共查询到19条相似文献,搜索用时 109 毫秒
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介绍了微动力学和催化反应综合的基本概念,论述了进行微动力学分析的基本方法,扼要分析了微动力学用于多相催化的研究实例,认为微动力学将成为多相催化研究中重要的研究方法。 相似文献
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吸附量热技术和多相催化微观动力学 总被引:2,自引:0,他引:2
本文介绍了多相催化研究中的吸附量热技术、多相催化微观动力学及其计算机模拟, 以及吸附量热技术在定量表征固体催化剂表面中心和在多相催化微观动力学分析中的重要作用。 相似文献
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概述了多相催化反应动力学的几种研究方法及其特点,适用性,着重介绍了SSITKA技术和TOF的速率表征。 相似文献
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多相催化反应动力学研究的基本问题是动力学方程中的参数估计,它一直是动力学研究中的活跃领域·在参数估计中最常用的方法是最小二乘法.早在1947年[刘开始用线性最小二乘法处理动力学模型的数据.1958年在线性最小二乘法中应用置信区间问题[21.1959年MarguardM出非线性最小二乘法问.前人提出如何求非线性最小二乘法的初值[4],及加权最小二乘法的重要性问,并对最小二乘法在动力学中的应用做了综述卜].在多相催化动力学研究中,关干线性最小二乘法遇到根本性困难的问题前人未涉及.我们曾在动力学研究中发现线性最小二乘法的法… 相似文献
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在阴离子交换树脂催化剂上合成二丙酮醇的动力学研究 总被引:1,自引:0,他引:1
动力学研究表明,在碱性树脂催化剂上丙酮缩合制二丙酮醇是一个1-1级可逆反应,本文对此多相催化的反应机理进行了探讨。 相似文献
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多相催化过程不仅在化学工业上占有相当的地位,同时也是化学动力学上的一个重要部分。为了解决各种实际问题,各国科学家对多相催化反应的机构曾进行详细的研究,并建立很多的催化学说。某些学说指出:多相催化反应是由于反应物分子在催化剂表面的吸附(如 Faraday 1833年的物理吸附学说,Taylor1931年的活性吸附学说等)和变形(1856年的分子变形假说等)所致;另一些学说则着重说明催化剂表面上活性中心的结构和作用(1929年的多质点集团论和1946年的活性集团学说)。根据化学动力学上的中间状态论,在多相催化反应中有不稳定的活化络合物(activated complex)形成,因此可用统计热力学方法计算它的绝对速度(Eyring 等的绝对反应速度论)。学说虽多,各有说法,迄今尚不能建立一个普 相似文献
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Rate‐Reactivity Model: A New Theoretical Basis for Systematic Kinetic Characterization of Heterogeneous Catalysts
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Gregory S. Yablonsky Evgeniy A. Redekop Denis Constales John T. Gleaves Guy B. Marin 《国际化学动力学杂志》2016,48(6):304-317
Non‐steady‐state kinetic measurements contain a wealth of information about catalytic reactions and other gas–solid chemical interactions, which is extracted from experimental data via kinetic models. The standard mathematical framework of microkinetic models, which are typically used in computational catalysis and for advanced modeling of steady‐state data, encounters multiple challenges when applied to non‐steady‐state data. Robust phenomenological models, such as the steady‐state Langmuir–Hinshelwood–Hougen–Watson equations, are presently unavailable for non‐steady‐state data. Herein, a novel modeling framework is proposed to fulfill this need. The rate‐reactivity model (RRM) is formulated in terms of experimentally observable quantities including the gaseous transformation rates, concentrations, and surface uptakes. The model is linear with respect to these quantities and their pairwise products, and it is also linear in terms of its parameters (reactivities). The RRM parameters have a clear physicochemical meaning and fully characterize the kinetic behavior of a specific catalyst state, but unlike microkinetic models that rely on hypothetical surface intermediates and specific reaction networks, the RRM does not require any assumptions regarding the underlying mechanism. The systematic RRM‐based procedure outlined in this paper enables an effective comparison of various catalysts and the construction of more detailed microkinetic models in a rational manner. The model was applied to temporal analysis of products pulse‐response data as an example, but it is more generally applicable to other non‐steady‐state techniques that provide time‐resolved rates and concentrations. Several numerical examples are given to illustrate the application of the model to simple model reactions. 相似文献
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在石油催化裂解过程中,除了生成乙烯、丙烯及丁烯等烯烃,还会产生部分炔烃.目前工业上通常采用炔烃选择性加氢转化为对应的单烯烃,以除去其中炔烃.由于产品烯烃中的炔烃等杂质含量需极低,这就对用于加氢催化剂的活性和选择性提出了很高的要求,即催化剂需要选择性吸附炔烃并加氢,而不损失其中的烯烃.经过前期大量的基础研究工作,目前工业中炔烃选择性加氢应用最广泛的催化剂是负载型钯基催化剂.然而,单独的钯金属选择性并不理想,因而对其选择性以及活性进行调控成为了当前关注的研究课题.本文采用密度泛函理论计算结合微观反应动力学模拟手段,研究了钯金属表面应力存在条件下的活性与选择性,以及形成次表层物种的可能性和形成后的活性与选择性.研究发现,改变钯金属的晶格参数与表面应力,反应物、表面反应中间体和产物的吸附能都会产生相应的变化,且吸附能与晶格参数的变化存在线性关系,晶格参数越大,吸附越强.利用表面反应过渡态能量与初始态能量之间的线性关系,相应的乙炔加氢生成乙烯的反应速率可以通过微观反应动力学模拟得到.结果显示,不同晶格参数的钯催化剂催化乙炔加氢生成乙烯的反应活性位于相应火山型曲线的强吸附侧,即减弱乙炔和氢的吸附强度可提高乙烯的生成速率.在此基础上,本文研究了不同表面应力的钯催化剂在次表面吸附不同覆盖度碳原子和氢原子的情况,发现晶格参数越大越有利于碳原子和氢原子在次表面的吸附.同时,研究发现在次表面碳掺杂的条件下,不同表面应力条件下的钯催化剂的活性均有所增强.此外,由于乙烯在所有研究的钯催化剂表面脱附比进一步加氢容易,因而乙烯都可以选择性生成. 相似文献
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组合多相催化研究进展* 总被引:5,自引:0,他引:5
本文对组合多相催化研究进展进行了较全面的综述,介绍了组合多相催化过程、样品库制备、库表征-高通量筛选技术及相应的微型组合反应器,并讨论了组合多相催化技术的发展趋势. 相似文献
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作为一类具有大的比表面积、高孔隙率、合成方便、骨架规模可变、化学可修饰以及结构组成多样等优点的新型多孔材料,金属-有机框架(MOFs)在光电材料、药物传输、气体吸附分离及催化等领域有着广阔的应用前景,成为近年来研究的热点。异相催化是MOFs最具发展潜力的应用领域之一,各种表征方法和研究手段是开展MOFs异相催化研究的工作基础。本文主要围绕表征MOFs作为异相催化剂的常用技术手段进行介绍,包括X-射线单晶衍射、X-射线粉末衍射、热重分析、红外光谱/拉曼光谱分析、透射/扫描电镜等,旨在为开展相关MOFs催化研究提供一定参考。 相似文献
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V. V. Ustyugov V. V. Kaichev E. A. Lashina N. A. Chumakova V. I. Bukhtiyarov 《Kinetics and Catalysis》2016,57(1):113-124
