Study On Synthesis Of Modified Mesoporous Molecular Sieves SBA-15 And The Catalytic Cracking Performance For Polystyrene

Mesoporous molecular sieves SBA-15 and BaO（CaO, MgO）/SBA-15 were synthesized by direct synthesis method. The obtained materials were characterized by XRD, FT-IR, N₂ adsorption/desorption and CO₂-TPD. The results showed that the obtained materials were of the characteristics of mesoporous molecular sieves, better long-range order and crystallinity, and that acid and base groups have been combined with the frame of mesoporous molecular sieve so that the acidity and base of the sieve was improved. K₂O/BaO-SBA-15 materials were synthesized by impregnating BaO-SBA-15 in different concentration KNO3 aqueous solution. The obtained materials were characterized by XRD, FT-IR, N₂ adsorption/desorption and CO₂-TPD.The results indicated that, the introduction of K species by impregnation method partly destroyed the mesoporous structure, and it could be concluded that the long-range order of K₂O-SBA-15 became poor with the increase of K₂ O and the mesporous structure was destroyed when the amount of K₂O was more than 12%, and there was poor dispersion of K species for the presence of big K₂O crystallites. Furthermore, the introduction of K species significant changes the BET surface area, the pore volume and the average pore diameter of the mesoporous molecular sieves. The CO2-TPD characterization results indicated that numerous K₂O introduced into BaO-SBA-15 could enhance the basic strength of the catalysts.The activities of different catalysts were investigated on the cracking of PS. The performance of the catalysts was evaluated in terms of the yield of liquid products and selectivity. The results indicated that BaO-SBA-15 showed the best performance compared with alkaline earth metal oxides for the catalytic degradation of PS. The effect of Si/Ba molar ratio on catalytic cracking of PS were investigated and BaO-SBA-15 with Si/Ba molar ratio 60:1 was found to have best performance. In this work, BaO-SBA-15（60） was used as catalyst on the cracking of PS. Under theconditions of normal pressure, reaction temperature 370 ℃, reaction time 30 min and m（catalyst）/m（PS）=4%, the conversion and the yield of liquid were 94.5% and 91.2%.Under the conditions of reduced pressure, reaction temperature 370 ℃, reaction time30 min, m（catalyst）/m（PS）=4% and reaction pressure 0.08 Mp, the conversion and the yield of liquid were 96.4% and 92.9%. K2O/BaO-SBA-15 were used for the degradation of polystyrene（PS） and among the supported catalysts, the9%K2O/BaO-SBA-15 was found to have highest catalytic performance. In this work,K2O/BaO-SBA-15 were used as catalyst on the cracking of PS. Under the conditions of normal pressure, reaction temperature 370 ℃, reaction time 30 min and m（catalyst）/m（PS）=2%, the conversion and the yield of liquid were 95.8% and 93.5%.Under the conditions of reduced pressure, reaction temperature 370 ℃, reaction time30 min, m（catalyst）/m（PS）=2% and reaction pressure 0.08 Mp, the conversion and the yield of liquid were 97.5% and 95.1%.The effect of Si/Ba molar ratio on catalytic cracking of HIPS were investigated and BaO-SBA-15 with Si/Ba molar ratio 60:1 was found to have best performance. In this work, BaO-SBA-15（60） was used as catalyst on the cracking of HIPS. Under the conditions of normal pressure, reaction temperature 430 ℃, reaction time 30 min and m（catalyst）/m（HIPS）=4%, the conversion and the yield of liquid were 95.1% and90.2%. Under the conditions of reduced pressure, reaction temperature 430 ℃,reaction time 30 min, m（catalyst）/m（HIPS）=4% and reaction pressure 0.08 Mp, the conversion and the yield of liquid were 97.7% and 93.1%. K₂O/BaO-SBA-15 were used for the degradation of HIPS and among the supported catalysts, the9%K2O/BaO-SBA-15 was found to have highest catalytic performance. In this work,K₂O/BaO-SBA-15 were used as catalyst on the cracking of HIPS. Under the conditions of normal pressure, reaction temperature 410 ℃, reaction time 30 min and m（catalyst）/m（HIPS）=2%, the conversion and the yield of liquid were 96.2% and91.8%. Under the conditions of reduced pressure, reaction temperature 410 ℃,reaction time 30 min, m（catalyst）/m（HIPS）=2% and reaction pressure 0.08 Mp, the conversion and the yield of liquid were 97.6% and 93.9%.BaO-SBA-15（60） was used as catalyst on the cracking of EPS. Under the conditions of normal pressure, reaction temperature 410 ℃, reaction time 20 min and m（catalyst）/m（EPS）=4%, the conversion and the yield of liquid were 95.2% and 89.9%.Under the conditions of reduced pressure, reaction temperature 410 ℃, reaction time20 min, m（catalyst）/m（EPS）=4% and reaction pressure 0.08 Mp, the conversion and the yield of liquid were 98.5% and 93.2%. 9%K2O/BaO-SBA-15 were used as catalyst on the cracking of EPS. Under the conditions of normal pressure, reaction temperature410 ℃, reaction time 20 min and m（catalyst）/m（EPS）=2%, the conversion and the yield of liquid were 97.1% and 93.0%. Under the conditions of reduced pressure,reaction temperature 410 ℃, reaction time 20 min, m（catalyst）/m（EPS）=2% and reaction pressure 0.08 Mp, the conversion and the yield of liquid were 99.5% and95.5%.Moreover, the reusability of catalyst was examined, the results showed that there was no significant decrease in conversion and yield of liquid product after reused 6times.