Monomer recovery from polycarbonate by methanolysis

Abstract

Depolymerization and monomer recovery from polycarbonate (PC) by methanolysis was investigated. Methanolysis with molar ratios of methanol to polycarbonate ranging from 12.5 to 50 was carried out from 170°C to 300°C for up to 30 min. Polycarbonate decomposed into two monomers, bisphenol A (BPA) and dimethyl carbonate (DMC), and two useful by-products, phenol and 4-tertbutylphenol. The percentage depolymerization of polycarbonate increased markedly from 170°C to 230°C and decomposed completely when the temperature was higher than 260°C. Reaction time and molar ratio of MeOH/PC are two other important factors that affect polycarbonate methanolysis. The optimal depolymerization condition of PC was found at 240°C with the molar ratio of MeOH/PC equal to 37.5 and the time of 5 min. Under these conditions, polycarbonate would decompose completely and the monomer recovery of BPA and DMC were 90.7% and 95.2%, respectively.

Depolymerization of poly(bisphenol A carbonate) under mild conditions by solvent-free alcoholysis catalyzed by 1,8-diazabicyclo[5.4.0]undec-7-ene as a recyclable organocatalyst: a route to chemical recycling of waste polycarbonate

“…Pyrolysis shows the main disadvantage of low BPA selectivity due to the large production of byproducts. [8][9][10] Other options are based on the cleavage of carbonate bond through a chemical reaction such as, for instance, hydrolysis, [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] aminolysis, 22,23 alcoholysis, [11][12][13][14][15][16]29,[45][46][47][48] or also glycolysis. [17][18][19][20][21] In principle, a few of these approaches not only allow the regeneration of the monomer (BPA), but can also afford useful coproducts, for instance organic carbonates, or carbamates and ureas, if the polymer is reacted, respectively, with alcohols or amines.…”

“…54 Relative to other approaches, such as PC pyrolysis or hydrolysis, detailed studies on the alcoholysis of PC are relatively few. The reaction can proceed in neat alcohol (used as depolymerizing agent and solvent; no auxiliary solvent used) 12,15,16,[45][46][47][48] but, even in the presence of a catalyst, 15,47,48 severe experimental conditions are required (high temperatures (493 K); 16 utilization of the alcohol in near critical or supercritical conditions 12,15,46,47 ) because of the poor solubility of PC in the used reaction medium (MeOH, EtOH). Milder conditions have been applied when the alcoholysis reaction (eqn (1); R = Me) has been carried out in a solvent, such as THF, 1,2-dichloroethane, toluene, 1,4-dioxane, N-methyl-2-pyrrolidone, able to dissolve the polymeric material.…”

Non-isocyanate Polythiourethane Network from Biowaste: Achieving Circularity via Multidimensional Chemical Recycling with Valuable Small-Molecule Recovery and Reprocessability by Understanding the Dynamic Chemistry

“…Apart from dissociative reversions, associative exchange reactions are another class of dynamic chemistry that can be exploited to enable monomer or small-molecule recovery. ,,,− For example, transcarbamoylation is an effective approach to break down PU and recover carbamate compounds . With a thionourethane group being a sulfur-analogue of a urethane linkage with the carbonyl being substituted by thiocarbonyl, we hypothesize that thionourethane linkages may possess dynamic chemistry analogous to urethanes, i.e., trans­(thio)­carbamoylation (Figure b), which could benefit small-molecule recovery from NIPTU materials (see Figure ).…”

Investigation of the main regularities of glycolysis of polycarbonate plastic during catalysis by basic agents

“…Utilizing 13 C NMR spectroscopy, a qualitative characterization of the reaction products produced by KOH catalysis was completed. The results of the analysis showed that the resulting spectrum corresponds to a mixture of bisphenol A monohydroxyethyl ether (MHE-BPA) and bisphenol A bishydroxyethyl ether (BHE-BPA) (Fig.…”