Absorption of hydrophobic volatile organic compounds in renewable vegetable oils and esterified fatty acids: Determination of gas-liquid partitioning coefficients as a function of temperature

Air scrubbing is an effective technology to treat industrial polluted air loaded with VOCs. Water is the most widely used absorbent liquid, but when hydrophobic pollutants are treated, mass transfer between the gas phase and the liquid phase is limited. Therefore, organic solvents are an attractive option to improve the removal efficiency of hydrophobic VOCs. In this study, four esterified fatty acids (isopropyl isostearate, isopropyl laurate, isopropyl myristate and methyl oleate) and three vegetable oils (corn oil, peanut oil and sunflower oil) were evaluated as suitable absorption liquids for seven hydrophobic VOCs, i.e., toluene, m-xylene, ethylbenzene, butane, pentane, hexane and heptane. In addition, one synthetic silicone oil (polydimethylsiloxane) was used as a reference absorption liquid. Dimensionless gas-liquid partitioning coefficients (KGL, 1.3x10-4 - 2.4x10- 2) were determined as a function of temperature (25-50 degrees C) by an optimized dynamic absorption method (DynAb) using Selected-Ion Flow Tube Mass Spectrometry (SIFT-MS). Our experimental results show that, in all the absorption liquids tested, the lowest KGL coefficients were obtained for m-xylene + ethylbenzene, followed by toluene. Isopropyl myristate was found to be the most efficient liquid to absorb the target VOCs, except for heptane where methyl oleate was better. Knowledge of the KGL coefficients of hydrophobic VOCs in these absorption liquids is crucial for process optimization and modeling. Moreover, the effect of temperature is relevant for industrial applications where KGL temperature dependence relations are often lacking. This study evaluates for the first time the use of three renewable vegetable oils and four esterified fatty acids as pure solvents for the absorption of industrially widely used hydrophobic VOCs, where except for toluene, very little or no research had been carried out.