Hydroxy sulfonic acid catalyzed hydrolysis of cellulose

Abstract

Development of efficient catalytic methods for the hydrolysis of cellulose is a major research challenge in sustainable biofuel and polymer areas. In this study five hydroxy sulfonic acids were studied as simple model compounds for cellulase enzyme for the hydrolysis of cellulose. The catalytic activities were measured by analysis of total reducing sugar (TRS) yields produced in a series of reactions carried out at 150–190 °C using 0.050 M aqueous hydroxy sulfonic acid solutions. The highest catalytic activity was observed with isethionic acid, producing 62.7% TRS yield at 180 °C after 4 hr. In the second phase of the work, Density Functional Theory (DFT) calculations were used to study the interactions between hydroxy sulfonic acids and cellulose model compound D-cellobiose to supplement the experimental results. The D-cellobiose – hydroxy sulfonic binding energies and the distance between glycosidic oxygen and -SO₃H acidic H were evaluated and the -SO₃H to glycosidic oxygen distance was identified as the more important parameter co-related to the catalytic activity. The isethionic acid with highest cellulose hydrolysis activity showed the shortest -SO₃H to glycosidic oxygen distance of 1.744 Å.

Keywords:

• Cellulose
• sulfonic acids
• hydrolysis
• acid catalyst
• glucose
• cellobiose

Authors’ contributions

Ananda S. Amarasekara: writing the original draft and conceptualization. Victor C. Nwankwo: methodology and laboratory experiments. Harshica Fernando: computational study and data analysis

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

Authors thank United States Department of Energy – National Nuclear Security Administration (DOE-NNSA) grant DE-NA0003947, Welch Foundation grant L0002 – 20181021, National Science Foundation (NSF) grants: CBET-1704144, HRD-1036593, and US Department of Agriculture (USDA) grants AFRI 65209-31474, SUN-2-569230.PVAMU1 for financial support.