X-RAY-DIFFRACTION CHARACTERIZATION OF AG-RH CATALYSTS FOR OXYGENATE AND HYDROCARBON SYNTHESIS

Ag-Rh/SiO2 catalysts which exhibit activity and selectivity for oxygen ate and hydrocarbon synthesis have been characterized by X-ray diffrac tion (XRD). XRD patterns show that the catalysts prepared using Rh chl oride precursor contain Rh, Ag, AgCl, and AgClO2 crystallites. The siz e of these crystallites varied with the amount of Ag in the catalyst. The variation in crystallite size of Rh, Ag, AgCl, and AgClO2 with Ag/ Rh ratio has an impact on the activity and selectivity for synthesis o f oxygenates and hydrocarbons during CO hydrogenation and ethylene hyd roformylation reactions. The selectivity towards oxygenates is decreas ed on the Ag-Rh catalysts due to the presence of AgCl and AgClO2 cryst allites on the catalyst surface. Ag-Rh catalyst with Ag/Rh ratio of 0. 5 gives a higher activity and selectivity for ethanol and propanol dur ing CO hydrogenation and ethylene hydroformylation than the other Ag-R h catalysts. Ag-Rh catalysts prepared from Rh chloride and Ag nitrate precursors are less active and selective for oxygenate synthesis than those prepared from nitrate precursors. Ag-Rh catalysts for oxygenate synthesis should be prepared using nitrate precursors.