Abstract:

Using ultra-fine silicon oxide as carrier, ZSM-5 molecular sieves with high n(SiO₂)/n(Al₂O₃) ratio were extruded yielding catalyst for catalytic cracking of C₄ alkenes to propylene and ethylene. Precursors of calcium oxide and boron oxide were used to adjust the acidic property of the catalyst. The catalyst was pretreated with water vapor for 24 h at 580 ℃ under atmospheric pressure and water WHSV of 1 h^－1. The catalyst was evaluated at 500℃ under 0.1MPa with w(H₂O):w(C₄^＝)=0.2 and WHSV of 3 h^－1, the continuous operation of 25 days proved the stability of catalyst；the conversion of C₄ alkenes was higher than 68%, the yield of propylene and ethylene were higher than 30% and 6%, respectively, and the amount of carbon deposition on catalyst was 6.2%. The catalysts were characterized by BET, NH₃-TPD and Py-IR, which illustrated that the catalytic activity is corelated with B acid in the catalyst.