Catalysts Raney copper

Mitsui Toatsu Chemical, Inc. disclosed a similar process usiag Raney copper (74) shortiy after the discovery at Dow, and BASF came out with a variation of the copper catalyst ia 1974 (75). Siace 1971 several hundred patents have shown modifications and improvements to this technology, both homogeneous and heterogeneous, and reviews of these processes have been pubHshed (76). Nalco Chemical Company has patented a process based essentially on Raney copper catalyst (77) ia both slurry and fixed-bed reactors and produces acrylamide monomer mainly for internal uses. Other producers ia Europe, besides Dow and American Cyanamid, iaclude AUied CoUoids and Stockhausen, who are beheved to use processes similar to the Raney copper technology of Mitsui Toatsu, and all have captive uses. Acrylamide is also produced ia large quantities ia Japan. Mitsui Toatsu and Mitsubishi are the largest producers, and both are beheved to use Raney copper catalysts ia a fixed bed reactor and to sell iato the merchant market. 

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. 

Wainwright, Tomsett, Trimm, and coworkers/Mellor, Copperthwaite, and coworkers—Raney copper catalysts for WGS and methanol synthesis. In 1995, Wainwright and Trimm295 reviewed Raney178 copper catalysts for both water-gas shift and methanol synthesis applications and discussed the possibility of either a redox mechanism or a formate mechanism for Raney copper catalysts. Formates, they indicated, rapidly decompose to C02 and H2 over metallic copper surface. They... 

In 1997 and 1998, the authors306 307 also examined acid leached Raney copper catalysts, whereby the alloy was leached with either nitric or perchloric acid of 5, 14, or 27.5 wt% strength. The acid solution was added dropwise over 15 min to an equal volume of deionized water containing the alloy particles. After leaching at 50 °C, the particles were removed and washed to a pH of 7. Air drying at 120 °C was then carried out for one hour. The dissolution rates of catalyst components were observed to be functions of the extraction time (Table 56). 

Table 56 time307 Compositions of Raney copper catalysts as function of acid type and extraction ... 

J.A. Stanfield and P.E. Robbins, Raney Copper Catalysts, Proc. 2nd Int. Cong. Catal., Paris, 1960, pp. 2579-2599. 

The trail-blazing patent of Goto et al. ( ) for the oxidative dehydrogenation of aminoalcohols to the corresponding aminocarboxylic acid salts over Raney copper catalysts in strongly alkaline solutions was cast in terms of the general reaction... 

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. 

In A, a Raney copper catalyst would be able to hydro-dehydrogenate alcoholic functions (-H, +H) on metallic copper sites. About 10 to 15% of the copper would be hydroxylated copper able to catalyze the degradation reactions DOH, RC, RM. These sites would be more reactive than Cu towards Mn + in the oxido-reduction modification of the initial Raney copper, so that, beeing first exchanged, the rates of DOH, RC, RM decrease. 

Scheme 6.36 Production of acrylamide with a Raney copper catalyst.

In previous studies the authors have reported that metals oxides such as GaaOa, AI2O3, Zr02 and Cr203 contained in Cu/ZnO-based catalysts have an important role to improve simultaneously the activity and the selectivity[1, 2]. Unlike Cu/ZnO-based catalysts, Raney copper catalysts have not been widely reported in the literature as practical catalysts for methanol synthesis. However, 20 years ago Wainwright and co-workers have been the first to report the potentiel use of Raney Cu and Raney Cu-Zn as catalysts to produce methanol from syngas to use as synthetic liquid fuel [3]. Recent works of Wainwright et al. on methanol synthesis... 

This has been impressively demonstrated by Nitto Chemical Industries with the biocatalytic manufacture of acrylamide, an important building block for polymers and copolymers, produced in quantities of over 200000 t/y [80]. The chemocata-lytic route to acrylamide (32) uses a reduced Raney copper catalyst for hydration. This metal-catalyzed process has been shown to be superior to the acid-catalyzed hydration, but catalyst poisoning and waste-water problems due to heavy-metal content cause some problems (eq. (10)) [81, 82]. 

Preparation of Raney-copper catalysts. Raney-copper catalysts (particle size ... 

Variable experimental parameters in the preparation of Raney-copper catalysts were as follows (i) temperature of leaching, (ii) concentration of NaOH solution used, (iii) absence or presence of excess NaOH during the leaching process, (iv) absence or presence of different additives during the leaching process. 

The specific copper surface area (Sq ) of Raney-copper catalysts was always high if the leaching process was carried out at 50 °C, instead of 20 (see entries 1 and 3 in Table 1.). Similar effect was observed when excess NaOH was used in the leaching process. 

The high extent of leaching of the aluminium from the alloy resulted in a catalyst with low activity. In some cases the formed AI(OH)3 was responsible for the decrease of the catalytic activity. In the presence of additives such as carbohydrates the extent of removal of AI(OH)3 formed could be improved. Raney-copper catalysts containing high residual aluminium content had low Sq value. Details on the preparation of Raney-copper catalysts will be given elsewhere [7]. 

Hydrogenation of D-fructose over Raney-copper catalysts. 

Resuits obtained over siiica and CPG supported cataiysts are aiso included into Tabie 1. Siiica supported catalysts showed moderate activity. Over these catalysts the M/S ratio was beiow 2, i.e. the enantioselectivity of siiica supported copper catalysts was not better than that of the Raney-copper catalysts. 

By using sodium haiides or sodium borate the hydrogenation of D-fructose could be carried out almost to the completion. These results are shown in Table 3. In these experiments upon using Raney-copper catalysts the highest selectivity of D-mannitol, 82.7 %, was obsen/ed over a cobalt containing catalysts in the presence of sodium borate. Even higher D-mannitol selectivity, i.e. 88.2, was observed over CPG supported copper catalyst in the presence of sodium borate. 

Raney-copper catalysts showed relatively high activity in the hydrogenation of D-fructose to D-mannitol. The selectivity of D-mannitol over these catalyst was around 60-65 %. The highest D-mannitol selectivity, i.e. values around 85-88 %, was obtained over Cu/CPQ catalyst in the presence of sodium borate. This high selectivity could be maintained up to 95-97 % conversion. 

J. R. Mellor, N. J. Covflle, A. C. Sofianos, R. G. Copper, Raney copper catalysts for the water-gas shift reaction. 1. Preparation, activity and stability, Appl. Catal. A Gen. 164 (1997)... 

A few industrial important heterogeneous catalysts are prepared by melt processes. Examples are the Fe-catalyst for the Haber-Bosch process and the Pt/Rh-net for the ammonia oxidation in the Ostwald process (see also Section 6.4). Melting is also the initial process step for the preparation of Raney-nickel and Raney-copper catalysts. For these catalysts an alloy of Ni/Cu and A1 is prepared by melting. This alloy is later treated with NaOH to dissolve the A1 from the solid to create pores and reactive surface sites. Raney-Ni and Raney-copper are very important hydrogenation catalysts. 

A Study on the formation of furan derivatives from polyols by heterogeneous catalysis over metals has been described. The use of Raney copper catalyst modified by... 

However, a hquid phase dehydrogenation process, using Raney nickel or Raney copper catalysts in a high-boiling solvent at about 150°C, gave 80-95% secondary butanol conversion to MEK at more than 95% selectivity. 

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