Thiotolerant Ir/SiO2–Al2O3 bifunctional catalysts: effect of support acidity on tetralin hydroconversion

Abstract

Tetralin hydroconversion over supported iridium catalysts has been investigated under a pressure of 4 MPa in the presence of H₂S in a continuous high-pressure gas-phase microreactor. Decalin, naphthalene, ring-contraction bicyclic products and one-ring-opening products are formed. A screening of silica, alumina and amorphous silica–alumina (ASA) supports demonstrates that only ASA provides thiotolerance and ring opening/contraction selectivity to iridium nanoparticles. By testing Ir/ASA catalysts with various silica–alumina ratios but similar Ir particle size (1.5 nm), it is shown that the intermediate concentration of silica (40 wt%) leads to the highest activity and selectivity, in correlation to the Brönsted acidity measured by infrared spectroscopy of adsorbed pyridine.