Cleaning of h 2-and-co 2 containing feed gases

Abstract

The present invention relates to a process for cleaning a H2-and-CO2 rich gas feed, in particular for removing sulfur-containing impurities, and oxygen, while at the same time maintaining a low production of methanol in the cleaning process.

Description

[0001] CLEANING OF H2-AND-CO2 CONTAINING FEED GASES

[0002] TECHNICAL FIELD

[0003] The present invention relates to a process for cleaning a H2-and-CO2 rich gas feed, in particular for removing sulfur-containing impurities and oxygen (O2).

[0004] BACKGROUND

[0005] 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 ppb) or even lower. Oxygen (O2) will only rarely be an actual 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.

[0006] 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 catalysts.

[0007] 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 (O2) is also a critical substance leading to catalyst degradation and e.g. a downstream 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.

[0008] In the production of green chemicals, such as methanol (CH3OH, herein also referred to as MeOH), H2 and CO2 are the most common feed stocks. Both CO2 and H2 feed streams contain impurities, which must be removed before the H2 and / or CO2 gas is admitted to the

[0009] 03119-WO green chemicals production plant. There are many impurities and many ways to purify the feed streams and this invention describes a simple and effective layout.

[0010] A solution would be to purify the H2-rich gas feed stream and the CCh-rich gas feed stream individually and then combine the purified streams to a H2+CO2 syngas stream to the green chemicals production plant, such as MeOH synthesis plant. This layout may require a dedicated compressor for each of the feed streams and one for the combined stream, i.e. three expensive feed gas compressors. Furthermore, each purification system requires a reactor / absorber and heat exchange system.

[0011] Systems and processes for purification of CO2 streams are known from e.g. EP2457636, CN112999843, US2007028764, US200702877, US2022333015 and CN112957872.

[0012] Applicant’s co-pending patent application PCT / EP2024 / 060944 discloses a process for cleaning a CCh-rich gas feed via H2 addition, with first a O2 hydrogenation over a first catalyst and then removal of a sulfur-containing impurity over a second catalyst / absorbent.

[0013] SUMMARY

[0014] It would be desirable to be able to provide the removal of O2 and SO2 impurities in a H2-and- CO2 rich gas feed stream.

[0015] It has been found by the present inventor(s) that sulfur (S) impurity removal of CO2 feeds is necessary and can be carried out after addition of hydrogen by retaining sulfur impurities e.g. by adsorption on a metal-promoted guard material to such a degree, that the cleaned H2-and-CC>2 rich gas stream has a very low content of sulfur-containing impurities, such as <500 ppb. It has also been found that the metal-promoted guard material is capable of hydrogenating at least a part of O2 optionally present in the H2-and-CO2 rich gas stream to H2O and thus it is now possible to combine the optional O2 and sulfur-containing impurity removal, such as SO2 removal, in the same guard material.

[0016] It has also been discovered that any O2 in the H2-and-CO2 gas feed can influence the sulfur retainment capacity and mechanical integrity of a metal promoted guard material.

[0017] 03119-WO So, in a first aspect the present invention relates to a process for cleaning a H2-and-CO2 rich gas feed, said H2-and-CO2 rich gas feed comprising: at least 60 vol.% H2-and-CO2, one or more sulfur-containing impurities; wherein said process comprises the step of:

[0018] - passing the H2-and-CO2 rich gas feed over a guard material, retaining such as adsorbing one or more sulfur-containing compounds on said guard material, to provide a cleaned H2- and-CC>2-rich gas stream.

[0019] It is understood that the term “H2-and-CO2 rich gas feed” means a combined feed of a CO2- rich gas feed and a H2-rich gas feed.

[0020] It is understood that the term “passing the H2-and-CO2 rich gas feed over a guard material” means directly passing or indirectly passing the H2-and-CO2 rich gas feed over the guard material.

[0021] The term “directly” means that there are no units or process steps changing the composition of the associated gas, here the H2-and-CO2 rich gas feed. Conversely, the term “indirectly” means that there is a unit or process step changing the composition of the associated gas.

[0022] In an embodiment, the H2-and-CO2 rich gas feed comprises oxygen (O2), and the step of passing the H2-and-CO2 rich gas feed over the guard material comprises hydrogenating at least part of the O2 on said guard material.

[0023] The O2 may be present in the H2-rich gas feed and / or the CCh-rich gas feed and which are provided upstream for preparing the H2-and-CO2 rich gas feed.

[0024] The O2 is hydrogenated and leaves the guard material as water vapor.

[0025] The solution according to the present invention is thus to carry out the purification i.e. cleaning on the combined H2-and-CO2 rich gas feed stream rather than individually on a H2- rich gas feed and on a CCh-rich gas feed.

[0026] Thereby, the number of reactors, heat exchangers and compressors is significantly reduced, resulting in a simpler and less inexpensive process (process layout).

[0027] 03119-WO A process for production of a syngas stream is utilizing the cleaned H2-and-CO2 rich gas is also provided.

[0028] A process is also provided for production of a synthetic fuel stream by converting said syngas stream to at least one synthetic fuel stream.

[0029] Additional aspects are presented in the following description text, figures and claims.

[0030] For the purposes of the present application, the term “synthetic fuel stream” is used interchangeably with the term “synthetic fuel” and is at least one of: MeOH (methanol), DME (dimethyl ether), methane (CH4), aviation fuel, gasoline and diesel. The aviation fuel may also be sustainable aviation fuel (SAF), i.e. aviation fuel which is produced based on sustainable resources.

[0031] For the purposes of the present application, the term “and / or” means at least one of the associated three options. For instance, MeOH and / or DME means at least one of: MeOH, DME, MeOH and DME.

[0032] For the purposes of the present application, the term “aspect” and “embodiment” may be used interchangeably.

[0033] For the purposes of the present application, the term “present application” or “application” may be used interchangeably with the term “present invention” or “invention”, respectively.

[0034] For the purposes of the present application, the term “retaining” or “retained” in connection with the guard material is used interchangeably with any of the terms: adsorption and / or absorption, or respectively, adsorbed and / or absorbed. The term is also meant to include the chemical binding of a sulfur-containing impurity in the guard material, e.g. by forming ZnS, CuS and CU2S.

[0035] For the purposes of the present application, the term “sulfur-containing impurities” may be used interchangeably with the term “sulfur-containing compounds” or “sulfur compounds”.

[0036] 03119-WO For the purposes of the present application, the term “purification” and “cleaning” may be used interchangeably. For instance, the term “purification reactor” which refers to the reactor vessel where the purification takes place, may be used interchangeably with the term “cleaning reactor”.

[0037] Other definitions are provided in connection with one or more of above and below embodiments.

[0038] LEGENDS

[0039] Figure 1 (Fig. 1) shows a process layout according to the prior art.

[0040] Figure 2 (Fig. 2) shows a process layout according to an embodiment of the invention.

[0041] Figure 3 (Fig. 3) shows a process layout according to another embodiment of the invention.

[0042] Figure 4 (Fig. 4) shows experimental SO2 and O2 breakthrough curves from the guard material in the experiments described in Example I.

[0043] Figure 5 (Fig. 5) shows the methanol side product formation on the guard material from the experiment described in Example II.

[0044] DETAILED DISCLOSURE

[0045] For the purposes of the present application, 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.

[0046] The term “at least a part” or “at least a portion” of a certain item, the item being a process stream, a conduit associated with the process stream, or a compound, or a molecule, means a portion of the item or the entire item.

[0047] 03119-WO A cleaned H2-and-CO2 rich gas stream is defined as the outlet stream from the H2-and-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 cleaned H2-and-CO2 gas gas stream is lower than 500 ppb (parts per billion by volume), preferably lower than 100 ppb and most preferably lower than 50 ppb or lower than 10 ppb.

[0048] The sum of sulfur containing in the cleaned H2-and-CO2 gas 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.

[0049] Similarly, and suitably in addition to sulfur removal, cleaned H2-and-CO2 stream is defined as the outlet stream from the H2-and-CO2 gas cleaning process, in which minimum 95% of the oxygen in the feed is hydrogenated, or the O2 concentration in the cleaned H2-and-CO2 rich gas stream is lower than 200 ppm, preferably lower than 100 ppm and most preferably lower than 50 ppm.

[0050] Accordingly, in an embodiment, a cleaned H2-and-CO2 gas stream is defined as the outlet stream from the H2-and-CO2 cleaning process, in which:

[0051] - minimum 95% of the combined sulfur containing impurities in the feed is removed, or the sum of sulfur containing impurities in the cleaned H2-and-CO2 gas stream is lower than 500 ppb (parts per billion by volume), preferably lower than 100 ppb and most preferably lower than 50 ppb; and

[0052] - minimum 95% of the oxygen in the feed is hydrogenated, or the O2 concentration in the cleaned H2-and-CO2 gas stream is lower than 200 ppm, preferably lower than 100 ppm and most preferably lower than 50 ppm.

