Catalytic Transfer Hydrogenation and Ethanolysis of Furfural to Ethyl Levulinate Using Sulfonated Hf- or Ni-Catalysts Prepared with Mixed Solvents

Bifunctional Lewis (L) acid (Ni- or Hf-) site–Brønsted (B) acid catalysts designed to promote transfer hydrogenation reactions were prepared via hydrothermal and solvothermal methods using safe mixed solvents and sustainable precursors. By using N,N-dimethylformamide as a basis for the desired basicity, mixed solvents could be identified that allowed catalysts to be prepared with tunable ratios of Lewis to Brønsted acid sites (L/B). The as-prepared catalysts promoted transfer hydrogenation of furfural and ethanolysis to form ethyl levulinate (EL) using ethanol as a solvent and hydrogen donor source. Among the catalysts, sulfonated Hf-catalysts prepared with a cyclopentanone/formic acid mixed solvent (Hf-CPN/FA) with an L/B ratio of 6.4 gave 95% furfural conversion with 51.9% yield of EL, while the sulfonated Hf catalyst prepared with a cyclopentanone/γ-valerolactone mixed solvent (Hf-CPN/GVL) with a total Lewis and Brønsted acid site amount of 85.1 μmol/g gave 100% furfuryl alcohol (FAL) conversion with 72.5% yield of EL. Brønsted acid sites promoted reversible acetalization of furfural with ethanol into 2-furaldehyde diethyl acetal, while Lewis acid sites promoted furfural transfer hydrogenation into FAL and EL and further conversion into γ-valerolactone. The methods developed in this work eliminate dipolar aprotic solvents and harsh acids used in catalyst synthesis and allow sustainable production of EL from biomass-related chemicals

Mechanism of Glucose Conversion into 5‑Ethoxymethylfurfural in Ethanol with Hydrogen Sulfate Ionic Liquid Additives and a Lewis Acid Catalyst

Hydrogen sulfate ionic liquid additives with aluminum chloride catalyst in ethanol were found to promote efficient (30 min) one-pot, one-step transformation of glucose into 5-ethoxymethylfurfural (5-EMF) in 37% yields. Spectroscopic measurements (FT-IR, ¹H NMR) showed that ionic liquids form multiple hydrogen bonds with glucose and promote its ring opening through ionic liquid–AlCl₃ complexes to enable formation of 5-EMF via 5-hydroxymethylfurfural (5-HMF). Reactions performed in dimethyl sulfoxide using (protic, aprotic) ionic liquid additives with and without AlCl₃ catalyst showed that both the ionic liquid and AlCl₃ were required for efficient transformation of glucose into 5-EMF. The proposed reaction mechanism for 5-EMF synthesis in the ethanol–1-butyl-3-methylimidazolium hydrogen sulfate–AlCl₃ reaction system consists of ring opening of glucose to form the 1,2-enediol and dehydration to form 5-HMF that is followed by etherification to the 5-EMF product. The reaction system is effective for glucose transformation and has application to biomass-related compounds

Solvent Polarity of Cyclic Ketone (Cyclopentanone, Cyclohexanone): Alcohol (Methanol, Ethanol) Renewable Mixed-Solvent Systems for Applications in Pharmaceutical and Chemical Processing

Kamlet–Taft (KT) parameters were measured for four nonaqueous hydrogen bond donor (HBD)–hydrogen bond acceptor (HBA) solvent-pair mixtures: methanol–cyclopentanone, methanol–cyclohexanone, ethanol–cyclopentanone, and ethanol–cyclohexanone to define their solvent polarity as a function of composition. KT mixed-solvent polarities differed greatly from molar average property values. The preferential solvation (PS) model was used to correlate solvent polarity and showed that local compositions of 1:1 (HBD–HBA) complex molecules were highly asymmetric. Trends of KT parameters of both cyclohexanone and cyclopentanone mixtures were similar, although the specific hydrogen bonding interactions of HBD–HBA complex molecules in cyclohexanone mixtures were stronger than those of cyclopentanone mixtures according to density functional theory calculations, infrared spectroscopy, and solution macroscopic properties. Application of the PS model to pharmaceuticals showed that the solvent-pair mixtures have wide-working composition ranges (∼0 < <i>x</i>_HBA < ∼ 1) for aspirin, ibuprofen, niflumic acid, <i>p</i>-amino-benzoic, <i>p</i>-hydroxy-benzoic and salicyclic acid, limited composition ranges (Δ<i>x</i>_HBA ≈ 0.7) for benzoic acid and temazepam, and narrow composition ranges (Δ<i>x</i>_HBA ≈ 0.3) for others. By comparing mixed-solvent polarity with polarity of solvents being used for material, petroleum, and biomass processing, it can be concluded that cyclic ketone–alcohol mixtures have many applications