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1.
It has been found that immobilized cells ofC. pasteurianum possessing hydrogenase activity efficiently catalyze reversible reduction of concentrated (up to 0.5M) solutions of methyl
viologen with H2. A 0.5M aqueous solution of methyl viologen dissolves 240 times as much H2 as pure water under the same pressure of hydrogen. The experimentally obtained levels of methyl viologen reduction and H2 evolution are in satisfactory agreement with theoretical calculations. The potential of concentrated solutions of methyl
viologen containing immobilized hydrogenase as a H2 storage medium is discussed. 相似文献
2.
3.
The TiCl4-catalyzed Friedel–Crafts reaction with trifluoroacetaldehyde ethyl hemiacetal is shown to serve as an efficient route for the synthesis of CF3-substitituted compounds of biological and synthetic importance, producing 2,2,2-trifluoroethyl phenols in good yields under mild conditions. 相似文献
4.
Bulky AgGaS2 was synthesized as a p-type semiconductor photocatalyst by a conventional solid state reaction under N2 flow for hydrogen production under visible light. To remove impurity phases involved in the synthesized material and improve crystallinity, the material was treated at various temperatures of 873-1123 K under H2S flow. Impurity phases were identified as β-Ga2O3 and Ag9GaS6 with the cell refinements of XRD and the local coordination structure around gallium atom in AgGaS2 was investigated by EXAFS. As the H2S-treatment temperature increased, the contribution from impurity phases was diminished. When the temperature reached 1123 K, the impurity phases were completely removed and the material showed the highest photocatalytic activity. Thus, the post-synthetic H2S treatment could be applied for the synthesis of sulfide-type photocatalysts with high activity. 相似文献
5.
Dr. Leandro Cotos Maxime Donzel Dr. Mourad Elhabiri Dr. Elisabeth Davioud-Charvet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(15):3314-3325
A series of highly diversified 3-aroylmenadiones was prepared by a new Friedel–Crafts acylation variant/oxidative demethylation strategy. A mild and versatile acylation was performed between 1,4-dimethoxy-2-methylnaphthalene and various activated/deactivated benzoic and heteroaromatic carboxylic acids, in the presence of mixed trifluoroacetic anhydride and triflic acid, at room temperature and in air. The 1,4-dimethoxy-2-methylnaphthalene-derived benzophenones were isolated in high yield, and submitted to oxidative demethylation with cerium ammonium nitrate to produce 3-benzoylmenadiones. All 1,4-naphthoquinone derivatives were investigated as redox-active electrophores by cyclic voltammetry. The electrochemical data recorded for 3-acylated menadiones are characterized by a second redox process, the potentials of which cover a wide range of values (500 mV). These data emphasize the ability of the generated structural diversity at the 3-aroyl chain of these electrophores to fine-tune their corresponding redox potentials. These properties are of significance in the context of antimalarial drug development and understanding of the mechanism of bioactivation/action. 相似文献
6.
MOR zeolite has been extensively employed as a catalyst in industries. However, high Brønsted acidity in MOR leads to rapid deactivation due to coke deposition on the pore mouths; thus, the surface acidity of MOR needs to be moderated. Herein, we report a modification of MOR chemical composition via acid treatment and deposition of ceria nanoparticles using a wet impregnation method. The acid treatment successfully increases the Si/Al ratio of MOR from 8.39 to 11.58 and reduces the total acid site concentration of MOR from 990 μmol/g to 752 μmol/g. The acidity of MOR is decreased when the Si/Al ratio is increased since the quantity of Brønsted acid sites is proportional to the number of Al framework. In addition, the acid treatment also improves the external surface area of MOR. Furthermore, ceria particles were successfully deposited on the MOR surface using wet impregnation method. The ceria content of parent MOR sample is lower compared to that of preceded by the acid treatment, which may be attributed to the formation of more terminal silanol groups. Finally, catalytic test on Friedel–Crafts alkylation of toluene with benzyl alcohol shows that the synergy between dealumination and the impregnation of ceria significantly improves the activity of MOR zeolite. 相似文献
7.
Hua Ma Zhanliang Tao Feng Gao Jun Chen Huatang Yuan 《Frontiers of Chemistry in China》2006,1(3):260-263
The structure, morphology and hydrogen-storage capacity of MS2 (M = Mo, Ti) nanotubes prepared by different experimental methods were studied. It was found that the MoS2 nanotubes treated by KOH displayed the gaseous storage capacity of 1.2 wt% hydrogen (under the hydrogen pressure of 3 MPa
and 25°C) and the electrochemical discharge capacity of 262 mAh/g (at the discharge current density of 50 mA/g and 25°C) that
corresponds to about 1.0 wt % hydrogen. In comparison, TiS2 nanotubes can store 2.5 wt% hydrogen under the hydrogen pressure of 4 MPa and 25°C. The results show that MS2 compound nanotubes are promising materials for hydrogen storage.
