Catalytic microporous inorganic

In some cases, the membrane material is inherently catalytic and the membrane serves as both catalyst and separator, controlling the two important functions of the reactor simultaneously as shown in Figure 1.12(d). A number of meso- and microporous inorganic membrane materials have catalytic properties, such as titania and zeolites with acid sites. As an example, mesoporous Ti02... 

Once the multi-step reaction sequence is properly chosen, the bifunctional catalytic system has to be defined and prepared. The most widely diffused heterogeneous bifunctional catalysts are obtained by associating redox sites with acid-base sites. However, in some cases, a unique site may catalyse both redox and acid successive reaction steps. It is worth noting that the number of examples of bifunctional catalysis carried out on microporous or mesoporous molecular sieves is not so large in the open and patent literature. Indeed, whenever it is possible and mainly in industrial patents, amorphous porous inorganic oxides (e.g. j -AEOi, SiC>2 gels or mixed oxides) are preferred to zeolite or zeotype materials because of their better commercial availability, their lower cost (especially with respect to ordered mesoporous materials) and their better accessibility to bulky reactant fine chemicals (especially when zeolitic materials are used). Nevertheless, in some cases, as it will be shown, the use of ordered and well-structured molecular sieves leads to unique performances. 

Further variation of the stmctural and catalytic properties of four-coimected tetrahedral frameworks is obtained by the substitution of silicon or metal cations,giving materials known as SAPO s and MeAPO s, respectively. More than twenty metal aluminophosphate frameworks have been identified with Mg, Mn, Fe, Co, or Zn substituents. These give the possibility of framework redox activity (e.g. Fe +/Fe +) in catalysis as well as the usual Bronsted acidity. For further information about zeolitic and microporous phosphate frameworks see Porous Inorganic Materials and Zeolites) and recent reviews. ... 

This applies when catalytic centers are incorporated as dopants to the lattice of the base porous material. In fact, site isolation of electroactive centers immobilized in microporous materials and doping units in inorganic supports appears to promote efficient electrocatalysis for a variety of analytically significant processes. Some remarks can be made ... 

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