Abstract:We report a new and
robust strategy toward the development of high-performance
pressure sensitive adhesives (PSAs) from chemicals directly obtained
from raw biomass deconstruction. A particularly unique and translatable
aspect of this work was the use of a monomer obtained from real biomass,
as opposed to a model compound or lignin-mimic, to generate well-defined
and nanostructure-forming polymers. Herein, poplar wood depolymerization
followed by minimal purification steps (filtration and extraction)
produced … Show more
“…However, when using 2‐propanol instead of water/ethanol 1:1 (v/v) in the Ru/C experiments, the relative percentage of the monomers changed, ( Z )‐propenylsyringol and ( Z )‐isoeugenol being the most abundant ones (sum of the two monomers was 3.6%), and the total yield of monomeric phenols was slightly higher (7.7%). In studies using similar catalytic conditions, the yields of 4‐propylsyringol/guaiacol were around 5–15% (sum of both phenols) . Nevertheless, in studies using Ni‐based catalysts in different substrates with longer reaction times and usually higher temperatures, the reported yields were higher than ours (sum of the monomers between 10 and 42%) …”
Section: Resultscontrasting
confidence: 58%
“…), and the comparison between studies should be taken with caution. These two monomers (4‐propylguaiacol/syringol) have already been proven as chemicals of great interest, since, for example, they were the base for the successful synthesis of pressure‐sensitive adhesives …”
BACKGROUND: Materials from renewable sources are in great demand to reduce carbon fingerprint. Olive pomace is a waste with high lignin content (>25%) and generated in high volumes. Therefore lignin from olive pomace is susceptible to be transformed into added value chemicals such as monomeric phenols through its catalytic depolymerization combining hydrogen donors (i.e. molecular hydrogen, polar protic solvents and formic acid) and catalysts based on transition metals (i.e. palladium and ruthenium supported on carbon, and SHVO catalyst, also ruthenium-based).
RESULTS: The reaction conditions for the nitrogen and hydrogen experiments were temperatures of 250 and 200 ∘ C and initialpressures of 4 and 20 bar respectively. The bio-oil obtained after the catalytic process was approximately half of the initial sample weight, although somewhat lower under hydrogen conditions. The SHVO catalyst yielded 15 and 10% of monomeric phenols under nitrogen and hydrogen conditions respectively, while the other two catalysts yielded between 6 and 9% irrespective of the gas. CONCLUSION: Overall, the SHVO catalyst provided a richer mixture of phenolic compounds owing to its milder hydrogenation activity compared with the other catalysts, although at the end of the reaction the catalyst did not preserve its native form. The use of formic acid under nitrogen atmosphere was advantageous to increase the yields of phenols. The most abundant monomers in the experiments using SHVO catalyst under both atmospheres were 4-propylguaiacol, (Z)-propenylguaiacol, 4-propylsyringol, dihydroconiferyl alcohol, (Z)-propenylsyringol and dihydrosinapyl alcohol.
“…However, when using 2‐propanol instead of water/ethanol 1:1 (v/v) in the Ru/C experiments, the relative percentage of the monomers changed, ( Z )‐propenylsyringol and ( Z )‐isoeugenol being the most abundant ones (sum of the two monomers was 3.6%), and the total yield of monomeric phenols was slightly higher (7.7%). In studies using similar catalytic conditions, the yields of 4‐propylsyringol/guaiacol were around 5–15% (sum of both phenols) . Nevertheless, in studies using Ni‐based catalysts in different substrates with longer reaction times and usually higher temperatures, the reported yields were higher than ours (sum of the monomers between 10 and 42%) …”
Section: Resultscontrasting
confidence: 58%
“…), and the comparison between studies should be taken with caution. These two monomers (4‐propylguaiacol/syringol) have already been proven as chemicals of great interest, since, for example, they were the base for the successful synthesis of pressure‐sensitive adhesives …”
BACKGROUND: Materials from renewable sources are in great demand to reduce carbon fingerprint. Olive pomace is a waste with high lignin content (>25%) and generated in high volumes. Therefore lignin from olive pomace is susceptible to be transformed into added value chemicals such as monomeric phenols through its catalytic depolymerization combining hydrogen donors (i.e. molecular hydrogen, polar protic solvents and formic acid) and catalysts based on transition metals (i.e. palladium and ruthenium supported on carbon, and SHVO catalyst, also ruthenium-based).
