In my thesis, I studied and presented the basic properties and conversion of lignin into useful products and chemicals. Nowadays, due to the energy crisis and climate change, studies are increasingly focusing on the production of value-added products, various chemicals and fuels derived from renewable sources. One of the most common sources is lignocellulosic biomass. It consists of three main components, namely aromatic macromolecules (lignin) and polysaccharides (cellulose and hemicellulose). Lignin is a branched aromatic polymer that is very complex and, along with cellulose, is the most important and widespread organic substance on the plant world. Lignin serves as a structural component with a hydrophobic protective layer in the plant cell wall and binds cellulose and hemicellulose together. Traditionally lignin is isolated from lignocellulosic biomass during fractionation in the pulp and paper industry and during fermentation in biorefineries where it is mostly processed as a by-product and surplus in industry, but it is increasingly being shown that lignin will be able to replace fossil raw materials and thus can be used in the sustainable production of fuels, chemicals and materials. Its complex three-dimensional amorphous structure, high molecular weights and structural randomness pose a major challenge for its isolation from lignocellulosic biomass and further conversion to useful products, so different pre-treatment processes are required. Various delignification methods are used, such as kraft process, organosolv process, sulfite process, soda process, steam explosion and reductive catalytic fractionation. These methods of lignocellulose fractionation change the chemical structure of native lignin, which is still a major challenge in production of lignin value-added chemicals. Further conversion methods are required to achieve better lignin and to obtain value-added chemicals that require different operating conditions. My thesis presents the basic properties of lignin and its conversion path from lignocellulosic biomass with processes of its isolation, characterization, processing and finally to useful chemicals with added value.
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