Modeling of Structures and Reactivity of Solid Catalysts

Abstract

IntroductionComputer modeling tools are now well established in modeling catalytic systems and processes. In particular, they allow us to model catalyst and active-site structures, as well as reaction intermediates and mechanisms. This chapter focuses on their application to inorganic catalytic materials, in particular microporous materials and metal oxides. Especially, modeling of the structure at the atomic level of catalytic materials and of their surfaces is emphasized. The challenging question of unraveling reaction mechanisms is also addressed. * Corresponding author.Basic methodological aspects and earlier applications are summarized in the following section, after which reviews are presented of the main contemporary techniques for structure modeling and prediction. A summary of techniques and applications for the modeling of surface structures and properties is also provided, with special emphasis on microporous materials, in view of their importance and wide-ranging application in catalysis and other technologies. Metal oxides and other inorganic materials are also considered, and techniques and approaches applicable to the general modeling of structures and surfaces and reactions, both in and on solids, are described. Solid-State Modeling Techniques: Energy Calculations BasicsComputer modeling at the atomic and molecular level uses a wide range of methods, including those based on interatomic potentials (or forcefields) and quantum mechanical techniques. Use of the latter is essential when considering processes (such as reaction mechanisms) that depend on bond-breaking and making; they are considered later in this section and in Chapter 5.1.2. Our initial focus is, however, on modeling the structural properties of solids and their surfaces, where forcefield methods have been widely used.The complex and fascinating range of crystal structures adopted by inorganic materials has provided a powerful incentive for the development of effective tools for modeling and, more ambitiously, predicting their structures. These methods may be used to assist structure determination, to classify existing structures, and to explore and predict new topologies and corresponding structures. The field has a long history, with one of the most fruitful areas of application having been in zeolite science, where the early studies of Smith and coworkers [1, 2] (and vide infra) pioneered the application of principles based on network topologies. Techniques based on lattice energy minimization were developed and refined during the 1980s and 1990s and applied to many classes of solid; these approaches have subsequently been combined with simulated annealing and genetic algorithm techniques in order to provide powerful structure prediction tools as discussed later in this chapter. Lattice energy calculations have also been used to assess the viability of new hypothetical structures which have been generated by systematic topological enumeration methods; while new structures have additionally been generated by applications of simulate...