https://pubs.rsc.org/en/content/articlepdf/2020/GC/D0GC00096E

Spherical lignin particles : a review on their sustainability and applications

Lignin, the second most abundant biopolymer on the planet, serves land-plants as bonding agent in juvenile cell tissues and as stiffening (modulus-building) agent in mature cell walls. The chemical structure analysis of cell wall lignins from two partially delignified wood species representing between 6 and 65% of total wood lignin has revealed that cell wall-bound lignins are virtually invariable in terms of inter-unit linkages, and resemble the native state. Variability is recognized as the result of isolation procedure. In native state, lignin has a low glass-to-rubber transition temperature and is part of a block copolymer with non-crystalline polysaccharides. This molecular architecture determines all of lignin's properties, foremost of all its failure to undergo interfacial failure by separation from (semi-) crystalline cellulose under a wide range of environmental conditions. This seemingly unexpected compatibility (on the nano-level) between a carbohydrate component and the highly aromatic lignin represents a lesson by nature that human technology is only now beginning to mimic. Since the isolation of lignin from lignocellulosic biomass (i.e., by pulping or biorefining) necessitates significant molecular alteration of lignin, isolated lignins are highly variable in structure and reflect the isolation method. While numerous procedures exist for converting isolated (carbon-rich) lignins into well-defined commodity chemicals by various liquefaction techniques (such as pyrolysis, hydrogenolysis, etc.), the use of lignin in man-made thermosetting and thermoplastic structural materials appears to offer greatest value. The well-recognized variabilities of isolated lignins can in large part be remedied by targeted chemical modification, and by adopting nature's principles of functionalization leading to inter-molecular compatibility. Lignins isolated from large-scale industrial delignification processes operating under invariable isolation conditions produce polymers of virtually invariable character. This makes lignin from pulp mills a potentially valuable biopolymeric resource. The restoration of molecular character resembling that in native plants is illustrated in this review via the demonstrated (and in part commercially-implemented) use of pulp lignins in bio-degradable (or compostable) polymeric materials.

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About Making Lignin Great Again-Some Lessons From the Past.

Lignin-based electrodes for energy storage application

Biomass-based biorefineries: An important architype towards a circular economy

This paper examines the effect of mechanical activation on the amorphization of starch having different types of crystalline structure (A-type corn starch; B-type potato starch; and C-type tapioca starch). Structural properties of the starches were studied by X-ray diffraction analysis. Mechanical activation in a planetary ball mill reduces the degree of crystallinity in proportion to pretreatment duration. C-type tapioca starch was found to have the highest degree of crystallinity. Energy consumed to achieve complete amorphization of the starches having different types of crystalline structure was measured. The kinetic parameters of the process (the effective rate constants) were determined. The rate constant and the strongest decline in the crystallinity degree after mechanical activation change in the following series: C-type starch, A-type starch, and B-type starch.

Changes in the Crystallinity Degree of Starch Having Different Types of Crystal Structure after Mechanical Pretreatment

Until recently, most of energy and industrially produced chemicals were derived from fossil fuel-based resources. This along with the continued depletion of finite fossil resources and their attributed adverse environmental impacts, alternatively sourced and more sustainable resources are being pursued as feedstock replacements. Thus, biomass has been identified as an alternate renewable and more sustainable resource as a means to reduce this sector's dependence on fossil fuel-based resources and to alleviate their environmental impacts. As such, lignocellulosic biomass has been further identified and demonstrated as an abundant renewable resource for the production of biofuels, platform chemicals, and their respective value-added products. This review article provides an overview of the techniques developed for the valorization of biomass in the production of platform chemicals within a biorefinery, and the status for commercialization.

An overview of biorefinery-derived platform chemicals from a cellulose and hemicellulose biorefinery

Technical lignins are bulk feedstocks. They are generated as byproducts from pulping or cellulosic ethanol production. Since lignin undergoes significant structural changes in the chemical and physical treatments, all technical lignins are unique in terms of chemical structure, molecular weight, polydispersity, and impurity profile. Kraft lignin is potentially the largest source of technical lignin as new isolation technologies have been implemented on industrial scale in recent years. Lignosulfonate has been an integral product in sulfite pulping biorefinery. It has a well-established market in construction industry. Organosolv-like lignin production is increasing as cellulosic ethanol has been promoted as the substitute of fossil fuel. It may have unique applications because it has low molecule weight and is free from sulfur. Technical lignin application is expected to expand as the characteristics are improved with fractionation or chemical modification. The application of technical lignin has been focusing on developing products equivalent to those made by petroleum chemicals. The recent development in technical lignin supply should increase its market share as additives in polyurethanes and as the substitute of phenol-formaldehyde adhesives. Quality improvement of technical lignin may also encourage the study of lignin as an alternative feedstock for carbon fiber. In addition, technical lignin depolymerization has been extensively explored to provide renewable aromatic chemicals. Starting from controlled pyrolysis and thermal liquefaction as the baseline technologies, many different chemical depolymerization have been invented with a wide range of underlying chemical principles.

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The current and emerging sources of technical lignins and their applications.

In recent years, the advancement of sustainable chemistry concepts and approaches along with their demonstrated application has become a central part of the design, synthesis, and manufacture of a chemical. Sustainable chemistry not only utilizes the principles of green chemistry, but also expands to incorporate economic, societal, and environmental aspects. This is further elucidated by the incorporation of life cycle assessment/thinking to include the raw material production, manufacture, processing, use, and disposal stages, allowing for a comprehensive evaluation of the environmental and human health impacts attributed to a chemical. This contribution outlines an approach for the development of a preliminary framework for the sustainable synthesis of a chemical that is identified as an alternative for an existing chemical of concern. The framework is introduced concurrently with a case study for organophosphates that are selected as potential replacements for brominated flame retardants (BFRs). This f...

/pdf/framework-toward-more-sustainable-chemical-synthesis-design-4rs0jzpq0p.pdf

Tao Li

Papers

An overview of biorefinery-derived platform chemicals from a cellulose and hemicellulose biorefinery

The current and emerging sources of technical lignins and their applications.

Framework toward More Sustainable Chemical Synthesis Design—A Case Study of Organophosphates