Measurement and prediction of the diffusivity of Y-type zeolite

✍ Scribed by Takao Masuda; Kiyoshi Fukada; Yoshihiro Fujikata; Hideo Ikeda; Kenji Hashimoto

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 680 KB
• Volume: 51
• Category: Article
• ISSN: 0009-2509
• DOI: 10.1016/0009-2509(96)00045-0

✦ Synopsis

Intracrystalline diffusivities of Y type zeolite were measured in the temperature range of 323-573 K for four aromatics: benzene, toluene, and ortho-, alld para-xylene, and four paraffins: n-hexane, n-heptane, n-oclane and iso-octane. Three model equations tbr calculating the intracrystalinc dillhsivity were derived each based on one of the factors thought to control the dillhsion: the probability tbr a molecule to.jump from a supcrcage to a neighbouring supercagc through a narrow window, the Lemmrd Joner (12.6)-potential induced by the van der IYaals attraction and the electrostatic field formed in a supercage. The measured intracrystalline dillilsivity ,,'*'as found to be well represented by the model equations based on the electrostatic field nlecbauism.

~TRODUCTION

Y type-zeolite catalysts are widely used in hydrocarbon conversion processes, because of their high activities and selectivities (Venuto and Habib. 1979, Vansant, 1990). This catalytic performance is strongly dependent on the zeolite crystal sizes and the intracr3'stalline diffilsivi .ty (Meier and Olson, 1987).

There are several reports on the diffusivities of MFI .type zeolite below 373 K (Zikanova et.