Green Process for Transforming Lignocellulosic Residues Into Novel Bio-based Vitrimer Composites

One of the main research challenges in recent years has been to valorize waste and by-products coming from the agro-food industry. To this purpose, the CYCLEVIT project aims to valorize lignocellulosic residues to produce vitrimers. In particular, this work aims to present a more sustainable process for lignin and cellulose recovery compared to the traditional one which involves acid and alkaline hydrolysis. Indeed, cellulose and lignin are the basis to produce vitrimers. The key idea of the process presented was to combine autohydrolysis, to remove the hemicellulose from raw material, and organosolv to separate lignin from cellulose. The optimal condition for the recovery of lignin and cellulose was identified for the autohydrolysis process, based on both previous scientific work and a validated mathematical model. The solid obtained from autohydrolysis was subsequently subjected to the organosolv process, to evaluate the optimal condition for lignin and cellulose recovery. Different temperatures (180°C-200°C) and solid-liquid ratio (1:10 -1:20 g/ml) were tested. It is interesting to point out that the 60 % v/v of ethanol solution used for this process was obtained by mixing the ethanol with the liquor resulting from the autohydrolysis process. Based on the results obtained, a first process layout was proposed which allows a cellulose and lignin recovery of approximately 75% and 21% respectively and water savings of about 35%.