Synthesis and use of tuned precatalyst for carbon-monoxide and carbon-dioxide based fischer-tropsch catalyst for controlled product distribution

Abstract

The present invention belongs to the technical field of design and synthesis of carbon-monoxide and carbon-dioxide-based Fischer-Tropsch synthesis catalysts, and discloses a novel iron-based Fischer-Tropsch synthesis catalyst containing both iron and carbon and a synthesis method and use thereof. The present invention specifically relates to a catalyst mixture for use in hydrogenation of CO and / or CO2, which catalyst mixture comprises i) iron oxide promoted by alkali metal, alkaline earth metal or transition metal, and ii) iron carbide. The invention further relates to a method for production of iron carbide composite comprising different iron carbides, and the use of said carbide composite in combination with alkali metal, alkaline earth metal or transition metal promoted iron oxide for use in hydrogenation of CO and / or CO2.

Description

SYNTHESIS AND USE OF TUNED PRECATALYST FOR CARBON-MONOXIDE AND CARBON-DIOXIDE BASED FISCHER-TROPSCH CATALYST FOR CONTROLLED PRODUCT DISTRIBUTIONFIELD OF THE INVENTION The present invention belongs to the technicadl f oiefl design and synthesis of carbon-monoxide and carbon-dioxide-based Fischer-Tropsch synthesisly csatsta, and discloses a novel iron-based Fischepr-sTcrhosynthesis catalyst containing both iron and car abnodn a synthesis method and use thereof. The presentinvention specifically relates to a catalyst mixetu forr use in hydrogenation of CO and / or2C, wOhich catalystmixture comprises i) iron oxide promoted by alk maelital, alkaline earth metal or transition metadl, a ii)n ironcarbide. The invention further relates to a meth foord production of iron carbide composite comprising different iron carbides, and the use of said caerb ciodmposite in combination with alkali metal, ailnkael earth metal or transition metal promoted iron oxide fosre u in hydrogenation of CO and / or C2.O DESCRIPTION OF THE RELATED ART CO2hydrogenation is regarded as a promising procoers tshe f production of valuable chemicals and fuels via reverse water gas shift (RWGS) and Firs-cThroepsch synthesis (FTS) while also helping mitteiga anthropogenic CO2emissions [1, 2]. Optimizing C2O hydrogenation for value- added product yield invveosl three crucial factors: operating conditions [3, r 4e]a,ctor configuration [5, 6], and catalyst type, 8 [7]. The impact of catalyst type on enhancing the performea onfc the CO2 hydrogenation process is undeniable. Iron- based catalysts are favored among potential catsta dlyuse to their high activity, low cost, and thef oinlic nature of the products they yield. Iron catalysotrsm f Hägg carbideχ (-Fe5C2) in situ as the active phase duringCO2 hydrogenation [9, 10]. It is generally accepteadt t th e iron carbides serve as the active phaseng du threiFTS reaction [11-13]. In recent years, research aevrse focused on enhancing the performance of iraosne-db catalysts and investigating the relationship bentw ieroen carbide phases and catalytic performanc FeT iSn reactions [14, 15]. As known from the prior art, the C2O hydrogenation comprises two steps, the first oenseul rts in CO formation via reverse water gas shift (RWGS) reoanc atind the next one includes further hydrogena otfio CnO through Fischer-Tropsch (FT) synthesis that leaods the t formation of various saturated and unsatdurate hydrocarbons based on the following equations.o Oubsvlyi, different active sites are required in e raecahction pathway. ^^^ + ^^ ↔ ^^ + ^^^^^^ + ^^^ + ^^^^ → ^^^^^^^ + ^^^^^^^ + ^^^^ → ^^^^^ + ^^^^Iron-based catalysts have been used in both FT R aWndGS-FT, due to their high performance,availability and durability. However, the reacti coonnditions such as temperature, pressure a2n tdo H carbonratio can be adjusted in the presence of diffe creantatlysts for the formation of heavy (liquid) hycdarorbons [7]. Typically, iron catalysts need alkali metal promoonti to attain the desired activity and selectiv Tithy.eaddition of sodium (Na) has been reported to bef biceinal for olefin production [16, 17]. The presen ocf Na obviously enhances the surface basicity and cazrabtuiorin of iron-based catalysts, making them hig ahcltyive for CO2 hydrogenation into light olefins [18, 19]. Despite the existing research reports, the pre rocilsee of the iron oxide component in Fe-based cast salyin CO2 hydrogenation still needs to be better unders [t2o0o]d. Iron carbides undergo phase changes durieng thFTS, leading to low catalytic performance

[0021] .e Enxstive research has been devoted to developin-gs choerlle catalysts using a protective layer to enhancet tahbeili sty of iron carbides [22, 23]. Among thesea clyastts, those derived from metal-organic frameworks (MO kFn)o,wn as metal@C, have been extensively explored. However, the effectiveness of the carbon shellhe inse t catalysts is limited, as it can hinder thera incttion between gas molecules and the active phases

[0024] . Defects in carbon materials have been suggest oefdfe tro several beneficial effects in catalytic prsosce s.These defects facilitate the mass transfer of a renatsc,t provide anchoring sites for metal nanopaersti,c alnd serve as active sites for catalytic reactions.ra Inph gite, carbon defects have been identified aivse a scittes for acidic oxygen reduction reactions. Additionally,fe dcets in graphene layers are crucial in enhanciTnSg F performance [25, 26]. In defect-rich graphene-supported iron catalys ttusn, a ble interaction between the metal and theo srutppis achieved, with defects serving as favorablee nautcioln sites for anchoring iron nanoparticles. Weh itil is evident that carbon defects play significant ro inle FsTS reactions with iron-based catalysts, theci psree and unambiguous correlation between carbon defects F aTnSd performance remains a topic that still need bse to fully understood

[0027] . Moreover, the synergisticfe ecft between iron oxide and iron carbide, whicha ennchesalkene formation in CO2 hydrogenation, has remained unclear [28, 29]. Nthoenle ss, limited research hasexplored the influence of carbon materials in trheese pnce of iron oxide for C2O hydrogenation. The evolution process of transforming iron catal pyrsetcursors into FTS catalysts through thermal treatment is intricate and dynamic. Our understnagnd oif its function during CO2 hydrogenation remainsunclear due to various factors, including uniqueep par ation methods, initial oxide / carbide ratio, p thre senceof promoters, variations in reduction conditionnsd, a the proximity of active sites

[0030] . These comxpitlie scontribute to the ongoing debate surrounding thteur nea of the active phase in C2-OFTS reaction over Fe- based catalysts, making it controversial. There,f iotr ies crucial to design an appropriate cataly styicstem to gain deeper insights into the role of iron carbi idne tshe catalytic activity of this reaction

[0031] u.r Fthermore, it is essential to highlight that the carburizatioonc perss is influenced by the intricate surface mincvroireonment, where competitive reactions such as oxygen remo cvaarlb,on permeation, hydrogenation, and carbon deposition occur. Tang et al.

[0032] successfullyi mpualnated these processes, producing high-puri5tyC2 F aend establishing it as an efficient FTS catalyst. In addition, Skrypnik et al. [33, 34] prepared w-deellfined FexOyCz compositions through controlled decomposition of iron oxalate under an inert atmhoesrep and different temperatures to elucidate thlee o rfo different active Fe-species in C2O hydrogenation reactions. They established ao renlsahtiip between reaction pathways, catalyst performance, and the steadey-s ctoamt position of the catalyst, which provides an opportunity for catalyst design and preparation.Lyu et al.

[0035] produced nanocrystals ε o-Ffe2C encapsulated in graphene layers for the Fischroepr-sTch (FT) reaction. These nanocrystals demonstratedr rkeamblae activity and stability under practical FTn sthyesis conditions. Graphene layers exerted a confinemfefenctt e, stabilizing the metastable yet highly act εiv-Fee2C phase. The distinctive confinement structuεr-e60 ( Fe2C@graphene) effectively prevented the formatio ann ofamorphous carbon layer, thus preserving the caictal lyyt active phase from converting into less canr-boefficient phases. However, few studies have focused on introducineg ir thon carbide into the starting material in a physical mixture since F5Ce2is considered the active phase of FTS in the pnrceese of either a graphitic or amorphous shell. Nonetheless, little attention b heaesn given to fine-tuning the nature of the carb shoenll toward a more graphitic and defective carbon sutrruec,t which is known to exhibit superior C2hOydrogenation performance. Additionally, the impact of criticaple orating conditions on the formation of this carb sohnell during the reaction has been largely overlooked, 3

[0376] . For instance, Nawaz et al.

[0038] fabricated highislyp dersed F3eO4nanocrystals on activated carbon (AC) using a sole precipitation method. These nanoclsrys atrae proposed as a promising candidate for eninhganc the dually embedded carbide nanocomposites (coinngsis otf χ-Fe5C2and θ-Fe3C) in the Na- FeCa@AC / HZSM-5 catalyst. The sole precipitationh moedt effectively confined Fe@AC species within the rigid geometry of defective graphite patches, th muistigating the sintering and agglomeration of Fe nanoparticles. Furthermore, it was shown that thnecap esulation of perforated carbon layers during carburization greatly enhanced the stability of h thigehly active carbide phase while preventing tohrem fation of inactive carbon deposits. Jin et al.

[0039] recently synthesized a Fe / C cata tolys directly convert CO2 into light olefins. The catalyst displayed high selectivity for light olefins (up 6 to3.0%) at the CO2 conversion rate of 48. μ3molCO2·gFe−1·s−1. This outstanding performance was attributed to s tthroeng metal-support interaction facilitated byg oexny- containing functional groups, which enhanced thsepe drision of iron species and promoted the forma otfion more active phases. In another study, Chen et al.

[0040] synthesized Kpe-ddo FeCx catalysts through the carbothermal reduction of Fe-chitosan complexes. The approp Frieat ceation-to-chitosan ratio was a critical fac into cratalyst preparation since it significantly influenced thuelk b and surface carbide compositions. The propnor otifo the carbide phase was positively associated with thrmea nloized yield of C2+. Furthermore, the FexC catalyst core- shell structure was likely to enhance its durayb.ilit Recently, limited efforts have been dedicated tnoth seysizing and directly applying iron carbide in2 CO hydrogenation. Liu et al.

[0041] focused on prepar ainngd utilizing Fe5C2 and K-modified F5eC2 catalysts to investigate the relationship between the Fe ph caastea,lytic performance, and reaction pathways in2 CO hydrogenation. Introducing the K promoter increa tsheed selectivity of C2̶ C4 olefins and C5+ hydrocarbons to above 38.0 C-mol% and 23.9 C-mol%, respectiv aetly a, similar CO2 conversion. In another study, the same research group used a combination of pur5eC2 Fe and K-modified catalysts for the hydrogenation C oOf2.These mixture catalysts demonstrated exceptiontal y ctiac activity, surpassing most iron-based casttasl,yeven without pre-reduction before the reaction. b Tehset support for achieving high selectivity inr hoycdarbonsproduction was alkaline A2Ol3 (a-Al2O3). The close interaction between5C F2e and K / a-Al2O3 proved crucial for the catalytic performance. Specifically, the5C F2e-10K / a-Al2O3 catalyst achieved a C2O conversion rate of 40.9%, yielding 68.4% of valuable hydrocarbons.

[0042] Recently, Na-F3eO4showed high performance in C2O hydrogenation to5C+hydrocarbons

[0018] , wherethe Fe5C2, that has been considered to be the active phna tshe i FT, could be forme idn situ during reactionfrom the loaded Na-F3Oe4catalyst. In fact, after reduction of3FOe4to Fe in H2atmosphere, the x%3FCe: y% Fe5C2can be formed in CO / C2O / H2environment during the reaction. Most studies h raevpeorted that ironcarbide particles especially5 FCe2 and Fe3C have a decisive influence on the performance. [ N6e5v]ertheless,their production in pure form has been remainedtr coovnersial. Recently, the F5eC2was synthesized via carburization of Fe-oxalahteyd driate, added to F3Oe4and used in the CO2hydrogenation

[0041] . The performance was testehdo wuitt reduction in H2; probably because it was believed that H2reduction is the first step toward the formatioen5C F2, so it is not required when5FCe2was added physically. The synthesis of pure3FCe also has been a challenge. Recentl3yC, F@eC catalysts (core-shell carbides, in which iron carbide is encapsulated in grapheiknee- llayer) were fabricated through high temperature treatment of MIL-101(Fe) under2H, C2H4, and syngas (synthesis gas: a mixture of hydro agnedn carbon monoxide: H2 / CO = 1) and used syngas conversion5to+h Cydrocarbons

[0027] . In another study, graphene- encapsulated F3Ce / Fe catalyst supported on sporopollenin exineu claepss were synthesized and used for the RWGS reaction. Moreover, Mn-doped3C Fe NPs were prepared using Fe(3N)3O·9H2O as the Fe source, resole phenolic resin as the carbon source, and F127e a tsem thplate and applied in light olefin productionrm f CO2hydrogenation

[0066] . In addition to the mentioned methods,3C Fe embedded in graphitic layer was produced usinugco gsle as the carbon source and urea as nitrogen sourdce m anployed in FTS to light olefins (Chinese patent application No. CN107413362A,·2017-12-01). Moreo,ve ars reported in Korean patent No. KR101393413B1,·2014-05-12, iron carbide5 (CF2e) / carbon nanocomposite catalysts were synthesisziendg u ferro-oxalate activation at a high temperature urn CdOe atmosphere by a high temperature calcinaetiaocnti ron and applied in FTS. Yang X., et al.

[0075] teach the preparation of iron carbide (Fe5C2, F oer3C Fe5C2 / Fe3C) from iron oxalate dihydrate catalysts and their preparatiroonce pss. The reaction of ferric oxalate dihydrateth w CiO with CO affects the ratio of carbide phases form Tehde. authors examine the structure of the cata plyrsotdsuced and their performance in the hydrogenation of COd s aenlectivity. Gnanamani, M. K., et a [l.76] teach catalysts promoted with different alkalia mlset containing F3eO4, Fe5C2and Fe3C. The mixtures are prepared from alkali metal iemgpnrated iron oxalate dihydrate. Thestructure, performance and selectivity of the cyasta sl are investigated for the hydrogenation of2 C dOuringcatalytic reactions. Chun D. et al.

