(710a) Distribution Between C2 and C3 in the Low Temperature Fischer-Tropsch Synthesis over Cobalt and Iron Catalysts
AIChE Annual Meeting
2015
2015 AIChE Annual Meeting Proceedings
Catalysis and Reaction Engineering Division
Syngas Production and Gas-to-Liquids Technology II
Thursday, November 12, 2015 - 12:30pm to 12:50pm
Distribution between C2
and C3 in the low
temperature Fischer-Tropsch Synthesis over cobalt and iron catalysts
Material and Process
Synthesis Engineering, College of Science, engineering and Technology,
University of South Africa, Johannesburg, South Africa. Email: lux@unisa.ac.za.
Tel: +27 11 6709041 Keywords: Fischer-Tropsch
Synthesis, cobalt catalyst, iron catalyst, product distribution.
Abstract
Deviation of C2
(including olefin and paraffin) in the ASF distribution in the Fischer-Tropsch Synthesis (FTS) has been observed consistently but
relatively few studies have focused on this. Explanations for C2
deviation have been proposed by researchers and secondary reaction of ethene is suggested
as the cause for the deviation.[1] However, the distribution
between C2 and C3 has not been investigated as
comprehensively as the C2+ products in the FTS reaction. This study mainly focuses on the distribution
between C2 and C3 products in FTS over both a supported
cobalt catalyst (10%
Co/90% TiO2) and a precipitated iron catalyst (Fe/SiO2/K/Cu). The FTS experiments over the cobalt catalyst were conducted in a fixed
bed reactor, a CSTR, and a batch reactor under wide range of operating conditions including varying the H2/CO ratio in the feed, the
reaction temperature, and space velocity (SV) of the feed gas. The FTS experiments over the Fe catalyst were
conducted in fixed bed reactors with H2, CO, and syngas as activation
reagents respectively. The distributions between C2 and C3
were investigated both for olefins and paraffins. C3H6/C2H4
ratio was found to be a function of CO conversion only (as shown in Figure 1 below) regardless the reasons
(such as temperature, SV, and H2/CO ratio in the feed) causing the change
of conversion. The overall C3/C2 was
found to be decided by reaction temperature mainly and space velocity has no effect on it. The unique distribution
between C2 and C3olefinic
products suggests it is related to mechanism of FT reaction, as this phenomenon
could not be explained by kinetics because such distribution is not affected by
partial pressures of reactants and products. A model, based on competitive reactions
between CO and olefins is being developed to describe the product distributions
between C2 and C3 hydrocarbons.
Figure 1 distribution between C2 and C3 olefins as
a function of CO conversion for Co/TiO2 (left) and precipitated Fe
(right) catalysts
Reference:
[1] Van der Laan, G P and Beenackers, A A C M. Catal. Rev.-Sci. Eng., 1999, 41, 255¨C318.