Adsorption at variable temperatures of individual components (NO, NO2, CO, O2, C3H6) and their mi... more Adsorption at variable temperatures of individual components (NO, NO2, CO, O2, C3H6) and their mixtures simulating the feed of the selective catalytic reduction (SCR) of NOx with propene over NiZSM-5 catalysts was investigated by electron paramagnetic resonance, infrared, and mass spectroscopies to provide direct insights into the nature of the primary reaction intermediates and alternation of the valence state of the nickel centers. The key intermediates ({Ni–NO}2+, {Ni+–C3H6}, {Ni+–(CO)n}, and {Ni2+–O2–}) relevant to the SCR process were isolated and identified, and their structure together with spectroscopic signatures were ascertained by parallel density functional theory molecular modeling. Alternation of the nickel valence state during the SCR reaction, leading to formation of a Ni2+/Ni+ redox couple, was triggered by the reductive adsorption of NO and oxidative adsorption of O2. The sequence at which the reactant molecules were reactively coordinated was dictated by the oxidation state of the nicke...
ABSTRACT Electron magnetic resonance (EMR) is a group of closely related spectroscopic techniques... more ABSTRACT Electron magnetic resonance (EMR) is a group of closely related spectroscopic techniques which includes, apart from the most common continuous-wave electron paramagnetic resonance (CW-EPR), high-field electron paramagnetic resonance (HF-EPR), electron nuclear double resonance (ENDOR), electron spin resonance imaging (ESRI) and a number of Fourier transform-based pulsed techniques (FT-EPR), such as electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation spectroscopy. The first applications of EPR in materials chemistry and related fields were reported at the beginning of the 1960s. This chapter presents electron paramagnetic resonance spectroscopy (EPR) principal types and their characteristic features. It also deals with electron spin in a magnetic field. Finally, the chapter talks about the advanced EMR techniques.
Optical and EPR spectroscopic investigations of Cu-bearing vesuvianite (cyprine') were perfor... more Optical and EPR spectroscopic investigations of Cu-bearing vesuvianite (cyprine') were performed in order to obtain new evidence for the lattice position of Cu 2+ ions in this mineral and to confirm the origin of its blue colouration. The optical absorption spectrum of cyprine' can be best explained assuming that Cu 2+ ions occupy irregular B-site of local symmetry close to D 4h , which is consistent with EPR data and previous XRD analysis. The blue colour of cyprine' is determined by the absorption bands 15600 cm -1 in the σ-spectrum and 16700 cm -1 in the π-spectrum. The EPR spectrum composed of an asymmetric signals with g ∥=2.3404, g ⊥=2.0625, A ∥=14,78 mT and A ⊥=2.5 mT is characteristic of Cu 2+ in square planar symmetry. The molecular bonding parameters calculated on the basis of both optical and EPR spectra indicate that there is an appreciable covalent contribution to the predominantly ionic Cu-O bond
Various members of the tourmaline group (schorl, dravite, and elbaite) as well as the products of... more Various members of the tourmaline group (schorl, dravite, and elbaite) as well as the products of their gradual oxidation were investigated by EPR spectroscopy in X and Q bands at 293 K and 77 K. In the EPR spectra of the schorl and dravite samples the signals at g ≈ 2 and 4.3 were attributed to clustered and isolated Fe3+ ions, respectively. The EPR spectra of Fe-poor elbaite are dominated by signals at g ≈ 2.5 and 3.5, assigned to Mn2+ ions. In the schorl and dravite samples, gradually annealed in air above 750 K, the total intensity of the EPR spectrum increased with increasing temperature, due to the oxidation of Fe2+ ( d 6) to Fe3+ ( d 5) ions. The Fe3+ ion being a product of thermal oxidation initially occupies sites with g ≈ 4.3 and after heating at temperatures above 1070 K forms clusters with g ≈ 2.0. In the Fe-poor elbaite the total intensity of the spectrum gradually decreased with the increasing oxidation temperature up to 1150 K, due to the transformation of paramagnetic Mn2+ ( d 5) into Mn3+ ( d 4) ions. Simultaneously, the signal of Fe3+ at g ≈ 4.3 became more pronounced. At still higher temperatures ( T > 1150 K) the intensity of the signal around g ≈ 2.0 increased indicating further oxidation of Mn3+ to Mn4+ ( d 3).
