Preparation of SiO2 immobilized Co-based catalysts from ZIF-67 and the enhancement effect for Fischer-Tropsch synthesis

Abstract

ZIF-67-derived Co@C catalysts show great potential for Fischer-Tropsch synthesis (FTS) due to high cobalt (Co) loading and proper cobalt crystalline size, while improving the FTS activity and stability is still a major challenge. In this work, SiO2 was embedded to immobilize Co particles by introducing a silicon source into ZIF-67 using ex-situ or in-situ methods to prevent cobalt particles from aggregating. Due to exposure of more active cobalt sites and elimination of microcrystalline Co on the ex-situ soaking catalysts, increased FTS activity and decreased CH4 selectivity were achieved, but undesirable stability was observed due to the weak immobilization ability of SiO2. To enhance the immobilization effect of SiO2, E-ZIF-67@nSiO2 precursors were prepared by an in-situ soaking method in which the formation of ZIF-67 and introduction of SiO2 occurred simultaneously. The obtained E-Co3O4@4SiO2 catalyst exhibits not only much high FTS activity but also good stability.