Chemical Modification of a Lignin Model Polymer via Arylboronate Ester Formation under Mild Reaction Conditions

2009 ◽  
Vol 42 (16) ◽  
pp. 5906-5908 ◽  
Author(s):  
Andrew L. Korich ◽  
Kristine M. Clarke ◽  
David Wallace ◽  
Peter M. Iovine
Keyword(s):  
Chemical Modification ◽  
Reaction Conditions ◽  
Ester Formation ◽  
Lignin Model

Study of Chemical Modification of Some Starch Using the Amylographic Method

2008 ◽  
Vol 59 (1) ◽  
pp. 70-73
Author(s):  
Mihai Leonte ◽  
Traian Florea
Keyword(s):  
Chemical Modification ◽  
Heterogeneous Medium ◽  
Reaction Conditions

The amyl graphic behaviour for products like carboxymetil starch obtained in different reaction conditions was looked into. The procedure specific feature is the chemical modification that takes place in a heterogeneous medium though the reaction of the reactant starch particle in indestructible conditions.

Kinetics and Mechanism of Oxidation of Aliphatic Secondary Alcohols by Benzimidazolium Fluorochromate in Dimethyl Sulphoxide Solvent

2021 ◽  
Vol 37 (3) ◽  
pp. 626-633
Author(s):  
Bhawana Arora ◽  
Jitendra Ojha ◽  
Pallavi Mishra
Keyword(s):  
Activation Parameters ◽  
Sigmatropic Rearrangement ◽  
Dimethyl Sulphoxide ◽  
Secondary Alcohols ◽  
Hydrogen Ions ◽  
Reaction Conditions ◽  
First Order Kinetics ◽  
Aqueous Solvent ◽  
Ester Formation ◽  
Different Temperatures

Oxidation of secondary alcohols is an important part of synthetic organic chemistry. Various studies are carried out at different reaction conditions to determine the best mechanistic pathways. In our study, oxidation of different secondary alcohols was done by using Benzimidazolium Fluorochromate in Dimethyl Sulphoxide, which is a non-aqueous solvent. Oxidation resulted in the formation of ketonic compounds. The reaction showed first order kinetics both in BIFC and in the alcohols. Hydrogen ions were used to catalyze the reaction. We selected four different temperatures to carry out our study. The correlation within the activation parameters like enthalpies and entropies was in accordance with the Exnerʼs criterion. The deuterated benzhydrol (PhCDOHPh) oxidation exhibited an important primary kinetic isotopic effect (kH / kD = 5.76) at 298 K. The solvent effect was studied using the multiparametric equations of Taft and Swain. There was no effect of addition of acrylonitrile on the oxidation rate. The mechanism involved sigmatropic rearrangement with the transfer of hydrogen ion taking place from alcohol to the oxidant via a cyclic chromate ester formation.

scholarly journals Applicability of Recombinant Laccases From the White-Rot Fungus Obba rivulosa for Mediator-Promoted Oxidation of Biorefinery Lignin at Low pH

2020 ◽  
Vol 8 ◽  
Author(s):  
Jussi Kontro ◽  
Riku Maltari ◽  
Joona Mikkilä ◽  
Mika Kähkönen ◽  
Miia R. Mäkelä ◽  
...  
Keyword(s):  
White Rot ◽  
White Rot Fungus ◽  
Lignin Biodegradation ◽  
Reaction Conditions ◽  
Tempo Oxidation ◽  
Chemical Treatments ◽  
Mediator Systems ◽  
Phenolic Components ◽  
Lignin Model ◽  
Rich Side

Utilization of lignin-rich side streams has been a focus of intensive studies recently. Combining biocatalytic methods with chemical treatments is a promising approach for sustainable modification of lignocellulosic waste streams. Laccases are catalysts in lignin biodegradation with proven applicability in industrial scale. Laccases directly oxidize lignin phenolic components, and their functional range can be expanded using low-molecular-weight compounds as mediators to include non-phenolic lignin structures. In this work, we studied in detail recombinant laccases from the selectively lignin-degrading white-rot fungus Obba rivulosa for their properties and evaluated their potential as industrial biocatalysts for the modification of wood lignin and lignin-like compounds. We screened and optimized various laccase mediator systems (LMSs) using lignin model compounds and applied the optimized reaction conditions to biorefinery-sourced technical lignin. In the presence of both N–OH-type and phenolic mediators, the O. rivulosa laccases were shown to selectively oxidize lignin in acidic reaction conditions, where a cosolvent is needed to enhance lignin solubility. In comparison to catalytic iron(III)–(2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation systems, the syringyl-type lignin units were preferred in mediated biocatalytic oxidation systems.

