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Esterification and transesterification using modified-zirconia catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
43282 45961 2008 8 PDF Available
Title
Esterification and transesterification using modified-zirconia catalysts
Abstract

In this paper, modified zirconias (WZ, SZ, and TiZ) have been extensively compared under the same reaction conditions as catalysts for both the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the catalyzed rate of hydrolysis/esterification + transesterification of triglycerides has been quantified and compared to that of the rate of simultaneous esterification of FFAs present in the same reaction mixture. Tricaprylin and caprylic acid were used as representative compounds for the comparison of the catalyst for transesterification and esterification since they give reaction rates related to those of larger TGs and FFAs typically present in vegetable oils and animal fats. For the measurement of the kinetics for the simultaneous reaction of a TG-FFA mixture, the reaction of tricaprylin and oleic acid with ethanol was studied using the most promising of the Zr-based catalysts, WZ. Reaction was carried out in a well-mixed batch reactor under mild conditions (75–120 °C). TiZ, while more active than WZ for transesterification, had by far the lowest activity for esterification. SZ, while the most active catalyst (on a weight basis) for both transesterification and esterification reactions, exhibited significant sulfur loss, which greatly reduced its long term activity. As expected, esterification occurred at a much faster rate than transesterification. However, under simultaneous reaction conditions, by virtue of the water being produced in esterification and hydrolysis of the TG taking place, the conversion of the triglycerides to ester products was greatly increased. The resulting caprylic acid from hydrolysis did not accumulate in the reaction mixture due to its rapid esterification to ethyl caprylate. The activity results for WZ indicate how biodiesel can be efficiently produced from free-fatty-acid-containing feedstocks using a solid-acid-catalyzed pre-esterification step, and how a significant fraction of the triglycerides can also be converted at the same time assisted by initial hydrolysis with byproduct water from esterification.

Graphical abstractIn this work, the activities of titania zirconia (TiZ), sulfated zirconia (SZ), and tungstated zirconia (WZ) were investigated for the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the rate of hydrolysis/esterification + transesterification of triglycerides was quantified and compared to that of the rate of esterification of FFAs present in the same reaction mixture. Simultaneous reaction on tungstated zirconia of a mixture of oleic acid and of tricaprylin with ethanol at different reaction temperatures: (a) ethyl oleate yield, (b) ethyl caprylate yield.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Biodiesel; Esterification; Transesterification; Solid acid catalyst; Sulfated zirconia; Tungstated zirconia; Titania zirconia
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Esterification and transesterification using modified-zirconia catalysts
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 339, Issue 1, 15 April 2008, Pages 76–83
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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Any Questions? feel free to contact us