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1.
TiO2光催化反应机理及动力学研究进展   总被引:4,自引:0,他引:4  
光催化处理环境污染物是基于催化反应过程中的一些自由基对污染物的氧化或还原作用,反应途径通常是HO·攻击或穴直接攻击,对可见光敏感的化合物也可能通过激发态来分解。动力学的表述多数符合L-H模式,广泛研究了L-H模式下的吸附与催化活性的关系,对动力学的研究也是了解其反应机理的重要途径。  相似文献   

2.
用玻璃外循环无梯度反应器研究了丁烯异构化L-H机理复杂反应动力学. 用正交设计法估计了动力学方程中的参数. 色谱法测定了丁烯吸附热, 并研究了异构化生成反-2-丁烯及顺-2-丁烯的动力学方程.  相似文献   

3.
光电协同效应降解饮用水中邻氯酚的机理与动力学   总被引:8,自引:2,他引:6       下载免费PDF全文
要 在集成光解电解一体化反应器中, 以邻氯酚(2-CP)为模型污染物, 通过产物和动力学分析详细探讨了光电复合作用的协同效应机理, 建立了光电复合作用的动力学模式. 表观动力学常数的对比表明复合协同作用对于总有机碳(TOC)的去除具有显著的协同效应. 研究表明, 光电复合作用在研究条件下对污染物的降解具有多层次、多途径的互补效应, 降解反应的途径不止是单独的光解与电解途径的简单累加, 而是通过新的作用途径组合构成光电协同效应. 通过紫外光辐射激发和定向直流电场作用控制电极中毒和污染物分子的激发态及其迁移趋势, 从而大大提高了降解反应的效率. 通过光电复合作用能够触发构成高级氧化的多种自由基链反应, 从而取得水中有机污染物的快速、完全的矿化. 动力学分析表明, 光电协同作用在溶液中形成的羟基自由基(OH·)反应是去除TOC的主要途径.  相似文献   

4.
在Pt/Al2O3催化剂上乙醇深度氧化的稳态及非稳态动力学   总被引:1,自引:0,他引:1  
俞启全  金韵 《分子催化》1989,3(2):89-95
用玻璃外循环无梯度反应器研究了在Pt/Al_2O_3催化剂上乙醇深度氧化稳态动力学.乙醇深度氧化稳态动力学可用乙醇及氧吸附、CO_2吸附阻碍的L-H模型描述.动力学方程(1)式中的参数用正交设计法描述.用脉冲法测定了乙醇、氧及CO_2的吸附热.在实验中观察到在Pt/Al_2O_3催化剂上乙醇深度氧化的振荡现象.  相似文献   

5.
NO2^—离子的光催化反应   总被引:4,自引:1,他引:3  
对NO2离子的TiO2光催化反应研究发现,该光催化反应用于消除NO2离子效果显著.反应的动力学研究表明,NO2离子的TiO2光催化反应是一个较复杂的多步反应,其中,NO2离子在TiO2催化剂表面的光催化氧化是该反应的控制步骤,反应符合L-H动力学规律.研究还发现,反应气氛对该光催化反应有明显影响.在实验条件下未观测到产物对反应的影响.  相似文献   

6.
在La-Cr-Fe 钙钛矿型催化剂上用玻璃外循环无梯度反应器研究了丁烷、反-2-丁烯及顺-2-丁烯深度氧化动力学。丁烷、反-2-丁烯及顺-2-丁烯深度氧化动力学服从L-H机理模型。用正交设计法估计了动力学方程中的参数值。丁烷、反-2-丁烯及顺-2-丁烯深度氧化的L-H 机理模型为脉冲实验鉴别。用脉冲色谱法测定了“2-丁烯”及O_2的吸附热。丁烷、反-2-丁烯及顺-2-丁烯深度氧化的CO_2生成速度用(7)式描述。  相似文献   

7.
气相苯在TiO2光催化剂上吸附常数和光催化反应常数测定   总被引:2,自引:0,他引:2  
采用溶胶-凝胶法制备TiO2光催化剂以及掺杂Fe3 和Ce3 的TiO2光催化剂,进行间歇式光催化降解气相苯动力学实验,基于光催化Langmuir-Hinshelwood反应动力学模型(L-H模型),测定气相苯在3种光催化剂上的降解动力学常数和吸附平衡常数.根据光催化降解气相苯实验动力学曲线和L-H模型,估算出TiO2、Fe3 /TiO2和Ce3 /TiO2光催化剂光催化降解苯的反应速率常数k和Langmuir吸附常数K分别为0.5247g/m3·min、1.523g/m3·min、1.010g/m3·min和8.605×10-2m3/g、2.390×10-2m3/g、3.928×10-2m3/g.掺杂Fe3 和Ce3 可明显提高光催化剂光催化降解苯的反应速率常数k,其中Fe3 /TiO2,的反应速率常数k最大.  相似文献   

