Catalytic systems based on platinum and heteropoly compounds for oxidation of hydrocarbons with a dioxygen—dihydrogen gaseous mixture

Abstract

The oxidation of cyclohexane, saturated and aromatic hydrocarbons with an O₂—H₂ gaseous mixture was applied to study the catalytic properties of bicomponent systems based on platinum and heteropoly compounds (HPC). The consumption of gases and the yield of the products depend on the surface area, accessibility of the platinum species to the reactant, and composition of the HPC. The solid Pt samples suspended in an HPC solution, the Pt(5%)—PMo₁₂/Al₂O₃ bicomponent supported system, and the solid bicomponent sample prepared from the [Pt(NH₃)₄][H₂PMo₁₂O₄₀]₂·7H₂O complex salt were used as catalysts. Among the catalysts with the same molar compositions of the active components, the bicomponent materials are much more active in the oxidation than a combination of the Pt catalyst with an HPC solution. The bulk catalyst is a crystalline solid substance with the HPC structure with incorporated Pt species. Molybdenum is predominantly oxidized, and platinum is present in both the reduced and ionic states. The oxidation of saturated hydrocarbons affords alcohols and ketones. The yield of the positional isomers of the oxygenated products increases in the series primary << secondary < tertiary C-atoms. Benzene and toluene are converted into the corresponding phenols in equal yields. The scheme proposed for oxidation assumes the participation of the active hydroxyl radical.