Self-Templating Synthesis of 3D Hierarchical NiCo2O4@NiO Nanocage from Hydrotalcites for Toluene Oxidation

Rational design LDHs (layered double hydroxides) with 3D hierarchical hollow structures have generated widespread interest for catalytic oxidation due to the high complexity in shell architecture and composition. Herein, we reported a handy two-step method to construct a 3D hierarchical NiCo2O4/NiO nanocage. This synthetic strategy contains a partial in situ transformation of ZIF-67 (zeolitic imidazolate framework-67) into Co-NiLDH yolk-shelled structures following ethanol etching, and a structure-preserved transformation from Co-NiLDH@ZIF-67 to a biphase nanocage following calcination. CoNi-yh-T (varied reaction time and calcination temperature) nanocages were investigated systematically by Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), H2- temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD) and studied for toluene oxidation. The CoNi-6h-350 sample showed much higher activity with 90% toluene conversion (T90) at 229 °C at a high space velocity (SV = 60,000 mL g−1 h−1) than other catalysts (T90 >240 °C). Abundant surface high valence Co ions caused by the novel hierarchical nanostructures, together with adsorbed oxygen species and abundant medium-strength surface acid sites, played a key role for catalytic activities.

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Influence of Sulfur-Containing Sodium Salt Poisoned V2O5–WO3/TiO2 Catalysts on SO2–SO3 Conversion and NO Removal

Catalysts ◽

10.3390/catal8110541 ◽

2018 ◽

Vol 8 (11) ◽

pp. 541 ◽

Cited By ~ 3

Author(s):

Haiping Xiao ◽

Chaozong Dou ◽

Hao Shi ◽

Jinlin Ge ◽

Li Cai

Keyword(s):

Photoelectron Spectroscopy ◽

No Reduction ◽

Catalytic Performance ◽

Acid Sites ◽

Impregnation Method ◽

So2 Oxidation ◽

Sodium Salts ◽

X Ray ◽

Temperature Programmed ◽

Physical Features

A series of poisoned catalysts with various forms and contents of sodium salts (Na2SO4 and Na2S2O7) were prepared using the wet impregnation method. The influence of sodium salts poisoned catalysts on SO2 oxidation and NO reduction was investigated. The chemical and physical features of the catalysts were characterized via NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The results showed that sodium salts poisoned catalysts led to a decrease in the denitration efficiency. The 3.6% Na2SO4 poisoned catalyst was the most severely deactivated with denitration efficiency of only 50.97% at 350 °C. The introduction of SO42− and S2O72− created new Brønsted acid sites, which facilitated the adsorption of NH3 and NO reduction. The sodium salts poisoned catalysts significantly increased the conversion of SO2–SO3. 3.6%Na2S2O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2–SO3-conversion of 1.44% at 410 °C. Characterization results showed sodium salts poisoned catalysts consumed the active ingredient and lowered the V4+/V5+ ratio, which suppressed catalytic performance. However, they increased the content of chemically adsorbed oxygen and the strength of V5+=O bonds, which promoted SO2 oxidation.

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Mechanism and Performance of the SCR of NO with NH3 over Sulfated Sintered Ore Catalyst

Catalysts ◽

10.3390/catal9010090 ◽

2019 ◽

Vol 9 (1) ◽

pp. 90 ◽

Cited By ~ 10

Author(s):

Wangsheng Chen ◽

Fali Hu ◽

Linbo Qin ◽

Jun Han ◽

Bo Zhao ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Catalytic Reduction ◽

Nox Reduction ◽

Space Velocity ◽

Acid Sites ◽

X Ray Diffraction ◽

X Ray ◽

Diffuse Reflectance Infrared Spectroscopy ◽

And Performance ◽

Diffuse Reflectance Infrared

A sulfated sintered ore catalyst (SSOC) was prepared to improve the denitration performance of the sintered ore catalyst (SOC). The catalysts were characterized by X-ray Fluorescence Spectrometry (XRF), Brunauer–Emmett–Teller (BET) analyzer, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared spectroscopy (DRIFTS) to understand the NH3-selective catalytic reduction (SCR) reaction mechanism. Moreover, the denitration performance and stability of SSOC were also investigated. The experimental results indicated that there were more Brønsted acid sites at the surface of SSOC after the treatment by sulfuric acid, which lead to the enhancement of the adsorption capacity of NH3 and NO. Meanwhile, Lewis acid sites were also observed at the SSOC surface. The reaction between −NH2, NH 4 + and NO (E-R mechanism) and the reaction of the coordinated ammonia with the adsorbed NO2 (L-H mechanism) were attributed to NOx reduction. The maximum denitration efficiency over the SSOC, which was about 92%, occurred at 300 °C, with a 1.0 NH3/NO ratio, and 5000 h−1 gas hourly space velocity (GHSV).

