Preparation and thermal shock resistance of solar thermal absorbing corundum ceramics for concentrated solar power

The absorptivity of solar thermal absorber materials affects the heliothermal conversion efficiency of concentrated solar power systems. The solar absorbing ceramics were prepared by the fixed mixture of bauxit, Fe₂O₃, and TiO₂ with adding CuO in different percentages. The absorptivity and thermal shock resistance with the effect of adding CuO in different percentages were studied. Fe₂O₃ and TiO₂ have excellent optical properties, and CuO decreases the material's band gap to boost the electronic transition and increase the material absorptivity. The results showed that the material is sintered at 1380°C with an excellent absorptivity of 94.00% in the spectrum range of 0.3–2.5 μm, and the bending strength is 132.94 MPa. The bending strength was increased by 21.07% after 30 thermal shock cycles (1000°C-room temperature, air cooling). The liquid phase facilitates the synthesis of hercynite with excellent high temperature properties. The hercynite improves the thermal shock resistance of the material.     

Synthesis and characterization of CuO/TiO2 catalysts for low-temperature CO oxidation

In this paper, the CuO/TiO₂ catalysts prepared by the deposition–precipitation (DP) method were extensively investigated for CO oxidation reaction. The structural characters of the CuO/TiO₂ catalysts were comparatively investigated by TG-DTA, XRD, and XPS measurements. It was shown that the catalytic behavior of CuO/TiO₂ catalysts greatly depended on the TiO₂-support calcination temperature, the CuO loading amount and the CuO/TiO₂ catalysts calcination temperature. CuO supported on the anatase phase of TiO₂-support calcined at 400 °C showed better catalytic activity than those supported on TiO₂ calcined at 500 and 700 °C. Among all our investigated catalysts with CuO loading from 2% to 12%, the catalyst with 8 wt% CuO loading exhibited the highest catalytic activity. The optimum calcination temperature of the CuO/TiO₂ catalysts was 300 °C. The XRD results indicated that the catalytic activity of the CuO/TiO₂ catalysts was related to the crystal phase and particle size of TiO₂ support and CuO active component.     

Gas phase hydrogenation of maleic anhydride to tetrahydrofuran by Cu/ZnO/TiO2 catalysts in the presence of n-butanol

Cu/ZnO/TiO₂ catalysts were prepared via the coprecipitation method. The catalysts were characterized by X-ray diffraction, X-ray photoelectron spectrometry, temperature programmed reduction, and N₂ adsorption. The catalytic activity of Cu/ZnO/TiO₂ catalyst in gas phase hydrogenation of maleic anhydride in the presence of n-butanol was studied at 235–280 °C and 1 MPa. The conversion of maleic anhydride was more than 95.7% and the selectivity of tetrahydrofuran was up to 92.7%. At the same time, n-butanol was converted to butyraldehyde and butyl butyrate via reactions, namely, dehydrogenation, disproportionation, and esterification. There were two kinds of CuO species present in the calcined Cu/ZnO/TiO₂ catalysts. At a lower copper content, the CuO species strongly interacted with ZnO and TiO₂; at a higher copper content, both the surface-anchored and bulk CuO species were present. The metallic copper (CuO) produced by the reduction of the surface-anchored CuO species favored the deep hydrogenation of maleic anhydride to tetrahydrofuran. The deep hydrogenation activity of Cu/ZnO/TiO₂ catalyst increased with the decrease of crystallite sizes of CuO and the increase of microstrain values. Compensations of reaction heat and H₂ in the coupling reaction of maleic anhydride hydrogenation and n-butanol dehydrogenation were distinct.     

Biocompatibility,corrosion resistance and antibacterial activity of TiO2/CuO coating on titanium

In this work, TiO₂/CuO coating was prepared on titanium (Ti) by combination of magnetron sputtering and annealing treatment. The microstructure, biocompatibility, corrosion resistance and antibacterial property of TiO₂/CuO coating were investigated in comparison with pure Ti and TiO₂ coating. The results show that TiO₂/CuO coating is mainly composed of TiO₂ and CuO. In vitro cytocompatibility evaluation suggests that no obvious toxicity appears on the TiO₂/CuO coating, and the coating stimulates the osteoblast spreading and proliferation. Compared with Ti and TiO₂ coating, TiO₂/CuO coating exhibits improved corrosion resistance and antibacterial ability against S.aureus. This study is the first attempt to apply the combination of magnetron sputtering and annealing treatment to introduce the Cu into TiO₂ coating for surface modification of Ti-based implant materials, which may provide a research foundation for further development of bioactive multifunctional coatings to meet the better clinical demand.     

Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts

Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts. The solid acids were prepared by mounting H₂SO₄ on TiO₂ · nH₂O and Zr(OH)₄, respectively, followed by calcining at 823K. TiO₂-SO₄ ²⁻ and ZrO₂-SO₄ ²⁻ showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C, methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Br?nsted acid sites on the catalysts. Translated from The Chinese Journal of Process Engineering, 2006, 6(4): 571–575 [译自: 过程工程学报]     

Effect of Pretreatment Atmosphere on CuO/TiO2 Activities in NO + CO Reaction

Using TiO₂ as carrier, CuO/TiO₂ catalysts with different CuO loading were prepared by the impregnation method. The catalytic activities in NO+CO reaction were examined with a micro-reactor gas chromatography reaction system and the methods of TPR, XPS and NO-TPD. It was found that the catalytic activities were affected by pretreatment atmosphere, i.e. H₂ atmosphere > reduction–reoxidation > 10%CO/He > reaction gas (fresh sample). NO decomposition was better by low-valence Cu species than by high-valence Cu species, i.e. Cu⁰>Cu⁺>Cu²⁺. The XPS results indicated that Cu species on CuO/TiO₂ were Cu⁰, Cu⁺, normal Cu²⁺(Cu²⁺(I)) and chain-structured Cu²⁺(Cu²⁺(II)) as –Cu–O–Ti–O–. The activities of Cu²⁺(II) were much higher than that of Cu²⁺(I), but both species were very unstable in the reaction atmosphere and easily reduced by CO, which accounted for the variable activities of fresh catalysts with increasing reaction temperature. In NO+CO reaction, the redox process was a cycle of Cu⁺–Cu²⁺(I) at low reaction temperature but was a cycle of Cu⁰–Cu⁺ at high reaction temperature. As shown by NO-TPD, high catalytic activities could be attributed to the following factors, e.g. oxygen caves on the catalyst’s surface after pretreatment with H₂ and reduction–reoxidation, formation of Cu⁰ after pretreatment with H₂, and increment of Cu species dispersion and formation of Cu²⁺(II) after pretreatment with reduction–reoxidation.     

Surface modification of titanium dioxide for electrophoretic particles

To prepare stable electrophoretic ink (E Ink) needs color particles to be uniformly dispersed in the organic medium. Thus, t-he modification of inorganic particle surface is required. In this paper, Titanium dioxide modified by alumina has been studied. The surface composition and structures of modified particles have been characterized by X-ray photoelectron spectrometer (XPS), X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FT-IR). The dispersibility and electrophoretic mobility of these particles in tetrachloroethylene (TCE) have been investigated by laser particle size analyzer, static sedimentation and electrophoretic instrument. Effects of temperature, pH value and stirring rate on the dispersibility and the charge property of samples have been discussed. The results indicate the settle time of modified TiO₂ can last 120 h with the response time of 35 s under the optimized modifying conditions, in which temperature is 85°C–90°C, pH is 8–9 and stirring rate is 800 r·min⁻¹. The dispersibility and electrophoretic mobility have been significantly improved, which means that the modified TiO₂ is suitable for electrophoretic ink particles. __________ Translated from Journal of Chemical Engineering of Chinese Universities, 2006, 20(6): 893–897 [译自: 高校化学工程学报]     

Preparation and characterization of SO42-/TiO2 and S2O82-/TiO2 catalysts

Nanosized solid superacids SO₄ ²⁻/TiO₂ and S₂O₈ ²⁻/TiO₂, as well as MCM-41-supported SO₄ ²⁻/ZrO₂, were prepared. Their structures, acidities, and catalytic activities were investigated and compared using XRD, N₂ adsorption-desorption, and in situ FTIR-pyridine adsorption, as well as an evaluation reaction with pseudoionone cyclization. The results showed that SO₄ ²⁻/TiO₂ and S₂O₈ ²⁻/TiO₂ possess not only nanosized particles with diameters < 7.0 nm, a BET surface greater than 140 cm²/g and relatively regular mesostructures with pores around 4.0 nm, but also a pure anatase phase and strong acidity. Different from the Lewis acid nature of SO₄ ²⁻/ZrO₂/MCM-41, SO₄ ²⁻/TiO₂ and S₂O₈ ²⁻/TiO₂ exhibit mainly Bronsted acidities. The strongest Bronsted acid sites were produced on SO₄ ²⁻/TiO₂ promoted with H₂SO₄, while Lewis acid sites on S₂O₈ ²⁻/TiO₂ even stronger than those on SO₄ ²⁻/ZrO₂/MCM-41 were generated when persulfate solution was used as sulfating agent. Because of their distinct acid natures, SO₄ ²⁻/TiO₂ and S₂O₈ ²⁻/TiO₂ exhibited catalytic activities for the cyclization of pseudoionone that were much higher than that of SO₄ ²⁻/ZrO₂/MCM-41. It can be concluded that the existence of more Br?nsted acid sites was favorable for proton participation in the cyclization reaction. Translated from Journal of Chemical Engineering of Chinese Universities, 2006, 20(2): 239–244 [译自: 高校化学工程学报]     

Hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol on NiB/SiO2 amorphous alloy catalyst

NiB/SiO₂ amorphous alloy catalyst was prepared by power electroless plating method and characterized by induction coupled plasma (ICP), Brunauer-Emmett-Teller method (BET), transmission electron microscope (TEM) and X-ray diffraction (XRD) techniques. The catalytic performance of NiB/SiO₂ was investigated for the hydrogenation of furfuryl alcohol (FA) to tetrahydrofurfuryl alcohol (THFA). The effects of operational conditions, such as reaction temperature, pressure, and stirring rate were carefully studied. The proper conditions were determined as the following: pressure 2.0 MPa, temperature 120°C and stirring rate 550 r/min. A typical result with FA conversion of 99% and THFA selectivity of 100% was obtained under such conditions, which was close to that over Raney Ni. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(4), 483–486 [译自: 燃料化学学报]     

Preparation and microstructure analysis of Fe-doped PbTiO3 ceramic

Fe-doped PbTiO₃ (PT) powder and bulk materials were prepared successfully by sol-gel technique and a subsequent sintering process using Fe (C₅H₅)₂ as a dopant agent. The effects of pH and temperature on the Fe-doped PT system were investigated. Thermogravimetry/differential thermal analysis (TG/DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to analyze the composition and the microstructure of the PT ceramics. The results indicated that the thermal decomposition of xerogel included three stages: volatilization of adsorption water and organic composition, oxygenolysis of n-butyl and acetate, and transformation of the crystalline phase. Well-stabilized collosol and gel could be obtained at 60°C and pH = 4.5. It was found that PbTiO₃, PbFe₂O₄, and TiO₂ crystalline appeared in the Fe-doped PT system when the mass fraction of the dopant Fe was 0.03%. Furthermore, from STM analysis, it could be seen that the grain size of doped PT ceramics was homogeneous and about 1–2 μm, and the pore of the PT ceramic was small. As a result, the PT ceramic had high tightness. __________ Translated from Journal of Harbin Institute of Technology, 2007, 39 (1): 165–168 [译自: 哈尔滨工业大学学报]     

High activity TiO2 Photocatalysts Prepared by a Modified Sol–gel Method: Characterization and their Photocatalytic Activity for the Degradation of XRG and X-GL

A simple method for preparing high photocatalytic activity TiO₂ has been developed by controlled the hydrolysis of titanium butoxide with water generated “in situ” using an esterification reaction between the acetic acid and ethanol. The photocatalytic activity of the samples prepared was higher than that of the reference Degussa P25 TiO₂ for the liquid phase photocatatlytic degradation of active yellow XRG dye and cationic golden X-GL dye.     

Optimization of experimental conditions based on Taguchi robust design for the preparation of nano-sized TiO2 particles by solution combustion method

This investigation was aimed at preparing nanocrystalline TiO₂ powder by solution combustion method, and searching the optimum preparing conditions by employing Taguchi robust design method. Taguchi robust design method with L₁₈ orthogonal array was implemented to optimize experimental conditions for preparing nano-sized titania particles. Titanium IV n-butoxide was hydrolyzed to obtain titany1 hydroxide [TiO(OH)₂], and titanyl nitrate [TiO(NO₃)₂] was obtained by reaction of TiO(OH)₂ with nitric acid. Finally, the aqueous solution containing titanyl nitrate [TiO(NO₃)₂] and a fuel, glycine, were mixed and combusted to obtain the nano-sized titania. The optimum conditions obtained by this method are as follows (based on 1 mol of TiO₂ per batch): concentration of HPC, 0.053 mg cm⁻³; mole ratio of Ti:H₂O:IPA, 1:4:10; hydrolysis time, one hr; the amounts of HNO₃ and glycine are 10 ml and 0.5 g, respectively; nitrated temperature, 298 K and nitrated time, 2 h. TiO₂ nanocrystalline (∼15 nm) with high BET surface area (350 m² g⁻¹) and narrow band gap energy (2.7 eV) were thus obtained.     

