Platinum-catalyzed oxidation, effect

The platinum catalyzed oxidation of alcohols with molecular oxygen has been known for a long time.52,53 Palladium and iridium are also effective for this reaction but not rhodium or ruthenium.54 The reaction proceeds by the initial dehydrogenation of the alcohol to produce the aldehyde or ketone with the adsorbed hydrogen then reacting with the oxygen to give water.53>55-58 These... 

With pinitol and quebrachitol, the reaction is highly selective for one of the two axial hydroxyl groups in each compound (see formulas LXIII —> LXVII, and LXV —> LXIX, p. 170).61 This selectivity shows the steric effect of the methyl group. Nevertheless, the platinum-catalyzed dehydrogenation (in contrast to the action of Acetobacter) is not easily inhibited by substitution in the cyclitol molecule even the hindered axial hydroxyl groups in dambonitol (LXXVII) and in O-isopropylidenequebrachitol (LXVI, see p. 172) can be oxidized.62 63... 

The additive approach also was shown to be effective in making a silicone foam. Kittle and Ronk (9 ) demonstrated that addition of ferric oxide or alcohols to platinum catalyzed foam formulation would allow the material to foam when heated by micro-wave, whereas the same composition without ferric oxide or alcohol did not foam or cure. 

The foregoing discussion serves to show that disordered carbon structures are oxidized more readily than well-ordered graphite planes and that dislocations and active sites provide nucleation points for attack of the carbon crystallite. Another factor that must be considered is that dispersed electrocatalysts, such as platinum, on the carbon surface are not benign. The electrocatalysts interact with the carbon causing local oxidation or corrosion, i.e., the platinum catalyzes the corrosion of the carbon itself. In the presence of oxygen, which is the condition under which the electrocatalyst will operate, reduction intermediates from the oxygen (e.g., HOj) can have an accelerated corrosion effect. 

Oxidation. Carbon monoxide can be oxidized without a catalyst or at a controlled rate with a catalyst (eq. 4) (26). Carbon monoxide oxidation proceeds explosively if the gases are mixed stoichiometticaHy and then ignited. Surface burning will continue at temperatures above 1173 K, but the reaction is slow below 923 K without a catalyst. HopcaUte, a mixture of manganese and copper oxides, catalyzes carbon monoxide oxidation at room temperature it was used in gas masks during World War I to destroy low levels of carbon monoxide. Catalysts prepared from platinum and palladium are particularly effective for carbon monoxide oxidation at 323 K and at space velocities of 50 to 10, 000 h . Such catalysts are used in catalytic converters on automobiles (27) (see Exhaust CONTHOL, automotive). 

The reaction of alcohols with CO was catalyzed by Pd compounds, iodides and/or bromides, and amides (or thioamides). Thus, MeOH was carbonylated in the presence of Pd acetate, NiCl2, tV-methylpyrrolidone, Mel, and Lil to give HOAc. AcOH is prepared by the reaction of MeOH with CO in the presence of a catalyst system comprising a Pd compound, an ionic Br or I compound other than HBr or HI, a sulfone or sulfoxide, and, in some cases, a Ni compound and a phosphine oxide or a phosphinic acid.60 Palladium(II) salts catalyze the carbonylation of methyl iodide in methanol to methyl acetate in the presence of an excess of iodide, even without amine or phosphine co-ligands platinum(II) salts are less effective.61 A novel Pd11 complex (13) is a highly efficient catalyst for the carbonylation of organic alcohols and alkenes to carboxylic acids/esters.62... 

To date, the only shock tube apparatus equipped to study surface reactions is the KIST facility at ATK GASL in New York. The tests done so far have studied methane oxidation, CFI4 + 2O2 CO2 + 2H2O on the surface of an SCT ferrous-based reactor impregnated with platinum based catalyst. To isolate the effects of the screen and the catalyst on the reaction, three types of tests were run catalyzed screen with combustible gases,... 

Ruthenium trichloride catalyzes the production of oxygen at a platinum anode404 via higher oxidation state species, whilst one of the most effective catalysts for oxygen or chlorine evolution is formed by reduction of a solution containing [Fe2(S04)3] and K3[Ru(CN)6].404 This leads to a film on the electrode of ruthenium purple, Fe4[Ru(CN)6]3, with a structure analogous to that of Prussian blue. Oxygen can then be produced at 0.2 V vs. SCE.404... 

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