Method for producing hydrocarbons

Abstract

Subject of the invention is a method for producing hydrocarbons comprising the steps: (a) synthesizing a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1,4-benzene dicarboxylate as linker, and (b) pyrolyzing the metal- organic framework synthesized in step (a) to obtain a carbon-supported Fe-Ti-oxide catalyst, followed by (i) producing CO in a reverse water-gas-shift reaction by reacting CO2 with H2 over the carbon-supported Fe-Ti-oxide catalyst obtained in step (b), and (ii) producing hydrocarbons in a Fischer-Tropsch reaction by reacting CO produced in step (i) with H2.

Description

[0001] METHOD FOR PRODUCING HYDROCARBONS

[0002] Field of the invention

[0003] The invention relates to methods for producing hydrocarbons including uses of hydrocarbons obtained thereby.

[0004] Background of the invention

[0005] In response to the escalating greenhouse gas (GHG) emissions crisis, integrating the Reverse Water-Gas Shift (RWGS) reaction with Fischer-Tropsch (FT) synthesis has been identified as a promising two-step approach for converting CO2 and H2 into valuable products. However, the requirement for high temperatures to achieve significant CO2 conversion, along with the formation of undesired products (e.g., methane) at high pressures during the RWGS step, presents challenges for integrating the RWGS reaction with FT synthesis. In this context, developing a low-temperature RWGS catalyst that can suppress CO2 methanation, even under high pressure, is desirable for facilitating integration between the two processes.

[0006] Although most research has focused on the development of noble metal catalysts due to their high selectivity towards carbon monoxide, there is growing interest in using inexpensive and abundant non-noble metals. In particular, iron oxides have attracted attention as cost-effective and promising CO2 reduction catalysts for the RWGS process. However, at high temperatures in the presence of syngas, the formation of iron carbide becomes a prominent issue, ultimately leading to enhanced methanation and subsequent catalyst deactivation.

[0007] Recently, Castells-Gil et al., Chem. Catal. 2021 , 1 (2), 364-382, demonstrated that the oxidic form of iron can be stabilized through the formation of a mixed oxide based on the Fe-Ti-0 system, thus preventing its reduction to metallic iron and the subsequent formation of iron carbide. They synthesized carbon-supported titanomaghemite nanoparticles through the thermal decomposition of the metal-organic framework (MOF) known as MUV-101 [TiFe2O(X)3(Benzene-1 ,3,5-tricarboxylate)2 (X = OH-, O2H2O)]. For the thermal decomposition, the synthesized MUV-101 (Fe, Ti) was heated in a tubular oven up to 600 °C under inert atmosphere (N2; anhydrous conditions, i.e., in the absence of water) for 8 h. The resulting stabilized titanomaghemite phase exhibited an Fe / Ti ratio close to 2, which is not achievable through soft-chemistry routes, and a BET surface of 250 m2 / g. Further, the obtained nanoparticles demonstrated catalytic activity for the production of CO from CO2. Despite the performance of the MUV-101-derived catalyst, the high cost associated with the ligand limits its scalability for practical applications. Overall, there remains a general desire for an improved integration of an RWGS reaction with an FT synthesis.

[0008] Problem underlying the invention

[0009] It is an object of the present invention to provide a method for producing hydrocarbons which at least partially overcomes the drawbacks encountered in the art.

[0010] It is in particular an object of the present invention to provide a method for producing hydrocarbons in which a reverse water-gas shift reaction is performed at advantageously low temperatures.

[0011] It is furthermore an object of the present invention to provide a method for producing hydrocarbons of higher carbon numbers, especially C5+ hydrocarbons.

[0012] It is additionally an object of the present invention to provide method for producing hydrocarbons which shows improved catalyst activity, improved catalyst stability and / or improved catalyst CO selectivity in a reverse water-gas shift reaction.

[0013] It is also an object of the present invention to provide methods of using produced hydrocarbons which at least partially overcome the drawbacks encountered in the art.

[0014] Disclosure of the invention

[0015] Surprisingly, it has been found that the problem underlying the invention is overcome by methods according to the claims. Further embodiments of the invention are outlined throughout the description. Subject of the invention is a method for producing hydrocarbons comprising the steps:

[0016] (a) synthesizing a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker, and

[0017] (b) pyrolyzing the metal-organic framework synthesized in step (a) to obtain a carbon- supported Fe-Ti-oxide catalyst, followed by

[0018] (i) producing CO in a reverse water-gas-shift reaction by reacting CO2 with H2 over the carbon-supported Fe-Ti-oxide catalyst obtained in step (b), and

[0019] (ii) producing hydrocarbons in a Fischer-Tropsch reaction by reacting CO produced in step (i) with H2.

[0020] The logic sequence of steps in the method according to the present invention is as follows: step (a) is followed by step (b) which is followed by step (i) which is followed by step (ii), i.e., (a) ■=> (b) ■=> (i) ■=> (ii). Accordingly, step (i) can alternatively be named step (c), and step (ii) can alternatively be named step (d). The method according to the present invention only comprises these steps so that additional steps before and after each of steps (a), (b), (i) and (ii), respectively, may be present while the method is still a method according to the present invention. That is, the list of steps (a), (b), (i) and (ii) is not exclusive.

[0021] Preparations and definitions

[0022] A pyrolysis used for preparing a carbon-supported Fe-Ti-oxide catalyst used in the present invention refers to the thermal decomposition of the metal-organic framework (MOF), i.e., the metal-organic framework having the MIL-88B structure and comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker (or ligand). As known in the art, a thermal decomposition (also referred to as thermolysis) is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. Hence, for the pyrolysis for obtaining the catalyst used in the present invention a heating of the metal-organic framework above its decomposition temperature is required. The metal-organic framework thus serves as a precursor for the catalyst used in the present invention, i.e., the MOF is a catalyst precursor. The conditions of the pyrolysis are controlled, and the pyrolysis typically occurs under inert atmosphere, for example under a nitrogen (N2) atmosphere. The pyrolysis leads to the removal of organic ligands and to the generation of porous carbonaceous materials with unique properties. However, these unique properties cannot be described satisfactorily with one or a few structural properties which could be determined to a sufficient degree of precision. Accordingly, the carbon-supported Fe-Ti-oxide catalyst used in the present invention is defined via its synthesis route, namely that it is obtained by pyrolysis of a metal-organic framework with an MIL-88B structure which comprises Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker between the metal centres. It is preferred that the carbon-supported Fe-Ti-oxide catalyst according to the present invention is obtained by pyrolysis of a metal-organic framework with an MIL-88B structure which consists of Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker, i.e., as linker between the metal centres. That is the 1 ,4-benzene dicarboxylate acts as linker or linking molecule between Fe and Ti atoms forming metal centres in the MIL-88B structure. It is preferred that the MIL-88B structure which serves as a precursor contains no layered double hydroxides, more preferably no layered hydroxides and still more preferably no hydroxide species. It is preferred that the MIL-88B structure which serves as a precursor contains no NH2 groups and / or no NO3 groups, more preferably no nitrogen. It is preferred that the MIL-88B structure which serves as a precursor is not linked or bound to a polyacrylonitrile nanofiber membrane, is more preferably not linked or bound to a polyacrylonitrile-containing substance and is still more preferably not linked or bound to a fibre membrane.

[0023] More specifically, the pyrolysis process and subsequent carbonization - which occur before step (i) of the method according to the present invention - typically involve several key mechanisms. During the initial stages of pyrolysis, the decomposition of organic ligands leads to the release of volatile gases and the formation of metal oxide and / or metal carbide nanoparticles. These nanoparticles act as templates for the subsequent growth of carbon structures. Further pyrolysis at higher temperatures may induce the graphitization of the carbon, resulting in the formation of regularly well-ordered carbon frameworks. The pyrolysis will then regularly form graphitic carbon with increased crystallinity and conductivity. On the other hand, lower temperatures regularly result in amorphous carbon structures with enhanced surface area and porosity. In any event, the pyrolysis leads to a unique carbon structure, including e.g. porosity, and surface chemistry. One of the main advantages of the pyrolysis as used in the present invention for obtaining the catalyst for step (i) is the conversion of MOFs (MIL-88Bs) into carbon-based materials which exhibit better thermal stability, high surface areas, and tunable pore sizes.

[0024] In this context, it is preferred for a carbon-supported catalyst used in the method of the present invention that its carbon support is formed from a porous carbonaceous material. With the carbon support being porous gaseous species, especially CO2 and H2, can more easily penetrate the catalyst. This can enhance the activity of the catalyst in the reverse water-gas shift reaction of step (i).

[0025] As used herein, a steam pyrolysis is a pyrolysis which occurs in the presence of steam, i.e. , in the presence of gaseous water (H2O). A preferable steam pyrolysis is a thermal decomposition method in which inert gas, like N2, passes through a temperature-controlled water stream and enters a pyrolysis tube as wet gas which is facilitating more carbon burning. Hence, more stable and less carbonaceous material is typically obtained.

