USY分子筛表面酸性的调变及其在催化脱除芳烃中烯烃的应用

Surface acid modification of zeolite and its application in removal of olefins in aromatics

详细论述了柠檬酸对USY分子筛的改性作用,以脱除高溴指数芳烃中烯烃的反应为例对其催化活性进行了评价。实验结果表明:0.2mol/L柠檬酸溶液酸性适宜,对分子筛的骨架铝以及非骨架铝进行了有效的脱除,脱除的铝在分子筛中以无定形的非骨架铝形式存在。柠檬酸改性过程可使分子筛的介孔面积以及介孔孔容增大,这十分有利于减缓分子筛的失活速率。柠檬酸改性过程使分子筛表面的强B酸减少,强L酸增多,这有助于减缓分子筛上积炭的生成速率。经过柠檬酸改性的USY分子筛对脱除芳烃中微量烯烃的催化效果明显高于目前工业中在用的普通白土和改性白土。再生实验说明,经3次焙烧再生后,改性分子筛的活性依然在90%以上,具有很好的可再生性。

This paper discusses the citric acid treated USY zeolite in detail and the activity of the catalyst was evaluated by the reaction of olefins removal in aromatics with high bromine index. The results showed that the acidity of 0.2mol/L citric acid was suitable for treatment of USY zeolite. The Al removed from the framework of zeolite was in the form of extra-framework Al. It was found that the mesopore area and mesopore volume became larger after modification and the newly generated mesoporous could slow down the deactivation rate. The reduction of the B acid site and the enhancement of the L acid in the samples occurred after the treatment of citric acid. And the deactivation of USY zeolite catalysts was due to a limitation of access of the reactant to the active sites or a blockage of the access. After modified by citric acid,the USY zeolite exhibited a higher catalytic activity in removal of olefins in aromatics than the ordinary clay and the modified clay. Regeneration experiments demonstrated that the activity of the modified USY zeolite was still remained above 90% after three regenerations.