Preparation and characterization of highly active nanosized strontium-doped lanthanum cobaltate catalysts with high surface areas

2006 ◽  
Vol 51 (14) ◽  
pp. 1673-1681 ◽  
Author(s):  
Jianrong Niu ◽  
Wei Liu ◽  
Hongxing Dai ◽  
Hong He ◽  
Xuehong Zi ◽  
...  
1996 ◽  
Vol 457 ◽  
Author(s):  
Lin-chiuan Yan ◽  
Levi T. Thompson

ABSTRACTNew methods have been developed for the synthesis of high surface area cation-substituted hexaaluminates. These materials were prepared by calcining high temperature (ethanol extraction) or low temperature (CO2 extraction) aerogels at temperatures up to 1600°C. Cation-substituted hexaaluminates have emerged as promising catalysts for use in high temperature catalytic combustion. In comparing unsubstituted and cation-substituted hexaaluminates, we found that the phase transformations were much cleaner for the cation-substituted materials. BaCO3 and BaAl2O4 were intermediates during transformation of the unsubstituted materials, while the cation-substituted materials transformed directly from an amorphous phase to crystalline hexaaluminate. Moreover, the presence of substitution cations caused the transformation to occur at lower temperatures. Mn seems to be a better substitution cation than Co since the Mn-substituted materials exhibited higher surface areas and better heat resistances than the Co-substituted materials. The low temperature aerogel-derived materials possessed quite different characteristics from the high temperature aerogel-derived materials. For example, phase transformation pathways were different.


2014 ◽  
Vol 798-799 ◽  
pp. 100-105 ◽  
Author(s):  
Jocielys Jovelino Rodrigues ◽  
Liliane Andrade Lima ◽  
Gustavo Medeiros de Paula ◽  
Meiry Glaúcia Freire Rodrigues

A series of mesoporous materials have been synthesized in an acid medium, with various structures, such as SBA-15. These materials have many properties which make them potential catalysts. Among these we highlight their high surface areas and pore walls relatively thick, resulting in a greater hydrothermal stability. This work aims at the synthesis and characterization of molecular sieve SBA-15 with molar composition: 1.0 TEOS: 0.017 P123: 5.7 HCl: 193 H2O and Co/SBA-15 and catalysts for the reaction of Ru/Co/SBA-15 Fischer Tropsch process. The materials were characterized by the techniques of X-ray diffraction (XRD), chemical analysis by X-ray spectrometry, energy dispersive (EDX) and Nitrogen adsorption (BET method). X-ray diffraction showed that the calcined cobalt catalyst did not modify the structure of SBA-15 and that Co was present under the form of Co3O4 in the catalyst. The addition of cobalt in the SBA-15 decreased the specific superficial area of the molecular sieve.


2007 ◽  
Vol 7 (12) ◽  
pp. 4508-4514 ◽  
Author(s):  
Fei Gao ◽  
Yanhua Zhang ◽  
Chunling Wang ◽  
Cheng Wu ◽  
Yan Kong ◽  
...  

A series of V-Fe incorporated-SBA-15 has been synthesized by adjustment of the pH value of the gel mixtures and characterized by using XRD, N2-adsorption, ICP, FT-IR, Raman, and UV–vis techniques. Results indicated that all samples exhibited typical hexagonal arrangement of mesoporous structure with high surface areas and the heteroatoms were probably incorporated into the framework of SBA-15. Catalytic performances of the obtained materials were evaluated in the hydroxylation of phenol with H2O2, and the catalytic results revealed that the selectivity for catechol (CAT) and hydroquinone (HQ) could be controlled by adjusting the contents of V and Fe in the samples, and an appropriate nV/nFe mol ratio in SBA-15 could approach the optimal catalytic performance.


2008 ◽  
Vol 26 (9) ◽  
pp. 721-734 ◽  
Author(s):  
Sabina Beninati ◽  
Domenica Semeraro ◽  
Marina Mastragostino

The adsorption of paracetamol (PAR) and acetylsalicylic acid (ASA) onto high-surface-area, commercial activated carbons was investigated at 26°C via adsorption isotherms at different pH values, including pH 1.5 to simulate conditions existing in the stomach. A wide-ranging characterization of the carbons, including analysis of their morphology and surface chemistry, was undertaken, with the actual surface areas of the carbons available for PAR and ASA adsorption being estimated by taking the molecular sizes of the drugs into account. This provided an understanding of the differences in the drug adsorption behaviour of the carbons.


