Introduction of Cobalt

Sachtler and co-workers [162] studied the redox chemistry of cobalt ions introduced into MFI via SSIE with nco/n i = 0.4-1.0, employing IR, ESR and UV-Vis diffuse reflectance spectroscopy. The coordination of Co + was found to be tetrahedral the ions were in their high-spin state, detectable at 60 K. 

Surprisingly, the amount of Co + incorporated into the clinoptilolite structure was not very dependent on the cobalt content in the mixture (cf. Fig. 47). A very fast replacement of the Na and H+ cations by Co was observed in the initial stage of SSIE. The subsequent steady state degree of SSIE was temperature-dependent (cf. Fig. 48). 

Introduction of cobalt and nickel into zeolites by solid-state ion exchange was investigated by Jentys and colleagues and compared with preparations via conventional exchange in aqueous solution, impregnation and direct synthesis ([164-170], vide infra). For their studies, the authors employed TPD of NH3 (TPDA), IR spectroscopy, X-ray absorption spectroscopy (XANES and EXAFS) and XRD. TPDA revealed that 100% of the strong Bronsted acid sites were eliminated at an nco/nAi ratio of ca. 1.0 and 0.5 in the case of SSIE of C0CI2 in mixtures with H-ZSM-5 and NH4-Y, respectively. Therefore, the authors concluded 

The IR spectra (with and without application of pyridine as a probe molecule) of H-ZSM-5 and Co-ZSM-5 prepared via SSIE confirmed the suggestion that in the case of nco/nAi 1.0 the acid Bronsted OH groups were completely consumed. Two types of newly formed acid sites, most likely Lewis acid sites, were indicated, viz., C0CI+ species (vide supra) and possibly true Lewis sites , i.e., Al-containing extra-framework species (cf. [171,172]). 

Microcalorimetry and XPS measurements of NH3 adsorption were used by Auroux et al. [106] to characterize Co-ZSM-5 obtained through solid-state reaction in a similar way as reported for introduction of copper (vide supra) and 

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Under the conditions where the chain oxidation process occurs, this reaction results in chain termination. In the presence of ROOH with which the ions react to form radicals, this reaction is disguised. However, in the systems where hydroperoxide is absent and the initiating function of the catalyst is not manifested, the latter has a retarding effect on the process. It was often observed that the introduction of cobalt, manganese, or copper salts into the initial hydrocarbon did not accelerate the process but on the contrary, resulted in the induction period and elongated it [4-6]. The induction period is caused by chain termination in the reaction of R02 with Mn"+, and cessation of retardation is due to the formation of ROOH, which interacts with the catalyst and thus transforms it from the inhibitor into the component of the initiating system. 

Subsequently, in 1999 the same group showed that the activity of the ruthenium hydrotalcite was significantly enhanced by the introduction of cobalt(II), in addition to ruthenium(III),in the Brucite layer [115]. For example, cinnamyl alcohol underwent complete conversion in 40 min in toluene at 60 °C, in the presence of ruthenium/cobalt hydrotalcite, compared with 31% conversion under the same conditions with ruthenium hydrotalcite. A secondary aliphatic alcohol, 2-octanol, was smoothly converted into the corresponding ketone but primary aliphatic alcohols, for example, 1-octanol, exhibited extremely low activity. The authors suggested that the introduction of cobalt induced the formation of higher oxidation states of ruthenium, for example, Ru(IV) to Ru( VI), leading to a more active oxidation catalyst. However, on the basis of the reported results it is not possible to rule out low-valent ruthenium species as the active catalyst in a hydridometal pathway. The results obtained in the oxidation of representative alcohols with ruthenium hydrotalcite and ruthe-nium-cobalt-hydrotalcite are compared in Table 5. 

The most notable development for the magnetite system was the introduction of cobalt as an additional component by ICI in 1984 [395], [396]. The cobalt-enhanced catalyst formula was first used in an ammonia plant in Canada using ICI Catalco s AMV process (later also in other AMV license plants) and is also successfully applied in ICl s LCA plants in Severnside. 

The controlled grain structure allows forming an adherent protective oxide coating within days when placed in an electrowinning cell without the necessity of being preconditioned [13]. In sulfuric acid electrolytes, the introduction of cobalt ions into the solution reduces the anode overvoltage and the corrosion rate of lead. 

The next major advance was the introduction of cobalt and nickel, which form divalent molybdates having the formulas C0M0O4 and NiMo04. The first disclosure of Co-Fe-Bi-Mo-0 catalysts was made by Nippon Kayaku Co., Japan for use in the selective oxidation of propylene to acrolein (16). The presence of the divalent transition-metal cation along with iron and bismuth molybdate produced a catalyst with significantly enhanced activity and selectivity. This discovery was... 

Preparing LiNi02 with an excess amount of Li was found to be one of the methods to produce stoichiometric cathode material. Another, even more effective method for stabihzing the lithium nickel oxide structure was the introduction of cobalt and thus formation of the hthiated nickel cobalt oxide derivatives of LiNi02 material. These findings led to laboratory development and commercial production of various derivatives of lithium nickel oxide, summarized in Table 1.4. 

Carbon (0.7% to 1.6%) is an essential constituent, the content of which should be strictly controlled. The introduction of cobalt increases the hot hardness and the resistance to wear, but will slightly reduce toughness. 

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