Enhancement of catalytic activity by homo-dispersing S_2O_8^(2–)-Fe_2O_3 nanoparticles on SBA-15 through ultrasonic adsorption

Mesoporous superacids S2O82–-Fe2O3/SBA-15(SFS)with active nanoparticles are prepared by ultrasonic adsorption method.This method is adopted to ensure a homo-dispersed nanoparticle active phase,large specific surface area and many acidic sites.Compared with bulk S2O82–-Fe2O3,Br?nsted acid catalysts and other reported catalysts,SFS with an Fe2O3 loading of 30%(SFS-30)exhibits an outstanding activity in the probe reaction of alcoholysis of styrene oxide by methanol with 100%yield.Moreover,SFS-30 also shows a more excellent catalytic performance than bulk S2O82–-Fe2O3 towards the alcoholysis of other ROHs(R=C2H5-C4H9).Lewis and Bronsted acid sites on the SFS-30 surfaces are confirmed by pyridine adsorbed infrared spectra.The highly efficient catalytic activity of SFS-30 may be attributed to the synergistic effect from the nano-effect of S2O82–-Fe2O3 nanoparticles and the mesostructure of SBA-15.Finally,SFS-30 shows a good catalytic reusability,providing an 84.1%yield after seven catalytic cycles.

Preparation,characterization and catalytic behavior of hierachically porous CuO/α-Fe_2O_3/SiO_2 composite material for CO and o-DCB oxidation

Hierachically porous （HP） CuO/α-Fe2O3/SiO2 composite material was fabricated by sol-gel method and multi-hydrothermal processes using HP-SiO2 as support.The resulting material was characterized by N2 adsorption-desorption,X-ray diffraction and scanning electron microscopy.The as-prepared CuO/Fe2O3/HP-SiO2 sample,with α-Fe2O3 and CuO nanocrystals,possessed a co-continuous skeleton,through-macroporous and mesoporous structure.Its catalytic behavior for CO and o-DCB oxidation was investigated.The result showed that CuO/Fe2O3/HP-SiO2 catalyst exhibited high catalytic activity for both CO and o-DCB oxidation,indicating its potential application in combined abatement of CO and chlorinated volatile organic compounds.

Catalytic oxidation of gas-phase elemental mercury by nano-Fe_2 O_3

Heterogeneous oxidation of gas-phase Hg 0 by nano-Fe 2 O 3 was investigated on a fixed bed reactor, and the effects of oxygen concentration, bed temperature, water vapour concentration and particle size have been discussed. The results showed that Hg 0 could be oxidized by active oxygen atom on the surface of nano-Fe 2 O 3 as well as lattice oxygen in nano-Fe 2 O 3 . Among the factors that affect Hg 0 oxidation by nano-Fe 2 O 3 , bed temperature plays an important role. More than 40% of total mercury was oxidized at 300°C, however, the test temperature at 400°C could cause sintering of nano-catalyst, which led to a lower efficiency of Hg 0 oxidation. The increase of oxygen concentration could promote mercury oxidation and led to higher Hg 0 oxidation efficiency. No obvious mercury oxidation was detected in the pure N 2 atmosphere, which indicates that oxygen is required in the gas stream for mercury oxidation. The presence of water vapour showed different effects on mercury oxidation depending on its concentration. The lower content of water vapour could promote mercury oxidation, while the higher content of water vapour inhibits mercury oxidation.

Plasma Post Oxidation of Plasma Nitrocarburized SKD 61 Steel

Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of SKD 61 steel.Plasma nitrocarburizing was conducted for 12 h at 540℃in the nitrogen, hydrogen and methane atmosphere to produce theε-Fe-（2-3）（N,C） phase.The compound layer produced by plasma nitrocarburising was predominantly composed ofε-phase,with a small proportion ofγ′-Fe-4 （N,C） phase. The thickness of the compound layer and the diffusion layer are about 10μm and about 200μm,respectively. Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at constant temperature of 500℃for 1 h.The very thin magnetite （Fe-3O-4） layer of 1-2μm in thickness on top of the compound layer was obtained.Anodic polarization test revealed that plasma nitrocarburizing process contributed a significant improvement of corrosion resistance of SKD 61 steel.However,the corrosion characteristics of the nitrocarburized compound layer was deteriorated by oxidation treatment.

Plasma post oxidation of nitrocarburized AISI 4140 steel

Plasma nitrocarburizing and plasma oxidizing treatments were performed to improve the wear and corrosion resistance of AISI 4140 steel. Plasma nitrocarburizing was conducted for 3 h at 570 ℃ in the nitrogen, hydrogen and methane atmosphere to produce the ε-Fe2-3(N,C) phase. It was found that the compound layer produced by plasma nitrocarburising was predominantly composed of ε-phase, with a small proportion of γ′-Fe4(N,C) phase. The thickness of the compound layer was about 10 μm and the diffusion layer was about 300 μm in thickness, respectively. Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at a constant temperature of 500 ℃ for 1 h. The very thin magnetite (Fe3O4) layer 1-2 μm in thickness on top of the compound layer was obtained by plasma post oxidation. It was confirmed that the corrosion characteristics of the nitrocarburized compound layer can be further improved by the application of the superficial magnetite layer.

