scholarly journals A Rational Design of the Sintering-Resistant Au-CeO2 Nanoparticles Catalysts for CO Oxidation: The Influence of H2 Pretreatments

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 1952 ◽  
Author(s):  
Yuqi Sun ◽  
Wei Liu ◽  
Miao Tian ◽  
Liguo Wang ◽  
Zhongpeng Wang
Keyword(s):  
Thermal Stability ◽  
Co Oxidation ◽  
Noble Metal ◽  
Rational Design ◽  
Co Adsorption ◽  
Precipitation Method ◽  
Au Nps ◽  
Metal Support Interaction ◽  
H2 Pretreatment ◽  
Thermal Stability Of

The redox pretreatment of samples is one of the crucial ways of altering the catalytic properties of the supported noble metal materials in many heterogeneous reactions. Here, H2-reducing pretreatment is reported to enhance the thermal stability of Au-CeO2 catalysts prepared by the deposition–precipitation method and calcination at 600 °C for CO oxidation. In order to understand the improved activity and thermal stability, a series of techniques were used to characterize the physico-chemical changes of the catalyst samples. H2 pretreatment may lead to: (i) a strong metal–support interaction (SMSI) between Au nanoparticles (NPs) and CeO2, evidenced by the particular coverage of Au NPs by CeO2, electronic interactions and CO adsorption changes. (ii) the production of surface bicarbonates which can accelerate CO oxidation. As a result, the H2 pretreatment makes the Au NPs more resistant to sintering at high temperature and enhances the CO oxidation activity. Furthermore, this reduction pretreatment strategy may provide a potential approach to enhance the thermal-stability of other supported noble metal catalysts.

scholarly journals Zinc stearate from galvanizing waste materials and its use as thermal stabilizer in PVC industries

2016 ◽  
Vol 51 (4) ◽  
pp. 261-270
Author(s):  
FK Rony ◽  
SK Ray ◽  
A Hoque ◽  
M Asaduzzaman ◽  
S Sultana ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Product Yield ◽  
Zinc Stearate ◽  
Waste Materials ◽  
Precipitation Method ◽  
Thermal Stabilizer ◽  
Thermo Gravimetric Analyzer ◽  
Lead Zinc ◽  
Zinc Dross ◽  
Thermal Stability Of

Galvanizing industries of Bangladesh produce profuse amount of environmentally hazardous solid waste materials like zinc dross which contains significant amount of valuable zinc and harmful heavy lead. Zinc was extracted as zinc chloride (ZnCl2) from zinc dross. Zinc stearate (ZnSt2) samples were prepared by precipitation method from stearic acid, sodium hydroxide and ZnCl2 by varying the amount of the reagents and product yield found within the range 96.06-99.18%. Characteristic peaks of ZnSt2 were investigated by Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimeter (DSC) onset curve assigned accurate melting point within the range 122.84-124.03°C. Surface morphology of ZnSt2 was observed by Scanning Electron Microscope (SEM) and products had semi-crystalline structure. Thermal stability of ZnSt2 was evaluated by Thermo-gravimetric Analyzer (TGA) that complied with literature. A combination of ZnSt2 and Calcium stearate (CaSt2) at 1:1 ratio was used as thermal stabilizer in the powder commercial grade PVC resin and performed better thermal stability. The dehydrochlorination temperature of PVC with mixed stearates was 344.67±1.04°C for 10% (w/w) loading whereas for PVC, PVC with 10% (w/w) ZnSt2 and PVC with 10% (w/w) CaSt2, it was 269.83±1.04°C, 317.33±1.26°C and 323.33±2.08°C respectively.Bangladesh J. Sci. Ind. Res. 51(4), 261-270, 2016

Carbonate Apatite Bone Replacement

2013 ◽  
Vol 587 ◽  
pp. 17-20 ◽  
Author(s):  
Ishikawa Kunio
Keyword(s):  
Thermal Stability ◽  
Cell Response ◽  
Tissue Response ◽  
Precipitation Method ◽  
Carbonate Apatite ◽  
Inorganic Component ◽  
Bone Replacement ◽  
Thermal Stability Of

Inorganic component of bone is not hydroxyapatite but carbonate apatite. Although pure carbonate apatite (CO3Ap) has not been prepared due to the limited thermal stability of CO3Ap, dissolution - precipitation method using precursor block allows fabrication of pure CO3Ap. Fabrication of CO3Ap, cell response, tissue response and improvement of CO3Ap will be discussed.

scholarly journals Effect of the Preparation Method on the Physicochemical Properties and the CO Oxidation Performance of Nanostructured CeO2/TiO2 Oxides

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 847 ◽  
Author(s):  
Sofia Stefa ◽  
Maria Lykaki ◽  
Dimitrios Fragkoulis ◽  
Vasileios Binas ◽  
Pavlos K. Pandis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Co Oxidation ◽  
Rational Design ◽  
Mixed Oxides ◽  
Oxygen Storage ◽  
Precipitation Method ◽  
Stöber Method ◽  
X Ray ◽  
Oxidation Performance ◽  
The Stöber Method

Ceria-based mixed oxides have been widely studied in catalysis due to their unique surface and redox properties, with implications in numerous energy- and environmental-related applications. In this regard, the rational design of ceria-based composites by means of advanced synthetic routes has gained particular attention. In the present work, ceria–titania composites were synthesized by four different methods (precipitation, hydrothermal in one and two steps, Stöber) and their effect on the physicochemical characteristics and the CO oxidation performance was investigated. A thorough characterization study, including N2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS), transmission electron microscopy (TEM) and H2 temperature-programmed reduction (H2-TPR) was performed. Ceria–titania samples prepared by the Stöber method, exhibited the optimum CO oxidation performance, followed by samples prepared by the hydrothermal method in one step, whereas the precipitation method led to almost inactive oxides. CeO2/TiO2 samples synthesized by the Stöber method display a rod-like morphology of ceria nanoparticles with a uniform distribution of TiO2, leading to enhanced reducibility and oxygen storage capacity (OSC). A linear relationship was disclosed among the catalytic performance of the samples prepared by different methods and the abundance of reducible oxygen species.

