Pd/Al2O3催化剂上低浓度CO氧化的研究

采用共沉淀法和浸渍法制备了2%Pd-Al2O3催化剂,在固定反应器中评价不同制备方法(共沉淀和浸渍)、助剂(1%K和1%Mg)、预处理方法(快速氧化和缓慢还原)、空速(726h-1、1638h-1和5274h-1)情况下2%Pd-Al2O3催化剂对CO氧化的催化活性。结果表明,共沉淀法制备的2%Pd50%Zr-Al2O3催化剂有较高的反应活性,该催化剂经缓慢还原预处理活化,在温度为70℃时就可以使低浓度的CO完全氧化。     

低温CO催化氧化负载型Pd催化剂研究进展

综述了低温CO催化氧化负载型Pd催化剂在制备方法、载体的选用和催化机理等方面的研究进展,并介绍了该类催化剂的最新进展.在文章末对该催化剂领域尚待深入研究的问题进行了探讨.     

负载型金催化剂上的CO氧化

在过去的10年中，由于含有微小的纳米级金的负载型金催化剂的特殊活性，因此对此催化剂的研究热情空前高涨。这种催化剂上的一氧化碳低温氧化已经得到深入研究。尽管研究的步伐在加快，但是如制备参数和催化活性的关系、活性中心的性质和反应的机理等的议题仍然是时下争论的课题。这些争论的解决需要进一步的研究。     

铂金催化剂上CO选择性氧化机理研究进展

简要介绍了金、铂催化剂上CO的选择性氧化反应,详细论述了该反应动力学及反应机理的确立,指出载体、氧的活化位、氢气及不同促进剂的影响等是今后研究的方向.     

Pt-Fe催化剂次表层Fe结构表面的CO氧化反应性能

利用紫外光电子能谱等表面科学方法,研究了Pt-Fe模型催化剂的次表层Fe结构[即Pt/Fe/Pt(111)结构]在不同条件下CO的吸附及其氧化反应。结果表明,Pt/Fe/Pt(111)结构在H_2气氛或者超高真空中是种稳定结构,最外层的原子与Pt(111)相同,是密排的铂原子面;但次表层的原子中有约0.5单层的铁原子,使费米边附近(0~2.0)e V的电子态密度明显低于Pt(111)表面,从而改变表面的CO和O_2吸附以及反应性能。程序升温的紫外光电子能谱结果显示,Pt/Fe/Pt(111)表面在(100~300)K,CO的吸附受温度的影响不明显,且O_2能够吸附、活化并使共吸附的CO发生氧化反应;当温度为300 K时,O_2无法在Pt/Fe/Pt(111)表面吸附、活化,所以CO氧化反应无法进行。Pt/Fe/Pt(111)结构虽然能有效地减弱CO的吸附从而避免CO毒化的问题,但O_2的吸附和活化也受到显著抑制并影响到一定条件下CO的氧化反应。     

铂催化剂上乙烯和一氧化碳同时氧化反应多定态特性的实验研究

对铂催化剂上乙烯和一氧化碳同时氧化反应多定态特性的实验研究结果表明：在实验条件下体系最多存在有两个稳定的定态,随乙烯和／或一氧化碳浓度的增加,系统的点火温度升高,熄火温度下降,存在多定态的操作参数区域增大;在较高的乙烯和／或一氧化碳浓度条件下,系统将出现自持,实验观测不到熄火现象。通过对体系多定态特性的分析可知,同时氧化反应体系的多定态特性并不等于两个单独氧化反应体系多定态特性的简单迭加,在两个反应之间,除了热量的相互作用外,还存在着动力学抑制作用。     

纳米催化剂及其在CO催化氧化领域的研究进展

综述了纳米催化剂的研究进展与制备方法，详细介绍了用于CO催化氧化的纳米催化剂的研究概况，指出纳米催化剂的催化活性和选择性大大优于常规催化剂，纳米复合稀土催化剂在汽车尾气控制方面前景诱人。     

用于CO氧化的单原子催化剂研究进展

简述了用于CO氧化的单原子催化剂制备方法,总结了单原子催化CO氧化的反应机理,并以低温CO氧化为主线,重点介绍了近年来在实验和理论上研究的用于CO氧化的贵金属(Pt、Au、Pd、Rh、Ir、Ru)和非贵金属单原子催化剂,为今后研究单原子催化剂提供参考.     

