Pailhes method
The Pailhes method is a method for estimating the normal boiling point T B from a known boiling point at a low temperature, the critical pressure P c and a ratio T B / T c , which can be determined from the Lydersen method .
In the case of high-boiling components, the normal boiling point of which cannot be determined experimentally or only with difficulty, the method is primarily used to nevertheless determine this variable, which is important for many estimation methods, at least with some accuracy.
Determining equations
With
is calculated in the original publication as well as the critical pressure P c using the Lydersen method. However, both θ and P c can be determined using other suitable methods.
is a known saturation vapor pressure at a low temperature, often near room temperature .
Sample calculation
The following calculation applies to n -butylacetate (butyl acetate):
According to Lydersen, the following group contributions apply to T c :
- -CH3 / -CH2: 0.020 (atoms 1,5,6,7,8)
- -COO-: 0.047 (atoms 2,3,4)
and for P c :
- -CH3 / -CH2: 0.227
- -COO-: 0.47
This results in
With the molar mass M W = 116.161 g mol −1 , the critical pressure is given by
With P sat = 1.7732 kPa at T sat = 293.65 K this results
With this, all required values are determined and the determining equation can be occupied:
Normal boiling points published in the literature are between T B = 397.65 K and T B = 399.85 K.
See also
literature
- ↑ Pailhes F., "Estimation of the Boiling Temperature at Normal Pressure for Organic Compounds from Their Chemical Formula and a Known Boiling Temperature at Low Pressure", Fluid Phase Equilib., 41, pp. 97-107, 1988.
- ↑ Scheller WA, Torres-Soto AR, Daphtary KJ, "Isothermal Vapor-Liquid Equilibrium Data for the Heptane-Butyl Acetate System at 74.7 ° and 100 ° C", J. Chem. Eng. Data, 14 (1), pp. 17-19, 1969.
- ↑ Dortmund database .