Provided herein are methods of inhibiting polymerization of vinyl aromatic monomers. The methods include distilling a vinyl aromatic monomer in a distillation column to form a vinyl aromatic monomer distillate; removing the vinyl aromatic monomer distillate from the distillation column; combining the vinyl aromatic monomer distillate with 4-tert-butylcatechol (TBC) to form a treated distillate; and adding a reflux liquid that includes the treated distillate to the distillation column liquid of the distillation column. An added oxygen gas may be present in a distillation column liquid in an amount of at least 1 ppmw, based on the weight of the vinyl aromatic monomer.