Advanced Materials Research Vols. 550-553

Abstract: The Pd-doped TiO2 powder was prepared by the sol-gel method and characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, UV-Vis absorption spectroscopy and X-ray diffraction. The results show that palladium exists as PdO and that the PdO crystal forms in the Pd/TiO2 powder calcined at 973 K. When the Pd/TiO2 powder is calcined at a temperature between 573K and 973 K, TiO2 mainly exists in the anatase structure, and the average diameters of the anatase TiO2 and PdO particles are less than 45 nm. The crystal lattice constant a decreases while c increases with the increasing of the calcination temperature. Compared with the pure TiO2 powder prepared under the same conditions, the phase transformation temperature from the anatase structure to the rutile structure for TiO2 in the Pd/TiO2 powder increases, the excitation wavelength of Pd/TiO2 powder is broadened to the visible light region and the visible photocatalytic activity increases obviously.

Abstract: A Mo-Ni/Al₂O₃ catalyst for converting mercaptans into thioethers to remove the mercaptans in the FCC gasoline was studied. Under the optimized conditions, the catalyst showed its good catalytic reaction performance and the activity remained stable after the 1500 h life experiment. After the accelerated aging experiment under severe conditions, the catalyst finally lost its activity at 1850 h. The samples of the fresh and used catalyst were characterized by BET, TEM and XPS. The results showed that the binding energy of sulfided Ni species shifted to the low energy level indicated that the sulfided Ni species might have a reducible tendency in the catalytic run. This could be considered as a main reason of the catalysts deactivation. On the other hand, the metal agglomeration and carbon deposition and nitrides adsorption in the catalytic runs also led to the deterioration of the catalyst.

Abstract: The effect of catalyst on the performance of liquid-phase selective oxidation of cyclohexane as probe reaction over Co-Bi2(MoO4)3 prepared by precipitation method was investigated. The catalyst evaluation results show that the optimum catalyst atomic ratio is n(Mo):n(Bi):n(Co)=1.5:1:0.2 with high selecivity under certain conversion. Meanwhile selective oxidation of Bi2(MoO4)3 was slowed down, selecivity of cyclohexanone and cyclohexanol reached 74.1%, 22.2% respectively.The main composition of the catalyst is Bi2(MoO4)3. Co-Bi2(MoO4)3 had new catalyst sites with Bi3+, Mo6+ and Co2+ having a cooperative effects during oxidation of cyclohexane. Under this condition, selecivity of cyclohexanone improved greatly. Micro-structure and essence disciplinarian of Co-Bi2(MoO4)3 were disclosed by XRD and FTIR. This study could provide experimental data for the technical reform of industry equipment.

Abstract: In this paper, the synthesis of mesoporous molecular sieves MCM-41 was carried out in an open-vessel. The mesoporous structure of as-synthesized MCM-41 was characterized by X-ray diffraction (XRD) pattern, Fourier transform infrared (FT–IR) spectrum, NH3-Temperature Programmed Desorption (TPD), and N2 adsorption-desorption isotherms. The catalytic performances of MCM-41 for the synthesis of geranyl propionate (GP) with geraniol and propionic acid as reagents also were investigated. The characterization results show that the as-synthesized MCM-41 possesses typical hexagonal mesoporous structure with high long-range order and crystalline degree. The high GP selectivity of 64.25% with geraniol conversion of 17.21% was achieved under optimum conditions.

Abstract: A series of solid acid catalysts were synthesized by incipient wetness impregnation method by varying the wt% of silicotungstic acid on bentonite. Silicotungstic acid supported on bentonite was used to catalytic synthesise of n-butyl acetate with acetic acid and n-butyl alcohol . The main reaction parameters such as silicotungstic acid loading on bentonite, the amount of catalyst, molar ratio of reactants, reaction temperature and reaction time have been investigated. The optimum conditions were determined as follows : silicotungstic acid loading on bentonite 20 wt %, catalyst 0.7 g , mole ratio of n-butanol to acetic acid 1:1.1, reaction temperature 98 °C and reaction time 2 h . The esterification yield of n-butyl acetate was about 98.2 %. The catalyst could be used repeatedly for many times without distinct loss in activity.

Abstract: Fe₂O₃/H₂O₂, a kind of Fenton-like agent, was used to degrade an anion surfactant, sodium dodecyl benzene sulfonate(SDBS)，in an aqueous solution. Through a number of batch degradation experiments under various conditions, it was found that the reactivity of the system increased by increasing temperature. The SDBS degradation ratio will increase by, respectively, increasing H₂O₂ concentration and Fe₂O₃ dosage at some extent, but too high H₂O₂ concentration or Fe₂O₃ dosage will decrease the degradation efficiency. pH value has some influences on the reactivity of the system; from 2 to 10, the system maintains high efficiencies all the time. It also can be seen that Fe₂O₃/H₂O₂ Fenton-like reaction almost has the same efficiency as homogeneous Fenton reaction, while the former has a widely pH range (2-10), and Fe₂O₃ can be separated easily and has no secondary pollutants.

Abstract: In this paper, we prepared Dipentene Hydrogenation Catalyst by impregnating, with activated alumina as catalyst carrier and nickel nitrate solution as soaking liquid. The objective of this study was to investigate the influences of the amount of nickel loading, calcination temperature and hydrogen reduction temperature on catalyst activity. The results show that the optimum parameters are: 21% of nickel loading, the calcination temperature of 550-650 °C, the hydrogen reduction temperature of 325-350 °C. The purity of p-menthane prepared under the conditions was more than 97 %, reaching special class standards.

Abstract: The formation of propylene oxide from propylene by direct oxidation with O₂ has been studied with catalysts of rare earth chloride under different carboxylic acids and solvents, and the mechanism of this reaction has been discussed preliminarily. Significant PO-formation was only observed when catalyzed by EuCl₃ and in the presence of zinc powder and carboxylic acids. In using carboxylic acids, propanoic acid is the best for the epoxidation of propylene. The yields of the epoxide became higher than those without solvents, but basic substance was not suitable as solvent. In the catalytic system of EuCl₃, zinc powder and carboxylic acids, EuCl₃ plays a role in transferring electron, zinc powder was the e- donor and carboxylic acids was the H⁺ donor. The mechanism was consistent with the result of the experiment.

Abstract: A Mg₃(VO₄)₂ catalyst was synthesized and investigated for the oxidative dehydrogenation of cyclohexane to cyclohexene. Integral measurements were performed to determine the reaction network and products distribution, and differential measurements for kinetic investigations. The kinetic study indicated the oxidative dehydrogenation of cyclohexane to cyclohexene follow a parallel-consecutive network. The power law kinetic model was considered as a rough approximation of the experimental results. The rate constants, which included the activation energies, the pre-exponential factors as well as the orders of cyclohexane and oxygen, were evaluated.

Abstract: A series of CuxCe1-xO2-x/SBA-15/cordierite (x = 0-1) catalysts were prepared. The activity of the catalysts for CO combustion was evaluated. The catalysts were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). Deactivation behavior of the catalysts for the catalytic combustion of CO was investigated. The results show that all of the catalysts retained the SBA-15 mesoporous structure. It is proposed that deactivation of the catalysts is associated with the increase of the Cu+ and the decrease of the Cu2+ in the catalysts.