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Experimental and kinetic study of (trans)esterification reactions on Lewatit K1221

Evelien Van de Steene (UGent) , Jeriffa De Clercq (UGent) and Joris Thybaut (UGent)
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Abstract
(Trans)esterification reactions play a key role in today’s biorefineries. Conventionally, these reactions are performed using an acid and a base homogeneous catalyst, respectively for esterification and transesterification. Heterogeneous catalysis offers a competitive alternative for these reactions by not requiring dedicated catalyst separation and purification. A single, fixed bed catalytic reactor, comprising a top layer of acid catalyst for esterification of free fatty acids followed by a base catalyst bed for triglyceride transesterification, would allow intensifying present-day biorefinery conversion processes. In the present work, the attention is focused on the acid top layer, for which an acid ion-exchange resin has been considered. Apart from esterification, also acid catalyzed transesterification has been investigated on this resin. A fundamental kinetic model has been constructed to gain detailed insight in the (trans)esterification reactions that will be essential in the intensification of the corresponding biorefinery processes. Acid ion exchange resins have been selected as they are ecofriendly, noncorrosive and have a good stability and reusability. The investigated resin consists of a cross-linked polystyrene matrix with sulfonic acid groups as active sites. Due to its particular structure, the resin exhibits a remarkable swelling phenomenon when in contact with a polar solvent. Since an excess of methanol is used as (trans)esterification agent and water is formed by esterification, the resin is swollen during the reaction. The resin’s swelling determines the accessibility of its active sites and, hence, plays a critical role in the finally observed reaction kinetics. An experimental investigation of the temperature effect and that of the initial molar ratio of acetic acid and methanol for esterification and of ethyl acetate and methanol for transesterification, both catalyzed by Lewatit K1221, was performed. The experimental data have been adequately modelled using an Eley-Rideal reaction mechanism. Exchange between protonated methanol, which was assumed to, initially, occupy all active sites, and the acid or ester in esterification and transesterification, respectively, was explicitly accounted for. While the activation energy was determined at 49 kJ mol-1, irrespective of the reaction type, the difference in catalytic activity, is found back in the value for the rate coefficient, which is about 1 order of magnitude higher for esterification than for transesterification. A unique set of exchange coefficients was obtained, irrespective of the considered reaction, which indicates the model’s adequacy. Throughout the experimentation at 333 K and using an initial molar ratio 10:1, the catalyst’s active sites were found to be occupied by methanol for at least 60%.

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Citation

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Chicago
Van de Steene, Evelien, Jeriffa De Clercq, and Joris Thybaut. 2013. “Experimental and Kinetic Study of (trans)esterification Reactions on Lewatit K1221.” In Renewable Resources and Biorefineries 9, Abstracts, 153–154.
APA
Van de Steene, E., De Clercq, J., & Thybaut, J. (2013). Experimental and kinetic study of (trans)esterification reactions on Lewatit K1221. Renewable Resources and Biorefineries 9, Abstracts (pp. 153–154). Presented at the 9th International conference on Renewable Resources and Biorefineries (RRB-9).
Vancouver
1.
Van de Steene E, De Clercq J, Thybaut J. Experimental and kinetic study of (trans)esterification reactions on Lewatit K1221. Renewable Resources and Biorefineries 9, Abstracts. 2013. p. 153–4.
MLA
Van de Steene, Evelien, Jeriffa De Clercq, and Joris Thybaut. “Experimental and Kinetic Study of (trans)esterification Reactions on Lewatit K1221.” Renewable Resources and Biorefineries 9, Abstracts. 2013. 153–154. Print.
@inproceedings{3109874,
  abstract     = {(Trans)esterification reactions play a key role in today{\textquoteright}s biorefineries. Conventionally, these reactions are performed using an acid and a base homogeneous catalyst, respectively for esterification and transesterification.  Heterogeneous catalysis offers a competitive alternative for these reactions by not requiring dedicated catalyst separation and purification. A single, fixed bed catalytic reactor, comprising a top layer of acid catalyst for esterification of free fatty acids followed by a base catalyst bed for triglyceride transesterification, would allow intensifying present-day biorefinery conversion processes. In the present work, the attention is focused on the acid top layer, for which an acid ion-exchange resin has been considered. Apart from esterification, also acid catalyzed transesterification has been investigated on this resin. A fundamental kinetic model has been constructed to gain detailed insight in the (trans)esterification reactions that will be essential in the intensification of the corresponding biorefinery processes. Acid ion exchange resins have been selected as they are ecofriendly, noncorrosive and have a good stability and reusability. The investigated resin consists of a cross-linked polystyrene matrix with sulfonic acid groups as active sites. Due to its particular structure, the resin exhibits a remarkable swelling phenomenon when in contact with a polar solvent. Since an excess of methanol is used as (trans)esterification agent and water is formed by esterification, the resin is swollen during the reaction. The resin{\textquoteright}s swelling determines the accessibility of its active sites and, hence, plays a critical role in the finally observed reaction kinetics. An experimental investigation of the temperature effect and that of the initial molar ratio of acetic acid and methanol for esterification and of ethyl acetate and methanol for transesterification, both catalyzed by Lewatit K1221, was performed. The experimental data have been adequately modelled using an Eley-Rideal reaction mechanism. Exchange between protonated methanol, which was assumed to, initially, occupy all active sites, and the acid or ester in esterification and transesterification, respectively, was explicitly accounted for. While the activation energy was determined at 49 kJ mol-1, irrespective of the reaction type, the difference in catalytic activity, is found back in the value for the rate coefficient, which is about 1 order of magnitude higher for esterification than for transesterification. A unique set of exchange coefficients was obtained, irrespective of the considered reaction, which indicates the model{\textquoteright}s adequacy. Throughout the experimentation at 333 K and using an initial molar ratio 10:1, the catalyst{\textquoteright}s active sites were found to be occupied by methanol for at least 60\%.},
  author       = {Van de Steene, Evelien and De Clercq, Jeriffa and Thybaut, Joris},
  booktitle    = {Renewable Resources and Biorefineries 9, Abstracts},
  language     = {eng},
  location     = {Antwerp, Belgium},
  pages        = {153--154},
  title        = {Experimental and kinetic study of (trans)esterification reactions on Lewatit K1221},
  year         = {2013},
}