A review of lignin hydrogen peroxide oxidation chemistry with emphasis on aromatic aldehydes and acids

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ajinkya More ◽  
Thomas Elder ◽  
Zhihua Jiang
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Degradation ◽  
Reaction Medium ◽  
Dicarboxylic Acids ◽  
Aromatic Aldehydes ◽  
Product Distribution ◽  
Reaction Conditions ◽  
Alkaline Conditions ◽  
The Stability ◽  
Oxidation Chemistry

Abstract This review discusses the main factors that govern the oxidation processes of lignins into aromatic aldehydes and acids using hydrogen peroxide. Aromatic aldehydes and acids are produced in the oxidative degradation of lignin whereas mono and dicarboxylic acids are the main products. The stability of hydrogen peroxide under the reaction conditions is an important factor that needs to be addressed for selectively improving the yield of aromatic aldehydes. Hydrogen peroxide in the presence of heavy metal ions readily decomposes, leading to minor degradation of lignin. This degradation results in quinones which are highly reactive towards peroxide. Under these reaction conditions, the pH of the reaction medium defines the reaction mechanism and the product distribution. Under acidic conditions, hydrogen peroxide reacts electrophilically with electron rich aromatic and olefinic structures at comparatively higher temperatures. In contrast, under alkaline conditions it reacts nucleophilically with electron deficient carbonyl and conjugated carbonyl structures in lignin. The reaction pattern in the oxidation of lignin usually involves cleavage of the aromatic ring, the aliphatic side chain or other linkages which will be discussed in this review.

INFLUENCES OF PROCESS VARIABLES AND SUBCRITICAL FLUIDS ON EPDM-ASSISTED DEVULCANIZATION OF SBR-BASED GROUND TIRE RUBBER

2018 ◽  
Vol 91 (2) ◽  
pp. 401-416 ◽  
Author(s):  
Tao Zhang ◽  
Jinxing Cao ◽  
Xiaojun Wang ◽  
Ling Zhang ◽  
Yuncan Zhang
Keyword(s):  
Rotation Speed ◽  
Oxidative Degradation ◽  
Reaction Medium ◽  
Reaction Conditions ◽  
Tire Rubber ◽  
Ground Tire Rubber ◽  
Swelling Agent ◽  
Twin Screw ◽  
Subcritical Fluids ◽  
Subcritical Fluid

ABSTRACT The devulcanization reaction of SBR-based ground tire rubber (GTR) in GTR/EPDM blend was investigated through a co-rotating twin-screw extruder by increasing the screw rotation speed in the presence of subcritical fluids (water, ethanol, and propanol). The influences of the screw rotation speed, the promoting agents, and temperature were investigated. The results show that subcritical fluid, which is a swelling agent and reaction medium, promotes the devulcanization reaction, increases the selectivity of crosslink breakage, keeps the extrusion material from oxidative degradation, reduces the gel particle size of the devulcanized blends, and significantly improves the mechanical properties of the revulcanizate. Among different subcritical fluids (water, ethanol, propanol), the influence of subcritical ethanol is significantly obvious. When promoting agent 450 is added under the best reaction conditions (ethanol, 200 °C, 2.2 Mpa, and 600 rpm), the tensile strength and elongation at break of the revulcanizate retains 99.6% and 209% of vulcanized SBR (24.0 MPa, 356%), respectively.

Study of the Catalytic Effects of Trace Titanium on Oxidation of Pyronin B with Hydrogen Peroxide and its Application

2012 ◽  
Vol 602-604 ◽  
pp. 1233-1237
Author(s):  
Zhi Rong Zhou ◽  
Li Zhen Zhang
Keyword(s):  
Hydrogen Peroxide ◽  
Reaction Medium ◽  
Reaction Conditions ◽  
Relative Standard ◽  
Extraction Separation ◽  
Optimum Reaction ◽  
Kinetic Spectrophotometric ◽  
Replicate Measurements ◽  
Catalytic Effects

