Cohalt catalysts

Selective hydrogenation of oe,)3 unsaturated compounds in the presence of cohalt catalysts... 

Budiman, A. W., Song, S. H., Chang, T. S., Shin, C. H., Choi, M. J. (2012). Dry reforming of methane over cohalt catalysts a hterature review of catalyst development. Catalysis Surveys from Asia, 76(4), 183—197. 

One of the routes was the low temperature decomposition of CHHP with the addition of cobalt to the oxidation mixture. The problem of fast deactivation of the cobalt catalyst could partly be solved by introducing a water wash to remove the dibasic acids that were responsible for the fast precipitation of the cobalt catalyst. Nevertheless, even after adding the cohalt catalyst to later stages of the decomposition section, a fraction of the CHHP still remained unconverted. The selectivity losses were caused by radicals obtained from the cobalt-catalysed decomposition of CHHP, which not only reacted with the available cyclohexane, but also with the desired reaction products cyclohexanone and cyclohexanol. Such one-phase decomposition has recently been industrially implemented. 

In some parts of the world, as in Russia, fermented alcohol can serve as a cheap source for hutadiene. The reaction occurs in the vapor phase under normal or reduced pressures over a zinc oxide/alumina or magnesia catalyst promoted with chromium or cohalt. Acetaldehyde has been suggested as an intermediate two moles of acetaldehyde condense and form crotonaldehyde, which reacts with ethyl alcohol to give butadiene and acetaldehyde. 

A silver-gauze catalyst is still used in some older processes that operate at a relatively higher temperature (about 500°C). New processes use an iron-molyhdenum oxide catalyst. Chromium or cohalt oxides are sometimes used to dope the catalyst. The oxidation reaction is exothermic and occurs at approximately 400-425 °C and atmospheric pressure. Excess air is used to keep the methanol air ratio helow the explosion limits. Figure 5-6 shows the Haldor Topsoe iron-molyhdenum oxide catalyzed process. 

Cyclohexane is oxidized in a liquid-phase process to a mixture of cyclohexanone and cyclohexanol (KA oil). The reaction conditions are 95-120°C at approximately 10 atmospheres in the presence of a cohalt acetate and orthohoric acid catalyst system. About 95% yield can be obtained ... 

Oxidizing toluene in the liquid phase over a cohalt acetate catalyst produces henzoic acid. The reaction occurs at about 165°C and 10 atmospheres. The yield is over 90% ... 

A polypyrrole film electrochemically deposited on gold electrodes from an MeCN-liCl04/Co(OAc)2 solution shows electrocatalytic activity in dioxygen reduction [404]. The catalytic electroreduction of dithio dipropionic acid (PSSP) with the water-soluhle cohalt(II I)tetrakis(4-trimethyl-ammonium phenyl) porphyrin (CoTMAP) has heen studied. The Co catalyst adsorbed on the glassy carbon electrode plays a major role in the electroreductive cleavage of the S—S bond [405]. 

The ejfect of water on the conversion and selectivity of cohalt-catalyzed hydroformylations has long been noticed in industry [7,85,86], A systematic study [87] of this effect in hydroformylation of 1-octene with [Co2(CO)s] with and without P Bu3 revealed that addition of water, and especially when it formed a separate aqueous phase, significantly inaeased the hydrogenation activity of the phosphine-modified catalyst Under the same reaction conditions (190 °C, 56 bar CO H2 1 1, P Co 3 1), approximately 40 % nonanols were formed instead of 5 % observed with water-free solutions. No clear explanation could be given for this phenomenon, although the possible participation of water itself in the hydroformylation reaction through the water gas shift was mentioned. It was also established, that the [Co2(CO)g]-catalyzed hydroformylation was severly retarded in the presence of water. Under the conditions above, 95 % conversion was observed in 15 hour with no added water, while only 10 % conversion to aldehydes (no alcohols) was found in an aqueous/organic biphasic reaction. 

The dissociation also is rapid helow this temperature (between 450°C to 850°C), however, only in the presence of a catalyst, such as sdica, platinum sulfide or cohalt molybdate. Other sulfur species are also produced in the reaction. 

