Cobalt catalysts preparation

The isomerization of an allylic amine to an enamine by means of a formal 1,3-hydrogen shift constitutes a relatively small structural change. However, this transformation could be extremely valuable if it could be rendered stereoselective. In important early studies, Otsuka and Tani showed that a chiral cobalt catalyst, prepared in situ from a Co(ii) salt, a chiral phosphine, and diisobutylaluminum hydride (Dibal-H), can bring about the conversion of certain pro-chiral olefins to chiral, isomeric olefins by double bond migra-... 

Liu Y., Zhang Y., and Tsubaki N. 2007. The effect of acetic acid pretreatment for cobalt catalysts prepared from cobalt nitrate. Catal. Commun. 8 773-76. 

Trujillano R., Villain R, Louis C., and Lambert J.-R 2007. Chemistry of silica-sup-ported cobalt catalysts prepared by cation adsorption. 1. Initial localised adsorption of cobalt precursors. J. Phys. Chem. C 111 7152-64. 

Tetrahydropyran can be prepared by heating 1,5-dihydroxypentane at 190-210 C in the presence of butyltin trichloride (Scheme 4.12a). When the reaction is carried out using a cobalt catalyst [prepared by heating cobalt(II) oxalate (ethanedioate) under hydrogen at 600 °C] instead of the tin halide, the product is 3,4-dihydro-2 -pyran (Scheme 4.12b). 

Table I reports the results of typical polymerization runs of pentadiene by cobalt catalysts prepared from Al(C2H5)Cl2 complexed with thiophene or pyridine. The crude polymerization products obtained by these systems have a cis-1,4 content of about 75-80%. Fractions having a higher cis-1,4 content (about 85%) could be isolated by dissolving the crude polymers in benzene and reprecipitating with methylethyl ketone (MEK). This solvent dissolves only the low molecular weight polymers, which, in this case, have also a low cis-1,4 unit content.

The homogeneous catalytic [2+2+2]-cycloaddition of alkynes and nitriles was first discovered by Yamazaki and Wakatsuki [3] using the phosphine-stabilized cobalt(III) complex (Stmcture 5). At the same time, Bdnnemann and co-workers [5] observed the co-cyclization (eq. (2)) at cobalt catalysts prepared in situ, as well as using phosphine-free organocobalt(I) diolefm complexes. 

The power law kinetic equation could be a simplified form of a mechanistic scheme. A summary of some of the reported reaction orders for the partial pressure of hydrogen and carbon monoxide which have been obtained from power law fits by different groups are listed in Table 9. The partial pressure dependencies vary rather widely. The power law fits were obtained for different cobalt catalysts prepared using different supports and methods. The data in Table 9 show that there is not one best power law equation that would provide a good fit for all cobalt catalysts. Brotz [10], Yang et al. [12] and Pannell et al. [13] defined the Fischer-Tropsch rate as the moles of hydrogen plus carbon monoxide converted per time per mass of catalyst (r g+Hj) Wang... 

Table 3 The Reaction Performance of Cobalt Catalysts Prepared from Different Supports (Xu et al., 2005)...

Similar yields were obtained with a heterogenized cobalt catalyst prepared by copol5nneiization of Co(AAEMA)2 [2-(acetoacetoxy)ethyl methacrylate 1-)] with A,A-dimethylacrylamide and MA -methylenebis-(acrylamide). ... 

The activities and selectivities of three metals are reported in the tables 2 and Z. These catalysts are less active than the conventional one but the order of reactivity is the same. It is worth mentioning that these nickel and cobalt catalysts are more selective towards the production of secondary amines than the conventional nickel and cobalt catalysts prepared by impregnation. 

Manufacture. Furan is produced commercially by decarbonylation of furfural in the presence of a noble metal catalyst (97—100). Nickel or cobalt catalysts have also been reported (101—103) as weU as noncatalytic pyrolysis at high temperature. Furan can also be prepared by decarboxylation of 2-furoic acid this method is usually considered a laboratory procedure. 

