Bifunctional mechanism of dichloromethane oxidation over Pt/Al2O3: CH2Cl2 disproportionation over alumina and oxidation over platinum

The catalytic oxidation of dichloromethane (DCM, 1000 ppm) in wet air was carried out in a fixed bed reactor over a range of Pt/γ-Al2O3 catalysts. The dichloromethane oxidation occurs following a bifunctional mechanism. DCM is disproportionated over γ-Al2O3 into a 1/1/3molar mixture of CO, CH3Cl, and HCl; the DCM transformation is followed by CH3Cl and CO oxidation into CO2. A mechanism of DCM disproportionation is proposed involving, as intermediates, formate species as well as alumina hydroxyl groups formed by water adsorption.

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► DCM disproportionates into CO, CH3Cl, and HCl over γ-alumina.
► Pt oxidizes CO and CH3Cl into CO2.
► DCM oxidation follows a bifunctional mechanism over Pt/Al2O3.
► Oxygen does not intervene in CO formation.
► Water is necessary for hydroxyl group regeneration and catalysts stability.