Batchwise and continuous enantioselective hydrogenation of 1-phenyl-1,2-propanedione catalyzed by new Pt/SiO2 fibers

A new knitted silica fiber was investigated as a support material in enanti oselective hydrogenation of 1-phenyl-1,2-propanedione in a pressurized batc h reactor. The active metal was platinum and the catalyst was modified in s itu with (-)-cinchonidine. The catalysts were prepared by impregnation meth od using hexachloroplatinic acid as metal precursor. The main experimental parameters were the support calcination temperature and the metal loading o f the catalyst. The optimum catalyst dispersion, BET specific surface area and mean Pt particle size for enantio-differentiation were measured. A comp arison of alumina and silica supports revealed that the main parameters in the enantio-differentiation were the mean metal particle size and the metal dispersion. Optimal metal particle size and dispersion were detected which optimize the enantioselection. Experiments with continuously operated fixe d bed reactor demonstrated that continuous hydrogenation, over the new knit ted silica fiber catalyst, gives equally high enantiomeric excesses compare d to the batch operation. Continuous operation can be used as tool to study catalyst deactivation and reaction mechanisms in enantioselective hydrogen ation. (C) 2001 Elsevier Science B.V. All rights reserved.