| 1. |
|
|
| 2. |
- Bhalla, Aditya, et al.
(författare)
-
Performance of three delignifying pretreatments on hardwoods: hydrolysis yields, comprehensive mass balances, and lignin properties
- 2019
-
Ingår i: Biotechnology for Biofuels. - : BioMed Central (BMC). - 1754-6834. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundIn this work, three pretreatments under investigation at the DOE Bioenergy Research Centers (BRCs) were subjected to a side-by-side comparison to assess their performance on model bioenergy hardwoods (a eucalyptus and a hybrid poplar). These include co-solvent-enhanced lignocellulosic fractionation (CELF), pretreatment with an ionic liquid using potentially biomass-derived components (cholinium lysinate or [Ch][Lys]), and two-stage Cu-catalyzed alkaline hydrogen peroxide pretreatment (Cu-AHP). For each of the feedstocks, the pretreatments were assessed for their impact on lignin and xylan solubilization and enzymatic hydrolysis yields as a function of enzyme loading. Lignins recovered from the pretreatments were characterized for polysaccharide content, molar mass distributions, β-aryl ether content, and response to depolymerization by thioacidolysis.ResultsAll three pretreatments resulted in significant solubilization of lignin and xylan, with the CELF pretreatment solubilizing the majority of both biopolymer categories. Enzymatic hydrolysis yields were shown to exhibit a strong, positive correlation with the lignin solubilized for the low enzyme loadings. The pretreatment-derived solubles in the [Ch][Lys]-pretreated biomass were presumed to contribute to inhibition of enzymatic hydrolysis in the eucalyptus as a substantial fraction of the pretreatment liquor was carried forward into hydrolysis for this pretreatment. The pretreatment-solubilized lignins exhibited significant differences in polysaccharide content, molar mass distributions, aromatic monomer yield by thioacidolysis, and β-aryl ether content. Key trends include a substantially higher polysaccharide content in the lignins recovered from the [Ch][Lys] pretreatment and high β-aryl ether contents and aromatic monomer yields from the Cu-AHP pretreatment. For all lignins, the 13C NMR-determined β-aryl ether content was shown to be correlated with the monomer yield with a second-order functionality.ConclusionsOverall, it was demonstrated that the three pretreatments highlighted in this study demonstrated uniquely different functionalities in reducing biomass recalcitrance and achieving higher enzymatic hydrolysis yields for the hybrid poplar while yielding a lignin-rich stream that may be suitable for valorization. Furthermore, modification of lignin during pretreatment, particularly cleavage of β-aryl ether bonds, is shown to be detrimental to subsequent depolymerization.
|
|
| 3. |
- Saulnier, Brian K., et al.
(författare)
-
Effect of Dilute Acid Pretreatment and Lignin Extraction Conditions on Lignin Properties and Suitability as a Phenol Replacement in Phenol-Formaldehyde Wood Adhesives
- 2023
-
Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 71:1, s. 592-602
-
Tidskriftsartikel (refereegranskat)abstract
- Corn stover was subjected to dilute sulfuric acid pretreatment to assess the impact of pretreatment conditions on lignin extractability, properties, and utility as a phenol replacement in wood phenol-formaldehyde (PF) adhesives. It was identified that both formic acid and NaOH could extract and recover 60-70% of the lignin remaining after pretreatment and enzymatic hydrolysis under the mildest pretreatment conditions while simultaneously achieving reasonable enzymatic hydrolysis yields (> 60%). The availability of reaction sites for the incorporation of lignins into the PF polymer matrix (i.e., unsubstituted phenolic hydroxyl groups) was shown to be strongly impacted by the pretreatment time and the recovery. Finally, a lignin-based wood adhesive was formulated by replacing 100% of the phenol with formic-acid-extracted lignin, which exhibited a dry shear strength exceeding a conventional PF adhesive. These findings suggest that both pretreatment and lignin extraction conditions can be tailored to yield lignins with properties targeted for this co-product application.
|
|
| 4. |
- Saulnier, Brian K., et al.
(författare)
-
Impact of Dilute Acid Pretreatment Conditions on p-Coumarate Removal in Diverse Maize Lines
- 2020
-
Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 314
-
Tidskriftsartikel (refereegranskat)abstract
- Prior work has identified that lignins recovered from dilute acid-pretreated corn stover exhibit superior performance in phenol-formaldehyde resins used in wood adhesive applications when compared to diverse process-modified lignins derived from other sources. This improved performance is hypothesized to be due to the higher content of unsubstituted phenolic groups specifically p-coumarate lignin esters. In this work, a diverse set of corn stover samples are employed that exhibit diversity in p-coumarate content and total lignin content to explore the relationship between dilute acid pretreatment conditions, p-coumarate ester hydrolysis, xylan solubilization, and the resulting glucose enzymatic hydrolysis yields. The goal of this study is to identify pretreatment conditions that preserve a significant fraction of the p-coumarate esters while simultaneously achieving high enzymatic hydrolysis yields. Kinetic parameters for p-coumarate ester hydrolysis were quantified and pretreatment-biomass combinations were identified that result in glucose hydrolysis yields of more than 90% while retaining nearly 50 mg p-coumarate/g lignin.
|
|
| 5. |
- Singh, Sandip K., et al.
