Preface – Dedicated to Prof. Dr. Helmut Knözinger on the occasion of his 70th birthday

This special issue of the Zeitschrift für Physikalische Chemie is dedicated to Professor Helmut Knözinger who celebrates his 70th birthday on 10 July 2005. Born in Weilheim, Bavaria, there remained a lifelong attraction to this country and its capital. He studied physics at the Ludwig Maximilians Universität in München where he entered the Institute of Physical Chemistry as a graduate student of Georg-Maria Schwab and received his doctor degree in 1961. At this time the institute was already a Mekka for heterogeneous catalysis and continued to keep this status during the following decades, essentially also thanks to Helmut Knözinger and his work. Even after his ‘formal’ retirement as a professor at this institution he is still strongly involved into active research on this field. His research interests have been mainly concentrating on the characterization of the surfaces of catalysts by various spectroscopic methods and on the search for correlations between these properties and catalytic activity. The materials investigated cover a wide range from oxides, sulfides, metals and their supports to zeolites and solid superacids. The results have been documented in more than 400 publications, among which a paper together with P. Ratnasamy “Catalytic aluminas – surface models and characterization of surface sites” has so far received more than 1000 citations in the literature and can hence be regarded as a true ‘superstar’. Everybody in the community also knows him as coeditor of the Advances in Catalysis or of the Handbook of Heterogeneous Catalysis. Helmut Knözinger’s research achievements have received numerous honours, including the Max Planck Research prize, the Alwin Mittasch Medal, and the Prix Gay Lussac/A. v. Humboldt, – to mention just a few. Apart from that his activities in scientific organizations deserve special recognition: Among others he served as president of the International Association of Catalysis Societies and as chairman of the catalysis section of DECHEMA. His friends and colleagues wish him all the best for the years to come