[0053] Syngas is used as reference for synthesis gas, a gas mixture comprising hydrogen, carbon monoxide, carbon dioxide, methane and typically water as steam. It is referred to as syngas / synthesis gas because it is the feed for a downstream catalytic synthesis leading to the desired product. The proposed solution according to the invention ensures that the feed gases for any downstream conversion to synthesis gas and further synthesis to chemicals, herein also referred to as synthetic fuels, like MeOH, DME, CH4, FT (Fischer Tropsch) synthetic fuels, TIGAS based gasoline etc. will be unproblematic with regard to sulfur and

[0054] 03119-WO 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.

[0055] In a first aspect, therefore, said process for cleaning a H2-and-CO2 rich gas feed is provided.

[0056] In an embodiment, the molar ratio of H2 to CO2 (H2:CO2) in the H2-and-CO2 rich gas feed is at least 2 moles H2 per mole CO2, such as 2-5 moles H2 per mole CO2,, for instance 2.5-4.5 moles H2 per mole CO2 , or 3-4 moles H2 per mole CO2, or 2.8-3.2 moles H2 per mole CO2.

[0057] This enables providing already prior the cleaning step, a H2-and-CO2 rich gas feed which has the right proportion of H2 to CO2 suitably for downstream applications, such as methanol synthesis. For instance, the H2-and-CO2 rich gas feed may comprise 75 vol% H2 and 25 vol% CO2 (H2:CC>2 molar ratio of 3). While some hydrogen in the H2-and-CO2 rich gas feed is consumed by hydrogenation of O2 on the guard material, the cleaned H2-and-CO2-rich gas stream still contains a surplus of hydrogen with respect to CO2.

[0058] Now more specifically, the hydrogen-rich gas feed is provided in the H2-and-CO2 rich gas feed in an amount corresponding to the feed composition to the downstream process for production of synthesis gas, or synthetic fuels e.g. methanol. As an example, in the production of methanol, the feed composition to the methanol process is suitably around said 75 vol% H2, 25 vol% CO2 (12 wt% H2 and 88 wt% CO2), corresponding to a ratio of 3 moles H2 per mole of CO2 or within the range 2.8-3.2 moles H2 per mole of CO2. Where renewable natural gas (RNG, which is a methane-rich product) is the final product, the initial H2 / CO2 molar ratio is suitably around 4.

[0059] The advantage of this embodiment is that H2 and CO2 can be mixed and then compressed prior to the H2-and-CO2 cleaning. The H2-and-CO2 cleaning process can be located downstream the 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 hydrogen-rich gas feed also becomes hydrogenated. For instance, H2 provided from electrolysis of water / steam can contain varying amounts of O2, depending on the operation of the electrolyser.

[0060] 03119-WO In an embodiment, the H2-and-CO2 rich gas feed comprises at least 70 vol% H2-and-CO2, or at least 80 vol% H2-and-CO2, or at least 90 vol% H2-and-CO2, such as at least 95 vol% H2- and-CC>2, preferably at least 99 vol% H2-and-CO2, more preferably as at least 99.5 vol% H2- and-CC>2.

[0061] The H2-and-CC>2-rich gas feed is thus, in an embodiment, already of high purity with respect to H2 and CO2 prior to the process of the present invention.

[0062] The term “high purity” means in connection with this embodiment, at least 95 vol% H2-and- CO2.

[0063] More generally, for the purposes of the present application, the term “high purity” with respect to a given compound, means at least 95 vol% of the compound.

[0064] Suitably, the CO2 in the H2-and-CO2-rich gas feed is derived from a renewable source, such as:

[0065] - combustion or gasification of a lignocellulosic biomass such as wood products, algae, grass, forestry waste and / or agricultural residue;

[0066] - 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 Ell Directive 2018 / 2001 (RED II), Annex IX, part A;

[0067] - microbial conversion of nitrogen-rich renewable feedstock such as manure or sewage sludge;

[0068] - fermentation of hydrocarbon(sugar) rich feed streams such as corn, sugar cane and beets;

[0069] Thus, for instance, the CCh-rich gas feed can also be obtained from said direct air capture (DAC) processes, metallurgical processes, cement production or fossil fuel combustion.

[0070] 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.

[0071] 03119-WO This concentration step is often called a carbon capture process, and the process can take several forms. The most commonly used process includes an absorption step in which the CO2 is absorbed into an alkaline liquid and the CO2 loaded liquid is passed to a desorbing step in which the CO2 is desorbed from the alkaline liquid, producing a concentrated CO2 stream and a CO2 depleted alkaline liquid, which is then returned to the absorption step.

[0072] In e.g. combustion processes, the flue gas from a furnace / boiler will, besides CO2, SO2, N2, H2O, O2, also contains relatively low concentrations of NOx, originating from fuel-bound nitrogen and / or from N2 in the atmosphere. Depending on the cleaning steps of the flue gas and the degree of carryover and retainment in the carbon capture process (concentration step), the CO2 rich stream can contain both O2, SO2 and NOx.

[0073] NOx typically describes both NO, NO2 and N2O, which are the species normally found in combustion processes. NO is typically the dominant species in the combustion process but may not be it in the CO2-rich gas stream as NO is poorly soluble in the aqueous solutions of the carbon capture process, whereas NO2 is much more soluble and thus easier transported to the CO2 rich gas stream.

[0074] The guard material as described in the present invention is capable of hydrogenating O2 and reducing SO2 to H2S by means of reaction with H2 and thus NOx may also become hydrogenated / reduced on the guard material. Those reactions are:

[0075] NO + 2.5 H2-> NH3+ H2O

[0076] NO2+ 3.5 H2-> NH3+ 2 H2O

[0077] N2O + 4 H2-> 2 NH3+ H2O

[0078] From these chemical reactions, it is observed that both water and ammonia may be formed on the guard material. Neither water nor ammonia are retained on the guard material and therefore they may become part of the cleaned H2-and-CO2 rich gas stream. The NH3can under certain conditions become an issue as CO2, H2O and NH3can react and form ammonium bicarbonate (NF HCOs) and / or ammonium carbamate (NH4COONH2), or methyl

[0079] 03119-WO amines, which can solidify and result in (local) plugging, corrosion and fouling. This typically takes place at high pressure and low temperature.

[0080] If deemed necessary, the NH3 can be removed from the H2-and-CO2 rich gas stream by means of e.g. a water washing or a water condensation step, where the readily soluble NH3 is transferred from the gas phase to the liquid phase and will leave the process via the aqueous stream i.e. condensate stream.

[0081] Suitably, the H2 in the H2-and-CO2-rich gas feed is derived from a renewable source, such as electrolysis of water / steam powered by any of: wind, solar, hydro power, geothermal, thermonuclear energy.

[0082] Suitably, the H2 in the H2-and-CO2 rich gas feed is derived from a reforming unit after further hydrogen enrichment such as after water-gas shift (WGS) and hydrogen purification e.g. in a pressure swing adsorption (PSA) unit and / or a membrane unit. The reforming unit is supplied with a hydrocarbon gas feed or a pre-reformed hydrocarbon gas feed. The hydrocarbon gas feed is for instance natural gas.

[0083] It is understood that the term “suitably” may be used interchangeably with the term “optionally”, i.e. it refers to an optional embodiment.

[0084] It is understood that the use of the article “a” or “an” in connection with an embodiment or an item, means “one or more” or interchangeably “at least one”.

[0085] The H2-and-CC>2 rich gas feed comprises one or more sulfur-containing impurities. In an embodiment, the one or more sulfur-containing impurities within the H2-and-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.

[0086] In an embodiment, the guard material is active in reduction of SO2 to H2S and retainment of H2S, as well as catalytically active in the hydrogenation of O2, and is preferably a Cu-Zn-AI guard material.

[0087] 03119-WO It has been experimentally shown that the above-mentioned Cu / Zn / AI based guard material under specific conditions is able to remove both oxygen and sulfur compounds at least in a single purification reactor and with the high H2 / CO2molar ratio.

[0088] On the Cu / Zn / AI based guard material, the following purification reactions take place.

[0089] H2+ 0.5 02- H20 + 241.8 kJ hydrogenation hydrogenation

[0090] H2S + ZnO <- H20 + ZnS retainment on guard material

[0091] Reaction enthalpies are also given for the chemical reactions, which can take place to an extent which can change the process gas temperature. If the enthalpy is found on the product side of the chemical reaction, heat is released by the reaction and the process gas temperature will increase, i.e. the reaction is exothermal. The reactions including the sulfur impurities will not change the temperature as the sulfur concentrations will be very low.

