Preparation Of Platinum-tungsten Oxide Nanocomposite And Its Catalytic Hydrogenolysis Performance Of Glycerol

Biomass diesel converted from biomass is a green and sustainable energy source that can directly replace petroleum-based diesel.Due to the demands of green development and energy transformation,the biomass diesel industry has entered a period of rapid development.As the main by-product of biodiesel,the output of glycerol has also increased sharply,resulting in an oversupply situation.Therefore,the value-added of glycerol has important research significance for increasing the economic benefits of the biodiesel industry.Under certain reaction conditions,glycerol can obtain a series of value-added methods through oxidation,selective hydrogenolysis,selective dehydration,pyrolysis and gasification,steam reforming,thermal reduction to synthesis gas,selective transesterification,and selective etherification.product.Among them,1,3-propanediol,as one of the raw materials for the synthesis of polytrimethylene terephthalate（PTT）,has a higher value and a larger demand,which is of great significance to the value-added of glycerol,which has made the production of glycerol hydrogenolysis in recent years,3-Propanediol has been extensively studied.Although there have been more researches on the production of 1,3-propanediol by hydrogenolysis of glycerol,the industrial production of 1,3-propanediol is still restricted by many factors and cannot be realized.Among them,the stability of the catalyst is poor,the production cost is high,and the production Problems such as complex process,high deactivation rate,and large recovery loss have not been properly resolved.In this thesis,we select the Pt metal that is currently researched and use different synthesis methods to prepare two Pt-based catalysts for the selective hydrogenolysis of glycerol.The influencing factors of the Pt-based catalyst and the catalytic mechanism are discussed:（1）The Pt/ZSM-5 catalyst was prepared by the solution-gel method,and the acidity of the support was changed by changing the silicon-to-aluminum ratio of ZSM-5 to study the influence of different acidic sites on the catalytic effect.The NH₃-temperature programmed desorption（NH₃-TPD）was used to test the acidity of the catalyst surface.Comparing the catalytic effects of the supported catalysts with different acidic sites,it is found that the acidic sites required for the hydrogenolysis of glycerol are mainly weak acids and medium-strength acids.The presence of strong acids may cause excessive dehydration of glycerol,thereby reducing the selectivity of 1,3-propanediol.Compared with the catalysts obtained by other impregnation methods,the Pt/ZSM-5 catalyst has a simple synthesis process and is suitable for industrial large-scale production,but the catalyst activity is low,and further exploration and improvement are still needed.（2）A Pt/WO₃/ASA catalyst was prepared by using amorphous silica alumina（ASA）as the carrier and adding WO₃as a co-catalyst on the original basis to improve the catalyst activity.By comparing the different loading methods and loading sequence of Pt and WO₃,the influence of the combination sequence of Pt and WO₃on the catalyst was studied.（3）Pt/ASA and WO₃/ASA are physically mixed and then the catalytic reaction is carried out.Under the same reaction parameters,the glycerol conversion and 1,3-propanediol selectivity of the physically mixed catalyst are significantly lower than that of Pt/WO₃/ASA Therefore,it is concluded that when there is a mutual interface between Pt and WO₃,the catalyst activity is optimal.It can be inferred that there may be a synergistic effect between Pt and WO₃,so that Pt and WO₃can exert better effects.（4）Study the influence of the loading of different active components（Pt）and co-catalyst（WO₃）on the catalytic effect.When the Pt loading is 2%and the W loading is 10%,the catalyst exhibits the best effect.Comparing the effects of different reaction parameters on the catalytic performance,it is found that temperature has the greatest effect on activity and selectivity;catalytic activity and selectivity increase with the increase of hydrogen pressure;the extension of the reaction time helps to increase the conversion rate of glycerol and increase1,3-Propylene glycol selectivity.