Ni-Fe Alloy Catalyst Lignin Depolymerization

Lignin derived from lignocellulose is a renewable resource for the production of chemicals and fuels.It is difficult for large-scale application owing to its stability and complicated structure.The employment of lignin from paper industry was directly burned for energy but it would lead to environment pollution.There was a series of studies on the lignin conversion such as depolymerization over acid or base,pyrolysis,hydroprocessing and oxygenation.The degradation of lignin over hydroprocessing was the most efficient method to produce alkane fuels and high value-added chemicals such as phenols.However,there are some problems remained to be solved such as catalyst deactivation and low yield.Lignin primarily composed of methoxylated phenylpropanoid subunits is an abundant biomass that can be used to produce aromatics.Herein,a series of non-precious bimetallic Ni-Fe/AC catalysts were prepared for efficiently depolymerizing lignin.When organosolv birch lignin was used to determine the efficiency of the catalysts in methanol solvent,the Ni1-Fe1/AC(the ratio of Ni and Fe was 1:1)achieved the highest total yield of monomers(23.2 wt%,mainly propylguaiacol and propylsyringol)at 225℃,2 MPa H2,6 h.From GPC analysis,it also proved that lignin was efficiently depolymerized.The Ni-Fe alloy structure was formed according to the XRD,HRTEM,H2-TPR and XPS characterization.Based on the model compounds tests,the Ni1-Fe1/AC catalyst showed high efficiency in ether bond cleavage without hydrogenation of aromatic rings which could be attributed to the synergistic effect of the Ni and Fe in the alloy structure.The total yield of monomers by using Nii-Fei/AC catalyst reached to 39.5 wt%(88%selectivity to PG and PS)when birch wood sawdust was used as the substrate.