The effects of hydrochloric acid (HCl) on the formation of calcium hydroxyapatite (HAp) particles... more The effects of hydrochloric acid (HCl) on the formation of calcium hydroxyapatite (HAp) particles produced by aging Ca(OH)2 and sodium triphosphate (sodium tripolyphosphate, Natpp: Na5P3O10) mixed solution at 100 o C for 18 h were examined. The effect of addition of urea was also investigated. In the absence of HCl, the spherical secondary particles with ca. 60 nm in diameter composing by aggregation of spherical primary particles with ca. 20 nm in diameter were produced. Similar aggregated secondary spherical particles were formed up to HCl concentration ([HCl]) of 8 mM. On the contrary, the particles produced at [HCl]≥12 mM were elongated to c-axis and exhibit aggregated rod-like shape, though those produced at [HCl]=20 mM were spherical aggregates with ca. 20 nm in diameter. All the particles produced at [HCl]≤16 mM were HAp, though the sample produced at 20 mM was amorphous. The specific surface areas of the samples were ranged among 84-98 m 2 /g and were fairly agreed with the estimated value of spherical primary particle with 20 nm in diameter. The in situ IR spectra of the HAp particles exhibited very small bulk OH -band at 3570 cm -1 . This result indicated that the HAp particles are produced by aggregation mechanism and OH -ions along with c-axis in the poorly crystallized primary particles were disordered. The HAp particles with Ca/P molar ratio larger than theoretical value of 1.67 were not exhibited surface P-OH groups at 3656 and 3683 cm -1 . However, the addition of urea produces CaCO3 (calcite) together with HAp and no single HAp crystal was produced. It was revealed that forced hydrolysis reaction of tpp was accelerated by HCl and aggregated secondary spherical particles with unique structure and high specific surface area were obtained.
European Journal of Organic Chemistry, Nov 15, 2005
Organic chemistry Z 0200 Synthesis and Structures of Fullerene Bromides and Chlorides-[ca. 60 ref... more Organic chemistry Z 0200 Synthesis and Structures of Fullerene Bromides and Chlorides-[ca. 60 refs.].
ABSTRACT The structural properties of vanadium doped aluminium oxyfluorides and aluminium oxides,... more ABSTRACT The structural properties of vanadium doped aluminium oxyfluorides and aluminium oxides, prepared by a modified sol–gel synthesis route, were thoroughly investigated. The influence of the preparation technique and the calcination temperature on the coordination of vanadium, aluminium and fluorine was analysed by different spectroscopic methods such as Raman, MAS NMR and ESR spectroscopy. In all samples calcined at low temperatures (350°C), vanadium coexists in two oxidation states VIV and VV, with VIV as dominating species in the vanadium doped aluminium oxyfluorides. In the fluoride containing solids aluminium as well as vanadium are coordinated by fluorine and oxygen. Thermal annealing of 800°C leads to an extensive reorganisation of the original matrices and to the oxidation of VIV to VV in both systems.
European Journal of Organic Chemistry, Oct 1, 2003
Simple bromination of a fullerene mixture allowed the separation of C 78 from other fullerenes in... more Simple bromination of a fullerene mixture allowed the separation of C 78 from other fullerenes in form of crystalline C 78 Br 18. The first X-ray single-crystal structure of a halogenated higher fullerene, C 78 Br 18 , revealed that the addition pattern of 18 bromine atoms on the C 78 cage corresponds to a partial retention of the conjugated double bond systems Since the discovery of fullerenes, their chemistry has developed very rapidly. Most experimental work was performed with C 60 , yet only a small fraction of the investigations have been devoted to the chemistry of C 70. Higher fullerenes are obtained during fullerene formation as a minor admixture with C 60 and C 70. Their separation from C 60 and C 70 is achieved by multi-step, high-pressure liquid chromatography (HPLC). This results in a mixture of higher fullerenes, [1] which makes further separation a difficult but challenging task. Limited studies on individual higher fullerenes show that the existence of several isomers complicates their investigation drastically. [2] Among halogenated fullerenes, which are important synthons for further derivatization of fullerenes, some fluorides, from C 60 F 2 to C 60 F 48 , [3] one chloride, C 60 Cl 6 , [4] and three bromides, C 60 Br 6 , C 60 Br 8 , and C 60 Br 24 , [5] were isolated. Among C 70 halides, many fluorides (from C 70 F 34 to C 70 F 44), [6] C 70 Cl 10 , [7] C 70 Br 14 , [8] and C 70 Br 10 , [9] have been reported, the latter was the only studied crystallographically. Fluorinated higher fullerenes with C 76 , C 78 , C 82 , and C 84 were isolated and characterised to varying extents by MS, NMR, and IR spectra. [10] Here, we report that bromination of fullerenes results in a separation of one of the higher fullerenes, C 78 , from its mixture with C 70 and several higher fullerenes. The X-ray single-crystal structure of C 78 Br 18 showed that a partial separation of C 78 isomers occurred even during bromination. A CS 2 solution of C 70 (94.70%, TERMUSA) containing 1.90% C 60 and 3.40% of higher fullerenes (0.24% C 76 , 0.67% C 78 , and 2.49% C 84) was brominated in a glass am-[a
Structure D 2000 Structural Study of the Dehydration of Templated Zirconium Phosphate Fluorides.-... more Structure D 2000 Structural Study of the Dehydration of Templated Zirconium Phosphate Fluorides.-The ZrPOF-1 phases (II) are prepared hydrothermally and dehydrated at 250°C for 1 h. As revealed by single crystal XRD, the dehydrated phases of (IIb) and (IIc) crystallize in space group P2 1 /c with Z = 4 and the dehydrated phase of (IId) in the triclinic space group P1 with Z = 2. The loss of water results in a new orientation of the HPO 4 tetrahedra. After the dehydration, other oxygen atoms act as new acceptors for the OH groups of the HPO 4 tetrahedra. This new orientation leads to a shift of the compact sheets connected via the HPO 4 tetrahedra.
