The depolymerisation of cellulose to glucose has become an important reaction paving the way to various relevant biobased chemicals. However this reaction requires overcoming a high energy barrier, essentially because cellulose exhibits a strong hydrogen bond network and highly cohesive 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 in few applications due to either a low space time yield or severe reaction conditions of temperature or pressure. We show in this communication 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 concept is based on the formation of cavitation bubbles inside which water is dissociated to H and OH radicals. Once these cavitation bubbles implode, radicals are propelled onto the surface of cellulose where they induce the cleavage of the glycosidic bond. We will show that the nature of the gas atmosphere (O2, Ar, H2 and mixtures of Ar/H2 and Ar/O2) plays a very important role by increasing or lowering the amount of radicals formed. Under optimized conditions, glucose was quickly obtained with 60% yield within only 2 min of ultrasonic irradiation at 520 kHz. Very importantly, we will show that during the depolymerization of cellulose, in situ generated radicals are selectively transferred on the cellulose particle surface, avoiding any side oxidation of released glucose in the bulk solution. 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. Finally, we will discuss the applicability of this process to different grades of cellulose with different purities and particle sizes.

Use of high frequency ultrasound for the depolymerization of cellulose into glucose

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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