MoO3—Fe2O3 catalysts: Characterization and activity for isopropyl alcohol decomposition

The vapour-phase dehydration and dehydrogenation of isopropyl alcohol (IPA) have been carried out over pure MoO₃ and Fe₂O₃, produced by calcination of ammonium heptamolybdate and of iron (III) nitrate respectively, as well as MoO₃ mixed with 0·5 and 50 mol% Fe₂O₃, prepared from the same materials. All catalysts were calcined in air, in the temperature range 200–600°C for 5 h, and were characterized by thermal analysis (TG, DTA), XRD, IR and S_BET. Surface areas decreased with increasing calcination temperature, and the catalytic activity of the pure oxides MoO₃ and Fe₂O₃, as well as of MoO₃–0.5 mol % Fe₂O₃, increased with their S_BET. The activity of MoO₃–50 mol % Fe₂O₃, which was independent of its S_BET, could be attributed to the increased intensity of terminal Mo—O bonds as shown by IR spectra. The activation energies for the decomposition of IPA over catalysts calcined at 250 and 500°C are tabulated.     

Basic rules of NO oxidation by Fe2+/H2O2/AA directional decomposition system

Basic rules of NO oxidation by a Fe²⁺/H₂O₂/AA directional decomposition system were researched based on the technical background of flue gas NO_x removal. Effects of gas‐liquid interfacial area, main gas, and solution parameters on NO oxidation efficiency (η) were analyzed. The results showed that adequate contact area was the precondition for high η by a Fe²⁺/H₂O₂/AA system. η decreased with the increase in NO concentration, which illustrated that this method would be efficient in oxidizing NO at a low concentration. η tended to decrease linearly with the growth in gas flow, however, the NO oxidation rate (v) rose with the increase in NO concentration and gas flow. η increased with the initial concentrations of H₂O₂ and Fe²⁺, but the amplitude decreased. Controlling the initial concentrations of H₂O₂ and Fe²⁺ to achieve reasonable synergies between generation rate and consumption rate of ·OH could weaken the invalid consumption of reactants. η increased with the increase in temperature in the range 30–60 °C, but it nearly did not change with temperature after 60 °C. This oxidation technology and the traditional wet flue gas desulphurization technology exhibited temperature synergy. Under typical pH of wet desulphurization, η and H₂O₂ consumption rate did not change obviously.     

不同尺寸反应器内H2O2热分解氧化NO特性与氧化产物分析

采用实验方法研究了不同尺寸滴管炉反应器内H₂O₂热分解氧化NO特性。对比了不同H₂O₂蒸发条件对NO氧化率的影响规律。分析了气体温度、H₂O₂溶液浓度、H₂O₂：NO摩尔比、NO初始浓度及气体流量对NO氧化率的影响。检测了氧化产物并分析了产物的生成路径。结果表明：H₂O₂的快速蒸发是其热分解氧化NO的前提。减小H₂O₂液滴尺寸或液膜厚度可加速H₂O₂蒸发与分解,提高NO氧化率,扩宽NO氧化的温度范围。保证蒸发速率可削弱H₂O₂浓度对NO氧化率的影响。当H₂O₂：NO < 10时,NO氧化率随H₂O₂：NO的增加而增加;当H₂O₂：NO>10时,NO氧化率几乎不随H₂O₂：NO变化。H₂O₂热分解对于较高浓度的NO具有更高的氧化效率。H₂O₂热分解氧化NO的主要产物为NO₂。HO₂·直接将NO氧化为NO₂,·OH则先将NO转化为HONO,然后进一步氧化为NO₂。     

过氧化氢催化氧化苯甲醇制苯甲酸

以质量分数为 30 %的过氧化氢 (H2 O2 )为氧源 ,探讨了Na2 WO4·2H2 O催化氧化苯甲醇制苯甲酸反应中酸性添加物的影响 ,在大多数情况下 ,酸性越强 ,苯甲酸的收率越高。用NaHSO4·H2 O作酸性添加物 ,对反应条件的优化研究表明 ,氧化反应的最佳条件为n(苯甲醇 )∶n(Na2 WO4·2H2 O)∶n(NaHSO4·H2 O)∶n(H2 O2 ) =10 0∶1∶1∶30 0 ,回流 7h ,苯甲酸收率达 82 .7%。     