[0077] describe a method to control the distribution o5f+ C hydrocarbons in Fischer-Tropsch synthesis. They do this by activating aon - ibrased catalyst in an atmosphere of synthesis an gdasCO2 in varying proportions, whereby the activateadtal cyst contains magnetite and ferric silicidea inry vingproportions. Increasing the proportion of CO2 ien a thctivating atmosphere increases the proportio hnig ohf-carbon hydrocarbons produced in the Fischer-Trop sysnchthesis. In spite of wide applications of iron carbides, trheesearch in this field has been limited compaored t iron oxides, mainly due to the synthesis comploicnasti such as controlling the crystal phase, morpghyo,l aond composition of the carbide, which are the influaeln ftaictors for CO / CO2hydrogenation reaction. Inspired by the challenges mentioned earlier, trheese pnt description demonstrates the feasibility of adjusting the product distribution in C2-OFT by tuning the initial ratio of iron oxide / iro cnarbide in their physical mixture. The primary objective of the invtoers of the present invention was to explore tahteal cyticperformance of pure iron carbide, metal promotoend o irxide and their physical mixture. The synercgi estffiectbetween the oxide and carbide components has bneaelnyze ad to enhance C2O hydrogenation towards producing more C5+hydrocarbons. The effect of reducing the mixedde o / xciarbide on the carbon shell / layers to fine-tune the hydrocarbons distribution has a bleseon investigated. The influence of different pimroitxiesbetween active iron oxide and iron carbide has b aelseon examined. Moreover, the goal of the inven wtoarsto determine the optimum alkali metal promoted i oroxnide to iron carbide ratio to enhance the efnfici ye ofC5+ hydrocarbons formation by controlling the compios nit of active phases after reduction.Moreover, the pure particles of iron carbides, s ausch Fe5C2and Fe3C, are well known to be very difficult to obtain especially from the same prescourr, and therefore their reactivity in the FT reioanct has not been well documented. Therefore, a further aimhe of in tventors was to provide a method for the protiodnuc of iron carbide composite catalyst with a predetineermd composition. THE DISCOVERY ACCORDING TO THE PRESENT INVENTION In order to solve the above-mentioned technicabll permos, the inventors of the present invention haveperformed laborious experimental work, which hassul rte d in the present invention.The present invention is based on the followingx upneected findings: a) If Fe5C2, Fe3C and their mixture in the desired ratio are proedu vcia high temperature carburizationof the same precursor, preferably Fe-oxalate deahtey,d trhis allows an easily controllable and scaela mbelthod. With this method just by tuning the ratio of He:C aOnd their flow rate beside tuning the temperatuornetr colled mixture of Fe5C2, Fe3C could be obtained with 0:100 ratio. b) If iron carbide produced as mentioned above) a inn ad is added to iron oxide and the resultingly csattamixture is subjected to controlled reduction, th tehen pretreated (reduced) catalyst mixture signniftilcyaincreases CO2 conversion and changing the product selectivitryin dgu hydrogenation. c) If the catalyst mixture is used in form of mix-peodwder pellets, then the catalyst mixture res iunlts higher selectivity for C2-C4 olefins, C5+ hydrocarbons and less C4.H BRIEF DESCRIPTION OF THE INVENTION In particular, the invention relates to the follonwgi embodiment. 1. Use of an alkali-type, alkaline earth type or tritaionns metal promoted Iron-oxide-Iron Carbide mixture catalyst with tuned mixture ratios of Ir Conarbide for adjusting the5 C+ hydrocarbon product distribution of CO / CO2 hydrogenation processes, preferably the tunedu mreix rtatios for adjusting the C5+ hydrocarbon product distribution are Iron-Carb sidtreuctures.2. Preferably, the Iron-oxide-Iron Carbide mixturea clyastt is of an alkali-type, in particular of Na. Preferably, the Iron-Carbide structures in thel cyasta comprise F5eC2 and Fe3C.Preferably said composite promoted-Iron oxide / I croanrbide catalyst is used in modified Fischer- Tropsch reaction. 3. Preferably, the use involves iron-oxide-iron cidaerb mixture catalyst which is used in mixed-powerpellet form wherein the mixture is pressed, crus ahned sieved, preferably to produce 20–60 mesh glersa;nuwherein the mixed-powder pellet form allows a crlo dsiestance between iron oxide and iron carbidee psh,as which results in higher selectivity for2- CC4olefins and C5+hydrocarbons and less C4H 4. Preferably, the iron-oxide-iron carbide mixturaeta clyst comprises reduced catalyst, preferably graphitized layers of reduced catalyst, in paraticru Rl-Na-Fe3O4 / Fe5C2, preferably in 70 / 30 wt.%, respectively; wherein particularly preferably the catalyst alsoom cprises non-reduced catalyst, in particular NR-Na- Fe3O4 / Fe5C2, preferably in 70 / 30 wt.%, respectively. 5. The invention also relates to a method for thneth seysis of an alkali-type, alkaline earth type or transition metal promoted Iron-oxide-Iron Carbidiext mure catalyst, wherein the Iron-Carbide structures in the catalyst arem feodr with controlled F5eC2 / Fe3C ratios; preferably controlled Fe5C2 / Fe3C ratios are from Fe-oxalate dihydrate. 6. Preferably tuned mixture ratios for adjusting C th5e+hydrocarbon product distribution of CO / C2Ohydrogenation processes are provided by varyin aglte or ing the F5eC2 / Fe3C ratios.Preferably, phase-controlled synthesis of Iron-icdaerb is carried out whereby phase-controlled Iron carbides are formed, wherein preferably said phase-controlled synthesis of Iron-carbid cear isried out in an atmospheric environment under CO and He, preferably at a temperature between 350 to 450 °C. Preferably, phase-controlled Iron carbides aree fodr.m Preferably, a premixture catalyst is formed fromid s Iraon-Carbide structure and from Iron-oxides. Preferably, the Iron-Carbide structures in thel cyasta comprise at least F5Ce2 and Fe3C.Preferably, phase-controlled synthesis of Iron-icdaerb is carried out in an atmospheric environmentunder CO (0-40 ml / min, preferably 5-20 ml / min, mo pre ferably 5-15 ml / min) and He (40-90 ml / min), andtemperature varies between 350 to 450 °C. 7. Preferably, the method comprises tuning theh seysnist condition for the production of the pure5C F2,e pure Fe3C and a composite x%3 FCe: y% Fe5C2 (where x and y are percentage of the phases)ta toin o abn iron carbide composite catalyst for use said cataly csotm inbination with synthesized metal promoted3O-F4e for liquid hydrocarbon (C5+) production through CO / C2O hydrogenation with controlled selectivity 8. The method according to any of paragraphs 4 twoh 7e,rein the salt of or used to prepare the Iron oxide is selected from the group consisting of I (rIoI)n chloride, Iron (III) chloride and Iron (II,II I) nitrate. In a preferred embodiment NaN3O is mixed with H2O, and pure F3eO4 is introduced into this mixture. The method according to any of paragraphs 4 toh 8e,re win the alkali promoters (in particular 0.1-5 wt%, preferably 1-5 wt%) used are selected from a Nnda K, preferably Na.The method according to any of paragraphs 4 toh 8e,re win the co-promoters (0.1-5 wt%) used areselected from alkaline earth metals as well assi ttriaon metals such as Mg, Zn, Mn, Cu, Co.9. The method according to any of paragraphs 4 to wh 8e,rein in an embodiment the calcination temperature of the prepared iron-oxide, iron-caerb aids well as the mixture of iron-oxide and ironb-cidaer is between 300 to 450 °C, preferably 350 to 400 °rC 2 f too 20 hrs, preferably 4 to 12 hrs, e.g.6 to hr 1s0. In a particularly preferred embodiment the redu fcoerdm of the catalyst is obtained by treating the catalyst mixture in H2environment for 2-12 hours, preferably for 4-12ur hso, highly preferably for 4 hours, in particular at a temperature of 350-400°C, preferably at a temperature of 350°C and unders aptmheoric pressure. 10. The method according to any of paragraphs 2 w toh 9e,rein the calcination environment is2( H5-20 ml / min) diluted with an inert gas (optionally2, N Ar) preferably in a ratio of2H:Inert gas = 1: (1-20). 11. A composite promoted-Iron oxide / Iron carbide clyastta for CO / CO2hydrogenation obtained according to any of the methods of paragraph 20 t,o w 1herein said catalyst is composed of Iron-Caerbid (preferably present in Iron-Carbide structures)p croisming Fe3C and Fe5C2preferably in a tunable ratio, in particular of x% F3eC: y% Fe5C2(where x and y are percentage of the phases)r aonmdo pted-Fe-Oxide. Said composite promoted-Iron oxide / Iron carbideal cyast is useful in modified Fischer-Tropschreaction. Preferably the Iron-Carbide structures in the cyasta al re formed with controlled F5Ce2 / Fe3C ratios;preferably controlled F5eC2 / Fe3C ratios are from Fe-oxalate dihydrate. Preferably the tuned mixture ratios for adjustihneg C t5+ hydrocarbon product distribution of CO / C2 Ohydrogenation processes are provided by varyin aglte or ing the F5eC2 / Fe3C ratios.Preferably, the Iron-Carbide structures in thel cyasta comprise at least F5Ce2 and Fe3C.Preferably the composite promoted-Iron oxide / Iroanrb cide catalyst is obtainable by a method of any of paragraph 2 to 10. In further preferred embodiments of the composaitteal cysts, the invention relates to: 12. The composite promoted-Iron oxide / Iron carbidteal cyast according to paragraph 11, said catalyst being a catalyst mixture which comprises Na promdo irtoen oxide (Na-F3eO4) and iron carbide, where the iron carbide is selected from5 FCe2, Fe3C and the composite of 5 FCe2 and Fe3C. 13. The composite promoted-Iron oxide / Iron carbidteal cyast according to paragraph 12, wherein said catalyst mixture comprises Na promoted iron oxiNdea- (Fe3O4) and Fe3C; preferably the catalyst mixture comprises Na promoted iron oxide (Na3-OF4e) in 30-70 weight% and F3Ce in 70-30 weight% based on the physical mixture of Na-F3eO4 and Fe3C 14. The composite promoted-Iron oxide / Iron carbideal cyast as defined above, preferably according toany of paragraphs 11 to 13, wherein the iron-oxiriodne- carbide mixture catalyst comprises reducedaly csatt, preferably graphitized layers of reduced catalyst. 15. In a particularly preferred embodiment: compos pitreomoted-Iron oxide / Iron carbide catalyst according to claim 14, wherein the iron-oxide-iron carbide mixture catatl cyosmprises reduced catalyst, preferably graphditizelayers of reduced catalyst, in particular R-Na3O-F4e / Fe5C2, preferably in 70 / 30 wt.%, respectively; wherein particularly preferably the catalyst alsoom cprises non-reduced catalyst, in particular NR-Na- Fe3O4 / Fe5C2, preferably in 70 / 30 wt.%, respectively. 16. The composite promoted-Iron oxide / Iron carbidteal cyast as defined above, preferably according to any of claims 11 to 15, wherein the ratio of5C F2e to Fe3O4at the onset of reaction and thereby the nature of carbon layers can be tuned by the reduction trenatt amned adjusting the appropriate ratio of Na3O-F4e to Fe5C2in the initial catalyst. 17. The invention, in a further embodiment, alsot reesla to a process for producing x%3C F:e y% Fe5C2and promoted-Fe-Oxide according to paragraph 11 m foodrified Fischer-Tropsch, which comprises thes step of loading the catalyst into the reactor, where r tahteio of Iron-Carbide / promoted-Iron-oxide is vasri ferom 1:(0.1-10). Preferably in a synthesis method the catalystusb isje scted to a modified Fischer-Tropsch reaction. Highly preferably, the catalyst is reduced for 2- h1o2urs, preferably 4-12 hours in2, H preferably at atmospheric pressure. Preferably, 340 °C is applied before reaction. The invention also relates to the following emboednimts of the process: 18. The process according to paragraph 17, wheree ththeo md comprises that a Fe containing precursor, preferably Fe-oxalate dihydrate is heated to ae termatpure from 350 to 450 °C under gas mixture of a CnOdHe, where the flow rate of CO is 5-40 ml / min aned f tlhow rate of He is 0-90 ml / min, wherein preferyablthe iron carbide composite comprisin3gC F and Fe5C2. 19. The process according to paragraph 17 or 18,e winhe thre catalyst is reduced for 2-12 hours 2 in H at atmospheric pressure and at a temperature f5ro0m to 3450 °C, highly preferably at 340 °C beforaec rteion. 20. The process according to paragraph 12, wherein fe tehd gas is CO / 2H or CO2 / H2 or CO / CO2 / H2 when CO / CO2 varies (ratio of CO:CO2 = 1:(0.1-10)) while keeping2 H / (3CO2+2H2) = 1. The method according to any of paragraphs 12 to w 1h4e,rein the feed gas introduced to the reactor in the range of GHSV varies between 0.1 to 50 [L / g.r Hca]t for production of liquid hydrocarbons from x F%e3C : y% Fe5C2 and promoted-Fe-Oxide composite catalyst. The method according to any of paragraphs 12 to w 1h5e,rein the inlet temperature is between 240 to 340 °C and the pressure varies between 20 andr 5.0 ba 21. Ther invention also relates to a method A method for producing a liquid hydrocarbon5+ ()C, using a CO / CO2 / H2 mixture, which comprises the introduction of the synthesized x%3 FCe: y% Fe5C2 and alkaline / alkaline earth and transition metraolm-poted Fe3O4 into a fixed bed reactor, said liquid hydrocarbon produced according to trhoece pss of producing liquid hydrocarbon using x% Fe3C: y% Fe5C2 and promoted-Fe-Oxide composite catalyst for h pigrehssure high temperature modified Fischer-Tropsch. BRIEF DESCRIPTION OF THE DRAWINGSFigure 1: XRD (a) and XPS (b) images of the carbide syntzheeds bi y the method as mentioned in Example 1.Figure 2: TEM images of the carbide synthesized by the modet ahs mentioned in Example 1. Figure 3: a) The effect of physical mixing of F5Ce2 with Na-Fe3O4 on CO2 hydrogenation performance; b) GC-MS spectra of liquid product. Reaction condi:tio 3n40°C, 3 MPa and 4000 mL-1g h-1GHSV (both catalysts were reduced before reaction for 4h u Hnd2,e Nra-Fe3O4 / Fe5C2(70 / 30 wt%)). (GHSV = Gas Hourly Space Velocity.) Figure 4: a) H2-TPR profiles of Na-F3eO4and Na-F3eO4 / Fe5C2; b) CO2-TPD profiles of Na-F3eO4, Fe5C2and Na-Fe3O4 / Fe5C2; and c) enlarged C2O-TPD profile. Figure 5: TGA of a) Na-Fe3O4and b) Na- F3eO4 / Fe5C2under N2atmosphere. Figure 6: In situ DRIFT spectra obtained during C2O hydrogenation at 30 bar over a), b), c) Na3O-F4e and d), e), f) Na-Fe3O4 / Fe5C2. Figure 7: Comparison of DRIFT spectra of Na-3FOe4(lower line) and Na-F3eO4 / Fe5C2(upper line) after 30 min CO2hydrogenation at 340°C and 30 bar. Figure 8: a) The effect of reduction on the performance Na o-fFe3O4 / Fe5C2(70 / 30 wt.%) at 340°C, 3 MPa, and 4000 mL- g1h-1GHSV; and b) XRD patterns of the spent R-Na3O-F4 / eFe5C2and NR-Na-F3eO4 / Fe5C2. Figure 9: a) TEM images of spent R-Na-3FOe4 / Fe5C2, b) the IFFT analysis of F5Ce2and graphitic carbon along with a representation of amorphous carbon F,e3cO)4and carbon layers, and d) the graphitic carbon layers. Figure 10: TEM images of spent NR-Na-3FOe4 / Fe5C2 including a) The F3eO4, Fe5C2 and amorphous carbon layers; and b) The IFFT analysis of5C Fe2and representation of amorphous carbon layers. Figure 11: XPS spectra of the spent R-Na3-OF4e / Fe5C2and NR-Na-F3eO4 / Fe5C2a) Survey, b) Fe 2p and c) C 1s spectra. Figure 12: TPH spectra of spent R-Na-3FOe4 / Fe5C2 and NR-Na-F3eO4 / Fe5C2. Figure 13: The TPH / MS profiles showing individual peak coibnutrtions from the various carbon species: The enlarged area between 150-550 °C of a) R-N3aO-4F / Fee5C2 and b) NR- Na-F3eO4 / Fe5C2 and the high- temperature area for c) R-Na-3FOe4 / Fe5C2 and d) NR-Na-F3eO4 / Fe5C2. Figure 14: In situ DRIFT spectra obtained during C2O hydrogenation at 30 bar over a) R-Na3-OF4e and b) NR-Na-Fe3O4 / Fe5C2. Figure 15: a) The effect of integration manner of Na3-OF4e and Fe5C2 on the CO2 hydrogenation performance at 340 °C; 3 MPa and 4000 mL-1g h-1GHSV, b) XRD patterns of spent Na-3FOe4 / Fe5C2 integrated in two different manners (both catalysts were reducedre be refoaction for 4h under2 H, Na-Fe3O4 / Fe5C2 (70 / 30 wt.%), scheme showing the hydrocarbons distribution when N ta-Fe3O4 and Fe5C2 active sites are integrated via c) mixed-powder pellets and d) separate pellets. Figure 16: a) C2-C4 and, b) C5+ selectivity versus C2O conversion (yields are shown in dashed curves d,a thtaepresented by triangles are literature data, and co thrre sponding data are presented in Table 2).Figure 17: The influence of temperature, pressure and N3aO-4F / Fee5C2 ratio on a) C2-C4 yield and b) C5+ yield at 4000 mL g-1h-1GHSV. Figure 18: a) XRD patterns of spent Na-3FOe4 / Fe5C2 with different ratios; b) enlargedθ 2 region of the carbides; reaction condition: 340°C, 3 MPa and 4 m00L0 g-1h-1GHSV.Figure 19: XRD patterns of fresh, reduced, and spent a)e N3Oa-4F and b) Na-F3eO4 / Fe5C2 (70 / 30). Figure 20: Scheme proposed for the relationship betweenct sutrraul catalyst properties and performance. Figure 21: Schematic representation the interplay between in tfhluential factors, i.e., reduction treatment, oxide / carbide ratio and spatial distance, whichul rtess in tailoring an efficient CO2hydrogenation catalyst toward the formation of valuable hydrocarbons. Figure 22: Surface Response Graph of the production of m Fixee3Cd / Fe2C5with tuned parameters. Figure 23: Illustration of the CO2hydrogenation selectivity towards5+C products, and product selectivity of different Fe3C:Fe5C2:Na-Fe3O4at an embodiment of the present invention showhineg e tvidence of tuning the mixing of the Fe3C:Fe5C2:Na-Fe3O4catalyst resulted in different valuable liquid purocdts. Figure 24: The fitted XRD patterns of the synthesized5C F2e.Figure 25: The fitted XRD patterns of the synthesized3C F.e Figure 26: The fitted XRD patterns of the synthesized 50%3C F –e 50% Fe5C2. Figure 27: The fitted XRD patterns of the synthesized 37%3C F –e 63% Fe5C2. Figure 28: The fitted XRD patterns of the synthesized 78%3C F –e 22% Fe5C2. Figure 29: TEM and FFT analysis of the synthesized a5)C F2,e b) Fe3C, and c) Mixed-carbide (F5Ce2 / Fe3C (50 / 50)). Figure 30: The average particle size of the synthesized5aC)2F aend b) Fe3C. Figure 31: Summary of the phase evolution during situ XRD. Figure 32: N2-adsorption and desorption isotherms and texturroaple prties of the synthesized Na3-OFe4and Fe5C2. Figure 33: Fe 2P spectra of the synthesized3O F4e Figure 34: The effect of used promoters on the selectivfit tyh oe product distribution Figure 35: In-situ XRD of Na-Fe3O4 Figure 36: In-situ XRD of Na-Fe3O4 / Fe5C2 Figure 37: In-situ XRD of Na-Fe3O4 / Fe3C DETAILED DESCRIPTION OF THE INVENTION CO2 hydrogenation into sustainable chemical feedsto acnkds fuels is a pivotal focus of energy research. Fe-based catalysts have emerged as promising caatensdid due to their high efficiency in the 2 CO hydrogenation toward2 C−C4 olefins and C5+ hydrocarbons. F5eC2 is known as the active phase of the2 CO hydrogenation. Therefore, it is imperative to drisnce the roles of active phases in product distroibnu.tiAccordingly, in the present description,5C Fe2 is synthesized separately and physically mixedh w Niat-Fe3O4.The effects of reduction treatment, the proximifty ac otive phases, and the oxide / carbide ratio avre s itnigated.The results show that adding carbide to oxide f sicigannitly increases C2O conversion due to the controlled reduction of the oxide phase and enhanced2 a CdOsorption. The graphitized layers of reducedly csatta (R-Na-Fe3O4 / Fe5C2 (70 / 30 wt.%)) enhance the selectivity fo2r- C 4 olefins (38%) and C5+ hydrocarbons (39%) at a43% CO2 conversion. In contrast, amorphous carbon ino thne-r neduced catalyst (NR-Na-3FOe4 / Fe5C2 (70 / 30 wt.%)) favors more C2-C4 paraffins and CH4. Additionally, a closer distance (mixed-powderle ptesl) between Na-Fe3O4 and Fe5C2 results in higher selectivity for2 C-C4 olefins and C5+ hydrocarbons and less C4.HTherefore, the interplay between the influentiaclto fars, i.e., reduction treatment, oxide / carbideio r,a atnd spatial distance, could result in tailoring anc eieffnit CO2 hydrogenation catalyst toward the formation of valuable hydrocarbons. As it is disclosed in the present description, Nea3O-F4and Fe5C2were synthesized and physically mixed in various ratios for the C2O hydrogenation to5C+hydrocarbons. The results showed a significanrte iansce in CO2conversion while CO selectivity decreased whenbi cdaer was physically mixed with oxide. This enhancement was attributed to the regulated reodnuc otfi oxide phase in the Na-3FOe4 / Fe5C2mixture and improved CO2adsorption. Furthermore, the reduction of the mdix oexide / carbide improved catalytic performance, likely due to the presence of gracph ciatirbons with extended and distorted layers anfedct dse. However, amorphous carbon formed in the NR-N3aO-F4 / eFe5C2facilitated the production of light paraffins and CH4. Additionally, the proximity between Na-3FOe4and Fe5C2played a significant role in product distribution; a closer distance resulted in hig Ch2e-rC4olefins and C5+selectivity, while more hydrogenatedproducts formed when Na-3FOe4 and Fe5C2 were stacked in separate pellets. In additio wn,a ist revealed thatthe Na-Fe3O4 / Fe5C2ratio in the initial mixture significantly change thde carbide content at the onset of the reaction and, in turn, the C2O hydrogenation performance. It can be deduced that the ratio of5C F2e to Fe3O4at the onset of reaction and the nature of carbon shell / layers can be tuned by the reduction treattm anedn adjusting the appropriate ratio of Na3O-F4e to Fe5C2in the initial catalyst, as supported by the chtaerraizcation of the reduced and spent samples. To u spu,m the interaction of the essential variables, such asuc rteiodn treatment, oxide / carbide ratio, and proxyim, mit ay enable the development of a C2hOydrogenation catalyst that effectively promothees p troduction of valuable hydrocarbons. The present invention has the advantage of sho awi lnogw selectivity for CH4 and a high selectivity for liquid hydrocarbons having5 C+, and the conversion rate of C2 iOncreased compared to that of pure Na3O-F4.e Based on the above, the subject of the presenntt iinovne is a catalyst mixture for use in hydrogennatio of CO and / or CO2 and mixture of CO and C2O (usual raw product of Reverse Water Gas Shift Rtioenac process), which catalyst mixture comprises i) i oroxnide promoted by alkali metal, alkaline earth ml e otra transition metal, and ii) iron carbide. In a preferred embodiment the iron carbide is ap coosmite of different iron carbides, such as3C Fe and Fe5C2. In a preferred embodiment the catalyst mixtur ues iesd in reduced form. The reduced form is obtained by treating the casta mlyixture in H2 environment for 2-12 hours,preferably for 4 hours, at a temperature of 350°-C40,0 preferably at a temperature of 350°C and under atmospheric pressure. As it is disclosed in Exam 3,p ilte was found that reduction can affect consaidbelyr the morphology of the carbon shell around the carboidwea trds either amorphous or graphitic, which cande hrin or facilitate the gas diffusion through the carb sohnell and result in different distribution of procdeud hydrocarbons. The influence of reduction time un Hd2e orn the morphology of carbon shell in the spentp sleasm based on an embodiment of the present inventiodnu.c Rtieon was done under2 H at 350 C° for 0 to 12 hours depending on the mass of catalyst during reduc otxioyngen in the F3eO4 can be removed and reacts wit2h t Ho form H2O, while the Fe-Oxide is transferred to FeO, wh isic nhot stable, and further reduced to metallic iFroen.It was surprisingly revealed that the reductionen etxt can affect the product distribution via changg tihne carbonshell morphology and hydrogenation extent of thte rm inediates.In a preferred embodiment the catalyst mixtures iesd u in mixed-power pellet form. The mixed-powder pellet form is obtained in thelo fwoling manner: iron oxide and iron carbide powders is physically mixed, then the mixture is presseruds,h ced and sieved to produce 20–60 mesh granusle ist. is A disclosed in Example 4, the mixed-powder pellemt fo arllows a closer distance between iron oxide aronnd i carbide phases, which results in higher selecti fvoirty C2-C4olefins and C5+hydrocarbons and less C4.H In an embodiment the catalyst mixture comprises pr Noamoted iron oxide (Na-F3Oe4) and iron carbide, where the iron carbide is selected from5C F2e, Fe3C and the composite of5FCe2and Fe3C. In an embodiment the catalyst mixture comprises pr Noamoted iron oxide (Na-F3Oe4) and Fe3C. In a preferred embodiment the catalyst mixture compr Nisaes promoted iron oxide (Na-F3Oe4) in 30-70 weight% and Fe3C in 70-30 weight% based on the physical mixture N oaf-Fe3O4and Fe3C. In a more preferred embodiment the catalyst mixture comprises Na proemdo irton oxide (Na-F3eO4) in 70 weight% and F3eC in 30 weight% based on the physical mixture of Na3O-F4e and Fe3C. The present invention relates to the tuning theth seysnis condition for the production of the pure5C F2,e pure Fe3C and a composite x%3FCe: y% Fe5C2(where x and y are percentage of the phases) w ish nicohw called iron carbide composite. Further, the present iniovnen rtelates to the use of the mentioned composnite i combination with synthesized metal promoted3O-F4e for liquid hydrocarbon (C5+) production through CO / C2O hydrogenation with controlled selectivity. Specifically, one of the objects of the presente inntvion is to produce F5Ce2, Fe3C and their mixture in the desired ratio via high temperature carburizna otifo the same precursor, preferably Fe-oxalated draihtye in an easily controlled and scalable method. Specifically, 1 gr of Fe-oxalate dihydrate was heeda tto a temperature from 350 to 450 °C under CO / He mixed gas, where the flow rate of CO can be 5-4 / 0m minl and flow rate of He would be 0-90 ml / min. Ianc ft, one main part of the present invention relateshe to p thase-controlled synthesis of carbides via Faela-otex dihydrate where by the adjustment of CO (5-40 mnl / )m aind He (0-90 ml / min) flow rates at different temperatures (350-450 °C) and durations (4 h)r deinffte composition of F5eC2 / Fe3C carbides can be produced. The present invention further relates to a methoord p froducing a liquid hydrocarbon5 (+C), using a CO / CO2 / H2 mixture, which comprises the introduction of thyent shesized x% F3eC: y% Fe5C2 and alkaline / alkaline earth and transition metal-proemdo Fte3O4 into a fixed bed reactor. In one embodiment, the hydrocarbon distribution b cean tuned via altering the ratio of x%3 FCe: y%Fe5C2 / Na-Fe3O4 composite catalyst. In this regard, the differe rant ios have been used to optimizehydrogenation reaction in terms of higher convenrs ainod higher valuable hydrocarbon formation. Based on the above, the further subject of thee pnrte isnvention is a method for production of iron carbide composite comprising different iron carbsi,d wehere the method comprises that a Fe containing precursor, preferably Fe-oxalate dihydrate is hdea tote a temperature from 350 to 450 °C under gastu mreix of CO and He, where the flow rate of CO is 5-40m minl / and the flow rate of He is 0-90 ml / min. In an embodiment the iron carbide composite cominpgri Fs3C and Fe5C2.The invention further relates to the use of thebi cdaer composite in combination with alkali metal, alkaline earth metal or transition metal promotreodn i oxide for hydrogenation of CO and / or2 C.O In a preferred embodiment, the x%3C F:e y% Fe5C2 and Na-F3eO4 powders are mixed and then pressed, sieved and crushed in granules of 20-60 mesh, w inhi alenother embodiment the granules are made o xu%t of Fe3C: y% Fe5C2and Na-F3eO4separately. Typically, 0.5 to 2 gr of the granu wleesre loaded to the lab scale reactor in either the mixed-powder pellets or saetpea prellets modes, and the GHSV was kept betwe0en to 10 6000 ml / gr h. The reaction temperature was betw 2e4e0n to 340 °C and the pressure was 20 to 50 bar. The invention is further illustrated below by noimn-ilting examples. The skilled person is aware b thaasted on the examples alternative embodiments or var tiahnetrseof may also fulfill the object of the inveonnt.i EXAMPLES Example 1 - General methods Preparation of iron carbides Iron oxalate dihydrate powder was used after dry oinvgernight at 80 °C. 1 gr of the powder was transferred into a quartz reactor with a furnacde a cntivated to F5eC2at 350 °C under CO / He with the 10 / 90 flow rate for 4 hours, following the method outldin bey Liu et al. [41, 42]. Preparation of iron oxide A pure Fe3O4catalyst was synthesized using the co-precipnita mtioethod, following the procedure described by Wen et al.

