Abstract:
The activity coefficients at infinite dilution ( γ13 ) were calculated for alkanes, alkenes,
cycloalkanes, alkynes, ketones, alcohols and aromatic compounds from gas liquid
chromatography (glc) measurements at three temperatures (303.15 and 313.15 and 323.15) K.
The γ13 values were calculated from the retention data for two ionic liquids (ILs) with the
same cation but different anions. The ionic liquids: [methyltrioctylammonium
bis(trifluoromethylsulfonyl)imide and methyltrioctylammonium thiosalicylate] were used as
the stationary phase. The γ13
data for methyltrioctylammonium thiosalicylate were higher
than for methyltrioctylammonium bis(trifluoromethylsulfonyl)imide.
For each temperature and each ionic liquid, γ13
values were determined for two columns and
the average γ13
values were used for the calculation of the partial molar excess enthalpies at
infinite dilution, H E
1 Δ , using the Gibbs-Helmholtz equation. Graphs of In γ13
vs 1/T were
plotted to determine H E
1 Δ at T = 303.15 K. The selectivity, S12 , value for the
hexane/benzene separation was calculated from the ratio of the avarage γ13
values to
determine the suitability of the ILs as an entrainer for extractive distillation in the separation
of aromatic and aliphatic compounds.The S12
values were also compared to the literature
values for other ionic liquids. It was found that the longer chain alkyl group attached to the
cation or anion gave lower S12 values. Both ILs have S12 values greater than one and in
theory can be used as an entrainer for the hexane/ benzene separation. The capacities at
infinite dilutions, k1
, were also calculated from the inverse of the avarage γ13
values for each
IL at each temperature.
Description:
Dissertation submitted in fulfilment of the requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2009.
