STRUCTURE OF MN-ZR MIXED-OXIDE CATALYSTS AND THEIR CATALYTIC PROPERTIES IN THE CO HYDROGENATION REACTION

MnZr oxide catalysts with varying MnZr ratio were prepared by a coprecipitation method. Their structure and catalytic properties were studied by means of N2 adsorption, XRD, TPR, and CO hydrogenation as a probe reaction. The precipitated MnZr mixed oxide was composed of a mixture of large particles of manganese oxide and small particles of zirconium oxide. Addition of Mn retarded the growth of fine particles of zirconium oxide. By calcination at high temperature, part of the manganese oxide forms a solid solution with zirconium oxide and deposits on the surface of zirconium oxide as a thin layer. The type of Mn present in the mixed oxide affected the selectivity pattern in the CO hydrogenation. The bulk Mn exhibited a high selectivity to isobutene, but products contained hydrocarbons higher than C5. Mn dispersed on the surface of zirconium oxide showed a similar selectivity pattern to bulk Mn, but hydrocarbon chain growth was limited to C4 or lower. The formation of a solid solution enhanced production of lower hydrocarbons, especially methane. © 1992.close243