Depolymerization of Waste Nylon 6 in [Bmim]Cl/water Mixture

Abstract

Depolymerization of nylon 6 (PA 6) to obtain caprolactam in the mixture of water and ionic liquid ([Bmim]Cl) was a environmentally benign and high efficient method. There are two reasons for the using of ionic liquid: first is that high H+ concentration in the mixture and the other is that anions of ionic liquid can break the hydrogen bonding of PA 6. The products of depolymerization are analyzed by mass spectrometry and high-performance liquid chromatography and the main is caprolactam. The optimal conditions to obtain caprolactam are determined of reaction temperature 170 °C, IL/H2O (w/w) 13.4%, and reaction time 8 h, and thus the yield of caprolactam 30.7% and degradation of PA 6 94.1%.

Are ionic liquids a proper solution to current environmental challenges?

“…31%). 50 The hydrolysis of nylon-6,6 to hexamethylenediamine and adipic acid in hydrophobic ILs (in the presence of water and H 2 SO 4 , at temperatures ranging preferably from 50-100 °C) has also been described by Seddon et al in 2009 in a patent. 51 More recently, Kamimura et al have investigated 52 the depolymerization of more complex systems, in particular fibrereinforced plastics (FRP, a composite material widely used in bathtubs, boats, and so on, which consists of inorganic fibres, polystyrene and polyesters) in [C 3 C 1 pip]Tf 2 N].…”

Ionic-Liquid-Mediated Deconstruction of Polymers for Advanced Recycling and Upcycling

“…113 This effect is particularly important for polymers with properties that are dominated by hydrogen-bonding effects (e.g., polyamides). 114 Metallic atoms also can be added into the design of ILs, often in the form of metal salts, to promote deconstruction. These metals can coordinate with hydrogen-bonding groups in condensation polymers to cause rapid deconstructions with high yields.…”

“…In contrast, [Ch]­[Cl] at a comparatively weaker 424 kJ/mol binding strength deconstructed PET with a 3 wt % conversion to no capturable small-molecule product . This effect is particularly important for polymers with properties that are dominated by hydrogen-bonding effects (e.g., polyamides) …”

“…For example, recently developed solubility-switchable ILs may become of interest for expanding the library of targetable polymers. These ILs are capable of undergoing a simple, reversible chemical reaction (e.g., protection–deprotection reaction) that induces a marked shift in an IL’s hydrophilicity. ,,, Such ILs could be harnessed to solubilize and depolymerize hydrophobic plastics, undergo a switching reaction to become hydrophilic, and then be separated from the small-molecule products via liquid–liquid extraction. Membrane separation, crystallization, electrodialysis, and adsorption also have been demonstrated as potential options for IL recovery and may find future use in deconstruction processes. , …”

Ionic Liquid‐Assisted Depolymerization of Condensation Polymers: A Review

“…Chen and co-workers depolymerized nylon 6 in the mixture of water and [bmim]Cl at a reaction temperature of 170 °C, 13.4 wt % of IL/H 2 O for 8 h, to produce 30.7 % caprolactam with 94.1 % polyamide degradation. [127] Kamimura et al further depolymerized polyamide 6 in hydrophilic ionic liquid [emim][BF 4 ] in the presence of DMAP as an organocatalyst within a short reaction time. [128] It was the first attempt to…”