[0026] A metal-organic framework (in the art and herein sometimes abbreviated “MOF”) is a crystalline material in which metal centres are connected three-dimensionally by bridging ligands (so-called linkers; or linking molecules) in repeating coordination units. The expression “MIL-88B” (wherein MIL stands for “Materiaux de I'lnstitut Lavoisier1’’, a review of MIL structures is for example provided by H. Zhang et al. in Journal of Hazardous Materials, 429, 2022, 128271) refers to a specific metal-organic framework structure of the general formula M3X(H2O)2O(BDC)3, wherein M is a positive trivalent metal centre (M3+), X is one of Cl", F" and OH", and BDC is 1 ,4-benzene dicarboxylate. In the MIL-88B structure, the metal centres are arranged in trimeric M3O units, the so-called secondary building units (SBU), which are linked by 1 ,4-benzene dicarboxylate linkers (i.e., 1 ,4-benzene dicarboxylate molecules) to form a three-dimensional structure. Regularly, solvent molecules are coordinated to two of the three metal centres of each secondary building unit, which can be removed by heating or vacuum treatment. This results in coordinatively unsaturated metal centres that can interact directly with guest molecules. The MIL-88B structure contains rodshaped, one-dimensional pores parallel to the c-axis of the crystallographic unit cell and approximately oval, cage-like pores. Herein and in the art, the one or more metals forming the metal centre M are typically listed in brackets behind the expression “MIL-88B”. For example, MIL-88B containing only iron (Fe) is regularly noted down as “MIL-88B (Fe)”. In the present invention, MIL-88B containing iron and titanium (Ti) is used, which is referred to as “MIL-88B (Fe, Ti)”. This terminology also reflects that the iron and the titanium are present in the MIL-88B structure as metal centres. It is preferred that only iron and titanium form metal centres in the metal-organic framework which is pyrolyzed to obtain the catalyst according to the present invention, i.e., that the metal centres of the MIL-88B structure are exclusively formed by iron and titanium, respectively. Such a preferred MOF is also referred to as “bimetallic MIL-88B (Fe, Ti)”. Titanomagnetites have the general formula Fe3-xTixC>4, with 0 < x < 1 . A specific titanomagnetite is ulvdspinel (Fe2TiC>4; x = 1). It can also be said that the compositional parameter x gives the fraction of ulvdspinel ((1-x)FeaO4 xFe2TiC>4) or the mole fraction of Ti4+in a particular titanomagnetite or titanomagnetite composition. Ulvdspinel belongs to the spinel group of minerals.

[0027] Synthetic fuels are fuels which are not obtained from natural sources, i.e. , they are not fossil fuels. Rather, synthetic fuels are chemically synthesized from various raw materials. Synthetic fuels can serve as a replacement fuel for fossil fuels. Synthetic fuels are regularly manufactured using captured carbon dioxide or carbon monoxide, together with hydrogen. The hydrogen may in particular be obtained from water splitting, especially by sustainable electricity sources such as wind and solar power.

[0028] Effects of the invention

[0029] Amid rising concerns about greenhouse gas (GHG) emissions, carbon dioxide (CO2) emissions stand as one of the most crucial global problems, totaling 36.8 Gt in 2022. So far, two main strategies have been proposed for the mitigation of CO2 emissions: (i) carbon dioxide capture and storage (CCS), and (ii) carbon dioxide capture and utilization (CCU), where CO2 is used as a feedstock for chemicals and fuels. Among them, the CCU is preferred over the CCS because the latter presents a risk of CO2 leakage from storage reservoirs and the consequent environmental effects. Particularly, one of the CCU strategies is the CO2 Fischer-Tropsch Synthesis (CO2-FTS) process, which is a viable alternative for converting CO2 into valuable chemicals and fuels. However, controlling the product distribution remains a challenge due to the unpredictable nature of its reaction mechanism. Based on this, combining the Reverse Water-Gas Shift reaction (RWGS, Equation [Eq.] 1) with the FT synthesis (Eq. 2) is a promising approach to convert in two steps CO2 and H2 into valuable hydrocarbons, including alcohols, aromatics, olefins, and synthetic fuels.

[0030] CO2+ H2CO + H2O AH0= 41.2 kJ mol’1(1)

[0031] CO + 2H2«-> (-CH2-) + H2O AH0= -152 kJ mol’1(2)

[0032] The RWGS reaction is thermodynamically favorable at high temperatures; however, at low temperatures, the exothermic reactions such as CO2 methanation (Sabatier reaction), methanol production, and CO methanation are favored. This prevents higher CO production at moderate temperatures (Eq. 3-5). As a consequence, the RWGS reaction needs to be conducted at elevated temperatures (>700°C) to achieve high CO2 conversions, which creates a temperature gap when coupled with an FTS unit (250-400°C).

[0033] CO2+ 4H2CH4+ 2H2O AH0= -165 kJ mol’1(3)

[0034] CO2+ 3H2CH3OH +H2O AH0= -49.8 kJ mol’1(4)

[0035] CO + 3H2CH4+ H2O AH0= -206 kJ mol’1(5)

[0036] Likewise, operating at elevated temperatures compromises the durability of both the catalyst and the reactor, leading to reduced operational lifespans. Furthermore, at high temperatures, potential issues such as catalyst coking, attrition, and the sintering of active metal sites can be anticipated. Another critical point for harmonizing the RWGS and FT reactions, and making the process efficient, is that the pressure of both systems should be similar (around 20 bar).

[0037] In the present invention, a new carbon-supported Fe-Ti-oxide catalyst which meets the above-described requirements is synthesized and subsequently used. More specifically, the carbon-supported Fe-Ti-oxide catalyst used in the present invention showed high activity and stability for the RWGS reaction, achieving up to 97% CO selectivity with equilibrium CO2 conversion levels at moderate temperatures and high pressures. A kinetic study was conducted to determine the kinetic parameters that describe the catalytic system, revealing a good alignment between the experimental and simulated data. The parity plot and an R2value of 0.99 highlight the robustness and reliability of the estimated kinetic parameters. embodiments of the inventive method

[0038] In addition to other preferred embodiments of the inventive method described herein, the following embodiments are particularly preferred embodiments of the method according to the present invention:

[0039] It is preferred for a method according to the present invention that step (i) is carried out at a temperature of < 500°C, more preferably at a temperature of < 450°C and still more preferably at a temperature of < 425°C. In these preferred cases, the RWGS reaction in step (i) is performed at advantageously lowered temperatures and hence at less energy costs, but without compromising the yield of carbon monoxide obtained in step (i). It is preferred for a method according to the present invention that step (ii) is carried out over a catalyst comprising SiC>2 (silica) and Co (cobalt). When the catalyst used for producing hydrocarbons in a Fischer-Tropsch reaction in step (ii) comprises SiC>2 and Co, the yield of hydrocarbons obtained in step (ii) can be improved and favoured C5+ hydrocarbons can be produced in higher amounts.

[0040] It is preferred for a method according to the present invention that the method further comprises a step of removing water after step (i) and before step (ii). Water present in step (ii) might hamper the Fischer-Tropsch reaction. Accordingly, when the method according to the present invention comprises a water removal step between step (i) and step (ii), i.e., when that the method further comprises a step of removing water after step (i) and before step (ii), the yield of hydrocarbons obtained in step (ii) can be improved.

[0041] It is preferred for a method according to the present invention that CO2 and / or H2 remaining after step (i) is at least partially, and preferably completely, recycled as an additional CO2 feed and / or H2 feed to the carbon-supported Fe-Ti-oxide catalyst. When CO2 remaining after step (i) is at least partially recycled as an additional CO2 feed to the carbon-supported Fe-Ti-oxide catalyst, less or even no CO2 is vented to the atmosphere and the carbon footprint of the method according to the present invention can be improved. Additionally, a purer syngas is fed to the FT reactor favouring optimal reaction conditions. This is advantageous because if CO2 is present and is especially present in a too large proportion, the CO2 despite being inert could undesirably reduce the FT performance. When H2 remaining after step (i) is at least partially recycled as an additional H2 feed to the carbon- supported Fe-Ti-oxide catalyst, valuable H2 is not lost, but is advantageously used in the method according to the present invention to further enhance the CO yield in step (i).

[0042] It is preferred for a method according to the present invention that the carbon-supported Fe-Ti-oxide catalyst substantially consists of titanomaghemite particles. In the context of the present invention, the catalyst’s composition is preferably determined by Transmission Electron Microscopy (TEM) and High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).

[0043] It is preferred for a method according to the present invention that the carbon-supported Fe-Ti-oxide catalyst substantially consists of particles which have an average particle size of 3 to 7 nm, more preferably of 4 to 6 nm and still more preferably of 5 nm. In the context of the present invention, the catalyst’s particle size is preferably determined by Transmission Electron Microscopy (TEM) and High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM).

[0044] It is preferred for a method according to the present invention that that the carbon-supported Fe-Ti-oxide catalyst has an atomic Ti / Fe ratio of 3: 1 to 1 : 1 , more preferably of 2.5: 1 to 1 .5: 1 and especially preferred of about 2. In the context of the present invention, the atomic Ti / Fe ratio is preferably determined by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0045] It is preferred for a method according to the present invention that the Fe-Ti-oxide comprises titanomaghemite. Without wishing to be bound by theory, it is believed that titanomaghemite acts as a particularly active catalyst component in a reverse water-gas shift reaction. Accordingly, with the presence of titanomaghemite in the catalyst used in step (i), the reverse water-gas shift reaction can exhibit improved catalyst activity, improved catalyst stability and improved catalyst CO selectivity, respectively.

[0046] It is preferred for a method according to the present invention that the Fe-Ti-oxide comprises Fe2TiO4. Without wishing to be bound by theory, it is believed that Fe2TiO4 acts as a particularly active catalyst component in a reverse water-gas shift reaction. Accordingly, with the presence of Fe2TiO4 in the catalyst used in step (i), the reverse water-gas shift reaction can exhibit improved catalyst activity, improved catalyst stability and improved catalyst CO selectivity, respectively.

[0047] It is preferred for a catalyst used in step (i) of the method according to the present invention that a powder X-ray diffraction (PXRD) analysis, in particular a PXRD analysis performed as described in further detail herein, of the metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker (acting as a template for the catalyst) shows reflections in 20 at about 9.47, 10.63, 13.33, 16.4, 16.94, 18.92, 19.49, 21.1 , 23.57, 25.09, 25.48, 26.67, 28.74 and / or 29.96 degrees. More preferably, the PXRD analysis of the MOF (the MIL-88B) shows all the afore-listed reflections. A pyrolysis of such a metal-organic framework can yield a catalyst for use in step (i) of a method according to the present invention in a particularly reliable manner.

