The influence of CO2,C3H6,NO, H-2, 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 activ e material, is proposed. This catalyst, which is known for being active for CO oxidation at low temperatures, was prepared and characterised by BET, S EM, XRD, XPS and CO-TPD. The catalyst was tested for its capacity to oxidis e carbon monoxide using oxygen only and oxygen in combination with other co mpounds typically present in cold start exhausts from Otto engines, i.e. CO 2, C3H6. NO, H-2, H2O or SO2. When the catalytic activity was tested with o nly 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, the y inhibited the CO oxidation to various degrees. The degree of inhibition f or the compounds investigated was found to be: SO2 > H2O > NO = C3H6 > H-2 > 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 pro cess of the metal oxide surface and/or the adsorption of CO. (C) 2001 Elsev ier Science B.V. All rights reserved.