Preparation of Catalysts II, Proceedings of the Second International Symposium PDF
Preview Preparation of Catalysts II, Proceedings of the Second International Symposium
Studies in Surface Science and Catalysis 3 PREPARATION OF CATALYSTS II Scientific Bases for the Preparation of Heterogeneous Catalysts Proceedings of the Second International Symposium, Louvain-la-Neuve, September 4-7,1978 Editors B. Delmon, P. Grange, P. Jacobs and G. Poncelet ELSEVl ER SCI ENTlF IC PUBLISHING COMPANY Amsterdam - Oxford - New York 1979 ELSEVIER SCIENTIFIC PUBLISHING COMPANY 335 Jan van Galenstraat P.O. Box 211, 1000 AE Amsterdam, The Netherlands Distributors for the United States and Canada: ELSEVIER/NORTH-HOLLAND INC, 52, Vanderbilt Avenue New York, N.Y. 10017 Library of Congress Cataloging In PublIcatIon Data Main entry under title: Preparation of catalysts 11. (Studies in surface science and catalysis j 3) Includes bibliographical references and index. 1. Catalysts--Congresses. I. Delmon, Bernard. 11. Series. QD505.P722 91l.395 79-1397 ISBN 0-444-41733-8 ISBN 0444417338 (Vol. 3) ISBN 0-44441801.6 (Series) 0 Elsevier Scientific Publishing Company, 1979 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical. photocopying, recording or oth- erwise, without the prior written permission of the publisher, Elsevier Scientific Publishing Company, P.O. Box 330,1000 AH Amsterdam, The Netherlands. Printed in The Netherlands VIII ORGANIZING COMMITTEE Members Dr. s.P.S. ANDREW, Imperial Chemical Industries Ltd., Great Britain. Dr. H. BOHLBRO, Haldor Topsbe, Denmark. Dr. R. CAHEN, Labofina S.A., Belgium. Prof. J.W.E. COENEN, Unilever Research, The Netherlands. Prof. B. DELMON, Universite Catholique de Louvain, . Be 1g ium , Prof. B. DEROUANE Universite de Namur, Belgium. Prof. J.W. HIGHTOWER, Rice University, Houston, Texas, U.S.A. Dr. P. LAMBERT, Union Chimique Belge, Belgium. Dr. A. LECLOUX, Solvay et Cie., Belgium. Dr. J.L. LE PAGE, Institut Franpais du Petrole, France. Dr. R. MONTARNAL, Institut Francais du Petrole, France. Dr. L. MOSCOU, AKZO-Chemie Nederland, The Netherlands. Prof. E. PLUMAT, Universite Libre de Bruxelles, Belgium. Secretaries Dr. P. GRANGE, Universite Catholique de Louvain, Belgium. Dr. P.A. JACOBS, Katholieke Universiteit Leuven, Belgium. Dr. G. PONCELET, Universite Catholique de Louvain, Belgium. IX FOREWORD As a result of the First International Symposium on "The Scientific Bases for the Preparation of Heterogeneous Catalysts" it clearly appeared to the local organizers that a large international audience was interested by the topics treated. However, the scope of the symposium was probably too large, and possibly did not allow sufficient discussion and interaction between participants. It was clear from the beginning that for the Second Symposium a smaller number of scientific domains involved in the preparation of industrial heterogeneous catalysts should be discussed. The scientific program was set up by an Organizing Committee formed by representatives of industries, universities and research institutes. This committee was composed by experts in the field of catalyst pre- paration from different countries. At the first meeting of the Organizing Committee, it was felt that the symposium should focus on two unit processes, IMPREGNATION and ACTIVATION of supported catalysts, and more particularly on : the chromatographic effect, transport in pores, calcination, activa- tion by reduction and sulfidation, carrier effects and compound forma- tion. It was also decided that new trends in the preparation of real catalysts should be included in the scientific program as they were in the First Symposium. Over 90 papers treating these topics were submitted. The Organizing Committee at a second meeting selected 36 communications which fitted most closely the imposed topics. It was decided not to discuss the selected unit processes separately but rather to structurate the pro- gram sessions around distinct groups of catalysts treating impregna- tion and activation. The symposium topics were introduced by four plenary lectures and three extended communications, each of them delivered by scientists who, with a remarkable cooperation spirit, accepted to adapt their contribution to the audience and to the sub- ject and style of the Symposium. The Organizing Committee also felt that the standardisation of methods of catalysts characterization remained a topic of much inte- rest, and that progress in international agreement and cooperation was important. Encouraged by the success of an almost informal dis- cussion included in the program of the First Symposium, it was found necessary to devote half-a-day to catalyst normalisation. Three scientific papers and reports from national and international committees were scheduled. A round-table discussion was planned to evaluate the importance of a scientific approach for the impregnation and activation of