[0048] It is preferred for a catalyst used in step (i) of the method according to the present invention that a powder X-ray diffraction (PXRD) analysis, in particular a PXRD analysis performed as described in further detail herein, of the catalyst itself shows reflections in 20 at about 30.28, 35.65, 43.38, 53.64, 57.23, 62.89, 71.39, 74.43 and / or 79.46 degrees. More preferably, the PXRD analysis of the catalyst itself shows all the afore-listed reflections. A catalyst having a specific crystallographic structure as demonstrated by such a PXRD analysis result can have improved activity and / or improved stability in the reverse water- gas shift reaction of step (i) of the inventive method.

[0049] It is preferred for a method according to the present invention that a PXRD analysis, in particular performed as described in further detail herein, of the catalyst used in step (i) thereof does not show a reflection pattern which corresponds to Fe2C>3, and does especially not show a reflection pattern which corresponds to a-Fe2C>3.

[0050] It is preferred for a catalyst used in step (i) of the method according to the present invention that the catalyst has a Raman spectrum showing two peaks at about 1360 cm-1(D band) and at about 1590 cm-1(G band). In this context is particularly preferred for a catalyst used in step (i) of the method according to the present invention that the ratio IG / ID of the Raman intensity IG of the G band to the Raman intensity ID of the D band is in the range of 1 .20 to 1.40, more preferably in the range of 1.25 to 1.35, and still more preferably in the range of 1.27 to 1.33. When the Raman spectrum of the catalyst shows the indicated peaks at about 1360 cm-1(D band) and at about 1590 cm-1(G band), the micromorphology of the catalyst can provide an increased number of catalytically active sites. Hence, the catalyst showing the preferred Raman spectrum can have improved activity and / or improved stability in a reverse water-gas shift reaction of step (i) of the inventive method. These effects are even more pronounced when the intensity the ratio IG / ID is in the range of 1.20 to 1.40, still more pronounced when the intensity the ratio IG / ID is in the range of 1.25 to 1.35 and particularly pronounced when the intensity the ratio IG / ID is in the range of 1.27 to 1.33.

[0051] It is preferred for a catalyst used in step (i) of the method according to the present invention that the catalyst shows in a temperature-programmed reduction coupled with mass spectrometry (TPR-MS) analysis a peak at a temperature of 230 °C, a broad peak in the range of 250-450 °C and / or a broad peak above 500 °C. The TPR-MS data indicate that the catalyst used in step (i) of the method according to the present invention should preferably not be exposed to temperatures above 500°C when catalysing a reaction and in particular when catalysing a reverse water-gas shift reaction in order to avoid metallic Fe formation and hydrogenation / decomposition of the carbon support. It is preferred for a catalyst used in step (i) of the method according to the present invention that the catalyst has a BET surface area of < 500 m2 / g, more preferably of < 200 m2 / g. With such a reduced BET surface area, less gaseous reactants may disadvantageously be entrapped in the catalysts. In turn, the catalyst activity in the reverse water-gas shift reaction of step (i) can be improved. It is preferred for a catalyst used in step (i) of the method according to the present invention that the catalyst has a BET surface area of > 150 m2 / g. With such a BET surface area, there is still enough surface available for improving the catalyst activity in the reverse water-gas shift reaction of step (i). It is particularly preferred for a catalyst used in step (i) of the method according to the present invention that the catalyst has a BET surface area in the range of > 150 m2 / g to < 500 m2 / g, more preferably in the range of > 150 m2 / g to < 200 m2 / g. With such a setting of the BET surface, the improvements in terms of catalyst activity in the reverse water-gas shift reaction of step (i) can be optimized.

[0052] It is preferred for a method according to the present invention that the pyrolysis for obtaining the carbon-supported Fe-Ti-oxide catalyst is a steam pyrolysis, i.e. , that step (b) occurs in the presence of steam. When the pyrolysis is a steam pyrolysis, the obtained carbon- supported Fe-Ti-oxide catalyst typically has a higher degree of crystallinity. The increased crystallinity can make the catalyst more stable and also more reactive in the reverse water- gas shift reaction of step (i) as the number of distinct reaction sites is increased. Hence, the preferred steam pyrolysis can yield a catalyst with improved activity and / or improved stability in the reverse water-gas shift reaction of step (i).

[0053] It is preferred for a method according to the present invention that the preferable steam pyrolysis is carried out under an atmosphere consisting of inert gas and steam, more preferably consisting of nitrogen and steam. With the use of such a preferred atmosphere the pyrolysis of the metal-organic framework which functions as a precursor for the catalyst used in step (i) can be improved in terms of shorter reaction times and / or completeness of conversion of the MOF (the MIL-88B) into the carbon-supported Fe-Ti-oxide catalyst. Additionally, when the steam pyrolysis is carried out under an atmosphere consisting of inert gas and steam and is particularly preferably carried out under an atmosphere consisting of nitrogen and steam, the pyrolysis can be performed at advantageously lowered temperatures which further contribute to the economics of the catalyst, i.e., contribute to lowered costs for the preparation of the catalyst, thereby also lowering the costs for the method according to the present invention. It is preferred for a method according to the present invention that the pyrolysis is a steam pyrolysis which is carried out under a steam partial pressure of < 10 kPa, more preferably of < 8 kPa, still more preferably of < 4 kPa, and even more preferably < 1 kPa. Particularly preferred steam partial pressures for the pyrolysis are 0.86, 3.13 and 7.28 kPa, more preferred 0.86 and 3.13, and especially preferred 0.86 kPa.

[0054] It is preferred for a method according to the present invention that the pyrolysis in step (b) is carried out for < 7 hours, preferably for < 4 hours. It is preferred for a method according to the present invention that the pyrolysis in step (b) is carried out for > 1 hour, preferably for > 2 hours. It is particularly preferred for a method according to the present invention that the pyrolysis in step (b) is carried out for > 1 hour to < 7 hours, preferably for > 2 hours to

[0055] < 4 hours. With such preferred reduced pyrolysis times, the synthesis for obtaining the carbon-supported Fe-Ti-oxide catalyst for step (i) can become more economic, thereby reducing the costs for the catalyst preparation and thus also reducing the costs for the method according to the present invention. Thereby, the method’s scalability for practical applications is further improved.

[0056] It is preferred for a method according to the present invention that the pyrolysis in step (b) is carried out at a temperature of > 450 °C, more preferably at a temperature of > 475 °C, and still more preferably at a temperature of > 500 °C. When the pyrolysis in step (b) is carried out at a temperature of > 450 °C, a particularly effective decomposition of the MOF (the MIL-88B) acting as the catalyst precursor can be achieved. This effect is further improved for a pyrolysis which is carried out in step (b) at a temperature of > 475 °C, and the effectiveness is particularly pronounced for a pyrolysis which is carried out in step (b) at a temperature of > 500 °C.

[0057] It is preferred for a method according to the present invention that the pyrolysis in step (b) is carried out at a temperature of < 700 °C, more preferably at a temperature of < 600 °C, and still more preferably at a temperature of < 550 °C. When the pyrolysis in step (b) is carried out at a temperature of < 700 °C, it is actually performed at advantageously lowered temperatures which contribute to the economics of the catalyst and hence of the inventive method, namely to lowered costs for the preparation of the catalyst used in step (i). This cost effect is even higher for a pyrolysis which is carried out in step (b) at a temperature of

[0058] < 600 °C, and the cost effect is particularly pronounced for a pyrolysis which is carried out in step (b) at a temperature of < 550 °C. It is preferred for a method according to the present invention that the pyrolysis in step (b) is carried out at a temperature in the range of > 450 °C to < 700 °C, more preferably at a temperature in the range of > 475 °C to < 600 °C, and still more preferably at a temperature in the range of > 500 °C to < 550 °C. When the pyrolysis is carried out in step (b) at a temperature in the range of > 450 °C to < 700 °C, a particularly effective decomposition of the MOF (the MIL-88B) can be achieved while still working at advantageously low temperatures which in turn lowers the costs for the preparation of the catalyst and hence lowers the costs of the inventive method. These effects are further improved when the pyrolysis is carried out in step (b) at a temperature in the range of > 475 °C to < 600 °C, and even further improved when the pyrolysis is carried out in step (b) at a temperature in the range of > 500 °C to < 550 °C.

[0059] It is preferred for a method according to the present invention that the pyrolysis in step (b) is a steam pyrolysis which is carried out under a steam partial pressure of < 10 kPa, for < 7 hours and at a temperature of < 700 °C, more preferably under a steam partial pressure of < 10 kPa, for < 7 hours and at a temperature of >450 °C to < 700 °C. It is more preferred that the pyrolysis in step (b) is a steam pyrolysis which is carried out in step (b) under a steam partial pressure of < 8 kPa, for < 4 hours and at a temperature of < 600 °C, more preferably under a steam partial pressure of < 8 kPa, for < 4 hours and at a temperature of >450 °C to < 600 °C.

[0060] It is preferred for a catalyst used in step (i) of the method according to the present invention that after the pyrolysis in step (b) the catalyst is cooled down to a temperature of < 40 °C and is then passivated in continuous flow comprising air. It is more preferred that after the pyrolysis the catalyst is cooled down to a temperature of < 30 °C and is then passivated in continuous flow comprising air. It is further preferred for a catalyst used in step (i) of the method according to the present invention that after the pyrolysis the catalyst is cooled down to a temperature of < 40 °C and is then passivated in continuous flow comprising air and inert gas, more preferably comprising air and nitrogen. It is still further preferred for a catalyst used in step (i) of the method according to the present invention that after the pyrolysis the catalyst is cooled down to a temperature of < 30 °C and is then passivated in continuous flow comprising air and inert gas, more preferably comprising air and nitrogen. It is particularly preferred that air is fed to the catalyst with the continuous flow at a rate of 4 to 6 mL min-1, more preferably at a rate at about 5 mL min-1. It is moreover preferred that inert gas and in particular nitrogen is fed to the catalyst with the continuous flow at a rate of 20 to 30 mL min-1, more preferably at a rate of about 25 mL min-1. In the context of the afore-described preferred passivation procedures it is particularly preferred that the continuous flow occurs for a time period of at least 2 hours, more preferably for 2 to 3 hours, still more preferably for about 2 hours. With such preferred passivation procedures, an improved stability can be imparted to the catalyst used in step (i) of the method according to the present invention.

