Preparation of Fe/BN catalysts and their catalytic performance in Fischer-Tropsch synthesis
In order to develop catalysts based on high thermal conductivity support and improve the performance of Fischer-Tropsch synthesis,ball milling boron nitride(BN)with high specific surface area was used as support to prepare a series of Fe/BN catalysts(Fe/BN-120,Fe/BN-160 and Fe/BN-200)by solvothermal method(solvothermal temperatures are 120℃,160℃ and 200℃,respectively),and their catalytic performance in Fischer-Tropsch synthesis was studied(temperature of 280℃,pressure of 2.0 MPa,V(H2):V(CO):V(Ar)= 16:8:1 and space velocity of 3000 mL/(g·h)of syngas,measured by the reaction result at 48 h).The catalysts were characterized by N2 absorption/desorption,inductively coupled plasma-atomic emission spectrometer(ICP-AES),X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and H2/CO temperature programmed reduction(H2/CO-TPR).The results show that compared with Fe/BN-120,the average particle size of γ-Fe2O3 in Fe/BN-160 and Fe/BN-200 increases from 7.2 nm to 13.6 nm and 14.7 nm,respectively,and the binding energy of Fe 2p gradually shifts towards the lower binding energy.Compared with Fe/BN-120 and Fe/BN-160,the reduction and carbonization of Fe/BN-200 are significantly promoted under the action of electronic effect and size effect.In the atmosphere of CO2 and H2O in Fischer-Tropsch,the reduced α-Fe and Fe3O4 react with the BOx on the surface of ball milling boron nitride under high temperature conditions to produce iron borate.With the increase of solvothermal temperature,the carbonization degree of catalyst increases gradually.Compared with Fe/BN-120(CO conversion rate is 39.1％,CH4 selectivity is 24.3％,C5+ selectivity is 37.8％),CO conversion rate of Fe/BN-200 increases to 68.9％,CH4 selectivity decreases to 12.9％and C5+ selectivity increased to 51.1％.The catalytic activity and product distribution can be regulated by changing the solvothermal temperature on Fe/BN catalyst,which provides a way to improve the performance of Fe-based catalyst supported by boron nitride.
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