EP4698305A1

EP4698305A1 - Cleaning of co2 containing feed gases

Info

Publication number: EP4698305A1
Application number: EP24721921.5A
Authority: EP
Inventors: Martin ØSTBERG; Birgitte Staal HAMMERSHØI; Mads Kristian KAARSHOLM; Christian PILEKÆR; Thomas Sandahl Christensen; Morten Thellefsen
Original assignee: Haldor Topsoe AS
Current assignee: Topsoe AS
Priority date: 2023-04-21
Filing date: 2024-04-22
Publication date: 2026-02-25
Also published as: CN120957802A; AU2024259560A1; TW202504673A; KR20260005259A; CL2025003116A1; AR132495A1; WO2024218391A1

Abstract

The present invention relates to a process for cleaning a CO₂-rich gas feed, in particular for removing sulfur-containing impurities, and optionally oxygen.

Description

CLEANING OF CO₂ CONTAINING FEED GASES

TECHNICAL FIELD

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

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 catalytic conversion of CO₂ to other chemical products (e.g . power-to-X), impurities such as sulfur- containing compounds in the CO₂ stream may poison the synthesis catalyst, even when present at concentrations of 0.00001 % (100 ppbV) or even lower. Oxygen (02) will only rarely be an actually poison for the catalyst, but the ability to oxidize the catalyst materials may lead to structural damage to the catalyst leading to mechanical or catalytic degradation if present in higher concentrations, e.g . higher than 100 ppm.

Despite the high purity of certain CO₂ sources, it has been discovered that further purification is required to avoid catalyst poisoning or degradation of downstream synthesis catalyst.

Sulfur compounds are well-known as catalyst poisons, which react with the active material on the catalysts and render them catalytically inactive. For some catalysts, oxygen (02) is also a critical substance leading to catalyst degradation and e.g . the Cu-based methanol catalyst is prone to oxidation by oxygen and therefore high concentrations of oxygen present in the CO2 (or H2) feed gases to a methanol plant have to be removed at a position upstream the methanol catalyst.

The catalyst/absorbent systems developed to remove sulfur impurities from CO2 have been found to be sensitive to relatively high oxygen concentrations as well, and a solution has been developed to remove the 02 from the CO2 gas before the CO2 gas enters the sulfur removal process.

Systems and processes for purification of CO2 streams are known from e.g. EP2457636, CN112999843, US2007028764, US200702877, US2022333015 and CN 112957872. SUMMARY

It has been found by the present inventor(s) that sulfur cleaning of CO2 feeds is necessary and can be carried out after addition of 2% H2 by adsorption on a metal-promoted guard material to such a degree, that the CO2 stream afterwards contains <10 ppbV sulfur. It has also been discovered that any oxygen in the CO2 feed can influence the sulfur capacity and mechanical integrity of a guard material.

So, in a first aspect the present invention relates to a process for cleaning a CCh-rich gas feed, said CC -rich gas feed comprising at least 80 wt% CO2 and one or more sulfur- containing impurities; wherein said process comprises the step of: passing the CCh-rich gas feed together with a hydrogen-rich feed over a guard material, and adsorbing one or more sulfur-containing compounds on said guard material, to provide a cleaned CC -rich gas stream.

A process for production of a syngas stream is also provided, said process comprising the process described above, and further comprising : providing at least a portion of said cleaned CCh-rich gas stream from the process described above; providing a second hydrogen-rich feed, optionally obtained from the process of electrolysis of water in one or more electrolysis unit(s); reacting said portion of the cleaned CCh-rich gas stream with the second hydrogenrich feed, to provide at least one syngas stream.

A process is also provided for production of a synthetic fuel stream, said process comprising the process described above, and further comprising the step of converting said at least one syngas stream to at least one synthetic fuel stream, preferably being a MeOH (methanol) stream, a DME (dimethyl ether) stream, or a synthetic fuel stream, where the synthetic fuel could be aviation fuel, gasoline, diesel or similar.

Additional aspects are presented in the following description text, figures and claims.

