Chak-tong Au

Followers

Following

Co-author

Public Views

Eswar Prasad Korilimilli

Mahindra Ecole Centrale

PROF. OM PRAKASH SINHA

Amity University

Virginie Boucher

CSIC (Consejo Superior de Investigaciones Científicas-Spanish National Research Council)

Prof.Dr. İbrahim USLU

Gazi University

Kenneth Vecchio

University of California, San Diego

Maderas. Ciencia y Tecnologia

Universidad del Bio-bio

Mohammed Wasim Siddiqui

Bihar Agricultural University

Werner Treptow

Universidade de Brasília - UnB

T. Mavromoustakos

National & Kapodistrian University of Athens

Giovanni Villani

Consiglio Nazionale delle Ricerche (CNR)

Interests

Uploads

Papers by Chak-tong Au

Facile route using highly arrayed PMMA spheres as hard template for the fabrication of 3D ordered nanoporous MgO

Chinese Journal of Chemical Physics, 2007

Using magnesium nitrate as Mg source and regularly packed polymethyl methacrylate (PMMA) spheres ... more Using magnesium nitrate as Mg source and regularly packed polymethyl methacrylate (PMMA) spheres were synthesized via a combined strategy of emulsifier-free emulsion polymerization and water floating technique as hard template, we fabricated ordered nanoporous magnesium oxide. The synthesized PMMA and MgO samples were characterized by N 2 adsorption-desorption, X-ray diffraction, high-resolution scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. It was observed that the synthesized PMMA spheres possessed a uniform diameter of approximately 284 nm and were in a highly ordered array, and the MgO generated by using the PMMA-templating method exhibited polycrystallinity with three-dimensionally ordered pores. BET surface area of the synthesized MgO sample is 100.7 m 2 /g, pore volume is 0.46 cm 3 /g, wall thickness is 4-24 nm, and pore sizes are in the range of 10-120 nm. Such a 3D high-surface-area nanoporous strongly basic MgO is useful in the applications of catalyst supports and acidic gas adsorbents.

Download

Cu2O/BiVO4 heterostructures: synthesis and application in simultaneous photocatalytic oxidation of organic dyes and reduction of Cr(VI) under visible light

Chemical Engineering Journal

Preparation of triethylenetetramine-modified zirconosilicate molecular sieve for carbon dioxide adsorption

Environmental Progress & Sustainable Energy, 2015

ABSTRACT

Synthesis of KOH/SnO2 solid superbases for catalytic Knoevenagel condensation

Catalysis Communications, 2015

Abstract KOH/SnO 2 solid superbases of specific morphology and uniform pore structure were synthe... more Abstract KOH/SnO 2 solid superbases of specific morphology and uniform pore structure were synthesized. The SnO 2 support was prepared by reflux digestion using graphene oxide as template and employed for the loading of KOH by means of grinding and thermal treatment. With base strength of 26.5 ≤ H − − 1 , the 20 wt.%KOH/SnO 2 catalyst exhibits excellent activity in Knoevenagel condensation under mild conditions. The catalytic efficiency is closely related to the base strength and the amount of superbasic sites. The findings disclose a new route for the synthesis of versatile solid superbases using SnO 2 as supports.

Excellent catalytic performance, thermal stability, and water resistance of 3DOM Mn2O3-supported Au–Pd alloy nanoparticles for the complete oxidation of toluene

