Oxidation of organosolv lignin in a novel surfactant-free microemulsion reactor

Production of 4-Ethylphenol from Lignin Depolymerization in a Novel Surfactant-Free Microemulsion Reactor

“…This is mainly due to the adsorption of water ionization-generated ions on the surface of microemulsion droplets, consistent with the characteristic of oil-in-water (O/W) microregions . However, when the W OA value increases from 7.5 to 31.4 wt %, the increasing number of O/W microemulsion droplets can increase the probability of collision between themselves, and they may start forming hydrophobic and hydrophilic channels, decreasing the κ value of the system. , As a result, the microstructure transforms from the O/W to bicontinuous (B.C) microregion at this range. With the further increase in W OA (more than 31.4 wt %), the water-in-oil (W/O) microemulsion is formed with n -octane as the continuous phase.…”

“…Figure presents their phase diagram at room temperature, in which the component content is expressed as the mass fraction (wt %). There are two distinct regions in the phase diagram . In particular, the colored region is described as a single-phase microemulsion region, which is optically isotropic and transparent.…”

“…Furthermore, the above O/W microemulsion without lignin was also investigated, and the average size of its droplets is around 23 nm (Figure D), suggesting that the addition of lignin significantly enlarges the size of the microemulsion. This observation can be attributed to the aggregation of amphipathic lignin at its surface . As a result, it can improve the contact between the lignin and water-soluble IL catalyst for the following lignin depolymerization.…”

“…As one of the process intensification techniques, an emulsion system is a potential alternative to facilitate chemical reactions through compartmentalizing and concentrating reactants, solubilizing substrates, and increasing the interfacial area between immiscible liquids vastly. , Several emulsion systems were proposed for the depolymerization of lignin on the basis of the above advantages and lignin self-surfactivity, achieving an improved yield and selectivity of phenolic monomers. − A surfactant-free microemulsion (SFME), comprising amphoteric solvent, oil, and water phases, is an optically transparent, thermodynamically stable colloidal system with the droplets’ size between 10 and 100 nm. , These microemulsion droplets can act as innumerable microreactors for the chemical reaction and enable the contact between the catalyst and substrate easily. In our previous work, a novel SFME system for bagasse lignin oxidation was constructed, achieving a 40–500 wt % increase in phenolic monomers’ yield with comparison to those in single-solvent systems . Therefore, an SFME system would be a good choice to improve the 4-ethylphenol production from lignin depolymerization.…”

Review on the preparation of fuels and chemicals based on lignin

“…Aromatic compounds and aliphatic compounds with carboxylic acids can be prepared according to its oxidation degree. 75 Kong et al 76 used oxygen to catalyze oxidation, and the lignin in bagasse, poplar, bamboo and mango grass powder was degraded in the microemulsion reactor composed of octane, water and propyl alcohol. The yield of phenolic monomers was increasing signicantly while the yield of p-coumarin was 6.1%.…”