Thermal degradation of PVC: A review.

The present review is aimed at exploring the field of the catalytic cracking of polyolefins over solid acids, focusing on the role played by the catalysts toward the synthesis of fuels and chemicals as well as on the reaction systems currently used. Initially, conventional solid acids, such as micrometer sized crystal zeolites and silica–alumina, were used to establish the relationship among their activity, selectivity, and deactivation in the polyolefin cracking and the inherent properties of the catalysts (acidity, pore structure); however, the occurrence of steric and diffusional hindrances for entering the zeolite micropores posed by the bulky nature of the polyolefins highlighted the importance of having easily accessible acid sites, either through mesopores or by a high external surface area. This fact led toward the investigation of mesoporous materials (Al-MCM-41, Al-SBA-15) and nanozeolites, which allowed increasing the catalytic activities, especially for the case of polypropylene. Further advan...

Developing Advanced Catalysts for the Conversion of Polyolefinic Waste Plastics into Fuels and Chemicals

Pyrolysis of polypropylene (PP) and high density polyethylene (HDPE) into fuel like products was investigated over temperature range of 250– 400°C. The product yields as a function of temperature were studied. Total conversion as high as 98.66% (liquid; 69.82%, gas; 28.84%, and residue; 1.34%) was achieved at 300°C in case of PP and 98.12% (liquid; 80.88%, gas; 17.24%, and residue; 1.88%) in case of HDPE at 350°C. The liquid fractions were analyzed by FTIR and GC-MS. The results showed that the liquid fractions consisted of a wide range of hydrocarbons mainly distributed within the C6–C16. The liquid product obtained in case of PP is enriched in the naphtha range hydrocarbons. Similarly, the liquid product obtained in case of HDPE is also enriched in naphtha range hydrocarbons with preponderance in gasoline and diesel range hydrocarbons. The% distribution of paraffinic, olefinic, and naphthenic hydrocarbons in liquid product derived from PP is 66.55, 25.7, and 7.58%, respectively, whereas in case HDPE, th...

Pyrolysis Study of Polypropylene and Polyethylene Into Premium Oil Products

Electronic waste plastics (e-waste plastics) have been one of the emerging and fastest-growing waste streams due to the increasing number of generation in waste electrical and electronic equipment (WEEE). Given that brominated flame retardant (BFR) materials in e-waste plastics have been the major impediment for recycling treatment, chemical recycling has been proposed as an environmentally friendly method of recycling e-waste plastics for clean fuels production or chemical feedstocks. This paper summarized the current techniques of BFR-plastics recycling with a view to solving energy crisis and the environmental degradation of BFR-plastics. Emphasis was paid on the recent chemical treatment of BFR-plastics, including pyrolysis, co-pyrolysis and catalytic cracking, which are yet to be completely feasible in conversion of BFR-plastics for clean fuels production. Hydrothermal treatment is regarded as a novel high-efficiency technology to recycle BFR-plastics, which can be a potential process for the in situ debromination of oil products. An advanced chemical recycling technique, pyrolysis-catalytic upgrading process, is highlighted. The recycling route of pyrolyzing BFR-plastics prior to catalytic upgrading was intended to obtain high quantity oils, and then the upgrading process of pyrolysis oils was conducted by means of catalytic hydrodebromination with the aim of obtaining bromine-free oils for commercial applications. In short, the integration of pyrolysis with catalytic upgrading process can provide significant economic and environmental options in conversion of e-waste plastics into useful and high-value materials. Further investigations are required to develop the pyrolysis-catalytic upgrading process to become sustainable and commercially viable for clean fuels production.

Chemical recycling of brominated flame retarded plastics from e-waste for clean fuels production: A review

With generation of waste plastics increasing, current EU legislation dictates high recovery rates and policy favours waste management technology choices that occupy a high position on the waste management hierarchy. Pyrolysis is a thermochemical conversion technology that can be considered a ‘feedstock recycling’ process and may play an increasing role in integrated waste management systems of the future. The objective of this article is to present a review of current state-of-the-art commercial pyrolysis processes for the production of liquid transport fuels from waste polyolefins (polyethylenes and polypropylenes). Current plastic waste generation and management practices are briefly summarised. Waste management infrastructure in Europe is reliant on landfill, incineration and mechanical recycling, while feedstock recycling plays an insignificant role. Plastic-to-liquid platforms including delocalised pyrolysis followed by centralised upgrading, stand alone facilities, and integrated waste management infrastructure concepts are briefly discussed. Commercial operations and their process configurations are compared. Reactor technology for cracking of plastic waste is presented. Important issues like fuel quality and contamination are also discussed. Fuel finishing operations and fuel additives required to achieve an engine ready fuel are described in the final section. Recently published laboratory research in thermal and catalytic pyrolysis and integrated and co-processing studies are also summarised in this review.

/pdf/waste-polyolefins-to-liquid-fuels-via-pyrolysis-review-of-27l5tv6192.pdf

C.-T. Hsu

Papers

Acid-catalyzed conversion of chlorinated plastic waste into valuable hydrocarbons over post-use commercial FCC catalysts