Investigation on the porosity of zeolite NU-88 by means of positron annihilation lifetime spectroscopy

✍ Scribed by G. Consolati; M. Mariani; R. Millini; F. Quasso

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 196 KB
• Volume: 267
• Category: Article
• ISSN: 0168-583X
• DOI: 10.1016/j.nimb.2009.05.057

✦ Synopsis

Seven well characterized zeolites were investigated by positron annihilation lifetime spectroscopy. The lifetime spectra were analysed in four discrete components. The third one was associated with ortho-positronium annihilation in the channels, framed in terms of infinite cylinders. Differences between the radii determined from the positron annihilation technique and X-ray diffraction data were found and explained in terms of the physical structure of the channel. An analogous study on a high-silica NU-88 zeolite gave a value of 0.33 nm for the corresponding radius, in agreement with Ar and N 2 adsorption data as well as with the catalytic behaviour of this zeolite in several acid catalyzed reactions. The longest lifetime component in NU-88 reveals the existence of mesopores, with average radius of about 1.8 nm, which could explain the importance of hydrogen transfer reactions in this zeolite.