Investigation on Mn(3)O(4) Coated Ru Nanoparticles for Partial Hydrogenation of Benzene towards Cyclohexene Production Using ZnSO(4), MnSO(4) and FeSO(4) as Reaction Additives

Mn(3)O(4) coated Ru nanoparticles (Ru@Mn(3)O(4)) were synthesized via a precipitation-reduction-gel method. The prepared catalysts were evaluated for partial hydrogenation of benzene towards cyclohexene generation by applying ZnSO(4), MnSO(4) and FeSO(4) as reaction additives. The fresh and spent catalysts were thoroughly characterized by XRD, X ray fluorescence (XRF), XPS, TEM and N(2)-physicalsorption in order to understand the promotion effect of Mn(3)O(4) as the modifier as well as ZnSO(4), MnSO(4) and FeSO(4) as reaction additives. It was found that 72.0% of benzene conversion and 79.2% of cyclohexene selectivity was achieved after 25 min of reaction time over Ru@Mn(3)O(4) with a molar ratio of Mn/Ru being 0.46. This can be rationalized in terms of the formed (Zn(OH)(2))(3)(ZnSO(4))(H(2)O)(3) on the Ru surface from the reaction between Mn(3)O(4) and the added ZnSO(4). Furthermore, Fe(2+) and Fe(3+) compounds could be generated and adsorbed on the surface of Ru@Mn(3)O(4) when FeSO(4) is applied as a reaction additive. The most electrons were transferred from Ru to Fe, resulting in that lowest benzene conversion of 1.5% and the highest cyclohexene selectivity of 92.2% after 25 min of catalytic experiment. On the other hand, by utilizing MnSO(4) as an additive, no electrons transfer was observed between Ru and Mn, which lead to the complete hydrogenation of benzene towards cyclohexane within 5 min. In comparison, moderate amount of electrons were transferred from Ru to Zn(2+) in (Zn(OH)(2))(3)(ZnSO(4))(H(2)O)(3) when ZnSO(4) is used as a reaction additive, and the highest cyclohexene yield of 57.0% was obtained within 25 min of reaction time.