Methane dry reforming over Ni catalysts supported on Ce–Zr oxides prepared by a route involving supercritical fluids

AbstractCe0.5Zr0.5O2mixed oxides were prepared in a flow reactor in supercritical isopropanol with acetylacetone as a complexing agent. Variation of the nature of the Zr salt and the temperature of synthesis affected the phase composition, morphology and specific surface area of oxides. X-ray diffraction and Raman spectroscopy studies revealed formation of metastable t” and t’ phases. Oxides are comprised of agglomerates with sizes depending on the synthesis parameters. Loading NiO decreases the specific surface area without affecting X-ray particle sizes of supports. Such sintering was the most pronounced for a support with the highest specific surface area, which resulted in the lowest surface content of Ni as estimated by X-ray photoelectron spectroscopy and in the formation of flattened NiO particles partially embedded into the support. The catalytic activity and stability of these samples in the dry reforming of methane were determined by the surface concentration of Ni and the morphology of its particle controlled by the metal-support interaction, which also depends on the type of catalyst pretreatment. Samples based on ceria-zirconia oxides prepared under these conditions provide a higher specific catalytic activity as compared with the traditional Pechini route, which makes them promising for the practical application.

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Syngas Production via CO2 Reforming of Methane Over SrNiO3 and CeNiO3 Perovskites

Energies ◽

10.3390/en14102928 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2928

Author(s):

Naushad Ahmad ◽

Fahad Alharthi ◽

Manawwer Alam ◽

Rizwan Wahab ◽

Salim Manoharadas ◽

...

Keyword(s):

Catalytic Activity ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Pore Volume ◽

Active Sites ◽

Catalyst Deactivation ◽

Dry Reforming Of Methane ◽

Volume Number ◽

Syngas Production

The development of a transition-metal-based catalyst with concomitant high activity and stability due to its distinguishing characteristics, yielding an abundance of active sites, is considered to be the bottleneck for the dry reforming of methane (DRM). This work presents the catalytic activity and durability of SrNiO3 and CeNiO3 perovskites for syngas production via DRM. CeNiO3 exhibits a higher specific surface area, pore volume, number of reducible species, and nickel dispersion when compared to SrNiO3. The catalytic activity results demonstrate higher CH4 (54.3%) and CO2 (64.8%) conversions for CeNiO3, compared to 22% (CH4 conversion) and 34.7% (CO2 conversion) for SrNiO3. The decrease in catalytic activity after replacing cerium with strontium is attributed to a decrease in specific surface area and pore volume, and nickel active sites covered with strontium carbonate. The stability results reveal the deactivation of both the catalysts (SrNiO3 and CeNiO3) but SrNiO3 showed more deactivation than CeNiO3, as demonstrated by deactivation factors. The catalyst deactivation is mainly attributed to carbon deposition and these findings are verified by characterizing the spent catalysts.

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Influence of Pluronic® P123 Addition in the Synthesis of Bulk Ni Promoted MoS2 Catalyst. Application to the Selective Hydrodesulfurization of Sulfur Model Molecules Representative of FCC Gasoline

Catalysts ◽

10.3390/catal9100793 ◽

2019 ◽

Vol 9 (10) ◽

pp. 793 ◽

Cited By ~ 2

Author(s):

Valentin Hetier ◽

Diego Pena ◽

Alexandre Carvalho ◽

Laurence Courthéoux ◽

Valérie Flaud ◽

...

Keyword(s):

Catalytic Activity ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Intrinsic Activity ◽

Strong Increase ◽

Similar Amount ◽

X Ray ◽

Mos2 Catalysts ◽

The Impact

A way to improve hydrotreatment processes is to enhance the intrinsic activity of Ni or Co promoted MoS2 catalysts that are commonly used in such reactions. The aim of this work was to investigate the impact of the presence of Pluronic® P123 as a structuring agent during the synthesis of Ni promoted MoS2 catalysts (named NiMoS) in water at room temperature. A series of analyses, i.e., X-ray diffraction (XRD), chemical analysis, inductively coupled plasma mass spectrometry (ICP-MS), nitrogen adsorption-desorption isotherms, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), helped in characterizing the NiMoS-P123 and NiMoS catalysts, the latter being prepared in the absence of polymer. Both compounds contained MoS2 phase (~85 atomic% considering Mo atoms), a similar amount of mixed Ni-Mo-S phase (40–50% considering Ni) and some amount of NiS and Ni-oxidized impurity phases. The main differences between the two catalysts were a much larger specific surface area (126 m2·g−1 instead of 31 m²·g−1) and a better dispersion of the active phase as shown by the lower slab stacking (2.7 instead of 4.8) for NiMoS-P123, and the presence of C in NiMoS-P123 (9.4 wt.% instead of 0.6 wt.%), indicating an incomplete decomposition of the polymer during thermal treatment. Thanks to its larger specific surface area and lower slab stacking and therefore modification of active Mo site properties, the compound prepared in the presence of Pluronic® P123 exhibits a strong increase of the catalytic activity expressed per Mo atom for the transformation of 3-methylthiophene. Such improvement in catalytic activity was not observed for the transformation of benzothiophene likely due to poisonous residual carbon which results from the presence of Pluronic® P123 during the synthesis.