ABSTRACT TPR (Temperature Programmed Reduction) and EPR (Electron Paramagnetic Resonance) corrobo... more ABSTRACT TPR (Temperature Programmed Reduction) and EPR (Electron Paramagnetic Resonance) corroborated with UV-Vis methods were used to get a new insight into the status of nickel ions in chrysoprases from various localities. The investigation showed speciation of Ni into 2:1 highly dispersed phyllosilicates and extra-framework species grafted on the surface of chalcedony matrix. Both kinds of nickel exhibit a distorted octahedral coordination giving rise to a broad EPR spectrum with g = 2.17 and three characteristic d-d bands that can be parameterised with 10Dq = 8897cm-1 and B = 953cm-1.
Soot particles released from diesel engines have been considered as one of the main sources of ai... more Soot particles released from diesel engines have been considered as one of the main sources of air pollution, and the elimination of soot particles has become a crucial issue for air purification.
Abstract This special Issue of the Journal of Catalysis pays tribute to Professor Michel Che. In ... more Abstract This special Issue of the Journal of Catalysis pays tribute to Professor Michel Che. In addition to the Editorial Preface, colleagues share their recollections of his vigorous endeavour he displayed throughout his scientific life to promote efficient international collaborations, as well as to bridge fundamental science and its applications. His human qualities are unanimously valued, which has left a trail marked with friendship.
MnxCo1−xOδ/3DOM-m Ti0.7Si0.2W0.1Oy catalysts exhibited good catalytic performance for the simulta... more MnxCo1−xOδ/3DOM-m Ti0.7Si0.2W0.1Oy catalysts exhibited good catalytic performance for the simultaneous removal of soot and NOx.
Abstract A simple “green” method for the synthesis of cobalt‑zinc ferrites nanoparticles has been... more Abstract A simple “green” method for the synthesis of cobalt‑zinc ferrites nanoparticles has been proposed. XRD, SEM/EDX, TEM, Mossbauer and FTIR techniques have been applied to investigate structure and morphology of the obtained spinel ferrites. Analysis of the cation distribution showed that during the transition from cobalt ferrite to zinc ferrite the inversion degree of the Fe cations decreases from δ = 0.89 to δ = 0.00. IR spectra show the presence of characteristic peaks of the MA-O (at ~450 cm−1) and MB-O (at ~610 cm−1) vibrations as well as the vibrations of functional groups of the honey residuals. It was concluded that honey acts as reductant and stabilizer preventing agglomeration of the nanoparticles. The force constants of the tetrahedral and octahedral bonds have been calculated. Dependence of the Debye temperature on Zn content was also established for the first time: it is increased from 782 K to 805 K with Zn increasing. It was shown that the ZnFe2O4 sample exhibits the highest adsorption capacity (289 mg/g) towards lead cations. This result is explained in terms of surface acidity of the examined samples, estimated from the variations of the ionic-covalent bond parameter. The Langmuir, Freundlich and Dubinin-Radushkevich models were tested to evaluate the adsorption mechanism. The efficiency of heat release by the CoxZn1-xFe2O4 magnetic nanoparticles for magnetic hyperthermia was investigated as well. The registered induction heating curves depend on the Zn content in the CoxZn1-xFe2O4 samples. The sample with х(Zn) = 0.6 exhibits the maximal specific loss power equal to 2.56 W/g. The intrinsic loss power (ILP) value is 0.40, and is 2.7 times higher than the ILP value of commercial Fe3O4. The obtained ferrite materials can be, therefore, used in magnetic hyperthermia applications and Pb(II) adsorption.
Abstract Soot particles emitted from the diesel exhausts have caused serious air pollution and ca... more Abstract Soot particles emitted from the diesel exhausts have caused serious air pollution and catalytic soot combustion is promising for soot abatement. In this work, two kinds of soot oxidation catalysts, including phase-pure birnessite-type K2Mn4O8 (K-OL-1) and cryptomelane-type K2-xMn8O16 (K-OMS-2), were successfully prepared by a very simple method. In preparation of these catalysts, KMnO4 and glucose were used in various proportions and different calcination temperatures employed. The as-prepared catalysts exhibit excellent catalytic performance in the loose contact mode with the presence of water (10 %). Specifically, most of them completely remove soot particles below 450 °C. More importantly, the birnessite-type K2Mn4O8 catalysts exhibit good tolerance for sulfur and water and the presence of water in the interlayer space is the reason for this property. The possible reaction mechanisms for soot combustion on K2Mn4O8 catalysts are related to reaction of active oxygen species and NO2-assisted oxidation. This work shed a light on the important role of the interlayer gallery species (K+, H2O) in the catalytic activity of the birnessite materials in soot combustion, which so far has not been recognized. Meanwhile, the birnessite-type K2Mn4O8 catalysts are low-cost, the excellent catalytic performance and simple synthesis method give them a great potential for industrial applications.
