The Effects of Pt/Al2O3 Structure and Stability on the O-Methyl-10,11-dihydrocinchonidine Modified Enantioselective Hydrogenation of Activated Ketones

摘要

Commercially available catalysts were characterized and tested for the enantioselective hydrogenation of activated ketones. It was found that the catalyst with a lower reducible residue level (cat^Sium? F214; 5%Pt) and a narrower Pt crystal size distribution gave the best performance. Reductive pretreatment (RPT) of Pt/Al2O3 catalysts in hydrogen at 400°C improved their activity per surface Pt and their enantiomeric excesses (ee) at the expense of Pt dispersion (%D). Although the improvement in ee and activity over compensate for the slight loss in Pt dispersion from the RPT, catASium F214 already performs excellently without a RPT. The RPT was most needed for the catalyst with the highest reducible residue level (E 4759 5%Pt) even though it also suffers the highest loss of Pt surface via sintering during RPT.