Zeolites are crystalline aluminosilicates with three‐dimensional microporous structures. They have been used as ion‐exchangers, catalysts, and adsorbents in various fields such as oil refining, petro‐chemistry, agr...Zeolites are crystalline aluminosilicates with three‐dimensional microporous structures. They have been used as ion‐exchangers, catalysts, and adsorbents in various fields such as oil refining, petro‐chemistry, agriculture, and water and wastewater treatment. Their wide use is because of their many beneficial properties, such as framework and compositional flexibilities, physical and hydro‐thermal stabilities, non‐toxicity, high surface areas, exchangeable cations, and good cost‐benefit ratios. Although many zeolite applications depend on their microporous structures, this can cause diffusional constraints for bulky reactant and product molecules. There have been many efforts to overcome the intrinsic limitations of conventional zeolites by preparing nanosized and hierarchi‐cally structured zeolites. As a result of these efforts, several strategies have been established and the use of new zeolitic materials in various catalytic and adsorptive reactions has been investigated. Longer lifetimes, high catalytic performances, and postponed coking and catalyst deactivation can be achieved using hierarchical and nanosized zeolites. The aim of this review is to provide an over‐view of the enhanced properties of hierarchical and nanosized zeolites, and recent development methods for their synthesis. The advantages and disadvantages of each route are discussed, and the catalytic applications of nanozeolites and zeolites with secondary porosity, and a comparison with conventional zeolites, are briefly presented.展开更多
We prepared a novel nickel（II）hydroxide-modified carbon paste electrode（Ni（OH）2-X/CPE）for the electrocatalytic oxidation of formaldehyde.The electrode was prepared by a simple method without the use of linking c...We prepared a novel nickel（II）hydroxide-modified carbon paste electrode（Ni（OH）2-X/CPE）for the electrocatalytic oxidation of formaldehyde.The electrode was prepared by a simple method without the use of linking chemicals.The prepared Ni（OH）2-X/CPE material was characterized by scanning electron microscopy and energy dispersive X-ray spectrometry.The electrochemical performance of the proposed electrode was investigated using cyclic voltammetry,electrochemical impedance spectroscopy,and chronoamperometry.The results indicate that Ni（OH）2-X/CPE exhibits good electrocatalytic activity with regards to formaldehyde oxidation owing to its nanoporous structure and the large surface area of zeolite X.The values of the electron transfer coefficient and the catalytic rate constant were 0.7 and 6.1 × 104 cm3/（mol·s）,respectively.Therefore,the proposed electrode,which showed remarkable electroactivity with regards to formaldehyde oxidation with long-term stability and good reproducibility,could be useful in fuel cells.展开更多
A nickel salen complex was encapsulated in the supercages of nanozeolite NaA,LTA(linde type A)structure,using the flexible ligand method.The electrochemical behavior and electrocatalytic activity of a carbon paste ele...A nickel salen complex was encapsulated in the supercages of nanozeolite NaA,LTA(linde type A)structure,using the flexible ligand method.The electrochemical behavior and electrocatalytic activity of a carbon paste electrode(CPE)modified with Ni(II)‐Salen‐A(Ni(II)‐SalenA/CPE)for hydrazine oxidation in0.1mol/L NaOH solution were investigated by cyclic voltammetry,chronoamperometry,and chronocoulometry.First,organic‐template‐free synthesis of nanozeolite LTA was performed and the obtained material was characterized by various techniques.The average particle size of the LTA crystals was estimated to be56.1and72nm by X‐ray diffraction and particle size analysis,respectively.The electron transfer coefficient was found to be0.64and the catalytic rate constant for oxidation of hydrazine at the redox sites of Ni(II)‐SalenA/CPE was found to be1.03×105cm3/(mol·s).Investigation of the electrocatalytic mechanism suggested that oxidation of hydrazine occurred through reaction with Ni3+(Salen)O(OH)and also direct electrooxidation.The anodic peak currents revealed a linear dependence on the square root of the scan rate,indicating a diffusion‐controlled process,and the diffusion coefficient of hydrazine was found to be1.18×10?7cm2/s.The results indicated that Ni(II)‐SalenA/CPE displays good electrocatalytic activity toward hydrazine oxidation owing to the porous structure of nanozeolite LTA and the Ni(II)‐Salen complex.Finally,the general reaction mechanism for the electrooxidation of hydrazine on Ni(II)‐SalenA/CPE in alkaline solution involves the transfer of four electrons,in which the first electron transfer reaction acts as the rate‐limiting step followed by a three‐electron process to generate environmentally friendly nitrogen and water as final products.展开更多
In this work,the natural nanozeolite clinoptilolite（Nano CP） was successfully functionalized by propylsulfonic acid and applied as efficient heterogeneous catalyst for the synthesis of quinoxaline derivatives in aqu...In this work,the natural nanozeolite clinoptilolite（Nano CP） was successfully functionalized by propylsulfonic acid and applied as efficient heterogeneous catalyst for the synthesis of quinoxaline derivatives in aqueous media.The nanocatalyst was characterized by various techniques such as CHN,XRD,FT-IR,BET,TGA/DTA,SEM,TEM and TEM-EDS.The results show its applicability as green,reusable and promising catalyst in organic synthesis.It was found that the nanocatalysts could be recycled and reused eight times without significant loss of catalytic activities.展开更多
