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 enantioselective hydrogenation of 1-phenyl-1,2-propanedione in a pressurized batch reactor. The active metal was platinum and the catalyst was modified in situ with (-)-cinchonidine. The catalysts were prepared by impregnation method using hexachloroplatinic acid as metal precursor. The main experimental parameters were the support calcination temperature and the metal loading of the catalyst. The optimum catalyst dispersion, BET specific surface area and mean Pt particle size for enantio-differentiation were measured. A comparison 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 fixed bed reactor demonstrated that continuous hydrogenation, over the new knitted silica fiber catalyst, gives equally high enantiomeric excesses compared to the batch operation. Continuous operation can be used as tool to study catalyst deactivation and reaction mechanisms in enantioselective hydrogenation. (C) 2001 Elsevier Science B.V. All rights reserved.