Pore-forming agent induced synthesis of FeCoCuAl catalysts and their performance in hydrogenation of CO2 to high carbon hydrocarbons with ZSM-5
CO2 hydrogenation to high-carbon hydrocarbons(C5+)is one of the important ways to synthesize high-value chemicals and fuels,which can achieve carbon emission reduction as well as help to alleviate energy pressure.K-and Na-modified FeCoCuAl catalysts were prepared by precipitation and iso-volumetric impregnation methods,and the effects of the pore-forming agent 1,3,5-benzenetricarboxylic acid(BTA)on their catalytic performance in CO2-catalyzed hydrogenation to high-carbon hydrocarbons reaction(temperature of 300℃,pressure of 2.0 MPa,n(H2):n(CO2)= 3:1 and space velocity of 3600 h-1 of feed gas,reaction for 6 h)were investigated.ZSM-5 molecular sieve was introduced into FeCoCuAl-20.0BTA catalyst(n(BTA):n(Fe)= 20.0%)to construct a series of composite catalysts and their catalytic performance in the reaction of catalytic hydrogenation of CO2 to high-carbon hydrocarbons was investigated.The physicochemical properties of the catalysts were characterized by combining N2 adsorption/desorption,X ray diffraction(XRD),H2-temperature programmed reduction(H2-TPR),CO2 temperature programmed desorption(CO2-TPD),and H2 temperature programmed desorption(CO2-TPD),and the oil-phase compositions of the products were analyzed by GC-MS.The results show that compared with FeCoCuAl catalysts,the specific surface area and pore volume of FeCoCuAl-BTA catalysts increase,and generate more surface-active species(Fe or Fe-Co alloy),which lead to better catalytic performance of FeCoCuAl-BTA catalysts in CO2 catalytic hydrogenation reaction.The CO2 conversion rate and C5+ selectivity of FeCoCuAl-20.0BTA catalyst are up to 70% and 42%,respectively,and the products generated from CO2 hydrogenation catalyzed by FeCoCuAl-20.0BTA catalyst are mainly C2～C4 products,while on the composite catalyst constructed with FeCoCuAl-20.0BTA catalyst and ZSM-5 molecular sieve in the form of mechanical mixing of particles with the mass ratio of 1.0,the C2～C4 products generated on FeCoCuAl-20.0BTA can undergo in situ chain growth,isomerization and aromatization reactions on ZSM-5 molecular sieves,which lead to the improvement of CO2 conversion rate and C5+ selectivity,reaching 79% and 66%,respectively.
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