MICROCALORIMETRIC INVESTIGATION OF MORDENITE AND Y-ZEOLITES FOR 1-METHYLNAPHTHALENE ISOMERIZATION

Adsorption microcalorimetry of pyridine has been used to determine the concentration and the distribution of strengths of the acid sites of Y zeolites and mordenite samples. l-Methylnaphthalene was reacted over these samples at 623 K under atmospheric pressure in a continuous-how fixed-bed reactor. For Y zeolites the relative extents of l-methylnap hthalene isomerisation and disproportionation have been found to depen d on the density of the acid sites. Coke growth favours isomerisation over disproportionation as time-on-stream increases. However, both dis proportionation and coking are highly disfavoured in the channel syste m of mordenites, in spite of the relatively high density of the acid s ites. The accumulation of strongly adsorbed feed and/or product molecu les is responsible for the severe decay in activity of non-dealuminate d mordenite.