Degradation of Model Compounds for Cellulose and Lignocellulosic Pulp during Ozonation in Aqueous Solution

Holzforschung ◽  
2000 ◽  
Vol 54 (4) ◽  
pp. 397-406 ◽  
Author(s):  
Carola Olkkonen ◽  
Henrik Tylli ◽  
Ingegerd Forsskåhl ◽  
Agneta Fuhrmann ◽  
Tiina Hausalo ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
High Performance ◽  
Room Temperature ◽  
Model Compound ◽  
The Other ◽  
Model Compounds ◽  
Freeze Dried ◽  
Carbohydrate Complex ◽  
Ozonation Time ◽  
Acidic Compounds

Summary Ozonations of methylpyranosides, as model compounds for cellulose, were performed in unbuffered aqueous solution at room temperature. The degradation of the pyranosides was followed spectrophotometrically and with high-performance liquid chromatography (HPLC) as a function of ozonation time. The substrates studied were the α- and β-anomers of methyl-D-glucopyranoside, methyl-D-mannopyranoside and methyl-D-xylopyranoside. Methyl-α-D-xylopyranoside degraded more slowly than the other compounds, whereas the rate of degradation was fastest for methyl-β-D-mannopyranoside. In general the degradation of the α-anomers was slower than that of the corresponding β-anomers. HPLC and gas chromatography—mass selective (GC-MS) analyses of the ozonated glucopyranoside samples showed that monosaccharides, lactones, furanosides and acidic compounds are formed during ozonation. A lignin-carbohydrate complex (LCC), containing a D-xylose unit connected to an aromatic part through a βglycosidic bond, was used as a model compound for lignocellulosic pulp. The degradation of this compound during ozonation was also investigated. The results from UV analyses showed that the reaction was extremely fast at the beginning and that the degradation of benzene structures in the lignin mimicking part of the LCC was very rapid. The degradation of the carbohydrate part was slower. This suggests that lignin provides some protection for the cellulose in lignin-containing pulps against attack by ozone. IR and NMR analyses of the freeze-dried ozonated LCC samples showed further that C=O structures are produced during ozonation.

On the Chemistry of Tetrabenzyl Thiuram Disulfide and Tetramethyl Thiuram Disulfide with Bis (Triethoxysilylpropyl) Tetrasulfide in Silica Compounds

2003 ◽  
Vol 76 (4) ◽  
pp. 876-891 ◽  
Author(s):  
R. N. Datta ◽  
A. G. Talma ◽  
S. Datta ◽  
P. G. J. Nieuwenhuis ◽  
W. J. Nijenhuis ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Succinic Anhydride ◽  
Dynamic Properties ◽  
The Other ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Negative Effect ◽  
Higher Temperature ◽  
Analytical Tools

Abstract The use of thiurams such as Tetramethyl thiuram disulfide (TMTD) or Tetrabenzyl thiuram disulfide (TBzTD) has been explored to achieve higher cure efficiency. The studies suggest that a clear difference exists between the effect of TMTD versus TBzTD. TMTD reacts with Bis (triethoxysilylpropyl) tetrasulfide (TESPT) and this reaction can take place even at room temperature. On the other hand, the reaction of TBzTD with TESPT is slow and takes place only at higher temperature. High Performance Liquid Chromatography (HPLC) with mass (MS) detection, Nuclear Magnetic Resonance Spectroscopy (NMR) and other analytical tools have been used to understand the differences between the reaction of TMTD and TESPT versus TBzTD and TESPT. The reaction products originating from these reactions are also identified. These studies indicate that unlike TMTD, TBzTD improves the cure efficiency allowing faster cure without significant effect on processing characteristics as well as dynamic properties. The loading of TESPT is reduced in a typical Green tire compound and the negative effect on viscosity is repaired by addition of anhydrides, such as succinic anhydride, maleic anhydride, etc.

scholarly journals The Effect of Ultrasound, Oxygen and Sunlight on the Stability of (−)-Epigallocatechin Gallate

Molecules ◽  
2018 ◽  
Vol 23 (9) ◽  
pp. 2394 ◽  
Author(s):  
Jiajun Zeng ◽  
Huanhua Xu ◽  
Yu Cai ◽  
Yan Xuan ◽  
Jia Liu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
High Performance ◽  
Room Temperature ◽  
Degradation Rate ◽  
Epigallocatechin Gallate ◽  
Important Conclusion ◽  
Beneficial Effects ◽  
Periodontal Infection ◽  
The Stability ◽  
Ultrasonic Conditions

