| 内容提要: |
Since lignin is an abundant renewable biomass resource, it has been proved to be an alternative to fossil fuels for liquid fuels and value-added chemicals production. Hydrodeoxygenation (HDO) is an efficient chemical reaction for lignin upgrading which can break the C-O bonds with the effect of the catalyst under the H2 condition. Herein, we presented a novel temperature-programmed sulfidization method to prepare CoMo sulfide catalysts using Co-based layered double hydroxides (LDHs) as precursors and utilized the structure recoverability of hydrotalcites to introduce Mo into the interlamination by the hydration with MoO2- 4 solutions. By varying the Co/Fe/Al composition and proportion of the precursors, a series of CoMo sulfide catalysts were successfully prepared and characterized by nitrogen adsorption/desorption isotherms, X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma optical emission spectrometer (ICP-OES) and X-ray photoelectron spectroscopy (XPS). The characterization results indicated that the active sites of CoxS and MoS2 species on the catalysts were highly dispersed and the MoS2 showed a few-layer structure. For the HDO of eugenol, a typical lignin model compound, the Co3Al1-LDHs derived CoMo sulfide catalyst exhibited best HDO activity and selectivity with a 100% eugenol conversion and 65.8% total phenolics yield, under 3 MPa initial H2 pressure (measured at RT) at 300 °C for 3 hours. More important, we found that there exsited a strong interaction between Co and Mo sulfide species due to the intertwined contact, which facilitates a better HDO activity and selectivity than the sole Co sulfide catalyst. The Fe sulfide species in this catalyst system unfortunately promoted the further conversion of phenlics to form cycloalkanes. In addition, this hydrotalcites derived CoMo sulfide catalysts provided the possibility of aromatic production from various lignin-derived compounds. The HDO of eugenol could probably follow the following reaction route: firstly the highly selective cleavage of the CAr−OR bond, then the hydrogenation of the aromatic rings with a relatively lower selectivity, which could lead to more desired unsaturated phenolic products. |