scholarly journals Influence of Synthesis Conditions on the Physicochemical Properties and Catalytic Activity of Fe/Cr-Pillared Bentonites

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Fatma Tomul
Keyword(s):  
Catalytic Activity ◽  
Physicochemical Properties ◽  
Conventional Method ◽  
Synthesis Method ◽  
Textural Properties ◽  
Xrd Analysis ◽  
Paramagnetic Resonance ◽  
Synthesis Conditions ◽  
Pillaring Solution ◽  
Adsorption Desorption

The synthesis of Fe/Cr-pillared bentonites starting from a 2% clay suspension and also from dry clay using ultrasound treatment for both the aging and the intercalation steps of the pillaring solution considerably reduces the time and the amount of water required compared with the conventional synthesis method. The catalysts were characterized using scanning electron microscopy with an energy dispersive system (SEM-EDS), powder X-ray diffraction (XRD), N2and CO2-adsorption/desorption, electron paramagnetic resonance (EPR), Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric (TG) analysis and the catalytic activity of selected samples was evaluated for the phenol oxidation reaction. The results of XRD analysis showed that delaminated Fe/Cr-pillared bentonite with d001value 68 Å was observed after intercalation a direct mixture of the pillaring solution and dry clay. The adsorption-desorption isotherm analysis showed that the samples synthesized with the proposed methodology in intercalation stage have similar textural properties and these properties do not change remarkably with synthesis conditions. In addition, the characterisation studies showed that the physicochemical properties of samples synthesized by ultrasound were comparable to those of sample synthesized by conventional method in this study. The sample synthesized by conventional method show 50% phenol conversion. This value was higher than those of samples synthesized by the ultrasound.

Preparation and Characterization of Fe2O3/ SBA-15 for Fischer-Tropsch Process

2020 ◽  
Vol 850 ◽  
pp. 144-150
Author(s):  
Agija Stanke ◽  
Valdis Kampars ◽  
Oana A. Lazar ◽  
Marius Enachescu
Keyword(s):  
Average Pore Size ◽  
Direct Synthesis ◽  
Synthesis Method ◽  
Xrd Analysis ◽  
Hexagonal Structure ◽  
Catalyst Characterization ◽  
Average Pore ◽  
Pluronic P123 ◽  
Silica Source ◽  
Adsorption Desorption

In this study Fe2O3/SBA-15 catalyst was synthesized via direct synthesis method under acidic conditions using triblock copolymer Pluronic P123 as template, tetraethyl orthosilicate as a silica source and Fe (NO3)3∙9H2O as iron source. Template was removed using extraction and calcination. The obtained catalyst was characterized using XRD analysis, WDXRF spectroscopy, N2 adsorption-desorption analysis and STEM–EDX measurements. Results of catalyst characterization showed that the synthesized Fe2O3/SBA-15 is mesoporous silica with 2D p6mm hexagonal mesostructure loaded with 15.6 wt.% Fe2O3. Average pore size was 6.95 nm, homogeneous immobilized Fe2O3 nanoparticles do not disrupt the porous hexagonal structure of the support.

scholarly journals Carbon-Supported Fe Catalysts forCO2Electroreduction to High-Added Value Products: A DEMS Study: Effect of the Functionalization of the Support

2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
S. Pérez-Rodríguez ◽  
G. García ◽  
L. Calvillo ◽  
V. Celorrio ◽  
E. Pastor ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ethylene Glycol ◽  
Surface Chemistry ◽  
Physicochemical Properties ◽  
Electrochemical Properties ◽  
Textural Properties ◽  
Carbon Support ◽  
Product Distribution ◽  
Added Value ◽  
Fe Catalysts

Vulcan XC-72R-supported Fe catalysts have been synthesised for the electroreduction of CO2to high-added value products. Catalysts were obtained by the polyol method, using ethylene glycol as solvent and reducing agent. Prior to the metal deposition, Vulcan was subjected to different oxidation treatments in order to modify its surface chemistry and study its influence on the physicochemical and electrochemical properties of the catalysts, as well as on the product distribution. The oxidation treatments of the supports modify their textural properties, but do not affect significantly the physicochemical properties of catalysts. However, DEMS studies showed that the carbon support degradation, the distribution of products, and the catalytic activity toward the CO2electroreduction reaction depend significantly on the surface chemistry of the carbon support.

CuO/CeO2 and CuO/PrO2-CeO2 Catalysts for Preferential Oxidation of CO

2013 ◽  
Vol 773 ◽  
pp. 601-605 ◽  
Author(s):  
Zhi Jun Zhao ◽  
Ruo Yu Wang ◽  
Qian Long Zhao ◽  
En Peng Wang ◽  
Hai Quan Su ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Hydrothermal Method ◽  
Surface Area ◽  
Pore Volume ◽  
Crucial Role ◽  
Textural Properties ◽  
Bet Surface Area ◽  
Oxidation Of Co ◽  
Preferential Oxidation Of Co ◽  
Adsorption Desorption

The CuO/CeO2and CuO/PrO2-CeO2catalysts were prepared by the hydrothermal method, and characterized via XRD, SEM and N2adsorption-desorption techniques. The study shows that the BET surface area and pore volume of the CuO/PrO2-CeO2catalysts increase with the increase of praseodymium content. The CuO/CeO2catalyst presents higher catalytic activity in compare with the CuO/PrO2-CeO2catalysts although the addition of praseodymium promotes textural properties of the CuO/CeO2catalysts, and it proves that the interaction of CuO and CeO2has a crucial role in CO-PROX.