Applied Catalysis A: General, 2015

Abstract Three-dimensionally ordered macroporous (3DOM) Mn2O3-supported AuPdy alloy (xAuPdy/3DOM ... more Abstract Three-dimensionally ordered macroporous (3DOM) Mn2O3-supported AuPdy alloy (xAuPdy/3DOM Mn2O3; x = 1.0–3.8 wt%; Pd/Au molar ratio : y = 1.85, 1.92) catalysts were prepared using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods, respectively. Physicochemical properties of the samples were characterized by means of numerous techniques, and their catalytic activities were evaluated for toluene oxidation. It is found that the AuPdy alloy nanoparticles (NPs) with an particle size of 2–4 nm were uniformly dispersed on the surface of 3DOM Mn2O3, and the 3.8AuPd1.92/3DOM Mn2O3 sample performed the best: the temperature at 90% toluene conversion was 162 °C at 40,000 mL/(g h). Furthermore, the 3.8AuPd1.92/3DOM Mn2O3 sample was highly active even after calcination at 700 °C. The introduction of water vapor to the feedstock induced a positive effect on toluene oxidation over 3.8AuPd1.92/3DOM Mn2O3, but a negative effect over 1.9Au/3DOM Mn2O3 or 1.9Pd/3DOM Mn2O3. The excellent catalytic activity, thermal stability, and water resistance of 3.8AuPd1.92/3DOM Mn2O3 were associated with its good activation adsorption of oxygen on AuPd1.92 NPs and strong interaction between noble metal NPs and 3DOM Mn2O3. The 3DOM Mn2O3-supported AuPdy alloy NPs are promising industrial catalysts for efficient removal of volatile organic compounds.

An ab initio study of methane activation on lanthanide oxide

ABSTRACT

Molybdenum nitride for the direct decomposition of NO

Catalysis Letters, 2001

ABSTRACT

Substantial pretreatment effect on CO oxidation over controllably synthesized Au/FeOx hollow nanostructures via hybrid Au/β-FeOOH@SiO2

ACS Catalysis, 2013

ABSTRACT A novel synthetic strategy has been adopted to deposit Au nanoparticles (NPs) (ca. 5 nm)... more ABSTRACT A novel synthetic strategy has been adopted to deposit Au nanoparticles (NPs) (ca. 5 nm) on a hollow FeOx substrate using Au/β-FeOOH hybrid nanocrystals as the precursor. Through the encapsulation of Au/β-FeOOH by SiO2 shells and the calcination step, the Au/β-FeOOH can be transformed into Au/FeOx with the hollow structural feature. Because of the protective SiO2 shells, aggregation of the Au NPs is effectively prohibited, and the hemispherical morphology of the Au particles is essentially retained. The Au/FeOx hollow composite is obtained by removing the SiO2 shells, and the Au NPs in the final Au/FeOx hollow composite are small-sized yet stable enough because of the calcination history. The derived Au/FeOx hollow composite shows a substantial pretreatment effect on CO oxidation: with a pretreatment in the reaction feed at 180 °C for 0.5 h, the hollow Au/FeOx shows the T100 of CO oxidation decreasing from 180 to 88 °C. O2 temperature-programmed desorption and X-ray photoelectron spectroscopy characterizations revealed that the pretreatment may result in (i) the creation of electron holes in the p-type FeOx substrate and electron deficiency of Au nanoparticles as well as a strong Au–FeOx interaction; (ii) appropriate coverage of oxygen adspecies on the Au NPs; and (iii) increased surface oxygen density, especially at the Au–FeOx boundary region, as a result of the spillover effect of oxygen adspecies from Au NPs. All of these features are responsible for an overall enhanced activity of CO oxidation and better durability of the Au/FeOx hollow composite.

Synthesis, Microwave Electromagnetic, and Microwave Absorption Properties of Twin Carbon Nanocoils

The Journal of Physical Chemistry C, 2008

A Detailed Theoretical Treatment of the Partial Oxidation of Methane to Syngas on Transition and Coinage Metal (M) Catalysts (M = Ni, Pd, Pt, Cu)