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Translated from Acta Scientiarum Naturalium Universitatis Nankaiensis, 2005, 38(4) (in Chinese) 相似文献
8.
Lin Zhang Wenli Hou Qiujun Lu Meiling LiuChao Chen Youyu ZhangShouzhuo Yao 《Analytica chimica acta》2016
In this report, carbon-based gold core silver shell Au-Ag bimetallic nanocomposite (Au-Ag/C NC) was synthesized using carbon dots (C-dots) as the reductant and stabilizer by a facile green sequential reduction approach. The structure and morphology of the nanocomposite are characterized by ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The as synthesized Au-Ag/C NC exhibits good optic response toward hydrogen peroxide (H2O2) without adding any other chromogenic agents. The characteristic surface plasmon resonance (SPR) absorbance peak of Au-Ag/C NC declined and red-shifted with the solution color changing from reddish orange to light pink when adding H2O2 owing to the etching effect of H2O2 towards Ag. Thus, a simple colorimetric and UV strategy for sensitive detection of H2O2 is proposed. It provides the wide linear range for detection of H2O2 from 0.8–90 μM and 90–500 μM, and the detection limit was as low as 0.3 μM (S/N = 3). In addition, this colorimetric strategy can also be applied to directly distinguish and detect of lactate by naked eye and UV–Vis. The linear range of colorimetric sensing towards lactate was 0.1–22 μM and 22–220 μM, which was successfully applied in the analysis of lactate in human serum. 相似文献
9.
An efficient and chemoselective method for the Friedel–Crafts acylation of aromatic compounds using P2O5/Al2O3 and carboxylic acids. Both aromatic and aliphatic carboxylic acids reacted easily to afford the corresponding aromatic ketones in good yields. 相似文献
10.
11.
L. -K. Wu K. -Y. Chen S. -Y. Cheng B. -S. Lee C. -M. Shu 《Journal of Thermal Analysis and Calorimetry》2008,93(1):115-120
Hydrogen peroxide (H2O2) is popularly employed as a reaction reagent in cleaning processes for the chemical industry and semiconductor plants. By
using differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2), this study focused on the thermal decomposition
reaction of H2O2 mixed with sulfuric acid (H2SO4) with low (0.1, 0.5 and 1.0 N), and high concentrations of 96 mass%, respectively. Thermokinetic data, such as exothermic
onset temperature (T
0), heat of decomposition (ΔH
d), pressure rise rate (dP/dt), and self-heating rate (dT/dt), were obtained and assessed by the DSC and VSP2 experiments. From the thermal decomposition reaction on various concentrations
of H2SO4, the experimental data of T
0, ΔH, dP/dt, and dT/dt were obtained. Comparisons of the reactivity for H2O2 and H2O2 mixed with H2SO4 (lower and higher concentrations) were evaluated to corroborate the decomposition reaction in these systems. 相似文献
12.
Recent progress in photocatalytic decomposition of water to H2 and O2 using simple oxide semiconductor catalysts has been reviewed. Addition of Na2CO3 to Pt/TiO2 suspension in water enhanced the stoichiometric decomposition significantly. This Na2CO3 addition method has been proved to be very useful to accelerate water splitting over various kinds of oxide semiconductor photocatalysts. The role of CO3
2– anion on the acceleration of water splitting was clarified. Finally, it was firstly demonstrated in the world that water was decomposed efficiently and stoichiometrically to H2 and O2 using a 3 wt% NiOx/TiO2 photocatalyst under real solar light irradiation in Tsukuba, Japan by this Na2CO3 addition method. 相似文献
13.
A new amperometric biosensor for hydrogen peroxide was developed based on cross-linking horseradish peroxidase (HRP) by glutaraldehyde with multiwall carbon nanotubes/chitosan (MWNTs/chitosan) composite film coated on a glassy carbon electrode. MWNTs were firstly dissolved in a chitosan solution. Then the morphology of MWNTs/chitosan composite film was characterized by field-emission scanning electron microscopy. The results showed that MWNTs were well soluble in chitosan and robust films could be formed on the surface. HRP was cross-linked by glutaraldehyde with MWNTs/chitosan film to prepare a hydrogen peroxide biosensor. The enzyme electrode exhibited excellent electrocatalytic activity and rapid response for H2O2 in the absence of a mediator. The linear range of detection towards H2O2 (applied potential: −0.2 V) was from 1.67 × 10−5 to 7.40 × 10−4 M with correction coefficient of 0.998. The biosensor had good repeatability and stability for the determination of H2O2. There were no interferences from ascorbic acid, glucose, citrate acid and lactic acid. 相似文献
14.