LEGENDS

Figure 1 shows a simple layout of one embodiment of the process of the invention. Figure 2 shows a layout for production of a syngas stream.

Figure 3 shows another layout of the CO2 gas purification process

Figure 4 shows the data for Example II

DETAILED DISCLOSURE

Unless otherwise specified, any given percentages for gas content are %, ppm (parts per million) or ppb (parts per billion) by volume. All feeds are preheated as required. Unless specified, the concentrations will be given on dry basis, i.e. without taking any water present into account.

A cleaned CO2 stream is defined as the outlet stream from the CO2 cleaning process, in which minimum 95% of the combined sulfur containing impurities in the feed is removed or the sum of sulfur containing impurities in the clean CO2 stream is lower than 500 ppb (parts per billion by volume), preferably lower than 100 ppb and most preferably lower than 50 ppb.

The sum of sulfur containing in the cleaned CO2 stream should be understood as sulfur- equivalents, i.e. 100 ppb SO2 correspond to 100 ppb sulfur whereas 100 ppb CS2 correspond to 200 ppb sulfur.

Similarly cleaned CO2 stream is defined as the outlet stream from the CO2 cleaning process, in which minimum 95% of the oxygen in the feed is removed or the 02 concentration in the clean CO2 stream is lower than 200 ppm, preferably lower than 100 ppm and most preferably lower than 50 ppm.

Syngas is used as reference for a synthesis gas, a gas mixture comprising hydrogen, carbon monoxide, carbon dioxide and typically water as steam and methane. It is referred to as syngas I synthesis gas because it is the feed for a downstream catalytic synthesis leading to the desired product. In some application the feed downstream the referred purification can be mixed with hydrogen and be used as synthesis gas e.g. for methanol synthesis in other applications, the purified gas may after mixing with hydrogen and optionally steam need conversion in a reverse water gas shift reactor (RWGS) or combined RWGS and methanation reactor to form the final synthesis gas for the synthesis of the final product.

The proposed solution ensures that the feed gases for any downstream conversion to synthesis gas and synthesis for chemicals like MeOH, DME, FT (Fischer Tropsch) synthetic fuels, TIGAS based gasoline etc. will be unproblematic with regard to sulfur and oxygen poisoning of the downstream synthesis catalyst. This will ensure that operation can be made over time and allow catalyst lifetime as expected for industrial catalyst.

In a first aspect, therefore, a process for cleaning a CC -rich gas feed is provided.

The CCh-rich gas feed provided to the process suitably comprises at least 90 wt% CO2, such as at least 95 wt% CO2, such as at least 99.0 wt% CO2, preferably at least 99.5 wt% CO2, more preferably as at least 99.9 wt% CO2. The CC -rich gas feed is thus already of high purity prior to the process of the present invention.

Suitably, the CC -rich gas feed is derived from a renewable source, such as: combustion or gasification of a lignocellulosic biomass such as wood products, algae, grass, forestry waste and/or agricultural residue; combustion or gasification of municipal waste, in particular the organic portion thereof, where the municipal waste is defined as a feedstock containing materials of items discarded by the public, such as mixed municipal waste given in EU Directive 2018/2001 (RED II), Annex IX, part A; microbial conversion of nitrogen-rich renewable feedstock such as manure or sewage sludge; fermentation of hydrocarbon(sugar) rich feed streams such as corn, sugar cane and beets.

The CCh-rich gas feed can also be obtained from direct air capture processes, metallurgical processes, cement production or fossil fuel combustion.

The CO2 concentration in most of the above-mentioned gas streams may typically be too low for further chemical processing and a concentration step is required to increase the CO2 concentration to the desired value as mentioned above.

