Restructuring during pretreatment of platinum/alumina for enantioselective hydrogenation

The influence of reductive and oxidative heat treatment on the enantioselectivity of chirally modified Pt/alumina has been reinvestigated, using the hydrogenation of ketopantolactone as a test reaction. Enhancement in ee by 39–49% has been observed after treatment in hydrogen at 250–600°C, as compared to untreated or preoxidized catalysts. The changes in ee after reductive and oxidative treatments are reversible, and always the final treatment is decisive. A HRTEM study indicates that adsorbate‐induced restructuring of Pt crystallites during hydrogen treatment at elevated temperature can play a role in the selectivity improvement, but the changes are superimposed by the strong structure‐directing effect of the alumina support. The possible contribution of other effects (complete reduction of Pt ⁿ⁺ surface species, removal of impurities, or change of Pt particle size) could be excluded. This revised version was published online in July 2006 with corrections to the Cover Date.