铯—铷—钒系低温硫酸催化剂上SO2氧化反应速率的机理解释

以碱金属盐为助催化剂的铯－铷－钒系硫催化剂,在380－520℃下SO2氧化反应机理为三步催化反应,并推导出其动力机理模型：r=(k1P^1/2o2)/(k2 k3Pso3 Pso3/Pso2)(1-Pso3/Pso2P^1/2o2Kp)。采用内循环无梯度反应器测定了SO2氧化反应动力学数据,并利用Powell法对动力学模型进行参数估算,得到：k1=0.152exp(=62073/RT),k2=8.18exp(-2384/RT),k3=0.221exp(-18949/RT)。方差分别表明,在显著性水平0．01下,三步反应机理模型对反应速率实验值拟合较好,标准偏差为0．242。     

CO在铂催化剂上选择氧化的反应机理和本征动力学研究(续)

用气相色谱脉冲技术研究了在负载型铂催化剂上CO选择氧化过程的反应机理,获知了CO氧化和H2氧化两个平行竞争反应各自的反应历程和CO氧化具有高选择性的原因,并推导出动力学方程。采用最小容积准则的序贯实验设计法安排了动力学实验点。应用Gauss-Newton法对加权非线性最小二乘形式的目标函数进行了参数优化。对模型的残差分析证实了机理研究得到的动力学方程是合适的。     

Study on SO2 Poisoning Mechanism of CO Catalytic Oxidation Reaction on Copper–Cerium Catalyst

CuO–CeO₂ (Cu–Ce) catalyst with a CuO/CeO₂ mass ratio of 1 prepared by a sol–gel method is used in the CO catalytic oxidation reaction in the actual industrial sulfur-containing atmosphere. At a reaction temperature of 200 °C, the catalyst exhibits quite different stability under sulfur-containing and sulfur-free conditions. When 30 ppm SO₂ was added to the feed gas, the Cu–Ce catalyst had an initial CO conversion rate of 100%, gradually decreasing after 26 h, and this catalyst completely deactivated at about 50 h. However, the CO conversion rate of the catalyst under sulfur-free conditions could be nearly maintained at 100% within the measured time range (60 h). The results of IR, Raman, and XPS characterizations proved that the accumulation of cerium sulfate on the Cu–Ce catalyst would cover the active sites of the catalyst, eventually leading to the complete deactivation of the catalyst, which provides favorable evidence for the actual industrial anti-sulfur application.

Graphical Abstract

     

Elucidation of CO2 Formation Mechanism in CO + NO Reaction on Pd(111) and Pd(110) Surfaces Using IR Chemiluminescence Method

The infrared (IR) chemiluminescence technique was applied to steady-state CO oxidation by NO on Pd(111) and Pd(110). From a comparison of IR emission spectra of CO₂ between the CO + NO and CO + O₂ reactions, it was found that the vibrational energy states of CO₂ in the CO + NO reaction were similar to those in the CO + O₂ reaction. This indicates that the reaction path of CO₂ formation in CO + NO is the same as that in CO + O₂, although the vibrational states are very dependent on the surface structure.     

Reaction Mechanism of Anthraquinone Hydrogenation over Pd Based Monometallic and Bimetallic Catalyst

Catalysis Letters - In this work, the reaction mechanism of 2-ethylanthraquinone (eAQ) and Tetrahydro-2-ethyl anthraquinone (H4eAQ) hydrogenation over Pd and Pd-M bimetallic catalysts...     

