Fe-K/AC催化氧化脱硫剂制备及反应机理研究

采用正交实验法制备了负载铁、钾的活性炭(Fe-K/AC)热煤气催化氧化脱硫剂,考察了活性组分铁、钾含量、二价铁和三价铁比例、煅烧温度对催化氧化脱硫反应活性的影响。由正交实验极差分析可知,各因素影响程度依次为:钾含量>铁含量>煅烧温度> Fe²⁺/Fe³⁺,最优制备条件为,铁含量0.5%、钾含量5.0%、煅烧温度600 ℃、Fe²⁺/Fe³⁺比0.5。通过对脱硫剂的孔隙结构和表面形貌分析可知,活性炭表面负载的铁金属氧化物具有催化氧化硫化氢生成单质硫的活性,碱金属氧化物具有协同作用,可以改变表面酸碱性,促进硫化氢的催化转化,但过高的金属氧化物负载量会阻塞孔道,减小反应比表面积,从而降低脱硫剂的反应活性。     

Effect of the calcination temperature on the properties of Fe2O3/SiO2 catalysts for oxidation of hydrogen sulfide

The effect of the calcination temperature on the properties of supported iron oxide catalysts for hydrogen sulfide oxidation prepared by impregnation of silica with iron(III) nitrate has been studied. An increase in the calcination temperature was found to diminish the catalytic activity of the Fe₂O₃/SiO₂ catalysts in hydrogen sulfide oxidation. This behavior can be explained by the agglomeration of iron oxide particles and by a decrease in the surface concentration of active sites. It has been shown that an increase in the calcination temperature makes the catalyst more stable towards the sulfidation of the active component (Fe₂O₃) to the iron disulfide phase.     

炼焦过程氧化铅高温焦炉煤气均相脱硫的研究

考察了焦煤中少量氧化铅添加剂对炼焦过程高温焦炉煤气硫化氢浓度以及对焦炭质量的影响。实验表明，煤中添加少量的氧化铅，可以达到焦炉粗煤气脱硫的目的，并且对焦炭的质量影响很小。针对实验所用的煤种，相当于焦煤质量的0.6％的氧化铅添加量在炼焦前期具有最佳的抑制硫释放的效果。炼焦后期，半焦中的硫化铅分解或铅转变为气态铅。气态铅和硫化氢在离开炼焦室时，由于煤气降低温度，又生成硫化铅。从而实现均相脱硫。焦炭中超过一半的铅可以挥发出去。在炼焦收缩阶段，半焦中过多的铅的存在不利于硫化铅的分解。     

煤中混入氧化锌高温焦炉煤气脱硫行为的研究

在热力学模拟结果的基础上，利用在练变煤中添加氧化锌进行焦炉煤气均相脱硫的行为的研究。实验结果表明：在炼焦前期，煤中添加氧化锌可以有效抑制煤中硫的释放，实验所用煤样中的最佳的氧化锌添加量是理论计算所需量的1．4倍.顺炼焦后期，由于焦炉煤气中氢气的作用，半焦中硫化锌和氧化锌开始分解，气态锌和H2S随焦炉煤气的温度降低又生成硫化锌，从而实现了焦炉煤气的脱硫，而且对焦炭质量的影响很小，氧化锌的添加量的增加有利于焦炉煤气进一步的脱硫。     

