Ammonolysis of Polycarbonates with (Supercritical) Ammonia: An alternative for Chemical Recycling

Development of an acid-resistant solid-base catalyst for polycarbonate phenolysis

“…Various reactions such as hydrolysis, methanolysis, other alcoholysis 6-8 and aminolysis have been investigated to achieve PC monomerization. Various methods have been proposed for obtaining bisphenol A (BPA), including hydrolysis with high-temperature steam or supercritical water [9][10][11] and aminoysis, which involves the addition of various amines to synthesize BPA and corresponding urea derivatives [12][13][14] . However, recycling PC using these methods is di cult, as they result in a loss of carbonate monomers.…”

Catalyst-Free Approach for the Degradation of Bio- and CO2-Sourced Polycarbonates: A Step toward a Circular Plastic Economy

“…Following a century of innovation, commodity polymers have reshaped our modern lifestyle and quality by entering into numerous everyday consumer goods. However, their long-term accumulation in nature and oceans coupled with the lack of viable end-of-life recycling scenariogenerally limited to single usehas turned their magic into an environmental disaster. − This prompted the scientists to develop new approaches to recycle or upcycle the plastics. − While polyolefins or vinyl-type polymers are difficult to depolymerize by chemical pathways due to strong C–C bonds constituting their main-chain backbone, step-growth polymers with in-chain C–O or C–N linkages (such as polyesters, polycarbonates, polyurethanes) offer multiple chemical depolymerization opportunities. , In this context, solvolysis is now privileged by being enabled to regenerate the initial monomers (for close-loop recycling) or to develop new value-added chemicals (for open-loop recycling). − This is typically exemplified with a representative bisphenol A polycarbonate that was extensively depolymerized into the native bisphenol A via hydrolysis, or into mixtures of bisphenol A and carbonylated products ((a)­cyclic carbonates, oxazolidinones, or ureas) by alcoholysis or aminolysis (Scheme A). − However, most of these depolymerization pathways are generally slow and/or necessitate high temperatures (> 90 °C), and use thermally stable (1,5,7-triazabicyclo[4.4.0]­dec-5-ene and methanesulfonic acid (TBD:MSA) salts or ionic liquids) − or sophisticated (ZnO nanoparticles/ n Bu 4 NCl) catalysts, or cyclic amidine and guanidine bases (TBD or DBU) − to deliver degradation products with high yields. Further optimization of the depolymerization processes by combining catalyst innovations with the development of creative energy-efficient protocols still remains underdeveloped.…”

Steam Hydrolysis of Poly(bisphenol A carbonate) in a Fluidized Bed Reactor

“…Efforts have been aimed at the chemical fission of the carbonate bond (Scheme ), as it is susceptible to several types of chemical attacks. Some reported processes are hydrolysis, − methanolysis, − and ammonolysis. − The aim of solvolytic processes, in general, is the recovery of bisphenol A (BPA); in some cases, urea or dimethylcarbonate are obtained as carbonic acid derivatives. High yields of BPA were achieved in supercritical ammonia or during PC methanolysis in ionic liquids at moderate temperatures below 100 °C .…”

“…Some reported processes are hydrolysis, − methanolysis, − and ammonolysis. − The aim of solvolytic processes, in general, is the recovery of bisphenol A (BPA); in some cases, urea or dimethylcarbonate are obtained as carbonic acid derivatives. High yields of BPA were achieved in supercritical ammonia or during PC methanolysis in ionic liquids at moderate temperatures below 100 °C . Since the phenyl groups of PC are linked by a quaternary carbon, the carbonate bond is protected by the rigidity of the macromolecular backbone, providing some resistance if a solvolytic process is carried out.…”