Advanced Materials Research Vols. 233-235

Abstract: Photo-degradation of toluene at ppb levels by mixed-phase TiO₂ nanoparticles, synthesized by the oxidation of TiCl₄ in propane/air flame chemical vapor deposition (CVD) process, has been investigated experimentally by using a tubular photoreactor with thin TiO₂ films coated on the reactor wall by sedimentation. Effects of toluene at initial concentration at ppb levels, rutile mass fraction and photoluminescence (PL) spectra of TiO₂ nanoparticles on degradation degree have been investigated under the conditions of 5.7 seconds of residence time, 70% relative humidity, 38mg/cm² of TiO₂ loading, 25mW/cm² of irradiation with main wavelength of 254nm.

Abstract: The possibilities of dissolving grade pulp production from reed were investigated in this paper. Two – stage prehydrolysis – kraft pulping and CEHA bleaching process of reed for preparation of dissolving grade pulp were studied in laboratory. The optimum cooking and bleaching conditions were found out. The mechanism and its kinetics of reed in prehydrolysis process were also discussed. The results showed that under the laboratory conditions the rate for removal of materials at about 175°C follow approximately a pseudo first order law with two distinct phrases: the bulk removal and the residual removal of the materials. The prehydrolysis-factor (P-factor) was established. The advantage of using P-factor is predict compensating adjustments in cooking time and/or temperature to give the same degree of pulping and to produce pulp with predetermined characteristics. It is found that three distinct delignification rate stages about 75% of pentosans and about 50% of lignin were removed. A CEHA four stage bleaching is used for dissolving grade pulp. Total chlorine charge in bleaching is 6% (to oven-dry pulp). The results show that all of the indices fitted the quality standards of dissolving grade pulp.

Abstract: In this paper, using tetrabutyl titanate as source, H₂O₂(30%) as solvent, synthesis of titanium dioxide sol was achieved by sol-gel method. A transparent sol aging in air 30min, titanium dioxide films were prepared by using spin coating method. The photodegradation capability of 4-chlorophenol has been enhanced by using immobilized TiO₂ particles, where the titanium sol synthesized by a sol-gel method was used as the binder for the immobilization. Optimal conditions of TiO₂ film, 4-chlorophenol concentration, solution pH, and UV irradiation intensity have been found to enhance the photodegradation efficiency.

Abstract: Used ultra-fine silicon oxide as carrier, the catalyst was prepared with the ZSM-5 molecular sieve with high n (SiO₂)/n (Al₂O₃) ratio as active component for the catalytic cracking of C4 alkenes to propylene and ethylene. The precursors of CaO and La₂O₃ were used to adjust the acidic property of the catalyst. The catalyst was pretreated at 800with protection by inert gas or at 600with water vapor for 24 hours. At 500°C, 0.1MPa, w(H₂O)w(C₄^＝)=0.2, WHSV 3 h^-1, the catalyst evaluation was processed under the continuous operation for 25 days and the stability of catalyst was proved. The activity of the catalyst was reduced after long time treatment at the 800 °C or 600 °C with water vapor. The catalysts were characterized by BET, NH₃-TPD and Py-IR, the results showed that the catalytic activity of the catalyst concerns with the quantity of the B acid.

Abstract: The synthesis of chiral silicon-containing (R)-ketone-cyanohydrin by enantioselective transcyanation of acetyltrimethylsilane with acetone cyanohydrin was efficiently carried out using defatted Prunus domestic seed meal as (R)-hydroxynitrilase lyase for the first time. Under the optimal conditions including a reaction temperature of 25-35°C and a buffer pH of 5.0-5.4, both acetyltrimethylsilane conversion and enantiomeric excess of the product were above 99%. In contrast, this enzyme did not accepted its carbon counterpart 3,3-dimethyl-2-butanone as substrate. These results demonstrated that the silicon atom in substrate served as a more effective atom than the carbon atom to enhance the activity of the enzyme.

