(449z) Measurement and Correlation for Solubility of Adipic Acid, Glutaric Acid, Succinic Acid in Acetic Acid + Adipic Acid / Glutaric Acid / Succinic Acid Mixture

Adipic acid (AA) is an important raw material used in the production of nylon-66, which was generally prepared by oxidation of cyclohenxanone or cyclihexanol. In the production process of AA, byproducts such as glutaric acid (GA) and succinic acid (SA) are generated at the same time. After AA is separated from the crude product, the remaining is always called the mixed dibasic acids. The solvent crystallization method is feasible for obtaining the high purity of GA from mixed dibasic acids now. Obviously, it is necessary to obtain the solubility of SA, GA, AA in various mass fraction of SA / GA / AA + solvents at various temperatures. In this work, The solubility of system of succinic acid and adipic acid in acetic acid + various mass fraction of glutaric acid, succinic acid and glutaric acid in acetic acid + various mass fraction of adipic acid, glutaric acid and adipic acid in acetic acid + various mass fraction of succinic acid were determined at temperatures from (292.90 to 353.55) K using the dynamic method under atmospheric pressure, The experimental measurement data were correlated by Apelblat, λh, NRTL equation, the highest accuracy of which is the Apelblat equation. The fusion enthalpy of dibasic acid (succinic acid, glutaric acid, adipic acid) was determined by DSC. A laser monitoring system was introduced to observe the dissolving process. And the hydrogen-bonding interactions were derived from the GaussView5.0, it can be proved that the action of hydrogen bonding of (solute + solvent), (solute + solute) and (solvent + solvent).

Materials: AA (C₆H₁₀O₄) was purchased from Henan Shenma Nylon Chemical Co., Ltd. SA and GA were provided by Sinopharmm Chemical Reagent Co., Ltd. Their purity were 0.995 in mass fraction in solubility determination, which were confirmed by using a Shimadzu-228-High-performance liquid-phase chromatograph (HPLG). Acetic acid was obtained from Kewei Chemical Reagent Co., Ltd. (the purity is 0.999), The mass fraction purity of acetic acid was checked by gas chromatography (GC).

Experimental devices: The temperature of the studied system was controlled by a high accuracy smart thermostatic bath (model: XHGX-3030), which was obtained from Ningbo Scientz Biotechnology Co., Ltd. with a precision of ±0.1 K. The masses of the solute and solvent were determined by an electronic analytical balance (model: BSA224S) with a precision of 0.0001 g, which was obtained from Sartorius Scientific Instrument Co., Ltd. The major device was a 100 mL jacketed glass dissolution vessel.

First, The melting temperature T_m and enthalpy of fusion Î?_fusH of SA, GA, AA are obtained from DSC curve (DSC-60 from Shimadzu Co., a heating rate of 5 K·min^â??1), based on the DSC analysis, which are T_mSA = 458.35 K, T_mGA = 371.60 K, T_mAA = 424.26 K and 32.65 kJ·mol^-1, 20.16 kJ·mol^-1, 34.31 kJ·mol^-1, respectively.

Then, the solubility of system of succinic acid and adipic acid in acetic acid + various mass fraction of glutaric acid, succinic acid and glutaric acid in acetic acid + various mass fraction of adipic acid, glutaric acid and adipic acid in acetic acid + various mass fraction of succinic acid were determined at temperatures from (292.90 to 353.55) K using the dynamic method under atmospheric pressure, and the dissolving equilibrium point were measured by using the laser monitoring system.

Third, the experimental measurement data were correlated by Apelblat, λh, NRTL equation, the highest accuracy of which is the Apelblat equation.

This figure of the solubility (S)-temperature (T) were mapped, it can find from this figures that the influence rule of AA and SA in various mass fraction GA (0-30.07 wt%) + acetic acid, AA and GA in various mass fraction SA (0.45 to 1.56 wt%) + acetic acid, SA and GA in various mass fraction AA (0 to 3.64 wt%) + acetic acid.

At last, effect of the intermolecular interactions in solution, the forming of hydrogen-bonds between solute and solvent molecules would enhance the affinity and increase solubility. The main intermolecular force is hydrogen-bonds in carboxylic acid dimer. Take the Acetic acid and SA, acetic acid and GA, SA and GA as examples, The forming of hydrogen-bonds is verified through GaussView5.0, in which the geometric fully optimized configuration was obtained using the quantum chemical calculation method of basis set 6-31G* (d, p) under the B3LYP. Most hydrogen-bonds (Oâ?¦O) distance range from 2.50 to 2.80 Ã?, the (O-Hâ?¦O) distance is approximately 2.65 Ã? in carboxylic acid molecules