scholarly journals Sequential solvent fractionation of lignin for selective production of monoaromatics by Ru catalyzed ethanolysis

RSC Advances ◽  
2017 ◽  
Vol 7 (84) ◽  
pp. 53117-53125 ◽  
Author(s):  
Jae-Young Kim ◽  
Shin Young Park ◽  
Jae Hoon Lee ◽  
In-Gyu Choi ◽  
Joon Weon Choi
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Solvent Fractionation ◽  
The Impact ◽  
Lignin Structure

The purpose of this study was to investigate the impact of lignin structure, especially its average molecular weight (Mw) on the distribution of catalytically depolymerized products.

scholarly journals Characterisation of Sequential Solvent Fractionation and Base-catalysed Depolymerisation of Treated Alkali Lignin

BioResources ◽  
2015 ◽  
Vol 10 (3) ◽  
pp. 4137-4151 ◽  
Author(s):  
Aikfei Ang ◽  
Zaidon Ashaari ◽  
Edi Suhaimi Bakar ◽  
Nor Azowa Ibrahim
Keyword(s):  
Molecular Weight ◽  
Chemical Structure ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Solubility Parameters ◽  
Low Molecular Weight ◽  
Sequential Fractionation ◽  
Weight Average Molecular Weight ◽  
Solvent Fractionation ◽  
Alkali Lignin

An alkali lignin (OL) with a weight-average molecular weight (Mw) of 11646 g/mol was used to prepare low-molecular weight lignin for resin synthesis. The low-molecular weight lignin feedstock was obtained via base-catalysed depolymerisation (BCD) treatments at different combined severity factors. Sequential fractionation of the OL and BCD-treated lignins using organic solvents with different Hildebrand solubility parameters were used to alter the homogeneity of the OL. The yield and properties of OL itself and OL and BCD-treated OL dissolved in propan-1-ol (F1), ethanol (F2), and methanol (F3) were determined. Regardless of the treatment applied, a small amount of OL was dissolved in F1 and F2. The BCD treatment did not increase the yield of F1 but did increase the yields of F2 and F3. Gel permeation chromatography (GPC) showed that the repolymerization reaction occurred in F3 for all BCD-treated OL, so these lignins were not suitable for use as feedstocks for resin production. The GPC, 13Carbon-nuclear magnetic resonance, and Fourier transform infrared spectroscopy analyses confirmed that the F3 in OL exhibited the optimum yield, molecular weight distribution, and chemical structure suitable for use as feedstocks for resin synthesis.

The impact of ionic strength on the molecular weight distribution (MWD) of lignin dissolved during softwood kraft cooking in a flow-through reactor

Holzforschung ◽  
2016 ◽  
Vol 70 (6) ◽  
pp. 495-501 ◽  
Author(s):  
Binh T.T. Dang ◽  
Harald Brelid ◽  
Hans Theliander
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Average Molecular Weight ◽  
Ion Concentration ◽  
Small Scale ◽  
Kraft Cooking ◽  
Flow Through ◽  
Cooking Times ◽  
The Impact

Abstract The molecular weight distribution (MWD) of dissolved lignin as a function of time during kraft cooking of Scots pine (Pinus silvestris L) has been investigated, while the influence of sodium ion concentration ([Na+]) on the MWD was in focus. The kraft cooking was performed in a small scale flow-through reactor and the [Na+] was controlled by the addition of either Na2CO3 or NaCl. Fractions of black liquors (BL) were collected at different cooking times and the lignin was separated from the BL by acidification. The MWD of the dissolved lignin was analyzed by GPC. Results show that the weight average molecular weight (Mw) of dissolved lignin increases gradually as function of cooking time. An increase of [Na+] in the cooking liquor leads to Mw decrement. Findings from cooks with constant and varying [Na+] imply that the retarding effect of an increased [Na+] on delignification is related to the decrease in lignin solubility at higher [Na+].

scholarly journals The Impact of Lignin Structural Diversity on Performance of Cellulose Nanofiber (CNF)-Starch Composite Films

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 538 ◽  
Author(s):  
Yadong Zhao ◽  
Ayumu Tagami ◽  
Galina Dobele ◽  
Mikael E. Lindström ◽  
Olena Sevastyanova
Keyword(s):  
Molecular Weight ◽  
Cellulose Nanofibers ◽  
Composite Films ◽  
Structural Diversity ◽  
Decomposition Temperature ◽  
Solvent Fractionation ◽  
Film Performance ◽  
Oh Groups ◽  
Chemical Structures ◽  
The Impact

