Preparation of Ni/CeO2@ZIF-8 core-shell catalyst and its RWGS reaction performance
The ZIF-8-coated Ni/CeO2 core-shell catalysts were prepared using a liquid phase concentra-tion controlled nucleation method.The effects of the ZIF-8 shell on the physicochemical properties of the catalysts were investigated by a series of characterization techniques,and the effects of introducing ZIF-8 on the performance and pathways of the RWGS reaction on the catalysts were further explored.The results showed that the ZIF-8 shell could increase the specific surface area of the catalysts,while weakening the hydrogenation capacity and the adsorption strength of CO,and the CO selectivity was enhanced by 60.3%under the reaction conditions of 300℃,0.1 MPa,GHSV=6 L/(g·h)and CO2∶H2=1∶3.The interme-diate species in the reaction on the Ni-based catalysts before and after ZIF-8 coating were different.The main intermediate for CO was carboxylate while the bridged formate was for CH4.The presence of the ZIF-8 shell inhibited the further hydrogenation of the carboxylate to formate intermediate species,thus inhibi-ting the methanation reaction from proceeding and improving the CO selectivity of the RWGS reaction.
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