Preparation, characterization and catalytic activity towards green reactions of sulfonic functionalized SBA-15
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Preparation, characterization and catalytic activity towards green reactions of sulfonic functionalized SBA-15 Elena I. Basaldella · M. Soledad Legnoverde · Ignacio Jiménez-Morales · Enrique Rodríguez-Castellón · Bruno O. Dalla Costa · Carlos A. Querini
Received: 1 October 2010 / Accepted: 28 February 2011 / Published online: 18 March 2011 © Springer Science+Business Media, LLC 2011
Abstract Acidic heterogeneous catalysts based on the anchorage of sulfonic groups on SBA-15 mesoporous silica were synthesized. In a first synthesis step, samples containing mercapto groups were prepared by co-condensation of tetraethylorthosilicate with 3-mercaptopropyltrimethoxysilane, in presence of ethylene-propylene block copolymer as mesoporous silica structure director. In other samples, mercapto groups were introduced by post-functionalization of the traditional calcined SBA-15. In a second step, these mercapto groups were oxidized in order to get sulfonic acid groups on the surface. Characterization of the samples was carried out by N2 adsorption-desorption, FTIR, XPS and acid-base titration. Spectroscopic techniques showed that the effective incorporation of sulfonic groups depends on the synthesis methodology used. In turn, the SBA-15 post-
synthesis functionalization produces changes in structural characteristics like a decrease in BET surface and changes in the pore size distribution. The as-prepared materials were tested as acid catalysts in the alkylation of isobutane with 1-butene, and in the esterification of free fatty acids with methanol. The results obtained show a lack of activity in the alkylation reaction which can be associated with the formation and stabilization of the intermediate carbocation species. Keywords Mesoporous silica · SBA-15 · Functionalization · Sulfonation · Acid catalysts · Alkylation · Esterification
1 Introduction E.I. Basaldella () · M.S. Legnoverde Centro de Investigación y Desarrollo en Ciencias Aplicadas Dr. J.J. Ronco (CINDECA), Universidad Nacional de La Plata, CCT-La Plata CONICET, CIC, 47 No 257, 1900 La Plata, Argentina e-mail: [email protected] E.I. Basaldella · M.S. Legnoverde Departamento de Ingeniería Química, Facultad Regional La Plata, Universidad Tecnológica Nacional, 124 y 60, 1900 La Plata, Argentina I. Jiménez-Morales · E. Rodríguez-Castellón Departamento de Química Inorgánica, Unidad Asociada al Instituto de Catálisis (CSIC), Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain B.O. Dalla Costa · C.A. Querini Instituto de Investigaciones en Catálisis y Petroquímica (INCAPE), CONICET, Facultad de Ingeniería Química, Universidad Nacional del Litoral, (UNL), Santiago del Estero 2654, S3000AOJ, Santa Fe, Argentina
Synthesis of chemical products of great industrial importance often leads to the use of mineral acids as homogeneous catalysts. This type of synthesis presents as main drawback, the generation of considerable amounts of toxic residues. Consequently, in recent years there has been developed a great interest in the study of organic transformations
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