Guilin Zhou

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.

Synergistic Effect of Mo–Fe Bimetal Oxides Promoting Catalytic Conversion of Glycerol to Allyl Alcohol

AbstractIn this study, KIT-6 silica with well-ordered 3-D mesoporosity was developed as support to prepare Fe/KIT-6, Mo/KIT-6, and MoFe-x/KIT-6 (xu2009=u20090.25, 0.3, and 0.35) oxide catalysts for catalytic conversion of gas-glycerol into allyl alcohol. The catalysts were also characterized by XRD, BET, XPS, H2-TPR, and NH3-TPD. The catalytic conversion of glycerol showed a positive correlation with the surface moderate acid density of catalysts, following the order of Fe/KIT-6u2009<u2009MoFe0.25/KIT-6u2009<u2009MoFe0.35/KIT-6u2009<u2009MoFe0.3/KIT-6u2009<u2009Mo/KIT-6. Differently, the production of allyl alcohol was closely related with the moderate redox sites following a hydrogen transfer mechanism. The MoFe-x/KIT-6 showed much higher selectivity than the Fe/KIT-6 and Mo/KIT-6, which resulted from the strong synergistic effect between Fe2O3 and MoO3 altering the surface moderate acid strength, surface acid amounts, and reducibility of catalysts. The MoFe-0.3/KIT-6 exhibited a remarkable yield of 26.8% of allyl alcohol at 94.0% conversion of glycerol without external hydrogen donors supplied to the system, which benefits from the good balance between moderate acidity and weak reducibility of catalysts. The developed cubic Ia3d meso-structure was also benefit for improving the catalytic stability of MoFe0.3/KIT-6.Graphical AbstractAllyl alcohol can produce from gas–solid catalytic conversion of glycerol over the weekly acidic Fe2O3 and MoO3 supported on SiO2. The yield of allyl alcohol can be significantly improved over the MoO3–Fe2O3/SiO2 composite oxide catalysts, because of the strong interaction between MoO3 and Fe2O3. The catalytic conversion of glycerol was positively related with the surface weak acid site density of catalysts, while the allyl alcohol seems to form over the redox sites. Comparing with the single component Fe2O3/SiO2and MoO3/SiO2 catalysts, the strong synergistic effect of MoO3 with Fe2O3 guarantee the MoO3–Fe2O3/SiO2 having relatively high surface week acid site density and certain reducibility, which showed a good balance between weak acidity and reducibility thus obviously increasing the allyl alcohol yield from 26.8 to 94% catalytic conversion of glycerol through gas–solid catalytic reaction without any additives.n

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.

Effect of Calcination Temperature on Catalytic Performance of CeCu Oxide in Removal of Quinoline by Wet Hydrogen Peroxide Oxidation from Water

A facile citric acid-mediated complexation-calcination approach is reported in this paper to prepare the CeCu oxide composite with a porous structure that is highly efficient and durable for treating simulated quinoline wastewater by catalytic wet hydrogen peroxide oxidation (CWPO). As the results indicate, Cu species can be dissolved in CeO2 lattice to fabricate a solid solution. The calcination temperature is critical for an optimum catalyst structure and catalytic performance. As found in investigating the structure and catalytic performance of the CeCu oxide prepared at calcination temperatures ranging from 350 to 750 °C, the optimum temperature is 650 °C, at which a loose surface, a porous structure and considerable adsorbed surface oxide/hydroxyl oxide species are fabricated over the catalyst. This resultant catalyst also takes on the optimal performance with an oxidation conversion reaching 98% for quinoline, a removal efficiency of 80.6% for total organic carbon (TOC) and a low Cu leaching value of 19.3 mg L. Besides, the high performance is maintained by the catalysts in a wide pH range of 5.1-10.5. This work generally provides an efficient way to design and fabricate the catalyst for CWPO reaction, which can also be applied in other reactions.

Bridging Mo2C–C and highly dispersed copper by incorporating N-functional groups to greatly enhance the catalytic activity and durability for carbon dioxide hydrogenation

In this work, we report a facile and controllable method to enhance the catalytic activity and stability of Mo2C–C for CO2 hydrogenation by incorporating N-functional groups on the interface of Mo2C–C to simultaneously serve as basic sites for improving CO2 chemisorption and to immobilize copper particles to prevent aggregation. The incorporated N changed the surface chemical environment of Mo2C and Cu, resulting in the coexistence of Cu2+/Cu+/Cu0 and electron transfer from the copper to the molybdenum species (via MoOxCy–□–Cu+/Cu0). The strong coupling effects of N, Mo2C, and Cu on Cu–Mo2C–N–C is beneficial for further enhancing the adsorption and activation of CO2 and H2 molecules. Accordingly, the Cu–Mo2C–N–C catalysts exhibit greatly superior catalytic activity and stability toward CO2 hydrogenation compared with other catalysts. This facile method may be extended to other materials-based interface engineering to fabricate efficient CO2 hydrogenation catalysts.

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.