Method for directionally preparing phenolic compounds from fibrous biomass by means of pressurization liquefaction

The invention discloses a method for directionally preparing phenolic compounds from fibrous biomass by means of pressurization liquefaction. The method includes steps of firstly, carrying out pressurization liquefaction reaction, to be more specific, adding low-carbon alcohol, acid catalyst and biomass materials such as bamboo with high lignin contents into an autoclave and enabling the low-carbon alcohol, the acid catalyst and the biomass materials to carry out alcoholysis liquefaction reaction under the conditions of pressure of 3-7MPa, temperature of 160-240 DEG C and rotational speed of 400r/min; secondly, filtering a direct liquefaction product to obtain residue and filter liquid in directional extraction separation procedures. The method has the advantages that the filter liquid is neutralized by the aid of NaOH liquor, neutralized liquid is gradually graded and separated, and components of the phenolic compounds in the pressurization liquefaction products can be directionally gradually separated from one another by the aid of solvents such as distilled water and organic extracting agents; as shown by results of GC-MS (gas chromatography-mass spectrometer) analysis on the three types of phenolic compounds with different molecular weights, the contents of phenolic substances in the phenolic compounds are higher than 75%; as shown by GPC (gel permeation chromatography) analysis on the three types of phenolic compounds, Mn in the phenolic compounds ranges from 100 to 800, and Mw in the phenolic compounds ranges from 400 to 2000.