(författare)
-
Lignin properties and cell wall response to deconstruction by alkaline pretreatment and enzymatic hydrolysis in brown midrib sorghums
- 2022
-
Ingår i: Industrial crops and products (Print). - : Elsevier. - 0926-6690 .- 1872-633X. ; 178
-
Tidskriftsartikel (refereegranskat)abstract
- Lignin has an adverse impact on the deconstruction of plant cell wall biopolymers in biorefining processes and its reduction and/or alteration during biosynthesis is one target for decreasing plant cell wall recalcitrance. In this work, the impact of two brown midrib mutations (bmr6 and bmr12) in two sorghum background lines (the commercial hybrid Atlas and near-isogenic BTx623) on lignin properties and the plants’ response to cell wall deconstruction to monomeric sugars via alkaline pretreatment and enzymatic hydrolysis is investigated with the goal of assessing how differences in lignin content and properties impact the plant’s response to pretreatment. We identify that both bmr sorghum lines show significantly lower abundance of water-extractable sugars (glucose, sucrose, and fructose) and alkali-saponifiable p-coumarate. Furthermore, both these properties exhibited identical trends across both background lines. Next, both untreated and mild alkali-pretreated bmr sorghums were shown to exhibit higher glucose hydrolysis yields following enzymatic hydrolysis than the control lines. Following pretreatment, the Atlas bmr sorghums exhibited more lignin solubilization and the solubilized lignin was of lower molar mass than the background control line suggesting that differences in the lignin response to pretreatment resulted these differences. Finally, significant differences were observed in the lignin content, lignin monomer distribution, and inter-unit linkages in the Atlas bmr line relative to the control line with key differences including lower syringyl monomer content in both bmr lines, higher relative abundance of β-O-4 linkages in the bmr6 line, and the presence of 5-hydroxy guaiacyl monomers and benzodioxane (α-O-5/β-O-4) linkages in the bmr12 line.
|
|
| 6. |
|
|
| 7. |
- Kumavat, Sandip R., et al.
(författare)
-
Two-Dimensional CH3NH3PbI3 with High Efficiency and Superior Carrier Mobility : A Theoretical Study
- 2019
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 123:9, s. 5231-5239
-
Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) halide perovskites have distinct tunable compositional and structural properties, which make 2D materials a good candidate to improve the characteristics of photovoltaic applications. We have explored strain-dependent structural, electronic, and optical properties of organic inorganic hybrid perovskite CH3NH3PbI3 monolayers using density functional calculations. Here, we have calculated carrier mobility of electrons and holes and the band gap of the CH3NH3PbI3 monolayer. The results suggest that with increasing tensile and compressive strains, the band gap increases up to 5% (in the case of tensile strain), whereas decreases toward instability, i.e., 9% (in the case of compressive strain). The carrier mobility of 2D CH3NH3PbI3 is approximately 16 times larger than that of the bulk form of CH3NH3PbI3. Furthermore, we have also investigated optical properties, which show good activity in the visible as well as in the high-ultraviolet region of the spectrum. In addition, the 2D CH3NH3PbI3 monolayer shows good transmittance (>80%) in a lower energy range as well as high absorption coefficient of 14.09 X 10(5) cm(-1) at 8.8 eV, which is up to 40% higher than that of the bulk form of CH3NH3PbI3; however, under both types of strains, the absorption coefficient is decreased in the 2D CH3NH3PbI3 monolayer. For photovoltaic applications, we have calculated the open-circuit voltage (V-oc), fill factor (FF), short-circuit current density (J(sc)), and power conversion efficiency (eta) of the 2D CH3NH3PbI3 monolayer. Our theoretical results suggest that the power conversion efficiency (eta) is 28%, which is higher than that of its bulk form and 5% less than the Shockley-Queisser limit (33%), suggesting that 2D CH3NH3PbI3 is a good candidate for the solar cell application.
|
|
| 8. |
- Munshi, Sandip, et al.
