CO oxidation over a Pt-Rh system. 1. Reaction on individual metals

The reaction of CO oxidation over thin films of rhodium and platinum prepared by vacuum evaporation of the metals on an inert support has been investigated at low pressures (P < 2×10^-5 mbar). Rhodium has been found to be more active than platinum in this reaction. The reasons of the higher activity of Rh are discussed.     

CO oxidation over the Pt-Rh system. 2. Reaction on an alloy

The oxidation of CO over thin films of a Pt-Rh alloy prepared by sequential vacuum evaporation of the metals on an inert support has been investigated at low pressures (P < 2'10^-5 mbar). The results are compared with the data on the individual surfaces of Pt and Rh. It is found that the activity of the alloy is intermediate between the activities of the individual metals. The effect of alloy formation on the catalytic activity in CO oxidation is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Kinetic model of CO oxidation on heterophase surface analyzed regarding COads spillover, I. Homotopic method. Effect of temperature and CO pressure

The homotopic method has been used to analyze the kinetic models of CO oxidation on two surface patches conjugated by CO_ads spillover. On each patch reaction proceeds via a three-stage mechanism but with different constants. The stability of steady-states solution has been studied. CO_ads spillover from one patch to another changes substantially the bifurcation picture of steady states and produces islands.     

Kinetics of CO oxidation on the surface of heterophase catalysts. Modeling by the Monte Carlo method

The Monte Carlo method has been used to simulate CO oxidation on a lattice consisting of various alternating patches: M1, where s(CO)>s(O₂) and M2, where s(CO)2). The reaction is shown to proceed over all the surface at low temperature as CO_ads spillover from M1 to M2 and backwards.     

Modeling of CO oxidation rate oscillations on a chain of surface patches

Autooscillations of CO oxidation rate are considered for a surface, which is a chain of uniform M1–M4 patches differing by their properties. For chain 5333 due to CO_ads diffusion, induced oscillations propagate from oscillating patches M1 (scheme 5) to patches M2–M4 (Scheme 3), which themselves do not sustain the oscillation mode.     

Canard explosion and internal signal stochastic bi-resonance in the CO oxidation on platinum surface

Canard explosion means a dramatic change fromsmall amplitude quasi-harmonic oscillation to largeamplitude relaxation oscillation, accompanied by anexponential increase of period, of a limit cycle withina very narrow interval of a control parameter. Thisphenomenon was first found in the Van Der Pol equa-tions[1], and later has been found also in chemical[2]and biological[3] systems. Generally speaking, it is theresult of multi-time scales in the system, and can bedealt with singular perturbati…     

Modelling the Oxidation of CO at the Interface of Heterophase Metal Catalysts

CO oxidation on a surface composed of two types of patches was simulated by the Monte Carlo method. Each patch has kinetic properties close to those of Pt(100) and Rh(100). The reaction rate was shown to increase significantly at the interface, involving CO_ads on platinum and O_ads on rhodium, under particular conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ir-in-CeO_2催化剂上CO氧化过程中表面碳酸盐的量热研究

应用Tian-Calvet热流量热仪与脉冲微反系统相结合的脉冲量热装置研究了Ir-in-CeO2(Ir主要包裹在CeO2里)催化剂上CO氧化过程表面碳酸盐的形成及其转化.结果表明,碳酸盐的吸附强度与CeO2表面价态直接相关.在反应中首先形成约0.07个单层覆盖度的不可逆吸附碳酸盐,随后形成约0.02个单层覆盖度的可逆吸附碳酸盐并随着Ce3+转变为Ce4+而分解.     

Features of the Reaction of the CO Molecule with a Platinum Atom and Its Diatomic Cluster

The potential energy profile of the Pt⋯CO and Pt₂⋯CO systems was calculated within the formalism of density functional theory. It was shown that bonding in these systems is only achieved after a triplet-singlet transition, which is unusual for the interaction of a CO molecule with the surface of a platinum crystal. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 278–282, September–October, 2005.     

