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Lignin characterization/analyses
The properties of lignin samples are to a great extent influenced by their chemical and molecular structure. RISE has long experience and advanced equipment for characterization of lignin on different structural levels.
Lignin is a complex polyaromatic macromolecule that has the potential to be used in the production of a variety of sustainable materials and chemicals. Lignin is a three-dimensional heterogeneous biopolymer that is largely attached to polysaccharides such as cellulose and hemicellulose and is found in vascular plant secondary cell walls. The chemical structure of lignin is extremely complicated, with its backbone consisting primarily of three methoxylated phenylpropane units. The phenylpropane units randomly polymerize with each other, resulting in a three-dimensional cross-linked amorphous structure. The structure and polymeric properties vary depending on origin i.e. plat species, industrial processing as well as isolation and purification procedure.
Technical lignin is lignin extracted from diverse biomasses using technical procedures such as wood pulping. The most common technical lignin’s are lignosulphonates (separated from sulphite pulping), kraft lignin’s (separated from kraft pulping black liquor), organosolv lignin’s (separated from organosolv pulping), soda lignin’s (separated from soda pulping), and lignin residue following enzymatic treatment of biomass.
Lignin can be characterized by its purity, molecular structure, and thermal characteristics.
- Dry matter content – Moisture and non-volatile part of lignin (gravimetric analysis)
- Lignin content- the total amount of acid insoluble (acid hydrolysis) and acid soluble content (UV spectroscopy)
- Carbohydrate content- Glucose, xylose, arabinose, galactose, and mannose (ionic chromatography)
- Ash content- inorganic residue (gravimetrically determined at defined temperatures)
- Metals/elemental content- Al, Ca, Mg, Mn, K, P, Na, Ba, Fe, S (ICP-OES)
- Extractive contents- Fatty acids, resin acids, fatty alcohols, sterols glycerides and styryl esters (Soxtec apparatus and GC-MS).
- Hydroxyl groups- aliphatic, phenolic, carboxylic groups (31PNMR)
- Structural elements-Pyrolysis (GC-MS) and NMR
- Molar mass distribution-weight average molar mass (Mw) and number average molar mass (Mn) (SEC)
- Thermal properties-Thermal decomposition (TGA) and glass transition temperature (DSC)
