A catalytic reactive distillation approach to high density polyethylene pyrolysis – Part 2 – Middle olefin production

• Published in: Catalysis today 2021-11, Vol.379 (C), p.212-221
• Main Authors: Santos, Everton, Rijo, Bruna, Lemos, Francisco, Lemos, M.A.N.D.A.
• Format: Article
• Language: English
• Subjects: Catalytic pyrolysis; HDPE; HZSM-5; Reactive distillation; Thermal pyrolysis; Wax formation
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2020.06.014

[Display omitted] •Upgrading of an integrated reactor/separator system for the pyrolysis of HDPE.•New reactor structure enhances control of the pyrolysis reaction products.•Tuning the conditions for obtaining high liquid product yields in pyrolysis.•Production of valorised pyrolysis waxes with a wide range of properties.•Near complete pyrolysis conversion with a catalyst to polymer ratio of only 1 %. A catalytic reactive distillation reactor, previously described, was improved to increase the production of middle and heavy hydrocarbons, to be used as feedstock or fuel in the viewpoint of a Circular Economy of plastics. The thermal and catalytic pyrolysis experiments were run using high density polyethylene (HDPE) under several experimental conditions, with a 1 % (w/w) of HZSM-5 for catalytic pyrolysis. Three different temperatures were tested in each case and the influence of the reaction time was evaluated at 500 °C and 430 °C for thermal pyrolysis and catalytic pyrolysis, respectively. Thermal pyrolysis of HDPE produced the higher amount of solid products (80 %wt. or higher) under the form of a waxy cream-colored material (wax) for all the experimental sets. For catalytic pyrolysis, the major product fraction was always liquid. The analysis of the liquid products showed that, for both thermal and catalytic pyrolysis, the products obtained were within the range of C5 to C11, with a higher yield on C8 and C9 in the case of thermal pyrolysis and on C6 and C7 for catalytic pyrolysis. The aim of this study was the development of an integrated reactor/separation system to increase the middle olefin production. It is possible with this reactor design to direct the pyrolysis of HDPE to the production of middle olefins that can be reused in the petrochemistry industry, as chemical feedstock, including in the production of new plastics.