Conversion of Carbon dioxide to hydrocarbons over hybrid catalysts containing methanol synthesis catalyst and zeolite

The hydrogenation of carbon dioxide to C₂, C₃, and C₄ paraffins was examined by using hybrid catalysts containing a Cu-Zn catalyst with Zr-modified H-ZSM-5 zeolite, or Pd-modified β zeolite with H-ZSM-5, or Pt/SiO₂ with H-ZSM-5, or Pd/SiO₂ with H-ZSM-5 β zeolite. Various factors which affect catalyst activities were examined such as reaction temperature, pressure, and the influence of the SiO₂/Al₂O₃ ratio. The tests were conducted at 260-300^°C, 2-3 MPa, a W/F of 10 g.h/mol, and with a H₂/CO₂ mole ratio of 3. The influence of the SiO₂/Al₂O₃ ratio on H-ZSM-5 zeolite played an important role in hydrocarbon distribution. When H-ZSM-5 was used on the zeolite with low alumina content (SiO₂/Al₂O₃=100), the product contained olefins and dimethyl ether with a large amount of C₅ and C₆, whereas that for the zeolite with high alumina content (SiO₂/Al₂O₃=40) showed an excellent conversion of carbon dioxide to hydrocarbon. Under mild temperature at 280°C, CO₂ conversion reached 23% with a hydrocarbon selectivity as high as 80%, while keeping the dry gas (CH₄) selectivity below 1% by using the hybrid catalysts. When Pd/SiO₂ with β zeolite was used for the hybrid catalysts, butane was produced with a high selectivity over 50% at 280°C and 3 MPa with a small amount of coke deposition.