Hydrogenation Of Ethyl Levulinate By Pd And Ru Nanocatalysts

Biomass is expected to be the most promising renewable carbon resource to replace fossil resources. A variety of transportation fuel molecules and chemicals could be obtained from biomass via catalytic conversion. The synthesis of gamma-valerolactone is one of the important routes of biomass conversion.The traditional reaction pathyway is the hydrogenation levulinic acid wherein the presence of carboxylic acid groups may cause catalytic activity decline. Recently, it has been shown that levulinate ester can be produced in very high yield in alcoholic solvents, which can reduce the humin production and improve the overall efficiency compared with the production of levulinic acid. In this dissertation, supported Pd and Ru catalysts were prepared via wet incipient impregnation. The structure-activity relationship between metal and carrier, metal particle size, oxidation states of metal particles and support materials were systematically studied. The following conclusions were drawn:1. Pd nanoparticles supported on Nb2O5-doped activated carbon were prepared via wet incipient impregnation. Nb2Os plays a bifunctional role in the catalytic process:stabilizing Pd nanoparticles and acting as an acidic co-catalyst. This synergistic effect between Nb2O5 and Pd led to unprecedented high activity of supported Pd catalysts in EL hydrogenation. The synergy is related to both the Nb2O5 loading and the calcination temperature. In an optimum condition, EL conversion of 87% and GVL selectivity of 97% was achieved under mild reaction conditions (100 ℃ and 0.5 MPa H2).2. Monometallic Ru nanoparticles supported on silica was prepared via wet incipient impregnation. The catalyst efficiently hydrogenate ethyl levulinate to ethyl hydroxyl pentenonate at room temperature and 0.5 MPa H2. The active sites are likely due to the easily reducible RuOx species on Ru nanoparticles weakly interacting with silica. The amount of such RuOx species relates to the pre-treatments of the Ru nanoparticles. Similar behavior was also observed on other siliceous materials such as ZSM-5. Moreover, the ZSM-5 as solid acid catalyst promotes the hydrogenation reaction rate.