Activity coefficients at infinite dilution for hydrocarbons in furfuryl alcohol at T=(278.15 and 298.15) K, determined by g.l.c.
Introduction
The separation of aromatic from aliphatic compounds is important in oil refineries involved in the production of transport fuels. Highly polar solvents such as sulfolane and N-methyl-pyrrolidinone, which also have low volatility, are used to effect such separation [1]. Furfuryl alcohol (C5H6O2) is a polar solvent with a high boiling point (443.2 K) and low vapour pressure, and as a result, has the potential of being a good solvent for separating aromatic and aliphatic compounds. It is a by-product of the sugar industry, where it is made by the acid hydrolysis of bagasse, followed by oxidation.
In this work, the activity coefficients at infinite dilution were determined using a g.l.c. method for moderately volatile solvents, recently reported by one of the authors [2]. These activity coefficients were used to calculate the selectivity at infinite dilution [3] for the separation of benzene from the alkanes, cycloalkanes, alkenes and alkynes used in this work. The activity coefficients were also used to determine the partial molar excess enthalpy of mixing at infinite dilution. This property gives an indication of the type and magnitude of the interaction between each of the hydrocarbons and furfuryl alcohol. The activity coefficient results are compared to recently reported data [4] on a related set of mixtures involving hydrocarbons in furfural.
Section snippets
Chemicals
The furfuryl alcohol was supplied by Illovo Sugar Company and was distilled before use. The mass fraction purity, as analysed by g.l.c. was found to be better than 0.99. The water content of the furfuryl alcohol was always better than 0.003 mole fraction, as determined by Karl Fisher titration. The solutes used were: pentane, hexane, heptane, cyclopentane, cyclohexane, cycloheptane, hex-1-ene, hept-1-yne, hex-1-yne, hept-1-yne and benzene. They were all supplied by Aldrich. It was unnecessary
Results
The activity coefficients, γ13∞, were determined form the following equation [1]:where the net solute retention volume VN is given byandandHere, pi refers to the carrier gas inlet pressure, po the outlet pressure, J32po the mean column pressure, n3 the amount of liquid solvent on the column, T the column temperature, p1* the saturated vapour pressure of the solute at temperature T, t
Discussion
The large value of γ13∞ for an alkane or a cycloalkane, or an alkene in furfuryl alcohol (table 3) is a reflection of the disparity in polarity between each of the solutes and the solvent. This disparity is also reflected in the large positive values of H1E∞ in table 4. The large endothermic effect for those mixtures is due to the dissociation of the furfuryl alcohol on mixing.
The smaller values of γ13∞ for the alk-1-ynes or benzene in furfuryl alcohol reflects the competition between the
Acknowledgements
The authors thank the National Research Foundation (South Africa) and the Warsaw University of Technology for financial support including travel costs (for M.K. Kozłowska) from Poland to South Africa. The work was partly done under the auspices of a collaborative South Africa–Poland Research agreement.
References (9)
- et al.
J. Chem. Thermodyn.
(2000) - et al.
J. Chem. Thermodyn.
(1993) - et al.
J. Chem. Thermodyn.
(2004) - et al.
J. Chem. Eng. Data
(2002)