Corncob Hydrolysis Using Graphene Oxide Activated Coconut Shell Biochar Catalyst

Purpose

Graphene oxide (GO) synthesized by Hummers method is an effective catalyst for biomass hydrolysis and sugar production. However, due to its small size and hydrophilicity, its post-reaction separation by filtration of the aqueous reaction mixture is challenging. Therefore, GO was supported on larger biochar particles, and the catalytic activity of the composite particles was evaluated.

Methods

Mesoporous biochar was prepared using phosphoric acid-activated coconut shell at a relatively low carbonization temperature of 450 °C. The catalytic activity of the biochar-supported GO catalyst on corncob hydrolysis was investigated using the I-optimal response surface methodology. Neat GO and sulfonated high-temperature biochar (SBC700) were used as references.

Results

Optimized reaction conditions for high sugar yields were identified. Under these conditions, the biochar-supported catalyst showed a sugar yield comparable to neat GO and SBC700 despite its lower sulfonic acid density. The biochar-supported catalyst could be recycled and reused with about 35% decrease in the sugar yield after the first use. A similar reduction in the activity of SBC700 suggested no significant loss of GO from the biochar-supported catalyst under the hydrolysis conditions.

Conclusion

The sugar yield per unit mass of corncob was found to be linearly dependent on the catalyst concentration and the reaction time. The acid density, a measure of the concentration of acidic groups on the catalyst surface, is an important factor determining the catalytic activity. The study suggests that increasing the acid density by augmenting the GO loading of the biochar particles could lead to higher sugar yields.

Graphical Abstract