Assessing and Improving Quality of Pyrolysis Oil and Its Fractions from Waste Polyolefins for Refinery Use

Pyrolysis of PE/PP waste polyolefin blend (1:1 wt) was carried out in conical reactor at 440 °C in the presence of CO2 to produce pyrolysis oil (PO), which was filtered and separated into pyrolysis naphtha, kerosene, and gas oil fractions by rectification. The distribution of heteroatoms and metals into individual liquid and solid fractions was measured. PO was contaminated with separated red polar liquid (0.5 wt %) resulting from additive degradation; by entrained filler particles (in the amount of 170 mg kg–1 and diameter size from 0.5 μm to 152 μm); nitrogen compounds (219 mg kg–1); organic chlorides (115 mg kg–1); sulfur compounds (11 mg kg–1); silicon (21 mg kg–1); iron (6 mg kg–1); phosphorus (3 mg kg–1); and bromine (2 mg kg–1). The advantage was that metals (Ca, Ti, Si, Mg, Al, Fe, Zn, K, Na, and Cu) were concentrated in the solid pyrolysis residue. For sulfur, iron, and phosphorus, the levels of contaminants increased along with boiling point of the fraction; in contrast, the amount of organic chlorides decreased with increasing boiling point of the fraction from naphtha (264 mg kg–1) to distillation residue (20 mg kg–1). An irregular distribution of nitrogen compounds was observed as the boiling point of the fraction increased, with the highest nitrogen concentration of 486 mg kg–1 in kerosene. The purification of gas oil pyrolysis fraction by adsorption with the help of silica gel, alumina, and activated carbon was also investigated. Alumina has demonstrated the highest ability from tested adsorbents to remove nitrogenous and chlorinated compounds. PO fractions represent hydrocarbon mixtures and have significant potential for chemical recycling in refineries after the removal of contaminants.