Influence of Aromatic Structure on the Thermal Behaviour of Lignin

Abstract

Lignin, a natural biopolymer and abundant by-product, is a particularly promising feedstock for carbon-based materials and a potentially sustainable alternative to phenolic resins, which are typically derived from crude oil. The source and method used to isolate lignin have a large impact on the thermal properties of the polymer, and can affect resultant materials prepared from lignin. Previous investigations into lignin characterisation often utilise a variety of feedstocks and isolation methods, which can make robust comparisons challenging. We present a systematic investigation into the chemical composition of lignins extracted using an identical Organosolv isolation method but from different biomass feedstocks: hemp hurds, eucalyptus chips, flax straw, rice husk and pine. We show how the aromatic structure of lignin can affect the thermal behaviour of the polymer, which correlates to the structure of resulting carbons. Carbons from lignins with a high syringyl unit content display a pronounced foaming behaviour which, on activation, results in a high-surface area material with hierarchical porosity.

Hetero-Porous, High-Surface Area Green Carbon Aerogels for the Next-Generation Energy Storage Applications

“…The G-band is due to the vibrations of sp 2 bonded carbon atoms in the 2D hexagonal lattice and the D-band represents the in-plane terminated disordered tangling bonds in graphite. In both KLCAs and SLCAs, the ratio of intensity of the G-band to D-band (I G /I D ) is more than 1, indicating the presence of partially graphitized carbon structures formed as a result of rearrangement of the carbon structure during the carbonization process, which is advantageous for making superior supercapacitor (SC) electrodes [ 48 ]. XRD patterns of KL and SL were recorded and represented in Figure 2 e. In the case of KL, a diffraction peak was observed at 2θ = 18.7°, while for SL the peak was located at 2θ = 21.6°.…”

“…It has been observed from differential scanning calorimetry (DSC) ( Figure S1c ) that the KL has glass transition temperature (T g ) at 135 °C, while SL showed lower T g at 80 °C, indicating the early stage softening of SL compared to KL. Rowlandson et al reported the melting of lignin which can produce an intermediate melt region where viscosity is dependent on the S/G ratio [ 48 ]. A low S/G ratio lignin such as KL will have high melt viscosity and difficulty to flow because of the abundance of β-5 linkages which limit the molecular rotation, while a high S/G ratio SL will have a low melt viscosity and hence can flow inside the materials closing the pores generated during carbonization.…”

Application of Experimental Design to Hydrogen Storage: Optimisation of Lignin-Derived Carbons

“…In-depth characterisation of the organosolv extracted lignin feedstock was reported in the authors' previous work [56]. The completed experimental design and measured responses are shown in Table 2.…”

Sulfur infiltration and allotrope formation in porous cathode hosts for lithium‐sulfur batteries

“…Also, AC carbon fibers from lignin 20,21 with ultramicropores and micropores have been used as interlayer between the cathode and the separator to physically trap the soluble polysulfides. If one considers synthetic materials to start with a material of consistent composition, compared to biomass, phenolic resin has very similar chemical structure to that of lignin, 22 and on crosslinking with an amine, carbonization and activation it yields a microporous carbon material, 22 containing heteroatoms such as nitrogen which increases the conductivity of the cathode host and oxygen which might form groups trapping the soluble polysulfides, such as hydroxyl groups. It is notable that pyridinic nitrogen both traps the soluble polysulfides and acts as an electrocatalyst to accelerate the chain of redox reactions in Li‐S batteries 23 …”