Kinetics of the catalytic reduction of 3-alk-1-enyl-thiophene Optimization of the operating conditions in a batch reactor Original Research Article

The access to 3-alkylthiophenes in large quantities and high purity is not straightforward: a new and convenient method for their synthesis has been devised on a pilot scale, in three steps. The last reaction implies the hydrogenation of 3-oct-1-enyl-thiophene into 3-octylthiophene and has been successfully performed in methanol under 0.2 MPa of hydrogen atmosphere with palladium on charcoal as a catalyst. However, this hydrogenation is not applicable to every thiophenic substrate bearing a double bond. We have indeed observed a poisoning effect of the thiophenic ring. To understand the reaction mechanism and find the best conditions for scaling up the reaction, the kinetics of the catalytic reduction of 3-oct-1-enyl-thiophene have been studied. The operating conditions have been optimized in order to avoid transfer limitations. The experimental results have been modelled by kinetic models, giving rise to physically meaningful parameters and leading to a better understanding of the reduction mechanism of vinyl thiophene.