Amorphous microporous mixed oxides AMMs

Holzwarth et al. (51) reported the synthesis and IR thermographic-imaging screening of a 37-member, focused discrete heterogeneous catalyst library L6 for oxidations and reductions. The library was prepared using sol-gel solution synthetic protocols (47, 51) to produce the library individuals as amorphous microporous mixed oxides (AMMs), which have previously shown heterogeneous catalytic properties (54, 55). The scaffolding metal oxides contained either Ti (subset 1, Fig. 11.7) or Si (subset 2), and many active metal components were used. The complete structure of L6 is reported... 

Microporous crystalline solids in which transition metals are tetrahedrally substituted via template-mediated hydrothermal synthesis have remarkable properties in selective oxidation reactions [66]. Unfortunately, the microporous structure and the rigidity of the crystalline frameworks limit the substitution degree, variety of substituted metal, and their general applicability. For this reason, the amorphous microporous mixed oxides (AMMs) with uniform microporosity and wide compositional variability are devoid of Bronsted acidity, but are not associated with the redox-active elements. However, metals such as Ti, V, and Mo incorporated in amorphous silica were good catalysts in allylic oxidation or epoxidation of olefins [67]. 

Figure 11.7 Structure of the amorphous microporous mixed (AMMs) oxides discrete catalytic library L6.

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