Comparison of the properties of lignins as potential carbon precursors

Abstract

Due to growing interest in the application of renewable resources in industry, there is a need for new carbon precursors. Lignin is a natural polymer and the main by-product of the paper industry, but its application on an industrial scale is limited. Due to its chemical composition and high aromatic carbon content, combined with a lack of toxicity, it may be a promising candidate for a carbon precursor, as well as – in carbon electrode technology – a carbon binder. The main disadvantage of lignins is the variety of their types, with differing properties. There is a need to establish the relationship between the structure of lignin and its carbon precursor potential. In this work, an attempt was made to find the dependence between the lignin structure and its properties before (chemical composition, structural studies) and after thermal treatment under an inert atmosphere (carbon residue, bonding properties and degree of carbonization and graphitization), using different techniques (FTIR, Raman spectroscopy, XPS, TG, SEM) on two softwood lignins – alkali lignin and kraft lignin. The results proved that both lignins are good candidates for carbon precursors (high mass residue after heat treatment), but only kraft lignin exhibits the bonding properties which are crucial for application as a carbon binder.