Co3O4 hollow nanotubes for the catalytic oxidation of C2-chlorinated VOCs

Structured Co3O4 catalysts with a hollow nanotube morphology were prepared by several synthesis routes based on the Kirkendall effect. The resulting samples were kinetically evaluated in the gas-phase oxidation of vinyl chloride and 1,2-dichloroethane, two model C2-chlorinated volatile organic compounds; and exhaustively characterised by means of BET measurements, X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry and temperature-programmed techniques (adsorption of ammonia and chlorinated VOC, O2-TPD, H2-TPR and TPO). The performance of the prepared nanotubes was essentially controlled by the presence of active oxygen species at the surface, which in turn depended on the Co2+/Co3+ molar ratio, and the adsorption capacity of the catalyst for the chlorocarbon. Both pollutants were efficiently converted to deep oxidation products at relatively low temperatures. In addition, the optimal catalyst exhibited an appreciable stability when operating during 120 h.Ministry of Science and Innovation (PID2019-107105RB-I00 AEI/FEDER, UE and PDC2022-133897-I00) // Basque Government (IT1509-22) // University of the Basque Country UPV/EHU (PIF18/185

Catalytic Oxidation of Vinyl Chloride over SrCO3-Co3O4 Catalysts: Effect of the Sr:Co Molar Ratio

Co3O4 catalysts modified with SrCO3 with various Sr:Co molar ratios were synthesized by a co-precipitation method and their catalytic behavior was examined for the gas-phase oxidation of vinyl chloride. The physical-chemical properties of the samples were thoroughly characterized by means of ICP-AES, BET measurements, XRD, H2-TPR, XPS and SEM-EDX. The obtained results revealed that the incorporation of strontium carbonate introduced changes in the textural and structural properties as well as modifications in the surface chemical composition of the catalysts. The performance of the samples was found to be controlled by the concentration of active species on the surface (Co2+/Co3+ and Oads/Olatt ratios) and the reducibility of the samples. As for the stability of the catalysts, clear evidences of deactivation (more severe when increasing the SrCO3 content) were noticed, probably caused by the decomposition of the SrCO3 phase and the formation of SrCl2 accompanied by a loss of textural properties and active surface oxygen species

Promotion of Cobalt Oxide Catalysts by Acid-Etching and Ruthenium Incorporation for Chlorinated VOC Oxidation

In this work, Ru-promoted cobalt oxide catalysts with a nanotube morphology were prepared by a synthesis route based on the Kirkendall effect followed by an acid treatment and subsequent optimized Ru impregnation. The resulting samples were thoroughly characterized by means of N2 physisorption, X-ray energy-dispersive spectroscopy, X-ray diffraction, scanning electron microscopy techniques, X-ray photoelectron spectroscopy, and temperature-programmed techniques (O2-temperature-programmed desorption, H2-temperature-programmed reduction, and temperature-programmed oxidation) and evaluated in the gas-phase oxidation of 1,2-dichloroethane. It has been demonstrated that Ru addition improves the oxygen mobility as well as the amount of Co2+ and Oads species at the surface by the formation of the Ru–O–Co bond, which in turn governs the performance of the catalysts in the oxidation reaction. Moreover, the acid-etching favors the dispersion of the Ru species on the surface of the catalysts and strengthens the interaction among the noble metal and the cobalt oxide, thereby improving the thermal stability of the Ru-promoted oxides. Thus, the resulting catalysts are not only active, as the chlorinated pollutant is efficiently converted into deep oxidation products at relatively low temperatures, but also quite stable when operating for 120 h