[0061] The metal-organic framework used as a precursor for the catalyst used in the method of the present invention has the structure MIL-88B. Because the metal-organic framework has the structure MIL-88B, a particularly quick and complete conversion thereof into the desired catalyst for use in step (i) is achieved by the pyrolysis in step (b). This adds to the economics of the catalyst and thus of the inventive method, and also adds to the catalyst’s activity and stability in the RWGS reaction of step (i), respectively. It is preferred for a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metall centres and 1 ,4-benzene dicarboxylate as linker used in the present invention that it is obtained by a solvothermal reaction. It is further preferred that the solvothermal reaction is performed using FeCh, titanium(IV) isopropoxide, and terephthalic acid in a / V, / V-dimethylformamide / isopropanol solution. It is also preferred that the solvothermal reaction is performed in the presence of acetic acid. It is particularly preferred that the solvothermal reaction is performed using FeCh, titanium(IV) isopropoxide, and terephthalic acid in a / V, / V-dimethylformamide / isopropanol solution and in the additional presence of acetic acid. It is preferred for the metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker used in the present invention that it is present in crystalline form, particularly preferred in the form of brownish rod-shaped and / or spindle-shaped crystals. It is preferred for the metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker used in the present invention that it has an Fe:Ti molar ratio of 3:1 to 1 :1 , more preferably of about 2:1.

[0062] In the first part of the method of the present invention the carbon-supported Fe-Ti-oxide catalyst used in step (i) of the method according to the present invention is synthesized. This catalyst synthesis comprises the steps:

[0063] (a) synthesizing a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker, and

[0064] (b) pyrolyzing the metal-organic framework synthesized in step (a), preferably in the presence of steam, to obtain the carbon-supported Fe-Ti-oxide catalyst. This synthesis of the carbon-supported Fe-Ti-oxide catalyst is performed before step (i) of the method according to the present invention. Accordingly, the method according to the present invention comprises the steps:

[0065] (a) synthesizing a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker, and

[0066] (b) pyrolyzing the metal-organic framework synthesized in step (a), preferably in the presence of steam, to obtain a carbon-supported Fe-Ti-oxide catalyst, followed by

[0067] (i) producing CO in a reverse water-gas-shift reaction by reacting CO2 with H2 over the carbon-supported Fe-Ti-oxide catalyst obtained in step (b), and

[0068] (ii) producing hydrocarbons in a Fischer-Tropsch reaction by reacting CO produced in step (i) with H2.

[0069] Further subjects

[0070] Subject of the invention is also a method according to the present invention followed by a step in which hydrocarbons produced by the method are used as synthetic fuel. The preferred embodiments of the method described herein including the claims are likewise preferred for this specific method according to the present invention in an analogous manner. Generally, any use of hydrocarbons produced by a method according to the present invention as synthetic fuel described herein may also be considered as a corresponding method which is followed by a step in which hydrocarbons produced thereby are used as synthetic fuel.

[0071] Brief description of the drawings

[0072] Fig. 1 shows SEM images of rod- and spindle-shaped crystals of bimetallic MIL-88B (Fe,Ti). Fig. 2 shows a PXRD pattern of MIL-88B (Fe,Ti) powder (upper pattern), as compared to the corresponding simulated powder pattern (lower pattern).

[0073] Fig. 3 shows SEM images and EDS mapping showing the distribution of Fe and Ti through-out rod- and spindle-shaped MIL-88B (Fe,Ti) crystals.

[0074] Fig. 4 shows TGA and DTG curves of MIL-88B (Fe,Ti) with a total weight loss of about 60%. Fig. 5 shows PXRD patterns of FeTi@C550-25, FeTi@C600-25 and FeTi@C700-25 compared with the simulated PXRD patterns of titanomaghemite (lowest pattern), and ilmenite (second lowest pattern). Fig. 6 shows PXRD patterns of FeTi@C550-5, FeTi@C550-25 and FeTi@C550-40 compared with the simulated PXRD pattern of titanomaghemite.

[0075] Fig. 7 shows TEM, HAADF-STEM and particle size distribution of a) FeTi@C550-5, b) FeTi@C550-25, and c) FeTi@C550-40.

[0076] Fig. 8 shows TEM images for FeTi@C-550-5 catalyst (A-B) and STEM-EELS characterization with individual Fe, Ti chemical elemental maps (C-F).

[0077] Fig. 9 shows HAADF-STEM and elemental mapping of fresh FeTi@C550-25.

[0078] Fig. 10 shows HAADF-STEM and elemental mapping of fresh FeTi@C550-40.

[0079] Fig. 11 shows TGA curves of FeTi@C550-X (X = 5, 25, 40) solids.

[0080] Fig. 12 shows N2 adsorption curves of FeTi@C550-X (X = 5, 25, 40 °C) solid at 77 K.

[0081] Fig. 13 shows Raman spectroscopy curves of FeTi@C550-X (X = 5, 25, 40 °C).

[0082] Fig. 14 shows TPR and MS profiles of FeTi@C550-5 catalyst under H2 / Ar (10%) atmosphere with temperature.

[0083] Fig. 15 shows catalytic CO2 reduction results of FeTi@CX-25 (X = 550, 600, 700 °C).

[0084] Fig. 16 shows catalytic CO2 reduction results of FeTi@C550-X (X = 5, 25, 40 °C) with CO production rates.

[0085] Fig. 17 shows PXRD patterns of spent catalysts FeTi@C550-X (X = 5, 25, 40 °C) after 60h on the stream.

[0086] Fig. 18 shows temperature optimization results of FeTi@C550-5 catalyst at GHSV = 12000 mL g-1h’1, P = 30 bar, H2 / CO2 = 3.

[0087] Fig. 19 shows temperature optimization results of FeTi@C550-5 catalyst at different space velocity values of a) 6000 mL g1h1, and b) 24000 mL g’1tr1, P = 30 bar, H2 / CO2 = 3.

[0088] Fig. 20 shows a) pressure optimization at H2 / CO2 = 3 and b) feed H2 / CO2 optimization results of FeTi@C550-5 at P = 30 bar. T = 425 °C and GHSV = 6000 mL g-1h’1.

[0089] Fig. 21 shows a stability check of FeTi@C550-5 catalyst in RWGS after 60 h on the stream. Fig. 22 shows HAADF-STEM and elemental mapping images of spent FeTi@C550-5 catalyst after 60 h on the stream.

[0090] Fig. 23 shows experimental data fitting at P = 30 bar, T = a) 375, b) 400, c) 425 °C with space time values, and a molar fraction parity plot of all components.

[0091] Fig. 24 shows experimental data fitting at a) P = 20 bar, b) P = 40 bar and T = 375, 400, 425 °C with space time values.

[0092] Fig. 25 shows molar fraction parity plots of a) CO2, b) CO and c) CH4.

[0093] Fig. 26 shows Arrhenius plots of RWGS (upper plot) and Sabatier (lower plot) reactions.

[0094] Fig. 27 shows experimental data fitting with a) temperature at P = 40 bar, GHSV = 80,000 mL g-1tr1b) pressure at T = 425 °C, GHSV = 80,000 mL g-1tr1c) space velocity at T = 425 °C, P = 40 bar. H2 / CO2 = 3. Fig. 28 shows flow switching diagrams for testing catalysts in the process of RWGS (a), FTS (b) and RWGS-FTS (c).

[0095] Fig. 29 shows a time plot of CO2 conversion and CO selectivity in the RWGS process [425°C, 30 bar, H2 / CO2 = 1 / 1 , 24000 mL gcat’1h’1].

[0096] Fig. 30 shows a time plot of CO conversion and CH4 selectivity in the FTS process [220°C, 20 bar, H2 / CO = 2 / 1 , 15000 mL gcat’1h’1].

[0097] Fig. 31 shows a time plot of the overall CO2 conversion and CH4 selectivity in the combined RWGS-FTS process [425°C (RWGS) and 210-220°C (FTS), 30 bar, H2 / CO = 1 / 1 , 24000 mL gcaf1h’1].

[0098] Figs. 32a and 32b show time plots of (a) the CO and CO2 conversion and (b) selectivity for CH4 and C5+ at the 2nd(FTS) stage of the combined RWGS-FTS process [425°C (RWGS) and 210-220°C (FTS), 30 bar, H2 / CO = 1 / 1 , 24000 mL gcat’1h’1].

[0099] Fig. 33a and 33b show time plots of (a) CO conversion and (b) CH4 selectivity for FTS [220°C, 30 bar, GHSV = 24000 mL gcat’1IT1] with model syngas (H2 / CO2 / CO = 4 / 4 / 1) and for the 2ndstage of the RWGS-FTS process [425°C / 220°C, 30 bar, H2 / CO = 1 / 1 , 24000 mL gcar1h’1].

[0100] Figs. 34a and 34b show time plots of the overall CO2 conversion and CH4 selectivity (a), and conversion of CO and CO2 at the 2ndstage (b) in the RWGS-FTS process [H2 / CO2 = 1 ; 30 bar; 1ststage: catalyst - S-882@C 550-5°C, 425°C, 24000 mL gcat'1h’1; 2ndstage: catalyst - Co(31)-mSiO2-IWI, 220°C, 4800 mL gcat’1h’1].

[0101] Figs. 35a and 35b show chromatograms of the gaseous product of the RWGS-FTS process obtained from the GC channels with (a) alumina and (b) polysiloxane columns combined with flame-ionization detectors.

[0102] Fig. 36 shows am SIMDIS chromatogram of the solid RWGS-FTS product.

[0103] Fig. 37 shows a molar fraction distribution of the solid RWGS-FTS product.

