Xiaolai Wang

Excellent catalytic performance of ZnxCo1−xCo2O4 spinel catalysts for the decomposition of nitrous oxide

Abstract The catalytic decomposition of N2O to N2 and O2 was carried out on the ZnxCo1−xCo2O4 (x=0.0–0.98) spinel catalysts. The results showed that the partial replacement of Co2+ by Zn2+ in Co3O4 spinel oxide led to a significant improvement in the catalytic activity for the N2O decomposition, and the catalytic activity depended on the degree of Co2+ substitution by Zn2+. The Zn0.36Co0.64Co2O4 catalyst is the most active in the studied samples. The conversion of N2O reached 100% over the Zn0.36Co0.64Co2O4 catalyst at 200 and 300 °C in the absence and presence of excess O2 and water, respectively.

Oxygen-enriched activated carbons from pomelo peel in high energy density supercapacitors

We used low-cost pomelo peel (PP) as a biomass-derived porous activated carbon to fabricate a high energy density symmetric supercapacitor. The porous activated carbon was prepared from the pomelo peel (PP) via pyrolysis and a KOH activation process, followed by heat treatment under an argon atmosphere. The resulting porous carbon possesses a very high specific surface area (2105 m2 g−1) and abundant oxygen functionalities, which lead to a wide voltage window of 1.7 V, a specific capacitance of 43.5 F g−1 and a high energy density of 17.1 W h kg−1 for the as-assembled AC//AC symmetric supercapacitor. These impressive electrochemical characteristics may indicate the PP to act as a new biomass source of carbonaceous materials for low-cost and high performance electrical energy storage devices.

Scale up and stability test for oxidative coupling of methane over Na2WO4-Mn/SiO2 catalyst in a 200 ml fixed-bed reactor

Abstract The study of scale up for the oxidative coupling of methane (OCM) has been carried out in a 200 ml stainless steel fixed-bed reactor over a 5wt% Na 2 WO 4 -1.9wt% Mn/SiO 2 (W-Mn/SiO 2 ) catalyst. The effects of reaction conditions were investigated in detail. The results showed that, with increasing reaction temperature, the gas-phase reaction was enhanced and a significant amount of methane was converted into CO x ; with the CH 4 /O 2 molar ratio of 5, the highest C 2 (ethylene and ethane) yield of 25% was achieved; the presence of steam (as diluent) had a positive effect on the C 2 selectivity and yield. Under lower methane gaseous hourly space velocity (GHSV), higher selectivity and yield of C 2 were obtained as the result of the decrease of released heat energy. In 100 h reaction time, the C 2 selectivity of 66%–61% and C 2 yield of 24.2%–25.4% were achieved by a single pass without any significant loss in catalytic performance.

Effect of calcination temperature on structure and performance of Ni/TiO2-SiO2 catalyst for CO2 reforming of methane

Abstract The influence of calcination temperature on the structure and catalytic behavior of Ni/TiO2-SiO2 catalyst, for CO2 reforming of methane to synthesis gas under atmospheric pressure, was investigated. The results showed that the Ni/TiO2-SiO2 catalyst calcined at 700° C had high and stable activity while the catalysts calcined at 550 and 850° C had low and unstable activity. Depending on the calcination temperature, one, two, or three of the following Ni-containing species, NiO, Ni2.44Ti0.72Si0.07O4, and NiTiO3 were identified by combining the temperature programmed reduction (TPR) and X-ray diffraction (XRD) results. Their reducibility decreased in the sequence: NiO > Ni2.44Ti0.72Si0.07O4 > NiTiO3. It suggests that high and stable activities observed over the Ni/TiO2-SiO2 catalyst calcined at 700°C were induced by the formation of Ni2.44Ti0.72Si0.07O4 and smaller NiO species crystallite size.

