The depolymerisation of cellulose to glucose has become a challenge for a range of relevant biobased chemicals. However, this reaction requires overcoming a high energy barrier, due to highly cohesive hydrogen bond network and van der Waals interactions. Nowadays the selective depolymerization of cellulose can be carried out with enzymes or supercritical water. However, these technologies are still limited due to either a low space time yield or severe reaction conditions of temperature or pressure. We show that high frequency ultrasound (HFUS) can selectively depolymerize cellulose into glucose in water without any catalyst, at low temperature (60°C) and pressure (Patm). The depolymerization mechanism is described involving the formation of cavitation bubbles inside which water is dissociated to H and OH radicals. Once these cavitation bubbles containing high energy are in contact with cellulose, they implode, inducing the cleavage of the glycosidic bond. Interestingly, in situ generated radicals are selectively transferred on the cellulose surface, without any side oxidation of released glucose. Also, we show that the nature of the gas atmosphere (O2, Ar, H2 and mixtures of Ar/H2 and Ar/O2) can increase or decrease the amount of radicals formed. The depolymerization of cellulose was visualized by electronic microscopies (STEM and MED), monitored by means of X-ray diffraction and chromatographic technics (SEC-MALLS, A4F-MALLS and HPLC), and glucose production estimated by mass spectrometry. As a result, under optimized conditions, pure glucose was obtained within only 2 min of ultrasonic irradiation at 520 kHz with 60% yield.

Selective radical depolymerization of cellulose to glucose induced by high frequency ultrasound

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.