Synthesis and characterization of catalysts based on mesoporous silica partially hydrophobized for technological applications

Abstract

In this work, mesoporous silica mobil composition of matter no. 41 (MCM-41) was synthesized by the sol-gel method. Two different surface modifications were made to transform this material into a very active adsorbent and catalyst support: (i) impregnation of iron nanoparticles and (ii) hydrophobization via chemical vapor deposition (CVD) with ethanol. The materials prepared with different iron contents, i.e., 2.5, 5, and 10 %, after hydrophobization, were characterized by several techniques. CHN analysis and Raman spectroscopy proved that approximately 15 % of carbon is deposited during CVD process mainly as organized carbonaceous structures. The specific surface area was determined by the BET method as up to 1080 m g, which explains the excellent results of the materials in the adsorption of model dyes methylene blue and indigo carmine. Mössbauer spectroscopy, thermogravimetric (TG)/DTG analysis, and transmission electron microscopy (TEM) images showed that the iron supported may be partially reduced during the CVD process to Fe species, which are stabilized by the carbon coating. This iron species plays an important role in the oxidation of different contaminants, such as quinoline and methylene blue. The results obtained in the catalytic tests showed to be very promising.

Amine-Functionalized Mesoporous Silica as a Support for on-Demand Release of Copper in the A3-Coupling Reaction: Ultralow Concentration Catalysis and Confinement Effect

“…The catalyst synthesis process is summarized in Figure and detailed in the Experimental Section. The methodology for making MCM-41 has been previously reported by us (the Moura group) and is an adaptation of the Grün method, which is a modification of the original method by Kresge and Beck in 1992. , The modification of silica with silane coupling agents was inspired by the method reported by the Resasco group, which is carried out at room temperature, unlike reflux methods found in the literature. , Post-synthetic functionalization was chosen to ensure the shape and size homogeneity of the pores, but there are other methods where the organosilane reagent is added during the synthesis of the material and co-condensed within the inorganic network. The co-condensation method gives a more homogeneous distribution of the organic groups through the surface of the support, but it compromises the regularity of the porous structure .…”

“…The catalyst synthesis process is summarized in Figure 1 and detailed in the Experimental Section. The methodology for making MCM-41 has been previously reported by us (the Moura group 60 ) and is an adaptation of the Grun method, 61 which is a modification of the original method by Kresge and Beck in 1992. 62,63 The modification of silica with silane coupling agents was inspired by the method reported by the Resasco group, 64 which is carried out at room temperature, unlike reflux methods found in the literature.…”

“…MCM-41 was synthesized according to a procedure described by us (Moura) in a previous report. 60 The functionalization was carried out by modifying a method used by Zapata et al 64 Initially, a suspension containing 0.5 g of parent MCM-41 in 10 mL of dry toluene was prepared in a polypropylene tube and sonicated for 1 h. Then 25 mL of a (3-aminopropyl)trimethoxysilane (APTMS) solution in dry toluene was added to the suspension, with the amount of APTMS calculated according to the desired degree of functionalization. In this work, the loadings were 1.5, 3.0, 4.5, and 6.0 mmol g −1 .…”