Molecular Description of Heterogeneous Catalysis

The ability to predict catalyst performance as a function of chemical composition, molecular structure and morphology is the formdation for the science and technology of catalysis. We aim to describe the use of currently available theoretical and computational methods for both qualitative and quantitative predictions on the molecular events on which the catalytic reaction is based. This relates to the prediction of catalyst structure and morphology as well as the simulation of dynamic changes that occur on the catalyst surface as the result of reaction. 

We will provide the reader with an introduction to fundamental concepts in catalytic reactivity and catalyst synthesis derived from the results of computational analysis along with physical and chemical experimental studies. The tremendous advances in nanoscale materials characterization, in itu spectroscopy to provide atomic and molecular level resolution of surfaces and adsorbed intermediates under reaction conditions, predictive ab initio quantum mechanical methods and molecular simulations that have occurred over the past two decades have helped to make catalysis much more of a predictive science. This has significantly enhanced the technology of catalysis well beyond the historical ammonia synthesis and petrochemical processes. 

Herein we attempt to highlight advances in the molecular science of heterogeneous catalysis. We will focus on the mechanistic phenomena that make catalysis possible. This enables one to begin to answer the chemist s questions What are the fundamental processes that occur at the catalyst surface and how do they act to control its remarkable behavior What are the molecular system parameters that control rate and selectivity for 

In the middle of the last century, synthesis techniques were develop ed that enabled the fabrication of well-defined and highly regular micropwrous silica materials, such as zeolites, with pore sizes comparable to the size of the molecules one would like to catalyze . The appropriate matching of size and shape of these micropores with shape and size of reactant, intermediate or product molecules has been demonstrated to be an important factor in the control of catalytic p erformance. This is analogous to the lock and key reactivity principle which was developed in the early part of the last century as a way to describe the activity of enzymes, the biochemical proteins in living systems. This process involves matching the shape and size of the catalytic cavity with that of the reactant molecules. 

The mechanisms which control zeolite catalytic systems show features similar to those known in biochemistry and lead to the formulation of a more general question What are the basic differences between chemocatalysis for reactions carried out in man-made catalytic systems and biocatalysis for reactions as they occur in biochemical systems  

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