Acidic Property of BEA Zeolite Synthesized by Seed-directed Method

The acidic property of a BEA zeolite prepared by a seed-directed synthesis (SDS) method without organic structure directing agent (OSDA) was analyzed by a method of ammonia infrared / mass spectroscopic (IRMS) temperature-programmed desorption (TPD). The number of Brønsted acid sites on the SDS-BEA zeolite was larger than that on a conventional BEA zeolite synthesized from using OSDA. The enthalpy of ammonia desorption, distributed mainly in a range between 115 and 145 kJ mol-1, was in agreement with the acid strength region generated by isomorphous substitution of Si4+ by Al3+ in the BEA framework. These observations confirm that the microstructure around the incorporated Al in the SDS-BEA zeolite was equivalent to that in the conventional one.