Abstract
Alkyl lactates are green solvents that are successfully employed in several industries such as pharmaceutical, food and agricultural. They are considered prospective renewable substitutes for petroleum-derived solvents and the opportunity exists to obtain these valuable chemicals from the chemical recycling of waste poly(lactic acid). Alkyl lactates (ethyl lactate, propyl lactate and butyl lactate) were obtained from the catalysed alcoholysis reaction of poly(lactic acid) with the corresponding linear alcohol. Reactions were catalysed by a Zn complex synthesised from an ethylenediamine Schiff base. The reactions were studied in the 50–130 °C range depending on the alcohol, at autogenous pressure. Arrhenius temperature-dependent parameters (activation energies and pre-exponential factors) were estimated for the formation of the lactates. The activation energies (Ea1, Ea2 and Ea−2) for alcoholysis in ethanol were 62.58, 55.61 and 54.11 kJ/mol, respectively. Alcoholysis proceeded fastest in ethanol in comparison to propanol and butanol and reasonable rates can be achieved in temperatures as low as 50 °C. This is a promising reaction that could be used to recycle end-of-life poly(lactic acid) and could help create a circular production economy.
Highlights
Alkyl lactates (AL) are classified as green solvents according to the principles of green chemistry, and are considered prospective renewable substitutes for petroleum-derived solvents [1,2,3]
The working hypothesis was that longer-chain alcohols would sterically hinder the poly(lactic acid) (PLA) alcoholysis reaction
Zn(1)2 a catalyst that has previously be shown to be active for the production of methyl lactate from the alcoholysis of PLA, has in this paper been shown to generate EtLa, propyl lactate (PrLa) and butyl lactate (BuLa) under the same alcoholysis reaction with the corresponding linear alcohol
Summary
Alkyl lactates (AL) are classified as green solvents according to the principles of green chemistry, and are considered prospective renewable substitutes for petroleum-derived solvents [1,2,3]. ALs are already employed in several industries such as the pharmaceutical, food, agricultural and polymer industries and their use is expected to increase further in the near future [1,7]. EtLa is an additive in paints, foods, cosmetics and cleaning items, as well as a solvent in the manufacturing of microelectronics and pharmaceutical products [7,9,10]. Studies have shown the possibility of using EtLa for the recovery of phenolics and carotenoids (phytonutrients) from fruits and vegetables including palm oil [11,12,13]. Planer, et al [14] have demonstrated the use of EtLa as a solvent in olefin metathesis. Its application as an entrainer in the reactive distillation of azeotropic mixtures of methyl acetate and methanol has been exhibited [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
