【摘要】 用IR谱、NH₃的TPD和X射线衍射等方法系统地研究了锑改性对HZSM-5沸石酸性的影响,并对锑在HZSM-5表面的分散情况进行了探讨,发现锑在HZSM-5表面的分散存在一个阈值（17%Sb₂O₃）。锑可使Bronsted酸中心中毒,随着锑含量增加,Bronsted酸量减少,而Lewis酸量变化不大,锑含量大于阈值之后,剩余Bronsted酸量也趋于恒定.锑很可能是在HZSM-5表面某些特定位置单层分散的,而孔口及外表面的酸中心是这些可被占据位值的一部分。此外,甲苯甲基化活性、选择性以及对二甲苯异构化活性也与催化剂含量阈值有密切的关系。更多还原

【Abstract】 The effect of antimony oxide on the acidic properties of HZSM-5 has been studied by IR spectroscopy, TPD of NH,, XRD and selective poisoning by 4-methylquinoline. Moreover, the dispersion of antimony oxide on the surface of HZSM-5 was also studied. The results showed that there was a threshold value of Sb2O3 content (17%) for antimony oxide dispersed on the surface of HZSM-5. It was quite possible that antimony oxide dispersed on some special surface sites of HZSM-5 in a kind of monolayer form, and the pore opening and external surface acid sites were a part of these sites that could be occupied. Bronsted acid sites could be poisoned by antimony oxide, the amount of Bronsted acid sites decreased with the increase of Sb2O3 content, while the amount of Lewis acid sites was almost unchanged. When Sb2O3 content of HZSM-5 was higher than the threshold value, the amount of residual Bronsted acid sites became a constant too. The activity and selectivity for toluene methylation and activity for p-xylene isomerization on HZSM-5 modified with antimony oxide had an inevitable connection with the threshold value of Sb2O3 content.更多还原