Revolutionizing Plastics Chemical Recycling with Table Salt

Abstract

AbstractChemical recycling enables plastics to be a part of the circular economy as it can cope with contaminated as well as mixed plastics waste. Herein, two important discoveries are reported. One innovation is the use of table salt (NaCl) to facilitate the low temperature pyrolysis of polyolefins comprised of high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), linear low‐density polyethylene (LLDPE), and polypropylene (PP) at the ratio of (4:2:2:3), respectively, thus enabling the efficient recycling of these mixed plastics. For comparative analysis, two different Pt catalysts as well as a control are investigated. Compared to the control, the use of table salt at 10 wt.% increased both the oil and gas contents by 80% and enabled 100% conversion to gas and oil without producing any undesirable wax. The second innovation is that metallized plastics are successfully pyrolyzed with table salt with excellent conversion efficiencies. The obtained oil fraction is further characterized using gas chromatography‐mass spectrometry (GC‐MS). In addition, the re‐use of salt, the effect of salt particle size and effect of the wt.% are explored. The thermal properties of the wax (solid) are characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Economic estimation revealed a 3.5‐fold increase in revenue can be generated by the novel method as compared to pyrolysis without any salt. In contrast, pyrolysis with a conventional Pt/alumina system incurs huge losses. These findings suggest that table salt can offer a transformative approach toward an inexpensive (4 cents per kg) and efficient pyrolysis methodology for the conversion of mixed plastics waste to useful hydrocarbon products.