Thermal and catalytic decomposition behavior of PVC mixed plastic waste with petroleum residue

The pyrolysis and hydropyrolysis of PVC mixed plastic waste alone and with petroleum residue was carried out at 150 and 350 °C under N₂ gas and at 430 °C under 6.5 MPa H₂ gas pressure. The behavior of plastic waste during thermal and catalytic decomposition has also been studied in single- and two-stage reaction processes. In the individual pyrolysis process, both the petroleum residue and polystyrene (PS) undergo more than 90% conversion to liquid and gaseous products, whereas low-density polyethylene (LDPE) and high-density polyethylene (HDPE) yielded lower conversions products, and polypropylene (PP) and polyvinyl chloride (PVC) afforded somewhere a moderate to high conversion products. In a single-stage pyrolysis reaction, PVC was processed with petroleum residue at 150 and 430 °C, under N₂ gas for 1 h at each temperature in a glass reactor. The model PVC and waste PVC showed slight variations in the products distribution obtained from the glass reactor. In two-stage process, model PVC, vacuum gas oil (VGO) and a number of different catalysts were used in a stainless steel autoclave micro tubular reactor at 350 °C under the stream of N₂ gas for 1 h and at 430 °C under 950 psi (6.5 MPa) H₂ pressure for the duration of 2 h. Significantly, different products distributions were obtained. Among the catalysts used, fluid catalytic cracking (FCC) and hydrocracking catalysts (HC-1) were most effective in producing liquid fuel (hexane soluble) materials. The study shows that the catalytic coprocessing of PVC with VGO is a feasible process by which PVC and VGO materials can be converted into transportation fuels.