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

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 (Co(x)AIBEA series) and a two-step postsynthesis method (Co(x)SiBEA series). Calcination at 500 degrees C, for 3 h in air and then reduction at 500 degrees C in flow of 95% H-2-5% Ar stream of as prepared Co(x)AIBEA and Co(x)SiBEA zeolites led to obtain Red-C-Co(x)AIBEA and Red-C-Co(x)SiBEA catalysts with different properties in Fischer-Tropsch reaction. The most active catalysts were Red-C-Co(10)SiBEA and Red-C-Co(20)SiBEA with high CO conversion of 90-95% and selectivity towards liquid products of 85% containing C-7-C-18 n-alkanes, isoalkanes and small amount of olefins. In the case of Red-C-Co(x)AIBEA catalysts the CO conversion was of 68% and selectivity towards liquid products of 57%. The identified liquid products were mainly C-7-C-16 n-alkanes. Moreover, Red-C-Co(x)SiBEA catalysts demonstrated better stability and resistance to coke formation than Red-C-Co(x)AIBEA ones. It is probably related to higher dispersion of cobalt nanoparticles in Red-C-Co(x)SiBEA than in Red-C-Co(x)AIBEA catalysts and absence of strong Bronsted acidic sites in the former after removal of aluminum in the first step of two-step postsynthesis preparation procedure. (C) 2015 Elsevier Inc. All rights reserved.