The Journal of Physical Chemistry A, 1998

This paper presents a detailed theoretical treatment of the partial oxidation of methane to synga... more This paper presents a detailed theoretical treatment of the partial oxidation of methane to syngas (OMS) on transition and coinage metal (M) catalysts (M) Ni, Pd, Pt, Cu). The adsorption energies for a number of intermediates in the dissociation of methane on the metals were calculated using medium sized cluster models of 7-13 atoms. Reaction energies for methane dissociation, syngas formation, and byproduct generation were determined. The activation energies were estimated by means of the analytic BOC-MP formula. On the basis of these results, several significant aspects involved in the OMS on the metal catalysts have been elucidated. (1) The total dissociation energy (D e) for the complete dissociation of methane to give surface carbon and hydrogen (CH 4,s f C s + 4H s) can be regarded as a measure for the activity of the metal in methane dissociation. The order of the calculated D e 's is consistent with the order of methane conversions over the metals. (2) In the presence of coadsorbed oxygen, oxygen at metal on-top site increases the adsorption energy of H and promotes methane dehydrogenation. Oxygen at the hollow site may or may not promote methane dehydrogenation, depending on the metal. (3) For the possible reactions for the coupling of the intermediates on the metal surfaces, CH x,s + CH x,s f C 2 H 2x,s , the trend in the calculated combination energies is in agreement with experimental observation.

Download

Synthesis and magnetic properties of carbon-coated Ni/SiO2 core/shell nanocomposites

Science in China Series G: Physics, Mechanics and Astronomy, 2009

ABSTRACT A simple method for the synthesis of carbon-coated Ni/SiO2 core/shell nanocomposites is ... more ABSTRACT A simple method for the synthesis of carbon-coated Ni/SiO2 core/shell nanocomposites is reported. The Ni nanoparticles were coated with silica layers via a combined procedure of sol-gel fabrication and hydrogen reduction prior to carbon coating via acetylene decomposition at an appropriate temperature. It was found that the anti-acid ability of the Ni/SiO2 composites was greatly enhanced after carbon coating. The results of magnetization measurement show that the real part (μ′) of complex permeability of the as-obtained sample is almost independent of frequency, and the imaginary part (μ″) stays small up to a frequency of 1 GHz. The encapsulation of Ni particles with SiO2 results in the rise of Ni nanoparticles resistivity. The outcome is the reduction in effect of eddy current at high frequency, making the real part μ′ almost constant and the imaginary part μ″ very small. Thus, this simple method may be effective for preparing composites of soft magnetic properties, especially in the high-frequency range.

Enhanced exchange bias and coercivity arising from heterojunctions in Ni–NiO nanocomposites

Physical Chemistry Chemical Physics, 2014

Photo-degradation catalyst screening by high throughput experiments

Journal of Molecular Catalysis A: Chemical, 2006

... a Department of Chemical Engineering, Hunan University, 410082 China. b Department of Chemist... more

Pd-, Pt-, and Rh-Loaded Ce0.6Zr0.35Y0.05O2 Three-Way Catalysts: An Investigation on Performance and Redox Properties

Journal of Catalysis, 2002

The redox behaviors, oxygen mobilities, and oxygen storage capacities of Ce 0.6 Zr 0.4 O 2 (CZ), ... more The redox behaviors, oxygen mobilities, and oxygen storage capacities of Ce 0.6 Zr 0.4 O 2 (CZ), Ce 0.6 Zr 0.35 Y 0.05 O 2 (CZY), and 0.5 wt% M/CZY (M = Pd, Pt, Rh) as well as the three-way catalytic performance of the noble metal-loaded CZY materials have been investigated. It is observed that at a space velocity of 60,000 h −1 and in an atmosphere close to the theoretical air-to-fuel ratio (i.e., 14.6), the CZY-supported precious metal catalysts showed good threeway catalytic activity. X-ray diffraction investigations revealed that there are two phases (cubic Ce 0.75 Zr 0.25 O 2 , major; cubic ZrO 1.87 , minor) in CZ, CZY, and 0.5 wt% M/CZY. These materials are porous and large in surface area. According to the results of Ce 3d X-ray photoelectron spectroscopic studies, the doping of Y 3+ ions into the CZ lattice would cause the concentrations of oxygen vacancies and Ce 3+ ions to increase. The results of H 2 (or CO)-O 2 titration and temperature-programmed reduction-reoxidation experiments indicate the presence of a reversible redox behavior of Ce 4+ /Ce 3+ couples. The results of 18 O/ 16 O isotope exchange studies show that in the presence of oxygen vacancies and noble metals, the mobility of lattice oxygen on/in CZY is promoted. Based on the above outcomes, we suggest that by incorporating Y 3+ ions into CZ and loading Pd, Pt, or Rh on CZY, one can enhance (i) lattice oxygen mobility, (ii) Ce 3+ ion concentration, and (iii) oxygen uptake capacity of the CZY solid solution, generating a class of materials suitable for the catalytic conversion of automotive exhaust.

