Abstract: Systems and methods are provided for reducing or minimizing fouling within the primary fractionator of a pyrolysis reaction system. The reduced or minimized fouling can be achieved in part by providing one or more pump-around trays in the primary fractionator below the level of the fractionation trays for an intermediate product produced by the fractionator. Including a pump-around section below the fractionation trays can improve vapor distribution within the fractionation trays, which are believed to have an increased likelihood of accumulation of foulant deposits. Optionally, other vapor distribution devices can be included along with the pump-around section.

Abstract: Methods are provided for passivating and/or solubilizing crosslinked popcorn polymer formed from vinyl aromatic precursors. The passivation and/or solubilization can be performed by exposing the crosslinked popcorn polymer to an aromatics-containing solvent at a suitable temperature and/or by heat treating the crosslinked popcorn polymer in the presence of steam and oxygen followed by exposure to an aromatics-containing solvent. The vinyl aromatic polymer can be exposed to the aromatics-containing solvent for a suitable period of time at a temperature of 200° C. or more. Optionally, the aromatics-containing solvent can be at least partially in the liquid phase during the exposure of the vinyl aromatic polymer.