Mihail Yordanov Mihaylov

Mihail Yordanov Mihaylov
Bulgarian Academy of Sciences | BAS · Institute of General and Inorganic Chemistry

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85
Publications
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2,665
Citations
Citations since 2016
15 Research Items
1555 Citations
2016201720182019202020212022050100150200250300350
2016201720182019202020212022050100150200250300350
2016201720182019202020212022050100150200250300350
2016201720182019202020212022050100150200250300350
Additional affiliations
January 1998 - present
Bulgarian Academy of Sciences
Position
  • Professor (Associate)

Publications

Publications (85)
Article
Efficient CO2 capture is necessary to solve the current environmental problems of global warming. Porous materials are promising for this purpose and adsorption capacity is a critical issue. Large cations in zeolites can often attach two small molecules, but it is not yet well established whether this applies to CO2. Here we present a detailed FTIR...
Article
Coal fly ash zeolites (CFAZs) of type X with low (Na-X) and medium (Na-Ca-X) content of calcium were synthesized by alkaline conversion of lignite coal fly ash generated by combustion of lignite with lower and higher limestone amounts, extracted from different coal deposits and burned in separate thermal power plants. The concentration and state of...
Article
Full-text available
Nickel-decorated mesoporous cerium–iron oxide composites were synthesized by a combination of incipient wetness impregnation and template-assisted hydrothermal techniques. The effects of the Fe/Ce ratio and the calcination temperature of cerium–iron oxides on the phase composition, texture, structure, and redox properties of the composites were stu...
Article
Full-text available
The variety of functionalities and porous structures inherent to metal-organic frameworks (MOFs) together with the facile tunability of their properties makes these materials suitable for a wide range of existing and emerging applications. Many of these applications are based on processes involving interaction of MOFs with guest molecules. To optim...
Article
Nano-scaled UiO-66 and UiO-66-NH2 crystals are synthesized via a solvothermal procedure and investigated regarding their applicability in CO2 sensing devices. The interaction between CO2 and UiO-66 as well as UiO-66-NH2 is studied via FTIR and dielectric measurements with a home-made sensing-cell contraption. The affinity towards low CO2 concentrat...
Article
Metal-organic frameworks (MOFs) and MOF-based materials find increasing and diverse applicability. The performance of MOFs in adsorption and catalysis is strongly related to their acid-basic properties. Here we report on the development of acidity (protonic and Lewis) and basicity during thermo-vacuum treatment of two MOFs of practical importance,...
Article
A porous scandium MOF denoted STA-27 (St Andrews Porous Material-27) has been synthesised solvothermally using the 2,3,5,6-tetrakis(4-carboxyphenyl)pyrazine anion (TCPP4-) as the tetratopic carboxylate linker. STA-27 possesses a unique scandium-based 1D rod secondary building unit (SBU) comprising corner-sharing scandium Sc2O11 dimers connected via...
Poster
Full-text available
Surface azides (N3‐) are formed on reduced ceria after adsorption of NO. They are characterized by antisymmetric N‐N‐N stretching modes at 2045‐2042 cm‐1. The N3‐ species are thermally stable up to 300 oC but the stability decreases in presence of water. Similarly to NCO‐, azides are inert toward pure NO or O2 at ambient temperature but readily int...
Poster
Full-text available
At the initial stages of NO adsorption on activated (oxidized) ceria nanoparticles mainly symmetric nitrites and trans‐hyponitrites ([N2O2]2−) are simultaneously produced as a result of NO disproportionation. At further stages non‐symmetric NO2‐ species, N2O and small amount of nitrates are formed. In the presence of small amounts of oxygen, the hy...
Article
Adsorption of NO and co-adsorption of NO and O2 on ceria have been re-investigated by FTIR spectroscopy. To provide unambiguous assignments of the IR bands, adsorption of ¹⁵NO and co-adsorption of ¹⁴NO + ¹⁵NO isotopic mixtures have also been studied and DFT calculations performed. At the initial adsorption stages mainly symmetric nitrite species (2...
