Proposal for a Viscous Test Mixture—Densities, Viscosities, and Vapor–Liquid Equilibrium Data of the Binary Mixture 2-Methyl-2-butanol + 2-Methyl-1-propanol

Abstract

Standardized test mixtures are needed to determine the effectiveness and efficiency of distillation columns and their internals. Despite the wide range of different test mixtures and the variations in their physical properties, no standard test mixture is available that contributes viscosities above 1.5 mPa s at typical distillation conditions. To investigate the impact of viscosity on separation effectiveness and efficiency and validate models for higher viscosities, a new test mixture is proposed. On the basis of a screening, the binary mixture 2-methyl-2-butanol/2-methyl-1-propanol was chosen, showing liquid phase viscosities up to 5 mPa s and satisfying the requirements for separation efficiency tests. For this mixture, vapor–liquid equilibria were measured from 2 to 95 kPa. A slight negative deviation from ideal behavior is accounted for using the nonrandom two-liquid model. Furthermore, for both pure substances as well as their mixtures liquid densities were determined from 293.15 to 363.15 K and viscosities in a temperature range from 273.15 to 333.15 K. Nonidealities were modeled with a Redlich–Kister approach. Thus, vital information for the assessment of separation efficiency with a new test mixture is given and subsequent studies on the influence of viscosity on fluid dynamics and separation efficiency in distillation columns are enabled.

A New Test System for Distillation Efficiency Experiments at Elevated Liquid Viscosities: Vapor–Liquid Equilibrium and Liquid Viscosity Data for Cyclopentanol + Cyclohexanol

“…Often, distillation efficiency experiments are carried out at total reflux, and the Fenske equation is used for the calculation of distillation column efficiency. To be able to use the Fenske equation, a binary test system has to obey certain rules. ,, Therefore, those rules were considered, in addition to the requirements imposed by the experiments for quantifying the effect of liquid viscosity on distillation efficiency using lab-scale glass columns, to form the following comprehensive set of search criteria. The system must be surface tension neutral. Zuiderwig classified the binary mixtures into positive, negative, and neutral test systems , based on the difference in surface tensions of the pure components in a mixture, at their boiling points.…”

“…Low operating temperatures are achieved by conducting the experiments at vacuum pressures. The lower limit for pressure was set to 2 kPa, as operating the distillation columns below 2 kPa is not a standard case . In addition, sampling becomes extremely difficult at P < 2 kPa.…”

“…19 Bocker and Ronge 20 used chlorobenzene/ethylbenzene with polybutadiene in different concentrations, and conducted distillation experiments to study the effect of viscosity on packed column efficiency. Bradtmoller and Scholl 21 performance. In addition, they noted that, with the use of a polymer, the influence of local viscosity versus bulk viscosity on the change of mass transfer should have been considered.…”

“…Böcker and Ronge used chlorobenzene/ethylbenzene with polybutadiene in different concentrations, and conducted distillation experiments to study the effect of viscosity on packed column efficiency. Bradtmöller and Scholl noted that the accumulation of a nonvolatile component (polybutadiene) added at the vapor–liquid interface would have increased the mass transfer resistance, and might have had an effect on the column performance. In addition, they noted that, with the use of a polymer, the influence of local viscosity versus bulk viscosity on the change of mass transfer should have been considered. , …”

“…Onken and Artl have summarized the properties of the standard test systems for distillation. However, it does not include a test mixture that will have liquid viscosities above 1.5 mPa·s at typical distillation conditions …”