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

The influence of operational conditions on the transformation of synthesis gas into hydrocarbons was studied. Mixtures of ZnO-Cr2O3 (Zn-Cr) and amorphous silica-alumina (SA) were used as catalysts. The 1:1 Zn-Cr:SA mixture gives a carbon monoxide conversion of 53% at ca. 400-degrees-C; it is similar to that obtained using a Zn-Cr:erionite mixture. The increase of temperature, pressure, and time factor favors CO conversion. Methanol is formed over the Zn-Cr catalyst, and this reaction is the limiting step of the global process. A mechanism is proposed whereby MeOH-DME are the intermediates, which diffuse into the SA where they are converted to hydrocarbons. It can be considered that C1 and C2 Species are the hydrocarbon ''precursors'' during the methanol to hydrocarbons transformation.