Catalytic Oxidation of Dimethyl Disulfide over Bimetallic Cu-Au and Pt-Au Catalysts Supported on γ-Al2O3, CeO2, and CeO2-Al2O3

Dimethyl disulfide (DMDS, CH3SSCH3) is an odorous and harmful air pollutant (volatile organic compound (VOC)) causing nuisance in urban areas. The abatement of DMDS emissions from industrial sources can be realized through catalytic oxidation. However, the development of active and selective catalysts having good resistance toward sulfur poisoning is required. This paper describes an investigation related to improving the performance of Pt and Cu catalysts through the addition of Au to monometallic "parent" catalysts via surface redox reactions. The catalysts were characterized using ICP-OES, N-2 physisorption, XRD, XPS, HR-TEM, H-2-TPR, NH3-TPD, CO2-TPD, and temperature-programmed O-18(2) isotopic exchange. The performance of the catalysts was evaluated in DMDS total oxidation. In addition, the stability of a Pt-Au/Ce-Al catalyst was investigated through 40 h time onstream. Cu-Au catalysts were observed to be more active than corresponding Pt-Au catalysts based on DMDS light-off experiments. However, the reaction led to a higher amount of oxygen-containing byproduct formation, and thus the Pt-Au catalysts were more selective. H-2-TPR showed that the higher redox capacity of the Cu-containing catalysts may have been the reason for better DMDS conversion and lower selectivity. The lower amount of reactive oxygen on the surface of Pt-containing catalysts was beneficial for total oxidation. The improved selectivity of ceria-containing catalysts after the Au addition may have resulted from the lowered amount of reactive oxygen as well. The Au addition improved the activity of Al2O3-supported Cu and Pt. The Au addition also had a positive effect on SO2 production in a higher temperature region. A stability test of 40 h showed that the Pt-Au/Ce-Al catalyst, while otherwise promising, was not stable enough, and further development is still needed.