碳四烯烃催化裂解制丙烯和乙烯

以超细SiO_2为载体、高硅铝比的ZSM-5分子筛为活性组分,通过挤条成型制成ZSM-5/SiO_2催化剂,用MgO、CaO和B_2O_3对催化剂进行改性,考察了催化剂的稳定性,并采用XRD和SEM对催化剂进行了表征。表征结果显示,成型、改性和蒸汽处理对ZSM-5分子筛的晶型没有造成影响。实验结果表明,经CaO-B_2O_3改性后再在600℃、常压、蒸汽重时空速1h~(-1)的条件下处理24h的Cao-B_2O_3/ZSM-5/SiO_2催化剂的稳定性较好;采用该催化剂,在520℃、0.1MPa、水与碳四原料质量比0.2、重时空速3h~(-1)的条件下连续反应25d,反应产物组成稳定,碳四烯烃转化率大于65%,丙烯收率大于31%,乙烯收率大于6%,催化剂的积碳量(质量分数)为4.0%。

Catalytic Cracking of C4 Alkenes to Propylene and Ethylene

The catalyst for catalytic cracking of C_4 alkenes to propylene and ethylene was prepared through extrudation using ultra-fine silicon oxide as support and ZSM-5 molecular sieves with high n(SiO_2):n(Al_2O_3)as active component.CaO,MgO and B_2O_3 were added to adjust the acidic property of the prepared catalyst.The catalysts were characterized by means of XRD and SEM,and their stabilities were investigated.XRD analysis showed that the crystal form of the ZSM-5 wasn't affected by forming,modifying and pretreating of the catalyst.The catalyst modified by CaO-B_2O_3 and pretreated with water vapor for 24 h under 600℃,atmospheric pressure and water WHSV 1 h~(-1)had good stability.Under reaction conditions of 520℃,0.1 MPa,m(H_2O):m(C_4)0.2 and WHSV 3 h~(-1),the catalyst evaluation was carried out through continuous operation for 25 d,and the conversion of the C_4 alkenes was more than 65 %,and the yields of propylene and ethylene were more than 31% and 6%,respectively.The amount of the carbon deposition on the catalyst was 4.0%.