Inexpensive and tuneable protic ionic liquids based on sulfuric acid for the biphasic synthesis of alkyl levulinates

Production of levulinic acid and alkyl levulinates: a process insight

“…33 Particularly active in the direct esterification of biomass-derived LA, ionic liquids, as 1-Methyl imidazolium hydrogen sulphate [MIM][HSO4], catalysed the LA esterification to BL, obtaining a final yield of 89.6 mol% at 90 °C in 90 min. 92 In addition to the efficient catalytic activity, with the possibility to be recycled without loss of functionality (demonstrated 10 cycles for [Hmim][(HSO4)(H2SO4)2]), 304 ionic liquids have been tested as a solvent in alkyl levulinate production from biomass. Liang et al 288 reported the important role of 1-butyl-3-methyl imidazolium chloride (BmimCl) in the depolymerization of cellulose, derived from wood residue, which produced a ML yield of 38.7 mol% in the optimum conditions.…”

Beckmann Rearrangement with Improved Atom Economy, Catalyzed by Inexpensive, Reusable, Bro̷nsted Acidic Ionic Liquid

“…In contrast to sulfonic acid-functionalized ILs, protic ionic liquids (PILs) based on sulfuric acid and amines are generated by a one-step acid–base reaction and require no costly reactants. − Technoeconomic analysis, including life-cycle assessment (LCA), showed that the cost of triethylammonium hydrogen sulfate or 1-methylimidazolium hydrogen sulfate ILs can be as low as $0.78 and $1.46 kg –1 , respectively, which is lower than common organic solvents such as acetone or ethyl acetate . Using sulfuric acid in excess with respect to the base yields highly Bro̷nsted acidic ILs and further lowers the cost, which can be decreased even more by the use of diamines and triamines instead of monoamines. , As we estimated in 2021, the laboratory-scale synthesis cost of PILs from diethylenetriamine and bis­(hexamethylene)­triamine can be as low as $31.6 and $68.9 kg –1 , respectively (for the estimation, the updated prices available directly from the Merck catalogue were taken), whereas the cost of 1,4-butanosultone reagent used for the synthesis of sulfonic acid-functionalized ILs is $129 per 100 g. Moreover, modulating the ratio of sulfuric acid to base, as well as the structures of di/triamines, allows for fine-tuning of the physicochemical parameters of ILs, such as acidity, viscosity, and density …”

In Situ Synthesis of Protic Ionic Liquids for Biomass Pretreatment

“…10 Fortunately, a subset of ILs called protic ionic liquids (PILs) have emerged as potential candidates for the realization of inexpensive ILs. 8,11,12 Due to the ease and simplicity of their synthesis, these PILs are generally considered as cost-effective alternatives to conventional ILs. PILs also have unique efficacies for lignocellulosic biomass processing due to their biocompatibility, reusability, scalability, cost-effectiveness, and ability to selectivity extract lignin.…”

“…The cost of producing ILs is largely driven by the cost of the raw materials needed to synthesize them, but the cost is also impacted by the IL synthesis method and the IL purification steps . Fortunately, a subset of ILs called protic ionic liquids (PILs) have emerged as potential candidates for the realization of inexpensive ILs. ,, Due to the ease and simplicity of their synthesis, these PILs are generally considered as cost-effective alternatives to conventional ILs. PILs also have unique efficacies for lignocellulosic biomass processing due to their biocompatibility, reusability, scalability, cost-effectiveness, and ability to selectivity extract lignin. − Despite the promise that PILs present for minimizing cost, they are still more expensive than many traditional solvents.…”