deactivation of a zeolite catalyst during its use to catalyse the oligomerisation of olefins , is often believed to be a result of the formation of high boiling polymers as by - products . these by - products can remain on the catalyst and undergo further conversion to higher molecular weight polymers , which resemble heavy tars and in some cases even have the appearance of coke - like material . these materials can coat the catalyst particles and plug pores in the catalyst , thereby causing catalyst deactivation . the invention relates to an improved method for regenerating such a catalyst .