Characterisation of ceria supported chromia catalysts
TL;DR: A series of ceria supported chromia catalysts of different loading were prepared and the effect of support in stabilising various chemical and molecular states of chromium with the calcination temperature were studied as discussed by the authors.
Abstract: A series of ceria supported chromia catalysts of different loading were prepared and the effect of support in stabilising various chemical and molecular states of chromium with the calcination temperature were studied. XRD results showed that the chromia phase is randomly dispersed, disordered, and the crystallite size may be smaller than the detection limit. BET surface area and pore volume results suggested some plugging of pores on the support by chromia phase. EGA analysis suggested the existence of the surface heterogenity involving weakly and strongly chemisorbed CO 2 . EGA and NIR DRS studies revealed the bulk-like behaviour in the catalysts having chromia loading of more than 5 wt.%. EGA, FTIR and UV–VIS–DRS studies supported the formation of anchored surface chromium species. Moreover, the nature of molecular states of chromium and the coordinative environment under various thermal conditions were investigated using FTIR and UV–VIS–DRS techniques.
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TL;DR: In this paper, a review of the most popular IR spectroscopy applications for catalytic applications is presented, starting from the very general basis of the spectroscopic method applied and focusing on the adsorption of chelating compounds on surfaces of mineral oxides.
433 citations
TL;DR: Various chromium-containing catalysts were tested for the total oxidation of trichloroethylene (TCE) as a model reaction for the catalytic combustion of chlorinated organic pollutants to demonstrate higher activity and higher CO2 selectivity than traditional alumina supported chromia.
Abstract: Various chromium-containing catalysts were tested for the total oxidation of trichloroethylene (TCE) as a model reaction for the catalytic combustion of chlorinated organic pollutants. A spinel-type cobalt chromite (CoCr2O4) among others was proven to be a very promising catalyst showing higher activity and higher CO2 selectivity than traditional alumina supported chromia. Even if both Cr3+ and Cr6+ species were observed on the surface of CoCr2O4, the Cr6+ species was stable under reducing environment. The presence of Cr3+-Cr6+ pair sites and the effect of redox treatments on the activity were investigated to explain the nature of possible active sites for TCE decomposition. Higher selectivity to CO2 of CoCr2O4 was ascribed to the abundance of its Cr3+ species, together with its activity for water gas shift reaction.
108 citations
TL;DR: In this paper, a possible pathway of soot oxidation over Cu0.05Ce0.95-CA is proposed, based on the relationship of the performance and physicochemical features of catalysts, which pathway follows the mechanism associated with redox couple and oxygen spill over effect.
62 citations
TL;DR: In this paper, the role of chromium oxides and ceria and their synergistic effect in textural properties, redox performance and surface species over the Cr1−xCex/TP catalysts were investigated in detail by means of Brunauer-Emmertt-Teller (BET) surface area analysis, X-ray diffraction (XRD), transmission electron microscope (TEM), temperature-programmed reduction of H2 (H2-TPR), NO-TPD), photoluminescence spectra, and in situ diffuse reflectance infrared
32 citations
TL;DR: In this paper, mesoporous ceria and SBA-15 silica were modified with iron and chromium oxide nanoparticles and characterized by XRD, N2-physisorption, FTIR, UV-vis, Moessbauer spectroscopy and TPR-TG in hydrogen.
30 citations
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TL;DR: In this paper, three peaks of oxygen release with maxima at 670, 750 and 920 K were observed in dependence on chromium content and surface area of the silica, related to three different kinds of unstable Cr6+oxide existing besides stable Cr6-surface compounds.
Abstract: During temperature programmed heating of Cr6+-oxide supported on dispersed silica up to three peaks of oxygen release with maxima at 670, 750 and 920 K are observed in dependence on chromium content and surface area of the silica. The peaks are related to three different kinds of unstable Cr6+-oxide existing besides stable Cr6+-surface compounds.
11 citations
TL;DR: The nature and stability of chromium species on the surface of CrOx/ZrO2 catalyst (Cr content 1.6 wt%) have been investigated using IR spectroscopy.
9 citations