Catalysis is the science that allows facilitating the chemical processes by employing a substance ‎(‎catalyst‎)‎ that actively participates in the reaction mechanism while not being consumed during the process‎.‎ The practical totality of the most relevant chemical processes ‎(‎by volume of product‎)‎ up to date involves the utilization of catalysts as a crucial part of the technology‎.‎ Thus‎,‎ some of the most important bulk chemicals ‎(‎nitric‎,‎ sulfuric‎,‎ and terephtalic acids‎)‎ are produced via catalytic oxidation while others such as ammonia involves catalytic hydrogenation processes‎.‎ Bulk polymers such as polyethylene and polypropylene and many high added‎-value fine chemicals produced at lower scale are generated with the key participation of a catalyst‎.‎ This book intends to provide an overview of some of the most relevant industrial catalytic technologies available today‎.‎ Thus‎,‎ important heterogeneous catalytic processes such as Fischer‎-Tropsch‎,‎ three‎-way conversion of gaseous pollutants‎,‎ and preferential oxidation of CO in H2 streams have dedicated chapters in this compendium‎.‎ Deactivation of catalysts‎,‎ a central issue in any catalytic technology‎,‎ is adequately tackled by excellent reviews from relevant authors‎.‎ The upgrading of petroleum to fuels and chemicals is also covered by including chapters on hydrocracking of heavy oils and Fischer‎-Tropsch‎-derived streams‎.‎ Finally‎,‎ enzymes‎,‎ which can be considered as natural catalysts‎,‎ are described in a review chapter as essential components involved in the production of pharmaceutical‎,‎ cosmetic‎,‎ food‎,‎ and even bulk chemicals‎.‎