Heterogeneous catalytic process for alcohol fuels from syngas. Thirteenth quarterly technical progress report, January--March 1995

The principal objectives of this project are to discover and evaluate novel heterogeneous catalysts for conversion of syngas to oxygenates having use as fuel enhancers, to explore novel reactor and process concepts applicable in this process, and to develop the best total process for converting syngas to liquid fuels. The authors have tested a number of K/Pd promoted Zn/Mn/Cr spinel oxide catalysts within an experimental design to determine the effect of K, Pd, temperature and pressure on catalyst performance. High temperature operation (at 440 C) results in drastic loss in selectivities to total alcohols (down to 18--30%), and this obscures the effect of the catalyst formulation variables. It appears that at higher temperatures, the tube walls can also catalyze syngas conversion with a more hydrogen-rich syngas mix. Comparison with tests in a copper-lined tube with 1:1 syngas confirm this hypothesis. The design suggested that higher Pd loadings would be beneficial for isobutanol synthesis. The 6 wt% and a 9 wt% Pd formulation were tested with 1:2 syngas in copper-lined tubes. The 6 wt% Pd catalyst, at 440 C and 1,500 psi, produced 71 g/kg-hr of isobutanol with a methanol/isobutanol product mole ratio < 1. Under the same conditions, the 9 wt% Pd catalyst is again inferior, producing 52 g/kg-hr of isobutanol with a methanol/isobutanol product mole ratio = 1.7. Of particular interest here is that the 6 wt% Pd catalyst produces more higher alcohols than methanol on a molar basis at good rates using a syngas mix that could be derived from a Shell gasifier