Isobaric vapor−liquid equilibrium (VLE) data have been measured with a modified Rose−Williams still for the binary systems of methanol (1) + diethylamine (2), methanol (1) + N,N-diethylethanolamine (2), and N,Ndiethylethanolamine (1) + diethylamine (2) at p = (60.0 and 101.3) kPa. All of the experimental data pass the thermodynamic consistency test by the method of Herington and the point test of Van Ness. The system of methanol + diethylamine (DEA) at two pressures exhibits a maximum temperature azeotrope. The other two systems did not show that behavior. The experimental VLE data were well-correlated with the Wilson and universal quasichemical (UNIQUAC) activity coefficient models, and the average absolute deviations (AAD) of the vapor-phase mole fraction Δy between the experimental and the calculated values for all of the measured systems are less than 0.01.

The isobaric vapor–liquid equilibrium (VLE) data of {N-methylethanolamine + N-methyldiethanolamine (MDEA), N-methylethanolamine + ethylene glycol, ethylene glycol + MDEA} at P = (40.0, 30.0, and 20.0) kPa were investigated in this work. All of the VLE data of the three binary systems were verified to be thermodynamically consistent by both Herington area test and Van Ness point test. At the same time, the universal quasichemical (UNIQUAC), nonrandom two-liquid (NRTL), Wilson, and Margules activity coefficient equations were chosen to correlate the experimental results, deriving the coefficient parameters and estimating the standard error values. The correlation values showed that estimated data reached a good agreement with the experimental data in this study.

In this work, isobaric vapor−liquid equilibrium (VLE) data for the three binary systems composed of diethylamine (1) + ethanol (2), ethanol (1) + N,N-diethylethanolamine (2), and diethylamine (1) + N,N-diethylethanolamine (2) at p = (80.0 and 40.0) kPa have been measured using a modified Rose−Williams still. All of the experimental data passed thermodynamic consistency tests, including the area test of Herington and the point test of Van Ness and co-workers. No azeotropic behavior was observed at the two reduced pressures. The Wilson, NRTL, and UNIQUAC activity coefficient models were used to correlate the experimental data. The obtained results indicated that the UNIQUAC model was more suitable than the Wilson and NRTL models for correlating the measured isobaric VLE data.

Isobaric vapor−liquid equilibrium (VLE) data for the binary systems of {ethane-1,2-diol + butane-1,4-diol, ethane-1,2-diol + 2-(2-hydroxyethoxy)ethan-1-ol, butane-1,4-diol + 2-(2-hydroxyethoxy)ethan-1-ol, and 2-(2-hydroxyethoxy)ethan-1-ol + 2-[2-(2-hydroxyethoxy)ethoxy]-ethanol} have been experimentally measured at 10.0 kPa, 20.0 kPa, and 40.0 kPa using a modified Rose−Williams still in this study. The experimental data of the binary systems were wellcorrelated by universal quasichemical (UNIQUAC), nonrandom two-liquid (NRTL), and Wilson activity coefficient models at the three subatmospheric pressures, and the calculated values of the three models agreed well with the experimental data. Then the VLE data of the four binary systems were checked by the Herington area test and Van Ness point test, which showed thermodynamic consistency. ■ INTRODUCTIONAs an important organic chemical raw material, ethane-1,2-diol (EG) is mainly used in the production of polyester fibers, antifreeze, nonionic surfactants, ethanolamines, and explosives. In the fields of tobacco industry, textile industry, and cosmetic industry, EG also has a wide range of applications. 1 Several papers 2 have reported that petroleum is the raw material for the synthesis of EG. However, owing to the increasing consumption and soaring price of petroleum, the nonpetroleum process in production of EG is significant. The present route based on the syngas from coal has aroused more attention in many countries. 3 To the route of synthesis of EG based on the syngas, the first step is synthesizing dimethyl oxalate (DMO), and then EG is synthesized by DMO hydrogenation.When EG is synthesized by DMO hydrogenation, butane-1,4-diol (BDO), 2-(2-hydroxyethoxy)ethan-1-ol (DEG), and 2-[2-(2-hydroxyethoxy)ethoxy]ethanol (TEG) are also obtained as byproducts. Each of byproduct has its own application. For example, BDO is widely used as a polymer feedstock among the four carbon-based diols. 4 DEG is commonly used as antifreeze, lubricating, and finishing agents and aircrafts at the airports. 5 For TEG, natural gas dehydration is an important operation in the gas processing and conditioning industry. 6 The refined EG and byproducts are generally obtained from the crude reaction mixture by distillation. Therefore, the separation equipment is necessary for obtaining higher purities of EG 7 and byproducts.Fundamental knowledge of vapor−liquid equilibrium (VLE) data is essential in the separation process design. On the other hand, because of the high boiling point of the polybasic alcohol, the separation equipment running at low pressure is necessary to decrease energy consumption. So the VLE data about the polybasic alcohols at subatmospheric pressure are very useful in designing the separation process of EG. To our disappointment, up to now, there are few VLE data which are available in published literature about the four binary systems. Therefore, this study focused on isobaric VLE for the binary systems of EG (1) + BDO (2), EG (1) + DEG (2), BDO (1) + DEG (2), and DEG (1)...