scholarly journals Zn-Al Mixed Oxides Decorated with Potassium as Catalysts for HT-WGS: Preparation and Properties

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1094 ◽  
Author(s):  
Katarzyna Antoniak-Jurak ◽  
Paweł Kowalik ◽  
Kamila Michalska ◽  
Wiesław Próchniak ◽  
Robert Bicki
Keyword(s):  
Photoelectron Spectroscopy ◽  
Mixed Oxides ◽  
Catalyst Activity ◽  
Molar Ratio ◽  
X Ray ◽  
Molar Ratios ◽  
Mixed Oxide Catalysts ◽  
Wgs Reaction ◽  
Temperature Programmed ◽  
Co Precipitation

A set of ex-ZnAl-LDHs catalysts with a molar ratio of Zn/Al in the range of 0.3–1.0 was prepared using co-precipitation and thermal treatment. The samples were characterized using various methods, including X-ray fluorescence spectroscopy (XRF), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy FT-IR, N2 adsorption, Temperature-programmed desorption of CO2 (TPD-CO2) as well as Scanning electron microscopy (SEM-EDS). Catalyst activity and long-term stability measurements were carried out in a high-temperature water–gas shift (HT-WGS) reaction. Mixed oxide catalysts with various Zn/Al molar ratios decorated with potassium showed high activity in the HT-WGS reaction within the temperature range of 330–400 °C. The highest activity was found for the Zn/Al molar ratio of 0.5 corresponding to spinel stoichiometry. However, the catalyst with a stoichiometric spinel molar ratio of Zn/Al (ZnAl_0.5_K) revealed a higher tendency for surface migration and/or vaporization of potassium during overheating at 450 °C. The correlation of the activity results and TPD-CO2 data show that medium basic sites enhance the progress of the HT-WGS reaction.

scholarly journals CeO2:Mn3O4 Catalytic Micro-Converters Tuned for CH4 Detection Based on Catalytic Combustion under Real Operating Conditions

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2196
Author(s):  
Cristian E. Simion ◽  
Ovidiu G. Florea ◽  
Mihaela Florea ◽  
Florentina Neaţu ◽  
Ştefan Neaţu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Normal Pressure ◽  
Operating Regime ◽  
Operating Conditions ◽  
Molar Ratio ◽  
Atmospheric Conditions ◽  
X Ray ◽  
Temperature Programmed ◽  
Co Precipitation ◽  
Adsorption Desorption

Mesoporous CeO2:Mn3O4 materials (3:7 and 7:3 molar ratio) were prepared by co-precipitation and deposited as porous thick films over alumina (Al2O3) planar substrate provided with Pt meander. The aim was oriented towards detecting low levels methane (CH4) at moderate operating temperatures. Herein we demonstrated that the sensitivity of catalytic micro-converters (CMCs) towards a given peak of CH4 concentration corresponds to specific gas-surface interaction phenomena. More precisely, a transition from thermal conductivity to combustion rate is likely to occur when CMCs are operated under real atmospheric conditions (normal pressure, presence of relative humidity, and constant operating temperature). The response to CH4 was analyzed over different gas flows and different gas concentrations under the same operating regime. The materials were fully characterized by adsorption-desorption isotherms, H2-Temperature Programmed Reduction (H2-TPR), X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning Electron Microscopy (SEM), and Raman spectroscopies. Thus, the applicative aspect of using CeO2:Mn3O4 as moderate temperature CMC for CH4 detection is brought to the fore.

scholarly journals Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 346
Author(s):  
Sonam Goyal ◽  
Maizatul Shima Shaharun ◽  
Ganaga Suriya Jayabal ◽  
Chong Fai Kait ◽  
Bawadi Abdullah ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalyst Support ◽  
Oxidation Potential ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Optimum Parameters ◽  
Reduction Of Co2 ◽  
Enhanced Yield

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

scholarly journals Simultaneous Catalytic Oxidation of a Lean Mixture of CO-CH4 over Spinel Type Cobalt Based Oxides