8.
丁烯-1异构化复杂反应动力学   总被引:1,自引:0,他引:1  
MoBiP_(1∶8)/SiO_2催化剂的X衍射实验证实存在BiPO_4物相,用吸附指示剂正丁胺滴定法测定了催化剂显中等强度酸性。催化剂上吸附吡啶的红外光谱实验证实催化剂存在质子酸和Lewis酸中心。用脉冲法测定了丁烯-1及丁烯-2的吸附热。用玻璃外循环无梯度反应器研究了MbBiP_(0.8)/SiO_2催化剂的丁烯-1异构化动力学。动力学方程服从丁烯异构化三角反应的L-H机理。用线性最小二乘法估计简化的L-H机理动力学方程中的参数,法方程的系数矩阵的条件数高达10~8。用正交设计法估计了丁烯-1异构化复杂反应动力学方程中的参数得到满意的结果。反-丁烯-2及顺-丁烯-2异构化生成速度分别为:  相似文献   

9.
光催化降解污染物制氢反应与原位红外表征   总被引:6,自引:0,他引:6  
研究了在Pt/TiO2悬浮体系中单组分和双组分污染物为电子给体光催化分解水制氢反应. 比较了污染物甲醛、甲酸和草酸为电子给体光催化放氢反应效率,发现其活性为:草酸 >甲酸 >甲醛.原位ATR(衰减全反射)红外研究结果表明,光催化放氢活性与污染物吸附特性有关.还研究了草酸与甲酸双组分污染物体系的光解水放氢和污染物降解动力学,发现总的放氢和污染物降解速率与污染物组分在TiO2表面的吸附强度和溶液浓度有关.污染物在TiO2表面的竞争吸附决定了反应动力学.原位ATR-IR方法研究双组分混合物体系的吸附,直观地证实了上述结果.  相似文献   

10.
在Fe-Zn-Mg催化剂上丁烯-1氧化脱氢制丁二烯动力学   总被引:1,自引:0,他引:1  
用玻璃流动外循环反应器研究了Fe_(4.9)Zn_(0.9_Mg_(0.1)(原子比)催化剂上丁烯-1氧化脱氢动力学,丁烯-1氧化脱氢制丁二烯、丁烯-1及丁二烯深度氧化生成CO_2的动力学用双反应分子强吸附的L-H(Lang muir Hinshelwood)机理方程描述。速度方程的参数用非线性最小二乘法估计,得丁二烯生成速度r_D和CO_2生成速度r_(co)_2的动力学方程式。  相似文献   

11.
Visible‐light photocatalysis has evolved over the last decade into a widely used method in organic synthesis. Photocatalytic variants have been reported for many important transformations, such as cross‐coupling reactions, α‐amino functionalizations, cycloadditions, ATRA reactions, or fluorinations. To help chemists select photocatalytic methods for their synthesis, we compare in this Review classical and photocatalytic procedures for selected classes of reactions and highlight their advantages and limitations. In many cases, the photocatalytic reactions proceed under milder reaction conditions, typically at room temperature, and stoichiometric reagents are replaced by simple oxidants or reductants, such as air, oxygen, or amines. Does visible‐light photocatalysis make a difference in organic synthesis? The prospect of shuttling electrons back and forth to substrates and intermediates or to selectively transfer energy through a visible‐light‐absorbing photocatalyst holds the promise to improve current procedures in radical chemistry and to open up new avenues by accessing reactive species hitherto unknown, especially by merging photocatalysis with organo‐ or metal catalysis.  相似文献   

12.
Semiconductor photocatalysis is a trustworthy approach to harvest clean solar light for energy conversions, while state‐of‐the‐art catalytic efficiencies are unsatisfactory because of the finite light response and/or recombination of robust charge carriers. Along with the development of modern material characterization techniques and electronic‐structure computations, oxygen vacancies (OVs) on the surface of real photocatalysts, even in infinitesimal concentration, are found to play a more decisive role in determining the kinetics, energetics, and mechanisms of photocatalytic reactions. This Review endeavors to clarify the inherent functionality of OVs in photocatalysis at the surface molecular level using 2D BiOCl as the platform. Structure sensitivity of OVs on reactivity and selectivity of photocatalytic reactions is intensely discussed via confining OVs onto prototypical BiOCl surfaces of different structures. The critical understanding of OVs chemistry can help consolidate and advance the fundamental theories of photocatalysis, and also offer new perspectives and guidelines for the rational design of catalysts with satisfactory performance.  相似文献   

13.
Green and efficient procedures are essential for the chemoselective hydrogenation of functionalized nitroarenes to form industrially important anilines. Herein, it is shown that visible‐light‐driven, chemoselective hydrogenation of functionalized nitroarenes with groups sensitive to forming anilines can be achieved in good to excellent yields (82–100 %) in water under relatively mild conditions and catalyzed by low‐cost and recyclable graphitic carbon nitride. The process is also applicable to gram‐scale reaction, with a yield of aniline of 86 %. A study of the mechanism reveals that visible‐light‐induced electrons are responsible for the hydrogenation reactions, and thermal energy can also promote the photocatalytic activity. A study of the kinetics shows that this reaction possibly occurs through one‐step hydrogenation or stepwise condensation routes. A wide range of applications can be expected for this green, efficient, and highly selective photocatalysis system in reduction reactions for the synthesis of fine chemicals.  相似文献   

