Catalytic Pyrolysis Of PS Over Alkaline Mesoporous Molecular Sieves

Several mesoporous molecular sieves, modified by Al,Mg,Ca or Ba, were synthesized under hydrothermal conditions. And some strong alkaline grouPS like K₂O, were incorporated into the frame of the mesoporous molecular sieves to obtain the stronger alkaline mesoporous molecular sieves catalysts. The obtained materials were used as catalysts in the pyrolysis of polystyrene(PS). The synthesized mesoporous molecular sieves were characterized by XRD and nitrogen adsorption-desorption. The results showed that the obtained materials were mesoporous molecular sieves with better long-range order and crystallinity.The catalytic cracking performances of different modified mesoporous molecular sieves were evaluated in model reactions of PS pyrolysis according to the yields of liquid products and PS monomer. The results showed that alkaline mesoporous molecular sieves BaO-MCM-41 and K₂O-BaO-MCM-41 had better catalytic performance.BaO-MCM-41 was used in catalytic pyrolysis of PS. The effects of content of BaO, reaction temperature, pressure and time on catalytic pyrolysis results of PS were examined. And the reusable performance of the catalyst were also examined. The results showed that BaO-MCM-41 had better catalytic performance and reusable performance. Under the obtained optimum reaction conditions of m(catalyst)/m(PS)=2%, reaction temperature 410℃, reaction pressure 0.01MPa and reaction time 20min, the conversion of PS was≥98%, the yield of liquid product was≥96% and the content of styrene in liquid product was≥72%. There is no obvious changes in PS conversion, liquid product yield and styrene content after the catalyst was reused for 6 times.K₂O-BaO-MCM-41 was used in catalytic pyrolysis of PS. The effects of content of K₂O, reaction temperature, pressure and time on catalytic pyrolysis results of PS were examined. The results showed that K₂O-BaO-MCM-41 had better catalytic performance and the obtained optimum reaction conditions were m(catalyst)/m(PS)=2%, reaction temperature 410℃, reaction pressure 0.01MPa and reaction time 20min. Under the obtained optimum reaction conditions, the conversion of PS was≥98%, the yield of liquid product was≥96% and the content of styrene in liquid product was≥75%. The reusable performance of the catalyst were also examined. The results showed that there is no obvious changes in PS conversion, liquid product yield and styrene content after the catalyst was reused for 5 times. It was showed that K₂O-BaO-MCM-41 had better reusable performance.