Catalysts Raney

An acidic solvent is recommended for use with palladium. Other catalysts that have been used for this reduction include copper chromite and any of the three Raney catalysts, cobalt, iron, or nickel. 

Palladium and platinum (5—10 wt % on activated carbon) can be used with a variety of solvents as can copper carbonate on siHca and 60 wt % nickel on kieselguhr. The same is tme of nonsupported catalysts copper chromite, rhenium (VII) sulfide, rhenium (VI) oxide, and any of the Raney catalysts, copper, iron, or nickel. 

R F Handmade Paints Inc., 245 R.S.A. Coi"poration, 246 RAG Group AG, 165 RAIMONT , phosphoric acid, 114 Raisio Chemicals Ltd., 156 Rajsliree Agro Chem, 174 Rallis hidia Ltd., 175 RAMROD , propachlor, 114 RANEY , catalysts, 114 RAPICHLENE , methylene chloride, 114 Rasa Industries Ltd., 187 Raschig GmbH, 165... 

In addition to the Raney nickel catalysts, Raney catalysts derived from iron, cobalt, and copper have been examined for their action on pyridine. At the boiling point of pyridine, degassed Raney iron gave only a very small yield of 2,2 -bipyridine but the activity of iron in this reaction is doubtful as the catalyst was subsequently found to contain 1.44% of nickel. Traces of 2,2 -bipyridine (detected spectroscopically) were formed from pyridine and a degassed, Raney cobalt catalyst but several Raney copper catalysts failed to produce detectable quantities of 2,2 -bipyridine following heating with pyridine. 

R. G. Herman et al. (8) studied these catalyst systems In great detail and suggested a Cu-fl solution In ZnO as active phase where Cu- - non-dlssoclatlvely chemisorbs and activates CO and ZnO activates H2. In the range of 15 to 85Z CuO In the catalyst, up to 16% Cu+1 became dissolved In the ZnO (9) and Cu+1 has been widely accepted as active site (10). Recently, however, Raney Cu-Zn catalysts have been shown to be very active methanol synthesis catalysts (11). The active component for these Raney catalysts was found to be metallic Cu with an activity maximum at 97 wt% Cu (12). 

During water storage slow oxidation takes place. In particular the most active Raney catalysts show. severe deactivation (they should not be stored more than a few weeks). Other types of catalysts though less active are much more stable. In fine chemistry activity is often not the most important catalytic property. This certainly holds for Raney nickel. On a nickel... 

C and 4 h for Raney catalysts. Due to lower reducibility and stronger interaction of Co- and Ni-oxides with alumina, 10 wt % metal was used. Despite the higher metal content of these catalysts they were less active than the alumina supported noble metals and their selectivity to RNH2 was lower than that of Ru. The selectivity pattern on noble metals was in good agreement with literature data [1,4],... 

The selectivity of RNH2 on M/A1203 and Raney catalysts decreased in the order Co Ni Ru>Rh>Pd>Pt. This order corresponds to the opposite sequence of reducibility of metal-oxides [8] and standard reduction potentials of metalions [9], The difference between Group VIII metals in selectivity to amines can probably been explained by the difference in the electronic properties of d-bands of metals [3], It is interacting to note that the formation of secondary amine, i.e. the nucleophilic addition of primary amine on the intermediate imine can also take place on the Group VIII metal itself. Therefore, the properties of the metal d-band could affect the reactivity of the imine and its interaction with the amine. One could expect that an electron enrichment of the metal d-band will decrease the electron donation from the unsaturated -C=NH system, and the nucleophilic attack at the C atom by the amine [3], Correlation between selectivity of metals in nitrile hydrogenation and their electronic properties will be published elsewhere. 

Raney catalysts are usually shipped under water, so if water is an undesirable solvent, it must be displaced by appropriate washings with the desired solvent. Care should be taken when using ketones. Special care should be taken with nitrobenzene, which undergoes highly exothermic hydrogenation at room temperature (see Section 2.1.3).53... 

Skeletal (Raney ) catalysts are made by a very simple technique. An alloy of two metals in roughly equal proportions, where one metal is the desired catalytic material, and the other is dissolvable in hydroxide, is first made. This alloy is crashed and leached in concentrated hydroxide solution. The soluble metal selectively dissolves, leaving behind a highly porous spongelike structure of the desired catalytic metal. Catalysts formed by this technique show high activity and selectivity, and have found wide use in industry, particularly for hydrogenation and dehydrogenation reactions. 

