US EPA

1462662 

Journal Article 

Synthesis of esters: Development of the rate expression for the Dowex 50 Wx8-400 catalyzed esterification of propionic acid with 1-propanol 

Ali, SH; Tarakmah, A; Merchant, SQ; Al-Sahhaf, T 

2007 

Yes 

Chemical Engineering Science
ISSN: 0009-2509 

62 

12 

3197-3217 

10.1016/j.ces.2007.03.017 

WOS:000247673100010 

http://linkinghub.elsevier.com/retrieve/pii/S0009250907002394
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The kinetics of the esterification reaction of propionic
acid with 1-propanol over the ion-exchange resin Dowex 50Wx8-400 has been studied in this
investigation. Kinetic experiments were conducted using a 1 L Lab-Max system at a stirrer speed
of 900 rpm over a temperature range of 303.15 -333.15 K. The catalyst loading was varied from 10
to 60 g dry cat/L and acid to alcohol molar ratios of 1: 1, 1:2, 1:4, 2:1 and 4:1 were employed.
The equilibrium constants for this reaction were determined in separate experiments at 303.15,
313.15 and 323.15 K. The values were equal to 33.18, 30.62 and 28.37, respectively, with a
standard enthalpy change of reaction of 6.4 kJ/mol. These values show the reaction to be mildly
exothermic. It was found that both external and internal diffusion limitations did not affect the
overall reaction rate. The conversion of propionic acid increased with increasing temperature and
catalyst loading and decreased with increasing initial mote fraction of acid. The increase in
chain length of acid or alcohol or branching had a retarding effect on the conversion. Several
kinetic models were tested to correlate the kinetic data, the pseudo-homogeneous (P-H) model, the
Eley-Rideal (E-R) model, the Langmuir-Hinshelwood (L-H) model, the modified Eley-Rideal (M-E-R)
model and the modified Langmuir-Hinshelwood (M-L-H) model. In all models, the activity
coefficients were estimated using UNIFAC to account for the non-ideal thermodynamic behavior of
reactants and products. A correction factor for the resin affinity for water (alpha) was used in
both M-E-R and M-L-H models. The above models predicted the kinetic behavior of the studied
system with an overall error ranging from 1.65% to 13.32%. Water was found to be more strongly
adsorbed than other species present in the system. The M-E-R model between adsorbed 1-propanol
and non-adsorbed propionic acid which assumes surface reaction as the rate controlling step, with
a equal to 2, was found to be the best model with the least overall error (1.65%). The activation
energy for the esterification was estimated to be 67.3 kJ/mol by this model. (c) 2007 Elsevier
Ltd. All rights reserved. 

batch reactor; catalysis; esterification; kinetics; 1-propyl propionate; reaction engineering