Hydrogenation of tetralin over Pt catalysts supported on sulfated zirconia and amorphous silica alumina

Abstract

Pt supported on sulfated zirconia (SZ) and amorphous silica alumina (ASA) was explored for the hydrogenation of tetralin. Pt/ASA had a higher concentration and strength of acid sites than the SZ-supported counterpart, for which the acid site concentration of the carrier decreases after catalyst synthesis due to sulfur elimination. The strong acidity of Pt/ASA caused higher deactivation due to coke deposition, while Pt/SZ was comparatively stable. Pt/ASA also exhibited higher porosity and Pt dispersion than Pt/SZ. The adsorption of CO, the XANES analysis and gravimetric sorption of benzene showed that the Pt particles on SZ were strongly electron deficient, a feature that has been speculated to be associated with the electron withdrawing effect of sulfate groups. For tetralin hydrogenation, Pt/SZ was more active than Pt/ASA above 423 K while the opposite was observed at 413 K. The apparent activation energies were 98 and 45 kJ mol⁻¹ on Pt/SZ and Pt/ASA, respectively. Pt/ASA was more active than Pt/SZ in the presence of quinoline, while Pt/SZ retains the highest activity in the presence of dibenzothiophene (with or without quinoline). The lower apparent activation energy on Pt/ASA in the absence of quinoline or dibenzothiophene and its higher activity in the presence of quinoline were attributed to its strong Brønsted acidity, promoting the hydrogenation at the perimeter of Pt particles. The higher sulfur resistance of Pt/SZ was attributed to the electron deficiency of the supported Pt particles. In this respect, surface sulfate anions induce stronger electron deficiency in supported Pt than the acidity of the support.