Fe2+/H2O2体系内各种自由基在氧化NO中的作用

Fe²⁺/H₂O₂体系可分解产生多种氧化性自由基, 主要包括O₂^-·、·OH和HO₂·。本文实验研究了O₂^-·、·OH及HO₂·在Fe²⁺/H₂O₂体系氧化NO气体过程中的作用。结果表明:在本实验条件下, O₂^-·对NO气体的氧化作用不明显;·OH及HO₂·是该体系氧化NO气体的主要活性物质, 其中·OH的氧化作用更大。加快自由基的生成速率可以增强Fe²⁺/H₂O₂体系对NO气体的氧化能力, 但O₂的生成速率同时加快。只有少量·OH及HO₂·参与NO的氧化, ·OH与HO₂·之间的快速反应是Fe²⁺/H₂O₂体系氧化NO过程中H₂O₂利用率低的主要原因。     

Fe2+/H2O2体系O2生成路径

掌握Fe²⁺/H₂O₂体系O₂的生成路径,可为避免H₂O₂无效分解,开发经济高效的Fe²⁺/H₂O₂体系利用技术指明方向。采用添加自由基捕获剂的方法,探究Fe²⁺/H₂O₂体系内各种自由基对O₂生成速率的影响,进而确定O₂的生成路径。结果表明:Fe²⁺/H₂O₂体系内不会产生大量O₂^-·,O₂^-·不是生成O₂的主要反应物质;O₂^-·被全部捕获后,体系中仍产生大量O₂^-·,但此时无O₂生成,证明生成O₂的反应由·OH和HO₂·两种自由基直接参与。分析认为反应·OH+HO₂·-H₂O+O₂是体系内O₂生成的主要路径。控制Fe²⁺/H₂O₂体系定向生成·OH,抑制HO₂·的产生,是提高Fe²⁺/H₂O₂体系中H₂O₂利用率的有效手段。     

光照及需氧条件下Al2O3-AlBrx催化醇的选择性氧化反应

以脱脂棉为模板制备了多孔管状结构的Al2O3材料,用不同浓度的氢溴酸对多孔管状结构的Al2O3材料进行化学剪裁,制备了活性量可控,比表面积可调,不同形貌的负载型催化剂Al2O3-AlBr x。采用电场发射扫描电镜(SEM)和X射线衍射仪(XRD)对催化剂进行了表征。结果表明,该催化剂较好地复制了棉纤维的宏观和微观结构,呈现出明显的生物形貌特征。在光照条件下以空气为氧化剂的醇的选择性氧化反应中,发现催化剂Al2O3-AlBr x-3可以高选择性地将醇氧化为相应的醛、酮或酸,并对反应机理进行了探讨。该催化剂循环使用3次仍保持较高的催化活性。     

锰掺杂CeO2-CoO的制备及其催化苯甲醇液相选择性氧化

以硝酸盐作前体,通过均匀共沉淀法制备了掺锰复合氧化物CeO2-MnO2-CoO,采用X-射线粉末衍射(XRD)对复合氧化物进行了表征,并研究了复合氧化物在苯甲醇液相氧化反应中的催化性能.结果表明,复合氧化物的组成、反应时间、溶剂种类和氧化剂用量等对苯甲醇转化率和苯甲醛选择性均有影响.采用叔丁基过氧化氢作氧化剂,正己烷为...     

抗坏血酸对Fe2+/H2O2体系氧化NO的促进作用

采用实验方法研究了低成本环境友好型添加剂抗坏血酸(AA)对Fe²⁺/H₂O₂体系氧化NO气体及其对体系内H₂O₂分解的影响,分析了AA对体系氧化NO能力及H₂O₂分解的影响机制。研究结果表明:AA通过加速Fe³⁺向Fe²⁺的转化而促进Fe²⁺/H₂O₂体系对NO的氧化。[AA]₀:[Fe²⁺]₀对体系氧化NO的能力及H₂O₂的分解具有重要影响。综合考虑NO氧化脱除量及H₂O₂消耗量,合理的[AA]₀:[Fe²⁺]₀为1/3~1/2。AA的分次添加方式可大幅度提升体系氧化NO气体的能力。研究结果可望为发展基于H₂O₂为氧化剂的烟气NO绿色氧化技术提供理论基础。     

