The roles of metal-promoter interface on liquid phase selective hydrogenation of crotonaldehyde over Ir-MoOx/BN catalysts

A series of MoO x -promoted Ir/BN catalysts were tested for liquid phase selective hydrogenation of crotonaldehyde. The MoO x -promotion could significantly improve the reactivity up to 5-fold. Such improvement was mainly due to the formation of Ir-MoO x interfacial sites in the promoted catalyst, which accelerated the adsorption and activation of crotonaldehyde molecule as evidenced by a much lower activation energy (18.9 kJ mol −1 on the 0.3Mo-3Ir/BN versus 38.4 kJ mol −1 on the 3Ir/BN). The kinetic results revealed negative reaction order of crotonaldehyde (up to -1.1) and high reaction order of H 2 (up to 2.2), indicating the high coverage of crotonaldehyde on the catalyst surface suppressed the adsorption of H 2 due to its low solubility in the liquid phase. Therefore, the adsorption and activation of H 2 on the catalyst might be the rate determining step. However, the preferred adsorption of crotonaldehyde on the Ir-MoO x interface alleviated the suppression of H 2 adsorption, which was another reason for the higher activity.