QUIZ #13
Nitric oxide and oxygen react to form nitrogen dioxide in a continous adiabatic reactor. The feed
contains NO and O2 in a stoichiometric proportion at 700 °C and a 70 % conversion is achieved. Use
the heat capacities given below to calculate the outlet temperature if the reaction is carried out in a
continous flow reactor.
Data:
Cp(NO2)=75.7 J/mol, Cp(NO) =37.7 J/mol, Cp(O2) =35.7 J/mol
Solution:
NO, O2
NO, O2, NO2
700 °C
T=?
𝑁𝑂 + 1⁄2 𝑂2 → 𝑁𝑂2
Take a basis of 100 moles of feed inlet. Stoichiometric inlet gives 66.7 moles for NO and 33.3 moles
for O2. For 70% conversion, the mole balance yields: NO=20.0, O2=10.0, NO2=46.7.
Find the required values from your book: ∆Hf,NO=90.37 kJ/mol, ∆Hf,NO2=33.8 kJ/mol.
Species
nin
hin (kJ/mol)
nout
hout (kJ/mol)
20.0
90.37 + ∫ (37.7 × 10−3 )𝑑𝑇
700
NO
66.7
𝑇
(37.7 × 10−3 )𝑑𝑇
90.37 + ∫
25
25
700
O2
33.3
0.00 + ∫
𝑇
−3
(35.7 × 10 )𝑑𝑇
10.0
0.00 + ∫ (35.7 × 10−3 )𝑑𝑇
25
25
𝑇
NO2
0
---
46.7
33.8 + ∫ (75.7 × 10−3 )𝑑𝑇
25
Since the reaction is adiabatic, energy balance yields: 𝑛𝑖𝑛 ℎ𝑖𝑛 = 𝑛𝑜𝑢𝑡 ℎ𝑜𝑢𝑡
Solving the above equation yields T=1130 °C.