Combined Transformation of Oat Husks into 5-Hydroxymethylfurfural. Part I: Cascade Production of Low Crystalline and Lignin-Free Cellulose for Chemicals

Abstract

In this work proposed cascade three-stage oat husk processing for isolation of low crystalline and lignin-free cellulose being perspective for chemical transformations. Such a product seems to be perspective for obtaining products which are important for chemical industry. The approach proposed includes stages of peroxide oxidative delignification, alkali treatment and mechanical activation in planetary mill. The optimal parameters of oxidative delignification were determined: the process temperature 100°C, the solid to liquid ratio 1 : 26, the hydrogen peroxide and acetic acid concentration 6 and 25 wt %, respectively, and the time of preliminary mechanical activation 30 min. Semiproduct was subjected to additional alkaline treatment and mechanical activation in a planetary mill to reduse residual lignin content and crystallinity degree. As a result of the cascade three-stage processing, it was possible to obtain a sample of cellulose with a low residual lignin content of 1.9 wt % and low crystallinity of 35%. To our knowledge, a cascade three-stage processing for the isolation of cellulose from oat husks which includs peroxide oxidative delignification, alkali treatment and mechanical activation has been proposed for the first time. In addition, peroxide oxidative delignification using a manganese sulfate catalyst was also carried out for the thirst time for oat husk biomass.