An Integrated Approach for Added-Value Products from Lignocellulosic Biorefineries

Abstract

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Catalytic wet peroxide oxidation of vanillic acid as a lignin model compound towards the renewable production of dicarboxylic acids

“…Comparatively with other lignin model compounds found in previous oxidation studies with TS-1, VA shares a similar aromatic structure to guaiacyl, which is the most common structural unit in softwood lignins, and can represent the behaviour of the aromatic ring-opening reactions towards the production of C 4 -DCA. VA can also be found as a product of lignin oxidation with O 2 , which is an important process to achieve aromatic compounds (Rodrigues et al, 2018). In a second phase of the work, TS-1 catalyst was modified with transition metals (Fe, Co, Cu) and tested in the oxidation reaction.…”

Added-Value Chemicals from Lignin Oxidation

“…The lack of established processes that add value to lignin can be attributed mainly to its chemical recalcitrance and complex and heterogeneous composition and structure. Adding to this complexity, the lignin structure is highly dependent on the type of plant and species, the delignification process, and the depolymerization method applied [ 2 , 26 ]. Lignin is a complex three-dimensional amorphous and highly branched aromatic polymer constituted of methoxylated phenylpropane units.…”

“…Lignin is a complex three-dimensional amorphous and highly branched aromatic polymer constituted of methoxylated phenylpropane units. Its crucial function in woody biomass is to provide strength, rigidity, and resistance to degradation [ 2 ]. There are three primary monomers, syringyl (S), guaiacyl (G), and p -hydroxyphenyl (H), derived from the monolignols p -coumaryl, coniferyl, and sinapyl alcohols ( Figure 1 ).…”

“…Lignocellulosic biomass, including hardwood, softwood, and herbaceous crops, is an abundant renewable resource mainly composed of cellulose, hemicellulose, and lignin [ 1 , 2 ]. The typical lignin content may vary from 18 to 33% in softwoods, 15 to 30% in hardwoods, and 5 to 30% in herbaceous crops [ 2 , 3 ]. However, most biorefineries are currently focused on the valorization of cellulose and hemicellulose, a so-called sugar-based platform.…”

Strategies for the production of biochemicals in bioenergy crops

“…Furthermore, the effectiveness of hydrothermal treatments at releasing vanillin and syringaldehyde from biomass of CAD mutant plants was recently evidenced [111,112]. Development of environmentally friendly processes towards valorization of lignin streams generated in biorefineries has garnered interest, and it would be interesting to evaluate the yield of vanillin and syringaldehyde obtained from the depolymerization of lignins that derive from CAD mutants [113]. Interestingly, it has been demonstrated that the ratio of vanillin to syringaldehyde in biomass can be modulated by altering the expression of coniferaldehyde 5-hydroxylase (CAld5H) in a CAD mutant background ( Fig.…”