A simple and sensitive kinetic spectrophotometric method for the determination of trace amounts titanium (IV), based on the catalytic effect of Ti (IV) on the oxidation pyronin B with hydrogen peroxide in 0.02 mol/L sulfuric acid, is described. The reaction rate is monitored spectrophotometrically by measuring the decrease in absorbance of pyronin B at 555 nm. The detection limit of the method is 0.017 μg/L, and the linear range is 0.055–1.0 µg/L. The influences of reaction medium and acidity, concentrations of reactants, reactive temperature and foreign ions is also discussed. The optimum reaction conditions were established. The relative standard deviation for 11 replicate measurements of 0.010 and 0.020 μg/25mL of titanium (IV) were 2.8 % and 2.3 %, respectively. In combination with solvent extraction separation, the method has been successfully applied to the determination of trace titanium (IV) in rock samples. The results are in good agreement with the certified volumes with the relative standard deviations (RSD) of 1.6 %–3.6 %.

Degradation Behavior of Poly(ethylene glycol) Diblock and Multiblock Polymers with Hydrolytically Degradable Ester Linkages

2004 ◽  
Vol 69 (8) ◽  
pp. 1643-1656 ◽  
Author(s):  
Alena Braunová ◽  
Michal Pechar ◽  
Karel Ulbrich
Keyword(s):  
Ethylene Glycol ◽  
Hydrolytic Degradation ◽  
Dicarboxylic Acids ◽  
Drug Carriers ◽  
Poly Ethylene Glycol ◽  
Model Study ◽  
Alkaline Conditions ◽  
Rate Of Hydrolysis ◽  
Poly Ethylene ◽  
The Stability

Diblock and multiblock polymers of poly(ethylene glycol) containing degradable ester bonds between the blocks were synthesized and characterized. Monofunctional poly(ethylene glycol) (PEG 2000) was modified by aliphatic dicarboxylic acids (malonic, succinic, glutaric, maleic) to obtain monocarboxylic polymers PEG-COOH containing ester bonds. Diblock polymers (4000) were prepared by polycondensation of a diamine (ethane-1,2-diamine, L-lysine) and the semitelechelic PEG-COOH. The relationship between the structure of the linkage connecting two PEG blocks and the rate of its hydrolytic degradation was studied at pH 5.5, 7.4 and 8.0. The rate of hydrolysis of all polymers was significant already under mild alkaline conditions (pH 7.4 and 8.0) and increased with increasing pH. The ester bonds of polymers with saturated dicarboxylic acid moieties were stable at pH 5.5. However, the presence of double bond in the acid moiety substantially decreased the stability of the polymer not only in alkaline but also in acid medium. The results of this model study can be utilized in the design of biodegradable high-molecular-weight drug carriers and polymers for preparation of "stealth" systems intended for therapeutic application.

Influence of reaction conditions on product distribution in the green oxidation of cyclohexene to adipic acid with hydrogen peroxide

2011 ◽  
Vol 175 (1) ◽  
pp. 619-624 ◽  
Author(s):  
Peng Jin ◽  
Zhonghua Zhao ◽  
Zhipeng Dai ◽  
Donghui Wei ◽  
Mingsheng Tang ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Adipic Acid ◽  
Product Distribution ◽  
Reaction Conditions ◽  
Green Oxidation

Solid State Analysis and Theoretical Explorations on Polymorphic and Hydrate Forms of p-Hydroxybenzaldehyde Isonicotinichydrazone: Effect of Additives on Polymorphic Crystallization

2018 ◽  
Author(s):  
Lincy Tom ◽  
Victoria A. Smolenski ◽  
Jerry P. Jasinski ◽  
M.R. Prathapachandra Kurup
Keyword(s):  
Hirshfeld Surface ◽  
Framework Analysis ◽  
Reaction Conditions ◽  
Space Groups ◽  
Effect Of Additives ◽  
Ft Ir ◽  
Packing Arrangement ◽  
The Stability ◽  
Ir And Raman ◽  
Isonicotinic Hydrazide

