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Study of Brønsted acid site in H-MCM-22 zeolite by temperature-programmed desorption of ammonia

Research paper by Jan Vaculík, Michal Setnička, Roman Bulánek

Indexed on: 01 Mar '16Published on: 01 Mar '16Published in: Journal of Thermal Analysis and Calorimetry



Abstract

Interaction of ammonia with H-MCM-22 zeolite (Si/Al = 24.5) was investigated by temperature-programmed desorption technique in order to obtain information on thermodynamics of the process. Average activation energy for desorption of ammonia from Brønsted acid sites of H-MCM-22 zeolite was estimated from the data obtained under conditions varying in heating rate and also flow rate of carrier gas. It resulted in value of Ed = 127 kJ mol−1 for heat rate variation method, whereas flow rate variation led to Ed value of 111 kJ mol−1. Obtained Ed values are compared with those reported in the literature for other zeolitic materials and discussed in the broader context of zeolite acidity. Comparison of Ed values estimated here for H-MCM-22 zeolite with corresponding data for other protonic zeolites shows that H-MCM-22 displays mediocre/lower activation energy for ammonia compared with other high-silica zeolites.