Article
A fully interpenetrated 8,3-connected zirconium MOF with the the-i topology type, STA-26, has been prepared using the 4,4',4"-(2,4,6-trimethylbenzene-1,3,5-triyl)tribenzoate (TMTB) tritopic linker with formic acid as a modulating agent. In the as-prepared form it possesses Im-3m symmetry compared with the Pm-3m symmetry of the non-interpenetrated a...
Article
A microporous Al trimesate-based Metal Organic Framework (MOF), denoted MIL-96(Al), was selected as a porous hybrid filler for the processing of Mixed Matrix Membranes (MMMs) for CO2/N2 post combustion separation. First, the structural model of MIL-96(Al) initially reported was revisited using a combination of synchrotron-based single crystal X-ray...
Article
Adsorption of CO2 on MIL-53(Al) and NH2-MIL-53(Al) has been studied by FTIR spectroscopy at different temperatures and equilibrium pressures. For better interpretation of the spectra ¹³CO2 was also utilized. It is established that with both samples at low coverages CO2 forms O-bonded complexes with the structural OH groups (OH...O¹²CO). These speci...
Article
Metal-organic frameworks (MOFs) possessing open metal sites (e.g., from the CPO-27 series) are a promising class of materials for hydrogen storage. However, there is still no consensus on the vibrational signatures of H2 adsorbed on different sites. In this work we report results of a combined Fourier transform infrared (FTIR) spectroscopy and dens...
Article
Full-text available
Metal cations that are exchanged in zeolites are generally characterized by a low coordination number and can adsorb more than one small molecule. For instance, Cu + ions exchanged in ZSM-5 (and in other zeolites) can bind, at low temperature, up to three CO and up to two NO molecules. Although mixed aqua-carbonyl complexes are easily formed, here...
Article
Full-text available
FTIR spectra of (12)CO2 and (12)CO2 + (13)CO2 mixtures adsorbed on MIL-53(Al) reveal the formation of highly symmetric dimeric (CO2)2 species connected to two structural OH groups.
Article
To design new deNOx materials and processes we need to know in details the mechanism of NO interaction with solid surfaces. Many NOx conversion catalysts contain ceria as a component and cerium changes its oxidation state in the course of redox catalytic processes. Here we show that the interaction between NO and reduced ceria leads to formation of...
Article
Full-text available
Acidity of solids is decisive for their interaction with guest molecules. One of the most used methods for measuring the acidity of surface hydroxyl groups is the hydrogen bond method based on the spectral shift of the OH stretching modes induced by the adsorption of weak bases. However, many materials of practical interest (e.g. metal organic fram...
Article
Hydrogen dissociation and spillover on supported metal nanoparticles have received renewed interest because these chemical processes are closely related to applications in heterogeneous catalysis and hydrogen storage. In heterogeneous catalysis, spillover can control the reaction rate and selectivity of a wide range of reactions, e.g. hydrogenation...
Article
Cations exchanged in zeolites are generally characterized by a low coordination number and can thus attach simultaneously more than one small guest molecule. For instance, Cu+ ions in ZSM-5 can accept, at low temperature, up to three CO and up to two NO molecules. However, only one N2 molecule can be coordinated to such sites. Although mixed aqua-c...
Article
Full-text available
We show that the first stages of interaction between NO and reduced ceria comprise the formation of azides, N3-, with simultaneous oxidation of Ce3+ to Ce4+. This finding impose revision of some current views of catalytic NO conversion and may contribute to design new deNOx materials and processes.
Article
Full-text available
The reduction of a 1.3% Rh/TiO2 sample with carbon monoxide leads to the formation of uniform Rh nanoparticles with a mean diameter of dp ≈ 2.2 nm. Adsorption of CO on the reduced Rh/TiO2 produces linear and bridged carbonyls bound to metallic Rh(0) sites and only a few geminal dicarbonyls of Rh(I). The ν(CO) of linear Rh(0)-CO complexes is strongl...