Adsorption at variable temperatures of individual components (NO, NO2, CO, O2, C3H6) and their mi... more Adsorption at variable temperatures of individual components (NO, NO2, CO, O2, C3H6) and their mixtures simulating the feed of the selective catalytic reduction (SCR) of NOx with propene over NiZSM-5 catalysts was investigated by electron paramagnetic resonance, infrared, and mass spectroscopies to provide direct insights into the nature of the primary reaction intermediates and alternation of the valence state of the nickel centers. The key intermediates ({Ni–NO}2+, {Ni+–C3H6}, {Ni+–(CO)n}, and {Ni2+–O2–}) relevant to the SCR process were isolated and identified, and their structure together with spectroscopic signatures were ascertained by parallel density functional theory molecular modeling. Alternation of the nickel valence state during the SCR reaction, leading to formation of a Ni2+/Ni+ redox couple, was triggered by the reductive adsorption of NO and oxidative adsorption of O2. The sequence at which the reactant molecules were reactively coordinated was dictated by the oxidation state of the nicke...
ABSTRACT Electron magnetic resonance (EMR) is a group of closely related spectroscopic techniques... more ABSTRACT Electron magnetic resonance (EMR) is a group of closely related spectroscopic techniques which includes, apart from the most common continuous-wave electron paramagnetic resonance (CW-EPR), high-field electron paramagnetic resonance (HF-EPR), electron nuclear double resonance (ENDOR), electron spin resonance imaging (ESRI) and a number of Fourier transform-based pulsed techniques (FT-EPR), such as electron spin echo envelope modulation (ESEEM) and hyperfine sublevel correlation spectroscopy. The first applications of EPR in materials chemistry and related fields were reported at the beginning of the 1960s. This chapter presents electron paramagnetic resonance spectroscopy (EPR) principal types and their characteristic features. It also deals with electron spin in a magnetic field. Finally, the chapter talks about the advanced EMR techniques.
Optical and EPR spectroscopic investigations of Cu-bearing vesuvianite (cyprine') were perfor... more Optical and EPR spectroscopic investigations of Cu-bearing vesuvianite (cyprine') were performed in order to obtain new evidence for the lattice position of Cu 2+ ions in this mineral and to confirm the origin of its blue colouration. The optical absorption spectrum of cyprine' can be best explained assuming that Cu 2+ ions occupy irregular B-site of local symmetry close to D 4h , which is consistent with EPR data and previous XRD analysis. The blue colour of cyprine' is determined by the absorption bands 15600 cm -1 in the σ-spectrum and 16700 cm -1 in the π-spectrum. The EPR spectrum composed of an asymmetric signals with g ∥=2.3404, g ⊥=2.0625, A ∥=14,78 mT and A ⊥=2.5 mT is characteristic of Cu 2+ in square planar symmetry. The molecular bonding parameters calculated on the basis of both optical and EPR spectra indicate that there is an appreciable covalent contribution to the predominantly ionic Cu-O bond
Various members of the tourmaline group (schorl, dravite, and elbaite) as well as the products of... more Various members of the tourmaline group (schorl, dravite, and elbaite) as well as the products of their gradual oxidation were investigated by EPR spectroscopy in X and Q bands at 293 K and 77 K. In the EPR spectra of the schorl and dravite samples the signals at g ≈ 2 and 4.3 were attributed to clustered and isolated Fe3+ ions, respectively. The EPR spectra of Fe-poor elbaite are dominated by signals at g ≈ 2.5 and 3.5, assigned to Mn2+ ions. In the schorl and dravite samples, gradually annealed in air above 750 K, the total intensity of the EPR spectrum increased with increasing temperature, due to the oxidation of Fe2+ ( d 6) to Fe3+ ( d 5) ions. The Fe3+ ion being a product of thermal oxidation initially occupies sites with g ≈ 4.3 and after heating at temperatures above 1070 K forms clusters with g ≈ 2.0. In the Fe-poor elbaite the total intensity of the spectrum gradually decreased with the increasing oxidation temperature up to 1150 K, due to the transformation of paramagnetic Mn2+ ( d 5) into Mn3+ ( d 4) ions. Simultaneously, the signal of Fe3+ at g ≈ 4.3 became more pronounced. At still higher temperatures ( T > 1150 K) the intensity of the signal around g ≈ 2.0 increased indicating further oxidation of Mn3+ to Mn4+ ( d 3).