Lignin fractions having different molecular weights and varied chemical structures isolated from kraft lignins of both softwood and hardwood via a sequential solvent fractionation technique were incorporated into a tunicate cellulose nanofibers (CNF)—starch mixture to prepare 100% bio-based composite films. The aim was to investigate the impact of lignin structural diversity on film performance. It was confirmed that lignin’s distribution in the films was dependent on the polarity of solvents used for fractionation (acetone > methanol > ethanol > ethyl acetate) and influenced the optical properties of the films. The –OH group content and molecular weight of lignin were positively related to film density. In general, the addition of lignin fractions led to decrease in thermal stability and increase in Young’s modulus of the composite films. The modulus of the films was found to decrease as the molecular weight of lignin increased, and a higher amount of carboxyl and phenolic –OH groups in the lignin fraction resulted in films with higher stiffness. The thermal analysis showed higher char content formation for lignin-containing films in a nitrogen atmosphere with increased molecular weight. In an oxygen atmosphere, the phenol content, saturated side chains and short chain structures of lignin had impacts on the maximum decomposition temperature of the films, confirming the relationship between the chemical structure of lignin and thermo-oxidative stability of the corresponding film. This study addresses the importance of lignin diversities on composite film performance, which could be helpful for tailoring lignin’s applications in bio-based materials based on their specific characteristics.

scholarly journals Initiator Feeding Policies in Semi-Batch Free Radical Polymerization: A Monte Carlo Study

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1291 ◽  
Author(s):  
Ali Seyedi ◽  
Mohammad Najafi ◽  
Gregory T. Russell ◽  
Yousef Mohammadi ◽  
Eduardo Vivaldo-Lima ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Monte Carlo ◽  
Free Radical ◽  
Methyl Methacrylate ◽  
Radical Polymerization ◽  
Average Molecular Weight ◽  
Free Radical Polymerization ◽  
Monte Carlo Algorithm ◽  
Single Shot ◽  
The Impact

A Monte Carlo simulation algorithm is developed to visualize the impact of various initiator feeding policies on the kinetics of free radical polymerization. Three cases are studied: (1) general free radical polymerization using typical rate constants; (2) diffusion-controlled styrene free radical polymerization in a relatively small amount of solvent; and (3) methyl methacrylate free radical polymerization in solution. The number- and weight-average chain lengths, molecular weight distribution (MWD), and polymerization time were computed for each initiator feeding policy. The results show that a higher number of initiator shots throughout polymerization at a fixed amount of initiator significantly increases average molecular weight and broadens MWD. Similar results are also observed when most of the initiator is added at higher conversions. It is demonstrated that one can double the molecular weight of polystyrene and increase its dispersity by 50% through a four-shot instead of a single shot feeding policy. Similar behavior occurs in the case of methyl methacrylate, while the total time drops by about 5%. In addition, policies injecting initiator at high monomer conversions result in a higher unreacted initiator content in the final product. Lastly, simulation conversion-time profiles are in agreement with benchmark literature information for methyl methacrylate, which essentially validates the highly effective and flexible Monte Carlo algorithm developed in this work.

scholarly journals Composting of Polylactide Containing Natural Anti-Aging Compounds of Plant Origin

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1582 ◽  
Author(s):  
Moraczewski ◽  
Malinowski ◽  
Sikorska ◽  
Karasiewicz ◽  
Stepczyńska ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Visual Assessment ◽  
Thermal Strength ◽  
Scanning Calorimetry ◽  
Microscopic Appearance ◽  
Composting Process ◽  
Phase Transition Temperatures ◽  
The Impact ◽  
Industrial Composting

The paper presents the effects of biodegradation of polylactide containing natural anti-aging compounds. Polymer containing 0.5; 5 and 10 wt % of coffee, cocoa or cinnamon extracts were subjected to industrial composting for 7, 14, 21 or 28 days. The effect of the composting process on polylactide properties was examined based on visual assessment, scanning electron microscopy, average molecular weight, differential scanning calorimetry, thermogravimetry, and tensile strength. The impact of the tested extracts on the effects of the composting process was compared with the impact of a commercially available anti-aging compound. It was found that the tested extracts in most cases did not adversely affect the effects of the composting process compared to pure polylactide, often resulting in intensification of biodegradation processes. As a result of the composting process, changes in the macro- and microscopic appearance of the samples and a decrease in molecular weight, phase transition temperatures, thermal resistance, and thermal strength were observed on a scale close to or greater than the reference anti-aging compound.