Poster
The coordination chemistry of Cu+ cations in zeolites raises a big interest. About 20 years ago, it was established that Cu+ sites in Cu-ZSM-5 can form mono- di- and tricarbonyls, as well as mono- and di-nitrosyls. Later, it was reported that mixed complexes of the Cu+(H2O)xCO, Cu+(NH3)xCO and Cu+(CH3COCH3)CO types can also exist. A possible reason...
Article
Full-text available
The OH/OD isotopic shift factors (i = νOH/νOD) of isolated silanols on SiO2 and [Si]BEA are between 1.3563 and 1.3568, values lower than the theoretical shift of 1.3744. However, i of the harmonic OH modes almost coincides with the theoretical value which indicates that the experimental deviations in this case are mainly due to anharmonicity. The a...
Article
Full-text available
We report a combined computational and experimental IR study of polycarbonyl species on Ni–MOR zeolite formed after adsorption of 12C16O/13C18O isotopic mixtures, which allowed us to suggest a justified assignment of the vibrational bands in the complex IR spectra. For identification of all individual IR bands of the polycarbonyl complexes containi...
Article
A novel preparation strategy was performed to obtain uniform and size controlled, in a large scale, copper nanoparticles, hosted into mesoporous silica matrix. The method includes the initial deposition of finely dispersed copper nanoparticles, using a conventional incipient wetness impregnation of silica matrix with small amount of nitrate precurs...
Article
Full-text available
Ni+ cations were produced in a Ni–ZSM-5 zeolite by partial reduction with CO, and the ability of the Ni+ and Ni2+ sites to coordinate 14N2, 15N2, and/or CO molecules was studied by FTIR spectroscopy. With Ni+ cations, CO produces mono-, di-, and tricarbonyl species while only mono- and dicarbonyls are formed with Ni2+. Adsorption of 14N2 at 100 K r...
Article
In this review, some of the advantages of the use of isotopically labelled molecules for FTIR characterisation of porous materials are summarised. The most important sites determining the properties of these materials are the hydroxyl groups and the incorporated cations. D H exchange is very useful for characterisation of hydroxyls and here some ne...
Article
Using a combination of state-of-the-art computational modeling and Fourier transform infrared (FTIR) spectroscopy study of the surface species formed during interaction of CO2 or CO with activated (stoichiometric), reduced, and hydroxylated ceria, CeO2, we assigned various experimentally observed vibrational modes to individual types of surface spe...
Article
A Au/SiO2 sample was prepared by ammonia-assisted grafting using HAuCl4 as a gold precursor. Gold on the sample evacuated at 673 K is essentially in metallic form: adsorption of CO at 100 K results in formation of Au0-CO species (IR band at 2122 cm-1 shifting to 2103 cm-1 at high coverage). Coadsorption of CO and O2 even at ambient temperature lead...
Article
Three different silica-supported nickel samples were prepared by successive adsorption, reduction, and passivation (SARP) of nickel. The materials obtained were characterized by various techniques (TEM, XRD, H2 chemisorption, FTIR spectroscopy of adsorbed CO, FMR). Metal nickel particles were uniformly distributed by size with all samples. With inc...
Poster
Full-text available
It has been reported that reduction of Co-ZSM-5 and Ni-ZSM-5 with CO resulted in creation of univalent Co+ and Ni+ cations. Similar results have been obtained with BEA zeolite. It has also been suggested that these univalent cations can be important active sites in some catalytic processes as selective reduction of NOx by hydrocarbons. Co+ in Co-ZS...
Article
Three MTW (H-ZSM-12) zeolite samples were synthesized by (i) direct hydrothermal method, (ii) desilication of the hydrothermal obtained product and (iii) mesostructuration of zeolite ZSM-12 seeds in the presence of hexadecyltrimethylammonium bromide. The samples were characterized by XRD, nitrogen adsorption isotherms, SEM, 27Al-MAS NMR and FTIR sp...
Article
The carbonyls formed after CO adsorption on Ru/ZrO2 are strongly affected by the sample pretreatment. A procedure leading to reproducible results is activation of the sample at 673 K first in oxygen and then in vacuo followed by adsorption of CO at 373 K. After this treatment three main bands are formed in the carbonyl region at ca. 2130, 2070, and...