Oxidative coupling of methane over BaCl2-TiO2-SnO2 catalyst

The performance of BaCl 2 -TiO 2 -SnO 2 composite catalysts in oxidative coupling of methane reaction has been investigated. A series of BaCl 2 -TiO 2 , BaCl 2 -SnO 2 , TiO 2 -SnO 2 , and BaCl 2 -TiO 2 -SnO 2 catalysts were prepared, and characterized by BET, XRD, XPS, CO 2 -TPD and H2-TPR, respectively. The synergistic effect among BaCl 2 , SnO 2 and TiO 2 compositions enhances the catalytic performance. The best C2 selectivity and ethylene yield are obtained on the catalyst with the equal molar amount of the three compositions (BaCl 2 : TiO 2 : SnO 2 molar ratio of 1:1:1). The optimal reaction conditions are as follows: 800°C, 44 mL-min −1 for methane, 22 mL-min −1 for oxygen and a space velocity of 5000 mL-h −1 -g −1 , and the C 2 H 4 yield over the catalyst is 20.1% with the CH 4 conversion of 43.8% and C2 selectivity of 53.3%.

A novel solid-gas process to synthesize LaMnO3 perovskite with high surface area and excellent activity for methane combustion

Abstract A novel solid-gas route to prepare LaMnO3 perovskite catalysts for methane combustion has been developed. The method was carried out using a polyvinylpyrrolidone-metal complex as precursor via a solid-gas process to obtain the target materials. The structure and properties of the precursor and the catalysts were characterized by FT-IR, TG-DSC, XRD and N2 adsorption-desorption techniques. The results indicate that the catalysts synthesized via the solid-gas process possess higher surface areas, better thermal resistance and catalytic activity as compared to those prepared with the conventional sol-gel citrate method.

Selective electrochemical sensing of calcium dobesilate based on the nano-Pd/CNTs modified pyrolytic graphite electrode.

A new palladium nanoparticle functionalized multi-wall carbon nanotubes (nano-Pd/CNTs) modified pyrolytic graphite electrode (PGE) has been fabricated for electrochemical sensing of calcium dobesilate (CD) in pharmaceutical capsules. The nano-Pd/CNTs were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The nano-Pd/CNTs composite showed a strong electrocatalytic property for CD. The anodic peak current is 6-fold than that obtained in bare PGE and the oxidation potential has an obvious shift to negative. The anodic peak current is proportional to the concentration of CD in the range of 1.0 x 10(-7) to 7.0 x 10(-4)mol L(-1), with a linear relative coefficient r=0.999 and a detection limit 4.0 x 10(-8)mol L(-1) (S/N=3). This kind of electrode shows good stability, sensitivity, reproducibility, large linear range and low detection limit towards electrochemical determination of CD. The proposed method provides a selective and sensitive electrochemical sensor of calcium dobesilate.

A “pillared” process to construct graphitic carbon nitride based functionalized mesoporous materials

We present a novel method to prepare mesoporous materials via in situ self-assembly of graphitic carbon nitride nanosheets and silica nanoparticles. Combining the advantages of g-C3N4 nanosheets and mesoporous structure, the as-prepared materials exhibit superior adsorption capabilities for heavy metal ions and organic pollutants.

Effect of Structure of CeOHCO3 Precursor of CeO2 on Its Catalytic Performance

Abstract A modified hydrothermal process method based on using urea instead of water as the solvent was used to prepare CeOHCO3. Pure CeOHCO3 with a single crystalline structure was produced by varying the experimental conditions. CeO2 particles obtained from these CeOHCO3 precursors were tested for CH4 oxidation. The temperatures for 90% methane conversion were 604 and 647°C for CeO2 catalysts obtained from hexagonal and orthorhombic CeOHCO3, respectively, indicating that the CeO2 catalyst from hexagonal CeOHCO3 (CeO2-A) was more active than that from the orthorhombic form (CeO2-D). The specific surface area and pore volume of CeO2-A were 45 m2/g and 0.35 cm3/g, respectively, which were higher than those of CeO2-D. H2-TPR showed a much lower reduction temperature and enhanced reducibility with CeO2-A. XPS and O2-TPD results demonstrated there were more oxygen vacancies on the surface of CeO2-A than on CeO2-D, which implied increased oxygen mobility. The CeOHCO3-structure dependent activity was investigated and found to originate from the morphologies of the CeOHCO3 precursors. Hexagonal CeOHCO3 had a rod-like shape while orthorhombic CeOHCO3 had a sphere-like morphology. After calcination, the obtained CeO2 had the morphology of the precursor. The difference in morphology gave CeO2 catalysts with different texture, structure, reducibility, and thus catalytic activity.