Innovative One-Step Liquefying Method with High Conversion of Biomass Using Raney Nickel and NaOH as Combined Catalysts

A novel liquefaction method was developed for transforming different types of biomass, such as fir, bamboo, pine, and corncob, into bio-oil efficiently with Raney nickel (R-Ni) and NaOH as combined catalysts in a 2-propanol/H2O system, which was carried out in a 50 mL stainless-steel autoclave at 245 °C, corresponding to the working pressure maintained at 8 MPa. The conversion of biomass could reach 97–99%. Besides, a high bio-oil yield of 63.98% and higher heating value of 30.09 MJ/kg were achieved when fir was used as the feedstock. The gas chromatography–mass spectrometry analyses indicated that the major compounds in bio-oils were phenols, followed by acids, alcohols, ketones, and hydrocarbons, which were mainly light-weighted molecules with low boiling points measured by thermogravimetric analysis. Additionally, the R-Ni catalyst could be repeatedly used at least 5 times without the loss of activity.