| Adipic acid is an important raw material,which is widely used in chemical production,organic synthesis industry,pharmaceutical industry,and lubricant manufacturing etc.With the development of green chemistry,the direct oxidation of cyclohexane to adipic acid without the use of nitric acid has attracted increasing attention.For this method,oxygen is used as the oxidant and acetic acid(HAc)is used as the solvent.Its major liquid products are cyclohexanol,cyclohexanone and and water.The major byproducts are glutaric acid and succinic acid.There exist various solid-liquid equilibrium(SLE),liquid-liquid equilibrium(LLE)and vapor-liquid equilibrium(VLE)systems in the reaction mixtures.However,a large number of related phase equilibrium data has not been reported.Besides,it is impossible to determine all physical property data in the actual chemical process in view of different temperature,pressure and solvent composition.In order to predict more phase equilibrium data of the cyclohexane oxidation system,it is extremely essential to establish a thermodynamic model,which can be obtained by correlating related basic physical property data.The main contents are as follows:1.The SLE data for adipic acid,glutaric acid and succinic acid in binary cyclohexanol + cyclohexanone,cyclohexanol + cyclohexane,cyclohexanone +cyclohexane,cyclohexanol + HAc,cyclohexanone + HAc solvent mixtures at(298 to348)K were determined by the dynamic method under atmospheric pressure.The comparisons for the solubilities of the three diacids in the aforementioned binary solvent mixtures were made.The results show that glutaric acid with an odd number of carbon atoms is much more soluble than succinic acid and adipic acid with an even number of carbon atoms.This phenomenon is called odd-even effect.The experimental solubilities of adipic acid,glutaric acid and succinic acid in the studied solvent mixtures were correlated by the Apelblat equation,and the corresponding averaged relative deviation between the experimental and calculated data were0.479%,0.489% and 0.726%,respectively.The results suggest that Apelblat equation can be used to correlate the solubilities of adipic acid,glutaric acid and succinic acid in the studied solvent mixture systems.2.The nonrandom two-liquid(NRTL)model were applied to correlate the measured SLE data and the reported LLE data for ternary systems simultaneously.Theaveraged relative deviation for SLE between the experimental and calculated data was1.78%.The root mean square deviation for LLE between the experimental and calculated data was 0.50%.The results suggest that the NRTL model can be applied to correlate the data for SLE and LLE of the cyclohexane oxidation system.3.The NRTL model and the obtained model parameters were uesd to predict:(1)the solubilities for adipic acid,glutaric acid and succinic acid in ternary cyclohexanol+ cyclohexanone + cyclohexane and cyclohexanol + cyclohexanone + HAc solvent mixtures;(2)the LLE data for ternary water + cyclohexane + cyclohexanol system at295 K and quaternary water + cyclohexane + cyclohexanol + cyclohexanone system at318K;(3)the VLE data for binary cyclohexanol + cyclohexane,cyclohexane +cyclohexanone,cyclohexanone + cyclohexanol systems.The averaged relative deviation for SLE between the experimental and predicted data was 1.42%.The root mean square deviation for LLE systems between the literature and predicted data were0.11% and 0.75%,respectively.The root mean square deviation for VLE systems between the literature and predicted data were 3.65%,2.07% and 3.35%,respectively.The results prove that the NRTL model and parameters can be applied to predice the data of SLE,LLE and VLE for the cyclohexane oxidation system in terms of different temperature,pressure and solvent composition. |
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