Study On Green Sythesis Of Glutaric Acid And Heterogeneous Catalysts

The demand of glutaric acid?an important fine chemical intermediate?is increasing year by year,while the production method of glutaric acid in the industry at present mainly depends on the production of adipic acid,so the manufacture can not be guaranteed.Traditional laboratory synthesis process of glutaric acid can not be achieved in large scale,because raw materials are expensive and strong oxidant and heavy metal catalysts are used.In recent years,green synthesis of glutaric acid has been proposed using H₂O₂?oxidant?,tungsten-containing compound?catalysts?,and cyclopentene glutaraldehyde?substrates?.Due to the homogeneous catalysts and phase transfer catalysts are difficult to recycle and reuse,researchers began to develop heterogeneous catalysts to overcome the shortcomings of homogeneous catalysts and phase transfer catalysts.In this paper,WO₃/M_xO_y catalysts were prepared by dipping method,and then Zr?WO₄?₂ catalyst was prepared by coprecipitation.The effects of catalysts preparation conditions and reaction conditions on the yield of glutaric acid were determined.The structure of the catalysts and the existence state of tungsten species were studied by FT-IR,UV-vis DRS,XRD,BET and TG-DTA.The main work and research results in this paper are as follows:Three kinds of WO₃/M_xO_y?M_xO_y=ZrO₂,Al₂O₃,SnO₂?supported catalysts were prepared by dipping method and applied in the oxidation of cyclopentene and gultarldehyde using H₂O₂ as an oxidant.The effects of the loading of tungsten species,the calcination temperature of catalysts,the type of carrier,reaction temperature,reaction time,and material ratio on the yield of glutaric acid were determined.About the three catalysts,the best catalytic activity is obtained when ZrO₂ acts as the support,the optimum calcination temperature is 500?C,and the best loading of tungsten species is 30%.Glutaric acid yield can reach 70%?cyclopentene acts as substrate?under the condition n?H₂O₂?:n?cyclopentene?=4.2,85?C,7 h;and glutaric acid yield can reach99%?glutaraldehyde acts as substrate?under the condition n?H₂O₂?:n?glutaraldehyde?=2,85?C,6 h,using 30%WO₃/ZrO₂ catalyst,50%H₂O₂ as oxidant.Characterizations of XRD and FT-IR indicate that the dispersion of tungsten species on ZrO₂ is higher than that of Al₂O₃ and SnO₂.UV-vis DRS suggests that isolated tungsten species[WO₄],low-condensed polymerized tungsten species,as well as WO₆ unit are existed in WO₃/ZrO₂ catalysts.The TG-DTA analysis shows that calcination temperature of WO₃/ZrO₂ catalysts should be?600?C or tungsten species on ZrO₂ will be decomposed into inactive WO₃.Zr?WO₄?₂ catalyst were synthesized via chemical coprecipitation method,and applied for the oxidation of cyclopentene and 25%glutaraldehyde.The effects of calcination temperature,catalyst dosage,reaction temperature,reaction time,and molar ratio of substrate to H₂O₂ on the yield of glutaric acid were determined.Glutaric acid yield can reach 70%?cyclopentene acts as substrate?under the conditions n?H₂O₂?:n?cyclopentene?=4.2,85?C,7 h;and 90%?glutaraldehyde acts as substrate?under the conditions n?H₂O₂?:n?glutaraldehyde?=2,85?C,6 h,using Zr?WO₄?₂ catalyst,50%H₂O₂ as oxidant.Characterizations of XRD,UV-vis DRS and FT-IR indicate that,the Zr?WO₄?₂and WO₃/ZrO₂ catalysts prepared by the two methods,respectely,were quite different in the phase,structure,and the existence state of tungsten species.The characterization of FT-IR and UV-vis DRS indicates that tungsten species exist in the form of WO₄^2-.The TG-DTA analysis shows that calcination temperature of Zr?WO₄?₂ catalyst should be?600?C or tungsten species on Zr?WO₄?₂ will be decomposed into inactive WO₃.The heterogenetic property of Zr?WO₄?₂ catalyst was investigated.Experimental results show that the Zr?WO₄?₂ catalyst could be used 6 times.The characterizations of FT-IR and UV-vis show that Zr?WO₄?₂ has no obvious change in structure after repeated use and had high stability.