Activated carbon catalytic reactions with

C-H activation with transition-metal complexes will open a new chemistry of catalytic carbon-carbon bond formation because of its potent ability to generate reactive carbon-metal complexes. The design of a catalytic reaction which involves C-H activation followed by reaction with a reagent such as an electrophile is particularly important to provide an environmentally friendly non-salt process, which proceeds under neutral conditions. 

Catalytic tests in sc CO2 were run continuously in an oil heated flow reactor (200°C, 20 MPa) with supported precious metal fixed bed catalysts on activated carbon and polysiloxane (DELOXAN ). We also investigated immobilized metal complex fixed bed catalysts supported on DELOXAN . DELOXAN is used because of its unique chemical and physical properties (e. g. high pore volume and specific surface area in combination with a meso- and macro-pore-size distribution, which is especially attractive for catalytic reactions). The effects of reaction conditions (temperature, pressure, H2 flow, CO2 flow, LHSV) and catalyst design on reaction rates and selectivites were determined. Comparative studies were performed either continuously with precious metal fixed bed catalysts in a trickle bed reactor, or discontinuously in stirred tank reactors with powdered nickel on kieselguhr or precious metal on activated carbon catalysts. Reaction products were analyzed off-line with capillary gas chromatography. 

In order to explain the high catalytic effect of cobalt naphthenate, Bailey et al. 45) suggested that the cobalt atom forms coordination complexes with the nitrogen and oxygen atoms in two isocyanate groups whereby the positive charges on the carbon atoms are increased and the isocyanate groups are activated for the reaction with the hydroxyl compound ... 

Catalytic Reactions with Modified Activated Carbon 645... 

Active carbons accelerate reactions to which various other war gases are subject and this phase has been given much study. One development is to impregnate carbons with salts that enhance the catalytic power and destroy the toxicity of a gas by a chemical change. This provides protection against certain toxic gases that cannot be eliminated by adsorption alone.6... 

This chapter begins with a general description of the several strategies to het-erogenize transition-metal complexes onto solid supports, with a special emphasis on those methodologies that have been used for complex grafting onto carbon materials. It will include sections that will focus on the various transition-metal complexes that have been immobilized onto several carbon materials activated carbons, black carbons, carbons xerogels, and carbon nanotubes the specific catalytic reactions with these carbon-based systems are also discussed in some detail. 

The initial biotransformation in a one-pot process, however, can also be used to prepare in situ an activated reagent which then reacts with an added substrate. Also not exactly fitting into the above-mentioned scheme of a one-pot two-step process, also here more than one synthetic step is carried out without a work-up in between. An elegant example in this area was reported by Novo Nordisk researchers, who converted in a first step acetic acid into acetic peracid through a catalytic reaction with a lipase and hydrogen peroxide, followed by a subsequent epoxidation of alkenes, for example, 46, with the in situ formed peracid [44]. By means of this method, a range of epoxides were prepared with yields up to >99%. A selected example is shown in Scheme 19.16. A related example was reported by Riisch gen. Klaas and Warwel [45], who started from dimethyl carbonate and hydrogen peroxide for in situ preparation of the needed peracid. 

Highly reactive Pd(0) powder is prepared by the reduction of Pd(II) salts with Li or K and used for catalytic reactions] 19,20]. Pd on carbon in the presence of PI13P is used as an active catalyst similar to PdfPh, ),] ]. 

TT-Allylpalladium chloride (36) reacts with the nucleophiles, generating Pd(0). whereas tr-allylnickel chloride (37) and allylmagnesium bromide (38) reacts with electrophiles (carbonyl), generating Ni(II) and Mg(II). Therefore, it is understandable that the Grignard reaction cannot be carried out with a catalytic amount of Mg, whereas the catalytic reaction is possible with the regeneration of an active Pd(0) catalyst, Pd is a noble metal and Pd(0) is more stable than Pd(II). The carbon-metal bonds of some transition metals such as Ni and Co react with nucleophiles and their reactions can be carried out catalytic ally, but not always. In this respect, Pd is very unique. 

Unsaturated nitriles are formed by the reaction of ethylene or propylene with Pd(CN)2[252]. The synthesis of unsaturated nitriles by a gas-phase reaction of alkenes. HCN, and oxygen was carried out by use of a Pd catalyst supported on active carbon. Acrylonitrile is formed from ethylene. Methacrylonitrile and crotononitrile are obtained from propylene[253]. Vinyl chloride is obtained in a high yield from ethylene and PdCl2 using highly polar solvents such as DMF. The reaction can be made catalytic by the use of chloranil[254]. 

Catalysis. Catalytic properties of the activated carbon surface are useful in both inorganic and organic synthesis. For example, the fumigant sulfuryl fluoride is made by reaction of sulfur dioxide with hydrogen fluoride and fluorine over activated carbon (114). Activated carbon also catalyzes the addition of halogens across a carbon—carbon double bond in the production of a variety of organic haUdes (85) and is used in the production of phosgene... 

The potential for the use of catalysis in support of sustainability is enormous [102, 103]. New heterogeneous and homogeneous catalysts for improved reaction selectivity, and catalyst activity and stabihty, are needed, for example, new catalytic materials with new carbon modifications for nanotubes, new polymers. 

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