(−)-Epigallocatechin gallate (EGCG), is the main catechin found in green tea, and has several beneficial effects. This study investigated the stability of EGCG aqueous solution under different stored and ultrasonic conditions to determine whether it can be used with an ultrasonic dental scaler to treat periodontal infection. Four concentrations (0.05, 0.1, 0.15, 2 mg/mL) of EGCG aqueous solution were prepared and stored under four different conditions (A: Exposed to neither sunlight nor air, B: Exposed to sunlight, but not air, C: Not exposed to sunlight, but air, D: Exposed to sunlight and air) for two days. The degradation rate of EGCG was measured by high performance liquid chromatography (HPLC). On the other hand, an ultrasonic dental scaler was used to atomize the EGCG solution under four different conditions (a: Exposed to neither air nor sunlight, b: Not exposed to air, but sunlight, c: Not exposed to sunlight, but air, d: Exposed to air and sunlight), the degradation of EGCG was measured by HPLC. We found that the stability of EGCG was concentration-dependent in water at room temperature. Both sunlight and oxygen influenced the stability of EGCG, and oxygen had a more pronounced effect on stability of EGCG than sunlight. The most important conclusion was that the ultrasound may accelerate the degradation of EGCG due to the presence of oxygen and sunlight, but not because of the ultrasonic vibration. Thus, EGCG aqueous solution has the potential to be used through an ultrasonic dental scaler to treat periodontal infection in the future.

The Chemical Evolution of a Nitrogenase Model, 20 Alkyl Molybdates(VI) and the Mechanism of Hydrocarbon Production by Nitrogenase [1]

1982 ◽  
Vol 37 (3) ◽  
pp. 380-385 ◽  
Author(s):  
G. N. Schrauzer ◽  
Laura A. Hughes ◽  
Norman Strampach
Keyword(s):  
Aqueous Solution ◽  
Alkaline Hydrolysis ◽  
Room Temperature ◽  
Bond Cleavage ◽  
Model Compounds ◽  
Hydrocarbon Production ◽  
Acidic Solutions ◽  
Reducing Conditions ◽  
Hydrolysis Of ◽  
Derivatives Of

Abstract Colorless alkylmolybdates(VI) of composition R-MoO3-are generated in aqueous solutions by the alkaline hydrolysis of complexes R-Mo(Bpy)(0)2Br(Bpy = 2,2′-bipyridyl, R = CH3 and higher alkyl). At room temperature in alkaline aqueous solution, the new organometallic derivatives of oxomolybdate(VI) are remarkably resistant against Mo-C bond hydrolysis. Decomposition occurs more rapidly on heating, affording unrearranged alkanes according to the eq.: R-MoO3- + OH-→RH + Mo04=. In acidic solutions, the methylmolybdate(VI) species decomposes with the formation of a mixture of methane and ethane while higher alkylmolybdates carrying hydrogen in the β-position relative to molybdenum undergo Mo-C bond heterolysis by way of β-elimina-tion: R-CH2CH2-MoO3 → Mo+4 (aq) + H+ + R-CH = CH2. The Mo-C bond of alkylmolybdates is resistant to oxidants but is very sensitive to cleavage under reducing conditions. Reductive Mo-C bond cleavage occurs particularly rapidly in the presence of thiols and reduced ferredoxin model compounds. The latter reactions simulate the terminal steps of hydrocarbon producing reactions of nitrogenase with alternate substrates such as CN-, R-CN or R-NC, confirming previous mechanistic conclusions concerning the mechanism of nitrogenase action.

Zn-MOF derived micro/meso porous carbon nanorod for high performance lithium–sulfur battery

RSC Advances ◽  
2016 ◽  
Vol 6 (97) ◽  
pp. 94629-94635 ◽  
Author(s):  
Xinye Qian ◽  
Lina Jin ◽  
Shanwen Wang ◽  
Shanshan Yao ◽  
Dewei Rao ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Porous Carbon ◽  
High Performance ◽  
Room Temperature ◽  
Solution Method ◽  
Metal Organic Framework ◽  
Metal Organic ◽  
Sulfur Battery ◽  
Aqueous Solution Method ◽  
Lithium Sulfur

A unique micro/meso porous carbon nanorod (MPCN) was fabricated by carbonizing a zinc metal–organic framework (Zn-MOF) precursor, which was prepared by a facile aqueous solution method at room temperature.