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Synthesis of Zirconia Doped Molybdenum Oxide as Efficient Catalysts for Ultrasound Assisted Synthesis of Substituted Pyrazoles

Asian Journal of Chemistry ◽

10.14233/ajchem.2021.23260 ◽

2021 ◽

Vol 33 (9) ◽

pp. 2007-2014

Author(s):

Amal A. Muftah ◽

Shobha A. Waghmode ◽

Sharda R. Gadale

Keyword(s):

Photoelectron Spectroscopy ◽

Mixed Oxides ◽

Sol Gel ◽

Temperature Stability ◽

Acid Sites ◽

High Yield ◽

Ultra Sound ◽

Electron Microscopes ◽

Temperature Programmed ◽

Substituted Pyrazoles

To explore green methodology for the synthesis of mixed oxide, its catalytic activity and temperature stability of series of ZrO2/MoO3 and ZrO2 were prepared by sol-gel method and characterized by XRD, FT-IR, X-ray photoelectron spectroscopy (XPS), temperature programmed Desorption (TPD), Raman spectroscopy and transmission electron microscopes (TEM). These mixed oxides were showed high stability with nanocrystalline nature. Due to highly acidic nature of the catalysts, ultra sound assisted synthesis of substituted pyrazoles was carried out successfully with high yield. The reaction was carried out in solvent free medium, which showed green approach and energy saving reaction. Condensation of dibenzoyl methane and hydrazine to form substituted pyrazoles with 97.7% yield. The acid strength and acid amount of synthesized catalysts were determined by temperature programmed desoprtion (TPD), incorporation of zirconia into the molybdenum, network has changed its surface acid properties due to the Zr2+ and Mo6+ ions. After addition of ZrO2 on MoO3, it showed weak and strong acid sites.

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Highly bioactive zeolitic imidazolate framework-8–capped nanotherapeutics for efficient reversal of reperfusion-induced injury in ischemic stroke

Science Advances ◽

10.1126/sciadv.aay9751 ◽

2020 ◽

Vol 6 (12) ◽

pp. eaay9751 ◽

Cited By ~ 23

Author(s):

Lizhen He ◽

Guanning Huang ◽

Hongxing Liu ◽

Chengcheng Sang ◽

Xinxin Liu ◽

...

Keyword(s):

Ischemic Stroke ◽

Rational Design ◽

Artery Occlusion ◽

Zeolitic Imidazolate Framework ◽

Synthetic Strategy ◽

Action Mechanisms ◽

Neuroprotective Therapy ◽

Penetration Ability ◽

Cerebral Artery Occlusion

Rational design of potent antioxidative agent with high biocompatibility is urgently needed to treat ischemic reperfusion-induced ROS-mediated cerebrovascular and neural injury during ischemia strokes. Here, we demonstrate an in situ synthetic strategy of bioactive zeolitic imidazolate framework-8–capped ceria nanoparticles (CeO2@ZIF-8 NPs) to achieve enhanced catalytic and antioxidative activities and improved stroke therapeutic efficacy. This nanosystem exhibits prolonged blood circulation time, reduced clearance rate, improved BBB penetration ability, and enhanced brain accumulation, where it effectively inhibits the lipid peroxidation in brain tissues in middle cerebral artery occlusion mice and reduces the oxidative damage and apoptosis of neurons in brain tissue. CeO2@ZIF-8 also suppresses inflammation- and immune response–induced injury by suppressing the activation of astrocytes and secretion of proinflammatory cytokines, thus achieving satisfactory prevention and treatment in neuroprotective therapy. This study also sheds light on the neuroprotective action mechanisms of ZIF-8–capped nanomedicine against reperfusion-induced injury in ischemic stroke.

