Liquid–Liquid Equilibria for Dipropylene Glycol–Hydrocarbon Binary Systems: Experimental Data and Regression

Abstract

Propylene glycols (mono-and di-) have an important potential as solvents in liquid−liquid extraction of aromatics and in azeotropic distillation. Literature and databases provide few accurate experimental data on liquid−liquid and vapor−liquid equilibria in systems consisting of propylene glycols and hydrocarbons (paraffinic, naphthenic, and aromatic hydrocarbons). However, an increasing interest in this field can be observed in recent years. This paper reports the results of an experimental study on the liquid−liquid equilibria in binary systems consisting of dipropylene glycol and paraffinic, naphthenic, and aromatic hydrocarbons with six, seven, and eight atoms of carbon. The experimental data were obtained in a high-precision thermostatic equilibrium cell. The first and most important result was that all normal paraffinic and naphthenic hydrocarbons are partially miscible with dipropylene glycol (4-oxa-2,6-heptanediol), whereas aromatics are completely dissolved. To obtain the binary interaction parameters of the Non-Random Two-Liquid (NRTL) activity coefficients, a regression procedure was applied to the experimental data (only for normal paraffinic and naphthenic hydrocarbon−dipropylene glycol systems) for each measured system. The NRTL parameters of the partially miscible binaries (complemented by the NRTL parameters for completely miscible binaries) can be subsequently used for simulations of liquid−liquid extraction, solvent recovery, and extractive-distillation processes.

Liquid-liquid Equilibrium Determination and Data Correlation for 2,2,4-trimethyl Pentane - tripropylene Glycol Binary System

“…Liquid-liquid equilibrium determination for the TPG with 2,2,4-trimethylpentane was performed at atmospheric pressure, in a glass equilibrium cell (with volume of 100 cm 3 ) to determine the cloud point, the procedure being similar as described by Nicolae and Oprea [11]. The main compound (the component in high quantity in the mixture), previously weighed is introduced in the equilibrium cell, and the other compound is introduced in the cell with a syringe also previously weighed.…”

“…(7) to write the equations of the activity coefficients of the two components, in both liquid phases, are obtained the expressions of liquid activity coefficients, eq. (8) - (11): 12 12 ( 2 + 1 12 ) 2 ] (8) ln 2 = ( 1 ) 2 [ 12 ( 12 2 + 1 12 ) 2 + 21 21 ( 1 + 2 21 ) 2 ] (9) ln 1 = ( 2 ) 2 [ 21 ( 21 1 + 2 21 ) 2 + 12 12 ( 2 + 1 12 ) 2 ] (10) ln 2 = ( 1 ) 2 [ 12 ( 12 2 + 1 12 ) 2 + 21 21 ( 1 + 2 21 ) 2 ] (11) The parameters 12 , 12 , 21 , 21 are adjustable parameters and are calculated as functions of the binary interaction parameters 12 , 21 , 12 and the temperature T:…”

“…The possibility of using propylene glycols as solvents is studied by a research group from our university. 1,2-propylene glycol was the first solvent studied [10], and the research continued with dipropylene glycol [11][12][13] and with tripropylene glycol [14]. But propylene glycols application as solvents is not limited to aromatics extraction, they can be used for gas dehydration [15] or alcohols extraction as mentioned by Bumbac and Dumitrescu [16].…”

Synthesis and simulation of a distillation columns system for the propylene glycols mixtures separation

“…The propylene glycols have an important potential as solvents in liquid‐liquid extraction of aromatics and in extractive distillation 20,21 . There are recent studies that reports liquid‐liquid equilibrium data for binary systems consisting of DPG with paraffinic, naphthenic, or aromatic hydrocarbons with six, seven, and eight atoms of carbon and vapor‐liquid equilibrium data for binary mixtures formed by DPG with inferior aromatics: benzene, toluene, ethyl benzene, o‐xylene, m‐xylene, and p‐xylene 22,23 . There are several recently published articles in which TPG is used as: solvent in various applications such as the gelation behavior of two ethoxylated emulsifiers, 24 additive addition to diesel fuel 25 liquid desiccant used in industrial dehumidifiers 26 …”