Tandem catalytic synthesis of light isoparaffin from syngas via Fischer–Tropsch synthesis by newly developed core–shell-like zeolite capsule catalysts

Abstract

One-step synthesis of light isoparaffin from syngas via Fischer–Tropsch synthesis (FTS) belongs to the tandem catalysis process, for which the most used catalyst is hybrid catalyst prepared by simply mixing FTS catalyst and zeolite catalyst. The zeolite capsule catalyst with a core–shell structure has proved its excellent performance for tandem catalysis process [1], as well as the one-step synthesis of light isoparaffin from syngas mentioned before [2]. However, the usually used hydrothermal synthesis way for zeolite shell preparation limits the design and preparation of various zeolite shell enwrapping different core catalysts, the industrial scalability of zeolite capsule catalyst, and so on. In this report, with a traditional FTS catalyst of 10wt% Co/SiO2 as core catalysts, we present two methods for H-ZSM-5 zeolite capsule catalyst preparation. One is an improved hydrothermal synthesis process named stepwise-synthesis, another is an initially reported method that does not employ hydrothermal synthesis approach for H-ZSM-5 zeolite shell preparation. For the last one, we call it physically adhesive (PA) method in this report. The two types of H-ZSM-5 zeolite capsule catalysts prepared by these two methods are investigated via FTS reaction to evaluate their catalytic performance on the direct synthesis of light isoparaffin from syngas. Since the space-confined and synergistic function offered by the special core–shell structure, both of two types of H-ZSM-5 zeolite capsule catalysts could readily realize the one-step synthesis of light isoparaffin with higher selectivity, better than that of the conventional hybrid catalyst. The PA method presented in this report is very cost-saving, reliable and scalable, with which we can realize the industrialization of zeolite capsule catalyst more readily.