Deactivation and regeneration of a Ni supported hierarchical Beta zeolite catalyst used in the hydroreforming of the oil produced by LDPE thermal cracking

The deactivation and regeneration of Ni supported over hierarchical Beta zeolite catalyst was investigated. Ni/h-Beta was deactivated by coke deposition during the hydroreforming of the product from LDPE thermal cracking, being this coke mostly located inside the micropores (71% coverage). Its regeneration by calcination in stagnant air at 550 °C followed by reduction under H2 up to 550 °C removed largely the coke and retrieved its activity. During the cycle of reaction–regeneration, the nickel particles fractured and moved out to the external surface forming larger size polynanocrystalline aggregates. NH3 TPD proved that the total acidity of the catalyst increased slightly after the regeneration treatment. No collapse of the structure of the Beta structure was appreciated although some changes of the textural properties of the catalyst were observed after the regeneration treatment. The hydroreforming tests pointed out that, after the regeneration, the hydrocracking augmented originating lighter products (gases and gasolines), due to the stronger acidity. The olefins were largely hydrogenated (>90%) while the amount of aromatics and isoparaffins decreased, likely because of the worse hydrogen transfer provoked by nickel sintering or to steric hindrances caused by the lower pore volumes detected. The main changes were observed after the first cycle, so a rather stable catalyst was obtained afterwards.