Tetrahydrofuran recyclization to thiolane (the Yuriev reaction) was studied in the presence of alumina. Thiolane formation at 200-500-degrees-C was found to be accompanied by cracking of both the initial matter and the product, yielding hydrocarbons and coke deposition on the catalyst surface. Catalysts of various composition were investigated. Lewis acid sites appeared to play a prominent role in their activity in the generation of thiolane, i.e., the rate per site increased with the strength of the site. Taking into account kinetic, IR and NMR data, we postulated the reaction mechanism : the interaction between tetrahydrofuran and the catalyst yielded an oxo compound, subsequently dissociating on Al3+3-O- paired sites. Thiolane formed upon interaction of the intermediate alkoxy complexes and H2S activated on the surface.