2020 ◽  
Vol 15 (2) ◽  
pp. 490-500
Author(s):  
Neha Neha ◽  
Ram Prasad ◽  
Satya Vir Singh
Keyword(s):  
Mixed Oxides ◽  
Structural Disorder ◽  
Catalytic Performance ◽  
Molar Ratio ◽  
Total Oxidation ◽  
Spinel Type ◽  
Molar Ratios ◽  
Long Term Stability ◽  
Nickel Cobalt ◽  
Temperature Programmed

A series of nickel-cobalt bimetal oxides in varying molar ratios and its single metal oxides were synthesized by reactive calcination of coprecipitated basic-carbonates. Several characterization techniques, such as: Bruneuer Emmett Teller (BET), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infra Red (FTIR), and Hydrogen Temperature Programmed Reduction (H2-TPR), were performed over the oxides. Activities of oxides were evaluated in methane total oxidation in the presence or the absence of CO. The best catalytic performance was observed over NiCo catalyst with a Ni/Co molar ratio of 1:1, and the complete conversion of CO-CH4 mixture was achieved at 390 °C. Moreover, the presence of carbon monoxide improves CH4 total oxidation over nickel-cobalt mixed oxides. Structural analysis reveals that the insertion of nickel into the spinel lattice of cobalt oxide causes the structural disorder, which probably caused the increase of the amount of octahedrally coordinated divalent nickel cations that are responsible for catalytic activity. Stability of the best-performed catalyst has been tested in the two conditions, showing remarkable long-term stability and thermal stability, however, showed deactivation after thermally ageing at 700 °C. Copyright © 2020 BCREC Group. All rights reserved 

scholarly journals Bulk Versus Surface Modification of Alumina with Mn and Ce Based Oxides for CH4 Catalytic Combustion

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1771 ◽  
Author(s):  
Stefan Neatu ◽  
Mihaela M. Trandafir ◽  
Adelina Stănoiu ◽  
Ovidiu G. Florea ◽  
Cristian E. Simion ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalytic Combustion ◽  
Mixed Oxides ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Programmed ◽  
Catalytic Combustion Of Methane ◽  
Adsorption Desorption

This study presents the synthesis and characterization of lanthanum-modified alumina supported cerium–manganese mixed oxides, which were prepared by three different methods (coprecipitation, impregnation and citrate-based sol-gel method) followed by calcination at 500 °C. The physicochemical properties of the synthesized materials were investigated by various characterization techniques, namely: nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and H2–temperature programmed reduction (TPR). This experimental study demonstrated that the role of the catalytic surface is much more important than the bulk one. Indeed, the incipient impregnation of CeO2–MnOx catalyst, supported on an optimized amount of 4 wt.% La2O3–Al2O3, provided the best results of the catalytic combustion of methane on our catalytic micro-convertors. This is mainly due to: (i) the highest pore size dimensions according to the Brunauer-Emmett-Teller (BET) investigations, (ii) the highest amount of Mn4+ or/and Ce4+ on the surface as revealed by XPS, (iii) the presence of a mixed phase (Ce2MnO6) as shown by X-ray diffraction; and (iv) a higher reducibility of Mn4+ or/and Ce4+ species as displayed by H2–TPR and therefore more reactive oxygen species.

Hydroformylation of Dicyclopentadiene over Rh Catalysts Supported on Fe2O3, Co3O4 and Fe2O3–Co3O4 Mixed Oxide

2017 ◽  
Vol 42 (1) ◽  
pp. 8-13 ◽  
Author(s):  
Yubo Ma ◽  
Zhixian Gao ◽  
Wumanjiang Eli
Keyword(s):  
Mixed Oxide ◽  
Photoelectron Spectroscopy ◽  
Supported Catalyst ◽  
Precipitation Method ◽  
X Ray ◽  
Analysis Techniques ◽  
Rh Catalyst ◽  
Temperature Programmed ◽  
Co Precipitation ◽  
Effect Of The Support

