Yanglong Guo

Effect of TiO2 crystal structure on the catalytic performance of Co3O4/TiO2 catalyst for low-temperature CO oxidation

Co3O4 catalysts supported on TiO2 with different crystalline structures (anatase (A), rutile (R) and P25 (Degussa)) were prepared by a deposition–precipitation method, and characterized by nitrogen adsorption/desorption, XRD, HR-TEM, EPR, Raman spectroscopy, XPS and H2-TPR techniques. The results show that Co3O4/TiO2 (A) exhibited the highest activity among the three Co3O4/TiO2 catalysts: CO can be completely oxidized to CO2 at −43 °C. When rutile TiO2 or P25 were used as the support, its catalytic activity was decreased obviously, because the TiO2 crystal structure has an influence on the physicochemical and catalytic properties of the Co3O4 catalysts. The results show that the Co3O4/TiO2 (A) catalyst contains Ti3+ species, which is in an unstable state and can affect the properties of Co3O4 by the interaction between the deposited Co3O4 and anatase TiO2 support. The Co3O4/TiO2 (A) catalyst exhibits highly defective structure and good oxygen adsorption ability. The reducibility of Co3O4 is improved by the anatase TiO2 support, resulting in Co3O4/TiO2 (A) possessing the better redox property than the other Co3O4/TiO2 catalysts, which is an important factor for its high catalytic activity.

A high activity photocatalyst of hierarchical 3D flowerlike ZnO microspheres: Synthesis, characterization and catalytic activity

In this study, three-dimensional (3D) hierarchical flowerlike ZnO microspheres have been hydrothermally synthesized by means of two surfactants at 100 °C and characterized by XRD, SEM, TEM, TG, FT-IR and UV-Vis spectroscopies. The results show that the 3D flowerlike ZnO microspheres are composed of 2D nanosheets. A possible formation mechanism is proposed: 0D Zn(5)(CO(3))(2)(OH)(6) colloids tend to form 2D nanosheets with the aid of sodium dodecyl sulfonic, and then, these nanosheets can assemble to 3D flowerlike microspheres by means of two surfactants of sodium dodecyl sulfonic and PEG 600. The flowerlike ZnO has low bandgap energy and exhibits high catalytic activity for photocatalytic degradation of Rhodamin B, which is attributed to its unique morphology and uniform hierarchical structure that significantly facilitates the diffusion and mass transportation of organic molecules and oxygen species in the degradation reaction.

A novel Ce/AlPO-5 catalyst for solvent-free liquid phase oxidation of cyclohexane by oxygen

Cerium-containing AlPO-5 with an AFI structure has been prepared by hydrothermal synthesis in the presence of HF, and characterized by XRD, XPS, SEM, N2 adsorption/desorption, solid state 27Al, 31P MAS NMR and TG-DTA techniques. The results show that all the samples have good crystallinity, high dispersity of Ce and high surface area, and Ce(III) replaces the position of Al(III) and enters the framework of AlPO-5. Ce/AlPO-5 is a very efficient catalyst for the oxidation of cyclohexane in a solvent-free system with oxygen as an oxidant. In the condition of 0.5 MPa O2 and 413 K for 4 h, the conversion of cyclohexane is 13%, the total selectivity of cyclohexanol and cyclohaxnone is above 92%. In addition, the Ce/AlPO-5 catalyst is very stable in the cyclohexane oxidation system.

Hierarchical Organization and Catalytic Activity of High-Surface-Area Mesoporous Ceria Microspheres Prepared Via Hydrothermal Routes

Mesoporous Ce(OH)CO(3) microspheres with flowerlike three-dimensional (3D) hierarchical structure were successfully synthesized via different hydrothermal systems, including glucose/acrylic acid, fructose/acrylic acid, glucose/propanoic acid, and glucose/n-butylamine systems. After Ce(OH)CO(3) microspheres were calcined, mesoporous CeO(2) microspheres with the same flowerlike morphology as Ce(OH)CO(3) microspheres were obtained. Especially, flowerlike CeO(2) microspheres prepared via the glucose/acrylic acid system are composed of many interconnected mesoporous petal-like nanosheets with thicknesses of 40-60 nm and have high surface area (211 m(2) g(-1)), large pore volume (0.32 cm(3) g(-1)), and narrow pore size distribution ( approximately 3.8 nm in diameter). A possible formation mechanism of Ce(OH)CO(3) microspheres is proposed: the large N-containing organic compounds in situ produced in the above reaction systems played a crucial role in controlling the assembly of Ce(OH)CO(3) building blocks into the flowerlike Ce(OH)CO(3) microspheres. For trichloroethylene combustion, flowerlike CeO(2) microspheres were found to exhibit much higher catalytic activity than general CeO(2) prepared with the conventional methods and the T(10%) and T(90%) were as low as 100 and 204 degrees C, respectively.