Hydrothermal synthesis of Zeolite NaA from Kaolin

2019 ◽  
Vol 12 (05) ◽  
pp. 1950075 ◽  
Author(s):  
Peng Wang ◽  
Qi Sun ◽  
Yujiao Zhang ◽  
Jun Cao ◽  
Xingmao Li
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Synthesis ◽  
Synthesis Method ◽  
Textural Properties ◽  
Treatment Temperature ◽  
Low Grade ◽  
Tem Analysis ◽  
X Ray ◽  
Zeolite Naa ◽  
Adsorption Desorption

Zeolite NaA was successfully synthesized from low-grade kaolin via hydrothermal synthesis method. The properties of the zeolite NaA were characterized by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray fluorescence (XRF), scanning electron microscopy (SEM)-energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and thermogravimetry (TG)-differential thermal analysis (DTA). TEM analysis indicated the formation of body-centered cubic crystal zeolite NaA and the polycrystallinity of the zeolite NaA structure. The textural properties of the zeolite NaA were further studied by N2 adsorption-desorption technique. In addition, the TG-DTA study confirmed that the heat treatment temperature of the zeolite NaA should be controlled below 600∘C.

Internal pressure effect on cathodoluminescence enhancement of ZnS:Mn2+ synthesized by a sealed vessel

2007 ◽  
Vol 22 (10) ◽  
pp. 2838-2844 ◽  
Author(s):  
B.J. Park ◽  
W.B. Im ◽  
W.J. Chung ◽  
H.S. Seo ◽  
J.T. Ahn ◽  
...  
Keyword(s):  
Synthesis Method ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Paramagnetic Resonance ◽  
X Ray ◽  
Synthesis Conditions ◽  
Epr Signal ◽  
Xrd Patterns ◽  
Electron Paramagnetic ◽  
Mn Concentration

ZnS:Mn2+ phosphors were synthesized by a modified solid-state reaction method. In the synthesis method, a sealed vessel is used, where heat and pressure are simultaneously utilized. The effects of various synthesis conditions such as temperature, Mn concentration, and pressure on the cathodoluminescence (CL) were investigated. Among them, pressure had an effect on CL property as much as others. It was observed that CL intensities of ZnS:Mn2+ phosphors increased with the increase of pressure and the best sample showed higher intensity than that of a commercial one by 180%. X-ray diffraction (XRD) and electron paramagnetic-resonance (EPR) were used to understand the enhancement. No change of XRD patterns was observed but the full width at half-maximum (FWHM) of the most intense cubic (111) peak of ZnS:Mn2+ decreased with the increase of pressure. EPR signal intensity of Mn2+ increased with the increase of pressure. The improved crystallinity and more substitution of Zn2+ with Mn metal were believed to be responsible for the enhancement.

scholarly journals Synthesis of Ni-Modified ZSM-5 Zeolites and Their Catalytic Performance in n-Octane Hydroconversion

2020 ◽  
Vol 8 ◽  
Author(s):  
Qiang Wei ◽  
Pengfei Zhang ◽  
Xiaodong Liu ◽  
Wenbin Huang ◽  
Xiayun Fan ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Synthesis Method ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
Isomerization Selectivity ◽  
Nimo Catalysts ◽  
Adsorption Desorption

Ni-modified ZSM-5 zeolites with different nickel contents were successfully prepared by the in situ synthesis method and the impregnation method. The synthesized samples were characterized by XRD, SEM, N2 adsorption–desorption isothermals, and Py-FTIR. The characterization results show that both the textural properties and crystallization of Ni-modified ZSM-5 zeolites were preserved well, and their acidic properties can be modulated after nickel modification. The corresponding NiMo catalysts supported on Ni-modified ZSM-5 zeolites were prepared by the incipient wetness co-impregnation method, and their catalytic performances were evaluated in n-octane hydroconversion. Compared to the those modified by the in situ synthesis method, ZSM-5 zeolite-supported catalysts modified by the impregnation method exhibit higher stability and higher isomerization selectivity. This is due to the synergistic effect between Brønsted acid sites and Lewis acid sites on the Ni-modified ZSM-5 zeolites, especially for the NiMo/1Ni-Z5 catalyst.

