Impervious and influence in the liquid fuel production from municipal plastic waste through thermo-chemical biomass conversion technologies - A review

Plastic waste is an environmental burden substance, which poses a high threat to the society during disposal. Rather than disposal, recycling of this waste to liquid fuel gains importance owing to its high utility. Among various techniques, thermo-chemical recycling techniques hold more benefits in generating high value added liquid fuels. In this review, the details of municipal plastic waste generation are provided with a brief description of the plastic waste management option and importance of recycling is explained. The overview of the thermo-chemical treatment focusing on the pyrolysis, gasification and hydrocracking process was elaborated. Catalysts mediated pyrolysis have wide-open their prospective for the generation of bio-oil, hydrocarbons, syngas and deterioration of undesired substances. Generally, advance development of enthusiastic catalysts for the synthesis of bio-oil would be vital for scaling up the pyrolysis process to succeed in commercial manufacture of biofuels from waste plastics. Overall rate treatment depends on operating parameter which determines the process efficiency and product yield. Hence, critical assessment of various parameter that has remarkable effect in the thermo-chemical treatment process was documented in detail. Moreover, endorsements of liquid fuel production, economic viability, and energy requirement of the treatment process, were delivered to attain effectual plastic wastes management.

Plastic waste to liquid oil through catalytic pyrolysis using natural and synthetic zeolite catalysts

This study aims to examine the catalytic pyrolysis of various plastic wastes in the presence of natural and synthetic zeolite catalysts. A small pilot scale reactor was commissioned to carry out the catalytic pyrolysis of polystyrene (PS), polypropylene (PP), polyethylene (PE) and their mixtures in different ratios at 450°C and 75min. PS plastic waste resulted in the highest liquid oil yield of 54% using natural zeolite and 50% using synthetic zeolite catalysts. Mixing of PS with other plastic wastes lowered the liquid oil yield whereas all mixtures of PP and PE resulted in higher liquid oil yield than the individual plastic feedstocks using both catalysts. The GC-MS analysis revealed that the pyrolysis liquid oils from all samples mainly consisted of aromatic hydrocarbons with a few aliphatic hydrocarbon compounds. The types and amounts of different compounds present in liquid oils vary with some common compounds such as styrene, ethylbenzene, benzene, azulene, naphthalene, and toluene. The FT-IR data also confirmed that liquid oil contained mostly aromatic compounds with some alkanes, alkenes and small amounts of phenol group. The produced liquid oils have high heating values (HHV) of 40.2-45MJ/kg, which are similar to conventional diesel. The liquid oil has potential to be used as an alternative source of energy or fuel production.