Catalysts cobalt modified

Catalyst Cobalt Modified cobalt Rhodium Modified rhodium ... 

The 0X0 and aldol reactions may be combined if the cobalt catalyst is modified by the addition of organic—soluble compounds of 2inc or other metals. Thus, propylene, hydrogen, and carbon monoxide give a mixture of aldehydes and 2-ethylhexenaldehyde [123-05-7] which, on hydrogenation, yield the corresponding alcohols. 

The catalysts used in hydroformylation are typically organometallic complexes. Cobalt-based catalysts dominated hydroformylation until 1970s thereafter rhodium-based catalysts were commerciahzed. Synthesized aldehydes are typical intermediates for chemical industry [5]. A typical hydroformylation catalyst is modified with a ligand, e.g., tiiphenylphoshine. In recent years, a lot of effort has been put on the ligand chemistry in order to find new ligands for tailored processes [7-9]. In the present study, phosphine-based rhodium catalysts were used for hydroformylation of 1-butene. Despite intensive research on hydroformylation in the last 50 years, both the reaction mechanisms and kinetics are not in the most cases clear. Both associative and dissociative mechanisms have been proposed [5-6]. The discrepancies in mechanistic speculations have also led to a variety of rate equations for hydroformylation processes. 

Shell Chemical has a process that does both the Oxo reaction and hydroformyiation in one step in the same reactor. They use a special catalyst, thought to be cobalt modified with a trialkyl or triaryl phosphine ligand— but they are holding this one pretty close to the vest. Overall yields are 70-80%, with straight-chain alcohols representing greater than 80%. Major by-products are paraffins that are recovered and used to make olefins and then recycled back as feed. This process can also use internal olefins (with the double-bond somewhere besides the alpha position) and yield similar normakiso alcohol ratios. ... 

Also, Klabunovskii reported pressure dependences of the OYs in enantio-differentiating hydrogenations of ethyl acetoacetate (EAA) with ruthenium (67), Raney cobalt (65), and RNi catalysts (69) modified with TA, c. Additives. Additives which are added to the reaction system often exert a remarkable effect on the OY of the enantio-differentiating hydrogenation of M A A (23-25). Water is one such additive. For example, in most hydrogenations with amino acid MRNis, the direction of differentiation was reversed by the addition of small amounts of water as shown in Fig. 14 (23, 25). 

Higher n/b ratios in cobalt-modified catalysts are apparently achieved as a result of the phosphine presenting more steric bulk to the insertion reaction of the alkene. The effect is predominately steric, since there is little correlation with regiochemistry and phosphine bacisity. A combination of electronic (Xi) and steric (cone angle 0) effects provide a more rational explanation of the increase in nib ratio with added phosphines.16,17... 

In 1975 Johnson and Nowack reported that benzene was hydrogenated to cyclohexene in 20.3% yield at 58% conversion over a cobalt ion (0.05%) modified 0.5% Ru-Ca(OH)2 in the presence of water at 180°C and 6.8 MPa H2.33 The yield of cyclohexene was definitely higher than those ever reported for the cyclohexene intermediate in the hydrogenation of benzene.34-36 Similar nickel- and iron-ion-modified 0.5% Ru-Ca(OH)2 or nickel-modified 0.5% Ru-A1203 also gave good selectivities to cyclohexene although in somewhat lower yields than over the cobalt-modified catalyst. It appears that the presence of water and small amounts of transition metal... 

Our work is a tentative to rationalize the influence of the preparation parameters over the composition, active phase and catalytic activity. Modifying the pH of precipitation between 6.0 and 8.5, the surface area, the bulk, the surface composition and the active phases of the catalysts were modified significantly. Raman spectroscopy has revealed the presence of M0O3 phase only in the catalyst prepared at pH 6.0. From the literature data, we know that the precipitation of the Ni(OH)2 and Co(OH)2 occurs at pH 7 and 7.5, respectively. At pH higher than 7.5 our calculations suggest the presence of nickel or/and cobalt oxides but these phases were not detected with any of the characterization techniques used. 

Colloidal metal clusters, which offer a high surface area for better activity, have been stabilized by polymers. Thus, a homogeneous dispersion of a cobalt-modified platinum cluster was stabilized by a coordinating polymer, poly(/V-vinyl-2-pyrrolidone).74 Addition of the cobalt(II) [or iron(III)] doubled the activity and increased the selectivity from 12 to 99% when the catalyst was used to reduce cin-namaldehyde (5.23). 

Cobalt compounds are useful chemical catalysts for the synthesis of fuels (Fi-scher-Tropsch process), the synthesis of alcohols and aldehydes from olefins, hydrogen and carbon monoxide at elevated temperatures and pressures ( oxo process , hydroformylation ). They are also used in petroleum refining and the oxidation of organic compounds. In the oxo process, cobalt carbonyl, Co2(CO)g, is employed or generated in situ. For the selective production of n-butanol from propylene, hydrogen and CO, an organophosphine-modified cobalt carbonyl complex is used as the catalyst. Cobalt salts are proven oxidation catalysts examples include the production of terephthalic acid by the oxidation of p-xylene, and the manufacture of phenol by the oxidation of toluene. 

Unmodified cobalt catalyst Phosphine modified cobalt catalyst Phosphine modified rhodium catalyst... 

