Preparation of Co/SiO 2 Using Several Glycols for Enhanced Fischer-Tropsch Synthesis Activity and Dispersion of Co 0 Nan
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Preparation of Co/SiO2 Using Several Glycols for Enhanced Fischer-Tropsch Synthesis Activity and Dispersion of Co0 Nanoparticles with Unique Co0 Particle Size Effect Naoto Koizumi • Shigenobu Suzuki • Satoshi Niiyama • Takayoshi Shindo • Muneyoshi Yamada
Published online: 15 June 2011 Ó Springer Science+Business Media, LLC 2011
Abstract Co/SiO2 catalysts with highly dispersed Co0 and reducible Co were prepared by impregnation using an aqueous solution of Co nitrate containing ethylene glycol or its homologs. Addition of glycols enhanced FTS activity by a factor of 4. Particle size of Co0 decreased from 30 to below 6 nm, while TOF of the catalysts was independent of the Co0 particle size. Keywords Fischer-Tropsch synthesis Co/SiO2 Glycol Co0 particle size effect
1 Introduction Fischer-Tropsch synthesis (FTS) is a versatile process for the synthesis of transportation fuels, because it enables syngas to be produced from, in principle, any carbon
N. Koizumi S. Suzuki S. Niiyama Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aoba 6-6-07, Aramaki, Aoba-ku, Sendai 980-8579, Japan T. Shindo Department of Engineering in Applied Chemistry, Graduate School of Engineering and Resource Science, Akita University, 1-1 Tegatagakuen-machi, Akita 010-8502, Japan M. Yamada Akita National College of Technology, 1-1, Iijima-Bunkyo-cho, Akita 011-8511, Japan N. Koizumi (&) Earth and Mineral Sciences Energy Institute, The Pennsylvania State University, C-211 Coal Utilization Laboratory, University Park, PA 16802, USA e-mail: [email protected]
resources. Furthermore, diesel fraction of hydrocarbons synthesized by FTS has superior combustion characteristics compared with the petroleum-derived one. It was reported that Co-based FTS catalysts exhibits high activity and selectivity for the synthesis of diesel fraction under relatively low temperatures and medium pressures [1–3]. Over the last two decades, many research groups have studied Co-based catalysts for the purpose of improving catalytic activity and selectivity for acquisition of the diesel fraction from both fundamental and technological aspects [3–13]. Co-based catalysts are usually prepared by impregnating Co precursors, calcining them and reducing Co3O4 to FTS active Co0 particles. For the catalysts prepared using Co nitrate precursor, the particle size of Co0 was reported to be 20–40 nm for Co/SiO2 [11, 12, 14, 15], and 5–10 nm for Co/Al2O3 [16, 17], respectively. Turnover frequencies (TOFs) of Co/SiO2, Co/Al2O3 and Co/TiO2 were similar and almost independent of the particle sizes of Co0 when they were larger than 10 nm [3], whereas a remarkable size effect of Co0 particles was recently found in a small particle range (2–10 nm) for Co supported on carbon nanofiber (CNF) [10] and ITQ-2 [13]. In this small particle size range, TOF of these catalysts increased linearly with increasing Co0 particle size. For these supported catalysts with Co0 particles above 10 nm, however, TOFs were nearly constant, independent of the particle size of C
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