Conversion of low H/sub 2//CO ratio synthesis gas to hydrocarbons. Annual report, October 1, 1981-September 30, 1982

The first goals of this project are: (1) to understand the influence of mass transfer on the performance of Fischer-Tropsch slurry reactors, and (2) to determine the nature of carbon formed during reaction. Experiments aimed at the understanding of mass transfer effects have been initiated and are discussed in this report. Fischer-Tropsch synthesis has been carried out in a bubble-column slurry reactor filled with Parawax. A fused-iron catalyst, promoted with potassium and copper, was used. Experiments have been performed at 250/sup 0/C and 10 atm to determine the dependence of the synthesis rates on the partial pressures of H/sub 2/ and CO. Following a break in period, the catalyst activity remained constant over a 4-day period of operation. For each set of partial pressures, a Schulz-Flory distribution of C/sub 1/-C/sub 10/ products was observed. The rate of formation of each product can be described by a power law expression of the form r = kP/sub H/sub 2///sup a/ P/sub CO//sup b/. The value of a is typically 0.9 to 1.0, in excellent agreement with what has been observed for experiments conducted in a well-stirred, slurry reactor using the same catalyst. A positive order CO dependence was observed. The striking differencemore » between the CO dependencies observed between the two reactors is believed to be due to the presence of severe mass-transfer effects in the bubble-column reactor. Our theoretical studies have shown that when liquid-phase mass-transfer limitations set in, the gradient in CO becomes more severe than in H/sub 2/. This gives rise to a higher H/sub 2//CO ratio at the catalyst surface. Studies conducted in the stirred-slurry reactor have shown that at H/sub 2//CO ratios of 10 to 20 the rate of product synthesis becomes positive order in CO partial pressure. 5 figures, 1 table.« less