Enantioselective hydrogenation of ethyl pyruvate in flow reactor overpt-CD/Si02 catalysts

Abstract

The continuous enantioselective hydrogenation of ethyl pyruvate (EP) in a continuous flow reactor at 25°C on l%Pt-CD/Si02 catalysts has been studied. The catalytic study included the analysis of variables such as: particle size, feed flow, H2 pressure and the addition of chiral modifier to the reactor feed. The catalysts were prepared using impregnation of Pt colloids which are stabilized with different quantities of cinchonidine (CD) on Si02. This process gives chiral properties to the catalyst and allows changing the particle size for the reaction of interest. The catalysts were characterized by adsorption/desorption isotherms of N2 a 77 K, TEM, XPS and the analysis of producis by GC-MS. The monitoring of the reaction indicates a significant increases in the conversion when deereasing the contact time and a maximum in the enantiomeric excess (ee) of 63 % to the (R)-ethyl lactate which is obtained after using 200mg of l%Pt/Si02 catalyst (1.6nm) at 10 bar of H2 and a flow of 0.3 mL/min of a mixture EP (0.01M) and CD (0.034M) in cyclohexane. © 2009 Sociedad Chilena de Química.