Fuel-Oil Production from Catalytic Pyrolysis of Waste Plastic over the Solid Super Acid SO₄^2-/TiO₂-SiO₂

SO₄^2-/TiO₂-SiO₂ solid super acid catalysts were prepared by sol-gel and impregnation methods, and applied in the catalytic pyrolysis of waste plastics containing polypropylene in the present work. At the same time, the effects of the catalyst composition, calcination temperature, pyrolysis temperature and catalyst amount on the pyrolysis of waste plastics were also investigated in details. The results showed that the optimum conditions for the preparation of solid super acid SO₄^2-/TiO₂-SiO₂ were H₂SO₄/TiO₂-SiO₂ mass ratio of 3, TiO₂/SiO₂ molar ratio of 1, and calcination temperature 500℃. Under the optimum pyrolysis conditions (temperature 420℃, catalyst amount 2 g/10 g waste plastics), SO₄^2-/TiO₂-SiO₂ gave a yield of liquid fuel up to 78.6%. The n-butylamine-TPD characterization showed that the polypropylene catalytic pyrolysis mainly occurred over the super acid sites of SO₄^2-/TiO₂-SiO₂ catalysts. XRD results showed that rutile TiO₂ was beneficial for the formation of super acid sites.