Study On Oxidation Characteristics Of Disproportionated Rosin And Dehydroabietic Acid

In this paper, with disproportionated rosin as raw material, purification technology research of dehydroabietic acid was carried out, and the oxidation characteristics of disproportionated rosin and dehydroabietic acid at low temperature and under high temperature were discussed. The main contents and results achieved were:(1) The purification process of dehydroabietic acid with the method of salt crystallization was improved and the process was optimized. In single factor experiment, the best reaction temperature was 75℃, the best reaction time was 30 min, the best times for purification was 3-3. Orthogonal experiment was used to optimize the purification process. Through range analysis, the primary and secondary order of three factors influencing purification of dehydroabietic acid was that, reaction time> reaction temperature> purification times. Through the analysis of variance, the three factors purification times, reaction temperature and reaction time had no significant effect on purification of dehydroabietic acid. The obtained optimum conditions of process was that, reaction time was 20 min, reaction temperature was 65℃, times of purification was 4-3, the purity and yield of dehydroabietic acid were 98.9% and 16.9%.(2) The oxidation characteristics of disproportionated rosin and dehydroabietic acid at low temperatures was discussed. When dehydroabietic acid was at 50～70℃, the oxidation reaction was very slow. When disproportionated rosin was at 60℃ and 70℃, it had response characteristics of induction period, namely the early response was slow and the later was rather fast. Possible cause of low temperature oxidation reaction of disproportionated rosin was dihydroabietic acid.(3) The oxidation characteristics of disproportionated rosin and dehydroabietic acid at high temperature were studied. When disproportionated rosin was heated in oxygen, air, nitrogen during 150-290℃, oxygen was an important factor in causing color change. When disproportionated rosin was heated from 150～290℃, the color changed 11.5# (iron-cobalt color) in oxygen, the color changed 5.5# in air, the color changed 2# in nitrogen. When disproportionated rosin was heated in oxygen, the color changing order was that, in oxygen> in air> in nitrogen.The content affected the color change of dehydroabietic acid, large changes when high purity. When they were heated to 270℃, they had the same color 10 #. In nitrogen, even when they were heated to 270℃, the color had no big change, namely the oxidation reaction did not occur.(4) Through component analysis of disproportionated rosin and dehydroabietic acid before and after oxidation reaction by HPLC, it was found that when disproportionated rosin was heated to 270℃ in oxygen and air, the content of dehydroabietic acid reduced obviously. When disproportionated rosin was in oxygen and air, the content reduced 17.4% and 12.4%. When dehydroabietic acid was in air, it reduced 5.0%. Therefore, disproportionated rosin oxidized more easily than dehydroabietic acid.