Study And Optimization Of Synthesis Process Of DL-tartaric Acid

Tartaric acid is an important chemical product,widely used in food,medicine,light chemical industry,textile and other fields,such as telecommunications equipment,leather,electroplating,printing and dyeing,glass ceramics and so on.However,there are numerous shortcomings in the traditional synthesis process of DL-tartaric acid,such as long reaction period,low product yield and difficult separation of catalyst in homogeneous system.Moreover,the mother liquor contains high concentration of heavy metal tungsten.If discharged directly,it will cause resource waste,environmental pollution and increased production costs.Therefore,it is of great value to study and optimize the traditional synthesis process of DL-tartaric acid.In this paper,there are two parts as following:In the first part:a synthetic route of DL-tartaric acid via the key intermediate,calcium(hydrogen)epoxysuccinate,was proposed.Using maleic anhydride as a raw material,calcium carbonate as calcium source,calcium epoxysuccinate hexahydrate or calcium hydroxide epoxysuccinate intermediates were synthesized via epoxidation reaction,and 92.5%or 95.0%yield is obtained respectively.Then,calcium ion was removed by acidification and filtration,and DL-tartaric acid was prepared via hydrolysis reaction.Finally,the pH value of mother liquor was adjusted to acquire the co-product DL-potassium hydrogen tartrate,and 82.2%yield is obtained.At the same time,the factors such as reaction temperature,reaction time,catalyst dosage and oxidant dosage were investigated.Under the optimal reaction conditions,the intermediates mother liquors and DL-tartaric acid mother liquor were recycled for three times respectively.The yield remains stable when intermediates mother liquors are recycled for three times,and as regards DL-tartaric acid mother liquor,the yield is over 95.0%each time.The process shortens the reaction period and improves the utilization rate of raw materials and reaction yields,making it accessible to industrialization.The structures of intermediates and products were identified by melting point,FT-IR,1H-NMR and 13C-NMR.In the second part:New supported catalysts were studied.Tungsten catalysts supported on MCM-41,metal oxides(TiO2,Al2O3,SiO2)or g-C3N4 were prepared.Meanwhile,bi-supported tungsten catalysts were prepared for the synthesis of DL-tartaric acid.Among them,the catalytic activity of W/g-C3N4 is the highest with the yield of 65.1%.Besides,the circulation performance of the catalyst was investigated,and the structures of catalysts were determined by FT-IR.