Quantitative analysis of products from lignin depolymerisation in high temperature water

Different types of lignin have been depolymerized via oxidative cleavage in sub- and supercritical water. As expected, a wide range of products of different structure and molecular weight have been obtained. Instead of analysing them one by one, we believe that it'is equally useful and much more feasible to determine certain global parameters such as type of aromatic substituents, OH functionality or molecular weight distribution, particularly if the objective is to obtain a mixture of compounds with a particular application. To this end, each sample (products of lignin depolymerisation) was fractionated according to its solubility in water and ethyl acetate and the yield of the different fractions was determined. Then each fraction was analysed using CHNS elemental analysis; P-35- and C-13 NMR and aqueous Gel Permeation Chromatography (GPC). Important conclusions about the effect of the reaction on the lignin structure can be deduced. These conclusions agree with previous observations found in literature. Based on these conclusions, some further insights have been proposed.