MCM-41

MCM-41 (Mobil Composition of Matter No. 41) is a mesoporous material with a hierarchical pore structure from a family of silicate and aluminosilicate solids, which was first developed in 1992 by researchers at Mobil Oil Corporation and is used as a catalyst or catalyst carrier .

construction

MCM-41 has a regular hexagonal arrangement of cylindrical mesopores that form a one-dimensional pore system. It is characterized by an adjustable pore diameter, a sharp pore radius distribution, a large surface and a large pore volume. The pores are larger than with zeolites and the pore size distribution can be easily adjusted. The mesopores have a diameter of 2 nm to 6.5 nm.

properties

In contrast to zeolites, the framework of MCM-41 has no Brönsted acid centers, as it does not contain any aluminum in the lattice. The acidity of alumina- doped MCM-41 is therefore more similar to that of amorphous aluminosilicates.

MCM-41 is hydrothermally unstable. The reason lies in the small wall thickness and the low degree of crosslinking of the silicate units in the framework.

Manufacturing

To set the defined pore diameter, surfactants are used that form micelles in the synthesis solution, which then serve as a template for the formation of the mesoporous framework structure. The most commonly used template for the synthesis of MCM-41 is cetyltrimethylammonium bromide (CTAB).

The surfactant initially forms rod-shaped micelles, which then accumulate in hexagonally arranged collections. When inorganic silicate species are added, these are placed around the micelles that have formed. Subsequent calcination causes condensation of the silanol groups so that the silicon atoms are bonded to one another via oxygen atoms. The organic template is oxidized and disappears.

Individual evidence

↑ ^a ^b ^c Markus Reichinger: Porous silicates with hierarchical pore structure: Synthesis of micro- / mesoporous MCM-41 and MCM-48 materials from zeolitic building blocks of the MFI framework structure type . 2007, urn : nbn: de: hbz: 294-19882 (dissertation, Ruhr University Bochum).
^ ^A ^b Marius-Christian Silaghi, Celine Chizallet , Pascal Raybaud: Challenges on molecular aspects of dealumination and desilication of zeolites . In: Microporous and Mesoporous Materials . tape 191 , June 2014, p. 82-96 , doi : 10.1016 / j.micromeso.2014.02.040 .

[reichinger_2007-1] Markus Reichinger: Porous silicates with hierarchical pore structure: Synthesis of micro- / mesoporous MCM-41 and MCM-48 materials from zeolitic building blocks of the MFI framework structure type . 2007, urn : nbn: de: hbz: 294-19882 (dissertation, Ruhr University Bochum).

[silaghi_2014-2] A ^b Marius-Christian Silaghi, Celine Chizallet , Pascal Raybaud: Challenges on molecular aspects of dealumination and desilication of zeolites . In: Microporous and Mesoporous Materials . tape 191 , June 2014, p. 82-96 , doi : 10.1016 / j.micromeso.2014.02.040 .