A8.1.1 This practice is for conversion of the actual distillation temperature obtained at sub-ambient pressure to AET corresponding to the equivalent boiling point at atmospheric pressure, 101.3 kPa (760 mm Hg), by means of equations derived by Maxwell and Bonnell.10
A8.2.1 Final data on atmospheric equivalent temperatures are to be obtained by computation. Tables 3-5 are provided only as a guide in estimating the AET during distillation.
A8.3.1 Convert observed vapor temperature to atmospheric equivalent temperature using Eq A8.1:
10 Maxwell and Bonnell, Industrial Engineering Chemistry, Vol 49, 1957, p. 1187.
AET = atmospheric equivalent temperature, °C, and T = observed vapor temperature, °C.
= 5.143222 - 0.972546 log10 P A = 2579.329 - 95.76 log10 P (A8.2)
P = operating pressure, kPa, (operating pressure $0.266 kPa), or
= 5.994295 - 0.972546 log10 P A = 2663.129 - 95.76 log10 P (A8.3)
P = operating pressure, mm Hg (operating pressure $2 mm
A8.3.2 The equations are correct only for fractions that have a Watson ^-factor of 12.0 ± 0.2. The ^-factor shall be assumed to be 12 and any effect of ^-factor ignored unless there is mutual agreement to the contrary.
A8.3.3 If correction is required, calculate the ^-factor using Eq A8.4:
B = mean average boiling point, °C, and D = relative density at 15°C.
A220.127.116.11 By custom, either the mid vapor temperature of the fraction or the mid-point of a gas chromatographic distillation of the fraction can be used for the mean average boiling point. In either case the method must be specified.
A18.104.22.168 An estimate of the ^-factor can be made using Fig. A8.1.
A8.3.4 Calculate the correction to be applied to the AET using Eq A8.5:
Pa = atmospheric pressure, kPa (mm Hg), and Po = observed pressure, kPa (mm Hg).
A22.214.171.124 An estimate of the correction can be made using Fig. A8.2.
Observed vapor pressure
FIG. A8.2 Boiling Point Corrections for K-Factor
Was this article helpful?