文摘Zeolites are crystalline aluminosilicates with three‐dimensional microporous structures. They have been used as ion‐exchangers, catalysts, and adsorbents in various fields such as oil refining, petro‐chemistry, agriculture, and water and wastewater treatment. Their wide use is because of their many beneficial properties, such as framework and compositional flexibilities, physical and hydro‐thermal stabilities, non‐toxicity, high surface areas, exchangeable cations, and good cost‐benefit ratios. Although many zeolite applications depend on their microporous structures, this can cause diffusional constraints for bulky reactant and product molecules. There have been many efforts to overcome the intrinsic limitations of conventional zeolites by preparing nanosized and hierarchi‐cally structured zeolites. As a result of these efforts, several strategies have been established and the use of new zeolitic materials in various catalytic and adsorptive reactions has been investigated. Longer lifetimes, high catalytic performances, and postponed coking and catalyst deactivation can be achieved using hierarchical and nanosized zeolites. The aim of this review is to provide an over‐view of the enhanced properties of hierarchical and nanosized zeolites, and recent development methods for their synthesis. The advantages and disadvantages of each route are discussed, and the catalytic applications of nanozeolites and zeolites with secondary porosity, and a comparison with conventional zeolites, are briefly presented.
基金support of this work by the University of Mazandaran Research Council
文摘We prepared a novel nickel（II）hydroxide-modified carbon paste electrode（Ni（OH）2-X/CPE）for the electrocatalytic oxidation of formaldehyde.The electrode was prepared by a simple method without the use of linking chemicals.The prepared Ni（OH）2-X/CPE material was characterized by scanning electron microscopy and energy dispersive X-ray spectrometry.The electrochemical performance of the proposed electrode was investigated using cyclic voltammetry,electrochemical impedance spectroscopy,and chronoamperometry.The results indicate that Ni（OH）2-X/CPE exhibits good electrocatalytic activity with regards to formaldehyde oxidation owing to its nanoporous structure and the large surface area of zeolite X.The values of the electron transfer coefficient and the catalytic rate constant were 0.7 and 6.1 × 104 cm3/（mol·s）,respectively.Therefore,the proposed electrode,which showed remarkable electroactivity with regards to formaldehyde oxidation with long-term stability and good reproducibility,could be useful in fuel cells.
文摘A nickel salen complex was encapsulated in the supercages of nanozeolite NaA,LTA(linde type A)structure,using the flexible ligand method.The electrochemical behavior and electrocatalytic activity of a carbon paste electrode(CPE)modified with Ni(II)‐Salen‐A(Ni(II)‐SalenA/CPE)for hydrazine oxidation in0.1mol/L NaOH solution were investigated by cyclic voltammetry,chronoamperometry,and chronocoulometry.First,organic‐template‐free synthesis of nanozeolite LTA was performed and the obtained material was characterized by various techniques.The average particle size of the LTA crystals was estimated to be56.1and72nm by X‐ray diffraction and particle size analysis,respectively.The electron transfer coefficient was found to be0.64and the catalytic rate constant for oxidation of hydrazine at the redox sites of Ni(II)‐SalenA/CPE was found to be1.03×105cm3/(mol·s).Investigation of the electrocatalytic mechanism suggested that oxidation of hydrazine occurred through reaction with Ni3+(Salen)O(OH)and also direct electrooxidation.The anodic peak currents revealed a linear dependence on the square root of the scan rate,indicating a diffusion‐controlled process,and the diffusion coefficient of hydrazine was found to be1.18×10?7cm2/s.The results indicated that Ni(II)‐SalenA/CPE displays good electrocatalytic activity toward hydrazine oxidation owing to the porous structure of nanozeolite LTA and the Ni(II)‐Salen complex.Finally,the general reaction mechanism for the electrooxidation of hydrazine on Ni(II)‐SalenA/CPE in alkaline solution involves the transfer of four electrons,in which the first electron transfer reaction acts as the rate‐limiting step followed by a three‐electron process to generate environmentally friendly nitrogen and water as final products.
基金supported by the Islamic Azad University, Ayatollah Amoli Branch,I.R.Iran
文摘In this work,the natural nanozeolite clinoptilolite（Nano CP） was successfully functionalized by propylsulfonic acid and applied as efficient heterogeneous catalyst for the synthesis of quinoxaline derivatives in aqueous media.The nanocatalyst was characterized by various techniques such as CHN,XRD,FT-IR,BET,TGA/DTA,SEM,TEM and TEM-EDS.The results show its applicability as green,reusable and promising catalyst in organic synthesis.It was found that the nanocatalysts could be recycled and reused eight times without significant loss of catalytic activities.
