Ultrasound-assisted acid hydrolysis of cellulose to chemical building blocks: Application to furfural synthesis

• Published in: Ultrasonics sonochemistry Vol. 40; no. Pt B; pp. 81 - 88
• Main Authors: Santos, Daniel, Silva, Ubiratan F., Duarte, Fabio A., Bizzi, Cezar A., Flores, Erico M.M., Mello, Paola A.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2018
• Subjects: Chemical building block; Furanic platform; Ultrasound assisted acid hydrolysis; Waste valorization; Waste valorization; Ultrasound assisted acid hydrolysis; Chemical building block; Furanic platform
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2017.04.034

[Display omitted] •Ultrasound-assisted acid hydrolysis selectively produced furfural from cellulose.•Acoustic power, amplitude, sonication temperature and acid for hydrolysis were studied using a cup horn system.•Furfural synthesis was achieved using mild temperature conditions.•About 78% of furfural yield was obtained using ultrasound with 4molL−1 HNO3 for 60min at 30°C. In this work, the use of ultrasound energy for the production of furanic platforms from cellulose was investigated and the synthesis of furfural was demonstrated. Several systems were evaluated, as ultrasound bath, cup horn and probe, in order to investigate microcrystalline cellulose conversion using simply a diluted acid solution and ultrasound. Several acid mixtures were evaluated for hydrolysis, as diluted solutions of HNO3, H2SO4, HCl and H2C2O4. The influence of the following parameters in the ultrasound-assisted acid hydrolysis (UAAH) were studied: sonication temperature (30 to 70°C) and ultrasound amplitude (30 to 70% for a cup horn system) for 4 to 8molL−1 HNO3 solutions. For each evaluated condition, the products were identified by ultra-performance liquid chromatography with high-resolution time-of-flight mass spectrometry (UPLC-ToF-MS), which provide accurate information regarding the products obtained from biomass conversion. The furfural structure was confirmed by nuclear magnetic resonance (1H and 13C NMR) spectroscopy. In addition, cellulosic residues from hydrolysis reaction were characterized using scanning electron microscopy (SEM), which contributed for a better understanding of physical-chemical effects caused by ultrasound. After process optimization, a 4molL−1 HNO3 solution, sonicated for 60min at 30°C in a cup horn system at 50% of amplitude, lead to 78% of conversion to furfural. This mild temperature condition combined to the use of a diluted acid solution represents an important contribution for the selective production of chemical building blocks using ultrasound energy.