[0043] . Initially, Fe2C·4lH2O and FeC3l·6H2O were dissolved in 0.3 mol−1L HCl. Then,the ammonia water was added into the above solu dtrio pnwise while stirring until the pH of the resinugltsuspension reached 10. After aging at 60°C for 6in0ut mes, the black precipitate was separated using a magnetic device and washed three times with deeiodni wzater. Finally, pure F3Oe4 was obtained after overnight drying at 80°C. The Na-promoted F3Oe4 was prepared using the impregnation method. Tyllyp,ic NaaNO3 was mixedwith H2O, and pure F3eO4 was introduced into this mixture. The suspensioans w sonicated for 30 minutes andleft standing for 4 hours; this process was repde tahtreice. The solvent evaporated, and the sampsle d wriead overnight at 80°C. Following this, Na-3FOe4 was calcined at 350°C for 4 hours. The actualo Nnate cnt of these samples was determined through EDX analysis. Powder X-ray Diffraction (XRD) XRD studies of all samples were performed on ak Ruig MainiFlex II instrument with a Ni-filtered CuαK source in the range ofθ 2 = 10 - 90° for Na-F3eO4 and Na-Fe3O4 / Fe5C2 and 2θ = 30 - 60° for F5eC2. Samples imaging was conducted with an FEI TECNAI G2 20 X-inTw high-resolution transmission electron microscope, equipped with electron diffraction,r oaptieng at an accelerating voltage of 200 kV. Threfa scue properties, specific surface area, and pore siszterib duitions were investigated using a Quantachr NomOeVA 3000e gas sorption instrument by2 a Ndsorption at liquid N2 temperature. Temperature-Programmed Reduction (TPR) TPR was carried out in a BELCAT-A apparatus using ex aternally heated reactor (quartz tube with 9 mm outer diameter). Before the measurements, tthaely csat samples were heated in He flowing at 150o°rC f 60 min. Then, the sample was cooled in flowingo He 50 t °C. The sample was flushed, the reactor watsed helinearly at a rate of 5°C / min from 700°C, and th2e c Honsumption was detected by a thermal conductivity detector (TCD). Temperature-Programmed Desorption (TPD) TPD was carried out in a BELCAT-A apparatus. P troio trhe measurement, about 100 mg of the sample was pretreated in He flow at 150°C for 60 min. Arf cteooling to 50°C, the sample was exposed to2C anOdflushed in He to remove all physically adsorbede mcuol es. The TPD program was initiated by heating to up700 °C with a ramp of 5°C / min, and the2C cOonsumption was detected by TCD. X-ray Photoelectron Spectroscopy The Fe-carbide samples were prepared for measutre wmitehn double-sided carbon tape on a stainless- steel sample holder. A Specs XPS instrument eqduip wpiteh an XR50 dual anode X-ray source and a Phsoibo 150 hemispherical analyzer was used for the memaseunrte. The X-ray gun was operated with 150W power (14 keV). No sample charging was observed. A sur svpeeyctrum was collected with a pass energy of 40 eV and 1 eV step size. High-resolution spectra ofe C,, N Fa, and O were collected with a pass energy0e oVf 2 and 0.1eV step size. Data was evaluated with CaSsa sXoPftware version 2.3.22PR1.0. All high-resolution spectra were corrected with a Shirley backgrounldl . pe Aaks were fitted with a Gauss-Lorentzian protduc function, where the Lorentzian contribution is 30 e%x,cept F5eC2peaks, which have an asymmetric peak shape. Temperature-Programmed Hydrogenation (TPH) For TPH analysis, the reactor outlet was conne tcote ad mass spectrometer (UGA series). Two sets of experiments were conducted on Na3-OF4e / Fe5C2: (1) TPH spectra were obtained after pretreatm inen Ht2at 350 °C and 1 atm followed by reaction at 340 °C 3 a0nd bar in H2 / CO2=3 and (2) TPH spectra were collected after heating the sample in2 N to 350 °C and 1 atm followed by reaction at 340 a °nCd 30 bar in H2 / CO2=3. Ineach TPH experiment, 500 mg of calcined catalyst l woa ded into a stainless-steel reactor. The teamtuprerwas then increased to 350 °C at a ramp of 1 °C / fmolilno,wing which a flow of pretreatment gas at 1m a wtas introduced, and the reactor temperature was he 3ld50 at °C for a specified period. Then, the temperera wtuas reduced to 340 °C following the reaction. Followi pnrgetreatment and reaction, the catalyst was co inole Adrto room temperature, and the gas was switched2 t aot H 1 atm while the temperature was increased0 to °C 80at 5 °C / min. CH4 was monitored using mass signals (m / z) of 153 ( fCraHgments of CH4) instead of 16 to avoid the interference of water vapor and2 C cOracking. In Situ Diffuse Reflectance Infrared Fourier Traonrsmf Spectroscopy (DRIFTS) Infrared spectroscopy measurements were carried wi othut an “Agilent Cary-670” Fourier transform infrared (FTIR) spectrometer equipped with a “Hcakrr Pi raying Mantis” diffuse reflectance attachme Tnhte. sample holder had two B2aF windows in the infrared path. The spectrometerp wuarsged with dry nitrogen. The spectrum of the pretreated catalyst was use bdac aksground. At room temperature, a2 C tOo H2 mixture with a molar ratio 1:3 was introduced into the DTRSIF cell. The tubes were externally heated to avoid condensation. The catalyst was heated linearlyr u tnhdee reaction feed from room temperature to 350 w °itCh a heating rate of 20 K / min, and IR spectra weres mureead at 50 K intervals. All spectra were recor idne tdhe range of 4000 to 900 c–m1with a resolution of 2 cm–1. Typically, 32 scans were performed. Due to thoert shoptical path within the DRIFTS cell, the contribounti of reactant gases was negligible. Only the m inotesntse features of gas-phase products were observable. Catalytic Performance Tests CO2hydrogenation to hydrocarbons was carried out p inre assurized fixed-bed flow reactor with a 9 mm inner diameter. For non-reduced (NR) samplees, ca thtalyst bed was initially heated in a nitrogNen2) ( atmosphere before introducing the mixture of2C aOnd H2(H2 / CO2= 3) at temperatures ranging from 320 to 340 °C. The reactor was pressurized to 3-5 MPa a w GithHSV = 4000 mL−h1gcat−1. The catalytic results were collected after at least 8 hours on stream. In the case of reduced samples (R), the catalyesrtes t wreated in H2 at 350 °C for 4 hours. Subsequently,the feed gas was switched to a mixture o2f a Hnd CO2under the same reaction conditions as for NR seasm.pl The catalysts were initially heated up unde2.r T Nhe Na-Fe3O4 / Fe5C2catalysts were packed in two different manners: mixed-powder pellets and separate pe Flloerts m.ixed-powder pellets, the appropriate amouf n Nta o- Fe3O4and Fe5C2powders was physically mixed with a mortar andtl pee ins different ratios (30 / 70, 50 / 50 and 70 / 30). The mixture was then pressed, crushed s,i aenvded to produce 20-60 mesh granules3O. F4e and Fe5C2were pressed, crushed, and pelleted at 20-60 moersh ep farate pellets. These pellets were subseqyu meinxteldand loaded into the fixed-bed reactor. Unless owtihser noted, all tests in Examples 2, 3 and 5 woenredu cctedusing mixed-powder pellets. Unless otherwise no atelld o,f the Na-Fe3O4 / Fe5C2were reduced for four hours in H2. The samples without reduction are named NR-N3aO-4F / Fee5C2. The products were analyzed online using a gas cahtroogmraph. CO, C2O, and CH4were analyzed using a carbon molecular sieve column (PORAPAK) withe arm thal conductivity detector (TCD). C4H and C2-C8hydrocarbons (C2+) were also analyzed using a flame ionization dtoetre (cFID) with a SUPELCO column. Chromatograms of the FID and the TCD were corredla thterough CH4, and the product selectivity was obtained based on carbon balance, C-mol%. The2c CoOnversion^ (^^2) and product selectivity^ (^) were calculated via the following equations, whereine na mns the number of moles, and c is the numberrb oof cnas in molecule i. ^^^ ^^^^^^^^^^ ^^^^^^ = 100 ×(1) +^^,-. / ^^0^. / ^^^ / 1 ^^2^ = 100(2)Example 2 – Study on synergetic improvement in catalyticfo premrance of oxide / carbide The N2adsorption / desorption isotherms of both samplesspla dyied type IV isotherm patterns with distinct hysteresis loops, as shown in Fig. 32. T Nhae-Fe3O4sample shows a type H1 hysteresis loop, characteristic of mesoporous materials with cyliicnadlr pores. In contrast, F5Ce2exhibits an H3-type hysteresis loop, suggesting the presence of parallel platep-esdha or wedge-shaped pores

