Thermochemical treatment of waste polypropylene (PP) using marble sludge as catalyst-II: Evaluation of chemicals recovery potential from pyrolytic fluids

Abstract

In this study, waste polypropylene (PP) was pyrolysed together with marble processing industry effluents physicochemical treatment sludge (named as K1) catalyst, and the valuable component recovery and usage potential from resulting liquid and gaseous products were investigated. In the fixed bed pyrolysis reactor under inert conditions with N₂ gas, the studied experimental variables were temperature and mixing ratio. The resultant liquid and gaseous fractions were characterized via GC-MS, Fourier transform infrared, thermogravimetric analysis and calorific value analyses. Liquid products contain predominantly paraffinic and olefinic, but minor aromatic hydrocarbons (HCs) and also minor amounts of oxygenated compounds with 20–30% K1 catalyst. Heating values of the liquid products were around 10 kcal.g⁻¹. The gas products predominantly contain alkanes, alkenes and aromatic HC compounds with economic value such as benzene isotridecanol, heptanol, ketone and terpene. Ca and Mg carbonate structure of K1 catalyst increased the compound diversity in the pyrolysis gas, especially in the aliphatic groups. The detected low C number alkane compounds were pentane, heptane, cyclohexane and high C number long-chain n-alkane aliphatic compounds were docosane, hexacosane and hexatriacontane. The recoverable compounds are economically and environmentally important as they can be used in many industries such as cleaning, cosmetics, pharmacology and petrochemistry as feedstock. The proposed pyrolysis provided symbiotic solution to these two types of wastes and the resultant products of this application have potential for energy and compound recovery. Recovery methods can be further studied.