The Mechanism for the Selective Oxidation of CO Enhanced by H2O on a Novel PROC Catalyst

Preferential oxidation (PROX) reaction of CO in H₂ catalyzed by a new catalyst of FeO _x /Pt/TiO₂ (Fe: Pt: TiO₂ = 100: 1: 100) was studied by dynamic in-situ DRIFT-IR spectroscopy. The oxidation of CO is markedly enhanced by H₂ and H₂O, and the enhancement by H₂/D₂ and H₂O/D₂O takes a common hydrogen isotope. Dynamics of DRIFT-IR spectroscopy suggests that the oxidation of CO with O₂ in the absence of H₂ proceeds via bicarbonate intermediate. In contrast, rapid oxidation of CO in the presence of H₂ proceeds via HCOO intermediate and the subsequent oxidation of HCOO by the reaction with OH, that is, CO + OH→ HCOO and HCOO + OH → CO₂ + H₂O. The latter reaction is a rate determining step being responsible for a common hydrogen isotope effect by H₂/D₂ and H₂O/D₂O.     

Oscillations During Catalytic Oxidation of Propane over a Nickel Wire

Catalytic oxidation of propane with oxygen over a nickel wire at the temperature range 650–750°C and the reagent pressure ca. 1 Torr occurs in a self-oscillating mode. Periodic changes of the reagent concentration are found to be accompanied by significant synchronous changes of the catalyst temperature.     

A Review on CO Oxidation Over Copper Chromite Catalyst

CO is a toxic and detrimental air pollutant. It not only affects human beings but also vegetation and indirectly increases global warming. An estimate has shown that vehicular exhaust contributes about 64% of the CO pollution in developed countries. Due to the exponentially increasing number of automobiles on roads, CO concentrations have reached an alarming level in urban areas and regulatory measures had been adopted to curb the menace of vehicular pollution. To control vehicular exhaust pollution, end-of-pipe-technology using noble metals catalytic converters are recommended. The increasing prices of noble metals with the increasing number of vehicles motivates the investigation of material concepts to reduce the precious metal content in automotive catalysts or to find a substitute for noble metals. Among non-noble metals, copper chromite is found to be most promising and exhibits comparable activity for CO oxidation to that of precious metals. Further, low cost, easy availability and advance synthesis methods with stabilizer, promoter, etc. advocates for the use of copper chromite as an auto exhaust purification catalyst. There is a lot of literature available on copper chromite catalyst for CO oxidation, but still there is a gap in the literature for a review article solely devoted to copper chromite catalyst for CO oxidation. Therefore, in an attempt to fill this gap, the present review updates and evaluates the progress and future scope for copper chromite catalyst for purification of exhaust gases of low sulfur contents. The requirement to develop successful methods to reclaim the components of the spent copper chromite catalyst for its safe disposal is also discussed. The paper is useful for people who want to quickly know the state of art and all the aspects concerning the investigated materials. A total of 265 references have been cited.     

Study on the Mechanism of CO Formation in Reverse Water Gas Shift Reaction Over Cu/SiO2 Catalyst by Pulse Reaction, TPD and TPR

The mechanism of reverse water gas shift reaction over Cu catalyst was studied by pulse reaction with QMS monitoring, temperature programmed desorption (TPD) and temperature programmed reduction (TPR) of Cu/SiO₂ catalyst. The reduced and/or oxidized copper offered low catalytic activity for the dissociation of CO₂ to CO in the pulse reaction study with 1 ml volume of He/CO₂, but the rate of CO formation was significantly enhanced with H₂ participating in the reaction. The TPD spectra of CO₂ obtained by feeding H₂/CO₂ over copper at 773 K provided strong evidence of the formation of formate at high temperature. The formate derived from the association of H₂ and CO₂ is proposed to be the key intermediate for CO production. The formate dissociation mechanism is the major reaction route for CO production.