Hydrothermal Carbonization – 1. Influence of Lignin in Lignocelluloses

Abstract

Hydrothermal carbonization is an attractive process for converting biomass with high water content into different products. The requirements on the products, which may be soil improvement or substitution of lignite or carbon black, are opposed to biomass as a feedstock that has a very complex and variable composition. The goal of this work was to study the influence of an ingredient, here lignin, on carbonization, with the focus being not only on the composition but also on the structure of the product formed.

Properties of Hydrochar as Function of Feedstock, Reaction Conditions and Post-Treatment

“…As usually observed [4,5,8] the carbon content of the hydrochar is higher and the oxygen content is lower compared with the original biomass ( Table 1). The effect is rather small for pure lignin (Table 1) [8].…”

“…The effect is rather small for pure lignin (Table 1) [8]. Concerning the structure of biomass or hydrochar, TGA and IR analysis gives more information.…”

“…The experiments were conducted in autoclaves with an internal volume of 10 mL (for details see [8]). The biomass feedstocks studied were model compounds like cellulose, xylan and lignin.…”

“…The temperatures used in HTC (around 200 • C) are too low to convert lignin completely [8]. Typically, under these experimental conditions a particle stays solid and in the original shape.…”

“…Typically, under these experimental conditions a particle stays solid and in the original shape. The composition changes slightly [8] and some holes are formed ( Figure 1, right picture at the bottom). This means that lignin mainly reacts via a solid-to-solid conversion, shown as reaction pathway B in Figure 1 (see also [9]).…”