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1.
使用配有团簇产生和化学反应源的飞行时间质谱装置,研究了锆氧阴离子团簇ZrxOy-与乙烷和丁烷的反应. 在反应中发现了Zr2O5H-和Zr3O7H-产物. 用密度泛函理论研究了乙烷在Zr2O5-上的反应通道,发现乙烷脱氢反应可以发生,从而证明观察到的产物是源于脱氢反应. 该工作揭示了锆氧负离子团簇与烷烃反应中的新通道.  相似文献   

2.
低温陈化超声波共沉淀法制得SO42-/ZrO2-La2O3前驱体, 经H2SO4处理, 在不同温度下焙烧得到纳米晶催化剂SO42-/ZrO2-La2O3;用Hammett指示剂法测定其酸性. 用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价. 结果表明经超声波搅拌和低温(-15 ºC)陈化,650 ºC焙烧4 h得到的固体超强酸表现出较高催化活性.  相似文献   

3.
本文制备了用于费托合成反应的钴改性Fe3O4-MnO2双功能催化剂,并探究了钴负载量对Fe-Co协同效应的影响以及Fe1CoxMn1催化剂的费托合成反应性能. 实验发现,在Fe3O4-Mn催化剂中加入Co可促进铁氧化物的还原、增加反应过程中铁位点的活性. 此外,Co的加入可增强Fe-Co金属间的电子转移,加强两者的协同作用,提高催化性能. Co负载较高的Fe1CoxMn1催化剂可进一步促进加氢反应能力,使产品分布向短链烃方向转移. 在280 °C、2.0 MPa和3000 h-1的最佳工况条件下,Fe1Co1Mn1催化剂的液体燃料收率最高.  相似文献   

4.
以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co3O4/SiO2催化剂.通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构.在所有的催化剂中,XRD和Raman光谱都只检测到了Co3O4晶相的存在.与Co3O4体相相比,XPS结果表明在200 oC焙烧的(Co3O4(200)/SiO2)催化剂中Co3O4表面上存在着过量的Co2+.与XPS的结果一致,TPR结果表明Co3O4(200)/SiO2催化剂中Co3O4表面上存在氧缺陷, 并且XAFS结果也表明Co3O4(200)/SiO2催化剂中Co3O4具有更多的Co2+.提高焙烧温度使得过量的Co2+进一步氧化为Co3+,同时降低了表面氧缺陷浓度,从而得到计量比的Co3O44/SiO2催化剂.在所有的负载催化剂中Co3O4(200)/SiO2催化剂表现出了最好的CO氧化催化性能,表明过量Co2+和表面氧缺陷的存在能够促进Co3O4催化CO氧化反应的活性.  相似文献   

5.
本文基于离子分子SH2-基态势能面,应用含时波包方法研究了反应S-(2P)+H2(1Σ+g)→SH-(1Σ)+H(2S)的动力学行为. 给出了反应几率和积分截面随碰撞能的变化关系,结果表明,在讨论的所有碰撞能量范围内二者均存在显著的振荡结构. 当初始转动量子数j=0,2,4,6,8,10和振动量子数v=0,1,2,3,4时,从总反应几率数值计算中可以看出,双原子H2的振动激发和转动激发显著提高了反应活性. 同时积分散射截面的理论值与前人的实验值相符合.  相似文献   

6.
采用激光溅射法制备了同位素标记的氧化锰团簇正离子Mnm18On+,并研究了其在快速流动反应管中与硫化氢在热碰撞条件下的反应,氧化锰团簇正离子与硫化氢反应前后的质量分布与强度变化由飞行时间质谱仪检测.实验表明,绝大多数氧化锰团簇正离子可与硫化氢发生氧-硫交换反应产生水分子,反应通式为:Mnm18On++H2S→Mnm18On-1S++H218O.通过密度泛函理论计算了氧化锰团簇正离Mn2O2+、Mn2O3+和Mn2O4+与H2S反应的机理,结果显示,在这些反应体系中氧-硫交换反应通道同时具有热力学和动力学优势,印证了实验中观察到的现象.气相团簇研究发现的氧-硫交换反应与相关凝聚相体系反应结果一致  相似文献   