[0092] Additional side reactions must be considered when large amounts of H2are present together with the CO2:

[0093] CO2+ H2+ 41 kJ <- CO + H2O RWGS

[0094] CO2+ 3 H2CH3OH + H2O + 49 kJ methanol formation

[0095] CH3OH + H2S <- CH3SH + H2O methyl mercaptan

[0096] The so-called Reverse Water Gas Shift (RWGS) reaction is endothermal and will cool the process as the reaction proceeds. However, at the temperature ranges used in this invention, the equilibrium formation of CO is low and the temperature decrease will be less than about 10°C.

[0097] As the purification reactor typically will be installed at high pressure, especially the exothermal methanol formation reaction can proceed and uncontrolled temperature increase must be avoided by proper process design, control and operation.

[0098] 03119-WO The highly exothermal O2 hydrogenation reaction to form gaseous water will heat up the process gas as the reaction proceeds. At the relevant operating temperatures, there will be no chemical equilibrium to suppress the extent of the reaction and thus it will proceed to full completion if allowed. For a H2 stream with 1 vol% O2, the adiabatic temperature increase will be around 160°C if carried out in the pure H2 stream. If the H2 is mixed with the CO2 to form a 3:1 H2 / CO2 mixture, the adiabatic temperature increase will be around 110°C, due to both the dilution effect and the higher heat capacity of CO2 compared to H2. This temperature increase can be considered substantial, and the design of the feed gas purification plant must be able to handle this temperature increase without causing formation of undesired side products.

[0099] The easiest way of suppressing the methanol formation is to control the temperature of the guard material, keeping the reaction kinetics sufficiently slow such that very little methanol is formed. On the other hand, the guard material temperature must be high enough to ensure efficient O2 hydrogenation and high sulfur retention capacity, i.e. there is an optimal operating window in which the purification reactor has to be operated. In Example II, the degree of methanol formation and its undesired effects are investigated.

[0100] The Cu / Zn / AI based guard material can be active in any of the above six (6) chemical reactions, where the proper operating conditions favour SO2 and O2 hydrogenation and H2S adsorption / absorption. The side reactions forming CO and CH3OH may not necessarily be a problem as these compounds can be converted in the downstream synthesis / process plant. The methanol formation reaction can result in an increase in reactor temperature which again can increase the reaction kinetics and forming even more methanol. A combination of high temperature and high methanol concentration can result in the formation of methyl mercaptan, which is highly undesired as the mercaptan is less efficiently adsorbed / absorbed on the guard material and thus the risk of sulfur poisoning of the catalysts in the downstream process plant increases.

[0101] The O2 hydrogenation reaction is also highly exothermic and will also increase the temperature in the purification reactor and it should be ensured that the O2 concentration in the feed stream to the purification reactor has a reasonable low concentration. As recited in connection with an embodiment of the invention, if the O2 concentration in the H2-rich gas feed stream is deemed too high, it may be necessary to hydrogenate the O2 in a

[0102] 03119-WO hydrogenation reactor positioned upstream the mixing point with the CCh-rich gas feed stream.

[0103] In an embodiment, the process comprises a prior step of: providing a H2-rich gas feed, providing a CCh-rich gas feed, and mixing the H2-rich gas feed and the CCh-rich gas feed into said H2-and-CO2 rich gas feed i.e. combined feed of the CCh-rich gas feed and the H2- rich gas feed.

[0104] In an embodiment,

[0105] - the H2-rich gas feed comprises at least 70 vol% H2, or at least 80 vol% H2, or at least 90 vol% H2, such as at least 95 vol% H2, preferably at least 99 vol% H2, more preferably at least 99.5 vol% H2; and / or

[0106] - the CC>2-rich gas feed comprises at least 70 vol% CO2, or at least 80 vol% CO2, or at least 90 vol% CO2, such as at least 95 vol% CO2, preferably at least 99 vol% CO2, more preferably as at least 99.5 vol% CO2.

[0107] Suitably, the CCh-rich gas feed is derived from a renewable source, as recited above.

[0108] In an embodiment, the process further comprises: compressing via a feed gas compressor said H2-and-CC>2 rich gas feed to provide a high pressure (HP) H2-and-CC>2 rich gas feed, and optionally a condensate stream comprising one or more water soluble species selected from at least one of: SO2, H2S and HCI, optionally HNO3, NH3, and other water soluble species found in said H2-and-CC>2 rich gas feed; heating the HP H2-and-CC>2 rich gas feed to provide a pre-heated HP H2-and-CC>2 rich gas feed, as said H2-and-CC>2 rich gas feed. The other water-soluble species found in said H2-and-CC>2 rich gas feed are from instance at least one of: NO2, NHs and CO2.

[0109] The feed gas compressor typically has 3-5 stages, which will increase the mixed gas pressure to 60-90 barg which is the normal pressure of a methanol plant. For FT fuels, the pressure is typically 25-50 barg, such as 25-40 barg or such as 30-50 barg. Between the compressor stages, the gas is cooled and depending on the water concentration in the mixed gas, some water can condense and will be withdrawn as condensate. The condensate will also absorb an amount of soluble gases such as said CO2, HCI, SO2, H2S,

[0110] 03119-WO NH3and NO2. This means that under some conditions, the compressor will work as a purification unit, removing impurities from the gas prior to (upstream) the purification reactor. A lower impurity concentration in the feed to the purification reactor will result in a longer lifetime of the guard material and thus decrease operating costs of the process plant.

[0111] Hence, this basic property of a compressor is utilized to carry out a pre-purification of the mixed gas i.e. the H2-and-CC>2 rich gas feed, and enhancement of this pre-purification can be carried out by increasing the water concentration in the mixed gas and / or decreasing the temperature in the compressor inter stage cooler(s), thus increasing the amount of condensate formed.

[0112] There are several ways of increasing the water concentration in the mixed gas to the compressor such as: a. Adding an amount of steam or spraying liquid water into the individual streams and / or the combined stream in any position upstream the feed compressor. b. Carrying out Ch-hydrogenation by means of a hydrogenation catalyst, preferably carried out on the H2-rich gas feed stream and preferably with O2 already in the H2-rich gas feed stream. In principle, O2 can be added to the H2-rich gas feed stream to increase the amount of water formed. c. If the CCh-rich gas feed stream is derived, thus originates, from a carbon capture plant, the water concentration in the CCh-rich gas feed stream can be increased by adjusting the process parameters in the CO2 stripping section of the carbon capture plant, e.g. by lowering the operating pressure and / or increasing the temperature in the overhead condenser.

[0113] Thereby, a H2-and-CO2 feed gas with reduced impurity concentration is withdrawn as the HP H2-and-CC>2 rich gas feed, since e.g. SO2, H2S and HCI are advantageously withdrawn in the condensate stream. Suitably, other impurities such as NO2, NH3 are also removed and carried into the condensate stream. These impurities may be detrimental to the guard material.

[0114] In an embodiment, the guard material is arranged within a reactor vessel, said reactor vessel being arranged to receive said H2-and-CC>2 rich gas feed and provide said cleaned H2-and- CC>2-rich gas stream.

[0115] 03119-WO It has been shown experimentally that not only does the sulfur absorption efficiency of the guard material decrease over time as the Cu and Zn sites becomes saturated with sulfur compounds, but also the Ch-hydrogenation, RWGS and methanol activities decrease. This is due to the fact that the sites for absorbing the sulfur also are catalytically active in those reactions, whereas the sulfur loaded sites are less catalytically active or even inactive for the reactions.

[0116] It has also been shown experimentally that increasing the temperature in the guard material both increase the sulfur absorption capacity and the catalytic activity for the Ch- hydrogenation, RWGS and methanol reactions.

[0117] These findings are utilized to provide the best possible operation of the gas purification reactor in the process plant to prolong the sulfur absorption lifetime of the guard material while keeping the formation of side products as low as possible. When the plant has been built and put into operation, there are not many parameters which can be freely adjusted, but the temperature of the purification can to a degree be varied. Within a reactor of freshly loaded guard material, the potential for sulfur absorption and side reaction formation is high and thus it will be advantageous to operate the purification reactor at low temperature to suppress the side product formation and initially accept at lower sulfur capacity. As the sulfur absorption proceeds and side reaction activity decreases, the temperature can be increased to increase the sulfur absorption capacity without compromising the formation of side products. This operating scheme is further described in Example III.

[0118] The control of the inlet temperature to the guard material is preferably carried out in a process plant, where the feed streams are relatively stable. This is due to the high heat capacity of the guard material, which makes ordinary temperature control slow.