cata- lysts. The discussion also focused on the role of this symposium in fostering scientific research in the field and for enabling a better interaction between industrial and fundamental investigation. A summary of these discussions is given by the Symposium Chairman in his concluding remarks. Approximately 350 participants representing 30 nations attended the Symposium. Almost 60% of the participants came from industry. IUPAC accepted to sponsor the symposium. In his introductory remarks IUPAC's President, Prof. G. Smets, mentioned that this sponsor ship is only awarded provided three prerequisites are fulfilled: . fair geographical representation of the contributors . quality of the geographical site . quality of the organisation. There is no doubt that the first condition was met. Whether the two other ones were fulfilled, the appreciation is left to those who attended the symposium. If the participants agree that the organisation of the symposium went on smoothly, this is the result of a high number of personal efforts, which the local organizers would like to acknowledge. P. GRANGE P.A. JACOBS G. PONCELET XI ACKNOWLEDGEMENTS In the name of the Organizing Committee, we want to thank the Rector of the Universite Catholique de Louvain, Mgr. E. Massaux, who agreed that the Second International Symposium could be held in Louvain-la-Neuve. For all the facilities generously provided by the university, we also sincerely thank the Rector. The Organizers acknowledge the sponsorship of IUPAC and the bene- volent appreciation of its President for the project of this 2nd International Symposium. The introductory remarks of IUPAC's Presi- dent, Prof. G. Smets, were also gratefully appreciated by the local Organizers, the Scientific Committee and all those who participated to the set-up of the Symposium. We also thank the Societe Chimique de Belgique, Division de Cata- lyse, for sponsoring the Symposium, and in particular its President, Dr. A. Lecloux, for his welcome address. The local Organizers are pleased to mention the exceptional and enthousiastic participation of the members of the Organizing Committee. Their work and contribution go well beyond what usually is expected from members of scientific committees of symposia: they determined the topics of the Second Symposium and selected the papers, they structurated the scientific program, acted as session chairmen, and animated the discussions. This symposium was really the collective achievement of a11 the members of the Organizing Committee. To all of the members of the Organizing Committee, we convey our deepest gratitude. While preparing these Proceedings, we learned the death of one member of the Organizing Committee. All those who knew Dr. R. Montarnal appreciated his human qualities, enthousiasm and scientific competence. Special thanks are due to Dr. R. Cahen for his efficient help in contacting several scientists of industry and collecting financial contributions. The efforts of Dr. L. Moscou and Prof. E. Derouane, who success- fully took in charge the complete organization of the Minisymposium on Catalyst Normalisation, are also greatly appreciated. We also would like to thank Prof. D.L. Trimm, Dr. J.P. Brunelle, Dr. N. Pernicone and Prof. E. Matijevic for their highly stimulating lectures. XI1 The Organizers also acknowledge all those who submitted a paper, including those whose contribution could be not accepted. Special thanks are due to the authors of the papers included in the Proceed- ings. They were the artisans of the success of the symposium. TWO departments of the university deserve to be congratulated: the 'Relations Exterieures de l'Universit6 de Louvain' (REUL), and in particular Mrs. F. Bex and her team, and the 'Service de Logement' headed by Mr. E. Vander Perre. Finally, we want to acknowledge the help of all those of the 'Groupe de Physico-Chimie Minerale et de Catalyse' who, in charge of different organisational aspects before and during the symposium, contributed to its success: Dr. M.A. Apecetche, Dr. N. De Keyzer, Dr. F. Delannay, Dr. P. Gajardo, M. Genet, Dr. P. Gerard, Dr. J. Lemaitre, A. Mathieu, L. Petit, C. Pierard, D. Pirotte, M. Rodriguez, P. Scokart and Dr. M.L. Somme-Dubru. XI11 FINANCIAL SUPPORT The Organizing Committee gratefully acknowledges the "Ministere de 1'Education Nationale et de l a Culture Franqaise" and the "Fonds National de la Recherche Scientifique" for their financial guarantee. The pecuniary security provided by the Soci6t6 Chimique de Belgique is also acknowledged. Financial support was also contributed by the following catalysts manufacturers and companies: AKZO Nederland, b.v., The Netherlands BASF, W. Germany Catalysts and Chemicals Europe, Belgium Condea, W. Germany Cyanamid of Great Britain, England Essochem Europe, Belgium Haldor Topsde, Denmark Harschaw Chemie, The Netherlands Imperial Chemical Industries Ltd., England Johnson Matthey and Co. Ltd., England Mallinckrodt Inc., Calsicat Division, U.S.A., and Catalysts International, France Metallurgie Hoboken-Overpelt, Belgium Montedison, S.p.A., Italy , Procatalyse France Solvay et Cie., Belgium Siidchemie AG, Sparte Girdler Katalysatoren, W. Germany Unilever, The Netherlands Universal Matthey Products Ltd., England U.O.P. Processes, U.S.A. Labofina S.A. has contributed to the costs of the printing of the announcing booklets. The organizers are indebited to these companies. 