The reaction of p-hydroxybenzaldehyde with an equimolar amount of isonicotinic hydrazide afforded two polymorphic and hydrate forms of p-hydroxybenzaldehyde isonicotinichydrazone (HBIH) by varying the experimental reaction conditions. The compounds are fully characterized by means of single crystal and powder diffraction methods, vibrational spectroscopy (FT-IR and Raman), thermal and elemental analysis. The compound crystallizes in three different forms in two different space groups, P21/c (form PA and PB) and Pbca (PC). The Hirshfeld surface analysis shows the differences in the relative contributions of intermolecular interactions to the total Hirshfeld surface area for the HBIH molecules. The calculated pairwise interaction energies (104-116 kJ/mol) can be related to the stability of the crystals. Energy framework analysis identifies the interaction hierarchy and their topology. The geometry and conformation of the three forms are essentially similar which differ only by packing arrangement.

Solid State Analysis and Theoretical Explorations on Polymorphic and Hydrate Forms of p-Hydroxybenzaldehyde Isonicotinichydrazone: Effect of Additives on Polymorphic Crystallization

2018 ◽  
Author(s):  
Lincy Tom ◽  
Victoria A. Smolenski ◽  
Jerry P. Jasinski ◽  
M.R. Prathapachandra Kurup
Keyword(s):  
Hirshfeld Surface ◽  
Framework Analysis ◽  
Reaction Conditions ◽  
Space Groups ◽  
Effect Of Additives ◽  
Ft Ir ◽  
Packing Arrangement ◽  
The Stability ◽  
Ir And Raman ◽  
Isonicotinic Hydrazide

The reaction of p-hydroxybenzaldehyde with an equimolar amount of isonicotinic hydrazide afforded two polymorphic and hydrate forms of p-hydroxybenzaldehyde isonicotinichydrazone (HBIH) by varying the experimental reaction conditions. The compounds are fully characterized by means of single crystal and powder diffraction methods, vibrational spectroscopy (FT-IR and Raman), thermal and elemental analysis. The compound crystallizes in three different forms in two different space groups, P21/c (form PA and PB) and Pbca (PC). The Hirshfeld surface analysis shows the differences in the relative contributions of intermolecular interactions to the total Hirshfeld surface area for the HBIH molecules. The calculated pairwise interaction energies (104-116 kJ/mol) can be related to the stability of the crystals. Energy framework analysis identifies the interaction hierarchy and their topology. The geometry and conformation of the three forms are essentially similar which differ only by packing arrangement.

DFT Study and Synthesis of Novel Bioactive Bispyrazole Using Mg/AlLDH as a Solid Base Catalyst

2020 ◽  
Vol 14 ◽  
Author(s):  
Soufiane Akhramez ◽  
Youness Achour ◽  
Mustapha Diba ◽  
Lahoucine Bahsis ◽  
Hajiba Ouchetto ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Experimental Finding ◽  
Biological Activities ◽  
Condensation Reaction ◽  
Aromatic Aldehydes ◽  
Mechanistic Study ◽  
Knoevenagel Reaction ◽  
Solid Base ◽  
Reaction Conditions ◽  
Aryl Aldehyde

