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

Fabio M. Lamberti; Luis A. Román-Ramírez; Andrew P. Dove; Joseph Wood

doi:10.3390/polym14091763

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

Fabio M. Lamberti
, Luis A. Román-Ramírez
, Andrew P. Dove
, Joseph Wood

London South Bank University

University of Birmingham
Division of Chemical and Energy Engineering

Research output: Contribution to journal › Article › peer-review

17 Citations (Scopus)

13 Downloads (Pure)

Abstract

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 .

Original language	English
Article number	1763
Pages (from-to)	e1763
Journal	Polymers
Volume	14
Issue number	9
DOIs	https://doi.org/10.3390/polym14091763 https://doi.org/10.3390/polym14091763
Publication status	Published - 26 Apr 2022

Bibliographical note

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

SDG 8 Decent Work and Economic Growth
SDG 12 Responsible Consumption and Production

Keywords

poly(lactic acid)
chemical recycling
4-(dimethylamino)pyridine
dual catalysts
triazabicyclodecene
zinc acetate dihydrate
magnesium acetate tetrahydrate
methanolysis
alcoholysis

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10.3390/polym14091763
10.3390/polym14091763Licence: CC BY 4.0

polymers-14-01763Final published version, 2.04 MBLicence: CC BY 4.0
Polymers-14-01763

Cite this

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

abstract = "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 .",

keywords = "poly(lactic acid), chemical recycling, 4-(dimethylamino)pyridine, dual catalysts, triazabicyclodecene, zinc acetate dihydrate, magnesium acetate tetrahydrate, methanolysis, alcoholysis",

author = "Lamberti, \{Fabio M.\} and Rom{\'a}n-Ram{\'i}rez, \{Luis A.\} and Dove, \{Andrew P.\} and Joseph Wood",

note = "Publisher Copyright: {\textcopyright} 2022 by the authors. Licensee MDPI, Basel, Switzerland.",

year = "2022",

month = apr,

day = "26",

doi = "10.3390/polym14091763",

language = "English",

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T1 - Methanolysis of Poly(lactic Acid) Using Catalyst Mixtures and the Kinetics of Methyl Lactate Production

AU - Lamberti, Fabio M.

AU - Román-Ramírez, Luis A.

AU - Dove, Andrew P.

AU - Wood, Joseph

PY - 2022/4/26

Y1 - 2022/4/26

N2 - 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 .

AB - 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 .

KW - poly(lactic acid)

KW - chemical recycling

KW - 4-(dimethylamino)pyridine

KW - dual catalysts

KW - triazabicyclodecene

KW - zinc acetate dihydrate

KW - magnesium acetate tetrahydrate

KW - methanolysis

KW - alcoholysis

UR - https://www.scopus.com/pages/publications/85129837599

U2 - 10.3390/polym14091763

DO - 10.3390/polym14091763

M3 - Article

SN - 2073-4360

VL - 14

SP - e1763

JO - Polymers

JF - Polymers

IS - 9

M1 - 1763

ER -

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

Abstract

Bibliographical note

UN SDGs

Keywords

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