Resumen de Enantioselective hydrogenation of 1-phenyl-1,2-propanodione on pt/ zro2 catalysts
Claudia Urbina, Gina Pecchi, Cristian Campos, Patricio Reyes
The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298K and pressure of 40 bar of H2 over zirconia supported Pt catalysts has been studied. Three different zirconia were prepared : i) ZrO2- P obtained by a precipitation procedure from ZrOCl2 ii) MSZrO2 obtained by a sol-gel procedure using cetryltrimethylammonium bromide (CTMABR) as surfactant to get a mesostructured solid iii) CNTsZrO2 obtained after impregnation of carbon nanotubes with ZrO(NO)3 followed by pyrolisis and calcination. Pt (1 wt%) was introduced on the support by impregnation of an aqueous solution of H2PtCl6. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K, hydrogen chemisorption, XRD and TEM techniques. The reactions were carried out in a stainless steel batch reactor using cyclohexane as solvent and cinchonidine as chiral modifier. The presence of CD in the reaction medium is necessary to induce an enantiomeric excess (ee) of the desired product R-1phenyl-1 hydroxi-2-propanone. In all the studied systems, the relation between the enantioselectivity and the CD concentration added in situ exhibits a bell type curve; indicative of the importance of competitive adsorption between the modifier and the substrate on the catalyst surface. On the other hand, confinement effect led to an important enhancement in the activity in those catalysts supported on mesostructured supports, mainly in the Pt/CNTsZrO2 catalyst.