Facile synthesis of ordered magnetic mesoporous γ-Fe2O3/SiO2 nanocomposites with diverse mesostructures

On the basis of a sol-gel process, a facile, low cost, and one-step approach for preparing ordered magnetic mesoporous gamma-Fe(2)O(3)/SiO(2) nanocomposites by an evaporation-induced self-assembly (EISA) approach is presented. Various mesostructured silica materials (P6mm or Im3m) incorporated with different amounts of iron oxide (n(Si)/n(Fe) = 9/1, 8/2, 7/3, respectively) were synthesized and characterized by XRD, TEM, N(2)-sorption analyses, and superconducting quantum interference device (SQUID) magnetometer. The HCl-leaching experiments together with TEM micrographs and nitrogen sorption analysis suggested that most of the gamma-Fe(2)O(3) domains of several nanometers were embedded in the silica walls, rather than dispersed in the mesopores, which could cause the significant pore clogging reported in some studies. The release behaviors of lysozyme from these magnetic porous nanocomposites were investigated for the possible application of drug targeting and control release. The influence of iron precursors was also studied and a possible mechanism was proposed. The hydrolysis of Fe(3+) ions under weakly acidic conditions and the induced formation of Si-O-Fe bonds may account for the synthesis of this kind of nanocomposite. These multifunctional nanostructured materials would have a wide range of applications in toxin removal, catalysis, waste remediation, and biological separation as well as novel drug-carrier technologies.

Facile synthesis of 3D flowerlike CeO2 microspheres under mild condition with high catalytic performance for CO oxidation

Three-dimensional (3D) hierarchical flowerlike CeO(2) microspheres with 5-8μm diameter were hydrothermally synthesized by using multiple surfactants at very mild condition (100°C) and characterized by XRD, low-temperature N(2) adsorption, SEM, TEM, TG, FT-IR, and UV-vis spectroscopies. The results show that the flowerlike ceria prepared with the co-surfactant of sodium dodecyl sulfonic and PEG 600 possesses multilevel pore structure and low band gap energy. A possible formation mechanism of flowerlike ceria is that 3D flowerlike microspheres are assembled by 1D nanowires formed through an aggregation of 0D nanoparticles. Based on the unique structure and morphology, the prepared flowerlike CeO(2) exhibits more amount of surface capping oxygen, higher concentrations of Ce(3+) and O vacancy, and more (100) lattice planes, resulting in its higher catalytic activity for CO oxidation than general bulk ceria. Furthermore, photoluminescence property testing shows that flowerlike CeO(2) exhibits the violet blue light emission with a blue shift, because of the quantum size effect, differing from general ceria.

Preparation and characterization of Pd–Ag/ceramic composite membrane and application to enhancement of catalytic dehydrogenation of isobutane

Pd–Ag/ceramic composite membrane, prepared by the improved electroless plating, was characterized. It exhibited higher hydrogen permeating flux (0.759 mol s−1 m−2 at 773 K, ΔP=1.936 atm) and the separation factor of hydrogen to nitrogen or argon was close to infinite. Effects of various operating parameters on the catalytic dehydrogenation of isobutane in the membrane reactor, such as reaction temperature and pressure, space velocity of feed gas, flow rate of purge gas, and molar ratio of nitrogen to isobutane in feed gas, on the conversion of isobutane were investigated. The conversion of isobutane (50.5% at 723 K) in the membrane reactor exceeded the equilibrium conversion (18.8%) and that (15.5%) in the fixed-bed reactor. Maintaining a certain partial pressure of hydrogen in the reaction side of the membrane reactor is favorable to reduce the deactivation rate of catalyst and membrane by carbon deposition.

Non-syngas direct steam reforming of methanol to hydrogen and carbon dioxide at low temperature.

A non-syngas direct steam reforming route is investigated for the conversion of methanol to hydrogen and carbon dioxide over a CuZnGaO(x) catalyst at 150-200 °C. This route is in marked contrast with the conventional complex route involving steam reformation to syngas (CO/H2) at high temperature, followed by water gas shift and CO cleanup stages for hydrogen production. Here we report that high quality hydrogen and carbon dioxide can be produced in a single-step reaction over the catalyst, with no detectable CO (below detection limit of 1 ppm). This can be used to supply proton exchange membrane fuel cells for mobile applications without invoking any CO shift and cleanup stages. The working catalyst contains, on average, 3-4 nm copper particles, alongside extremely small size of copper clusters stabilized on a defective ZnGa2O4 spinel oxide surface, providing hydrogen productivity of 393.6 ml g(-1)-cat h(-1) at 150 °C.

Current status and perspectives of rare earth catalytic materials and catalysis

Abstract Rare earth elements possess 4f orbitals without full electron occupancy and lanthanide contraction. This characteristic results in their unique catalytic performance when they are used as active components or as catalyst supports. Research into and the development of rare earth catalytic materials will significantly promote the high-efficiency utilization of abundant rare earth elements, such as lanthanum and cerium. Currently, rare earth catalytic materials play an important role in such areas as the petroleum chemical industry, the catalytic combustion of fossil fuels, automotive emissions control, the purification of industrial waste air, and solid solution fuel cells. In this paper, we review the application of and recent research progress that has been made on rare earth catalytic materials, including relative theoretical research. The effects of rare earth elements on the structure, activity, and stability of the catalysts of interest are described.

Green light-emitting LaPO4:Ce3+:Tb3+ koosh nanoballs assembled by p-sulfonato-calix[6]arene coated superparamagnetic Fe3O4

Superparamagnetic fluorescent nanocomposites based on doped lanthanide phosphate and magnetite nanoparticles are accessible through a facile one-pot method. The bifunctional nanocomposites adopt a koosh ball structure with both fluorescent and superparamagnetic properties for individual components maintained in the final nanostructure.