Lignin in Wood and Plants

Lignin in Wood and Plants


Lignin, a highly aromatic macromolecule building plant cells, and cellulose are two of the
most commonly occurring natural polymers. Lignin is an abundant, natural, highly branched macromolecule with a high ratio of aromatic rings, present in the cell walls of plants alongside cellulose. The structure of lignin is based on the combination of the three building blocks, phenylpropane derivatives known as monolignols: p-coumaryl, coniferyl, and sinapyl alcohols .The ratio of each
structure is closely connected to the plant source and directly influences the structure and
properties of the isolated lignin .

Difficulties in extracting lignin

Difficulties with obtaining lignin with repeatable characteristics hinder the potential application prospects . Currently, only 5% of the produced lignin is used in low-value applications, and the rest is used as a resource for the production of electricity and recovery of energy . However, in recent years, the
interest in lignin has been resurfacing, mainly because of the highly aromatic character of
the macromolecule, which can become a renewable source of aromatic hydrocarbons and
an alternative to petroleum-based chemicals.

The potential of lignin as a renewable,natural, abundant source of aromatic hydrocarbons was recognized already in the 1950s,but at the same time, almost all of it got wasted away due to the difficulties in obtaining chemically pure lignin. Some of the fungi enzymes, so-called ‘brown rot’, may be used
to obtain chemically pure lignin via a time-consuming process, whereas other industrial
methods of lignin isolation, such as sulfite, kraft, and soda-pulping processes cause partial
destruction of the lignin structure; moreover, their products contain functional groups or
impurities originating from the used chemicals.

Lignosulfonate from lignin

Lignosulfonate is a grade of technical lignin, obtained as a by-product in the paper and wood pulping industries, a result of the used lignin isolation method, i.e., sulfite process. In this work, sodium lignosulfonate is used as a starting material to manufacture sulfonamide derivatives of lignin in a two-step modification procedure. Since this direction of the lignin modification is rather rarely investigated and discussed, it makes a good starting point to expand the state of knowledge and explore the properties of lignosulfonamides.

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