Synthesis Of Vanillin By Glyoxylic Acid Method

The process of the synthesis of vanillin by glyoxylic acid method was inversitgated in this dissertation, which covers the preparation of oxidant CuO, optimization of the oxidation reaction process, improvement of the acidification and decarboxylation process and process exploration of recovering guaiacol by alkali washing process.Good results of oxidation reaction was obtained with the use of the oxidant CuO prepared by the wet process,. When the molar ratio of CuO to mandelic acid was n+0.5, pH value was p+3.5, reaction temperature was T+45℃and reaction time was t+4 h, the oxidation yield reached 94.1%. When the reaction time was prolonged or the molar ratio of CuO to mandelic acid was increased, the oxidation reaction proceeded more completely and the oxidation yield was further improved to reach more than 95%.Research on the acidification and decarboxylation process shows that, after the filtration of the oxidation liquid, cooling down the reaction solution with 50ml methanol to T-20℃, acidification with 50% sulfuric acid to adjust pH value to 4-5, then heating the solution to T+15℃and keeping the temperature constant in 15 min, the oxidation yield reached more than 95%. During the acidification and decarboxylation process, cuprous oxide has an adverse effect, so it should be filtered before the acidification and decarboxylation process. And methanol has no adverse effect, so it can be added to make the solution homogeneous and sample analysis results more stable.Research on the recovering guaiacol by alkali washing process shows that, when the content of guaiacol in benzene was 25 g/L and the concentration of NaOH was 3.0 mol·L-1, the recovery rate of guaiacol reached 95.2% which achieved an ideal result. The recovering guaiacol by alkali washing process is an innovative recycling process in present recovery process, it has some advantages of low energy consumption, less loss of raw materials and recycling. It is worthy of further industrial application research.