Effect of calcination temperature on Ce/OPA catalyst in HDPE catalytic pyrolysis to fuel grade liquid product

Abstract

Catalytic pyrolysis of plastic polymers is becoming an important method for the conversion of plastic materials into valuable chemicals and fuel production. The effect of calcination temperature on cerium loaded on oil palm ash (Ce/OPA) catalyst and products in catalytic pyrolysis of HDPE plastic were studied. The catalysts were synthesized via wet impregnation method and calcined at 500 °C, 750 °C and 1000 °C. The surface morphology and surface structure of the catalysts were also analyzed. The catalytic pyrolysis was done in a batch reactor at 450 °C with 15 mL.min−1 of N2 and 10:1 of plastic-to-catalyst weight ratio for an hour. The liquid products of the pyrolysis were analyzed via mass spectrometry GC-TCD, GC–MS, FTIR, bomb calorimeter and viscometer. It is found the Ce/OPA catalyst that calcined at 500 °C for four hours showed better catalytic pyrolysis activity and has largest specific surface area (10.77 m2.g−1) and and pore volume (0.032 cm3.g−1) than the catalyst that calcined at 750 °C (4.52 m2.g−1 and 0.029 cm3.g−1) and 1000 °C (3.70 m2.g−1 and 0.006 cm3.g−1). The Ce/OPA catalyst that calcined at 500 °C catalytic cracked the HDPE waste with less solid yield (25.2 wt%) and more gas yield (18.40 wt%). Meanwhile, the Ce/OPA that calcined at 750 °C and 1000 °C produced the most gases product (14.4 wt%), but the gas products that was rich in CH4 and H2 achieved when Ce/OPA that calcined at 1000 °C was used. This is because a cation-disordered phase formed in the Ce/OPA catalyst during high-temperature calcination, thereby decreasing the oxygen storage/release capacity and lowering the catalyst’s pore volume and surface area. The liquid products with calorific value ranging from 50.34 MJ.kg−1–50.39 MJ.kg−1 and viscosity value between 1.06cP-1.29cP were also obtained. However, the calcination temperature did not affect the liquid product properties. In conclusion, the calcination temperature significantly affected the catalytic activity of Ce/OPA and improved properties of products.