Efficient 5-hydroxymethylfurfural production in ChCl-based deep eutectic solvents using boric acid and metal...

Area of Science:

• Green Chemistry and Sustainable Processes
• Biomass Conversion and Valorization
• Chemical Engineering and Process Optimization

Background:

• Bio-based 5-hydroxymethylfurfural (5-HMF) production is crucial for sustainable chemical synthesis.
• Deep eutectic solvents (DESs) offer an environmentally friendly and effective medium for biomass conversion.
• Choline chloride (ChCl)-based DESs are increasingly explored for their catalytic and solvent properties.

Purpose of the Study:

• To compare the efficacy of acidic ChCl-based DESs versus ChCl-fructose DES for 5-HMF production.
• To investigate the influence of different acidic catalysts (boric, oxalic, citric, p-toluenesulfonic acid) on 5-HMF yield.
• To optimize reaction parameters including DES composition, catalyst loading, temperature, time, and water content for maximizing 5-HMF yield from fructose and glucose.

Main Methods:

• Synthesis and characterization of ChCl-fructose and ChCl-glucose DESs.
• Comparative study of 5-HMF production using different acidic catalysts in ChCl-based DESs.
• Optimization of reaction conditions (mass ratio, catalyst amount, temperature, time, water content) for maximizing 5-HMF yield.

Main Results:

• ChCl-fructose DES demonstrated superior performance in converting fructose to 5-HMF compared to acidic ChCl-based DES.
• A maximum 5-HMF yield of 65.2% was achieved using ChCl-fructose DES (6:4 w/w) with 20% water and 80 mg boric acid at 120 °C for 120 minutes.
• A 33.7% yield of 5-HMF from glucose was obtained in ChCl-glucose DES (6:4 w/w) with 20% water, 120 mg boric acid, and 25 mg CrCl3·6H2O under identical conditions.

Conclusions:

• Choline chloride-based DESs, particularly ChCl-fructose, provide an efficient and cost-effective route for bio-based 5-HMF production.
• Optimized water content is beneficial for enhancing 5-HMF yield in ChCl-fructose and ChCl-glucose DESs.
• Despite high viscosity leading to mass transfer resistance, ChCl-based DESs offer a promising approach for sustainable 5-HMF synthesis.