Toluene Degradation by Thermal Catalytic Oxidation over K-OMS-2 Catalysts

The goal of this research was to synthesize two different catalysts, namely K-OMS-2 and MnOx. The K-OMS-2 was an octahedral manganese complex prepared by hydrothermal method, while manganese oxide (MnOx) was directly synthesized by precipitation method. Both catalysts were employed to decompose toluene, an organic solvent that is widely used in industries. The catalysts were characterized by means of X-ray diffraction (XRD) and N2-physorption. The surface areas of K-OMS-2 and MnOx were 83.50 and 20.04 m2/g, respectively. The precipitation route gave XRD patterns of γ-Mn2O3 structure, and a successful structure of an octahedral molecular sieve manganese oxide was obtained by the hydrothermal method. The toluene degradation was carried out in gas hourly space velocity (GHSV) range of 20,000-60,000 h-1 with toluene concentration of 7,700 ppmv. The higher GHSV over K-OMS-2 gave the lower contact time consequently resulting in the lower %toluene degradation, whereas the best GHSV over γ-Mn2O3 was suitable at 40,000 h-1. The complete oxidation temperature of toluene over K-OMS-2 occurred at 260 °C and was lower than the temperature by γ-Mn2O3 at 300 °C. The higher surface area of K-OMS-2 may not facilitate internal toluene diffusion to active K-OMS-2 sites because molecular toluene (5.6 Å) cannot migrate through its smaller pore diameter (4.6 Å); however, the fully oxidized K-OMS-2 can provide higher average oxidation state (AOS) and higher amount of lattice oxygen assisting toluene degradation compared to γ-Mn2O3. The full factorial design of experiment (DOE) exhibited a strong effect of temperature and catalyst types on toluene removal; in contrast gas hour space velocity (GHSV) exhibited no significant effect on %toluene removal even with increasing GHSV.

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Total Oxidation of Toluene and Propane over Co3O4 Catalysts: Influence of Precipitating pH and Washing

Catalysts ◽

10.3390/catal10080900 ◽

2020 ◽

Vol 10 (8) ◽

pp. 900

Author(s):

Imane Driouch ◽

Weidong Zhang ◽

Michèle Heitz ◽

Jose Luis Valverde ◽

Anne Giroir-Fendler

Keyword(s):

Spinel Phase ◽

Space Velocity ◽

Catalytic Performance ◽

Precipitation Method ◽

Molar Ratio ◽

X Ray Diffraction ◽

Total Oxidation ◽

Ph Values ◽

Surface Areas ◽

Weight Hourly Space Velocity

A series of Co3O4 catalysts were synthesized by an ammonia precipitation method at various precipitating pH values (8.0, 8.5, 9.0, 9.5, and 10.0) and with different numbers of washings. Their performance in the total oxidation of two selected hydrocarbons, toluene and propane, was evaluated at a reactant/oxygen molar ratio of 1/210 and a Weight Hourly Space Velocity (WHSV) of 40,000 mL g−1 h−1. The physicochemical properties of the catalysts were characterized by thermogravimetric and differential thermal analysis (TG/DTA), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and N2 absorption–desorption. The results show that the catalysts are in the cubic spinel phase (Fd-3m (227), a = 8.0840 Å) with average crystalline sizes of 29−40 nm and specific surface areas of 12–20 m2 g−1. All catalysts allowed 100% conversion of both toluene and propane at temperatures below 350 °C. The precipitating pH and the number of washings were observed to significantly affect the catalytic performance. The optimal synthesis condition was established to be pH 8.5 with two washings. The best catalyst gave 100% conversion of toluene and propane at 306 °C and 268 °C, respectively.

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Structural and morphological characterization of CdS nanoparticles

Current Physical Chemistry ◽

10.2174/1877946810999200730222025 ◽

2020 ◽

Vol 10 ◽

Author(s):

Manish Dwivedi ◽

Vijay Tripathi ◽

Dhruv Kumar ◽

Dwijendra K. Gupta

Keyword(s):