[0044] . Despite the smurafallc se area and pore volume of the5C Fe2samples, indicating their non-porous nature, t shteilly demonstrate notable catalytic activity, as discussed in the next senc.ti Tohis underscores that the textural propertie csa orbfides may not be the decisive factor in the RWGS-FT rieoanc.t Table 1: TPH peak temperatures and corresponding peak p aere ceantagesCarbidic Amorph Carbide Graphitic α1 α2 α3 β γ1 γ2 γ3 δ1 δ2 T 260.9 320.2 374.5 470.7 570.9 615.2 670.5 710.9 728 R Af 0.47 1.34 1.35 0.79 1.19 13.19 27.69 52.25 5.68 α1 α2 α3 β1 β2 γ1 γ2 γ3 δ1 δ2 T 240.9 302.1 369.4 474.7 549.2 598.7 654.8 686.7 .9717756.2 NR Af0.88 1.30 0.98 1.65 0.60 2.42 36.51 41.41 19.18 0.48 T: Temperature (°C) Af: Fractional peak area (%) R: R- Na-Fe3O4 / Fe5C2 (reduced in H2 before reaction) NR: NR-Na-Fe3O4 / Fe5C2(Not reduced before reaction) The XRD pattern of the synthesized carbide ist irlalutsed in Fig.1 (a); peaks appearedθ a 3t92.7, 40.8, 42.9, 43.7, 44.7, 45.9 and 58.3° can be assigne Fde5C to2phase, which is in accordance with the JCPDS 00- 36-1248, while small peaks at 42.88 and 54.4° cea antt bributed to F3eC (JCPDS 00-35-0772)

[0042] . Besides,XPS spectra of synthesized carbide were collec atsed p,resented in Fig. 1 (b). The peak in the Fe / 2p an 3d1 / 2 spectra at 707.2 and 710.1 eV can 233 be aesdc troib Fe5C2

[0041] . The Fe 2P spectra of the synthesized Fe3O4are provided in Fig.33. (JCPDS = Joint Commi ottnee Powder Diffraction Standards.) The TEM images of the synthesized carbide are illustrated in 2 Fi wg.ith 200, 20, 5 and 3 nm resolution, respecti.v Aelsy shown in Fig. 2 (b-d), the fringes of F5Ce2are evident in the synthesized sample. The CO2hydrogenation performance of pure5C F2e and Na-F3eO4is illustrated in Fig. 3 (a). It can be observed that in the presence of pure carbide4, is CH the main product

[0021] , constituting approximlyat 4e2% of the total products, followed by2- CC4hydrocarbons with an olefin / paraffin ratio of aopxpirmately 4 to 5. In contrast, Na-F3eO4yields more C2-C4and C5+hydrocarbons. However, it's worth noting that t ChOe2conversion over F5eC2(37.5%) is higher than that of Na-3FOe4(31.2%), while it's more active in C4H production. Therefore, F5Ce2can be considered an active phase in C=O bonvda aticotni. It has been revealed that the structure of F5Ce2is critical for its interaction with C2O, H2, and CO. Defective F5Ce2favors efficient CO2and CO adsorption

[0045] . Comparing the performance of these two catalystths t whei ir physical mixture, it can be speculatedt tha the mixed catalyst outperforms the individual comnepnots in terms of C2O conversion (43.9%) and selectivity toward C5+ hydrocarbons (39%) while producing lower amounft CsO o (8.12%) compared to that of Na3-OFe4 (17.36%). Therefore, the highes5t+ C yield, approximately 16%, is achieved with theF Nea3O- 4 / Fe5C2 mixture (Fig. 3(a) 4thdata series), which might be due to the transfotiormna of more CO toward light olefins and5+ C hydrocarbons as a result of the presence5 oCf2 F ien the initial catalyst. Interestingly, it can c boencluded that using pure F5eC2 inhibits the conversion of 2 C-C4 olefins into C5+ hydrocarbons, while Na-F3Oe4 / Fe5C2mixture can significantly enhance this transformona.ti Therefore, while F5eC2 can efficiently produce valuable C2-C4 olefins as intermediates for5+ C formation, an optimal ratio between oxide andi cdaerb is necessary for the formation of C5+ hydrocarbons. The GC-MS spectra of the liquid purcotsd (Fig. 3(b)) confirm the formation of heavier unsaturated hydrocarbons. To assess the hydrogen reduction and2a CdOsorption capacity of the tested catalysts, wnedu ccoted H2- TPR and CO2-TPD analyses, while TGA was used to measure the rirmal stability. The H2-TPR profiles of the fresh oxide and Na-3FOe4 / Fe5C2samples are presented in Fig. 4(a). The N3aO-4Fe profile (lower line) shows two main H2consumption regions, with peaks centered at 30 a0n°dC 575°C. Typically, the first2H consumption region from 250 to around 400 °C can at btreibuted to the reduction process of Fe3 →O4 FeO, while the second, broader region from 400 to 750 m °aCy reflect the reduction of Fe →O α-Fe

