燃煤流化床中CaO催化还原N2O机理研究

应用热失重与傅立叶红外光谱联用仪研究了CaO在流化床燃煤气氛下对N2O的分解还原机理。实验结果表明CaO的催化作用使N2O浓度降低的初始温度由1150K降低至1050K;在CO的作用下N2O降低的初始温度由1050K降低至1000K。对实际流化床燃煤过程中CaO的作用分析认为,CaO对N2O的催化分解能力与煤的含硫量密切相关;它与HCN的气固反应减少了产生N2O的来源以及CaO对N2O的多相催化反应是降低N2O的主要原因之一。     

Generating oxygen adatoms on Au(997) by thermal decomposition of NO<Subscript>2</Subscript>

We report our investigation of the interaction of NO₂ with the Au(997) vicinal surface by high-resolution photoelectron spectroscopy using synchrotron radiation as the excitation source. At 170 K, both core-level and valence-band photoemission results illustrate the decomposition of NO₂ on the Au(997) surface at low NO₂ exposures, forming coadsorbed NO(a) and O(a) species. After annealing at 300 K, NO(a) desorbs from Au(997) whereas O(a) remains on the surface. Upon annealing at 750 K, we observe no signal for adsorbed oxygen on Au(997). These results clearly demonstrate that thermal decomposition of NO₂ is an effective method to generate oxygen adatoms on Au(997) under ultrahigh-vacuum conditions.     

Effects of acetylene at low concentrations on nitrification, mineralization and microbial biomass nitrogen concentrations in forest soils

Temperate forest surface soils at the varying distances from main trunks (e.g., Pinus koraiensis and Quercus mongolica) were used to study the effects of acetylene (C₂H₂) at low concentrations on nitrification, mineralization and microbial biomass N concentrations of the soils, and to assess the contribution of heterotrophic nitrification to nitrous oxide (N₂O) emissions from soils. The use of acetylene at partial pressures within a range from 10 to 100 Pa C₂H₂ in headspace gas gave a significant decrease in N₂O emission at soil moisture of c. 45% water-filled porosity space, and the decrease was almost the same in each soil after exposure of C₂H₂ at low concentrations. Heterotrophic nitrification could account for 21%―48% of total N₂O emission from each soil; the contribution would increase with increasing distances from the Pinus koraiensis trunks rather than from the Quercus mongolica trunks. Under the experimental conditions, the use of C₂H₂ at low concentrations showed no significant influence on soil microbial biomass N, net N mineralization and microbial respiration. However, 100 Pa C₂H₂ in headspace gas could reduce carbon dioxide (CO₂) emissions from soils. According to the rapid consumption of 10 Pa C₂H₂ by forest soils and convenience for laboratory incubations, 50 Pa C₂H₂ in headspace gas can be used to study the origin of N₂O emissions from forest soils under aerobic conditions and the key associated driving mechanisms. The N₂O and CO₂ emissions from the soils at the same distances from the Quercus mongolica trunks were larger than those from the Pinus koraiensis trunks, and both emissions decreased as the distances from trunks increased. The stepwise regression analysis showed that 95% of the variability in soil CO₂ emissions could be accounted for by the concentrations of soil total C and water soluble organic C and soil pH, and that 72% of the variability in soil N₂O emissions could be accounted for by the concentrations of soil total N, exchangeable NH⁺₄-N and microbial biomass N and 25% of the variability in heterotrophic nitrification by the soil microbial biomass N concentration. The emissions of N₂O and CO₂ from forest soils after exposure of C₂H₂ at low concentrations were positively related to the net nitrification of the soils.     

Synthesis, Characterization and Calorimetry of Ni（C4H8N2O3）2Cl2

A coordination complex was synthesized from NiCl2 and dipeptide glycylglycine（GG）. It was characterized by element analysis, NMR and TG methods, and then was determined to be Ni（C4HsN2O3）2Cl2. Using an isoperibolic reaction calorimeter, the standard molar enthalpy of formation of Ni（GG）2Cl2（solid） has been determined to be -（1 674.66±2.02） kJ · mol^-1 at 298.15 K.     

The impact of HS radicals on the measured rate constant of H<Subscript>2</Subscript>S with OH radicals

The rate constant for the reaction of OH radicals and hydrogen sulfide (H₂S) was studied in different bath gases (including N₂, air, O₂ and He) by using relative technique at 298 K. The small difference of the measured rate constants between N₂ and those with the presence of O₂ suggested possible influence of HS self reaction. Further experiments with NO_x presence for scavenging HS demonstrated this assumption. The rate constant of (5.48±0.12) ×10^–12 cm³ molecule^–1 s^–1 obtained with 4.09 ×10^–4 mol m₃ NO presence may be accurate for estimating the atmospheric lifetime of H2S. The results provided circumstantial evidence that the rapid reaction of HS with N₂O is suspected.     

