Palladium oxide catalyst

Similar to p-keto esters, P-keto amides may be readily hydrogenolyzed by conditions. Thus, 3-acyloxyindole (10), a P-keto amide, is cleanly hydrogenolyzed to the corresponding 3-alkyl derivative in ethanol over Adams palladium oxide catalyst (eq. 5.37).126... 

With regard to other catalysts, little is known about the activity of palladium oxide catalysts for oxygen gas evolution. As discussed earlier in this section, it seems to be a poorer catalyst than Ru, Ir, or Rh oxides. A report by Razina and Gur eva [258] suggests that PdO has relatively good... 

At present, one catalytic combustion system has been implemented at a full scale the XONON Cool Combustion technology, developed by Catalytica Energy Systems 157,158). The system is operated as follows Fuel from a lean-mix prebumer and the main fuel stream together with compressed air pass through the catalyst module (palladium oxide catalyst deposited on corrugated metal foil) in which the gas reaches a temperature up to 1623 K. The UHC and CO are combusted to essentially full conversion, downstream of the catalyst in the homogenous combustion zone. The guaranteed emission levels are as follows NOj < 3 ppm. 

Hydrogenation of 1-octyne and phenylacetylene in C2 to n-C4 alcohols and n-C6 to n-Cg alkenes by palladium oxide catalysts 15... 

Supported palladium oxide catalysts present the best performance for methane combustion in lean conditions. Consequently, the interactions between methane and palladium oxide or metallic palladium supported on AI2O3, Zr02 and BN at 673 K have been studied by microcalorimetry. At this temperature, methane reduced the palladium oxide, and the heat of reduction of palladium oxide was shown to depend on the dispersion and the support. The lowest heats of reduction corresponded to the highest rates of methane combustion [75]. 

Palladium oxide catalysts for high temperature combustion and their manufacture JP 08309184 Petrol. Energy Centre Foundation Catalyst consisting of PdO on a zirconia-based support and its manufacturing... 

A SiC mesh based burner, with an internal heating system. Catalyst with passive channels based on PdJPdO Design of catalyst system for natural gas combustion using a supported palladium oxide catalyst p. 

As in the palladium(II)-catalysed indole annulation, a diastereomerically pure substrate was designed to help elucidate the mechanism of the benzofuran and dihydrobenzo-furan syntheses (Scheme 9.21). When aryl allyl ether 163 was treated with the palladium oxidation catalyst, dihydrobenzofuran 164 was produced as an exclusive di-astereomer in 60% yield. This observation confirmed that an oxidative Heck reaction pathway, featuring arene palladation, alkene insertion and /3-hydride elimination, was operative. 

Postole, G., Bonnetot, B., Gervasini, A., etal. (2007). Characterisation of BN-supported palladium oxide catalyst used for hydrocarbon oxidation, Appl Catal. A General 316, pp. 250-258. 

Alvarz-Galvan, M.C., de la Pena O Shea, V.A., Fierro, J.L.G., and Arias, P.L. Alumina-supported manganese and manganese-palladium oxide catalysts for VOCs combustion. Catal. Commun. 2003, 4, 223—228. 

In a more interesting process, all of the fuel/air mixture is added to a combustor with three sections. The first section contains an active palladium oxide catalyst that can operate up to about 800°C before being reduced to palladium metal which is less active. The palladium oxide catalyst is regenerated by reoxidation of the metal as temperature falls. A more stable catalyst in the second section continues the catalytic combustion. In the third section, combnstion is completed by thermal reaction and the gas temperature increases to 1300°-1400 C. Overall, less than 1 ppm NOX is formed. Palladium oxide is supported on a monolith coated with temperature resistant barium hexaaluminate. ... 

Palladium catalysts are useful alternatives to Adams platinum oxide catalyst described in Section 111,150. The nearest equivalent to the latter is palladium chloride upon carbon and it can be stored indefinitely the palladium salt is reduced to the metal as required ... 

