Hydrocracking of polyethylene to hydrocarbon fuels over Pt/USY catalysts: Assessment of the hydrogen donors

Abstract

Hydrocracking is an effective approach to convert waste polyolefins into value-added fuels. Efficient hydrogen transfer from the hydrogen donors to the polyolefins is crucial to the hydrocracking process. In this work, we evaluated the hydrocracking effectiveness of different hydrogen donors (H2, tetralin and H2+tetralin) in polyethylene hydrocracking over a Pt/USY catalyst by analyzing and comparing the product distribution under varied H circumstances. The hydrocracking pathway using gaseous (H2) and liquidous (tetralin) hydrogen donors was proposed. The results show that the most effective H-donor for fuel oil production is H2, which yielded 65.8% oil abundant in C6–C12 range after reaction at 350 °C for 60 min. Tetralin can be dehydrogenated by Pt/USY catalyst to provide active H for PE hydrocracking, but the hydrocracking effectiveness is inferior to that using H2 because of catalyst deactivation caused by the by-products such as naphthalene from tetralin dehydrogenation. For the same reason, using H2+tetralin as H-donors is not as efficient for oil production as using sole H2 as H-donor. The reaction pathway of PE hydrocracking over Pt/USY catalyst using H2 and tetralin as the H-donor is different. Hydrocracking with H2 follows the hydrogenolysis pathway. When tetralin is presented, the hydrogenolysis pathway is cut off, followed by the thermal reactions between tetralin and PE, which inhibits PE cracking and decreases oil production.