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

Abstract

Abstract A series of MoOx-promoted Ir/BN catalysts were tested for liquid phase selective hydrogenation of crotonaldehyde. The MoOx-promotion could significantly improve the reactivity up to 5-fold. Such improvement was mainly due to the formation of Ir-MoOx 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\u2009kJ mol-1 on the 0.3Mo-3Ir/BN versus 38.4\u2009kJ mol-1 on the 3Ir/BN). The kinetic results revealed negative reaction order of crotonaldehyde (up to -1.1) and high reaction order of H2 (up to 2.2), indicating the high coverage of crotonaldehyde on the catalyst surface suppressed the adsorption of H2 due to its low solubility in the liquid phase. Therefore, the adsorption and activation of H2 on the catalyst might be the rate determining step. However, the preferred adsorption of crotonaldehyde on the Ir-MoOx interface alleviated the suppression of H2 adsorption, which was another reason for the higher activity.