EFFECTIVE CONVERSION OF CARBON DIOXIDE AND HYDROGEN TO HYDROCARBONS

Recent studies on effective catalytic conversion of carbon dioxide to hydrocarbons were summarized. Firstly, requisites of catalyst structure to realize rapid methanation of carbon dioxide were investigated in detail. The support having a meso-macro bimodal pore structure was found to be superior for both diffusion rates of reactants and products and high dispersion of active catalyst substances, respectively. The Ni-based composite catalyst combined with a small amount of La(2)0(3) and a very small amount of Ru exhibited a very high methanation rate. The role of Ru in the composite catalyst was elucidated as the portholes of hydrogen spillover for the active sites in Ni part. Next, Cu-Zn-Cr-Al mixed oxide catalysts were synthesized by the intrinsic uniform gelation method to synthesize methanol with a comparable reaction rate of syngas conversion to methanol. Furthermore, the performance of methanol synthesis catalyst was markedly improved by modification with Pd or Ag as anticipated an effect of spillover. Gasoline synthesis from carbon dioxide and hydrogen was firstly achieved by adopting a two-stage reactor connected in a series manner as follows: in the first reactor the modified methanol synthesis catalyst was packed, and in the second reactor an H-Fe-silicate catalyst, which has the ZSM-5 (MFI) structure and the activity of methanol to gasoline conversion without acceptance of any effect from the unconverted hydrogen, was packed.