Recent Efforts to Prevent Undesirable Reactions From Fractionation to Depolymerization of Lignin: Toward Maximizing the Value From Lignin

Abstract

Lignin is a major component of lignocellulosic biomass along with cellulose and hemicellulose, currently underutilized with the bulk of technical lignin being combusted for heat generation in plant. From the technoeconomic perspective, the success of a future biorefinery is highly dependent on lignin valorization. However, structural complexity, heterogeneity of lignin, and several undesirable reactions associated with the nature of lignin and process conditions obstruct the effective utilization of lignin. Lignin condensation has been a long-lasting problem from conventional to recent biorefineries, which makes the recovered lignin more difficult to decompose. Also, the undesirable condensation and repolymerization during the depolymerization of lignin is more problematic as this significantly limits its ability to be depolymerized to low molecular weight products at high yields. To solve this problem, which ultimately enables maximizing lignin utilization, there have been many efforts in various aspects. In this review, we focus on the undesirable reactions occurring during the fractionation and depolymerization process of lignin and introduce recent efforts to suppress or minimize those unwanted reactions. The aim of all these efforts is to maximize lignin conversion to low molecular weight products.

Synergistic Effect on the Non-Oxygenated Fraction of Bio-Oil in Thermal Co-Pyrolysis of Biomass and Polypropylene at Low Heating Rate

“…Sinapyl, coniferyl and p-coumaryl alcohols respectively contains 2, 1 and no methoxy moieties. The proportions of S-, G-and H-units in feed depend on type of biomass origin, whether hardwood, softwood or herbaceous biomass [48,50]. Corncobs as an herbaceous biomass used as the feedstock in the present work contains mainly S-unit which less susceptible to undergo condensation and repolymerisation [50].…”

“…The proportions of S-, G-and H-units in feed depend on type of biomass origin, whether hardwood, softwood or herbaceous biomass [48,50]. Corncobs as an herbaceous biomass used as the feedstock in the present work contains mainly S-unit which less susceptible to undergo condensation and repolymerisation [50]. Another source of hydrogen is the dehydrogenation reaction of alcohols to aldehydes and ketones [51] in which the alcohols are obtained by reaction between PP and hydroxyl radicals from cellulose pyrolysis.…”

Development of lignin-based polycarboxylates as a plasticizer for cement paste via peracetic acid oxidation

“…When lignin radicals collide with each other, new bonds, such as β-β and β-5, are produced. Consequently, Mn increases due to the condensation reaction (Kim and Kim 2018). Additionally, Cx-lig (dialysis) had a greater Mw than Cx-lig (non-dialysis).…”

Single and Mixed Feedstocks Biorefining: Comparison of Primary Metabolites Recovery and Lignin Recombination During an Alkaline Process

“…The use of angiosperm dicotyledon feedstock like hemp and euphorbia allow to produce a lignin enriched in syringyl units (S units). S units have a -OCH 3 moiety at the C3 and C5 of the phenylpropane structure leading to the unavailability of C5 to be involved in the formation of new C-C bond and therefore mitigate the condensation (Kim and Kim, 2018).…”