Improving thermal decomposition process of recycled plastics for sustainable gas and liquid fuel production

Abstract

In the U.S.A., plastic waste is about 12.7 % of the total municipal waste which is approximately 32 million tons annually. Recovery of plastics is usually done through waste-toenergy or recycling options. Plastic-to-fuel (PTF) presents a unique opportunity to not only address environmental issues but also energy crisis. Also, PTF can address a critical problem for low recyclability rate of plastics. The development of PTF infrastructure can help prevent land-filling of plastics, extending the lifespan of landfills, reducing plastic loitering, producing synthetic crude oil, reducing pollutions associated with high sulfur contents in fossil fuels because plastic oil has ultralow sulfur content, and creating green jobs. In this paper, we reviewed existing methods of converting plastics into fuel. Additionally, we evaluated various factors, such as operating temperature, types of reactor and catalyst, plastic to catalyst ratios, and residence time which affect the conversion efficiency and product quality of plastic feedstock. We used MgSi and Cloisite 30B as catalysts for the first time for decomposition of different plastics and yielded comparative results to zeolite as a catalyst. In case of HDPE, oil yield with zeolite was 71% whereas it was 68% and 67% in case of MgSi and Cloisite 30B respectively. Zeolite with PP produced better results as oil yield was 75% whereas it was 70% and 65% in case of MgSi and Cloisite 30B respectively. Zeolite with LDPE produced about 70% oil whereas yield was 66% and 65% in case of MgSi and Cloisite 30B. Fourier transform infrared spectroscopy (FTIR), Ultraviolet visible spectroscopy (UV-Vis), and Gas chromatography (GC) were carried out and spectra results for all the samples were consistent and were in fuel range.