Temperature-programmed desorption-diffusion of ammonia in molecular sieves V. ZSM-5 zeolite

✍ Scribed by Lucio Forni; Francesco P. Vatti; Emanuele Ortoleva

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 652 KB
• Volume: 3
• Category: Article
• ISSN: 0927-6513
• DOI: 10.1016/0927-6513(94)00051-v

✦ Synopsis

Some ZSM-5 zeolite samples with an SiO2/A1203 ratio of 10.3 have been analysed by temperature-programmed desorption (TPD) of ammonia to investigate how the rate-determining step of the desorption-diffusion process depends on some experimental parameters and on the physicochemical characteristics of the zeolite. By comparison with previous results on a ZSM-5 sample with SIO2/A1203 = 33.6, a shift of the probable rate-determining step from intracrystalline diffusion of the desorbed gaseous base to desorption of the latter without appreciable readsorption has been noticed. On the other hand, both the change of the temperature ramp from 10 to 2 K/min and the substitution of Na + for H + by ion exchange shift the rate-determining step to desorption with free readsorption of the desorbed base.