Bimetallic Ru-Ni/TiO2 catalysts for hydrogenation of N-ethylcarbazole: Role of TiO2 crystal structure

Hydrogenation of N-ethylcarbazole (NEC), the hydrogen lean form of a liquid organic hydrogen carrier, on TiO2 supported Ru-Ni bimetallic catalysts is investigated. Crystal structure of TiO2 plays a critical role on the hydrogenation activity and selectivity towards fully hydrogenated product. Ru/anatase catalyst exhibits higher selectivity but lower reactivity compared to Ru/rutile catalyst. Ni addition significantly promotes the performance of Ru/anatase catalyst while causes severe performance deterioration of Ru/rutile catalyst. Commercial P25, a mixture of anatase and rutile phases in approximate ratio A/R∼1/4, is found to be the best TiO2 support for NEC hydrogenation. Ru/P25 catalyst outperforms both Ru/rutile and Ru/anatase and its activity can be further slightly improved by Ni addition. The unexpected synergism between the two different TiO2 phases for Ru based NEC hydrogenation catalysts is related to metal-support interaction and Ru-Ni interaction.