球形氧化铝负载锰基双金属氧化物催化剂催化臭氧深度氧化NO

在工业锅炉烟气处理领域,由于锅炉容量低,烟气温度往往无法满足传统选择性催化还原(SCR)所需温度窗口.工业锅炉烟气成分的复杂性也给氮氧化物治理带来了严峻考验.臭氧深度氧化NO结合湿法洗涤同时脱硫脱硝技术具有独特的应用优势.传统臭氧氧化技术中,NO被臭氧氧化为NO2,进而在脱硫塔中实现一体化脱硫脱硝.但由于NO2溶解度相对较低,需要在脱硫浆液中加入添加剂提高脱硝效率,造成运行成本增加.NO经臭氧深度氧化后,NO2进一步转化为溶解度高的N2O5,传统脱硫石膏浆液即可实现高效吸收N2O5,从而有效提高氮氧化物吸收效率.但由于N2O5生成反应速率低,深度氧化存在臭氧投入量大、反应时间长及臭氧残留多的缺点.臭氧耦合催化剂深度氧化NO可有效解决以上问题.首先,本文采用溶胶-凝胶法合成一系列单金属氧化物(Mn,Co,Ce,Fe,Cu,Cr)作为臭氧深度氧化NO的催化剂.结果发现锰氧化物表现出最高的催化活性,在70oC下,O3/NO摩尔比为2.0时经过0.12 s的反应时间催化剂即可实现80%以上的转化效率.但根据N2O5生成的总包反应(2NO+3O3=N2O5+3O2)可以看出,O3/NO摩尔比为1.5时即可实现N2O5的完全转化.由于催化臭氧氧化反应温度较低,中间产物在催化剂表面聚集,占据大量活性位,进而导致无法实现1.5摩尔比的高效转化.通过采用球形氧化铝作为载体,避免粉末状催化剂紧凑型布置,增加换热面积,可有效降低催化剂表面中间产物聚集;同时延长了气体与催化剂的接触时间,提高反应效率.在球形氧化铝载体上负载锰基双金属氧化物(Ce-Mn,Fe-M,Cr-Mn,Cu-Mn和Co-Mn),在初始NO浓度为410 mg/m3,反应温度100oC,O3/NO摩尔比1.5,催化反应时间0.12 s的工况下,催化剂最终实现95%(Fe-Mn)和88%(Ce-Mn)的转化效率,剩余NO和NO2的浓度分别低于20 mg/m3(Fe-Mn)和50 mg/m3(Ce-Mn),臭氧残留浓度低于25 mg/m3.同负载单一锰氧化物(83%转化率)相比,双金属氧化物进一步提高了N2O5生成效率.因此,臭氧耦合催化剂深度氧化NO结合湿法吸收在工业锅炉超低排放(NOx<50 mg/m3)领域具有广泛应用前景.通过XRD、氮气吸附、H2-TPR和XPS等手段研究了催化剂的晶体结构、孔结构参数、氧化还原性能和表面原子价态.催化臭氧深度氧化NO主要与催化剂对臭氧的分解性能和对NO的氧化性能有关.较大的比表面积和孔容有利于催化剂的吸附.氧空位有利于臭氧的吸附和分解.Mn4+和Mn3+的均衡分布既有利于NO的吸附氧化又有利于臭氧的吸附分解,最终提高了N2O5生成效率.     

High effective electrocatalytic oxidation of cyclohexanol on stable Fe-Mn/Mn<Subscript>2</Subscript>O<Subscript>3</Subscript> membrane electrode

A new composite electrode material with iron-manganic oxide coating (Fe-Mn/Mn₂O₃) was prepared, and its catalytic performance for oxidizing cyclohexanol was investigated in this work. The new electrode material, based on iron substrate covered with electrolytic manganese, was obtained by further coating the manganese surface with 50 % manganese nitrate solution and then conducting program thermal decomposition treatment. X-ray diffraction (XRD) was used to determine the surface crystal phase compositions, which were Mn and Mn₂O₃. The catalytic results showed an excellent electrocatalytic performance on the oxidation of cyclohexanol, and the main products were cyclohexanone and hexanedioic acid. According to our experiment results and the literature reports, the existence of mixed valent Mn^III and Mn^IV played a key role in the electrocatalytic oxidation process. A probable process was proposed: the Mn^IV seized the hydrogen from cyclohexanol, the resulting cyclohexaneoxy radical was oxidized into cyclohexanone, and then the absorbed cyclohexanone was further oxidized into hexanedioic acid.     

锰氧化物中氧空位的构建及其催化氧化苯系物作用机制研究进展

作为一种过渡金属氧化物,锰氧化物以其多晶型、储/释氧能力强、蕴含丰富氧物种、结构缺陷可控等优点被广泛应用于苯系物的热催化氧化。其中,具有众多特性的氧空位能有效促进苯系物的完全催化氧化,因而成为各界研究的焦点。我们综述了常见的氧空位构建方法及表征技术,并总结了在苯系物催化氧化过程中,锰氧化物中氧空位的几种重要作用机制对催化活性和抗水性能的积极影响。最后文章对氧空位构建新方法、形成机理、具体过程及其在锰氧化物热催化氧化苯系物领域中的应用进行了总结和展望。     

