Cellular and multi-cellular polystyrene and polystyrenic foams and methods of forming such foams are disclosed. The foams include an expanded polystyrene formed from expansion of an expandable polystyrene including an adsorbent comprising alumina, wherein the multi-cellular polystyrene exhibits a multi-cellular size distribution. The process for forming a foamed article includes providing a formed styrenic polymer and contacting the formed styrenic polymer with a first blowing agent and an adsorbent comprising alumina to form extrusion polystyrene. The process further includes forming the extrusion styrenic polymer into an expanded styrenic polymer and forming the expanded styrenic polymer into a foamed article.