Catalytic effect of cobalt

In order to explain the high catalytic effect of cobalt naphthenate, Bailey et al. 45) suggested that the cobalt atom forms coordination complexes with the nitrogen and oxygen atoms in two isocyanate groups whereby the positive charges on the carbon atoms are increased and the isocyanate groups are activated for the reaction with the hydroxyl compound ... 

In the previous section efficient catalysis of the Diels-Alder reaction by copper(II)nitrate was encountered. Likewise, other bivalent metal ions that share the same row in the periodic system show catalytic activity. The effects of cobalt(II)nitrate, nickel(II)nitrate, copper(II)nitrate and zinc(ll)nitrate... 

Water Treatment. Sodium sulfite is an agent in the reduction of chlorine or oxygen in water. Dissolved oxygen in boiler water tends to enhance pitting and other types of corrosion. In boilers operated at below 4.82 MPa (700 psi), a residual concentration of 30 ppm of sodium sulfite is generally effective. Catalytic amounts of cobalt are often added to accelerate the reaction of oxygen with sulfite (321,322) (see Water, industrial water treatment). 

Other studies in this specific area are also based on the catalytic effect of a variety of metal ions such as copper (II), cobalt (II), nickel (II), iron (III), and manganese (II) on the luminol-hydrogen peroxide reaction providing a rapid and efficient detection mode for these five ions, when an online CL detector is used before separation by CE [88], This contribution combines capillary ion analysis (CIA) and CL detection by means of a postcapillary reactor similar to the one originally developed by Rose and Jorgenson [80] and finally modified by Wu... 

Experimental observations indicate that the oxidation of cobalt (II) to cobalt (III) and the formation of ethylenediamine from N-hydroxyethylethylene-diamine occur simultaneously. This is quite the opposite to what is usually assumed in other instances of transition metal catalysis of organic reactions—for example, the catalytic effect of manganese in the oxidation of oxalic acid (7, 8), of iron in the oxidation of cysteine to cystine (22) and of thioglycolic acid to dithioglycolic acid (5, 23), of copper in the oxidation of pyrocatechol to quinone and in the oxidation of ascorbic acid (29, 30), and of cobalt in the oxidation of aldehydes and unsaturated hydrocarbons (4). In all these reactions the oxidation of the organic molecule occurs by the abstraction of an electron by the oxidized form of the metal ion. 

Table III. Effect of Ligand Environment on Catalytic Activity of Cobalt Complexes...

A systematic attempt to correlate the catalytic effect of different surfaces with their adsorptive capacity was made by Taylor and his collaborators. Taylor and Burns, for example, investigated the adsorption of hydrogen, carbon dioxide, and ethylene by the six metals nickel, cobalt, palladium, platinum, iron, and copper. All these metals are able to catalyse the hydrogenation of ethylene to ethane, while nickel, cobalt, and palladium also catalyse the reduction of carbon monoxide and of carbon dioxide to methane. 

The following method, which is an adaptation of that of Duval,6 makes use of the catalytic effect of charcoal in forming cobalt-nitrogen bonds and avoids the unnecessary use of ammonium chloride. This procedure is much shorter than air-oxidation methods and yields a relatively pure product in acceptable yield. 

The method of preparation of the catalyst has been found to alter the effect of the promoter (196). With standard VPO prepared with an organic solvent, the effects of cobalt and of iron were found to be the same as those previously described 182,193-195,202,208). The improvement in catalytic performance is proposed to be a consequence of the stabilization of dimers, which are the proposed active sites. However, catalysts prepared from V0P04 2H2O in organic solvents are not characterized by a promotional effect of iron. This lack of promotion is attributed to the loss of crystallinity and surface area of the rosette crystals formed by in the preparation. Similarly, the increase in activity attributed to cobalt is thought to be a structural effect, influencing the development of the (100) plane of (VO)2P207. 

