Utilization of Natural Zeolites in Catalysis of C-C Bond Formation Processes

The processes of new C-C bond formations are crucial for the organic synthesis. The application domains of the reactions proceeding with formation of new C-C bonds have constantly developed along with the development of the world-wide economy branches. Thus, starting from raw materials such as oil, coal and natural gas a great variety of complex organic compounds are obtained that can be used to prepare numerous synthetic products such as: drugs, dyes, pesticides, cosmetics, detergents, etc. Such transformations are possible to be achieved due to the organic chemistry development, especially the synthetic chemistry where the structures can be converted and new C-C bonds created. The majority of these reactions proceed by mechanisms involving reaction intermediates. In the first section of the present chapter the condensation reaction of the carbonyl compounds and the corresponding reaction mechanism are briefly presented. In order to improve the obtaining methods of the resulting products (increasing in the specific reaction rate, minimization of the side products, the reaction directing straight to the final product, etc.) the presence of either homogeneous or heterogeneous catalysts is quite necessary. Among the numerous catalytic processes with C-C bond formation those based on the aldol condensation in heterogeneous catalysis are the most important and thoroughly studied. The synthetic catalysts usually taken in such processes are described in the second section of the present chapter where the reaction mechanisms with both acid and base catalysis are given. Apart from the synthetic catalysts the natural zeolites deserve mention due to their advantages as efficient catalysts of a low price. The material in the final two sections of this chapter is focused on the clinoptilolite in the zeolite volcanic tuff as well as on its properties studied and tested in the aldol condensation reaction of acetaldehyde with formaldehyde.

Keywords: Natural zeolites, volcanic tuffs, clinoptilolite (natural) zeolite, ion exchange, dealumination, physical (thermal) activation, thermal activation, chemical treatments, biological treatments, catalytic applications, catalytic processes, adsorption process, heterogeneous catalysis, mineral acids, C-C bonds, acetaldehyde, formaldehyde, aldol condensation, acrolein, crotonaldehyde.