[0119] Other reactor temperature controlling designs and strategies can be implemented around the process gas purification reactor, i.e. the reactor vessel. The process gas is understood here as the H2-and-CO2 rich gas feed. Some examples are: a. Designing the purification reactor with two or more separated beds of guard material and installing a heat exchanger between the beds. The beds and heat exchanger(s) can be located in a single vessel or be separated in individual vessels. This resembles a normal

[0120] 03119-WO lead / lag layout with absorption beds, however with heat exchange between the beds and both beds in active use. b. Designing the purification reactor with two or more separated beds of guard material and allow for addition of another stream to the main process gas flow between the separated beds, such that the temperature to the downstream bed is adjusted to the desired level. This can be e.g. a stream of recirculated purified (and cooled) process gas, a stream of unpurified process gas or any other gas. Some mixing devices may be needed to ensure an even temperature distribution to the bed. c. Installing heat exchange surfaces within the guard material, such that the guard material is in close vicinity of a heating / cooling surface, close to isothermal conditions can be obtained by proper control of the flow and temperature of the heat exchange media, which can be process gas, water / steam, heat transfer oil, molten salt, air etc. The guard material can be placed either within tubes and with heat exchange media outside the tubes or vice versa. So-called pillow plate heat exchangers can also be used. d. As the 02-hydrogenation reaction can result in a significant temperature increase, provided the O2 concentration is high, the O2 hydrogenation can beneficially be carried out on the H2.rich gas feed stream prior to mixing with the CCh-rich gas feed stream.

[0121] For instance, the guard material is arranged as a fixed bed. For instance, the reactor vessel is arranged as an adiabatic reactor. For instance, the reactor vessel is arranged as a cooled reactor.

[0122] Some of these electrofuel (e-fuel) or green plants are designed to use renewable energy for the generation of H2 via electrolysis and e.g. solar and wind power are by nature varying on both short (minutes) and long (hours and days) term and thus many of such e-fuel plants are required to be able to react quickly to such variations in the feed streams and thus plant load. For very varying process load operation, the temperature control of the purification reactor may be too slow reacting. With a drop in plant load, e.g. from 100% to 10-20%, the residence time in the purification will increase by a factor 5-10, which means that there is a higher risk that e.g. the methanol reaction can start heating up the guard material, increasing reaction rate and increase the risk of excessive methanol formation.

[0123] A faster reaction control scheme to avoid this reaction run-off is to avoid the significant increase in residence time in the purification reactor i.e. reactor vessel. This can be done, as

[0124] 03119-WO recited in an embodiment of the invention, by recycling an amount of the purified mixed gas from the outlet of the reactor vessel to a position upstream the purification reactor, aiming to ensure the same flow through the reactor vessel and thus the same residence time in the guard material. This ensures, provided the temperature is stable, that the methanol formation will not increase. The advantage of recycling the purified mixed gas is that the overall gas composition to the reactor vessel does not change (significantly) and thus risks of initiating other side reactions are minimal. In principle, other gas streams can be added or recycled to maintain the process gas flow, but it comes with a risk of affecting the chemical behaviour of the entire process. The temperature of the recycle stream may need to be adjusted, should the temperature out of the reactor vessel and / or the temperature increase in the recirculation compressor be too high. A heat exchanger can be installed both before and after the recirculation compressor. Preferably, the recycle stream can be added to the mixed gas, i.e. the H2-and-CO2 rich gas feed, before the mixed gas heat exchanger thus eliminating the need for an extra heat exchanger.

[0125] The purified mixed gas can be recycled to a position upstream the main compressor, as recited in another embodiment of the invention, thus eliminating the need for the recirculation compressor. Then only a pressure reduction system is required. While simple, the operating cost of compression of the recycled gas may be prohibitively high.

[0126] Accordingly, in an embodiment, the process comprises: withdrawing a portion of the cleaned H2-and-CC>2-rich gas stream and recycling at least a portion thereof to any position upstream the reactor vessel; preferably: i) by recycling said at least a portion of the cleaned H2-and- CC>2-rich gas stream via a recycle compressor and optionally a heat exchanger to a mixing point between the feed gas compressor and the inlet to the reactor vessel; or ii) by recycling said at least a portion of the cleaned H2-and-CO2-rich gas stream to a position upstream the feed gas compressor.

[0127] As explained in further detailed above, this enables increasing the space velocity (reducing the residence time) in the reactor vessel and thereby reducing undesired methanol formation and attendant reactor run-off.

[0128] In embodiment i) recited above, the process further comprises recycling said at least a portion of the cleaned H2-and-CO2-rich gas stream via a recycle compressor and optionally a

[0129] 03119-WO heat exchanger to a mixing point between the feed gas compressor and the inlet to the reactor vessel.

[0130] The inlet flow to the purification reactor, i.e. reactor vessel, can be kept constantly high and thus the residence time in the reactor can be maintained at the design value, thereby keeping the methanol formation at a sufficiently low level.

[0131] This is advantageous also in connection with plants with unsteady / intermittent operation, such as plants which operate on renewable energy sources (e.g. wind, solar, hydro power) to produce the required hydrogen via electrolysis of water / steam. This solution provides a shorter response time for maintaining the flow to the reactor vessel constant compared to e.g. a temperature control scheme. Keeping the flow to the reactor vessel constant by the recirculation scheme is a simple way of controlling the fluctuations caused by the intermittent operation upstream. The mass / volume ratio of the guard material is typically quite high, meaning that the reactor heat capacity is high and a control scheme with temperature control will react much slower than the described recirculation control scheme.

[0132] In embodiment ii) recited above, the process further comprises: recycling said at least a portion of the cleaned H2-and-CO2-rich gas stream to a position upstream the feed gas compressor.

[0133] As explained, by recycling to a position upstream the feed gas compressor, there is no need for a recycle compressor, but a pressure reduction valve, thereby simplifying the process and reducing the associated penalty costs in terms of capital expenditures and operating expenditures (CAPEX and OPEX) where a recycle compressor is provided.

[0134] In an embodiment, the sulfur containing impurity is SO2 and the concentration of SO2 in the H2-and-CC>2-rich gas feed is 0.03-15 ppm SO2, such as 0.3-5 ppm SO2, such as 0.3-2 ppm SO2.

[0135] The H2-rich gas feed in particular may - in many cases - comprise oxygen (O2), depending on the origin. In some electrolysis processes for producing hydrogen from water / steam, there can be some carryover of O2 to the hydrogen-rich gas feed stream, resulting in up to 0.5-2 vol% O2, such as 1 vol% O2 in the hydrogen-rich gas feed stream. Oxygen may also

[0136] 03119-WO contaminate, poison or lead to degradation of downstream catalysts and guard material, so any oxygen in the H2-rich gas feed should be reduced or eliminated.

[0137] In an embodiment, the content of O2 in the H2-rich gas feed is 50-20,000 ppm O2, such as 50-5,000 ppm 02, or such as 100-3,000 ppm 02.

[0138] For the purposes of the present application, individual values of an item within a range, may be combined with individual values of the same item within a different range.

[0139] For instance, in connection with the above embodiment, where the content of O2 in the H2- rich gas feed and / or in the CO2-rich gas feed is 50-20,000 ppm O2, such as 50-5,000 ppm O2, or such as 100-3,000 ppm O2, this includes 50-3,000 ppm O2 or 5,000-20,000 ppm O2.

[0140] Suitably, the hydrogen-rich gas feed to the process comprises at least 98 vol% H2 such as at least 99 vol% H2 such as at least 99.5 vol% H2.

[0141] The present invention enables taking advantage of the undesired O2 in the H2-rich gas feed. For instance, where the Ch-content in the Fh-rich gas feed is high such as at the higher values of the above Ch-ranges, the Fh-rich gas feed is hydrogenated prior to being mixed with the CCh-rich gas feed.

[0142] Accordingly, in an embodiment, the F -rich gas feed is supplied to an Ch-hydrogenation reaction zone to hydrogenate at least a portion of the O2 to H2O.

[0143] The hydrogenation produces water, which increases wash-out as condensate stream in the feed gas compressor and also capacity of the guard material. Although the F -rich gas feed may be regarded at least as a partly Ch-depleted F -rich gas feed, any oxygen left in this Fh- rich gas feed which is then combined (mixed) with the CCh-rich gas feed (and which may also contain some O2) into the Fh-and-CCh feed gas, is further hydrogenated on the guard material for sulfur and oxygen removal. The hydrogen-rich gas feed acts as a reductant for one or more sulfur-containing impurities, and optionally for oxygen, in the Fh-and-CCh-rich gas feed. Furthermore, this also serves to remove O2 for better control temperature increase in the associated gas streams.

[0144] 03119-WO In an embodiment, the Ch-hydrogenation reaction zone comprises a hydrogenation catalyst, wherein:

[0145] - the hydrogenation catalyst comprises an alumina and / or silica carrier impregnated with a metal, such as: Cu, Mn, Pt, Pd, or combinations thereof; or

[0146] - the hydrogenation catalyst comprises a Cu / Zn / AI based material; or

[0147] - the Ch-hydrogenation reaction zone is arranged as a fixed bed of hydrogenation catalyst pellets or as one or more layers of monolithic type hydrogenation catalyst, and the hydrogenation catalyst comprises an alumina and / or silica carrier impregnated with Pt and / or Pd.