scholarly journals An Investigation on Polymerization of Ethylene by Ziegler-Natta Catalyst in the Presence of a Promoter: Polymerization Behavior and Polymer Microstructure

2018 ◽  
Vol 13 (3) ◽  
pp. 412 ◽  
Author(s):  
Yaghoob Gholami ◽  
Majid Abdouss ◽  
Sadegh Abedi ◽  
Farhad Azadi ◽  
Pezhman Baniani ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Polymerization Rate ◽  
Ethyl Chloride ◽  
Chain Length Distribution ◽  
Polymer Microstructure ◽  
Polymerization Behavior ◽  
Natta Catalyst ◽  
The Impact ◽  
Ziegler Natta Catalyst

The effect of a halocarbon (ethyl chloride) as a promoter on a Ziegler-Natta catalyst composed of‌ T‌iCl4 (catalyst), AlEt3 (activator) and Mg(OEt)2 (support) in the polymerization of ethylene have been investigated. In addition, the impact of this compound on the structural and thermal properties of the produced polyethylene has been studied. The catalyst activity and polymerization rate increased almost up to twice when a suitable molar ratio of ethyl chloride to triethylaluminum (TEA) was used. There was no change in the type of the profile of the polymerization rate during the polymerization time. A reduction in the polymer molecular weight was observed in the presence of the promoter and hydrogen. In addition, the MWD curve shifted toward lower values in the presence of ethyl chloride. Furthermore, a numerical method was used to obtain the most probable chain-length distribution, number   average molecular weight and weight fraction corresponding to each site type in the presence and absence of the promoter. Since, the catalyst had an irregular shape, the produced polymer also showed a similar morphology. In addition, the promoter used in the polymerization did not have any effect on the produced polymer morphology. The DSC results indicated that the presence of the promoter in the polymerization led to a decrease in the melting point of the produced polymer; whereas, there were no remarkable changes in the crystallization temperature of the polymers. Copyright © 2018 BCREC Group. All rights reservedReceived: 2nd October 2017; Revised: 5th April 2018; Accepted: 26th April 2018How to Cite: Gholami, Y., Abdouss, M., Abedi, S., Azadi, F., Baniani, P., Arsalanfar, M. (2018). An Investigation on Polymerization of Ethylene by Ziegler-Natta Catalyst in the Presence of a Promoter: Polymerization Behavior and Polymer Microstructure. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (3): 412-419 (doi:10.9767/bcrec.13.3.1574.412-419)Permalink/DOI: https://doi.org/10.9767/bcrec.13.3.1574.412-419  

scholarly journals Valorization of Lignin via Oxidative Depolymerization with Hydrogen Peroxide: Towards Carboxyl-Rich Oligomeric Lignin Fragments

Molecules ◽  
2020 ◽  
Vol 25 (11) ◽  
pp. 2717
Author(s):  
Ulrike Junghans ◽  
Justin J. Bernhardt ◽  
Ronja Wollnik ◽  
Dominik Triebert ◽  
Gerd Unkelbach ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Molecular Weight ◽  
Average Molecular Weight ◽  
Scale Up ◽  
Water Mixture ◽  
Pulp Bleaching ◽  
Solvent Fractionation ◽  
Whole Process ◽  
Acetone Water ◽  
Lignin Depolymerization

The extraction and characterization of defined and carboxyl-rich oligomeric lignin fragments with narrow molecular weight distribution is presented herein. With regard to the well-known pulp bleaching process, oxidative lignin depolymerization was investigated using hydrogen peroxide in an aqueous alkaline solution (i.e., at T = 318 K, t = 1 h) and subsequent selective fractionation with a 10/90 (v/v) acetone/water mixture. While the weight average molecular weight (MW) of lignin in comparison to the starting material was reduced by 82% after oxidation (T = 318 K, t = 1 h, clignin = 40 g L−1, cH2O2 = 80 g L−1, cNaOH = 2 mol L−1) and subsequent solvent fractionation (T = 298 K, t = 18 h, ccleavage product = 20 g L−1), the carboxyl group (–COOH) content increased from 1.29 mmol g−1 up to 2.66 mmol g−1. Finally, the successful scale-up of this whole process to 3 L scale led to gram amounts (14% yield) of oligomeric lignin fragments with a MW of 1607 g mol−1, a number average molecular weight (MN) of 646 g mol−1, a narrow polydispersity index of 3.0, and a high –COOH content of 2.96 mmol g−1. Application of these oligomeric lignin fragments in epoxy resins or as adsorbents is conceivable without further functionalization.

