脱铝丝光分子筛应用于MTP反应:Al的落位和晶体形貌的影响

甲醇制烯烃/丙烯工艺(MTO/MTP)是当前煤基碳资源绿色催化转化的重要过程之一.在MTO/MTP工艺中,分子筛通常面临低碳烯烃选择性低、水热稳定性差和寿命短等挑战.开发高选择性和高稳定性的分子筛催化剂对煤基乙烯/丙烯等化学品的工业生产具有重要意义.本文选择了具有12元环孔道的低硅丝光分子筛(Si/Al=6)为母体,对...

Selectiveconversionofmethanoltopropyleneoverhighlydealuminatedmordenite:Allocationandcrystalmorphologyeffects

The growing consumption of light olefins has stimulated intensive researches on methanol to olefin (MTO) process which possesses great advantages for coal conversion to value-added chemicals in an environmentally benign way. The catalysts commonly used for MTO process faces several chal-lenges such as poor selectivity control, low hydrothermal stability and short lifetime. In the present study, we prepared a series of mordenite zeolites with variable Al contents (Si/Al molar ratios of 51-436) by a sequential dealumination treatment of air-calcination and acid leaching. The textural properties, acidity and Al location before and after the dealumination treatment have been system-atically studied and their effect on MTO especially the methanol to propylene (MTP) performance was thoroughly investigated. The mordenite zeolites with the Si/Al ratios over 150 selectively cata-lyzed methanol conversion in the MTP pathway, providing a high propylene selectivity of 63％ and propylene/ethylene ratio of > 10. Compared to the low-silica MOR catalysts, highly dealuminated MOR showed much higher stability and longer lifetime, which can be further enhanced via harsh hydrothermal pretreatment. Furthermore, the lifetime was highly related to the crystal size along c-axis. The excellent performance of highly dealuminated MOR is likely ascribed to the mesopores formed upon dealumination and the scarce Al sites located in the T sites shared by the 8-member ring (MR) side pockets and 12-MR pore channels.