Article
Full-text available
The possibilities to identify polycarbonyl species using different CO isotopic mixtures (12C16O+13C16O and 12C16O+13C18O) are regarded. The examples concern two nickel-containing catalysts, Ni–ZSM-5 and Ni/SiO2. Ni+ ions, present in Ni–ZSM-5 reduced by CO, can coordinate up to three CO molecules each. Ni+(CO)2 dicarbonyl structures are well establi...
Article
Accessible iron in oxidized Fe–ZSM-5 and Fe–BEA zeolites is mainly in the form of Fe3+ species that do not interact with CO. Some exchanged cations are stabilized as Fe2+ species and form carbonyls detected in the 2205–2190 cm−1 region. Evacuation of the samples at 673 K provokes autoreduction of part of Fe3+ and creation of more Fe2+ sites detecta...
Conference Paper
Full-text available
Reduction of Co-ZSM-5 with CO or pentene results in creation of Co + ions. The relative amount of these ions increases with cobalt loading. After reduction with CO, Co + polycarbonyls were formed. Destruction of these species by evacuation at 573 K results in disappearance of Co + ions probably as a result of their disproportionation to Co 2+ and C...
Article
Mesoporous nitrided MCM-41 was synthesized and physically characterized. The nitrogen species are predominantly present as imido NH groups as shown by infrared spectroscopy. The NH groups are located in the framework and are therefore inaccessible for reactant and probe molecules. Deuterium exchange experiments support this interpretation. The surf...
Article
The state of the accessible copper ions in a Cu-basolite C300 sample (copper benzene-1,3,5-tricarboxylate) was studied by CO as an IR probe molecule. Low temperature CO adsorption on a sample activated at 473 K results in a series of carbonyl bands. Three intense sharp bands at 2141, 2128 and 2123 cm(-1) are very sensitive to the CO equilibrium pre...
Article
Infrared spectroscopy of adsorbed CO has been used to characterize the effect of adsorbed methanol on the Lewis acidity of 4 nm rutile TiO(2) nanoparticles. Measurements of CO absorbance and vibrational frequency have revealed that CO adsorbs primarily at one class of Lewis acid sites on clean TiO(2) particles, where evidence for lateral interactio...
Article
Iron was introduced by ionic exchange inside the FER structure in order to yield a Fe-FER series with increasing metal loading. Characterization of the Fe2+ cations by adsorption of CO at liquid nitrogen temperature followed by infrared spectroscopy allowed to identify three distinct sites for iron. The most abundant iron species are located on eas...
Article
Fe–FER zeolites were characterized by FTIR spectroscopy of adsorbed CO and NO. Two aged samples (Fe–FER-1 and Fe–FER-4 with Fe content of 1.1 and 3.7 wt%, respectively) and one freshly prepared 57Fe rich sample (57Fe–FER, designed for Mo¨ ssbauer studies and containing 1.5 wt% Fe) were studied. Both CO and NO are adsorbed onto Fe2+ cations and have...
Article
An Fe,H-ZSM-5 sample (Si/Al ratio of 13.5, Fe concentration of 1.18 wt %) was prepared by liquid ion exchange from solution of FeCl2 under nitrogen atmosphere at 370 K. When the sample is treated with oxygen at 673 K, iron is mainly in the Fe3+ state, including (i) Fe3+−OH hydroxyl groups monitored in the IR spectra by a band at 3672 cm−1, (ii) oli...
Article
FTIR spectroscopy was applied to the investigation of the nitrosyl complexes formed with the extra-framework iron species in Fe-ferrierite (Fe-FER). To clarify the loading effect oil the nature Of file species formed. six ferrierites with Fe loadings varying between 0 and 3.7 wt % were prepared via ionic exchange and investigated. A Fe/SiO(2) and a...
Article
MgO-supported gold prepared by adsorption of Au(CH3)2(acac) (acac is acetylacetonate) on partially dehydroxylated MgO was activated for CO oxidation catalysis by treatment in flowing helium at 473 K. X-ray absorption spectra showed that the activation involved reduction of the gold and formation of clusters (with an average diameter <10 Å) in which...
