阳离子改性HZSM-5沸石上低碳醇转化为芳烃

低碳醇等含氧化合物能在HZSM-5上选择转化为汽油和芳烃.HZSM-5用某些阳离子改性可提高甲醇和乙醇的芳构化活性.本文研究了阳离子改生HZSM-5沸石的酸性质变化与低碳醇芳构化反应性能之间的关系. 1.催化剂制备:将直接法ZSM-5原粉制成氢型(HZ),SiO_2/Al_2O_3为37.再用离子交换法进行改性,制得Cu,Zn,Cd,Mn和Ga改性沸石,代号和金属含量(％)分

CONVERSION OF LOWER ALCOHOLS INTO AROMATICS OVER CATION-MODIFIED HZSM-5 ZEOLITES

The acidity of the modified HZSM-5 zeolites was characterized by NH3-TPD, pyridine-TG and pyridine-IR methods. The catalytic conversion of C1-C4 alcohols was carried out in a pulse microreictor at 450C. The results show that the modification of HZSM-5 with Cu, Cd or Zn results in a decrease in B acidity, an increase in L acidity and an appearance of new L acid sites characterized by IR band between 1609-1616cm-1. No considerable change in acidic properties is observed for Ga-modified zeolite. The Ga-, Cd- and Zn-modified zeolites, especially the latter two, show a great improvement in the yield of aromatics from methanol due to the additional dehydrcgenatirig activity of the modifying species, but the Cu-modified zeolite is not so. C2-C4 alcohols also give high yield of aromatics over the Zn-modifiei zeolite, but the yield is somewhat lower than that from methanol.