SO42-TiO2-ZrO2复合氧化物固体酸催化剂的长叶烯芳构化催化性能

摘要

本工作用溶胶-凝胶法制备不同组成的SO42-/TiO2-ZrO2复合氧化物固体酸催化剂,用微型催化反应评价结合X-射线粉末衍射(XRD)、孔结构/BET表面积测试和NH3-程序升温脱附(NH3-TPD)等表征了SO42-/TiO2-ZrO2复合氧化物固体酸催化剂结构、表面酸性和长叶烯芳构化催化性能.复合氧化物固体酸SO42-/TiO2-ZrO2催化剂具有优良的长叶烯芳构化催化性能,并且其芳构化催化性能与催化剂组成和表面酸性密切相关.随催化剂中nZr/(nZr+nTi)增加,催化剂表面中等强度的酸中心量增加,芳构化产物选择性和收率明显增加,在nZr/ (nZr+nTi)=0.5时达极大值.随nZr/(nZr+nTi)进一步增加,不仅催化剂表面酸中心量减少、原料转化率明显下降,而且催化剂酸强度增强,导致芳构化产物选择性和收率下降.催化长叶烯芳构化的二元复合氧化物固体酸SO42-/TiO2-ZrO2催化剂适宜的组成为nZr/(nZrnTi)=0.5.%The SO42-/TiO2-ZrO2 composite oxides solid acid catalysts with different compositions were prepared by sol-gel method, and their structure and catalytic properties for aromatization of longifolene to 7-isopropyl-l,l-dimethyltetralin (Ⅲ) were studied by using microreactor tests combined with X-ray diffraction (XRD), pore structure/BET surface area measurements and NH3 temperature-programmed desorption (NH3-TPD). It is shown that the SO42-/TiO2-ZrO2 composite oxides solid acid catalysts exhibit the unique catalytic properties for aromatization of longifolene, and the catalyst composition exerts great influence on their catalytic properties. With increasing Zr/Zr+Ti molar ratio in the catalyst, the number of acidic sites with moderate acid strength increases, leading to the increases of selectivity and yield of aromatization product Ⅲ, reaching the maximum around Zr/Zr+ Ti molar ratio of 0.5. Further increasing Zr/Zr+Ti molar ratio, the number of acidic sites decrease, resulting in the decrease of longifolene conversion. Moreover, the increase of acid strength of acidic sites results in the remarkable decrease of selectivity to aromatization product (Ⅲ). The optimum composition of SO42-/TiO2-ZrO2 composite oxides solid acid catalysts for aromatization of longifolene is Zr/Zr+Ti molar ratio of 0.5.