Research On Complex Extraction Of Acetic Acid From Dilute Solution

The acetic acid from dilute solutions of top product of solvent recovery tower in PTAworkshop of YPC was aimed as the background. On basis of all kinds of separative ways, thecomplex extraction with high capacities and selectivities was chosen to separate the aceticacid from dilute solutions.Tributylphosphate (TBP) and trialkylamine (7301) were selected as complexing agent,and kerosene, toluene, n-octanol and chloroform were chosen as diluent. Appropriatematerials of ternary mixed extractant were selected out based on liquid-liquid equilibriumexperiment. The effect of the phase ratio between the aqueous phase and organic phase, initialconcentration of acetic acid, the concentration of 7301 and n-octanol, the aqueousequilibrium pH value, temperature and the concentration of three salts on the extractionequilibrium had been systematically investigated. Extractant were regenerated with negativevoltage distillation, and the condition of stripping, testing and verifying the distributioncoefficients of regenerative extractant were studied. Orthogonal test results were analyzedand the distribution coefficients were forecasted with statistic software and BP neuralnetworks. Finally the chief influence factors, the best proportion of ternary mixed extractantand the optimal condition were obtained. The extraction mechanism of acetic acid has beenstudied with infrared spectra. The chief effect of diluents during extraction was explained.The liquid-liquid model considering physical extraction with specific physical meaning wasinduced. Quantitative description of effect of polar diluent concentration on complexcomposition appeared to be clear. Based on muti-step extraction characteristic andoperational condition, the process of extraction of acetic acid by rotating diskscontactor(RDC) was studied. The operation conditions of RDC within experimental scalewere analyzed and optimized by orthogonal test. Aimed at certain production task anddemand, the process of complex extraction of acetic acid by RDC was preliminarily designedin a certain operational condition. The economic evaluation was carried out.The experimental results are as follows:(1) Trialkylamine (7301) was selected ascomplexing agent, and n-octanol and kerosene as diluent in synthesis consideration. The bestproportion of ternary mixed extractant is 30%7301-50% n-octanol-20% kerosene accordingto the analysis. (2) With the increase of the initial concentration of acetic acid of the aqueous,the phase ratio between the aqueous phase and organic phase, equilibrium pH values of theaqueous phase and temperature, the distribution coefficients decreased . With the increase ofconcentration of 7301 and n-octanol in a scale, the distribution coefficients increased. Withthe concentration of sodium chloride, sodium sulfate and sodium nitrate increasing, the III徐晨:醋酸稀溶液络合萃取过程研究 2004 年 5 月distribution coefficients increase with different extent. The order of the effect of salting-out issodium nitrate> sodium chloride> sodium sulfate. (3) High temperature is benefit forback-extraction of the complexation of acetic acid, and it is key for boil-up ratio to controlthe tower bottom temperature between the 175℃and 185℃. Regenerative extractant keeps thesame extraction capacity during the extraction and baci-extraction time and time. (4)According to the infrared spectra of the organic sample-loading solutions with differentR(7301/aceticacid) , hydrogen-bond and ionic-bond between acetic acid and trialkylamine mightexist at the same time. In term of the law by complex extraction of acetic acid, theliquid-liquid equilibrium model of complex extraction of acetic acid considering physicalextraction comed at, so did the mathematical model of the effect of pH values of the aqueousphase on extraction equilibrium of acetic acid. With the increase of concentration of n-octanol,the reaction stoichiometry of acetic acid and 7301 increases. (5) The optimal conditions at theran...