RESULTS: The reaction conditions for the nitrogen and hydrogen experiments were temperatures of 250 and 200 ∘ C and initialpressures of 4 and 20 bar respectively. The bio-oil obtained after the catalytic process was approximately half of the initial sample weight, although somewhat lower under hydrogen conditions. The SHVO catalyst yielded 15 and 10% of monomeric phenols under nitrogen and hydrogen conditions respectively, while the other two catalysts yielded between 6 and 9% irrespective of the gas. CONCLUSION: Overall, the SHVO catalyst provided a richer mixture of phenolic compounds owing to its milder hydrogenation activity compared with the other catalysts, although at the end of the reaction the catalyst did not preserve its native form. The use of formic acid under nitrogen atmosphere was advantageous to increase the yields of phenols. The most abundant monomers in the experiments using SHVO catalyst under both atmospheres were 4-propylguaiacol, (Z)-propenylguaiacol, 4-propylsyringol, dihydroconiferyl alcohol, (Z)-propenylsyringol and dihydrosinapyl alcohol.
“…1, a β-O-4 content of 69% only yields a maximum monomer yield of 36%. Monomeric units from lignin depolymerization have been shown to be highly valuable as they offer a diverse platform to synthesize chemicals 10–20 and functional replacements for conventional polymers 21–25 .Fig. 1Lignin structure overview.…”
The ratio of syringyl (S) and guaiacyl (G) units in lignin has been regarded as a major factor in determining the maximum monomer yield from lignin depolymerization. This limit arises from the notion that G units are prone to C-C bond formation during lignin biosynthesis, resulting in less ether linkages that generate monomers. This study uses reductive catalytic fractionation (RCF) in flow-through reactors as an analytical tool to depolymerize lignin in poplar with naturally varying S/G ratios, and directly challenges the common conception that the S/G ratio predicts monomer yields. Rather, this work suggests that the plant controls C-O and C-C bond content by regulating monomer transport during lignin biosynthesis. Overall, our results indicate that additional factors beyond the monomeric composition of native lignin are important in developing a fundamental understanding of lignin biosynthesis.
“…Currently, the utilization of renewable resources to prepare catalysts, hydrogels, and elastomers has attracted growing interest due to the sustainability concerns [15][16][17][18][19]. Being the most abundant renewable aromatic polymers, lignins are usually underutilized as a byproduct in the paper manufacturing and biorefining industries [19,20]. Only less than 2% of industry lignins are converted into high value-added chemicals.…”
In this study, a lignin-based polyacid catalyst was synthesized via two steps to enhance water resistance of urea–formaldehyde (UF) resins. The first steps involved a hydroxymethylation reaction to increase the hydroxyl content in lignin. Then, hydroxymethylated lignins were reacted with maleic anhydride to form maleated lignin-based polyacids. The acid groups were expected to function as acid catalysts to catalyze the curing process of UF resin. In order to elucidate the structural variation, 3-methoxy-4-hydroxyphenylpropane as a typical guaiacol lignin structural unit was used as a model compound to observe the hydroxymethylation and the reaction with maleic anhydride analyzed by 1H and 13C NMR. After the structural analysis of synthesized lignin-based polyacid by FTIR and 13C NMR, it was used to produce UF resin as an adhesive in plywood and medium density fiberboard (MDF) production, respectively. The results showed that when the addition of lignin-based polyacid was 5% in plywood, it could effectively improve the water resistance of UF resins as compared to commercial additive NH4Cl. It also exhibited a lower formaldehyde emission. Like plywood, lignin-based catalysts used in medium density fiberboard production could not only maintain the mechanical properties, but also inhibit the water adsorption of fiberboards.
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