ENANTIOSELECTIVE HYDROGENATION OF 1-PHENYL-1,2-PROPANODIONE ON Pt/ ZrO2 CATALYSTS

Abstract

The enantioselective hydrogenation of 1-phenyl-1,2-propanedione at 298K and pressure of 40 bar of H 2 over zirconia supported Pt catalysts has been studied. Three different zirconia were prepared : i) ZrO 2-P obtained by a precipitation procedure from ZrOCl 2 ii) MSZrO 2 obtained by a sol-gel procedure using cetryltrimethylammonium bromide (CTMABR) as surfactant to get a mesostructured solid iii) CNTsZrO 2 obtained after impregnation of carbon nanotubes with ZrO(NO) 3 followed by pyrolisis and calcination. Pt (1wt%) was introduced on the support by impregnation of an aqueous solution of H 2 PtCl 6. 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/CNTsZrO 2 catalyst.

Immobilised chiral inducer on Pt-based mesoporous titanate nanotubes as heterogeneous catalysts for enantioselective hydrogenation

“…All the catalysts were selective for the hydrogenation of the carbonyl groups (see Scheme 3). 1R-PP was the main reaction product, and the ee C1 was similar to those reported for systems in which the chiral inducer was added in situ and adsorbed on the surface of the catalyst[58,59]. All the system showed different trend in the ee during the reaction.…”

Photocatalytic Degradation of Trichloroethylene Over Silver Nanoparticles Supported on Tio2

“…Several procedures has been developed to prepare metal nanoparticles [20][21][22]. Ag nanoparticles were prepared by the reduction of an aqueous solution of AgNO 3 with HCOOH under mild conditions and then the colloidal dispersion impregnated on a TiO 2 support.…”

Chiral Pt/ZrO2 Catalysts. Enantioselective Hydrogenation of 1-phenyl-1,2-propanedione

“…ZrO 2 nanotubes may also be obtained by covering carbon nanotubes with oxide gels followed by calcination [33]. These solids display high surface areas and are materials with potential catalytic applications [34]. Two types of chiral modifiers have been widely studied: tartaric acid used as modifier of Ni catalysts [35] and cinchona alkaloid and analogs, where cinchonidine (CD) [36,37] is the most representative example.…”

“…In this work, Pt-supported catalysts in which the active phase was obtained from a colloidal dispersion, followed by impregnation on nanostructured ZrO 2 support were synthesized, [33,34]. The colloid dispersion was prepared by reduction of a Pt precursor in the presence of the previously mentioned ligand used as chiral modifier and also as stabilizer of the colloid, because it limits the excessive growing of the metal nanoparticles.…”