Hongmei Xie

High Efficiency CeCu Composite Oxide Catalysts Improved via Preparation Methods for Propyl Acetate Catalytic Combustion in Air

Abstract A famous hard-template method (HT), coprecipitation method (PC), and complex method (CA) were used to prepare CeCu composite oxide catalysts. The prepared catalysts were characterized via XRD, BET, Raman, XPS, FI–IR, and O2–TPD, and their catalytic activity and stability were evaluated for the propyl acetate catalytic combustion. The results showed that the CeCu oxide solid solution and oxygen vacancies were formed in the prepared CeCu oxide catalysts, even for CeCu–PC and CeCu–CA having a specific amount of isolated crystalline or amorphous CuO species. Comparing with the CeCu–PC and CeCu–CA of low porosity, CeCu–HT developed a mesoporous structure with a much larger specific surface area through a negative replica on the structure of KIT-6, and in it, CuO was completely dissolved in the CeO2 lattice to form more CeCu oxide solid solution and a large amount of oxygen vacancies. As a result, the CeCu–HT catalyst has more surface-adsorbed oxygen species, more –OH group which can also change into surface-adsorbed oxygen species at relatively high temperatures, higher oxygen desorption ability, and higher oxygen mobility than CeCu–PC and CeCu–CA. The CeCu–HT catalyst shows high and stable propyl acetate catalytic combustion performance at 190u2006°C. The propyl acetate catalytic combustion activity on the prepared CeCu oxide catalysts can be ranked as: CeCu–HTu2009>u2009CeCu–PCu2009>u2009CeCu–CA, which follows the orders of CeCu oxide solid solution content, surface-active oxygen content, and oxygen desorption and mobility of the CeCu composite oxide catalysts.

Catalytic combustion of volatile aromatic compounds over CuO-CeO2 catalyst

Ce1−xCuxO2 oxide solid solution catalysts with different Ce/Cu mole ratios were synthesized by the one-pot complex method. The prepared Ce1−xCuxO2 catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). Their catalytic properties were also investigated by catalytic combustion of phenyl volatile organic compounds (PVOCs: benzene, toluene, xylene, and ethylbenzene) in air. XRD analysis confirmed that the CuO species can fully dissolve into the CeO2 lattice to form CeCu oxide solid solutions. XPS and H2-TPR results indicated that the prepared Ce1−xCuxO2 catalysts contain abundant reactive oxygen species and superior reducibility. Furthermore, the physicochemical properties of the prepared Ce1−xCuxO2 catalysts are affected by the Ce/Cu mole ratio. The CeCu3 catalyst with Ce/Cu mole ratio of 3.0 contains abundant reactive oxygen species and exhibits superior catalytic combustion activity of PVOCs. Moreover, the ignitability of PVOCs is also affected by the respective physicochemical properties. The catalytic combustion conversions of ethylbenzene, xylene, toluene, and benzene are 99%, 98.9%, 94.3%, and 62.8% at 205, 220, 225, and 225 °C, respectively.

Reduction of CO 2 to CO via reverse water-gas shift reaction over CeO 2 catalyst

CeO2 catalysts with different structure were prepared by hard-template (Ce-HT), complex (Ce-CA), and precipitation methods (Ce-PC), and their performance in CO2 reverse water gas shift (RWGS) reaction was investigated. The catalysts were characterized using XRD, TEM, BET, H2-TPR, and in-situ XPS. The results indicated that the structure of CeO2 catalysts was significantly affected by the preparation method. The porous structure and large specific surface area enhanced the catalytic activity of the studied CeO2 catalysts. Oxygen vacancies as active sites were formed in the CeO2 catalysts by H2 reduction at 400 °C. The Ce-HT, Ce-CA, and Ce-PC catalysts have a 100% CO selectivity and CO2 conversion at 580 °C was 15.9%, 9.3%, and 12.7%, respectively. The highest CO2 RWGS reaction catalytic activity for the Ce-HT catalyst was related to the porous structure, large specific surface area (144.9 m2∙g−1) and formed abundant oxygen vacancies.

Removal of Carbon Monoxide by Oxidation from Excess Hydrogen Gas on Co3O4-NiO/AC Catalyst

The present work investigates the catalytic properties of the Co-Ni-supported activated carbon (AC) catalyst for the oxidation removal of CO in excess hydrogen gas to obtain High purity hydrogen. X-ray diffraction (XRD), temperature-programmed desorption of O2 (O2-TPD), and temperature-programmed reduction (TPR) were used to study the properties of the prepared catalyst. XRD, and TPR results indicate that the highly dispersed NiO and Co3O4 are the main phase in the prepared catalyst. The O2-TPD results show that the Co3O4-NiO/AC catalyst has strong adsorption and activation capacity to O2 molecules. Active oxygen species can be formed on the surface of Co3O4-NiO/AC catalyst, which is the active species to oxidize CO molecules. CO conversion can exceed 99.5% in the temperature range of 443~463 K, and CO oxidation selectivity exceeds 62.2% in less than 463 K.

Promoting Effects of Ni for Toluene Catalytic Combustion Over CoNi/TiO2 Oxide Catalysts

Abstract The supported CoNi/TiO2 composite oxide catalysts were prepared by impregnation method. The physical and chemical properties of the prepared catalysts were studied by XRD, XPS and H2-TPR. The results show that the Co3O4, NiO and NiCo2O4 species are formed in the CoNi/TiO2 composite oxide catalysts. The interaction between the Co and Ni species can effectively enhance the properties of the CoNi/TiO2 oxide catalysts. The introduction of Ni species can effectively enhance the surface hydroxyl oxygen species and adsorbed oxygen species content, and the Co3+ species content can be enhanced on the surface of the prepared CoNi/TiO2 composite oxide catalysts. The low temperature reducibility and toluene catalytic combustion activity of the CoNi/TiO2 composite oxide catalysts can be improved by the Ni species. The toluene catalytic combustion activity of CoNi/TiO2 composite catalysts can be obviously affected by the Co/Ni molar ratio. The CoNi/TiO2 composite oxide catalyst, which has a Co/Ni molar ratio of 1.0, has the best toluene catalytic combustion activity and wide scope of the concentration of toluene. The toluene catalytic combustion conversion can exceed 99u2006% at 340u2006°C. That is to say, the toluene concentration in air can be decreased to 80 ppm from 8000 ppm.