The CCh-rich gas feed comprises one or more sulfur-containing impurities. The one or more sulfur-containing impurities within the CCh-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 content of SO2 in the CO2-rich gas feed is 0.1-50 ppm SO2, such as 0.2-10 ppm SO2, such as 1-10 ppm SO2, such as 0.5-5 ppm SO2, such as 1-5 ppm SO2. The CCh-rich gas feed may also comprise water. However, high concentrations of water can limit/inhibit the uptake of sulfur compounds on the guard material and limiting the water concentration will provide for a more efficient operation of the guard system. Suitably, therefore, the total content of H2O in the combined feed of the CC -rich gas feed and the hydrogen-rich feed, after mixing of said feeds, is no more than 10 vol%, preferably no more than 5.0 vol%, preferably no more than 1.0 vol%, e.g. approximately 0.5 vol%.

The CC -rich gas feed may - in certain cases - comprise oxygen (O2). Oxygen may also contaminate, poison or lead to degradation of downstream catalysts and guard material, so any oxygen in the CO2-rich gas feed should often be reduced or eliminated. The total content of O2 in the CO2 -rich gas feed, is 50-10,000 ppm O2, such as 50-5,000 ppm O2, such as 100- 3,000 ppmV O2.

Generally, the process comprises the step of: passing the CCh-rich gas feed together with a hydrogen-rich feed over a guard material, and adsorbing one or more sulfur-containing compounds on said guard material, to provide a cleaned CCh-rich gas stream.

In an embodiment, the CCh-rich gas feed additionally comprises oxygen (O2), and the process comprises the additional step of: passing the CCh-rich gas feed together with said hydrogen-rich feed over a catalyst active in hydrogenation of oxygen and reducing the oxygen in the CO2/H2 gas mixture, to provide a first CCh-rich gas stream, prior to the step of passing the CCh-rich gas feed over the guard material for absorbing one or more sulfur-containing impurities, to provide a cleaned CO2 rich gas stream.

The CCh-rich gas feed to be purified may be first mixed with a hydrogen-rich feed, which acts as a reductant for one or more sulfur-containing impurities, and optionally for oxygen, in the CCh-rich gas feed. The hydrogen-rich feed to the process comprises at least 90 wt% hydrogen such as at least 95 wt% hydrogen such as at least 98 wt% hydrogen.

In one embodiment, hydrogen is suitably added such that, the total content of H2 in the combined feed of the CCh-rich gas feed and the hydrogen-rich feed, after mixing of said feeds, is 0.2-10 vol% H2 such as 0.5-3 vol% H2. The advantage of this embodiment is that addition of H2 is controlled, so as to limit undesired side reactions, e.g. methanol formation. The addition of hydrogen should always be sufficient to achieve excess H2 in the product gas exiting the guard material. In one embodiment, hydrogen is suitably added such that, the molar ratio HziOz is greater than 2 in the combined feed of the CCh-rich gas feed and the hydrogen-rich feed, after mixing of said feeds and the purified CO2 leaving the CO2 purification system contains 0.2-10 vol% H2 such as 0.5-3 vol% H2. The advantage of this embodiment is that addition of H2 is controlled, so as to limit undesired side reactions, e.g. methanol formation while still having to sufficient H2 surplus to ensure high degree of hydrogenation of any oxygen and the sulfur impurities. Furthermore, with this embodiment the total gas flow is kept at a minimum, thus providing the smallest possible reactor and equipment size.

In another embodiment of the invention, hydrogen is added to the CC -rich gas feed in an amount corresponding to the feed composition to the downstream process for production of synthesis gas, methanol, synthetic fuels and other chemical products. As an example, for the production of methanol, the feed composition to the methanol process will be around 12 %w/w H2 and 88 %w/w CO2. This corresponds to a ratio of 3 moles H2 per mole of CO2. The advantage of this embodiment is that H2 and CO2 can be mixed and preferably compressed prior to the CO2 cleaning. The CO2 cleaning process can be located downstream the final compression step or between intermediate compression steps, whichever is best suited with regard to cost, water concentration, risk of carbonate formation on the guard material and risk of formation of undesired side products such as water and methanol. Another advantage of this embodiment is that any O2 present in the H2 rich feed will also become hydrogenated. H2 from electrolysis of water can contain varying amounts of O2, depending on the operation of the electrolyser.

