镁铁和镁铁铝催化剂氢还原过程的研究

以水滑石为前体 ,制备了镁铁和镁铁铝复合氧化物催化剂 ,运用原位穆斯堡尔谱研究了催化剂在H2 气氛中的还原行为。结果表明 :由于Mg、Al的加入和固溶体的形成 ,相对地稳定了FeO物相 ,阻碍了H2 对铁离子的还原 ,使得Fe2 进一步还原为金属Fe0 的能力减弱 ;在还原过程中催化剂首先生成含Fe2 的固溶体FeO MgO或FeO MgO Al2O3,然后再完全还原成金属Fe0。     

Reduction of TiO2 with Hydrogen Plasma

Experiments were performed in a thermal plasma furnace to examine the reduction of TiO₂ by hydrogen plasma. The plasma gas composition was 50% hydrogen–50% argon, the plasma torch input power was 13 kW, the TiO₂ initial mass was 10 g and the processing time was varied from 10 to 90 min. The reaction product contained between 67% and 73% titanium by mass for all tests. This level of reduction was consistent with chemical equilibrium modeling. There was no detectable enhancement of reduction due to the presence of atomic hydrogen. The Ti-O microstructures produced were characterized using quantitative SEM analysis. The microstructures showed a number of similarities with structures described by previous researchers.     

Reduction Mechanism of Transition Metal Oxide Particles in Thermally Induced Nanobubbles during Pulsed Laser Melting in Ethanol

Pulsed laser melting in liquid (PLML) is a technique to fabricate spherical submicrometer particles (SMPs) wherein nanosecond pulsed laser (several tens to several hundreds of mJ pulse⁻¹ cm⁻²) irradiates raw particles dispersed in liquid. Raw particles are transiently heated above the melting point to form spherical particles, which enables pulsed heating of surrounding liquid to form thermally induced bubbles by liquid vaporization. These transient bubbles play an important role as a thermal barrier to rapidly heat the particle. Reduced SMPs are generated from raw metal-oxide nanoparticles by PLML process in ethanol. This reduction cannot be explained by high-temperature thermal decomposition, but by mediation of molecules decomposed from ethanol. Computational simulations of ethanol decomposition by pulsed heating for 100 ns at the temperature 1000–4000 K revealed that ethylene is generated as the main product. Gibbs free energies of oxide reduction reactions mediated by ethylene greatly decreased compared to those without ethylene mediation. This explanation can be applied to reductive SMP formation from various transition metal oxides by PLML.     

氢还原重量法测定三氯化钌产品中钌含量的研究与应用

建立了氢还原重量法测定三氯化钌产品大样中钌含量的新方法,研究并优化了测定条件,结合AAS法、ICP-AES法和氯化铵纯度考察了杂质元素对了分析结果的误差影响。结果表明：含钌量0.3 g～0.6 g的三氯化钌与5 g～7 g氯化铵能完全形成(NH4)2RuCl6配合物,于约100 ℃烘干水分、350 ℃分解铵盐、750 ℃氢还原为海绵钌和105 ℃干燥水气的条件下,测定3.94%、5.88%、7.32%、9.47%、10.84%和12.93%的钌含量,极差、标准偏差(S)、相对标准偏差(RSD,n=22)和重复性限(r)分别为±0.01%、0.0030%～0.0050%、0.0369%～0.0761%和0.008%～0.014%。样品加标准回收率99.96%～99.98%。本法结果准确、精密,且与YS/T 562-2009标准分析方法的吻合。     

氢还原重量法测定氯化钯产品中的钯含量

建立了氢还原重量法测定氯化钯产品钯含量的新方法,系统研究了测定条件,结合ICP-AES法考察了杂质元素对了分析结果的误差影响。结果表明：含钯量约3 g的氯化钯于750 ℃氢还原为海绵钯和105 ℃干燥水气的条件下,测定59.78%、59.98%和60.03%的钯含量,极差、标准偏差(S)、相对标准偏差(RSD,n=22)和重复性限(r)分别为±0.01%、0.0047%～0.0050%、0.0079%～0.0083%和0.009%～0.014%。样品加标准回收率99.98%。本法结果准确、精密,且与GB/T 15072.4-2008标准分析方法的吻合。     