单分散Co3O4@SiO2核壳催化剂的制备及N2O催化分解性能

N₂O是一种重要的温室气体,且对臭氧层有很大的破坏作用,而直接催化分解法是除去N₂O最经济有效的方法之一。针对目前报道较多的钴氧化物催化剂活性较差的问题,将包覆型Co₃O₄核壳材料引入N₂O直接催化分解反应,利用核壳结构的限域特性与壳层的多孔孔道使Co₃O₄分散性增加,粒径减小,金属载体相互作用与接触反应界面增强,从而提高了催化剂在N₂O直接催化分解反应中的低温活性。此外,还制备了一系列不同金属含量的Co₃O₄@SiO₂球形核壳催化剂来研究包覆结构对催化剂性能的影响,通过X射线荧光光谱（XRF）、透射电镜（TEM）、X射线衍射（XRD）、N₂物理吸附、H₂-程序升温还原（H₂-TPR）等表征,证实在保证稳定单分散核壳结构的前提下,活性Co₃O₄位点越多,催化剂反应活性越好。     

构建Bi2O2CO3/g-C3N4异质结光催化完全氧化苯甲醇至苯甲醛

在保证选择性的前提下高效光催化氧化苯甲醇为苯甲醛仍然是当下面临的一个巨大挑战。g-C₃N₄的价带位置适中,具有温和的氧化能力,已被开发用来光催化氧化苯甲醇以保证反应的选择性,但由于其电子空穴复合率高导致反应的转化率难以提升。由于Bi₂O₂CO₃的超薄片层结构不仅可以增加催化剂的比表面积形成更多的活性中心,同时可以形成局部电场,更有效地分离光生电子-空穴对,因此通过构建Bi₂O₂CO₃/g-C₃N₄异质结来加快光生载流子分离进而提升反应速率。其中最优的催化剂可以在反应9 h后使苯甲醇完全氧化为苯甲醛,降低了分离成本。     

O3/H2O2高级氧化法预处理酒精废水的实验研究

实验探讨了O3/H2O2高级氧化法预处理某制药酒精废水过程中H2O2投加量、pH值、反应时间、臭氧发生器氧气流量等因素对CODCr去除率的影响。实验得出的最佳反应条件是：H2O2投加量98 mmol/L,pH值11,氧气流量60 L/h,反应时间90 min,在最佳条件下反应后废水CODCr去除率46.3%,TOC去除率50.5%,B/C从0.08提高到0.32,废水可生化性明显提高,能够满足后续生化处理的需要。     

无定型MnO2的制备及其催化苯甲醇选择氧化性能

用KMnO₄和MnSO₄为原料，通过简单的氧化还原过程合成了无定形MnO₂，并用于催化苯甲醇氧化制苯甲醛，发现制得的无定形MnO₂在催化苯甲醇氧化制苯甲醛中表现出较高的活性和苯甲醛选择性（100%）。考察了反应温度、氧浓度、催化剂用量以及反应时间对苯甲醇氧化的影响。结果表明，较高的反应温度和氧浓度以及合适的催化剂用量有利于无定形MnO₂催化苯甲醇氧化生成苯甲醛，在反应温度110 ℃、常压和通氧条件下反应3 h, 苯甲醇转化率和苯甲醛选择性均为100%。     

SiO2负载MoP催化剂的制备及其对苯甲醇选择性氧化的催化性能

在SiO2载体上，以乙酰丙酮钼与次磷酸铵为原料，未经煅烧直接还原制备负载型磷化钼（MoP/SiO2）催化剂，通过XRD、N2-物理吸附、TEM和XPS等手段对催化剂进行表征。研究了浸渍液中P/Mo摩尔比（n(P):n(Mo)=1:1，2:1，3:1）、还原温度（500、550、600 ℃）对MoP相的影响，并考察其在苯甲醇选择性氧化生成苯甲醛反应中的催化性能。结果表明，浸渍液中P/Mo摩尔比为2、还原温度为550 ℃时，所获得的MoP/SiO2催化剂（MoP/SiO2-550-2）在苯甲醇选择性氧化生成苯甲醛反应中具有最好的转化率（99.7%）和优异的产物选择性（99.8%），这是由于MoP/SiO2-550-2催化剂上形成了更多小颗粒的MoP相。     