[0148] A hydrogenation catalyst comprising an alumina and / or silica carrier impregnated with Pt and / or Pd enables operation at a lower temperature than e.g. the Cu / Zn / AI based material.

[0149] The H2-and-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 provides for a more efficient operation of the guard system. The water is advantageously removed as condensate stream carrying undesired impurities. Suitably, there is an upper limit of the water content in the H2-and-CCh rich gas feed to the reactor vessel comprising the guard material. Accordingly, in an embodiment, the content of H2O in the H2-and-CC>2 rich gas feed, i.e. the combined feed of the CCh-rich gas feed and the hydrogen-rich feed after mixing of said feeds and prior to being passed over the guard material, 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%.

[0150] In an embodiment, more than 95% of the O2 in the H2-and-CO2-rich gas feed is hydrogenated, or the concentration of O2 in the cleaned H2-and-CO2-rich gas stream is <200 ppm, such as < 100 ppm, or such as < 50 ppm.

[0151] 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 as well as catalytically active in the hydrogenation of O2, 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 H2-and-CO2 rich gas feed to H2S, which is much more efficiently adsorbed on the guard than the SO2. Again, the guard is also capable

[0152] 03119-WO of reacting oxygen content in the H2-and-CC>2 feed stream with hydrogen to form water, i.e. by hydrogenation of O2.

[0153] The process provides a cleaned H2-and-CO2 rich gas stream. This cleaned H2-and-CO2 rich gas stream comprises for instance:

[0154] - less than 500 ppb (< 500 ppb), such as less than 100 ppb, preferably less than 50 ppb sulfur (sulfur containing impurities), or preferably less than 25 ppb sulfur, more preferably less than 10 ppb;

[0155] - less than 200 ppm O2, such as less than 100 ppm O2, preferably less than 50 ppm O2.

[0156] In an embodiment, the guard material is a Cu-Zn-AI guard material having a chemical composition of 25-60 wt% Cu, 15-70 wt% Zn, and 1-20 wt% Al, such as 2-20 wt% Al e.g. 2- 10 wt% Al or 2-15 wt% Al. It may comprise minor amounts of at least one of K, Cs and C. The elements will either be found in a reduced or oxidised state.

[0157] In a particular embodiment, the guard material is coprecipitated Cu / ZnO / alumina-based guard material, in which Cu is ~ 40 wt%, ZnO is ~30 wt% and alumina ~10 wt%.

[0158] For the purposes of the present application, the sign ~ means + / -10% . For instance, Cu can be 40, 36 or 44 wt% i.e. within 10%; or 42, 38 wt% i.e. within 5%.

[0159] The H2-and-CC>2 cleaning process is preferably operated in the pressure range 1-120 bar, such as 1-100 bar or 1-90 bar, preferably 1-50 bar, depending on the pressure of the H2- and-CC>2 gas feed stream, or the individual H2-rich gas feed steam and CCh-rich gas feed stream, as well as the pressure of the downstream conversion process. Further, 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 F^-and-CCh cleaning process is preferably operated in the interval 120-250°C.

[0160] Accordingly, in an embodiment, the step of passing the CCh-rich gas feed and hydrogen-rich feed over a guard material, takes place at a temperature in the interval 120-250°C and a pressure in the interval 1-120 bar.

[0161] 03119-WO For instance, the temperature is 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, or 240°C.

[0162] In an embodiment, the temperature of the guard material is in the range 140-200°C, preferably 150-180°C. Within these and including these values it has been found that the temperature is sufficiently high to ensure optimal purification while at the same time being sufficiently low to keep the methanol formation under control.

[0163] The above temperature range is, in an embodiment, achieved by said step of withdrawing a portion of the cleaned F^-and-CCh-rich gas stream and recycling at least a portion thereof to any position upstream the reactor vessel. Thereby, not only is the temperature sufficiently high to ensure optimal purification and at the same time sufficiently low to keep the methanol formation under control, but at the same time it is possible to ensure a constant inlet flow to the reactor vessel, thereby maintaining the residence time therein at the design value despite intermittent operation upstream for providing at least the hydrogen-rich feed.

[0164] The temperature is understood as reaction temperature in an isothermal reactor, or inlet temperature in an adiabatic reactor. In an adiabatic reactor the adiabatic temperature increase is preferably not greater than 50°C.

[0165] For instance, the pressure is 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 bar.

[0166] In an embodiment, 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 F^-and-CCh rich gas stream is < 500 ppb, such as < 100 ppb, or such as < 50 ppb, or such as < 10 ppb.

[0167] As recited above, in an embodiment, the CO2 in the F^-and-CCh rich gas feed, or the CO2- rich gas feed, is derived from a renewable source such as:

[0168] - combustion or gasification of a lignocellulosic biomass such as wood products, algae, grass, forestry waste and / or agricultural residue;

[0169] - combustion or gasification of municipal waste, in particular the organic portion thereof, where the municipal waste is defined as a feedstock containing materials of

[0170] 03119-WO items discarded by the public, such as mixed municipal waste given in Ell Directive 2018 / 2001 (RED II), Annex IX, part A;

[0171] - microbial conversion of nitrogen-rich renewable feedstock such as manure or sewage sludge;

[0172] - fermentation of hydrocarbon(sugar) rich feed streams such as corn, sugar cane and beets;

[0173] The term “derived from a renewable source” means that the process further comprises a prior step according to the above, e.g. a prior step of combustion or gasification of a lignocellulosic biomass such as wood products, algae, grass, forestry waste and / or agricultural residue.

[0174] As recited above, the cleaned H2-and-CO2-rich gas stream is sufficiently pure that the risk of catalyst poisoning of downstream processes is significantly reduced.

[0175] An integrated process can also take place, in which H2-and-CO2 rich gas cleaning, syngas production and subsequent downstream syntheses occur.

[0176] Accordingly, in an embodiment, the process further comprises:

[0177] - reacting at least a portion of the cleaned H2-and-CO2-rich gas stream in the presence of a catalyst active in reverse water gas shift (RWGS), preferably in an electrically heated reactor for RWGS (e-RWGS), to provide at least one syngas stream; or

[0178] - reacting at least a portion of the cleaned H2-and-CO2 rich gas stream directly in: a methanol converter in the presence of a methanol synthesis catalyst, or a methanation reactor in the presence of a methanation catalyst.

[0179] It is understood that the term “directly in: a methanol converter in the presence of a methanol synthesis catalyst, or a methanation reactor in the presence of a methanation catalyst” means without the production of synthesis gas by use of RWGS.

[0180] RWGS, methanol synthesis and methanation are well known in the art. For details on e- RWGS, which is a more recent technology, reference is given to e.g. applicant’s WO 2022079098.

[0181] 03119-WO The RWGS increases the CO content in the syngas and further serves to e.g. adjust, the module “M” of the syngas (M=(H2-CO2) / (CO+CO2)) on molar basis, for e.g. downstream methanol synthesis in a methanol converter. For downstream methanol synthesis, M is preferably 2.0-2.1. For downstream Fischer-Tropsch (FT) process the molar ratio of H2 / CO is preferably 2.

[0182] In an embodiment, RWGS is conducted to provide the at least one syngas stream for downstream methanation. The H2 / CO molar ratio is suitably around 4, as earlier recited. After RWGS, the H2 / CO molar ratio of the syngas is suitably around 3 disregarding CO2 (or said ratio (H2-CO2) / (CO+CO2) is 3), in line with the methanation reaction: CO + 3H2-> CH4+ H2O.

[0183] In an embodiment, a process for producing a synthetic fuel stream is provided. Accordingly, the process further comprises the step of converting said at least one syngas stream to at least one synthetic fuel stream which is at least one of: MeOH (methanol), DME (dimethyl ether), methane, aviation fuel, kerosene, gasoline and diesel fuel.

[0184] Again, it is understood that the term “synthetic fuel stream” is used interchangeably with the term “synthetic fuel” and is at least one of: MeOH (methanol), DME (dimethyl ether), methane, aviation fuel, kerosone, gasoline and diesel. The aviation fuel may also be sustainable aviation fuel (SAF), i.e. aviation fuel which is produced based on sustainable resources.

[0185] For the purposes of the present application, the term “aviation fuel” is regarded as a different synthetic fuel than “kerosene”. The term “aviation fuel” may be used interchangeably with the term “jet fuel” and includes SAF, in compliance with specific standards for use in jet fuel engines. The term “kerosene” is broader and refers to a flammable hydrocarbon liquid often used as a fuel or solvent.

[0186] In one aspect, the process of converting said at least one syngas stream to at least one synthetic fuel stream is a Fisher-Tropsch (FT) process, which provides the synthetic fuel stream. In another aspect, the process of converting said at least one syngas stream to at least one synthesis fuel stream is a TIGAS process, which provides gasoline as the synthetic fuel stream. In yet another aspect, the process of converting said at least one

[0187] 03119-WO syngas stream to at least one synthesis fuel stream is a methanol-to-jet fuel (MTJ) process, which provides at least an aviation fuel, suitably SAF, as the synthetic fuel stream.