Phenol can be produced directly from benzene by use of N2O as an oxidizing agent in the gas phase. Catalysts are modified ZSM-5 or ZSM-11 materials, containing elements such as antimony, arsenic, beryllium, boron, cobalt, chromium, copper, gaUium, indium, iron, nickel, scandium, vanadium or zinc. (208)... 

Propybtaphthalene Cobalt modified and also nonmo Cied NaY catalysts can induce the polymerization of l-propyl n hthalene. However the mechanism of this polymerization is obscure and probably invdves isomerization reaction. 

Improvements in rate, selectivity, and catalyst lifetime may be achieved when cobalt hydroformylation catalysts are modified by addition of a tertiary phosphine. When the phosphine added is dppe, the complex formed, [HCo(CO)2(dppe)], is a weak catalyst for the hydroformylation of 1-pentene, exhibiting poor selectivity to formation of the unbranched product (Equation 3.1a). ... 

Uses Drier, chelating catalyst in modified polyurethanes and alkyds, clear and brightly pigmented oil- or alkyd-modified polyurethanes, in conventional alkyds which tend to discolor, traffic paints, anticorrosive primers, marine topcoats, wood furniture coatings Features Replaces cobalt drier Properties Sp.gr. 0.85 dens. 7.1 Ib/gal flash pt. 27 C Dapro 7007 [Elementis Spec. U.S.]... 

Jeong B, Uhm S, Lee J (2010) Inm-cobalt modified electrospun carbon nanofibers as oxygen reduction catalysts in alkaline fuel cells. Electrochem Soc Trans 33 1757-1767... 

Rhodium Ca.ta.lysts. Rhodium carbonyl catalysts for olefin hydroformylation are more active than cobalt carbonyls and can be appHed at lower temperatures and pressures (14). Rhodium hydrocarbonyl [75506-18-2] HRh(CO)4, results in lower -butyraldehyde [123-72-8] to isobutyraldehyde [78-84-2] ratios from propylene [115-07-17, C H, than does cobalt hydrocarbonyl, ie, 50/50 vs 80/20. Ligand-modified rhodium catalysts, HRh(CO)2L2 or HRh(CO)L2, afford /iso-ratios as high as 92/8 the ligand is generally a tertiary phosphine. The rhodium catalyst process was developed joindy by Union Carbide Chemicals, Johnson-Matthey, and Davy Powergas and has been Hcensed to several companies. It is particulady suited to propylene conversion to -butyraldehyde for 2-ethylhexanol production in that by-product isobutyraldehyde is minimized. 

Common catalyst compositions contain oxides or ionic forms of platinum, nickel, copper, cobalt, or palladium which are often present as mixtures of more than one metal. Metal hydrides, such as lithium aluminum hydride [16853-85-3] or sodium borohydride [16940-66-2] can also be used to reduce aldehydes. Depending on additional functionahties that may be present in the aldehyde molecule, specialized reducing reagents such as trimethoxyalurninum hydride or alkylboranes (less reactive and more selective) may be used. Other less industrially significant reduction procedures such as the Clemmensen reduction or the modified Wolff-Kishner reduction exist as well. 

Ligand-Modified Cobalt Process. The ligand-modified cobalt process, commercialized in the early 1960s by Shell, may employ a trialkylphosphine-substituted cobalt carbonyl catalyst, HCo(CO)2P( -C4H2)3 [20161 -43-7] to give a significantly improved selectivity to straight-chain... 

Propane, 1-propanol, and heavy ends (the last are made by aldol condensation) are minor by-products of the hydroformylation step. A number of transition-metal carbonyls (qv), eg, Co, Fe, Ni, Rh, and Ir, have been used to cataly2e the oxo reaction, but cobalt and rhodium are the only economically practical choices. In the United States, Texas Eastman, Union Carbide, and Hoechst Celanese make 1-propanol by oxo technology (11). Texas Eastman, which had used conventional cobalt oxo technology with an HCo(CO)4 catalyst, switched to a phosphine-modified Rh catalyst ia 1989 (11) (see Oxo process). In Europe, 1-propanol is made by Hoechst AG and BASE AG (12). 

Primary Amyl Alcohols. Primary amyl alcohols (qv) are manufactured by hydroformylation of mixed butenes, followed by dehydrogenation (114). Both 1-butene and 2-butene yield the same product though in slightly different ratios depending on the catalyst and conditions. Some catalyst and conditions produce the alcohols in a single step. By modifying the catalyst, typically a cobalt carbonyl, with phosphoms derivatives, such as tri( -butyl)phosphine, the linear alcohol can be the principal product from 1-butene. 

An unusual method for the preparation of syndiotactic polybutadiene was reported by The Goodyear Tire Rubber Co. (43) a preformed cobalt-type catalyst prepared under anhydrous conditions was found to polymerize 1,3-butadiene in an emulsion-type recipe to give syndiotactic polybutadienes of various melting points (120—190°C). These polymers were characterized by infrared spectroscopy and nuclear magnetic resonance (44—46). Both the Ube Industries catalyst mentioned previously and the Goodyear catalyst were further modified to control the molecular weight and melting point of syndio-polybutadiene by the addition of various modifiers such as alcohols, nitriles, aldehydes, ketones, ethers, and cyano compounds. 

The physical properties of low melting point (60—105°C) syndiotactic polybutadienes commercially available from JSR are shown in Table 1. The modulus, tensile strength, hardness, and impact strength all increase with melting point. These properties are typical of the polymer made with a cobalt catalyst modified with triphenylphosphine ligand. 

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