Waste resource utilization: Spent FCC catalyst-based composite catalyst for waste tire pyrolysis

• Composite FCC catalysts were used to improve waste tire pyrolysis product yields. • CaO or heavy oil could enhance the catalytic pyrolytic effect of FCC catalysts. • Heavy oil enhances interactions between the spent FCC catalysts and waste tires. • CaO decreases the sulfur contents of the final tire pyrolysis oil products. • Proposed composite catalysts extend the application of pyrolysis to waste tires. Waste tires are complex organic materials composed of various rubbers and fillers. Spent fluid catalytic cracking (FCC) catalysts cannot efficiently catalyze the pyrolysis of all organic components in waste tires. In this study, we attempted to improve the yield and quality of products obtained from the pyrolysis of waste tires. To this end, we prepared two composite catalysts (i.e., spent FCC catalysts + heavy pyrolysis oil and spent FCC catalysts + calcium oxide) with spent FCC catalysts as the main component, and studied their synergistic effects on the catalytic pyrolysis of the tires. In this study, the composite catalyst improved the recovery volume of the pyrolysis oil at 205 and 360 °C and increased the BTEX content in the oil by 14.7% and 8%, respectively. The experimental results showed that the heavy oil component in the composite catalyst enhanced interactions between the spent FCC catalysts and waste tires, thereby improving the yield and quality of tire pyrolysis oil (TPO). The alkaline material in the composite catalyst played a role in sulfur fixation and reduced the sulfur content of the TPO. The application of spent FCC catalysts to waste tire pyrolysis can meet the demand for low-cost catalysts for waste tires and improve the quality of the resulting TPO. Our findings collectively reflect the economic and social benefits of using composite catalysts for waste tire pyrolysis.