Palladium pumice catalysts

The interaction of cyclopropane with deuterium was examined over rhodium-pumice catalyst at 50° intervals from 0 to 200°, and the propane distributions ramble those observed with palladium, being unaffected by changes in temperature or the initial reactant ratio. However, A is somewhat lower than with palladium, being close to 0.78 throughout the entire... 

The metal-catalysed hydrogenation of cyclopropane has been extensively studied. Although the reaction was first reported in 1907 [242], it was not until some 50 years later that the first kinetic studies were reported by Bond et al. [26,243—245] who used pumice-supported nickel, rhodium, palladium, iridium and platinum, by Hayes and Taylor [246] who used K20-promoted iron catalysts, and by Benson and Kwan [247] who used nickel on silica—alumina. From these studies, it was concluded that the behaviour of cyclopropane was intermediate between that of alkenes and alkanes. With iron and nickel catalysts, the initial rate law is... 

A remarkable number of palladium-catalyzed aerobic oxidation reactions of alcohols have been reported to date [15]. Unfortunately, although some progress has been made with heterogeneous Pd catalysts, such as Pd on activated carbon [16], Pd on pumice [17], Pd-hydrotalcite [18], Pd on Ti02 [19] and Pd/SBA-15 [20], most of these systems suffer from low catalytic activities and a limited substrate scope. 

Typical catalysts for the fixed-bed vapor-phase hydrogenation include nickel sulfide deposited on alumina. For example, First Chemical Corporation (since 2002 a subsidiary of DuPont) employs the Lonza process, with a fixed-bed catalyst of copper on pumice. First Chemical is the world s second largest merchant producer of aniline, at Pascagoula, Mississippi, and Baytown, Texas, and supplies North American Bayer Corporation with its aniline requirements for polyurethanes8. Similar processes are operated by Bayer, with a palladium catalyst on an alumina support, modified with vanadium and lead. A catalyst of nickel sulfide on ammonia has also been revealed. 

Other possible carriers for catalysts are asbestos, pumice, kieselgur, silica gel, silica, active charcoal, and oxides, carbonates, and sulfates of magnesium, calcium, barium, zinc, aluminum, iron, chromium, and zirconium. Details for the preparation of palladium catalysts on barium sulfate have been recorded by Mozingo.137... 

The reaction between cyclopropane and deuterium has been investigated over pumice-supported palladium, rhodium, and platinum catalysts between 0 and 200°, and the resulting deuteropropanes have been analysed mass-spectrometrically. The exchange reaction between propane and deuterium over these catalysts has been similarly studied. In every case there is extensive multiple exchange, and the distribution of deuterium atoms in the propanes is more characteristic of the metal than of the reacting hydrocarbon. Experiments with the isomeric propyl chlorides confirm that exchange proceeds through the equilibria... 

Catalytic reductions have been carried out under an extremely wide range of reaction conditions. Temperatures of 20 C to over 300 C have been described. Pressures from atmospheric to several thousand pounds have been used. Catal3rsts have included nickel, copper, cobalt, chromium, iron, tin, silver, platinum, palladium, rhodium, molybdenum, tungsten, titanium and many others. They have been used as free metals, in finely divided form for enhanced activity, or as compounds (such as oxides or sulfides). Catalysts have been used singly and in combination, also on carriers, such as alumina, magnesia, carbon, silica, pumice, clays, earths, barium sulfate, etc., or in unsupported form. Reactions have been carried out with organic solvents, without solvents, and in water dispersion. Finally, various additives, such as sodium acetate, sodium hydroxide, sulfuric acid, ammonia, carbon monoxide, and others, have been used for special purposes. It is obvious that conditions must be varied from case to case to obtain optimum economics, yield, and quality. 

A. M. Venezia, Chem. Ind. (Milan), 1998, 80, 741-746. Pumice-Supported Palladium Catalysts. 

Although Sabatier and Senderens had hydrogenated oleic acid vapor to produce stearic acid, they did not extend this work themselves. The appendix to Chapters 11 and 12 in their book describes early work to about 1916, by others who used nickel and palladium catalysts. They described the use of nickel supported on pumice, kieselguhr, asbestos, and wood charcoal. ... 

---