G.F. Froment – författare

Many processes of the chemical industry are based upon heterogeneous catalysis. Two important items of these processes are the development of the catalyst itself and the design and optimization of the reactor. Both aspects would benefit from rigorous and accurate kinetic modeling, based upon information on the working catalyst gained from classical steady state experimentation, but also from studies using surface science techniques, from quantum chemical calculations providing more insight into possible reaction pathways and from transient experimentation dealing with reactions and reactors. This information is seldom combined into a kinetic model and into a quantitative description of the process. Generally the catalytic aspects are dealt with by chemists and by physicists, while the chemical engineers are called upon for mechanical aspects of the reactor design and its control. The symposium "Dynamics of Surfaces and Reaction Kinetics in Heterogeneous Catalysis" aims at illustrating a more global and concerted approach through a number of prestigious keynote lectures and severely screened oral and poster presentations.

The 2nd International Symposium on Hydrotreatment and Hydrocracking of Oil Fractions, which is also the 7th in the series of European Workshops on Hydrotreatment, took place in Antwerpen, Belgium from November 14 to 17.The Symposium emphasized how oil refining faces increasingly severe environmental regulations. These and the increasing application of heavier crudes containing more S-, N- and metal components call for more efficient hydrotreatment and hydrocracking processes. It is clear from the keynote lectures, the oral contributions and the posters of this meeting that adapting the operating conditions will not suffice. Adequate catalysts need to be developed, with different composition and structure. Surface science techniques and molecular modeling are now well established tools for such a development. They should be of help in widely different aspects, like the role of precursors in the preparation or the modifications undergone by the catalyst under reaction conditions. The improvement of hydrotreatment and hydrocracking also needs accurate modeling of the chemical reactor. This requires more representative hydrodynamics and kinetic models whose validity extends to the very low S- and N-contents. These areas should be vigorously developed.

The symposium on Hydrotreatment and Hydrocracking of Oil Fractions aims to provide a global perspective and an inspection of the state-of-the-art of these processes. New American, European and Japanese environmental regulations call for advanced hydrotreatment processes for HDS and HDN for the removal of S- and Ni-components from oil fractions. These will alter the product slate of the oil refineries and the hydrocarbon composition of these products. Hydrocracking will play an important part in this shift.Adapting the operating conditions will not suffice to reach the desired product specifications and yields. Adequate catalysts will have to be developed. Powerful tools are now available for this, e.g. surface science techniques, molecular modeling and new types of reactors operated in a nonsteady mode.Another instrument in the improvement of hydrotreatment and hydrocracking units is the availability of more realistic kinetic models. These are based on a judicious insight into the reaction mechanism, also provided by the above-mentioned tools. Progress in the analytical techniques has allowed the reduction of the lumping of components in these kinetic models and first order kinetic equations are gradually replaced by equations accounting for the adsorption of the various components.More detailed and more realistic reactor models are now based on rigorous hydrodynamic models and their application has become possible through the rapidly increasing possibilities of computers.

The symposium "Reaction Kinetics and the Development of Catalytic Processes" is the continuation of the very successful International Symposium "Dynamics of Surfaces and Reaction Kinetics in Heterogeneous Catalysis", held in September 1997 in Antwerp, Belgium. These proceedings contain a unique series of top level plenary lectures mainly focused on• the dynamics of catalytic surfaces• the interaction of the reacting molecules with the solid catalyst• the elementary steps of reaction pathways and molecular kinetics.Surface science techniques, molecular modeling, transient kinetic studies, sophisticated and specific reactors are included to a growing extent in the kinetic modeling and the development of catalytic processes. How this is practiced today and how it will evolve in the coming years, and what benefit can be expected for a more fundamentally based approach is the aim of the symposium.

Reaction Kinetics and the Development and Operation of Catalytic Processes is a trendsetter. The Keynote Lectures have been authored by top scientists and cover a broad range of topics like fundamental aspects of surface chemistry, in particular dynamics and spillover, the modeling of reaction mechanisms, with special focus on the importance of transient experimentation and the application of kinetics in reactor design. Fundamental and applied kinetic studies are well represented. More than half of these deal with transient kinetics, a new trend made possible by recent sophisticated experimental equipment and the awareness that transient experimentation provides more information and insight into the microphenomena occurring on the catalyst surface than steady state techniques. The trend is not limited to purely kinetic studies since the great majority of the papers dealing with reactors also focus on transients and even deliberate transient operation. It is to be expected that this trend will continue and amplify as the community becomes more aware of the predictive potential of fundamental kinetics when combined with detailed realistic modeling of the reactor operation.

Catalyst Deactivation 1994 was an expansion of earlier, highly successful symposia. The objective of the symposium was to promote a scientific approach of the phenomenon of catalyst deactivation which will contribute to the development of catalysts which are less subject to structural transformations and more resistant to poisons and coke formation. These aspects are dealt with in 12 plenary lectures, 48 oral presentations and 35 poster papers, which were critically selected from an impressive response from some 30 countries.Both fundamental and applied aspects were covered. The deactivation of catalysts in important industrial processes like fluid bed catalytic cracking hydrotreatment, hydrodesulfurization, catalytic reforming, hydrodenitrogenation, steam reforming, hydrodemetallization, hydrocracking, Fischer-Tropsch synthesis, propane dehydrogenation, phthalic anhydride synthesis received considerable attention. Mechanisms of poisoning, sintering and coking were further investigated and modelled and new experimental techniques for the characterization and the quantification of deactivation were also introduced.

This Symposium on Catalyst Deactivation ensues those held at Berkeley (1985), Antwerp (1980) and Berkeley (1978).The three main topics emphasised at this most recent symposium were: the techniques used in deactivation studies, the mechanisms of catalyst deactivation, and modelling. With respect to the first, it became apparent that the study of deactivation faces even more difficulties than the characterization of fresh catalysts and the measurement of activity or selectivity, due to the multiplicity of interacting processes occurring during deactivation. Quite substantial progress has been made recently in the understanding of the mechanisms of various deactivation processes, particularly coking, and extra time was accorded to these topics at the symposium. The third topic corresponds to a problem which is very central to development studies and to the chemical engineering aspect of catalysis: it deals with the representativity of accelerated tests and the modelling of the deactivation phenomena.

The symposium "Reaction Kinetics and the Development of Catalytic Processes" is the continuation of the very successful International Symposium "Dynamics of Surfaces and Reaction Kinetics in Heterogeneous Catalysis", held in September 1997 in Antwerp, Belgium. These proceedings contain a unique series of top level plenary lectures mainly focused on

. the dynamics of catalytic surfaces

. the interaction of the reacting molecules with the solid catalyst

. the elementary steps of reaction pathways and molecular kinetics.

Surface science techniques, molecular modeling, transient kinetic studies, sophisticated and specific reactors are included to a growing extent in the kinetic modeling and the development of catalytic processes. How this is practiced today and how it will evolve in the coming years, and what benefit can be expected for a more fundamentally based approach is the aim of the symposium.

Studies in catalyst deactivation play a major role in the identification of the real catalytic system, in particular, the structure and texture of the solid, which is often in a metastable state, as it is operated in the industrial reactor. These studies also allow the identification of the experimental conditions which preserve this active and selective state. This is crucial for a real understanding of catalysts and catalysis. Another area of catalytic science concerns reactions kinetics, which, if properly determined, are of paramount importance in the elucidation of mechanisms. The behavior of the kinetics during aging and deactivation and an accurate modeling of the evolution of activity and selectivity are essential information for the process performance. These are just two typical examples, but quite generally, the science of catalyst deactivation is going to be more oriented to fundamental issues.