7.
采用水热法合成MnOOH一维纳米线,通过MnOOH在不同气氛和温度中煅烧得到尺寸和形貌相似的不同锰氧化物,并用于以O2为氧源的苯甲醇液相氧化反应. 结果表明,MnO2对苯甲醇氧化反应具有较高的催化活性. 通过XPS、SEM、TEM和H2-TPR等手段对催化剂的形貌和结构进行了表征,并讨论了可能影响反应活性的一些因素. MnO2的良好催化性能可能与其晶格氧具有较高的迁移率以及氧化还原能力有关. 通过简单的焙烧处理,可以使MnO2催化剂在苯甲醇氧化反应中具有良好的重复使用性.  相似文献   

8.
Cr2O3是双功能催化合成气转化的重要氧化物组分,其可将合成气转化为重要的中间物种甲醇. 结合密度泛函理论计算和微观动力学模拟,本文系统研究了干净Cr2O3(001)和(012)表面,以及氢覆盖或含有氧空位的还原(012)表面的结构及催化合成气转化至甲醇的活性. 本文探讨了合成气转化为甲醇的分步或协同反应路径,并确定CO或CHO氢化是决速步骤. 微观动力学分析表明,Cr2O3(001)表面难以催化合成气转化为甲醇,在673 K 时,两个还原性(012)表面的反应速率(25∽28 s-1)比干净的(012)表面(4.3 s-1)高出约五倍. 计算结果表明了Cr2O3表面还原性对催化活性的重要性,或许可以为双功能催化体系中氧化物组分的设计提供参考.  相似文献   

9.
用密度泛函理论(DFT)的B3lyp方法在6-311++g(d,p)水平上对Al2O3Hx(x=1—3)分子的几何构型, 电子结构, 振动频率等性质进行了系统研究. 并给出了它们可能基态结构的总能量(ET), 零点能(Ez), 摩尔热容(Cv), 标准熵(S), 原子化能(ΔEm), 垂直电离能(IP)及垂直电子亲和能(EA). Al2O3H和Al2O3H2分子可能的基态的几何构型都为平面结构. Al2O3H3的两个可能为基态的几何构型都是在立体Al2O3(D3h)的几何结构基础上加三个氢原子构成. 这三个分子的能量最低结构为Al2O3H(2A′)Cs, Al2O3H2(1A′) Cs, Al2O3H3 (2A) C1.  相似文献   

10.
以天然木棉为模板,利用造孔及纳米颗粒自组装两步法合成了分级多孔的Cafe2O4/C复合催化剂. Cafe2O4/C复合催化剂保留了木棉模板的中空纤维形貌,且该中空纤维是由碳及均匀分布在碳表面的Cafe2O4纳米颗粒组成. 该复合催化剂具有较强的甲基紫微波催化降解活性. 研究了Cafe2O4负载量、微波功率、催化剂用量、甲基紫的初始浓度和pH值对微波诱导甲基紫降解的影响. 结果表明,Cafe2O4/C微波降解甲基紫的催化反应具有较高的反应速率和较短的反应时间. 其降解反应符合一级动力学模型. Cafe2O4/C 高的催化活性得益于催化反应和吸附特性之间的协同作用.  相似文献   

11.
《Ultrasonics sonochemistry》2014,21(6):1976-1981
This report describes the effects of H2O2 concentration (0.01, 0.1, 1, and 10 mM) on the sonochemical degradation of phenol and bisphenol A (BPA) using an ultrasonic source of 35 kHz and 0.08 W/mL. The concentration of the target pollutants (phenol or BPA), total organic carbon (TOC), and H2O2 were monitored for each input concentration of H2O2. The effects of H2O2 on the sonochemical degradation of phenol was more significant than that of BPA because phenol has a high solubility and low octanol–water partition coefficient (Kow) value and is subsequently very likely to remain in the aqueous phase, giving it a greater probability of reacting with H2O2. The removal of TOC was also enhanced by the addition of H2O2. Some intermediates of BPA have a high Kow value and subsequently have a greater probability of pyrolyzing by the high temperatures and pressures inside of cavitation bubbles. Thus the removal efficiency of TOC in BPA was higher than that of phenol. The removal efficiencies of TOC were lower than the degradation efficiencies of phenol and BPA. This result is due to the fact that some intermediates cannot readily degrade during the sonochemical reaction. The H2O2 concentration decreased but was not completely consumed during the sonochemical degradation of pollutants. The initial H2O2 concentration and the physical/chemical characteristics of pollutants were considered to be important factors in determining the formation rate of the H2O2. When high concentration of H2O2 was added to the solution, the formation rates were relatively low compared to when low concentrations of H2O2 were used.  相似文献   