Studies of several systems with air electrode electro-synthesizing H<Subscript>2</Subscript>O<Subscript>2</Subscript> on the spot for degrading aniline in aqueous

A gas diffusion electrode (air electrode) with a high current efficiency of electro-synthesizing H₂O₂ using O₂ in air was prepared. The several systems with air electrode as cathode of electro-synthesizing H₂O₂ on the reaction spot for degrading aniline in aqueous—electro-Fenton system, photo-excitation electro-H₂O₂ system and photo-electro-Fenton system, were developed. The rates of decomposition of H₂O₂ and mineralization of aniline were experimentally measured respectively under different conditions, and the results indicated there has an excellent parallel relation between decomposition rate of H₂O₂ and mineralization rate of aniline. Especially, photo-electro-Fenton system, where H₂O₂ is decomposed the fastest, is the best system of oxidizing and degrading organic toxicants. Compared photo-electro-Fenton system with photo-Fenton system, important role is revealed in the interface of air electrode. In this paper, the mineralization mechanism of aniline in the photo-electro-Fenton system was also discussed. Foundation item: Supported by the National Natural Science Foundation of China (200710026) and Foundation of Environmental Sciences Academy of Jiangsu Province. Biography: Cao xiao-yu (1979-), male, Master candidate, research direction: Electrochemistry     

He-H2 mixture and Er3NiHx packing for the refrigeration enhancement of pulse tube refrigerator

The computation with the theory of modified Brayton Cycle indicates that higher cooling power and coefficient of performance for a pulse tube refrigerator can be achieved with He-H2 mixture as working gas than those with pure He in the temperature region of 30 K. In addition, it is found that Er3Ni, a regenerative material, is able to absorb H2 and produces Er3NiHx. The computation presents that the regenerative performance of Er3NiHx is better than that of Er3Ni due to its higher volume specific heat. Experimental results show that the pulse tube refrigeration performance in 30 K temperature region is enhanced greatly with He-H2 mixture and Er3NiHx packing.     

Effect of CO<Subscript>2</Subscript> and H<Subscript>2</Subscript>O on gasification dissolution and deep reaction of coke

To more comprehensively analyze the effect of CO₂ and H₂O on the gasification dissolution reaction and deep reaction of coke, the reactions of coke with CO₂ and H₂O using high temperature gas-solid reaction apparatus over the range of 950-1250℃ were studied, and the thermodynamic and kinetic analyses were also performed. The results show that the average reaction rate of coke with H₂O is about 1.3-6.5 times that with CO₂ in the experimental temperature range. At the same temperature, the endothermic effect of coke with H₂O is less than that with CO₂. As the pressure increases, the gasification dissolution reaction of coke shifts to the high-temperature zone. The use of hydrogen-rich fuels is conducive to decreasing the energy consumed inside the blast furnace, and a corresponding high-pressure operation will help to suppress the gasification dissolution reaction of coke and reduce its deterioration. The interfacial chemical reaction is the main rate-limiting step over the experimental temperature range. The activation energies of the reaction of coke with CO₂ and H₂O are 169.23 kJ·mol-1 and 87.13 kJ·mol-1, respectively. Additionally, water vapor is more likely to diffuse into the coke interior at a lower temperature and thus aggravates the deterioration of coke in the middle upper part of blast furnace.     

Kinetic study on the reaction between CO2-CO and wustite using the isotope exchange method

To investigate the reaction between CO₂-CO and wustite using the isotope exchange method at 1073, 1173, 1273, and 1373 K, the experiment apparatus was designed to simulate the fluidized bed. The chemical rate constant was estimated by considering the effect of gas phase mass transfer on the reaction. It is found that the chemical rate constant is inversely decreased with the increase in the ratio of CO₂/CO by volume. The activation energy of reaction is in a linear relationship with the ratio of CO₂/CO by volume, and the average activation energy is 155.37 kJ/mol.     

