A Study On The Purification Technology Of Crude Sebacic Acid In Waste Water

The sebacic acid is a kind of important organic intermediate which is widely used to produce nylon,plastic,spicery and so on.At the present industry process, 25-30 tons/(ton sebacic acid) waster water effluent. Exclusive of sodium sulfate and phenol, a small amount sebacic acid and other fatty acids dissolved in it. How to process the waste water, reduce the emissions, and enable its converting into resources have the extremely vital practical significance.This subject is mainly composed of two aspects.The first part is the establishment of HPLC analysis method.The second part is the research of purification technology of crude sebacic acid which is recovered from waste water.HPLC factors appropriate to analyse sebacic acid and organic acid were established,include:the select of chromatographic column;the select of the mobile phase's constitution and pH value;the select of detector;the select of current velocity. HPLC factors were determined as below: chromatographic column is C18 column;mobile phase is V(methanol):V(potassium dihydrogen phosphate-phosphoric acid buffer solution,pH=2.1)=5:6;detector is ultraviolet absorption detector,and the wavelength is 210nm; current velocity is 1ml per minute.Under this HPLC conditions,calibration curve and linear equation between concentration of pure sebacic acid and peak area of high performance liquid chromatograph were abtained. Crude sebacic acid was qualitative analysed preliminary by HPLC-MS.And the main extraneous component in it was determined as HOOC(CH₂)₉COOH.We combined adjusting the pH value and cooling crystallization to purify sebacic acid. In the experiment, we investigated the influence of temperature,composition and amount of solution to the effect of purity and yield of the product, analysed the change of pH during the experiment. Based on the data gotten above, we improved the method of purification named adjusting pH and cooling crystallization. In the improved method, we take two steps to remove the extraneous components. In the first step, after the sebacic acid and sodium-hydroxide were dissolved, we adjust the pH of the solution to about 6.3.Some deposit which contains a high value of extraneous components need be removed by filtration. In the second step, we add ethanol to the filtrate abtained in the first step to increase the dissolvability of the extraneous components. Then adjust the pH to make the sebacic acid precipitate greatly and the extraneous components are left in the solution.By means of the two purification steps above,the purity of sebacic acid in the product can reach 99.51wt%, the yield can reach 74.6%. The result is quite satisfiable.