Three-Dimensional Mesoporous Ni-CeO2 Catalysts with Ni Embedded in the Pore Walls for CO2 Methanation

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation.

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Oxidative Coupling of Methane over Mn2O3-Na2WO4/SiC Catalysts

Catalysts ◽

10.3390/catal9040363 ◽

2019 ◽

Vol 9 (4) ◽

pp. 363

Author(s):

Jieun Kim ◽

La-Hee Park ◽

Jeong-Myeong Ha ◽

Eun Duck Park

Keyword(s):

Electron Microscopy ◽

High Temperatures ◽

Oxidative Coupling ◽

Exothermic Reaction ◽

Nitrogen Adsorption ◽

Catalytic Performance ◽

Oxidative Coupling Of Methane ◽

X Ray Diffraction ◽

Transmission Electron ◽

Adsorption Desorption

The oxidative coupling of methane (OCM) is operated at high temperatures and is a highly exothermic reaction; thus, hotspots form on the catalyst surface during reaction unless the produced heat is removed. It is crucial to control the heat formed because surface hotspots can degrade catalytic performance. Herein, we report the preparation of Mn2O3-Na2WO4/SiC catalysts using SiC, which has high thermal conductivity and good stability at high temperatures, and the catalyst was applied to the OCM. Two Mn2O3-Na2WO4/SiC catalysts were prepared by wet-impregnation on SiC supports having different particle sizes. For comparison, the Mn2O3-Na2WO4/SiO2 catalyst was also prepared by the same method. The catalysts were analyzed by nitrogen adsorption–desorption, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The transformation of SiC into α-cristobalite was observed for the Mn2O3-Na2WO4/SiC catalysts. Because SiC was completely converted into α-cristobalite for the nano-sized SiC-supported Mn2O3-Na2WO4 catalyst, the catalytic performance for the OCM reaction of Mn2O3-Na2WO4/n-SiC was similar to that of Mn2O3-Na2WO4/SiO2. However, only the surface layer of SiC was transformed into α-cristobalite for the micro-sized SiC (m-SiC) in Mn2O3-Na2WO4/m-SiC, resulting in a SiC@α-cristobalite core–shell structure. The Mn2O3-Na2WO4/m-SiC showed higher methane conversion and C2+ yield at 800 and 850 °C than Mn2O3-Na2WO4/SiO2.

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Selective Catalytic Reduction of NO with NH3 over Ce-W-Ti Oxide Catalysts Prepared by Solvent Combustion Method

Applied Sciences ◽

10.3390/app8122430 ◽

2018 ◽

Vol 8 (12) ◽

pp. 2430 ◽

Cited By ~ 1

Author(s):

Xinbo Zhu ◽

Yaolin Wang ◽

Yu Huang ◽

Yuxiang Cai

Keyword(s):

Selective Catalytic Reduction ◽

Catalytic Reduction ◽

Space Velocity ◽

Combustion Method ◽

Catalytic Performance ◽

Solution Combustion ◽

X Ray ◽

Nh3 Scr ◽

Scr Of No ◽

Temperature Programmed

In this work, a series of Ce-W-Ti catalysts were synthesized using a solution combustion method for the selective catalytic reduction (SCR) of NO with NH3 at low temperatures. The reaction performance of NH3-SCR of NO was significantly improved over the Ce-W-Ti catalysts compared to Ce0.4Ti and W0.4Ti catalysts, while Ce0.2W0.2Ti showed the best activity among all the samples. The Ce0.2W0.2Ti catalyst exhibited over 90% removal of NO and 100% N2 selectivity in the temperature range of 250–400 °C at a gas hourly space velocity (GHSV) of 120,000 mL·g−1·h−1. The Ce-W-Ti catalysts were characterized using N2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectrometry and temperature programmed desorption of NH3 to establish the structure-activity relationships of the Ce-W-Ti catalysts. The excellent catalytic performance of the Ce0.2W0.2Ti catalyst could be associated with the larger specific surface area, highly dispersed Ce and W species, increased amount of surface adsorbed oxygen (Oads) and enhanced total acidity on the catalyst surfaces.

