Papers by Keyword: Oxidation

Abstract: Alumina was modified by doping with metal oxide and then used as the support for depositing gold by an impregnation-ammonia washing method to obtain Au/M_xO_y/Al₂O₃ (M=Co, Zr and Ce) catalysts. These samples were characterized by inductively coupled plasma-atomic emission spectrometry (ICP-AES), transmission electron microscope (TEM) and X-ray diffraction (XRD). The effects of Co₃O₄ content, metal oxide and mixed metal oxides on the catalytic activity for the selective oxidation of cyclohexane to cyclohexanone and cyclohexanol using molecular oxygen as oxidant were studied. The results showed that better catalytic performance was obtained over Au/M_xO_y/Al₂O₃ catalysts compared with over Au/Al₂O₃ catalysts. 9.69% conversion of cyclohexane and 93.31% selectivity to cyclohexanone, cyclohexanol and cyclohexyl hydroperoxide, with 1.02 ratio of cyclohexanone to cyclohexanol were obtained over the Au/M_xO_y/Al₂O₃ catalyst at 150 , 1.5 MPa for 3 h. Moreover, according to the recycling test, the catalyst could be reused four times without remarkable loss of activity.

Abstract: A method for synthesizing of 2-nitrobenzaldehyde from 2-nitrobenzyl alcohol using ionic liquids (ILs) has been developed. The conversion of 2-nitrobenzyl alcohol and the selectivity of 2-nitrobenzaldehyde in the ionic liquids are higher than those in the traditional dichlorethane solvent. In addition, a reaction mechanism for the oxidation of 2-nitrobenzyl alcohol to 2-nitrobenzaldehyde is proposed.

Abstract: A new type composite catalyst of V₂O₅ comprising Co-Mo/V₂O₅ was prepared by immersion method and characterized by XRD. The characteristic peaks of CoMoO₄(2θ=28.51°) and CoMoO₃(2θ=18.06 °)are both observed in the XRD patterns of Co-Mo/V₂O₅(5%, 20%) catalysts. The oxidation of cyclohexane with hydrogen peroxide was used as a probe reaction to investigate the effects of some conditions, such the sort and volume of solvent, catalyst amount, oxidant amount, reaction temperature and time, on reaction. Using 0.5 ml of cyclohexane, 10 ml of acetonitrile, 3 ml of hydrogen peroxide and 0.03 g of catalyst at a reaction temperature of 55°C for 3 h, the cyclohexane conversion was 32.3% and the total selectivity to cyclohexanol and cyclohexanone was 100%.

Abstract: MgAl₂O₄ was respectively prepared by hydrothermal method (MgAl₂O₄-HT), co-precipitation method (MgAl₂O₄-CP) and solid reaction method (MgAl₂O₄-SR). The as-synthesized MgAl₂O₄ was used as support to prepare CoO_x/MgAl₂O₄ catalysts for the liquid phase oxidation of benzyl alcohol to benzaldehyde by H₂O₂. The catalytic performance and properties of these supports and catalysts were comparatively investigated by catalytic test, XRD, XRF, N₂ isothermal adsorption-desorption, TEM and H₂-TPR technologies. The properties of support MgAl₂O₄ was strongly depended on the preparation method of the support, which affected the catalytic activity of CoO_x/MgAl₂O₄ catalysts in the reaction. CoO_x/MgAl₂O₄-HT exhibited the higher catalytic reactivity and better reusability than CoO_x/MgAl₂O₄-CP and CoO_x/MgAl₂O₄-SR in the reaction, because MgAl₂O₄-HT was high-surface-area porous nanometer spinel MgAl₂O₄.

