Temperature programmed CO2 hydrogenation over a Li-Ni-Co-O catalyst monitored in situ by a.c. electrical parameters coupled to multiple-ion monitoring of the product species

• Published in: Journal of materials science 1996-07, Vol.31 (13), p.3375-3386
• Main Authors: OVENSTON, A, QIN, D, WALLS, J. R
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/BF00360737

Product analysis with temperature increasing between 573 and 873 K has been studied for carbon dioxide hydrogenation. A nonstoichiometric mixed oxide, Li(0.9)Ni(0.5)Co(0.5)O(2-delta) was investigated. The exit gas stream was monitored by using the multiple-ion monitoring facility of a quadrupole mass spectrometer. The a.c. electrical characteristics of the catalyst pellet between 100 Hz and 1 MHz were simultaneously monitored in situ. A clear correlation between catalytic behavior and electrical properties was obtained. Surface dipole effects during chemisorption and reaction phases were revealed. At the lower frequencies, desorption of the gases at 873 K resulted in a decrease in both conductance and capacitance until desorption was completed, as shown by the decay curves on the mass spectrometer. As a result of the chemical reaction, the catalyst becomes partially reduced, as shown by the changes in conductance-temperature-frequency characteristics. The reaction was compared between the freshly oxidized material and the catalyst in the reduced state. Its original oxidized state could be recovered by reoxidation at 973 K for 1 h in air. (Author)