Nitridation of HZSM-5 and its application in ethylation of ethylbenzene with ethanol to para-diethylbenzene

Nitrided HZSM-5 samples which maintained good crystallinity and high specific surface area were prepared by a nitridation process at a high temperature and used in the acid-catalyzed ethylation of ethylbenzene with ethanol to p-diethylbenzene (p-DEB). The selectivity for p-DEB was significantly increased, and the activity of the catalyst was more stable than that of unmodified HZSM-5 zeolite. Three nitrogen-incorporated HZSM-5 zeolite samples, HZSM-5-5N, HZSM-5-10N, and HZSM-5-15N, were obtained by the nitridation of HZSM-5 with pure ammonia at 800°C for 5, 10, and 15 hr, respectively. HZSM-5 was pretreated at a high temperature before the nitridation was performed. The nitrogen contents were detected by alkaline digestion with molten NaOH at 400°C, and the resulting NH3was titrated with H2SO4. HZSM-5 showed a higher initial activity, but the selectivity for p-DEB was lower than that of HZSM-5-10N and there was a rapid decrease in catalytic activity after several hours. In contrast, the selectivity of HZSM-5-10N was enhanced from 52 to 82%, and the conversion of ethylbenzene was comparatively stable during the reaction time.