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The Different Morphology of Co3O4 Catalysts and Application in the Abatement of Carbon Monoxide

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.19527 ◽

2021 ◽

Vol 21 (12) ◽

pp. 6082-6087

Author(s):

Chih-Wei Tang ◽

Hsiang-Yu Shih ◽

Ruei-Ci Wu ◽

Chih-Chia Wang ◽

Chen-Bin Wang

Keyword(s):

Carbon Monoxide ◽

Catalytic Activity ◽

Co Oxidation ◽

Nitrogen Adsorption ◽

Catalytic Performance ◽

Precipitation Method ◽

X Ray Diffraction ◽

X Ray ◽

Temperature Programmed ◽

Adsorption Desorption

The increase of harmful carbon monoxide (CO) caused by incomplete combustion can affect human health even lead to suffocation. Therefore reducing the CO discharged by vehicles or factories is urgent to improve the air quality. The spinel cobalt (II, III) oxide (Co3O4) is an active catalyst for CO abatement. In this study, we tried to fabricate dispersing Co3O4 via the dispersion-precipitation method with acetic acid, formic acid, and oxalic acid as the chelating dispersants. Then, the asprepared samples were calcined at 300 ºC for 4 h to obtain active catalysts, and assigned as Co(A), Co(F) and Co(O) respectively, the amount of the dispersants used are labeled as I (0.12 mole), II (0.03 mole) and III (0.01 mole). For comparison, another CoAP sample was prepared via alkaliinduced precipitation and calcined at 300 ºC. All samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscope (SEM), and nitrogen adsorption/desorption system, and the catalytic activity focused on the CO oxidation. The influence of chelating dispersant on the performance of abatement of CO was pursued in this study. Apparently, the results showed that the chelating dispersant can influence the catalytic activity of CO abatement. An optimized ratio of dispersant can improve the performance, while excess dispersant lessens the surface area and catalytic performance. The series of Co(O) samples can easily donate the active oxygen since the labile Co–O bonding and indicated the preferential performance than both Co(A) and Co(F) samples. The nanorod Co(O)-II showed preferential for CO oxidation, T50 and T90 approached 96 and 127 ºC, respectively. Also, the favorable durability of Co(O)-II sample maintains 95% conversion still for 50 h at 130 ºC and does not emerge deactivation.

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Catalytic oxidation of CO over CuO/CeO2 nanocomposites synthesized via solution combustion method: effect of fuels

REVIEWS ON ADVANCED MATERIALS SCIENCE ◽

10.1515/rams-2020-0002 ◽

2020 ◽

Vol 59 (1) ◽

pp. 131-143 ◽

Cited By ~ 1

Author(s):

Thanh Son Cam ◽

Tatyana Alekseevna Vishnievskaia ◽

Vadim Igorevich Popkov

Keyword(s):

Low Temperature ◽

Co Oxidation ◽

Combustion Method ◽

X Ray Diffraction ◽

Solution Combustion ◽

Solution Combustion Method ◽

X Ray ◽

Low Temperature Co Oxidation ◽

Temperature Programmed ◽

Adsorption Desorption

AbstractA series of CuO/CeO2 catalysts were successfully synthesized via solution combustion method (SCS) using different fuels and tested for CO oxidation. The catalysts were characterized by energy-dispersive X-ray analysis (EDXA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), N2 adsorption-desorption isotherms and H2 temperature-programmed reduction (H2-TPR). It was found that the used fuels strongly affected the characterization and the low-temperature reduction behavior of CuO/CeO2 catalysts. The CuO/CeO2-urea catalyst exhibited higher catalytic activity toward CO oxidation (t50=120∘C, t100=159∘C) than the 5 other synthesized catalysts. In addition, the CuO/CeO2-urea catalyst displayed high stability for CO oxidation during five cycles and water resistance. The enhanced catalytic CO oxidation of the synthesized samples can be attributed by a combination of factors, such as smaller crystallite size, higher specific surface area, larger amount of amorphous copper(II) oxide, more mesoporous and uniform spherical-like structure. These findings are worth considering in order to continue the study of the CuO/CeO2 catalyst with low-temperature CO oxidation.

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Nanoparticles of Ni-Co Alloy Derived from Layered Double Hydroxides and Their Catalytic Performance for CO Methanation

NANO ◽

10.1142/s1793292016501186 ◽

2016 ◽

Vol 11 (10) ◽

pp. 1650118 ◽

Cited By ~ 6

Author(s):

Jingge Liu ◽

Ang Cao ◽

Jing Si ◽

Lihong Zhang ◽

Qinglan Hao ◽

...