[0188] Accordingly, in an embodiment, the process of converting said at least one syngas stream to at least one synthetic fuel stream is:

[0189] - a Fisher-Tropsch (FT) process; or

[0190] - a process whereby the syngas stream is first converted to methanol and / or DME, and subsequently to: gasoline, e.g. via a TIGAS process, or aviation fuel e.g. via a methanol-to- jet fuel (MTJ) process.

[0191] The FT, TIGAS and MTJ processes are well-known in the art.

[0192] In an embodiment, the step of converting said at least one syngas stream to at least one synthetic fuel stream is a Fisher-Tropsch (FT) process, and a recycle stream from the FT- process, such as FT-tail gas or hydrogenated FT-tail gas, is supplied upstream the RWGS, e.g. upstream the e-RWGS.

[0193] Specific embodiments

[0194] Fig. 1 shows an embodiment according to prior art. The purification of a CO2-rich gas feed stream 1 and a H2-rich gas feed stream 3 is carried out individually via dedicated feed gas compressors 2, 4 as well as dedicated purification units 6, 8. Cleaning (purification) unit 6, i.e. reactor vessel 6, comprises for instance a fixed bed of a guard material being supplied with compressed CO2-rich gas feed 5, the guard material being active in reduction of SO2 to H2S and adsorption of H2S, as well as catalytically active in the hydrogenation of O2, such as a Cu-Zn-AI guard material. The hydrogen required in the hydrogenation in the cleaning unit 6 is provided by a minor H2-rich gas stream 7’, suitably so that the hydrogen content in the in the feed gas entering the cleaning unit 6 is 3 vol% or lower. Cleaning (purification) unit 8, i.e. reactor vessel 8, comprises for instance a fixed bed of catalytic material being supplied with compressed H2-rich gas feed 7, of which the minor H2-rich gas stream 7’ has been derived. The guard material is here for instance capable of carrying out catalytic hydrogenation of the oxygen to H2O. The thus cleaned (purified) CO2-rich gas feed 9 and H2-rich gas feed 11 are combined into a stream 13 and pressurized via feed gas compressor 10 into a combined

[0195] 03119-WO compressed feed gas stream 15, which may be further converted to syngas in syngas conversion section 30 to at least one synthetic fuel stream 17, such as a methanol (MeOH) stream in a MeOH synthesis plant.

[0196] Fig. 2 shows an embodiment according to the invention of the H2+CO2 gas purification process 100. CO2-rich gas feed 101 comprising O2 and one or more sulfur-impurities is mixed with H2-rich gas feed 103, optionally comprising O2 into a H2-and-CO2 rich gas feed 105. The process comprises compressing via feed gas compressor 102 the H2-and-CC>2 rich gas feed 105 to provide a high pressure (HP) H2-and-CC>2 rich gas feed 107, and optionally a condensate stream 109 comprising dissolved SO2, H2S, HCI and other water soluble gas species; heating via heat exchanger 104 the HP H2-and-CO2 rich gas feed 107 to provide a pre-heated HP H2-and-CC>2 rich gas feed 107’. The molar ratio of H2 to CO2 (H2:CC>2) in the H2-and-CC>2 rich gas feed is at least 2 moles H2 per mole CO2, suitably 3-4 moles H2 per mole CO2. The H2-and-CC>2 rich gas feed 107’ is then passed over a guard material 110’ in cleaning (purification) unit 110, i.e. reactor vessel 110, retaining e.g. adsorbing, one or more sulfur-containing compounds and hydrogenating at least a part of the O2 on said guard material, to provide a cleaned H2-and-CO2-rich gas stream 109. The guard material is active in reduction of SO2 to H2S and adsorption of H2S, as well as catalytically active in the hydrogenation of O2, preferably a Cu-Zn-AI guard material. As in connection with Fig. 1 , the cleaned H2-and-CO2-rich gas stream 109 may be further converted to syngas in syngas conversion section 30 to at least one synthetic fuel stream 17, such as a methanol (MeOH) stream in a MeOH synthesis plant.

[0197] Fig. 3 shows another embodiment according to the invention of the H2+CO2 gas purification process 100. The process is as in Fig. 2, and further comprises recycling at least a portion 109’ of the cleaned H2-and-CO2-rich gas stream 109 via a recycle compressor 112 to a mixing point 114 such as a juncture or a mixing unit, between the feed gas compressor 102 and the cleaning unit 110 i.e. reactor vessel 110. The new combined H2+CO2 rich gas feed 111 is then supplied to the reactor vessel 110. The recycling, suitably in combination with the heating (preheating) shown in Fig. 2, enables to minimize undesired methanol formation.

[0198] Fig 4 shows the SO2 and O2 breakthrough curves from a laboratory reactor loaded with Cu / Zn / AI guard material. The normalized outlet concentration is defined as the outlet concentration divided by the inlet concentration. The details of the experiments are found in

[0199] 03119-WO Example I. The time on stream is set to zero at the time SO2 is first admitted to the process gas to the reactor. Prior to that period, the guard material is reduced and H2O, CO2 and H2 added for initial stabilization of the guard material.

[0200] At 90°C, the O2 hydrogenation activity is very low and almost no O2 is hydrogenated, even with a fresh guard material, i.e. the normalized O2 concentration is close to 1. There is some SO2 capture activity / capacity but the SO2 breakthrough start already after 20 hours on stream with SO2. At this temperature, O2 hydrogenation can only be carried out by installing another type of hydrogenation catalyst downstream the guard material.

[0201] Increasing the temperature to 150°C significantly increases SO2 capture activity / capacity and the SO2 breakthrough is delayed to 60 hours on stream and the increase in SO2 outlet concentration is slower than at 90°C. The O2 hydrogenation activity is high at the beginning of the experiment, i.e. all O2 is hydrogenated. As the guard material absorbs the sulfur impurities, the O2 hydrogenation activity decreases and the normalized outlet O2 concentration increases with more or less the same rate as the SO2.

[0202] Increasing the temperature even further to 180°C result in an even higher SO2 capture activity / capacity, delaying the SO2 breakthrough to 200 hours. The O2 hydrogenation activity remain high even when the sulfur impurity absorption on the guard material proceeds, but a very small increase in O2 concentration is observed after 300-350 hours and it is expected to increase further as the normalized SO2 outlet concentration increase.

[0203] Fig 5 shows the methanol concentration at the outlet of laboratory reactor during the same experiments as described in Fig 4 and Example I. At 90°C, no methanol is found in concentrations above the detection limit at the outlet of the reactor and the data has not been plotted in the figure. At 150°C, an initial formation of methanol is measured, however the formation is significantly decreased shortly after admission of SO2 (at time = 0 hours) to the process gas and after ~60 hours on stream, the methanol concentration has dropped below the detection limit. At 180°C, the methanol formation is significantly higher, both before and after admission of SO2. However, the methanol formation decreases as the guard material absorbs sulfur species and it is expected that the methanol concentration eventually drops to zero.

[0204] 03119-WO EXAMPLES

[0205] EXAMPLE (I)

[0206] Experiments have been carried out in a laboratory fixed bed reactor at isothermal condition to test the combined SO2 and O2 removal efficiency and methanol formation on 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 three temperature zones in the oven. These zones are controlled by internal thermocouple readings to obtain isothermal reaction condition in the fixed bed.

[0207] The guard material is placed on a grid in a SilcoNert 2000™ coated stainless-steel reactor 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 pure gases and special gas mixtures. These include nitrogen (N2), hydrogen (H2), carbon dioxide (CO2), 2 vol% O2 in N2, and 100 ppm 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.

[0208] The guard material used is a coprecipitated Cu (~40 wt%) / ZnO (~30 wt%) / alumina- (~10 wt%) based guard material. The Cu is initially found as Cu-oxide (CUO / CU2O), which will be reduced to Cu-metal at the beginning of the experiment. The guard material will also contain an amount of carbon and potassium and / or cesium.

[0209] The guard material was loaded into the reactor as industrial-sized tablets, each tablet was separated with a 2 mm glass sphere to improve the tablet’s surface exposure to the reactor feed gas. This so-called Single Pellet String reactor is loaded with 30 tablets, simulating the top layer (10-15 cm) of an industrial fixed bed guard reactor.

[0210] Before measuring SO2 and O2 removal from the FL-and-CCh-rich feed gas, the guard material was reduced in 2% H2 in N2 at 220°C and 3 barg.

[0211] 03119-WO The experiments were carried out at an operating pressure of 30 barg and at 90°C, 150°C and 180 °C.

[0212] The approximate composition of the combined feed gas to the reactor, herein referred to as process gas, was 60 vol% H2, 20 vol% CO2, 10 vol% CH4, 10 vol% N2 with the impurity concentrations of 7 ppm SO2 and 2,500 ppm O2. Water was added to the process gas to achieve a concentration of ~0.5 vol%.

