Industrial hydrogenation catalysts

Two porous catalysts in the form of cylindrical pellets were used industrial hydrogenation catalyst Cherox 42-00 with monodisperse pore structure (Chemopetrol Litvinov, Czech Rep. height x diameter = 4.9 x 5.0 mm) and laboratory prepared a-alumina, A5 (based on boehmite from Rural SB, Condea Chemie, Germany) with bidisperse pore structure (height x diameter = 3.45 x 3.45 mm). 

Catalytic asymmetric hydrogenation was one of the first enantioselective synthetic methods used industrially (82). 2,2 -Bis(diarylphosphino)-l,l -binaphthyl (BINAP) is a chiral ligand which possesses a Cg plane of symmetry (Fig. 9). Steric interactions prevent interconversion of the (R)- and (3)-BINAP. Coordination of BINAP with a transition metal such as mthenium or rhodium produces a chiral hydrogenation catalyst capable of inducing a high degree of enantiofacial selectivity (83). Naproxen (41) is produced in 97% ee by... 

In the petroleum (qv) industry hydrogen bromide can serve as an alkylation catalyst. It is claimed as a catalyst in the controlled oxidation of aHphatic and ahcycHc hydrocarbons to ketones, acids, and peroxides (7,8). AppHcations of HBr with NH Br (9) or with H2S and HCl (10) as promoters for the dehydrogenation of butene to butadiene have been described, and either HBr or HCl can be used in the vapor-phase ortho methylation of phenol with methanol over alumina (11). Various patents dealing with catalytic activity of HCl also cover the use of HBr. An important reaction of HBr in organic syntheses is the replacement of aHphatic chlorine by bromine in the presence of an aluminum catalyst (12). Small quantities of hydrobromic acid are employed in analytical chemistry. 

Metals and alloys, the principal industrial metalhc catalysts, are found in periodic group TII, which are transition elements with almost-completed 3d, 4d, and 5d electronic orbits. According to theory, electrons from adsorbed molecules can fill the vacancies in the incomplete shells and thus make a chemical bond. What happens subsequently depends on the operating conditions. Platinum, palladium, and nickel form both hydrides and oxides they are effective in hydrogenation (vegetable oils) and oxidation (ammonia or sulfur dioxide). Alloys do not always have catalytic properties intermediate between those of the component metals, since the surface condition may be different from the bulk and catalysis is a function of the surface condition. Addition of some rhenium to Pt/AlgO permits the use of lower temperatures and slows the deactivation rate. The mechanism of catalysis by alloys is still controversial in many instances. 

Fe, and B SI, Tl, Th, and Ce). The transforaed materials exhibit high specific activity In methanation, ammonia synthesis, and ethylene hydrogenation reactions. The similarity between the industrial methanation catalysts and catalysts obtained by decomposition of various Intermetallics Is striking. Most catalysts obtained by decomposition of a binary alloy Involve an associative combination of... 

The hydrogenation processes were performed at a relatively low temperature and pressure in the presence of promoted Raney Ni 2400 and Raney Co 2724 catalysts (13) in this study but any common nitrile hydrogenation catalysts (e.g. Fe, Ru, Rh, bulk or supported catalysts) could be used. The advantage of using a low temperature and pressure process is that it lowers the investment cost of an industrial process. Raney Ni 2400 is promoted with Cr and Raney Co 2724 is promoted with Ni and Cr. The particle sizes for both catalysts were in the range 25 - 55 pm. The BET surface area of Raney Ni 2400 and Raney Co 2724 are 140 m2/g and 76 m2/g, respectively, and the active surface area of the Ni and Co catalysts are 52 and 18 m2/g, respectively, based on CO chemisorption (Grace Davison Raney Technical Manual, 4th Edition, 1996). 

Nickel is frequently used in industrial homogeneous catalysis. Many carbon-carbon bond-formation reactions can be carried out with high selectivity when catalyzed by organonickel complexes. Such reactions include linear and cyclic oligomerization and polymerization reactions of monoenes and dienes, and hydrocyanation reactions [1], Many of the complexes that are active catalysts for oligomerization and isomerization reactions are supposed also to be active as hydrogenation catalysts. 

Whilst hydrogenation catalysts based on early transition metals are as active and selective as those based on late transition metals, they are usually not as compatible with functional groups, and this represents the major difficulty for their use in organic synthesis. Nonetheless, titanocene derivatives have been used in industry to hydrogenate unsaturated polymers. 

As already mentioned, the most important industrial application of homogeneous hydrogenation catalysts is for the enantioselective synthesis of chiral compounds. Today, not only pharmaceuticals and vitamins [3], agrochemicals [4], flavors and fragrances [5] but also functional materials [6, 7] are increasingly produced as enantiomerically pure compounds. The reason for this development is the often superior performance of the pure enantiomers and/or that regulations demand the evaluation of both enantiomers of a biologically active compound before its approval. This trend has made the economical enantioselective synthesis of chiral performance chemicals a very important topic. 

SR of methane/natural gas is one of the largest catalytic processes in the world and is by far the most important method for producing industrial hydrogen today. The process is well described in literature and it is typically carried out at 800-950 °C over nickel-based catalysts." The main reactions are methane SR (11) and water-gas-shift (WGS) (12). 

Naud, E, Malan, C., Spindler, E, Ruggeberg, C., Schmidt, A.T and Blaser, H.-U. Ru-(Phosphine-Oxazohne) Complexes as Effective, Industrially Viable Catalysts for the Enantioselective Hydrogenation of Aryl Ketones. Adv. Synth. Catal. 2006, 348, 47-50. 

Supported metal catalysts are much easier to employ and have obvious attractions for industrial use from their ease of handling and economic considerations of obtaining maximum utilisation of the catalytically active metal, by using very small particles with a high surface-to-volume ratio, which are stable on the support and not susceptible to sintering. In spite of the inherent difficulties of variable activity, kinetics and activation energies [11] associated with their use, supported metals have been extensively used as hydrogenation catalysts. 

Hydrogenation catalysts, particularly metals, are also relatively well characterized because of extensive study. This has occurred partly for commercial reasons catalyzed organic reactions of great industrial importance—e.g.y hydrogenation and reforming—involve reducing conditions. In part, however, this has occurred because of the esthetic attrac-... 

Fig. 1 Conversion of glucose as a function of time in five successive hydrogenations for the different catalysts (a) RNi (b) RNiMo (c) RNiCr (d) RNiFe (e) RNilndl (f) RNilnd2. The initial rates rQ (mol h 1g ) are given for the first and fifth reactions. Tne lower curve in (e) corresponds to a catalyst after many industrial hydrogenations.

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