Enhancing tetralin hydrogenation activity and sulphur-tolerance of Pt/MCM-41 catalyst with Al(NO3)3, AlCl3 and Al(CH3)3

Abstract

High efficiency and sulfur-tolerant Pt–Al/MCM-41 catalysts were prepared with Al(NO₃)₃, AlCl₃ and Al(CH₃)₃ as promoters. The highest tetralin conversion and the best sulfur-tolerance were achieved on the Al(CH₃)₃-promoted catalyst. The pseudo first-order rate constants of this catalyst for tetralin hydrogenation are about 2–5 and 8–10 times as high as that of the Al-free one under sulfur-free and sulfur-containing conditions, respectively. AlCl₃ also improves the catalytic activity and sulfur-tolerance considerably while Al(NO₃)₃ has certain promoting effects on sulfur-tolerance. These promoting effects can be ascribed to (i) the anchor and isolation effects improving the platinum dispersion which benefits tetralin hydrogenation and sulfur-tolerance. (ii) The electron-withdrawing effect is in the order Al(NO₃)₃ > AlCl₃ > Al(CH₃)₃, resulting in a similarly electron deficient Pt^δ+ order of the corresponding catalysts. The sulfur-tolerance is in favour of electron deficient Pt^δ+, though the opposite of this is true for the tetralin hydrogenation. (iii) The acid sites and especially the hydroxyl sites, provide additional active sites and spillover hydrogen which also contribute to the tetralin hydrogenation and sulfur-tolerance of the catalysts.