Metal microstructures in zeolites

Metal Microstructures in Zeolites Bremen, Germany, 22-24 September, 1982 Although the pioneering studies of Rabo, Schomaker and Pickert which were published in 1965 showed that zeolites could be used as supports for very small metal clusters it is only recently that a rapid growth of the subject has occurred, This workshop held in the University of Bremen on'the preparation, properties and applications of 'Metal Microstructures in Zeolites' is thus a timely one. Some 90 participants from 19 countries attended showing the widespread interest in this subject. The conference was very well organized and plenty of time was allowed for the presentation of approximately 30 papers and for the lively discussion which followed most presentations: The lecture theatre was excellent. The University catering facilities were more than adequate. Participants were scattered around many hotels in Bremen but most participants organized themselves into small groups in the evenings to sample the excellent restaurants available in abundance in the old part of Bremen. An enjoyable time was had by all. The proceedings of the workshop were published as a monograph by Elsevier and presented to each participant at the conference so no record of the discussions will be available. The proceedings are reviewed by Dr Townsend in this issue of Zeolites so no attempt will be made to cover the papers presented at the workshop. However, some points of personal interest may be worth mentioning. An excellent review of the mechanism of formation and stabilization of metals in the pores of zeol[tes was made by Peter Jaeobs. It was interesting to find that, although early experiments seemed very promising for industrial applications of these systems, until now the only processes which exist use exclusively Pt as the active material and always in combination with an acid support for hydrocracking, shape-selective cracking and isomerization reactions. The Pt phase is used exclusively for the de-

hydrogenation-hydrogenation of saturated and unsaturated hydrocarbons. Surely with the amount of research going on in the conversion of synthesis gas to hydrocarbons as reported in this workshop and elsewhere some commercial process must result. However, the papers presented at Bremen indicated that many problems need still to be overcome before a zeolite catalyst can replace ex isting F ischer-Tropsch catalysts. It was obvious listening to the results being reported in this conference that there is a need for experiments which give us information of the exact structure of the metal aggregates which exist in the zeolite pores, There is also a need for all working in this field to ascertain that no structural breakdown of the zeolites framework has occurred in the preparation or activation stages. The paper by Gallezot and Bergeret indicates that the latest electron microscopic and X-ray diffraction techniques, especially small angle X-ray scattering, are :nvaluable in this area. The atomic structure of metal aggregates can also be determined by the radial electron distribution (RED) and by the extended X-ray absorption fine structure (EXAFS) methods. We await with excitement further results on the effect of chemisorption on the crystallographic structure of the aggregates, The use of n.m,r, chemical shift of [29Xe as reported by Fraissard etal. seems to offer an exceedingly important new tool for studyTng very small metal aggregates which may not be detectable by electron microscopy. Although the results reported in this paper gave us much insight of the metal aggregates we await with anticipation the results of lower temperature experiments using magic angle spinning n.m,r, which are about to commence where the ZlgXe probe molecules are 'stationary' in the time scale of the experiment.

Lovat V. C. Rees

Metal Microstructures in Zeolites P. A. Jacobs; N. I. Jaeger, P..Tint and G. Shulz-Ekloff (Eds) Elsevier Scientific Publishing Company, Amsterdam, New York, 1982, ISBN 0-'444-42112-2, vii + 284 pp, price US~76.75/Dfl 165.00 The importance" in catalysis of highly dispersed metals supported on a stable inorganic carrier is well-known. The potential utility of zeotites as such carriers lies in the possibility that their unique properties can lead to the stabilization of metal dispersions which are difficult to attain on conventional carriers, and also to the stabilization of unusual oxidation states within the crystalline matrix. There has been a rapid growth in studies on these problems

86 ZEOLITES, 1983, Vol 3, January

in recent years, and a useful book which reviews this rapid progress would be both timely and appropriate.

Metal Microstructures in Zoo~ires is a publication which covers the recent proceedings of the Workshop on this subject which was held in Bremen in September 1982. The book, which is hard-cover and in camera-ready format, includes 30 papers. The relative attention paid to different