Solubility of CO2 in solid-state PET measured by pressure-decay method

The solubility of CO₂ in solid-state PET was measured using a pressure-decay method. In order to calculate the solubility of CO₂ in the amorphous region of PET, the crystallinity of solid state PET dissolved in CO₂ at different pressures and temperatures was measured by differential scanning calorimetry (DSC). The solubility increases with increasing pressure and it follows a linear relationship and obeys Henry’s law when the pressure is below 8 MPa. The effect of temperature on solubility is weak and the solubilities at different temperatures are almost the same under low pressures. At higher pressure, the solubility decreases with an increase in temperature. The solubility of CO₂ in the amorphous region of PET at 373.15 K, 398.15 K and 423.15 K was correlated with the Sanchez-Lacombe equation of state with a maximal correlation error of 6.69%. __________ Translated from Journal of East China University of Technology (Natural Science Edition), 2007, 33(4): 445–449 [译自: 华东理工大学学报(自然科学版)]     

Uniform dispersion of CuO nanoparticles on mesoporous TiO2 networks promotes visible light photocatalysis

Here, we focus our efforts on synthesizing a uniform dispersion of CuO nanoparticles on mesoporous TiO₂ networks for the first time. H₂PtCl₆ was added through a photocatalytic reaction to produce 0.5% Pt/CuO–TiO₂ nanocomposites. XRD patterns confirmed that the prepared TiO₂ formed the anatase phase. TEM images showed close contacts between CuO and TiO₂ with 5–10 nm particle sizes. One of the advantages of the synthesized mesoporous CuO–TiO₂ nanocomposites was the high pore volume (0.540 cm³ g⁻¹) and large surface area (300 m² g⁻¹). The H₂ evolution over the mesoporous 3 wt% CuO–TiO₂ nanocomposites using a glucose hole scavenger [10 vol%] was determined to be ~13000 μmol/g, a value that was 1300 times greater than that of mesoporous TiO₂. The H₂ evolution rate was increased by up to 1300 and 20 times for 3 wt% CuO–TiO₂ and 0.1 wt% CuO–TiO₂ nanocomposites, respectively, compared with that of mesoporous TiO₂. The increase in H₂ evolution over mesoporous CuO–TiO₂ nanocomposites was explained by the increased light harvesting capacity, high glucose molecule diffusion and efficient charge carrier separation. Moreover, the construction of a heterostructure with a p–n CuO–TiO₂ heterojunction expedited the separation of charge carriers and promoted the evolution of H₂. In addition, H₂ evolution was substantially increased by the synergistic effects of Pt and CuO on the mesoporous TiO₂ networks. Photoelectrochemical and photoluminescence measurements were employed to prove the H₂ evolution mechanism over the CuO nanoparticles deposited on the mesoporous TiO₂ networks.     

Kinetics of pozzolanic reaction for preparation of flue gas desulfurizer from fly ash and Ca(OH)2

A kinetic model of the pozzolanic reaction for the preparation of flue gas desulfurizers from fly ash and Ca(OH)₂ was deduced on the basis of solid phase reaction kinetic theory. Kinetic expressions and parameters were obtained and verified by experiment. A comparison of calculated results with experimental results showed that precision in kinetic expressions was good. The apparent reaction rate constants of the pozzolanic reaction could be raised by increasing the specific surface area of fly ash and the hydration temperature, and by using a suitable additive. Translated from Chemical Reaction Engineering and Technology, 2006, 22(4): 329–334 [译自: 化学反应工程与工艺]     

Properties and catalytic mechanism of γ-glutamyltranspeptidase from B.subtilis NX-2

Since γ-glutamyltranspeptidase (GGT) especially catalyses the transfer of the γ-glutamyl moiety to a variety of amino acids and short peptides, GGT has important practical value for enzymatic synthesis of γ-glutamyl compounds. In this paper, the GGT produced from Bacillus subtilis NX-2 was purified by a combination of ammonium sulfate fractionation and ion exchange chromatography, and the properties of purified GGT were investigated. At the conditions of pH 10.0, D-glutamine (D-Gln)/L-tryptophan (L-Trp) with a molar ratio of 5: 7, a temperature 40°C and a reaction time of 4 h, a higher conversion rate of 42% was obtained. According to the time course, the catalytic mechanism of enzymatic synthesis of γ-D-glutamyl-L-tryptophan (γ-D-Gln-L-Trp) was discussed. It was demonstrated that the GGT can catalyze not only the reaction of transpeptidation, but also the irreversible hydrolysis of the products which results in the decrease of the yield of the products. The affinity parameter of GGT to D-Gln (Km) was 5.08 mmol·L⁻¹ and the maximum reaction rate of transpeptidation (r _max) was determined as 0.034 mmol·min⁻¹·L⁻¹, while the affinity parameter of GGT to γ-D-Gln-L-Trp (K’_m) was 2.267 mmol·L⁻¹, and the maximum reaction rate of hydrolysis (r’_max) was 0.012 mmol·min⁻¹·L⁻¹. __________ Translated from Journal of Chemical Engineering of Chinese Universities, 2008, 22(2): 288–293 [译自: 高校化学工程学报]     