The methodology of constructing a phenomenological model for complex heterogeneous catalytic reactions is described in detail. The proposed approach is applicable to development of mathematical models describing the onset of self-oscillations in hydrocarbon oxidation on the transition metal surface. The approach is based on construction of a microkinetic scheme taking into account the formation of main reaction products and intermediates, on estimation of the heat of reaction, activation energy, and preexponential factor for elementary steps and includes development and a subsequent analysis of the corresponding mathematical model. Catalytic reactions are considered in the ideal adsorption layer approximation without taking into account the relationship between coverages and spatial coordinates. Accordingly, the mathematical model is an independent system of ordinary differential equations. This methodology is used to develop a point (lumped) model for ethane oxidation over nickel, which is based on a 36-step microkinetic scheme taking into account the oxidation and reduction of nickel and the formation of total (CO2 and H2O) or partial (CO and H2) ethane oxidation products, as well as the dehydrogenation of ethane into ethylene. The proposed model predicts the onset of self-oscillations in this reaction at atmospheric pressure in the temperature range from 850 to 1400 K. The kinetic oscillations are caused by the cyclic oxidation and reduction of nickel. The self-oscillations of the reaction rate are accompanied by oscillations of the catalyst temperature. The results of modeling are compared with experimental data. 相似文献
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Copéret C Chabanas M Petroff Saint-Arroman R Basset JM 《Angewandte Chemie (International ed. in English)》2003,42(2):156-181
Surface organometallic chemistry is an area of heterogeneous catalysis which has recently emerged as a result of a comparative analysis of homogeneous and heterogeneous catalysis. The chemical industry has often favored heterogeneous catalysis, but the development of better catalysts has been hindered by the presence of numerous kinds of active sites and also by the low concentration of active sites. These factors have precluded a rational improvement of these systems, hence the empirical nature of heterogeneous catalysis. Catalysis is primarily a molecular phenomenon, and it must involve well-defined surface organometallic intermediates and/or transition states. Thus, one must be able to construct a well-defined active site, test its catalytic performance, and assess a structure-activity relationship, which will be used, in turn-as in homogeneous catalysis-to design better catalysts.By the transfer of the concepts and tools of molecular organometallic chemistry to surfaces, surface organometallic chemistry can generate well-defined surface species by understanding the reaction of organometallic complexes with the support, which can be considered as a rigid ligand. This new approach to heterogeneous catalysis can bring molecular insight to the design of new catalysts and even allow the discovery of new reactions (Ziegler-Natta depolymerization and alkane metathesis). After more than a century of existence, heterogeneous catalysis can still be improved and will play a crucial role in solving current problems. It offers an answer to economical and environmental problems faced by industry in the production of molecules (agrochemicals, petrochemicals, pharmaceuticals, polymers, basic chemicals). 相似文献
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The formation of aryl–aryl bonds and heteroaryl analogues is one of the most important C–C bond forming processes in organic chemistry. Recently, a methodology termed Direct Arylation (DA) has emerged as an attractive alternative to traditional cross-coupling reactions (Suzuki–Miyaura, Stille, Negishi, etc.). A parallel focus of the pharmaceutical and other chemical industries has been on the use heterogeneous catalysis as a favourable substitute for its homogeneous counterpart in cross-coupling reactions. Only very recently has heterogeneous catalysis been proposed and applied, to DA reactions. In this perspective, we consider the terms ‘heterogeneous’ and ‘homogeneous’ and the problems associated with their delineation in transition-metal catalysed reactions. We highlight the reports at the interface of DA and heterogeneous catalysis and we comment briefly on the methods used which attempt to classify reaction types as homo- or heterogeneous. In future work we recommend an emphasis be placed on kinetic methods which provide an excellent platform for analysis. In addition two analytical techniques are described which if developed to run in situ with DA reactions would illuminate our understanding of the catalysis. Overall, we provide an entry point, and bring together the mature, yet poorly-understood, subject of heterogeneous catalysis with the rapidly expanding area of DA, with a view towards the acceleration of catalyst design and the understanding of catalyst behaviour. 相似文献