scholarly journals Preparation and Characterization of Chemically-Modified Biomaterials and Their Application as Adsorbents of Penicillin G

2018 ◽  
Vol 1 (1) ◽  
pp. 114-124 ◽  
Author(s):  
Jesie Silva ◽  
Lizebel Morante ◽  
Tesfamichael Demeke ◽  
Jacqueline Baah-Twum ◽  
Abel Navarro
Keyword(s):  
Chemical Modification ◽  
Functional Groups ◽  
Negative Impact ◽  
Ph Dependence ◽  
Sem Analysis ◽  
Penicillin G ◽  
Tea Leaves ◽  
Reaction Conditions ◽  
Spent Tea Leaves

The prevalence of antibiotics in water creates microbial resistance and has a negative impact on the ecosystem. Biomaterials such as spent tea leaves are rich in functional groups and are suitable for chemical modification for diverse applications. This research proposes the use of spent tea leaves of chamomile (CM), green tea (GT), and peppermint (PM) as structural scaffolds for the incorporation of carboxyl, sulfonyl, and thiol groups to improve the adsorption of Penicillin G (Pe). Adsorbents characterization reported a higher number of acidic functional groups, mainly in thiolated products. Scanning electron microscopy (SEM) analysis showed changes on the surfaces of the adsorbents due to reaction conditions, with a stronger effect on thiolated and sulfonated adsorbents. Elemental analysis by Energy dispersive X-ray spectrophotometry (EDS) corroborated the chemical modification by the presence of sulfur atoms and the increase in oxygen/carbon ratios. Batch experiments at different pH shows a strong pH-dependence with a high adsorption at pH 8 for all the adsorbents. The adsorption follows the trend CMs > GTs > PMs. Thiolation and sulfonation reported higher adsorptions, which is most likely due to the sulfur bridge formation, reaching adsorption percentages of 25%. These results create a new mindset in the use of spent tea leaves and their chemical modifications for the bioremediation of antibiotics.

Stability of Pt/γ-Al2O3 Catalysts in Lignin and Lignin Model Compound Solutions under Liquid Phase Reforming Reaction Conditions

ACS Catalysis ◽  
2013 ◽  
Vol 3 (3) ◽  
pp. 464-473 ◽  
Author(s):  
Anna L. Jongerius ◽  
John R. Copeland ◽  
Guo Shiou Foo ◽  
Jan P. Hofmann ◽  
Pieter C. A. Bruijnincx ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Model Compound ◽  
Reaction Conditions ◽  
Lignin Model Compound ◽  
Lignin Model

The Reactions of Lignin Model Compounds with Hydrogen Peroxide at Low pH

Holzforschung ◽  
2003 ◽  
Vol 57 (1) ◽  
pp. 52-88 ◽  
Author(s):  
T. Kishimoto ◽  
J. F. Kadla ◽  
H.-m. Chang ◽  
H. Jameel
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction System ◽  
Model Compounds ◽  
Reaction Conditions ◽  
Lignin Model Compounds ◽  
Lignin Model Compound ◽  
Lignin Model ◽  
Decreasing Ph ◽  
Hydroxyl Compounds ◽  
Acidic Hydrogen

Summary In peroxymonosulfuric acid bleaching, the presence of hydrogen peroxide is dependent on the reaction conditions and the conversion ratios used to generate the peroxy acid. Substantial amounts of hydrogen peroxide may be present in the reaction system under certain conditions. An understanding of the reactions of hydrogen peroxide under these conditions would be beneficial. Therefore, several simple lignin model compounds were reacted with acidic hydrogen peroxide, pH 1-3, at 70°C. In all cases the phenolic lignin model compounds reacted much faster than their non-phenolic counterparts. In fact, the extent of reaction was very much dependent on the structure of the lignin model compound. The α-hydroxyl compounds, 4-(1-Hydroxy-ethyl)-2-methoxy-phenol and 1-(3,4-Dimethoxy-phenyl)-ethanol, reacted faster than the corresponding α-carbonyl compounds with both reacting much faster than the aromatic compounds, with simple alkyl substituents. A new reaction mechanism for α-hydroxyl compounds is proposed, in which benzyl carbocation formation is followed by nucleophilic addition of hydrogen peroxide. Unlike the mechanisms proposed in the past, no evidence of aromatic hydroxylation via perhydronium ion was observed. The reactivities were very pH dependent, in that higher reactivity was associated with lower pH. Decreasing pH further increased the amount of condensation products identified, such that condensation was competitive with degradation. These condensation reactions were also present under the Caro's acid bleaching conditions at pH below 2. However, under all conditions the reactivity of acidic peroxide was found to be much less than that of peroxymonosulfuric acid.

