The remarkable effect of the preparation procedure on the catalytic activity of CoBEA zeolites in the Fischer–Tropsch synthesis

Abstract

This work deals with the investigation of the influence of the preparation procedure and Co content on the activity of CoBEA zeolite in Fischer–Tropsch synthesis. For this purpose the Co-containing zeolites were prepared by a conventional wet impregnation (CoxAlBEA series) and a two-step postsynthesis method (CoxSiBEA series). Calcination at 500 °C, for 3 h in air and then reduction at 500 °C in flow of 95% H2–5% Ar stream of as prepared CoxAlBEA and CoxSiBEA zeolites led to obtain Red-C-CoxAlBEA and Red-C-CoxSiBEA catalysts with different properties in Fischer–Tropsch reaction. The most active catalysts were Red-C-Co10SiBEA and Red-C-Co20SiBEA with high CO conversion of 90–95% and selectivity towards liquid products of 85% containing C7–C18 n-alkanes, isoalkanes and small amount of olefins. In the case of Red-C-CoxAlBEA catalysts the CO conversion was of 68% and selectivity towards liquid products of 57%. The identified liquid products were mainly C7–C16 n-alkanes. Moreover, Red-C-CoxSiBEA catalysts demonstrated better stability and resistance to coke formation than Red-C-CoxAlBEA ones. It is probably related to higher dispersion of cobalt nanoparticles in Red-C-CoxSiBEA than in Red-C-CoxAlBEA catalysts and absence of strong Brønsted acidic sites in the former after removal of aluminum in the first step of two-step postsynthesis preparation procedure.