chapter one the estimation of physical properties

PURE COMPONENT CONSTANTS
2.18 CHAPTER TWO
The estimates from Eqs. (2-2.10) to (2-2.12) are
Tc
477.67/[0.5851 0.1120 0.0145] 699.8 K
P [0.1285 0.1121 0.1375]
c
2
42.2 bar
3 1
Vc
25.1 353.7 378.8 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
Tc
Difference 703.0 699.8 3.2 K or 0.5%
P Difference 43.0 42.2 0.8 bar or 1.8%
c
If Marrero and Pardillo’s recommended method for estimating T b is used (Eq. 2-4.5),
the result for T c is 700.6, an error of 0.3% which is more accurate than with the
experimental T b .
Example 2-7
method.
Estimate T c , P c , and V c for the four butanols using Marrero and Pardillo’s
solution
The Atom/Group Pairs for the butanols are:
Pair # Atom/Group Pair 1-butanol
2-methyl-
1-propanol
2-methyl-
2-propanol
2-butanol
2 CH 3 —&—CH 2 — 1 0 0 1
3 CH 3 —&CH— 0 2 0 1
4 CH 3 —&C 0 0 3 0
29 —CH 2 —&—CH 2 — 2 0 0 0
30 —CH 2 —&CH— 0 1 0 1
42 —CH 2 —&—OH 1 1 0 0
63 CH— & —OH 0 0 0 1
80 C &—OH 0 0 1 0
Using values of group contributions from Table 2-5 and experimental values from
Appendix A, the results are:
Property/Butanol
1-butanol
2-methyl-
1-propanol
2-methyl-
2-propanol
2-butanol
T c ,K
Experimental 563.05 547.78 506.21 536.05
Calculated (Exp T b ) a 560.64 549.33 513.80 538.87
Abs. percent Err. (Exp T b ) a 0.43 0.28 1.50 0.53
Calculated (Est T b ) b 560.40 558.52 504.56 533.93
Abs. percent Err. (Est T b ) b 0.47 1.96 0.33 0.40
P c , bar
Experimental 44.23 43.00 39.73 41.79
Calculated 44.85 45.07 41.38 43.40
Abs. percent Err. 1.41 4.81 4.14 3.86
V c ,cm 3 mol 1
Experimental 275.0 273.0 275.0 269.0
Calculated 272.1 267.2 275.0 277.8
Abs. percent Err. 1.07 2.14 0.01 3.26
a
Calculated with Eq [2-2.10] using T b from Appendix A.
b
Calculated with Eq [2-2.10] using T b estimated with Marrero / Pardillo method Eq. (2-4.5).
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