Mesoporous mixed oxides

A series of experiments have been eonducted in an attempt to improve the thermal stability of the Ti-Zr mesoporous mixed oxide prepared Ifom inorganic precursors. The results show that the crystallinity of the Ti-Zr mesoporous mixed oxide depends strongly on the Ti/Zr molar ratio in the gel mixtures, and a better crystalline mesoporous structure can be obtained on the sample with the 1 1 Ti/Zr molar ratio. It is also found that surfactant content, addition of sulfate species and auxiliary organic additive such as DDA, TritonX-lOO, triethanolamine and ethanol would play a key role in tailoring the mesopore structures and improving thermal stability of the obtained materials. In addition, the mixing order of organic surfactants, i.e., CTAB and DDA, also affects the the crystallinity of the product. 

Novel Mn-based Mesoporous Mixed Oxidic Solids... 

Novel Mn-based mesoporous mixed oxidic solids... 

Figure 25.11 Model of the formation of mesoporous mixed oxide materials with block copolymers acting as structure-directing agent and complexing ligand. (Adapted with permission from Ref. [87]. Copyright 2004, American Chemical Society.)...

Mesoporous mixed oxide catalysts via non-hydrolytic sol-gel a review. Appl. Catal. A, 451, 192-206. 

Tailored refractive index of inorganic mesoporous mixed-oxide Bragg stacks with bio-inspired hygrochromic optical properties. /. Mater. Chem. C, 1 (39), 6202-6209. 

Luo, J. Meng, M. Qian, Y. et al. Mesoporous Mixed Oxide La-Co-Ce-0 Catalysts Prepared by Citric Acid Complexation-Organic Template Decomposition Method. Chin J. Catal. 2006, 27(6), 471-473. 

In this work, we report in detail on the synthesis and characterization of ordered CuO-Ce02 mesoporous mixed oxides (with 10,15 and 20 mol % CuO content) by rrsing a hard template method with KlT-6 silica acting as a template. The obtained Cu0-Ce02 oxides were characterized by a variety of techniqrres, such as N2 adsorption/desorption, XRD, H2-TPR/TPD, H2-TPR/TPO/TPR, selective N2O chemisorption, and tested for performance in WGS reaction conducted in a continrrorrs-flow fixed-bed reactor. 

The objective of this work is to study the potential of modified ZSM5 zeolite, MCM41 mesoporous silica, hydrotalcites (HD) and HD originated mixed oxides as catalysts for degradation of PE, PP PS and PVC using thermal analytical measurements and laboratory reactor experiments. 

Recent Advances on NO Reduction Related to Mixed Oxides, Supported Metals and Ion-Exchange Mesoporous... 

Since the strategy was initially based on catalytic purposes, the surfaces considered initially were mostly (i) highly divided oxides (here are included simple oxides, mixed oxides, zeoUtic materials, mesoporous systems, hybrid organic inorganic materials, metal organic frameworks, etc.) and (ii) highly divided metals (supported or unsupported small metal particles). 

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. 

These perspectives are enhanced by using templates, as already observed in the case of the so-called mesoporous materials. First attempts are already showing the possibility of including organic units in the walls of the materials. It is also important to note that, at the present time, silica is the most popular material that can be prepared by the sol-gel process. The chemistry that we have presented here will certainly expand this range of materials and combine it with other oxides or mixed oxides. Beside these suggestions which are more or less obvious in the context of the chemistry of this kind of materials, other directions will be also of interest for the preparation of new materials. 

An important class of mixed oxides is constituted by zeolites. Zeolites were first defined to comprise only microporous crystalline aluminosilicates (micro-porous, pore diameter <20 A, mesoporous, 20-500 A, macroporous, > 500 A). However today other microporous crystalline materials are included, such as... 

Hybrid array Ordered mesoporous mixed metal oxide... 

Figure 17 Formation of 2D-hexagonal mesoporous mixed metal oxides by liquid crystal templating mechanism [134,135]...

Amorphous Sn-, Si-, and Al-containing mixed oxides with homogeneous elemental distribution, elemental domains, and well-characterized pore architecture, including micropores and mesopores, can be prepared under controlled conditions by use of two different sol-gel processes. Sn-Si mixed oxides with low Sn content are very active and selective mild acid catalysts which are useful for esterification and etherification reactions [121]. These materials have large surface areas, and their catalytic activity and selectivity are excellent. In the esterification reaction of pentaerythritol and stearic acid catalytic activity can be correlated with surface area and decreasing tin content. The trend of decreasing tin content points to the potential importance of isolated Sn centers as active sites. 

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