Eco-Friendly Cavity-Containing Iron Oxides Prepared by Mild Routes as Very Efficient Catalysts for the Total Oxidation of VOCs

Iron oxides (FeOx) are non-toxic, non-expensive and environmentally friendly compounds, which makes them good candidates for many industrial applications, among them catalysis. In the present article five catalysts based on FeOx were synthesized by mild routes: hydrothermal in subcritical and supercritical conditions (Fe-HT, Few200, Few450) and solvothermal (Fe-ST1 and Fe-ST2). The catalytic activity of these catalysts was studied for the total oxidation of toluene using very demanding conditions with high space velocities and including water and CO2 in the feed. The samples were characterized by X-ray diffraction (XRD), scanning and high-resolution transmission electron microscopy (SEM and HRTEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption-desorption isotherms. It was observed that the most active catalyst was a cavity-containing porous sample prepared by a solvothermal method with a relatively high surface area (55 m2 g−1) and constituted by flower-like aggregates with open cavities at the catalyst surface. This catalyst displayed superior performance (100% of toluene conversion at 325 °C using highly demanding conditions) and this performance can be maintained for several catalytic cycles. Interestingly, the porous iron oxides present not only a higher catalytic activity than the non-porous but also a higher specific activity per surface area. The high activity of this catalyst has been related to the possible synergistic effect of compositional, structural and microstructural features emphasizing the role of the surface area, the crystalline phase present, and the properties of the surface.

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Lanthanum based high surface area perovskite-type oxide and application in CO and propane combustion

Eclética Química Journal ◽

10.26850/1678-4618eqj.v34.1.2009.p31-38 ◽

2018 ◽

Vol 34 (1) ◽

pp. 31

Author(s):

Paulo Roberto Nagipe Da Silva ◽

Ana Brígida Soares

Keyword(s):

Catalytic Activity ◽

Photoelectron Spectroscopy ◽

Perovskite Phase ◽

High Surface ◽

High Surface Area ◽

Propane Combustion ◽

Total Oxidation ◽

X Ray ◽

Co Precipitation ◽

Perovskite Type

The perovskite-type oxides using transition metals present a promising potential as catalysts in total oxidation reaction. The present work investigates the effect of synthesis by oxidant co-precipitation on the catalytic activity of perovskite-type oxides LaBO3 (B= Co, Ni, Mn) in total oxidation of propane and CO. The perovskite-type oxides were characterized by means of X-ray diffraction, nitrogen adsorption (BET method), thermo gravimetric and differential thermal analysis (ATG-DTA) and X-ray photoelectron spectroscopy (XPS). Through a method involving the oxidant co-precipitation it’s possible to obtain catalysts with different BET surface areas, of 33-44 m2/g, according the salts of metal used. The characterization results proved that catalysts have a perovskite phase as well as lanthanum oxide, except LaMnO3, that presents a cationic vacancies and generation for known oxygen excess. The results of catalytic test showed that all oxides have a specific catalytic activity for total oxidation of CO and propane even though the temperatures for total conversion change for each transition metal and substance to be oxidized.

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Evolution of the pore and framework structure of NaY zeolite during alkali treatment and its effect on methanol oxidative carbonylation over a CuY catalyst

Journal of Chemical Research ◽

10.1177/1747519820915418 ◽

2020 ◽

Vol 44 (11-12) ◽

pp. 710-720

Author(s):

Lifei Yan ◽

Tingjun Fu ◽

Jiajun Wang ◽

Nilesh Narkhede ◽

Zhong Li

Keyword(s):