Little information is however available about the effect of catalyst mesoporosity on FT catalytic behavior. Broad distribution of mesopore sizes in amorphous oxides makes it difficult to quantify this effect. On the contrary, SBA-15 and MCM-41 periodic mesoporous silicas [7-8] with uniform pore size distributions could provide new insights into the effects of catalyst pores on the structure and catalytic behavior of FT catalysts. This paper focuses on the effects of support mesoporosity on the structure and catalytic behavior of cobalt supported FT catalysts. In addition, we aim to demonstrate that the support mesoporosity could provide an efficient tool for the control of catalytic performance of supported FT catalysts. 

A recent paper by Cooper et al. [155] reported a fairly strong catalytic effect of an unidentified zinc compound on the reaction of an aromatic isocyanate with 3,3 -dichlorobenzidine. Axelrood et al. [184] found diethylene triamine and stannous octoate to be powerful cateilysts for the reaction of phenyl isocyanate and an aromatic diamine, whereas di-butyltin dilaurate and cobalt naphthenate had only a mild effect in their system. 

THE EFFECT OF HYDROGEN SULFIDE ON THE CATALYTIC ACTION OF COBALT IN CARBON GASIFICATION AND DEPOSITION REACTIONS... 

It is evident from these experiments that sulfur is having a tremendous effect on the cobalt /graphite-hydrogen system. The catalytic activity of cobalt in this reaction is effectively suppressed by the addition of sulfur. Furthenttoie, it seems likely that there in a modification in the wetting characteristics of cobalt on graphite in the presence of sulfur. 

The catalytic effectiveness of the well-crystallized catalysts (DS3 to DSe) was evaluated by a simple laboratory test (screenings). Mercaptan removals of 70 to 83 % are obtained. This important catalytic activity is attributed to a) the meaningful contamination by C03 anions in the interlayer domain, which induces the pursued basic character as described by Constantino et al. [27,28] for the decomposition of MBOH to acetone and acetylene by MgAlC03 hydrotalcite at 353 K, and b) to the dispersion of the cobalt phtalocyanine complex in the interlayer space, since an aggregation of the cobalt phtalocyanine complexes decreases the thiol oxidation effectiveness [22]. 

The Co-exchanged zeolites were not effective catalysts for the oxidation of cyclohexane. The cobalt exchanged ions were not stabilized enough by the zeolite interactions and part of these cations were released in the oxidation medium. Thus, we decided to explore the activity of P-zeolites in which cobalt ions were incorporated into the framework. We hoped that the incorporation would increase the stability of the cation within the solid. We studied the catalytic activities of cobalt substituted P-zeolites containing aluminium (Co-Al-BEA) and boron (Co-B-BEA) towards the oxidation of cyclohexane into adipic acid. 

Saunders and Frisch (2) cite certain catalysts used to Induce an isocyanate-urethane (allophanate) reaction. They are zinc octoate, cobalt napthanate and cobalt octoate and are claimed to yield 95% allophanate. An experiment was designed observing the catalytic effect of these metal complexes under varied concentrations and over time. Ferric acetylacetonate, a catalyst known to Influence an isocyanate-carboxyl reaction, was included 1n the study. The catalysts were added individually and 1n combinations of two into a polyurethane-polyisocyanate system. Concentrations varied from 1.50% to 8.00% by weight. 

Other Oxygen-containing Derivatives. Acetone and furan condense in an acidic medium to form (54). The yield is increased by the addition of metal salts, e.g. IiC104. The increase has been attributed to acidity (pH) effects rather than to effects of metal ion templates. This is the first demonstration of the importance of the effects of pH in metal-assisted cyclizations. Compound (54) is cleaved by m-chloroperoxybenzoic acid to form the novel octaketone (55), with a n s-enedione configuration. The endoperoxide (56) is converted into a bis-epoxide on treatment with catalytic amounts of cobalt(n) 5,10,15,20-tetraphenylporphine at — 10°C, and the epoxide rearranges to (57) at 20... 

Systematic kinetic studies on the catalytic effect of pentadentate Schiff-base cobalt(II) complexes in the oxidation of... 

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