工业、生活污泥与煤混合燃烧的灰熔特性研究

针对煤粉锅炉掺烧污泥后污泥对混合燃料灰熔特性的影响行为,利用矿物三元相图、XRD等分析手段,研究了不同特性污泥(生活污泥、工业污泥)与煤掺混燃烧过程中不同矿物组分的相互作用机制及灰渣的灰熔融特性变化特征。结果表明,三元相图能够有效预测煤和污泥掺混后灰熔融温度的变化趋势;低含量的氧化铁形成低温共熔体以及透辉石、钙长石会降低煤和污泥混合后的灰熔融温度;而钙镁橄榄石、莫来石和单体形式存在的氧化铁能提高煤和污泥混合后的灰熔融温度。工业污泥中的高硫组分在混烧过程中易形成硫酸盐的低温共融体。生活污泥中磷对灰熔点的影响与氧化铝及碱金属的比例有关,当氧化铝的含量占主要成分时,磷的存在趋向于降低灰熔点,而当碱金属占主要成分时,磷的存在趋向于提高灰熔点。     

Mechanochemical reactions of elementary sulfur and iron sulfides with hydrogen,oxygen, and water

Mechanochemical reactions of elementary sulfur and iron sulfides with hydrogen, oxygen, and water were studied. Three reactions were discovered: (1) between elementary sulfur and dihydrogen, (2) between pyrite and dihydrogen, and (3) between elementary sulfur and water; these reactions are accompanied by hydrogen sulfide evolution. Mechanochemical synthesis of iron sulfide from the constituent elements in water involves hydrogen sulfide, which is generated by the reaction of elementary sulfur with water. We show that elementary sulfur is generated during pyrite oxidation by dioxygen during or after dispersion. In an oxygen-free medium, pyrite is more reactive to water than iron sulfide. Pyrite reacts with dihydrogen and water in an oxygen-free medium directly, avoiding the dissociation stage.     

配煤灰渣中矿物质在高温中转变的定量分析及其对结渣的影响

利用沉降炉系统对榆林和平朔的配煤进行结渣特性实验,测定不同实验温度下煤的结渣指数,并利用X射线衍射分析(XRD)对灰渣中矿物质组成进行了定量分析。结果表明,灰渣中主要存在四种结晶矿物质分别为氧化铁、钙长石、莫来石、氧化硅,以及无定形的玻璃体。其中,灰中氧化铁含量和灰渣中钙长石、莫来石含量对燃煤的结渣倾向性起显著性影响;灰中氧化铁和灰渣中钙长石含量越高、灰渣中的莫来石含量越低,煤燃烧的结渣倾向性越大。通过配煤可以降低煤灰中的氧化铁含量,并降低灰渣中的钙长石生成量和提高灰渣中的莫来石生成量,从而显著降低神木类煤的结渣倾向性。     

The effect of surface conditions on the activation of FeTi

It is very important to know the changes in the surface conditions of FeTi after heat treatment and to identify the sites where hydrogen is chemisorbed in order to understand the activation mechanism of the FeTi hydrogenation reaction. FeTi powder was mixed with various metal powders and the hydrogen absorption curves were observed after heat treatment at various temperatures. It is believed that the chemisorbing sites are iron clusters which are formed during the heat treatment process by a segregation reaction. Iron clusters are easily contaminated by the small amount of oxygen in the atmosphere during heat treatments and thus the activation of the compound is retarded. The activation of the FeTi alloys thus involves two competing processes: the generation of iron clusters and the contamination of the iron by oxygen. If FeTi powder is mixed with powdered copper or nickel, which have lower oxide stabilities than that of iron, no activation is achieved, regardless of the heat treatment conditions. Elements with higher oxide stabilities, such as aluminium, silicon, manganese and magnesium, promote the activation of FeTi. In particular, manganese and magnesium, which can chemisorb hydrogen, markedly increase the activation.     

Determination of manganese in environmental samples (e.g. coal fly ash) by electrothermal AAS after its separation with a liquid chelating ion exchanger

An electrothermal atomic absorption spectrometric method is described for the determination of manganese in various coal fly ash samples after its separation with dissolved monothioxo-beta-diketone as chelating ion exchanger. The detection limit is 1 ng ml(-1). To study the accuracy of the method, a reference material of similar composition was analysed and recovery of spiked manganese was performed.     

