Zeolite mesopores

Composite zeolite/mesoporous materials show remarkably high catalytic activity, stability and selectivity in the isomerization of n-octane due to high zeolitic acidity combined with improved accessibility of active sites and easier transport of bulky molecules provided by mesopores. The best catalyst performance can be achieved by the optimisation of the contributions of micro- and mesopores in the composite material. 

Dispersion of POMs onto inert solid supports with high surface areas is very important for catalytic application because the surface areas of unsupported POMs are usually very low (—10 m2g). Another advantage of dispersion of POMs onto inert supports is improvement of the stability. Therefore, immobilization of POMs on a number of supports has been extensively studied. Silica and active carbon are the representative supports [25], Basic supports such as MgO tend to decompose POMs [101-104], Certain kinds of active carbons firmly entrap POMs [105,106], The maximum loading level of POMs on active carbons is 14 wt% [107], Dispersion of POMs onto other supports such as zeolites, mesoporous molecular sieves, and apatites, is of considerable interest because of their high surface areas, unique pore systems, and possibility to modify their compositions, morphologies, and sorption properties. However, a simple impregnation of POM compounds on inert supports often results in leaching of POMs. 

PDMS nanocomposites with layered mica-type silicates were also reported.374 A two-step sol-gel process of the in situ precipitation of silica led to the development of siloxane-based nanocomposites with particularly high transparencies.3 5 Some unusual nanocomposites prepared by threading polymer chains through zeolites, mesoporous silica, or silica nanotubes were reviewed.3 6 Poly(4-vinylpyridine) nanocross-linked by octa(propylglycidyl ether) polyhedral oligomeric silsesquioxane was reported.377... 

Palm oil has been cracked at atmospheric pressure and a reaction temperature of 723 K to produce biofuel in a fixed-bed microreactor. The reaction was carried out over microporous HZSM-5 zeolite, mesoporous MCM-41, and composite micromesoporous zeolite as catalysts. The products obtained were gas, organic liquid product, water, and coke. The organic liquid product was composed of hydrocarbons corresponding to gasoline, kerosene, and diesel boiling point range. The maximiun conversion of palm oil, 99 wt.%, and gasoUne yield of 48 wt.% was... 

Nanoporous Materials Gordon Research Conference, June 15-20, 2008, Colby College, Waterville, ME., now includes zeolites, mesoporous systems, metal organic materials as subject matter. 

To avoid the limitations of the small apertures and cavities provided by zeolites, mesopores have been created inside zeolites X, Y and DAY.[140] By dealumination of the zeolite structure, mesoporous regions that are completely surrounded by micropores were obtained, and these intrazeolitic cavities were then used as the space in which to assemble metal complexes. The preparation of a cobalt-salen-5 complex provided a catalytic material that shows improvements in the conversion,... 

The book explores various examples of these important materials, including perovskites, zeolites, mesoporous molecular sieves, silica, alumina, active carbons, carbon nanotubes, titanium dioxide, magnesium oxide, clays, pillared clays, hydrotalcites, alkali metal titanates, titanium silicates, polymers, and coordination polymers. It shows how the materials are used in adsorption, ion conduction, ion exchange, gas separation, membrane reactors, catalysts, catalysts supports, sensors, pollution abatement, detergency, animal nourishment, agriculture, and sustainable energy applications. 

Unfortunately, the use of TS1 (as well as TS2 discovered in 1990 by the group of Ratnasamy (27)) in catalytic oxidations is restricted to the relatively small substrates able to enter the pores of these zeolites (apertures 0.55 nm). Therefore, many research groups attempted to incorporate titanium in large pore molecular sieves BEA zeolites, mesoporous molecular sieves MCM41 and MCM48. Other transition metal zeolites were also synthesized and tested in oxidation one of the main problems of these systems is the release of redox cations in liquid phase (24). Progress remains to be made to develop molecular sieves catalyzing the oxidation... 