ABSTRACT TPR (Temperature Programmed Reduction) and EPR (Electron Paramagnetic Resonance) corrobo... more ABSTRACT TPR (Temperature Programmed Reduction) and EPR (Electron Paramagnetic Resonance) corroborated with UV-Vis methods were used to get a new insight into the status of nickel ions in chrysoprases from various localities. The investigation showed speciation of Ni into 2:1 highly dispersed phyllosilicates and extra-framework species grafted on the surface of chalcedony matrix. Both kinds of nickel exhibit a distorted octahedral coordination giving rise to a broad EPR spectrum with g = 2.17 and three characteristic d-d bands that can be parameterised with 10Dq = 8897cm-1 and B = 953cm-1.
Soot particles released from diesel engines have been considered as one of the main sources of ai... more Soot particles released from diesel engines have been considered as one of the main sources of air pollution, and the elimination of soot particles has become a crucial issue for air purification.
Abstract This special Issue of the Journal of Catalysis pays tribute to Professor Michel Che. In ... more Abstract This special Issue of the Journal of Catalysis pays tribute to Professor Michel Che. In addition to the Editorial Preface, colleagues share their recollections of his vigorous endeavour he displayed throughout his scientific life to promote efficient international collaborations, as well as to bridge fundamental science and its applications. His human qualities are unanimously valued, which has left a trail marked with friendship.
MnxCo1−xOδ/3DOM-m Ti0.7Si0.2W0.1Oy catalysts exhibited good catalytic performance for the simulta... more MnxCo1−xOδ/3DOM-m Ti0.7Si0.2W0.1Oy catalysts exhibited good catalytic performance for the simultaneous removal of soot and NOx.
Abstract A simple “green” method for the synthesis of cobalt‑zinc ferrites nanoparticles has been... more Abstract A simple “green” method for the synthesis of cobalt‑zinc ferrites nanoparticles has been proposed. XRD, SEM/EDX, TEM, Mossbauer and FTIR techniques have been applied to investigate structure and morphology of the obtained spinel ferrites. Analysis of the cation distribution showed that during the transition from cobalt ferrite to zinc ferrite the inversion degree of the Fe cations decreases from δ = 0.89 to δ = 0.00. IR spectra show the presence of characteristic peaks of the MA-O (at ~450 cm−1) and MB-O (at ~610 cm−1) vibrations as well as the vibrations of functional groups of the honey residuals. It was concluded that honey acts as reductant and stabilizer preventing agglomeration of the nanoparticles. The force constants of the tetrahedral and octahedral bonds have been calculated. Dependence of the Debye temperature on Zn content was also established for the first time: it is increased from 782 K to 805 K with Zn increasing. It was shown that the ZnFe2O4 sample exhibits the highest adsorption capacity (289 mg/g) towards lead cations. This result is explained in terms of surface acidity of the examined samples, estimated from the variations of the ionic-covalent bond parameter. The Langmuir, Freundlich and Dubinin-Radushkevich models were tested to evaluate the adsorption mechanism. The efficiency of heat release by the CoxZn1-xFe2O4 magnetic nanoparticles for magnetic hyperthermia was investigated as well. The registered induction heating curves depend on the Zn content in the CoxZn1-xFe2O4 samples. The sample with х(Zn) = 0.6 exhibits the maximal specific loss power equal to 2.56 W/g. The intrinsic loss power (ILP) value is 0.40, and is 2.7 times higher than the ILP value of commercial Fe3O4. The obtained ferrite materials can be, therefore, used in magnetic hyperthermia applications and Pb(II) adsorption.
Abstract Soot particles emitted from the diesel exhausts have caused serious air pollution and ca... more Abstract Soot particles emitted from the diesel exhausts have caused serious air pollution and catalytic soot combustion is promising for soot abatement. In this work, two kinds of soot oxidation catalysts, including phase-pure birnessite-type K2Mn4O8 (K-OL-1) and cryptomelane-type K2-xMn8O16 (K-OMS-2), were successfully prepared by a very simple method. In preparation of these catalysts, KMnO4 and glucose were used in various proportions and different calcination temperatures employed. The as-prepared catalysts exhibit excellent catalytic performance in the loose contact mode with the presence of water (10 %). Specifically, most of them completely remove soot particles below 450 °C. More importantly, the birnessite-type K2Mn4O8 catalysts exhibit good tolerance for sulfur and water and the presence of water in the interlayer space is the reason for this property. The possible reaction mechanisms for soot combustion on K2Mn4O8 catalysts are related to reaction of active oxygen species and NO2-assisted oxidation. This work shed a light on the important role of the interlayer gallery species (K+, H2O) in the catalytic activity of the birnessite materials in soot combustion, which so far has not been recognized. Meanwhile, the birnessite-type K2Mn4O8 catalysts are low-cost, the excellent catalytic performance and simple synthesis method give them a great potential for industrial applications.
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