E. Sastre

Synthesis of ordered mesoporous and microporous aluminas: strategies for tailoring texture and aluminum coordination

Organised mesoporous and microporous aluminas have been synthesised by a sol-gel route in non-aqueous media using polyethylene oxide surfactants as directing agents. The use of 1,4-dioxane as solvent enables the control of pore size in mesoporous aluminas. Aluminum coordination is modified by addition of ammonium fluoride, ethyl acetoacetate or triethanolamine to the synthesis gel. The chelating ligands modify the alumina porous structure and generate microporosity.

Ordered assembling of precursors, of colloidal faujasite mediated by a cationic surfactant

The synthesis of ordered microporous materials have been carried out by adding a cationic surfactant, cetyltrimethylammonium bromide, to TMA-containing solutions precursors of colloidal faujasite. The influence of the synthesis temperature on the physicochemical properties and catalytic activity in m-xylene conversion of the calcined samples has been studied. Calcination of the as-made, MCM-41-like samples produces a strong unit cell contraction, and microporosity develops. No FAU structural elements are detected by IR spectroscopy. The reaction rate for m-xylene transformation is much higher than that of conventional Al-MCM-41, but lower than that of USY, whereas the isomerization/disproportionation ratio is close to 10.

Activity enhancement of mesoporous aluminosilicates synthesized from ZSM-5 precursors

Abstract MCM-41-related mesoporous materials have been obtained from solutions precursor of colloidal zeolite ZSM-5. These materials show a catalytic activity in m-xylene isomerization much higher than that of conventional Al-MCM-41, and approach that of ZSM-5. The activity has been found to depend upon the synthesis parameters.

06-P-23 - Improved thermal stability of mesoporous alumina support of catalysts for the isomerization of light paraffins

Publisher Summary This chapter discusses the improved thermal stability of mesoporous alumina support of catalysts for the isomerization of light paraffins. Mesoporous alumina samples have been synthesized using poly(ethylene oxide)-based nonionic surfactants. The effect that the addition of n-alkylamines to the synthesis gel has on the texture and thermal stability of mesoporous aluminas is studied. Textural and structural characterization using nitrogen adsorption, powder X-ray diffraction, 27 Al nuclear magnetic resonance (NMR) and Fourier Transform infrared spectroscopy (FTIR) as well as catalytic n-hexane hydroisomerization tests are performed.

Synthesis optimization of pore size tuned HSO3-(CH2)3-MCM-41 catalysts for glycerol monoesters preparation

A series of high-acidity, tailored pore size, MCM-41 catalysts was prepared and tested for the esterification of glycerol with stearic acid making use of the spontaneous structure swelling occurring at high temperature hydrothermal synthesis. Optimal conditions for surfactant removal, propylthiol post-synthesis grafting and oxidation were found, leading to final sulphur loadings comparable to those of the materials synthesized by co-condensation. A relevant influence of the pore size on the catalytic performance was found, leading to an optimal size of the porous system which maximized the yield to the desired monostearine.

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.

Mesostructured titanium-aluminium mixed oxides synthesized using non-ionic surfactants

Abstract Mesostructured Al-Ti mixed oxides with high surface area and a disordered pore structure have been synthesized by a sol-gel route in the presence of a non-ionic surfactant and a chelating ligand. No segregated TiO 2 phase is detected in these mixed oxides at calcination temperatures up to 700°C for TiO 2 loading ranging form 11 to 26 wt%.

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.

MODELIZATION OF SAPO–37 AND ITS VERIFICATION THROUGH PHYSICOCHEMICAL CHARACTERIZATION AND CHEMICAL REACTIVITY

A topological model for SAPO–37 which includes up to the third coordination sphere, and which fits reported atom distributions has been developed. The model predicts a low proportion of AI(4Si0P) groups, and therefore no large zeolitic domains in SAPO–37 are expected. However, it is shown that samples with the same chemical composition present different framework atom distributions depending on the synthesis procedure. SAPO–37 with different Si content show weaker acidity than USY zeolites; the former being more active for less acid demanding reactions, and less active for reactions needing strong acid sites.