Article
A sample consisting of gold dispersed on high-area porous lanthanum oxide was prepared by adsorption of dimethylgold acetylacetonate. X-ray absorption spectroscopy and infrared (IR) spectroscopy were used to characterize the gold species and their ligands, and CO as a probe molecule was used with IR spectroscopy to follow the changes in the gold sp...
Article
The IR spectra that characterize La(2)O(3)-supported gold clusters show that the original Au(0) species can be oxidized by CO(2) during the catalytic CO oxidation reaction, indicating that CO(2) is the actual gold oxidizing agent.
Conference Paper
Full-text available
FTIR spectroscopy of adsorbed CO has been applied to study the properties of Mg, Ca, Sr and Ba cations exchanged in EMT zeolite. Since EMT is the hexagonal variant of Y zeolites, the properties have been interpreted in terms of cations occupying SII positions in two types of supercages. No difference in molecular level was observed with these two s...
Conference Paper
Full-text available
The interaction between Ni(CO)4 and two MFI zeolites, H-ZSM-5 and Ni-H-ZSM-5, has been studied by FTIR spectroscopy. Adsorption of Ni(CO)4 on H-ZSM-5 is reversible at room temperature and leads to formation of two kinds of species: (i) physically adsorbed Ni(CO)4 (IR band at 2048 cm −1) and (ii) β-Ni(CO)4 (IR bands at 2130, 2067 and 2000 cm −1), i....
Article
A Pt/TiO2 sample has been studied by adsorption and co-adsorption of CO and NO. It has been found that platinum is present in different oxidation states on the surface of the activated sample. Pt4+ ions are coordinatively saturated and form complexes neither with CO nor with NO. Pt3+ ions form, after CO adsorption, linear Pt3+–CO species stable up...
Article
A Pt/TiO2 sample has been studied by adsorption and co-adsorption of CO and NO. It has been found that platinum is present in different oxidation states on the surface of the activated sample. Pt4+ ions are coordinatively saturated and form complexes neither with CO nor with NO. Pt3+ ions form, after CO adsorption, linear Pt3+–CO species stable up...
Article
Full-text available
Adsorption of CO on Rh−ZSM-5 leads to the formation of the well-known Rh+(CO)2 gem-dicarbonyls, with vibrational frequencies νs(CO) at 2114 cm-1 and νas(CO) at 2048 cm-1, and the Rh2+(CO)2 species (2176 and 2142 cm-1). The dicarbonyl structures have been proven by 12CO−13CO co-adsorption. The Rh2+(CO)2 species are not able to accommodate a third CO...
Article
The use of IR spectroscopy of adsorbed CO for determination of gold speciation on supported gold catalysts is reviewed. Different ionic and metallic sites (Au3+, Au+, Au0, and Au–) can be differentiated on the basis of the frequency and stability of their surface carbonyl species formed after CO adsorption. In addition, the study of CO adsorption a...
Article
The state of gold on a Au/NaY zeolite sample prepared from Au(CH3)2(C5H7O2) and subjected to various treatments was monitored by infrared spectroscopy of adsorbed CO as a probe molecule. Spectra of CO adsorbed on a sample exposed to air and evacuated at room temperature indicate predominantly zerovalent gold nanoclusters (Auδ+−CO band at 2147 cm-1,...
Article
In this work we report some new nonclassical carbonyls of iridium formed after CO adsorption on Ir-ZSM-5 (Ir-MFI). Mainly Ir+ cations were found on sample activated at 523 K and reduced by CO at the same temperature. With CO they formed Ir+(CO)2 gem-dicarbonyls (2104 and 2033 cm(-1)) that decomposed at 673 K without leaving a measurable fraction of...
Article
Adsorption of CO on gold supported in zeolite NaY at 85 K led to the formation of (i) various carbonyls and isocarbonyls typical of the zeolite and (ii) carbonyls formed at cationic gold sites (observed in the 2186-2171 cm(-1) region). Analysis of the behavior of the bands allows their assignment to carbonyls of Au(3+) ions. At temperatures higher...