[0046] . The shoulder peak observed in Na3-OFe4at 480 °C could be attributed to the reduction bu olfk Fe3O4species to FeO. In contrast to Na-F3Oe4, the Na-Fe3O4 / Fe5C2catalyst exhibits multiple reduction peaks for t trhaensition from Fe3O4to FeO, suggesting a more distinct reduction s itnag thee reduction of surface3FOe4to FeO. In addition, it can be observed that the3O F4e reduction to FeO could be facilitated in Na3-OF4e / Fe5C2, as this peak appeared at lower temperatures (around 51.5 H °oCw)ever, further reduction t αo-Fe was hindered, as explained in Example 5 (XRD of the reduced Na3O-F4e / Fe5C2catalyst (Fig. 19 (b)). The decrease in peak intensity of the Na3O-F4 / eFe5C2, notably the transition from Fe →O α-Fe, could be due to the lower oxide content in the physic malilxyed sample (70%) compared to Na3-OF4e. To analyze the C2O adsorption capability of the samples,2C-TOPD of the samples before the reaction was performed as depicted in Fig. 4(b). The locna otiof the CO2desorption peak and its area indicate the interaction of different Fe-oxide phases with2 C aOnd the corresponding amount of these Fe-oxidese psh ian the sample. This provides an indication of the slaem'sp basicity. In the Na-F3Oe4 profiles, a broad peak below 100 °C can be attributed to weakly adsorbed2 C onO the catalyst surface with basic sites

[0047] c.o Inmparison, a distinct peak representing strong2 C aOdsorption appears at approximately 550 °C, woith si ngnificant signs of decomposition according to the TGA (Fig.5(a It) c).an be observed that the5C Fe2 exhibited a shallow low- intensity peak at about 400 °C, which represensts low iter basicity compared to that of Na3-OF4e. Therefore, the Na-Fe3O4 / Fe5C2 basicity arises mainly from the Na-3FOe4, as observed in the corresponding2 C-TOPD spectra in Fig.4(b). However, the sharp peak of the Na3-OF4e / Fe5C2 mixture between 450 and 550 °C can be due to the sample decomposition at high temperatures accor tdoin thge TGA curve (Fig. 5(b)), appearing at alm tohsetsame temperatures. Therefore, this sharp peakke ilsy l aissociated with sample decomposition rathaenr th estrong adsorption of C2O. Hence, we focused on the low-temperature rangfoere be 450 °C to avoid misinterpretation. It can be inferred that the mixing of Na-3FOe4 with Fe5C2 led to a gradual shift of these low-temperature peaks to higher adsorption temperatures. This s uhgifgtests that C2O adsorbed strongly to the active sites on the Fe-based catalyst surfaces in the physicalu mreix otf the two components (Na-3FOe4 with Fe5C2) compared to Na-Fe3O4. This difference could contribute to the highenrv ceorsion and C5+ yield observed. To obtain a clear insight into the mechanism of2 C hOydrogenation in the presence of both catalysts,operando DRIFT was performed. To this end, aft rer d auction in H2 at 350 °C and 1 bar, it was cooled downto room temperature. The DRIFT cell was then prreizsesdu with the reaction gas mixture2 ( / HCO2 = 3) to 30 bar and heated up to 340 °C with a ramp of 20 °nC. / m Wihen the temperature reached 220 °C, the DRIFT spectra were collected each 1 minute until the e termatpure reached 340 °C, and then, four spectra were collected at this temperature after 6, 10, 20, 3 a0nd minutes of reaction time. The DRIFT spectraa o-fF Ne3O4and Na-Fe3O4 / Fe5C2under CO2hydrogenation are illustrated in Fig.6. A strong band at 2400–2200–c1m is attributed to gas-phase C2,O and two strong twin-bands observed in the range of 3750–3550 c–1m correspond to the combined tones of gas and aeddso CrbO2molecules. It can be observed that the reaction starts at almost °C 32 a0s the peaks of CO and C4H appear. The gas phase spectrum of CO has its characteristic bands betw 2e1e1n0 and 2177 c−m1. The RWGS reaction took place on both catalysts to different extents, leading to f tohremation of more CO on the Na-3FOe4, as can be observed in Fig. 6(b) and 6(e). The formation of C4H is clearly observable in all spectra indicated it bsy typical gas phase spectrum with main bands centered at 301513 a0n5d cm−1. After reaching reaction temperature (340 °C), ba ansdssigned to carbonate specie3s̶,, (C ca.1712, 1555 and 1453 cm−1), bicarbonate species (HC3̶,O ca.1630 and 1419 and 1224−c1)m and formate species (HCO̶,O ca. 2854, 1560 and 1360−c1m) appeared in both catalysts. In addition, the C s-tHretching of alkanes (2875−2990 cm−1) and alkenes (3030−3180−c1m) gradually strengthened with the reaction procneged ini both samples (Fig.6(a) and 6(d)). It is noteworthy, th inat Na-Fe3O4, the bands corresponding to C-H stretching of alkanes are considerably larger than those of N3Oa-4F / Fee5C2(Fig. 7(a)), which can confirm the robust hydrogenation and, therefore, formation of moreur saatetd compounds on Na-3FOe4. Therefore, the time profile of the reaction indeicsat that the mechanism for the formation of hydrocarbons is as follows: C2O is adsorbed onto the catalyst surface as carbo snpeatceies, and hydrogenation of this carbonate species proceeds to form bicartbeosn and subsequently formate species. Then, hydrogenation of the formate produces CO by the RSW reGaction, which proceeds more on Na3O-F4,e which can be probably due to 100%3O Fe4 content, while in Na-F3eO4 / Fe5C2 70 wt.% of the catalyst is F3Oe4. Besides, the adsorbed CO is hydrogenated to forsmorb aedd CHx species, ultimately yielding paraffins (to a greater extent on Na-F3Oe4) and olefins via the FT reaction. Since5C F2e is the active phase of FT, it can be speculated that the presence of this phase ina th-Fee3 NO4 / Fe5C2 hindered extra hydrogenation of intermediates to saturated hydrocarbons, thus increasing thein osle afs shown in GC-MS peaks in Fig. 3(b). Example 3 – Study on the influence of reduction on oxideb / cidaer performance and structure The Na-Fe3O4 / Fe5C2 samples were tested under two conditions: aftdeurc rteion (R) at 350 °C and atmospheric pressure unde2r f Hlow and without (NR) reduction to investigate t ihnefluence of reduction on the CO2 hydrogenation performance. In the mixed oxide / icdaerb samples, reduction improved performance in both CO2 conversion (43.9%) and5+ C selectivity (≈ 39%), while CH4 selectivity decreased to around 15%. However, when the oxide / carbide sample was notc reeddu (NR-Fe3O4 / Fe5C2), it exhibited a CO2 conversion of about 37.2% and a high C4H selectivity (approximately 43%), as shown in F 8ig(a.). Therefore, it can be inferred that the reduction of 3 FOe4 and Fe5C2 enhances the probability of chain propagation r aendduces CH4 formation.The diffraction peaks of F3Oe4 are observable in both samples θ at o 2f 30, 35.33, 42.91, 56.77 and 62.25°, corresponding to the plane facets (2201)1,) (,3 (200), (511), and (400) (JCPDS 00-01-079-04

[4187] ). Furthermore, the peaks corresponding t5oC F2e (2θ = 43-45°) were only detected in R-Na3-OFe4 / Fe5C2, which had been reduced for 4 hours before the reactihoins. m Tay be due to surface amorphous carbides nteoctt deed by XRD (Fig. 8(b)), or it could be related to thxeid oation and deactivation of F5Ce2during the reaction. Notably, neither increasing nor decreasing thec rteiodnu time improved the performance. The TEM images of the R-Na-3FOe4 / Fe5C2 samples reveal that the carbide particles arep esnucla tedwithin a thick layer of graphitic carbon (Fig. 9d(a))-. In contrast, some areas show disordered asntodrt deid structures, along with defects in the graphiticb coanr (Fig.9(d)). It is plausible that, apart froemdu rcing Fe3O4to metallic Fe, some dissociated and released onx iyognes may bond with the carbon in the carbiden dgu trhie reduction process. These oxygen-containing grooupusld c increase the carbon interlayer distance,n lega tdoi the formation of graphitic layers during the reoanc,ti as depicted in Fig.9(b) and 9(c). The migration of N+a can also occur during the reaction, transition frinogm iron oxide to carbide. The oxygen-containing groups within the carbon inteerlrasy might facilitate their penetration through l tahyeers. The extensive intercalation of oxygen and+N waithin the graphite interlayers results in a m doriseorderedpattern and defects in the graphitized shell, w onithly localized short-range ordering, as shown g in. F 9(id).In the TEM images of the spent NR-Na3-OFe4 / Fe5C2(Fig. 10(a) and 10(b)), the carbides are primarily enclosed by an amorphous shell, with a small, g thrianphitic carbon shell observed around them. The difference in the nature of the carbon shellse in tw tho spent samples is likely a result of the retidounc, leadingto more graphitic shells around the reduced sam. p Tlheis facilitated the diffusion of intermediatehsro tughthe interlayer spacing of the carbon. Therefore, T tEhM images of the two samples after the reac stuiopnport the hypothesis that the presence of graphitic cna irsb moore pronounced in the R-Na3-OFe4 / Fe5C2. At the sametime, the NR-Na-F3eO4 / Fe5C2 exhibits a prevalence of amorphous carbon. Hel. [ e4t9 a] also showed a carbon-based confinement shell on the Fe-based nanocuab-eFe (N@C), which led to suitable reactants / productsdiffusion channels on the shell. At the same ti tmhe, exposure of the active site was precisely raetegdu.lSince XRD analysis primarily provides informatiobno aut bulk phases, XPS analysis examines thesurface species. The survey of the reduced andre ndounc-ed samples is illustrated in Fig. 11(a). Int c baeobserved that the Na / C ratio on the surface of R-F-Ne3aO4 / Fe5C2 is about 1.76%, which is approximately 1.3 times higher than that of NR-Na-3FOe4 / Fe5C2 (1.4%). In Fig. 11(b), the divalent Fe (2F+,e Fe 2p3 / 2 at 710.7 eV and Fe 2p1 / 2 at 724.3 eV), and trivalent Fe3+(,F Fee 2p3 / 2 at 713.3 eV and Fe 2p1 / 2 at 726.6 eVre) we detected in both of the spent catalysts, indica tthineg presence of surface iron oxides

[0050] (There renfcee Fe 2P spectra of the synthesized3O F4e is provided in Fig.33). A peak at approximate0ly7.73 and 721.7 eV canalso be attributed to iron carbide species [51 is]. n Itoticeable that the peaks corresponding2 to+ a Fned carbideare more prominent in the R-Na-3FOe4 / Fe5C2 sample, indicating a higher concentration of scuerf oaxide and carbide on the reduced sample after reduction. Hveorw,e the surface composition of2F+,e Fe3+, and Fe5C2 in the R-Na-Fe3O4 / Fe5C2 and NR-Na-F3eO4 / Fe5C2 samples are 72.91%, 20.64%, 6.45% and 73.09%8,% 21.3 and 5.53%, respectively. Regarding the C 1s XPSctr sape (Fig. 11(c)), the primary contributions comroem f C−C / C−H aliphatic species, while the smaller pe ianks both spectra can be assigned to C−O / C=O fromadsorbed hydrocarbons

[0052] . The graphitic peak8 a4t.32 eV can be observed in the C 1s spectra [5h3i]c,h wcan be an indication of a boost in2- C 4 olefins formation due to facilitated transport th oef intermediates tothe carbide surface in the confined graphitic chealsn.n To find a deep insight into the role of reductionn th oe catalytic behavior of the samples, carbonuasceo species of the R-Na-F3Oe4 / Fe5C2and NR-Na-F3eO4 / Fe5C2catalysts were studied by the TPH / MS analysis. TPH spectra show a methane evolution rate duee to re tahction of carbon in the spent samples wi2t,h a Hsillustrated in Fig. 12(a). According to the data F in g.12, it can be seen that the temperaturee o mf tohst intensepeak increases for R-Na-3FOe4 / Fe5C2, which is an indication of strongly adsorbed canrsb.o However, in NR- Na-Fe3O4 / Fe5C2, the main proportion of the peak appeared at teramtuprees lower than 700 °C, demonstrating lower graphitic layers and higher carbide cont aesnt s,hown in Fig. 12(b). The hydrogen adsorbed on NR-Na3-OF4e / Fe5C2is higher than that on R-Na-3FOe4 / Fe5C2due to its sharp peak (Fig.12(a)). It has been demonstrated thaapth gerne-like nanosheets with a lower degree of gitrizaapthionexhibit a larger capacity for hydrogen adsorpti5o4n]. [ Consequently, the higher hydrogen adsorptaiopna c ityon NR-Na-Fe3O4 / Fe5C2is attributed to its lower graphitic shell cont.e Tnhte substantial hydrogen adsorption on NR-Na-Fe3O4 / Fe5C2leads to an elevated2 / HCO ratio on the active sites, thereby facilitatin thge hydrogenation of reaction intermediates and impged thine formation of CHx[49, 55]. Shifts in peak temperature due to the pretreatm enevnitronment are also observable in the individualpeak contributions of various carbon species,lu as tr ial ted in Fig. 13. The deconvoluted spectraa rle tvheatthe spectra of NR-Na-F3Oe4 / Fe5C2were best fitted by seven peaks, whereas ther sap oefc Rt -Na-Fe3O4 / Fe5C2could be well fitted by eight peaks. These peakns b cea assigned to adsorbed / atomic carbαo),n a (morphous surface methylene chains or filmβs), ( bulk iron carbideγ (), and graphitic carbonδ) (. The corresponding peak temperatures and fractional peak areas are tabdu ilnat Teable S1. Notably, the peak temperaturesw fol alo specific order, namely, in the order of decreas reinagctivity with H2

