Abstract
In this study, lignin obtained from almond shell by soda delignification treatment was directly depolymerized to produce phenolic monomers without the need of isolating it after its extraction. Thus, the black liquor from the delignification treatment, where lignin is dissolved, was treated in a high pressure reactor at 300 °C for 80 minutes to depolymerize the dissolved lignin. In this way, the step of precipitating lignin from the liquor was suppressed intensifying the whole process of lignin valorization. On the other hand, in order to have a reference, lignin from black liquor was isolated using selective precipitation methods and was submitted to a depolymerization process with the same conditions applied to the black liquor, employing in this case sodium hydroxide dissolution (4 wt.%) in a solid:liquid ratio of 1:20. After both depolymerization treatments, three main products were obtained: oil, residual lignin and char. These products were quantified and analytically characterized by Gas chromatography/Mass spectroscopy (GC/MS) and gel permeation chromatography (GPC). The direct treatment of soda black liquor to depolymerize the lignin dissolved in there, gave better results regarding oil and char yields than depolymerizing the isolated solid lignin.
