Hydrogenation Of CO_x To High Value-added Chemicals

CO_x（CO/CO₂）has a wide range of sources and low price.If hydrogen from renewable energy is used to convert CO_x into high value-added chemicals,it is of great significance to alleviate the shortage of fossil resources,reduce the dependence on fossil resources and the sustainable development of energy and environment in China.In this paper,a series of work has been carried out on the catalytic conversion of CO_x.Na_x-Fe-Co catalyst was prepared by the modification of disodium ethylenediaminetetraacetic acid（EDTA-2Na）,which can effectively convert CO₂ into high value-added chemicals(C₂-C₄⁼and C₅-C₁₁).XRD analysis shows that CO and EDTA-2Na can enhance the sintering resistance of Fe.EDTA^4-can be decomposed into small organic molecules in the process of calcining complex impregnation,which can promote the reduction of iron species.At the same time,sodium in EDTA-2Na can promote the surface basicity of the catalyst,which is conducive to improving the product distribution of hydrocarbons.Supported iron catalysts for Fischer Tropsch synthesis（FTS）are mainly supported on alumina or silica.However,the interaction between metal and support hindered the formation of active phase iron carbide,resulting in low activity of the catalyst.In this study,10Fex Ey Na/Al₂O₃ catalyst was prepared by EDTA complex impregnation.The dispersion of iron species on alumina support was improved by Coulomb interaction between positively charged hydroxyl（OH₂⁺）and[Fe（EDTA）]^-complex anion.In situ FT-IR experiments show that the catalyst prepared with EDTA is easier to enrich the active species,which improves the conversion of CO.Zn O-Zr O₂ solid solutions with different Zn contents were synthesized by the urea co-precipitation method,which were coupled with H-ZSM-5 zeolite to form bifunctional catalysts.Using methanol and dimethyl ether as active intermediates,syngas and benzene were converted into toluene and xylene in one step.It was found that the appropriate ratio of Zn O-Zr O₂ significantly improved the catalytic performance;The appropriate amount of acid can improve the selectivity of toluene/xylene and reduce the selectivity of ethylbenzene and C₉⁺aromatics.H-ZSM-5 zeolite has a ten membered ring with the same diameter as aromatics,which is beneficial to the activation of benzene,so the conversion of benzene is higher;H-ZSM-35 and H-MOR zeolites have small eight membered ring channels,which are not conducive to the passage of benzene,and the selectivity of ethylbenzene is high.The distance between the active centers of the bifunctional catalyst is the main factor affecting the performance of the catalyst.The performance of alkylation of syngas with biphenyl was studied.Comparing different types of zeolite,it was found that the bifunctional catalyst composed of H-ZSM-5 and ZnAlCrO_x was an ideal catalyst.The activity of nano-H-ZSM-5 is higher than that of micro-H-ZSM-5 under the same Si/Al ratio.The stability test results of alkylation of syngas with biphenyl and alkylation of methanol with biphenyl show that using syngas instead of methanol as methylation reagent can not only improve the conversion of biphenyl,but also greatly improve the stability of the reaction.The selectivity of 4-methylbiphenyl and 4,4’-dimethylbiphenyl was effectively improved by a series of composite modification of Ce,Si,P and Mg with H-ZSM-5.Finally,the effect of bifunctional catalysts composed of ZnAlCrO_x and zeolite（H-ZSM-5,SAPO-11,H-MCM-22 and H-β）on the alkylation of syngas with naphthalene was studied.H-ZSM-5 and SAPO-11 with the same kinetic diameter as 2-methylnaphthalene（2-MN）and2,6-dimethylnaphthalene（2,6-DMN）are ideal catalysts for alkylation of syngas with naphthalene.