Reference

Role of metal vanadate additives on the decomposition reaction kinetics of nickel tetrahydroxy/carbonate as a precursor during the thermal genesis of nickel(II) oxide catalyst

Role of metal vanadate additives on the decomposition reaction kinetics of nickel tetrahydroxy/carbonate as a precursor during the thermal genesis of nickel(II) oxide catalyst. Gabr, R. M.; Girgis, M. M.; El-Awad, A. M. (Fac. Sci., Assiut Univ., Assiut, Egypt). Thermochim. Acta, 196(2), 279-90 (English) 1992. CODEN: THACAS. ISSN: 0040-6031. DOCUMENT TYPE: Journal CA Section: 67 (Catalysis, Reaction Kinetics, and Inorganic Reaction Mechanisms) The catalytic effect of copper and magnesium metavanadate additives on the thermal decompn. of nickel tetrahydroxy carbonate (NTHC) was studied by using the TG and DTA methods. Math. anal. of the TG data showed that first-order kinetics are applicable in all cases using the Coats-Redfern equation. Thermodn. kinetic parameters (i.e. energy and entropy of activation and preexponential factor) are reported. Addnl., the kinetic parameters of the decompn. reaction were calcd. by adopting a computer-oriented kinetic anal. of the a-t data, obtained in isothermal conditions in the temp. range 200-450°. Comparative studies of the kinetics of the thermal decompn. of NTHC salt in isothermal and non-isothermal conditions were performed. These indicate that the overall rate of salt decompn. is controlled by the rate at which the gaseous products can diffuse away from the reaction centers. The participation of O in interface reactions yielded highly oxidized Ni3+ phases, which are necessary participants in the sequence of the anion (CO32-) breakdown. Accordingly, advance of the interface proceeded by a chain-type mechanism involving regeneration of the active intermediate Ni3+. 14958-34-0 and 39430-27-8 which are cas registry numbers of substances are two of reagents here. The effect of CuV2O6 additive is discussed on the basis of the redox couple Cu2+ + e J Cu+, which accelerates the decompn. reaction via a charge-transfer mechanism. Mixing the salt with MgV2O6 resulted in a retardation effect, for which a tentative explanation has been made in terms of the ability of such an additive to occupy a grain boundary, which hinders the decompn. process. A decompn. reaction mechanism involving the participation of Ni3+ ions is proposed. .