Ag对Pd/Al2O3催化分解NO反应的促进作用

研究了不同含量的银对Pd/Al₂O₃催化分解NO反应活性的影响。结果表明，低温下，Pd/Al₂O₃催化剂对NO的分解反应活性不高；反应温度达到720 ℃时，NO分解活性迅速上升。O₂-TPD研究表明，Pd/Al₂O₃上氧的脱附速率也是在720 ℃左右达到最大值，因此，在温度低于720 ℃时，氧从催化剂表面的脱附是NO分解反应的速率控制步骤。Pd/Al₂O₃中添加适量的Ag对NO分解反应有促进作用。O₂-TPD研究表明，这种促进作用与Pd表面氧物种的起始脱附温度向低温移动有关。     

Efficient H2 production on CoSx/Zn0.3Cd0.7S heterojunction by selective oxidation of p-chlorobenzyl alcohol in organic phase

Developing high-efficient photocatalysts for H₂ production is still the focus of current research. A series of CoS_x/Zn_0.3Cd_0.7S (CoS_x/ZCS) samples with different mass ratios were successfully synthesized for H₂ production by the oxidation of p-chlorobenzyl alcohol (Cl-PhCH₂OH). Herein, Zn_0.3Cd_0.7S (ZCS) solid-solution nanoparticles are distributed on the surface of CoS_x polyhedron, and CoS_x is obtained from ZIF-67, composed of Co_1−xS and CoS₂. The photocatalytic H₂ production was performed by Cl-PhCH₂OH oxidation in N,N-Dimethylformamide (DMF) solution under visible light irradiation, and 5% CoS_x/ZCS sample showed the best photocatalytic activity, with the H₂ generated rate high to 2.80 mmol g⁻¹ h⁻¹. Meanwhile, the selectivity of Cl-PhCH₂OH oxidation to p-chlorobenzaldehyde (Cl-PhCHO) is 97.6%, and the rate is 2.95 mmol g⁻¹ h⁻¹. Moreover, the reasons for the excellent photocatalytic performance of CoS_x/ZCS samples were deeply analyzed by experimental and theoretical results, such as trapping agents, photoelectrochemistry test, electron paramagnetic resonance (EPR), specific surface area, and density functional theory (DFT) calculation. This work provides a new theoretical guidance and experimental experience for the application of H₂ application and design of novel photocatalysts.     

Performance investigation of Fe3O4 blended poly (vinylidene fluoride) membrane on filtration and benzyl alcohol oxidation: Evaluation of sufficiency for catalytic reactors

Fe_3O_4-PVDF membranes were prepared by blending of magnetic Fe_3O_4 powders with polyvinylidene fluoride to investigate whether those were usable or not in catalytic membrane reactors. Filtration performances and catalytic activity of membranes in microwave conditions were measured in separate processes. Composite Fe_3O_4-PVDF membranes were characterized by TG-DTA, FTIR, XRD, SEM and contact angle techniques.Disappearing of α-phases at PVDF was observed with increasing amount of additives from XRD diffraction patterns. Decomposition of polymer fastened due to catalytic effect of Fe_3O_4. Finger-like structures and large number of small pores were observed at the SEM images. Those provided effective transportation of substrate among the active sites of catalyst. At the experiments conducted in batch reactor, 51%, 77%, 66% and 63% benzyl alcohol conversion were recorded for 2%, 4%, 6% and 8% Fe_3O_4-PVDF composite pieces respectively. Catalyst were separated magnetically and reused several times. On the other hand Fe_3O_4 blended PVDF membranes provided improved flux and BSA rejection compared with performance of bare PVDF membrane; 41.6% BSA rejection was obtained with 4% Fe_3O_4-PVDF whereas it was only 6.7% for PVDF. Fe_3O_4-PVDF composites performed high activity for the benzyl alcohol oxidation in batch reactor and also better filtration at filtration cell. These results promise to obtain practical and low cost membrane material for catalytic reactors usable in microwave support to get fast results.     

萃取法测定氯丙烯氧化液油相中双氧水含量

建立了氯丙烯氧化液油相中双氧水含量的测定方法。考察了硫酸溶液的用量、碘化钾溶液的用量及萃取后静置时间等条件对双氧水含量分析的影响。结果表明,最佳分析条件为样品用水萃取后,依次加入硫酸溶液、碘化钾溶液、4滴钼酸铵溶液,用硫代硫酸钠标准溶液滴至近终点。该方法准确、快速、灵敏,测定的相对标准偏差为0.69%~1.58%,回收率为91.7%~102%。