[0104] Figs. 38a and 38b show time plots of (a) the overall CO2 conversion and CH4 selectivity, and (b) CO and CO2 conversion at the 2ndstage in the RWGS-FTS process [H2 / CO2 = 1 ; 30 bar; 1ststage: catalyst - S-882@C 550-5°C, 425°C, 12000 mL gcat'1h'1; 2ndstage: catalyst - Co(31)-mSiO2-IWI, 220°C, 2400 mL gcar1h-1].

[0105] Fig. 39 shows a hydrocarbons synthesis flow diagram.

[0106] Fig. 40 shows an experimental setup of a steam pyrolysis. Experimental

[0107] Reverse water-gas-shifts catalysts and tests

[0108] Materials and reagents

[0109] Iron(ll) chloride anhydrous (FeCh), benzene-1 ,4-dicarboxylic acid (BDC), titanium isopropoxide (TTIP), N,N-Dimethylformamide anhydrous (DMF), and Propanol-2 (IPA) were purchased from Sigma-Aldrich (Merck). Glacial acetic acid and ethanol were purchased from Fisher Scientific. Before their use in the synthesis, DMF, IPA, and acetic acid were degassed by the freeze-pump-thaw method. The other reagents were used without any additional purification steps.

[0110] Synthesis of bimetallic MIL-88B (Fe,Ti)

[0111] In an argon atmosphere glove box, 1.66 g (10 mmol) of 1 ,4-benzene dicarboxylic acid (BDC) was dissolved in 140 mL of anhydrous DMF at room temperature under stirring, followed by the addition of 10 mL of degassed glacial acetic acid under stirring. Then, 60 mL of IPA was added and the resulting solution was kept under stirring for 10 minutes. Then, 0.42 g (3.33 mmol) FeCh anhydrous was added to the solution under stirring until all the solid was dissolved. Subseguently, 490 pL (1.65 mmol) TTIP was added dropwise under stirring and stirred for an extra 15 min. The jar was taken out of the glove box and heated at 120 °C for 24 h. The obtained solid was collected by centrifugation at 7800 rpm for 5 min, washed three times with DMF and three times with absolute ethanol. Finally, the resulting powder was dried at 85 °C overnight.

[0112] Synthesis of Carbonized MIL-88B (Fe,Ti)

[0113] The steam pyrolysis of MIL-88B (Fe, Ti) was conducted in a guartz reactor placed in a vertical tubular furnace following the method reported by Khan et al., ACS Catal. 2023, 13 (3), 1804-1811. The experimental setup is shown in Fig. 40 (where MOFMS stands for MOF-mediated synthesis). Steam partial pressure at a given temperature can be calculated using the Antoine eguation: P = wherein P is the pressure in mmHg, A, B and C are the Antoine eguation parameters, and T is the temperature. The water content was controlled by varying the temperature of the water cooler connected to the bubbler. In a typical experiment, 500 mg of MIL-88B (Fe, Ti) powder was placed in the reactor under a continuous flow of wet N2 (25 mL min-1) and heated at different temperatures (550, 600, and 700 °C) for 7 or 4 h using a heating ramp of 2 °C min-1. After cooling down of the reactor the sample was passivated in continuous flow of N2 (25 mL min-1) and air (5 mL min-1) for 2 hours.

[0114] Catalyst Characterization

[0115] Powder X-ray diffraction (PXRD) analyses were carried out using a Bruker D8 Advanced diffractometer configured in the Bragg-Brentano geometry fitted with a copper tube operating at 40 kV and 40 mA. The diffractograms for the MOF-derived materials were acquired over a 20 range of 10-90°, employing a step size of 0.2° with a time per step of 8 seconds. The diffractograms for the MIL-88B (Fe, Ti) were acquired over a 20 range of 4-40°, employing a step size of 0.018° with a time per step of 1 second. The crystalline phases were identified by comparison data from the Powder Diffraction File PDF-4; see Blanton et al., Powder Diffr. 2019, 34 (4), 352-360.

[0116] Scanning electron microscopy (SEM) images were recorded using a Zeiss Merlin scanning electron microscope (SEM), which operated at a constant acceleration voltage of 8 kV and an emission current of 50 pA. The SEM equipped with an energy-dispersive X-ray spectroscopy (EDX) detector (Oxford Instruments) was used for elemental mapping.

[0117] N2 adsorption-desorption measurements were performed at 77 K using a Micromeritics ASAP 2040 instrument. Before measurements samples were degassed at 120 °C for 12 h under vacuum.

[0118] Thermogravimetric (TG) data were collected under a nitrogen atmosphere using a Mettler- Toledo thermal analyzer at a heating rate of 5 °C min"1in the 25-700 °C temperature range and a gas flow of 25 mL min-1for MIL-88B (Fe, Ti). For the MOF-derived materials the thermal decomposition was performed in air atmosphere under the conditions described above.

[0119] Temperature programmed reduction (TPR) coupled with mass spectrometer (MS) was conducted using a Micromeritics ASAP 2920. Firstly, the sample (50 mg) was placed in a U-tube quartz reactor and pretreated (5 °C min-1) in Ar flow at 120 °C for 30 min. Subsequently, the gas flow was switched to 10% H2 / Ar flow at a rate of 50 mL / min. The heating ramp was set at 10 °C per minute up to 600 °C. A thermal conductivity detector (TCD) was employed to monitor the H2 reduction process.

[0120] X-ray photoelectron spectroscopy (XPS) measurements were performed using a Kratos / Shimadzu Amicus equipped with Dual Mg / AI anodes and single channeltron detector. The XPS spectra of the samples were acquired at a base pressure of 3- 1 O'7Pa using Al anode at fixed analyzed pass energy of E = 150 eV. Binding energies were referenced to the sp2hybridized (C=C) carbon for the C 1s peak set at 284.4 eV. The data were analyzed using CasaXPS software (version 2.3.16).

[0121] Raman spectra were recorded using a confocal Raman microscope WITec Apyron equipped with a 532 nm laser and power of 0.5 mW. An objective Zeiss LD EC Epiplan- Neofluar Die 50x 1 0.55 was used to collect Raman spectra with an integration time of 0.5 s and accumulation number of 20. Raman spectra from different locations were collected for each sample.

[0122] High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images, coupled with energy dispersive X-ray spectroscopy (EDS), were obtained using a Cs-probe corrected Titan microscope from Thermo Fisher Scientific, operating at an accelerating voltage of 300 kV. Imaging and spectroscopy data sets were acquired and analyzed with the Velox software package, also from Thermo Fisher Scientific. The generated maps underwent minor post-filtering through the application of a Gaussian filter with a sigma value of 0.8.

[0123] Transmission electron microscopy (TEM) of the samples was performed with a Titan ST microscope from Thermo Fisher Scientific operating at an accelerating voltage of 300 kV. For each sample, the size of at least 150 particles was measured and the average size and the standard distribution were obtained.

[0124] Catalytic tests

[0125] Catalytic tests were conducted using the Avantium 4-channel Flowrence unit, and in each experiment, the first reactor was used as a blank for subsequent calculations. Catalysts were reduced in the presence of an H2 / CO2 = 5 mixture for a duration of 4 hours at 425 °C and at atmospheric pressure. Subsequently, the reactors were pressurized stepwise in the 15-50 bar range, and then a feed mixture with an H2 / CO2 = 3 ratio was introduced into the reactors. The flow rate of this mixture varied depending on the desired gas hourly space velocity (GHSV), which ranged from 6,000 to 24,000 ml goat'1h’1. The effect of feed H2 / CO2 ratio was also studied in 0.5-4 range. In each analysis, 8 vol% helium (He) flow was included in the feed mixture as an internal standard. The reactor tubes were made of stainless steel, with an inner diameter of 2 mm and a length of 300 mm. To ensure that the catalyst remained in the isothermal zone of the furnace, the reactors were initially loaded with 0.2 mL of silicon carbide particles (100 pm particle size). The pressurization system employed a membrane-based controller, regulated by the flow of diluent nitrogen (N2). For each change in reaction conditions, 10 minutes were allowed for stabilization.

[0126] CO2 conversion (XQQ2, %), product selectivity (Sy, %) and space time yield of CO (STYQQ, mmolgo gcat'1h-1) was calculated using the equations below (Eq. 6-8): CCo2blank. CHereactor. and CHeblankare reactor and blank concentration values of CO2 and He, respectively. Cyis the concentration of y product determined by gas chromatography (GC), and GHSVQO2is the space velocity of CO2. Product analysis was performed on a dry basis in an Agilent 7890B GC with RGA configuration, equipped with two sample loops one TCD and 2 Fl Ds detectors. After flushing the loops for 15 min, the products are injected. One sample loop is directed toward the TCD channel using argon as the gas carrier, with 2 Hayesep precolumns and a MS5A column, where He, H2, O2, N2, CH4, and CO are separated in the MS5A column; and further separation of permanent gases is done on another Hayesep column (Haysep Q 6 Ft G3591-80013) to separate CO2 going to the MS5A column. Another Hayesep column (Hayesep Q 0.5 m G3591-80023) prevents the heavier components in the reaction mixture to reach the molecular sieve column. The other sample loop is directed toward an Innowax precolumn (15 m, 0.2 mm o.d., 0.4 pm film) to slow down oxygenates and heavy hydrocarbons. In the first minute of the method, the gases coming from the precolumn are sent to the Gaspro column (Gaspro 30 M, 0.32 mm o.d). After 2.5 min, the valve is switched and gases are sent to another Innowax column (30 m, 0.2 mm o.d., 0.4 pm). Products from both columns are analyzed through a flame ionization detector (FID). The Gaspro column separates C1-C7 paraffins and olefins, while the Innowax column separates heavier hydrocarbons, oxygenates and aromatics.

[0127] The carbon balance was closely monitored and recorded in all the analytical procedures as 100±5%. The yields of methanol and other hydrocarbons were found to be less than 1 % in all cases. To ensure the reliability and consistency of the obtained data, each experimental run was repeated a minimum of four times.

