Neil Cruise

SO2 promoted oxidation of ethyl acetate, ethanol and propane

The effect of SO2 addition on the oxidation of ethyl acetate, ethanol, propane and propene, over Pt/gamma -Al2O3 and Pt/SiO2 has been investigated. The reactants (300-800 vol, ppm) were mixed with air and led through the catalyst bed. The conversions below and above light-off were recorded both in the absence and in the presence of 1-100 vol. ppm SO2. For the alumina-supported catalyst, the conversion of ethyl acetate, ethanol and propane was promoted by the addition of SO2, while the conversion of propene was inhibited. The effect of SO2 was reversible, i.e. the conversion of the reactants returned towards the initial values when SO2 was turned off. However, this recovery was quite slow. The oxidation of propane was inhibited by water, both in absence and presence of SO2. For the silica-supported catalyst no significant effect of SO2 could be observed on the conversion of ethyl acetate, ethanol or propane, whereas the conversion of propene was inhibited by the presence of SO2. In situ FTIR measurements revealed the presence of surface sulphates on the Pt/gamma -Al2O3 catalyst with and after SO2 addition. It is proposed that these sulphate groups enhance the oxidation of propane, ethyl acetate and ethanol by creating additional reaction pathways to Pt on the surface of the Pt/gamma -Al2O3 catalyst.

The influence of CO2, C3H6, NO, H2, H2O or SO2 on the low-temperature oxidation of CO on a cobalt-aluminate spinel catalyst (Co1.66Al1.34O4)

A preparation method for making a high temperature stable monolith catalyst, using a cobalt-rich cobalt-aluminate spinel (Co1.66Al1.34O4) as the active material, is proposed. This catalyst, which is known for being active for CO oxidation at low temperatures, was prepared and characterised by BET, SEM, XRD, XPS and CO-TPD. The catalyst was tested for its capacity to oxidise carbon monoxide using oxygen only and oxygen in combination with other compounds typically present in cold start exhausts from Otto engines, i.e. CO2, C3H6. NO, H2, H2O or SO2. When the catalytic activity was tested with only CO and O-2 present in the feed gas, complete conversion was reached at room temperature. When other compounds were present in the gas mixture, they inhibited the CO oxidation to various degrees. The degree of inhibition for the compounds investigated was found to be: SO2 > H2O > NO = C3H6 > H2 > CO2. The main reason for the loss of activity is suggested to origin from the compounds adsorption and formation of different species on the cobalt oxide surface, which seems to inhibit the reduction and/or re-oxidation process of the metal oxide surface and/or the adsorption of CO.