Andrzej Leś 《Theoretical chemistry accounts》1985,66(6):375-393
Intermolecular potential energy curves for the hydrogen bonded systems H2O·H2S, H2O·H2Se and H2S·H2S were calculated with nonempirical pseudopotentials using optimized-in-molecules basis sets augmented by polarization functions. The H2O·H2O interaction energy curve has been also considered as a test case. The present results for H2O·H2S and H2S·H2S indicate much weaker intermolecular interactions than those found in previous ab initio calculations. The H2O·H2Se interaction was found to be quite similar to H2O·H2S.This work was partly supported by the Polish Academy of Sciences within the Project PAN-09, 7.1.1.1On leave from Quantum Chemistry Laboratory, Dept. of Chemistry, University of Warsaw, Pasteura 1, 02-093. Warsaw, Poland 相似文献
15.
The effect of calcination temperature on the physico-chemical characterization of manganese nodule leached residue (MNLR) and water-washed manganese nodule leached residue (WMNLR) has been investigated on the basis of chemical analysis, XRD, TG-DTA, FTIR, surface hydroxyl groups, surface oxygen, reducing and oxidizing sites, surface area. XRD and IR confirm the presence of amorphous iron oxyhydroxides, delta-MnO2, which are converted to alpha-Fe2O3 and gamma-Mn2O3 phases above 400 degrees C of calcination, respectively. A solid solution of Fe2O3 and Mn2O3 is formed above 700 degrees C. The surface area, surface hydroxyl group, surface oxygen, reducing and oxidizing sites increase with the increase in calcination temperature up to 400 degrees C and then decrease with further rise in calcination temperature up to 700 degrees C. The catalytic activity of the sample towards H2O2 decomposition shows the similar trend as surface properties. A suitable Mn(3+)Mn4+ couple favours H2O2 decomposition reaction. The activity has been correlated with various physico-chemical properties. 相似文献
16.
Michael addition of alkoxides or diethyl methylmalonate to 2-chloroacrylonitrile provides functional carbanions which are able to react with 1,3-dinitrobenzene following a vicarious nucleophilic substitution to give new substituted nitroarenes. 相似文献
17.
The hydrogen bonds between H2S and H2O molecules are calculated through anab initio, LCAO MO SCF method using a Gaussian type orbital double-zeta basis set. The capacity of the H2S molecule to act as an electron acceptor is confirmed.
Consultant of the Instituto Mexicano del Petróleo. 相似文献
18.
E. Kochanski 《Theoretical chemistry accounts》1975,39(4):339-346
The interaction energy between two hydrogen molecules near the van der Waals minimum is computed as the sum of the SCF interaction energy of the supermolecule and the so-called Hartree-Fock dispersion energy. The most stable configuration is the perpendicular planar one (T configuration), this configuration being stable through the first order term. The energy averaged over the four configurations is in agreement with the available experimental data. The perturbative polarization energy is negligible near the van der Waals minimum but it seems that the charge transfer energy must be taken into account. 相似文献
19.
Profiles of temperature programmed reduction (TPR) of V2O5 under H2 have been studied through water analysis. This new approach enhances the sensitivity of the method. The influence of experimental parameters on the temperature corresponding to the maximum reduction rate,T m, has been studied. The hydrogen concentration and heating rate are the two major factors that influenceT m. In our method, the amount of solid and the flow rate are also important factors in monitoring of profile distortions attributed to water condensation at the outlet of the reactor. An approach of the mechanism of reduction of V2O5 has been carried out. The best kinetic model which describes the reduction rocess is the Avrami-Erofeev tridimensional nucleation model. 相似文献
20.
K. Y. Chen C. M. Lin C. M. Shu C. S. Kao 《Journal of Thermal Analysis and Calorimetry》2006,85(1):87-89
Information about the kinetics and thermal
decomposition of hydrogen peroxide (H2O2)
has been required for safety reasons, due to its broad applications in many
chemical industries. To determine the inherent hazards during H2O2
manufacturing, transportation, disposal, usage, and so on, this study deliberately
selected various H2O2 concentrations
and analyzed them by differential scanning calorimetry (DSC). In addition,
thermokinetic parameters were not only established for each of these reactions,
but also aimed at comprehensive, kinetic models with various tests conducted
at different heating rates.
To build up a comprehensive kinetic
model, various tests were conducted by heating rates of 1, 2, 4, 10°C
min–1, respectively. According to dynamic
DSC tests, the experimental curves show that H2O2
decomposition has one exothermic peak and may start to decompose under 47–81°C.
The total heat of decomposition is about 192–1079 J g–1.
Not only can these results prevent accidents caused by H2O2
during storage and transportation, but also assess its inherent hazards and
thereby design procedures for emergency response while runaway reactions occurring. 相似文献