Supported catalysts, for hydrogenation

Scheme VII classifies potential spectator ligands according to their ligation mode. Ansa, doubly charged A-type ligands, have been prominent in catalytic investigations up to now and are usually employed in a neutral, heteroleptic form. The additional Ln-R moiety directs the catalytic reactivity in a nonspectator manner Due to its kinetic lability, the Ln-R bond is accessible to ligand exchange reactions, as shown in ansa-cyclopentadienyl-supported catalysts for hydrogenation and polymerization reactions [83]. Biphenol or binaphthol ligands [175], the latter of which was recently successfully applied (e.g. in...

Scheme 11.1 Synthesis of zeolite supported catalyst for hydrogenation reaction.

In light of the excellent performances of carbon supported catalysts for hydrogen oxidation in fuel cells, and the problem of obtaining and maintaining sufficient conductivity for polymer supports at the low potentials required, the prospects for polymer supported catalysts appear to be weak. 

Scheme 7.17. Supported catalysts for hydrogen transfer reaction.

Gronchi P., Kaddouri A., Centola P., Del Rosso R. Synthesis of nickel supported catalysts for hydrogen production by sol-gel method. J. Sol-Gel Sci. Technol. 2003 26 843-846 Gughehni M., Festa D., Innocenzi P.C., Colombo P., Gobbin M. Borosihcate coatings on mild steel. J. Non-Cryst. Solid 1992 147 148 474-477... 

Rossi, L.M., Silva, F.P., Vono, L.L.R., Kiyohara, P.K., Duarte, E.L., Itri, R., Landers, R. and Machado, G. (2007) Superparamagnetic nanopartide-supported palladium a highly stable magnetically recoverable and reusable catalyst for hydrogenation reactions. Green Chemistry, 9 (4), 379-385. 

Jacinto, M.J., Landers, R. and Rossi, L.M. (2009) Preparation of supported Pt(0) nanopartides as efficient recyclable catalysts for hydrogenation of alkenes... 

Baruwati, B., Polshettiwar, V. and Varma, R.S. (2009) Magnetically recoverable supported ruthenium catalyst for hydrogenation of alkynes and transfer... 

Catalysts for hydrogenation can be also supported on ion exchange resins. For example, rhodium(III) chloride, attached to a 3-carboxy-butenolic acid/DVB cation exchange resin with... 

This (R)-polyBINAP support, when treated with [Rh(cod)2]BF4 or [ RuC12(C6H6) 2]. afforded a heterogeneous asymmetric catalyst for hydrogenation of dehydroaminoacid derivatives and ketones.100 As an extension, a copolymer with BINOL and BINAP units randomly distributed... 

The existence of two different rhodium species co-existing on the silica support can be used as an advantage by controlling their relative amount. Under standard hydroformylation conditions, the cationic species and the neutral hydride complex are both present in significant amounts. Hence hydroformylation and hydrogenation will both proceed under a CO/H2 atmosphere. Indeed a clean one-pot reaction of 1-octene to 1-nonanol was performed, using the supported catalyst for a hydroformylation-hydrogenation cascade reaction. 98 % of the 1-octene was converted in the... 

Scheme 2.15 Supported metal catalysts for hydrogenation and hydroformylation reactions.

The siHca-supported Zr(IV) hydrides 1 obtained by hydrogenolysis of the singlesite siHca-supported species [(=SiO)ZrNp3] are well-known catalysts for hydrogen/ deuterium exchange in saturated hydrocarbons [2, 3], olefin polymerization [4] and alkane or polyolefin hydrogenolysis [5, 6]. They also display a key role in stoichio-... 

Similarly, we can ask what would be the best catalyst for hydrogenating an olefin such as ethylene. Since olefins (alkenes) are more strongly chemisorbed than hydrogen, we choose a metal that just barely chemisorbs H2—this means Co, Rh, Ir, Ni, Pd, or Pt. In practice, nickel is the least expensive choice. Again, it should be finely divided (maximum surface area) for greatest catalytic efficiency and be dispersed on the internal surfaces of a porous support such as alumina with surface area on the order of 200 m2 g 1.8... 

Microwave irradiation also shows a beneficial effect in the preparation of solid-supported palladium catalysts for hydrogenation reactions. Thus, alumina- and silica-supported palladium catalysts were synthesised by conventional and microwave heating, and their physical properties and catalytic activity in the hydrogenation of benzene were compared. The alumina-based system prepared under microwave conditions showed turnover numbers an order of magnitude higher than the conventionally prepared catalysts28. 

A supported catalyst for ethylene polymerization which requires no alkyl aluminum for activation was first claimed by the Phillips Petroleum Company (32). It consists of chromium oxide on silica, reduced with hydrogen. Krauss and Stach (93) showed that the active sites are Cr(II) centers. The presence of solvent, or even aluminum alkyls, diminishes... 

All the hydrogen transfer reactions shown highlight the potential for application of copper-supported catalysts as hydrogen reservoir systems. This leads to the possibility of applying the concept of catalytic electronic activation introduced by Williams and realizing sequences of domino transformations that accomplish otherwise impossible reactions [84, 85]. 

Silicas are used as supports in a variety of catalytic processes. Typical applications are Ni-, Pd-, or Pt-sup-ported catalysts for hydrogenation reactions and V2O5-supported catalysts in the oxidation of SO2 in gases from roasting sulfides or sulfur to yield SO3. 

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