REACTIONS OF ZEOLITES WITH VOLATILE HALID ES .5. INVESTIGATION OF PHOSGENE-DEALUMINATED MORDENITES WITH SI-29, AL-27, NA-23 MAS NMR TECHNIQUE

Solid state MAS NMR data revealed that upon dealumination of mordenite with phosgene part of the framework Al remains in the channels as oct ahedrally coordinated aluminium compounds. Concomitant to the aluminiu m removal, a large part of the sodium is also eliminated from Na-morde nite. Several Na-containing species can be detected, the nature of whi ch has not yet been identified. Some residual sodium in the form of Na Cl could be detected. As a result of aluminium removal, framework vaca ncies, internal silanol groups are generated. The transformation of Si Cl groups to SiOH groups in H-mordenite samples is due to hydrolysis b y ambient moisture. The low amounts of both Si(OH)(2) and SiOH groups underline the role of the framework reconstruction during dealuminatio n.