氢还原重量法测定氯化钯产品中的钯

系统研究了氢还原重量法测定氯化钯产品中钯含量的测定条件,考察了杂质元素对钯分析结果的误差影响。结果表明:于选定条件下,测定59.78%~60.03%含量的钯,极差、标准偏差(SD)、相对标准偏差(RSD,n=22)和重复性限(r)分别为±0.01%,0.0047%~0.0050%,0.0079%~0.0083%和0.009%~0.014%,样品加标回收率达到99.98%,钯分析结果准确、可靠、精密度高。     

Pd-Catalyzed Reduction of Aldehydes to Alcohols Using Formic Acid as the Hydrogen Donor

Facile and selective reduction of aromatic aldehydes as well as aliphatic aldehydes to alcohols was achieved using formic acid as the hydrogen donor in the presence of a catalytic amount of Pd(OAc)₂ and Cy₃P. It was found that both hydrogen atoms in the formic acid molecule can serve as the hydride source.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

富氧条件下钯催化剂上氢气还原氧化氮微观反应动力学研究

 通过单位键指标-二次指数势(UBI-QEP)方法估算反应的表观活化能进行反应机理的随机模拟,并结合实验结果研究了富氧条件下Pd基催化剂上H2还原NO的反应. 结果表明,反应的控制步骤是H2吸附活化产生H*(*表示活性位,H*表示吸附的H原子)的过程,当反应温度低于270 ℃时, H*来自基元反应O*+H*2OH*+H*,反应温度上升到310 ℃时, H*2+*2H*成为H*的主要来源. NO以(NO)*2的形式吸附在Pd催化剂表面,还原产物N2O来自两条途径,分别是(NO)*2的分解以及相邻的两个NO*分子之间的结合; N2主要来自N2O*的分解以及相邻的N*和NO*分子的结合; NH3则由中间产物HNO*经过逐步加氢生成. 富氧条件下, NO和O2之间存在吸附和反应的竞争,低温下NO在Pd表面的吸附几率远大于O2, 此时H2优先还原NO. 反应温度的升高导致各物种的吸附能力下降,其中NO的降低最明显,因此高温下催化剂表面的主要吸附物种由NO变为O2, 此时H2优先与O2反应. 在150～310 ℃范围内,实验结果和模拟数据非常吻合.     

氢还原重量法测定三氯化钌产品中钌的含量

建立了氢还原重量法测定三氯化钌产品大样中钌含量的新方法,研究并优化了测定条件,结合原子吸收光谱法(AAS)、电感耦合等离子体原子发射光谱法(ICP-AES)和氯化铵纯度考察了杂质元素对了分析结果的误差影响。结果表明,钌含量为0.3~0.6g的三氯化钌与5~7g氯化铵能完全形成(NH4)2RuCl6配合物,于约100℃烘干水分、350℃分解铵盐、750℃氢还原为海绵钌和105℃干燥水气的条件下,测定3.94%,5.88%,7.32%,9.47%,10.84%和12.93%含量的钌,极差、标准偏差(S)、相对标准偏差(RSD,n=22)和重复性限(r)分别为±0.01%,0.0030%~0.0050%,0.0369%~0.0761%和0.008%~0.014%。样品加标回收率99.96%~99.98%。方法的结果准确,精密度好,且与YS/T562—2009标准分析方法的吻合。     

Methane Conversion to Hydrogen and Higher Hydrocarbons by Double Pulsed Glow Discharge

Pulsed atmospheric glow plasma, sustained by corona discharge, was utilized to convert methane. Analysis by gas chromatography showed that hydrogen and C₂-products are the main constituents of outlet mixture while C₂₊-products with small concentrations were also detected. The chemical energy efficiency turned out to be about 9% for the best result obtained by this type of reactor. It has been shown that more improvement of energy efficiency is possible by increasing the pulse repetition rate.     

