Nickel Urushibara catalysts

Nickel precipitated from aqueous solutions of nickel chloride by aluminum or zinc dust is referred to as Urushibara catalyst and resembles Raney nickel in its activity [48. ... 

Review. Shiota has reviewed some recent applications of Urushibara catalysts. A new, related nickel catalyst known as U-Ni-N (neutral) has been obtained by refluxing precipitated nickel with isopropanol. As shown in equations I and II this new catalyst shows high selectivity. 

Uridine tri-O-benzoate, 639 Urushibara catalysts, 659 Urushibara nickel A, 659... 

Selective hydrogenations, Japanese chemists have prepared (3) by hydrogenation with Urushibara nickel A catalyst of either (1) or (2). ... 

Benzonitrile added to Urushibara nickel-zinc catalyst (s. Synth. Meth. 12, 93) in water, and refluxed ca. 8hrs. until the oil drops of benzonitrile on the water have disappeared benzamide. Y 78%. — Water as solvent suppresses the activity of the catalyst for hydrogenation but promotes the activity for hydration. F. e. s. K. Watanabe, Bull. Ghem. Soc. Japan 37, 1325 (1964). 

Hydrogenation over nickel catalyst at high temperatures and pressures affects aromatic rings. Over Urushibara nickel at 106-150° and 54atm, ethyl benzoate gave ethyl hexahydrobenzoate in 82% yield [48]. 

Various active nickel catalysts obtained not via reduction of nickel oxide with hydrogen have been described in the literature. Among these are the catalysts obtained by the decomposition of nickel carbonyl 10 by thermal decomposition of nickel formate or oxalate 11 by treating Ni-Si alloy or, more commonly, Ni-Al alloy with caustic alkali (or with heated water or steam) (Raney Ni) 12 by reducing nickel salts with a more electropositive metal,13 particularly by zinc dust followed by activation with an alkali or acid (Urushibara Ni) 14-16 and by reducing nickel salts with sodium boro-hydride (Ni boride catalyst)17-19 or other reducing agents.20-24... 

Urushibara Ni A (U-Ni-A) 6 The solids prepared by the reaction of zinc dust with aqueous nickel chloride solution, in the same way as described above, are transferred into 160 ml of 13% acetic acid and digested at 40°C until the evolution of hydrogen gas subsides or the solution becomes pale green. The catalyst can be washed with water on a glass filter under gentle suction with care to prevent the catalyst from contacting air, and then with the solvent for hydrogenation. 

Besides Urushibara Ni and Ni boride catalysts, various finely divided nickel particles have been prepared by reaction of nickel salts with other reducing agents, such as sodium phosphinate 20,85 alkali metal/liquid NH3 21 NaH-f-AmOH (designated Nic) 22,86Na, Mg, and Zn in THF or Mg in EtOH 24 or C8K(potassium graphite)/THF-HMPTA (designated Ni-Grl) 23,87 Some of these have been reported to compare with Raney Ni or Ni borides in their activity and/or selectivity. 

Urushibara Co catalysts can be prepared exactly in the same way as the corresponding Ni catalysts, using cobalt chloride hexahydrate instead of nickel chloride hexahydrate as starting material. Similarly as with Raney catalysts, Urushibara Co has been found to be more effective and selective than Urushibara Ni in the hydrogenation of nitriles, affording high yields of primary amines.105,106... 

Unhindered simple olefins are usually rapidly hydrogenated under very mild conditions over platinum metal catalysts such as platinum, palladium, and rhodium as well as over active nickel catalysts such as Raney Ni, nickel boride, and Urushibara Ni. For example, 0.1 mol of cyclohexene is hydrogenated in 7 min over 0.05 g of Adams platinum oxide in ethanol at 25°C and 0.2-0.3 MPa H2 (eq. 3.1).5 1-Octene and cyclopentene (eq. 3.2) are hydrogenated in rates of 11.5 and 8.6 mmol (258 and 193 ml H2 at STP) g Ni 1-min 1, respectively, over P-1 Ni in ethanol at 25°C and 1 atm H2.18 Hydrogenation of cyclohexene over active Raney Ni proceeds at rates of 96-100 ml H2 at STP (4.3-4.5 mmol) g Ni min-1 in methanol at 25°C and 1 atm H2 49,50 and can be completed within a short time, although usually larger catalyst substrate ratios than required for platinum catalyzed hydrogenations are employed (eq. 3.3).50... 

