Nickel oxide stoichiometric composition

In all of these oxide phases it is possible that departures from the simple stoichiometric composition occur dirough variation of the charges of some of the cationic species. Furthermore, if a cation is raised to a higher oxidation state, by the addition of oxygen to tire lattice, a conesponding number of vacant cation sites must be formed to compensate tire structure. Thus in nickel oxide NiO, which at stoichiomen ic composition has only Ni + cations, oxidation leads to Ni + ion formation to counterbalance the addition of extra oxide ions. At the same time vacant sites must be added to the cation lattice to retain dre NaCl sUmcture. This balanced process can be described by a normal chemical equation thus... 

When the pressure over nickel hydroxide is reduced to 10- torr, dehydration begins at 210° but a black nickel oxide is formed which therefore contains a stoichiometric excess of oxygen (23). If the residual pressure is decreased to 10 torr, dehydration proceeds at a measurable rate at 200°. The color of the oxide is then yellowish green. When the decomposition of the hydroxide is carried out to the point of a constant weight, the composition of the product is NiO, 0.16 H2O (24). 

The stoichiometric compositions of pure and doped nickel oxides were determined by chemical analysis (30). As presented in Section II, the difference 2[Ni3+] — [Ni ) is evaluated and results are expressed in at.% Oexc if the difference is positive or in at.% Niexc if the difference is negative. Chemical analyses (30) and magnetic measurements (33) have shown that pure nickel oxide prepared under vacuum at 250° contains a small excess of metallic nickel (Table X). The surprising result is that oxides containing up to 4 at.% Li (total) or 1.5 at.% Li (actually dissolved) present a stoichiometric composition which is similar to that of pure NiO(250°) (Table X). Nickel oxide containing 9.5 at.% Li (total) presents an excess of oxygen (0.052 at.% Oexc) which is small, however, compared to the amount of lithium ions actually incorporated in the lattice (1.95 at.% Li) (Table X). 

Desulfurized natural gas or naphtha is then mixed with process steam and preheated before passing to the primary reformer. The steam ratio, which is the molar ratio of steam to carbon, is typically between 3.0 and 4.0 moles of steam per atom of carbon in the hydrocarbon feedstock. An excess of steam over the stoichiometric quantity is required to suppress carbon-forming reactions and to provide a favorable equilibrium composition for the reaction of methane. The primary reformer consists of a large number of tubes packed with supported nickel oxide catalyst and contained in a furnace. The purpose of>the furnace is to heat the reactants to... 

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