Thermal and catalytic degradation of structurally different types of polyethylene into fuel oil

The degradation of four different types of polyethylene (PE) namely high density PE (HDPE), low density PE (LDPE), linear low density PE (LLDPE), and cross-linked PE (XLPE) was carried out at 430 degrees C by batch operation using silica-alumina as a solid acid catalyst and thermally without any catalyst. For thermal degradation, both HDPE and XLPE produced a significant amount of wax-like compounds and the yields of liquid products (58-63 wt%) were lower than that of LDPE and LLDPE (76-77 wt%). LDPE and LLDPE produced a very small amount of wax-like compounds. Thus the structure of the degrading polymers influenced the product yields. The liquid products from thermal degradation were broadly distributed in the carbon fraction of n-C-5 to n-C-25 (boiling point range, 36-405 degrees C). With silica-alumina, all of the polyethylenes were converted to liquid products with high yields (77-83 wt%) and without any wax production. The liquid products were distributed in the range of n-C-5 to n-C-20 (mostly C-5-C-12). A solid acid catalyst indiscriminately degraded the various types of polyethylene into light fuel oil with an improved rate. (C) 1997 Elsevier Science Limited.