Formation of deagglomerated PLGA particles and PLGA-coated ultra fine powders by rapid expansion of supercritical solution with ethanol cosolvent

Rapid expansion of supercritical solution (RESS) was used for preparing polymer particles and polymer coating of ultra fine powders. The polymer of pharmaceutical interest was Poly(lactic-co-glycolic acid) (PLGA with PLA: PGA ratio of 85: 15 and MW of 50,000–75,000) and the simulated core particles were 1.4-μm SiO₂ and 70-nm TiO₂ particles. The supercritical solution was prepared by dissolving PLGA in supercritical carbon dioxide with ethanol as a cosolvent. Supercritical solution of CO₂-PLGA was sprayed through capillary nozzles to ambient conditions, resulting in formation of submicron PLGA particles. Similarly, rapid expansion of supercritical solution of CO₂-PLGA suspended with the core particles could provide solvent evaporation and deposition of submicron PLGA particles on the surface of the core particles, resulting in the formation of coating films on dispersed particles of SiO₂ and agglomerates of TiO₂. The influences of the core particle size, spray nozzle diameter as well as powder-to-polymer weight ratio were also investigated and discussed with respect to the coating performance.     

Behavior of copper oxide in silicoborate glazed glasses

Copper-containing glazed glasses in the B₂O₅-SiO₂-Al₂O₃-CaO-CuO system with a copper oxide molar content of 5 to 25%, added during synthesis of the glasses, was investigated. The glasses with a minimum content of 15% B₂O and 15–25% CuO crystallized during processing with separation of fine-needle CuO crystals. However, all glasses formed a good glaze coating when applied on ceramics at temperatures of 900–1000°C. The CuO crystals totally dissolved in the melt. __________ Translated from Steklo i Keramika, No. 8, pp. 9–11, August, 2007.     

Enhancing thermostability of β-mannanase by protective additives

The effects of some sugars (glucose, mannose, fructose, sucrose and chitosan) and polyols (glycol, glycerol and sorbitol) as protective additive on the thermostability of β-mannanase were studied. The optimal reaction temperatures of β-mannanase and the thermodynamics and the deactivation kinetics with or without additives were also investigated. The experimental results show that sucrose, chitosan and sorbitol could apparently improve the thermal stability of β-mannanase when their concentration was kept at 2 g/L. The optimal combination additive proportion was sucrose: chitosan : sorbitol = 1 : 2 : 2 (molar ratio) using the orthogonal experimental design. The sucrose, chitosan, glycerol, sorbitol and the combination additive might increase the optimal reaction temperature from 50°C to about 60°C due to their good protection effect. The thermal deactivationcurves of β-mannanase accorded with the kinetic rules of first order reaction, and the corresponding kinetic and thermodynamic parameters were calculated. Meanwhile, the protective mechanism of the additives against deactivation of enzyme was also discussed. __________ Translated from Journal of Tianjin University, 2007, 41(1): 114–118 [译自: 天津大学学报]     

Properties of La1-xCexCoO3 system perovskite-type catalysts for diesel engine exhaust removal

A series of complex oxide La_1−x Ce _x CoO₃ catalysts was synthesized at a low temperature through a combustion process, in which x is among 0, 0.1, 0.2, 0.4 and 0.6 corresponding to the quantity of La³⁺ partial substitution by Ce⁴⁺. The catalysts were characterized for phase composition using chemical analysis and X-ray diffraction. The catalytic activity of the catalysts in removal of NO _x , total hydrocarbon (THC) and particulate matter (PM) from diesel exhaust gases were examined in detail using temperature-programmed reaction technique. The results show that after partial substitution of La³⁺ with Ce⁴⁺, the oxygen vacancy concentration increases significantly and a Co³⁺-Co²⁺ system is formed. Consequently, the catalytic activity in the removal of THC and NO _x is significantly improved. But for the PM, the effect is not so obvious. The possible catalytic mechanism for this was presented. It is also worth noting that the doped catalysts showed good stability. Translated from Journal of Fuel Chemistry and Technology, 2006, 34(1): 85–90 [译自: 燃料化学学报]