Formation and decomposition of surface ethoxy species on acidic zeolite Y.

On the basis of in situ MAS NMR technique under flow conditions,1-4 the combined in situ MAS NMR-UV/Vis spectroscopy5 has recently been developed to obtain complimentary information on solid catalysts and, therefore, to better elucidate the mechanism involved in heterogeneous catalysis. While NMR spectroscopy allows the identification of species on the working catalyst in more detail, UV/Vis spectroscopy offers the high sensitivity for detecting the formation of aromatic compounds and unsaturated carbenium ions. In this contribution, the first solid-state 13C MAS NMR evidence is presented for the existence of surface ethoxy species on acidic zeolites. Moreover, the further decomposition of these surface ethoxy species to hydrocarbons and carbenium cations was studied by the combined in situ MAS NMR-UV/Vis spectroscopy at elevated reaction temperatures.