Production of Aromatic Compounds by Catalytic Depolymerization of Technical and Downstream Biorefinery Lignins

Abstract

Lignocellulosic materials are promising alternatives to non-renewable fossil sources when producing aromatic compounds. Lignins from Populus salicaceae. Pinus radiata and Pinus pinaster from industrial wastes and biorefinery effluents were isolated and characterized. Lignin was depolymerized using homogenous (NaOH) and heterogeneous (Ni-, Cu- or Ni-Cu-hydrotalcites) base catalysis and catalytic hydrogenolysis using Ru/C. When homogeneous base catalyzed depolymerization (BCD) and Ru/C hydrogenolysis were combined on poplar lignin, the aromatics amount was ca. 11 wt.%. Monomer distributions changed depending on the feedstock and the reaction conditions. Aqueous NaOH produced cleavage of the alkyl side chain that was preserved when using modified hydrotalcite catalysts or Ru/C-catalyzed hydrogenolysis in ethanol. Depolymerization using hydrotalcite catalysts in ethanol produced monomers bearing carbonyl groups on the alkyl side chain. The analysis of the reaction mixtures was done by size exclusion chromatography (SEC) and diffusion ordered nuclear magnetic resonance spectroscopy (DOSY NMR). 31P NMR and heteronuclear single quantum coherence spectroscopy (HSQC) were also used in this study. The content in poly-(hydroxy)-aromatic ethers in the reaction mixtures decreased upon thermal treatments in ethanol. It was concluded that thermo-solvolysis is key in lignin depolymerization, and that the synergistic effect of Ni and Cu provided monomers with oxidized alkyl side chains.

Innovative flow‐through reaction system for the sustainable production of phenolic monomers from lignocellulose catalyzed by supported Mo2C.

“…Depolymerization of ethanosolv lignin obtained from poplar sawdust [24] was tryed using 35‐Mo 2 C/AC in ethanol at 200 °C. Too high reactivity was observed.…”

“…Apparent mass values in DOSY spectra were estimated using PS calibration (blue figures) and PEG calibration (red figures). [24] The mass of LDO from FT-RCF was almost constant in all FT processes: 46 � 5 wt.%, 48 � 2 wt.% and 52 � 7 wt.% for FT1, FT2 and FT3 (Figure 3), while 44.4 � 1.8 wt.% (where 1.8 % accounts for the standard deviation) was achieved in the absence of catalyst. LDO in FT were very similar to that achieved in batch mode (ca.…”

Extraction of Phenolic Compounds from Populus Salicaceae Bark

“…An HP-5MS capillary column [(5-phenyl)methylpolysiloxane, 60 m × 0.32 mm] was used at the stationary phase. This stationary phase is commonly used in the analysis of phenolic compounds [11]. Helium was used as a carrier gas (104 mL•min −1 ) and the inlet injector was kept at 230 • C. The temperature program started at 50 • C and heating at 10 • C/min was carried out until a temperature of 325 • C was attained and then held for 15 min.…”

“…To produce bioenergy out of these residues represents an inefficient way to valorize them because of the low value-added of the final use, in which the great chemical richness of poplar bark cannot be fully exploited. The development of biorefinery strategies for the full and optimal valorization of lignocellulosic residues such as poplar sawdust and bark is the best way to increase sustainability in the production of bio-based fuels and products, find renewable sources for aromatic compounds [11], and succeed in the development of a circular economy [4]. Recently, an alternative application of poplar bark was proposed as an efficient bio-based thermal insulation material in the field of "green building" [12].…”

Biomolecules from Plant Residues

“…The effect of NaOH was attributed to the removal of extracts and lignin in the cell wall of the fiber, which led to an improvement in the interfacial adhesion characteristics. Another work that shows the interest to take advantage of lignocellulosic materials is that of Cornejo et al [21], where these materials are proposed as promising alternatives to non-renewable fossil sources in order to produce aromatic compounds. These authors isolated and characterized Populus salicaceae, Pinus radiata and Pinus pinaster lignins from industrial waste and biorefinery effluents.…”