| 1. |
- Goetz, Lee, et al.
(författare)
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Poly(methyl vinyl ether-co-maleic acid)-Polyethylene Glycol Nanocomposites Cross-Linked In Situ with Cellulose Nanowhiskers
- 2010
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 11:10, s. 2660-2666
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposites were developed by cross-linking cellulose nanowhiskers with poly(methyl vinyl ether-co-maleic acid) and polyethylene glycol. Nuclear Magnetic resonance (NMR) studies showed cross-linking occurs between the matrix and cellulose nanowhiskers via an esterification reaction. Proton NMR 12 relaxation experiments provided information on the mobility of the polymer chains within the matrix, which can be related to the structure of the cross-linked nanocomposite: The nanocomposite was found to consist of mobile chitin portions between crosslinked junction points and immobilized chain segments near or at those junction points, whose relative fraction increased upon further incorporation of cellulose nanowhiskers. Atomic force microscopy images showed homogeneous dispersion of nanowhiskers in the matrix even at high nanowhisker content, which can he attributed to cross-linking of the nanowhiskers in the matrix. Relative humidity conditions were found to affect the mechanical properties of the composites negatively while the nanowhiskers content had a positive effect. It is expected that the cross-links between the matrix and the cellulose nanowhiskers trap the nanowhiskers in the cross-linked network, preventing nanowhisker aggregation subsequently producing cellulose nanocomposites with unique mechanical behaviors. The results show that in situ cross-linking of cellulose nanowhiskers with a matrix polymer is a promising route to obtain nanocomposites with well dispersed nanowhiskers, tailored nanostructure, and mechanical performance.
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| 2. |
- Bylin, Susanne, 1982, et al.
(författare)
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Lignin Structure and Aggregation Behavior in a Two-Component Ionic Liquid Solvent System
- 2014
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Ingår i: BioResources. - : BioResources. - 1930-2126 .- 1930-2126. ; 9:4, s. 6002-6018
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Tidskriftsartikel (refereegranskat)abstract
- Ionic liquids are of potential interest in the processing of lignocellulosic biomass. In this study, the ionic liquid co-solvent system of 1-methylimidazole (MIM) and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc) was used to solvate LignoBoost lignin fractionated from black liquor obtained from a kraft paper mill. Lignin ethanol-precipitated (LEP) and ethanol-soluble (LES) fractions were characterized via gel permeation chromatography (GPC) and 13C- and 31P-nuclear magnetic resonance spectroscopy (NMR) to determine structural characteristics and their relationship to polymer solubility in the system. Polymer integrity and solubility were optimal at ~20% lignin loading (w/w). Results showed that LEPs were generally of higher apparent molecular weight (Mw) and enriched with condensed/aliphatic ether linkages and aliphatic hydroxyls. The LESs had a lower apparent Mw and were enriched with carboxylic and phenolic groups. This newly gained knowledge on lignin fractionation and aggregation in the present solvent system provides future opportunities for tuning fractionation/extraction to suit a specific biomass-derived product, e.g., carbon fibers
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| 3. |
- Goetz, L. A., et al.
(författare)
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Preparation of Microwave-Assisted Polymer-Grafted Softwood Kraft Pulp Fibers. Enhanced Water Absorbency
- 2011
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Ingår i: Journal of Applied Polymer Science. - : Wiley. - 1097-4628 .- 0021-8995. ; 119:1, s. 387-395
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Tidskriftsartikel (refereegranskat)abstract
- A wood pulp cellulose-based hydrogel material was prepared with poly(methyl vinyl ether-co-maleic acid) (PMVEMA), polyethylene glycol (PEG), and softwood ECF kraft pulp via microwave and thermal esterification and compared via hydrogel absorption and retention of water and 0.10M NaCl. The microwave initiated reaction time was optimized to 105 s at 1600 W based on maximum water absorption of 96 g/g of the 49% PMVEMA pulp hydrogels. The influence of reaction variables such as pulp fiber size and the weight ratios of PMVEMA to pulp were investigated. The maximum water absorbency of the milled pulp fibers microwave initiated products was 151 g/g, whereas the maximum water absorbency of the milled pulp fibers thermally initiated hydrogels was 198 g/g. In addition, the microwave initiated hydrogels retained a maximum of 67% of absorbed water after centrifugation at 770 rpm for 10 min, whereas the thermally initiated hydrogels retained a maximum of 49% of water absorbed. Fourier transform infrared spectroscopy (FTIR) was used to confirm the esterification of the PMVEMA with the pulp cellulose. Microwave initiated crosslinking successfully produced a pulp hydrogel with a shorter reaction time and comparable or improved water absorption and retention properties when compared with the traditional thermally crosslinked pulp hydrogel system.