The one or more sulfur-containing compounds adsorbed onto the guard material are typically selected from COS, SO2 and H2S, preferably SO2. The guard material is suitably active in absorption of SO2 and H2S, and is preferably a Cu-Zn-AI guard material. In the presence of H2, the guard material is capable of catalytically reducing the SO2 in the CO2 feed rich to H2S, which is much more efficiently adsorbed on the guard than the SO2. The guard is also capable of reacting oxygen content in the CO2 feed stream with hydrogen to form water.

The process provides a cleaned CO2-rich gas stream. This cleaned CO2-rich stream typically comprises: less than 500 ppb, preferably less than 100 ppb, preferably less than 50 ppb sulfur and more preferably less than 25ppb sulfur, less than 200 ppmV O2, less than 100 ppmV O2, less than 50 ppmV C The guard material used in the process of the invention is suitably located within a reactor vessel, said reactor vessel being arranged to receive the CCh-rich gas feed and the hydrogen-rich feed, optionally in admixture. The guard material is preferably having a chemical composition of 25-60 %w/w Cu, 15-70 %w/w Zn, and optionally 2-10 %w/w Al. It may comprise minor amounts of K and C as well. The elements will either be found in a reduced or oxidised state.

The CO2 cleaning process is typically operated in the pressure range 1- 100 bar, preferably 1- 50 bar, depending on the pressure of the CO2 feed stream and the pressure of the downstream conversion process.

To provide the best compromise between high catalytic/adsorption efficiency and low tendency for carbonate formation and evolution of undesired side reactions, such as water and methanol formation, the CO2 cleaning process is typically operated in the 120-250 °C temperature range. A pressure in the interval 1-90 bar is also typical.

In one aspect, more than 95% of the one or more sulfur containing impurities are retained on the guard material or the total concentration of sulfur containing impurities in the cleaned CC -rich gas stream is < 500 ppb, such as < 100 ppb, such as < 50 ppb.

As noted above, the cleaned CC -rich gas stream is sufficiently pure that catalyst poisoning of downstream processes is significantly reduced. The invention therefore provides a process for production of a syngas stream, said process comprising the process as described above, and further comprising : providing at least a portion of said cleaned CCh-rich gas stream from the process described herein; providing a second hydrogen-rich feed, optionally obtained from the process of electrolysis of water in one or more electrolysis unit(s); reacting said portion of the cleaned CCh-rich gas feed with the second hydrogen-rich feed, to provide at least one syngas stream.

In this process, the step of reacting the portion of the cleaned CC -rich stream feed with the second hydrogen-rich feed, to provide at least one syngas stream may be carried out in the presence of a catalyst active in reverse water gas shift.

An integrated process can also take place, in which CO2 cleaning, syngas production and subsequent downstream syntheses occur. Therefore, a process for production of a synthetic fuel stream is provided, said process comprising providing at least one syngas stream, as described herein, and further comprising the step of converting said at least one syngas stream to at least one synthetic fuel stream, preferably being a MeOH stream, a DME stream, or a synthetic fuel stream, preferably wherein said synthetic fuels are aviation fuel, gasoline or diesel fuels. In one aspect, the process of converting said at least one syngas stream to 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 syngas stream to at least one synthetis fuel stream is a TIGAS process, which provides a synthetic fuel stream.

Specific embodiments

Figure 1 shows a simple layout of one embodiment of the process of the invention. A CCh-rich gas feed 1 is mixed with a hydrogen-rich feed 2 and passed over a guard material 10 in reactor vessel 100. Sulfur-containing compounds are adsorbed on the guard material 10 and a cleaned CC -rich gas stream 50 is outputted.

Figure 2 shows a layout for production of a syngas stream. The reactor vessel 100, CCh-rich gas feed 1, hydrogen-rich feed 2 and cleaned CCh-rich gas stream 50 are according to Figure 1. Subsequently, a second hydrogen-rich feed 202 is reacted with the cleaned CCh-rich stream feed 50, in a syngas section 300 to provide at least one syngas stream 301.

