Hydrogen on Co

Aj Hydrodesulfurization Removal of sulfur compounds from crude oil by reaction with hydrogen on CO - Mo on alumina. 

The reaction by which the complex is formed is thought to proceed via a formyl (HCO)Fe(CO)4 species, resulting from an attack of the hydride hydrogen on CO bonded to iron. 

Similar turnover rates recently reported on Co single crystals with different exposed crystal planes are consistent with the structure-insensitive nature of CO hydrogenation on Co (105, 106). Tlirnover rates on crystals with zig-zag grooved [Co (1120)] and close-packed [Co(OOOl)] surfaces differ by less than a factor of two, and CO hydrogenation activation energies are also similar on the two surfaces. The grooved surface favors chain growth... 

Nitrile. - The commercial electrolytic reduction of adiponitrile to hexa-methylenediamine at a nickel cathode has been described. The same reaction is carried out commercially by catalytic hydrogenation on Co and Ni catalysts. The hydrogenation is carried out in the presence of NH3 in order to inhibit the formation of secondary and tertiary amines.The production of secondary amines is however a useful commercial process. Thus oleyl nitrile is converted to the unsaturated secondary amine on a Cu0-Cr203 catalyst in the absence of NH3 and NaOH. 

As a consequence, catalysts with improved sulfur tolerance are needed. Alternatively, gas cleaning in a ZnO bed is necessary if H2S or thiols have to be removed, whereas thiophenes require reduction to H2S by hydrogen on Co-Mo catalysts [116] before adsorption in the ZnO bed ... 

Groot IMN, Juanes-Marcos JC, Dfaz C, Somers MF (2010) Dynamics of dissociative adsorption of hydrogen on CO-precovered Ru(OOOl) surface a comparison of theoretical and experimental results. R. A. Olsen and G. J. Kroes, Phys Chem Chem Phys 12 1331... 

Mendes FMT, Perez CAC, Noronha FB, Schmal M. TPSR of Co Hydrogenation on Co/Nb205/ AI2O3. Catal Today. 2005 101 45-50. 

Table IV illustrates nonadditive catalytic properties of the (Co + Pd)/Si02 system. As distinct from palladium, CO hydrogenation on Co/Si02 gives predominantly hydrocarbons. The addition of cobalt has little effect on the activity of palladitim and its selectivity for methanol, but leads to formation of ethanol in appreciable amounts. The action of palladium on the properties of cobalt for CO hydrogenation and ethane hydrogenolysis is similar to its action on ruthenium, i.e., the activity of cobalt in these reactions fall by one order of magnitude.

A mercury cathode finds widespread application for separations by constant current electrolysis. The most important use is the separation of the alkali and alkaline-earth metals, Al, Be, Mg, Ta, V, Zr, W, U, and the lanthanides from such elements as Fe, Cr, Ni, Co, Zn, Mo, Cd, Cu, Sn, Bi, Ag, Ge, Pd, Pt, Au, Rh, Ir, and Tl, which can, under suitable conditions, be deposited on a mercury cathode. The method is therefore of particular value for the determination of Al, etc., in steels and alloys it is also applied in the separation of iron from such elements as titanium, vanadium, and uranium. In an uncontrolled constant-current electrolysis in an acid medium the cathode potential is limited by the potential at which hydrogen ion is reduced the overpotential of hydrogen on mercury is high (about 0.8 volt), and consequently more metals are deposited from an acid solution at a mercury cathode than with a platinum cathode.10... 

A number of measurements made on the methanation of C02 may be correlated by using Equation 5 with the same values of AH as for the CO hydrogenation. On the basis of diffusion considerations, the value of KwS for C02 hydrogenation was taken as 80% of that for CO hydrogenation. Attempts were made to correlate data when both CO and C02 were methanated by using simple diffusion for both with the C02 rate set at 80% of the CO rate. In order to get good agreement with experimental data, it is necessary to introduce a variable water-gas shift reaction activity. 

It is obvious that one can use the basic ideas concerning the effect of alkali promoters on hydrogen and CO chemisorption (section 2.5.1) to explain their effect on the catalytic activity and selectivity of the CO hydrogenation reaction. For typical methanation catalysts, such as Ni, where the selectivity to CH4 can be as high as 95% or higher (at 500 to 550 K), the modification of the catalyst by alkali metals increases the rate of heavier hydrocarbon production and decreases the rate of methane formation.128 Promotion in this way makes the alkali promoted nickel surface to behave like an unpromoted iron surface for this catalytic action. The same behavior has been observed in model studies of the methanation reaction on Ni single crystals.129... 

The hydrogenation of CO and C02 on transition metal surfaces is a promising area for using NEMCA to affect rates and selectivities. In a recent study of C02 hydrogenation on Rh,59 where the products were mainly CH and CO, under atmospheric pressure and at temperatures 300 to 500°C it was found that CH4 formation is electrophobic (Fig. 8.54a) while CO formation is electrophilic (Fig. 8.54b). Enhancement factor A values up to 220 were... 

Figure 8.57. Effect of catalyst potential on the rates of formation of C2H6, C2H4) HzCO, CH3OH and CH3CHO during CO hydrogenation on Pd/YSZ. The rate of CH4 formation is of the order 10 9 mol/s and is only weakly affected by UWr Single pellet design P=12.5 bar, T=350°C. pH2/pco= -8, flowrate 85 cm3 STP/min.5 59...

C02 hydrogenation on Pd was investigated29 under atmospheric pressure and at temperatures 540°C to 605°C. The CO formation rate (reverse water-gas shift reaction) exhibits purely electrophilic behaviour with a rate increase by up to 600% with increasing sodium coverage (Fig. 9.20). This purely electrophilic behaviour is consistent with low reactant coverages and enhanced electron acceptor C02 adsorption on the Pd surface with increasing sodium coverage (Rule G2). 

Cobalt(II) complexes of three water-soluble porphyrins are catalysts for the controlled potential electrolytic reduction of H O to Hi in aqueous acid solution. The porphyrin complexes were either directly adsorbed on glassy carbon, or were deposited as films using a variety of methods. Reduction to [Co(Por) was followed by a nucleophilic reaction with water to give the hydride intermediate. Hydrogen production then occurs either by attack of H on Co(Por)H, or by a disproportionation reaction requiring two Co(Por)H units. Although the overall I easibility of this process was demonstrated, practical problems including the rate of electron transfer still need to be overcome. " " ... 

Two significant communications indicate the considerable potential of transition metal complexes as multifunctional homogeneous catalysts in the silane field (5, 53). Here the same catalyst activates silanes toward different substrates and it is probable that all proceed via a common metal hydrido intermediate. Both Co2(CO)8 and (Ph3P)3CoHX [X = H2, N2, or (H)Si(OEt)j] catalyze 0-silylation and hydrosilylation the hydrogen on Si may be replaced by R O, R COO, R CONH, or R3SiO [e.g., Eqs. (117)-(120)], and excellent yields of silylated product result. Phenolic groups do... 

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