Preparations of Heterogeneous Catalysts

Microwave radiation can be used to prepare new catalysts, enhance the rates of chemical reactions, by microwave activation, and improve their selectivity, by selective heating. The heating of the catalytic material usually depends on several factors including the size and shape of the material and the exact location of the material in the microwave field. Its location depends on the type of the microwave cavity used [2]. 

The objective of this chapter is to describe some advances in catalysis achieved by use of microwave irradiation. The aspects of microwave catalytic reactions which differ from traditional thermal methods are emphasized. The input of microwave energy into a reaction mixture is quite different from conventional (thermal) heating and it is the task of the synthetic chemists to exploit this special situation as fully as possible. 

The interaction of microwaves (MW) with solid materials has proven attractive for the preparation and activation of heterogeneous catalysts. It has been suggested that microwave irradiation modifies the catalytic properties of solid catalysts, resulting in increasing rates of chemical reactions. It is evident that microwave irradiation creates catalysts with different structure, activity and/or selectivity. Current studies document a growing interest in microwave-assisted catalyst preparation and in the favorable effects of microwaves on catalytic reactions. 

Preparation of catalysts usually involves impregnation of a support with a solution of active metal salts. The impregnated support is then dried, calcined to decompose the metal salt, and then reduced (activated) to produce the catalyst in its active form. Microwaves have been used in all stages of catalyst preparation. Beneficial effects of microwave heating, compared with conventional methods, have been observed especially in the drying, calcination, and activation steps. 

---

Volume 1 Preparation of Catalysts I.Scientific Bases for the Preparation of Heterogeneous Catalysts. Proceedings of the First International Symposium, Brussels, October 14-17,1975... 

Metal carbonyls form a large and important group of compounds which are used widely in the chemical industry, particularly in the preparation of heterogeneous catalysts and as precursors in CVD and metallo-organic CVD (MOCVD). 

Proceedings of the 2nd International FEZA (Federation of the European Zeolite Associations) Conference, Taormina, Italy, September 1-5, 2002 edited by R. Aiello, G. Giordano and F. Testa Scientific Bases for the Preparation of Heterogeneous Catalysts Proceedings of the 8th International Symposium, Louvain-la-Neuve, Leuven, Belgium, September 9-12, 2002... 

Volume 118 Preparation of Catalysts VII Proceedings of the 7th International Symposium on Scientific Bases for the Preparation of Heterogeneous Catalysts, Louvain-la-Neuve, Belgium, September 1-4, 1998 edited by B. Delmon, PA. Jacobs, R. Maggi, J.A. Martens, P. Grange and G. Poncelet... 

The effectiveness of zeolites in catalysis and separation can often be improved by the textural and chemical properties of the matrices in which they are imbedded. Chitosan gels issued from renewable resources are already used as supports for the preparation of heterogeneous catalysts in the form of colloids, flakes or gel beads [1, 2], In this study we present several methods for the incorporation of zeolites in chitosan matrices and characterize the synergic effect of the components on the properties of the composite. 

Controlled Preparation of Heterogeneous Catalysts for Chemo- and Enantioselective Hydrogenation Reactions... 

---