In Figure 3 one embodiment for the layout of the CO2 gas purification process is shown. The CO2 gas feed (1) comprising O2 and one or more sulfur-impurities is mixed with an amount of a H2 rich gas (2). The mixed gas is sent to a compressor (5) in which 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 to H2O. The substantially O2 free CO2 gas stream (17) is then cooled in heat exchanger (18) such that the feed gas (20) to the sulfur removal reactor (22) has the optimal temperature. In the reactor a guard material (10) is installed, removing sulfur impurities. The off-gas from the sulfur removal reactor (26) is substantially free of oxygen and sulfur impurities and can be further processed to synthesis gas and other products.

EXAMPLES

Experiments have been carried out in a laboratory fixed bed reactor at isothermal condition to test the SO2 removal efficiency of the guard material. The fixed bed reactor is placed in an electrically-heated oven and heated to the desired operating temperature. Two internal thermocouples measure the inlet and exit temperatures in the catalytic bed. The oven is equipped with external thermocouples controlling the temperature zones in the oven. These zones are controlled by internal thermocouple readings to obtain isothermal reaction condition in the fixed bed. The guard material is placed in the SilcoNert 2000™ coated stainless steel reactor on a grid and the reactor is aligned to be in the center of the electrical oven. Feed gases are mixed from gas cylinders using mass flow controllers controlling feed of the individual gases. These include nitrogen (N2), hydrogen (H2), carbon dioxide (CO2), and 15 or 100 ppmV 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.

The guard material used is a coprecipitated Cu/ZnO/alumina-based guard material. In the individual test, where the guard material can be separated in several fractions (beds), the weight of the total guard material and the number of fractions I beds are given. Each fraction will typically be equally sized. The guard material has been crushed and sieved before loading to a particle fraction between 600 pm to 1000 pm from the original material size to achieve an optimal size in the laboratory reactor. Before measuring SO2 removal from the CO2 feed gas, the guard material was reduced in 2% H2 in N2 at 220°C and 3 barg.

Table 1 lists the different tests carried out with SO2 in the CO2 feed gas and the exit analysis given are after 200 hours with continuous dosing of SO2.

Table 1

The sulfur feed and exit gas concentration were measured on Agilent 7890A GC system equipped with an 01 5380 pulsed flame photometric detector (PFPD). Except experiments 1 and 2, where an Agilent 8355, S with a S Chemiluminescence Detector was used which had a higher detection limit of 100 ppbV. For the test # 5b and 6, SO2 exit analyses in Table 1 are estimated based on a sulfur balance as no SO2 was measured below the detection limit of SO2 at 50 ppbV. These results are shown in italic.

EXAMPLE (II)

The O2 hydrogenation activity was investigated for Topsoe's O2Xtract™ hydrogenation catalyst, comprising Pd and Pt as the active components. The hydrogenation activity was measured in a CO2 feed gas comprising 2.5 vol% H_2i 2,000 ppm O2 and either 0 or 10 ppm SO2. The catalyst space velocity was 180,000 Nm³/h/m³ and the temperature was varied in the range 50-350 °C. O2 concentrations were measured at the inlet and outlet of the catalyst with a dedicated O2 in CO2 sensor and O2 hydrogenation conversion was based on these concentrations. The conversions as a function of catalyst temperature are seen in figure 4. It is evident that the hydrogenation catalyst is very active in O2 hydrogenation, but also that the catalyst activity is significantly hampered by the presence of SO2. To be able to operate the O2 hydrogenation catalyst without risking sulfur poisoning, the temperature should be higher than 200 °C and preferably closer to 250-350 °C or above.

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

The CO2 feed gas contains 1 vol% O2 and 5 ppm SO2. The CO2 feed gas is mixed with the entire H2 feed and compressed to 90 barg and preheated to 185 °C in a dedicated heat exchanger, i.e. heat exchanger 7 in figure 3 is split up in 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 hot end of heat exchanger 18.

