Pyrolysis of raw and film PP/LDPE mixtures by step heating process

Chemical recycling of is one of the promising ways for waste plastics disposal. In this work, the kinetics and reaction mechanism of polyolefins pyrolysis was studied in detail by sectional heating process. Thermal degradation properties were analyzed by thermo gravimetric analysis (TGA) and pyrolysis reactor. The overall kinetic of the process was studied by Ozawa-Flynn-Wall (OFW) method and Coats-Redfern method. The apparent activation energy (E) and pre-exponential factor (A) were 212 kJ/mol, 4.90x10(17) min(-1) and 251 kJ/mol, 5.49x10(20) min(-1), respectively. Step heating process was used in pyrolysis reactor with three different temperatures: 430, 450 and 470 celcius, corresponding to the beginning, fastest and ending degradation temperature obtained by TGA results. GC-MS results showed that the main products were oil except for that in film specimen at 430 celcius. C-12 products were dominant for all specimens. The highest yield of aliphatic hydrocarbon was 78% for raw specimens at 470 celcius and 62% for film specimens at 450 celcius. The content of alkanes increased from 19.8% to 25.3% with increasing operation temperature for raw specimens, while the yield of alkenes was about 68% and nearly unchanged under different temperatures. The recovery of oil products could be a potential source of transport fuel.