Manganese oxides microporous

In the preparation of microporous manganese oxide materials different chemical properties were observed for the microwave and thermal preparations. In the conversion of ethylbenzene to styrene the activity and selectivity of the materials was different [26]. 

Seredych M, Bandosz TJ. Manganese oxide and graphite oxide/Mn02 composites as reactive adsorbents of ammonia at ambient conditions, Microporous and Mesoporous Materials 2012, 150, 55-63. 

This review concerns the synthesis, characterization, and catalytic activity of microporous ferrierite zeolites and octahedral molecular sieves (QMS) and octahedral layer (OL) complexes of mixed valent manganese oxides. The ferrierite zeolite materials along with borosilicate materials have been studied as catalysts for the isomerization of n-butenes to isobutylene, which is an important intermediate in the production of methyltertiarybutylether (MTBE). The CMS materials have tunnels on the order of 4.6 to 6.9 A. These materials have been used in the total oxidation of CO to C02, decomposition of H2O2. dehydrogenation of CeHi4, C0H14 oxidation, 1-C4H3 isomerization, and CH4 oxidation. The manuscript will be divided into two major areas that describes zeolites and OMS/OL materials. Each of these two sections will include a discussion of synthesis, characterization, and catalytic activity. 

Other kinds of mesoporous manganese based materials have been also reported by transformation of layered bimessite (18). Finally amorphous microporous manganese oxidic materials prepared by the reaction between KMn04 and oxalic acid and incorporation of hetero-cations like Cu, Cr and Zn in them have been recently prepared and tested as catalysts (19, 20). 

There are two examples of transition metal oxides forming ordered microporous materials (1) manganese oxide and (2) molybdenum vanadium mixed oxide, both of which contain MOg octahedra as the basic structural units to form one-dimensional channel pores. 

The first ordered microporous transition metal oxides were microporous manganese oxides, known as octahedral molecular sieves (OMS). The manganese oxide OMS are classified into three families the pyrolusite-ramsdellite family with a (1 x n) channel structure the hollandite-romanechite family with a (2 x n) channel structure ... 

This orthorhombic Mo-V oxide was prepared by hydrothermal reaction of (NH4)6Moy024 and VOSO4. Similar to manganese oxide OMS, cations ([NH4]" ") occupy both channels. To form an empty channel, [NH4]" cations are removed by calcination. Ordered microporosity was first confirmed by a single uptake of N2 and Ar adsorption at very low P/Pq (type 1 behaviour), and the pore diameter was estimated by the molecular probe technique to be ca 0.4 nm (Figure 3.3). This value is close to the aperture diameter of the seven-membered channel. The micropore volume calculated by the Dubinin-Astakhov (DA) equation for smaller gases is about 0.025 cm g , which is the calculated pore volume of a seven-membered channel. These results indicate that this seven-membered ring channel is a micropore. 

Both microporous manganese oxides " and the Mo-V were prepared by heating aqueous solutions of the metal precursors. In order to produce pure samples, conditions (pH, temperature, reaction time, and concentration of metal precursor) must be carefully controlled. Further investigation is needed to demonstrate the importance of these bifunctional (redox and microporosity) materials for understanding the formation mechanism of these microporous materials and for the development of a new strategy to form other microporous transition metal oxides. 

Inorganic molecular sieves in which all of the framework cations are coordinated octahedrally comprise a small but significant family of microporous solids. The octahedral molecular sieves, or OMS materials, related to manganese oxide minerals of the hollandite family, are the most important of these. Examples have been prepared by Suib and co-workers through the hydrothermal treatment of layered manganese oxides. Careful choice of additional metal ion content of such preparations controls the inorganic phase that forms. The... 

Zhang, L., T. Wei, W. Wang, and X. Zhao. 2009. Manganese oxide—carbon composite as supercapacitor electrode materials. Microporous andMesoporous Materials 123 260-267. 

The catalytic oxidation of stable alkanes to more valuable products such as alcohols and ketones is known to occur with microporous manganese oxide molecular sieves (OMS). MOMS materials have Lewis acid sites as well as Bronsted acid sites coexisting on the active surface, although the Lewis acid sites dominate, as is typical for manganese oxides [53]. 

ZR Tian. From microporous to mesoporous manganese oxide crystalline phases syntheses, characterization, and applications. PhD dissertation. Storrs.CT University of Connecticut, 1998. 

Zhang, L. L. et al. 2009. Manganese oxide-carbon composite as supercapacitor electrode material. Microporous and Mesoporous Materials, 123,260-267. 

Shikoku Kogyo Shikensho developed a microporous manganese oxide type adsorbant which is able to separate lithium from sea water at a cost of about the market price in 1994 [8]. 

C. R. Jacob, S. R. Varkey, and R. Ratnasamy, Selective oxidation over copper and manganese salens encapsulated in zeolites, Microporous Mesoporous Mater. 22, 465 74 (1998). 

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