Copyrolysis of oils/waxes of individual and mixed polyalkenes cracking products with petroleum fraction

Copyrolysis of 10 mass% solutions (oils/waxes from individual or mixed polymers with heavy naphtha) is a route for treatment of plastic waste. Linear low-density polyethylene (LLDPE), mixture of high-density polyethylene/low-density polyethylene/linear low-density polyethylene/polypropylene (HDPE/LDPE/LLDPE/PP = 1:1:1:1mass) and linear low-density polyethylene/low-density polyethylene/polypropylene/high-density polyethylene/polyvinyl chloride/polyethylene terepthalate/polystyrene (LLDPE/LDPE/PP/HDPE/PVC/PET/PS = 1:1:2:2:0.05:0.05:0.156 mass) were converted to oils/waxes, gases and solid residues by thermal decomposition in batch reactor at 450 °C. Oils/waxes were dissolved in virgin heavy naphtha to create the feedstock. The influence of residence time from 0.08 to 0.51 s at temperatures 780 °C and 820 °C on product distribution during the copyrolysis was studied. The yields obtained from gaseous and liquid products of solutions are compared to the yields obtained from virgin heavy naphtha. It was studied how addition of the oil/wax influences formation of C₂ and C₃ hydrocarbons (mainly ethene and propene) and aromatics in comparison to the virgin heavy naphtha. The ethene and propene yields from copyrolysis of solutions are comparable or higher than from virgin heavy naphtha. Copyrolysis of solution LLDPE/LDPE/PP/HDPE/PVC/PET/PS gives the maximum yields of propene from all studied oils/waxes. The result suggests that oils/waxes from polymers are suitable feedstocks for copyrolysis with virgin heavy naphtha.     

Wood/plastic copyrolysis in an auger reactor: Chemical and physical analysis of the products

Previous studies observed that slow copyrolysis of wood and plastic in enclosed autoclaves produced an upgraded raw bio-oil with increased hydrogen content. We now demonstrate that fast simultaneous pyrolyses of 50:50, w/w, pine wood/waste plastics in a 2 kg/h lab scale auger-fed reactor at 1 atm, with a short vapor residence time, generates higher heating value upgraded bio-oils. Three plastics: polystyrene (PS), high density polyethylene (HDPE) and polypropylene (PP) were individually copyrolyzed with southern yellow pine wood at 525, 450 and 450 °C, respectively, to generate modified bio-oils upon condensation. These liquids exhibited higher carbon and hydrogen contents, significantly lower oxygen contents, higher heats of combustion and lower water contents, acid values and viscosities than pine bio-oil. The formation of cross-over wood/plastic reaction products was negligible in the oils. Simultaneous pyrolysis process design requires using a temperature at which the plastic’s thermal decomposition kinetics produce vapors rapidly enough to prevent vaporized plastic from condensing on wood chars and exiting the reactor.