Rh catalysts supported on Fe2O3, Co3O4 and Fe2O3–Co3O4 mixed oxide were prepared by the co-precipitation method. The effect of the support on the performance of the Rh catalysts for the hydroformylation of dicyclopentadiene was investigated using X-ray photoelectron spectroscopy, H2-temperature-programmed reduction, H2-temperature-programmed desorption and Brunauer–Emmett–Teller analysis techniques. The results indicated that the Fe2O3–Co3O4 supported catalyst had a higher dispersion of Rh and thus more Rh+ sites. As a result, the Fe2O3–Co3O4 supported Rh catalyst exhibited higher activity compared with counterparts supported on Fe2O3 and Co3O4.

scholarly journals Heterogeneous Fenton-like oxidation of p-hydroxybenzoic acid using Fe/CeO2-TiO2 catalyst

2019 ◽  
Vol 79 (7) ◽  
pp. 1276-1286 ◽  
Author(s):  
Tijani Hammedi ◽  
Mohamed Triki ◽  
Mayra G. Alvarez ◽  
Jordi Llorca ◽  
Abdelhamid Ghorbel ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Photoelectron Spectroscopy ◽  
Catalytic Properties ◽  
Molar Ratio ◽  
Hydroxybenzoic Acid ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Temperature Programmed

Abstract This paper is built on the Fenton-like oxidation of p-hydroxybenzoic acid (p–HBZ) in the presence of H2O2 and 3%Fe supported on CeO2-TiO2 aerogels under mild conditions. These catalysts were deeply characterized by X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The effect of thermal treatment, pH (2–3, 5, 7), H2O2/p–HBZ molar ratio (5, 15, 20, 25) and reaction temperature (25 °C, 40 °C and 60 °C) on the catalytic properties of supported Fe catalysts are studied. Our results highlight the role of CeO2 and the calcination of the catalyst to obtain the highest catalytic properties after 10 min: 73% of p–HBZ conversion and 52% of total organic carbon (TOC) abatement.

scholarly journals Synthesis of DME by CO2 hydrogenation over La2O3-modified CuO-ZnO-ZrO2/HZSM-5 catalysts

2017 ◽  
Vol 23 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Yajing Zhang ◽  
Yu Zhang ◽  
Fu Ding ◽  
Kangjun Wang ◽  
Wang Xiaolei ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Direct Synthesis ◽  
Catalytic Performance ◽  
Co2 Hydrogenation ◽  
Precipitation Method ◽  
X Ray ◽  
Temperature Programmed ◽  
And Performance ◽  
Co Precipitation ◽  
Adsorption Desorption

A series of La2O3-modified CuO-ZnO-ZrO2/HZSM-5 catalysts were prepared by an oxalate co-precipitation method. The catalysts were fully characterized by X-ray diffraction (XRD), N2 adsorption-desorption, hydrogen temperature pro-grammed reduction (H2-TPR), ammonia temperature programmed desorption (NH3-TPD), and X-ray photoelectron spectroscopy (XPS) techniques. The effect of the La2O3 content on the structure and performance of the catalysts was thoroughly investigated. The catalysts were evaluated for the direct synthesis of dimethyl ether (DME) from CO2 hydrogenation. The results displayed that La2O3 addition enhanced catalytic performance, and the maximal CO2 conversion (34.3%) and DME selectivity (57.3%) were obtained over the catalyst with 1% La2O3, which due to the smaller size of Cu species and a larger ratio of Cu+/Cu.

scholarly journals Structural, Surface Morphology and Optical Properties of ZnS Films by Chemical Bath Deposition at Various Zn/S Molar Ratios

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Fei-Peng Yu ◽  
Sin-Liang Ou ◽  
Pin-Chuan Yao ◽  
Bing-Rui Wu ◽  
Dong-Sing Wuu
Keyword(s):  
Chemical Bath Deposition ◽  
Photoelectron Spectroscopy ◽  
Visible Region ◽  
Film Surface ◽  
Optical Transmittance ◽  
Molar Ratio ◽  
Infrared Spectrometry ◽  
X Ray ◽  
Molar Ratios ◽  
Zns Films

