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Department of Chemical Engineering, Kuwait University. P.O.Box 5969, 13060 Safat, Kuwait, e-mail: Samiali@kuc01.kuniv.edu.k .

ABSTRACT

The influence of Ca promotion of 2 wt % of Pd/SiO₂ on CO hydrogenation to methanol was studied using different levels of Ca loading (up to 2 wt % of Ca) and two different SiO₂ supports (Davisil grades 634 and 644). Ca was found to have a selective promoting effect on Pd for CO hydrogenation towards methanol. The highest increase in the average site activity for methanol formation (TOF_CH3OH) was found to be at low-to- moderate Ca loading levels (0.4 to 0.7 wt%), which was related to the direct involvement of the promoter in methanol synthesis. However, having Ca loading higher than 0.7 wt % resulted in the decrease of the activity of the Pd catalyst probably due to the partial blockage of the active surface of the catalyst by the promoter. The type of the  SiO₂ support, on the other hand, was found to have some impact on the activity of Pd for CO hydrogenation. This was attributed to differences in the levels of metallic impurities present (Na, Mg and Ca) with possible promoting effects (SiO₂ grade 644 had higher concentrations of these impurities than grade 634).

Key Words: Ca; CO hydrogenation; methanol; Pd/ SiO₂