Separation of organosulfur compounds from heptane by liquid–liquid extraction with tricyanomethanide based ionic liquids. Experimental data and NRTL correlation

Abstract

This work is an attempt to determine appropriate solvents for extractive desulfurization, which is the dominant alternative to the risky and expensive solution, which is hydrodesulfurization (HDS). The main part of this research is the study on (liquid + liquid) phase equilibria in {IL (1) + heptane, or thiophene, or 2-methylthiophene, or benzothiophene (2) binary systems and {IL (1) + thiophene/2-methylthiophene/benzothiophene (2) + heptane (3)} ternary system. In this work, five new synthesized tricyanomethanide – based ILs that is: N-(3-cyanopropyl)-N-methylmorpholinium tricyanomethanide, [Mo1,3CN][TCM], N-(3-hydroxypropyl)-N-methylmorpholinium tricyanomethanide, [Mo1,3OH][TCM], N-(3-cyanopropyl)pyridinium tricyanomethanide, [Py3CN][TCM], N-(3-hydroxypropyl)pyridinium tricyanomethanide, [Py3OH][TCM], N-(2-hydroxyethyl)pyridinium tricyanomethanide, [Py2OH][TCM] are analyzed as an extractant in desulfurization of model fuel. Based on the experimental ternary LLE data, the selectivity and solute distribution ratio are calculated and used to determine the efficiency of the tested ILs as solvents for the extraction of sulfur compounds from model fuel. The experimental results have been compared to literature data for other tricyanomethanide-based ILs and were discussed in terms of the selectivity and solute distribution ratio of separation of related systems. The NRTL equation was successfully used to correlate the LLE in binary systems as well as the experimental tie-lines.