Combined Activated Carbon with Spent Fluid Catalytic Cracking Catalyst and MgO for the Catalytic Conversion of Waste Polyethylene Wax into Diesel-like Hydrocarbon Fuels

Abstract

Catalytic pyrolysis of polymer waste is an attractive alternative process for the conversion of large hydrocarbon compounds to useful products for the most reliable fueling and valuable chemicals, growing toward a circular economy and enhancing the reduction of waste materials. In this study, catalytic pyrolysis of waste polyethylene wax (WPEW) using a dual acid–acid catalyst and acid–base catalyst, which had various pore size distributions and included a strong active site, maximized the desirable yield and product distribution. The effect of the process conditions and synergy of activated carbon (AC) blended into both a spent fluid catalytic cracking catalyst (FCC) and magnesium oxide (MgO) catalyst was examined in a 3000 cm 3 custom-built reactor at varying operating temperatures (400–470 °C), inert nitrogen gas flow rates (50 mL min –1 ), catalyst loading (1–5 wt %), and FCC-AC and MgO-AC ratios in the catalytic conversion of WPEW to obtain the highest amount of diesel-like oil. The results indicated that thermal cracking of WPEW at 420 °C by a fixed inert N 2 flow rate of 50 mL min –1 obtained the highest liquid yield of 81.64 wt % and a diesel-like fraction of 35.51 wt %, while the catalytic conversion of WPEW under optimum conditions (temperature: 420 °C; fixed inert N 2 flow rate: 50 mL min –1 ; catalyst load: 5 wt %; MgO-AC ratio: 0.5:0.5) achieved the highest liquid diesel-like yield of 41.92 wt %. Physicochemical analyses showed that the highest heating value of WPEW pyrolytic oil was 44.20 MJ kg –1 , and the viscosity was 1.7 mm 2 s –1 at 40 °C. The combination of MgO-AC as a dual catalyst illustrates a positive synergistic effect on the catalytic activity performance markedly, outstanding catalytic characteristics alongside high selectivity in pyrolysis of WPEW to paraffinic hydrocarbons in the diesel-like fraction.