Magnetic and Electric Properties of Phase Separated Glass Ceramics in CoO–TiO2–SiO2 System Prepared by Melt Quenching Process

2008 ◽  
Vol 1118 ◽  
Author(s):  
Hiroki Nakamura ◽  
Tetsuo Kishi ◽  
Yuji Muro ◽  
Ryuji Tamura ◽  
Kazuyasu Tokiwa ◽  
...  
Keyword(s):  
High Performance ◽  
Room Temperature ◽  
Glassy Phase ◽  
Glass Ceramics ◽  
The Other ◽  
Melt Quenching ◽  
Nano Structure ◽  
Quenching Process ◽  
Magnetic And Electric Properties ◽  
Co Doped

ABSTRACTThe developments of high performance magnetic materials are required in various applications such as high sensitive magnetic sensing and hyperthermia in cancer treatment. Recently, Co-doped TiO2 has been received considerable attention as a candidate for such materials because of their ferromagnetic properties at room temperature. On the other hand, the phase-separated glasses and the derived glass-ceramics having unique micro-nano structure are utilized for various applications. In this study, the phase separated glass-ceramics in CoO-TiO2-SiO2 system with Al2O3 addition were prepared by melt-quenching process. The as-quenched samples consisted of the TiO2-rich phase and the SiO2-rich one which were formed by a nucleation-growth mechanism of phase separation. From the results of XRD measurements, the samples were found to have a TiO2 crystalline phase and a SiO2-rich glassy phase. The samples showed the magnetic property, which were regarded as a mixture of ferromagnetic and paramagnetic phases. The samples also showed the electric conductivity at room temperature. However, the conductivity of the sample decreased with increase of the Co content, and the temperature dependence of the conductivity of the ferromagnetic samples was different from the other ones. As a result, the Co ions in the phase-separated glass-ceramics in TiO2-SiO2 system were found to affect on both the magnetic and the electric conductive characteristics.

Radiation Chemistry of DNA Model Compounds, IX. Carbohydrate Products in the γ-Radiolysis of Thymidine in Aqueous Solution. The Radical-Induced Scission of the N-Glycosidic Bond

1976 ◽  
Vol 31 (2) ◽  
pp. 227-233 ◽  
Author(s):  
Miral Dizdaroglu ◽  
Klaus Neuwald ◽  
Clemens Von Sonntag
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Room Temperature ◽  
Radiation Chemistry ◽  
Oh Radical ◽  
Glycosidic Linkage ◽  
Model Compounds ◽  
Sugar Moiety ◽  
G Value ◽  
Radical Attack

In the γ-radiolysis of deoxygenated N2O-saturated aqueous solutions of thymidine (10-3 M, room temperature, dose rate 4· 1018 eV/g.h., dose 6.7 1017-3.3 • 1018 eV/g) the following products (G-values in parentheses) have been identified : 2,5-dideoxy-pentos-4-ulose (1) (0.01), 2,4-dideoxy-pentodialdose (2) (0.02), 2,4-dideoxy-pentos-3-ulose (3) (0.03), 2,3-dideoxy-pentos-4-ulose (4) (0.01), 2-deoxy-pentos-4-ulose (5) (0.1), 2-deoxyribonic acid (6) (0.02) and thymine (8) ( ≤ 0.2). In the presence of oxygen (N2O/O2 80/20 v/v saturated) products 1-4 are absent, G (5) = 0.2, G (6) = 0.07 and G (8) ≤ 0.4. Furthermore, 2-deoxy-tetrodialdose (7) which is absent in deoxygenated solution is formed with a G-value of 0.03. Mechanisms are proposed to account for the scission of the N-glycosidic linkage. Product 6 is thought to be due to a primary OH radical attack at C-1′ of the sugar moiety, 8 arises from an attack at C-3′, 1, 4 and 5 from an attack at C-4′, and 2 and 7 from an attack at C-5′.

