Higher alcohol synthesis reaction study VI: effect of Cr replacement by Mn on the performance of Cs- and Cs, Pd-promoted Zn Cr spinel catalysts

The effect of Mn addition on the catalytic behavior of Cs-promoted and Cs- and Pd-promoted Zn/Cr spinels has been examined for production of mixtures of methanol and isobutanol from a 1:1 mixture of CO and H-2 (synthesis gas) at temperatures of 400 degrees C, 440 degrees C and 460 degrees C and pressures of 1000 and 1500 psig. For all catalysts examined the optimum conditions are 440 degrees C and 1500 psig. The best catalyst tested contains 3 wt% Cs and 6 wt% Pd. It yields a total alcohol rate of 203 g/kg h, a methanol-to-isobutanol mole ratio of 0.66 and a hydrocarbon byproduct rate of 105 g/kg h. The addition of Pd increases the total alcohol production rate, the isobutanol production rate, the hydrocarbon byproduct rate and decreases the methanol production rate. For Cs-promoted catalysts the replacement of Cr with Mn results in improved catalytic performance when a Pd promotor is absent. This trend is in contrast to that of K-promoted catalysts which perform best when both Mn and Pd are present. (C) 1999 Elsevier Science B.V. All rights reserved.