12.
《Ultrasonics sonochemistry》2014,21(5):1787-1796
Application of Advanced Oxidation Processes (AOP) such as sono, photo and sonophoto catalysis in the purification of polluted water under ambient conditions involve the formation and participation of Reactive Oxygen Species (ROS) like OH, HO2, O2, H2O2 etc. Among these, H2O2 is the most stable and is also a precursor for the reactive free radicals. Current investigations on the ZnO mediated sono, photo and sonophoto catalytic degradation of phenol pollutant in water reveal that H2O2 formed in situ cannot be quantitatively correlated with the degradation of the pollutant. The concentration of H2O2 formed does not increase corresponding to phenol degradation and reaches a plateau or varies in a wave-like fashion (oscillation) with well defined crests and troughs, indicating concurrent formation and decomposition. The concentration at which decomposition overtakes formation or formation overtakes decomposition is sensitive to the reaction conditions. Direct photolysis of H2O2 in the absence of catalyst or the presence of pre-equilibrated (with the adsorption of H2O2) catalyst in the absence of light does not lead to the oscillation. The phenomenon is more pronounced in sonocatalysis, the intensity of oscillation being in the order sonocatalysis > photocatalysis  sonophotocatalysis while the degradation of phenol follows the order sonophotocatalysis > photocatalysis > sonocatalysis > sonolysis > photolysis. In the case of sonocatalysis, the oscillation continues for some more time after discontinuing the US irradiation indicating that the reactive free radicals as well as the trapped electrons and holes which interact with H2O2 have longer life time (memory effect).  相似文献   

13.
A fluorophotometric method for the determination of hydrogen peroxide (H2O2) using fluorescin was developed. This method was based on the oxidative reaction of fluorescin, a colorless, non-fluorescent lactoid fluorescein, by H2O2 to give highly fluorescein fluorescence emission. In the determination of H2O2, the calibration curve exhibited linearity over the H2O2 concentration range of 1.5–310 ng mL−1 at an emission wavelength of 525 nm with an excitation of 500 nm and with relative standard deviations (n = 6) of 2.51%, 2.48%, and 1.31% for 3.1 ng mL−1, 30.8 ng mL−1, and for 308 ng mL−1 of H2O2, respectively. The detection limit for H2O2 was 1.9 ng mL−1 six blank determinations was performed (ρ = 6). This proposed method was applied to detection of other reactive oxygen species and nitrogen species (ROS/RNS) such as singlet oxygen (1O2), hydroxyl radical (OH), peroxynitrite (ONOO) etc., and it was possible to detect them with a high sensitivity. In addition, this proposed method was applied to the recovery tests of H2O2 in calf serum, human saliva, rain water, and wheat noodles; the results were satisfactory.  相似文献   

14.
A new series of iron(III) complexes [Fe(L1)(HL1)], [Fe(L1)Cl]; [H2L1 = N′-(2-methoxythiobenzoyl)pyridine-2-carbohydrazide], [Fe(L2)(acac)], [Fe(HL2)2Cl]; [H2L2 = N′-(4-methoxythiobenzoyl)pyridine-2-carbohydrazide] and [Fe(L3) (acac)]; [H2L3 = N′-(2-hydroxythiobenzoyl)pyridine-2-carbohydrazide] were prepared by stirring/refluxing/mixing the respective ligand with FeCl3/Fe(acac)3 in chloroform/methanol. All the compounds were characterized by elemental analyses, magnetic susceptibility, IR, UV and Mössbauer spectral data. The complexes posses high/ low spin state and have tetrahedral/octahedral geometry.  相似文献   

