MCM-41

About: MCM-41 is a research topic. Over the lifetime, 2355 publications have been published within this topic receiving 91416 citations.

Reduced forms of Rh(III) containing MCM-41 silicas as hydrogenation catalysts for arene derivatives

Abstract: Rhodium containing mesoporous siliceous materials with MCM-41 pore architecture have been prepared via a template directed hydrolysis-polycondensation of tetraethoxysilane and rhodium(III) chloride in aqueous ammonia. The effect of aging and hydrothermal conditions on rhodium incorporation and on the porous structure of the resulting solids has been examined using elemental analysis, powder X-ray diffraction (XRD), N2 sorption measurements and transmission electron microscopy (TEM). Optimized synthetic conditions afforded MCM-41 materials with Si/Rh 1400 and 120. Subsequent reduction of rhodium oxides species by hydrogen emphasized that the growth of Rh0 particles (2–3 nm) is controlled by the porosity of the support. The conditions and efficiency of this step were evaluated through H2-TPR (temperature programmed reduction) and IR monitored CO adsorption studies. The resulting materials showed a good catalytic activity and stability in the hydrogenation of arene derivatives under mild pressure and temperature. Cis/trans selectivity of dimethylcyclohexanes was discussed in the light of dispersion measurements.

Ship-in-a-Bottle Synthesis of Copper Phthalocyanine Molecules within Mesoporous Channels of MCM-41 by a Chemical Vapor Deposition Method

Abstract: We report a “ship-in-a-bottle” synthesis where encapsulation of copper phthalocyanines (CuPc) into mesoporous channels of silicate MCM-41 was achieved by chemical vapor deposition (CVD) using 1,2-dicyanobenzene (DCNB). Silanol protons of MCM-41 were ion-exchanged with copper ions before CVD, and when the initial amount of DCNB was much larger than that of copper ions, CuPc molecules in the channels were found to form a cofacial structure that was confirmed by diffuse reflectance spectra.

Ethane dehydrogenation over pore-expanded mesoporous silica supported chromium oxide: 1. Catalysts preparation and characterization

Abstract: Pore-expanded MCM-41 silica was prepared in two steps, namely synthesis of MCM-41 in the presence of cetyltrimethylammonium bromide (CTAB) at 100 °C followed by a hydrothermal pore expansion treatment in the presence of dimethyldecylamine (DMDA) at 120 °C for 72 h. The as-synthesized material (PE-MCM-41), the material obtained after selective ethanol extraction of DMDA (PE-MCM-41E) and the organic-free material obtained after calcination of PE-MCM-41 (PE-MCM-41C) were used as supports for chromium oxide up to a chromium loading of 7 wt.%. All catalysts were thoroughly characterized by X-ray diffraction, N 2 adsorption, temperature programmed reduction (TPR), Raman and X-ray photoelectron spectroscopy (XPS), and used for ethane dehydrogenation (DH). N 2 adsorption measurements showed that the pore and surface characteristics strongly depend on the catalyst preparation method and relatively independent of chromia loading. The structural properties of the chromium-loaded materials were associated with the effect of water on the support, which is dependent on how well the silica framework is protected by the occluded surfactant(s) against direct contact with water. XPS analysis showed that in most cases, the surface chromium contained significant amounts of Cr(III) and Cr(VI) and minor amounts of Cr(II). Furthermore, H 2 -TPR results revealed that the extent of reduction of the catalysts depend on the chromia loading and the preparation method.