Outstanding performance of rehydrated Mg-Al hydrotalcites as heterogeneous methanolysis catalysts for the synthesis of biodiesel
Fecha
2018Autor
Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión aceptada / Onetsi den bertsioa
Identificador del proyecto
Impacto
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10.1016/j.fuel.2017.09.061
Resumen
There is still a need for active, selective and stable heterogeneous catalysts for the synthesis of biodiesel. In this work, magnesium-aluminium hydrotalcites with Mg/Al molar ratios within the 1.5–5 range were synthesized by coprecipitation and used as transesterification catalysts for the synthesis of biodiesel. The mixed oxides obtained after calcination recovered the hydrotalcite structure in ...
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There is still a need for active, selective and stable heterogeneous catalysts for the synthesis of biodiesel. In this work, magnesium-aluminium hydrotalcites with Mg/Al molar ratios within the 1.5–5 range were synthesized by coprecipitation and used as transesterification catalysts for the synthesis of biodiesel. The mixed oxides obtained after calcination recovered the hydrotalcite structure in the form of meixnerite after rehydration in boiling water. The solids were characterized by XRD, TGA, N2 adsorption-desorption, and SEM. Basic properties were assessed by means of Hammett indicators and CO2-TPD. Rehydrated materials with the highest Mg/Al ratios showed some distinctive features: low surface area, well defined flake-like crystals, high basicity and strong basic sites with H_ values above 11. They were also the most active catalysts allowing to achieve 51–75% sunflower oil methanolysis conversion after 8 h of reaction under mild conditions (60 °C, 1 atm), methanol/oil molar ratio of 12 using between 2 and 6 wt% of catalyst. The conversion increased up to 96% (92% fatty acid methyl esters yield) using 2 wt% catalyst and methanol/oil molar ratio of 48. Catalyst leaching was not a serious problem with these solids that could be reutilized maintaining very good activities. A general accordance between solids basic properties and their catalytic performance has been observed. These results are among the best reported in the literature for heterogeneous methanolysis catalysts and have been attributed to the high basicity of the rehydrated solids and the presence of strong and accessible basic sites probably consisting in interlayer hydroxide anions at the edges of the crystals. [--]
Materias
Biodiesel,
Hydrotalcites,
Methanolysis,
Rehydration,
Transesterification
Editor
Elsevier
Publicado en
Fuel 211 (2018), 173–181
Departamento
Universidad Pública de Navarra. Departamento de Química Aplicada /
Nafarroako Unibertsitate Publikoa. Kimika Aplikatua Saila /
Universidad Pública de Navarra/Nafarroako Unibertsitate Publikoa. Institute for Advanced Materials and Mathematics - INAMAT2
Versión del editor
Entidades Financiadoras
The authors thank the Spanish Ministerio de Economía y Competitividad (MINECO), the former Ministerio de Ciencia e Innovación (prj. refs. TRACE, TRA2009_0265 and ENE2015-66975-C3-1-R) and the European Regional Development Fund (ERDF/FEDER) for the financial support. MINECO and FEDER are also acknowledged for the pre-doctoral aid awarded to Ainara Moral (Ref. num. BES-2013-062799) funded under the ENE2015-66975-C3-1-R project (“Structured Catalytic Systems for Biofuels Production”). J.E., O.S. and M.M. acknowledge the Basque Government (IT1069-16) and the Spanish MINECO/FEDER (ENE2015-66975-C3-3-R and CTQ2015-73901-JIN) for the financial support.