Thermodynamic calculations for Propene
hydrogenation
Sukaran Arora
October 5, 2016
Propene Data
f HCo 3 H6 (g), 298.15 K
o
SC
3 H6 (g), 298.15 K
CP, C3 H6 (g)
20.41
267
5
8 10 T 2 + 0.2173 T
+ 6.6782
kJ/mol
J mol1 K1
J mol1 K1
o
where f HCo 3 H6 (g), 298.15 K is the standard enthalpy of formation at 298.15 K, SC
3 H6 (g), 298.15 K
is the standard entropy of formation at 298.15 K, and CP, C3 H6 (g) is the heat capacity at constant
pressure. The relation for temperature dependence of CP, C3 H6 (g) is obtained by fitting the data
sourced from NIST for CP, C3 H6 (g) between 298.15 K and 800 K.
o
All the above values except SC
(obtained from wiredchemist.com) are obtained from
3 H6 (g), 298.15 K
NIST database. Use the following relations for temperature dependence of f HCo 3 H6 (g) and SCo 3 H6 (g) .
ZT
f HCo 3 H6 (g), T(K) = f HCo 3 H6 (g), 298.15 K +
CP, C3 H6 (g)
298.15
ZT
o
o
SC
= SC
+
3 H6 (g), T(K)
3 H6 (g), 298.15 K
CP, C3 H6 (g)
dT
T
298.15
At T = 723 K, we get the following values.
f HCo 3 H6 (g), 723 K
o
SC
3 H6 (g), 723 K
61.0
347.9
kJ/mol
J mol1 K1
dT
1000
PROPENE DATA
H2 Data
o
f HH
2 (g), 298.15 K
o
SH
2 (g), 298.15 K
A
B
C
D
E
F
G
H
0
130.68
33.07
-11.36
11.43
-2.77
-0.16
-9.99
-172.71
0
kJ/mol
J mol1 K1
All the above values are obtained from NIST database. Using the same relations for temperature
o
o
dependence of f HH
and SH
as above for C3 H6 , at T = 723 K or t = 0.723, we get the
2 (g)
2 (g)
following values.
o
f HH
2 (g), 723 K
o
SH2 (g), 673 K
12.43
156.56
kJ/mol
J mol1 K1
C3 H8 Data
f HCo 3 H8 (g), 298.15 K
o
SC
3 H8 (g), 298.15 K
CP, C3 H8 (g)
-104.7
270
4
1 10 T 2 + 0.2755 T
+ 0.577
kJ/mol
J mol1 K1
J mol1 K1
o
where f HCo 3 H8 (g), 298.15 K is the standard enthalpy of formation at 298.15 K, SC
3 H8 (g), 298.15 K
is the standard entropy of formation at 298.15 K, and CP, C3 H8 (g) is the heat capacity at constant
pressure. The relation for temperature dependence of CP, C3 H8 (g) is obtained by fitting the data
sourced from NIST for CP, C3 H8 (g) between 298.15 K and 800 K.
o
All the above values except SC
(obtained from wiredchemist.com) are obtained from
3 H8 (g), 298.15 K
NIST database. Use the following relations for temperature dependence of f HCo 3 H8 (g) and SCo 3 H8 (g) .
ZT
f HCo 3 H8 (g), T(K) = f HCo 3 H8 (g), 298.15 K +
CP, C3 H8 (g)
298.15
ZT
o
o
SC
= SC
+
3 H8 (g), T(K)
3 H8 (g), 298.15 K
CP, C3 H8 (g)
dT
T
298.15
At T = 723 K, we get the following values.
f HCo 3 H8 (g), 723 K
o
SC
3 H8 (g), 723 K
-56.4
365.9
2
kJ/mol
J mol1 K1
dT
1000
PROPENE DATA
C3 H6 + 2 H2 C3 H8
o
o
o
o
Hrxn,
723 K = f HC3 H8 (g), 723 K f HC3 H6 (g), 723 K 2 f HH2 (g), 723 K
o
o
o
o
Srxn,
723 K = SC3 H8 (g), 723 K SC3 H6 (g), 723 K 2 SH2 (g), 723 K
Substituting values obtained for f H o and S o for C3 H8 , C3 H6 , and H2 , we get the following result.
o
Hrxn,
723 K = 129.8 kJ/mol
o
Srxn, 723 K = 138.6 J mol1 K1
Using the following relation to obtain Gorxn, T(K) .
o
o
Gorxn, T(K) = Hrxn,
T(K) T Srxn, T(K)
Gorxn, 723 K = 129.8 723
138.6
1000
Gorxn, 723 K = 29.7 kJ/mol
Use the following relation to obtain equilibrium constant at 723 K :
Go
rxn/RT
K = exp
+29.71000/(8.314723)
K = exp
K = 138.9
For obtaining the equilibrium conversion for a feed consisting of 100 mL/min of H2 with 1.8 mL/min
of C3 H6 and 1.8 mL/min of Ar used as an internal standard, we write the following equations (at
some conversion x).
pC3 H6 = poC3 H6 (1 x).
!
poH2
o
pH2 = pC3 H6
x = poC3 H6 (55.55 x).
poC3 H6
pC3 H8 = poC3 H6 x.
K=
(pC3 H8 /po )
(pC3 H6 /po ) (pH2 /po )
where po = 1 bar and poC3 H6 = 1.75 kPa.
K=
po
poC3 H6
x
(1 x)(55.55 x)
Solving the above equation gives
x = xeq = 0.99 or 99%.
