Kinetic and thermodynamic study on acid hydrolysis of corn cob, rose stem, and pineapple crown

Abstract

Acid hydrolysis was performed to produce reducing sugars from pineapple crown (PC), corn cob (CC), and rose stem (RS); the holocellulose contents of PC, CC, and RS were 69.36%, 70.17%, and 63.89%, respectively. The highest production of reducing sugars was obtained at 150 °C and 1.5 M sulfuric acid (H₂SO₄) for PC (46.04 g/100 g) and 2.0 M (H₂SO₄) (41.61 and 15.96 g/100g respectively) for CC and RS with a reaction time of 150 min. The Saeman equation adequately described the hydrolysis kinetics. The production of reduced sugars was the predominant reaction (k₁> k₂, k_r> 1) instead of decomposition for PC and CC, and that of RS was dominated by the decomposition. The E_a obtained from the Arrhenius equation showed that PC and CC (3.676 kJ/mol mean value from all concentrations used) are more easily hydrolyzable materials than RS (E_a=10.95 kJ/mol mean value). The trends in the thermodynamic parameters, ΔH, and ΔG, showed that hydrolysis is an endothermic and non-spontaneous process. The temperature had a greater influence on the production and decomposition of reducing sugars than did the concentration of H₂SO₄ for PC and CC.

Keywords:

• Acid hydrolysis
• activation energy
• reducing sugars
• Saeman’s model
• thermodynamic

Credit author statement

All authors participate equally, unless otherwise mentioned in the manuscript.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this study.

Additional information

Funding

The authors thank the Tecnológico Nacional de México (TecNM) for financial support and project 12300.21-P and CONACYT for the grant to D. Gutierrez-López.