2008 ◽  
Vol 18 (5) ◽  
pp. 54894-1-54894-10 ◽  
Author(s):  
Zoran Susteric ◽  
Tomaz Kos

Abstract Rheological properties of elastomeric nanocomposites with organically modified Montmorillonite clays, as possible replacements or supplements to classical active fillers, such as carbon black or silica, have been intensively studied in recent years. Possessing large specific surface areas acquired through the melt-mixing processes of elastomeric intercalation and subsequent filler exfoliation, the clay particles have indeed proved to be highly eligible reinforcing and thermally stabilizing ingredients for application in elastomers. In fact, their performance has shown to be in many respects superior to that of classical fillers, particularly owing to some unusual, though beneficial, exhibited properties. Namely, apart from uncommonly high surface activity, manifested by creation of a host of van der Waals type secondary linkages with elastomer molecules, the main curiosity of clay filler is its dissipative action. Using dynamic mechanical functions under different deformational and temperature conditions, as means for rheological characterization of nanocomposites, the foregoing nano-scale traits are clearly reflected in substantial stiffness at low strains and, unexpectedly, dwindling energy loss with increasig filler content and/or decreasing temperature. Besides, rheological analysis of this kind, together with appropriate theoretical grounds, has enabled elucidation of peculiar conduct, as well as macroscopic insight into the very nature of secondary interactions in elastomers.


2014 ◽  
Vol 699 ◽  
pp. 163-168
Author(s):  
Nazri Murat Muhamad ◽  
Azman Miskam Muhamad ◽  
Ahmad Mohd Azmier ◽  
Zainal Alimuddin Zainal Alauddin ◽  
Zulfikar Ishak Mohammad

The wet impregnation method for catalytic microcombustor was characterized by using platinum as a catalyst. The main purpose of this study is to increase the surface porosity of the catalyst support. A high surface porosity indicates that a high amount of catalyst was deposited within the surface areas. The performance of the catalytic microcombustor improves with increasing catalytic surface area. The stainless steel catalyst support was treated with sulfuric acid solution containing polyvinyl (3.89 wt%) and propargyl alcohol (1.48 wt%). Combustion test was performed using LPG-air to test the performance of the catalyst. The surface support treated with polyvinyl (PVA) showed a higher surface porosity and combustion blow-out limit compared with propargyl alcohol. The combustion mode changes from surface to submerged combustion after the catalyst was deposited in the support surface.


2004 ◽  
Vol 848 ◽  
Author(s):  
Ang Thiam Peng ◽  
Zhong Ziyi ◽  
James Highfield

ABSTRACTA study on the comparison of porous TiO2-SiO2 mixed oxides synthesized variously via the “amine directed” method is reported. The amine capping groups were octylamine, dodecylamine, octyldecylamine, aniline, and isobutylamine. The mixed oxide is characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Brunauer-Emmett-Teller analysis (BET). While XRD, SEM and TEM provide mainly (bulk) structural information on the mixed oxide preparations, BET (N2 physisorption) probes into their surface area and texture. IR evidence suggests that intimate chemical mixing of both oxides has occurred, while BET measurements show that high surface areas are attainable and that the mixed oxide is more thermally stable than pure (control) samples of TiO2.


2019 ◽  
Vol 3 (1) ◽  
pp. 3-13 ◽  
Author(s):  
Wenhui Zeng ◽  
Calvin O. Nyapete ◽  
Alexander H.H. Benziger ◽  
Paul A. Jelliss ◽  
Steven W. Buckner

Background: There is increasing academic and industrial interest in fabricating reactive metal and metalloid nanoparticles for a number of energetics applications. Objective: Because of inherent thermodynamic instability, the greatest challenge for producing such metal nanoparticles is to kinetically stabilize their high surface areas toward reactive atmospheric constituents. Such stabilization can effectively produce nanocomposite materials that retain their high energy content or other useful properties with a respectable shelf-life. The primary focus is to summarize methods of synthesis and characterization of these energetically valuable nanoparticles. Method and Results: Method and Results: A popular and convenient method to passivate and protect reactive metal nanoparticles is to either graft pre-assembled polymer molecules to the nanoparticle surface or use the reactive nanoparticle surface to initiate and propagate oligomer or polymer growth. Conclusion: Reactive nanoparticles composed of aluminum, magnesium, zinc, titanium, or boron may be effectively passivated, capped, and protected by a variety of organic polymers. Such treatment mitigates degradation due to atmospheric reaction, while retaining the unique properties associated with the metal-polymer nanocomposites.


2021 ◽  
Author(s):  
Asfaw Gezae Daful ◽  
Meegalla R. Chandraratne ◽  
Marie Loridon

This chapter presents the most promising features and applications of biochar along with their optimal pyrolysis conditions. Biochars have a range of physicochemical properties depending on the feedstock and pyrolysis conditions, which greatly affect their wide applications. The biochar production and its characteristics, including the effect of feedstocks and different process-parameters on the properties and yield of biochar are thoroughly examined. The higher pyrolysis-temperature can give higher carbon-contents, pH, and surface-areas of biochars while volatiles and molar-ratios of O/C, H/C and N/C decrease with pyrolysis-temperature. Higher carbon-content and neutral-pH biochars have high affinity for organic pollutants due to high surface areas, making them attractive for adsorption and catalysis purposes. Biochars with higher-pH are preferred for soil application to correct soil-acidity. Thus, the pyrolysis temperature should be selected as per the final application of the biochar. Characterization of biochars of different feedstocks and pyrolysis conditions is reviewed and presented along with their proximate and ultimate analysis.


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