Characterization of acidic zeolite catalysts by thermodesorption and cracking of n-nonane

Abstract

The possibility of employing a catalytic microreactor with the quadrupole mass spectrometer detector in characterization of acidic zeolites by means of combined thermodesorption and cracking of nonane was explored. The studied commercial zeolites H-USY (Si/Al=4.5), HY (Si/Al=15), HZSM-5 (Si/Al=15), HMOR (Si/Al=5.7) exhibited differences in catalytic activity, stability and thermodesorption profiles. Conversion of nonane varied from 31% for HY (15) to 80% for HZSM-5 (15) at 500°C. For zeolites H-USY (4.5) and HMOR (5.7) fast deactivation accompanied by substantial coking was observed. For the least acidic zeolite HY (15) thermodesorption profiles of nonane were not affected by the catalytic reactions of desorbing molecules, while for HMOR (5.7) and HZSM-5 (15) cracking of the molecules desorbing from the micropores occurred. Regeneration of the catalysts by temperature programmed oxidation of coke up to 700°C resulted in structural damage of the FAU-type zeolites.