14.
Recent advances in direct‐use plasmonic‐metal nanoparticles (NPs) as photocatalysts to drive organic synthesis reactions under visible‐light irradiation have attracted great interest. Plasmonic‐metal NPs are characterized by their strong interaction with visible light through excitation of the localized surface plasmon resonance (LSPR). Herein, we review recent developments in direct photocatalysis using plasmonic‐metal NPs and their applications. We focus on the role played by the LSPR of the metal NPs in catalyzing organic transformations and, more broadly, the role that light irradiation plays in catalyzing the reactions. Through this, the reaction mechanisms that these light‐excited energetic electrons promote will be highlighted. This review will be of particular interest to researchers who are designing and fabricating new plasmonic‐metal NP photocatalysts by identifying important reaction mechanisms that occur through light irradiation.  相似文献   

15.
Charge carrier transfer processes are very important and play a vital role in photocatalytic reactions. A fundamental understanding of the kinetics and mechanisms of these charge transfer processes is crucial from the viewpoint of developing efficient photocatalysis systems for large-scale industrialization. In this work, recent efforts concerning the understanding of the kinetics and the mechanisms of the charge transfer in photocatalytic processes have been reviewed. Fundamental aspects involved in these charge transfer processes, such as charge generation, charge trapping, charge recombination, and electron and hole transfer are primarily discussed. Moreover, some recent studies focusing on enhancing the photocatalytic efficiency by improving the charge transfer and separation are also reviewed.  相似文献   

16.
The in situ open‐circuit voltages (Voc) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO2 under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO2 and from the methanol molecule. The electron injection from methanol to TiO2 is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO2 surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO2 leads to the upshift of the Fermi level of electrons in TiO2, which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano‐TiO2 is continuously changing during photocatalysis as electrons are injected from methanol to TiO2. Combined with the apparent Langmuir–Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO2 CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of Voc with time during photocatalysis.  相似文献   

17.
张西旺  王怡中 《化学通报》2005,68(11):807-813,866
光催化氧化作为高级氧化技术的一种在环境保护领域具有重要的应用前景。就目前而言,量子效率低、反应速度慢等缺点制约了光催化氧化的应用。投加无机氧化剂能够通过抑制空穴电子对的复合及产生其它氧化物种等方式强化光催化、提高光催化效率,推进光催化在实际中应用的进程。本文较详细地阐述了不同无机氧化剂强化光催化的机理、研究进展,并对无机氧化剂在光催化氧化中的应用前景进行展望。  相似文献   

18.
Plasmon‐mediated carrier transfer (PMCT) at metal–semiconductor heterojunctions has been extensively exploited to drive photochemical reactions, offering intriguing opportunities for solar photocatalysis. However, to date, most studies have been conducted using noble metals. Inexpensive materials capable of generating and transferring hot carriers for photocatalysis via PMCT have been rarely explored. Here, we demonstrate that the plasmon excitation of nickel induces the transfer of both hot electrons and holes from Ni to TiO2 in a rationally designed Ni–TiO2 heterostructure. Furthermore, it is discovered that the transferred hot electrons either occupy oxygen vacancies (VO) or produce Ti3+ on TiO2, while the transferred hot holes are located on surface oxygens at TiO2. Moreover, the transferred hot electrons are identified to play a primary role in driving the degradation of methylene blue (MB). Taken together, our results validate Ni as a promising low‐cost plasmonic material for prompting visible‐light photochemical reactions.  相似文献   

19.
姚百新  王亚  臧荣斌  杨秀丽  解明华 《化学通报》2021,84(11):1224-1230
氯氧化铋(BiOCl)较大的禁带宽度使得其只能对紫外光产生响应,严重制约了其进一步光催化应用。为实现BiOCl对可见光的利用,以In2S3为可见光光敏剂,并基于高效实用的机械研磨手段构建BiOCl/In2S3复合可见光催化剂。通过扫描电子显微镜(SEM)、X射线衍射(EDS)、X射线衍射(XRD)、红外光谱(FT-IR)和紫外-可见漫反射光谱(UV-Vis DRS)等方法对催化剂的形貌和结构进行表征。选择盐酸四环素(TC)可见光催化降解为评价模型,系统研究了BiOCl/In2S3复合比例对光催化活性的影响。结果表明两者复合比例为1:1时具有最佳的光催化活性,在可见光照射下对TC的降解效率高达91.4%,且经3次循环降解效率仍保持在87.3%。机理研究表明,In2S3被可见光激发产生电子注入BiOCl的导带(CB),能有效提升载流子的分离效率,而h+和?O2-是光降解过程中的主要活性物质。该项研究工作充分表明了In2S3对BiOCl的高效光敏活性,展示了物理复合法在新型高效可见光催化体系构建中的重要意义。  相似文献   

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