Abstract: A bi-modal radial flow reactor comprising a cylindrical outer housing surrounding at least five cylindrical, concentric zones, including at least three annulus vapor zones and at least two catalyst zones. The at least two catalyst zones comprise an outer catalyst zone and an inner catalyst zone. The at least three annulus vapor zones comprise an outer annulus vapor zone, a middle annulus vapor zone, and a central annulus vapor zone, wherein the central annulus vapor zone extends along a centerline of the bi-modal radial flow reactor. The outer catalyst zone is intercalated with the outer annulus vapor zone and the middle annulus vapor zone, and the inner catalyst zone is intercalated with the middle annulus vapor zone and the central annulus vapor zone. A removable head cover can be fixably coupled to a top of the cylindrical outer housing to seal a top of the bi-modal radial flow reactor.

Abstract: A bi-modal radial flow reactor comprising a cylindrical outer housing surrounding at least five cylindrical, concentric zones, including at least three annulus vapor zones and at least two catalyst zones. The at least two catalyst zones comprise an outer catalyst zone and an inner catalyst zone. The at least three annulus vapor zones comprise an outer annulus vapor zone, a middle annulus vapor zone, and a central annulus vapor zone, wherein the central annulus vapor zone extends along a centerline of the bi-modal radial flow reactor. The outer catalyst zone is intercalated with the outer annulus vapor zone and the middle annulus vapor zone, and the inner catalyst zone is intercalated with the middle annulus vapor zone and the central annulus vapor zone. A removable head cover can be fixably coupled to a top of the cylindrical outer housing to seal a top of the bi-modal radial flow reactor.

Abstract: 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.

Abstract: 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.