Design of a hierarchical Co@ZSM-5/SiC capsule catalyst for direct conversion of syngas to middle olefin

Abstract

Fischer-Tropsch (FT) synthesis as a strongly exothermic reaction has diffusely manufactured clean fuels from syngas. However, it is difficult to obtain the concentrated product distributions. Here, we design ZSM-5 encapsulated cobalt particles on the thermal conductivity of the SiC matrix. The Co@NaZSM-5/SiC capsule catalyst with hierarchical structure is ingeniously assembled through a solvent-free synthesis route. Due to the joint functions of acidic zeolite, SiC thermal conductivity and macropores, the olefin selectivity enhances to 32.3% on the Co@NaZSM-5/SiC catalyst. Moreover, the ratio of O5-11/C5-11 approaches 49.1% suggesting the elevated middle olefin proportion. The H+ ion-exchanged Co@HZSM-5/SiC capsule catalyst shows a high isoparaffin selectivity of 27.3%, since the olefin isomerization reaction is accelerated over strong acid sites. Besides, Co2C phase is readily formed during the FT reaction, which is an activity center for olefin synthesis. The capsule catalyst with the proper acidity, thermal conductivity, and hierarchical structure is a promising prospect for tuning production distribution in FT reaction.