多相催化过程中催化剂表面吸附层的介尺度行为

发布时间：2018-01-15 02:16

本文关键词：多相催化过程中催化剂表面吸附层的介尺度行为　出处：《中国科学院大学(中国科学院过程工程研究所)》2017年硕士论文　论文类型：学位论文

【摘要】：在多相催化反应过程中,反应物和生成物可以在催化剂表面上形成复杂的吸附层结构,这些结构对多相催化的宏观表现有着重要影响。目前描述多相催化反应过程主要有三种模型,分别是宏观模型、微观模型和介观模型。忽略这种结构,采用平均化的处理方式,往往造成严重偏差,这是目前宏观模型的主要缺陷;而直接描述原子、分子过程的微观模型又包含了太多的冗余信息,以致巨大的计算开销都难以达到实际需要的时空规模。虽然通过局部覆盖度修正动力学速率的介观模型引入结构对动力学行为的影响,但其仍然采用局部平均化的分析方法,并未摆脱宏观模型的本质缺陷,因此,这样的介观模型仍未准确反映结构对体系的影响。在气-固流态化系统的研究中,能量最小多尺度(EMMS)模型已被证明可以有效关联不同尺度。由此提出的EMMS原理认为,复杂系统的稳定性条件可以表示为主导机制间竞争中的协调,复杂系统的稳态可能描述为不同主导机制所对应状态之间的组合。依据EMMS原理的指导,本论文通过准确刻画催化剂表面吸附层结构的介尺度关键特征,将这些特征与相关的主导机制进行关联,以相互竞争的主导机制之间的协调关系证明稳定性条件的存在,为介尺度模型的建立奠定了良好的基础。通过本论文的研究可以发现,动力学因素对催化剂表面吸附层结构有着重要的影响,联立稳定性条件和守恒方程的介尺度模型是关联宏观与微观,高效、准确地考虑介尺度结构影响的有效途径。本论文回答了催化剂表面吸附层结构是什么,为什么要考虑吸附层结构,如何表征吸附层结构以及不同的吸附层结构对应的主导机制是什么四个问题。依据此思路,本论文可以分为四章,分别为绪论、基于LH机理的A-B模型、基于LH机理的A-B2模型以及结论和展望。第一章绪论部分对本论文的研究背景以及基本思路进行阐述,详细解释了催化剂表面吸附层结构对宏观动力学行为的影响,并对已有模型的优缺点进行了比较。第二章和第三章是本论文的主体,分别在不同的体系,A-B体系和A-B2体系,研究了动力学因素对催化剂表面吸附层结构的影响,并提炼出不同相对应的主导机制,说明主导机制竞争中的协调作用赋予了催化剂表面吸附层结构的动力学特征。同时,由于解离作用的影响,在第三章中还详细对比了不同体系间动力学因素对吸附层结构影响的差异性,完整的阐述了不同体系间动力学因素对吸附层结构动力学行为的共性与差异性。第四章结论与展望分为两部分,分别对本论文进行了全面的总结,并对之后进一步的工作进行了展望。
[Abstract]:In the course of catalytic reactions, the reactants and products can be formed in the complex structure of the adsorption layer on the surface of the catalyst, has an important impact on macroeconomic performance of these structures on heterogeneous catalysis. The description of heterogeneous catalytic reactions are mainly three kinds of models are macro model, microscopic model and mesoscopic model. Ignore this structure, using the average of the treatment, often cause serious error, which is the main defect of macro model at present; and direct description of atomic and molecular processes, the microscopic model also contains a lot of redundant information, so that the huge computational overhead are difficult to meet the actual needs of the temporal and spatial scale. Although the influence of mesoscopic model correction of dynamic rate coverage through the partial introduction of structure on dynamic behavior, but it is still using the analysis method of partial averaging, nature did not get rid of the defects of the macro model, therefore, this Not like the mesoscopic model accurately reflects the influence of structure on the system. In the study of gas-solid fluidization system, energy minimization multi-scale (EMMS) model has been proved to be effective in different scales. The principle that EMMS Association proposed the stability conditions of complex systems can be represented as the dominant mechanism in the coordination of competition steady state, complex systems can be described as the dominant mechanism corresponding to different combination between states. According to the EMMS principle, this paper describe the adsorption characteristics of meso scale key layer structure of the catalyst surface, the correlation mechanism leading to these characteristics and the stability conditions that to coordinate the relationship between leading competing mechanism the existence of established for the meso scale model has laid a good foundation. Through the research of this paper can be found that the dynamics on the catalyst surface adsorption layer. Structure has an important influence, mesoscale model of simultaneous stability conditions and conservation equations associated with macro and micro, efficient and effective way to accurately consider the impact of meso scale structures. This thesis answers the catalyst surface adsorption layer structure is what, why should we consider the adsorption layer structure, leading to different structure and characterization of adsorption layer the adsorption layer structure of the corresponding mechanism is what four questions. Based on this idea, this paper can be divided into four chapters, namely the introduction, the A-B model based on LH mechanism, LH mechanism and A-B2 model based on the conclusion and prospect. The first chapter elaborates on the research background and basic ideas, detailed explanation the influence of adsorption layer structure on the macro dynamic behavior of the catalyst surface, and the advantages and disadvantages of the existing model are compared. The second chapter and the third chapter is the main body of this paper, respectively Different system, A-B system and A-B2 system, studies the dynamic factors influencing adsorption layer structure on the surface of the catalyst, and extract the dominant different corresponding mechanism, coordination mechanism of leading role in the competition with the catalyst surface adsorption layer structure characteristics. At the same time, due to the effect of dissociation, in the third chapter also a detailed comparison of the differences between different systems of dynamic factors influence the adsorption layer structure, a full description of the similarities and differences of adsorption layer structure dynamic behavior of dynamic factors between different systems. The conclusion and Prospect of the fourth chapter is divided into two parts, respectively in this thesis is summarized, and the further the work is prospected.

【学位授予单位】：中国科学院大学(中国科学院过程工程研究所)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36

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