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| 4. |
- Hallac, B. B., et al.
(författare)
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Biomass Characterization of Buddleja davidii: A Potential Feedstock for Biofuel Production
- 2009
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118. ; 57:4, s. 1275-1281
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Tidskriftsartikel (refereegranskat)abstract
- A compositional analysis was performed on Buddleja davidii to determine its general biomass characteristics and provide detailed analysis of the chemical structures of its cellulose and lignin using NMR. B. davidii is a new potential lignocellulosic bioresource for producing bioethanol because it has several attractive agroenergy features. The biomass composition of B. davidii is 30% lignin, 35% cellulose, and 34% hemicellulose. Solid-state CP/MAS C-13 NMR showed that 33% of the cellulose is para-crystalline and 41% is at inaccessible surfaces. Both quantitative C-13 and P-31 NMR were used to examine the structure of lignin. The lignin was determined to be guaiacyl and syringyl with an h:g:s ratio of 0:81:19.
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| 5. |
- Hallac, B. B., et al.
(författare)
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Effect of Ethanol Organosolv Pretreatment on Enzymatic Hydrolysis of Buddleja davidii Stem Biomass
- 2010
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 49:4, s. 1467-1472
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Tidskriftsartikel (refereegranskat)abstract
- Ethanol organosolv pretreatment was performed on Buddleja davidii to evaluate this bioresource as a potential feedstock for bioethanol production. B. davidii was pretreated and delignified, while 85% of the glucose content of the untreated material was retained in the pretreated solid fraction. The enzymatic hydrolysis showed that organosolv pretreatment produced solid substrates that were readily digestible by cellulases. Gel-permeation chromatography was used to determine the degree of polymerization (DP) of cellulose, and solid-state cross polarization/magic angle spinning 13C NMR experiments were conducted to study the changes in crystallinity and ultrastructure of cellulose. The results showed a decrease in DP along with an increase in the relative proportions of para-crystalline and amorphous cellulose and a decrease in cellulose Ia̧ and Ib̃. Removal of lignin and hemicellulose, reduction in DP, and decrease in the crystalline allomorphs (Ia̧ and Ib̃) increased the amenability of the biomass to enzymatic degradation.
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| 6. |
- Hu, Z. J., et al.
(författare)
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Chemical profiles of switchgrass
- 2010
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 101:9, s. 3253-3257
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Tidskriftsartikel (refereegranskat)abstract
- Chemical analysis Studies were conducted for four populations of switchgrass (Alamo, Kanlow, GA993, and GA992), Panicum virgatum L., which were partitioned into leaves, internodes. and nodes. The variations in carbohydrate compositions, lignin and extractives content, higher heating value (HHV), and the syringyl:guaiacyl ratio of switchgrass were determined. The experimental results indicated that bulk chemical profiles for the four populations of switchgrass were comparable. However, the results from three morphological components of switchgrass, leaves, internodes and nodes, provided a significant diversity among the analytical results Studied.
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| 7. |
- Köhnke, Tobias, 1978, et al.