Keyword(s):

Metallic Nanoparticles ◽

Carbon Deposition ◽

Catalytic Performance ◽

X Ray Diffraction ◽

Co Methanation ◽

Transmission Electron ◽

Temperature Programmed ◽

The Stability ◽

Double Hydroxides ◽

Adsorption Desorption

Sintering of the active metallic nanoparticles and carbon deposition are the key problems faced for CO methanation catalysts. For overcoming those problems, bimetallic nanocatalyst is a promising route. In this work, a series of Al2O3 supported Ni-Co alloy catalysts were prepared by reducing NiCoAl layered double hydrotalcite (LDHs), and characterized with X-ray diffraction (XRD), temperature programmed reduction TPR, N2 adsorption-desorption, transmission electron microscopy (TEM) and temperature programed oxidation (TPO) techniques. The resultant catalysts were mesoporous with nanoparticles of Ni-Co alloy ranging from 7.9[Formula: see text]nm to 9.2[Formula: see text]nm which were highly dispersed in alumina matrix. The sample Ni7Co3-Al2O3 catalysts showed very good catalytic performance during the stability test at 500/600[Formula: see text]C for 300[Formula: see text]h, meanwhile exhibited excellent anti-sintering ability and anti-carbon deposition ability, owing to the formation of Ni-Co alloy and the feature of LDHs. This strategy for improving anti-sintering and anti-carbon deposition should be extendable for catalysts of other reactions.

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SBA-15 Supported Bimetallic Catalysts for Enhancement Isomers Production During n-Heptane Decomposition

International Journal of Chemical Reactor Engineering ◽

10.1515/ijcre-2013-0120 ◽

2014 ◽

Vol 12 (1) ◽

pp. 345-354 ◽

Cited By ~ 10

Author(s):

Talib M. Albayati ◽

Aidan M. Doyle

Keyword(s):

Electron Microscopy ◽

Bimetallic Catalysts ◽

Flow Reactor ◽

Heterogeneous Reaction ◽

Plug Flow ◽

Nitrogen Adsorption ◽

Catalytic Performance ◽

X Ray Diffraction ◽

Transmission Electron ◽

Adsorption Desorption

Abstract Santa Barbara Amorphous (SBA)-15 supported 1% (Pt–Ni), 1% (Pt–Co) and 1% (Ni–Co) bimetallic catalysts in a heterogeneous reaction for enhancement hydroisomerization and hydrocracking production during reforming or decomposition of n-heptane. The structural and textural features of the nanoporous silicas, both with and without encapsulated nanoparticles, were characterized using small-angle X-ray diffraction, scanning electron microscopy, EDAX, nitrogen adsorption–desorption porosimetry (Brunauer–Emmett–Teller) surface area analysis, Fourier-transform infrared spectroscopy and transmission electron microscopy. The catalytic performance was evaluated at 250–400°C under atmospheric pressure in a plug-flow reactor in a catalyst testing rig under tightly controlled conditions of temperature, reactant flow rate and pressure. The species leaving the reactor were analysed by Gas Chromatography. The results show that 1% (Pt–Ni)/SBA-15, 1% (Pt–Co)/SBA-15 and 1% (Ni–Co)/SBA-15 had a high activity for conversion of n-heptane (around 85%). The selectivity of isomerization is not high, so further studies have to be carried out in the future.

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Rapid Synthesis of Eu2Zr2O7 Nanocrystals via Salt-Assistant Combustion Method

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.79-82.405 ◽

2009 ◽

Vol 79-82 ◽

pp. 405-408

Author(s):

Yu Ping Tong ◽

Chang Yong Li ◽

Shun Bo Zhao

Keyword(s):

Low Cost ◽

Three Dimensional ◽

Combustion Method ◽

Treatment Temperature ◽

Fluorescent Properties ◽

Solution Combustion ◽

Excitation Spectra ◽

Transmission Electron ◽

Average Size ◽

20 Nm

Eu2Zr2O7 nanocrystals with cubic structure were successfully synthesized by salt-assistant combustion method. The Eu2Zr2O7 nanocrystals were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Emission/ excitation spectra. The effect of thermal treatment temperature on the crystal size of nanocrystals was studied. The results indicated that Eu2Zr2O7 nanocrystals obtained by this method were well-dispersed and uniform in particle size distribution with average size of 20 nm. By comparison, it was found that the introduction of KCl in the solution combustion reaction process can effectively prevent nanocrystallites from sintering and forming inseparable three-dimensional network, and result in the formation of well-dispersed nanoparticles. The method provides a convenient, low-cost and nontoxic route for the synthesis of nanostructures of oxide materials. Moreover, the strong fluorescent property of the Eu2Zr2O7 nanocrystals obtained by salt-assistant combustion method at 385 nm upon excitation was measured at room temperature. The results showed that Eu2Zr2O7 nanocrystals obtained by salt-assistant combustion method put up excellent fluorescent properties.