Phosphates having these types of open structures can act as shape-selective acid catalysts, for example, for the cracking and isomerization of hydrocarbons. For examples of lamellar materials, see Section 5.3 and see Intercalation Chemistry). Microporous catalysts are described above and in (see Porous Inorganic Materials and Zeolites). Mesoporous AlPO materials have larger pores within a matrix of amorphous A1P04. ... 

The water and n-hexane adsorption isotherms of the zeolitic mesoporous materials obtained are compared to that of a 4S0 nm colloidal silicalite-1 in Figure 5. The water adsorption isotherms are distinctively type HI, whereas the n-hexane isotherms are type 1. The lowest water isotherm was for the colloidal silicalite-1, where the first point measured for the n-hexane isotherm was already at 80 mg g. The amount of n-hexane adsorbed reached 2S0 mg g at high pressure, which roughly corresponds to the filling of silicalite-1 micropores. 

The focus of this chapter is on electron-transfer processes occmring in porous media, with particular emphasis on zeolitic, mesoporous materials and sol-gel-derived materials. The definition of different classes of porous solids as specified by lUPAC is based on the pore diameter ... 

We have discussed in some detail ET reactions occurring in zeolites, mesoporous materials and sol-gels. The unifying theme across these three different types of materials is their porosity. ET reactions within the pores with molecules as small as propylene to complex enzymes such as glucose oxidase have been discussed. However, what is also apparent from the discussions are that each host matrix imposes its own unique characteristics on the reactions within its pores. We conclude by highlighting the uniqueness of each matrix. 

In addition to ZSM-5 zeolites, mesoporous MCM-41 can be grown on stainless steel [246]. 

The catalysts commonly used to promote plastic degradation are a variety of acid solids such as amorphous silica-alumina, different types of zeolites, mesoporous aluminosilicates (MCM-41), sulfated zirconia, etc. Interesting results have also been obtained in polymer cracking over activated carbons... 

There are now four major classes of materials in which organic components exert a significant structural role in controlling the inorganic oxide microstructure zeolites, mesoporous oxides of the MCM-41 class, biomineralized materials, and microporous octahedral-tetrahedral or square pyramidal-tetrahedral transition metal phosphate frameworks (TMPO) with entrained organic cations. ... 

Synthesis and characterization of nanocrystal zeolite/mesoporous matrix composite material... 

TEM investigations have confirmed that upon alkaline treatment of the iron zeolites mesopores have been created (Fig. 3). In addition, the presence of a significant number of similarly sized iron nanoparticles before and after desilication can be observed. This suggests that the iron nanoparticles, which were absent in s-FeS, are mostly spectators in the process of silicon entrapment. 

NiO in super cage (reducible at low temperatures), monolayer NiO in super cage and beta cage (reducible at high temperatures), NiO-Al203 complex oxides such as spinel in zeolite mesopores (not reduced in TPR experiments). 

Acid catalysis (e.g., metal-substituted material, zeolite/ mesoporous composites, sulfonic acid-functionalized)... 

A key enabler often employed in the synthesis of zeolites is the template, often called an organic directing agent. The template type is frequently different for microporous zeolites, mesoporous materials, and macroporous materials. The template can be an individual molecule (e.g., quaternary salts or linear amines), in-situ formed micelle clusters, or preformed structures (e.g., polyethylene spheres). 

Sonogashira) involving bulky substrates Synthesis of jasminaldehyde sodalite and NaA zeolite Mesoporous MFI zeolite leaching and agglomeration Much higher activity (98%) than conventional ZSM-5 (3.9%), 1140]... 

Petushkov A, Ndiege N, Salem AK, Larsen SC (2010) Toxicity of silica nanomaterials zeolites, mesoporous siliea, and ammphous silica nanoparticles. Chapter 7. Elsevier, Amsterdam Pillai O, Dhaniknla AB, Panehagnula R (2001) Curr Opin Chem Biol 5(4) 439-446 Pitt WG (2008) Adv Drag Deliv Rev 60 1095-1096... 

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