Download

A Comparison of BaF2/La2O3and BaBr2/La2O3Catalysts for the Oxidative Coupling of Methane

Journal of Catalysis, 1996

The 10 mol% BaBr 2 /La 2 O 3 catalyst is superior to the 10 mol% BaF 2 /La 2 O 3 catalyst in CH 4... more The 10 mol% BaBr 2 /La 2 O 3 catalyst is superior to the 10 mol% BaF 2 /La 2 O 3 catalyst in CH 4 conversion but slightly inferior in C 2 selectivity. At 750 • C, the former has a CH 4 conversion of 44.7% and a C 2 selectivity of 40.5% (C 2 yield = 18.1%); whereas the latter has a CH 4 conversion of 27.0% and a C 2 selectivity of 43.7% (C 2 yield = 11.8%). The halide ions behave very differently in the two catalysts. The Br − ions disperse on La 2 O 3 while the F − ions diffuse into the La 2 O 3 lattice, leading to the formation of hexagonal LaF 3 and rhombohedral LaOF. In situ Raman studies of the two catalysts confirmed the generation of BaCO 3 and La 2 O 2 CO 3 during OCM reactions. The BaBr 2 /La 2 O 3 catalyst has higher CO 2 adsorption capacity and is superior to BaF 2 /La 2 O 3 in forming the crystal phase of hexagonal La 2 O 2 CO 3 as well as forming O n− 2 (1 < n < 2)ions in oxygen. We conclude that the dispersion of Br − ions on the surface has enhanced the basicity of the catalyst. Consequently, both H-abstraction ability and CO 2 adsorption capability of the catalyst increase. The novel role of Br − ions is to destabilize the La 2 O 2 CO 3 being formed. Influenced by the presence of Br − ions, the La 2 O 2 CO 3 formed in OCM conditions decomposes at 690 • C instead of 790 • C. We speculate that the weakening of CO bonds in CO 2− 3 is due to the delocalization of Br − electron into the π * orbital of CO 2− 3. During OCM reactions above 690 • C, decomposition and formation of CO 2− 3 occur simultaneously and randomly in the crystal frame of hexagonal La 2 O 2 CO 3 , creating active sites which are beneficial for methane activation.

Download

Hole-Doped La1.85Sr0.15CuO4–δXσ(X=F, Cl) and Electron-Doped Nd1.85Ce0.15CuO4–δXσ Halo-Oxide Catalysts for the Selective Oxidation of Ethane to Ethene

Journal of Catalysis, 2001

The catalytic performance and characterization of Ln 1.85 A 0.15 CuO 4-δ and Ln 1.85 A 0.15 CuO 4... more The catalytic performance and characterization of Ln 1.85 A 0.15 CuO 4-δ and Ln 1.85 A 0.15 CuO 4-δ X σ (Ln = La, Nd; A = Sr, Ce; X = F, Cl) for the oxidative dehydrogenation of ethane (ODE) to ethene have been investigated. The hole-doped catalysts performed better than the electron-doped ones. Under the reaction conditions of temperature, 660 • C; C 2 H 6 /O 2 /N 2 molar ratio, 2/1/3.7; and contact time, 1.67 × 10 −4 h g mL −1 ; La 1.85 Sr 0.15 CuO 3.930 Cl 0.053 showed 82.8% C 2 H 6 conversion, 73.2% C 2 H 4 selectivity, and 60.6% C 2 H 4 yield; Nd 1.85 Ce 0.15 CuO 3.981 F 0.092 showed 72.1% C 2 H 6 conversion, 61.8.0% C 2 H 4 selectivity, and 44.6% C 2 H 4 yield. The sustainable performance during a period of 60 h on-stream reaction at 660 • C demonstrated that the F-and Cl-doped catalysts are durable. The results of X-ray powder diffraction indicated that the Sr-substituted cuprates were of T structure whereas the Ce-doped cuprates were of T structure. The results of X-ray photoelectron spectroscopic (XPS) studies revealed that there were Cu 2+ and Cu 3+ in the Sr-doped cuprate catalysts and Cu + and Cu 2+ in the Ce-doped cuprate catalysts. The results of the XPS, thermogravimetric analysis (TGA), and 18 O 2-pulsing studies demonstrated that the incorporation of halide ions into the Ln 1.85 A 0.15 CuO 4-δ lattice promoted the activity of lattice oxygen. By comparing the results of XPS, TGA, and O 2 temperature-programmed desorption with the catalytic performance of the catalysts, we conclude that (i) lattice O 2− species at the surface are active for the selective oxidation of ethane; (ii) in excessive amount, O − species accommodated in oxygen vacancies are prone to induce the total oxidation of ethane; and (iii) a suitable Cu 3+ or Cu + concentration and/or oxygen nonstoichiometry in Ln 1.85 A 0.15 CuO 4-δ X σ are required for the best catalytic performance of the catalysts.