1 THE DESIGN OF CATALYSTS" D.L. TRIHt? Laboratory of Industrial Chemistry, The University of Trondheim, Norway Realisation of the importance of catalyst preparation to the activity, selectivity and life of a catalyst has led to increasing interest in the scientific basis of different preparations. This, in turn, has led to improved performance, and to the necessity of defining carefully what catalyst should be - can prepared rather than optinising a catalyst that be prepared. This paper describes a general approach to the problem of recoonition of which catalyst should be prepared for a given reaction. The design of a catalyst is discussed in terms of a flow diagram in which means of identification of major and minor constituents of a catalyst are inter- related. Factors influencing the choice of the chemical constituents are considered together with the choice of a support, which often depends more on the desired physical characteristics of the catalyst. Both theoretical concepts and empirical observations can be combined i n the overall design to oive a limited number of possibilities for experimental testing. Finally, correlation of suggestions from the design with catalyst preparation is considered briefly, with particular reference to impregnation and activation. INTRODUCTION It is well known that the activity and selectivity of a heterogeneous catalyst depends on the inherent activity of the components, on the physical structure of the catalyst and on the operating conditions for the reaction. This has led to attention being focused on catalyst preparation, since this is a major point for control of chemical composition and physical structure of the catalyst. For a long time catalyst preparation was regarded as one of the last strongholds of alchemy, but the advent of modern methods of surface analysis (ref. l),c oupled to increasing scientific knowledge, have elevated the subject from an art to a science (refs. 2, 3). As a result, it begins to be possible to manufacture a catalyst to a wide variety of given specifications. Although our capability is far from perfect, this possibility raises new 2 questions. In particular, given that we may know how to prepare a catalyst, it is necessary to ask which catalyst should be prepared. Since this question covers factors such as chemical composition, physical structure and mechanical strength, the answer may well involve optimisation of several non-related parameters. While the bulk of the proceedings of this meeting will be concerned with how to prepare catalysts, this paper is focused primarily on how to decide which catalyst to prepare. As can be seen from figure 1, the interacting requirements of a catalyst complicate the decision. As a result, it is not surprising that most successful1 catalysts have been developed on an empirical basis. In recent years, however, procedures have been developed to place the selection of catalysts on a more scientific footing. Generally, these involve a theoretical study in which general knowledge of catalysis, arguments by analogy and various theoretical concepts are applied to a particular problem (refs. 4, 5, 6, 7). c8talyst i nigh activity and s*lmctivity .ffmct racn ktiUrlC l-chlrntul 1 cood contacting a The chemical mtun of 1 Is blfunctimlity 1 OPtlU shape tboordm cto nftlraol of c-ntr WUlrad 7 b Ikh.nica1 r t m / b Effect of rdditirar b Porosity c Lrs adI mt tnnrfw C Stability c surfau Lru Choice of catalyst Figure 1. Factors influencing catalyst selection. It isregrettablethat our understanding of catalysis is still not good enough to guarantee success, but the approach has been found to be very useful in explaining why a given catalyst is active and, in some cases, in successfully predicting new catalysts (ref. 5). Insufficient knowledge is available to be independent of experimental testing, but the approach acts as a valuable guide to experimentation. As a result, the time needed for catalyst identification and testing can be significantly decreased, for the investment of only a short time on catalyst design. The procedure has been discussed in a few papers in recent years (refs. 4, 5, 6, 7), usually with emphasis on a given reaction. A more general approach is attempted in the present paper, with particular emphasis on those aspects of design that are of interest in the context of catalyst preparation. The broader
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