Cobalt incorporation

Reaction of CpH with excess Co2(C0)s (CH2CI2, 40°C, 40-48 h) yielded CpCo(C0)2 5, (0.8-1.0 mmol Co/g., IR (KBr), 2012 and 1953 cm-1). Residual Co2(C0)s was removed via Soxhlet extraction with benzene or CH2CI2. Interestingly, reaction of 4 with C02 (C0)8 yielded 5 directly and as efficiently. Apparently, dehydration of 4 occurred under these conditions. The "overall yield" (based on cobalt incorporation) for this synthetic sequence is 15%. 

Wei L, Lee CW, Li L et al (2008) Assessment of (n, m) selectively enriched small diameter single-walled carbon nanotubes by density differentiation from cobalt-incorporated MCM-41 for macroelectronics. Chem Mater 20 7417-7424... 

The first research group to propose a description of the structure of CoMo catalysts was led by Schuit and Gates (13). This group introduced the so-called monolayer model directly derived from the physical studies of CoMo oxide precursors supported on y-alumina carried out by J. T. Richardson (14) (Richardson first proposed the existence of a special Co/Mo entity.) In this model the upper or first layer contained only sulfur atoms, each bonded to a molybdenum atom of the second layer (below the first one), these molybdenum atoms being bonded to two oxygen atoms also located in this second layer. When a sulfur atom was removed by reduction (H2 flow) of Mo5+ to Mo3+, a vacancy was formed at the surface and became the preferential adsorption site of a sulfur atom in the organic gas phase. The presence of cobalt incorporated into underlying layers of the alumina... 

The promotion effect of the CoMoS site appears to occur through increased hydrogen activation, which facilitates removal of sulfur atoms after cleavage of C-S bonds on exposed molybdenum ions/ Cobalt incorporated into the support may also act as a structural promoter by enhancing dispersion of the sulfided species. ... 

Tang and co-workers have also prepared cobalt-containing hyperbranched polymers by the reaction of cobalt complexes with a preformed hyperbranched polymer 274 containing acetylene groups.321 The percent of cobalt incorporated into the polymers ranged from 27.8 to 36.7 wt %, and upon high temperature pyrolysis, the polymers formed ceramics with magnetic properties. 

Zinc and cobalt appear to occupy the same protein sites in alkaline phosphatase, as demonstrated by the results of competition between the two metals for these sites (Table II). Varying molar proportions of zinc are added to the apoprotein prior to addition of a five-fold molar excess of cobalt. Excess metal is removed by gel filtration and the cobalt incorporated is then measured. When cobalt alone is added to the apoprotein, nearly 4 gram atoms of the metal are incorporated (fine 1, Table II). In the remaining experiments, the sum of zinc and cobalt bound is nearly 4 in all instances. Hence, the four protein sites can apparently bind zinc and cobalt interchangeably (9). 

Figure 6. Cobalt incorporation into alkaline phosphatase...

The stage of cobalt incorporation differs for aerobic and anaerobic organisms producing V. B 2. Thus, in P. shermanii incorporation of cobalt occurs at the stage of precorrin 2, while in P. denitrificans it occurs later at the stage of hydrogenobyrinic acid. Today the biosynthesis of V. B,2 is considered to be clarified except for a few details. 

Dofour et al. [17] investigated the influence of synthesis method, precursor and effect of Cu addition on the WGS activity of Fe-Cr-Co catalysts. They prepared FeCr, FeCrCu, FeCrCo and FeCrCuCo formulations by oxidation precipitation method, using chloride (Cl) and sulphate (S) metal precursors. The catalytic activity results of FeCrCo and FeCrCuCo catalysts are presented in Figure 2.2. All the materials prepared from sulphate precursor showed higher carbon monoxide conversion than those synthesized with chloride. As expected Cu-promoted catalysts show better activity than Fe-Cr-Co catalysts. For the catalysts synthesized by chloride precursor, in the case of cobalt, incorporation of this metal into the magnetite lattice could improve the covalency of Fe and... 

However, the early cobalt incorporation during the anaerobic pathway could not be essential for ring contraction since metal free corrinoids have been found in anaerobic bacteria 94) like Chromatium vinosum and Rhodospirillum rubrum in the absence of cobalt. Moreover, metal free corrinoids are produced by strictly anaerobic methanogenic bacteria in the absence of cobalt. Thus further biosynthetic explorations are necessary to discover the primitive anaerobic corrin formation in Archaebacteria. 

Cobalt. Cobalt-substituted aluminophosphates have been the most extensively investigated MeAPO-n systems. In comparison to the first row transition metals, which usually prefer octahedral coordination geometry, the Co + ions rather easily adopt tetrahedral stereochemistry with the oxide ions as the ligands. This can be explained by the fact that the ligand field stabilization energies for Co + ions (d ) disfavor the tetrahedral coordination relative to octahedral one to a lesser extent than for most of the other d configurations. The characteristic royal blue color of the obtained CoAPO products is a good indication that the cobalt incorporation into the aluminophosphate framework has been achieved. 

A direct experimental detection of the state of cobalt traces in the particulate corrosion products is very difficult to obtain. One practical reason for this difficulty is the cobalt concentration, which is usually far too low for the usual structure analysis methods such as X-ray identification of the prevailing chemical compound moreover, the similarity of the crystallographic data of cobalt and nickel ferrites to those of Fe304 complicates the interpretation of the analytical results. However, there are two observations which raise doubts about whether the above-mentioned assumption of cobalt incorporation from the primary coolant into the... 

