Kinetics of poly(ethylene terephthalate) glycolysis by diethylene glycol. I. Evolution of liquid and solid phases

Kinetics of catalytic glycolysis of PET wastes with sodium carbonate

“…It is believed that when the sufficient amount of BHET and soluble oligomers was formed, the reaction continued to proceed in the single liquid phase until the equilibrium was reached. A transition from a heterogeneous reaction to a homogeneous reaction during depolymerisation was also observed for the non-catalytic glycolysis of PET [16], the methanolysis of PET with supercritical methanol [7], and the non-catalytic glycolysis of polycarbonate [48]. This finding was in stark contrast with the depolymerisation mechanism observed for the alkaline hydrolysis of PET since, apart from being an irreversible reaction, it always occurred in the heterogeneous phase [9].…”

“…Great attention is currently paid to chemical recycling, which basically involves the recovery of monomers leading to the yield of interesting value-added chemicals or intermediates from PET waste [3][4][5][6]. PET is a polyester with functional ester groups that can be cleaved by reagents, such as water, acids or bases (hydrolysis) [7][8][9], alcohols (alcoholysis) [10,11], amines (aminolysis) [12,13], ammonia (ammonolysis) [14] and glycols (glycolysis) [15,16]. Particularly, the glycolysis reaction is the molecular degradation of PET polymer by glycols, typically ethylene glycol (EG), where ester linkages are broken and replaced by hydroxyls terminals to give bis(2-hydroxyethyl terephthalate) (BHET), according to the following reaction scheme,…”

Polymeric Cracking of Waste Polyethylene Terephthalate to Chemicals and Energy

“…PET recycling processes can be based on the reversibility of this condensation reaction (chemical recycling by hydrolysis or solvolysis 8 ), which results in total recycling. Numerous papers deal with this reversible reaction for PET recycling and potential techniques include different methods of hydrolysis, 9 -12 glycolysis, [13][14][15][16][17], and methanolysis. 18 -20 However, these processes demand intensive bottle cleaning: polyethylene caps, paper, binder, and residual content have to be thoroughly removed.…”

Chemical recycling of poly(ethylene terephthalate). Application to the synthesis of multiblock copolyesters

“…For example, saturated and unsaturated polyesters [10][11][12], polyurethanes [13][14][15], coating materials [16][17][18][19] and additives [20][21][22] have been synthesized from such building blocks in recent years. A large number of reagents have been used for glycolysis of PET such as ethylene glycol [23][24][25][26], diethylene glycol [27,28], propylene glycol [29], neopentyl glycol [14], 1,4-butanediol [30,31], and some synthetic oligoesters [32,33]. To the best of our knowledge, no one has ever been used BHET as diol for the PET glycolysis.…”