Blue Shift ◽

Chemical Precipitation ◽

Morphological Characterization ◽

Precipitation Method ◽

Cds Nanoparticles ◽

Cubic Phase ◽

Simple Chemical ◽

Xrd Patterns ◽

Average Size ◽

Physical Tools

Aims: CdS nanoparticles are an attractive material having application in various field like as pigment in paints, biotag for bioimaging and many more optoelectronic as well as biological applications. Present study aims to synthesize and characterize the CdS nanoparticles to make it applicable in different areas Objectives: Preparation CdS nanoparticles by using simple and facile chemical methods and further physical and structural characterization using various physical tools Methods: In present work CdS nanoparticles has been synthesized by using rationally simple chemical precipitation method with some modi-fication on temperature and incubation time in existed methods. Characterizations were done by employing XRD, SEM, TEM, AFM tech-niques Results: Simple chemical method produces the CdS nanoparticles with the size about 100-200 nm in length and 5-10 nm in diameter. The SEM studies show that the CdS nanoparticles can agglomerate and form a continuous network like structure. The X-ray diffraction (XRD) measurements show the single-phase formation of CdS nanoparticles with the structure of cubic phase, and the broadening of XRD patterns indicates that the prepared samples are nanostructured. Our analysis on CdS nanoparticles by using transmission electron microscope and atomic force microscope (AFM) revealed that the nanoparticles form both spherical and nearly rod shaped with the average size applicable for biotagging. UV-Vis spectroscopic analysis reveals blue shift in the absorption peak probably caused by quantum confinement Conclusion: The observed CdS nanoparticles were appeared yellow in color. The XRD pattern of the CdS nanoparticles showed that the materials were of nanometric sized regime with a predominantly cubic phase along with the rod and round morphology. The study and char-acterization of CdS nanoparticles will bring us a new approach to understand biological problem by tagging nanoparticles with biomolecules and further suggests that the CdS nanoparticles formulate it more suitable biocompatible nanomaterial for biotagging and bioimaging

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Effect of Fe and Co promoters on CO methanation activity of nickel catalyst prepared by impregnation – co-precipitation method

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2020-0076 ◽

2020 ◽

Vol 18 (5-6) ◽

Author(s):

Buyan-Ulzii Battulga ◽

Tungalagtamir Bold ◽

Enkhsaruul Byambajav

Keyword(s):

Synergetic Effect ◽

Space Velocity ◽

Catalytic Performance ◽

Precipitation Method ◽

Molar Ratio ◽

Alumina Support ◽

Co Methanation ◽

Temperature Range ◽

Co Precipitation ◽

Catalyst Distribution

AbstractNi based catalysts supported on γ-Al2O3 that was unpromoted (Ni/γAl2O3) or promoted (Ni–Fe/γAl2O3, Ni–Co/γAl2O3, and Ni–Fe–Co/γAl2O3) were prepared using by the impregnation – co-precipitation method. Their catalytic performances for CO methanation were studied at 3 atm with a weight hourly space velocity (WHSV) of 3000 ml/g/h of syngas with a molar ratio of H2/CO = 3 and in the temperature range between 130 and 350 °C. All promoters could improve nickel distribution, and decreased its particle sizes. It was found that the Ni–Co/γAl2O3 catalyst showed the highest catalytic performance for CO methanation in a low temperature range (<250 °C). The temperatures for the 20% CO conversion over Ni–Co/γAl2O3, Ni–Fe/γAl2O3, Ni–Fe–Co/γAl2O3 and Ni/γAl2O3 catalysts were 205, 253, 263 and 270 °C, respectively. The improved catalyst distribution by the addition of cobalt promoter caused the formation of β type nickel species which had an appropriate interacting strength with alumina support in the Ni–Co/γAl2O3. Though an addition of iron promoter improved catalyst distribution, the methane selectivity was lowered due to acceleration of both CO methanation and WGS reaction with the Ni–Fe/γAl2O3. Moreover, it was found that there was no synergetic effect from the binary Fe–Co promotors in the Ni–Fe–Co/γAl2O3 on catalytic activity for CO methanation.

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Microstructure Characterization of Metal Mixed Oxides

MRS Advances ◽

10.1557/adv.2017.591 ◽

2017 ◽

Vol 2 (64) ◽

pp. 4025-4030 ◽

Cited By ~ 1

Author(s):

T. Kryshtab ◽

H. A. Calderon ◽

A. Kryvko

Keyword(s):

Mixed Oxides ◽

Profile Analysis ◽

Atomic Resolution ◽

Precipitation Method ◽

X Ray Diffraction ◽

Reconstruction Procedure ◽

Transmission Electron ◽

Xrd Patterns ◽

Co Precipitation

ABSTRACTThe microstructure of Ni-Mg-Al mixed oxides obtained by thermal decomposition of hydrotalcite-like compounds synthesized by a co-precipitation method has been studied by using X-ray diffraction (XRD) and atomic resolution transmission electron microscopy (TEM). XRD patterns revealed the formation of NixMg1-xO (x=0÷1), α-Al2O3 and traces of MgAl2O4 and NiAl2O4 phases. The peaks profile analysis indicated a small grain size, microdeformations and partial overlapping of peaks due to phases with different, but similar interplanar spacings. The microdeformations point out the presence of dislocations and the peaks shift associated with the presence of excess vacancies. The use of atomic resolution TEM made it possible to identify the phases, directly observe dislocations and demonstrate the vacancies excess. Atomic resolution TEM is achieved by applying an Exit Wave Reconstruction procedure with 40 low dose images taken at different defocus. The current results suggest that vacancies of metals are predominant in MgO (NiO) crystals and that vacancies of Oxygen are predominant in Al2O3 crystals.

