duced in Japan and are currently spreading through the European Community and Switzerland. The most advanced catalyst now contains three metals of the platinum group and controls the emission of carbon monoxide, nitrogen oxides, and unburned gasoline molecules by use of a very complex network of catalytic reactions. This application has contributed more than any other to public awareness of catalysis and of its many applications for the benefit of mankind.
For viable commercial application, catalysts of any type—heterogeneous, homogeneous, or enzymatic—must exhibit a number of properties, the principal ones being high activity, selectivity, and durability and, in most cases, regenerability. The activity of a catalyst influences the size of the reactor required to achieve a given level of conversion of reactants, as well as the amount of catalyst required. The higher the catalyst activity, the smaller are the reactor size and the inventory of catalyst and, hence, the lower are the capital and operating costs. High catalyst activity can also permit less severe operating conditions (e.g., temperature and pressure), and this too can result in savings in capital and operating costs. The amount of reactant required to produce a unit of product, the properties of the product, and the amount of energy required to separate the desired product from reactants and by-products are all governed by catalyst selectivity. As a consequence, catalyst selectivity strongly influences the economics of a process. Catalyst productivity and the time on-stream are dictated by catalyst stability. All catalysts undergo a progressive loss in activity and/or selectivity with time due to chemical poisoning, denaturing, thermal deactivation or decomposition, and physical fouling. When the decrease in performance becomes too severe, the catalyst must be either regenerated or replaced. In view of this, high stability and ease of regeneration become important properties.
Catalysis is a complex, interdisciplinary science. Therefore, progress toward a substantially improved vision of the chemistry and its practical application depends on parallel advances in several fields, most likely including the synthesis of new catalytic materials and understanding the path of catalytic reactions. For this reason, future research strategies should be focused on developing methods with an ability to observe the catalytic reaction steps in situ or at least the catalytic site at atomic resolution. There is also a need to link heterogeneous catalytic phenomena to the broader knowledge base in solutions and in well-defined metal complexes.
Substantial progress and scientific breakthroughs have been made in recent years in several fields, including atomic resolution of metal surfaces,