NiO/CaO

Fig. 18 ISS relative substrate oxide intensities as a function of overlayer coverages for NiO/MgO, MgO/ NiO, NiO/CaO and CaO/NiO. The lines are guides to the eye, not fits.

NiO, CaO, BijOi, Mn02, La20s, Fc203, V2O5, C03O4... 

Moon et al. [59] presented a breadboard fixed-bed fuel processor for isooctane, which was composed of an ATR and high-and low-temperature shift reactors. The fuel processor was applied for testing different catalysts. A NiO/CaO/Al203 catalyst performed equivalent to a Ni/Fe/MgO/AlaOs catalyst for the autothermal reforming reaction. 

Values of vNO were reported for NO adsorbed on NiO-MgO and NiO-CaO surfaces. Adsorption of NO on non-stoichiometric Ni-Cu manganites produces numerous surface species (mono- and dinitrosyls, adsorbed N2O, nitrites and nitrates) ... 

Fragneau, M. and Revcolevschi, A., Crystallography of the Directionally Solidified NiO-CaO Eutectic. J. Amer. Ceram. Soc. 66 C162-163 (1983). 

J. W. Dbbereiner discovered many triads elements and compounds, the combining weight the central compcmeiit being the average of Its partners (e.g. CaO. SrO. BaO. and NiO, CuO. ZnO). 

The decomposition of MgC03 (magnesite) is an interface process [734] between 813—873 K and E = 150 kJ mole-1. In the presence of C02, E was increased to 234 kJ mole-1 but was reduced slightly on the addition of ZnO or NiO. Admixture with CaO reduced the value of E to 54 kJ mole-1. This is a surprising result since the value of E for decomposition [734,753] of the mixed carbonate (Ca, Mg)C03, dolomite, is 220 kJ mole-1, larger than the value for each constituent. The influence of PCOz and of alkali metals on MgC03 decomposition has been the subject of a DTA study [404]. 

These studies have allowed the spectroscopic identification of a number of electronically excited states of the metal oxides, but there appear to have been no analytical applications of the reactions to date. The emitting states, as summarized by Toby [14], are CaO(A n), SrO(ATl), PbO(a32+, b32+), ScO(C2II), YO(C2n), FcO(C ), A10(A2ni B2X+), and BaO(A i)1, D 2+). Nickel carbonyl reacts with ozone to produce chemiluminescence from an excited electronic state of NiO, which is probably produced in the Ni + 03 reaction [42, 43],... 

Vijh (6) has suggested more recently that if one assumes the adsorbed species formed in this reaction to be a covalent one, the available data can be interpreted in terms of the Sabatier-Balandin views on heterogeneous catalysis. According to his interpretation, he has indicated a volcanic relationship between the catalytic activity (defind as the temperature at which the reaction first becomes appreciable) against the heat of formation per equivalent of the oxide catalyst, AHe. Based on this volcanic relationship, he has concluded that the rate-determining step (r.d.s.) of the reaction on the oxide catalysts such as CiO, NiO and CoO probably involves rupture of a M-0 bond. On the other hand, r.d.s. on oxides such as MgO,CaO and Ce02 would involve the formation of a M-0 bond. 

In contrast to MgO, the other alkaline-earth oxides, such as CaO, SrO, and BaO, were found to be poor supports for NiO, as they provided catalysts with low activities, selectivities, or stabilities (Fig. 14) (239). Although the reduced Ni0/Al203 catalyst provided high initial conversions (CH4, 91% C02, 98%) and selectivities (>95% for both CO and H2), it was characterized by the fastest carbon deposition, which led to the complete plugging of the reactor after only 6 h of reaction (197). The reduced Ni/Ti02 catalyst gave relatively low initial... 

Recently, Ruckenstein and Wang (264-266) also successfully developed excellent CoO/MgO solid-solution catalysts for C02 reforming of methane. They reported that Co/MgO exhibited a good catalytic performance with a CO yield of 93% and a H2 yield of 90% at the high space velocity of 60,000 mL (g catalysts)-1 h-1 and 1163 K, which remained unchanged during 50 h of investigation (264). In contrast, Co/CaO, Co/SrO, and Co/BaO each provided low CO yields, and Co/CaO also had a low stability. The results indicate that the CoO/MgO catalysts are characterized by performances similar to those of NiO/MgO. 

The simplest of structures is the rock salt structure, depicted in Figure 2.2a. Magnesium oxide is considered to be the simplest oxide for a number of reasons. It is an ionic oxide with a 6 6 octahedral coordination and it has a very simple structure — the cubic NaCl structure. The structure is generally described as a cubic close packing (ABC-type packing) of oxygen atoms in the (111) direction forming octahedral cavities. This structure is exhibited by other alkaline earth metal oxides such as BaO, CaO, and monoxides of 3d transition metals as well as lanthanides and actinides such as TiO, NiO, EuO, and NpO. 

Fig. 1.43 Electrical conductivity of the stabilized zirconia (Zr02)o.85(CaO)o.i5 4s a function of Po, at different temperatures. Pq was controlled by the use of a two phase mixture such as CU-CU2O, Ni NiO etc. Open and closed marks are data obtained from different samples.

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