Framework Activity

The porous material [Cu3(btc)2(H20)3], also known as HKUST-1, contains large cavities. The copper metal is coordinated to water molecules that can 

Industrial Catalysis and Separations Innovations for Process Intensification 

Ferey et al. reported the Bronsted acid catalysis reaction on Friedal-Crafts benzylation using two different MIL-100 cations, Fe and Cr. Although the structure is identical [MjOFg gjCOH) , j5(H20)2(btc)J in both cases, the Fe-based MIL-100 showed superior performance over that the Cr-based MIL-100 and even smpassed the reported HY and HBEA zeolites [74], Irr MIL-100(Cr+ ), the Cr-OH sites showed mediirm Bronsted acidic strerrgth as corrfrrmed by low-temperature CO chemisorption studies [75], 

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Closer to industrial application however, is the gas phase hydroxylation with nitrous oxide as the oxidant (Equation 39). The reaction is carried out at 350°C with a selectivity to phenol of 98%, at 27% benzene conversion. The catalyst is Fe-ZSM-5 a zeolite containing A1 and Fe in the silicalite-1 framework. Active sites are thought to be binuclear clusters of iron oxide, formed in the channels by the migration of Fe, during thermal treatments of the zeolite. Selectivity is of... 

Zeolites have also transformed the field of chiral catalysis, because of the possibility of introducing extra-framework active sites in the pores of these materials. There is, however, one subject yet to be investigated-the synthesis of chiral zeolite structures and/or chiral framework sites. 

However alkali cations, in appropriate zeolite structures may generate, in association with the zeolite framework, active electrophiles which in turn may initiate nucleophilic reactions. 

In the present study the catalytic site is introduced on the support at the interface between zeolite and support. The diffusion pathway through the framework to the catalytic site on the support must be minimized, while the channels must be oriented in the direction of the support. Advantages offered by these composites are i) combination of a catalytic site which can not be synthesized or stabilized in the zeolite lattice with framework shape selectivity and ii) bifunctional catalysis by addition of framework activity. A schematical drawing of the composite system design is given in Figure 1. 

It is well established that MOFs themselves can function as heterogeneous catalysts [10-13,108] due to the presence (either in the pristine MOF or introduced afterwards by post-synthesis modifications) of active sites located at the metallic nodes and/or functional organic linkers. Therefore, combination of two (or more) different framework active sites (such as acid/base), or a framework active site with encapsulated species located inside the pores, affords a means for preparing multifunctional catalysts. In this way, sequential catalytic transformation (usually referred to as tandem or cascade processes [24,109,110]) can... 

Fateeva A, Chater PA, Ireland CP, Tahir AA, Khimyak YZ, Wiper PV, Darwent JR, Rosseinsky MJ (2012) A water-stable porphyrin-based metal-organic framework active for visible-light photocatalysis. Angew Chem Int Ed 51 7440-7444... 

The 5th Framework Programme must be more flexible, both in its research activities and in the decision-making process. The Commission proposes that a simplified decision-making procedure should apply to research policy, including the use of qualified majority voting rather than unanimity in the Council of Ministers. 

Ongoing research under the 4th Framework Programme includes a variety of projects and other activities relevant for the 7th ECNDT Conference. 

Within this framework, by considering the physical situation of the electrode double layer, the free energy of activation of an electron transfer reaction can be identified with the reorganization energy of the solvation sheath around the ion. This idea will be carried through in detail for the simple case of the strongly solvated... 

Cao J and Voth G A 1996 A unified framework for quantum activated rate processes I. General theory J. Chem. Phys. 105 6856... 

Some details of END using a multiconfigurational electronic wave function with a complete active space (CASMC) have been introduced in terms of an orthonormal basis and for a fixed nuclear framework [25], and were recently [26] discussed in some detail for a nonoithogonal basis with electron translation factors. 

Many problems with MNDO involve cases where the NDO approximation electron-electron repulsion is most important. AMI is an improvement over MNDO, even though it uses the same basic approximation. It is generally the most accurate semi-empirical method in HyperChem and is the method of choice for most problems. Altering part of the theoretical framework (the function describing repulsion between atomic cores) and assigning new parameters improves the performance of AMI. It deals with hydrogen bonds properly, produces accurate predictions of activation barriers for many reactions, and predicts heats of formation of molecules with an error that is about 40 percent smaller than with MNDO. 

Catalytic Properties. In zeoHtes, catalysis takes place preferentially within the intracrystaUine voids. Catalytic reactions are affected by aperture size and type of channel system, through which reactants and products must diffuse. Modification techniques include ion exchange, variation of Si/A1 ratio, hydrothermal dealumination or stabilization, which produces Lewis acidity, introduction of acidic groups such as bridging Si(OH)Al, which impart Briimsted acidity, and introducing dispersed metal phases such as noble metals. In addition, the zeoHte framework stmcture determines shape-selective effects. Several types have been demonstrated including reactant selectivity, product selectivity, and restricted transition-state selectivity (28). Nonshape-selective surface activity is observed on very small crystals, and it may be desirable to poison these sites selectively, eg, with bulky heterocycHc compounds unable to penetrate the channel apertures, or by surface sdation. 

In a reversal of the reaction with SiCl, aluminum can be introduced into the framework by reaction of the hydrogen or ammonium form with gaseous AlCl (36). Similarly, reaction with aqueous ammonium fluoroaluminates replaces framework-Si with Al (37). When alumina-bound high siUca 2eohtes are hydrothermaHy treated, aluminum migrates into framework positions and generates catalyticaHy active acid sites (38). The reaction can be accelerated by raising the pH of the aqueous phase. 

Another framework (69,70) highlights 10 R D activities and six levels of performance ... 

Titanium Silicates. A number of titanium siUcate minerals are known (160) examples are Hsted in Table 19. In most cases, it is convenient to classify these on the basis of the connectivity of the SiO building blocks, eg, isolated tetrahedra, chains, and rings, that are typical of siUcates in general. In some cases, the SiO units may be replaced, even if only to a limited extent by TiO. For example, up to 6% of the SiO in the garnet schorlomite can be replaced by TiO. In general, replacement of SiO by TiO bull ding blocks increases the refractive indices of these minerals. Ti has also replaced Si in the framework of various zeofltes. In addition, the catalytic activity of both titanium-substituted ZSM-5 (TS-1) and ZSM-11 (TS-2) has received attention (161), eg, the selective oxidation of phenol, with hydrogen peroxide, to hydroquinone and catechol over TS-1 has been operated at the 10,000 t/yr scale in Italy (162). 

A sohd solution of a pure magnesium aluminate spiael (MgAl20 with MgO is an effective metal oxide adsorbent (43). Such a soHd solution (Mg2A10 ) does not destroy the spiael framework the MgO adsorbs SO and the adsorption activity of the dispersed MgO ia the spiael is much greater than that of pure MgO itself (43). 

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