NiO catalyst

The principal commercial source of 1-butanol is -butyraldehyde [123-72-8] obtained from the Oxo reaction of propylene. A mixture of n- and isobutyraldehyde [78-84-2] is obtained in this process this mixture is either separated initially and the individual aldehyde isomers hydrogenated, or the mixture of isomeric aldehydes is hydrogenated direcdy and the n- and isobutyl alcohol product mix separated by distillation. Typically, the hydrogenation is carried out in the vapor phase over a heterogeneous catalyst. For example, passing a mixture of n- and isobutyraldehyde with 60 40 H2 N2 over a CuO—ZnO—NiO catalyst at 25—196°C and 0.7 MPa proceeds in 99.95% efficiency to the corresponding alcohols at 98.6% conversion (7,8) (see Butyraldehydes Oxo process). 

Using a temperature-programmed surface reaction (TPSR) technique, Li et al. (154) showed that this complete oxidation of methane took place on the NiO catalyst during the CHfOi reaction. Weng et al. (145) used in situ microprobe Raman and in situ time-resolved IR spectroscopies to obtain a relationship between the state of the catalyst and the reaction mechanism. These authors showed that RuC>2 in the Ru/SiC>2 catalyst formed easily at 873 K in the presence of a CH4/02/Ar (2/1/45, molar) mixture and that the dominant pathway to synthesis gas was by the sequence of total oxidation of CH4 followed by reforming of the unconverted CH4 by C02 and H20. Thus, these results indicate that the oxidation of methane takes place principally by the combustion mechanism on the oxidized form of this catalyst. 

Figure 8 The particle-size distribution function for a NiO catalyst determined by small-angle scattering...

Another method has been suggested to measure the activity of the surface oxygens on NiO catalysts as a quantity proportional to the ratio PcOj/Fco of the gas mixture of C02 and CO which, on contacting the surface of NiO, does not change in its composition [59]. The contact time allowed should be short so as not to oxidize or reduce the bulk oxygen, but long enough so that the local equilibrium between the gas phase and the surface is established. Thus the use of a differential reactor is most effective. In this way, the activities of the surface species alone can in principle, be determined. 

Figure 8 Steam reforming of hexane at flow rates of 2 0 and 0 64 Ib/hr of water and hexane, respectively Axial bed-temperature and composition profiles for a metal monolith (250 cells/in consisting of Kanthal support/7-Al203 washcoat/NiO catalyst, and a packed bed of Girdler G-9(X pellets (j in. X in ) of alumina impregnated with nickel. (From Ref. 9.)...

It has been postulated in Section III, A that preparation of the NiO catalyst at 250° favors recession of nickel ions beneath the surface. It may therefore be postulated that after complete coverage of the catalyst by N2O at the beginning of the catalytic run (order zero) the protrusion of nickel ions produced by adsorbed (and reacting) N2O- species is more intense [as shown by stronger bonds with adsorbed oxygen, Eq. (21)] than the protrusion produced by the adsorption of molecular oxygen [as shown by weaker bonds with adsorbed oxygen, Eq. (23)]. 

When the rate is measured for a catalyst pellet and for small particles, and the diffusivity is also measured or predicted, it is possible to obtain both an experimental and a calculated result for rj. For example, for a first-order reaction Eq. (11-67) gives directly. Then the rate measured for the small particles can be used in Eq. (11-66) to obtain k. Provided is known, d) can be evaluated from Eq. (11-50) for a spherical pellet or from Eq. (11-56) for a fiat plate of.catalyst. Then 7caic is obtained from the proper curve in Fig. 11-7. Comparison of the experimental and calculated values is an overall measure of the accuracy of the rate data, effective diffusivity, and the assumption that the intrinsic rate of reaction (or catalyst activity) is the same for the pellet and the small particles. Example 11-8 illustrates the calculations and results for a flat-plate pellet of NiO catalyst, on an alumina carrier, used for the ortho-para-hydrogen conversion. 

All NiO catalysts used here showed the phenomenon of wildness described by Reilly (16). This state of the catalyst is characterized by a sharp drop in bed temperature, a large increase in product gas, and considerable laydown of carbon. The selectivity of butene dehydrogenation to butadiene falls effectively to zero. Several experiments were performed in an attempt to find the cause of wildness. There can be little doubt that this condition is due to reduction of nickel oxide to nickel metal, and it is the latter which disrupts the carbon-carbon bonds. X-ray analysis of a wild NiO catalyst showed the presence of approximately 50% metallic nickel, and reduction would probably go to completion if the reactor did not choke with carbon. 

Au-NiO catalyst (entry 4). The activity and selectivity of the Au-Ni catalyst, prepared by the reduction of the Au-NiO catalyst under a H2 atmosphere at 400 °C for 3 h, was greatly decreased (entry 5). The oxidative esterification activity of the Au-NiO catalyst showed a strong dependence on the Au and NiO composition in the supported nanoparticle. The maximum activity was observed for 20 mol% of Au. 

On the other hand, if the oxidative esterification reaction is considered as a general synthetic method for esters, it is quite significant that the Au-NiO, catalyst can almost completely suppress production of the ester by-product derived from oxidation of the alcohol reaction partner. As a general organic synthetic method for esters, it is not controlled by the equilibrium theory, and it is expected to develop as a green manufacturing method that does not require acid or alkali and does not proceed via organic acids. 

For M ECs, research has been focused on finding materials for efficient hydrogen gas generation at the cathode. Selembo et al. studied metal-based electrodes such as stainless steel, nickel, and platinum. Their results showed good performance for a metal coated with an NiO, catalyst [23]. They noted, however, that long-term stability of the catalyst needs improvement. 

Radwan, N., El-Shall, M. andHassan, H. (2007). Synthesis and Characterization of Nanoparticle C03O4, Cuo and Nio Catalysts Prepared by Physical and Chemical Methods to Minimize Air Pollution, Appl Catal. A Gen., 331, pp. 8-18. 

Gallon, H.J., Tu, X., Twigg, M.V. and Whitehead, J.C. (2011). Plasma-Assisted Methane Reduction of a NiO Catalyst — Low Temperature Activation of Methane and Formation of Carbon Nanofibres. AjsjoZ. Catal. B Environ., 106, pp. 616-620. 

Additional studies are required in order to understand the role of defective sites over the catalyst surface on alkane activation. For example, promoted NiO catalysts, such as Ni-Nb-O or supported NiO, also seem to be interesting catalysts for the ODH of ethane, while NiO is very active but unselective. The role of different oxygen species related to non-stoichiometric Ni + sites also seems to be an important factor to be discussed. 

Oemar U, Hidajat K, Kawi S (2011) Role of catalyst support over PdO-NiO catalysts on catalyst activity and stability for oxy-C02 reforming of methane. Appl Catal Gen... 

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