Abstract The performance of several differently treated clinoptilolite zeolites in the degradation of polypropylene was investigated in this study. The composition of degradation products, especially liquid fractions resulted over studied catalysts, was compared to understand the role of catalysts. The degradation was carried out in a semi-batch reactor with a mixture of polypropylene and catalysts at 400 °C. The liquid products from the catalytic degradation of polypropylene are distributed in a narrower range of carbon numbers compared with those obtained by thermal degradation. With dealuminated clinoptilolite catalysts, the distribution of liquid products shifted to lower numbers of carbon atoms due to the increase of the portion of medium acid sites and micropore diameter. The increase of temperature accelerated the cracking of intermediately degraded fragments to lower hydrocarbons.