27 Al and 29Si solid-state NMR studies of dealuminated mordenite

摘要: 27 Al and 29Si MAS CP NMR have been used to monitor structural modifications of mordenite subjected hydrothermal dealumination, acid leaching calcination. Six, four- possibly five-coordinate extraframework aluminium species are formed upon expulsion from the framework. 1H–29Si monitors creation Si—OH defect sites. Calcination dealuminated greatly reduces number such defects, indicating that they substantially ‘healed’ by silicon atoms other parts crystal, also via dehydration hydroxy groups form bridging oxygen The occupancies crystallographically inequivalent Si(0AI) sites calculated spectra show occupy some T2 tetrahedral in parent material.