Evaluation of the catalytic activity of oxide nanoparticles synthesized by the polymeric precursor method on biodiesel p
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ovanni Pimenta Mambrini Departamento de Química, Universidade Federal de Viçosa, s/n - Campus Universitário, CEP 36570-000, Viçosa, Minas Gerais, Brazil
Elaine Cristina Paris Embrapa Instrumentação, CEP 13560-970, São Carlos, São Paulo, Brazil
Juliano Aurelio Peres Departamento de Química, Universidade Federal de São Carlos, CEP 13.565-905, São Carlos, São Paulo, Brazil
Luis Alberto Colnago and Caue Ribeiroa) Embrapa Instrumentação, CEP 13560-970, São Carlos, São Paulo, Brazil (Received 28 June 2012; accepted 19 September 2012)
This paper shows a comparison between different nanostructured oxides, obtained by polymeric precursor method, regarding their activity for biodiesel conversion from oil–methanol mixtures. The basicity/acidity and surface area (SA) of the oxides were taken in account to analyze the catalytic activity in the transesterification reaction. The temperature dependence for the heterogeneous catalysts was analyzed, where only CaO showed activities at 70 °C (;98% of conversion), while the other oxides, SnO2, ZnO, TiO2, CaTiO3, were observed active only at 150 °C for the reaction parameters adopted. The results revealed that the highest activity observed is not associated to SA only but mainly with the surface basicity. This suggest that, for oxides synthesized by the polymeric precursor method, the surface basicity surpasses the particle size effects in catalysis in a way to promote the transesterification reaction.
I. INTRODUCTION
Biodiesel is a promising alternative fuel since it can be used in diesel engines without any modification. Furthermore, biodiesel shows interesting properties such as biodegradability, nontoxicity, and renewability. This biofuel is produced by the transesterification reaction of vegetable oils with alcohols, and the most common method to its production is the use of homogeneous catalysts, such as sodium ethoxide or methoxide.1 However, the removal of these catalysts from the final products is not easy because, in case of water presence, soapy fractions are formed as a competitive reaction, which emulsifies the final products with unreacted fractions. The separation in that cases is a very complex process, increasing the cost of the biodiesel processing.2 Then, compared with the commonly applied homogeneous catalysts, heterogeneous catalysts are much more easily separated from the reaction medium, avoid the emulsification, and may be recycled for several runs, implying also lower corrosion in production equipments.3–5 However, the activities of the heterogeneous catalysts are a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.349 3020
J. Mater. Res., Vol. 27, No. 23, Dec 14, 2012
http://journals.cambridge.org
Downloaded: 24 Jan 2015
generally lower than that of a homogeneous catalyst, such as KOH.6 In this way, a great research effort has been performed to obtain an effective heterogeneous catalyst.7–9 Currently, several types of heterogeneous nanocatalysts are explored for the formation of biodiesel, such as ceramic oxides,
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