Issue 24, 1996

FTIR investigation of the co-adsorption of acetonitrile and carbon monoxide on Cu-ZSM-5

Abstract

The adsorption of acetonitrile and its co-adsorption with CO on a solid-state ion-exchanged Cu-ZSM-5 catalyst have been studied. Acetontrile is adsorbed on both Cu+ and Cu2+ centres of Cu-ZSM-5. The adsorption of acetonitrile on Cu+ sites proceeds in a sequential fashion resulting in the formation of [Cu(CD3CN)n⩽ 3]+ complexes. Complexes with n⩽ 2 are stable at room temperature while those with n > 2 exist only in the presence of excess CD3CN in the gas phase. [Cu(CD3CN)n⩽ 2]+ complexes readily adsorb CO forming [Cu(CD3CN)n⩽ 2(CO)m⩽ 2]+ species in which the Cu+⋯CO bonds are significantly weakened by the presence of CD3CN ligands compared to the CD3CN-free Cu+⋯CO complexes. On [Cu(CD3CN)n > 2]+ complexes CO is observed to displace one or two CD3CN ligands forming [Cu(CD3CN)n⩽ 2(CO)m⩽ 2]+ complexes. The weakening of the Cu+⋯CO bond in the CD3CN-containing complexes can primarily be attributed to the increased electron density around the Cu+ sites, brought about by charge donation from the lone pair electron on the nitrogen atom of the adsorbed CD3CN toward Cu+. With two or more CO ligands the CD3CN⋯Cu+ bond weakens owing to the Cu+⋯CO interaction and probably to steric crowding around the Cu+ adsorption site. The characteristics of the IR absorption bands observed in the adsorption and decomposition of C2H5NO2 and Cu-ZSM-5 are very similar to those seen upon CH3CN adsorption, suggesting that adsorbed nitrile species are indeed formed in the selective catalytic reduction of NOx.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1996,92, 5165-5175

FTIR investigation of the co-adsorption of acetonitrile and carbon monoxide on Cu-ZSM-5

J. Szanyi and M. T. Paffett, J. Chem. Soc., Faraday Trans., 1996, 92, 5165 DOI: 10.1039/FT9969205165

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