Heterogeneous and/or homogeneous chromia-catalysed decomposition of hydrogen peroxide

Thermal decomposition and creation of reactive solid surfaces

“…Correlating the catalytic results reported earlier [7,8] with the findings of the present investigation, it is suggested that the creation of the Zener phase (coupled Cr3+--fr 6+ -ions), the active redox catalytic centres, is optimized at the surface, wherever the chromium chromate species form throughout the course of the thermal genesis of the catalysts.…”

Low-temperature adsorption of oxygen on calcined chromia: IR spectroscopic and sorptiometric evidence for oxygen-assisted topochemical reduction of surface chromate species

“…These Cr(III)-Cr(VI) centres have been approximated to Zener electron-mobile phases [33] and are suggested [8,9] to optimise the redox catalytic activity on calcined chromias.…”

“…When allowed to interact electronically with nearby Cr(III)-O species [6,7], the chromates are stabilised with respect to thermal decomposition, hydrolysis or chemical reduction [3,6,8]. The availability of electronically-coupled Cr(III)-Cr(VI) species nevertheless provides the electron-mobile environment required for surface redox reactions [1,2,9]. Whereas, localised adsorption occurs on coordinatively-unsaturated Cr(III) sites, the electron availability occurs through the interaction with nearby Cr(VI) ions [7,10,11].…”

“…Whereas, localised adsorption occurs on coordinatively-unsaturated Cr(III) sites, the electron availability occurs through the interaction with nearby Cr(VI) ions [7,10,11]. Accordingly, calcined chromia catalysts have shown potential in a range of important redox reactions, such as CO oxidation [11], dehydrogenation of alcohols [1], and H 2 O 2 decomposition [9].…”

“…It is worth noting that the high volatility of Cr(VI)-O compounds has led environmentalists to classify these compounds as detrimental within the atmosphere [16]. For this reason industrial applications of calcined chromia catalysts have been largely hampered [9], despite their success in numerous laboratory applications [1,2,17,18]. However, chromia catalysts synthesised by calcination and a subsequent elimination of unstable chromates, as described above, would still possess sufficient catalytic potential in redox processes while posing no acute threat to the environment [8].…”