2009 Volume 52 Issue 4 Pages 172-179
Our recently developed potential characterization method for studying the zeolite acidity is reviewed. In this method, ammonia TPD is a principle technique and first the principle of the method was explained. In order to overcome the drawback existed in the usual TPD, IRMS-TPD method was developed, in which IR and MS were measured simultaneously to monitor the thermal behavior of ammonia molecules on the surface and in the gas phase. The developed method made it possible not only to measure the Brønsted and Lewis acid sites individually but also to clarify the distribution of Brønsted acid sites. In addition, DFT calculations were carried out to confirm the obtained information of the Brønsted acidity. Based on these studies, a new technique was developed by combining the IRMS-TPD experiment and DFT calculation to precisely characterize the zeolite acidity. Using the developed method, the modified Y zeolites active for the cracking of hydrocarbons were studied.
