This is a book for developers of catalysts, and for practitioners working in the field of design, operation, and optimization of chemical reactors in which heterogeneous catalysis is performed. It is designed to give a better understanding of the phenomena which can influence catalyst performance. Since two disciplines, chemistry and chemical engineering, meet in catalyst research and development, this book covers the chemical point of view for engineers, and the engineering point of view for chemists. It starts with an introduction explaining selectivity, activity and effectiveness providing the fundamentals for the newcomer. Catalyst preparation and catalyst testing are also described.A method is introduced that can be used to calculate the effectiveness of catalyst pellets as a function of shape, size, pore size, type of kinetics and diffusion, and temperature and pressure conditions. Optimization of catalysts and troubleshooting are also covered. This is a book without any rilvals because of its practical relevance.