Methanolysis of Castor Oil Catalysed by Solid Potassium and Cesium Salts of 12-Tungstophosphoric Acid
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Methanolysis of Castor Oil Catalysed by Solid Potassium and Cesium Salts of 12-Tungstophosphoric Acid A. Zieba Æ L. Matachowski Æ E. Lalik Æ A. Drelinkiewicz
Received: 4 July 2008 / Accepted: 12 September 2008 / Published online: 7 October 2008 Ó Springer Science+Business Media, LLC 2008
Abstract Methanolysis of castor oil to methyl esters, a key step in Biodiesel production, was studied with the use of KOH, H2SO4 and 12-tungstophosphoric acid (H3PW12O40, HPW) as the homogeneous catalysts. Reaction was also performed in the presence of solid salts of HPW, namely MxH3-xPW12O40, where M = K or Cs and x = 2, 2.5 and 3 (abbreviated as K2, K2.5, K3 and Cs2, Cs2.5, Cs3, respectively). The HPW salts were precipitated by K2CO3 and Cs2CO3 or CsCl. Their properties were characterized by BET, electron microscopy (SEM, EDS) and colloidal particles size distribution (laser diffraction technique). The potassium doped HPW samples, K2 and K2.5, prove to be much more active catalysts (ca. 3 times) than their Cs-containing analogues. Among the K, Cs salts, K2 salt was the most active catalyst. The activity of catalysts was found to depend on preparation stages such as the temperature of drying or annealing and aging of the samples. Microscopic studies evidenced colloidal form of Cs and K salts particles under the catalytic reaction. The size of colloidal particles was found to depend upon the type of cation, Cs? or K?, as well as the ‘‘history’’ of catalysts preparation (temperature of drying). Based on the results obtained in this work, we concluded that activity was determined by the accessibility of the reactants to acid sites which is facilitated by the high surface area and open structure of the colloidal form. This may lead to better
The work was presented during the conference Catalysis for Society, Krakow, May 11–15, 2008. A. Zieba L. Matachowski E. Lalik A. Drelinkiewicz (&) Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezpominajek 8, 30-239 Krakow, Poland e-mail: [email protected]
utilization of acid sites and higher activity of samples with lower content of K? or Cs? cations in the HPW. Keywords Biodiesel Transesterification Castor oil Heteropolyacid
1 Introduction The production of biodiesel (fatty acid methyl esters, FAME) as a fuel in diesel engines greatly increased due to its environmental benefits. Biodiesel can be produced from renewable sources like vegetable oils, animal fats and recycled greases (from food industry). In transesterification with methanol (methanolysis), the triglycerides (TG) of fatty acids (C14–C20) are converted into respective fatty acid methyl esters (FAME) and glycerol as a by-product (Scheme 1). Transesterification reaction is catalysed by bases, acids as well as enzymes. The most commonly tested vegetable oils included palm oil, soybean oil, sunflower oil, coconut oil and rapeseed oil. Castor oil derived from Riccinus communis plants is mentioned frequently in the literature as a potential raw material for biodiesel, however its transesteri
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