Research Benzyl Alcohol In Pt / Mg (Ca) -ZSM-5 Catalyst At Room Temperature And Reaction Mechanism Of Selective Oxidation

High yield, base-free, aqueous phase alcohol oxidation was achieved by basic zeolites (Ca-ZSM-5and Mg-ZSM-5) supported Pt nanoparticles catalysts at room temperature. This Pt-based catalytic process is environmental friendly and is found to be support and solvent dependant. Based on the catalysis results and the observation of various radicals, such as Pt-H intermediate, HOO·and·OH species by the in-situ EPR spin trapping technique, a cooperative effect among Pt nanoparticles, zeolites supports and water solvent was proposed. Briefly, by following the Langmuir-Hinshelwood mechanism, alcohol molecules were adsorbed on Pt catalyst surface and O2molecules were most likely adsorbed at the interface of Pt and the support. Then the O—H bond cleavage occurs over the Pt catalyst, the surface H transferred to the O2, producing HOO· radicals. With the help of water solvent, the hydrogenation of HOO· with Pt-H produced H2O2molecule, which was subsequently decomposed into·OH radicals. This homolytic O—O bond cleavage was suggested to be the rate determining step of the whole oxidation reaction. The OH radicals could attack the C—H bond on the Pt surface, resulting in the generation of aldehyde/ketone molecule. Finally, the catalytic cycle was completed through the oxidation of another alcohol molecule by-OH radicals to afford aldehydes/ketone. This new selective catalytic activity of Pt/Ca-ZSM-5is of general interest in the field of catalysis with Pt nanoparticles, since the efficient hydride abstraction from organic substrates to Pt surface opens up exciting possibilities to use Pt-based catalysts for C—H bond activation and transformation using molecular O2as a green oxidant.