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The Influence of Fe/Al Molar Ratio on Microreactor-Based Catalyst Preparation and Carbon Nanotube Preparation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1036.130 ◽

2021 ◽

Vol 1036 ◽

pp. 130-136

Author(s):

Ting Qun Tan ◽

Lei Geng ◽

Yan Lin ◽

Yan He

Keyword(s):

Carbon Nanotubes ◽

Catalytic Activity ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Small Diameter ◽

High Specific Surface Area ◽

Detection Methods ◽

Molar Ratio ◽

High Catalytic Activity

In order to prepare carbon nanotubes with high specific surface area, small diameter, low resistivity, high purity and high catalytic activity, the Fe-Mo/Al2O3 catalyst was prepared based on the microreactor. The influence of different Fe/Al molar ratios on the catalyst and the carbon nanotubes prepared was studied through BET, SEM, TEM and other detection methods. Studies have shown that the pore structure of the catalyst is dominated by slit pores at a lower Fe/Al molar ratio. The catalytic activity is the highest when the Fe/Al molar ratio is 1:1, reaching 74.1%. When the Fe/Al molar ratio is 1:2, the catalyst has a higher specific surface area, the maximum pore size is 8.63 nm, and the four-probe resistivity and ash content of the corresponding carbon nanotubes are the lowest. The higher the proportion of aluminum, the higher the specific surface area of the catalyst and the carbon nanotubes, and the finer the diameter of the carbon nanotubes, which gradually tends to relax. The results show that when the Fe/Al molar ratio is 1:2, although the catalytic activity of the catalyst is not the highest, the carbon nanotubes prepared have the best performance.

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Structural and Morphological Quantitative 3D Characterisation of Ammonium Nitrate Prills by X-Ray Computed Tomography

Materials ◽

10.3390/ma13051230 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1230

Author(s):

Fabien Léonard ◽

Zhen Zhang ◽

Holger Krebs ◽

Giovanni Bruno

Keyword(s):

Computed Tomography ◽

Specific Surface ◽

Ammonium Nitrate ◽

Surface Area ◽

Specific Surface Area ◽

Volume Fraction ◽

Fuel Oil ◽

X Ray ◽

Oil Retention ◽

X Ray Computed

The mixture of ammonium nitrate (AN) prills and fuel oil (FO), usually referred to as ANFO, is extensively used in the mining industry as a bulk explosive. One of the major performance predictors of ANFO mixtures is the fuel oil retention, which is itself governed by the complex pore structure of the AN prills. In this study, we present how X-ray computed tomography (XCT), and the associated advanced data processing workflow, can be used to fully characterise the structure and morphology of AN prills. We show that structural parameters such as volume fraction of the different phases and morphological parameters such as specific surface area and shape factor can be reliably extracted from the XCT data, and that there is a good agreement with the measured oil retention values. Importantly, oil retention measurements (qualifying the efficiency of ANFO as explosives) correlate well with the specific surface area determined by XCT. XCT can therefore be employed non-destructively; it can accurately evaluate and characterise porosity in ammonium nitrate prills, and even predict their efficiency.

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Preparation of Zirconia Nanofibers by Electrospinning and Calcination with Zirconium Acetylacetonate as Precursor

Polymers ◽

10.3390/polym11061067 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1067 ◽

Cited By ~ 5

Author(s):

Vyacheslav V. Rodaev ◽

Svetlana S. Razlivalova ◽

Andrey O. Zhigachev ◽

Vladimir M. Vasyukov ◽

Yuri I. Golovin

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Heterogeneous Catalysts ◽

Tetragonal Zirconia ◽

Nitrogen Adsorption ◽

Average Diameter ◽

High Specific Surface Area ◽

X Ray ◽

Adsorption Analysis

For the first time, zirconia nanofibers with an average diameter of about 75 nm have been fabricated by calcination of electrospun zirconium acetylacetonate/polyacrylonitrile fibers in the range of 500–1100 °C. Composite and ceramic filaments have been characterized by scanning electron microscopy, thermogravimetric analysis, nitrogen adsorption analysis, energy-dispersive X-ray spectroscopy, and X-ray diffractometry. The stages of the transition of zirconium acetylacetonate to zirconia have been revealed. It has been found out that a rise in calcination temperature from 500 to 1100 °C induces transformation of mesoporous tetragonal zirconia nanofibers with a high specific surface area (102.3 m2/g) to non-porous monoclinic zirconia nanofibers of almost the same diameter with a low value of specific surface area (8.3 m2/g). The tetragonal zirconia nanofibers with high specific surface area prepared at 500 °C can be considered, for instance, as promising supports for heterogeneous catalysts, enhancing their activity.

