Glyoxalic Acid Preparation Of Vanillin Process Development

Vanillin is the most widely applied practical synthetic spices and chemical intermediates in the world of spice field. Synthesis of vanillin using by glyoxylic acid has the following features such as the process is short, the yield is high, the product quality is good, the environmental pollution is light, waste emissions can be treated by biochemical methods and so on. The technology has successfully realized industrialization. This thesis introduces the properties, application, synthesis method and condition of industrial production of vanillin, explores the process for the synthesis of vanillin using guaiacol and glyoxylic acid, determines the optimum technological conditions for each stage of the process, and thereby improving the yield and quality of vanillin. This thesis also introduces the process for guaiacol recovery, selection of oxidant, the process for oxidant recovery, the use of HPLC and analysis.Anlayzed the economic feasibility for this project in glyoxalic acid preparation of vanillin technology.At the stage of condensation reaction, when the molar ratio of raw materials was that glyoxylic acid:guaiacol:sodium hydroxide=1:2:3, reaction temperature was 35℃, reaction time was 6-8h, pH value was 10-11, the molar ratio of de ionized water to ethyl acid was 100:1, and the apparatus was purged with nitrogen before the reaction, the result of the condensation is good and the yield of the 3-methoxy-4-hydroxy mandelic acid was up to 93%.At the stage of oxidation reaction, using five hydrated copper sulfate as oxidant had a better oxidation. The soluble copper salt complexes generated by the two valence copper ionsunder alkaline conditions had good oxidation effect. When the molar ratio of 3-methoxy-4-hydroxy mandelic acid and oxidizing agent was 1:2.5, reaction temperature was 95℃, oxidation reaction time was 8h, pH value was 13.5, decarboxylation reaction time was 0.5h, the yield of oxidation product is 94%. The oxidation yield can be improved by improving the molar ratio or reaction time, but the energy consumption and raw material cost were also increased. The reduction product Cu2O obtained by the redox reaction can be regenerated and reused after recycling. The concrete process is that the reduction product Cu2O was added to H2SO4 solution firstly, then the H2O2 (mass fraction of 30%) was added to the mole by drop following by mixing. After the drip, stirred for 30 minutes continually to ensure the reaction can be fully and appeared blue copper sulpHate solution. After the water evaporated with negative pressure, regenerated oxidant copper sulfate can be used in the next oxidation reaction.Anlayzed the economic feasibility for this development process.