Melchiorre, Massimo (2024) Solvents from biomass: synthesis and applications in sustainable catalysis, storage energy devices, and cultural heritage. [Tesi di dottorato]

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Abstract

Solvents are fundamental compounds for chemistry and find applications in many industrial sectors. Given their fossil origin and harmfulness, their use generally increases the environmental impact of products and processes. Therefore, the use of solvents and chemicals with a low environmental impact and a low (eco)toxicological profile is a current and highly relevant issue, especially for the replacement of dipolar aprotic solvents (e.g. dimethylformamide). The strategies to avoid issues related to hazardous solvents are mainly three: the use of solvent-free conditions (e.g. mechanochemistry); the use of aqueous solvents (e.g. water-tolerant compounds); and the direct drop-in replacement with bio-based and low risk-profile organic solvents or molecular systems (e.g. natural deep-eutectic solvents). Despite the first two strategies are the most attractive for many applications, they cannot cover the full spectrum of solvent applications, therefore the third route is anyway necessary to rule out and replace the most concerning organic solvents (e.g. DMF, DMSO, NMP, ethers, chlorinated, aliphatic). This PhD research project fits in this area and aims at introducing 4-oxo-dioxolanes (DOXs) as a new class of dipolar aprotic solvents. First, a panel of six DOXs was prepared, characterized, and tested as reaction media for Pd-promoted reactions (i.e. Mizoroki-Heck cross-coupling) and stoichiometric (i.e. Menshutkin).2 Then, a convenient strategy was developed to prepare DOXs by catalytic ketalization of bio-based α-hydroxy acids (e.g. lactic acid) promoted by Lewis acid catalysts (i.e. Fe(III) salts).1 Among the prepared DOXs, the solvent candidate with the highest polarity, 5-methyl-1,3-dioxolan-4-one (LA-H,H), was used to prepare electrolytes suitable for energy storage devices (i.e. supercapacitors and Li-ion batteries). Within this topic, also γ-valerolactone (GVL) was comparatively investigated as a solvent for high power (i.e. supercapacitor), high energy (e.g. lithium-ion battery), and hybrid storage systems (e.g. lithium-ion capacitor).3 Eventually, some representative DOXs (i.e. 5-methyl-1,3-dioxolan-4-one, and 2,2,5-trimethyl-1,3-dioxolan-4-one) and other bio-based organic solvents (i.e. GVL, solketal, ethyl lactate, 2-ethylhexyl pelargonate), were applied for the restoration of original cultural heritage artifacts as replacing solvents for acetone, ethanol and isooctane.4 An overall graphical abstract is reported in Figure A.

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