Diffusion of paraffins in dealuminated Y mesoporous molecular sieve

Mesoporous materials have been intensely studied recently, mainly as possible component for FCC ( Fluid Catalytic Cracking) catalysts due to their large surface area and accessibility to large hydrocarbon molecules. It is thus of interest for the oil industry to understand the diffusion behavior of some standard molecules in these materials. Y Zeolites, usually employed in fluid catalytic cracking, can be modified by removal of aluminum atoms from the zeolitic framework to present a greater mesoporous contribution. Dealumination of Y zeolite framework is also known to improve the stability of the catalyst thus making it more suitable for the FCC operation. This study presents diffusion measurements performed with the ZLC (Zero-Length Column) method, developed in the late eighties by Eic and Ruthven (1988a, b). The ZLC method has been largely used for a number of systems, either in gas or in liquid phases. We have now applied the ZLC method for gas phase diffusion measurements of linear paraffins (C-7-C-10) in dealuminated Y zeolite (USY). Experimental data were obtained at different temperatures (150 to 240degreesC) and flow rates ( 40 to 120 ml/min) and correlated through a transient Fickian diffusion model.