Catalytic\nPyrolysis of a Model Plastic Mixture with\na Montmorillonite Clay Catalyst and Upgrading via Distillation

Plastic recycling has become a focal point in the field\nof sustainability\nand circular economy, where pyrolysis is an emerging technology to\nhandle a mixture of different types of plastics to be converted into\nsimpler compounds. However, pyrolysis does not come without challenges,\nparticurly due to the wide product distribution, where waxes, oil,\nand light hydrocarbons are produced. Moreover, pyrolysis is seldom\nsufficient in generating a liquid that meets the end-product specifications,\nrequiring subsequent processing steps. In this work, the objective\nwas to investigate the effect of a montmorillonite catalyst in a fluidized-bed\nreactor to avoid wax formation without the compromise of liquid yield.\nThe feedstock was a model plastic mixture that simulated the share\nof different polyolefins (LDPE, HDPE, PP, PS) in the MSW (Municipal\nSolid Waste). Among the five tested temperature levels, the optimal\npyrolysis temperature (525 °C) was found with no formation of\ndetectable wax. The reuse of the spent catalyst was tested by regeneration,\nand the experiment was repeated. The regenerated catalyst resulted\na similar liquid yield, but with deviating aromatic content which\nwas hypothesized to be associated with reduced activity, resulting\nin more styrene from PS. The produced pyrolysis liquid was upgraded\nby distillation to separate the light (BP < 200 °C) and heavy\n(BP > 200 °C) fractions. A clear difference between bottom\nand\ndistillate fractions was observed; aliphatics concentrated to the\nbottom fraction and aromatics to the distillate fraction. The results\ndemonstrated that the montmorillonite catalyst excludes the formation\nof wax in a fluidized-bed reactor with a relatively high liquid yield\n(75% of dry feed) and that regeneration of the catalyst is possible\nwithout compromising the liquid yield. In addition, distillation proved\nto be a potential choice as a downstream step as the product can be\nrefined to be better suited for the petrochemical industry. The use\nof a montmorillonite catalyst could be an industrially tempting choice\ndue to the cost-effectiveness and the potential for continuous regeneration.