[0213] The process gas flow was 40 Nl / h (0°C, 1 atm).

[0214] The process gas simulates a process plant, wherein all the H2 is mixed into the CO2 stream prior to process gas purification (as depicted in figure 2 and 3) in a 3:1 H2 / CO2 molar ratio and passing the purified H2 / CO2 gas mixture to a downstream synthesis gas plant. The presence of CH4 and N2 in the reactor feed was a consequence of using mixtures of SO2+CH4 and O2+N2, necessary for safety reasons in the experiments.

[0215] The sulfur feed and exit gas concentration were measured on Agilent 7890A GC system equipped with an Ol 5380 pulsed flame photometric detector (PFPD). The CO and methanol concentration were measured with an Agilent 7890A GC system equipped with an Flame Ionization detector (FID)

[0216] The O2 concentration was measured with a TecMicro analyzer (0-5,000 ppm O2) from TecSense GmbH.

[0217] In Fig. 4, the normalized O2 and SO2 concentrations at the reactor outlet are shown as a function of temperature and time on stream of the experiment. The normalized concentrations are defined as the outlet concentration divided by the inlet concentration, i.e. a normalized concentration of 0% correspond to complete removal / conversion, whereas 100% correspond to no removal / conversion. For an absorbent, it is expected that the normalized outlet concentration starts at a low value (preferably 0%) and over time increase and ultimately the normalized outlet concentration reaches 100% when the absorbent become fully saturated. For a catalyst, the normalized outlet concentration should ideally stay constant over time. However, poisoning / deactivation of the catalyst will result in a gradual increase in relative concentrations over time.

[0218] 03119-WO The SO2 is retained on the tablets and the sulfur can be found on the tablets when carrying out post experiment analyses on the spent guard material.

[0219] The O2 is believed to be hydrogenated to H2O and carried out of the reactor as water vapor. The reason for the increase in relative O2 concentration at the reactor outlet is due to deactivation of the guard material’s catalytic sites active in O2 hydrogenation.

[0220] EXAMPLE (II)

[0221] This example describes the effects of excessive methanol formation in the purification reactor and possible consequences.

[0222] The exothermal methanol formation reaction is shown below:

[0223] CO2+ 3 H2CH3OH + H2O + 49 kJ

[0224] The reaction is catalyzed by the Cu / Zn / AI based guard material but requires a temperature of 120°C or higher, preferably 200°C or higher to become industrially relevant for the production of e.g. methanol. Thus, under normal operation of the purification reactor, the reaction rate is low and little methanol formation is foreseen.

[0225] With fresh guard material in the purification reactor, the guard material activity is at its maximum and deviations in process conditions may initiate the formation of methanol. The released heat of reaction will increase the temperature and result in a higher catalytic activity for methanol formation and in worst case, there will be an uncontrolled temperature increase in the purification reactor. Since the reaction is exothermal, the chemical equilibrium constraints will prevent the temperature from increasing to extreme values, i.e. melt down of the guard material and reactor will not take place.

[0226] In a 3:1 H2 / CO2 molar ratio process gas, the heat of reaction will result in a 15-20°C temperature increase per vol% methanol formed. For a guard material at 180°C initial temperature the equilibrium methanol concentration at 60 barg will around 3 vol% and the temperature will increase to ~ 230 °C and remain there as the net production of methanol become 0 at chemical equilibrium.

[0227] 03119-WO An increasing temperature in the purification reactor will effect the guard material negatively and some consequences are:

[0228] The water formed together with methanol will bind to the Al and form a Zn / AI-based spinel structure, which is inactive in the absorption of sulfur compounds and thus the retention capacity of the guard material decrease.

[0229] The methanol can react with the formed H2S and form methylmercaptan, CH3SH, which is less effective captured on the guard material and thus have a higher risk of escaping to the downstream production plant, causing premature deactivation of those catalysts.

[0230] The combination of high water concentration and temperature will increase the equilibrium slip from the guard material and thus there is a higher risk of H2S slip from the guard material to the downstream production plant, causing premature deactivation of the catalysts installed.

[0231] EXAMPLE (III)

[0232] This example describes a process control scheme to provide best sulfur impurity capture and O2 hydrogenation in the mixed H2 / CO2 stream to provide a purified stream for further processing while optimizing the utilization of the sulfur guard material and minimizing the risk of excessive methanol formation.

[0233] The process layout is depicted in Fig 2. Fig 4 and Fig 5 show the general behavior of the Cu / AI / Zn based sulfur guard material. It should be remembered that Fig. 4 and 5 show data from laboratory experiment and the data represent the top layer of the guard bed in the reactor. A large fraction of the guard bed will be considered fresh catalyst with behavior as seen before and around 0 operating hours on stream in the figures.

[0234] When the plant is in operating with a freshly loaded guard material, the temperature to the inlet of the H2 / CO2 mixture purification reactor is kept low, e.g. to around 150°C. This ensures a very low degree of methanol formation and thus stable reactor temperature while the O2 hydrogenation and sulfur removal activity is sufficiently high to provide a purified H2 / CO2 mixture to the downstream synthesis plant.

[0235] 03119-WO After a given operating time, depending on the impurity concentrations in the H2 / CO2 mixture and the amount of sulfur guard material in the purification reactor, the guard material become saturated with sulfur and the slip of SO2 will gradually start increasing.

[0236] This is undesirable and thus the temperature of the inlet to the H2 / CO2 mixture purification reactor is increased, e.g. to around 180°C. This increase in temperature increases the sulfur capture activity and retention capacity and thus no or very low slip of SO2 can be continued for a prolonged time, increasing the utilization of the guard material, reducing operating costs and increasing operating time between replacement of the guard material. As the guard material now is partly saturated with sulfur, the methanol formation is significantly hampered, and the increased operating temperature will not give rise to excessive methanol formation.

[0237] The temperature is kept at a relative high temperature to ensure optimal purification while at the same time at a sufficiently low temperature to keep the methanol formation under control, preferably in said 150-180°C temperature range.

[0238] The guard reactor temperature can at a later stage be further increased to utilize even more of the sulfur guard capacity while keeping the methanol formation under control.

[0239] Also, should the plant load decrease, increasing the residence time of the H2 / CO2 mixture in the purification reactor and thus allowing for more methanol formation, the inlet temperature to the H2 / CO2 mixture purification reactor can be decreased to lower the reaction rate of the methanol formation and thus avoid excessive methanol formation.

[0240] There are many different ways of adapting the temperature control of purification reactor, where only a few shall be mentioned: a. Use a pre-calculated temperature ramp, based on the impurity concentrations in the H2 / CO2 mixture and the amount of installed guard material, slowly increasing the inlet temperature over time. b. Carry out chemical analyses of the H2 / CO2 mixture at inlet and outlet of the purification reactor to monitor impurity concentrations and methanol formation and based on the analytical values, adjust the inlet temperature accordingly.

[0241] 03119-WO c. Monitor the temperature increase in a number of positions in the guard bed to evaluate the activity of the exothermal methanol formation reaction and lower the inlet temperature if the temperature increase exceed a given threshold value.

[0242] EXAMPLE (IV)

[0243] This example describes another process control scheme to provide optimal sulfur capture and O2 hydrogenation in the mixed H2 / CO2 stream to provide a purified stream for further processing while minimizing the risk of excessive methanol formation in the purified stream.

[0244] The process layout is depicted in Fig 3. The inlet temperature to the H2 / CO2 mixture purification reactor is kept constant at a temperature which provides both fast O2 hydrogenation and high sulfur absorption capacity on the guard material loaded in the reactor. The temperature is kept at a relative high temperature to ensure optimal purification while at the same time at a sufficiently low temperature to keep the methanol formation under control, preferably in the 150-180°C temperature range.

[0245] If the load of the plant suddenly decreases, the residence time in the purification reactor will increase and the kinetically controlled methanol formation reaction will be allowed to proceed further than desired and if nothing is done, the reactor temperature will increase, further increasing the reaction rate and in worst case resulting in excessive methanol and possible methyl mercaptan formation.

[0246] Using the control scheme as shown in Fig 3, a fraction of the purified H2 / CO2 mixture is withdrawn and recirculated to a position upstream the purification reactor by means of a recirculation compressor. Using this scheme, the flow of the H2 / CO2 mixture inlet to the purification reactor can be kept constantly high and thus the residence time in the reactor can be maintained at the design value, keeping the methanol formation at a sufficiently low level. The operation of the recirculation compressor can be controlled by e.g. a flow and / or pressure signal at the inlet of the purification reactor.