(författare)
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Ice templated xylan-nanocrystalline cellulose aero/hydrogels
- 2012
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Ingår i: Abstracts of Papers, 243rd ACS National Meeting, San Diego, CA, United States, March 25-29, 2012.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the current trend for a more effective utilization of biomass, increased attention has been focused to the engineered exploitation of xylans as biopolymer resources in the development of new materials. The xylan backbone has an affinity to cellulose and will adsorb irreversibly on cellulosic surfaces, an inherent property that provides great opportunities for the use of xylan in cellulose-based composites. This paper demonstrates how foams of xylan and nanocrystalline cellulose can be formed by using a freeze-casting technique, i.e. templating of porous structures by solidification of a solvent. Effects of xylan molecular structure and solidification conditions on pore morphology and xylan ultrastructure are evaluated and different ways to stabilize the formed structures are presented. Furthermore, it is demonstrated how crosslinking during the freeze-casting process enables production of nanoreinforced hydrogels with tailored porous structures.
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| 8. |
- Nagy, M., et al.
(författare)
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Catalytic hydrogenolysis of ethanol organosolv lignin
- 2009
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Ingår i: Holzforschung. - 1437-434X .- 0018-3830. ; 63:5, s. 513-520
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Tidskriftsartikel (refereegranskat)abstract
- The production of ethanol based on lignocellulosic materials will bring about the coproduction of significant amounts of under-utilized lignin. This study examines the potential of conventional heterogeneous and novel homogeneous catalysts for the selective cleavage of the aryl-O-aryl and aryl-O-aliphatic linkages of ethanol organosolv lignin to convert it from a low grade fuel to potential fuel precursors or other value added chemicals. The development of hydrogenolysis conditions that effectively increase the solubility of lignin were initially examined with Ru(Cl)(2)(PPh3)(3) and demonstrated the ability to decrease the molecular weight and enhance the solubility of the lignin polymer. Later studies examined several heterogeneous and homogeneous hydrogenation catalysts at optimized reaction conditions resulting in 96.4% solubility with Ru(Cl)(2)(PPh3)(3), increase in H/C ratio with Raney-Ni, Pt/C and extensive monomer formation with NaBH4/I-2. The changes in molecular structure of lignin were followed by size exclusion chromatography, qualitative and quantitative NMR spectroscopy and elemental analysis. These studies demonstrated that aryl-O-aryl and aryl-O-aliphatic linkages could be cleaved and the hydrogenated lignin had a decrease in oxygen functionality and the formation of products with lower oxygen content.
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| 9. |
- Nagy, M., et al.
(författare)
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Phosphitylation and quantitative P-31 NMR analysis of partially substituted biodiesel glycerols
- 2009
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 88:9, s. 1793-1797
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Tidskriftsartikel (refereegranskat)abstract
- The main step during biodiesel production is the catalytic transesterification of triglycerides. Glycerol and fatty acids are by-products of the biodiesel production and considered as contaminants in the final product. By selectively measuring the amount of fatty acids and glycerol with different substitution levels, the yield of this step and the quality of the final biodiesel can be determined. This study examines the application of phosphitylation of glycerol hydroxyl groups with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane followed by P-31 NMR analysis to provide a rapid quantitative analytical technique for the determination of substitution patterns on partially esterified glycerols, alcohols and the detection of fatty acids. P-31 NMR chemical shift data was established with a series mono and di-substituted esters of glycerol, fatty acids and alcohols, then utilized to characterize commercial glycerol and biodiesel samples. (C) 2009 Elsevier Ltd. All rights reserved.
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| 10. |
- Nagy, M., et al.
(författare)
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Quantitative NMR Analysis of Partially Substituted Biodiesel Glycerols
- 2009
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Ingår i: Journal of Biobased Materials and Bioenergy. - : American Scientific Publishers. - 1556-6560 .- 1556-6579. ; 3:1, s. 108-111
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Tidskriftsartikel (refereegranskat)abstract
- Phosphitylation of hydroxyl groups in biodiesel samples with 2-chloro-4,4,5,5-tetramethyl-1,3,2-dioxaphospholane followed by P-31-NMR analysis provides a rapid quantitative analytical technique for the determination of substitution patterns on partially esterified glycerols. The unique P-31-NMR chemical shift data was established with a series mono and di-substituted fatty acid esters of glycerol and then utilized to characterize an industrial sample of partially processed biodiesel.
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