Study On Isolation Of Dehydroabietic Acid By Reaction-Crystallization

In this paper the methods of isolation of rosin acid were studied using rosin (theadvantageous resources in GX) as raw material. The new technology of isolation ofdehydroabietic acid by reaction-crystallization in combination and the abrupt change points ofacidification curve were presented, and the yield and puirty of dehydroabietic acid have beenimproved. This research can improve the quality of rosin acid and its modification product,broaden the application of rosin product and accelerate the development of a series of rosinacid downstream products as well. As a result, the problems of industrialization of rosin havebeen resolved from the source of products. It provide important value of science theoreticsand practical significance to make rosin become a new "foundation stone" for green chemicalsynthesis and increase its economic value and application fields. This paper covers thecontents as follows:The materials and products were analyzed by gas chromatograph, using BP×5 bonedphase, fused silica capillary column (30m×032 mm×0.25μm), and the gas Chromatographyconditions have been considered, the temperature program was as follows: 423K for 0 min,then 30K·min^-1 to 483K, and finally 2K·min^-1 to 523K. Nitrogen was used as gas carrier, witha flow rate of 45mL·min^-1. The flow rates of hydrogen gas and air were 30mL·min^-1and 300mL·min^-1, respectively. The pressure before column was 0.07MPa, and the plit flow ratio wasset at 50: 1, the flow rate of tail gas was 24mL·min^-1, the temperature of injector and detectorwas 533K. The amount of injected material was 1.0μL.According to the fact that the several rosin acids present manifest differences inacid-strength, dehydrochloric acid was isolation by reaction-crystallization coupled withfractional acidification. At the first, the disproportionated rosin was dissolved by alkaliaqueous, and then the neutrals was extracted with ethyl ether, at last hydrochloric acid wasused for the fractional acidification. The precipitatite obtained was filtrated, and washed withwater, dried and weighed, and was analyzed by gas chromatography. At the same time, theeffects of factors such as the concentration of hydrochloric acid, the value of pH, acidificationtimes, the concentration of rosin acids salt, have been investigated. The result shown that, theoptimum processing condition for isolation of dehydroabietic acid were obtained, that is, thehigh purity dehydroabietic acid was obtained as the abrupt change point of the value of pH8.60 appeared, acidification times was 8, the concentration of rosin acids salt water: rosin was30: 1, the concentration of dehydrochloric acid was 0.1mol/L, and the purity of dehydroabieticacid was up to 99.99%. The yield of dehydroabietic acid is 22.86% using businessdisproportionated rosin as raw material. However, the yield is up to 59.69% using self-made disproportion rosin.The isolation of dehydroabietic acid by the reaction-crystallization in combinationwith ultrasound wave was studied. In the experiment, disproportionated rosin andethanolamine were used as reactants and ethanol was used as the solvent, and thendehydroabietic acid was obtained by recrystallization and acidification. The effects ofconcentration of ethanol(C), reaction temperature(T), reaction time(t), ultrasoundintensity(I) and agitating velocity(V) on the purity and yield of dehydroabietic acid wereinvestigated. The experimental results shown that, the sequence of factors which influencethe yield of dehydroabietic acid in accordance with significant degree are C＞I＞T＞t＞V,the sequence of factors which influence the purity of dehydroabietic acid in accordancewith significant degree are t＞I＞V＞T＞C, and the optimal conditions for isolation ofdehydroabietic acid have been obtained as follows: ultrasound intensity 400W, reactiontemperature 40℃, reaction time 50min, concentration of ethanol 20％, agitating velocity200 r/min.The yield of dehydroabietic acid is 43.32％, and the purity is 99.02％. Under theoptimal conditions, using self-made disproportionated rosin with high dehydroabietic acidas raw material, the yield and purity of dehydroabietic acid are 65.16％and 99.99％,respectively. The melting point and specific rotation of dehydroabietic acid weredetermined, the results are in good agreement with the value of literature.