High performance room temperature all-solid-state Na-Se S battery with Na3SbS4–coated cathode via aqueous solution

2020 ◽  
Vol 48 ◽  
pp. 250-258 ◽  
Author(s):  
Ziqi Zhang ◽  
Haonan Cao ◽  
Meng Yang ◽  
Xinlin Yan ◽  
Chuang Yu ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Solid State ◽  
High Performance ◽  
Room Temperature

Reactivity of a benzylic lignin-carbohydrate model compound during enzymatic dehydrogenative polymerisation of coniferyl alcohol

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Kimiaki Shimizu ◽  
Yasuyuki Matsushita ◽  
Dan Aoki ◽  
Hayato Mitsuda ◽  
Kazuhiko Fukushima
Keyword(s):  
Mass Spectrometry ◽  
Model Compound ◽  
Degradation Products ◽  
Coniferyl Alcohol ◽  
Gas Chromatography Mass Spectrometry ◽  
Benzyl Ether ◽  
Model Compounds ◽  
Dimer Model ◽  
Carbohydrate Complex ◽  
Lignin Model

Abstract Lignin is thought to be covalently bound to carbohydrates like hemicellulose during biosynthesis to form a lignin-carbohydrate complex (LCC). However, successive polymerisation with monolignols after the formation of LCC has not yet been clarified. To investigate the reaction of LCC, its enzymatic dehydrogenative polymerisation was conducted using deuterium-labelled coniferyl alcohol and model compounds, i.e., a lignin model (β-O-4 dimer model) compound (LM) and an LCC model (benzyl ether type) compound (LCCM). The obtained polymers (DHPs) were methylated and subjected to thioacidolysis, and the degradation products were quantified by gas chromatography-mass spectrometry (GC-MS). The results showed that the amount of coniferyl alcohol connected to the LCCM via β-O-4 binding was almost the same as that bound to the LM. However, the amount of unreacted LCCM was larger than that of LM, suggesting that the LCCM is less likely to form condensed structures, i.e., 5-5, β-5, and 4-O-5 structures. This could be due to the steric hindrance of the carbohydrate at the benzylic position.

scholarly journals Utilization ofm-Phenylenediamine-Furfural Resin for Removal of Cu(II) from Aqueous Solution-A Thermodynamic Study

2010 ◽  
Vol 7 (3) ◽  
pp. 757-762
Author(s):  
Tariq S. Najim ◽  
Israa G. Zainal ◽  
Dina A. Ali
Keyword(s):  
Activation Energy ◽  
Aqueous Solution ◽  
Free Energy ◽  
Room Temperature ◽  
Adsorption Process ◽  
Sorption Process ◽  
The Other ◽  
Weak Values ◽  
Solid Liquid Interface ◽  
Solid Liquid

m-Phenylenediamine was condensed with furfural in absence of catalyst at room temperature. The producedm-phenylenediamine-furfural resin was used for the removal of Cu(II) from aqueous solution. The pH for the optimum removal of Cu(II) was 6. The negative values of Gibbs free energy at low concentration of Cu(II) (20, 30 ppm) indicative of the spontaneous adsorption process, while, at higher Cu(II) concentration (40,50 ppm) the positive and weak values of ∆G° indicate that the process is feasible but non spontaneous. The values of ∆H° were positive indicating that the sorption process is endothermic. On the other hand, the values of activation energy (Ea) were inconsistent with the values of ∆H° both are positive and lie in the range of physisorption. The entropy ∆S° of the process was positive indicative of the randomness of the Cu(II) ions at the solid / liquid interface. The values of sticking probability S* were less than one which indicate a preferable adsorption process and the mechanism is physisorption.

scholarly journals Synthesis of Highly Stable Cobalt Nanomaterial Using Gallic Acid and Its Application in Catalysis

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Saba Naz ◽  
Abdul Rauf Khaskheli ◽  
Abdalaziz Aljabour ◽  
Huseyin Kara ◽  
Farah Naz Talpur ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Catalytic Activity ◽  
Methyl Orange ◽  
Green Synthesis ◽  
Aqueous Medium ◽  
Gallic Acid ◽  
Azo Dyes ◽  
Room Temperature ◽  
Model Compound ◽  
Characterization Studies

We report the room temperature (25–30°C) green synthesis of cobalt nanomaterial (CoNM) in an aqueous medium using gallic acid as a reducing and stabilizing agent. pH 9.5 was found to favour the formation of well dispersed flower shaped CoNM. The optimization of various parameters in preparation of nanoscale was studied. The AFM, SEM, EDX, and XRD characterization studies provide detailed information about synthesized CoNM which were of 4–9 nm in dimensions. The highly stable CoNM were used to study their catalytic activity for removal of azo dyes by selecting methyl orange as a model compound. The results revealed that 0.4 mg of CoNM has shown 100% removal of dye from 50 μM aqueous solution of methyl orange. The synthesized CoNM can be easily recovered and recycled several times without decrease in their efficiency.

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