Heterogeneous Extractive Batch Distillation of Chloroform - Methanol – Water : Feasibility and Experiments

A novel heterogeneous extractive distillation process is considered for separating the azeotropic mixture chloroform – methanol in a batch rectifying column, including for the first time an experimental validation of the process. Heterogeneous heavy entrainer water is selected inducing an unstable ternary heteroazeotrope and a saddle binary heteroazeotrope with chloroform (ternary diagram class 2.1-2b). Unlike to well-known heterogeneous azeotropic distillation process and thanks to continuous water feeding at the column top, the saddle binary heteroazeotrope chloroform – water is obtained at the column top, condensed and further split into the liquid – liquid decanter where the chloroform-rich phase is drawn as distillate. First, feasibility analysis is carried out by using a simplified differential model in the extractive section for determining the proper range of the entrainer flowrate and the reflux ratio. The operating conditions and reflux policy are validated by rigorous simulation with ProSim Batch Column® where technical features of a bench scale distillation column have been described. Six reproducible experiments are run in the bench scale column matching the simulated operating conditions with two sequentially increasing reflux ratio values. Simulation and experiments agree well. With an average molar purity higher than 99%, more than 85% of recovery yield was obtained for chloroform and methanol

Stratification strength and light climate explain variation in chlorophyll a at the continental scale in a European multilake survey in a heatwave summer

To determine the drivers of phytoplankton biomass, we collected standardized morphometric, physical, and biological data in 230 lakes across the Mediterranean, Continental, and Boreal climatic zones of the European continent. Multilinear regression models tested on this snapshot of mostly eutrophic lakes (median total phosphorus [TP] = 0.06 and total nitrogen [TN] = 0.7 mg L−1), and its subsets (2 depth types and 3 climatic zones), show that light climate and stratification strength were the most significant explanatory variables for chlorophyll a (Chl a) variance. TN was a significant predictor for phytoplankton biomass for shallow and continental lakes, while TP never appeared as an explanatory variable, suggesting that under high TP, light, which partially controls stratification strength, becomes limiting for phytoplankton development. Mediterranean lakes were the warmest yet most weakly stratified and had significantly less Chl a than Boreal lakes, where the temperature anomaly from the long-term average, during a summer heatwave was the highest (+4°C) and showed a significant, exponential relationship with stratification strength. This European survey represents a summer snapshot of phytoplankton biomass and its drivers, and lends support that light and stratification metrics, which are both affected by climate change, are better predictors for phytoplankton biomass in nutrient-rich lakes than nutrient concentrations and surface temperature

Thermodynamic Insights on the Feasibility of Homogeneous Batch Extractive Distillation. 4. Azeotropic Mixtures with Intermediate Boiling Entrainer

This paper shows how knowledge of the univolatility and nidistribution line location and residue curve analysis help to assess the feasibility of batch extractive rectifying or stripping distillation of azeotropic mixtures by using an intermediate boiling entrainer. We consider five minimum boiling (minT) azeotropic mixtures AB with entrainer E, namely, acetone−heptane with benzene, methanol−toluene with triethylamine, methyl acetate−cyclohexane with carbon tetrachloride, dichloromethane−ethanol with acetone, and ethyl acetate−heptane with benzene; and one maximum boiling (maxT) azeotropic mixture, namely, chloroform−ethyl acetate with either 2-chlorobutane, isobutylchloride, bromopropane, or bromochloromethane. All ternary diagrams A−B−E belong to the 1.0-1b class, for which all three possible univolatility, !AB, !BE, and !AE, and unidistribution lines, KA, KB, and KE can exist. With application of the general feasibility criterion of Rodriguez-Donis et al. (Ind. Eng. Chem. Res. 2009, 48 (7), 3544−3559), both azeotropic components, A and B, accomplish the criterion, and they can be recovered, A in an extractive rectifier and B in an extractive stripper. The process efficiency of each alternative depends strongly on the location of the !AB univolatility line interception with the triangle edge, and also depends on the !BE (!AE) in the minT (maxT) case and of the unidistribution line KE closeness to the (E−B) (A−E) edge. Besides, choice of the rectification of A instead of the stripping of B is set by the ratio of !AE/!BE, the ratio of relative volatility variation of the binary mixtures between A or B and E

Thermodynamic Insights on the Feasibility of Homogeneous Batch Extractive Distillation. 2. Low-Relative-Volatility Binary Mixtures with Heavy Entrainer.

All former studies reported that the separation of the low relative volatility binary mixture by using a heavy entrainer in a batch rectifier imposed the obligatory withdrawal of the most volatile original component. In this paper, we demonstrate that this does not always happen and that the product sequence can be unambiguously determined from the sole analysis of thermodynamic properties of residue curve maps and the occurrence of unidistribution lines and univolatility lines, following the general feasibility criterion enounced in part I for the separation of azeotropic mixtures using heavy or light entrainers. For low relative volatility mixtures, the original component having an intermediate boiling temperature can be also drawn as the first distillate product. Cases concerning 94% of statistically occuring zeotropic ternary mixtures are investigated, allowing to define the product sequence without any previous calculation of the liquid composition profile inside the column. Preliminary feasibility results are confirmed by computing maps of extractive and rectifying liquid composition profiles using a simplified mass balance. Final validation is done via rigourous simulation using ProSim Batch software

Thermodynamic Insights on the Feasibility of Homogeneous Batch Extractive Distillation. 1. Azeotropic Mixtures with Heavy Entrainer.

Feasibility assessment of batch homogeneous extractive distillation for the separation of an A-B mixture feeding entrainer E traditionally relies on the systematic computation of rectifying and extractive composition profile maps under various reflux ratio and entrainer flowrate conditions. This is a well-settled methodology for determining the product sequence and the corresponding column configuration. However, we show that all related literature examples can be simply explained by using thermodynamic insights of residue curve maps, in particular, the unidistribution and univolatility curves. A general feasibility criterion at infinite reflux is proposed and finite reflux operation is also discussed. Illustration is provided for the most common cases, namely the separation with a heavy entrainer of minimum boiling (class 1.0-1a) and maximum boiling azeotropes (class 1.0-2). New cases not published so far are presented and operating conditions are also discussed. These results demonstrate the obligatory incorporation of the univolatility lines for explaining the unexpected behaviour of some particular ternary mixtures to be separated by the homogeneous extractive distillation proces