In this semi batch pyrolysis study, the effect of different zeolite catalysts containing used FCC, HZSM-5 and mordenite on the degradation of virgin poly butadiene (PBR) were considered. The liquid, gas and coke yield as well as composition of liquid product as a function of different catalysts effect in the stirred reactor were compared. Main products obtained were light hydrocarbons within the gasoline range. The formation of aromatic products depended appreciably on the catalyst type and catalyst/polymer ratio. The results showed that C6 was main component of pyrolysis product with up to 32%. The results also showed that crosslink mechanism played an important role in the rubber pyrolysis. A huge number of double bonds in the PBR chains could prepare the proper media for crosslink mechanism in slow pyrolysis while flash pyrolysis followed the chain scission mechanism in the most times of degradation. Crosslink nets could increase the activation energy and the resistance against the chain scission degradation by difficult chain mobility and heat transfer. (C) 2015 Elsevier Ltd. All rights reserved.