Download

The Making and Characterization of BaO- and BaCl2-Promoted Y2O3Catalysts for the OCM Reaction

Journal of Catalysis, 1997

ABSTRACT

Synthesis and abnormal photoluminescence of core/shell structured Fe∕ZnO nanoparticles

Journal of Applied Physics, 2008

ABSTRACT Core/shell Fe/ZnO nanocomposite with average diameter of 200 nm has been synthesized suc... more ABSTRACT Core/shell Fe/ZnO nanocomposite with average diameter of 200 nm has been synthesized successfully by means of a combined sol-gel/reduction method. The saturation magnetization of the Fe/ZnO samples is relatively high due to the core α-Fe particles. According to the transmission electron microscopy image, the Fe nanoparticles are coated with a thin shell of ZnO. Being encapsulated, the nanoparticles are stable in ambient environment. The photoluminescence spectrum recorded at room temperature display ultraviolet band at 390 nm as well as three broader bands at 522, 635, and 700 nm in the region of green to infrared. Such phenomena differ from those reported in previous publications.

The synthesis of novel ZnO microcrystals through a simple solvothermal method and their optical properties

Journal of Alloys and Compounds, 2011

Preparation of Nanosized Silicalite-1 and Its Application in Vapor-Phase Beckmann Rearrangement of Cyclohexanone Oxime

Industrial & Engineering Chemistry Research, 2012

ABSTRACT Series of silicalite-1 catalysts with particle size varying from 50 to 450 nm were synth... more ABSTRACT Series of silicalite-1 catalysts with particle size varying from 50 to 450 nm were synthesized by hydrothermal method using tetrapropylammonium hydroxide as a template and l-lysine as an additive. The crystal size of silicalite-1 could be easily controlled by regulating the amount of l-lysine. The series of silicalite-1 and their NaOH-modified derivatives were examined as catalysts for vapor-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam in the 330–390 °C range. It was found that the crystal size of silicalite-1 has an effect on catalytic activity, ε-caprolactam selectivity, and catalyst stability. With a decline in crystal size, there was improvement of catalytic activity and catalyst stability. It is deduced that silicalite-1, of a smaller crystal size, is less inclined to pore blocking by coke and hence has better resistance to deactivation.

Facile route using highly arrayed PMMA spheres as hard template for the fabrication of 3D ordered nanoporous MgO

Chinese Journal of Chemical Physics, 2007

Download

Cu2O/BiVO4 heterostructures: synthesis and application in simultaneous photocatalytic oxidation of organic dyes and reduction of Cr(VI) under visible light

Chemical Engineering Journal

Preparation of triethylenetetramine-modified zirconosilicate molecular sieve for carbon dioxide adsorption

Environmental Progress & Sustainable Energy, 2015

ABSTRACT

Synthesis of KOH/SnO2 solid superbases for catalytic Knoevenagel condensation

Catalysis Communications, 2015