SYNTHESIS OF HYDROCARBONS FROM SYNGAS USING MIXED ZN-CR OXIDES - AMORPHOUS SILICA-ALUMINA CATALYSTS

The influence of operational conditions on the transformation of synth esis gas into hydrocarbons was studied. Mixtures of ZnO-Cr2O3 (Zn-Cr) and amorphous silica-alumina (SA) were used as catalysts. The 1:1 Zn-C r:SA mixture gives a carbon monoxide conversion of 53% at ca. 400-degr ees-C; it is similar to that obtained using a Zn-Cr:erionite mixture. The increase of temperature, pressure, and time factor favors CO conve rsion. Methanol is formed over the Zn-Cr catalyst, and this reaction i s the limiting step of the global process. A mechanism is proposed whe reby MeOH-DME are the intermediates, which diffuse into the SA where t hey are converted to hydrocarbons. It can be considered that C1 and C2 Species are the hydrocarbon ''precursors'' during the methanol to hyd rocarbons transformation.