摘要
以正硅酸乙酯(TEOS)为调控剂,调节HZSM-5(SiO_2/Al_2O_3=50)的孔结构与酸性,采用XRD、BET、NH_3-TPD等表征调节前后HZSM-5催化剂的晶相、孔结构和酸性,考察了Si沉积改性对HZSM-5催化剂MTO催化活性的影响。结果表明,采用TEOS进行Si改性的方法不会改变HZSM-5的骨架结构,焙烧后SiO_2覆盖在HZSM-5的表面,调变了HZSM-5的孔径、钝化了HZSM-5的酸性,提高了其对MTO反应的催化活性。当TEOS与HZSM-5质量比为0.15时,可以达到较好的改性效果,在保持甲醇转化率为100%的前提下,低碳烯烃选择性达到了65.40%,较改性前提高了18个百分点,丙烯的选择性30.97%,提升率为58%。
Regulation the pore structure and acidity on HZSM-5(SiO_2/Al_2O_3=50) by TEOS,characterized by means of XRD,BET,NH_3-TPD,and investigated the catalytic performance on MTO for the HZSM-5 before and after modified by different coverage of silica(the amount of TEOS).Results showed that the framework structure of HZSM-5 was unchanged after modified by TEOS.SiO_2 covering on the surface of HZSM-5 played a role in adjusting the acidity and reducing the orifice of HZSM-5 and its MTO catalytic activity was obviously improved.The appropriate loading of silica was 0.15(mTEOS/mHZSM-5),the modified HZSM-5 showed the better catalytic result,that the conversion of methanol was 100%,the selectivity of light olefins was 65.40%,it was 18 percentage point higher than the before modification,the propylene selectivity was 30.97% and the promotion rate was 58%.
引文
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