The Effect of Degradation in Aqueous Media on Viscosity Average Molecular Weight of Single Polymer Polyester Composites

2017 ◽  
Vol 68 (9) ◽  
pp. 2034-2038 ◽  
Author(s):  
Katarzyna Bryll ◽  
Katarzyna Gawdzinska ◽  
Marcin Nabialek ◽  
Patrycja Pawlowska
Keyword(s):  
Molecular Weight ◽  
Sea Water ◽  
Average Molecular Weight ◽  
Aqueous Media ◽  
Distilled Water ◽  
Media Impact ◽  
Degradation Tests ◽  
Polyester Composites ◽  
Testing Standards ◽  
The Impact

In present study the authors determine the impact of active environment on destruction processes developing in single polymer polyester composites. The processes impact on the structure and selected (e.g. viscosity) mechanical features of these composites were examined. The work included the following stages: manufacturing of ordered and disordered linear fiber single polyester composites, preparation of samples in accordance with applicable testing standards, performing composites� degradation tests in different media (distilled water and sea water at 30oC,). Literature review has shown that this kind of material has not been examined in reference to active media impact on degradation processes. This work is part of the research on discussed composites� properties and recycling.

scholarly journals The impact of the of cationic polyelectrolyte polymerization degree in latexes coagulation dosage of synthetic emulsion rubbers

2019 ◽  
Vol 81 (1) ◽  
pp. 318-324
Author(s):  
Y. N. Orlov
Keyword(s):  
Molecular Weight ◽  
Condensation Product ◽  
Average Molecular Weight ◽  
Synthetic Fatty Acid ◽  
Cationic Polyelectrolyte ◽  
Degree Of Polymerization ◽  
Optimal Dosage ◽  
Nonionic Polymers ◽  
Methyl Styrene ◽  
The Impact

The literature data on the parameters of coagulation of butadiene-styrene and butadiene-?-methyl styrene latexes by cationic polyelectrolytes in comparison with low-molecular ammonium compounds and nonionic polymers are discussed. The optimal dosage of cationic polyelectrolyte during coagulation of synthetic emulsion rubber latex stabilized by a combination of synthetic fatty acid Soaps and disproportionated rosin with a mixture of sodium salts of the oligomeric condensation product ?-naphthalenesulfonic acid with formaldehyde (Leukanol) is determined, ceteris paribus, by its degree of polymerization. The decrease in the optimum dosage during the transition from high molecular weight polyelectrolytes to the oligomers caused by decrease of the cationic and anionic groups ratio required for a complete binding Leukanol in the formation of oligomer-oligomer complexes compared with the polymer-oligomer complexes. This is due, apparently, the fact that an increase in the average molecular weight of the polyelectrolyte increases the proportion of so-called tails and loops, consisting of units of the polyelectrolyte that are not associated with molecules Leukanol

The Structure of Radiation Cross-Linked Poly (ethylene oxide) Gels

1971 ◽  
Vol 29 ◽  
pp. 76-77
Author(s):  
C. E. Cluthe ◽  
G. G. Cocks
Keyword(s):  
Molecular Weight ◽  
Ethylene Oxide ◽  
Parallel Plate ◽  
Average Molecular Weight ◽  
Radical Reaction ◽  
Free Radical Reaction ◽  
Nitrogen Gas ◽  
Poly Ethylene Oxide ◽  
Poly Ethylene ◽  
Initial Viscosity

Aqueous solutions of a 1 weight-per cent poly (ethylene oxide) (PEO) were degassed under vacuum, transferred to a parallel plate viscometer under a nitrogen gas blanket, and exposed to Co60 gamma radiation. The Co60 source was rated at 4000 curies, and the dose ratewas 3.8x105 rads/hr. The poly (ethylene oxide) employed in the irradiations had an initial viscosity average molecular weight of 2.1 x 106.The solutions were gelled by a free radical reaction with dosages ranging from 5x104 rads to 4.8x106 rads.

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