室温CO催化氧化反应动力学的研究

本文采用无梯度反应器,考察了纳米金催化剂以及其它商品化的催化CO氧化催化剂,在不同CO浓度下催化CO氧化反应的转化率和反应速率,证明在CO初始浓度从ppm到pct数量级范围内,纳米金催化剂具有最好的催化CO室温转化的能力.     

Pt/Al2O3整体催化剂上选择性氧化脱除甲醇重整氢源中CO --副反应对CO脱除效果的影响分析

移动甲醇重整制氢是质子交换膜燃料电池（PEMFC）可行的供氢方式之一,包括水蒸气重整、部分氧化重整和自热重整。甲醇重整制氢方法不同,重整气体积组成在H245％～75％,CO215％～25％,CO1％～10％,H2O10％～20％和N20—20％变化。重整气进入PEMFC之前要经过CO水蒸气变换反应（如果采用水蒸气重整,不需要变换过程）,     

CO oxidation over supported Pt clusters at different CO coverage

CO adsorption and oxidation over supported Pt₁₄ with different CO coverage on TiO₂(110) surface were investigated using density functional theory (DFT) calculations and thermodynamic analysis. According to the phase diagram, Pt₁₄/TiO₂(110) and 11CO@Pt₁₄/TiO₂(110) were chosen to represent the low and high CO coverage of Pt clusters, respectively. Our study shows that the high coverage of CO can induce the structural change of supported Pt clusters and weaken the interaction between Pt clusters and TiO₂ support. The CO adsorption and oxidation mechanism depends on the CO coverage, which is determined by the experimental reactant composition, pressure, and temperature. At low CO coverage, the dissociated oxygen is active specie to form CO₂ by reacting with CO. At high coverage, the molecular oxygen can directly react with CO via the formation of OOCO intermediate. Our proposed mechanisms provide useful information for understanding the CO oxidation over Pt clusters with different CO coverage. © 2016 Wiley Periodicals, Inc.     

Investigation of CO and formaldehyde oxidation over mesoporous Ag/Co3O4 catalysts

CO and formaldehyde (HCHO) oxidation reactions were investigated over mesoporous Ag/Co₃O₄ catalysts prepared by one-pot (OP) and impregnation (IM) methods. It was found that the one-pot method was superior to the impregnation method for synthesizing Ag/Co₃O₄ catalysts with high activity for both reactions. It was also found that the catalytic behavior of mesoporous Co₃O₄ and Ag/Co₃O₄ catalysts for the both reactions was different. And the addition of silver on mesoporous Co₃O₄ did not always enhance the catalytic activity of final catalyst for CO oxidation at room temperature (20 °C), but could significantly improve the catalytic activity of final catalyst for HCHO oxidation at low temperature (90 °C). The high surface area, uniform pore structure and the pretty good dispersion degree of the silver particle should be responsible for the excellent low-temperature CO oxidation activity. However, for HCHO oxidation, the addition of silver played an important role in the activity enhancement. And the silver particle size and the reducibility of Co₃O₄ should be indispensable for the high activity of HCHO oxidation at low temperature.     

Rate efficiency design of multi-pathway reactions in CO oxidation over ZnO

The possibility of designing the rate efficiency for the multi-pathway reactions of carbon monoxide oxidation on zinc oxide has been comparatively demonstrated using steady state and cyclic operations.     

KOH修饰Au/Al2O3催化剂的低温CO氧化催化反应性能

采用等体积浸渍法制备了KOH-Au/Al<,2>O<,3>系列催化剂,考察了催化剂对低温CO氧化反应的初始活性和干、湿气氛下连续反应的稳定性能,并用电感耦合等离子发射光谱、红外光谱、高分辨透射电镜、紫外漫反射光谱等技术对催化剂进行了结构表征.结果表明:与母体催化剂(Au/Al<,2>O<,3>)相比,修饰催化剂(KOH...     

