HYDROGENATION OF CARBON-DIOXIDE OVER CU-ZN-CHROMATE/ZEOLITE COMPOSITE CATALYST - THE EFFECTS OF REACTION BEHAVIOR OF ALKENES ON HYDROCARBON SYNTHESIS

The hydrogenation of carbon dioxide was studied using composite catalysts comprised of Cu-Zn-chromate and HY zeolite, These composite catalysts enabled the reaction combining methanol synthesis and methanol-to-gasoline reaction, and achieved the formation of ethylene and propene as the first example of the composite catalysts. The addition of alkaline metals, especially cesium, to Cu-Zn-chromate enhanced the selectivities of those alkenes. The influences of the reaction pressure and the space velocity on the production of alkenes show that alkanes are obtained by the hydrogenation of the corresponding alkenes, The composite catalysts producing alkenes in high selectivity afforded heavier hydrocarbons preferentially, These results indicate that the hydrogenation of alkenes inhibits the carbon homologation of alkenes to result in the predominant formation of the corresponding lighter alkanes. From these observations, it was found that methanol synthesis catalysts used for the composite catalysts are required to be effective for methanol synthesis at high temperature (over 300 degrees C) and to bear the low activity of the hydrogenation of alkenes.