(författare)
-
Hydrogen-atom and oxygen-atom transfer reactivities of iron(
- 2022
-
Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:3, s. 870-884
-
Tidskriftsartikel (refereegranskat)abstract
- A series of iron(ii) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F−, Cl−; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that metal–ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state. The steric bulk of the quinoline moieties forces the axial ligands to deviate from the Fe–Naxial axis. A higher deviation/tilt is noted for the high spin complexes, while the acetonitrile coordinated complex displays least deviation. This deviation from linearity is slightly less in the analogous low-spin iron(ii) complex [FeII(L1-Qn)(NCMe)]2+ of the related asymmetric ligand L1-Qn due to the presence of only one sterically demanding quinoline moiety. The two iron(ii)-acetonitrile complexes [FeII(L2-Qn)(NCMe)]2+ and [FeII(L1-Qn)(NCMe)]2+ generate the corresponding iron(iv)-oxo species with higher thermal stability of the species supported by the L1-Qn ligand. The crystallographic and spectroscopic data for [FeIV(O)(L1-Qn)](ClO4)2 bear resemblance to other crystallographically characterized S = 1 iron(iv)-oxo complexes. The hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactivities of both the iron(iv)-oxo complexes were investigated, and a Box–Behnken multivariate optimization of the parameters for catalytic oxidation of cyclohexane by [FeII(L2-Qn)(NCMe)]2+ using hydrogen peroxide as the terminal oxidant is presented. An increase in the average Fe–N bond length in [FeII(L1-Qn)(NCMe)]2+ is also manifested in higher HAT and OAT rates relative to the other reported complexes of ligands based on the N4Py framework. The results reported here confirm that the steric influence of the ligand environment is of critical importance for the reactivity of iron(iv)-oxo complexes, but additional electronic factors must influence the reactivity of iron-oxo complexes of N4Py derivatives.
|
|
| 9. |
- Phongpreecha, Thanaphong, et al.
(författare)
-
Effect of catalyst and reaction conditions on aromatic monomer yields, product distribution, and sugar yields during lignin hydrogenolysis of silver birch wood
- 2020
-
Ingår i: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 316
-
Tidskriftsartikel (refereegranskat)abstract
- The impact of catalyst choice and reaction conditions during catalytic hydrogenolysis of silver birch biomass are assessed for their effect on aromatic monomer yields and selectivities, lignin removal, and sugar yields from enzymatic hydrolysis. At a reaction temperature of 220 °C with no supplemental H2, it was demonstrated that both Co/C and Ni/C exhibited aromatic monomer yields of >50%, which were close to the theoretical maximum expected for the lignin based on total β-O-4 content and exhibited high selectivities for 4-propylguaiacol and 4-propylsyringol. Pd/C exhibited a significantly different set of products, and using a model lignin dimer, showed a product profile that shifted upon inclusion of supplemental H2, suggesting that the generation of surface hydrogen is critical for this catalyst system. Lignin removal during hydrogenolysis could be correlated to glucose yields and inclusion of lignin depolymerizing catalysts significantly improves lignin removal and subsequent enzymatic hydrolysis yields.
|
|
| 10. |
- Singh, Sandip K., et al.
(författare)
-
Integrated Two-Stage Alkaline-Oxidative Pretreatment of Hybrid Poplar. Part 1 : Impact of Alkaline Pre-Extraction Conditions on Process Performance and Lignin Properties
- 2019
-
Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 58:35, s. 15989-15999
-
Tidskriftsartikel (refereegranskat)abstract
- We previously demonstrated that a two-stage pretreatment comprising of an alkaline pre-extraction followed by a Cu-catalyzed alkaline–oxidative treatment is effective at pretreating hardwoods under relatively mild reaction conditions. In this work, we focus on characterizing how biomass source and reaction conditions used during the alkaline pre-extraction impact the subsequent processing stages as well as lignin yields and properties. Specifically, three hybrid poplars were subjected to the first stage alkaline pre-extraction under various conditions including differences in time (15–300 min), temperature (95–155 °C), and alkali loadings (50–200 mg NaOH/g biomass), and the impact on total mass solubilization, lignin recovery, and lignin purity was determined. Empirical correlations were developed between reaction conditions and mass solubilization and lignin recovery during the pre-extraction stage. For select conditions, lignin properties were assessed and include β-O-4 content determined by 13C NMR, molecular mass distributions as determined by gel permeation chromatography, and susceptibility to depolymerization to aromatic monomers using thioacidolysis and formic acid catalyzed depolymerization. We found alkaline pre-extraction performed at higher temperatures generated lignins exhibiting lower contamination by polysaccharides, lower aromatic monomer yields from depolymerization, lower molar masses, and lower β-O-4 contents relative to the lower temperature pre-extractions. Finally, the pre-extracted biomass from select conditions was assessed for its response to the subsequent Cu-catalyzed alkaline–oxidative treatment and enzymatic hydrolysis. It was demonstrated that minor differences in delignification during pre-extraction have quantifiable impacts on the subsequent efficacy of the second stage of pretreatment and enzymatic hydrolysis with improved lignin removal during the first pre-extraction stage resulting in improved hydrolysis yields.
|
|
