Nickel-alloy catalyst

Cold-Nickel Alloy Catalysts for Steam Reforming... 

Fig. 6. Activities of copper-nickel alloy catalysts for the hydrogenolysis of ethane to methane and the dehydrogenation of cyclohexane to benzene. The activities refer to reaction rates at 316° C. Ethane hydrogenolysis activities were obtained at ethane and hydrogen pressures of 0.030 and 0.20 atm., respectively. Cyclohexane dehydrogenation activities were obtained at cyclohexane and hydrogen pressures of 0.17 and 0.83 atm, respectively (74).

Fresh reducing gas is generated by reforming natural gas with steam. The natural gas is heated in a recuperator, desulfurized to less than 1 ppm sulfur, mixed with superheated steam, further preheated to 620°C in another recuperator, then reformed in alloy tubes filled with nickel-based catalyst at a temperature of 830°C. The reformed gas is quenched to remove water vapor, mixed with clean recycled top gas from the shaft furnace, reheated to 925°C in an indirect fired heater, and injected into the shaft furnace. For high (above 92%) metallization a CO2 removal unit is added in the top gas recycle line in order to upgrade the quaUty of the recycled top gas and reducing gas. 

Nickel sulfide, NiS, can be prepared by the fusion of nickel powder with molten sulfur or by precipitation usiag hydrogen sulfide treatment of a buffered solution of a nickel(II) salt. The behavior of nickel sulfides ia the pure state and ia mixtures with other sulfides is of iaterest ia the recovery of nickel from ores, ia the high temperature sulfide corrosion of nickel alloys, and ia the behavior of nickel-containing catalysts. 

Clean sodium (0.19 g), free of paraffin or petroleum residues, is dissolved in deuterium oxide (1.2 ml) and Raney nickel alloy (0.25 g) is added in small portions over 8 min while maintaining the temperature at about 50°. When the addition is complete, the supernatant is poured off and the catalyst is washed by decantation with deuterium oxide (3x2 ml) followed by methanol-OD (2x1 ml). The catalyst should be prepared fresh as needed and the preparation carried out as rapidly as possible. 

Two different sets of experimental conditions have been used. Buu-Hoi et al. and Hansen have employed the method introduced by Papa et using Raney nickel alloy directly for the desulfurization in an alkaline medium. Under these conditions most functional groups are removed and this method is most convenient for the preparation of aliphatic acids. The other method uses Raney nickel catalysts of different reactivity in various solvents such as aqueous ammonia, alcohol, ether, or acetone. The solvent and activity of the catalyst can have an appreciable influence on yields and types of compounds formed, but have not yet been investigated in detail. In acetic anhydride, for instance, desulfurization of thiophenes does not occur and these reaction conditions have been employed for reductive acetylation of nitrothiophenes. Even under the mildest conditions, all double bonds are hydrogenated and all halogens removed. Nitro and oxime groups are reduced to amines. 

Yields obtained from catalyst prepared from 125 gm of aluminum-nickel alloy. In xylene as solvent. 

The chiral catalyst was made from Raney nickel, which was prepared by addition in small portions of 3.9 g Raney nickel alloy to 40 ml water containing9 g NaOH. The mixture was kept at 100 C for 1 h, and then washed 15 times with 40 ml water. Chirality was introduced by treatment of the Raney nickel for I h at lOO C with 178 ml water adjusted to pH 3.2 with NaOH and containing 2g (S,S)-tartaric acid and 20 g NaBr. The solution was then decanted, and the modifying procedure was twice repeated. Hydrogenation over this catalyst of acetylacctone (100 atm, 100" C) in THF containing a small amount of acetic acid gave an isolated yield of chiral pentanediol of 44% (99.6% optical purity). 

The product is hydrogenated in 4,000 cc of ethanol at room temperature and under normal atmospheric pressure with a catalyst prepared In the usual manner from 400 g of Raney nickel alloy. The calculated amount of hydrogen is taken up in approximately 75 hours. After filtration and evaporation to a small volume, the residue Is distributed between 1,000 cc of chloroform and water each. The chloroform solution is then dried over sodium sulfate and evaporated to a small volume. Precipitation of the hydrogenation product with petroleum ether yields an amorphous white powder which Is filtered by suction, washed with petroleum ether and dried at 50°C In a high vacuum. 1. athyl-2-podophyllinic acid hydrazide is obtained in a practically quantitative yield. 

The advanced all-metallic catalysts are believed to be formed by bonding active copper-nickel alloys onto stainless steel wires. Under the scanning electron microscope, it appears that the surface area may be more than twenty times the geometric surface area (42) ... 

In studies on the para-hydrogen conversion rate on nickel and its alloys with copper other authors also noted the poisoning effect of the sorbed hydrogen. Singleton (53) mentioned the poisoning of nickel film catalysts by the slow-sorbed hydrogen. Shallcross and Russell (54) observed a similar phenomenon for nickel and its alloys with copper at — 196°C. At higher... 

Recently, other authors when studying the activation of hydrogen by nickel and nickel-copper catalysts in the hydrogen-deuterium exchange reaction concentrated for example only on the role of nickel in these alloys (56) or on a correlation between the true nickel concentration in the surface layer of an alloy, as stated by the Auger electron spectroscopy, and the catalytic activity (57). 

Hardy and Linnett (59) studied the heterogeneous recombination of atomic hydrogen at room temperature on nickel and nickel alloy foils. They did not find any similarity to the behavior of palladium and its alloys with gold studied earlier (35). There was no evidence that, as a result of exposure to atomic hydrogen, hydride was formed in any metal catalyst investigated with a resulting change in the activity of the initial parent metal catalysts. 

The temperature behavior of the alloy catalysts in the heterogeneous recombination of hydrogen atoms was different for rich in nickel alloys from one side and for rich in copper from the other. For the three alloy catalyst films, i.e. Ni97Cu3, Ni77Cu23, and Ni57Cu43 (numbers represent... 

Evidence for a marked difference between the surface and bulk compositions of dilute copper-nickel alloys has been reported recently by a number of investigators (82, 87-90). Much of the experimental evidence comes from hydrogen adsorption data (74, 82, 87, 90). The conclusions of van der Plank and Sachtler were based on the premise that nickel chemisorbs hydrogen while copper does not (82, 87). The total adsorption of hydrogen at room temperature was taken as a measure of the amount of nickel in the surface. However, in hydrogen adsorption studies on the catalysts used to obtain the catalytic results in Fig. 6, the amount of adsorption on the copper catalyst, while small compared to the adsorption on nickel, is not negligible (74) However, the amount of strongly adsorbed... 

N ickel-chromium-molybdenum (tungsten) alloys Nickel—molybdenum alloys Nickel-molybdenum catalysts Pb Mo6S8... 

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