Residual sodium effect on the catalytic activity of Cu/ZnO/Al2O3 in methanol synthesis from CO2 hydrogenation

The effect of residual Na on the co-precipitated Cu/ZnO/Al2O3 catalyst has been investigated in connection with the characteristics of active componen t and methanol synthesis activity in CO2 hydrogenation. As revealed by XRD and N2O surface titration, NaNO3 present in calcined catalysts inhibits the interaction of CuO phase with ZnO matrix and thus decreases Cu-dispersion. During reduction treatment, NaNO3 seems to be converted to a basic compoun d of Na, which leads to a strong chemisorption of COP on the sodium incorpo rated catalysts. Characterization by TPR indicated that high incorporation of Na made the reduction of CuO phase difficult. The reaction results showe d that activities for methanol formation and CO formation decreased markedl y with increasing sodium content. From the correlation between catalytic ac tivity and Cu surface area, the sharp decrease in catalytic activity by Na incorporation can be interpreted mainly in terms of low Cu surface area, a result of poor dispersion. (C) 1998 Elsevier Science B.V. All rights reserv ed.