Isomerization pathway of N-ethylcarbazole hydrogenation products affected by metal-support interactions

N-ethylcarbazole (NEC) is a widely studied liquid organic hydrogen carrier, and a large number of catalysts with excellent reactivity has been designed and developed thus far. However, the phenomenon of isomeric transformation of 12H-NEC products during the reaction was not explained. Here, we studied the process based on three different Ru catalysts supported on zirconium-based supports, and based on the experimental results, we identified that supported metal-support strong interaction (SMSI), metal-support anion interaction (MSAI) and hydrogen spillover will have coupling effect on the hydrogenation reaction path and the occurrence of isomerization in 12H-NEC product. Higher 12 [H] B content in 12H-NEC under Ru/ZrN catalyst was caused by the large number of secondary active centers on the surface of the support reacting in the hydrogenation reaction. The active site for the isomerization of 12 [H] B to 12 [H] A may be the electronegativity interface formed by Ru and the support, while the electroneutral or electropositive interface rich in hydrogen is not conducive to the catalytic conversion. To sum up, an image model for the isomeric transformation of 12H-NEC products was proposed.