[0056] . It can be observed that the low-temperature spe ocft trhae NR-Na-F3eO4 / Fe5C2 could be deconvoluted to 4 peaks (Fig.13(a)), while that of R-Na3-OF4e / Fe5C2 could be separated into 3 peaks (Fig.13(b)). f Tirshte 3 peaks in both samples can be attributed to tshoerb aedd atomic carbons (carbidic). However, the p 4etahk in R-Na-Fe3O4 / Fe5C2 and the last two (4th and 5th) in NR-Na3-OF4e / Fe5C2 can be ascribed to the amorphous carbon. In addition, the high-temperature TPH spectra otfh b coatalysts (Fig. 13(c), 13(d)) were best deconvoluted into 5 peaks, comprising 3 carbideds 2 an graphitic carbons. The first two carbide pea rkes attributed to F5eC2 with different morphologies, where their hydrogteionna resulted in peaks around 571 and 615 °C for R-Na-F3eO4 / Fe5C2. In contrast, the corresponding methane peaksR o-Nf Na-Fe3O4 / Fe5C2 emerged at higher temperatures, approximately 599 and 6C5.5 Fu °rthermore, the peak area of the correspon pdeinagks is larger in the former catalyst. In this conte itx ct,an be speculated that the lower performanc tehe o Nf R-Na- Fe3O4 / Fe5C2 catalyst in CO2 hydrogenation toward5 C+ (Fig.8(a)) can be attributed to the weaker revaityct oi f Fe5C2 with H2 in this catalyst. The third carbide peak is like Fley3C, appearing around 670 and 687 °C in the TPH profiles of R-Na-F3eO4 / Fe5C2 and NR-Na-F3eO4 / Fe5C2, respectively. However, the contribution of3C Fe in NR-Na-Fe3O4 / Fe5C2 is significantly larger than that in R-Na-3FOe4 / Fe5C2.The hydrogenation of graphitic carbon can leadhe to fo trmation of CH4 at temperatures above 700 °C

[0057] . The corresponding peaks are larger in thea R-F-Ne3O4 / Fe5C2. This observation is consistent with the presence of a graphitic peak in the C 1s XPS sape ocft trhe R-Na-F3eO4 / Fe5C2 (Fig.11(c)) and aligns with theTEM images of the same sample (Fig. 9(b) and ( rde)v)e,aling the increased formation of graphitic l sh ienlthe R-Na-Fe3O4 / Fe5C2after the reaction. In this context, it can be speculated that redunc itnio H2before reaction plays a significant role in forming more graphitic shells during C2O hydrogenation, as observed in TEM and confirmed XP byS and TPH analysis. In addition, exposing the samplehe to re tactive gas (2H / CO2) without reduction in H2can result in the formation of more amorphous shells. It is noteworthy that there is a competition betnw ceaerburization and hydrogenation during FTS, which may prevent the carbonaceous species from fullyer cinogv the catalyst

[0057] . Moreover, the morphologfy o non-reduced catalyst (NR-Na-3FOe4 / Fe5C2) showed that carbonaceous species mainly appe inare thde amorphous and carbide form. Additional understanding regarding the surface i sepsec was obtained through in situ DiffuseReflectance Infrared Fourier Transform (DRIFT) erximpe nts conducted at 30 bar, The R-Na3O-F4e / Fe5C2initially reduced in H2at 350°C as described in the DRIFT studies inio snec 3t.1, while the NR-Na- Fe3O4 / Fe5C2heated in He to the reaction temperature (340 a °nCd) then exposed to the feed ga2s / C (HO2= 3) as illustrated in Fig. 14(a) and 14(b). Consist wenitth steady-state catalytic tests (Fig. 8(a)), NaR--N Fe3O4 / Fe5C2exhibits more significant activity in C4H formation (main bands centered at 3015 and 130-15 cm

[0058] ) compared to R-Na-F3Oe4 / Fe5C2. In addition, the spectrum of both R-Na3-OFe4 / Fe5C2 and NR-Na-F3eO4 / Fe5C2 display an asymmetry inthe rotational bands of C4H within the ν(C–H) region. This asymmetry is evident and isib auttr ed to C–Hbands from other potential products in the samieon re [g56]. However, C–H bands are pretty weak in F thTeIR spectra collected over R-Na-3FOe4 / Fe5C2 catalyst (Fig. 14(a)). Consequently, it is evid tehnatt the type and concentration of surface CH-containing speciese dri bffetween the reduced and non-reduced catalyhsets. Tmore significant bands at 2875−2990-1 c cman be attributed to additional alkane specie]s, [ a5s8 supported bythe TPH analysis, which indicates the high hydro agdesnorption capacity of the NR-Na-3FOe4 / Fe5C2. In summary, our findings suggest that the pretreantm environment of Na-F3Oe4 / Fe5C2 catalystinfluences the nature of carbonaceous species arntidcu plarly the carbon shell under C2-OFTS conditions. The R-Na-Fe3O4 / Fe5C2 exhibits a higher graphitic shell, while the sam wpliethout reduction displays more amorphous carbon. The carbon shell with a highaeprh girtic shell structure exhibits a lowe2r / C HO ratio around the active sites, resulting from a weaker adsonrp ctiaopacity of the corresponding carbides fo2,r a Hs shown in Fig. 12 and Fig. 13. This can reduce selecti tvoitwyard CH4 and enhance carbon chain growth

[0055] . The formation of more CH4 and hydrogenated products could also be confir bmye DdRIFT studies. To delve deeper into the performance of the mixxeid e o / carbide catalyst, Na-F3Oe4 and Fe5C2 werecombined using two distinct proximity modes, asb eorla ted in the following section.Example 4 – Study on the effect of oxide / carbide proximity The proximity of iron carbide to the oxide phaseay psl a significant role in the C2O hydrogenationperformance [2]. Pure carbide and Na-promote3dO4 Fe were integrated in two ways: mixed-powder pellets and separate pellet stacking. In the former ca1s.e7,% 3 CH4 was produced at a C2O conversion of 35.9%, while in the latter case, the C4H was reduced to around 15% at a2 C cOonversion of approximately 43.9%. In addition, a considerable increase i2n-C C4olefins can be observed when the proximity frome s tehparate pellet (3.5%) to the mixed-powder pellet (38%) mode cacnre inase. This underscores the importance of close- proximity between Na-F3eO4and Fe5C2in the CO2hydrogenation reaction. The increase in the amount of C4 H and C2-C4 paraffins can be ascribed to the higher hydrogioenatpossibility when oxide and carbide are not in cl coosnetact with each other. Consequently, intermed lia gthtolefins probably re-adsorb on the surface of thiede o,x resulting in more hydrogenated products wheepnar sate pellets are used in the reaction bed. Additiona thlley, CHxintermediates formed over Na-3FOe4could undergo hydrogenation (potentially due to hydrogen spillro)v beefore reaching the carbide surface, forminge m liogrht paraffins and CH4. However, the chain propagation probability wagsh heir in the presence of mixed-powder pellets, as depicted in Fig.15(a). The integration manner of the two active speciegsnif siciantly impacts the final phases and the distribution of hydrocarbons. Fig. 15(b) demonsetsra tthat when the oxide and carbide are closelym abslseed (Mixed-powder pellets), XRD peaks corresponding bo toth Fe3O4and Fe5C2can be observed in the spent catalyst. However, when the distance between thoe c tawtalytically active sites is increased throuegpha srate pellet integration, the carbide peaks are no lon dgeeterctable by XRD. As explained in Example 3, m thaisy be due to the carbide particles being covered b aym aonrphous shell. This kind of carbon shell retsstr tiche growth of catalytically active particles due tou scttrural confinement and diffusion limitations [27 T]h.is mightalso be attributed to the migration of+ N iaons into the graphitic carbon interlayers dur tinhge reaction. Incontrast, in separate pellets,+N ioans might not be able to diffuse as effectivesly in a the mixed-powder pellets. Furthermore, N+a ions can enhance the electron density and incr CeOas aedsorption rather than2 H adsorption, weakening the carbon-oxygen bond and improving p trhoebability of chain propagation in the mixed-powrde pellets

[0059] . Although both samples were reducefdor bee the reaction, fewer oxygen-containing groupasy m be present in the separate pellets due to a hi pgrhoebrability of hydrogenation due to the longera dniscte between Na-F3eO4 and Fe5C2. Therefore, the boost in2- CC4 olefins formation in the mixed-powder pellets c baen attributed to thelimiting hydrogenation effects of surface carboxteyla species, which allows the composite catalys fatv to rC–C bonds rather than C–H at reaction tempera6tu0r,e 6 [1]. Fig. 15(c) and 15(d) demonstrate the sceh oefmthe hydrocarbons distribution when the active s aitres integrated with two different modes. It can in bfe rredthat in the separate pellets, the hydrogenatio in t oefrmediates could led to the formation of more4 C aHndsaturated hydrocarbons. Example 5 – Study on oxide / carbide optimized ratio The ratio of oxide to carbide is an essential frac atfofecting the CO2-FTS performance of Fe-based catalysts. To figure out this point, three mixtu wreisth different Na-Fe3O4 / Fe5C2 mass ratios (30 / 70, 50 / 50, 70 / 30) were prepared and tested at temperatur 3e2s0 o°Cf and 340°C and pressures of 30 bar and 50 Th bear. results are presented in Figs.16(a) and 16(be)rm ins t of C2-C4 and C5+ selectivity (including CO) versus C2Oconversion, respectively. Each dataset was assi agne udmber (corresponding data are presented ine T 2a);bl number 0 was assigned to the Na3O-F4e without mixing with carbide. As shown in Figs. 1a6)( and 16(b), the physical addition of F5eC2 to Na-Fe3O4 significantly enhances C2O conversion. Furthermore, in both figures, the last four data points (9, 10, 11, and 12) bgeilnogn to the Na-F3eO4 / Fe5C2ratio of 70 / 30 exhibit the highest yield (dashed curves in Fig.16(a) and 16(b)) cormedpa to data points with other ratios. Table 2: Data corresponding to Figs. 16 and 17. GHSV T(°C) / No. Catalyst XCO2 SCO SC1 SC2-C4 SC5+ Ref. (mL / g h) P(bar) 0Na-Fe3O44000 340 / 30 31.24 17.36 10.71 40.1 31.8 1 4000 320 / 30 38.66 4.52 23.09 38.6 33.8 2 Na-Fe3O4 / Fe5C2 4000 340 / 30 35.99 9.64 24.44 29.9 36 3 (30 / 70)4000320 / 50 33.99 8.47 13.45 38.8 39.3 4 4000 340 / 50 33.33 8.72 13.26 35.2 42.8 5 4000 320 / 30 41.99 5.03 35.03 33.6 26.3 6 Na-Fe3O4 / Fe5C2 4000 340 / 30 45.63 6.12 33.03 33.6 27.2 This work 7 (50 / 50)4000320 / 50 39.58 7.04 33.96 33.2 28.8 8 4000 340 / 50 37.16 6.19 35.56 34.6 23.7 9 4000 320 / 30 41.33 8.45 14.13 40.1 35.3 10 Na-Fe3O4 / Fe5C2 4000 340 / 30 43.9 8.12 13.76 41.69 36.43 11 (70 / 30)4000320 / 50 42.49 7.02 17.26 43.4 32.4124000 340 / 50 43.21 6.69 17.01 40.9 35.4 13 Fe3O4 / K-Fe5C2 7200 320 / 30 34 4 30 40 26

[0069] 14 Fe / C 4000 320 / 20 31 30 12.6 43.4 14

[0070] 15 Fe5C2 / K-Al 2O3 3600 320 / 30 31.5 18.6 12.1 40.2 29.1

[0071] 160.8Fe@MC 12000 320 / 30 35.1 18.5 17.1155.42 8.965

[0072] 17 K / Fe@NC-400 7200 320 / 30 30.6 18.6 16.9 40.2 24.33] [7 18 FeZnK-NC 7200 320 / 30 34.6 21.2 19.1 37.6 22.1

[0074] It can also be noted that high pressure (50 baers) d no t seem to be promising in this catalytic smys,teas in almost all cases, the yield didn’t changesi cdoenrably with increasing pressure from 30 to 5r0 ( bFaig. 17). It can be observed that the physical mixtufr Nea o-Fe3O4 with Fe5C2 at 70 / 30 weight ratio could improve the yield of C2-C4 (with an olefin / paraffin ratio of approximately 5 a)nd C5+ by 41.5% and 21.23%, respectively. This makes it a promising catalysrt p frooducing light olefins, intermediates for fuerold puction. The XRD patterns of Na-F3Oe4 and Na-F3eO4 / Fe5C2 with different ratios, recorded after the reac,tionare presented in Fig. 18(a). The diffraction pe oafk Fse3O4 are observed in all samples

[0048] , although their intensities vary. Additionally, peaks correspond tiong Fe5C2 (2θ = 40-50°) can be only detected in Na3-OF4e and Na-Fe3O4 / Fe5C2 (70 / 30), as indicated by the dashed area. Howe nvoe pr,eaks attributed to iron carbides can be found in the other two samples. This abs menigchet be attributed to the presence of amorphoaurbsid ces that are not detectable by XRD, as explained inm Epxlea 3, or it can be ascribed to carbide oxidat oion Fe- oxides. Besides, it can be observed that in N3aO-4F / Fee5C2(70 / 30), the additional peak corresponds to the (4 0 -2) plane of F5eC2appeared atθ 2 = 44.709°, while it could not be detected in Na3O-F4e, which is an indication of the presence of the active faceth ien f tormer catalyst. Furthermore, it can be speculated that as the n pteargce of F5eC2 in the mixed catalyst decreases, theintensity of peaks corresponding to3O F4e increases. This may indicate phase changes froomrp ahmous to crystalline structures or the diffusion of more mecoulles into the framework of3FOe4. By reducing the Na-Fe3O4content in the samples (50 / 50 and 30 / 70), thee pnrcees of Na and its migration would likely decrease. Furthermore, the migration of Na+ ionusld wo not be facilitated due to the increased foromnat oifamorphous carbon. This can confirm the significa onfc tehe appropriate oxide / carbide ratio in thel cyasta .To better understand the active phases in the N3Oa4- / FFee5C2(70 / 30) and Na-F3eO4samples, the XRD profiles of fresh, reduced, and spent samplese acroerd red. In the XRD pattern of Na-3FOe4(Fig. 19(a)), all the iron oxides reduced α to-Fe after reduction, and after the reaction, thaerp sh peaks of F3eO4and carbides can be observed. The XRD of the Na3-OF4e / Fe5C2 (70 / 30) (Fig.19(b)) shows that the peaks corrnedspinog to Fe3O4and carbides can be observed in the fresh sam Hopwlee.ver, in the reduced sample, an additional peak of metallic iron (α-Fe) appeared atθ 2 = 44.7°, which is an indication of the reductiofn a o proportion of the Fe3O4 phase to α-Fe. Besides, the peaks of carbide and som3Oe4 F ceould still be detected in the XRD pattern of the reduced catalyst. It can be concluded tnha thte i reduced Na-F3Oe4 / Fe5C2, all of the Fe3O4 could not be entirely reduced to α-Fe. In the spent sample, the peaks o3Of F4e and carbides are visible clearly. This shows that the metallic iron underwent carburization a wnads converted to carbides, while some carbides were probably oxidized, resulting in sharp peaks o3fO F4e. In addition, as depicted in Fig. (18(b)), in atdiodni to the peak attributed to (510), a peak correspondin tghe to (40 -2) plane was detected only in the N3aO-F4 / eFe5C2. Therefore, it can be speculated that for Na3O-F4,e the carbides in the spent samples result from the carburization of metallic Fe. In contrast, the oexsid of the spent samples result from carbide oxoinda.ti However, for Na-F3eO4 / Fe5C2 (Figs. 9 and 10) carbides might be those that w foerrmeed via carburization of α-Fe plus a proportion of the introduced carbide p vhiaysical mixing, which was not oxidized during the reaction. It has been shown that Fxe cCould be oxidized in C2O hydrogenation