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Characterization of Manganese Oxide/Alumina Catalysts

Adsorption Science & Technology ◽

10.1177/026361749501200306 ◽

1995 ◽

Vol 12 (3) ◽

pp. 221-229 ◽

Cited By ~ 3

Author(s):

S.A. El-Hakam

Keyword(s):

Manganese Oxide ◽

Calcination Temperature ◽

Manganese Content ◽

Textural Properties ◽

Catalytic Decomposition ◽

Experimental Conditions ◽

Surface Areas ◽

Ft Ir ◽

Mn Content ◽

Alumina Catalysts

The effect of heat treatment of manganese oxide/alumina catalysts of various manganese content on the structural and textural properties and the catalytic decomposition of hydrogen peroxide were investigated. The FT-IR results have shown that depending on the calcination temperature and metal loading MnO2 and MnO3 are formed on the investigated samples. No spinel structure was detected under the experimental conditions. The surface areas were found to decrease with increasing calcination temperature and metal content up to 30 wt.% Mn. The mean pore radius increased with both calcination temperature and Mn content. The rate of catalytic decomposition of H2O2 was found to depend on the pH, the calcination temperature and the state of Mn on the catalyst surface.

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La and/or V oxide promoted Rh/SiO2 catalysts: Effect of temperature, H2/CO ratio, space velocity, and pressure on ethanol selectivity from syngas

Journal of Catalysis ◽

10.1016/j.jcat.2010.03.019 ◽

2010 ◽

Vol 272 (2) ◽

pp. 204-209 ◽

Cited By ~ 70

Author(s):

Nachal D. Subramanian ◽

Jia Gao ◽

Xunhua Mo ◽

James G. Goodwin Jr. ◽

Walter Torres ◽

...

Keyword(s):

Space Velocity ◽

Effect Of Temperature

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Hydrothermal Synthesis of Bi1.5ZnNb1.5O7 Nanopowders

Materials Science Forum ◽

10.4028/www.scientific.net/msf.561-565.495 ◽

2007 ◽

Vol 561-565 ◽

pp. 495-498 ◽

Cited By ~ 1

Author(s):

Jin Liang Huang ◽

Xiao Wang ◽

Liu Shuan Yang ◽

Chun Wei Cui ◽

Xing Hua Yang

Keyword(s):

Reaction Time ◽

Hydrothermal Synthesis ◽

Hydrothermal Method ◽

Pyrochlore Phase ◽

Synthesis Temperature ◽

Minimum Size ◽

Hydrothermal Reactions ◽

Prolonged Reaction Time ◽

Scherrer Equation ◽

Xrd Patterns

The cubic pyrochlore phase Bi1.5ZnNb1.5O7 nanopowder was successfully synthesized by the hydrothermal method (HTM) from the starting materials: Bi(NO3)3·5H2O, ZnO, Nb2O5 and the mineralizer: KOH. The XRD patterns prove that the cubic pyrochlore phase Bi1.5ZnNb1.5O7 nanopowder can be obtained by HTM, and TEM photographs show that the powders present the regularly granular shape, when the hydrothermal reactions were conducted at synthesis temperatures 140~220°C and reaction time for 6~48h. The crystalline sizes of the powders were calculated by the Scherrer equation to be about 43~49nm. The crystalline sizes decreased both with the increase in synthesis temperature and the prolonged reaction time until they reached to the minimum size about 43nm at 220°C for 24h.However, they tended to increase when the reaction time was above 24h.

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Third Order Nonlinear Optical Characteristics of Er3+ doped BaMoO4 Nanostructures

10.21203/rs.3.rs-289218/v1 ◽

2021 ◽

Author(s):

RA sharath ◽

K Mani rahulan ◽

N Angeline Little Flower ◽

annie sujatha ◽

g vinitha ◽

...

Keyword(s):

Nonlinear Optical ◽

Continuous Wave ◽

Visible Region ◽

Chemical Precipitation ◽

Precipitation Method ◽

Third Order ◽

Fluorescence Measurements ◽

Device Applications ◽

Nonlinear Optical Device ◽

Xrd Patterns

Abstract We report the third order nonlinear optical properties of Er3+-doped BaMoO4 nanostructures, and its dependence on Er dopant concentration. BaMoO4 nanostructures with different concentration of Er were synthesized by chemical precipitation method and were characterized by UV-Vis absorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and fluorescence measurements. The incorporation of Er ions shifted the absorption band of BaMoO4 towards higher wavelength and enhanced the light absorption in the visible region. XRD patterns showed that the powders crystallize in scheelite-type tetragonal structure. The nonlinear optical behavior of the nanostructures was investigated by a Z-scan technique at 532 nm using continuous wave Nd:YAG laser. Experimental results suggested that the addition of Er can considerably enhance the nonlinear absorption and refractive index coefficients of BaMoO4 which could be used as a potential for nonlinear optical device applications.

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