Synthesis of Vanillin by Glyoxylic Acid Method
|School||East China University of Science and Technology|
|Keywords||3 - methoxy-4 - hydroxy mandelic acid Vanillin Oxidation Synthesis Alkaline cleaning|
This paper studies the of glyoxylate synthesis of vanillin preparation process , including oxidant the CuO preparation , the oxidation process conditions improved , acidification decarboxylation conditions improved recycling the guaiacol technology exploration of four and caustic law . Oxidation effect as the oxidant in the oxidation reaction , using the wet process of CuO . When the molar ratio of CuO and mandelic acid as the n 0.5 , the pH of the reaction system value p 3.5 , T 45 ° C reaction temperature , reaction time t 4 h , the oxidation yield 94.1 % . If further increase the molar ratio of CuO and mandelic acid (gt; n 0.5:1), or prolonging the reaction time to make a more complete oxidation reaction , the oxidation yield is further increased to more than 95% . Acidified decarboxylation process , filter the oxidation mixture after the reaction solution was cooled to T - 20 ° C ( add 50 ml of methanol ) , 50 % sulfuric acid was added for acidification , acidified to pH 4-5 , and then the solution was heated to T - 15 ° C and thermostat 15min decarboxylation reaction completely, the yield reached 95%. Acidified decarboxylation process , cuprous oxide have an adverse effect on the acidification decarboxylation need to be filtered before acidification decarboxylation . And methanol acidified off the acid no negative effect on the reaction , methanol was added , the solution was homogeneous , the results are more stable when the sample analysis . In the the alkaline cleaning Recovery of guaiacol process , when the benzene Guaiac wood phenol content of 25 g / L the caustic washing with NaOH concentration of 3.0 mol L - 1 , lignans recovery rate of 95.2% , to achieve the desired results . The alkaline cleaning recovery of guaiacol process lignans recovery process innovation , with the advantages of low energy consumption, less loss of raw materials , can be recycled , it is worth further study of industrial application .