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Palladium-Incorporated α-MoC Mesoporous Composites for Enhanced Direct Hydrodeoxygenation of Anisole

Catalysts ◽

10.3390/catal11030370 ◽

2021 ◽

Vol 11 (3) ◽

pp. 370

Author(s):

Yue Yang ◽

Xiaochen Liu ◽

Yuanjie Xu ◽

Xing Gao ◽

Yihu Dai ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Rational Design ◽

Bond Activation ◽

Molar Ratio ◽

X Ray ◽

Transmission Electron ◽

Model Molecule ◽

Highly Dispersed ◽

Mesoporous Composites ◽

Temperature Programmed

Hydrodeoxygenation (HDO) is one of the promising catalytic routes for converting biomass derived molecules to high value products. A key step of HDO is the cleavage of an aromatic C–O bond to accomplish the deoxygenation step, however, which is energetically unfavorable. Herein, we report a series of palladium (Pd)-incorporated α-phase of molybdenum carbide (α-MoC) mesoporous composites for enhanced HDO activity of a biomass model molecule, anisole. The catalysts, x%Pd/α-MoC (x% is the molar ratio of Pd/Mo), were investigated by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), Brunauer–Emmett–Teller (BET), Raman, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) techniques. Pd is highly dispersed on α-MoC when x% ≤ 1%, but aggregate to form nanoparticles when x% = 5%. The x%Pd/α-MoC catalysts (x% ≤ 1%) show enhanced HDO activity in terms of turnover frequency (TOF) and apparent activation energy barrier (Ea) compared with α-MoC and β-Mo2C catalysts. The TOF of 1%Pd/α-MoC catalyst at 160 °C is 0.115 h−1 and the Ea is 48.2 kJ/mol. Moreover, the direct cleavage of aromatic C–O bond is preferred on 1%Pd/α-MoC catalyst. The enhanced HDO activity is attributed to superior H2 dissociation ability by the highly dispersed Pd sites on carbide. This work brings new insights for rational design of the catalyst for selective C–O bond activation.

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Behavior of Molybdenum–Vanadium Mixed Oxides in Selective Oxidation and Disproportionation of Toluene

Materials ◽

10.3390/ma12050748 ◽

2019 ◽

Vol 12 (5) ◽

pp. 748 ◽

Cited By ~ 2

Author(s):

Gheorghita Mitran ◽

Florentina Neaţu ◽

Octavian Pavel ◽

Mihaela Trandafir ◽

Mihaela Florea

Keyword(s):

Selective Oxidation ◽

Photoelectron Spectroscopy ◽

Mixed Oxides ◽

Strong Acid ◽

Acid Sites ◽

High Conversion ◽

Tetradecyltrimethylammonium Bromide ◽

X Ray ◽

Toluene Disproportionation ◽

Temperature Programmed

This study deals with the behavior of molybdenum–vanadium (Mo/V) mixed oxides catalysts in both disproportionation and selective oxidation of toluene. Samples containing different Mo/V ratios were prepared by a modified method using tetradecyltrimethylammonium bromide and acetic acid. The catalysts were characterized using several techniques: nitrogen adsorption–desorption isotherms, X-Ray diffraction (XRD), ammonia temperature-programmed desorption (TPD-NH3), temperature-programmed reduction by hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, Fourier-transform infrared-spectroscopy (FTIR) and ultraviolet-visible spectroscopies (UV–VIS). The XRD results evidenced the presence of orthorhombic α-MoO3 and V2O5 phases, as well as monoclinic β-MoO3 and V2MoO8 phases, their abundance depending on the Mo to V ratio, while the TPD-NH3 emphasized that, the total amount of the acid sites diminished with the increase of the Mo loading. The TPR investigations indicated that the samples with higher Mo/V ratio possess a higher reducibility. The main findings of this study led to the conclusion that the presence of strong acid sites afforded a high conversion in toluene disproportionation (Mo/V = 1), while a higher reducibility is a prerequisite to accomplishing high conversion in toluene oxidation (Mo/V = 2). The catalyst with Mo/V = 1 acquires the best yield to xylenes from the toluene disproportionation reaction, while the catalyst with Mo/V = 0.33 presents the highest yield to benzaldehyde.

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The Effect of Noble Metal (M: Ir, Pt, Pd) on M/Ce2O3-γ-Al2O3 Catalysts for Hydrogen Production via the Steam Reforming of Glycerol

Catalysts ◽

10.3390/catal10070790 ◽

2020 ◽

Vol 10 (7) ◽

pp. 790

Author(s):

Nikolaos D. Charisiou ◽

Georgios I. Siakavelas ◽

Kyriakos N. Papageridis ◽

Davide Motta ◽

Nikolaos Dimitratos ◽

...

