Characteristics of Lignin Structural Conversion in a Phase-Separative Reaction System Composed of Cresol and Sulfuric Acid

Abstract

The chemical structures of lignocresols derived from native lignins by the phase-separative treatment with cresol and sulfuric acid were characterized by spectral analyses and chemical degradations. The changes in the structure of lignin during the conversion process were discussed. Lignocresol had few conjugated systems, being pinkish white, its brightness comparable to milled wood lignin. Spruce lignocresol included 0.64mol/C9 of cresolic nuclei in the molecule (0.9mol/C9 in birch lignocresol), 77% of which were linked to lignin Cα-positions through carbon-carbon linkages, 16% possibly to Cy-positions, and the remaining 7% etherified to lignin side chains through its phenolic hydroxyl groups. The molecular weight (Mw) of lignocresol was ca. 3500 in spruce, lower in birch. Most of the β-and γ-positions in the side chains of Cg units remained intact, except the coniferyi alcohol and aldehyde units. These structural features were constant during the reaction time up to 60min. It is concluded that the fragmentation of lignin in the phase-separative reaction system was principally due to the cleavage of benzyl aryl ethers, and the skeleton of lignocresol represents those of lignin subblocks formed by the dehydrogenative polymerization of monolignols.

Polyacrylate-based Water-absorbent Hydrogels Prepared with Lignin-related Compounds: Process Conditions and Performance

“…Alkali lignin (AL) was separated from black liquor from bamboo kraft cooking via acid (Liu et al 2017). Lignophenols, including LC, LR, and LP, were derived from bamboo mills via the phase separation method (Funaoka and Fukatsu 1996) by using 72% sulphuric acid (H2SO4) as a catalyst and p-cresol, resorcinol, and pyrogallol as organic solvents, respectively. Lignosulfonate (LS) was supplied by the Tianjin Institute of Fine Chemicals (Tianjin, China).…”

“…Lignocresol-graftedpolyacrylic acid resin and lignosulfonate-grafted-polyacrylic acid resin had higher absorption capacities than alkali lignin-grafted-polyacrylic acid resin. This was because lignocresols contained more hydroxyl groups than alkali lignins (Funaoka and Fukatsu 1996;Qin et al 2015); thus more acrylic acid could be grafted on lignocresol than alkali lignin. As a result, the polymerization degree increased, which resulted in higher absorption capacities.…”

Effects of Lignophenols on Mechanical Performance of Biocomposites Based on Polyhydroxybutyrate (PHB) and Polypropylene (PP) Reinforced with Pulp Fibers

“…Lignophenols (Lps): Lignophenols were synthesized using poplar wood meal samples in a phase separation system (Funaoka and Fukatsu 1996). Dried pulp fiber was immersed in a lignophenol-acetone solution for 24 h to allow the lignophenol to become evenly dispersed in the pulp fiber surface.…”

Conversion and Separation Pattern of Lignocellulosic Carbohydrates through the Phase-separation System

“…The separated lignin derivatives (lignophenol) have several unique functions, which conventional lignins do not have, in spite of retention of the original interunit linkages: these include highly phenolic property, no conjugated system, light color comparable with native lignin, solid-liquid transformation and high immobilization capability for proteins (enzyme). 11,12 Furthermore, the molecular structures of lignophenol can be secondarily controlled using a nucleophilic attack of phenolic units to adjacent carbons, resulting in a change of the important functionalities such as phenolic activity and molecular weight. These original functions are due to the selective hybridization of monomeric phenol derivatives at C-1 positions, leading to liner type structures composed mainly of 1,1-bis(aryl)propane-type units.…”

“…The conversion and separation pattern of lignin component was reported in previous papers. [10][11][12] …”