ABSTRACT Magnesium fluoride sols for the wet chemical processing of porous MgF2 antireflective co... more ABSTRACT Magnesium fluoride sols for the wet chemical processing of porous MgF2 antireflective coatings were prepared by the reaction of MgCl2 with HF. The formation and crystallisation of MgF2 nanoparticles were followed by 19F NMR spectroscopy, X-ray diffraction (XRD) and dynamic light scattering (DLS) in the liquid phase. The crystallization of the resulting films was monitored by XRD experiments. At temperatures exceeding 550 °C the film material and glass substrates undergo a chemical reaction, MgO is formed and SiF4 evaporates as a volatile product. Microstructure and optical properties were characterized as a function of the annealing temperature. The mechanical stability of MgF2 films was evaluated by the Crockmeter test using both felt and steel wool. It is shown that porous MgF2 films prepared by this synthesis have a vast potential for the large-area processing of antireflective coatings.
C 60 F 18 single crystals were grown by vacuum sublimation from the product of reaction of C 60 w... more C 60 F 18 single crystals were grown by vacuum sublimation from the product of reaction of C 60 with K 2 PtF 6 at 460 K in vacuo. Solvent free C 60 F 18 containing only a few percent of C 60 F 18 O crystallizes in monoclinic lattice. The molecular structure of C 60 F 18 is very close to that found in the C 60 F 18 solvates with aromatic hydrocarbons. Two C.. .C distances are slightly elongated in the statistically averaged structure due to the presence of C 60 F 18 O.
Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
Nano metal fluorides are appropriate materials for different applications e.g. heterogeneous cata... more Nano metal fluorides are appropriate materials for different applications e.g. heterogeneous catalysis, ceramic materials for laser applications and antireflective layers on glass, respectively. An easy way to synthesize such nano metal fluorides is the fluorolytic sol-gel synthesis which was developed some few years ago for HS-AlF3 [1] and MgF2.[2] CaF2 exhibits similar optical properties as MgF2, and thus, is a promising candidate for antireflective (AR) coatings. That means, CaF2 exhibits a lower refractive index (n500 = 1.44) as compared to common soda lime glass (n500 = 1.53). Hence, we present an easy synthesis approach toward nanoscaled CaF2 sols to fabricate finally AR-CaF2 films by dip coating. Irrespective of the choice of the calcium precursor, the CaF2 films are porous in comparison to thin dense CaF2 films which are generated by physical vapor deposition. The characterization of CaF2 films was performed by different analytical methods like HR-SEM, XPS, EDX, EP (ellipsometric porosimetry), DLS (dynamic light scattering) and CA (contact angle measurement). Beside the good optical and mechanical properties, we have investigated the surface properties of CaF2 films on glass and silicon wafer e.g. surface morphology with elemental composition, open porosity, zeta potentials at the surfaces as well as the free energy of interaction between water and the CaF2 film.
Conventional simultaneous thermal analysis, capillary-coupled TG–MS, in situ and ex situ Raman an... more Conventional simultaneous thermal analysis, capillary-coupled TG–MS, in situ and ex situ Raman and Mössbauer spectroscopy, as well as chemical analysis have been used for the investigation of the first decomposition step of the mixed valence chloroferrate (dmpipzH2)6[Fe(II)Cl4]2[Fe(III)Cl4]2[Fe(II)Cl5][Fe(III)Cl6]. Under argon at ca. 200°C, an almost complete reduction proceeds in a solid state reaction forming Fe(II). It is accompanied by the release of HCl and, to a minor degree, carbon containing species. A multi-phase product with at least two chloroferrate species, coke, and C,H,N-containing polymers is formed. Binuclear iron complexes, such as (dmpipzH)2[Fe(II)2Cl6], and small amounts of (dmpipzH)[Fe(III)Cl4] have been proposed to be the major and minor component of the product mixture, respectively.
