beta-silicon carbide as a catalyst support in the Fischer-Tropsch synthesis: Influence of the modification of the support by a pore agent and acidic treatment
Résumé
The present work studies four beta-silicon carbide (beta-SiC) samples supplied by SICAT. They consisted of the parent material (SiC-A), SiC-A modified by a pore agent (SiC-B) or purified by an acidic treatment (SiC-C), and SiC-B purified by the referred acidic treatment (SiC-D). The pore agent treatment resulted in a modification of the pore size distribution, whereas the acidic one led to materials with less metal impurities content. The effects of these pretreatments in the resulting materials were characterized by N-2 adsorption-desorption, Hg intrusion porosimetry, temperature-programmed reduction (TPR), X-ray diffraction (XRD) and NaOH titrations. They were then used as supports in cobalt-based catalysts for the Fischer-Tropsch synthesis (FTS). The resulting catalysts were also characterized by the techniques mentioned above as well as by atomic absorption (AA) and oxygen pulses. It was observed that the acid washing, in addition to remove some metal impurities increased the number of acid sites over the SiCs, which seemed to promote the reducibility of the cobalt particles of the corresponding catalyst. On the other hand, the addition of pore agent strongly increased the macropore volume of the SiCs, which favoured the FTS products desorption, keeping the catalytically active sites available. All these facts caused that the catalyst supported on pore- and acid-treated SiC presented the highest catalytic activity. (C) 2014 Elsevier B.V. All rights reserved.