Selective Propylene Oxidation to Acrolein by Gold Dispersed on MgCuCr₂O₄ Spinel

Abstract

Gold nanoparticles supported on a MgCuCr2O4 spinel catalyze the aerobic oxidation of propylene to acrolein. At 200 °C, the selectivity is 83% at a propylene conversion of 1.6%. At temperatures above 220 °C, propylene combustion dominates. The good performance of Au/MgCuCr2O4 in selective propylene oxidation is due to the synergy between metallic Au and surface Cu+ sites. Kinetic experiments (H2 addition, N2O replacing O2) show that the reaction involves molecular oxygen. DFT calculations help to identify the reaction mechanism that leads to acrolein. Propylene adsorbs on a single Au atom. The adsorption of propylene via its π-bond on gold is very strong and can lead to the dissociation of the involved Au atom from the initial Au cluster. This is, however, not essential to the reaction mechanism. The oxidation of propylene to acrolein involves the oxidation of an allylic C–H bond in adsorbed propylene by adsorbed O2. It results in OOH formation. The resulting CH2–CH–CH2 intermediate coordinates to the Au atom and a support O atom. A second C–H oxidation step by a surface O atom yields adsorbed acrolein and an OH group. The hydrogen atom of the OH group recombines with OOH to form water and a lattice O atom. The desorption of acrolein is the most difficult step in the reaction mechanism. It results in a surface oxygen vacancy in which O2 can adsorb. The role of Cu in the support surface is to lower the desorption energy of acrolein.

Dynamic formation of single-atom catalytic active sites on ceria-supported gold nanoparticles

“…In addition, recent theoretical studies by Song et al . 45 46 also proposed a relevant mechanism for CO oxidation and propylene oxidation at an isolated Au site, which are compatible with our findings.…”

Bismuth Molybdate-Based Catalysts for Selective Oxidation of Hydrocarbons

“…Anyway, the simple oxide Cu 2 O is reported to exhibit significant activity and selectivity and has been often chosen as a model catalyst for the determination of the involved reaction mechanism [4]. It was reported that catalytic activity of Cu 2 O catalyst system is lower than that of bismuth molybdate catalysts; therefore, the Cu 2 O catalyst is less popular [56].…”

Synthesis of polycarboxylate superplasticizers using an acrylic acid‐rich wastewater from acrolein production

“…However, plenty of acrylic acidrich wastewater was generated by this procedure. [1][2][3] There are two kinds of approaches for this kind of wastewater including incineration and recycling. Recycling the wastewater is better than burning it.…”

“…Now, about 80% of acrolein has been produced by the oxidation of propylene. However, plenty of acrylic acid‐rich wastewater was generated by this procedure . There are two kinds of approaches for this kind of wastewater including incineration and recycling.…”