Isobaric vapor−liquid equilibrium (VLE) data for the two binary systems of {propane-1,2-diol + ethane-1,2-diol and propane-1,2diol + butane-1,2-diol} at p = (10.0, 20.0, and 40.0) kPa have been determined using a modified Rose−Williams still with continuous circulation of both vapor and liquid phases in this work. The thermodynamic consistency tests of the experimental VLE data were performed according to the methods of the Herington area test and Van Ness point test. The experimental isobaric VLE data were then correlated using the universal quasichemical (UNIQUAC), nonrandom two-liquid (NRTL), Margules, and Wilson activity coefficient models. Consequently, the calculation values showed good agreements with the experimental data measured in this study.

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)...