Study Of Diels-alder Reaction Between Furan Compounds And Olefins Catalyzed By Supported Transition Metal Solid Acid Catalysts

As an important industrial raw material with a wide range of uses,P-xylene needs to be distilled from petroleum or obtained from fossil energy such as natural gas and coal.In order to improve its significant consumption of fossil fuels and high separation costs,this project utilizes furan compounds from renewable energy biomass to undergo Diels Alder reaction with olefins(mainly ethylene)under the action of a silicon tungsten phosphorus solid acid catalyst to generate benzene series compounds;Because all raw materials can be obtained from regenerated biomass,it is considered that this path is environmentally friendly and green recyclable.However,there are still other side reactions related to acid catalysis in this pathway,so it is necessary to adjust the acidity,acid quantity and acid type of the acid catalyst,improve the yield and selectivity of benzene series compounds through excitation analysis and reaction conditions research,and suppress side reactions.Porous silicon tungsten phosphorus solid acids not only have a large specific surface area,but also can adjust the structure and acidity of the catalyst by changing the type of solid acid template and the doping ratio of tungsten and phosphorus.The experiment found that the doping limit of WOx species in the catalyst was about 20%,and the total acid content increased and then decreased with the doping limit as the peak.Before reaching the doping limit,tungsten oxide species were not found in FT-IR,XRD,UV-vis-DRS and the distribution of W element was uniform according to the SEM.When the doping amount of WOx reaches 25%,various analyses have found the appearance of agglomerated tungsten oxide.The uneven dispersion of WOx species causes pore blockage,while the introduction of P species can improve the pore size.BET analysis shows that phosphorus species can promote the dispersion of tungsten in the silica pores.TG analysis shows that the catalyst with P is more stable than that without P.Silicon tungsten phosphorus solid acid was used to catalyze the Diels Alder reaction of ethylene and 2,5-dimethylfuran to produce P-xylene.The research data shows that the W-P-Si-O solid acid catalyst with 20% WOx loading W:P=1:1 has the highest catalytic yield of P-xylene,because when W: P=1:1,the amount of acid in the middle strong acid site and the proportion of B/L site in the middle strong acid reach the maximum,and the strong B acid helps Reaction intermediate catalytic dehydration to produce P-Xylene,which is the main reason why the catalyst is superior to the traditional Lewis acid catalyst.Through the investigation of the reaction temperature,pressure,time,solvent and other reaction conditions,the experiment determined that the best reaction condition was that the reaction temperature was 220 ℃,the ethylene gas pressure was 3 MPa,and the reaction time was 24 hours in 1,4-dioxane.When the mass ratio of 2,5-dimethylfuran to solvent was1 to 10,the mass percentage of WOx was 20%,W: P(molar ratio)was 1:1,and the catalyst was 0.25 g,the highest yield of P-Xylene was 84.7%,and the selectivity was 88.8%.