[0062] . About 33% 3 FOe4 was observed in the spent sample by Wei et al. [18 p]r boymoting the F3eO4 with 0.7 wt.% Na. Moreover, sincethe peak ascribed to the plane (4 0 -2) could bte c dteed only in the spent Na-3FOe4 / Fe5C2, the formation ofsome Fe5C2 despite the competition between hydrogenation c an rbdurization under a reactive environmentcannot be ruled out. Example 6 – Study on structure-performance relationship Iron carbides are often reported to be the prim aacrtyive phase responsible for chain growth in FTS

[0063] . However, the results demonstrated that three p cuarbides, inappropriate oxide / carbide ratio, / o arndproximity, and non-proper reduction cannot enha tnhcee formation of long-chain hydrocarbons even ien thpresence of carbides. Furthermore, it can be codnecdlu that the nature of active phases and the mlor gpyho fcarbon shells of carbides can also be affectedhe by re tduction treatment. In the case of Na3O-F4e at the beginning of the reduction in2H, the surface O atoms of3FOe4are gradually removed to form metallic iron sites (α-Fe) as supported by XRD of the reduced catalyisgt. ( 2F0(a) reduced). By introducing the feed gas, iron carbide forms through carbon permeation to α t-hFee sites to form iron carbide. However, in then stpe sample, the appearance of3O F4e peaks confirms the oxidation of5FCe2during the reaction (Fig.20(a) spent). In the presence of Na-F3Oe4 / Fe5C2, at the beginning of the reduction in2, H the same phenomenon happens, and surface O atoms o3fO F4e are gradually removed to form metallic iron site Hso.wever, thepresence of 30 wt.% carbide in the catalyst hindde thre complete reduction of3 FOe4, resulting in the presenceof both α-Fe and F3eO4(non-reduced) phases after reduction based o XnR thDe of the reduced samples (Fig. 20(b) reduced). It has been shown that the carabtuiorinz rates were controlled by the oxygen-deple rtaiotne, and the dense iron carbide layer on th3eO F4e surface provided an effective barrier to the reamlov f oxygen

[0064] . These results show that iron carbide forme lady aer on some parts of3FOe4surface, impeding oxygen diffusion

[0032] . This is in accordance with the2-T HPR profiles (Fig. 5(a)), which show a small pe aareka in the region of α-Fe formation for Na-F3eO4 / Fe5C2compared to the sharp peak of Na3O-F4e, confirming the hindrance in a further reduction α to-Fe. By introducing the reaction gas2 / (CHO2), the C atoms react with the α-Fe to form carbide. Therefore, at the onset ocft rioena, both Fe5C2 (from α-Fe carburization plus the initial carbide in the catalyst) and3FOe4(the un-reduced proportion of the initial3O Fe4) are present. In addition, it can be observed that some peaks o5Cf F2e (at 2θ = 37.05 and 40.86°) disappeared after reductiohnil,e w the intensity of another peak aθt 2 = 42.75° increased in the spent sample (Fig.1 s9p(ebn)t). In the non-reduced catalyst (NR-Na3-OFe4 / Fe5C2), also both F3eO4 and Fe5C2 are present at the onset of the reaction (Fig. 20(c)). However, this catatl syhsowed poor CO2 hydrogenation performance in5+ C hydrocarbons, as shown in Fig. 8(a). FurthermoEreM, T images (Figs. (9) and (10)) and XPS (Fig. 11(c)) show more amorphous carbon shell / layers in thet s spaemnples, which is confirmed by TPH analysis (.Figs (12) and (13)). It was revealed that by using the Na3-OF4e / Fe5C2 catalyst without reduction, the oxide / carbideo ra atti the onset of the reaction remained intact (the sa sm aen initial catalyst), which altered the morpohgoyl of carbon shells to more amorphous. In addition, h ciagrhbide content, especially3 FCe in the spent NR-Na- Fe3O4 / Fe5C2 observed in TPH analysis (Fig. 13(d)), can shi tehled surface of F3eO4 and hinder oxygen depletion. This can be the reason for more nonh-gitriacp carbon layers in non-reduced catalysts. Loxwyg oen removal ability has been shown to favor the formonat oif carbon-less F3Ce rather than carbon-rich5 FCe2

[0056] .Therefore, it can be concluded that during hydroagtieon , some of the F5Ce2 transformed to a small amountof carbon-deficient F3eC, and some of the F5Ce2 transformed to a small amount of carbon-defici Feen3tC during hydrogenation. These physicochemical properties also correlatel w itehl the CO2 hydrogenation performance of the catalyst, as depicted in Fig.20(d). Accordinglyo,r me C5+ can be achieved in the reduced catalysts (ca inse II Fig. 20(d)) as a result of regulated active phastieos r, while more CH4 is obtained on non-reduced samples(case III in Fig. 20(d)) due to higher hydrogennat aiobility of the amorphous shells. Therefore, reduction treatment and, in turn, molropghyo of the carbon shells can significantly aff tehcet CO2 hydrogenation performance. In this context, morraeph gitic carbon layers are found to be respons foibrle the superior performance of the R-Na3-OF4e / Fe5C2, while the amorphous shells in the NR-Na3-OF4e / Fe5C2resulted in the formation of more C4H and saturated hydrocarbons. Example 7 – Study on preparation of F3Ce:Fe5C2mixture - model prediction We have performed a model prediction for produc otiof n the mixture of F3eC:Fe5C2based on Design of Experiment results. The mixtures of3C Fe:Fe5C2with different compositions were prepared as fwosllo: 1 gr of Fe-oxalate dihydrate was heated to a temupreera int the range of 350 to 450 °C under CO / He mi gxaesd, where the flow rate of CO can be 10-15 ml / min alnodw f rate of He would be 40-90 ml / min. The results are shown in Figure 22 and Table 3. E Trhroer is the difference between the experimental and the predicted F5Ce2wt% content. Table 3 Input parameters Experimental Predicted Error No. Code CO He T (°C) Fe3C Fe5C2Fe3C Fe5C2|Prd-Exp| (ml / min) (ml / min)(wt%) (wt%) (wt%)(wt%)1 05-16 10 40 350 21.47 78.53 22.15 77.85 0.68 2 06-03 10 0 350 17.01 82.99 17.05 82.95 0.04 3 06-04 40 0 350 18.62 81.38 18.66 81.34 0.04 4 06-09 5 45 350 37.21 62.79 33.52 66.48 3.69 5 06-21-3 5 45 370 48.3 51.7 47.74 52.26 0.56 6 06-29-2 5 45 380 48.54 51.46 57.33 42.67 8.79 7 07-17-2 10 90 450 100 0 100 0 0 8 07-25-1 10 40 450 100 0 100 0 0 9 07-25-2 5 45 450 100 0 100 0 0 10 07-25-3 10 90 350 8 92 8.03 91.97 0.03 11 09-08 20 30 400 57.27 42.73 57.27 42.73 0 12 11-02 5 45 400 80.1 19.9 77.78 22.22 2.32 13 11-03 10 40 400 58.55 41.45 56.73 43.27 1.82 Fe-oxalate used in each run: 1 gr Heating ramp: 5°C / min Isotherm time: 4 h Cooling ramp and atmosphere: 10 °C / min under He In Table 4 synthesis parameters for typically prcoeddu mixed FeCx samples are listed, as well as the predicted ratios of F5eC2:Fe3C could be seen as been well fitted to experime dnattaal using statistical analysis, producing surface of responses (Fig. 22) for thneth seysis of any kind of FeCx ratio with this simuiolant and experimental based technique.Typical method to produce a well working catalynst F iT synthesis to produce gasoline-based fuels is to take 1 gr of Fe-oxalate and heat it under floawte r of total of 50 ml / min of ratio of CO:He (1:9r)om f RT to 370 °C, to produce a 50:50 ratio3C Fe:Fe5C2. Another method is to use 1 gr of Fe-oxalate unhder fl tow rate of total of 50 ml / min of ratio CO:He(1:4) from RT to 400 °C, to produce a 58.5:41.5io ra Fte3C:Fe5C2. Example 8 – Study of physical properties of the synthesizerdtic pleas tested by N2sorption analyzer based on the BET method Table 4 Surface area Total pore volume Samples 2 3 Average pore size diameter (m / g) (cm / g) (nm) Na-Fe3O465.273 0.2376 14.5611 Fe5C227.933 0.0695 9.95206 Fe3C17.307 0.0357 8.25033 Fe5C2 / Fe3C (50 / 50)19.257 0.04518 9.38515As explained in Example 2, despite the small suerfa rcea and pore volume of the carbide samples, indicating their non-porous nature, they still denmstorate notable catalytic activity, as discusse tdhe in next section. This underscores that the textural proiepse ortf carbides may not be the decisive factohre in R tWGS- FT reaction. Example 9 – Results of X-ray diffraction analysis Figures 24 to 28 present the XRD patterns of sasm wplieth the results of rietveld refinement ( (R.R) this method uses a least squares approach toa re tfhineeoretical line profile until it matches thea msuered XRD profile.) which are presented in Table 5, and confirms thrmea fotion of pure F5eC2, pure Fe3C and the Mixed carbide with different ratios according to an emibmoednt of the present invention. The results of rietveld refinement (R. R.) arec inco ardance with the Esna du Plessis et al.

[0067] Z ahnodu et al.

