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Article

Methanolysis of Poly(lactic Acid) Using Catalyst Mixtures and the Kinetics of Methyl Lactate Production

1
School of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
2
Division of Chemical and Energy Engineering, London South Bank University, 103 Borough Road, London SE1 0AA, UK
3
School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Dan Rosu
Polymers 2022, 14(9), 1763; https://doi.org/10.3390/polym14091763
Received: 6 April 2022 / Revised: 19 April 2022 / Accepted: 21 April 2022 / Published: 26 April 2022
(This article belongs to the Special Issue Chemical Recycling of Polymers)
Polylactic acid (PLA) is a leading bioplastic of which the market share is predicted to increase in the future; its growing production capacity means its end-of-life treatment is becoming increasingly important. One beneficial disposal route for PLA is its chemical recycling via alcoholysis. The alcoholysis of PLA leads to the generation of value-added products alkyl lactates; this route also has potential for a circular economy. In this work, PLA was chemically recycled via methanolysis to generate methyl lactate (MeLa). Four commercially available catalysts were investigated: zinc acetate dihydrate (Zn(OAc)2), magnesium acetate tetrahydrate (Mg(OAc)2), 4-(dimethylamino)pyridine (DMAP), and triazabicyclodecene (TBD). Dual catalyst experiments displayed an increase in reactivity when Zn(OAc)2 was paired with TBD or DMAP, or when Mg(OAc)2 was paired with TBD. Zn(OAc)2 coupled with TBD displayed the greatest reactivity. Out of the single catalyst reactions, Zn(OAc)2 exhibited the highest activity: a higher mol% was found to increase reaction rate but plateaued at 4 mol%, and a higher equivalent of methanol was found to increase the reaction rate, but plateaued at 17 equivalents. PLA methanolysis was modelled as a two-step reversible reaction; the activation energies were estimated at: Ea1 = 25.23 kJ∙mol−1, Ea2 = 34.16 kJ∙mol−1 and Ea-2 = 47.93 kJ∙mol−1. View Full-Text
Keywords: methanolysis; poly(lactic acid); chemical recycling; zinc acetate dihydrate; magnesium acetate tetrahydrate; 4-(dimethylamino)pyridine; triazabicyclodecene; alcoholysis; dual catalysts methanolysis; poly(lactic acid); chemical recycling; zinc acetate dihydrate; magnesium acetate tetrahydrate; 4-(dimethylamino)pyridine; triazabicyclodecene; alcoholysis; dual catalysts
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MDPI and ACS Style

Lamberti, F.M.; Román-Ramírez, L.A.; Dove, A.P.; Wood, J. Methanolysis of Poly(lactic Acid) Using Catalyst Mixtures and the Kinetics of Methyl Lactate Production. Polymers 2022, 14, 1763. https://doi.org/10.3390/polym14091763

AMA Style

Lamberti FM, Román-Ramírez LA, Dove AP, Wood J. Methanolysis of Poly(lactic Acid) Using Catalyst Mixtures and the Kinetics of Methyl Lactate Production. Polymers. 2022; 14(9):1763. https://doi.org/10.3390/polym14091763

Chicago/Turabian Style

Lamberti, Fabio M., Luis A. Román-Ramírez, Andrew P. Dove, and Joseph Wood. 2022. "Methanolysis of Poly(lactic Acid) Using Catalyst Mixtures and the Kinetics of Methyl Lactate Production" Polymers 14, no. 9: 1763. https://doi.org/10.3390/polym14091763

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