Study on in-situ and ex-situ catalytic pyrolysis of waste tires based on low-cost catalysts

With the increase in the quantity of waste tires, the proper disposal of waste tires has received increasing attention. Pyrolysis is an environmentally friendly technology that converts waste tires into usable resources. However, the added value of the pyrolysis products is relatively low. In this paper, the effects of spent fluid catalytic cracking catalyst (sFCC), red mud (Rm) and fly ash (Fa) on the catalytic pyrolysis of waste tires at different locations were investigated. These catalysts were used in the pyrolysis experiments of waste tires by in-situ and ex-situ respectively. The distribution, characteristics and composition of the products were analyzed. The results showed that the content of light component in ex-situ catalytic pyrolysis oil was increased. The increase in light components exceeded 25% for all catalysts. The content of medium and heavy component was reduced. This indicates an enhancement in pyrolysis oil quality. The sFCC had the best regulating effect on the light components in pyrolysis oil, and the content of light components could reach up to 70.5%. Ex-situ catalytic pyrolysis of waste tires could promote the fragmentation of pyrolysis intermediates through the pore structure of the catalyst to increase the proportion of light components in pyrolysis oil, reduce the content of medium and heavy components, and lower the kinematic viscosity. The sFCC promoted the generation of more light components, and Rm showed the best desulfurization effect.