Valorization of Waste Plastics, waste rubber and spent lubricant oil through catalytic co-pysolysis

Abstract

The present study is concerned with the catalytic co-pyrolysis of waste plastics, waste tyre rubber and waste lubricants. In the first part of study, the co-pyrolysis of waste rubber and waste lubricating oil was carried out in a batch steel pyrolyzer where waste copper was employed as a catalyst and the reaction conditions were optimized for achieving maximum pyrolysis oil yield. The waste rubber and lubricant were copyrolyzed in different ratios and their optimum ratio was found to be 4:1, respectively in terms of maximum pyrolysis oil conversion. About 44% oil yield and 75.5% total conversion of the reactants were achieved under the reaction conditions of 500 oC temperature, 30 minute reaction time, 5.0 wt% of catalyst and heating rate of 0.5 oCs-1. The non-catalytic pyrolysis yielded about 37.7% oil with 65.0% total conversion under similar reaction conditions. The catalytically produced oil was found to have a higher calorific value (49.6 MJ/Kg) as compared to the non-catalytic oil (44.6 MJ/Kg). The catalytic pyrolysis oil was fractionated in gasoline, kerosene and diesel ranges and their fuel properties were investigated according to the ASTM methods. The results showed that fuel properties of the oil fractions were comparable with that of corresponding standard fuels. The product oil samples were analyzed by means of FT-IR spectroscopy and gas chromatography mass spectrometry (GC-MS) in order to investigate their chemical composition. It was found that the fraction distilled in gasoline range had a hydrocarbon distribution in the range of C6 to C13, hydrocarbons identified in the fraction distilled in kerosene range were distributed from C6 to C16 and the fraction distilled in diesel range was composed of hydrocarbons distributed in the range of C11 to C26. In the second part of study, three most common types of municipal waste plastics i.e. low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polyethylene terephthalate (PET) were co-pyrolized thermally and catalytically using waste iron dust (Fe), waste copper (Cu) and waste Aluminum (Al) each separately as catalyst in the steel reactor. Various reaction conditions like temperature, reaction time, mixing ratio, catalyst proportion and initial mass of the reactants were optimized for effective conversion of the waste plastics. Outcomes of the thermal and catalytic reactions were compared to evaluate the catalytic activity of waste Cu, Al and Fe in terms of pyrolysis oil yield and total percent conversion. The product oils were fractionated in gasoline, kerosene and diesel ranges. The physicochemical properties of the samples fractions were found to be in close resemblance with the physicochemical x properties of the standard fuels. The FT-IR analysis indicated aromatic, saturated and unsaturated hydrocarbons in all the samples. The GC-MS analyses confirmed the saturated, unsaturated and aromatic hydrocarbons in various fractions ranging from lighter to heavier hydrocarbons in accordance to their boiling point distribution. The catalytic pyrolysis oils were found to contain relatively lighter hydrocarbons as compared to the non-catalytic oil. The fractions of catalytic pyrolysis oil in the gasoline, kerosene and diesel range contained C4-C12, C11-C20 and C20-C33 compounds, respectively. Calorific values of the catalytic oil and fractionated samples were found to be higher than the corresponding standard fuels.