The C-C double bonds conjugated with carboxyl functions are usually much more readily hydrogenated than usual olefinic bonds, especially with nickel and palladium catalysts. Ethyl cinnamate is rapidly hydrogenated over Raney Ni under mild conditions (eq. 3.19).115 It is also hydrogenated over palladium oxide much faster (eq. 3.20) than over platinum oxide with which 2.9 h were required under the same conditions.5 Cinnamic acid was hydrogenated smoothly to dihydocinnamic acid as the sodium salt over Urushibara Ni in water under ordinary conditions (eq. 3.21).116... 

Orito and Imai have shown that the hydrogenation of benzene over nickel and cobalt catalysts is inhibited by alcoholic solvents and some ethers.5 As seen from the results shown in Table 11.2, benzene is hydrogenated extremely slowly or not at all in primary alcohols but very rapidly without solvent or in hydrocarbons. Benzene is hydrogenated at a considerable rate at 110°C even over Urushibara Ni A, which is known to be a poor catalyst toward the hydrogenation of aromatic nucleus,10 when used without solvent or in hydrocarbons after the water or alcohol on the catalyst has been carefully removed. 

X-ray photoelectron (XPS) studies of nickel boride, nickel phosphide, Raney nickel and Urushibara nickel showed that the electron density on the nickel was a function of the other metal present in these catalysts. 28J29 Boron, aluminum (Raney nickel) and zinc (Urushibara nickel) all increased the electron density on the nickel while phosphorous was an electron acceptor. Comparing the electron densities on the nickel in these catalysts with that on a nickel black prepared by the thermal decomposition of nickel formate (D-Ni) gave the series Ni-B > Ni-Al > Ni-Zn > D-Ni > Ni-P. 

Because of their reactivity, aryl hydroxylamines can sometimes be trapped by further reaction with another material present in the hydrogenation system. Aryl nitrones such as 17 are produced by the in situ condensation of the aryl hydroxylamine with an aldehyde which is present in the reaction medium (Eqn. 19.16).35 These reactions take place in good yield over a Urushibara nickel catalyst (Chapter 12) in aqueous alcohol at room temperature and four... 

Urushibara-nickel-A (U-Ni-A) is an excellent catalyst for reduction of cholestane-... 

Even in 1960 a catalytic route was considered the answer to the pollution problem and the by-product sulfate, but neady ten years elapsed before a process was developed that could be used commercially. Some of the earlier attempts included hydrolysis of acrylonitrile on a sulfonic acid ion-exchange resin (69). Manganese dioxide showed some catalytic activity (70), and copper ions present in two different valence states were described as catalytically active (71), but copper metal by itself was not active. A variety of catalysts, such as Urushibara or Ullmann copper and nickel, were used for the hydrolysis of aromatic nitriles, but aliphatic nitriles did not react using these catalysts (72). Beginning in 1971 a series of patents were issued to The Dow Chemical Company (73) describing the use of copper metal catalysis. Full-scale production was achieved the same year. A solution of acrylonitrile in water was passed over a fixed bed of copper catalyst at 85°C, which produced a solution of acrylamide in water with very high conversions and selectivities to acrylamide. 

A nickel catalyst analogous to Raney nickel is Urushibara nickel [21], produced by adding zinc dust to a solution of a nickel salt, generally nickel chloride. The zinc reduces the nickel to metallic nickel, which precipitates as very small particles mostly on the metallic zinc. The precipitate contains metallic zinc, zinc... 

The precipitate of nickel obtained on adding zinc dust to a solution of nickel chloride can be activated by treatment with aqueous ammonia (Urushibara Ni—NH3). This nickel catalyst contains appreciable amounts of residual ammonia and is suitable for reduction of nitriles to amines. Treating the nickel precipitate with sodium hydroxide solution gives the Urushibara Ni—B catalyst Urushibara Co—B catalyst is obtained analogously from cobalt chloride.180... 

Hydrogenation of 3-keto steroids. Urushibara nickel A is the best catalyst for reduction of cholestane-3-one to the 3a-ol. The ratio of epicholestanol to... 

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