Keyword(s):

Steam Reforming ◽

Photoelectron Spectroscopy ◽

Acid Sites ◽

Unsaturated Hydrocarbon ◽

Effect Of Temperature ◽

Incipient Wetness Impregnation ◽

X Ray ◽

Gaseous Products ◽

Metal Support Interaction ◽

Temperature Programmed

A promising route for the energetic valorisation of the main by-product of the biodiesel industry is the steam reforming of glycerol, as it can theoretically produce seven moles of H2 for every mole of C3H8O3. In the work presented herein, CeO2–Al2O3 was used as supporting material for Ir, Pd and Pt catalysts, which were prepared using the incipient wetness impregnation technique and characterized by employing N2 adsorption–desorption, X-Ray Diffraction (XRD), Temperature Programmed Reduction (TPR), Temperature Programmed Desorption (TPD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM). The catalytic experiments aimed at identifying the effect of temperature on the total conversion of glycerol, on the conversion of glycerol to gaseous products, the selectivity towards the gaseous products (H2, CO2, CO, CH4) and the determination of the H2/CO and CO/CO2 molar ratios. The main liquid effluents produced during the reaction were quantified. The results revealed that the Pt/CeAl catalyst was more selective towards H2, which can be related to its increased number of Brønsted acid sites, which improved the hydrogenolysis and dehydrogenation–dehydration of condensable intermediates. The time-on-stream experiments, undertaken at low Water Glycerol Feed Ratios (WGFR), showed gradual deactivation for all catalysts. This is likely due to the dehydration reaction, which leads to the formation of unsaturated hydrocarbon species and eventually to carbon deposition. The weak metal–support interaction shown for the Ir/CeAl catalyst also led to pronounced sintering of the metallic particles.

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CuO-In2O3 Catalysts Supported on Halloysite Nanotubes for CO2 Hydrogenation to Dimethyl Ether

Catalysts ◽

10.3390/catal11101151 ◽

2021 ◽

Vol 11 (10) ◽

pp. 1151

Author(s):

Alexey Pechenkin ◽

Dmitry Potemkin ◽

Maria Rubtsova ◽

Pavel Snytnikov ◽

Pavel Plyusnin ◽

...

Keyword(s):

Dimethyl Ether ◽

Space Velocity ◽

Halloysite Nanotubes ◽

Acid Sites ◽

Co2 Conversion ◽

X Ray Diffraction ◽

Transition Electron Microscopy ◽

Hydrogenation Of Co2 ◽

Acidic Sites ◽

Temperature Programmed

Hydrogenation of CO2 relative to valuable chemical compounds such as methanol or dimethyl ether (DME) is an attractive route for reducing CO2 emissions in the atmosphere. In the present work, the hydrogenation of CO2 into DME over CuO-In2O3, supported on halloysite nanotubes (HNT) was investigated in the temperature range 200–300 °C at 40 atm. HNT appears to be novel promising support for bifunctional catalysts due to its thermal stability and the presence of acidic sites on its surface. CuO-In2O3/HNT catalysts demonstrate higher CO2 conversion and DME selectivity compared to non-indium CuO/HNT catalysts. The catalysts were investigated by N2 adsorption, X-ray diffraction, hydrogen-temperature programmed reduction and transition electron microscopy. The acid sites were analyzed by temperature programmed desorption of ammonia. It was shown that CuO/HNT was unstable under reaction conditions in contrast to CuO-In2O3/HNT. The best CuO-In2O3/HNT catalyst provided CO2 conversion of 7.6% with 65% DME selectivity under P = 40 atm, T = 250 °C, gas hour space velocity 12,000 h−1 and H2:CO2 = 3:1.

