Kinetic Study of Neem Biodiesel Production.
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Date
2013-10
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Abstract
Aims: The kinetic features of neem biodiesel production were studied to establish
the conversion parameters that govern optimal product yield in minimum reaction span.
The mechanistic features of the dual acid/base catalytic conversion were investigated to
gain an insight into the influence of methoxide nucleophilic attack and catalytic restoration
on reaction yield in the final stage.
Study Design: The reaction kinetics was investigated by UV-Vis absorption
spectrophotometry. Neem biodiesel was extracted from neem oil via a two-stage chemical
process. The neem oil feedstock is comparatively high in free fatty acids and its reduction
is facilitated by an initial acid-catalysed pre-treatment. The second stage constitutes basecatalyzed
transesterification to neem biodiesel and the glycerol by-product at 55ºC. The
kinetic study focused on the second stage, which is underexplored with neem oil.
Place and Duration of Study: Chemistry Department, Arts and Sciences, The Petroleum
Institute, Abu Dhabi, UAE.
Methodology: Suitable time intervals were selected to monitor the transesterification, and
the absorbances of the resulting biodiesel were recorded in the far visible region at
700 nm (max.).
Results: It was found that the base-catalyzed reaction is rapid (<300 s) at the stipulated
temperature and reaches completion after significant conversion to the biodiesel product.
Absorbances were recorded after 1-minute cooling in an ice-water bath. Graphical
delineation of the results revealed that the transesterification step conforms to zero-order
kinetics. The difficulty encountered in making measurements was the fluctuating absorbances due to the separation of the phases – the rising biodiesel and the sinking
glycerol.
Conclusion: The purpose of this study assists in defining the rate determining stage
associated with the process. The biodiesel yield is 65% and inhibition of the reaction at
lower temperatures or introduction of an inhibitor could be considered to prolong the final
stage to acquire improved biodiesel yields.
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Keywords
Neem biodiesel, kinetics, mechanistic features, reaction order, spectrophotometry
Citation
Elkadi M, Pillay A E, Manuel J, Stephen S, Khan M Z. Kinetic Study of Neem Biodiesel Production. British Biotechnology Journal. 2013 Oct; 3(4): 500-508.