氢还原重量法测定亚硝酰硝酸钌溶液中的钌含量

采用盐酸前处理样品,干燥后通氢还原纯化,建立了氢还原重量法测定亚硝酰硝酸钌溶液中的钌含量的方法.结果表明,在称样量为4.0 g、盐酸加入量3 mL,程序升温750℃,保温90 min条件下,测定结果最好.测定钌含量为5.50％、10.89％ 的两种样品,两种样品钌含量分析结果的极差分别为0.11％、0.16％,相对标准...     

基于热解ZIF-8的氮掺杂碳电化学氧还原合成过氧化氢催化剂

氧气的两电子还原反应(2e-ORR)是绿色、安全的H₂O₂合成路线. 本工作以Zn²⁺和2-甲基咪唑合成的沸石型咪唑酸框架-8 (ZIF-8)为前驱体, 通过高温热解炭化, 利用ZIF-8中的锌在高温下的可挥发性, 制备了非金属氮掺杂石墨化多孔碳材料(p-ZIF), 系统考察了ZIF-8热解炭化温度(900、950和1000 ℃)对催化剂结构和2e-ORR催化性能的影响. p-ZIF不仅保留了ZIF-8规整的菱形十二面体形貌, 而且氮含量高, 拥有高的比表面积和多级孔结构. 在酸性条件下的2e-ORR反应中, 三个p-ZIF催化剂均显示了较低的过电位和较低的Tafel斜率, 而且稳定性良好. 其中在H₂O₂选择性最高的p-ZIF-950催化剂上, 过电位为86 mV, H₂O₂选择性最高可达89.2%. 在6 h恒电位反应中, p-ZIF-950催化剂能够以87 mmol•g_cat^-1•h^-1的恒定速率产生H₂O₂. 根据多种表征结果, 推测p-ZIF催化剂的孔径尺寸和石墨N含量是影响其2e-ORR催化性能的主要因素.     

富氧条件下氢气选择催化还原氮氧化物研究的进展

 富氧条件下, 氢气选择催化还原 (H2-SCR) 是消除氮氧化物的有效方法. 本文介绍了 H2-SCR 反应特点及其研究现状, 重点总结和评述了应用于 H2-SCR 反应的氧化物和分子筛负载的 Pt 或 Pd 催化剂, 以及 H2-SCR 反应机理, 并展望了今后 H2-SCR 研究的方向.     

炭载微过氧化物酶-11电极对O2和H2O2还原的电催化性能

氧还原;生物燃料电池;炭载微过氧化物酶-11电极对O2和H2O2还原的电催化性能     

Direct Reduction of Mechanically Activated Galena and Sphalerite with Hydrogen

In this paper the reduction of lead and zinc sulphide by hydrogen is described. It has been found that the rate of formation of elemental lead or zinc is favourably affected by mechanical activation of PbS and ZnS produced by intensive grinding. This effect was observed in the region 678–1048 K for galena and in the region 851–1023 K for sphalerite. It has appeared that disordering in the structure of both minerals results in the decrease in experimental activation energy. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reduction of Oxygen Bound with Hemoglobin by Electrolytic Method Using Hydrogen Gas in Phosphate-buff ered Solution

Hemoglobin( Hb) is widely used as an artificial red cell[1 ] to realize the function ofoxygen-delivery,one Hb molecule can bind up with four oxygen molecules through theFe2 +in Hb molecule to form oxygenated Hb( oxy Hb) .Heat treatment at60℃ is animportant step in the purification of Hb for the removal of stroma or unnecessaryproteins and the inactivation of viruses[2 ] .However,oxy Hb is quickly oxidized tomethemoglobin( met Hb,a status that Fe2 +is oxidized to Fe3+) ,and even furtheroxi…     

