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1.
在常压及650℃下,考察了CaO,SrO,La2O3,ZnO,TiO2,CeO2和MnO2膜上外加电流为16~90mA时传递物系的甲烷氧化偶联反应结果,结果发现,在n型p型半导体催化膜上,CO2,C2H4和C2H6的生成速率都随泵氧量的增加而增大,而C2烃选择性随泵氧量的增加而下降,但p型半导体膜上的C2烃选择性比n型半导体膜上的要高:q型半导体膜上C2烃选择性与其电导率大小顺序相一致,增强因子的  相似文献   

2.
刘育  薛锦玲 《分子催化》1998,12(5):389-391
考察了Na2WO4-Mn/SiO2催化剂上甲烷与二氧化碳反应制C2烃及其反应机理,820℃时,C2烃选择性可达94.5%,随着着温度继续升高,虽然甲烷的转化增加,但C2烃选择性逐渐降低。O2-TPD,CH4及脉冲实验表明,800℃脱附的表面昌格氧为活性氧物种,在催化甲烷活化的同时,CO2可在该催化剂上活化分解为活性氧物种。  相似文献   

3.
考察了Na2WO4-Mn/SiO2催化剂上甲烷与二氧化碳反应制C2烃及其反应机理,820℃时,C2烃选择性可达94.5%.随着温度的继续升高,虽然甲烷的转化增加,但C2烃选择性逐渐降低.O2-TPD、CH4及脉冲实验表明,800℃脱附的表面晶格氧为活性氧物种,在催化甲烷活化的同时,CO2可在该催化剂上活化分解为活性氧物种(CO2→CO+O*).  相似文献   

4.
主要用第四周期金属元素的氧化物与Al2O3的复合氧化物催化剂上甲烷氧化的结果证实了催化剂设计中的预测:(1)催化剂首先应能解离活化甲烷,(2)催化剂要能较快地活化O2分子.只有同时满足这两个条件,催化剂才可能有较好的甲烷部分氧化活性.第四周期元素中只有镍具有这样的性质.Cu,Mn,Cr,La,Ca,Zn等氧化物的添加可明显提高Ni-Al2O3催化剂的甲烷部分氧化性能,其中Cu的助催化性能最好.催化剂NiO-CuO-Al2O3,NiO-MnO-Al2O3,NiO-Cr2O3-Al2O3的反应活性和选择性顺序,与金属Cu,Mn,Cr上CO和H2脱附的顺序是一致的  相似文献   

5.
2%Mn2O3-5%Na2WO4/SiO2催化剂上的甲烷氧化偶联反应动力学   总被引:1,自引:0,他引:1  
吴金刚  李树本 《催化学报》1995,16(5):376-380
在Mn2O3-Na2WO4/SiO2催化剂上的甲烷氧化偶联反应可用Rideal-redox机理描述,它包括均相及多相两个步骤。甲基自由基的生成是一个多相过程,C2烃的生成是一个均相过程。催化剂的活性同氧化速率和CH4与表面氧种的反应速率有关,C2烃的选择性与甲基自由基氧化速率常数和甲基自由基偶联速率常数的比值有关,这些常数均可从实验中求得。  相似文献   

6.
助剂MgO对Pd/γ—Al2O3催化剂上CO氧化反应的作用   总被引:1,自引:0,他引:1  
以CO氧化为模型反应,考察了Pd/γ- Al2O3 体系中以不同方式加入MgO 对催化剂性能的影响,结果证实助剂MgO能较大幅度提高Pd/γ- Al2O3 对CO 氧化反应的催化活性。MgO能均匀地分散于γ- Al2O3 上,使CO的起燃温度降低达44℃。对样品的XRD、TPR、XPS及氧吸附等表征结果表明,共浸型的Pd- MgO/Al2O3 体系具有最高的Pd 分散度;分浸型的Pd- MgO/Al2O3 体系Pd 分散度亦高于Pd/Al2O3 ,且能提高催化剂表面活性Pd 的含量。表面MgO对氧的浓缩作用有利于CO 的氧化。并讨论了助剂MgO与Pd 的协同作用对其活性的影响  相似文献   

7.
在Mn2O3-Na2WO4/SiO4催化剂上的甲烷氧化偶联反应可用Rideal-redox机理描述,它包括均相及多相两个步骤.甲基自由基的生成是一个多相过程(表面反应),C2烃的生成是一个均相过程(气相反应).催化剂的活性同氧化速率(k1)和CH4与表面氧种的反应速率(k2)有关,C2烃的选择性与甲基自由基氧化速率常数和甲基自由基偶联速率常数的比值(k/k4)有关,这些常数均可从实验中求得.  相似文献   