[0128] Synthesis and characterization of MIL-88B (Fe, Ti) and FeTi@C materials

[0129] To synthesize the new heterometallic MIL-88B (Fe, Ti), a solvothermal reaction was performed using FeCh, titanium(IV) isopropoxide, and terephthalic acid (BDC) in a / V, / V-dimethylformamide (DMF) / isopropanol solution in the presence of acetic acid as a modulator. After 24 h of reaction, brownish rod and spindle-shaped crystals were isolated (Fig. 1). The phase purity of MIL-88B (Fe, Ti) was confirmed by matching the experimental powder X-ray diffraction (PXRD) pattern with the simulated pattern of the monometallic MIL-88B-Fe (Fig. 2). Scanning Electron Microscopy (SEM) further confirmed the formation of spindle- and rod-shaped crystals (Fig. 1), while Energy Dispersive X-ray Spectrometry (EDX) elemental mapping revealed a homogeneous distribution of Fe and Ti, consistent with the expected Fe:Ti molar ratio of 2:1 (Fig. 3).

[0130] The thermal stability of MIL-88B (Fe, Ti) was evaluated using thermogravimetric analysis (TGA), which revealed that the material maintained its crystallinity up to 450°C (Fig. 4). Complete decomposition of the framework occurred at 500°C.

[0131] Next, the carbonization of MIL-88B (Fe, Ti) was carried out at 550, 600, and 700 °C for 7 hours under an N2 / H2O atmosphere. Initially, a steam partial pressure of 3.13 kPa was fixed by setting the bubbler temperature to 25 °C. The resulting samples are denoted as FeTi@C550-25, FeTi@C600-25, and FeTi@C700-25, where the first number represents the pyrolysis temperature and the second the bubbler temperature. PXRD analysis revealed that titanomaghemite (Fe2TiO4) was obtained as a pure phase during steam pyrolysis at 550 °C. However, during pyrolysis at 600 and 700 °C, a mixture of Fe2TiO4 and ilmenite (FeTiOa) was observed (Fig. 5). Without wishing to be bound by theory, it is hypothesized that the presence of ilmenite may be due to the inversion of the metastable titanomaghemite spinel structure, which increases with higher pyrolysis temperatures. After determining the optimal pyrolysis temperature, the influence of water's partial pressure during the pyrolysis was investigated. Similarly, MIL-88B (Fe, Ti) was steam-pyrolyzed at 550°C and at steam partial pressures of 0.86, 3.13, and 7.28 kPa (corresponding to bubbler temperatures of 5, 25, and 40 °C, respectively). The PXRD patterns of FeTi@C550-5, FeTi@C550-25, and FeTi@C550-40 indicate that the steam content does not affect the final phase composition, as Fe2TiC>4 is the only crystalline phase formed during pyrolysis (Fig. 6).

[0132] Transmission Electron Microscopy (TEM) and High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images revealed that FeTi@C550-X solids consist of titanomaghemite nanoparticles, which are highly dispersed within a carbon matrix and have an average particle size of 5 nm (Fig. 7). Elemental analysis by STEM- EDX shows a homogeneous distribution of Fe and Ti, and inductively coupled plasma optical emission spectroscopy (ICP-OES) analysis confirmed the atomic Ti / Fe ratio of about 2 (Figs. 8, 9 and 10).

[0133] Next, thermogravimetric analysis (TGA) of the FeTi@C550-X solids was performed. TGA curves show mass losses of 20% (FeTi@C550-5), 9% (FeTi@C550-25), and 6% (FeTi@C550-40) (Fig. 11). These results confirm the partial gasification of carbon treated under steam, which increases with the water partial pressure. Indeed, N2 adsorption analyses are consistent with TGA results, showing a slight decrease in the BET-specific surface areas with carbon content decreases of 125, 73, and 63 m2g-1for FeTi@C550-5, FeTi@C550-25, and FeTi@C550-40, respectively (Fig. 12).

[0134] Subsequently, the graphitization degree of the carbon matrix was studied by Raman spectroscopy. The Raman spectra of all the catalysts displayed two characteristic peaks at 1360 and 1590 cm-1(Fig. 13). The first peak is a disorder-induced band (D band), characteristic of amorphous or defect graphite, and originates from the double resonance Raman process for sp2 carbon. The latter peak is assigned to the E2g mode of the infinite graphite crystal (G band). The intensity ratio of the two bands (IG / ID) was used to evaluate the graphitization degree of the different solids. Interestingly, it was found that the values of the IG / ID ratio are similar across all catalysts (1.27-1.33), suggesting the same degree of graphitization.

[0135] The reducibility of the materials was studied by temperature-programmed reduction coupled with mass spectrometry (TPR-MS) analysis (Fig. 14). The reduction profile exhibits a first peak at a temperature of 230 °C, which is attributed to the desorption of the trapped water, consistent with the mass spectra (m / z = 18). A second broad peak, observed in the range of 250-450 °C with a maximum at 350 °C, is presumably associated with the reduction of titanomaghemite to titanomagnetite. A broad peak above 500 °C is associated with the reduction of iron species to Fe(0) and the hydrogenation / decomposition of the carbon matrix, as indicated by the presence of carbon monoxide (m / z = 28) and methane (m / z = 16) in the MS profile.

[0136] Catalytic studies

[0137] The catalytic performance of the FeTi@C550-25, FeTi@C600-25, FeTi@C700-25, and FeTi@C550-X (X = 5, 25, 40) catalysts were first evaluated at 425 °C, 30 bar, and gas hourly space velocity (GHSVs) of 12000 mL g-1h-1. The ratio of fed hydrogen and carbon dioxide was H2 / CO2 = 3. The catalytic results indicated that a pyrolysis temperature range of 550 to 600°C did not significantly affect the CO2 conversion and CO selectivity, which remained constant at approximately 33% and 98%, respectively. In contrast, the FeTi@C700-25 catalyst showed a decrease in CO2 conversion (28 %) with lower selectivity towards CO (96%) (Fig. 15). These results confirm that the initial presence of the ilmenite phase has a detrimental effect on the performance of the catalyst. Similarly, no significant differences in the catalytic behavior of the FeTi@C550-X catalysts were observed. Indeed, the CO2 conversion, CO selectivity, and CO production rate values were comparable across all three catalysts (Fig. 16).

[0138] The main differences appear when comparing the PXRD patterns of FeTi@C550-X after the reaction. While no significant changes were observed for the FeTi@C550-5 catalyst (Fig. 17), new peaks appeared in the PXRD patterns of FeTi@C550-25 and FeTi@C550- 40, indicating the formation of ilmenite. Without wishing to be bound by theory, it is hypothesized that the higher carbon content in FeTi@C550-5 has a positive effect on stabilizing the titanomaghemite nanoparticles, thereby reducing the inversion of the spinel structure.

[0139] Based on these results, it was decided to investigate the effect of the operational conditions on the catalytic performance of the FeTi@C550-5 catalyst by varying temperature, pressure, contact time, and H2 / CO2 ratio. Fig. 18 demonstrates that increasing the temperature leads to an increase in CO2 conversion, reaching the RWGS equilibrium conversion levels. However, it was observed that increasing the temperature from 450 °C to 475 °C results in a decrease in CO selectivity and an increase in CH4 selectivity. For example, at a GHSV of 12,000 mL g"1h"1, CO selectivity decreases from 98% (at 450 °C) to 91 % (at 475 °C), while methane selectivity increases from 1.5% to 5.5%. This increase in CH4 selectivity could be attributed to the gasification of the carbon matrix at temperatures around 470 °C. Indeed, upon reducing the reaction temperature from 475 °C to 425°C (return point), a decrease in catalytic activity was observed, confirming the partial degradation of the catalyst (Fig. 18).

[0140] These results are consistent with the TPR analysis, which revealed the presence of carbon monoxide and methane in the MS profile at temperatures above 480 °C (Fig. 14). The effect of GHSV was also evaluated at each temperature. It was found that a lower GHSV increases the CO2 conversion, regardless of the reaction temperature. Conversely, higher selectivity values towards CO were observed when using a higher GHSV, particularly at higher temperatures. This results in an approximately threefold increase in the CO production rate when GHSV values are increased from 6000 to 24000 mL g-1IT1(Fig. 19). Next, the effect of reactor pressure on CO2 conversion and CO selectivity at 425°C and a GHSV of 6000 mL g-1h-1was studied, within the pressure range of 15-50 bar (Fig. 20a). It was found that increasing the pressure up to 50 bar caused a slight decrease in CO selectivity, from approximately 98% to 96%. However, it did not significantly affect CO2 conversion, which remained constant at approximately 38%. This may be attributed to the fact that, at 425 °C, the CO2 conversion obtained is already close to the equilibrium conversion. Then, the catalytic performance of FeTi@C550-5 was evaluated using an H2 / CO2 feed ratio from 1 to 4 at 425 °C (Fig. 20b). This optimization allows to ensure that the H2 / CO ratio at the outlet of the RWGS reactor is suitable for various applications, especially when it is coupled downstream with an optional FTS reactor. It was found that decreasing the H2 concentration yields lower CO2 conversions, but the CO selectivity was barely affected. On the contrary, at higher H2 / CO2 ratios, the CO2 conversion increases due to the greater availability of H2 to hydrogenate the carbonate species. However, a slight increase in methane selectivity was observed. These results are likely seen because the RWGS reaction is stoichiometrically equimolar in terms of reactants, while CO2 methanation is non-equimolar. Analysis of the composition at the outlet of the reactor confirmed the tendency for the H2 / CO ratio to decrease as the H2 / CO2 ratio decreased. For instance, when the reaction was performed at an H2 / CO2 ratio of 1 , a CO2 conversion of 22% was achieved (close to the equilibrium conversion), and an H2 / CO ratio of 3.38 was obtained. In contrast, at an H2 / CO2 ratio of 4, an H2 / CO ratio of 9 was obtained. These results indicate that working at low H2 / CO2 ratios would be suitable for the coupling of the RWGS-FTS process for longer hydrocarbons production, which requires an ideal H2 / CO ratio of 2.