[0247] This control scheme is well suited for plants with somewhat unsteady / intermittent operation, such as plants which operate on renewable energy sources (e.g. wind, solar, hydro power) to produce H2 via electrolysis of water / steam. Keeping the flow to the purification reactor

[0248] 03119-WO constant is a simple way of controlling such fluctuations. The mass / volume of the guard material is typically quite high, meaning that the reactor heat capacity is high and a control scheme with temperature control will react much slower than the described recirculation control scheme. In Fig 3, a heating device is installed downstream the mixed gas compressor to increase the temperature to the desired reactor inlet temperature. The heating device can be an electrical heater or a simple heat exchanger using water, steam, air, oil or process gas as the heating media.

[0249] The recirculated stream can be added either upstream or downstream this heating device or optionally a heat exchanger can be installed on the recirculation line before mixed with the main process gas flow.

[0250] Other streams than the purified H2 / CO2 mixture (cleaned H2-and-CO2 rich gas) can be recirculated, such as the semi-converted process gas from a methanol reactor located further downstream the H2 / CO2 mixture purification reactor.

[0251] 03119-WO

Claims

35CLAIMS1. A process for cleaning a H2-and-CO2 rich gas feed, said H2-and-CO2 rich gas feed comprising: at least 60 vol.% H2-and-CO2, one or more sulfur-containing impurities, wherein said process comprises the step of:- passing the H2-and-CO2 rich gas feed over a guard material, retaining one or more sulfur- containing compounds on said guard material, to provide a cleaned H2-and-CO2-rich gas stream.

2. The process according to claim 1 , wherein the H2-and-CO2 rich gas feed comprises oxygen (O2), and the step of passing the H2-and-CO2 rich gas feed over the guard material comprises hydrogenating at least part of the O2 on said guard material.

3. The process according to any one of the preceding claims, wherein the molar ratio of H2 to CO2 (H2:CC>2) in the H2-and-CO2 rich gas feed is at least 2 moles H2 per mole CO2, such as 2-5 moles H2 per mole CO2 , for instance 2.5-4.5 moles H2 per mole CO2, or 3-4 moles H2 per mole CO2, or 2.8-3.2 moles H2 per mole CO2.

4. The process according to any one of the preceding claims, wherein the H2-and-CO2 rich gas feed comprises at least 70 vol% H2-and-CO2, or at least 80 vol% H2-and-CO2, or at least 90 vol% H2-and-CC>2, such as at least 95 vol% H2-and-CO2, preferably at least 99 vol% H2- and-CC>2, more preferably as at least 99.5 vol% H2-and-CO2.

5. The process according to any one of the preceding claims, wherein the one or more sulfur-containing impurities within said H2-and-CO2-rich gas feed 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.

6. The process according to any one of the preceding claims, wherein the guard material is active in reduction of SO2 to H2S and retainment of H2S, as well as catalytically active in the hydrogenation of O2, and is preferably a Cu-Zn-AI guard material.03119-WO367. The process according to any one of the preceding claims, comprising a prior step of: providing a H2-rich gas feed, providing a CCh-rich gas feed, and mixing the hydrogen-rich gas feed and the CCh-rich gas feed into said H2-and-CO2 rich gas feed.

8. The process according to claim 7, wherein:- the H2-rich gas feed comprises at least 70 vol% H2, or at least 80 vol% H2, or at least 90 vol% H2, such as at least 95 vol% H2, preferably at least 99 vol% H2, more preferably at least 99.5 vol% H2; and / or- the CC>2-rich gas feed comprises at least 70 vol% CO2, or at least 80 vol% CO2, or at least 90 vol% CO2, such as at least 95 vol% CO2, preferably at least 99 vol% CO2, more preferably at least 99.5 vol% CO2.

9. The process according to any one of the preceding claims, further comprising: compressing via a feed gas compressor said H2-and-CO2 rich gas feed to provide a high pressure (HP) H2-and-CC>2 rich gas feed, and optionally a condensate stream comprising one or more water soluble species selected from at least one of: SO2, H2S and HCI, optionally HNO3, NH3, and other water soluble species found in said H2-and-CC>2 rich gas feed ; heating the HP H2-and-CC>2 rich gas feed to provide a pre-heated HP H2-and-CC>2 rich gas feed, as said H2-and-CC>2 rich gas feed.

10. The process according to any one of the preceding claims, wherein the guard material is arranged within a reactor vessel, said reactor vessel being arranged to receive said H2-and- CO2 rich gas feed and provide said cleaned H2-and-CO2-rich gas stream.

11. The process according to claim 10, comprising: withdrawing a portion of the cleaned H2- and-CC>2-rich gas stream and recycling at least a portion thereof to any position upstream the reactor vessel; preferably: i) by recycling said at least a portion of the cleaned H2-and- CC>2-rich gas stream via a recycle compressor and optionally a heat exchanger to a mixing point between the feed gas compressor and the inlet to the reactor vessel; or ii) by recycling said at least a portion of the cleaned H2-and-CO2-rich gas stream to a position upstream the feed gas compressor.03119-WO12. The process according to any one of the preceding claims, wherein the sulfur containing impurity is SO2 and the concentration of SO2 in the H2-and-CO2-rich gas feed is 0.03-15 ppm SO2, such as 0.3-5 ppm SO2, such as 0.3-2 ppm SO2.

13. The process according to any one of the preceding claims 2-12, wherein the content of O2 in the H2-rich gas feed and / or in the CCh-rich gas feed is 50-20,000 ppm O2 such as 50- 5,000 ppm O2, or such as 100-3,000 ppm O2.

14. The process according to any one of claims 7-13, wherein the H2-rich gas feed is supplied to an Ch-hydrogenation reaction zone to hydrogenate at least a portion of the O2 to H2O.

15. The process according to claim 14, wherein the Ch-hydrogenation reaction zone comprises a hydrogenation catalyst;- wherein the hydrogenation catalyst comprises an alumina and / or silica carrier impregnated with a metal, such as: Cu, Mn, Pt, Pd, or combinations thereof; or- wherein the hydrogenation catalyst comprises a Cu / Zn / AI based material; or- wherein the Ch-hydrogenation reaction zone is arranged as a fixed bed of hydrogenation catalyst pellets or as one or more layers of monolithic type hydrogenation catalyst, and the hydrogenation catalyst comprises an alumina and / or silica carrier impregnated with Pt and / or Pd.

16. The process according to any of the preceding claims, wherein the content of H2O in the H2-and-CCh rich gas feed 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%.

17. The process according to any of the preceding claims, wherein: more than 95% of the O2 in the H2-and-CCh-rich gas feed is hydrogenated, or the concentration of O2 in the cleaned H2-and-CCh-rich gas stream is < 200 ppm, such as < 100 ppm, or such as < 50 ppm.

18. The process according to any of the preceding claims, wherein the guard material is a Cu-Zn-AI guard material having a chemical composition of 25-60 wt% Cu, 15-70 wt% Zn, and 1-20 wt% Al.03119-WO19. The process according to any of the preceding claims, wherein the step of passing the H2-and-CC>2-rich gas feed over the guard material, takes place at a temperature in the interval 120-250°C and a pressure in the interval 1-120 bar.

20. The process according to any of the preceding claims, wherein the temperature of the guard material is in the range 140-200°C, preferably 150-180°C.

21. 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 H2-and-CO2 rich gas stream is < 500 ppb, such as < 100 ppb, or such as < 50 ppb, or such as < 10 ppb.

22. The process according to any one of the preceding claims, wherein the CO2 in the H2- and-CC>2 rich gas feed, or the CCh-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 Ell 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.- Direct Air Capture (DAC)23. The process according to claim according to any one of the preceding claims, further comprising:- reacting at least a portion of the cleaned H2-and-CO2-rich gas stream in the presence of a catalyst active in reverse water gas shift (RWGS), preferably in an electrically heated reactor for RWGS (e-RWGS), to provide at least one syngas stream; or03119-WO39- reacting at least a portion of the cleaned H2-and-CO2 rich gas stream directly in: a methanol converter in the presence of a methanol synthesis catalyst or a methanation reactor in the presence of a methanation catalyst.

24. The process according to claim 23, comprising producing a synthetic fuel stream by further converting said at least one syngas stream to at least one synthetic fuel stream which is at least one of: MeOH (methanol), DME (dimethyl ether), methane, aviation fuel, kerosene, gasoline and diesel fuel.

25. The process according to claim 24, wherein the step of converting said at least one syngas stream to at least one synthetic fuel stream is:- a Fisher-Tropsch process; or- a process whereby the syngas stream is first converted to methanol and / or DME, and subsequently to: gasoline, e.g. via a TIGAS process, or aviation fuel, e.g. via a methanol-to- jet fuel (MTJ) process.

26. The process according to claim 25, wherein the step of converting said at least one syngas stream to at least one synthetic fuel stream is a Fisher-Tropsch (FT) process, and wherein a recycle stream from the FT-process, such as FT-tail gas or hydrogenated FT-tail gas, is supplied upstream the RWGS, e.g. upstream the e-RWGS.03119-WO

Images