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Depolymerization of HDPE to wax in the presence of a catalyst formed by homonuclear macrocyclic zirconium complex chemically bonded to alumina support

Authors
Journal
Applied Catalysis A General
0926-860X
Publisher
Elsevier
Publication Date
Volume
303
Issue
1
Identifiers
DOI: 10.1016/j.apcata.2006.01.016
Keywords
  • Heterogeneous Catalyst
  • Depolymerization
  • Hdpe
  • Wax
  • Zr–Zr Catalyst
Disciplines
  • Chemistry

Abstract

Abstract A homonuclear macrocyclic Zr–Zr complex was prepared starting with 2,6-diformyl-phenol and 1,2-phenylene diamine and is chemically bonded with carbamate-modified alumina. The TPD of the catalyst having adsorbed NH 3 shows the presence of acid sites on the surface of the catalyst and the catalyst is stable under the reaction temperature studied. The catalytic depolymerization of commercially available high-density polyethylene (molecular weight 4.79 × 10 5) was carried out in the presence of nitrogen as well as oxygen at about pressure of 300 of kg/cm 2 and temperature of 370 °C. Catalytic depolymerization in the presence N 2 occurs with the time delay of 2 h (as opposed to 4 h for thermal depolymerization occurring above 400 °C) and stops with the formation of wax (as opposed to C 5–C 16 liquidous alkanes in thermal depolymerization). The wax thus formed was characterized and shown to be the Arge wax (available commercially) having a melting point of 80 °C and molecular weight of 392. We have proposed a kinetic model in which the catalyst forms a complex with polyethylene radical formed at high temperature, which gives depolymerization to form wax molecules.

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