MCM-41 Mobil Composition of Matter

Extending the use of zeolites into larger dimensions, say to catalyse enzymatic reactions and for the purification of colloidal precious metals, was the aim of researchers at Mobil Corporation (USA), who in 1992 discovered a viable and versatile synthetic procedure to prepare mesoporous materials, i.e. materials with ordered porosity in the range between 20 and 500 A (2-50 nm Kresge et al. 1992). Their first material was termed MCM-41 (Mobil Composition of Matter) and the mechanisms involved templating of a silica sol-gel synthesis by an amphiphilic surfactant. 

Besides the classical Si and Al-containing zeolites, there is an ongoing search toward other Lewis acidic zeolites and other microporous materials suitable for this reaction. Taaming et al. made a comparison between beta zeolites substituted with Al, Sn, Zr, and Tl. As with the homogeneous catalysts, this comparison pointed to Sn-based catalysts as extremely selective for this reaction. The authors obtained lactic acid and lactate yields of 90% and >99% at 125 and 80°C, respectively, with an Si Sn ratio of 125 [67]. Since then, numerous reports were published including Sn-montmorillonite [68], mesoporous Sn-MCM-41 (Mobil Composition of Matter) [69,70], Sn-MFI (Mordenite Framework Inverted) [70,71], Sn-deAl-beta [72], Sn-SBA-15 (Santa Barbara Amorphous type material) [70], Sn-MWW (Zeolite Framework Type M-22)... 

MCM-n Mobil composition of matter, ordered porous materials with different structures n — 22, 49, 58, 69 (zeolites) k = 41, 48 (mesoporous materials)... 

The ordered mesoporous materials (or crystalline mesoporous materials) such as MCM-41 (MCM stands for Mobil composite of matter), MCM-48 and SBA-15 (SBA stands for University of California, Santa Barbara) are a new generation of materials that are different from nonordered (amorphous) mesoporous materials. They are amorphous and not ordered at the atomic level from a classical crystallographic view point, but their regular channels or pores are ordered at the nanometer level. Because of this, these materials have certain characteristics of crystalline solids. Their structural information can be obtained by diffraction methods and other structural analysis techniques. The discovery of periodic mesoporous structures is a major advance in composite organic-inorganic materials synthesis. 

The first synthesis of an ordered mesoporous material was described in the patent literature in 1969. However, because of the lack of analysis, the remarkable features of this product were not recognized [75]. In 1992, a similar material was obtained by scientists in Mobil Oil Corporation who discovered the remarkable features of this novel type of silica and opened up a whole field of research [76]. MCM-41, which stands for Mobil Composition of Matter No. 41, shows a highly ordered hexagonal array of unidimensional pores with a very narrow pore size distribution [77, 78]. Other related phases such as MCM-48 and MCM-50, which... 

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