15.
The photo-Fenton degradation of carbamazepine (CBZ) assisted with ultrasound radiation (US/UV/H2O2/Fe) was tested in a lab thin film reactor allowing high TOC removals (89% in 35 min). The synergism between the UV process and the sonolytic one was quantified as 55.2%.To test the applicability of this reactor for industrial purposes, the sono-photo-degradation of CBZ was also tested in a thin film pilot plant reactor and compared with a 28 L UV-C conventional pilot plant and with a solar Collector Parabolic Compound (CPC). At a pilot plant scale, a US/UV/H2O2/Fe process reaching 60% of mineralization would cost 2.1 and 3.8 €/m3 for the conventional and thin film plant respectively. The use of ultrasound (US) produces an extra generation of hydroxyl radicals, thus increasing the mineralization rate.In the solar process, electric consumption accounts for a maximum of 33% of total costs. Thus, for a TOC removal of 80%, the cost of this treatment is about 1.36 €/m3. However, the efficiency of the solar installation decreases in cloudy days and cannot be used during night, so that a limited flow rate can be treated.  相似文献   

16.
We present in this work the direct observation of HO2 radicals after irradiation of benzene C6H6 at 248 nm in the presence of O2. HO2 radicals have been unambiguously identified using the very selective and sensitive detection of continuous wave cavity ring-down spectroscopy (cw-CRDS) coupled to a laser photolysis reactor. HO2 radicals were detected in the first vibrational overtone of the OH stretch at 6638.20 cm-1, using a DFB diode laser. This reaction might be important because 248 nm photolysis of H2O2 has often been used in the past for studying the OH-initiated degradation of C6H6, often using a large excess of C6H6 over H2O2. The possible importance of the title reaction with respect to these former laboratory studies has been quantified through comparison with HO2 signals obtained from 248 nm photolysis of H2O2: one obtains under our conditions (excess O2 and total pressure of 6.6 kPa helium) from the 248 nm irradiation of identical initial concentrations [C6H6]=[H2O2] the following relative initial radical concentrations: [HO2 ]=(0.28±0.05)×[OH]. Experiments with various O2 concentrations have revealed that the origin of the HO2 radicals is not the reaction of H-atoms with O2, but must originate from the reaction of O2 with excited C6H6 *. The quantum yield of C6H6 * formation has been deduced to ϕ=0.2±0.1. PACS  42.62.Fi; 82.20.Pm; 82.33.Tb  相似文献   

17.
The removal of Orange II (O-II) from aqueous solution under irradiation at 850 kHz has been studied. The effects of both homogeneous (with FeSO4/H2O2), and heterogeneous (Fe containing ZSM-5 zeolite/H2O2) Fenton type reagents are reported together with the effect of UV irradiation in combination with ultrasound both alone and with homogeneous Fenton-type reagent.Degrees of decolourisation of 6.5% and 28.9% were observed using UV radiation and ultrasound, respectively, whereas under the simultaneous irradiation of ultrasound and UV light, the decolourisation degree reached 47.8%, indicating a synergetic effect of ultrasound and UV light. The decolourisation was increased with the addition of Fenton’s reagent with an optimal Fenton molar reagent ratio, Fe2+:H2O2 of 1:50. In the combined process of ultrasound and UV light with the homogeneous Fenton system 80.8% decolourisation could be achieved after 2 h indicating that UV improves this type of Orange II degradation. The degree of decolourisation obtained using the heterogeneous sono-Fenton system (Fe containing ZSM-5 zeolite catalysts + H2O2 + ultrasound) were consistently lower than the traditional homogeneous ultrasound Fenton system. This can be attributed to the greater difficulty of the reaction between Fe ions and hydrogen peroxide.In all cases the Orange II ultrasonic decolourisation was found to follow first order kinetics.  相似文献   

