The invention relates to a method for strengthening graded
depolymerization of lignite through low-temperature
pyrolysis and oxidation pretreatment, which comprises the following steps: weighing lignite, putting the lignite into a low-temperature
pyrolysis system, introducing
inert gas, carrying out pretreatment until the temperature reaches the low-temperature
pyrolysis temperature, naturally cooling to
room temperature after the pyrolysis is ended, and collecting semicoke in the
system; adding the semicoke, an
oxidizing agent, an oxidizing auxiliary agent, an additive and a
solvent into a
system, carrying out oxidation pretreatment at
room temperature in an
air atmosphere, and filtering and separating to obtain residues; adding the residues and a
solvent into a system, and introducing
inert gas to carry out
thermal dissolution polymerization reaction; and after the reaction is finished, cooling the system to
room temperature, collecting gas in the system, and filtering and separating
solid residues and soluble substances. According to the method, the physicochemical structure of the lignite is regulated and controlled through a low-temperature pyrolysis pretreatment process, and relatively strong
ether bonds are weakened by utilizing a mild oxidation
pretreatment method, so that the yield of lignite
depolymerization products is improved, and the process of obtaining chemicals through lignite grading
depolymerization is enhanced.