Partial hydrogenation of benzene to cyclohexene over novel Ru-B/MoF catalysts

Abstract

A series of metal-organic framework (MOF) materials were synthesized together with the corresponding amorphous Ru-B/MOF catalysts, which were prepared by the impregnation-chemical reduction method. These materials were subsequently evaluated for the first time as catalysts for the partial hydrogenation of benzene to cyclohexene. The results for the initial hydrogenation rate (r0) for the different catalysts followed the trend Ru-B/MIL-53(Al)>Ru-B/MIL-53(Al)-NH2>Ru-B/UIO-66(Zr)>Ru-B/UIO-66(Zr)-NH2>Ru-B/MIL-53(Cr)>Ru-B/MIL-101(Cr)>>Ru-B/MIL-100(Fe), whereas the initial selectivity for cyclohexene (S0) was of the order of Ru-B/MIL-53(Al)≈Ru-B/MIL-53(Cr)>Ru-B/UIO-66(Zr)-NH2>Ru-B/MIL-101(Cr)>Ru-B/MIL-53(Al)-NH2>Ru-B/UIO-66(Zr)≈Ru-B/MIL-100(Fe). The Ru-B/MIL-53(Al) catalyst exhibited the highest r0 and S0 values of 23mmol·min-1· g-1 and 72%, respectively. The characterization results demonstrated that the Ru-B amorphous alloy nanoparticles were highly dispersed on MIL-53(Al) with the average diameter of 3.2 nm. In contrast, the Ru-B nanoparticles on MIL-100(Fe) had an average diameter of 46.6 nm. The smaller Ru-B nanoparticles not only provided more active sites for the hydrogenation to occur, but could also be beneficial in the formation of cyclohexene. The reaction conditions were further optimized for the Ru-B/MIL-53(Al) catalyst. At 180 °C under a H2 pressure of 5 MPa, a cyclohexene yield of 24% was obtained, highlighting the potential of MOF materials as catalyst supports for the partial hydrogenation of benzene. © Editorial office of Acta Physico-Chimica Sinica.