Physicochemical study of polymer-stabilized platinum catalysts for enantioselective hydrogenation of ketones

Abstract

Platinum-containing catalytic systems based on hyper-cross-linked polystyrene have been synthesized, and their structure has been investigated. The catalysts have been tested in the enantioselective hydrogenation of ethyl pyruvate as a model reaction. The product of this reaction—(R)-ethyl lactate—is usable as a chiral monomer in the synthesis of biodegradable polymers. The catalytic systems have been characterized by XPS, TEM, X-ray diffraction, diffuse reflectance IR spectroscopy, and low-temperature nitrogen adsorption. The formation of Pt(0) particles in the polymer matrix begins at the precursor introduction stage. The resulting active phase particles have a narrow size distribution with a peak occurring at 2 nm. The maximum enantiomeric excess attained in the test reaction is 75%. It is possible to premodify the catalyst without lowering the enantioselectivity of the hydrogenation process.