Effects of B_2O_3 and CaF_2 on Melting Temperatures of CaO-SiO_2-Fe_2O_3 System Fluxes

Fluorite is widely employed as fluxing agent in metallurgy flux , which inevitably leads to serious fluorine pollution.B2O3 is employed as fluxing agent of CaO-SiO2-Fe2O3steelmaking fluxes to substitute for CaF2.The effects of B2O3 and CaF2 on the melting properties of this system were investigated.The melting temperatures of fluxes including softening temperature （Ts）, hemispherical temperature （Th）, and flow temperature （Tf） were measured using the hemisphere method.The results indicate that the fluxing effect of B2O3is more significant than that of CaF2 .When the addition amount of B2O3 （mass percent） exceeds 6% , the melting temperatures of fluxes including Ts , Th and Tf are decreased lower than 1 300℃.The basicity of fluxes has a significant effect on the melting temperature , and the melting temperatures of the fluxes increase with the increase of fluxes basicity.However , when B2O3 is used as fluxing agent , the melting temperature changes little with the basicity increasing from 2.5 to 5.0. These characteristics are suitable for steelmaking process.Moreover , Fe2O3 has an important fluxing effect on this CaO-based steelmaking fluxes.This indicates that the fluxes system is suitable for steelmaking process.

α-Fe2O3 immobilized benzimidazolium tribromide as novel magnetically retrievable catalyst for one-pot synthesis of highly functionalized piperidines

Nanostructured ot-Fe2O3 were prepared by precipitation followed by calcination method. Cetyltrimethylammonium bromide （CRAB） was used as surfactant. The nano α-Fe2O3 was then silanized with （3-chloropropyl）-triethoxysilane （CPTES） by room temperature mixing ofα-Fe2O3 and CPTES to produce silane coated ct-Fe2O3 （CIPr-Si@Fe2O3）. As-synthesized CIPr-Si@Fe2O3 was functionalized via covalent grafting of benzimidazole to produce 3-（1-benzimidazole）Pr-Si@Fe2O3. This was further reacted with bromine to afford α-Fe2O3 immobilized benzimidazolium tribromide （α-Fe2O3-BIM tribromide）. This ionic liquid （IL） α-Fe2O3 BIM tribromide was characterized by FT-IR, XRD, TEM, SEM, TGA, VSM, EDX and BET analysis. The as-synthesized IL tribromide was used as catalyst for one-pot synthesis of highly substituted piperidines. The method is greener in terms of solvent selection, recovery of the catalyst and efficiency.

微波-超声波协同制备纳米球形氧化镝

在微波-超声波协同作用下,采用尿素为沉淀剂,与一定浓度的DyCl_(3)溶液充分反应之后,得到Dy_(2)O_(3)前驱体(Dy(OH)CO_(3)·H_(2)O),煅烧后得到纳米球形Dy_(2)O_(3)。探究了Dy^(3+)浓度、尿素浓度以及超声波功率对Dy_(2)O_(3)前驱体微观形貌的影响。采用扫描电子显微镜、同步热分析仪、X射线衍射仪、傅里叶红外光谱仪对Dy2O3前驱体煅烧前后的微观形貌、微观结构进行了表征,对煅烧分解机理进行了分析。结果表明:当控制Dy^(3+)浓度0.045 mol/L,尿素浓度2.5 mol/L,微波功率500 W,超声功率800 W,超声波模式1∶2,反应时间1 h,反应温度90℃时,可以得到粒径均一、表面光滑、分散程度好且粒径约为220 nm的Dy(OH)CO_(3)·H_(2)O。在800℃的煅烧温度下该前驱体可完全分解,最终得到粒径约为200 nm的纳米球形Dy_(2)O_(3)。

一种新型球状纳米氧化铁的制备

以Fe(NO_(3))_(3)·9H_(2)O为原料、以尿素为沉淀剂,用热解前驱体法制备出直径为40~60 nm的球状纳米氧化铁。使用XRD、SEM和EDS等手段对其表征,研究了Fe^(3+)浓度、反应温度等因素对纳米氧化铁的粒径和形貌的影响、确定了球状纳米氧化铁的制备条件并分析了球状纳米氧化铁的形成机理。结果表明:随着Fe(NO_(3))_(3)·9H_(2)O溶液温度的提高纳米氧化铁的结晶度随之提高、粒径增大。Fe(NO_(3))_(3)·9H_(2)O的浓度对纳米氧化铁样品的粒度和形貌的影响不大。球状氧化铁纳米的形成机理是:铁源在水热条件下水解和结晶生成棕黄色絮状沉淀FeOOH,FeOOH在高温高压条件下溶解和再结晶生成了球状纳米氧化铁。