TiO_2-Supported Binary Metal Oxide Catalysts for Low-temperature Selective Catalytic Reduction of NO_x with NH_3

Binary metal oxide（MnOx-A/TiO2）catalysts were prepared by adding the second metal to manganese oxides supported on titanium dioxide（TiO2）,where,A indicates Fe2O3,WO3,MoO3,and Cr2O3.Their catalytic activity,N2 selectivity,and SO2 poisonous tolerance were investigated.The catalytic performance at low temperatures decreased in the following order：Mn-W/TiO2〉Mn-Fe/TiO2〉Mn-Cr/TiO2〉Mn-Mo/TiO2,whereas the N2 selectivity decreased in the order：Mn-Fe/TiO2〉Mn-W/TiO2〉Mn-Mo/TiO2〉Mn-Cr/TiO2.In the presence of 0.01%SO2 and 6%H2O,the NOx conversions in the presence of Mn-W/TiO2,Mn-Fe/TiO2,or Mn-Mo/TiO2 maintain 98.5%,95.8%and 94.2%, respectively,after 8 h at 120°C at GHSV 12600 h？ 1 .As effective promoters,WO3 and Fe2O3 can increase N2 selectivity and the resistance to SO2 of MnOx/TiO2 significantly.The Fourier transform infrared（FTIR）spectra of NH3 over WO3 show the presence of Lewis acid sites.The results suggest that WO3 is the best promoter of MnOx/TiO2,and Mn-W/TiO2 is one of the most active catalysts for the low temperature selective catalytic reduction of NO with NH3.     

氧化石墨烯还原程度的控制

石墨烯作为只有一个原子层厚度的二维碳材料,具有优异的柔韧性、导电性等一系列优点,从而广泛应用于许多领域。氧化还原法是最常用且最有前景的石墨烯制备方法,然而在氧化过程中,大量含氧官能团的生成破坏了石墨烯的共轭结构,因此需要去除含氧官能团得到还原氧化石墨烯,以修复结构、恢复其高导电性。而许多领域运用石墨烯时,既需要其具有高导电性,又有一定量的含氧官能团或缺陷。因此,控制氧化石墨烯的还原程度尤为必要,既要充分利用含氧官能团的优点并保证石墨烯的导电性,又要根据石墨烯的应用需求,得到官能团种类及含量可控的还原氧化石墨烯,从而实现石墨烯材料的多元化应用。本文综述了近年来化学还原法、热还原（包括热退火和水/溶剂热还原）法和电化学还原法控制氧化石墨烯还原程度的研究现状,总结了几种方法的还原机制和效果以及部分还原氧化石墨烯的应用并进行了展望。     

Atropisomeric Hydrogen Bonding Control for CO2 Binding and Enhancement of Electrocatalytic Reduction at Iron Porphyrins

The manipulation of the second coordination sphere for improving the electrocatalytic CO₂ reduction has led to breakthroughs with hydrogen bonding, local proton source, or electrostatic effects. We have developed two atropisomers of an iron porphyrin complex with two urea functions acting as multiple hydrogen-bonding tweezers to lock the metal-bound CO₂ in a similar fashion found in the carbon monoxide dehydrogenase (CODH) enzyme. The αα topological isomer with the two urea groups on the same side of the porphyrin provides a stronger binding affinity to tether the incoming CO₂ in comparison to the αβ disposition. However, the electrocatalytic activity of the αβ atropisomer outperforms its congener with one of the highest reported turnover frequencies at low overpotential. The strong H/D kinetic isotope effect (KIE) observed for the αα system indicates the existence of a tight water hydrogen-bonding network for proton delivery which is disrupted by addition of an acid source. The small H/D KIE for the αβ isomer and the enhanced electrocatalytic performance on addition of stronger acid indicate the free access of protons to the bound CO₂ on the opposite side of the urea arm.