The nickel or cobalt catalyst causes isomerization of the double bond resulting in a mixture of C-19 isomers. The palladium complex catalyst produces only the 9-(10)-carboxystearic acid. The advantage of the hydrocarboxylation over the hydroformylation reaction is it produces the carboxyUc acids in a single step and obviates the oxidation of the aldehydes produced by hydroformylation. 

Nitropyridazines are reduced catalytically either over platinum, Raney nickel or palladium-charcoal catalyst. When an N-oxide function is present, palladium-charcoal in neutral solution is used in order to obtain the corresponding amino N-oxide. On the other hand, when hydrogenation is carried out in aqueous or alcoholic hydrochloric acid and palladium-charcoal or Raney nickel are used for the reduction of the nitro group, deoxygenation of the N- oxide takes place simultaneously. Halonitropyridazines and their N- oxides are reduced, dehalogenated and deoxygenated to aminopyridazines or to aminopyridazine N- oxides under analogous conditions. 

Palladium catalysts have been prepared by fusion of palladium chloride in sodium nitrate to give palladium oxide by reduction of palladium salts by alkaline formaldehyde or sodium formate, by hydrazine and by the reduction of palladium salts with hydrogen.The metal has been prepared in the form of palladium black, and in colloidal form in water containing a protective material, as well as upon supports. The supports commonly used are asbestos, barium carbonate, ... 

The temperature rise in the inlet stage is limited by taking advantage of the unique properties of palladium combustion catalysts. Under combustion conditions, palladium can be either in the form of the oxide or the metal. Palladium oxide is a highly active combustion catalyst, whereas palladium metal is much less active. Palladium oxide is formed under oxidizing conditions... 

Palladium catalyst foe partial ee DUCTION OF ACETYLENES, 46, 89 Palladium on charcoal, catalyst for reductive methylation of ethyl p-mtrophenylacetate, 47, 69 in reduction of l butyl azidoacetate to glycine J-butyl ester 4B, 47 Palladium oxide as catalyst for reduction of sodium 2 nitrobenzene sulfinate, 47, S... 

The postulated steps that constitute the Suzuki coupling process are shown in Scheme 25. After oxidative addition of the organic halide to the palladium(o) catalyst, it is presumed that a metathetical displacement of the halide substituent in the palladium(ii) complex A by ethoxide ion (or hydroxide ion) takes place to give an alkoxo-palladium(ff) complex B. The latter complex then reacts with the alkenylborane, generating the diorganopalladium complex C. Finally, reductive elimination of C furnishes the cross-coupling product (D) and regenerates the palladium(o) catalyst. 

The most successful class of active ingredient for both oxidation and reduction is that of the noble metals silver, gold, ruthenium, rhodium, palladium, osmium, iridium, and platinum. Platinum and palladium readily oxidize carbon monoxide, all the hydrocarbons except methane, and the partially oxygenated organic compounds such as aldehydes and alcohols. Under reducing conditions, platinum can convert NO to N2 and to NH3. Platinum and palladium are used in small quantities as promoters for less active base metal oxide catalysts. Platinum is also a candidate for simultaneous oxidation and reduction when the oxidant/re-ductant ratio is within 1% of stoichiometry. The other four elements of the platinum family are in short supply. Ruthenium produces the least NH3 concentration in NO reduction in comparison with other catalysts, but it forms volatile toxic oxides. 

Some companies are successfully integrating chemo- and biocatalytic transformations in multi-step syntheses. An elegant example is the Lonza nicotinamide process mentioned earlier (.see Fig. 2.34). The raw material, 2-methylpentane-1,5-diamine, is produced by hydrogenation of 2-methylglutaronitrile, a byproduct of the manufacture of nylon-6,6 intermediates by hydrocyanation of butadiene. The process involves a zeolite-catalysed cyciization in the vapour phase, followed by palladium-catalysed dehydrogenation, vapour-pha.se ammoxidation with NH3/O2 over an oxide catalyst, and, finally, enzymatic hydrolysis of a nitrile to an amide. 

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