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Enhanced Fischer–Tropsch Synthesis Rates by the Combined Presence of Aqueous and Organic Media in Biphasic Systems
journal contribution
posted on 2020-03-25, 21:29 authored by Felipe Anaya, Daniel E. ResascoWe
report that when the Fischer–Tropsch synthesis (FTS)
catalyzed by Ru particles supported on multiwall carbon nanotubes
(Ru/CNT) is conducted in a biphasic decalin/water solvent mixture,
the observed rate is significantly higher than in single-phase organic
or aqueous medium. Multiwall carbon nanotubes of varying wettability
and doped with Ru nanoparticles were tested as catalysts and stabilizers
of biphasic emulsions in a batch reactor under FTS reaction conditions
(H2:CO = 4:1, 220 °C, 55 bar). First, in comparison
to the runs conducted in pure organic solvent, both rate and selectivity
increased with the addition of a second (aqueous) phase. Likewise,
a large increase in reaction rate was found when a second (organic)
phase was incorporated, relative to that measured in pure aqueous
phase. Notably, this rate increase was more substantial when the nanotubes
employed were more hydrophobic and exhibited higher oil wettability.
At the same time, for a given (Ru/CNT) catalyst, the rate increased
with the oil/water solvent ratio, suggesting that not only the promotion
by water but also the interaction of the catalyst surface with the
organic solvents at the oil/water interfaces plays a key role in enabling
higher rates. Because the rate changes are not due to changes in rates
of mass transfer, it is concluded that the intrinsic kinetics was
enhanced. Among the possible explanations for the enhanced kinetics,
we discuss here some concepts recently proposed in the literature,
including the water-promotion of H-assisted CO dissociation and the
disruption of dense CO surface layers by the organic solvent.
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Keywords
CO surface layersOrganic Mediaoil wettabilityreaction rateBiphasic SystemsMultiwall carbon nanotubesrate changesH-assisted CO dissociationH 2multiwall carbon nanotubes55 barrate increaseRu particlesmass transfercatalyst surfaceFTS reaction conditionsbatch reactorphasebiphasic emulsionsRu nanoparticles
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