Plasma Assisted Preparation of CoPt/SiO₂ Fischer‐Tropsch Catalysts: A Comparison of the Precursor Pre‐Thermal Treated Temperatures

Abstract

A series of amorphous silica supported Co‐based catalysts were prepared using traditional incipient wetness impregnation methods followed by thermal treatment at different temperatures. Glow discharge plasma effects on cobalt species in the forms of cobalt nitrate, mixture of cobalt nitrate and Co3O4, and pure Co3O4 were compared and investigated by various characterizations and Fischer‐Tropsch synthesis (FTS) tests. Plasma enhancing metal dispersion effect was mostly happened during the decomposition of cobalt nitrate in plasma field; when cobalt species was already in the form of Co3O4, no apparent particle size change by plasma treatment was observed. Under the promotion of Pt, all the catalysts maintained at high reduction degree, thus the cobalt dispersion was almost linearly related to the number of active sites. The CoSi‐100D+P catalyst with both high cobalt dispersion and high cobalt reducibility, had the maximum number of active sites, and presented the highest FTS activity. Meanwhile, the product selectivity could also be affected by plasma treatment, hydrocarbons were shifted to lower carbon numbers. This effect could be observed even on the CoSi‐400C+P sample, in which the precursor was pre‐thermal treated at high temperature (400 °C), and cobalt species was already all transformed into Co3O4.

Properties of Carbon Xerogels Supported Cobalt‐Based Catalysts and Their Performance in CO Hydrogenation Reaction

“…Cobalt particles were homogeneously dispersed on both Co/CÀ X catalysts, indicating that the worm-like mesoporous structure of CÀ X was beneficial for the anchoring of cobalt crystallites. Much higher cobalt dispersion was found on the plasma treated sample, the average cobalt particle size on Co/CÀ X-C was around 13 nm, while that on Co/CÀ X-P was in the range of 5-6 nm, consistent with our previous findings, [11,25,26] glow discharge plasma is an effective technique for the preparation of highly dispersed cobalt-based catalysts. As to the other two carbon material supported catalysts, a very high cobalt dispersion was illustrated on Co/ACÀ C, cobalt particles with size of 2-5 nm were well dispersed in AC support.…”