The catalytic performance of gas-phase amination over Pd–La catalysts supported on Al2O3 and MgAl2O4 spinel

Both γ-Al2O3 and MgAl2O4 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/Al2O3 and Pd–La/MgAl2O4 catalysts were characterized by XRD, BET, NH3-TPD, pyridine-IR, and XPS techniques. The replacement of Al2O3 with MgAl2O4 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 NH3-TPD and pyridine-IR results. The XPS analysis showed that the MgAl2O4 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/MgAl2O4 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/MgAl2O4 catalyst was up to 400 h, and the yield of 2,6-DIPA after 200 h reaction was still more than 80%.