Supported Rhodium Catalysts

The per cent of dicyclohexylamine formed in hydrogenation of aniline increases with catalyst in the order ruthenium < rhodium platinum, an order anticipated from the relative tendency of these metals to promote double bond migration and hydrogenolysis (30). Small amounts of alkali in unsupported rhodium and ruthenium catalysts completely eliminate coupling reactions, presumably through inhibition of hydrogenolysis and/or isomerization. Alkali was without effect on ruthenium or rhodium catalysts supported on carbon, possibly because the alkali is adsorbed on carbon rather than metal (22). 

The catalytic performance of the fluoropolymer ligands 1 and 2 was first tested in the fluorous biphase hydroformylation of 1-alkenes, styrene and n-butyl acrylate. The reaction was conducted in a batch reactor in a 40/20/40 vol% hexane/toluene/perfluoromethylcyclohexane solvent mixture (10 mL). The catalyst was formed in situ by adding [Rh(CO)2(acac)] (5 rmol, P/Rh = 6) to the polymer-containing solvent mixture followed by introduction of syngas (30 bar, CO/H2 = 1/1). Table 2 summarises the results obtained. The salient features of the results are Firstly, the activity of the fluorous soluble polymer catalysts are significantly higher than that reported for solid polymer- and aqueous soluble polymer-supported rhodium catalysts.18-22 For example, the average turnover frequency (TOF) for the fluorous biphase hydroformylation of 1-decene is 136 mole aldehyde h-1 per mol of rhodium catalyst with an aldehyde selectivity of 99%. In comparison, a rhodium catalyst supported on the... 

Partial oxidation runs at 700-1000 °C, typically on a platinum or rhodium catalyst supported on alumina or other oxides and c) Autothermal Reforming (ATR) which combines steam reforming and partial oxidation reactions to produce a roughly thermo-neutral reaction ... 

Auto thermal reforming has a theoretical thermally neutral value for y = 1.115. auto thermal reforming typically runs at 700-1000 °C on platinum or rhodium catalysts supported on alumina or other oxides. Since auto thermal reforming reactions are thermally neutral, then feeds must be pre-heated to within 200 °C of the reactor outlet temperature. 

Rhodium catalysts supported via chelating phosphines as described above have been used as Asymmetric Hydrogenation catalysts." ... 

Hydrogenation of carbon dioxide over rhodium catalyst supported on silica... 

A similar explanation may well be valid for a study by Yates and Sinfelt of the specific activity of rhodium catalysts supported on silica for the hydrogenolysis of ethane to methane 49). As in the example just discussed, there appears to be a sharp contrast in order of magnitude between the specific activity of catalysts with particle size below 40 A (the sensitive range of Poltorak) and above that size (130-2500 A) where bulk behavior is expected. In this case, I speculate that, with very small particles, hydrocarbon surface residues which appear to play an important role in the hydrogenolysis of ethane may well perturb the metallic character of the small rhodium particles, just like adsorbed oxygen in the case of Poltorak and co-workers. 

The decrease in the activity of the rhodium catalyst supported on the pillared clay (Rh/BENPIL) after the reaction was carried out at 100 °C is significant. 

The diastereoselective hydrogenation of N-(2-methylbenzoyl)-f5j-proline methyl ester 1 into optically active 2-methylcyclohexane carboxylic acids was studied on rhodium catalysts supported on active carbon, graphite and alumina. The diastereoselectivity was highly dependent upon the nature of the support. Without modification of the catalysts by EDCA, a 40% d.e. was measured over Rh/AljOj, in contrast to Rh/C or Rh/G catalysts which were unselective. The adsorption of the aromatic substrate via a specific face on Rh/ AljOj was interpreted in terms of electronic and/or steric factors on the basis of TEM and XPS studies. EDCA addition had comparatively little effect on the initial rates and d.e. of Rh/AljO, because the amine was preferentially adsorbed on the acidic sites of the alumina support. In contrast, the... 

The diastereoselective hydrogenation of N-(2-methylbenzoyl)-(5)-proline methyl ester 1 into optically active 2-methylcyclohexane carboxylic acids was studied on rhodium catalysts supported on active carbon, graphite and alumina. The following points were highlighted ... 

From the standpoint of applied research, the optimization of the rhodium catalyst (support and thermal pretreatment) and of reaction conditions (solvent, addition of amine) have led to a final d.e. of 68%, which is much higher than those obtained in our previous investigations and is encouraging for further studies in view of the difficulties to achieve the chiral synthesis of cyclohexyl derivatives. 

A number of rhodium catalysts supported on FibreCat (the 2000 series, see Figure 5) have been developed for the catalysis of selective hydrogenation reactions... 

Catalytic Hydrogenation of Olefins in Supercritical Carbon Dioxide Using Rhodium Catalysts Supported on Fluoroacrylate Copolymers... 

Cominos et al. [324] tested platinum, mthenium and rhodium catalysts supported by alumina and ceria and bimetallic platinum catalysts, namely platinum/rhodium, platinum/cobalt and platinum/mthenium all supported by y-alumina. The samples were tested as coatings in microchannels. The feed was composed of 58 vol.% hydrogen, 21 vol.% carbon dioxide, 1.12 vol.% carbon monoxide, 4.6 vol.% oxygen and 15 vol.% nitrogen, which corresponded to an O/CO ratio of 8. Over mthenium/ platinum, rhodium/platinum and rhodium conversion close to 100% was achieved. 

A different type of membrane reactor for the partial oxidation of methane was presented by Ikeguchi etal. [529]. While air was fed to the membrane on the retenate side, methane was fed to the permeate side. In this way oxygen ions permeated through the membrane and reacted with methane on the permeate side over a 1 wt.% rhodium catalyst supported on magnesia. The membrane was about 800- im thick. 

Early converters were designed to oxidize CO, H2, and unburnt hydrocarbons (oxidizing converters). More recently, "three-way converters have been developed to oxidize hydrocarbons, H2, and CO, and reduce NO emissions simultaneously. This goal is achieved by using a suitably promoted Platinum-Rhodium catalyst supported on alumina and by carefully controling the air/fuel ratio. The catalyst is a thin porous alumina layer "wash-coated" on the wall of the monolith channels. Typically the wash-coat is about a few tens of a micrometer thick, except at the corners of the channel where it is thicker. 

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