Characterization of Wood-based Industrial Biorefinery Lignosulfonates and Supercritical Water Hydrolysis Lignin

Venla Hemmilä,Arantxa Eceiza,Stergios Adamopoulos,Reza Hosseinpourpia

doi:10.1007/s12649-019-00878-5

Venla Hemmilä, Arantxa Eceiza + Show 2 more

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https://doi.org/10.1007/s12649-019-00878-5

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Abstract

Understanding the properties of any particular biorefinery or pulping residue lignin is crucial when choosing the right lignin for the right end use. In this paper, three different residual lignin types [supercritical water hydrolysis lignin (SCWH), ammonium lignosulfonate (A-LS), and sodium lignosulfonate (S-LS)] were evaluated for their chemical structure, thermal properties and water vapor adsorption behavior. SCWH lignin was found to have a high amount of phenolic hydroxyl groups and the highest amount of β-O-4 linkages. Combined with a low ash content, it shows potential to be used for conversion into aromatic or platform chemicals. A-LS and S-LS had more aliphatic hydroxyl groups, aliphatic double bonds and C=O structures. All lignins had available C3/C5 positions, which can increase reactivity towards adhesive precursors. The glass transition temperature (Tg) data indicated that the SCWH and S-LS lignin types can be suitable for production of carbon fibers. Lignosulfonates exhibited considerable higher water vapor adsorption as compared to the SCWH lignin. In conclusion, this study demonstrated that the SCWH differed greatly from the lignosulfonates in purity, chemical structure, thermal stability and water sorption behavior. SCWH lignin showed great potential as raw material for aromatic compounds, carbon fibers, adhesives or polymers. Lignosulfonates are less suited for conversion into chemicals or carbon fibers, but due to the high amount of aliphatic hydroxyl groups, they can potentially be modified or used as adhesives, dispersants, or reinforcement material in polymers. For most value-adding applications, energy-intensive purification of the lignosulfonates would be required.Graphic

Highlights

Utilization of lignocellulosic raw materials provides an excellent alternative to petroleum based ones, as they are sustainable, do not compete with food sources, and can have a positive impact on reduction of global greenhouse emissions
Molecular weight of the tested Supercritical water hydrolysis (SCWH) lignin was even lower than what has previously been reported for SCWH lignins ( Mw 3369 Da and 2003 Da, and Mn 1216 Da and 1009 Da) [17]
The results indicated a considerable amount of carbon content in SCWH lignin (59.0%)

Summary

Introduction

Utilization of lignocellulosic raw materials provides an excellent alternative to petroleum based ones, as they are sustainable, do not compete with food sources, and can have a positive impact on reduction of global greenhouse emissions. Unlike kraft and hydrolysis lignin, lignosulfonates are water-soluble over almost the entire pH-range [3] and are currently used as dispersants for various applications [6]. They provide up to 90% of commercial lignin and have annual worldwide production of approximately 1.8 million tons [7]. Characterization studies have shown that lignosulfonates have high molecular weight and contain high amounts of sulfonate groups Both of these properties are crucial in determining their dispersing efficiency and use for other applications [8,9,10,11]. Characterization studies have led to the partial elucidation of the structure of lignosulfonates, much of their overall global structure and shape is still not well known

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