Double-layered cobalt hydroxides

Layered Cobalt Hydroxides. The above results demonstrate the importance of the interlayer Co rather than the framework cobalt, in forming the required metallic Co catalyst. A structure with optimal catalytic activity would consist of one where there were only Co/Al hydroxide sheets, a structure closely approximated to by the hydrotalcite series of double layered hydroxides. 

Impregnation of cobalt and molybdenum (without sodium) increases largely the isomerizing activity of the catalyst the /3-pinene is then completely converted. The catalysts prepared with sodium molybdate and sodium hydroxide (Co-Mo-Na and Na-Co-Mo-Na) have lower isomerizing activities while their HDS activities are significantly increased. As in the case of alumina supported catalysts the sulfided CoMo phase protected by a double layer of alkaline ions on the carbon support gives the best results in HDS of /3-pinene. The behaviour of this catalyst was examined in desulfurization of the turpentine oil (40% a-pinene, 25% /3-pinene, 25% A -carene and 10% camphene + dipentene + myrcene, 1500 ppm S). The results are recorded in Table 6. 

Cobalt Clays and Double-Layered Hydroxides as Fischer—Tropsch Catalysts... 

BRUCEETAL. Cobalt Clays Double-Layered Hydroxides... 

Impedance analysis is a powerful thermoelectrochemical instrument. It proved useful to study the capacity of cobalt hydroxide film formation in double-layer electrolyte capacitors [56]. Also, experiments with the capacity of electrodes in solid state electrolytes have been published, e.g. with silver hahde/graphite... 

Anionic complexes can easily be prepared by the sulfonation of the aromatic rings in the complexes. Sulfonated cobalt phthalocyanine intercalated in a layered double hydroxide host was a stable catalyst for the oxidation of thiols162,163 and phenol derivatives.164 It was concluded that the complex has been intercalated with the plane of the phthalocyanine ring perpendicular to the sheet of the host (edge-on orientation) (Fig. 7.2). 

There are probably several mineral phases, particularly for the highly alkaline systems, that remain to be discovered. Mixed hydroxides may control solubility. Calcium zincate (CaZn2(OH)6), for example, is thermodynamically more stable than Zn(OH)2 above pH 11.5 and may be important in cementitious systems. Another group of minerals is that of the hydrotalcite-like minerals, the layered double hydroxides (LDH, M2+2M3+l/yXy (OH)6 where X is an anion). Cobalt, Ni and Zn can form such minerals (Johnson Glasser 2003) under neutral to alkaline conditions. For the majority of species, however, solubility-limiting phases do not appear to control dissolved concentrations. 

Recently, the cobalt(II)-tetrasulfonatophthalocyanine system was reinvestigated for its catalytic activity while intercalated into a Mg5Al2 -layered double hydroxide. The intercalate exhibited catalytic properties in the activation of atmospheric dioxygen for the oxidation of a thiolate to a disulfide (97a) and for the oxidation of 2,6-di-tert-butylbenzene to (nearly exclusively) the 2,6,2, 6 -tetra-tert-butyldiphe-noquinone (97b). In marked contrast to the results reported for the homogeneous catalyst, this intercalated catalyst remained active for... 

Ukrainczyk, L., Chibwe, M., Pinnavaia, T.J. Boyd, S. A. (1994). ESR study of cobalt(II) tetrakis(N-methyl-4-pyridiniumyl)porphyrin and cobalt(II) tetrasulfophthalocyanine intercalated in layered aluminosilicates and a layered double hydroxide. Journal of Physical Chemistry, 98, 2668-76. 

Perez Bernal, M. E., Ruano Casero, R. and Pinnavaia, T. J. (1991). Catalytic autoxidation of 1-decanethiol by cobalt(II) phthalocyaninetetrasulfonate intercalated in a layered double hydroxide. Catal. Lett. 11, 55. 

Chibwe, M. and Pinnavaia, T. J. (1993). Stabilization of a cobalt(II) phthalocyanine oxidation catalyst by intercalation in a layered double hydroxide host. J. Chem. Soc., Chem. Commun., 278. 

PREPARATION AND CHARACTERISATION OF COBALT CONTAINING LAYERED DOUBLE HYDROXIDES... 

M Chibwe, ME Perez-Bernal, R Ruano-Casero, TJ Pinnavaia. Layered Double Hydroxide Supported Cobalt(n) Phthalocyanines as Possible Environmental Remediation Oxidation Catalysts. Adelaide. Austraha Proceedings of the International Clay Conference, 1995 87-91. 

Immobilized cobalt(II) and zinc(II)phthalocyanine anchored on silica or intercalated in the galleries and cavities of layered double hydroxides (hydrotalcite) and NaX zeoMte catalyze or photocatalyze the oxidation of 2-mercaptoethanol and sodium thiosulfate. The activity of the immobilized catalysts for oxidation and photooxidation is lower than that of the complexes in homogeneous phase. This is due to the hindered diffusion of dioxygen and sulfur-containing compounds to the active catalyst sites. 

Wang X, Chen X, Evans DG, Yang W (2011) A novel biosensor ftn reduced L-glutathione based on cobalt phthalocyaninetetrasulfonate-intercalated layered double hydroxide modified glassy carbon electrodes. Sens Actuators, B 160 1444—1449... 

Fig. 10.2 Schematic illustrations and HRTEM images of the different stages in the fabrication of carbon nanorings (CNRs) in the cobalt(II)-aluminum (III) layered double hydroxide (LDH) containing co-intercalated dodecyl sulfonate (DSO) anions and methyl methacrylate (MMA) CoAl-DSO-MMA-LDH matrix (a) the (CoAl-DSO-MMA-LDHCoAl-DSO-MMA-LDH precursor, (b) CoAl-DSO-MMA-LDH after calcination in an Ar atmosphere at 800 °C and (c) isolated CNRs obtained after dissolution of the matrix. Reproduced with permission from [117], Copyright 2013 Wiley...

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