In the classical oxo process the catalyst cohalt carbonyl is formed in situ by introducing divalent cobalt into the reactor. High temperature is required for this catalyst formation that gives a mixture of aldehydes and alcohols containing only 60-70% of linear product. A new BASF process using cobalt carbonyl hydride shows improved selectivity and efficient catalyst recovery. The catalyst is prepared by passing an aqueous solution of cobalt salt over a promoter and extracting the catalyst from the water phase with olefin. 

Unmodified Cohalt. Typical sources of the soluble cobalt catalyst include cobalt alkanoates, cobalt soaps, and cobalt hydroxide (see Cobalt). These are converted in situ into the active catalyst, HCo(CO)4, which is in equilibrium with dicobalt octacarbonyl. 

A.A. Khassin, T.M. Yurieva, V.N. Parmon, Fischer Tropsch Synthesis over Cohalt Containing Catalysts in Slurry Reactor. Effect of the Metallic Co Particle Size on the Selectivity, React. Kinet. Catal. Lett. 64 (1998) 55 62. 

Toluene is fed to the reactor with air and a cohalt salt catalyst while the reactor is kept at 120°-180°C. and 30 p.s.i.g. Crude benzoic acid taken from the bottom of the reactor is fed to a distillation column while vapors from the top containing toluene. 

The process gas from the combustion chamber is cooled in the waste heat boiler to the temperature required for the first reactor of ca. 300°C. In this reactor, filled with a cohalt-molybdenum catalyst (on an aluminum oxide support), the conversion of up to 80 to 85% of the hydrogen sulfide is carried out. After condensing out the sulfur formed at temperatures below 170°C, the temperature of the reaction gases is increased to the reaction temperature of the second reactor (ca. 220°C), which contains a highly active aluminum oxide catalyst with a large surface area (200 to 300 m /g) in which the residual hydrogen sulfide and sulfur dioxide react with one another. 

Toluene is oxidized in die liquid phase in the presence of a soluble cohalt-based catalyst The neutralization of benzoic add by potash yields insoluble potassium benzoate, which is separated by centrifuging. The disproportionation of potassium benzoate takes place between 400 and 430 C, under C02 pressure ranging from 13 to 3.106 Pa absolute, in the presence of a catalyst consisting of cadmium or zinc oxides. The reaction takes place in the solid phase. Tercphthalic add is released from its salt by the action of sulfuric add. 

The usual catalysts are based on cohalt, nickel, molybdenum and tungsten sulfides, generally combined and deposited on alumina. The most widely used formula is a composite sulfide of molybdenum and colbalt on alumina. Run length and catalyst life are longer than those of the catalytic systems employed in first step hydrogenation, Le. 6 to 12 months and 3 to 5 years, and the regeneration method is identical. 

Dibromomethane reacts with activated alkenes in the presence of a halide acceptor and cohalt or nickel catalysts to give cyclopropane derivatives (equation 186). ... 

The action of redox metal promoters with MEKP appears to he highly specific. Cohalt salts appear to he a unique component of commercial redox systems, although vanadium appears to provide similar activity with MEKP. Cohalt activity can he supplemented hy potassiiun and zinc naphthenates in systems requiring low cin-ed resin color lithium and lead naphthenates also act in a similar role. Quatemaiy ammonium salts (14) and tertiary amines accelerate the reaction rate of redox catalyst systems. The tertiary amines form beneficial complexes with the cobalt promoters, facilitating the transition to the lower oxidation state. Copper naphthenate exerts a imique influence over cin-e rate in redox systems and is widely used to delay cure and reduce exotherm development during the cross-linking reaction. 

Research into such catalysts started in the 1960s, when Jasinski (1964) discovered that cohalt phthalo-cyanine could catalyze the ORR in an alkaline medium. Fe and Co are the most commonly used metals for these catalysts. The origin of the electrocataly tic activity of N-containing non-Pt catalysts was generally recognized to he the N4-chelates (or Nj-chelates) of transition metals, due to the simultaneous presence of metal precursors, active carbon, and a nitrogen source under pyrolysis conditions. Beck (1977) proposed that the mechanism of the ORR catalyzed by such catalysts was mainly involved hy a modified... 

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