Transition metal catalysts supports

Reactions Utilizing Transition Metal Catalysts Supported on Organic Resins... 

The enhanced activity of transition metal catalysts supported on reducible oxides in the selective hydrogenation of the C=0 bond is generally attributed to... 

Reaction of Methanol with Carbonyl Compounds. - Similar to the reaction of methanol with carboxylic acid, esters, or nitriles shown in Sections 5.2 and 6.2, attempts were made to use the HCHO which is formed by dehydrogenation of methanol. Ueda et al. performed the reaction of methanol with acetone over various transition metal catalysts supported on MgO using an acetone/methanol molar ratio of 1/10. The best performances are obtained with a catalyst containing 3.1 wt% of Fe. The main products are methyl vinyl ketone, methyl ethyl ketone, and 2-propanol. The yields are 7.1, 2.8, and 2.8 mol%, respectively, based on the charged acetone at the conversion of 20.1% selec-tivities are 34.8, 13.9, and 13.9 mol%, respectively, based on acetone. The yield of methyl vinyl ketone is much lower than that achieved in the reaction with HCHO. Unfortunately, there is no information about the reaction of methanol that exists in the feed ten times greater than acetone. It is considered that methyl ethyl ketone and 2-propanol are formed by hydrogenation of methyl vinyl ketone and acetone, respectively, with methanol. 

Shin S-YA, Simon LC, Soares JBP, Scholz G, McKenna TFL (2009) Gas-phase polymerization with transition metal catalysts supported on montmorillonite - a particle morphological study. Macromol Symp 285(1) 64—73... 

Abstract—Carbon nanotubules were produced in a large amount by catalytic decomposition of acetylene in the presence of various supported transition metal catalysts. The influence of different parameters such as the nature of the support, the size of active metal particles and the reaction conditions on the formation of nanotubules was studied. The process was optimized towards the production of nanotubules having the same diameters as the fullerene tubules obtained from the arc-discharge method. The separation of tubules from the substrate, their purification and opening were also investigated. 

This type of co-catalytic influence is well loiown in heterogeneous catalysis, in which for some reactions an acidic support will activate a metal catalyst more efficiently than a neutral support. In this respect, the acidic ionic liquid can be considered as a liquid acidic support for the transition metal catalysts dissolved in it. 

The metal catalyzed production of polyolefins such as high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and polypropylene (PP) has grown into an enormous industry. Heterogeneous transition metal catalysts are used for the vast majority of PE and all of the PP production. These catalysts fall generally within two broad classes. Most commercial PP is isotactic and is produced with a catalyst based on a combination of titanium chloride and alkylaluminum chlorides. HDPE and LLDPE are produced with either a titanium catalyst or one based on chromium supported on silica. Most commercial titanium-based PE catalysts are supported on MgCl2. 

Olefin metathesis has been discovered on heterogeneous catalysts, which are typically transition-metal oxides supported on oxide supports, for example... 

Besides supported (transition) metal catalysts, structure sensitivity can also be observed with bare (oxidic) support materials, too. In 2003, Hinrichsen et al. [39] investigated methanol synthesis at 30 bar and 300 °C over differently prepared zinc oxides, namely by precipitation, coprecipitation with alumina, and thermolysis of zinc siloxide precursor. Particle sizes, as determined by N2 physisorpt-ion and XRD, varied from 261 nm for a commercial material to 7.0 nm for the thermolytically obtained material. Plotting the areal rates against BET surface areas (Figure 3) reveals enhanced activity for the low surface area zinc... 

A variety of reactions have been conducted. Catalysts based on noble metals on Deloxan amino poly siloxane supports have been used. Hitzler et al. (1998) have reported alkylation of mesitylene with propylene or wopropanol in SC propylene or CO2 using a solid acid Deloxan catalyst. Pesiri et al. (1998) have carried out selective epoxidation in SC CO2 with transition metal catalysts (V, Ti, Mo) and tert-BHPO high conversion and selectivity have been reported. 

The use of dendrimers as supports to anchor transition metal catalysts has attracted considerable attention over the past decades [48] (see also Chapter 4 of this book). Several groups studied the use of dendrimers immobilised on insoluble supports [49], and this type of material meet the requirements for catalysis in interphases. Alper reported the use of diphosphine functionalised polyamidoamine (PAMAM) dendrimers... 

Even if the ionic liquid is not directly involved in creating the active catalytic species, a co-catalytic interaction between the ionic liquid solvent and the dissolved transition metal complex often takes place and can result in significant catalyst activation. When a catalyst complex is, for example, dissolved in a slightly acidic ionic liquid some electron-rich parts of the complex (e.g., lone pairs of electrons in the ligand) may interact with the solvent, providing increased activity to the resulting catalytic centre. Acidic ionic liquids can be considered as liquid acid supports for transition metal catalysts dissolved therein. 

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