Highly efficient generation of H2O2 at composite polyaniline/heteropolyanion electrodes: effect of heteropolyanion structure on H2O2 yield

A new highly efficient electrochemical H₂O₂ generating system based on polyaniline film doped with heteropolytungstate anions was developed. The oxygen reduction characteristics of polyaniline–heteropolytungstate composites were investigated using the rotating disk–ring electrode technique. Polyaniline electrode with immobilized heteropolytungstate anions of the Dawson structure (P₂W₁₈O₆₂⁶⁻) exhibits a 75% efficiency of H₂O₂ generation in the acid medium while polyaniline doped with heteropolytungstate anions of the Keggin structure (PW₁₂O₄₀³⁻) reduces O₂ predominantly by four electrons. It was established that the chemosorption of H₂O₂ during the reduction of O₂ governs the efficiency of hydrogen peroxide generation.     

H6P2W18O62·14H2O as an efficient catalyst for the green synthesis of α-aminophosphonates from α-amino acids

Abstract

A simple, efficient and eco-friendly protocol has been described for the synthesis of α-aminophosphonates via Kabachnik-Fields reaction, catalyzed by H₆P₂W₁₈O₆₂·14H₂O as a reusable catalyst. The reaction was realized by condensation of amino acids, various aromatic aldehydes and triethylphosphite under solvent-free conditions, the corresponding α-aminophosphonates were formed in good yields. All the new products were characterized by IR, ¹H, ¹³C and ³¹P-NMR analyses. This method offers advantages such as simplicity workup with the green aspects, good yields and short reaction times.     

Full-dimensional quantum dynamics study of exchange processes for the D + H2O and D + HOD reactions

The exchange processes of D + H(2)O and D + HOD reactions are studied using initial state-selected time-dependent wave packet approach in full dimension. The total reaction probabilities for different partial waves, together with the integral cross sections, are obtained both by the centrifugal sudden (CS) approximation and exact coupled-channel (CC) calculations, for the H(2)O(HOD) reactant initially in the ground rovibrational state. In the CC calculations, small resonance peaks in the reaction probabilities and quick diminishing of the resonance peaks with the increase of total angular momenta J do not lead to clear step-like features just above the threshold in the cross sections for the title reactions, which are different in other isotopically substituted reactions where the hydrogen atom was included as the reactant instead of the deuterium atom [B. Fu, Y. Zhou, and D. H. Zhang, Chem. Sci. 3, 270 (2012); B. Fu and D. H. Zhang, J. Phys. Chem. A 116, 820 (2012)]. It is interesting that the shape resonance-induced features resulting from the reaction tunneling are significantly diminished accordingly in the reactions of the deuterium atom and H(2)O or HOD, owing to the weaker tunneling capability of the reagent deuterium atom in the title reactions than the reagent hydrogen atom in other reactions. In the CS calculations, the resonance peaks persist in many partial waves but cannot survive the partial-wave summations. The cross sections for the D(') + H(2)O → D(')OH + H and D(') + HOD → D(')OD + H reactions are substantially larger than those for the D(') + HOD → HOD(') + D reaction, indicating that the D(')/H exchange reactions are much more favored than the D(')/D exchange.     

AlCl3.6H2O as a catalyst for simple and efficient synthesis of gem-dihydroperoxides from ketones and aldehydes using aqueous H2O2

AlCl₃.6H₂O was explored as an efficient catalyst for the synthesis of ingem-dihydroperoxides (DHPs) from ketones and aldehydes. The reactions took place within a short period of time using (30%) aqueous H₂O₂ as a ??green?? oxidant in acetonitrile under neutral conditions at room temperature to afford the products in high yields.     

First observation of highly efficient dehydrogenation of methanol to anhydrous formaldehyde over novel Ag-SiO2-MgO-Al2O3 catalyst

Novel Ag-SiO2-MgO-Al2O3 catalyst prepared by sol-gel method showed extremely high activity and selectivity (both equal to 100%) in the direct dehydrogenation of methanol to anhydrous formaldehyde.     