Background: In this study, an efficient synthesis of novel bispyrazole heterocyclic molecules by condensation of substituted aromatic aldehydes with 1,3-diketo-N-phenylpyrazole by using Mg/Al-LDH as heterogeneous catalyst is reported. The attractive features of this protocol are as follows: mild reaction conditions, good yields and easiness of the catalyst separation from the reaction mixture. Further, a mechanistic study has been performed by using DFT calculations to explain the observed selectivity of the condensation reaction between aryl aldehyde and 1,3-diketo-N-phenylpyrazole via Knoevenagel reaction. The local electrophilicity/ nucleophilicity that allows explaining correctly the experimental finding. Methods: The bispyrazole derivatives 3a-m were prepared by condensation reaction of substituted aromatic aldehydes with 1,3-diketo-Nphenylpyrazole by using Mg/Al-LDH as heterogeneous catalyst under THF solvent at the refluxing temperature. Objective: To synthesize a novel bispyrazole heterocyclic molecule may be have important biological activities and thus can be good candidates for pharmaceutical applications. Results: This protocol describes the Synthesis of Bioactive Compounds under mild reaction conditions, good yields and easiness of the catalyst separation from the reaction mixture. Further, a mechanistic study has been performed by using DFT calculations to explain the observed selectivity of the condensation reaction between aryl aldehyde and 1,3-diketo-N-phenylpyrazole via Knoevenagel reaction. The local electrophilicity/ nucleophilicity that allows explaining correctly the experimental finding. Conclusion: In summary, the pharmacologically interesting bis-pyrazole derivatives have been synthesized through Mg/Al-LDH as a solid base catalyst, in THF as solvent. Thus, the synthesized bioactive compounds containing the pyrazole ring may be have important biological activities and thus can be good candidates for pharmaceutical applications. Therefore, the catalyst Mg/Al-LDH showed high catalytic activity. Besides, a series of bispyrazole molecules were synthesized with a good yield and easy separation of the catalyst by simple filtration. Moreover, DFT calculations and reactivity indexes are used to explain the selectivity of the condensation reaction between aryl benzaldehyde and 1,3-diketo-Nphenylpyrazole via Knoevenagel reaction, and the results are in good agreement with the experimental finding.

Novel Products in the CO2-Laser Induced Reaction of Trichloroethylene

1995 ◽  
Vol 60 (1) ◽  
pp. 104-114 ◽  
Author(s):  
Boyd L. Earl ◽  
Richard L. Titus
Keyword(s):  
Irradiation Time ◽  
Product Distribution ◽  
Incident Power ◽  
Cell Geometry ◽  
Reaction Conditions ◽  
Peak Areas ◽  
Induced Decomposition ◽  
Nmr Methods ◽  
Induced Reaction ◽  
Novel Products

Previous reports on the thermal or CO2-laser induced decomposition of trichloroethylene have identified only one condensible product, hexachlorobenzene (in addition to HCl and mono- and dichloroacetylene). We have found that trichloroethylene vapor exposed to cw irradiation on the P(24) line of the (001 - 100) band of the CO2 laser at incident power levels from 8 - 17 W produces numerous products, of which the 13 major ones have been identified using IR, GC/MS, GC/FTIR, and NMR methods. All of these products have 4, 6, or 8 carbons, are highly unsaturated, and are completely chlorinated or contain a single hydrogen. C4HCl5 and C6Cl6 isomers (three of each) account for S 55% to 85% of total products (based on peak areas in the total ion chromatograms in GC/MS runs), depending on reaction conditions. In addition to characterizing the products, we discuss the dependence of the product distribution on laser power, irradiation time, and cell geometry, and we outline a possible mechanism.

scholarly journals Hydrogen Peroxide Oxidation of Coordinated Thiocyanate Ion in cis- and trans-[Coen2NH3NCS]2+: The Preparation and Properties of trans-[Coen2NH3CN]2+

1973 ◽  
Vol 51 (24) ◽  
pp. 4152-4158 ◽  
Author(s):  
Albert Richard Norris ◽  
James William Lennox Wilson
Keyword(s):  
Hydrogen Peroxide ◽  
Spectral Properties ◽  
Peroxide Oxidation ◽  
Reaction Conditions ◽  
Thiocyanate Ion ◽  
Hydrogen Peroxide Oxidation ◽  
Percent Conversion ◽  
Cis And Trans ◽  
In Cis

The hydrogen peroxide oxidation of thiocyanate ion in cis- and trans-[Coen2NH3NCS]2+ leads to the formation of the corresponding cis- and trans-cyanoammine- and diamminebis(ethylenediamine)cobalt-(III) complexes. The spectral properties of the previously unreported trans-[Coe2NH3CN]2+ are reported and compared to the spectral properties of the cis-isomer.Observations are made concerning the reaction conditions which favor a high percent conversion of trans-[Coen2NH3NCS]2+ to trans-[Coen2NH3CN]2+.

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