以方沸石负载Ni(Ⅱ)催化剂修饰的电极电氧化甲醇(英文)

There is a high overvoltage in the oxidation of methanol in fuel cells,and so modified electrodes are used to decrease it.A modified electrode that used Ni(II) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed.Analcime zeolite was synthesized by hydrothermal synthesis,and Ni(II) ions were incorporated into the analcime structure,which was then mixed with carbon paste to prepare modified electrode.The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry.The effects of the scan rate of the potential,concentration of methanol,and amount of zeolite were investigated.The rate constant for the catalytic reaction of methanol was 6 × 103 cm3 mol-1 s-1 from measurements using chronoamperometry.The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.     

Controlling of Solution Concentration on Nucleation During Hydrothermal Synthesis of Analcime

Hydrothermal experiments of analcime nucleation and glass dissolution were carried out in autoclaves under the conditions of autogeneous pressures, temperatures of 150 °C ～ 210 °C, and 0.25 M ～ 0.75 M NaOH solutions. The curves of the glass dissolution and analcime formation are S‐shaped. Yet, the two curves are essentially parallel to each other. The time required for a complete dissolution of glass or the commencement of analcime formation is shorter when the concentration of NaOH solution or the temperature is higher. The amount of the weight percent of analcime synthesized is obviously less than the glass dissolved at a given time of an experiment. The weight difference between glass dissolved and analcime (dehydrated) formed is calculated to be represented as the solution concentration. During an experiment, the solution concentration increases gradually to a maximum, then decreases slowly to a constant value with time. On the other hand, nucleation is also gradually increased to a maximum, then is decreased finally to zero with time in a bell‐shaped curve. It is clear that nucleation of analcime is mainly controlled by the solution concentration.     

Static and Ultrasonic‐assisted Aging Effects on the Synthesis of Analcime Zeolite

The synthesis of zeolite ANA under static hydrothermal conditions was performed accompanied by an additional static and ultrasonic‐assisted aging of the reaction mixture prior to crystallization. The aging process was compared with stirring‐assisted aging, microwave‐assisted aging and syntheses without any aging. The influence of aging time on the crystallization time of zeolite ANA was investigated. The static and ultrasonic‐assisted aging can shorten the crystallization time of the ANA phase. Moreover, ultrasonic‐assisted aging leads to altered morphologies of the particles. The products were characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM).     

以方沸石负载Ni(II)催化剂修饰的电极电氧化甲醇Seyed Naser Azizi,Shahram Ghasemi,Neda Salek Gilani简

There is a high overvoltage in the oxidation of methanol in fuel cells, and so modified electrodes are used to decrease it. A modified electrode that used Ni(Ⅱ) loaded analcime zeolite to catalyze the electrooxidation of methanol in alkaline solution was proposed. Analcime zeolite was synthesized by hydrothermal synthesis, and Ni(Ⅱ) ions were incorporated into the analcime structure, which was then mixed with carbon paste to prepare modified electrode. The electrocatalytic oxidation of methanol on the surface of the modified electrode in alkaline solution was investigated by cyclic voltammetry and chronoamperometry. The effects of the scan rate of the potential, concentration of methanol, and amount of zeolite were investigated. The rate constant for the catalytic reaction of methanol was 6×10³ cm³ mol^-1 s^-1 from measurements using chronoamperometry. The proposed electrode significantly improved the electron transfer rate and decreased the overpotential for methanol oxidation.     

Topological Analysis of Mesoporous Solids and Their Ordered Pore Structures by Periodic Nodal Surfaces,PNS

It is shown that Periodic Nodal Surfaces, PNS, give a general and easy to use tool to analyze and characterize mesoporous solids. The comparison of PNS ( Symmetry) with different MCM‐48 micrographs indicates two different possible structure types, both closely related to the structure of analcime, and the possibility of a polymorphism for MCM‐48.     

Isomorphous Substitution of Iron and Nickel into Analcime Zeolite

Studies on the effects of iron and nickel incorporation into the hydrothermal synthesis of ANA zeolite were carried out. The presented work reveals that pure Fe‐Al analcime is synthesized by using starting composition with a higher iron(III) content than reported in previous publications. Furthermore, the iron(III) and nickel(II) contents play important roles in the framework of the synthesized zeolite. XRD, FT‐IR spectroscopy, diffuse reflectance UV/Vis spectroscopy, nitrogen adsorption and SEM were used to characterize the synthesized zeolites. These investigations showed that loading of iron and nickel ions in ANA zeolite changes the pore size and morphology of analcime zeolite.     