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Texture Evaluation of Sol-Gel Derived Mesoporous Bioactive Glass

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.284-287.230 ◽

2013 ◽

Vol 284-287 ◽

pp. 230-234

Author(s):

Yu Jen Chou ◽

Chi Jen Shih ◽

Shao Ju Shih

Keyword(s):

Surface Area ◽

Calcination Temperature ◽

High Surface ◽

Sol Gel ◽

High Surface Area ◽

Nitrogen Adsorption ◽

Bioactive Glasses ◽

Transmission Electron ◽

Sol Gel Process ◽

Adsorption Desorption

Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.

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NANOSEEDING EFFECT IN ZSM-5 CRYSTALLIZATION PROCESS

NANO ◽

10.1142/s1793292013500276 ◽

2013 ◽

Vol 08 (03) ◽

pp. 1350027

Author(s):

YI LU ◽

NAI-QIAN ZHANG ◽

QIN TONG ◽

JIN-KU LIU ◽

DAN-JING HONG

Keyword(s):

Crystallization Process ◽

Nitrogen Adsorption ◽

Particle Size Effect ◽

Isomerization Reaction ◽

Transmission Electron Micrograph ◽

Electron Micrograph ◽

X Ray Diffraction ◽

Transmission Electron ◽

Induction System ◽

Temperature Programmed

ZSM-5 zeolites were hydrothermally synthesized in three different seeding pathways under the direction of tetrapropylammonium bromide (TPABr) template. In order to investigate the seeding effect in ZSM-5 crystallization process, ZSM-5 crystals and pre-fabricated MFI-type nanoseeds were added into the original self-induction system, respectively. The final ZSM-5 zeolites were systematically investigated based on XRD (X-ray diffraction), SEM (scanning electron micrograph), TEM (transmission electron micrograph), nitrogen adsorption characterizations and NH3 -TPD (ammonia-temperature programmed desorption). The self-induction system produced ca. 20 μm ZSM-5 zeolite displaying hexagonally uniform prisms. After the addition of ZSM-5 crystal seeds, the crystal sizes were decreased greatly to ca. 5 μm. When MFI-type nanoseeds were adopted, irregular aggregate particles consisting of 20–50 nm primary particles were rapidly synthesized. The varied hydrothermal crystallization kinetics of the three synthesis system was also explored. Adjusting the seed agents alone, ZSM-5 crystals with diverse structural, morphological, textural and hydrothermal behaviors could be fabricated conveniently. The three ZSM-5 zeolites loaded by 0.05 wt.% Pt were assessed for the xylene isomerization reaction to investigate the particle size effect on the catalytic properties.

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Porosity Design of Shaped Zeolites for Improved Catalyst Lifetime in the Methanol-to-Hydrocarbons Reaction

Catalysts ◽

10.3390/catal9060545 ◽

2019 ◽

Vol 9 (6) ◽

pp. 545 ◽

Cited By ~ 2

Author(s):

Rogéria Bingre ◽

Renna Li ◽

Qiang Wang ◽

Patrick Nguyen ◽

Thomas Onfroy ◽

...

Keyword(s):

Pore Volume ◽

Active Sites ◽

Coke Formation ◽

Effective Diffusivity ◽

Nitrogen Adsorption ◽

Breakthrough Time ◽

Methanol To Hydrocarbons ◽

Catalytic Stability ◽

Temperature Programmed ◽

Adsorption Desorption

Additional porosity, such as meso- and macropores, was introduced in zeolite extrudates with the intention intuit of improving the effective diffusivity of the catalysts. The samples were characterized in depth by nitrogen adsorption-desorption, mercury intrusion porosimetry, ammonia temperature programmed desorption and adsorption of pyridine followed by infrared spectroscopy. The results revealed no significant change in the acidity but an increase of the pore volume. According to significant improvement in the effective diffusivity, the samples were tested in the methanol-to-hydrocarbons reaction. The catalytic stability was greatly enhanced with an increase in the pore volume, demonstrating a relation between effective diffusivity and resistance to deactivation by coke formation. Further experiments also revealed a higher toluene adsorption capacity and a raise in the breakthrough time over the most porous samples due to better accessibility of toluene molecules into the active sites of the zeolite.

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