Catalytic Copyrolysis of Used Waste Plastic and Lubricating Oil Using Cu-Modification of a Spent Fluid Catalytic Cracking Catalyst for Diesel-like Fuel Production

This work provided catalytic copyrolysis of spent lubricating oil (SLO) with waste low-density polyethylene (LDPE) using copper modification of a spent fluid catalytic cracking (sFCC) catalyst to produce diesel-like fuels in a microbatch reactor, which will lead to effective waste management, ensure sustainability, and serve as an alternative energy source. The effects of LDPE blended with SLO, temperature, reaction time, and catalyst loading using an inert nitrogen atmosphere were investigated on the yields and distributions of copyrolyzed oil, while metal modification of the sFCC was prepared and used to investigate the catalytic activity. The temperature and time of reaction played an important role in the gaseous contribution to the pyrolysis of SLO. The addition of the LDPE ratio in the catalytic copyrolysis, including Cu loading on a spent FCC template, also enhanced the acidity and was responsible for the catalytic activity, which could improve the product distribution and chemical compounds in a range of diesel-like fuels. It was shown that the pyrolyzed oil was in the range of C7–C26 with a maximum diesel-like fraction of 23.11 ± 2.88 wt % compared with the catalytic pyrolysis of SLO alone, which contained a diesel-like fraction of only 12.45 ± 1.92 wt %. It was noticed that the acid active site of the catalyst resulted in a carbon–carbon bond cleavage and further secondary reaction, leading to the conversion of the long residue fraction into a light oil product. In addition, the LDPE ratio in the catalytic copyrolysis could improve the product distribution and chemical compounds in a range of diesel-like compounds, as confirmed by the GC/MS analysis. Catalytic copyrolysis oil of the optimal process condition (0.7:0.3 mass molar of SLO/LDPE, 450 °C, 60 min, 3 wt % Cu-sFCC, and 10 wt % catalyst loading) mainly contains light hydrocarbons in the C7–C19 range. Accordingly, both the product selectivity and the conversion of the long residue to the diesel-like fraction were nearly stable (59.01 ± 1.36%) during the catalyst reusability test from one to three cycles without regeneration and significantly decreased after the fifth cycle. This is an indication that the copyrolysis enhanced the conversion of SLO by LPDE blended into smaller hydrocarbon compounds, and the catalytic activity therefore showed a major tendency toward the formation of diesel-like fractions (C8–C18).