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Lignin oxidation technology for versatile lignin dispersants

Periodic Reporting for period 2 - LigniOx (Lignin oxidation technology for versatile lignin dispersants)

Reporting period: 2018-11-01 to 2020-04-30

Lignin is the most important by-product from lignocellulosic biorefineries, and valuable renewable resource for bio-based industries. Annually over 70 million tons of lignin is extracted from wood as a by-product of the pulping industry. Substantial amount of lignin is also expected to originate from the 2nd generation bioethanol production. These lignocellulosic biorefineries are currently actively looking for opportunities to valorise the lignin by-products in high-value products instead of direct energy production. Furthermore, lignin offers a renewable low-cost raw material for chemical industry, improving resource sufficiency and promoting replacement of fossil based chemicals and materials. However, to fully exploit these raw material streams, there is an urgent need to commercialise economically and sustainably viable lignin upgrading process technologies that are adaptable to lignin side-streams originating from different processes and raw materials.

The aim of the LigniOx Innovation Action is to demonstrate the techno-economic viability of alkali-O2 oxidation technology (LigniOx) for the conversion of variable lignin-rich side-streams into versatile dispersants, and especially high-performance concrete plasticizers. Both the oxidation technology and the end-product performance will be demonstrated at industrially relevant operation conditions, enabling industrial process installations and entry of novel lignin products into the markets after the project. The valorisation of lignin side-streams will significantly improve the cost-competitiveness and resource efficiency of lignocellulosic biorefineries, and will create low-cost, sustainable raw materials for the chemical industry. The versatile LigniOx technology can be integrated into lignocellulosic biorefineries, or be operated as a stand-alone unit by chemical industry, as demonstrated in the project.
In LigniOx project, industrially applicable oxidation and post-treatment concepts have been developed for lignin by-products originating from variable industrial processes (kraft, organosolv, bioethanol production) and feedstock (softwood, hardwood, wheat straw). In all cases, oxidation conditions and concepts have been optimized in order to obtain high-performing lignin derived concrete plasticizer, as well as techno-economically feasible and safe oxidation process. For kraft lignin, a techno-economically feasible process concept that can be integrated into the kraft pulp mill has been developed and patented. Optimal oxidation conditions have also been defined for the hydrolysis and organosolv lignins. Based on oxidation protocols developed, a pilot scale oxidation reactor has been constructed, and the LigniOx oxidation has been successfully scaled-up in industrially applicable conditions for all the project lignins. After final optimization of the post-treatment at pilot scale, the process is ready for the first demonstration trials with kraft lignin.

Performance of the produced LigniOx lignins has been tested in mortar and concrete in comparison to commercial reference admixtures. LigniOx lignins show potential to compete with commercial fossil-based concrete admixtures, especially naphta or melamine condensates. Somewhat higher dosage was needed compared to the polycarboxylate ether (PCE) based reference tested in concrete. Oxidised kraft and organosolv lignins had better plasticization performance than oxidised hydrolysis lignin samples. However, also with oxidized hydrolysis lignin the plasticization performance was clearly better than with lignosulphonates, and in best cases, could compete with synthetic naphta condensates. In addition to concrete plasticizers, there are several other end-use possibilities for LIgniOx lignins as versatile dispersants. All the LigniOx lignins have shown good dispersion performance for special carbon black, and at significantly lower dispersant dosage provided an equal performance as the commercial polyacrylic acid and lignosulphonate based reference products. LigniOx lignin has also been tested as a surfactant to enhance the enzymatic hydrolysability in bioethanol production, and also here, comparable yield improvement was shown as with a commercial reference surfactant.

Process simulations have been performed to evaluate the integration effects at kraft pulp mill together with the techno-economic and life cycle assessment (LCA). Based on process simulations, the process concept developed and patented for the LigniOx integration into kraft pulp mill seems techno-economically feasible, and the LigniOx integration can even provide benefits compared to the current lignin isolation processes. Based on LCA of the kraft pulp mill concept, a significant reduction in the global warming potential in comparison with fossil-based plasticizer was shown. At bioethanol production plant, recirculation of solid residue from oxidation stage back to the ethanol process improved the yield. However, reduced filtration rate and increased sodium load to the bioethanol process were the drawbacks. LCA for the LigniOx integration into bioethanol plant is on-going.
The work carried out in the LigniOx project leads the way towards commercially viable process that can be integrated into the biorefineries, or to be operated in stand-alone unit. Techno-economically promising process concepts have been developed for lignins originating from variable processes (kraft, organosolv, bioethanol production) and feedstocks (softwood, hardwood, wheat straw), and oxidation was successfully scaled-up for all lignin types using the pilot reactor constructed in the project. For kraft lignin, the process is ready for the demonstration trials. The LigniOx lignins show plasticizing performance that can compete with some commercial fossil based concrete admixtures, but could also be an alternative to polyacrylic acid based commercial dispersants of special carbon black. Substantial reduction of global warming potential compared to the current synthetic products was also shown in LCA assessment of kraft lignin based LigniOx. As a result of LigniOx project, lignin upgrading technology for production of versatile lignin based dispersants will be ready for the industrial installation right after the project, and the new LigniOx products are expected to enter the markets within 3-5 years, creating new business opportunities for lignocellulosic biorefineries and chemical industry. In addition to the first target product (concrete plasticizer), the LigniOx technology will enable several additional application possibilities in products where anionic surface active agents currently are used, contributing to the establishment of a more sustainable and low carbon industry.