2.6 Lignin Hydrogenolysis
The hydrogenolysis of birch organosolv lignin was carried out in 100 mL stainless steel autoclave (Beijing Shijisenlang Chemical Machinery Co., Ltd., China). Typically, 0.3 g birch organosolv lignin 0.06 g catalyst and 20 mL water/ethanol (1:1) were added into the autoclave vessel. The vessel was purged three times with nitrogen before sealed and pressured to 1 MPa with hydrogen. The reaction was carried out at 280 ºC for 2 h. After reaction, the reaction vessel was cooled to room temperature. The reaction mixture was filtered to remove catalyst and the filtrate was extracted with ethyl acetate to obtain lignin oil. And then, the lignin oil was analyzed by GC-MS, gel permeation chromatography (GPC) and two-dimensional heteronuclear single quantum correlation (2D HSQC). The yield of the aromatic monomers was calculated using the following Eq. (3):
Yield of the aromatic monomers (%) = WA/WF×100% (3)
Where WA is the weight of aromatic monomers after the hydrogenolysis of lignin; WF is the weight of feed lignin.