Study On The Post-processing Of Aqueous Phase In The Purification Of Acetyl Acetone By Axeotropic Distillation

Acetyl acetone is an important reagent in analytical and coordination chemistry, which is widely used in many industrial production units. Acetyl acetone is mainly produced by isomerization reaction of isopropenyl acetate. Acetic acid and acetic anhydride are main by-products in reaction product which are difficult to separate by using traditional distillation for their closed boiling points with acetyl acetone. Azeotropic distillation is used in the separation process with water as entrainer. In this process, large quantity of water was fed into the distillation column which increases energy consumption. Meanwhile masses of wastewater with small quantity of acetyl acetone and acetic acid were left at the bottom of the column. Direct emissions would cause significant pollution and loss of acetyl acetone. Focusing on solving those problems, two kinds of process of wastewater treatment were investigated. One process was neutralizing wastewater by adding alkaline and recycling saline water into the column after removing crystal salt. In another work, the process of recycling acetyl acetone from waste water by extraction was investigated systematically. Simulation and experiment of the distillation of extraction phase were both studied and a feasible process was developed.The main contents of this thesis are as follows:(1) Salt effects of sodium acetate on VLE of water+acetyl acetone+acetic acid and in LLE of water+acetyl acetone were investigated. Adding of sodium acetate increased immiscible area of water and acetyl acetone. The salt exhibited salting-out effects on acetyl acetone and acetic acid and the efficiency on acetyl acetone was a little greater than that of acetic acid.(2) The process was neutralizing wastewater by adding alkaline and recycling saline water was studied with experiment. The influence of Ph value and crystallization temperature of saline water on the quality of product was studied. The experiment continued for 140 h, all the operation condition and product quality were stable, indicating the feasibility of this process.(3) Liquid-liquid equilibrium data of the solubility curves and the tie-line compositions for ternary systems of water+acetyl acetone+ethyl acetate and water+acetyl acetone+propyl acetate, together with the tie-line compositions for ternary systems of water+acetyl acetone+ cyclohexane were determined. Distribution and selectivity coefficients were evaluated for the immiscibility region, which were found to be bigger at lower temperature. The reliability of the experimental tie-lines was confirmed by using Bachman and Othmer-Tobias correlation. The experimental data were fitted using the NRTL and UNIQUAC equations, parameters of these two models were regressed.(4) Isobaric vapor-liquid equilibrium (VLE) data for the binary systems of cyclohexane+ acetyl acetone, acetic acid+cyclohexane, water+acetyl acetone and acetyl acetate+acetyl acetone were determined at 101.3 kPa, and those for acetic acid+acetyl acetone system were determined at 60.0 kPa. A minimum boiling azeotrope was found in acetic acid+cyclohexane and water+acetyl acetone system. The non-ideality of the vapor phase of the acetic acid+ acetyl acetone and acetic acid+cyclohexane system were investigated by using Hayden-O'Connell equation. Thermodynamic consistency was tested for all of the VLE data by using Herington method. The experimental data were correlated satisfactorily by the Wilson, NRTL, UNIQUAC models. Correlation results were in good agreement with experimental data which provided the basic data for rectifying process design of the relevant components.(5) The extraction of acetyl acetone and acetic acid from aqueous by cyclohexane and ethyl acetate were experimental studied. The extraction ability of ethyl acetate on acetyl acetone and acetic acid was better than cyclohexane and the distribution of acetyl acetone were both much bigger than that of acetic acid. The increasing of temperature significantly increased the distribution of acetic acid with cyclohexane as extractant. The temperature effect was not so obvious for ethyl acetate. The extraction process with modified rotating disc column was experimental studied. For cyclohexane, extraction efficiency was deeply affected by rotation speed rather than the phase ratio. The extraction percent of acetyl acetone was less than 10% at a rotation speed of 200 r/min but more than 60% at a rotation speed of 800 r/min. The extraction effect of ethyl acetate was far better than cyclohexane, there was no acetyl acetone left in residual extracted water at a rotation speed of 600 r/min.(6) Based on the VLE data, simulation and experiment of the distillation of extraction phase were both studied; sensitivity analysis of distillation column was investigated. It was found that solvents were easy to be separated from extraction phase and recycling used in the extraction process. The optimal parameters of distillation column were obtained. The purity of cyclohexane and ethyl acetate were more than 99.2% and 96.6% respectively. The recovery percent of both solvents was more than 99%.