Coking during ethene conversion on ultrastable zeolite Y Original Research Article

A multi-technique approach has been adopted to investigate both the formation of coke and its effects during the conversion of ethene on ultrastable zeolite Y at 773 K. It is shown that pulsed field gradient (PFG) NMR diffusion measurements in combination with other characterization techniques (product analysis, thermogravimetric analysis, nitrogen adsorption, FT-infrared and 13C NMR spectroscopy) gives particular insight into the deactivation process. Site poisoning is responsible for the initial loss of activity. There then follows a period in which the amount of coke increases while it is transformed into more aromatic species. At high levels of coking, pore blockage becomes the most significant factor.