Platinum catalysts, sulfided

Aromatic amine-Ketone. The interaction between anihne, the simplest of the aromatic amines with acetone in the presence of various catalysts to yield N-isopropylaniline was examined (Table 17.3). Among the catalysts tested, sulfided platinum catalysts were found to be the most active catalysts for this reaction. 

The current work indicates that sulfided platinum catalysts are, in general, more active and selective than Pt, Pd, or sulfided Pd catalysts for reductive alkylation of primary amines with ketones. The choice of the catalyst preparation parameters, especially the support, plays a major role in determining the performance of the catalyst. Diamines, especially of lower molecular weight, tend to react with ketones even at room temperature to form heterocycles such as imidazolidine, diazepanes, and pyrimidines. Hence, a continuous reactor configuration that minimizes the contact between the amine and the ketone, along with a highly active catalyst is desired to obtain the dialkylated product. In general, sulfided Pt appears to be more suited for the reductive alkylation of ethylenediamine while unsulfided Pd or Pt may also be used if 1,3-diaminopropane is the amine. 

Venkataraman, R., H.R. Kunz, and J.M. Fenton. 2004. CO-tolerant, sulfided platinum catalysts for PEMFCs.. Electrochem. Soc. 151 A710-A715. 

Venkataraman R, Kunz H R and Fenton J M (2004) CO-Tolerant, Sulfided Platinum Catalysts for PEMFCs, J. Electrochem. Soc., 151, pp. A710-A715. 

Reduction. Benzene can be reduced to cyclohexane [110-82-7], C5H12, or cycloolefins. At room temperature and ordinary pressure, benzene, either alone or in hydrocarbon solvents, is quantitatively reduced to cyclohexane with hydrogen and nickel or cobalt (14) catalysts. Catalytic vapor-phase hydrogenation of benzene is readily accomplished at about 200°C with nickel catalysts. Nickel or platinum catalysts are deactivated by the presence of sulfur-containing impurities in the benzene and these metals should only be used with thiophene-free benzene. Catalysts less active and less sensitive to sulfur, such as molybdenum oxide or sulfide, can be used when benzene is contaminated with sulfur-containing impurities. Benzene is reduced to 1,4-cydohexadiene [628-41-1], C6HS, with alkali metals in liquid ammonia solution in the presence of alcohols (15). 

The chief advantages of the contact process are the high purity of the product and the fact that the product is a concentrated acid. Disadvantages are the high cost of the catalysts and the fact that if sulfides are used as raw materials, costly purification of the sulfur dioxide is necessary, because impurities such as arsenic trioxide and selenium dioxide poison the catalyst (i.e., render the catalyst inactive). Platinum catalysts are particularly sensitive to these impurities, while vanadium catalysts are claimed to be free from this disadvantage. 

When treated with hydrogen and a platinum catalyst, an unknown compound X absorbs 5 equivalents of hydrogen to give n-butylcyclohexane. Treatment of X with an excess of ozone, followed by dimethyl sulfide and water, gives the following products ... 

Malz, Jr. and Greenfield studied the preparation of tertiary amines by reductive alkylation of aliphatic secondary amines with ketones, using platinum metals and their sulfides as catalysts.40 Excellent yields of tertiary amines were obtained with unhindered ketones, such as cyclohexanone and acetone, and relatively unhindered secondary amines. In this study, 5% Pd-C and various transition metal sulfides were compared in the reductive alkylation of dibutylamine with cyclohexanone. By using the reaction conditions suitable to each catalyst, excellent yields of tertiary amines were obtained, as shown in Table 6.5. Approximately 5-15% of the excess cyclohex-... 

Platinum catalysts have been shown to be highly selective for the hydrogenation of halonitrobenzenes to haloanilines. A number of effective platinum catalysts or catalyst systems have been described in the literature, mostly in patents.96 Dovell and Greenfield found that the sulfides of the platinum metals and cobalt were highly selective in the hydrogenation of halo-substituted nitrobenzenes.117-119 There was no detectable dechlorination with the sulfides of palladium, platinum, rhodium, ruthenium, and cobalt no detectable debromination occurred with platinum sulfide trace debromination occurred with rhodium sulfide and cobalt sulfide and appreciable debromination occurred with palladium sulfide. Typical hydrogenations with 5% platinum sulfide on carbon catalyst are given in eqs. 9.52 and 9.53 with 2,5-dichloronitrobenzene and p-bromobenzene, respectively.118... 

Some of other effective platinum catalysts are sulfided platinum on carbon120 or platinum catalysts with inhibitors such as bis(2-hydroxyethyl)sulfide,121 morpholine,122 polyamines,123 phosphorous acid,105 phosphoric acid,124 and dicyandiamide.96 Dicy-andiamide was originally used as an effective inhibitor for Raney Ni, as described above (see eq. 9.50).113 Hydrogenations of halonitrobenzenes with use of these platinum catalysts are summarized in Table 9.5. In one patent, it is claimed that ethano-lamine is a better inhibitor than morpholine for Pt-C. Thus, 3,4-dichloronitrobenzene was hydrogenated over Pt-C modified with iron oxide in the presence of 1.2 mol% ethanolamine to give 3,4-dichloroaniline containing only 235 ppm of 4-chloroaniline, compared to 548 ppm with morpholine as the inhibitor.125... 

Chloroquinoxalin-2(1 W)-one 4-oxide has been selectively hydrogenated to 6-chloro-quinoxalin-2(l/f)-one, using sulfided and non-sulfided catalysts, with the catalyst of choice being sulfided platinum. 

Poisoning of metal catalysts may provide a tool for improving selec> tivity by affecting the concentrations of ensembles required by different reaction paths. This is illustrated by steam reforming on sulfur passivated nickel catalysts and the results are compared with observations for sulfided platinum-rhenium catalysts for catalytic reforming and for a chlorine poisoned palladium catalyst for partial oxidation of methane. 

Note 2 More efficient methods than electrolysis for obtaining hydrogen from water are under investigation. One of these is thermochemical decomposition. Another is photochemical decomposition by solar radiation, either directly or via a solar power generator. Photolytic decomposition of water with platinum catalyst has been achieved. Hydrogen can also be obtained by photolytic decomposition of hydrogen sulfide with cadmium sulfide catalyst. 

Oxonium fluorination Perchloryl fluoride. Oxygenation Platinum catalyst. Oxymercuration Mercuric acetate. Ozonization Dimethyl sulfide. 

The literature is filled with various processes and catalyst compositions and systems for these transformations. Promoted platinum and sulfided platinum are the most selective group VIII metal catalysts but depending on reaction conditions and the nature of the halogenonitrobenzene, some undesirable halo-azo and azoxy compounds are left in the product (refs. 3, 11). 

Although the exchange of the hydroxyl hydrogen in methanol with deuterium in various deuterium compounds such as deuterium oxide and deuterium sulfide has been reported 1-3) and the preparation of methanol-d (CH3OD) by the saponification of esters and decomposition of Grignard reagent with deuterium oxide has been described 4 6), the catalytic exchange of deuterium gas with methanol over Adams platinum catalyst has not been previously studied. 

We selectively hydrogenated 6-chloro-2(IH)-hydroxyquinoxaline-4-oxides to 6-chloro-2(IH)-quinoxalinone, using sulfided and non-sulfided catalysts. The catalyst of choice is platinum sulfide. Our catalyst studies included sulfided and non-sulfided platinum, palladium, rhodium, ruthenium, sulfided nickel, Raney nickel, and cobalt. 

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