The 185 °C feed gas is then preheated to 300 °C in the feed/effluent exchanger by heat exchange with the hot gas from the outlet of O2 hydrogenation reactor 11. At this temperature, the O2 hydrogenation catalyst is active and not poisoned by the SO2 in the mixed gas. The O2 hydrogenation reaction is highly exothermic and increase the temperature by 35 °C to 335 °C, more than compensating for the temperature approach in the feed/effluent heat exchanger. To control the reactor inlet temperature, 15-20 % of the hot gas from the O2 hydrogenation reactor (17) bypasses 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 bypassed hot gas to end up with a mixed temperature of 220 °C to the downstream guard material (10), well within the optimal temperature range for this process. The SO2 become hydrogenated to H2S and captured on the Cu and Zn sites of the guard material. The cleaned process gas can then be directed to the methanol synthesis plant at a temperature well suited for the methanol converter.

It is also an option to bypass a fraction of the cold gas to the feed/effluent heat exchanger instead of the hot gas bypass as described above.

Typically feed/effluent heat exchangers are designed with a minimum temperature approach of 10-20 °C to provide an economical and still efficient heat exchanger. In case the CO2 feed contain 0.2 vol% O2, the adiabatic temperature increase in the O2 hydrogenation reactor in this example with be 7 °C, which is in the lower than the normal design rules. The heat exchange surface can be increased to decrease the design temperature approach, or a small support heater can be installed to increase the temperature by the necessary 3-13 °C. In principle an amount of O2 could also be added to the CO2 gas, providing more hydrogenation reaction and thus heat evolved but that may option be too expensive with regard to H2 consumption, and the extra water formed will reduce the capacity of the guard material and conversion efficiency in the downstream methanol plant. An alternative solution could also be to carry out the O2 hydrogenation and sulfur removal before the addition of the total amount of hydrogen, i.e. with 3 vol% H2 which is still sufficient for the O2 and sulfur hydrogenation. Due to the lower gas volume, the adiabatic temperature increase is now 21 °C and a feed/effluent heat exchanger will work efficiently without modifications.

For high O2 concentrations in the CC -rich and H2-rich feed streams, the formed water vapor may beneficially be removed at a position upstream the guard material and synthesis plant. Water removal can be achieved by cooling the gas mixture to a temperature below the water dew point to condense and withdraw a fraction of the water as liquid. The present invention has been described with reference to a number of aspects and figures. However, the skilled person 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.

Claims

1. A process for cleaning a CC -rich gas feed (1), said CC -rich gas feed (1) comprising at least 80 wt% CO2 and one or more sulfur-containing impurities; wherein said process comprises the step of: passing the CCh-rich gas feed (1) together with a hydrogen-rich feed (2) over a guard material (10), and adsorbing one or more sulfur-containing compounds on said guard material (10), to provide a cleaned CC -rich gas stream (50).

2. The process according to claim 1, wherein the CC -rich gas feed (1) comprises at least 90 wt% CO2, such as at least 95.0 wt% CO2, preferably at least 99 wt% CO2, more preferably as at least 99.5 wt% CO2.

3. The process according to any one of the preceding claims, wherein the one or more sulfur-containing impurities within said CC -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. The process according to any one of the preceding claims, wherein the guard material (10) is active in reduction of SO2 to H2S and adsorption of H2S, and is preferably a Cu-Zn-AI guard material.

5. The process according to any one of the preceding claims, wherein the guard material (10) is located within a reactor vessel (100), said reactor vessel (100) being arranged to receive said CCh-rich gas feed (1) and said hydrogen-rich feed (2), optionally in admixture.

6. The process according to any one of the preceding claims, wherein the sulfur containing impurity is SO2 and the concentration of SO2 in the CCh-rich gas feed (1) is 0.1-50 ppm SO2, such as 1-10 ppm SO2, such as 1-5 ppm SO2.

