Novel utilization of mesoporous molecular sieves as supports of cobalt catalysts in Fischer-Tropsch synthesis

Yasuo Ohtsuka, Yoshimoto Takahashi, Masato Noguchi, Takashi Arai, Satoshi Takasaki, Naoto Tsubouchi, Ye Wang

Research output: Contribution to journalArticlepeer-review

86 Citations (Scopus)

Abstract

Mesoporous molecular sieves (MCM-41 and SBA-15) with different pore diameters have been studied as supports of high loading of Co catalysts, and the performances in FT synthesis have been examined with a fixed bed stainless steel reactor at 2.0MPa for the purpose of efficient production of C 10-C20 fraction as the main component of diesel fuel. The method of exchanging template ions in uncalcined MCM-41 with Co2+ ions is effective for holding 10-20% Co within the mesopores while keeping the structure regularity of MCM-41 to some extent, compared with the conventional impregnation method using calcined MCM-41. At 523K, CO conversion and selectivity to C10-C20 hydrocarbons are both higher at larger loading of 20% Co for the exchanged catalysts with pore diameters of 2.7-2.9nm. When four kinds of 20% Co/SBA-15 with the diameters of 3.5-13nm, prepared by the impregnation method using an ethanol solution of Co acetate, are used in FT synthesis at 523K, the catalyst with the diameter of 8.3nm shows the largest CO conversion, which is higher than those over MCM-41 supported Co catalysts. At a lower temperature of 503K, however, the acetate-derived Co is almost inactive. In contrast, the use of Co nitrate alone or an equimolar mixture of the acetate and nitrate as Co precursor drastically enhances the reaction rate and consequently provides high space-time yield (260-270gC/kg cath) of C10-C20 hydrocarbons. The X-ray diffraction and temperature-programmed reduction measurements show that the dependency of the catalytic performance of 20% Co/SBA-15 on its precursor originates probably from the differences in not only the reducibility of the calcined catalyst but also the dispersion of metallic Co. Catalyst characterization after FT synthesis strongly suggests the high stability of the most effective Co/SBA-15 in the dispersion and reducibility of the oxide species and in the mesoporous structure.

Original languageEnglish
Pages (from-to)419-429
Number of pages11
JournalCatalysis Today
Volume89
Issue number4
DOIs
Publication statusPublished - 2004 Jun 1

Keywords

  • Cobalt catalysts
  • Diesel fraction
  • FT synthesis
  • MCM-41
  • SBA-15

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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