KINETICS OF THE CATALYTIC REDUCTION OF 3-ALK-1-ENYL-THIOPHENE - OPTIMIZATION OF THE OPERATING-CONDITIONS IN A BATCH REACTOR

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 i mplies the hydrogenation of 3-oct-1-enyl-thiophene into 3-octylthiophe ne and has been successfully performed in methanol under 0.2 MPa of hy drogen atmosphere with palladium on charcoal as a catalyst. However, t his hydrogenation is not applicable to every thiophenic substrate bear ing a double bond. We have indeed observed a poisoning effect of the t hiophenic 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 unde rstanding of the reduction mechanism of vinyl thiophene.