Oxidative Conversion of Glucose to Formic Acid as a Renewable Hydrogen Source Using an Abundant Solid Base Catalyst

Area of Science:

• Green Chemistry and Catalysis
• Renewable Energy Storage
• Biomass Conversion

Background:

• Formic acid is a highly desirable liquid hydrogen carrier due to its stability and high hydrogen content.
• Developing efficient and selective methods for formic acid production from abundant resources is crucial for sustainable energy solutions.
• Previous research explored various catalysts, but mild reaction conditions and high yields from biomass remain challenging.

Purpose of the Study:

• To investigate the selective production of formic acid from monosaccharides using solid catalysts in aqueous solutions.
• To evaluate the catalytic activity and reusability of calcium oxide under mild reaction conditions.
• To elucidate the reaction pathway for formic acid formation from glucose.

Main Methods:

• Screening of simple solid base oxides, with a focus on calcium oxide derived from seashell or limestone.
• Reaction of monosaccharides (glucose and xylose) with hydrogen peroxide in aqueous solution at 343 K for 30 minutes.
• Analysis of reaction products and intermediates to determine formic acid yields and reaction mechanisms.
• Testing the reusability of the catalyst after post-calcination.

Main Results:

• Calcium oxide demonstrated the highest catalytic activity among tested oxides, achieving 50% formic acid yield from glucose and 66% from xylose.
• The reaction proceeds via C-C bond cleavage involving aldehyde groups in the acyclic form of glucose.
• Key intermediates include fructose, glyceraldehyde, and dihydroxyacetone, formed through base-catalyzed isomerization and retroaldol reactions.
• The catalyst maintained its activity after multiple reuse cycles following simple post-calcination.

Conclusions:

• Calcium oxide is a highly effective and reusable solid catalyst for the selective production of formic acid from monosaccharides.
• The study demonstrates a promising pathway for producing a valuable hydrogen carrier from biomass under mild, environmentally friendly conditions.
• The findings contribute to the development of sustainable hydrogen storage technologies.