Abstract: Alumina sol sealing is one of new green technology for anodized Al alloy. The corrosion mechanism of films sealed by sol and corrosion behaviour of films sealed by sol, Na₂Cr₂O₇, boiling water were analyzed by their curves of open circuit voltage-time (E-T) and potentiodynamic polarization curve. It is found that corrosion tendency of sol sealing film is less than other sealed films by E-T inspection. Fluctuation of open-circuit potential is furious in the immersing prophase and slows down in the anaphase for anodized sealed films. At this time corrosive reactions gradually reach steady state. Open-circuit potential greatly waves for the rough sealed films. Potentiodynamic polarization curves of sealed films show that passive area is the longest for films sealed by sol which has the minimum corrosive current , the passivate current, anodic current and cathode current, but the maximum pitting potential and open-circuit potential. Corrosion parameters are the second for the film sealed by dichromate. Anodic reactions are strongly inhibited by sol sealing films in Cl^- corrosive solution. Sol sealing films weaken cathode O₂ depolarize reaction. Cl^- ions erode anodized Al material on which covered with sol film and produce corrosion. The corrosion of sol-gel film goes through two periods: pitting induced phase and pitting corrosion period.

Abstract: WO₃/ZrO₂ solid superacid catalysts were prepared by coprecipitation and impregnation, then were characterized by XRD, N₂ adsorption-desorption, Hammett indicator and pyridine chemisorption IR. The acid strength, acid type, acid volume, etc were compared under the different preparation conditions. The results indicated that the catalyst prepared by coprecipitation had stronger acid strength than the catalyst prepared by impregnation. The samples prepared by impregnation had more Lewis acid sites. With the increasing of the W/Zr ratio, the acid strength tended to increase at first and then decrease, and the catalyst with 10% WO₃ loading amount had the strongest acidity. The higher the calcination temperature, the less the Lewis acid sites.

Abstract: FeS-1, VS-1 or CuS-1 precursors are loaded and highly dispersed on the surface of mesoporous materials SBA-15, MCM-41 or SiO₂ by impregnating method. The samples were characterized by X-ray diffraction, FT-IR spectroscopy, TEM and N₂ adsorption. Their catalytic performances for styrene epoxidation with anhydrous TBHP as an oxidant agent were studied. The results suggest that zeolite primary and secondary building units are highly dispersed on the samples and the samples have still retained mesoporous structure. All of the catalysts exhibit good catalytic activities, producing styrene oxide and benzaldehyde as the main products. Cu/SBA-15 shows high activity and selectivity, which are comparable with that of other samples. We find that, under the conditions of preferable precursors, n(TBHP)/n(styrene) =1.5, reaction temperature 80°C, and reaction time 2.0h, the conversion and yield of styrene epoxide reached 65.9% and 42.2%, respectively.

Abstract: With chemical coprecipitation method, high purity hydroxyapatite was successfully prepared in this paper. The microstructure and components of HA were characterized by XRD, SEM, FTIR, atomic emission spectrum and particle size analyzer. The results demonstrate that synthesized HA is very pure and is harmless to human body. Average particle size of HA powder is about 10.4μm. Crystallization degree of hydroxyapatite increases with the increase of sintering temperature and the optimal preparing technique is sintering at 750 for 2h with temperature-rising rate of 5°C·min-1. Grain growing activation energy of HA can be calculated as 24.8 kJ·mol-1 according to the relationship between grain size and sintering temperature. HA’s grain growth mechanism is interfacial diffusion controlling mechanism.

Abstract: The microwave-hydrothermal method for synthesizing g-MnO₂ has been investigated for the first time. The dandelion-like g-MnO₂ active material with 1.0-5.0 μm in diameter was obtained from KBrO₃ and MnSO₄ via the novel method. Compared with traditional low-temperature hydrothermal method, this approach lowers the temperature by 30-40 °C, and shorts the reaction time 6-14 h. Electrochemical properties of dandelion-like γ-MnO₂ were elucidated by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy tests. The synthesized material shows a relative high specific capacitance, and the MnO₂ obtained at the condition of 75 °C for 2 h shows the best electrochemical properties with a specific capacitance of 239.3 F·g^-1 at the current density of 100 mA·g^-1 in 6 M KOH electrolyte solution.