Severity function describing the hydrolysis of xylan using carbonic acid

Area of Science:

• Biomass conversion
• Green chemistry
• Carbohydrate chemistry

Background:

• Xylan, a major component of hemicellulose, is a valuable biomass resource.
• Efficient hydrolysis of xylan into xylose monomers is crucial for biorefining and biofuel production.
• Current methods often rely on mineral acids, posing environmental and economic challenges.

Purpose of the Study:

• To investigate the efficacy of hot, compressed liquid water saturated with carbon dioxide for xylan hydrolysis.
• To compare the hydrolysis efficiency with and without carbon dioxide saturation.
• To explore the potential of carbonic acid as a catalyst for biomass hydrolysis.

Main Methods:

• Beech wood derived xylan was treated with hot, compressed liquid water saturated with carbon dioxide.
• Parallel experiments were conducted using only hot, compressed liquid water and dilute sulfuric acid.
• Reaction parameters including time, temperature, and carbon dioxide partial pressure were varied.
• Hydrolysis products were analyzed to determine the yield of xylose monomers.

Main Results:

• Xylan hydrolysis predominantly yielded xylose monomer units when treated with hot, compressed liquid water saturated with CO2.
• Treatment without CO2 saturation resulted in significantly lower hydrolysis and a smaller fraction of monomers.
• Hydrolysis severity correlated with reaction time, temperature, and CO2 partial pressure.
• The dissociation constant of carbonic acid was approximated in the temperature range of 170-230°C.

Conclusions:

• Carbon dioxide saturation significantly enhances the hydrolysis of xylan in hot, compressed liquid water.
• Carbonic acid generated in situ shows potential as an effective catalyst for biomass hydrolysis, offering an alternative to mineral acids.
• This approach is particularly relevant for bioprocessing plants that generate carbon dioxide, promoting a circular economy.