8.
CuZSM-5分子筛上苯酚羟化制苯二酚   总被引:4,自引:0,他引:4  
在Na2O-SiO2-CuO-H2O体系中以15%TPABr-85%HMDA为模板剂合成了CuZSM-5分子筛,并用XRD,IR及SEM等方法进行了表征,考察了CuZSM-5分子筛催化苯酚与过氧化氢的羟化活性,研究了催化剂用量、反应温度、反应时间及n(PhOH)/n(H2O2)等对羟化活性的影响.  相似文献   

9.
研究了Fe-P-O催化剂对甲烷氧化偶联(OCM)的低温催化活性,考察了催化剂组分的优化,最适宜的反应温区,反应过程参数,助催化剂组分,催化剂的晶型结构和活性相以及F:元素键合状态的XPS谱.确定了8%LiNO3-0.8Fe/P催化剂在650℃,CH4:O2:Ar=2:1:2及GHSV=3000h-1条件下,可获得甲烷转化率为11.90%和C2烃选择性为69.81%的结果.添加LiNO3为助催成分,可有效改善催化剂表面酸活性中心的分布,防止OCM中深度氧化和表面积炭,提高C2和C2烃选择性.该催化剂为可变价型,是六方形和料方形两种晶型结构的复合磷酸铁,活性相为斜方形FePO4物相.  相似文献   

10.
CuZSM—5分子筛上苯酚羟化制苯二酚   总被引:1,自引:0,他引:1  
于剑锋  张春雷 《催化学报》1997,18(2):130-134
在Na2O-SiO2-CuO-H2O体系中以15%TPABr-85%HMDA为模板剂合成了CuZSM-5分子筛,并用XRD,IR及SEM等方法进行了表征,考察了CuZSM-5分子筛催化苯酚与过氧化氢的羟化活性,研究了催化剂用量,反应温度,反应时间及n(PbOH)/n(H2O2)等对羟化活性的影响。  相似文献   

11.
电化学氟化的新进展   总被引:1,自引:0,他引:1  
沈雪明  胡昌明 《有机化学》1993,13(2):122-128
电化学氟化是利用电极反应将氟直接引入有机或无机物的一种重要方法。有机物的电化学氟化方法有两种: 一是Simons于1941年发明的, 用镍作阳极, 在无水氟化氢溶液中, 电解制备全氟化合物的方法。此方法在近年来有不少改进。另一是1970年Rozhkov提出的, 以有机溶剂(如含Et3N.3HF的MeCN)为介质, 在铂阳极上,氧化得到单氟化产物的方法。本文全面地综述了这两种方法, 并着重于最新民发展。  相似文献   

12.
由于过渡金属替代的多金属氧酸盐(polyoxometalates)的催化、磁性、电化学等性质,越来越受到人们的关注~([1-7]). 目前世界上约有10亿人生活在缺碘地区,碘的缺乏严重影响人类健康.对食物、生物临床、环境及工业中碘含量检测很有实际意义.  相似文献   

13.
Light-emittingelectrochemicalcellisanewpromisingdeviceforlarge-areadisplay'.Theelectrochemicaldopinginthepolymerblendofpoly(ethyleneoxide)(PEO)andpoly(l,4-phenylenevinylene)(PPV)usedintheLECplaysaveryimpo~roleinitselectroluminescence.TheaimofthisinvestigationistounderstandiftheadditionofPEOaffectstheelectrochemicalbehaviorofPPVandtheeffectsofdopantsonsuchablendsystem.Accordingtotheprocessesreportedintheliteramresl',wepreparedthepolymerblendonaPtelectrodewhichwasusedastheworkingelectrode…  相似文献   

14.
Basic problems of metal electrochemical shaping theory are considered. Exact and approxi1mate (quasi-steady-state, locally one-dimensional) methods for solving direct and inverse problems are analyzed. Experimental methods for improving the electrochemical shaping accuracy are considered.Translated from Elektrokhimiya, Vol. 40, No. 12, 2004, pp. 1438–1480.Original Russian Text Copyright © 2004 by Davydov, Volgin, Lyubimov.  相似文献   

15.
In this work, a simple procedure for construction of disposable electrochemical paper-based analytical devices (ePADs) by screen-printing using low-cost materials and a home craft electronic printer is proposed. The devices were constructed using liner paper as a substrate and carbon ink prepared with graphite powder and wood glue. The ePAD was evaluated as an electrochemical sensor and biosensor. The proposed conductive carbon-based ink can be easily prepared and is an eco-friendly and non-toxic material. The developed ePAD was simple to produce and can be used as a low-cost electrochemical sensor, at less than US $0.20 per device.  相似文献   