Optimization of Reaction Conditions for Preparing Carboxymethyl Cellulose Guaze

2013 ◽  
Vol 709 ◽  
pp. 40-44 ◽  
Author(s):  
Xi Hui Zhao ◽  
Qun Li ◽  
Ye Mi
Keyword(s):  
Fourier Transform ◽  
Reaction Time ◽  
Chemical Modification ◽  
Carboxymethyl Cellulose ◽  
Moisture Absorption ◽  
Large Degree ◽  
Reaction Conditions ◽  
Cotton Gauze ◽  
High Degree ◽  
Optimized Conditions

Chemical modification was employed for converting cotton gauze to carboxymethyl cellulose (CMC) gauze by treating them with sodium monochloroacetate and sodium hydroxide. Fourier Transform Infrared spectra (FTIR) were used to characterize the product. The reaction was optimized against temperature, concentration and reaction time for obtaining high degree of conversion. Under optimized conditions, the CMC gauze has a large degree of substitution (DS) of 0.43, and it has shown better moisture absorption ability than that of common cotton gauze.

scholarly journals Synthesis and Characterization of Novel Phyto-Mediated Catalyst, and Its Application for a Selective Oxidation of (VAL) into Vanillin under Visible Light

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 839 ◽  
Author(s):  
Afnan Al-Hunaiti ◽  
Qassem Mohaidat ◽  
Ibrahim Bsoul ◽  
Sami Mahmood ◽  
Deeb Taher ◽  
...  
Keyword(s):  
Visible Light ◽  
Selective Oxidation ◽  
Vanillyl Alcohol ◽  
Reaction Conditions ◽  
Excellent Photocatalytic Activity ◽  
Lignin Model ◽  
Turn Over Frequency ◽  
Average Size ◽  
Turn Over

Here, we report an efficient and highly selective oxidation of lignin model substrate using phyto-mediated ZnFe2O4 nanoparticle using Boswellia carterii extract. The nanocatalyst with an average size of 8 nm showed excellent photocatalytic activity of the synthesized carbonyl containing products under visible light irradiation. The catalytic activity and selectivity towards oxidation of vanillyl alcohol to vanillin with selectivity up to 99% at conversion over 98% and turn-over frequency values up to 1600 h−1 were obtained in the presence of H2O2 and base. The cubic spinel nano-ZnFe2O4 catalyst was characterized by powder-XRD, FESEM, HR-TEM and Mössbauer analysis. The demonstrated catalyst was robust and stable under the reaction conditions. Furthermore, it was easy to be separated from the reaction mixture and be reused for subsequent reactions up to 5 times without significant reactivity or selectivity loss.

Conversion of guaiacol as lignin model component using acid-treated, multi-walled carbon nanotubes supported Ru–MnO bimetallic catalysts

2020 ◽  
Vol 98 (2) ◽  
pp. 57-65 ◽  
Author(s):  
Wei Long ◽  
Pingle Liu ◽  
Wei Xiong ◽  
Fang Hao ◽  
He’an Luo
Keyword(s):  
Carbon Nanotubes ◽  
Liquid Phase ◽  
Bimetallic Catalysts ◽  
Catalytic Performance ◽  
Particle Dispersion ◽  
Reaction Conditions ◽  
Multi Walled Carbon Nanotube ◽  
Multi Walled Carbon Nanotubes ◽  
Lignin Model ◽  
Walled Carbon Nanotubes

Acid-treated, multi-walled carbon nanotube (AMWCNT) supported Ru and MnO bimetallic catalysts were prepared for liquid phase hydrodeoxygenation of guaiacol. The physicochemical properties of the prepared catalysts were characterized by FTIR, XRD, NH3-TPD, CO2-TPD, TEM, and XPS. MnO species were loaded on the inner surface of carbon nanotubes and were helpful for Ru particle dispersion. The 6%Ru-8%MnO/AMWCNTs with smaller Ru particle size, better dispersion, and more basic sites gave the best catalytic performance of 99.38% conversion of guaiacol and 85.84% selectivity to cyclohexanol. The effects of reaction conditions on liquid phase guaiacol hydrodeoxygenation were discussed and a possible reaction path was proposed.

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