[0141] To better understand the catalyst's stability under reaction conditions, a 60-hour stability test was conducted at 425 °C and 30 bar. As shown in Fig. 21 the catalytic performance of the FeTi@C550-5 catalyst shows no signs of deactivation. Indeed, PXRD and STEM-EDX analyses of FeTi@C550-5 after 60 hours on stream reveal that the nanoparticles remain intact without any structural changes during the reaction (Fig. 22).

[0142] Kinetic Analysis

[0143] Kinetic experiments were conducted to determine the kinetic parameters that describe the catalytic system. The catalytic tests were performed at three different temperatures (375, 400, and 425 °C). For each temperature, the effects of pressure and space-time were studied. Under these reaction conditions, methanol and C2+ hydrocarbon selectivities were less than 1 %; therefore, they were not considered in the kinetic analysis to avoid numerical instability. Importantly, in all experiments, the CO2 conversion levels were kept around 10% to ensure operation within the kinetic regime.

[0144] The kinetic model proposed by Hou and Hughes, Chem. Eng. J. 2001 , 82 (1), 311-328, was adopted and successfully converged to a solution. This model incorporates Freundlich’s concept of non-linear adsorption, where the adsorption terms for CO2 and CH4 are neglected due to the high steam concentration at high temperatures. The proposed rate equations by Hou and Hughes are as follows: Where ki, k2, k3are the kinetic constants for the RWGS, Sabatier and CO methanation reactions, respectively, p; is the partial pressure of components i, and Keq. is the equilibrium constant of reaction j, which was determined from thermodynamic simulations in ASPEN Plus V12 software using a Gibbs reactor under the specified reaction conditions. KQQ, KH2, K|_|2Oarethe adsorption constants for CO, H2and H2O, respectively.

[0145] Figs. 23 and 24 present a comparison between the experimental and calculated data at three different temperatures (375, 400, 425 °C) and at 3 different pressures (20, 30 and 40 bar). Generally, it was observed that the simulated data matched the experimental results, showing an increase in CO and CF with increasing space-time values. Indeed, the parity plots for all components indicate an R2value of 0.9921 (Fig. 23, d). Similarly, the parity plots for each component revealed R2values of 0.9914 for CO2, 0.9908 for CO, and 0.7752 for CF (Fig. 25). These results confirm the good alignment between the experimental and simulated data using the aforementioned kinetic model. The optimal kinetic parameters were determined with 95% confidence intervals, see Table 1.

[0146] Table 1. Estimated kinetic model parameters at reference temperature of T = 665 K

[0147] In addition, the SSE (sum of square errors) value of 4.3e-5 demonstrates the reliability of the fitting. The obtained kinetic constants suggest that the CO methanation reaction rate is slow, which is probably due to the low partial pressure of CO in the reaction medium. The activation energy values for the RWGS and Sabatier reactions were calculated to be 120.56 and 90.64 kJ / mol, respectively. These are in good agreement with the values obtained from the Arrhenius plot (Fig. 26). Further investigation into the kinetics was conducted under various reaction conditions, including temperature, pressure, and space-velocity. The experimental data fitting for CO2, CO, and CH4 is shown in Fig. 27. The formation of CO increased significantly with temperature due to the endothermicity of the RWGS reaction, where the CO2 is mostly converted to CO with a selectivity value of 97% (Fig. 27, a). Due to the stoichiometry of the RWGS and Sabatier reactions, the formation of CH4 is only promoted at higher pressure. A slight promotion of CO formation with increasing pressure was also observed; this is primarily due to the increased adsorption of CO2 and H2 at higher pressures (Fig. 27, b). Lastly, part c) of Fig. 27 shows how CO2, CO, and CH4 mol fractions change with space velocity. At high GHSV values (indicating lower contact time between reactant and catalyst), the conversion of CO2 decreased, which in turn reduced the formation of CO and CH4.

[0148] Conclusions from RWGS catalyst preparations and tests

[0149] The present invention successfully achieved the synthesis of the carbon-supported Fe-Ti-oxide catalyst used in the present invention in a cost-effective manner. It was shown that this is an active catalyst for the reverse water-gas shift reaction, achieving equilibrium CO2 conversion levels and exhibiting an impressive 97% selectivity to CO. Moreover, the catalyst demonstrated remarkable stability, maintaining its performance over 60 hours of continuous operation. HAADF-STEM and elemental mapping images revealed a consistent and stable particle size distribution, with no signs of sintering or phase changes in the mixed iron-titanium oxide phase and these findings were corroborated by PXRD and XPS analyses. H2-TPR analysis shed light on the behavior of the carbon support, indicating that carbon methanation begins at temperatures exceeding 490 °C. Consequently, the reaction temperature was set at 450 °C to prevent undesired reactions, also showing that advantageously low reaction temperatures could be realized with the catalyst used in the present invention. The kinetic experiments yielded valuable insights, with the RWGS reaction rate found to be nearly independent of the partial pressures of H2 and CO2, leading to the adoption of existing rate equations. Importantly, methanol and C2+ yields remained negligible at less than 1%, making them less significant in the kinetic calculations. The carbon-supported Fe-Ti-oxide catalyst used in the present invention inventive not only offers an economically viable synthesis but also shows promising performance in RWGS, holding significant implications as feedstock for a subsequent Fischer-Tropsch synthesis as in the inventive method and hence generally for the hydrocarbon production industry. The present invention thus demonstrates an advantageous use of the developed efficient and cost- effective catalysts in important industrial processes. Fischer-T ropsch catalysts and tests

[0150] Synthesis and characterization of cobalt-silica catalyst

[0151] A cobalt-silica catalyst for the Fischer-T ropsch synthesis (FTS) was prepared by incipient wetness impregnation (IWI). More specifically, a degassed mesoporous silica support (Kieselgel Merck 10184, Sigma-Aldrich) was impregnated with an aqueous solution of cobalt(ll) nitrate. The volume of the solution corresponded to the total pore volume of the support. The resulting mixture was dried overnight under vacuum at 100 °C and then calcined at 400 °C (ramp 1° / min, 2 h) in a flow of air (150 mL / min) in a quartz tube oven. The content of cobalt in the prepared catalyst was determined by the method of wavelength- dispersive X-ray fluorescence (using Bruker S8 Tiger). The catalyst was labelled “Co(31)- mSiC>2-IWI”, wherein the number in brackets stands for the cobalt concentration in wt.%, and “mSiCh” stands for “mesoporous silica”. For preparing the Co(31)-mSiC>2-IWI catalyst, double impregnation with intermediate vacuum drying was used. Textural properties and cobalt content of the prepared catalyst are given in Table 2.

[0152] Table 2. Cobalt content, characteristics of the porous system, and specific surface area of the prepared catalyst.

[0153] On the basis of the H2 chemisorption measurements (using Micromeritics ASAP 2020)

[0154] Testing of catalysts in the combined RWGS-FTS process

[0155] Combined RWGS-FTS tests were performed using a PID EngTech catalytic unit. As a catalyst of the 1ststage (RWGS) the MOF-derived Fe-Ti-catalyst labelled FeTi@C550-5 and prepared as described above was used (herein also referred to as “S-882@C 550- 5°C”). As a catalyst of the 2nd(FTS) stage the Co(31)-mSiO2-IWI catalyst was used. The catalysts were loaded into stainless steel flow reactors without dilution by inert; a catalyst fraction of 100-150 mcm was used. Before combined RWGS-FTS testing, catalysts were activated and tested individually (Fig. 28, parts a and b). Table 3. Conditions for activation and testing of catalysts in the RWGS, FTS and RWGS- FTS processes.

[0156] In the first step, the S-882@C 550-5°C catalyst was activated at 425 °C for 4h in the flow of H2 / CO2 mixture and then tested in the RWGS process (Fig. 28, part a). The average CO2 conversion in this process is 16.3%, and the average CO selectivity is 98.6% (Fig. 29).

[0157] At the second step the Co(33)-mSiC>2-IWI catalyst was activated at 400°C for 10h in the flow of N2 / H2 mixture and then tested in the FTS process (Fig. 28, part b). After 20 h a steady-state FTS performance was achieved. This process is characterized by an average

[0158] CO conversion of 24.3% and average CH4 selectivity of 5.3% (Fig. 30).

[0159] Finally, RWGS and FTS reactors were connected in series and a combined RWGS-FTS test was performed (Table 3, Fig. 28, part c). Time dependence of the overall CO2 conversion and CH4 selectivity is presented in Fig. 31. The RWGS-FTS process had an average overall CO2 conversion of 17.2%, an average CH4 selectivity of 11.7% and an average C5+ selectivity of 33.5% (for the case of 220°C at 2ndstage). Time plot of the conversion of CO and CO2, as well as of the selectivity for CH4 and C5+ in the processing of the RWGS product at the 2nd(FTS) stage are presented in Figs. 32a and 32b. The average CO conversion at the 2ndstage at a temperature of 220°C is 43%, and at a temperature of 210°C it is 32%. At the same time, there is no CO2 conversion at the 2ndstage (Fig. 32a). Increased H2 / CO ratio resulted in high methane selectivity of the FTS process at 220°C; average S(CH4) is 25%. With a decrease in the temperature of the 2ndstage to 210°C, S(CH4) decreased to 9% (Fig. 32b).

[0160] In order to evaluate the effect of water formed at the 1ststage on the FTS process, the feed of the 2ndstage was modeled (the same ratio of CO, CO2 and H2 as in the RWGS product was used for the FTS feed). The conditions of this FTS test are summarized in Table 4.

[0161] Table 4. Conditions of testing of catalysts in the FTS process with a model syngas.