Catalytic Activity ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

Dimethyl Carbonate ◽

Alkali Treatment ◽

Oxidative Carbonylation ◽

Framework Structure ◽

Y Zeolite ◽

Cage Structure ◽

X Ray

Alkali treatment is widely used on aluminosilicate zeolites with high Si/Al ratios in order to fabricate mesopores in the framework. However, for zeolites with low Si/Al ratios, the effect of alkali treatment on the pore and framework structure needed further study. In this work, Y zeolite is treated with NaOH solutions of different concentrations and is used as the support for Cu-based catalysts for oxidative carbonylation of methanol to dimethyl carbonate. The physicochemical properties of the supports and corresponding catalysts are characterized by N2 adsorption–desorption, X-ray diffraction, X-ray fluorescence, transmission electron microscopy, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, and H2-temperature-programmed reduction analyses. The results show that no obvious mesopores are formed under alkali treatment, even at high NaOH concentration. However, amorphous species present in the micropores of Y zeolite are removed, which increases the micropore surface area as well as the crystallinity. Simultaneously, the cage structure is partially destroyed, which also leads to a slight increase of the pore volume and surface area. The altered micropore structure eventually increases the content and accessibility of the exchanged Cu species, which is beneficial to the catalytic activity. When the concentration of NaOH is 0.6 M, the space time yield of dimethyl carbonate for the corresponding catalyst was 151.4 mg g−1 h−1 which is 3.3-fold higher than that of the untreated-Y-zeolite-supported Cu catalyst. However, further increasing the alkali treatment strength can seriously destroy the basic aluminosilicate structure of the Y zeolite and decrease its intrinsic ion-exchange capacity. This results in the formation of agglomerated CuO on the catalyst surface, which was not conducive to catalytic activity.

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Catalytic activity of nanostructured Au: Scale effects versus bimetallic/bifunctional effects in low-temperature CO oxidation on nanoporous Au

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.4.13 ◽

2013 ◽

Vol 4 ◽

pp. 111-128 ◽

Cited By ~ 29

Author(s):

Lu-Cun Wang ◽

Yi Zhong ◽

Haijun Jin ◽

Daniel Widmann ◽

Jörg Weissmüller ◽

...

Keyword(s):

Catalytic Activity ◽

Low Temperature ◽

Co Oxidation ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

Scale Effects ◽

Structural Parameters ◽

Kinetic Measurements ◽

X Ray ◽

Low Temperature Co Oxidation

The catalytic properties of nanostructured Au and their physical origin were investigated by using the low-temperature CO oxidation as a test reaction. In order to distinguish between structural effects (structure–activity correlations) and bimetallic/bifunctional effects, unsupported nanoporous gold (NPG) samples prepared from different Au alloys (AuAg, AuCu) by selective leaching of a less noble metal (Ag, Cu) were employed, whose structure (surface area, ligament size) as well as their residual amount of the second metal were systematically varied by applying different potentials for dealloying. The structural and chemical properties before and after 1000 min reaction were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The catalytic behavior was evaluated by kinetic measurements in a conventional microreactor and by dynamic measurements in a temporal analysis of products (TAP) reactor. The data reveal a clear influence of the surface contents of residual Ag and Cu species on both O2 activation and catalytic activity, while correlations between activity and structural parameters such as surface area or ligament/crystallite size are less evident. Consequences for the mechanistic understanding and the role of the nanostructure in these NPG catalysts are discussed.

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Nanostructured TiO2 modified by perfluoropolyethers: Gas phase photocatalytic activity

Journal of Materials Research ◽

10.1557/jmr.2010.0008 ◽

2010 ◽

Vol 25 (1) ◽

pp. 96-103 ◽

Cited By ~ 5

Author(s):

Claudia L. Bianchi ◽

Silvia Ardizzone ◽

Giuseppe Cappelletti ◽

Giuseppina Cerrato ◽

Walter Navarrini ◽

...

Keyword(s):

Gas Phase ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

Surface Composition ◽

High Surface ◽

Ammonium Phosphate ◽

Water Contact ◽

Electronic Band ◽

X Ray ◽

Bet Analysis

A high-molecular-weight perfluoropolyether (PFPE-YR) and a perfluoropolyether containing ammonium phosphate (PFPE-F10) have been evaluated as fluorinated coating for high-surface-area titanium oxides. Coated nano-TiO2 shows hydrophobic properties and excellent buoyancy on water. In addition to photoactivity toward the degradation of toluene in gas phase, specific trial analyses have been completed to estimate the modified titanium oxide features. Brunauer–Emmett–Teller (BET) analysis for the surface area determination, ultraviolet-visible spectroscopy (UV-Vis) for the material electronic band gap, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) for the morphology, structure, and surface composition, respectively, and water contact angle and infrared (IR) analysis have been performed to estimate the wettability and stability of coated titanium.