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Comparision on the Low-Temperature NH3-SCR Performance of γ-Fe2O3 Catalysts Prepared by Two Different Methods

Catalysts ◽

10.3390/catal9121018 ◽

2019 ◽

Vol 9 (12) ◽

pp. 1018

Author(s):

Naveed Husnain ◽

Enlu Wang ◽

Shagufta Fareed ◽

Muhammad Tuoqeer Anwar

Keyword(s):

Photoelectron Spectroscopy ◽

Catalytic Reduction ◽

Acid Sites ◽

High Concentration ◽

X Ray ◽

Nh3 Scr ◽

Transmission Electron ◽

Temperature Programmed ◽

Diffuse Reflectance Infrared

Maghemite (γ-Fe2O3) catalysts were prepared by two different methods, and their activities and selectivities for selective catalytic reduction of NO with NH3 were investigated. The methods of X-ray powder diffraction (XRD), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H2-TPR), ammonia temperature-programmed desorption (NH3-TPD), transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) were used to characterize the catalysts. The resulted demonstrated that the γ-Fe2O3 nanoparticles prepared by the facile method (γ-Fe2O3–FM) not only exhibited better NH3-SCR activity and selectivity than the catalyst prepared by the coprecipitation method but also showed improved SO2 tolerance. This superior NH3-SCR performance was credited to the existence of the larger surface area, better pore structure, a high concentration of lattice oxygen and surface-adsorbed oxygen, good reducibility, a lot of acid sites, lower activation energy, adsorption of the reactants, and the existence of unstable nitrates on the surface of the γ-Fe2O3–FM.

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Comprehensive Comparison between Nanocatalysts of Mn−Co/TiO2 and Mn−Fe/TiO2 for NO Catalytic Conversion: An Insight from Nanostructure, Performance, Kinetics, and Thermodynamics

Catalysts ◽

10.3390/catal9020175 ◽

2019 ◽

Vol 9 (2) ◽

pp. 175 ◽

Cited By ~ 9

Author(s):

Yan Gao ◽

Tao Luan ◽

Shitao Zhang ◽

Wenchao Jiang ◽

Wenchen Feng ◽

...

Keyword(s):

Metal Oxides ◽

Photoelectron Spectroscopy ◽

Catalytic Performance ◽

Acid Sites ◽

Tio2 Sample ◽

Kinetics And Thermodynamics ◽

No Conversion ◽

X Ray ◽

Nh3 Scr ◽

Temperature Programmed

The nanocatalysts of Mn−Co/TiO2 and Mn−Fe/TiO2 were synthesized by hydrothermal method and comprehensively compared from nanostructures, catalytic performance, kinetics, and thermodynamics. The physicochemical properties of the nanocatalysts were analyzed by N2 adsorption, transmission electron microscope (TEM), X-ray diffraction (XRD), H2-temperature-programmed reduction (TPR), NH3-temperature-programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). Based on the multiple characterizations performed on Mn−Co/TiO2 and Mn−Fe/TiO2 nanocatalysts, it can be confirmed that the catalytic properties were decidedly dependent on the phase compositions of the nanocatalysts. The Mn−Co/TiO2 sample presented superior structure characteristics than Mn−Fe/TiO2, with the increased surface area, the promoted active components distribution, the diminished crystallinity, and the reduced nanoparticle size. Meanwhile, the Mn4+/Mnn+ ratios in the Mn−Co/TiO2 nanocatalyst were higher than Mn−Fe/TiO2, which further confirmed the better oxidation ability and the larger amount of Lewis acid sites and Bronsted acid sites on the sample surface. Compared to Mn−Fe/TiO2 nanocatalyst, Mn−Co/TiO2 nanocatalyst displayed the preferable catalytic property with higher catalytic activity and stronger selectivity in the temperature range of 75–250 °C. The results of mechanism and kinetic study showed that both Eley-Rideal mechanism and Langmuir-Hinshelwood mechanism reactions contributed to selective catalytic reduction of NO with NH3 (NH3-SCR) over Mn−Fe/TiO2 and Mn−Co/TiO2 nanocatalysts. In this test condition, the NO conversion rate of Mn−Co/TiO2 nanocatalyst was always higher than that of Mn−Fe/TiO2. Furthermore, comparing the reaction between doping transition metal oxides and NH3, the order of temperature−Gibbs free energy under the same reaction temperature is as follows: Co3O4 < CoO < Fe2O3 < Fe3O4, which was exactly consistent with nanostructure characterization and NH3-SCR performance. Meanwhile, the activity difference of MnOx exhibited in reducibility properties and Ellingham Diagrams manifested the promotion effects of cobalt and iron dopings. Generally, it might offer a theoretical method to select superior doping metal oxides for NO conversion by comprehensive comparing the catalytic performance with the insight from nanostructure, catalytic performance, reaction kinetics, and thermodynamics.

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