An Oxalate‐Bridged Binuclear Iron(III) Ionic Liquid for the Highly Efficient Glycolysis of Polyethylene Terephthalate under Microwave Irradiation

Abstract

An oxalate‐bridged binuclear iron(III) ionic liquid combined with an imidazolium based cation, (dimim)2[Fe2Cl4(μ‐ox)], was synthesized and characterized by a wide range of techniques. This halometallate ionic liquid was active in catalyzing the depolymerization of polyethylene terephthalate (PET) by glycolysis, under conventional and microwave‐assisted heating conditions. Both methodologies were very selective towards the production of bis(2‐hydroxyethyl)terephthalate (BHET). The employment of microwave heating proved beneficial in terms of time and energy saving when compared to the use of thermal heating. Indeed, dielectric spectroscopy studies revealed that the binuclear iron‐containing ionic liquid exhibits an excellent heating response under an electromagnetic field. The catalyst provided quantitative conversions to BHET in the glycolysis of post‐consumer PET bottles in only 3 h through microwave heating, as compared to 80 % conversion after 24 h under conventional heating.

Expanding Plastics Recycling Technologies: Chemical Aspects, Technology Status and Challenges

“…Other metallic ILs have been shown to be effective catalysts for this reaction under a variety of conditions. 742 Yue et al 743 used basic ILs at catalysts in PET glycolysis to isolate BHET in yields of up to 71% after 2 hours at 190 °C.…”

Multiple Hydrogen Bonds Promote the Nonmetallic Degradation Process of Polyethylene Terephthalate with an Amino Acid Ionic Liquid Catalyst

“…Researchers have also developed a series of glycolysis catalysts, such as metal salts, − zeolites, metal oxides, − solid superacids, deep eutectic solvents, ,, and ionic liquids (ILs). − Traditional catalysts are developed based on Zn, Mn, and other metal elements. ,, In the degradation process, the metal elements form coordination action with the ester bond of PET . The ester group is positively charged by the action of the coordination bond.…”

Expanding Plastics Recycling Technologies: Chemical Aspects, Technology Status and Challenges

“…Other metallic ILs have been shown to be effective catalysts for this reaction under a variety of conditions. 723 Yue et al 724 used basic ILs at catalysts in PET glycolysis to isolate BHET in yields of up to 71% after 2 hours at 190 °C.…”