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Efficient Dye-Sensitized Solar Cells Composed of Nanostructural ZnO Doped with Ti

Catalysts ◽

10.3390/catal9030273 ◽

2019 ◽

Vol 9 (3) ◽

pp. 273 ◽

Cited By ~ 17

Author(s):

Mati Rahman ◽

Mingdeng Wei ◽

Fengyan Xie ◽

Matiullah Khan

Keyword(s):

Solar Cells ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

High Surface ◽

Dye Sensitized Solar Cells ◽

Solar Cell Performance ◽

X Ray ◽

Dye Sensitized ◽

Dye Loading ◽

Sensitized Solar Cells

Photoanode materials with optimized particle sizes, excellent surface area and dye loading capability are preferred in good-performance dye sensitized solar cells. Herein, we report on an efficient dye-sensitized mesoporous photoanode of Ti doped zinc oxide (Ti-ZnO) through a facile hydrothermal method. The crystallinity, morphology, surface area, optical and electrochemical properties of the Ti-ZnO were investigated using X-ray photoelectron spectroscopy, transmission electron microscopy and X-ray diffraction. It was observed that Ti-ZnO nanoparticles with a high surface area of 131.85 m2 g−1 and a controlled band gap, exhibited considerably increased light harvesting efficiency, dye loading capability, and achieved comparable solar cell performance at a typical nanocrystalline ZnO photoanode.

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Characteristics of High Surface Area Molybdenum Nitride and Its Activity for the Catalytic Decomposition of Ammonia

Catalysts ◽

10.3390/catal11020192 ◽

2021 ◽

Vol 11 (2) ◽

pp. 192

Author(s):

Seo-Hyeon Baek ◽

Kyunghee Yun ◽

Dong-Chang Kang ◽

Hyejin An ◽

Min Bum Park ◽

...

Keyword(s):

Surface Area ◽

Photoelectron Spectroscopy ◽

High Surface ◽

High Surface Area ◽

Catalytic Decomposition ◽

Molybdenum Nitride ◽

X Ray ◽

Temperature Programmed Oxidation ◽

Oxidation Reduction ◽

Temperature Programmed

High surface area (>170 m2 g−1) molybdenum nitride was prepared by the temperature-programmed nitridation of α-MoO3 with pure ammonia. The process was optimized by adjusting the experimental variables: the reaction temperature, heating rate, and molar flow rate of ammonia. The physicochemical properties of the as-formed molybdenum nitride were characterized by X-ray diffraction, N2 sorption, transmission electron microscopy, temperature-programmed oxidation/reduction, and X-ray photoelectron spectroscopy. Of the experimental variables, the nitridation temperature was found to be the most critical parameter determining the surface area of the molybdenum nitride. When the prepared molybdenum nitride was exposed to air, the specific surface area rapidly decreased because of the partial oxidation of molybdenum nitride to molybdenum oxynitride. However, the surface area recovered to 90% the initial value after H2 treatment. The catalyst with the highest degree of nitridation showed the best catalytic activity, superior to that of unmodified α-MoO3, for the decomposition of ammonia because of its high surface area.

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Characterization of High Surface Area Silicon Oxynitrides

MRS Proceedings ◽

10.1557/proc-271-801 ◽

1992 ◽

Vol 271 ◽

Cited By ~ 5

Author(s):

Peter W. Lednor ◽

Rene De Ruiter ◽

Kees A. Emeis

Keyword(s):

Fourier Transform ◽

Infrared Spectroscopy ◽

Surface Area ◽

Photoelectron Spectroscopy ◽

High Surface ◽

High Surface Area ◽

X Ray ◽

Silicon Oxynitrides

ABSTRACTHigh surface area silicon oxynitrides have been prepared by nitrida- tion of silica with ammonia. Characterization by Fourier-transform infrared spectroscopy has allowed quantitative determination of hydroxyl, amido and imido groups. Data obtained by X-ray photoelectron spectroscopy show that the nitrogen is well distributed in the surface of the materials.