Reduction of 1-3 mm iron ore by H2 in a fluidized bed

The reduction of 1-3 mm fine powder of iron ore by H₂ was conducted in a lab-fabricated kg class high temperature fluidized bed. The results show that the differential pressure in the fluidized bed, which has small fluctuation with time, increases with the increase of gas flowing velocity. The utilization ratio of gas decreases when the reaction lasts longer time indicating that the reaction is faster at the beginning of reduction and becomes slower in the latter process. The higher the reaction temperature is, the higher the utilization ratio of gas is, but the difference of utilization ratio among the different temperatures becomes smaller with time. The utilization ratio of gas and the metallization ratio can reach 9% and 84% respectively at 750℃ for 20 min, which shows the reduction reaction by H₂ is very fast. The increase of metallization ratio with gas velocity performs quite good linearity, which shows that a higher velocity of reducing gas can be used to improve the productivity of the reactor when H₂ is used as reducing gas. With the increase of charge height, the metallization ratio decreases, but the utilization ratio of gas increases. The reaction temperature can be reduced to 700-750℃ from 800-850℃ when H₂ is used as reducing gas.     

Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO<Subscript>2</Subscript> thin films

In-situ pure TiO₂ and Fe-doped TiO₂ thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO₂ thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO₂ thin films by adding precursor K₄(FeCN)₆·3H₂O into the Na₃PO₄ electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K₄(FeCN)₆·3H₂O increasing, eventually affecting the ethanol sensing performances of TiO₂ thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe³⁺ substituting for Ti⁴⁺.     

Analysis of active sites for N2 and H^＋ reduction on FeMo-cofactor of nitrogenase

Dinitrogen (N2) and proton (H ),which act as physiological substrates of nitrogenase,are reduced on FeMo-co of the MoFe protein. However,researchers have different opinions about their exact reduction sites. Nitrogenases were purified from the wild type (WT) and five mutants of Azotobacter vinelandii (Av),including Qα191K,Hα195Q,nifV-,Qα191K/nifV- and Hα195Q/nifV-; and the activities of these en-zymes for N2 and H reduction were analyzed. Our results suggest that the Fe2 and Fe6,atoms closed to the central sulfur atom (S2B) within FeMo-co,are sites for N2 binding and reduction and the Mo atom of FeMo-co is the site for H reduction. Combining these data with further bioinformatical analysis,we propose that two parallel electron channels may exist between the 8Fe7S cluster and FeMo-co.     

Cathodic behavior of molten CaCl<Subscript>2</Subscript>-CaO and CaCl<Subscript>2</Subscript>-NaCl-CaO

The cathodic behavior of molten CaCl₂, CaCl₂-CaO and equimolar CaCl₂-NaCl-CaO was studied by cyclic voltammograms and constant potential polarization at temperatures of 1123 to 1173 K on molybdenum and titanium electrodes. The diffusion coefficient of Ca²⁺ (CaO) in molten CaCl₂-CaO was calculated from the linear relationship between the square root of scan rate and the peak current density. The deposition potentials and the potential temperature coefficient of CaO in molten CaCl₂-0.5mol%CaO and CaCl₂-NaCl-0.5mol%CaO were also obtained from their cyclic voltammograms. The result shows that CaO is more easily reduced than CaCl₂. The addition of NaCl in molten CaCl₂-CaO induces the underpotential electrodeposition of CaO.     

Giant magneto-optical faraday effect of nanometer Fe-In<Subscript>2</Subscript>O<Subscript>3</Subscript> granular films

The giant magneto-optical Faraday effect of nanometer ferromagnetic metal-semiconductor matrix Fe-ln2O3 granular films prepared by the radio frequency sputtering are studied. The result shows that the Faraday rotation angle θF value of the granular film samples with Fe volume fraction x = 35% is of the order of 10^5（°）/cm at room temperature. Temperature dependence of the Faraday rotation angle θF of Fe0.35（In2O3）0.65 granular films shows that θF value below 10 K increases rapidly with the decrease of the temperature, and when T= 4.2 K, θF value is 106（°）/cm. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that when the temperature decreases to a critical point Tp = 10 K, the transformation of state from ferro-agnetic to spin-glass-like occurs in Fe0.35（In2O3）0.65 granular films. The remarkable increase of the Faraday rotation angle θF value of Fe0.35（In2O3）0.65 granular films below 10 K seems to arise from the sp-d exchange interaction of the granular film samples in the spin-glass-like state.     

Synthesis and Magnetic Properties of Spin-Liquid Tb2Ti2O7

Polycrystalline samples of a novel spin-liquid compound Tb2Ti2O7 were prepared by a standard solid-state reaction. X-ray diffraction at room temperature confirms that the synthesized compound of Tb2Ti2O7 is single phase with cubic unit cell constant a0 of 1.015 44 nm. Magnetic susceptibility measurements in the temperature range between 100 and 300 K give an effective moment of 9.44 μB and Curie-Weiss temperature of 12.68 K, respectively, indicating the dominance of antiferromagnetic interactions. However, below 50 K, the magnetic behavior of Tb2Ti2O7 deviates from Curie-Weiss law, whose origin remains suspicion.     

