Solid-State Ion Exchange - Phenomenon and Mechanism

Highly exchanged MeI-Y (MeI = Li, Na, K, Rb, Cs) as well as La-Y zeolites were prepared through solid-state ion exchange between NH4-Y (98%) and the respective chlorides. It was shown that, except for the case of Li-Y, both low- temperature and high-temperature exchange processes occurred. With the system MeICl/NH4-Y the high-temperature reaction seemed to proceed more easily the lower the lattice energy of the alkaline chloride. In La-Y, the bare La3+ ions introduced via solid-state ion exchange were catalytically inactive. However, La-Y obtained via solid-state ion exchange was rendered an active catalyst for both ethylbenzene disproportionation and n-decane cracking after a brief contact with traces of water vapor. For the solid-state reaction itself, the presence of water is not a prerequisite

Activation and aromatization of methane and ethane over Mo(VI)/HZSM-5 and W(VI)/HZSM-5 zeolites catalysts

The activation and aromatization of CH4 and C2H6 under non-oxidizing conditions were investigated over Mo(VI)/HZSM-5 and W(VI)/HZSM-5 zeolite catalysts. Mo(VI)/HZSM-5 exhibits good activity and selectivity for the conversion of CH4 to aromatics, but for C2H6 conversion the catalyst displays high selectivity to CH4. W(VI)/HZSM-5 is inactive for CH4 activation, but exhibits high selectivity for C2H6 aromatization. The W(VI) species can act as a modifier to improve the activity and the stability of Mo(VI)/HZSM-5 for CH4 conversion