chapter one the estimation of physical properties

PURE COMPONENT CONSTANTS
2.6 CHAPTER TWO
Example 2-2 Estimate T c , P c , and V c for 2-ethylphenol by using Constantinou and
Gani’s group method.
solution The First-Order groups for 2-ethylphenol are one CH 3 , four ACH, one
ACCH2, and one ACOH. There are no Second-Order groups (even though the ortho
proximity effect might suggest it) so the First Order and Second Order calculations are
the same. From Appendix Tables C-2 and C-3
Group k N k N k (tc1k) N k (pc1k) N k (vc1k)
CH 3 1 1.6781 0.019904 0.07504
ACH 4 14.9348 0.030168 0.16860
ACCH2 1 10.3239 0.012200 0.10099
ACOH 1 25.9145 0.007444 0.03162
5
NF
k k
k1
52.8513 0.054828 0.37625
T 181.128 ln[52.8513 W(0)] 718.6 K
c
P [0.054828 W(0) 0.10022]
c
2
1.3705 42.97 bar
3 1
Vc
(0.00435 [0.37625 W(0)])1000 371.9 cm mol
The Appendix A values for the critical temperature and pressure are 703.0 K and 43.0
bar. An experimental V c is not available. Thus the differences are
T
c
Difference 703.0 718.6 15.6 K or 2.2%
1
Pc
Difference 43.0 42.97 0.03 kJ mol or 0.1%.
Example 2-3 Estimate T c , P c , and V c for the four butanols using Constantinou and
Gani’s group method
solution
The First- and Second-Order groups for the butanols are:
Groups/Butanol
1-butanol
2-methyl-
1-propanol
2-methyl-
2-propanol
2-butanol
# First-Order groups, N k — — — —
CH 3 1 2 3 2
CH 2 3 1 0 1
CH 0 1 0 1
C 0 0 1 0
OH 1 1 1 1
Second-Order groups, M j — — — —
(CH 3 ) 2 CH 0 1 0 0
(CH 3 ) 3 C 0 0 1 0
CHOH 0 1 0 1
COH 0 0 1 0
Since 1-butanol has no Second-Order group, its calculated results are the same for both
orders. Using values of group contributions from Appendix Tables C-2 and C-3 and
experimental values from Appendix A, the results are:
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