Experimental measurements for the liquid-liquid equilibrium of ternary systems [(water + methyl oleate + model mixtures of tar (naphthalene, phenanthrene and anthracene)] issued from the biomass gasification process

Abstract

Energy, fuel and chemical production like syngas from biomass is increasingly attracting interest in the world, with increasing potential to replace conventional fossil fuels in the energy market.Biomass gasification has been studied widely as an efficient and sustainable technology for the syngas production.Thus, raw syngas contains a significant quantities of undesirable impurities known as syngas contaminants, especially tar which can cause major problems to the gasification process; therefore it is crucial to eliminate the generated tar in this process by one of the most promising method “the tar scrubbing oil” using a suitable extracting solvent. With this aim, an experimental study of the liquid–liquid equilibrium of the ternary systems of water + solvent (methyl oleate-biodiesel solvent) + model mixtures of tar (naphthalene, phenanthrene and anthracene) that are presented in the raw syngas was conducted at 303.2 K, 323.2 K and 343.2 K. Due to the low solubility of the studied model molecule of tars in the aqueous phase, an extraction of these analytes (naphthalene, phenanthrene and anthracene) from the aqueous phase was performed by an auxiliary solvent (dichloromethane), in which was dissolved an internal standard (hexadecane) before analysis in the GC–MS using the internal standard technique. A control analysis was systematically performed in order to ensure that all of the solute was extracted from the aqueous phase. As for the analysis of the organic phase, it was carried out in the GC–MS using the internal standard technique without any prior extraction. Coulometric Karl Fischer (KF) titration was used to quantify water in the organic phase. Partition coefficient and selectivity of the biodiesel solvent were also discussed. This work is followed by a modeling study of the same systems using the nonrandom two-liquid (NRTL) and UNIQUAC (universal quasichemical) models.