Oxygenated mixture catalysts

Gold nanoparticle catalysts have a good potential for a future process for the direct epoxidation of propene. In a single reactor, propene can be selectively epoxidized using a hydrogen-oxygen mixture. Catalysts containing titanium... 

The calculated half-life of 1 mol % (1.5 wt %) of pure gaseous ozone diluted with oxygen at 25, 100, and 250°C (based on rate constants from Ref. 19) is 19.3 yr, 5.2 h, and 0.1 s, respectively. Although pure ozone—oxygen mixtures are stable at ordinary temperatures ia the absence of catalysts and light, ozone produced on an iadustrial scale by silent discharge is less stable due to the presence of impurities however, ozone produced from oxygen is more stable than that from air. At 20°C, 1 mol % ozone produced from air is - 30% decomposed ia 12 h. 

Oxychlorination of Ethylene or Dichloroethane. Ethylene or dichloroethane can be chlorinated to a mixture of tetrachoroethylene and trichloroethylene in the presence of oxygen and catalysts. The reaction is carried out in a fluidized-bed reactor at 425°C and 138—207 kPa (20—30 psi). The most common catalysts ate mixtures of potassium and cupric chlorides. Conversion to chlotocatbons ranges from 85—90%, with 10—15% lost as carbon monoxide and carbon dioxide (24). Temperature control is critical. Below 425°C, tetrachloroethane becomes the dominant product, 57.3 wt % of cmde product at 330°C (30). Above 480°C, excessive burning and decomposition reactions occur. Product ratios can be controlled but less readily than in the chlorination process. Reaction vessels must be constmcted of corrosion-resistant alloys. 

The catalyst (spheres or rings with a diameter of 3-10 mm) contains 7-20% silver on high-purity a-AI203 having a surface of only <2 m2/g. Cesium or another alkali or earth alkali salt is added in an amount of 100-500 mg/kg catalyst for upgrading the selectivity. However, small amounts of halogen compounds, e.g., dichloroethane, are added to the ethylene/oxygen mixture to inhibit the total oxidation of the ethylene. 

Aqueous cyanide effluent containing a little methanol in a 2 m3 open tank was being treated to destroy cyanide by oxidation to cyanate with hydrogen peroxide in the presence of copper sulfate as catalyst. The tank was located in a booth with doors. Addition of copper sulfate (1 g/1) was followed by the peroxide solution (27 1 of 35 wt%), and after the addition was complete an explosion blew off the doors of the booth. This was attributed to formation of a methanol vapour-oxygen mixture above the liquid surface, followed by spontaneous ignition. It seems remotely possible that unstable methyl hydroperoxide may have been involved in the ignition process. 

Caballero, M. A. Aznar, M. P. Gil, J. Martin, J. A. Frances, E. Corella, J., Commercial steam reforming catalysts to improve biomass gasification with steam-oxygen mixtures. 1. Hot gas upgrading by the catalytic reactor. Industrial and Engineering Chemistry Research 1997,36(12), 5227-5239. 

The checkers found that the reduction requires 4-5 days, whereas the submitter reported the reaction requires 24 hours. Fresh catalyst is added whenever the rate of hydrogen uptake significantly decreases. When fresh catalyst is added to the reaction vessel, it is important that it first be wet with solvent and that the hydrogen be well evacuated. Opening the mixture to the atmosphere without careful evacuation will produce a hydrogen-oxygen mixture which may explode on contact with fresh catalyst. 

Figure 3.8. Dynamic redox experiments in propylene oxygen mixtures around the same sample area m (a) fresh catalyst (b) domains (c) bulk domains with CS nucleation (arrowed) and (d) CS planes. The domains and CS planes are formed even in the presence of oxygen gas (after Gai 1981).

CoTAA plays a particular role here. The thermal activation of this compound is fully described in Section 4.2.4. in connection with its anodic formic-acid activity in sulfuric acid. Thermally pretreated mixtures of CoTAA and activated carbon BRX in the proportion of 1 2 w/w show their peak activity as oxygen-reduction catalysts as a function of treating temperature at about 600 °C (Fig. 22). 

To solubilise a dialkylmethylamine during oxidation to the V-oxide with hydrogen peroxide, methanol was used as diluent in place of water. After oxide formation was complete, platinum black was added to decompose excess peroxide, and an explosion occurred. This was attributed to ignition of the methanol vapour—oxygen mixture by glowing catalyst particles. 

A few benzisoselenazol-3(2//)-oncs were covalently immobilized to the solid support, either silica [165] or polymer [246] (147-150) (Fig. 8). They exhibited appreciable catalytic activity similar to the activity of ebselen. The most interesting prospective oxygen-transfer catalyst is benzisoselenazolone covalently bound to a silica support (147) named HALICAT. It has been applied to hydrogen peroxide oxidation of the sulfides and TBHP oxidation of the aromatic aldehydes and alky-larenes. The catalyst can be easily filtered off from the mixture after the reaction and reused several times [165],... 

Oxygen-blown ATR with natural gas is used today in very large units that generate a mixture of CO and H2 for the Fischer-Tropsch process or methanol synthesis. This is attractive in part because the units can produce the hydrogen-to-carbon monoxide ratio needed in the synthesis step. Since the heat of reaction is added by combustion with oxygen, the catalyst can be incorporated as a fixed bed that can be scaled up to achieve further benefits of larger plant size in both the... 

Treatment of an aqueous solution of ruthenium chloride and staimous chloride with borohydride gave a precipitate of a ruthenium-tin-boride. The ruthenium is present as the metal and the boron as the boride with electron donation to the ruthenium. The tin exists as a mixture of tin(ll) and tin(IV) oxides which interact with the ruthenium through the oxygens. These catalysts are useful... 

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