The protective function of hydrogen sulfide for lysozyme against riboflavin-sensitized photo-oxidation

Hydrogen sulfide is the third endogenous signaling gasotransmitter, following nitric oxide and carbon monoxide. Recent studies showed that hydrogen sulfide could alleviate many diseases which were related to the oxidative damage of tissues. It reminded us that hydrogen sulfide might serve as an antioxidant to reduce oxidative pressure. This study showed that hydrogen sulfide protected lysozyme from photo-oxidation induced by riboflavin (RF). Laser flash photolysis was used to explore the mechanisms of antioxidant activity of hydrogen sulfide. The scavenging effects of hydrogen sulfide on the triplet state of riboflavin (3RF(*)) and radicals of tryptophan and tyrosine (TyrO· and TrpN·) were attributed to the protection of lysozyme from photo-oxidation. The results suggested that hydrogen sulfide could serve as an antioxidant in alleviation of oxidative pressure.     

煤灰及各种矿物质对SO2排放特性的影响

利用TG-DTG采用低加热速率实验研究了煤阶、脱灰及煤中主要矿物质成分对煤燃烧过程中SO2排放特性的影响,并对矿物质成分的影响机理进行了讨论。结果表明,煤中硫质量分数的高低对烟气中SO2的排放有明显影响,排放水平与硫质量分数不成比例;煤中硫向SO2转化率与煤阶之间没有明显的关联;脱灰能较小程度地促进SO2的生成,抚顺煤主要矿物质成分中Na、K、Mg以及Ca等碱金属与碱土金属明显抑制SO2的排放,同时纳米级的TiO2也减少烟气中SO2体积分数,这些成分对SO2抑制作用的顺序为MgNa≈K>Ca>Mg>Ti的次序加速焦炭的氧化;Si和Al属于惰性成分,对煤中硫的迁徙以及煤的燃烧特性没有显著影响。     

Dendritic metalloporphyrins as catalysts for organic transformations

Dendritic manganese, iron, and ruthenium porphyrins with dendritic wedges attached to the periphery of meso-tetraphenylporphyrin (TPP) or meso-triarylporphyrin macrocycle were reported to be active catalysts for epoxidation or cyclopropanation of alkenes or oxidation of sulfides. The dendritic manganese and iron porphyrin catalysts exhibit considerably higher regioselectivity and shape selectivity than the respective parent catalyst [M(TPP)Cl] (M = Mn, Fe). Systematic increase in shape selectivity, diastereoselectivity, epoxide/sulfoxide selectivity, or catalyst stability with increasing generation number of the dendritic wedges is observed for the alkene epoxidation or sulfide oxidation reactions catalyzed by these dendritic manganese, iron, and ruthenium porphyrins. To cite this article: C.-M. Che, C. R. Chimie 6 (2003).     

Rapid laser fluorometric method for the determination of uranium in soil, ultrabasic rock, plant ash, coal fly ash and red mud samples

A simple and rapid laser fluorometric determination of trace and ultra trace level of uranium in a wide variety of low uranium content materials like soil, basic and ultra basic rocks, plant ash, coal fly ash and red mud samples is described. Interference studies of some common major, minor and trace elements likely to be present in different, geological materials on uranium fluorescence are studied using different fluorescence enhancing reagents like sodium pyrophosphate, orthophosphoric acid, penta sodium tri-polyphosphate and sodium hexametaphosphate. The accurate determination of very low uranium content samples which are rich in iron, manganese and calcium, is possible only after the selective separation of uranium. Conditions suitable for the quantitative single step extraction of 25 ng to 20 μg uranium with tri-n-octylphosphine oxide and single step quantitative stripping with dilute neutral sodium pyrophosphate, which also acts as fluorescence enhancing reagent is studied. The aqueous strip is used for the direct laser fluorometric measurement without any further pretreatment. The procedure is applied for the determination of uranium in soil, basalt, plant ash, coal fly ash and red mud samples. The accuracy of the proposed method is checked by analyzing certain standard reference materials as well as synthetic sample with known quantity of uranium. The accuracy and reproducibility of the method are fairly good with RSD ranging from 3 to 5% depend upon the concentration of uranium.     

