Abstract
Cu-containing natural and synthetic clinoptilolite were prepared by Cu cation exchange and impregnation with copper nitrate solution. The samples were characterized and tested for the synthesis of dimethyl carbonate. The state of Cu(I) and Cu(II) species was proved by in situ FTIR spectroscopy using CO and NO as probe molecules. The observed bands of νCu(I)–CO and νCu(II)–NO modes are relatively broad indicating a location of the Cu cations at several sites in the zeolite lattice. Cu-clinoptilolite catalysts oxidize CO and NO to a certain extent even at room temperature where CO2 is partly captured in the zeolite cavities.The interaction of the catalysts with MeOH/CO/O2 gas mixtures was studied by in situ FTIR spectroscopy and operando DRIFTS/MS. Oxygenated products like dimethoxy methane and methyl formate were found besides CO2 in the gas phase while formate, methyl formate and methoxy species were adsorbed at the catalyst surface. In contrast to Cu-Y catalysts no dimethyl carbonate formation could be detected. Obviously, the different channel system of clinoptilolite and the distinct lower BET surface area are disadvantageous concerning dimethyl carbonate formation.
Published Version
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