Catalytic Activity of Shock Modified ZnO for CO Oxidation and Methanol Synthesis

摘要

Alteration of the catalytic activity of inorganic powders by dynamic shock compression has been reported in the literature for over twenty years. Previous work reported by Batsanov et al., ''Kinet. and Catal.'', 8:1140 (1967) for the effect of shock compression on ZnO catalysis revealed an enhanced activity for CO oxidation that decreased during the rate measurements. The purpose of this paper is to report steady-state rate measurements of CO oxidation and methanol synthesis over shock compressed ZnO powders under reaction conditions believed to be transport limitation free. Based on the information to date, our best explanation of the enhanced catalytic activity of ZnO powders is that shock compression modifies the ability of the particle surface to form active centers under reaction conditions. The shock compression probably does not itself put long lived active centers at the surface or major changes in activation energies or selectivity would be observed. However, if local strain or defects were induced in the surface, it would be possible for atomic rearrangement of the surface to result in additional sites like those on unshocked ZnO. In that way, the catalytic chemistry of all the powders would only be different in the number of sites available for catalysis. The minima in Figure 3 may then result from a surface distortion in the unshocked powder that is released by a relatively mild shock compression. 9 refs., 3 figs., 2 tabs. (ERA citation 10:037244)