Synthesis of tetrahydropyran from tetrahydrofurfuryl alcohol over Cu–Zno/Al2O3 under a gaseous-phase condition

Abstract

Tetrahydropyran (THP) represents an O-containing hetero-cyclic compound that can be used as a promising solvent or monomer for polymer synthesis. In this work, Cu–ZnO/Al2 O3 catalysts have been prepared by a facile precipitation–extrusion method and used for the synthesis of THP through gaseous-phase hydrogenolysis of tetrahydrofurfuryl alcohol (THFA). The effect of the molar ratio of Cu/Zn/Al, reaction temperature, and hydrogen pressure was investigated. An 89.4% selectivity of THP was achieved at 270◦ C and 1.0 MPa H2. Meanwhile, the optimum molar ratio of Cu/Zn/Al was determined to be 4:1:10. The Cu–ZnO/Al2 O3 catalyst exhibited high catalytic activity and stability for 205 h on-stream. A possible reaction mechanism involving several consecutive reactions was proposed: THFA was firstly rearranged to 2-hydroxytetrahydropyran (2-HTHP), followed by the dehydration of 2-HTHP to 3,4-2H-dihydropyran (DHP) over acid sites; finally, the DHP was hydrogenated to THP. The synergy of acid sites and metal sites of Cu–ZnO/Al2 O3 played an important role during the production of THP.