Objectif The objective of this work has been the development of a highly selective and temperature tolerant catalyst for the synthesis of dimethyl ether (DME). The key steps in DME synthesis are methanol synthesis, partial methanol dehydration and the water gas shift reaction. This combination results in a synergistic effect which relieves the unfavourable thermodynamics which apply to methanol synthesis. Almost full conversion of synthesis gas to DME is achieved in a single pass at moderate pressures. However, the reaction is strongly exothermic and large amounts of heat have to be removed.The relationships between the catalytic properties of HZSM-5 type zeolites and their degree of dealumination have been investigated. An optimum range of acidity and site density has been identified leading to the preparation of zeolites with a higher temperature tolerance while still preserving sufficient activity to make them suitable as dehydration catalysts. The most promising zeolites were mixed with standard methanol catalysts and were tested. Byproduct selectivity is highly dependent on the way in which the 2 catalysts are mixed.Long terms catalyst stability has been demonstrated and a 450-hour pilot plant test has been conducted.Dimethyl ether (DME) and water, rather than methanol, can be reacted with carbon monoxide using a rhodium catalyst to produce acetic acid, which can be derivatised to yield methyl acetate and acetic anhydride. The DME itself can be synthesised directly from synthesis gas much more efficiently, and at lower pressures, than can methanol.The advantages of using this process are:the separate synthesis of methanol at high pressure can be avoided;synthesis gas recycling, which is necessary in the methanol synthesis reactor, is avoided;separate synthesis of carbon monoxide is avoided since it can be provided by selecting reaction conditions and synthesis gas composition so as to leave over sufficient carbon monoxide in the effluent from the dimethyl ether reactor.Calculations have shown that this process is much more economical than the conventional methanol carbonylation route.An improved process has been developed for the conversion of methanol, or preferably dimethyl ether (DME), into liquid hydrocarbons for use as high octane motor fuel.DME is preferred as feedstock since:less water is generated and so the catalyst lifetime is increased;approximately 20% of the heat of reaction can be released before entering the adiabatic reactor, thereby reducing the exit temperature.One of the achievements of the research programme has been the generation of a comprehensive set of data linking the zeolite catalyst's degree and rate of dealumination to process parameters such as temperature, steam partial pressure and time. The ultimate catalyst lifetime can be extended by applying steam modified zeolites. The concept is based on the application of a ZSM-5 zeolite with an initially high aluminium concentration which is exposed to steam under selected conditions to reduce its activity to a suitable level. The zeolite is then in a state where it suffers only very slow dealumination ensuring a more stable catalytic performance leading to a more uniform product composition.Similar considerations apply in the production of light olefins for use as diesel or jet fuel.Steam treatments - mainly of medium pore and, in particular, ZSM-5 type zeolites - were varied systematically by applying different contact times, temperatures and steam partial pressures. Selected zeolites were subjected to additional modifications either before or after steam treatment. All samples were characterised by physical, physico-chemical and chemical (catalytic) techniques. The development of these techniques was initiated at an early stage of the project and methods were refined throughout the research period.TO OBTAIN AN IMPROVED UNDERSTANDING AT A FUNDAMENTAL LEVEL, OF THE PHENOMENA RELATING TO ZEOLITE STEAM DEALUMINATION AND TO STUDY THE ASSOCIATED CHANGES IN CATALYTIC PROPERTIES.FURTHER OBJECTIVES COMPRISE THE USE OF ZEOLITE DEALUMINATION AS A MEANS OF TAILORING THE ACIDIC PROPERTIES OF ZEOLITES AND TO SEEK NEW APPLICATIONS OF DEALUMINATED ZEOLITES IN CATALYSIS.WITHIN THE SCOPE OF THE PROJECT IS THE ESTABLISHMENT OF RELIABLE CHARACTERIZATION METHODS. Champ scientifique engineering and technologyenvironmental engineeringwaste managementwaste treatment processesrecyclingnatural scienceschemical sciencesinorganic chemistryinorganic compoundsnatural scienceschemical sciencesorganic chemistryalcoholsnatural scienceschemical sciencescatalysisengineering and technologyenvironmental engineeringenergy and fuels Programme(s) FP1-BRITE - Multiannual research and development programme (EEC) in the fields of basic technological research and the applications of new technologies (BRITE), 1985-1988 Thème(s) Data not available Appel à propositions Data not available Régime de financement CSC - Cost-sharing contracts Coordinateur FACULTES UNIVERSITAIRES NOTRE-DAME DE LA PAIX DE NAMUR Contribution de l’UE Aucune donnée Adresse Rue de Bruxelles 61 NAMUR / NAMEN Belgique Voir sur la carte Liens Site web Opens in new window Coût total Aucune donnée Participants (1) Trier par ordre alphabétique Trier par contribution de l’UE Tout développer Tout réduire Haldor Topsøe A/S Danemark Contribution de l’UE Aucune donnée Adresse 55,Nymøllevej 2800 Lyngby Voir sur la carte Coût total Aucune donnée