A binder-free electrode for efficient H2O2 formation and Fe2+ regeneration and its application to an electro-Fenton process for removing organics in iron-laden acid wastewater

The electro-Fenton process,with its capacity for in-situ H₂O₂formation and Fe²⁺regeneration,is a striking alternative to the traditional chemical-Fenton process.However,the frequent requirement of extra binders for electrode fabrication leads to low catalyst utilization,a complex fabrication process,and weak conductivity.Herein,a three-dimensional (3D) porous electrode was fabricated in-situ on a Ni foam (NF)substrate integrated with nitrogen-doped carbon nanotub...     

Facile and convenient method of deuterium gas generation using a Pd/C-catalyzed H2-D2 exchange reaction and its application to synthesis of deuterium-labeled compounds

The Pd/C-catalyzed H(2)-D(2) exchange reaction using a H(2)-D(2)O combination provided a general, efficient and environmentally friendly route for the preparation of deuterium gas (D(2)). H(2) sealed in a reaction flask was converted into nearly pure D(2), which could be used for the Pd/C-catalyzed one-pot reductive deuteration of various reducible functionalities and the chemoselective one-pot deuterogenation of olefin and acetylene. Additionally, we established the capturing method of the generated D(2) in a balloon, which was successfully applied to the Pd/C-catalyzed reductive mono-N-alkylation of a primary amine using nitrile as the alkylating reagent.     

Highly efficient heterogeneous acylations of aromatic compounds with acid anhydrides and carboxylic acids by montmorillonite-enwrapped titanium as a solid acid catalyst

Montmorillonite-enwrapped titanium hydroxide species (Ti⁴⁺-mont) acted as a highly efficient heterogeneous acid catalyst for the acylation of aromatic compounds with acid anhydrides or carboxylic acids. The catalytic activity of the Ti⁴⁺-mont was higher than those of other acid catalysts such as zeolites, SO ₄ ^2? /ZrO₂ and p-toluenesulfonic acid. For example, the reaction of anisole with dodecanoic acid in the presence of the Ti⁴⁺-mont catalyst gave 1-(4-methoxyphenyl)-1-dodecanone in 97% yield. Furthermore, the Ti⁴⁺-mont catalyst was easily separated from the reaction mixture and was recyclable.     

Highly active and stable porous polymer heterogenous catalysts for decomposition of formic acid to produce H2

Formic acid (FA) has attracted extensive attention as a hydrogen storage material. Here, we develop two heterogeneous catalysts based on porous organic polymers (POPs). After loading the Ru species, the catalyst bearing the triphenylphosphine ligand showed excellent performance in terms of activity and stability for the decomposition of FA to produce hydrogen.     

Biproton transfer in associates of the formic acid molecule with H2O...YH systems (YH=H2O,HOF and HOOH)

An ab initio (STO-3G basis set) method is used to calculate the pathways and activation barriers of cooperative biproton migrations in the associates of the formic acid molecule with water and YH (YH=H₂O, HOF, and HOOH). The associate with YH=H₂O exhibits a cooperative triproton transfer with an activation barrier of 4.46 (C_s symmetry) or 3.08 kcal/mole (C₂ symmetry); in the systems with Y=HOF and HOOH, the biproton transfer is accompanied by synchronous shifts of two hydroxyl groups and has the activation barriers of 75.03 (C₂, Y=HOF), 75.74 (C_s, Y=HOF), and 89.62 kcal/mole (Y=HOOH). The hypothesis of stereochemical similarity for low-barrier cooperative processes in molecular associates is proposed. Scientific Research Institute of Physical and Organic Chemistry, Rostov State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 5, pp. 834–844, September–October, 1996. Translated by I. Izvekova     

One-pot synthesis of thiazole-2-imine derivatives by CoFe2O4@SiO2-PA-CC-Guanidine-SA MNPs as an efficient and recyclable catalyst

A novel and atom-economic protocol for the synthesis of thiazole-2-imine derivatives was developed. Synthesis of thiazole-2-imine derivatives from primary amines, phenyl isothiocyanate and phenacyl bromide derivatives by the CoFe₂O₄@SiO₂-PA-CC-Guanidine-SA magnetic nanocatalyst in excellent yields was reported. This nanocatalyst is easily separated from the reaction mixture and can be reused for several times. For the characterization of the catalyst used of Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and vibrating-sample magnetometry (VSM) techniques.     

