Reduction platinum

Extensive hydrogenolysis of vinyl ethers does not occur always over platinum. Reduction of 28 proceeded smoothly to 29 (/09). It is likely that the high pressure and low temperature used in this experiment helped to minimize hydrogenolysis. For effective use of subambient ( —30°C) temperatures in stopping hydrogenolysis of vinyl functions, see (/Oa). 

According to TPR data, platinum reduction on SZ surface (sample Pt/SZ) in the absence of chemisorption interaction starts from 90 °C. However, in the samples with alumina this process shifts toward higher temperatures, and a maximum rate of hydrogen consumption is observed at 210 and 225 °C for Pt/SZA and Pt/ A. 

H Hiraike, M Kimura, Y Itokawa. Determination of K vitamins (phylloquinone and menaquinones) in umbilical cord plasma by a platinum-reduction column. J Chromatogr 430(1) 143-148, 1988. 

FIGURE 2.35 Schematic of SECM configuration for showing localized modification of platinum substrate. E threshold potential of platinum reduction of the order -1.6 V/SCE. (Ghilane, J., M. GuiUoux-Viry, C. Lagrost, J. Simonet, P. Hapiot, 2007, J. Am. Chem. Soc. 129 6654. Used with permission.)... 

Similar experiments were done with palladium under the conditions described in Section 2.3. First of all, a charged sheet (at a potential of the order of that used for platinum reduction, that is, -2 V versus SCE) of palladium in superdry DMF containing Csl appears to play the role of a reducing material. When this piece of palladium after chemical treatment is put in contact with a solution of AcQ or 1,4-dinitrobenzene, the corresponding color assigned to that of the anion radical... 

If two redox electrodes both use an inert electrode material such as platinum, tlie cell EMF can be written down iimnediately. Thus, for the hydrogen/chlorine fiiel cell, which we represent by the cell Fl2(g) Pt FICl(m) Pt Cl2(g) and for which it is clear that the cathodic reaction is the reduction of CI2 as considered in section... 

CATALYTIC REDUCTION WITH ADAMS PLATINUM OXIDE CATALYST... 

Hydrocinnamic acid may also be prepared by the reduction of cinnamic acid with sodium and alcohol or with sodium amalgam or with hydrogen in the presence of Adams platinum oxide catalyst (Section 111,150) ... 

The Adams platinum oxide catalyst gives satisfactory results in the reduction of ozonidea. 

Catalytic reduction over a platinum catalyst fails because of poisoning of the catalyst (101). 

Nitro groups are readily reduced to primary amines by a variety of methods Cat alytic hydrogenation over platinum palladium or nickel is often used as is reduction by iron or tin m hydrochloric acid The ease with which nitro groups are reduced is especially useful m the preparation of arylamines where the sequence ArH ArN02 ArNH2 IS the standard route to these compounds... 

Common catalyst compositions contain oxides or ionic forms of platinum, nickel, copper, cobalt, or palladium which are often present as mixtures of more than one metal. Metal hydrides, such as lithium aluminum hydride [16853-85-3] or sodium borohydride [16940-66-2] can also be used to reduce aldehydes. Depending on additional functionahties that may be present in the aldehyde molecule, specialized reducing reagents such as trimethoxyalurninum hydride or alkylboranes (less reactive and more selective) may be used. Other less industrially significant reduction procedures such as the Clemmensen reduction or the modified Wolff-Kishner reduction exist as well. 

One factor contributing to the inefficiency of a fuel ceU is poor performance of the positive electrode. This accounts for overpotentials of 300—400 mV in low temperature fuel ceUs. An electrocatalyst that is capable of oxygen reduction at lower overpotentials would benefit the overall efficiency of the fuel ceU. Despite extensive efforts expended on electrocatalysis studies of oxygen reduction in fuel ceU electrolytes, platinum-based metals are stiU the best electrocatalysts for low temperature fuel ceUs. 

Reduction of the aromatic nuclei contained in catalytic C-9 resins has also been accomplished in the molten state (66). Continuous downward concurrent feeding of molten resin (120°C softening point) and hydrogen to a fixed bed of an alumina supported platinum—mthenium (1.75% Pt—0.25% Ru) catalyst has been shown to reduce approximately 100% of the aromatic nuclei present in the resin. The temperature and pressure required for this process are 295—300°C and 9.8 MPa (lOO kg/cni2), respectively. The extent of hydrogenation was monitored by the percent reduction in the uv absorbance at 274.5 nm. 

Reduction. Most ketones are readily reduced to the corresponding secondary alcohol by a variety of hydrogenation processes. The most commonly used catalysts are palladium, platinum, and nickel For example, 4-methyl-2-pentanol (methyl isobutyl carbinol) is commercially produced by the catalytic reduction of 4-methyl-2-pentanone (methyl isobutyl ketone) over nickel. 

Dispersed Metals. Bifimctional zeoHte catalysts, principally zeoHte Y, are used in commercial processes such as hydrocracking. These are acidic zeoHtes containing dispersed metals such as platinum or palladium. The metals are introduced by cation exchange of the ammine complexes, foUowed by a reductive decomposition (21) ... 

The standard potential for the anodic reaction is 1.19 V, close to that of 1.228 V for water oxidation. In order to minimize the oxygen production from water oxidation, the cell is operated at a high potential that requires either platinum-coated or lead dioxide anodes. Various mechanisms have been proposed for the formation of perchlorates at the anode, including the discharge of chlorate ion to chlorate radical (87—89), the formation of active oxygen and subsequent formation of perchlorate (90), and the mass-transfer-controUed reaction of chlorate with adsorbed oxygen at the anode (91—93). Sodium dichromate is added to the electrolyte ia platinum anode cells to inhibit the reduction of perchlorates at the cathode. Sodium fluoride is used in the lead dioxide anode cells to improve current efficiency. 

The PGM concentrate is attacked with aqua regia to dissolve gold, platinum, and palladium. The more insoluble metals, iridium, rhodium, mthenium, and osmium remain as a residue. Gold is recovered from the aqua regia solution either by reduction to the metallic form with ferrous salts or by solvent-extraction methods. The solution is then treated with ammonium chloride to produce a precipitate of ammonium hexachloroplatinate(IV),... 

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