 100 ppm, such as < 50 ppm. Petition 870250087370, dated 09 / 26 / 2025, p. 26 / 40 3 / 5 10. Process according to any of the preceding claims, characterized in that the step of passing the CO2-rich gas feed (1) and the hydrogen-rich feed (2) over an active catalyst in hydrogenation (12) occurs at a temperature in the range of 200 to 400oC and at a pressure in the range of 1 to 90 bar (100 kPa to 9000 kPa).

11. Process according to any of the preceding claims, characterized in that the total H2 content in the combined feed of the CO2-rich gas feed (1) and the hydrogen-rich feed (2), after mixing said feeds and passing the mixture over the optional O2 hydrogenation catalyst and protective material, is from 0.2 to 10% by volume of H2, such as from 0.5 to 3% by volume of H2.

12. Process according to any one of claims 1 to 9, characterized in that the total H2 content in the combined feed of the CO2-rich gas feed (1) and the hydrogen-rich feed (2), after mixing said feeds, corresponds to a ratio of 2 to 5 moles of H2 per mole of CO2.

13. Process according to any of the preceding claims, characterized in that the total H2O content in the combined feed of the CO2-rich gas feed (1) and the hydrogen-rich feed (2), after mixing said feeds, is not greater than 10% by volume, preferably not greater than 5.0% by volume, preferably not greater than 1.0% by volume, for example, approximately 0.5% by volume.

14. Process according to any of the preceding claims, characterized in that the step of passing the CO2-rich gas feed (1) and the hydrogen-rich feed (2) over a protective material (10) occurs at a temperature in the range of 120 to 250oC and at a pressure in the range of 1 to 90 bar (100 Petition 870250087370, dated 09 / 26 / 2025, page 27 / 40 4 / 5 kPa to 9000 kPa).

15. A process according to any of the preceding claims, characterized in that more than 95% of one or more sulfur-containing impurities are retained in the protective material or the total concentration of sulfur-containing impurities in the clean CO2-rich gas stream is < 500 ppb, such as < 100 ppb, such as < 50 ppb.

16. Process according to any of the preceding claims, characterized in that the CO2 feed (1) is derived from a renewable source such as: - combustion or gasification of lignocellulosic biomass, such as wood products, algae, grasses, forest residues and / or agricultural residues; - combustion or gasification of municipal waste, in particular its organic part, municipal waste being defined as a feedstock containing materials from items discarded by the public, such as mixed municipal waste, as defined in EU Directive 2018 / 2001 (RED II), Annex IX, Part A; - microbial conversion of renewable nitrogen-rich feedstock such as manure or sewage sludge; - fermentation of hydrocarbon-rich (sugar) feedstocks such as corn, sugarcane and beet.

17. Process for the production of a synthesis gas stream, characterized in that it comprises the process as defined in any one of claims 1 to 16, and further comprises: - providing at least a portion of said clean CO2-rich gas stream (50) from the process as defined in any one of claims 1 to 16; - optionally providing a second hydrogen-rich feed (202), optionally obtained from the water electrolysis process in one or more electrolysis units; - reacting said portion of the clean CO2-rich feed stream (50) with the second hydrogen-rich feed (202) to provide at least one synthesis gas stream (301).

18. Process according to claim 17, characterized in that the step of reacting said part of the clean CO2-rich feed stream (50) with the second hydrogen-rich feed (202), to provide at least one synthesis gas stream (301), is carried out in the presence of an active catalyst in the reverse water-gas shift.

19. Process for producing a synthetic fuel stream, characterized in that it comprises the process as defined in claim 17 or 18, and further comprising the step of converting said at least one synthesis gas stream (301) into at least one synthetic fuel stream, preferably a MeOH stream, a synthetic fuel stream or a TIGAS stream. Petition 870250087370, dated 09 / 26 / 2025, pp. 29 / 40

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