Modification Effect Of Molecular Sieve On Alumina Catalyst For Methanol Dehydration To Dimethyl Ether

Dimethyl ether（DME） is a new kind of clean energy that could replace liquefied petroleum gas and diesel. The synthetic method of DME is mainly used vapor phase dehydration from methanol. In this method, the catalysts of reaction are alumina and molecular sieve. Alumina catalyst is widely used in industrial equipment because of its high selectivity, good mechanical strength and low price. Molecular sieve catalyst also has industrial application value due to its high catalytic activity.In this thesis, γ-Al₂O₃ catalyst was prepared by pseudo-boehmite. The modification effect of molecular sieve on alumina catalyst for methanol dehydration to dimethyl ether was discussed. Three kinds of zeolite molecular sieves which have similar structures were selected in modification. The effects of their species, silica alumina ratio and contents on vapor phase dehydration reaction of methanol were investigated. The main conclusions are as follows:The calcination temperature of γ-Al₂O₃ catalyst is preferred to 550 ℃. With the addition of molecular sieves, the surface acidic of catalysts was changed. In range of 36⁸0, high silica alumina ratio of ZSM-22 is advantageous for reaction. The adding amount experiments suggest that, three kinds of molecular sieves have a similar trend. The content of active component is advised to 10%. The catalyst modified by ZSM-22 has low activity. The initial conversion rate of methanol is high when adding 20% ZSM-5, but the deactivation start quickly. The catalyst contained 20% ZSM-5 appears carbon deposition phenomenon. The catalyst modified by ZSM-23 has the best stability in 120 h reaction. So the modification of catalyst requires not only appropriate acid strength, but also befitting acid amount.