Mesoporous γ-Alumina with Isolated Silica Sites for Direct Liquid Hydrocarbon Production during Fischer–Tropsch Reactions in Microchannel Reactor

Abstract

Effective incorporation of isolated silica sites on the surface of mesoporous γ-alumina catalyst has been achieved using octadecyl dimethyl (3-(trimethoxy-silyl) propyl) ammonium chloride as both silica source and mesopore template. The synthesized γ-Al2O3 with isolated silica sites was used as support for cobalt catalyst in Fischer–Tropsch synthesis (FTS), both in microchannel and fixed bed reactors. 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) analysis clearly showed the presence of isolated Si(−OAl)4 and Si(−OAl)3(−OSi)1 species in the mesoporous alumina framework. Isolated Si contributed to controlled Brönsted acidity at the surface. CH4 was suppressed in microchannel reactor compared to fixed bed reactor, due to better heat and mass transfer. CH4 yield was also low over catalyst supported on mesoporous alumina doped with isolated silica. Isolated Si incorporation on alumina surface led to desirable cracking to produce middle distillate hydrocarbons during FTS reactions, while the long-chain waxy hydrocarbons formation was suppressed, which resulted in desirable chain growth probability factor (α = 0.87) in microchannel reactor.