There are currentiy no commercial producers of C-19 dicarboxyhc acids. During the 1970s BASF and Union Camp Corporation offered developmental products, but they were never commercialized (78). The Northern Regional Research Laboratory (NRRL) carried out extensive studies on preparing C-19 dicarboxyhc acids via hydroformylation using both cobalt catalyst and rhodium complexes as catalysts (78). In addition, the NRRL developed a simplified method to prepare 9-(10)-carboxystearic acid in high yields using a palladium catalyst (79). 

Prepa.ra.tlon, There are several methods described in the Hterature using various cobalt catalysts to prepare syndiotactic polybutadiene (29—41). Many of these methods have been experimentally verified others, for example, soluble organoaluminum compounds with cobalt compounds, are difficult to reproduce (30). A cobalt compound coupled with triphenylphosphine aluminum alkyls water complex was reported byJapan Synthetic Rubber Co., Ltd. (fSR) to give a low melting point (T = 75-90° C), low crystallinity (20—30%) syndiotactic polybutadiene (32). This polymer is commercially available. 

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. 

In a typical process adiponitrile is formed by the interaction of adipic acid and gaseous ammonia in the presence of a boron phosphate catalyst at 305-350°C. The adiponitrile is purified and then subjected to continuous hydrogenation at 130°C and 4000 Ibf/in (28 MPa) pressure in the presence of excess ammonia and a cobalt catalyst. By-products such as hexamethyleneimine are formed but the quantity produced is minimized by the use of excess ammonia. Pure hexamethylenediamine (boiling point 90-92°C at 14mmHg pressure, melting point 39°C) is obtained by distillation, Hexamethylenediamine is also prepared commercially from butadience. The butadiene feedstock is of relatively low cost but it does use substantial quantities of hydrogen cyanide. The process developed by Du Pont may be given schematically as ... 

A cobalt-based catalyst, prepared by reducing Co(acac)3 with diethylalumi-num chloride in the presence of the bidentate ligand l,2-bis(triphenylphosphi-no)ethane, accelerates [87] the cycloadditions of norbornadiene (88) with a variety of acetylenes (Equation 3.30). 

The carbonylation of methanol was developed by Monsanto in the late 1960s. It is a large-scale operation employing a rhodium/iodide catalyst converting methanol and carbon monoxide into acetic acid. An older method involves the same carbonylation reaction carried out with a cobalt catalyst (see Section 9.3.2.4). For many years the Monsanto process has been the most attractive route for the preparation of acetic acid, but in recent years the iridium-based CATIVA process, developed by BP, has come on stream (see Section 9.3.2) ... 

The more active cobalt catalyst for pyrolytic reactions was prepared by microwave calcination of cobalt nitrate which was converted to cobalt oxide by rapid microwave heating [7]. 

One way in which cobalt dispersion can be increased is the addition of an organic compound to the cobalt nitrate prior to calcination. Previous work in this area is summarized in Table 1.1. The data are complex, but there are a number of factors that affect the nature of the catalyst prepared. One of these is the cobalt loading. Preparation of catalysts containing low levels of cobalt tends to lead to high concentrations of cobalt-support compounds. For example, Mochizuki et al. [37] used x-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) to identify cobalt silicate-like species in their 5% Co/Si02 catalysts modified with nitrilotriacetic acid (NTA). The nature of the support also has... 

As described above, understanding the mechanism of the dispersion increase is a difficult task. In this work we compare a catalyst prepared by cobalt nitrate impregnation onto alumina with one modified by the addition of mannitol, and use TGA and in situ microscopy to investigate the increased dispersion. Mannitol is a sugar alcohol that is structurally similar to sorbitol [31], as shown in Figure 1.1. 

Dumond F., Marceau E., and Che M. 2007. A study of cobalt speciation in Co/Al203 catalysts prepared from solutions of cobalt-ethylenediamine complexes. J. Phys. Chem. C 111 4780-89. 

Bezemer, G. L., Radstake, P.B., Koot, V., van Dillen, A. J., Geus, J. W., and de Jong, K. P. 2006. Preparation of Fischer-Tropsch cobalt catalysts supported on carbon nanofibers and silica using homogeneous deposition-precipitation. Journal of Catalysis 237 291-302. 

Kraum, M., and Baems, M. 1999. Fischer-Tropsch synthesis The influence of various cobalt compounds applied in the preparation of supported cobalt catalysts on their performance. Appl. Catal. A Gen. 186 189-200. 

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