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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
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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
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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
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
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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
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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
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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
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CuZSM—5分子筛上苯酚羟化制苯二酚 总被引:1,自引:0,他引:1
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
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Light-emittingelectrochemicalcellisanewpromisingdeviceforlarge-areadisplay'.Theelectrochemicaldopinginthepolymerblendofpoly(ethyleneoxide)(PEO)andpoly(l,4-phenylenevinylene)(PPV)usedintheLECplaysaveryimpo~roleinitselectroluminescence.TheaimofthisinvestigationistounderstandiftheadditionofPEOaffectstheelectrochemicalbehaviorofPPVandtheeffectsofdopantsonsuchablendsystem.Accordingtotheprocessesreportedintheliteramresl',wepreparedthepolymerblendonaPtelectrodewhichwasusedastheworkingelectrode… 相似文献
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A. D. Davydov V. M. Volgin V. V. Lyubimov 《Russian Journal of Electrochemistry》2004,40(12):1230-1265
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
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Disposable and Flexible Electrochemical Paper-based Analytical Devices Using Low-cost Conductive Ink
Wilson Tiago Fonseca Karla Ribeiro Castro Tássia Regina de Oliveira Ronaldo Censi Faria 《Electroanalysis》2021,33(6):1520-1527
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
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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.
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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
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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
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Karachevtseva L. A. Litvinenko O. A. Stronskaya E. I. 《Theoretical and Experimental Chemistry》2003,39(6):385-388
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