UC Santa Barbara

Biorenewable material has gained a greater focus in research to produce chemicals, fuels, plastics, and energy because of their abundance, diversity, and unique properties. Biorenewable materials include mainly terrestrial based plants that grow throughout the world. From the plant, there are constructed of three biopolymers, and in this study the biopolymer of interest is called lignin. Lignin is the second most abundant biopolymer and is known as the most abundant source of phenolic structures known to mankind. Current research focuses on utilizing lignin’s aromatic monomers as replacements for phenolic monomers derived from nonrenewable resources. The key problem in accomplishing this idea is the recalcitrant structure of lignin. The functional properties of technical lignin must be characterized in more detail in order for it to become a renewable raw material for the chemical industries. Herein, we have investigated the structure dependent properties of lignin from samples of fountain grass, walnut shell, and poplar. These samples were analyzed before and after successive organic solvent extractions. The lignin samples were fractionated according to their molar mass by these optimized organosolv extractions. Utilizing Ni/C for catalytic depolymerization achieved 50% aromatic products from fountain grass and walnut shell, respectively. Previously in our laboratory, we utilized Ni/C for catalytic depolymerization of Poplar lignin and achieved reported yields of 69%. Stemming from this idea, we wanted to approach the depolymerization of lignin with the removal of metal catalysts. Herein, we describe lignin hydrogenolysis/depolymerization of organosolv poplar lignin in ethanol/isopropanol solvent in the absence of added catalysts. Heating Organosolv Poplar Lignin (OPL) at 270 °C for 4 h in 50:50 (v:v) EtOH/i-PrOH in a closed pressure vessel gave an overall oil yield of 70 wt%, of which about 48% consisted of the monomers (E)-4-propenyl syringol and isoeugenol. Notably, these catalyst-free reactions in ethanol/ isopropanol media show monomer yields comparable to those reported for lignin depolymerization using precious metal catalysts and dihydrogen, which suggests unexpectedly favorable H-donor ability of this mixed alcohol medium. With the advancements in discovering a mixture to utilize an alcohol mixture to depolymerize lignin, we wanted to finish by connecting the bridge gap between utilizing lignin aromatic monomers straight to materials such as thermosets and thermoplastics. We report novel methodology on the extraction, isolation, and depolymerization of different biomass towards monomeric compounds of interest in the goal of further utilizing them into material networks.