氧化铜转化法制备氢氧化钡

以硫化钡为原料,在水溶液中与氧化铜反应,生成氢氧化钡。副产物硫化铜经氧化焙烧生成氧化铜,循环使用于下一次合成中。放出的二氧化硫经石灰乳吸收用来制备亚硫酸氢钙。     

A study on Zn-based catal-sorbents for the simultaneous removal of hydrogen sulfide and ammonia at high temperature

To simultaneously remove hydrogen sulfide and ammonia from hot coal gases, the ammonia decomposition abilities of various metal oxide catalysts were tested in the absence/presence of hydrogen sulfide, at 650 °C. Cobalt oxide, molybdenum oxide, and nickel oxide have high ammonia decomposition abilities (>95%) in the absence of hydrogen sulfide, but such abilities rapidly decreased during the reaction in the presence of hydrogen sulfide. To improve the simultaneous removal abilities of metal oxides, Zn-based catal sorbents were prepared via impregnation with various metals, such as cobalt, nickel, and molybdenum, on zinc oxide. The CZ-30 (promoted with 30 wt% cobalt oxide on zinc oxide) and NZ-30 (promoted with 30 wt% nickel oxide on zinc oxide) catal sorbents showed excellent sulfur removal capacities, which, calculated until the breakthrough point, were 0.35 and 0.39 g S/g catal sorbent, respectively, while MZ-30 promoted with molybdenum showed a low sulfur removal capacity of 0.08 g S/g catal sorbent. The ammonia decomposition ability of CZ-30, however, increased more than 18 times compared with Co₃O₄, whose ammonia decomposition ability was more than 95% until 465 min, even though the ammonia decomposition ability of NZ-30 sharply decreased after 30 min. The CZ catal sorbent is a good candidate for the simultaneous removal of ammonia and hydrogen sulfide.     

The mechanism of antimony(III) removal and its reactions on the surfaces of Fe-Mn binary oxide

Antimony is a regulated pollutant to be well controlled. This study compared the removal capability and mechanisms involved in the removal of Sb(III) by Fe-Mn Binary Oxide (FMBO), ferric hydroxide (FeOOH), and manganese dioxide (MnO(2)). FMBO shows a maximum Sb removal capacity of 1.76 mmol/g and was much higher than that of both FeOOH (0.83 mmol/g) and MnO(2) (0.81 mmol/g). Characterization techniques of FTIR and XPS indicated the different variation trends of functional groups, surface elemental composition, and chemical valence of Fe, Mn, and Sb after the adsorption of Sb(III) on these three adsorbents. As for FMBO, results indicated that the manganese oxide dominated in oxidation of Sb(III) to Sb(V) whereas the iron oxide adsorbed the Sb(III) and Sb(V). The oxidation and sorption mechanism was proposed to involve in the removal of Sb(III) by FMBO. FMBO may be promisingly used to remove Sb from drinking water and wastewater.     

苯环上氯取代位对四苯基金属卟啉催化烯烃环氧化性能的影响

以苯乙烯、环己烯和反式二苯乙烯为烯烃底物,以双氧水、叔丁基过氧化氢和异丙苯过氧化氢为氧化剂,以苯环上对位和邻位氯取代的四苯基金属卟啉为仿生催化剂,对烯烃的催化环氧化反应进行了对比研究.讨论了不同氯取代位的四苯基金属卟啉对烯烃环氧化性能的影响.实验结果表明,在没有助催化剂存在下,邻位氯代的四(2,6-二氯苯基)铁(锰)卟啉对烯烃的环氧化具有优异的催化性能,烯烃底物的转化率和环氧选择性都比对位氯代的四苯基铁(锰)卟啉高,且反应条件温和.其中FeⅢ(TDCPP)Cl的催化性能最好,环氧化选择性最高,催化氧化苯乙烯时,环氧苯乙烷的选择性达到了90.4%.相同金属离子不同配体的金属卟啉传递氧原子的能力为TDCPP>T(p-Cl)PP>TPP.氧化剂的结构对环氧化物的选择性有较大影响.过氧键连有吸电子基团的异丙苯过氧化氢对环氧化物的选择性最高.根据实验结果,对金属卟啉催化环氧化机理进行了分析.