Metal Organic Framework-Encapsulated Phosphotungstic Acid: An Effective Catalyst for Highly Efficient Acetalization of Vanillin Propylene Glycol

2020 ◽  
Vol 12 (7) ◽  
pp. 958-965
Author(s):  
Jing Liu ◽  
Xiaomin Li ◽  
Pan Chen ◽  
Yutian Mi ◽  
Jiandu Lei
Keyword(s):  
Propylene Glycol ◽  
Metal Organic Framework ◽  
Direct Synthesis ◽  
Synthesis Method ◽  
Empty Space ◽  
Synthesis Conditions ◽  
Heterogeneous Catalytic ◽  
Metal Organic ◽  
Ft Ir ◽  
Adsorption Desorption

Metal organic frameworks (MOFs) have exhibited potential for application as heterogeneous catalytic materials because they consist of empty space, which can be used for encapsulation. Encapsulation of H3PW12O40 (HPW) in MOFs, such as the fabrication of MIL-101, by direct synthesis method or impregnation has drawn significant interest. However, few researches have used MOFs as catalysts for acetalization. This study evaluates the use of HPW encapsulated in MIL-101(Cr) to make it a catalyst in the acetalization of vanillin propylene glycol. Samples fabricated using various techniques (encapsulation and impregnation) were characterized by SEM, TEM, N2 adsorption–desorption, XRD, and FT-IR. The synthesis conditions of HPW@MIL-101 and their effects on vanillin conversion were examined. The reaction kinetics was also investigated under optimal conditions. Vanillin conversion showed that introducing HPW directly into MIL-101(Cr) during synthesis induced a 14% increase, compared with impregnation. The results indicated that HPW@MIL-101(Cr) is an effective method for vanillin propylene glycol acetal production and is reusable.

Synthesis and Characterization of 5- and 6- Coordinated Alkali Pertechnetates

MRS Advances ◽  
2017 ◽  
Vol 2 (10) ◽  
pp. 525-542 ◽  
Author(s):  
Jamie Weaver ◽  
Chuck Soderquist ◽  
Paul Gassman ◽  
Eric Walter ◽  
Wayne Lukens ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Nuclear Waste ◽  
Synthesis Method ◽  
Oxide Glasses ◽  
Paramagnetic Resonance ◽  
Synthesis Conditions ◽  
Pure Compounds ◽  
Temperature Electron

ABSTRACTThe local chemistry of technetium-99 (99Tc) in oxide glasses is important for understanding the incorporation and long-term release of Tc from nuclear waste glasses, both those for legacy defense wastes and fuel reprocessing wastes. Tc preferably forms Tc(VII), Tc(IV), or Tc(0) in glass, depending on the level of reduction of the melt. Tc(VII) in oxide glasses is normally assumed to be isolated pertechnetate TcO4-anions surrounded by alkali, but can occasionally precipitate as alkali pertechnetate salts such as KTcO4and NaTcO4when Tc concentration is high. In these cases, Tc(VII) is 4-coordinated by oxygen. A reinvestigation of the chemistry of alkali-technetium-oxides formed under oxidizing conditions and at temperatures used to prepare nuclear waste glasses showed that higher coordinated alkali Tc(VII) oxide species had been reported, including those with the TcO5-and TcO6-anions. The chemistry of alkali Tc(VII) and other alkali-Tc-oxides is reviewed, along with relevant synthesis conditions.Additionally, we report attempts to make 5- and 6-coordinate pertechnetate compounds of K, Na, and Li, i.e. TcO5-and TcO6-. It was found that higher coordinated species are very sensitive to water, and easily decompose into their respective pertechnetates. It was difficult to obtain pure compounds, but mixtures of the pertechnetate and other phase(s) were frequently found, as evidenced by x-ray absorption spectroscopy (XAS), neutron diffraction (ND), and Raman spectroscopy. Low temperature electron paramagnetic resonance (EPR) measurements showed the possibility of Tc(IV) and Tc(VI) in Na3TcO5and Na5TcO6compounds.It was hypothesized that the smaller counter cation would result in more stable pertechnetates. To confirm the synthesis method, LiReO4and Li5ReO6were prepared, and their Raman spectra match those in the literature. Subsequently, the Tc versions LiTcO4and Li5TcO6were synthesized and characterized by ND, Raman spectroscopy, XANES, and EXAFS. The Li5TcO6was a marginally stable compound that appears to have the same structure as that known for Li5ReO6. Implications of the experimental work on stability of alkali technetate compounds and possible role in the volatilization of Tc are discussed.

Enhanced catalytic activity of low-Pt content nanocatalysts supported on hollow carbon spheres for the ORR in alkaline media

MRS Advances ◽  
2020 ◽  
Vol 5 (57-58) ◽  
pp. 2961-2972
Author(s):  
P.C. Meléndez-González ◽  
E. Garza-Duran ◽  
J.C. Martínez-Loyola ◽  
P. Quintana-Owen ◽  
I.L. Alonso-Lemus ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Anion Exchange ◽  
Average Particle Size ◽  
Synthesis Method ◽  
Alkaline Media ◽  
High Catalytic Activity ◽  
Average Particle ◽  
Carbon Spheres ◽  
Hollow Carbon ◽  
Hollow Carbon Spheres

In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

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