scholarly journals Engineering Improves Enzymatic Synthesis of L-Tryptophan by Tryptophan Synthase from Escherichia coli

2020 ◽  
Vol 8 (4) ◽  
pp. 519
Author(s):  
Lisheng Xu ◽  
Fangkai Han ◽  
Zeng Dong ◽  
Zhaojun Wei
Keyword(s):  
Thermal Stability ◽  
Amino Acid ◽  
Directed Evolution ◽  
Amino Acid Residue ◽  
Rational Design ◽  
Molecular Engineering ◽  
Mutant Enzyme ◽  
Tryptophan Synthase ◽  
Mutant Library ◽  
Thermal Stability Of

To improve the thermostability of tryptophan synthase, the molecular modification of tryptophan synthase was carried out by rational molecular engineering. First, B-FITTER software was used to analyze the temperature factor (B-factor) of each amino acid residue in the crystal structure of tryptophan synthase. A key amino acid residue, G395, which adversely affected the thermal stability of the enzyme, was identified, and then, a mutant library was constructed by site-specific saturation mutation. A mutant (G395S) enzyme with significantly improved thermal stability was screened from the saturated mutant library. Error-prone PCR was used to conduct a directed evolution of the mutant enzyme (G395S). Compared with the parent, the mutant enzyme (G395S /A191T) had a Km of 0.21 mM and a catalytic efficiency kcat/Km of 5.38 mM−1∙s−1, which was 4.8 times higher than that of the wild-type strain. The conditions for L-tryptophan synthesis by the mutated enzyme were a L-serine concentration of 50 mmol/L, a reaction temperature of 40 °C, pH of 8, a reaction time of 12 h, and an L-tryptophan yield of 81%. The thermal stability of the enzyme can be improved by using an appropriate rational design strategy to modify the correct site. The catalytic activity of tryptophan synthase was increased by directed evolution.

scholarly journals The Sintering of Au Nanoparticles on Flat {100}, {111} and Zigzagged {111}-Nanofacetted Structures of Ceria and Its Influence on Catalytic Activity in CO Oxidation and CO PROX

2020 ◽  
Author(s):  
O. S. Bezkrovnyi ◽  
P. Kraszkiewicz ◽  
W. Mista ◽  
L. Kepinski
Keyword(s):  
Electron Microscopy ◽  
Thermal Stability ◽  
Catalytic Activity ◽  
Beneficial Effect ◽  
Co Oxidation ◽  
Au Nanoparticles ◽  
Ceria Support ◽  
Ceria Catalysts ◽  
Thermal Stability Of

Abstract The thermal stability of Au nanoparticles on ceria support of various morphology (nanocubes, nanooctahedra, and {111}-nanofacetted nanocubes) in oxidizing and reducing atmospheres was investigated by electron microscopy. A beneficial effect of the reconstruction of edges of ceria nanocubes into zigzagged {111}-nanofacetted structures on the inhibition of sintering of Au nanoparticles was shown. The influence of different morphology of Au particles on various ceria supports on the reducibility and catalytic activity in CO oxidation, and CO PROX of Au/ceria catalysts was also investigated and discussed. It was shown, that ceria nanocubes with flat {110} terminated edges are more suitable as a support for Au nanoparticles, used to catalyze CO oxidation, than zigzagged {111}- nanofacetted structures. Graphic Abstract

Investigation of the thermal stability of Mn ferrite particles synthesized by a modified co-precipitation method

2012 ◽  
Vol 56 (3) ◽  
pp. 568-572 ◽  
Author(s):  
ChunHui Dong ◽  
GaoXue Wang ◽  
Lei Shi ◽  
DangWei Guo ◽  
ChangJun Jiang ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Precipitation Method ◽  
Co Precipitation ◽  
Thermal Stability Of

Thermal Stability of Au-Sn/Near Noble Metal Barrier Metallization Systems

1991 ◽  
Vol 30 (Part 2, No. 6A) ◽  
pp. L1056-L1058 ◽  
Author(s):  
Osamu Wada ◽  
Tsugio Kumai
Keyword(s):  
Thermal Stability ◽  
Noble Metal ◽  
Thermal Stability Of ◽  
Metal Barrier

Effect of Mg Content on Thermal Stability of β-Tricalcium Phosphate Ceramics

2014 ◽  
Vol 604 ◽  
pp. 192-195 ◽  
Author(s):  
Kristine Salma-Ancane ◽  
Liga Stipniece ◽  
Zilgma Irbe ◽  
Marina Sokolova ◽  
Guna Krieke ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Chemical Composition ◽  
Tricalcium Phosphate ◽  
Chemical Properties ◽  
Precipitation Method ◽  
Sintering Behavior ◽  
Remarkable Effect ◽  
Mg Content ◽  
Thermal Stability Of

β-Tricalcium phosphate bioceramics with small, close to bone-like amounts of Mg were obtained by modified precipitation method and following sintering. The effect of small amounts of Mg on the thermal stability, microstructure and sintering behavior of β-tricalcium phosphate bioceramics was evaluated. Addition of small amounts of Mg, can induce a remarkable effect on the physic-chemical properties of β-TCP and therefore the chemical composition of the starting materials should be controlled.

Sign in / Sign up

Export Citation Format

Share Document