Article
The species formed after adsorption of NO on a Cr-ZSM-5 sample pre-subjected to different red-ox treatments have been studied by FTIR spectroscopy. Only NO+, occupying cationic positions in the zeolite, is formed on a non-reduced sample. Adsorption of NO on samples reduced by hydrogen at temperatures between 473 and 773 K leads mainly to formation...
Article
Adsorption of IR probe molecules (CO and NO) has been used for characterization of a Pt-Cr(2)O(3)/WO(3)-ZrO(2) sample. For better assignments of the results obtained 'blank' experiments with WO(3)-ZrO(2), Pt/WO(3)-ZrO(2) and Cr(2)O(3)/WO(3)-ZrO(2) were also performed. The Cr(2)O(3)/WO(3)-ZrO(2) sample was prepared via sulfate route and surface sulf...
Article
Different carbonyls are formed after CO adsorption at ambient temperature on a Pt-Na-mordenite (Pt-Na-MOR) sample. Pt(3+)(CO)(2) dicarbonyls (nu(s) at 2205 cm(-1) and nu(as) at 2167 cm(-1)) are decomposed without formation of monocarbonyls. The respective mixed-ligand species, Pt(3+)((12)CO)((13)CO), formed after (12)CO-(13)CO coadsorption, display...
Article
CO adsorption on Rh-ZSM-5 leads to the formation of both the well-known Rh+(CO)2 gem-dicarbonyls and another kind of dicarbonyl species as yet unknown. The latter are most probably formed with the participation of Rhn+ (n>1) ions in cationic positions in the zeolite. These species are characterized by νs(CO) at 2176 cm−1 and νas(CO) at 2142 cm−1. T...
Article
In this work, we report on the formation of several non-classical carbonyls of platinum produced after CO adsorption on Pt/H–ZSM-5. These are: (i) two kinds of Pt3+(CO)2 dicarbonyls (νs at 2212cm−1 and νas at 2176cm−1; νs at 2196cm−1 and νas at ca. 2155cm−1), which are decomposed without producing monocarbonyls; (ii) Pt2+–CO (2150cm−1), which form...
Article
This work reports the formation of some new non-classical carbonyls of platinum formed after CO adsorption on Pt–H–ZSM-5. These are: (i) Pt3+(CO)2 dicarbonyls (2211 and 2175 cm−1), which are decomposed without producing monocarbonyls; (ii) Pt2+(CO)2 (2165 and 2150 cm−1), decomposed via Pt2+–CO species (2113 cm−1); and (iii) Pt+(CO)3 complexes (2162...
Article
Adsorption of CO on Ni/TiO2 sample results in the formation of Ni2+CO and Ti4+CO species which are observed in the 2210–2185 cm−1 region and are characterized by similar stabilities. This makes unambiguous assignment of the carbonyl bands problematic. An analogous situation is found with Ni/ZrO2 sample (carbonyls in the 2190–2155 cm−1 region), wher...
Article
On the basis of IR spectroscopy studies it is concluded that the redox couples Co(2+)/Co(+) and Ni(2+)/Ni(+) operate in the selective catalytic reduction of nitrogen oxides with hydrocarbons over Co-ZSM-5 and Ni-ZSM-5.
Poster
Full-text available
The aim of this work is to investigate the species produced after CO adsorption on cationic platinum sites in Pt­H­ZSM­5. To prevent formation of anionic carbonyls, we gently decomposed the platinum amine complexes on the parent sample by calcination in oxidizing atmosphere. We expected that the big cationic radius of Pt 2+ and/or Pt + cations woul...
Article
Low-temperature CO adsorption on NiNaY leads to formation of Ni2+–CO species (IR band at 2195 cm−1). In line with this, mainly mononitrosyls (1892 cm−1) are produced after NO adsorption on the sample. These results show the existence of one coordinative vacancy of the Ni2+ ions in NiNaY. The results are compared with those of Ni-H-ZSM-5. In the lat...