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Study of Heating Effect on Specific Surface Area, and Changing Optical Properties of ZnO Nanocrystals

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.403-408.1205 ◽

2011 ◽

Vol 403-408 ◽

pp. 1205-1210

Author(s):

Jaleh Babak ◽

Ashrafi Ghazaleh ◽

Gholami Nasim ◽

Azizian Saeid ◽

Golbedaghi Reza ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Energy Gap ◽

Sol Gel ◽

X Ray Diffraction ◽

X Ray ◽

Zno Nanocrystals ◽

Transmission Electron ◽

Zno Nanocrystal

In this work ZnO nanocrystal powders have been synthesized by using Zinc acetate dehydrate as a precursor and sol-gel method. Then the products have been annealed at temperature of 200-1050°C, for 2 hours. The powders were characterized using X-ray diffraction (XRD), UV-vis absorption and photoluminescence (PL) spectroscopy. The morphology of refrence ZnO nanoparticles have been studied using Transmission Electron Microscope (TEM). During the annealing process, increase in nanocrystal size, defects and energy gap quantitative, and decrease in specific surface area have been observed.

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Biodiesel Processing Using Sodium and Potassium Geopolymer Powders as Heterogeneous Catalysts

Molecules ◽

10.3390/molecules25122839 ◽

2020 ◽

Vol 25 (12) ◽

pp. 2839 ◽

Cited By ~ 1

Author(s):

Renata F. Botti ◽

Murilo D.M. Innocentini ◽

Thais A. Faleiros ◽

Murilo F. Mello ◽

Danilo L. Flumignan ◽

...

Keyword(s):

Catalytic Activity ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Heterogeneous Catalysts ◽

Average Pore Size ◽

Thermal Shrinkage ◽

Average Pore ◽

Base Catalysts ◽

Sodium And Potassium

This work investigates the catalytic activity of geopolymers produced using two different alkali components (sodium or potassium) and four treatment temperatures (110 to 700 °C) for the methyl transesterification of soybean oil. The geopolymers were prepared with metakaolin as an aluminosilicate source and alkaline activating solutions containing either sodium or potassium in the same molar oxide proportions. The potassium-based formulation displayed a higher specific surface area and lower average pore size (28.64–62.54 m²/g; 9 nm) than the sodium formulation (6.34–32.62 m²/g; 17 nm). The reduction in specific surface area (SSA) after the heat treatment was more severe for the sodium formulation due to the higher thermal shrinkage. The catalytic activity of the geopolymer powders was compared under the same reactional conditions (70–75 °C, 150% methanol excess, 4 h reaction) and same weight amounts (3% to oil). The differences in performance were attributed to the influences of sodium and potassium on the geopolymerization process and to the accessibility of the reactants to the catalytic sites. The Na-based geopolymers performed better, with FAME contents in the biodiesel phase of 85.1% and 89.9% for samples treated at 500 and 300 °C, respectively. These results are competitive in comparison with most heterogeneous base catalysts reported in the literature, considering the very mild conditions of temperature, excess methanol and catalyst amount and the short time spent in reactions.

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Low-Temperature Synthesis of Monolithic Titanium Carbide/Carbon Composite Aerogel

Nanomaterials ◽

10.3390/nano10122527 ◽

2020 ◽

Vol 10 (12) ◽

pp. 2527

Author(s):

Tingting Niu ◽

Bin Zhou ◽

Zehui Zhang ◽

Xiujie Ji ◽

Jianming Yang ◽

...

Keyword(s):

Titanium Dioxide ◽

Electron Microscope ◽

Low Temperature ◽

Titanium Carbide ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Carbon Composite ◽

Composite Aerogel ◽

X Ray

Resorcinol-formaldehyde/titanium dioxide composite (RF/TiO2) gel was prepared simultaneously by acid catalysis and then dried to aerogel with supercritical fluid CO2. The carbon/titanium dioxide aerogel was obtained by carbonization and then converted to nanoporous titanium carbide/carbon composite aerogel via 800 °C magnesiothermic catalysis. Meanwhile, the evolution of the samples in different stages was characterized by X-ray diffraction (XRD), an energy-dispersive X-ray (EDX) spectrometer, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and specific surface area analysis (BET). The results showed that the final product was nanoporous TiC/C composite aerogel with a low apparent density of 339.5 mg/cm3 and a high specific surface area of 459.5 m2/g. Comparing to C aerogel, it could also be considered as one type of highly potential material with efficient photothermal conversion. The idea of converting oxide–carbon composite into titanium carbide via the confining template and low-temperature magnesiothermic catalysis may provide new sight to the synthesis of novel nanoscale carbide materials.