CeCl_3·7H_2O as an efficient catalyst for one-pot synthesis of β-amino ketones by three-component Mannich reaction

<正>Cerium trichloride heptahydrate(CeCl_3·7H_2O) was found to be an efficient and recyclable catalyst for the three-component direct Mannich reaction of anilines and benzaldehydes with acetophenone.This protocol has advantages of high yield,no environmental pollution,mild condition,and simple work-up procedure.     

Apparent molal heat capacities of transfer from H2O to D2O of tetraalkylammonium bromides

The volumetric specific heats (in J-K^–1-cm^–3) of tetraalkylammonium bromides (R ₄ NBr) have been measured at 25°C in the concentration range 0.02 to 0.4 aquamolal in H ₂ O and D ₂ O with a differential flow microcalorimeter. The apparent molal heat capacities _c, calculated from the specific heats and known densities, were fitted with the equation _c= _c ^o +A_cm^1/2+B_cm whereA _c is the Debye-Hückel limiting slope andB _c is an adjustable parameter.The standard heat capacity of transfer C _ptr ^o = _c ^o (D ₂ O- _c ^o (H ₂ O) of R ₄ NBr is positive forR equal ton-propyl andn-butyl and negative for methyl and ethyl. Except for Me ₄ NBr in H ₂ O, allB _c are negative and become more so as the size of the cation increases;B _c is usually more negative in D ₂ O. These results can be interpreted with a two-state model for water and show that a positive C _ptr ^o is evidence that the solute is an overall structure maker, while a negative value indicates a net structure breaker. The negativeB _c is consistent with the existence of strong solute-solute structural (mostly hydrophobic-hydrophobic and hydrophobic-hydrophilic) interactions in the solution.     

A novel route for in-situ H2O2 generation from selective reduction of O2 by hydrazine using heterogeneous Pd catalyst in an aqueous medium

Hydrogen peroxide in high yields can be generated with high efficiency at mild conditions (25 degrees C and atmospheric pressure) with the formation of only environment-friendly by-products (N2 and H2O) by a reduction of O2 by hydrazine from its hydrate/salt with its complete conversion in a short reaction period (相似文献   

Phosphoric acid supported on alumina (H3PO4/Al2O3) as an efficient and reusable catalyst for the one-pot synthesis of benzoxanthene pigments

Phosphoric acid supported on alumina (H₃PO₄/Al₂O₃) is an efficient catalyst for the catalytic multi-component condensation reaction and a wide variety of syntheses of benzoxanthene pigments in good yields. The remarkable features of this new procedure are high conversions, shorter reaction times, cleaner reaction, and simple experimental and work-up procedures.     

Experimental and theoretical studies of charge transfer and deuterium ion transfer between D2O+ and C2H4

The charge transfer and deuterium ion transfer reactions between D(2)O(+) and C(2)H(4) have been studied using the crossed beam technique at relative collision energies below one electron volt and by density functional theory (DFT) calculations. Both direct and rearrangement charge transfer processes are observed, forming C(2)H(4) (+) and C(2)H(3)D(+), respectively. Independent of collision energy, deuterium ion transfer accounts for approximately 20% of the reactive collisions. Between 22 and 36 % of charge transfer collisions occur with rearrangement. In both charge transfer processes, comparison of the internal energy distributions of products with the photoelectron spectrum of C(2)H(4) shows that Franck-Condon factors determine energy disposal in these channels. DFT calculations provide evidence for transient intermediates that undergo H/D migration with rearrangement, but with minimal modification of the product energy distributions determined by long range electron transfer. The cross section for charge transfer with rearrangement is approximately 10(3) larger than predicted from the Rice-Ramsperger-Kassel-Marcus isomerization rate in transient complexes, suggesting a nonstatistical mechanism for H/D exchange. DFT calculations suggest that reactive trajectories for deuterium ion transfer follow a pathway in which a deuterium atom from D(2)O(+) approaches the pi-cloud of ethylene along the perpendicular bisector of the C-C bond. The product kinetic energy distributions exhibit structure consistent with vibrational motion of the D-atom in the bridged C(2)H(4)D(+) product perpendicular to the C-C bond. The reaction quantitatively transforms the reaction exothermicity into internal excitation of the products, consistent with mixed energy release in which the deuterium ion is transferred in a configuration in which both the breaking and the forming bonds are extended.