Article
Low-temperature CO adsorption on NiNaY leads to formation of Ni²⁺–CO species (IR band at 2195 cm⁻¹). In line with this, mainly mononitrosyls (1892 cm⁻¹) are produced after NO adsorption on the sample. These results show the existence of one coordinative vacancy of the Ni²⁺ ions in NiNaY. The results are compared with those of Ni-H-ZSM-5. In the lat...
Article
Adsorption of NO and coadsorption of NO and O2 on H-ZSM-5 have been studied at low and room temperature by means of FTIR spectroscopy. For better interpretation of the spectra, experiments involving isotopic labeled molecules have been performed. Low temperature adsorption of NO on H-ZSM-5 results initially in formation of NO which is H-bonded to t...
Article
Adsorption of NO and coadsorption of NO and O-2 on H-ZSM-5 have been studied at low and room temperature by means of FTIR spectroscopy. For better interpretation of the spectra, experiments involving isotopic labeled molecules have been performed. Low temperature adsorption of NO on H-ZSM-5 results initially in formation of NO which is H-bonded to...
Article
The state of the chromium ions on Cr/ZrO2 and Cr/TiO2 samples has been tested by the IR spectra of adsorbed CO and NO. CO adsorption on activated samples leads mainly to formation of carbonyls related to the support. At low temperature, CO is also bonded to Crn+−OH groups that are present in low concentration. When NO is adsorbed on these samples,...
Article
Ni-ZSM-5 and Ni/SiO2 samples have been characterized by the IR spectra of adsorbed and coadsorbed NO and CO. Adsorption of CO at room temperature on Ni/SiO2 leads to formation of Ni2+−CO species (ν(CO) at 2192 cm-1) that are easily destroyed by evacuation. The carbonyls formed on Ni-ZSM-5 after CO adsorption are two types and characterized by bands...
Article
Adsorption of CO on Ni−ZSM-5 reveals the existence of two kinds of Ni2+ ions, with the respective stretching frequencies being at 2220 and 2212 cm-1. The carbonyl complexes are resistant to evacuation at room temperature, which is explained by the high electrophilicity of cations in a ZSM matrix. At 85 K and in the presence of CO, part of the Ni2+−...
Article
Full-text available
The formation of Ni(CO)4 during interaction of CO with silica-supported highly dispersed nickel metal (d av4 nm) was investigated by FTIR spectroscopy. At temperatures below 145 K, in addition to linear and bridged nickel carbonyls, CO adsorption on Ni0/SiO2 leads to the formation of Ni(CO) x (x=2, 3) subcarbonyls (band at ca. 2090 cm–1) and neglig...
Article
Different Ni/SiO2 specimens have been synthesized by impregnation (sample Ni–i–Si) and grafting Ni2+ ions from nickel amminocomplex solution on (i) SiO2 (sample Ni–1–Si) and (ii) reduced Ni–1–Si (sample Ni–2–Si). They have been characterized by TPR, IR spectroscopy, DR UV–VIS spectroscopy, XPS, XRD, TEM, and FMR. Due to the formation of surface sil...
Article
Using IR spectroscopy of probe molecules, it has been established that the deposition of nickel ions on zirconia by ion-exchange results in blocking of part of the surface Zr4+ cations. Reduction of the Ni2+ leads to liberation of the ion-exchange active sites and thus a next ion exchange can be performed with the reduced sample. Samples, prepared...
Article
Three Ni/TiO2 samples have been synthesized by impregnation (sample Ni-i-Ti), adsorption of Ni2+ ions from alkaline media on TiO2 (sample Ni-1-Ti) and on reduced Ni-1-Ti (sample Ni-2-Ti). The samples have been characterized by TPR, IR spectroscopy of adsorbed CO and X-ray diffraction. Impregnation leads to a less homogeneous distribution of the act...
Article
Interactions of the complex bis(diethyl–diselenocarbamato)copper(II), (Cu(dsc)2) with some copper(II) salts in solution have been studied by EPR and electronic spectroscopy. The complex interacts with copper salts (CuX2, X = Cl, Br, NO3) to produce EPR silent dimers of the type [(dsc)CuX2Cu(dsc)] which are formed in equilibrium with mixed-ligand Cu...