In this study, ZnS thin films were prepared on glass substrates by chemical bath deposition at various Zn/S molar ratios from 1/50 to 1/150. The effects of Zn/S molar ratio in precursor on the characteristics of ZnS films were demonstrated by X-ray diffraction, scanning electron microscopy, optical transmittance, X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. It was found that more voids were formed in the ZnS film prepared using the precursor with Zn/S molar ratio of 1/50, and the other ZnS films showed the denser structure as the molar ratio was decreased from 1/75 to 1/150. From the analyses of chemical bonding states, the ZnS phase was indeed formed in these films. Moreover, the ZnO and Zn(OH)2also appeared due to the water absorption on film surface during deposition. This would be helpful to the junction in cell device. With changing the Zn/S molar ratio from 1/75 to 1/150, the ZnS films demonstrate high transmittance of 75–88% in the visible region, indicating the films are potentially useful in photovoltaic applications.

scholarly journals Evolution of Copper Supported on Fe3O4 Nanorods for WGS Reaction

Catalysts ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 415 ◽  
Author(s):  
Lingjuan Ma ◽  
Hongbin Ma ◽  
Dawei Han ◽  
Mingyue Qiu ◽  
Yafei Guan ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Ambient Pressure ◽  
Phase Evolution ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
In Situ Xrd ◽  
Wgs Reaction ◽  
Transmission Electron ◽  
Temperature Programmed

Rod-shaped Cu1Fe9Ox precursor was successfully prepared through an aqueous precipitation method. The shape and phase composition were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that Cu1Fe9Ox is composed of CuFe2O4 and Fe2O3. The reduction performance of Cu1Fe9Ox was studied by in situ XRD and H2 temperature-programmed reduction (H2-TPR). Cu/Fe3O4 nanorod catalyst is obtained through the controllable reduction of Cu1Fe9Ox nanorod, and the formed Cu/Fe3O4 nanorod catalyst does not have low-temperature water gas shift (WGS) activity, but exhibits high-temperature WGS reaction activity. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) studies showed that the main species of copper is Cu+ during the WGS reaction. The interaction between Cu and Fe3O4 rod and phase evolution of Cu species are quite different from Cu/Fe3O4 nanoparticles.

scholarly journals Effect of Residual Na+ on the Combustion of Methane over Co3O4 Bulk Catalysts Prepared by Precipitation

Catalysts ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 427 ◽  
Author(s):  
Andoni Choya ◽  
Beatriz de Rivas ◽  
Jose Gutiérrez-Ortiz ◽  
Rubén López-Fonseca
Keyword(s):  
Photoelectron Spectroscopy ◽  
Near Infrared ◽  
Diffuse Reflectance Spectroscopy ◽  
Negative Impact ◽  
Methane Combustion ◽  
Molar Ratio ◽  
Temperature Programmed Reduction ◽  
X Ray ◽  
Two Samples ◽  
Temperature Programmed

The effect of the presence of residual sodium (0.4 %wt) over a Co3O4 bulk catalyst for methane combustion was studied. Two samples, with and without residual sodium, were synthesized by precipitation and thoroughly characterised by X-ray diffraction (XRD), N2 physisorption, Wavelength Dispersive X-ray Fluorescence (WDXRF), temperature-programmed reduction with hydrogen followed by temperature-programmed reduction with oxygen (H2-TPR/O2-TPO), temperature-programmed reaction with methane (CH4-TPRe), ultraviolet–visible–near-infrared diffuse reflectance spectroscopy (UV-vis-NIR DRS), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that during calcination, a fraction of the sodium atoms initially deposited on the surface diffused and migrated into the spinel lattice, inducing a distortion that improved its textural and structural properties. However, surface sodium had an overall negative impact on the catalytic activity. It led to a reduction of surface Co3+ ions in favour of Co2+, thus ultimately decreasing the Co3+/Co2+ molar ratio (from 1.96 to 1.20) and decreasing the amount and mobility of active lattice oxygen species. As a result, the catalyst with residual sodium (T90 = 545 °C) was notably less active than its clean counterpart (T90 = 500 °C). All of this outlined the significance of a proper washing when synthesizing Co3O4 catalyst using a sodium salt as the precipitating agent.

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