18.
Iron supported systems are frequently used as catalysts in the Fischer–Tropsch synthesis being the Fe0 the active phase for the reaction. We have studied the influence of the calcination atmosphere (air or nitrogen) on the iron oxide reducibility and the metallic iron particle size obtained in Fe/SiO2 system. We have impregnated a silicagel with Fe(NO3)3·9H2O aqueous solution and the solid obtained was calcinated in air or N2 stream. These precursors, with 5% (wt/wt) of Fe, were characterized by Mössbauer Spectroscopy at 298 and 15 K. Amorphous Fe2O3 species with 3 nm diameter in the former, and α-Fe2O3 crystals of 48 nm diameter were detected in the last one. Both precursors were reduced in H2 stream. Two catalysts were obtained and characterized by Mössbauer spectroscopy in controlled atmosphere at 298 and 15 K, CO chemisorption and volumetric oxidation. α-Fe0, Fe3O4 and Fe2+ were identified in the catalyst calcined in air. Instead, only α-Fe0 was detected in the catalyst calcined in N2. The iron metallic crystal sizes were estimated as ≈2 nm for the former and ≈29 nm for the last one. The different oxide crystal sizes, obtained from the diverse calcination atmospheres, have led to different structural properties of the reduced solids. It has been possible to reduce totally the existing iron in an Fe/SiO2 system with iron loading lower than 10% (wt/wt).  相似文献   

19.
Fourier transform infrared spectroscopy has been applied to the study of cyclohexane adsorbed on Al2O3 and Pt/Al2O3 surfaces. Earlier studies of benzene on these same materials have also been extended to include benzene adsorbed on a Pt/Al2O3 surface which contains structured carbon residues. The data provide indirect evidence for the formation of a carbon residue on Pt/Al2O3 which retains the six-membered cyclic structure of the parent adsorbates. The carbon residue can be formed upon vacuum heating of the parent C6 ring molecules chemiorbed on Pt/Al2O3. There is spectroscopic evidence that cyclohexane dehydrogenates on Pt/Al2O3 at 300 K to form two different chemisorbed species; a π-bonded benzene and a dissociated σ-bonded benzene. These two chemisorbed species have CH stretching vibrations centered at 3030 and 2947 cm?1, respectively. Benzene added to a clean catalyst surface forms only a π-bonded benzene. However, benzene added to Pt/Al2O3 with ordered carbon residues forms both π- and σ-bonded benzenes. The addition of H2 at 300 K to any of the π- or σ-bonded benzenes or to the carbon residue results in the formation of cyclohexane physisorbed on the catalyst. The absence of CH3 groups upon hydrogenation suggests the lack of CC bond breaking during adsorption or hydrogenation. Simultaneous infrared and thermal desorption studies on chemisorbed deuterated benzene (from C6D12) indicate that the a-bonded species exchange H from the surface OH groups of the alumina support more readily than does the π-bonded benzene. In addition to hydrogen exchange with the support, thermal desorption experiments indicate the oxidation of a portion of the chemisorbed hydrocarbons and/or carbon residue by oxygen from the alumina support. Therefore, the support is capable of playing a direct role in reactions occurring on the catalyst surface.  相似文献   

20.
Mössbauer spectra of fayalite-, 7#x03B1;-Fe2SiO4, powder and single crystals were taken in the antiferromagnetic temperature region below T N?65 K. The orientation of the efg and H(0) with respect to the crystallographic axes was determined as function of the temperature and compared to neutron diffraction and magnetic susceptibility data. A similar study was performed with Li‐acmite LiFeSi2O6, whose magnetic structure can be regarded as a model compound for quasi one‐dimensional systems. Synthetic annite KFe3[AlSi3O10(OH)2] has to contain at least about 10% Fe3+ in order to be stable. A comparison of the evaluation of the spectra assuming either Lorentzian line shape of the doublets or quadrupole splitting distributions QSDs shows that Fe3+/Fe2+‐ratios can be determined precisely by both methods. However, M2/M1-site distributions cannot be evaluated with great accuracy. In ilvaite CaFe3[Si2O7/O/(OH)], there is a thermally activated intersite electron hopping between Fe2+ and Fe3+ at temperatures around 300 K in a double octahedron chain. At temperatures above 395 K there is extended electron delocalization in a narrow d‐ or polaron‐band. The substitution of Fe by Mn favours both effects and lowers the temperature of the crystallographic phase transition monoclinic to orthorhombic distinctly. In the solid solution series member acmite(50%)‐hedenbergite(50%) Na0.5Ca0.5Fe2[Si2O6] just intersite electron hopping between Fe2+ and Fe3+ in the M1 octahedron chain and no formation of polaron bands is observed. This is explained by the larger Fe–Fe‐intrachain distances compared to those in ilvaite or magnetite.  相似文献   

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