Microcalorimetric investigation of mordenite and Y zeolites for 1-methylnaphthalene isomerisation

Abstract

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. 1-Methylnaphthalene was reacted over these samples at 623 K under atmospheric pressure in a continuous-flow fixed-bed reactor. For Y zeolites the relative extents of 1-methylnaphthalene isomerisation and disproportionation have been found to depend on the density of the acid sites. Coke growth favours isomerisation over disproportionation as time-on-stream increases. However, both disproportionation and coking are highly disfavoured in the channel system of mordenites, in spite of the relatively high density of the acid sites. The accumulation of strongly adsorbed feed and/or product molecules is responsible for the severe decay in activity of non-dealuminated mordenite.