分形表面上CO氧化反应的蒙特卡罗模拟

众所周知,人们在理想完好的单晶表面上的动力学研究已取得了很大的成功[1],然而对许多实际催化剂来说,传统催化理论和实验之间不符的情况仍然俯拾皆是．现在人们对造成这种情况的原因已经有了更加深入的认识：大量的实验事实表明,在表面催化反应体系中,不但催化剂表面具有复杂的分形结构,而且催化剂表面上的活性中心分布也具有复杂的分形特性[2]．“分形”是指那些具有分数维数的几何对象．这些对象往往是不规则的,不能用通常的欧氏几何来描述[3]．将分形引入催化科学中最早的是Pfeifer和Avnir等[4]人,至今已有近二十年的历史,现…     

CO oxidation as a prototypical reaction for heterogeneous processes

CO oxidation, although seemingly a simple chemical reaction, provides us with a panacea that reveals the richness and beauty of heterogeneous catalysis. The Fritz Haber Institute is a place where a multidisciplinary approach to study the course of such a heterogeneous reaction can be generated in house. Research at the institute is primarily curiosity driven, which is reflected in the five sections comprising this Review. We use an approach based on microscopic concepts to study the interaction of simple molecules with well-defined materials, such as clusters in the gas phase or solid surfaces. This approach often asks for the development of new methods, tools, and materials to prove them, and it is exactly this aspect, both, with respect to experiment and theory, that is a trade mark of our institute.     

Reaction of CO oxidation on platinum,rhodium, a platinum-rhodium alloy,and a heterophase bimetallic platinum/rhodium surface

The reaction of CO oxidation on thin metal films of platinum, rhodium, and their alloy and on a heterophase bimetallic Pt/Rh surface that consisted of platinum particles of size 10–20 nm on the surface of rhodium was studied in the region of low reactant pressures (lower than 2 × 10^?5 mbar). At low temperatures (T < 200°C), the activity of samples increased in the order Rh > Pt/Rh > Pt-Rh alloy > Pt. Above 200°C, the rate of reaction on the heterophase Pt/Rh surface was almost twice as high as the sum of the rates of reaction on the individual metals; this fact is indicative of a synergistic effect. The nature of this effect is considered.     

单晶Au表面和Au/TiO2（110）模型催化剂表面CO氧化反应机理和活性位

在分子尺度上介绍了Au/TiO2(110)模型催化剂表面和单晶Au表面CO氧化反应机理和活性位、以及H2O的作用.在低温(<320 K), H2O起着促进CO氧化的作用, CO氧化的活性位位于金纳米颗粒与TiO2载体界面(Auδ+–Oδ––Ti)的周边. O2和H2O在金纳米颗粒与TiO2载体界面边缘处反应形成OOH,而形成的OOH使O–O键活化,随后OOH与CO反应生成CO2.300 K时CO2的形成速率受限于O2压力与该反应机理相印证.相反,在高温(>320 K)下,因暴露于CO中而导致催化剂表面重组,在表面形成低配位金原子.低配位的金原子吸附O2,随后O2解离,并在金属金表面氧化CO.     

Influence of NO on the Reduction of NO2 with CO over Pt/SiO2 in the Presence of O2

Reduction of NO2 with CO in the presence of NO and excess oxygen, a model mixture for flue gas, over a 0.1% Pt/SiO2 catalyst was studied. The related reaction mechanisms, such as oxidation of CO and NO, were discussed. It was found that there was a narrow temperature window （180-190 ℃） for the reduction of NO2 by CO. When the temperature was lower than the lower limit of the window, the reduction hardly occurred, while when the temperature was higher than the upper limit of the window, the direct oxidation of CO by O2 occurred and thereby NO2 could not be effectively reduced by CO. The presence of NO shifted the window to higher temperatures owing to the inhibition effect of NO on the activation of O2 on Pt, which made it possible to reduce NO2 by CO in flue gas.