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

Abstract

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,Ndimethylformamide 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.

Isomorphic Insertion of Ce(III)/Ce(IV) Centers into Layered Double Hydroxide as a Heterogeneous Multifunctional Catalyst for Efficient Meerwein–Ponndorf–Verley Reduction

“…Both the reduction of carbonyl compounds and the oxidation (dehydrogenation) of alcohols, especially secondary alcohols, are of particular importance from an industrial point of view. Although there are well-established processes for carrying out these basic conversions, these conversions suffer greatly from being time-consuming, wasteful, and requiring isolation/purification steps to remove undesired products and byproducts. , These aspects are far from the requirements of green chemistry, and the emerging demand to optimize the redox economy of the synthesis processes, i.e., to minimize the number of oxidation state changes throughout the process, has led to the golden age of catalytic transfer hydrogenations (CTHs). , Recently, this trend has been further strengthened as CTH reactions play a key role in many catalytic reaction cascades for the conversion of biomass-derived molecules into valuable products, which can greatly contribute to achieving the main goals of the circular economy. − …”

Coordination-Driven Self-Assembly of Schiff-Base-Tagged Ni–ZrO2/N–C Nanocatalysts for Selective Transformation of Renewable Methyl Levulinate

“…Developing efficient utilization of renewable biomass is one of the most effective green approaches to addressing the current energy crisis and environmental pollution. − γ-Valerolactone (GVL), as a bio-derived platform molecule, can be prepared by hydrogenation of lignocellulose degradation product levulinic acid and its esters. Generally, GVL possesses unique chemical and physical properties and has vast application prospects in the fields of fuel, chemicals, food, and more. − Therefore, the selective catalytic conversion of biomass for manufacturing GVL has become a research hotspot in recent years.…”