[0068] for Fe5C2 and Fe3C phases, respectively. The calculated cell parearmse atre provided in Table 5. Table 5: The results of rietveld refinement (R. R.) of t shyenthesized carbides PhaseSpaceFe5C2Fe3C Cell group(%)(%)a b c alpha beta gammavolume Fe5C2C 12 / c 1 100 0 11.45854.5354 5.0598 90 97.723 90 260.5675 Fe3C Pnma 0 100 5.08 6.7488 4.5318 90 90 90 155.3686 C 12 / c 1 11.5442 4.5570 5.0772 90 97.745 90 264.6606 Mixed 51.7 48.3 Pnma 5.0728 6.7478 4.5327 90 90 90 155.1559 Example 10 – Results of TEM and FFT analysisFigure 29 shows the TEM and FFT analysis of thep sleasm which further confirms the formation of the Fe5C2 and Fe3C in the synthesized samples based on an embod oimf e thnet present invention. The fringes of Fe5C2 (002) entrapped in amorphous carbon could bde in fin the TEM image of F5eC2 (Figure 29(a)). The fringes of Fe3C (201) encapsulated in graphitic carbon (wit3h40 n.m d-spacing) could be detected in the TEM images of F3eC (Figure 29(b)). The fringes of both5FCe2(002) and F3eC (201) and (002) could be found in the composite carbide5FCe2(50%) - Fe3C (50%) (Figure 29(c)). Example 11 – Results of particle size analysis Figure 30 shows the average particle size of thneth seysized F5eC2and Fe3C calculated from TEM images, which are around 17 and 41 nm, respec.tively Example 12 - Additional experimental data on the effectivesn oefs the iron-oxide / iron-carbide mixture catalyst. The Figure 23 and Table 6 show liquid product dibisutr ions obtained with iron oxide / iron carbidemixture catalysts. The results obtained with Na3O-F4e catalyst serves as a comparative example. Table 6 shows the performance of Na3-OF4e mixed with carbides of different composition. a Itn c be observed that addition of carbide enhanced th2e c CoOnversion and reduced CO selectivity compare thdo tsoe of Na-Fe3O4(the first row). Each sample is assigned a cohdee, co tmposition of the samples can be observed in the 2ndand 3rdcolumns. The integration manner (I. m.) is theh modet of mixing the oxide and carbide; For mixed-powder pellets, the appropriate amount ofF Ne3aO-4 and Fe5C2 powders was physically mixed with a mortar and pestle in different mass ratios (305 / 700 / 5,0, and 70 / 30). The mixture was then presseuds,h cerd, and sieved to produce 20–60 mesh granules. How feovre sre,parated pellets,3FOe4and Fe5C2were pressed, crushed, and pelleted at 20–60 mesh separately t,he anmd mixed in a bottle in the desired ratio. Typically, 0.5 to 2 gr of the powders in a spec FifiecOx / FeCx weight ratio (70 / 30, 50 / 50 or 30 / 70) and either the mixed-powder pellets or separate p meloledtes were loaded to the lab scale reactor. Then c,a ttalystwas reduced in 2 H environment for 0-12 hours before introduction th oef feed gas at 350 °C. The feed gas(CO2:H2 (3:1)) with the GHSV between 4000 to 5000 ml / g irs h introduced to the reactor. The reaction temperature was between 320 to 340 °C and theu prree wssas 30 to 50 bar. For instance, totally 0.5 g of catalyst 05-13 w thiteh FeOx / FeCx ratio of 70 / 30 were mixed in the md-ixepowder pellet mode, reduced for 4 hours at 350 T °hCe.n the reaction conducted at 320 °C and 30 baicrh whresulted in 38.66% C2O conversion, which the selectivity towards2- C 4 olefins and C5+ reached to 36.68%and 35.1%, respectively. In another test, totally 0.5 g of catalyst 05-13th w thi e FeOx / FeCx of 70 / 30 were mixed in the sepearat pellet mode, reduced for 4 hours at 350 °C. Then re thaction conducted at 320 °C and 30 bar whicuhlt reedsin 33.33% CO2 conversion, which the selectivity toward2s- C 4 olefins and C5+ reached to 3.41% and 22.69%,respectively. the reduce selectivity to olefin r inmte diates is due to the different integration marn onfe theoxide and carbide. Table 6Carbide FeOCat. Selectivity (%) compositionx / P GHSV Wt. I. m. T (C) XCO2 Code FeCx (bar) (ml / gr h) C2-C4 C2-C4 Fe5C2 Fe3C (g) CO C1 C5+ (olefin) (paraffin) Ox 0 0 100 / 0 0.5 MP 340 30 4000 31.2147.3610.71 40.1 31.8304-2670.4729.53 70 / 30 0.5 MP 320 30 4000 37.7 8 13.98 29.87 8.43 39.72 70 / 30 0.5 MP 340 30 4000 41.337.24 16.18 30.49 8.61 37.48 70 / 30 0.5 MP 320 50 4000 38.66.36 15.26 28.3 11.1 38.98 70 / 30 0.5 MP 340 50 4000 42.587.46 16.46 28.4 11.6 36.08 05-02 0 100 70 / 30 0.5 MP 340 30 4000 36.856.9 12.95 33.76 8.44 37.97 05-1178.5321.47 70 / 30 0.5 MP 340 30 4000 41.358.13 14.43 32.56 8.14 36.7406-0382.9917.01 70 / 30 0.5 MP 320 30 4000 34.997.59 12.25 30.83 6.21 43.12 70 / 30 0.5 MP 340 30 4000 38.668.83 13.03 31.99 5.73 40.42 70 / 30 0.5 MP 320 50 4000 35.548.38 14.69 28.19 8.94 39.8 70 / 30 0.5 MP 340 50 4000 38,058.4 15.44 29.74 8.85 37.56 06-0962.7937.21 70 / 30 0.5 MP 340 30 4000 39.49.21 13.7 30.7 6.06 40.33 05-1378.5321.47 70 / 30 0.5 MP 340 30 4000 38.667.4 13.32 36.68 7.5 35.1 70 / 30 0.5 MP 340 30 4000 43.98.12 13.76 35.02 6.67 36.43 70 / 30 0.5 MP 340 30 4000 36.758.43 17.21 34.58 10.92 28.86 70 / 30 0.5 MP 340 30 4000 41.339.3 18.78 37.24 11.76 22.92 70 / 30 0.5 SP 320 30 4000 33.34.55 28.09 3.41 39.19 24.75 70 / 30 0.5 SP 340 30 4000 35.95.55 29.96 3.35 38.45 22.69 70 / 30 0.5 SP 320 50 4000 33.34.96 29.64 2.03 38.66 24.71 70 / 30 0.5 SP 340 50 4000 35.441.49 31.31 2 38.57 23.63 30 / 70 0.5 MP 320 30 4000 38.664.52 23.09 38.57 33.82 30 / 70 0.5 MP 340 30 4000 35.99.64 24.44 29.94 35.98 30 / 70 0.5 MP 320 50 4000 33.998.47 13.45 38.83 39.25 30 / 70 0.5 MP 340 50 4000 33.338.72 13.26 35.22 42.8 50 / 50 0.5 MP 320 30 4000 41.995.03 35.03 33.62 26.32 50 / 50 0.5 MP 340 30 4000 45.636.12 33.03 33.63 27.22 50 / 50 0.5 MP 320 50 4000 39.587.04 33.96 33.16 28.84 50 / 50 0.5 MP 340 50 4000 37.16.19 35.56 34.59 23.66 05-31 0 100 70 / 30 0.5 MP 340 30 4000 40.483.49 12.8 27.7 5.27 42.74 06- 51.7 48.3 70 / 30 0.5 MP 340 30 4000 38.3110.2513.56 35.01 5.79 36.98 21-3 07- 0 100 70 / 30 0.5 MP 340 30 4000 38.983.31 13.82 33.87 4.89 39.11 17-2 90 10 70 / 30 2 MP 340 30 5000 40.2115.2111.53 30.67 4.13 37.64 0 100 70 / 30 2 MP 340 30 5000 41.124.1714.14 31.03 3.36 37.34 50 50 70 / 30 2 MP 340 30 5000 41.0164.7 12.3 26.5 3.1 43.4 MP: Mixed-powder pellets SP: Separate pelletsIn the Na-Fe3O4 without carbide, the sample is reduced comple ttoely Fe after reduction and after reaction some FeOx converted to FeCx. Sample 06-03, with the composition5C Fe2:Fe3C (83:17), in combination with Na-F3Oe4 works superior than the Na-F3eO4, because under reaction condition during FT sysnisth Fee3O4partially reduced to Fe; therefore, after reduction the non-reduced proopnor otif Fe3O4, the introduced Fe3C and the Fe are present. This helps the FeOx / FeCx ratio getting optimal urn rdeeaction with more FeOx than FeCx. The same f goores sample 05-31 with the composition5C Fe2:Fe3C (0:100). However, the behavior under reaction alm isost different due to the difference in the carbide tsy.pe The results o ifn situ XRD obtained with Na-F3eO4, Na-Fe3O4 / Fe5C2and Na-F3eO4 / Fe3C are shown inFigures 35 to 37. Figure 31 shows the schematirces rep ntation of the phase evolution during in siRtuD X.Example 13 – Additional study of catalyst comprising alkali male,t alkaline earth metal or transition metal promoted F3eO4. Reaction conditions: pretreatment without carbid 4e h –; pretreatment with carbide – 3 h; T = 340°C, P = 30 bar, t = 6 h or steady state condition; carb aolnance < 10%. Table 7 T (°C) Selectivity for hydrocarbons XCO2 SCO SCH Catalyst / P C2-C4 C2-C4 (%) (%) (%) C1 )(paraC5 C6 C7 C8+ (bar) (olefinffin)Na-Fe3O4 340 / 30 30.16 18.68 81.33 17.03 38.11 5.20 3.85 6.13 2.568.46 Na-Fe3O4340 / 30 40.80 14.33 85.67 17.61 38.95 7.34 4.17 8.38 3.226.01 + F5C2K-Fe3O4 340 / 30 40.03 15.30 84.71 13.43 36.11 4.17 6.27 12.524.55 7.67 K-Fe3O4 + 340 / 30 40.03 13.77 86.23 14.62 36.79 4.16 5.49 11.564.08 9.54 F5C2Mg-Fe3O4 340 / 30 35.17 5.97 94.0434.73 5.69 37.44 4.18 5.00 1.265.76 Mg-Fe3O4340 / 30 37.24 3.11 96.8939.93 3.95 37.50 3.86 4.97 1.535.16 + F5C2 Mn-Fe3O4 340 / 30 30.39 9.47 90.5421.74 21.73 23.53 4.64 6.53 2.0010.4 Mn-Fe3O4340 / 30 37.99 8.59 91.4238.12 2.32 36.40 3.75 4.78 1.514.56 + F5C2Zn-Fe3O4 340 / 30 32.90 15.16 84.84 45.46 1.19 32.82 1.91 1.57 0.681.21 Zn-Fe3O4 340 / 30 35.47 11.48 88.52 47.41 2.48 33.74 1.78 1.52 0.640.95 + F5C2REFERENCES [1] X. Shang, G. Liu, X. Su, Y. Huang, T. 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Claims

Claims 1. Use of an alkali-type, alkaline earth type orns triation metal promoted Iron-oxide-Iron Carbide mixture catalyst with tuned mixture ratios for asdtjiung the C5+hydrocarbon product distribution of CO / C2O hydrogenation processes.

2. The use of claim 1 of the iron-oxide-iron carbi mdeixture catalyst in modified Fischer-Tropsch reaction, preferably carbon-dioxide-based Fischreorp-sTch synthesis, wherein the Iron-oxide-Iron Cdaerbi mixture catalyst is of a Na alkali-type catalysdt a thne Iron-Carbide structures in the catalyst coismep Fre5C2and Fe3C.

3. The use of any of claim 1 or 2 wherein the iroxnid-oe-iron carbide mixture catalyst is used in mi-xed power pellet form wherein the mixture is presserdu,sh ced and sieved, preferably to produce 20–60 mesh granules; wherein the mixed-powder pellet formw asllo a closer distance between iron oxide and irorbnid cea phases, which results in higher selectivity fo2-rC C4olefins and C5+hydrocarbons and less C4.H 4. The use of any of claim 1 to 3 wherein the iroxnid-oe-iron carbide mixture catalyst comprises reduce catalyst, preferably graphitized layers of reduc aetdalyst, in particular R-Na-F3Oe4 / Fe5C2, preferably in 70 / 30 wt.%, respectively; wherein particularly preferably the catalyst alsoom cprises non-reduced catalyst, in particular NR-Na- Fe3O4 / Fe5C2, preferably in 70 / 30 wt.%, respectively.

5. A method for the synthesis of an alkali-type,a alilnke earth type or transition metal promoted Iron- oxide-Iron Carbide mixture catalyst, wherein the Iron-Carbide structures in the catalyst arme feodr with controlled F5eC2 / Fe3C ratios from Fe-oxalate dihydrate.

6. The method according to claim 5, wherein phasnetr-coolled synthesis of Iron-carbide is carried out whereby phase-controlled Iron carbides are form wehde,rein preferably said phase-controlled synthesis of Iron-carbid cear isried out in an atmospheric environment under CO and He, preferably at a temperature between 350 to 450 °C. preferably via Fe-oxalate dihydrate, in particu wlahrerein by the adjustment of CO and He flow rates different compositions of F5Ce2 / Fe3C carbides can be produced.

7. The method according to any of claims 4 to 6 m theethod comprises tuning the synthesis condition for the production of the pure 5 FCe2, pure Fe3C and a composite x% 3 FCe: y% Fe5C2 (where x and y arepercentage of the phases) to obtain an iron ca crboimdeposite catalyst for use said catalyst in comatbioin withsynthesized metal promoted-3FOe4 for liquid hydrocarbon (C5+) production through CO / C2O hydrogenation with controlled selectivity.

8. The method according to any of claims 4 to 7,r weihne the salt of or used to prepare the Iron oxide is selected from the group consisting of Iron c (IhI)loride, Iron (III) chloride and Iron (II, III) ntriate, wherein preferably the alkali promoters (0.1-5 wt a%re) used among Na, K, and wherein preferably the co-promoters (0.1-5 wt%) u asre d among alkaline earth metals as well astransition metals such as Mg, Zn, Mn, Cu, Co.

9. The method according to any of claims 4 to 8,r weihne a reduced form of the catalyst is obtained by treating the catalyst mixture in2 H environment for 2-12 hours, preferably for 4-12ur hso, highly preferably for 4 hours, in particular at a temperature of 350-400°C, preferably at a temperature of 350°C and unders aptmheoric pressure.

10. The method according to claim 9, wherein th2e en Hvironment is H2(5-20 ml / min) diluted with an inert gas (N2, Ar) in a ratio of H2:Inert gas = 1: (1-20).

11. A composite promoted-Iron oxide / Iron carbide clyastta for CO / CO2hydrogenation obtained according to any of the methods of claim 2 to 1h0e,r wein said catalyst is composed of x%3C F:e y% Fe5C2(where x and y are percentage of the phases) aonmdo pterd-Fe-Oxide is active in modified Fischer-Trcohps reaction.

12. The composite promoted-Iron oxide / Iron carbidteal cyast according to claim 11, said catalyst being a catalyst mixture which comprises Na promoted ioroxnide (Na-Fe3O4) and iron carbide, where the iron carbide is selected from5FCe2, Fe3C and the composite of5FCe2and Fe3C.

13. The composite promoted-Iron oxide / Iron carbidetal cyast according to claim 12, wherein said catalyst mixture comprises Na promoted iron oxiNdea- (Fe3O4) and Fe3C; preferably the catalyst mixture comprises Na promoted iron oxide (Na3-OF4e) in 30-70 weight% and F3Ce in 70-30 weight% based on the physical mixture of Na-F3eO4and Fe3C.

14. The composite promoted-Iron oxide / Iron carbideal cyastt according to any of claims 11 to 13, wherein the iron-oxide-iron carbide mixture catatl cyosmprises reduced catalyst, preferably graphdit liazeyers of reduced catalyst.

15. The composite promoted-Iron oxide / Iron carbidteal cyast according to claim 14, wherein the iron-oxide-iron carbide mixture catatl cyosmprises reduced catalyst, preferably graphditize layers of reduced catalyst, in particular R-Na3O-F4e / Fe5C2, preferably in 70 / 30 wt.%, respectively; wherein particularly preferably the catalyst alsoom cprises non-reduced catalyst, in particular NR-Na- Fe3O4 / Fe5C2, preferably in 70 / 30 wt.%, respectively.

16. The composite promoted-Iron oxide / Iron carbidetal cyast according to any of claims 11 to 15, wherein the ratio of F5eC2 to Fe3O4 at the onset of reaction and thereby the natur cear obfon layers can be tuned by the reduction treatment and adjusting ap thperopriate ratio of Na-F3Oe4 to Fe5C2 in the initial catalyst.

17. A process for producing x%3 FCe: y% Fe5C2 and promoted-Fe-Oxide for modified Fischer-Tropsch according to any of claims 11 to 16, which compsri tshee steps of loading the catalyst into the rera,c atotalysts is subjected to a modified Fischer-Tropsch reac wtiohnere the ratio of Iron-Carbide / promoted-Iron-oexid s varies from 1:(0.1-10).

18. The process according to claim 17, where the mde cthoomprises that a Fe containing precursor, preferably Fe-oxalate dihydrate is heated to ae termatpure from 350 to 450 °C under gas mixture of a CnOdHe, where the flow rate of CO is 5-40 ml / min aned f tlhow rate of He is 0-90 ml / min, wherein preferyablthe iron carbide composite comprisin3gC F and Fe5C2.

19. The process according to claim 17 or 18, whe trheein catalyst is reduced for 2-12 hours i2n a Ht atmospheric pressure. In an embodiment the temperature from 350 to 45,0 an °Cd highly preferably at 340 °C before reaction.

20. The process according to any of claims 17 to 1h9e,r wein the feed gas is CO2 / H or CO2 / H2or CO / CO2 / H2when CO / CO2varies (ratio of CO:CO2= 1:(0.1-10)) while keeping2H / (3CO2+2H2) = 1, preferably, wherein the feed gas introduced to the reactohre in ra tnge of GHSV varies between 0.1 to 50 [L / grcat. H] for production of liquid hydrocarbons from x%3FCe : y% Fe5C2and promoted-Fe-Oxide composite catalyst and wherein the inlet temperature is between 240 to ° 3C4 a0nd the pressure varies between 20 and 50 bar.

21. A method for producing a liquid hydrocarbon5+()C, using a CO / CO2 / H2mixture, which comprises the introduction of the synthesized x%3C F:e y% Fe5C2and alkaline / alkaline earth and transition metal- promoted F3eO4into a fixed bed reactor, said liquid hydrocarbon preferably being producecdco arding to the process of producing liquid hydrocarbon using x% F3Ce: y% Fe5C2and promoted-Fe-Oxide composite catalyst for h pigrehssure high temperature modified Fischer-Tropsch accordingn tyo o af claims 12 to 16.

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