Ethylene and propylene adsorption and the formation of hydrocarbon complexes with NO2 upon interaction of adsorbed olefins with an NO+O-2 mixture over HZSM-5 and CuZSM-5 zeolites studied by TPD and ESR

Adsorption of C2H4 and C3H6 On copper in oxidized samples of CuZSM-5 is fou nd to increase with the copper concentration; simultaneously, olefin adsorp tion on the Bronsted acid sites decreases. The Cu2+ cations in the square-p lanar coordination exhibit higher reactivity in olefin adsorption than copp er cations in the square-pyramidal coordination. Thermal treatment of CuZSM -5 with hydrogen results in regeneration of the Bronsted acid sites for ole fin adsorption and the disappearance of Cu2+ cations, the active sites of a dsorption, due to the reduction of Cu2+ to Cu+ and Cu-o. Desorption peaks a ppear in the TPD spectra upon the interaction between the adsorbed hydrocar bons and NO2. These peaks are not observed upon separate adsorption of the reactants, and they are likely due to decomposition of NO2-hydrocarbon comp lexes over both the Bronsted and copper-containing sites of the zeolite.