[0162] A comparison of the performances of the FTS process and the 2ndstage of the RWGS-FTS process is presented in Figs. 33a and 33b. As it can be concluded from Figs. 33a and 33b, the water presented in the RWGS product provides higher and more stable CO conversion at the 2ndstage of the RWGS-FTS process in comparison with the FT processing of the model syngas of composition H2 / CO / CO2 = 4 / 4 / 1 - 43% vs. 36% (after 20 h on-stream, Fig. 33a). At the same time, in the case of the RWGS product, lower CH4 selectivity of the 2ndstage is observed compared to FTS -25% vs 32% (after 20h on-stream, Fig. 33b).

[0163] For the next RWGS-FTS tests, in order to provide full conversion of CO formed at the 1ststage, the amount of catalyst in the 2ndreactor was increased by 5 times (from 100 to 500 mg). To avoid overheating and keep uniform temperature profile in the catalyst bed, it was diluted by SiC (120 grit, Alfa Aesar) in the ratio SiC / catalyst = 10 / 1. The conditions of the RWGS-FTS test are presented in Table 5.

[0164] Table 5. Conditions of activation and testing of catalysts in the RWGS-FTS process.

[0165] Average overall CO2 conversion is 13.8%. Complete CO conversion at the 2ndstage results in high CH4 selectivity (20%) of the RWGS-FTS process. In addition, a small portion of CO formed at the 1ststage is converted back to CO2 (Figs. 34a and 34b). The gaseous product of the RWGS-FTS process contained only alkanes (Figs. 35a and 35b).

[0166] The solid product of the RWGS-FTS process was collected in a trap located immediately after the reactor. This product was dissolved in carbon disulfide (to a concentration of 0.1 wt.%) and analyzed by the SIMDIS method (using Agilent 7890A). The thereby obtained chromatogram is presented in Fig. 36. It was established that the solid RWGS-FTS product is a mixture of hydrocarbons with the number of carbon atoms from 13 to 47, the ratio of which corresponds to the Anderson-Schulz-Flory (ASF) distribution. On the basis of the SIMDIS data the ASF parameter a / fa was determined, which was found to be 0.90 (Fig. 37). Combined RWGS-FTS test was also performed with an industrial cobalt-silica catalyst loaded to the 2nd(FTS) reactor. Conditions of the combined RWGS-FTS tests are presented in Table 6.

[0167] Table 6. Conditions of activation and testing of catalysts in the RWGS-FTS process.

[0168] Average overall CO2 conversion is 17.1 %. Similarly, under conditions of full CO conversion, a certain selectivity for methane was observed (19.0%), as well as part of CO is converted back to CO2- X(CO2) = -2.7% (Figs. 38a and 38b).

[0169] Conclusions from combined RWGS-FT tests

[0170] Combined RWGS-FTS catalytic tests have been performed using a series connection of reactors with S-882@C 550-5°C and Co(31)-mSiO2-IWI catalysts. RWGS-FTS process has an overall CO2 conversion of 17.2%, a methane selectivity of 11.7% and a C5+ selectivity of 33.5% (H2 / CO2= 1 ; 30 bar; 1ststage: 425 °C, 24000 mL gcar1h’1; 2ndstage: 220°C, 24000 mL gcat'1h-1). The solid RWGS-FTS product is a mixture of C13-C47 hydrocarbons with the Anderson-Schulz-Flory distribution (alpha is 0.90).

[0171] Exemplary hydrocarbons synthesis flow diagram

[0172] Fig. 39 shows an exemplary hydrocarbons synthesis operation 100 within a fuel plant. Therein, a CO2 rich feed 101 is fed to a reverse water-gas shift (RWGS) reactor 120. Additionally, a H2 rich feed 102 is also fed to the RWGS reactor 120. Optionally, a CO2+H2 mixture 103 feed may also be fed to the RWGS reactor 120. The RWGS reactor 120 contains a carbon-supported Fe-Ti-oxide catalyst as described herein, i.e., a catalyst which was obtained by pyrolysis of a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker between the metal centres, i.e., as linker or linking molecules between Fe and Ti. In the RWGS reactor 120 the fed CO2 and H2 are converted over the catalyst to yield an effluent stream 121 typically comprising syngas (CO+H2), CO2 and H2O. Downstream of the RWGS reactor 120, a Fischer-Tropsch (FT) synthesis unit 130 is arranged. The FT synthesis unit 130 receives at least a portion of the effluent stream 121 and itself yields a raw product 131 which typically contains hydrocarbons, carbon oxides and hydrogen. Part of the effluent stream 121 may also be recycled as an additional CO2 feed 12T to the RWGS reactor 120. Similarly, part of the raw product 131 and especially the hydrogen contained therein may be recycled as an additional hydrogen feed 13T to the RWGS reactor 120.

[0173] List of reference signs

[0174] 100: Hydrocarbons synthesis operation

[0175] 101 : CO2 rich feed

[0176] 102: H2 rich feed

[0177] 103: CO2+H2 mixture

[0178] 120: RWGS reactor

[0179] 121 : Effluent stream

[0180] 12T: Additional CO2 feed

[0181] 130: FT synthesis unit

[0182] 131 : Raw product

[0183] 13T: Additional hydrogen feed

[0184] Further disclosure

[0185] The present invention further provides the following items:

[0186] 1 . A method for producing hydrocarbons comprising the steps:

[0187] (i) producing CO in a reverse water-gas-shift reaction by reacting CO2 with H2 over a carbon-supported Fe-Ti-oxide catalyst obtained by pyrolysis of a metal-organic framework comprising Fe, Ti and 1 ,4-benzene dicarboxylate, and

[0188] (ii) producing hydrocarbons in a Fischer-Tropsch reaction by reacting CO produced in step (i) with H2.

[0189] 2. The method according to item 1 , wherein step (i) is carried out at a temperature of < 500°C. 3. The method according to item 1 or 2, wherein step (ii) is carried out over a catalyst comprising SiC>2 and Co.

[0190] 4. The method according to any preceding item, further comprising a step of removing water after step (i) and before step (ii).

[0191] 5. The method according to any preceding item, wherein CO2 and / or H2 remaining after step (i) is at least partially recycled as an additional CO2 feed and / or H2 feed to the carbon- supported Fe-Ti-oxide catalyst.

[0192] 6. The method according to any preceding item, wherein the Fe-Ti-oxide comprises titanomaghemite.

[0193] 7. The method according to any preceding item, wherein the Fe-Ti-oxide comprises Fe2TiC>4.

[0194] 8. The method according to any preceding item, wherein the carbon-supported Fe-Ti-oxide catalyst has a Raman spectrum showing two peaks at about 1360 cm'1(D band) and at about 1590 cm-1(G band).

[0195] 9. The method according to item 8, wherein the ratio IG / ID of the Raman intensity IG of the G band to the Raman intensity ID of the D band is in the range of 1.20 to 1.40.

[0196] 10. The method according to any preceding item, wherein the carbon-supported Fe-Ti-oxide catalyst has a BET surface area of < 500 m2 / g.

[0197] 11. The method according to any preceding item, wherein the metal-organic framework has the structure MIL-88B.

[0198] 12. The method according to any preceding item, wherein the pyrolysis is carried out at a temperature of < 700°C.

[0199] 13. The method according to any preceding item, wherein the pyrolysis is a steam pyrolysis, preferably carried out under an atmosphere consisting of inert gas and steam, more preferably under an atmosphere consisting of nitrogen and steam. 14. The method according to any preceding item, wherein the pyrolysis is carried out for < 7 hours, preferably for < 4 hours.

[0200] 15. Use of hydrocarbons produced by a method according to any preceding item as synthetic fuel.

Claims

CLAIMS1 . A method for producing hydrocarbons comprising the steps:(a) synthesizing a metal-organic framework of the structure MIL-88B comprising Fe and Ti as metal centres and 1 ,4-benzene dicarboxylate as linker, and(b) pyrolyzing the metal-organic framework synthesized in step (a) to obtain a carbon-supported Fe-Ti-oxide catalyst, followed by(i) producing CO in a reverse water-gas-shift reaction by reacting CO2 with H2 over the carbon-supported Fe-Ti-oxide catalyst obtained in step (b), and(ii) producing hydrocarbons in a Fischer-Tropsch reaction by reacting CO produced in step (i) with H2.

2. The method according to claim 1 , wherein step (i) is carried out at a temperature of < 500°C.

3. The method according to claim 1 or 2, wherein step (ii) is carried out over a catalyst comprising SiO2 and Co.

4. The method according to any preceding claim, further comprising a step of removing water after step (i) and before step (ii).

5. The method according to any preceding claim, wherein CO2 and / or H2 remaining after step (i) is at least partially recycled as an additional CO2 feed and / or H2 feed to the carbon- supported Fe-Ti-oxide catalyst.

6. The method according to any preceding claim, wherein the Fe-Ti-oxide comprises titanomaghemite.

7. The method according to any preceding claim, wherein the Fe-Ti-oxide comprises Fe2TiC>4.

8. The method according to any preceding claim, wherein the carbon-supported Fe-Ti-oxide catalyst has a Raman spectrum showing two peaks at about 1360 cm'1(D band) and at about 1590 cm-1(G band).

9. The method according to claim 8, wherein the ratio IG / ID of the Raman intensity IG of the G band to the Raman intensity ID of the D band is in the range of 1.20 to 1.40.

10. The method according to any preceding claim, wherein the carbon-supported Fe-Ti-oxide catalyst has a BET surface area of < 500 m2 / g, preferably of < 200 m2 / g.

11. The method according to any preceding claim, wherein the pyrolysis is carried out at a temperature of < 700°C.

12. The method according to claim 11, wherein the pyrolysis is carried out at a temperature in the range of > 450 °C to < 700 °C13. The method according to any preceding claim, wherein the pyrolysis is a steam pyrolysis, preferably carried out under an atmosphere consisting of inert gas and steam, more preferably under an atmosphere consisting of nitrogen and steam.

14. The method according to any preceding claim, wherein the pyrolysis is carried out for < 7 hours, preferably for < 4 hours.

15. The method according to any preceding claim followed by a step in which hydrocarbons produced by the method are used as synthetic fuel.

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