Jorge Gominho

By Ana Lourenço, Jorge Gominho and Helena Pereira

Analytical pyrolysis is used to chemically study complex molecular materials and is applied in a wide range of fields. Pyrolysis is a thermochemical process associated to the breaking of chemical bonds using thermal energy, transforming a nonvolatile compound into a volatile degradation mixture. This chapter refers to analytical pyrolysis of lignocellulosic materials, i.e., when pyrolysis is used for chemical characterization, applied to samples with small particle sizes, at 500–650°C, and with short residence times. The reactions that occur during pyrolysis of the structural components are discussed regarding the mechanisms and the pyrolysis products obtained from cellulose, hemicelluloses, and lignin. A compilation of data is made on the characterization of lignocellulosic materials using Py-GC/FID(MS) or Py-GC/MS as analytical tools including woods and barks of several species. The pyrogram profiles and important parameters on lignin chemical composition such as the H:G:S relation and the S/G ratio are summarized. Analytical pyrolysis is a versatile methodology that may be applied to characterize the lignin directly on the lignocellulosic material or after isolation from the cell wall matrix (e.g., as MWL or dioxane lignin) or from pulps or spent liquors. It is therefore an excellent tool to study lignin compositional variability in different materials and along various processing pathways.

Part of the book: Analytical Pyrolysis

By Ana Lourenço and Jorge Gominho

Lignin is an interesting natural polymer with characteristics that contribute for the development and growth of plants. Lignin presents high variability associated with the diversity of plants, which presents great challenges for its recovery after delignification (technical lignin), because lignin is prone to irreversible degradation, producing recalcitrant condensed structures that are difficult to disassemble afterward. Although researchers have made efforts to obtain lignin in high yields and with good characteristics for specific uses, this is not an easy task. The mind-set has changed and new biorefinery concepts are emerging, where lignin is the primary goal to achieve, and the so-called lignin-first approach has arisen. Lignin can be obtained firstly to prevent structural degradations, enabling an efficient and highly selectivity of the lignin monomers. Therefore, this concept places lignin and its valorization at the head of the biorefinery. However, lignin valorization is still a challenge, and to overcome this, lignin nanoparticles (LNPs) production presents a good way to achieve this goal. This chapter presents a resume of the several techniques to attain lignin, how to produce LNPs, and their possible applications (from pharmaceutical to the automobile and polymer industries).

Part of the book: Lignin