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Preparation of Nitrogen-Deficient Graphitic Carbon Nitride with a Large Specific Surface Area by Melt Pretreatment and Its Photocatalytic Performance

NANO ◽

10.1142/s1793292020500794 ◽

2020 ◽

Vol 15 (06) ◽

pp. 2050079

Author(s):

Xuelei Li ◽

Jinfeng Bai ◽

Jiaqi Li ◽

Chao Li ◽

Junru Zhang ◽

...

Keyword(s):

Visible Light ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Carbon Nitride ◽

Mesoporous Structure ◽

Graphitic Carbon ◽

Graphitic Carbon Nitride ◽

Large Specific Surface Area ◽

X Ray

In this study, nitrogen-deficient graphitic carbon nitride (M-LS-g-C3N4) with a mesoporous structure and a large specific surface area was obtained by calcination after melt pretreatment using urea as a precursor. X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, X-ray photoelectron spectroscopy (XPS), UV-Vis, ESR and photoluminescence (PL) were used to characterize the structure, morphology and optical performance of the samples. The TEM results showed the formation of a mesoporous structure on the 0.1[Formula: see text]M-LS-g-C3N4 surface. The porous structure led to an increase in the specific surface area from 41.5[Formula: see text]m2/g to 124.3[Formula: see text]m2/g. The UV-Vis results showed that nitrogen vacancies generated during the modification process reduced the band gap of g-C3N4 and improved the visible light absorption. The PL spectra showed that the nitrogen defects promoted the separation of photogenerated electron–hole pairs. In the visible light degradation of methyl orange (MO), the reaction rate constant of 0.1[Formula: see text]M-LS-g-C3N4 reached 0.0086[Formula: see text][Formula: see text], which was 5.05 times that of pure g-C3N4. Superoxide radicals and photogenerated holes were found to be the main active species in the reaction system. This study provides an efficient, green and convenient means of preparing graphitic carbon nitride with a large specific surface area.

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Electrochemical Properties of Supercapacitors Using Boron Nitrogen Double-Doped Carbon Nanotubes as Conductive Additive

NANO ◽

10.1142/s1793292019500802 ◽

2019 ◽

Vol 14 (07) ◽

pp. 1950080

Author(s):

Hao Hu ◽

Xiaogang Sun ◽

Wei Chen ◽

Jie Wang ◽

Xu Li ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Double Layer ◽

Specific Surface Area ◽

Electric Double Layer ◽

X Ray ◽

Nitrogen Doped ◽

Conductive Additive ◽

Double Layer Capacitors ◽

Boron Nitrogen

Carbon nanotubes (CNTs) were doped by ammonium borate as the sources of nitrogen and boron. Under the protection of Ar gas, boron-nitrogen doped CNTs were prepared through nitriding and boronization at high temperature. It is a conductive additive. Then, the obtained CNTs were mixed with activated carbon (AC), SP, sodium dodecyl sulfate (SDS), and cellulose fiber to prepare electrodes. With all the materials, a symmetric electric double-layer supercapacitor (EDLC) was assembled. Next, the materials and electrodes were also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The factors, chemical connections, and specific surface area of the CNTs were analyzed by X-ray energy spectrum analysis (EDS), X-ray photoelectron spectroscopy (XPS), as well as a specific surface area and porosimetry analyzer (BET). In addition, the electrochemical performances of electric double-layer capacitors were tested with the help of cyclic voltammetry, constant-current charging and discharging, and so on. From the results, we can make a conclusion, that is, both B and N atoms were added into the CNTs and formed bonds successfully with carbon atoms mutually. Besides, the specific surface area is about 1.5 times than that of the CNT. When the charge/discharge current density reaches 50[Formula: see text]mA/g, we can find that the mass specific capacitance of the capacitor can run up to 32.19[Formula: see text]F/g. Also, we observe that the maximum power density is close to 220[Formula: see text]W/kg (700[Formula: see text]mA/g), and the energy density can arrive 9.31[Formula: see text]Wh/kg (50[Formula: see text]mA/g). Based on the impedance test, the electrodes are characterized with low impedance. After 2000 cycles, the boron-nitrogen doped double-layer capacitors maintain a capacitance retention ratio of above 95%. Its power density can still achieve 220[Formula: see text]W/kg when the energy density keeps at 3.46[Formula: see text]Wh/kg. In other words, the electrochemical performance functions of the electric double-layer capacitors are enhanced while the CNTs serve as the electrodes.

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