Study On Propene Metathesis Of WO₃/SiO₂ And MgO Mixed Catalysts

Low-carbon olefins such as ethylene,propylene and butylene are important raw materials for the petrochemical industry.Therefore,the development of low-carbon olefin sources will help promote the efficient and sustainable development of the petrochemical industry.The olefin metathesis technology has the advantage of adjusting the output ratio of low-carbon olefins according to market demand,and the side reaction of propylene metathesis reaction is less,which is favorable for the study of olefin metathesis mechanism.With the development of MTO and propane dehydrogenation processes,the source of propylene will be further broadened,and the propylene metathesis reaction will have a better market prospect.The WO₃/SiO₂ catalyst is the only olefin metathesis catalyst that is currently industrialized due to its advantages of low cost and strong anti-toxicity.This article attempts to prepare highly active WO₃/SiO₂ catalyst,inhibit the side reactions and carbon deposition on the catalyst,explore the effect of MgO catalyst on the stability of the catalyst system,and finally the optimal process conditions for the WO₃/SiO₂ catalyst developed.Firstly,the suitable bulk C-type silica gel was selected as the carrier,and then the optimal preparation method of high-activity WO₃/SiO₂ catalyst was explored from the four perspectives of silica gel pretreatment temperature,silica particle size,impregnation method and WO₃ loading.MgO catalyst can inhibit the carbon deposition on WO₃/SiO₂ catalyst and reduce the acidity of WO₃/SiO₂ catalyst,thereby inhibiting the side reactions of acid catalysis and reducing the selectivity of by-products.Therefore,MgO catalyst can significantly improve the stability of propylene metathesis reactions.In this paper,the optimum conditions for the WO₃/SiO₂ catalyst are investigated from the three aspects of reaction temperature,reaction pressure and weight hourly space velocity of propylene.The results show that increasing the reaction temperature can increase the conversion of propylene,but it can also increase the selectivity of the by-product.In the pressure range of 1.0².0MPa,the activity of the catalyst is less affected by the pressure;under high airspeed conditions,the rapid carbon deposition on the catalyst is easily deactivated.