7. The process according to any one of the preceding claims, wherein the CC -rich gas feed (1), and/or hydrogen-rich feed (2), additionally comprise(s) oxygen (O2), and wherein the process comprises the additional step of: passing the CCh-rich gas feed (1) together with said hydrogen-rich feed (2) over a catalyst (12) active in hydrogenation of oxygen and reducing the oxygen in the CO2/H2 gas mixture, to provide a first oxygen depleted CCh-rich gas stream , prior to the step of passing the first oxygen depleted CC -rich gas feed over the guard material (10) for absorbing one or more sulfur-containing impurities, to provide a cleaned CO2 rich gas stream.

8. The process according to any one of the preceding claims, wherein the total content of O2 in the CCh-rich gas feed (1) is 50-10,000 ppm O2 such as 50-5,000 ppm O2, such as 100- 3,000 ppm O2.

9. The process according to any of the preceding claims, wherein more than 95% of the O2 is converted on the catalyst active in hydrogenation of oxygen or the total concentration of O2 in the cleaned CC -rich gas stream is < 200 ppm, such as < 100 ppm, such as < 50 ppm.

10. The process according to any of the preceding claims, wherein the step of passing the CC -rich gas feed (1) and hydrogen-rich feed (2) over a catalyst active in hydrogenation (12), takes place at a temperature in the interval 200-400 °C and a pressure in the interval 1-90 bar.

11. The process according to any one of the preceding claims, wherein the total content of H2 in the combined feed of the CCh-rich gas feed (1) and the hydrogen-rich feed (2), after mixing of said feeds and passing the mixture over the optional O2 hydrogenation catalyst and guard material, is 0.2-10 vol% H2 such as 0.5-3 vol % H2.

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

13. The process according to any one of the preceding claims, wherein the total content of H2O in the combined feed of the CC -rich gas feed (1) and the hydrogen-rich feed (2) , after mixing of said feeds, is no more than 10 vol%, preferably no more than 5.0 vol%, preferably no more than 1.0 vol%, e.g. approximately 0.5 vol%.

14. The process according to any of the preceding claims, wherein the step of passing the CC -rich gas feed (1) and hydrogen-rich feed (2) over a guard material (10), takes place at a temperature in the interval 120-250 °C and a pressure in the interval 1-90 bar.

15. The process according to any of the preceding claims, wherein more than 95% of the one or more sulfur containing impurities are retained on the guard material or the total concentration of sulfur containing impurities in the cleaned CCh-rich gas stream is < 500 ppb, such as < 100 ppb, such as < 50 ppb.

16. The process according to any one of the preceding claims, wherein the CO2 feed (1) is derived from a renewable source such as: combustion or gasification of a lignocellulosic biomass such as wood products, algae, grass, forestry waste and/or agricultural residue; combustion or gasification of municipal waste, in particular the organic portion thereof, where the municipal waste is defined as a feedstock containing materials of items discarded by the public, such as mixed municipal waste given in EU Directive 2018/2001 (RED II), Annex IX, part A; microbial conversion of nitrogen-rich renewable feedstock such as manure or sewage sludge; fermentation of hydrocarbon(sugar) rich feed streams such as corn, sugar cane and beets.

17. A process for production of a syngas stream, said process comprising the process according to any one of claims 1-16, and further comprising : providing at least a portion of said cleaned CCh-rich gas stream (50) from the process according to any one of claims 1-16; optionally, providing a second hydrogen-rich feed (202), optionally obtained from the process of electrolysis of water in one or more electrolysis unit(s); reacting said portion of the cleaned CCh-rich stream feed (50) with the second hydrogen-rich feed (202), to provide at least one syngas stream (301).

18. The process according to claim 17, wherein the step of reacting said portion of the cleaned CC -rich stream feed (50) with the second hydrogen-rich feed (202), to provide at least one syngas stream (301) is carried out in the presence of a catalyst active in reverse water gas shift.

19. A process for production of a synthetic fuel stream, said process comprising the process according to any one of claims 17-18, and further comprising the step of converting said at least one syngas stream (301) to at least one synthetic fuel stream, preferably being a MeOH stream, a synthetic fuel stream, or a TIGAS stream.