Synthesis of Aluminum‐Rich Analcime Using an Ethylene Diamine Derivative as Template

The hydrothermal synthesis of analcime (ANA) with N,N′‐dibenzyl‐N,N,N′,N′‐tetramethylethylenediamine (DBTMED) as template was systematically studied. The various parameters that affect the crystallization of analcime, such as temperature, time, Al source, and Si/Al ratio were investigated. Systematic variations of these parameters revealed that ANA was obtained from the reaction mixture with the optimized ratios of SiO₂/Al₂O₃ = 5–9.5 in presence of DBTMED, whereas template‐free clear solution methods require SiO₂/Al₂O₃ ratio of greater than 25. When experiments were conducted at 130 and 150 °C for 4 days, a mixture of analcime and zeolite P was present in the samples, and a pure analcime sample could be obtained with heating in the temperature range 160–180 °C. When microwave and conventional heating were used, analcime could be obtained after 2 days. The obtained products were characterized by XRD, SEM, and IR spectroscopy.     

Recrystallization of Zeolite Y to Analcime and Zeolite P with <SC>d</SC>‐Methionine as Structure‐Directing Agent (SDA)

In this study, the synthesis of template free zeolite Y and its recrystallization to two types of pure zeolite P and analcime in the presence of the amino acid d‐methionine as structure‐directing agent were investigated. The recrystallization occurred solely when specific heating cycles were applyed. A completely crystallized phase of zeolite Y for the mixture of zeolite P and analcime was observed in the presence of d‐methionine at a concentration of 0.015 <SC>m</SC>. The effect of different Si/Al ratios (2.3–9.3), crystallization temperatures (40–160 °C), and crystallization times (28–96 hours) on the achievement of two different zeolite types were studied as well. Pure zeolite P was obtained during conventional heating to 100 °C for 42 hours, whereas pure analcime zeolite was achieved by heating the mixture to 160 °C for 96 hours. The products were characterized by X‐ray diffraction, scanning electron microscopy, and IR spectroscopy.     

铁掺杂方沸石的合成及其磁性化

采用水热合成法, 按摩尔比n(SiO2):n(Al2O3):n(Na2O):n(Fe3+):n(H2O)=2.3:1:3.9:(0.02, 0.04, 0.08):185配料, 三乙胺为模板剂, 草酸为铁离子的络合剂, 经过室温搅拌成胶, 170 ℃下于不锈钢反应釜晶化60 h, 合成了三种掺杂铁量不同的方沸石, 为了解决粉末沸石分子筛难以从使用料液中分离问题, 对合成铁掺杂方沸石700 ℃下进行氢气还原制得了磁性沸石. 利用X射线衍射(XRD)、傅立叶变换-红外(FT-IR)光谱和扫描电子显微镜(SEM)对制得的产品进行表征. 结果表明, 合成的铁掺杂方沸石与纯方沸石结构相同, 磁性化沸石结构发生了变化. 考察样品对水中氟离子和铅离子的吸附性能发现, 铁掺杂方沸石和磁性沸石对它们的吸附性能没有促进作用.     

Flame atomic absorption spectrometry determination of trace amounts of copper after separation and preconcentration onto TDMBAC-treated analcime pyrocatechol-immobilized

A simple and reliable method has been developed for green separation and preconcentration of trace amounts of copper ions in aqueous solutions for subsequent measurement by flame atomic absorption spectrometry (FAAS). The Cu²⁺ ions are adsorbed selectively and quantitatively during the passage of an aqueous solution through TDMBAC-treated analcime pyrocatechol-immobilized. The retained copper ions were desorbed from the column with 5.0 mL of 4 mol L⁻¹ nitric acid solutions as eluent and were determined by FAAS. The linear range was 0.2-75 ng mL⁻¹ in the original solution with a correlation coefficient of 0.9987. In this case we can concentrate 0.1 μg of copper from 1000 mL of solution and the proposed method permits a large enrichment factor (about 200). The detection limit of the proposed method is 0.05 ng mL⁻¹ in the original solution (2σ_bl). Determination of copper in standard alloys showed that the proposed method has good accuracy (recovery was more than 97%). The method was successfully applied for recovery and determination of copper in several water samples.