Solvent-Activated Hafnium-Containing Zeolites Enable Selective and Continuous Glucose-Fructose Isomerisation

Area of Science:

• Catalysis
• Green Chemistry
• Biomass Conversion

Background:

• The conversion of lignocellulosic biomass into valuable chemicals is crucial for reducing petroleum dependence.
• Isomerization of glucose to fructose is a key transformation for producing bio-based chemicals.
• Existing catalysts and biological methods struggle to achieve high yields and selectivity for this reaction.

Purpose of the Study:

• To develop a novel catalyst for the efficient isomerization of glucose to fructose.
• To achieve thermodynamic equilibrium in a single step for intensified continuous operation.
• To elucidate the mechanism behind the catalyst's unique activity.

Main Methods:

• Synthesis and characterization of hafnium-containing zeolites.
• Continuous flow reactor studies for glucose isomerization.
• Operando spectroscopic techniques including X-ray absorption spectroscopy, FTIR, UV/Vis, and NMR spectroscopy for mechanistic investigation.

Main Results:

• Hafnium-containing zeolites demonstrated unprecedented catalytic activity for glucose isomerization.
• Achieved true thermodynamic equilibrium in a single step, with 58% glucose conversion and 94% fructose selectivity.
• Catalyst exhibited stable continuous operation for over 100 hours.
• Mechanistic studies revealed that isolated Hf(IV) atoms with monofunctional acidity are responsible for the catalytic activity.

Conclusions:

• Hafnium-containing zeolites are highly effective and stable catalysts for glucose isomerization.
• The catalyst's performance is enhanced through an in-situ activation process involving solvent interaction.
• This breakthrough offers a promising route for the sustainable production of petroleum-free chemicals from biomass.