Skeletal catalysts were first discovered in the 1920s by Murray Raney [1,2], In recognition of their inventor, the catalysts are often referred to as Raney catalysts, although this trademark is now owned by the Davison division of W.R. Grace Co., who supply a range of catalysts for industrial use. Another common name is metal sponge, which refers to the porous structure of the catalysts. 

M.M. Kalina, S.K. Berdongarova, G.A. Sadykova and A.B. Fasman, Physicochemical characteristics of Raney catalysts prepared from y-metallides of some binary and ternary systems, in Mater. Resp. Nauchno-Tekh. Konf. Molodykh Uch. Pererab. Nefti Neftekhim., 3rd, A. Abdukadyrov, Ed., Sredneaziat. Nauchno-Issled. Inst. Neftepererab. Prom-sti., Tashkent, USSR, 1976, pp. 100-101 (Chem. Abs. 189 204764z). 

H. Binder, A. Koehling and G. Sandstede, Raney catalysts, in From Electrocatalysis to Fuel Cells, G. Sandstede, Ed., University of Washington Press, Seattle, 1972, pp. 15-31. 

Principles of skeletal structure formation of Raney catalysts are discussed, first from the perspective of phase transformation by chemical leaching. Some ideas are then proposed for making new Raney catalysts. Rapid solidification and mechanical alloying (MA) are described as potential processes for preparing particulate precursors. A rotating-water-atomization (RWA) process developed by the author and co-workers is shown as an example of rapid solidification. 

Specific examples of RWA are further described. Raney copper precursor with a small amount of Pd was prepared by this process. Rapid solidification was effective in keeping most of the added Pd dissolved in the precursor. The specific surface area of the leached specimen increased by about 3 times in comparison with that of ordinary Raney copper catalyst. The conversion from acrylonitrile to acrylamide by the hydration reaction was about 60%, or more than 20% higher than that from ordinary Raney copper catalyst. In case of Ti or V addition, the conversion increased to 70-80%. Rapid solidification was quite effective in decreasing the defect rate of Raney catalysts from some precursors. The potential for design of new catalysts may be widely extended by rapid solidification. 

The relation between the size of fine particles in skeletal structure and X-ray broadening was also discussed. These results may bring important information to designing new Raney catalysts. 

They usually suppose that the mobility of atoms at leaching temperature is too low to rearrange for the phase transformation. However, transformation has clearly occurred except in a few cases. One of the motivations for our research studies on Raney catalysts is to clarify what happens during the leaching process. 

From a general phase transformation theory, the crystallographic structure and the specific surface area may depend on kinetics and thermodynamics. Therefore, if we can control these factors, new Raney catalysts can be developed. 

We have developed a process to make metastable materials by rapid solidification (7) and have applied it to various alloy systems (8). There were few reports on such a metastable processing to make precursors for Raney catalyst. The metastable processes maybe extend the probability of precursor design by decreasing the limit of additive amount to precursor. 

In this paper, a few examples of Raney catalysts produced by metastable processes and their catalytic properties are discussed. Then, some examples of multi alloy systems, their microstructures and general properties will be shown. Finally, we will discuss the possibility of forming large particle materials with high specific surface area. 

One of the excellent characteristics of Raney catalyst is a porous skeletal structure composed of ultra fine particles. 

Some examples of new Raney skeletal materials have been introduced by applying metastable processing to form their precursors. Applying these new materials to various organic reactions can lead to better catalytic results. The potential for routes to improved Raney catalysts is thereby demonstrated. 

Murray Raney Award Leeture Synthesis and Features of New Raney Catalysts from Metastahle Preeursors... 

B. - o-Carboxy phenyl) propionic acid. In an open 1-1. widemouthed round-bottomed flask are placed 18 g. (0.094 mole) of 0-carboxycinnamic acid and 550 ml. of 10% sodium hydroxide solution. The mixture is warmed to 90° (Note 8) on a steam bath and stirred mechanically. The steam bath is then removed while 54 g. (Note 9) of nickel-aluminum alloy (Raney catalyst) powder is added through the open neck of the flask in small portions (from the end of a spatula) at frequent intervals (Note 10). When addition of the alloy is complete (about 50 minutes), the mixture is stirred and maintained at 90-95° for 1 hour by warming on a steam bath. Distilled water is added as needed to maintain the total volume at approximately 550 ml. The hot mixture is filtered with suction, and the metallic residue is washed with 50 ml. of hot 10% sodium hydroxide solution and two 50-ml. portions of hot water in such a manner that the solid is always... 

Nickel, either as a Raney catalyst or in the form of nickel boride, is also effective in the reduction of the C=0 bond. An increase in the catalytic activity can be brought about by metal promoters (chromium and molybdenum). Copper chromite may also be used. 

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