16.
本文介绍了近年来纳米材料电化学与生物传感器在有机微污染物检测中的研究现状,分析了这些传感器中纳米材料修饰电极的特点,重点阐述了纳米材料在有机微污染物检测中的重要作用,列举了一些纳米材料电化学与生物传感器在有机微污染物检测中的应用。最后对纳米材料电化学与生物传感器用于有机微污染物的检测研究进行了简要评述和展望。  相似文献   

17.
A strange effect was observed while using the method of quasi-simultaneous determination of electrochemical voltage noise and impedance to obtain information on the kinetics of the hydrogen evolution reaction on Ag and Cu microelectrodes. Beyond a certain polarizing current density we found microvolt-amplitude potential oscillations on both electrodes with a frequency in the 5 Hz–5 kHz range. The oscillations were observed in every single experiment with Ag and Cu, while no oscillatory behavior was observed during the control experiments with the Pt microelectrode. The presence of the oscillations indicates that the mechanism of hydrogen evolution is more complex compared to the original assumption.   相似文献   

18.
The electrochemical properties of single crystals of cerium fluoride alloyed with bivalent cations Sr2+, Ca2+, Ba2+, Sr2+ + Ca2+, Sr2+ + Ba2+, Ba2+ + Ca2+ and also with La3+ and La3+ + Ba2+ cations are studied using the dynamic voltammetry and impedance spectroscopy. The conductivity of symmetrical cells with Ag electrodes is determined using the method of impedance spectroscopy in the frequency range from 450 to 5 kHz at the temperatures from 20 to 100°C: for CeF3: Sr2+ (0.5 mol %) + Ba2+ (0.5 mol %), σ = σ0 exp[(?0.284 ± 0.005/kT]; for CeF3:Ca2+ (0.5 mol %) + Sr2+ (0.5 mol %), σ = σ0 exp[(?0.292 ± 0.017/kT]. The steady-state and dynamic voltammogams of symmetrical electrochemical cells with nonpolarizable reference electrodes and CeF3 single crystals alloyed with Sr2+, Ca2+, and Ba2+ bivalent cations exhibited ohmic polarization. For cells with CeF3 containing La3+ as an admixture, a hysteresis was observed, which could not be eliminated by chemical and electrochemical treatment of crystals. In the dynamic voltammetric curves of asymmetric cells with nonpolarizable and silver electrode and CeF3 crystals alloyed with Sr2+, Ca2+, and Ba2+, a range of ideal polarizability (from 0 to ~?2.7 V), and also cerium redox processes and silver fluorination-boundary regeneration were observed. In the dynamic voltammetric curves of asymmetric cells with CeF3 containing La3+ admixture, no range of ideal polarizability was observed; however, the reactions of silver fluorination and reduction of solid-electrolyte cerium were well pronounced at the corresponding potentials.  相似文献   

19.
Most of the current analytical methods depend largely on laboratory-based analytical techniques that require expensive and bullky equipment,potentially incur costly testing,and involve lengthy detection processes.With increasing requirements for point-of-care testing(POCT),more attention has been paid to miniaturized analytical devices.Miniaturized electrochemical(MEC)sensors,including different material-based MEC sensors(such as DNA-,paper-,and screen electrode-based),have been in strong demand in analytical science due to their easy operation,portability,high sensitivity,as well as their short analysis time.They have been applied for the detection of trace amounts of target through measuring changes in electrochemical signal,such as current,voltage,potential,or impedance,due to the oxidation/reduction of chemical/biological molecules with the help of electrodes and electrochemical units.MEC sensors present great potential for the detection of targets including small organic molecules,metal ions,and biomolecules.In recent years,MEC sensors have been broadly applied to POCT in various fields,including health care,food safety,and environmental monitoring,owing to the excellent advantages of electrochemical(EC)technologies.This review summarized the state-of-the-art advancements on various types of MEC sensors and their applications in POCT.Furthermore,the future perspectives,opportunities,and challenges in this field are also discussed.  相似文献   

20.
The process of formation of macropores in silicon with stationary irradiation and a constant current density during the electrochemical process in dependence on the initial bias on the silicon anode, U 0, has been studied. Stable formation of macropores began when the bias reached U c, corresponding to a critical concentration of holes p c at the silicon–electrolyte interface. The process of macropore formation is unstable with U 0 > U c.  相似文献   

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