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Modification of Cobalt Oxide Electrochemically Deposited on Stainless Steel Meshes with Co-Mn Thin Films Prepared by Magnetron Sputtering: Effect of Preparation Method and Application to Ethanol Oxidation

Catalysts ◽

10.3390/catal11121453 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1453

Author(s):

Květa Jirátová ◽

Roman Perekrestov ◽

Michaela Dvořáková ◽

Jana Balabánová ◽

Martin Koštejn ◽

...

Keyword(s):

Stainless Steel ◽

Catalytic Activity ◽

Magnetron Sputtering ◽

Cobalt Oxide ◽

Photoelectron Spectroscopy ◽

Rf Magnetron Sputtering ◽

Deep Oxidation ◽

Active Components ◽

Total Oxidation ◽

X Ray

Magnetron sputtering is an advantageous method for preparing catalysts supported on stainless steel meshes. Such catalysts are particularly suitable for processes carried out at high space velocities. One of these is the catalytic total oxidation of volatile organic compounds (VOC), economically feasible and environmentally friendly method of VOC abatement. The reactive radio frequency (RF) magnetron sputtering of Mn and Co + Mn mixtures in an oxidation Ar + O2 atmosphere was applied to form additional thin oxide coatings on cobalt oxide layers prepared by electrochemical deposition and heating on stainless steel meshes. Time of the RF magnetron sputtering was changed to obtain MnOx and CoMnOx coatings of various thickness (0.1–0.3 µm). The properties of the supported CoOx–MnOx and CoOx–CoMnOx catalysts were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), temperature programmed reduction (H2-TPR), Fourier-transform infrared (FTIR) and Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The catalytic activity was investigated in the deep oxidation of ethanol, which was employed as a model VOC. According to the specific activities (amount of ethanol converted per unit mass of metal oxides per hour), the performance of CoOx–MnOx catalysts was higher than that of CoOx–CoMnOx ones. The catalysts with the smallest layer thickness (0.1 µm) showed the highest catalytic activity. Compared to the commercial pelletized Co–Mn–Al mixed oxide catalyst, the sputtered catalysts exhibited considerably higher (23–87 times) catalytic activity despite the more than 360–570 times lower content of the Co and Mn active components in the catalytic bed.

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Green Preparation of High Surface Area Cu-Au Bimetallic Nanostructured Materials by Co-Electrodeposition in a Deep Eutectic Solvent

10.26434/chemrxiv.14312087 ◽

2021 ◽

Author(s):

Elena Plaza Mayoral ◽

Paula Sebastián Pascual ◽

Kim Nicole Dalby ◽

Kim Degn Jensen ◽

Ib Chorkendorff ◽

...

Keyword(s):

Surface Area ◽

Nanostructured Materials ◽

Photoelectron Spectroscopy ◽

Choline Chloride ◽

High Surface ◽

High Surface Area ◽

Deep Eutectic Solvent ◽

Fold Increase ◽

Active Surface Area ◽

X Ray

In this work we present an electrodeposition method in a deep eutectic solvent (DES) to prepare bimetallic high surface area nanostructures of Cu and Au with tunable structure and composition. The metal electrodeposition performed in green choline chloride within a urea deep eutectic solvent allows us to tailor the size, morphology and elemental composition of the deposits. We combine electrochemical methods with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) to characterize the electrodeposited nanostructured materials. We assess the increase of the electroactive surface area through the analysis of the lead underpotential deposition (UPD) on the prepared films. We observe a 5 to 15-fold increase of the active surface area compared to flat surfaces of polycrystalline Cu or Au. Our work reports, for the first time, a green route for the electrodeposition of Cu-Au bimetallic nanostructures in a deep eutectic solvent.

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