Selected catalytic properties

This new generation of iron precatalysts was tested for the reduction of ketones and imines, in both ATH and, most recently, ADH. In both cases, no induction period 

The chiral array of aryl groups presented to the incoming substrate seems very similar for Ru(H)2(diamine)(diphosphine) and Fe(H)(CO)(P-NH-N-P) complexes. In each case, the complex with a stiucture derived from the (R,/ )-diamine produces the (5)-alcohol or (5)-amine from prochiral aryl ketones or imines. The origin for this 

These and other design principles will continue to be exploited in the on-going effort to replace chemical processes that are currently catalyzed by precious metal complexes with more abundant, sustainable and less toxic metals. 

thanks NSERC Canada for a Discovery grant and a graduate scholarship to D.E.R, the Canada Eoundation for Iimovation and Ontario Ministry of Research for equipment, and all of the students in the research group involved in this project and mentioned in the references. 

Rauchfuss, S. P. Schmidt, J. C. Jeffery, P. A. Tucker, in Catalytic Aspects of Metal Phosphine Complexes (eds E. C. Alyea, D. W. Meek), American Chemical Society, Washington, DC, 1982, pp. 303-311. 

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Scrimin. P.. Tecilla. P.. Tonellato, U. and Vignana. M. (1991) A water-soluble tweezers-like metalloreceptor Binding and selective catalytic properties. J. Chem. Soc., Chem. Commun.. 449. 

Qui L-G, Gu L-N, Hn G, Zhang L-D. Synthesis, structural characterization and selectively catalytic properties of metal-organic frameworks with nano-sized channels a modular design strategy. J Sohd State Chem 2009 182 502-8. 

A new dimension to acid-base systems has been developed with the use of zeolites. As illustrated in Fig. XVIII-21, the alumino-silicate faujasite has an open structure of interconnected cavities. By exchanging for alkali metal (or NH4 and then driving off ammonia), acid zeolites can be obtained whose acidity is comparable to that of sulfuric acid and having excellent catalytic properties (see Section XVIII-9D). Using spectral shifts, zeolites can be put on a relative acidity scale [195]. An important added feature is that the size of the channels and cavities, which can be controlled, gives selectivity in that only... 

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. 

Other important uses of stannic oxide are as a putty powder for polishing marble, granite, glass, and plastic lenses and as a catalyst. The most widely used heterogeneous tin catalysts are those based on binary oxide systems with stannic oxide for use in organic oxidation reactions. The tin—antimony oxide system is particularly selective in the oxidation and ammoxidation of propylene to acrolein, acryHc acid, and acrylonitrile. Research has been conducted for many years on the catalytic properties of stannic oxide and its effectiveness in catalyzing the oxidation of carbon monoxide at below 150°C has been described (25). 

Catalyst testing and evaluation have been revolutionized by computers, automated test reactors, and analytical methods. With modem equipment, researchers can systematically prepare and screen many catalysts in a short time and efftciendy deterrnine, not only the initial catalytic activity and selectivity, but also the stabiUty and the appearance of trace products that may indicate some new catalytic properties worthy of further development. 

To optimize selectivity, a wide array of diamine backbones were surveyed (Fig. 3.21). However, it appears that 1,2-cyclohexanediamine is unique in its catalytic properties. Only the closely related dihydrophenanthrene ligand 124 could... 

In all these cases the support has a dramatic effect on the activity and selectivity of the active phase. In classical terminology all these are Schwab effects of the second kind where an oxide affects the properties of a metal. Schwab effects of the first kind , where a metal affects the catalytic properties of a catalytic oxide, are less common although in the case of the Au/Sn02 oxidation catalysts9,10 it appears that most of the catalytic action takes place at the metal-oxide-gas three phase boundaries. 

Noble metal nanoparticles dispersed in insulating matrices have attracted the interest of many researchers fromboth applied and theoretical points of view [34]. The incorporation of metallic nanoparticles into easily processable polymer matrices offers a pathway for better exploitation of their characteristic optical, electronic and catalytic properties. On the other hand, the host polymers can influence the growth and spatial arrangement of the nanoparticles during the in situ synthesis, which makes them convenient templates for the preparation of nanoparticles of different morphologies. Furthermore, by selecting the polymer with certain favorable properties such as biocompatibiHty [35], conductivity [36] or photoluminescence [37], it is possible to obtain the nanocomposite materials for various technological purposes. 

The different classes of Ru-based catalysts, including crystalline Chevrel-phase chalcogenides, nanostructured Ru, and Ru-Se clusters, and also Ru-N chelate compounds (RuNj), have been reviewed recently by Lee and Popov [29] in terms of the activity and selectivity toward the four-electron oxygen reduction to water. The conclusion was drawn that selenium is a critical element controlling the catalytic properties of Ru clusters as it directly modifies the electronic structure of the catalytic reaction center and increases the resistance to electrochemical oxidation of interfacial Ru atoms in acidic environments. 

In the present study, we report the synthesis, characterisation and catalytic properties (in selective oxidation reactions) of copper acetate, copper tetradecachlorophthalocyanine and copper tetranitrophthalocyanine encapsulated in molecular sieves Na-X, Na-Y, MCM-22 and VPI-5. Both molecular oxygen and aqueous HjOj have been used as the oxidants. The... 

V-Sb-oxide based catalysts show interesting catal)dic properties in the direct synthesis of acrylonitrile from propane [1,2], a new alternative option to the commercial process starting from propylene. However, further improvement of the selectivity to acrylonitrile would strengthen interest in the process. Optimization of the behavior of Sb-V-oxide catalysts requires a thorough analysis of the relationship between structural/surface characteristics and catalytic properties. Various studies have been reported on the analysis of this relationship [3-8] and on the reaction kinetics [9,10], but little attention has been given to the study of the surface reactivity of V-Sb-oxide in the transformation of possible intermediates and on the identification of the sxirface mechanism of reaction. 

The catalytic properties were characterized in a simplified manner by two parameters the maximal conversion Cm and the corresponding temperature Tm- The selectivity of NO conversion to N2 is always very high (> 98%). The formation of NO2 is marginal on these Cu catalysts. 

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