Absorption of Volatile Organic Compounds in Biodiesel: Determination of Infinite Dilution Activity Coefficients by Headspace Gas Chromatography

Abstract

It has been reported in previous work, that biodiesel (rapeseed oil methyl ester) is a highboiling solvent well-suited for VOC (volatile organic compound) absorption. In order to use biodiesel effectively as an absorption solvent for a specific waste gas problem, it is important to determine the activity coefficients, at infinite dilution, of the VOCs to be separated with biodiesel. Here, a detailed investigation of VLE (vapor–liquid-equilibrium) of three volatile organic compounds of industrial significance, benzene, toluene and 1,2-dichloroethane (1,2-DCE) has been carried out in order to determine their infinite dilution activity coefficients in biodiesel. Biodiesel is a methanol transesterificated product of rape seed oil, and as a natural product exhibits regional differences in composition. There is, therefore, a need to characterize the material. Accordingly molar mass of biodiesel was determined and commercial available biodiesel types, winter biodiesel with volatile additives and summer biodiesel without volatile additives, were discussed from the point of view of a scrubbing process. Gas chromatography (GC) and Head Space GC techniques were employed. The molar mass of biodiesel has been determined as 294.86 kg kmol−1. The infinite dilution activity coefficients compare well with the data from previous work and the UNIFAC predictions representative for methyl oleate, which is the major component in biodiesel.