Classification of volatile products from the temperature-programmed pyrolysis of low- and high-density polyethylene

A fixed bed reactor under argon flow was used to pyrolyze small samples of low- (LDPE) and high-density (HDPE) polyethylene. A special gas-phase sampling technique was used to determine the composition of products eluted from the reactor as a function of temperature and time. Capillary gas chromatography was used to determine the total volatile product evolution rate. The maximum volatile product evolution temperature was 425 degrees C for LDPE and 430 degrees C for HDPE. The distribution of n-paraffins and 1-olefins was determined. The hydrocarbon fraction from LDPE contained 47.2 wt % n-paraffins at the maximum product evolution temperature; the weight percentages were 6.6 gaseous n-paraffins, 9.1 C-5-C-9, 23.7 C-10-C-15, and 60.6 C-16. The yield and distribution of hydrocarbons from pyrolysis of HDPE at the maximum product evolution temperature of 430 degrees C were similar to that found for LDPE. n-Paraffins constituted 48.8 wt %, of which 5.5 wt % were gaseous n-paraffins, 9.4 wt % C-5-C-9, 23.5 wt % C-10-C-15, and 61.6 wt % C16+. 1-Olefin products were also grouped by carbon number. Pyrolysis of LDPE produced 14 wt % of 1-olefins at the maximum product evolution temperature; weight percentages were 20.7 1-olefins gases, 22.8 C-5-C-9, 26.4 C-10-C-15, and the 30.1 C16+. Pyrolysis of HDPE produced 14.4 wt % of 1-olefins, of which 33.3 wt % were 1-olefin gases, 40.9 wt % C-5-C-9, 17.3 wt % C-10-C-15, and 8.5 wt % C16+.