Abstract: Two novel types of metallo-deuteroporphyrins bearing the disulphide bond were employed to investigate their catalytic activity in oxidation of cyclohexane with molecular oxygen (air) to cyclohexanol and cyclohexanone without the use of sacrificial co-reductant. The catalytic activity of metallo-deuteroporphyrin disulphide derivatives was obvious difference when different metals were incorporated into the porphyrin. However, the same metal cobalt porphyrin complexes exhibited the different catalytic efficiency due to the effect of substituents. Co(II)deuteroporphyrin disulphide derivative is more active than other metallo-porphyrin complexes. On the basis of the obtained results the new reaction process is discussed.

Abstract: Using Ferrate (K₂FeO₄) and polymer flocculant PAFC (PAFC) Collaborative approach, deal with the Acid Scarlet GR Wastewater. Study the effect of Ferrate dosage, PAFC dosage, Ferrate dosing time, Wastewater initial pH Value. Results show that Ferrate pre-oxidation can significantly improve the Coagulation for the removal of Acid Scarlet GR. when the initial concentration of Acid Scarlet GR is 25mg/L, Ferrate dosage is 90mg,PAFC dosage is 13mL,the removal of Acid Scarlet GR is 95.67%.pH on Ferrate removal of Acid Scarlet GR wastewater has little effect. When pH value is 4-8, the removal rate can reach more than 92%.When pH value is 5.6,the removal rate is the highest.

Abstract: Three studies on the oxidation behaviour of austenitic stainless steels were described in the present paper. (1) High temperature oxidation behaviour and its mechanism in austenitic stainless steels with high silicon: Sulfur contained as impurity in steel showed a harmful influence to the oxidation resistance of 19Cr-13Ni-3.5Si stainless steels. It was found that the abnormal oxidation was caused from the surroundings of MnS inclusions. (2) Effect of a small addition of yttrium on high temperature oxidation resistance of Si-containing austenitic stain less steels: The oxidation resistance of 19Cr-10Ni-1.5Si steels was improved remarkably even with only 0.01%Y addition, which is the same concentration as added for de-oxygenation. Y was enriched at the grain boundary of oxide scale and metal-oxide interface. It was suggested that Y-containing steels shoed good oxidation resistance, because the enriched Y at the grain boundary and metal-oxide interface prevented the diffusion of iron and oxygen ions through the oxide scale. (3) Effect of grain size on the oxidation behaviour of austenitic stainless steels: Type 304, 316 and 310 steels with finer grain size showed better oxidation resistance than those with coarser grain size at 850°C. The oxide scale of steels with coarser grain size easily spalled during the cooling process.

Abstract: In the present study, the isothermal early oxidation behaviour of the WE54 and Elektron 21 alloys were studied at a temperature of 773 K in pure O2 up to 150 min. The results showed that the oxidation kinetics depending on the chemical composition and microstructure of the investigated alloys. The oxidation kinetics of these alloys in as-cast and T6 conditions obtained a parabolic law, while in supersaturated state these alloys exhibited a linear kinetics. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses indicated that an oxide film, composed of MgO and (Y,Dy)2O3 in WE54 alloy and (Nd,Gd)2O3 in Elektron 21 alloy, had been formed.

Abstract: The Ni-base superalloy, INCONEL740, whose major alloying elements are 24.31 wt.%Cr-20 wt.%Co, was corroded in an Ar-0.2%SO2-gas atmosphere between 800 and 1000oC for 50, and 100 hr in an electric furnace. The scales formed after SO2-gas corrosion tests were generally adherent at 800 and 900oC. At 1000oC, massive scale spallation however occurred over the entire surface. The scales consisted of Cr2O3, (Ni,Co)Cr2O4, and TiO2, indicating that not sulfidation but an oxidation reaction prevailed owing to the thermodynamic stability of concerning oxides.

Abstract: The methods of thermal, thermogravimetric, mass spectrometric and high-temperature X-ray analysis have been used to determine the chemism of the processes involving the oxidation of a sulfide-metal copper-nickel alloy during continuous heating to 1190 K in an air flow. It has been found that the fineness of particles, the size of the sulfide phases in these particles, and the phase composition influence the phase transformation temperatures, as well as the kinetics and the sequence of the oxidation processes.