生物质燃料与煤混燃时NO_x/N_2O排放的研究

为寻找一种能够有效抑制流化床中NOx和N2O排放的途径．在一个实验室规模的小型鼓泡流化床上进行了生物质燃料（木屑）与煤混燃的研究．结果表明：木屑与煤混燃可以有效地降低NOx和N2O的排放,并且还发现,对NOx和N2O的削减能力与混合比例有关．掺入木屑的比例越大,削减的程度越强,但随温度的升高．削减程度有所下降．对木屑与煤混燃能降低NOx／N2O排放的原因进行了讨论．     

Magnetic properties of perpendicularly orientated L1<Subscript>0</Subscript> FePt nanoparticles

L10 FePt films were deposited on MgO (001) substrates heated to 700°C by magnetron sputtering.Assisted by the misfit of lattice between film and substrate,strong (001) texture was formed.The film at nominal thickness t N=5 nm was composed of nanoparticles with a size of～70 nm,and showed a high coercivity of～105 kOe at 4.2 K.At t N=～50 nm,as the film changed from discontinuous to continuous,the coercivity dropped about one order of magnitude.Micromagnetic simulation implies that the magnetization reversal is...     

Hydrogen storage properties of MgH<Subscript>2</Subscript> co-catalyzed by LaH<Subscript>3</Subscript> and NbH

To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH₂ + 10wt%LaH₃ + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H₂ within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH₃ and NbH upon dehydriding of MgH₂. By contrast, pure MgH₂, an MgH₂ + 20wt%LaH₃ composite, and an MgH₂ + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H₂, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH₂ + 10wt%LaH₃ + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH₂. The introduction of LaH₃ and NbH was beneficial to the hydrogen storage performance of MgH₂.     

Synthesis of LiCo<Subscript>0.3</Subscript>Ni<Subscript>0.7</Subscript>O<Subscript>2</Subscript> as cathode materials for lithium ion batteries by citric acid-assisted sol-gel method

The synthesis process of LiCo0.3Ni0.7O2 was investigated by FT-IR, mass spectroscopy, elemental analysis, SEM, BET, TG/DTA and XRD in this paper. The results revealed that lithium and transition metal ions were trapped homogeneously on an atomic scale throughout the precursor. Li2CO3, NiO and CoO are the intermediate products obtained after decomposition of the precursor and Li2CO3 undergoes direct reactions with NiO and CoO to form LiCo0.3Ni0.7O2. Moreover, the kinetics of formation of LiCo0.3Ni0.7O2 by dtrate sol-gel method is faster than the case of the conventional solid-state reaction between lithium carbonate and corresponding reactants. The single phase of LiCo0.3Ni0.7O2 was synthesized at temperature as low as 550℃. The discharge capacity of LiCo0.3Ni0.7O2 increases from 127 to 185 mAh/g as the caldnation temperature increasing from 550 to 750℃. After 100 cycles, the discharge capacity of the sample calcined at 750℃ is 155 mAh/g. The electrochemical study shows that the LiCo0.3Ni0.7O2 has high discharge capacity and good cycling behavior for lithium ion batteries.     

3,4-dichlorotoluene ammoxidation to 3,4-dichlorobenzonitrile over VPO/SiO<Subscript>2</Subscript> catalyst

Ammoxidation of 3,4-dichlorotoluene (DCT) to prepare 3,4-dichlorobenzonitrile (DCBN) over silica supported vanadium phosphorus oxide catalysts has been studied. On the VPO/SiO₂ catalyst, the influence of the reaction temperature, the molar ratio of air/DCT, the molar ratio of NH₃/DCT in the feed gas and the space velocity (v ₁) on the conversion, yield and selectivity was observed. The most appropriate reaction condition is: reactionT=673 K,n(DCT):n(NH₃):n(air)=1:7:30 andv ₁=250 h⁻¹. At this optimum reaction condition, the conversion of DCT is 97.8%; the molar yield of DCBN is 67.4%. It was found that the addition of element phosphorus can improve the yield of DCBN compared with VO/SiO₂ catalyst. Foundation item: Supported by Youth Chen-Guang Project of the Committee of Science and Technology of Wuhan (20015005042) Biography: Huang Chi(1972-), male, Ph D, Lecture, research direction: ammoxidation.