© Copyright 2005 by the American Chemical Society
VOLUME 109, NUMBER 6, FEBRUARY 17, 2005
Technical Dedication: Michel Boudart Special Issue Michel Boudart has been the guiding force in the field of heterogeneous catalysis for more than forty years. His elegantly stated concepts of quantitative reaction kinetics, his elucidation of catalytic sites, his experimental studies of new catalytic materials, and the activities of the many students and collaborators whom he has mentored continue to lead and shape the field. His remarkable record of achievement, recognized by top national awards from the American Chemical Society and the American Institute of Chemical Engineers and by his election to both the National Academy of Science and the National Academy of Engineering, reflects the field-defining leadership and scientific substance that this special issue of the Journal of Physical Chemistry B is intended to honor. Our recent advances in the understanding and manipulation of catalytic sites are rooted in concepts advanced by Michel Boudart throughout his career. Foremost among his accomplishments is the quantification of catalytic kinetics in terms of rigorous sequences of elementary steps. By introducing the concept of turnover rate (molecules converted per site per
second), he focused attention on the need to report rates normalized by the most rigorous assessment techniques available for determining the number of active sites. Michel Boudart then developed precise protocols for accurate measurement of exposed metal surfaces in supported catalysts. Many advances in the field can be traced to his clear articulation and frequent reminders of the need to follow rigorous procedures for collecting and reporting reaction rate data. This rigor has enabled comparisons of data among laboratories and has allowed detailed studies of the effects of catalyst synthesis and structure on surface reactivity. Most importantly, it has provided a bridge between practical catalysis and reactions on model surfaces. Turnover rates show, for example, that the hydrogenation of cyclohexene depends only weakly on surface structure, whereas other reactions, such as ammonia synthesis on iron, require specific sites with complex architectures. These studies have allowed detailed evaluations of his proposal that reactions can be facile or demanding, depending on their structural requirements. By reducing catalytic reactions to their essential elemen-
10.1021/jp040699l CCC: $30.25 © 2005 American Chemical Society Published on Web 02/10/2005
2036 J. Phys. Chem. B, Vol. 109, No. 6, 2005 tary chemical steps and insisting that kinetic constants be closely examined for reasonableness, he has taught an entire community the value and limitations of quantitative chemical kinetics and has enabled detailed analysis of the function of catalytic sites. Michel Boudart has also been a leader in the quest to observe catalytic sites directly. His early electron paramagnetic resonance studies on MgO led to one of the first observations of a catalytic sitesa defect site used for hydrogen activation. In an elegant series of Mo¨ssbauer spectroscopic studies, he demonstrated both the surface reconstruction of small supported iron particles in the presence of N2 and the requirement for specific surface structures in ammonia synthesis. His studies on palladium-based catalysts, which showed the formation of specific structures and their kinetic effects upon the addition of gold to palladium, represent a major step in the rational design of active sites. His work on interstitial compounds of tungsten and molybdenum has led to new carbide and nitride catalytic materials, as well as novel syntheses by topotactic and surface modification methods, and represents another classic example of deliberate
modification of surface composition to give specific catalytic consequences. The vision, leadership, and wisdom of Michel Boudart have been a major force in bringing the field of heterogeneous catalysis to its current frontier, where the design of specific catalytic materials for environmental protection, production of chemicals, and energy conversion processes can be contemplated and even implemented.
W. Nicholas Delgass Purdue UniVersity James A. Dumesic UniVersity of Wisconsin-Madison Enrique Iglesia UniVersity of California-Berkeley Fabio H. Ribeiro Purdue UniVersity
