Insights into the Reactivity of Thiophene: Heterogeneous Alkylation

The importance of thiophene derivatives in the fine chemical industry lies in the use of this class of molecules as raw materials in the synthesis of drugs, fragrances and pesticides. Nowadays, the synthesis of these molecules is multistep and expensive. The gas phase alkylation of thiophene on solid acid catalysts has been deeply studied by focusing on the possibility to control the product distribution of the reaction, paying particular attention to the relative amount of the 2- and 3-alkylthiophene, kinetic and thermodynamic products respectively. The difficulties in changing the 2:3 isomer ratio have been justified through the comprehension of thiophene behavior on the catalyst surface, that is responsible for the complex adsorption/desorption phenomena. It has been showed that the reaction is mainly affected by the strong adsorption of thiophene on the catalytic sites, with the critical step of the reaction represented by the saturation of the catalyst surface.