Analysis of liquid products and mechanism of thermal/catalytic pyrolysis of HDPE

The experiments of rapid thermal pyrolysis and catalytic pyrolysis of high density polyethylene (HDPE) were carried out using Py-GC/MS. The distribution of products of rapid pyrolysis and the influence of Fluid Catalytic Cracking catalyst on pyrolysate production were studied both qualitatively and quantitatively at the temperature of 500 °C. The corresponding reaction paths were proposed based on the experimental results. The results demonstrated that olefin production accounts for more than 70 mass% in the products of C7–C40, and remaining products were alkanes, diolefins and aromatics. At the presence of catalyst, product contents of C7–C12 increased from 16.39 to 20.59 mass%, and C33 + from 11.23 to 14.42 mass%, while C13–C32 decreased from 72.22 to 61.45 mass%. The distinctive effects of catalyst on production of monoolefine and alkane were investigated, showing that the proportion of C7–C12 increased and C13–C32 decreased. For the production of diolefin (C7–C32), however, the inhibition of catalyst was found. The thermal and catalytic pyrolysis of HDPE can be reasonably explained using free radical mechanism and carbonium ion mechanism, respectively.