The acidic properties of cobalt and silicon-substituted AlPO-5, -11, and -44 have been characterized by JSnchen et al. [111,276] by adsorption calorimetry of acetonitrile at 303 K, after activation at 720 K. Adsorption calorimetric measurements indicated that the adsorption potential of the samples for acetonitrile was enhanced upon cobalt incorporation. The heat curves exhibited at least two steps indicating the existence of acid sites of different strengths. The heats of adsorption indicated the formation of strong acid sites, due to the cobalt incorporation, as well as the presence of weaker acid sites, probably terminal P - OH groups. 

Kang, M. (2000) Effect of cobalt incorporated into the framework of SAPO-34 (CoAPSO-34s) on NO removal. /. Mol Catal A Chem., 161, 115-123. 

Cobalt(II) compounds are often incorporated in the gel. When the gel has absorbed a fair amount of moisture it will turn pink but will revert to blue on heating. 

Early catalysts for acrolein synthesis were based on cuprous oxide and other heavy metal oxides deposited on inert siHca or alumina supports (39). Later, catalysts more selective for the oxidation of propylene to acrolein and acrolein to acryHc acid were prepared from bismuth, cobalt, kon, nickel, tin salts, and molybdic, molybdic phosphoric, and molybdic siHcic acids. Preferred second-stage catalysts generally are complex oxides containing molybdenum and vanadium. Other components, such as tungsten, copper, tellurium, and arsenic oxides, have been incorporated to increase low temperature activity and productivity (39,45,46). 

Various ways of overcoming the PTA oxidation problem have been incorporated into commercial processes. The predominant solution is the use of high concentrations of manganese and cobalt ions (2,248—254), optionally with various cocatalysts (204,255,256), in the presence of an organic or inorganic bromide promoter in acetic acid solvent. Operational temperatures are rather high (ca 200°C). A lesser but significant alternative involves isolation of intermediate PTA, conversion to methyl/)-toluate, and recycle to the reactor. The ester is oxidized to monomethyl terephthalate, which is subsequentiy converted to DMT and purified by distillation (248,257—264). 

Cobalt in Driers for Paints, Inks, and Varnishes. The cobalt soaps, eg, the oleate, naphthenate, resinate, Hnoleate, ethyUiexanoate, synthetic tertiary neodecanoate, and tall oils, are used to accelerate the natural drying process of unsaturated oils such as linseed oil and soybean oil. These oils are esters of unsaturated fatty acids and contain acids such as oleic, linoleic, and eleostearic. On exposure to air for several days a film of the acids convert from Hquid to soHd form by oxidative polymeri2ation. The incorporation of oil-soluble cobalt salts effects this drying process in hours instead of days. Soaps of manganese, lead, cerium, and vanadium are also used as driers, but none are as effective as cobalt (see Drying). 

Adhesives in the Tire Industry. Cobalt salts are used to improve the adhesion of mbber to steel. The steel cord must be coated with a layer of brass. During the vulcanization of the mbber, sulfur species react with the copper and zinc in the brass and the process of copper sulfide formation helps to bond the steel to the mbber. This adhesion may be further improved by the incorporation of cobalt soaps into the mbber prior to vulcanization (53,54) (see Tire cords). 

Adhesion of Enamel to Steel. Cobalt compounds are used both to color and to enhance adhesion of enamels to steel (55). Cobalt oxide is often incorporated into the ground frit at rates of 0.5—0.6 wt %, although levels from 0.2 to 3 wt % have been used. The frit is fired for ten minutes at 850°C to give a blue enamel that is later coated with a white cover coat. 

Weld overlays of stainless steel or cobalt-based wear-resistant and hard-facing alloys such as Stellite may salvage damaged equipment. In addition, weld overlays incorporated into susceptible zones of new equipment may provide cost-effective resistance to cavitation damage. 

In the United States softer stocks have been employed using a drying oil which is incorporated with a drier such as cobalt naphthenate to harden the oil. 

The physical description of strongly pressure dependent magnetic properties is the object of considerable study. Edwards and Bartel [74E01] have performed the more recent physical evaluation of strong pressure and composition dependence of magnetization in their work on cobalt and manganese substituted invars. Their work contrasts models based on a localized-electron model with a modified Zener model in which both localized- and itinerant-electron effects are incorporated in a unified model. Their work favors the latter model. 

Incorporation of cobalt into the corrin ring system modifies the reduction potentials of... 

In the pulp and paper industry, anionic and cationic acrylamide polymers are used as chemical additives or processing aids. The positive effect is achieved due to a fuller retention of the filler (basically kaoline) in the paper pulp, so that the structure of the paper sheet surface layer improves. Copolymers of acrylamide with vi-nylamine not only attach better qualities to the surface layer of.paper, they also add to the tensile properties of paper in the wet state. Paper reinforcement with anionic polymers is due to the formation of complexes between the polymer additive and ions of Cr and Cu incorporated in the paper pulp. The direct effect of acrylamide polymers on strength increases and improved surface properties of paper sheets is accompanied by a fuller extraction of metallic ions (iron and cobalt, in addition to those mentioned above), which improves effluent water quality. 

The incorporation of anions from the electrolyte, such as borate and carbonate, into the oxide has also been shown to occur on iron and cobalt, such anions being restricted to the outer layers of the film. Attempts to find incorporation of chloride into passive iron surfaces from... 

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