The catalytic performance of gas-phase amination over Pd–La catalysts supported on Al 2O 3 and MgAl 2O 4 spinel

Abstract

Both γ-Al 2O 3 and MgAl 2O 4 spinel used as support for the palladium–lanthanum catalyst in the preparation of 2,6-diisopripylaniline (2,6-DIPA) by the gas-phase amination of 2,6-diisopropyl phenol (2,6-DIPP) were studied. The bulk and surface properties of Pd–La/Al 2O 3 and Pd–La/MgAl 2O 4 catalysts were characterized by XRD, BET, NH 3-TPD, pyridine-IR, and XPS techniques. The replacement of Al 2O 3 with MgAl 2O 4 spinel in the palladium–lanthanum supported catalyst not only neutralized some strong acid sites, but also transformed them into relatively weaker acid sites according to the NH 3-TPD and pyridine-IR results. The XPS analysis showed that the MgAl 2O 4 spinel support improved the reduction of PdO. All these factors increased the catalytic performance for gas-phase amination of 2,6-DIPP. On the Pd–La/MgAl 2O 4 catalyst, under the LHSV 0.3 h −1, the highest conversion of 2,6-DIPP was 98.5%, the highest selectivity and the highest yield of 2,6-DIPA was 88.9% and 87.5%, respectively. The whole run time of Pd–La/MgAl 2O 4 catalyst was up to 400 h, and the yield of 2,6-DIPA after 200 h reaction was still more than 80%.