Lignin properties as a function of cooking sulfidity – a knowledge for the future lignin producing mills

The project will be performed within the national research and educational program Resource Smart Processes that gathers the main industrial and academic actors within the Swedish forest industry and provides a strong collaborative environment with close connection to as well industry as state-of-the-art research infrastructure. As a master-thesis student in this program you will also participate in the networking and scientific events (workshops, conferences, project meetings) and collaborate closely both with the industrial and academic partners involved.

This project is together with: Chalmers, Stora Enso

Why?

Recovery of lignin from the spent cooking liquor in kraft pulp mills through the LignoBoost technology has opened up for an increased utilization of lignin building blocks in materials and chemicals. In that context, tailoring the properties of lignin through selection of cooking conditions is highly desirable, especially interesting being reducing the sulfur contect of the recovered lignin as influential for many applications. Sulfidity of the cooking liquor is the origin of the sulfur content in the recovered lignin and an important processing parameter governing strongly ligin reactions and structural changes during cooking. Yet, its influence on the structure and purity of the recovered lignin is not well-understood and is the focus of this work, where the main task will be to reveal the structural changes in lignin associated with variations in the sulfidity of the cooking liquor.

Stora Enso is the world leading producer of LignoBoost lignin and the initiator of this project, that will be performed in close collaboration with Chalmers (Forest Products and Chemical Engineering) equipped with experience and analytical tools for lignin characterization.

Aim and objectives

The specific objectives of the project are to account for following structural and compositional changes in lignin as a result of the sulfidity variations in the cooking liquor:
– Sulfur content
– Molecular weight distribution
-Linkages and functionalities (type & quantity).

Methodology

Batch cooking of wood chips (mimicking industrial conditios) with varying sulfidity and cooking time will be prformed in lab autoclaves.
Extracted lignin will be precipitated and recovered from the cooking liquor
Composition and structure of the obtained lignin fractions will be characterized by means of chromatography (size exclusion chromatography, ion chromatography, etv.) and spectroscopy (NMR, UV-Vis, FTIR, atom absorption spectroscopy) methods. Information on sulfur content, molecular weight distribution and occurrence of functionalities (e.g. linkage types and functional groups) will be interpreted in light of applied cooking conditions, sulfidity in particular. The work will be performed at Chalmers, Forest Products and Chemical Engineering in close collaboration with Stora Enso.
Depending on time and progress, partial characterization of the fibre and paper properties will be performed.

Prerequisites

The applicants should preferably have a background in chemical engineering, wood chemistry and process technology with a collaborative approach. The project can be performed in pair.

Project start

January 2024 or according to agreement

Examiner

Merima Hasani Merima Hasani, CTH merima.hasani@chalmers.se

Supervisor

Rickard Wadsborn, Stora Enso rickard.wadsborn@storaenso.com

Resurssmarta processer