Federico Mohino

Synthesis, characterization and catalytic activity of MCM-41-type mesoporous silicas functionalized with sulfonic acid

This paper reports the results obtained in the synthesis, characterization and catalytic activity of thiol-MCM-41 materials synthesized using an improved method of preparation. This novel method of synthesis includes the partial replacement of the surfactant used previously — hexadecyltrimethylammonium bromide, for a shorter chain surfactant such as dodecyltrimethylammonium bromide. It also includes the use of tetramethylammonium hydroxide (TMAOH) as co-structuring agent instead of NaOH. The materials obtained from this modified gels present a higher order in the channels arrangement confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. These materials incorporates an important amount of thiol groups which can be oxidized with H2O2 in order to obtain the corresponding sulfonic groups, with a very strong acidity. The catalysts so obtained have been tested in the esterification of glycerol with fatty acids — oleic and lauric. The results obtained indicate that the catalysts prepared with mixtures of surfactants are more selective to the monoglycerides than the ones synthesized only with hexadecyltrimethylammonium bromide, probably due to the higher order in the channels packing.

Selective synthesis of fatty monoglycerides by using functionalised mesoporous catalysts

Abstract This work describes the performance of “functionalised ordered mesoporous materials” in the esterification of glycerol with fatty acids, such as lauric and oleic acids. The influence of several properties of the catalysts on their activity and monoglyceride selectivity is discussed. For the MCM-41 structure synthesised by the co-condensation method, the influence of the gel composition, hydrophobicity, nature of the functional group and pore size is presented. The catalytic behaviour of structures like SBA-15, SBA-12 and SBA-2 functionalised with mercaptopropyl groups is also discussed.

Synthesis of MCM-41 materials functionalised with dialkylsilane groups and their catalytic activity in the esterification of glycerol with fatty acids

The synthesis of MCM-41-type materials functionalised with 3-mercaptopropyl(methyl)Si groups has been performed by co-condensation of the corresponding alkoxysilanes and tetramethoxysilane (TMOS), in the presence of CTAB and the amino acid leucine. The materials were oxidised to [CH3,SO3H]-MCM-41, characterised and tested as acid catalysts in the esterification of glycerol with fatty acids as lauric and oleic acids. A comparison with the performance of already reported CH3/SO3H-MCM-41 catalysts is presented.

A novel synthesis route of well ordered, sulfur-bearing MCM-41 catalysts involving mixtures of neutral and cationic surfactants

The effect of the addition of dodecylamine in the direct synthesis of MCM-41 silica bearing propylthiol groups, and using cetyltrimethylammonium bromide as surfactant, is studied. The presence of neutral head groups with shorter chains, helps the propylthiol groups to accommodate better into the micelles improving the nucleation and the pore ordering of this mesoporous material. By further oxidation, SO3H-functionalized heterogeneous catalysts with high activity and selectivity in the esterification of glycerol with fatty acids are obtained.

Synthesis, characterisation and catalytic activity of SO3H-phenyl-MCM-41 materials

Ordered Mesoporous Materials (OMS) functionalised with alkyl sulfonic acid groups have been proved to be efficient esterification catalysts. Among them, materials having MCM-41 type structure exhibit the best performance. In this paper we report the synthesis and characterisation of SO 3 H-phenyl-MCM-41 materials and their catalytic activity in the esterification of glycerol with lauric and oleic acids. We have studied several synthesis parameters: the amount of phenyl groups, the presence of additional methyl groups and the sulfonation procedure of the phenyl gorups. The materials obtained have been characterised by XRD, Elemental Analysis, Nitrogen adsorption, TGA and TEM. Finally, it has been studied the influence of the different synthesis parameters on the behaviour of the catalysts in the mentioned reaction of esterification.

08-P-10-Synthesis and catalytic properties of SO3H-mesoporous materials from gels containing non-ionic surfactants

Publisher Summary This chapter presents the synthesis and catalytic properties of sulfonic acid (SO 3 H)-mesoporous materials from gels containing nonionic surfactants. A variety of mesoporous silicates containing mercaptopropyl groups have been prepared by direct synthesis from gels containing nonionic surfactants. By adjusting several synthesis parameters, thiol-containing SBA-15 have been obtained from gels containing Pluronic 123, whereas a stable material probably related with SBA-12 has been synthesized from Brij 76. These materials possess large surface areas, pore sizes of 3.2 and 1.8 nm, respectively and have been structurally characterized by transmission electron microscopy. The oxidation of the thiol groups with hydrogen peroxide leads to sulfonic acid groups, which have been shown to catalyze the esterification of glycerol with oleic acid. Factors affecting the catalytic performance of these materials are also discussed.

07-P-17-A direct synthesis route to the mesoporous silicate SBA-2 bearing thiol groups

Publisher Summary This chapter presents a direct synthesis route to the mesoporous silicate SBA-2 bearing thiol groups. The mesoporous silicate SBA-2 is prepared in the presence of mercaptopropyltriethoxysilane (MPTES) and gemini surfactants in basic medium. The thiol-containing units are incorporated quantitatively, and at a loading of 10%, MPTES a high degree of structural order is retained, as shown by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Attempts to remove the templates by extraction are successful, and it is possible to oxidize thiol to sulfonic acid groups. The oxidized material containing -SO 3 H groups has been tested in the esterification of fatty acids and in the esterification of glycerol with oleic acid. Factors affecting the catalytic performance of these materials are discussed.