Research On Separation And Purification Of Mixed Dibasic Acids

Mixed dibasic acid is a byproduct of adipic acid industry,mainly composed of succinic acid,glutaric acid and adipic acid,because it is a mixture and contains many impurities such as nitrate,the application of mixed dibasic acid is greatly limited and the economic benefit is low.Therefore,the separation and purification of mixed dibasic acid from a chemical company in Hebei Province were studied in the thesis.A rapid gas chromatographic method for the detection of dibasic acids was established,and the composition and impurity characteristics of mixed dibasic acids were determined by detecting and analyzing the melting range,nitrate content,ash content and iron ion content.The solubility datas of succinic acid,glutaric acid and adipic acid in polyhalogenated hydrocarbon(HH-1),water,n-propanol,acetone and n-butanol were determined by dynamic method,and the dissolution data were fitted by Apelblat solubility equation.The effect of glutaric acid on the solubility of succinic acid and adipic acid was investigated.The results show that,the solubilities of glutaric acid is higher than that of succinic acid and adipic acid in those selected solvents due to the odd even effect,and adding glutaric acid to the solution will increase the solubilities of succinic acid and adipic acid.The experimental scheme of separating and purifying glutaric acid from mixed dibasic acid by dissolution crystallization method with HH-1 was determined according to the solubility datas.The control conditions of dissolution,crystallization,mother liquor circulation and recrystallization were optimized by single factor experiment.glutaric acid with purity of 99.15% was separated from mixed dibasic acid,its total yield was 44.08%.And successfully enlarged the laboratory level device to the kilogram level.Base on the composition of the residue after glutaric acid separation and the solubilization of glutaric acid,crude succinic acid with purity of 96.83% was obtained by adjusting the concentration of glutaric acid in the residue,and dissolving the glutaric acid and adipic acid from the residue by HH-1.Then through recrystallization by n-butanol,the purity of succinic acid reached 99.48%,and the total yield was 76.78%.In the aspect of adipic acid separation,the solid residue recovered from the solvent was used as raw material,and water as solvent,adipic acid with purity of 99.48% was obtained by controlling the gradient temperature and the concentration of adipic acid in aqueous solution,and the total yield reached 37.70%.Finally,glutaric acid,succinic acid and adipic acid were purified with activated carbon to improve product whiteness and remove ash,nitric acid and other impurities brought by mixed dibasic acid.Figure 35;Table 46;Reference 62...