FIGURE 7 Variations and fitting of as a function of (a) the
mass fraction of sulfuric acid at 23, 40 and 60 °C; (b) 1/T at
different sulfuric acid concentrations
Based on the above analysis, the value of can be calculated. A plot of
versus M c is shown in Figure 8 . At all
temperatures, the experimental data fit well to the resulting straight
line. The values of n and lgk * can be
obtained from the slope and intercept of the fitting line, respectively,
as shown in Table 2 . The value of k *increases with increasing temperature, and the value of n remains
essentially unchanged. n is a specific thermodynamic parameter
that is characteristic of different aromatic compounds, which is
consistent with the conclusions reported in other
studies.18,19,27