Investigation of the uptake and catalytic effect of calcium and potassium-based additives under low-temperature pyrolysis of polyvinyl chloride

Managing plastic waste containing polyvinyl chloride is difficult due to the release of hazardous substances such as hydrogen chloride. Alkaline metal has been proven to minimize the release of hydrogen chloride during thermal degradation of polyvinyl chloride. However, most past studies conducted heating experiments under a high temperature which promotes the production of aromatic hydrocarbons. In this study, low-temperature pyrolysis was utilized which focuses on the dehydrochlorination stage while minimizing further degradation of hydrocarbons. The effectiveness of calcium oxide, calcium carbonate and potassium carbonate in minimizing the release of hydrogen chloride was also evaluated. Among those three additives, calcium oxide and potassium carbonate have shown some potential in uptaking hydrogen chloride. Especially when the molar ratio of additive to PVC is 1:1.6, calcium oxide reduced the generation of hydrogen chloride to as low as 20%. Potassium carbonate also exhibits an uptake effect but has a slight catalytic effect when the molar ratio is less than 1:1. On the other hand, calcium carbonate not only shows little to no uptake effect, but also promotes the thermal degradation of hydrocarbon.