Zeolite NaY-supported gold complexes prepared from Au(CH3)2(C5H7O2): reactivity with carbon monoxide

Mononuclear gold complexes in zeolite NaY were synthesized from initially physisorbed Au(CH3)2(C5H7O2), and their reactions with CO in a flow system at 298 K and 760 Torr were investigated by infrared (IR) spectroscopy and mass spectral analysis of the effluent gases. CH4 and CO2 were formed as CO flowed through the sample either steadily or as successive pulses. The results are consistent with the inferences that (a) CO reacted with the supported gold to form gold carbonyls, (b) CH4 formed by reaction of methyl groups on gold with traces of H2O or hydroxyl groups on the zeolite and (c) CO on cationic gold reacted with traces of O2 and/or H2O to form CO2. In samples treated in steadily flowing CO, cationic gold was reduced to zerovalent gold, but the cationic gold in samples exposed to CO pulses was not reduced to zerovalent gold, although CO2 formed. Thus, CO adsorbed on cationic gold reacts to give CO2 in the absence of zerovalent gold, consistent with the inference that gold catalysts for CO oxidation need not contain zerovalent gold.