High-temperature chlorination of C 100 fullerene followed by X-ray structure determination of the... more High-temperature chlorination of C 100 fullerene followed by X-ray structure determination of the chloro derivatives enabled the identification of three isomers of C 100 from the fullerene soot, specifically numbers 18, 425, and 417, which obey the isolated pentagon rule (IPR). Among them, isomers C 1-C 100 (425) and C 2-C 100 (18) afforded C 1-C 100 (425)Cl 22 and C 2-C 100 (18)Cl 28/30 compounds,r espectively,w hichr etain their IPR cage connectivities.Incontrast, isomer C 2v-C 100 (417) gives C s-C 100 (417)Cl 28 whichu ndergoes as keletal transformation by the loss of aC 2 fragment, resulting in the formation of an onclassical (NC) C 1-C 98 (NC)Cl 26 with ah eptagon in the carbon cage.M ost probably,t wo nonclassical C 1-C 100 (NC)-Cl 18/22 chloro derivatives originate from the IPR isomer C 1-C 100 (382), although both C 1-C 100 (344) and even nonclassical C 1-C 100 (NC) can be also considered as the starting isomers.
Sc(3)N@D(5h)-C(80) and Sc(3)N@I(h)-C(80) were trifluoromethylated with CF(3)I at 400 °C, affordin... more Sc(3)N@D(5h)-C(80) and Sc(3)N@I(h)-C(80) were trifluoromethylated with CF(3)I at 400 °C, affording mixtures of CF(3) derivatives. After separation with HPLC, the first multi-CF(3) derivative of Sc(3)N@D(5h)-C(80), Sc(3)N@D(5h)-C(80)(CF(3))(18), and three new isomers of Sc(3)N@I(h)-C(80)(CF(3))(14) were investigated by X-ray crystallography. The Sc(3)N@D(5h)-C(80)(CF(3))(18) molecule is characterized by a large number of double C-C bonds and benzenoid rings within the D(5h)-C(80) cage and a fully different position of the Sc(3)N unit compared to that in the pristine Sc(3)N@D(5h)-C(80). A detailed comparison of five Sc(3)N@I(h)-C(80)(CF(3))(14) isomers reveals a strong influence of the exohedral additions on the behavior of the Sc(3)N cluster inside the I(h)-C(80) cage.
ABSTRACT A new sol–gel technique was developed for preparing vanadium-containing aluminium fluori... more ABSTRACT A new sol–gel technique was developed for preparing vanadium-containing aluminium fluoride catalysts for selective oxidation reactions. With this new synthesis, highly dispersed vanadium species can be obtained in the metal fluoride host lattice. The X-ray amorphous solids were investigated by conventional and advanced analytical methods such as for instance N2 adsorption experiments, FTIR spectroscopy, pyridine adsorption and NH3-TPD. The surface properties, acidity and catalytic performance were all dependent on the vanadium content of the samples. EDX, FTIR and Raman spectroscopy confirmed the high degree of dispersion of vanadium (oxidation state: III or IV or both) species in the aluminium fluoride matrix. The samples had relatively high BET surface areas and medium strength Lewis acid sites. Additional Brønsted acid sites were observed on samples with higher vanadium contents only. The catalytic performance of the vanadium-containing aluminium fluorides was investigated for the oxidative dehydrogenation (ODH) of propane. Depending on the vanadium content, the new catalyst system offers a surprisingly high catalytic activity and selectivity towards the desired product, propylene. The high degree of dispersion of the active vanadium species in the aluminium fluoride matrix and the type of the acid sites on the solid surface are crucial to the selectivity of the catalyst in the selective oxidation reaction.
The effects of hydrochloric acid (HCl) on the formation of calcium hydroxyapatite (HAp) particles... more The effects of hydrochloric acid (HCl) on the formation of calcium hydroxyapatite (HAp) particles produced by aging Ca(OH)2 and sodium triphosphate (sodium tripolyphosphate, Natpp: Na5P3O10) mixed solution at 100 o C for 18 h were examined. The effect of addition of urea was also investigated. In the absence of HCl, the spherical secondary particles with ca. 60 nm in diameter composing by aggregation of spherical primary particles with ca. 20 nm in diameter were produced. Similar aggregated secondary spherical particles were formed up to HCl concentration ([HCl]) of 8 mM. On the contrary, the particles produced at [HCl]≥12 mM were elongated to c-axis and exhibit aggregated rod-like shape, though those produced at [HCl]=20 mM were spherical aggregates with ca. 20 nm in diameter. All the particles produced at [HCl]≤16 mM were HAp, though the sample produced at 20 mM was amorphous. The specific surface areas of the samples were ranged among 84-98 m 2 /g and were fairly agreed with the estimated value of spherical primary particle with 20 nm in diameter. The in situ IR spectra of the HAp particles exhibited very small bulk OH -band at 3570 cm -1 . This result indicated that the HAp particles are produced by aggregation mechanism and OH -ions along with c-axis in the poorly crystallized primary particles were disordered. The HAp particles with Ca/P molar ratio larger than theoretical value of 1.67 were not exhibited surface P-OH groups at 3656 and 3683 cm -1 . However, the addition of urea produces CaCO3 (calcite) together with HAp and no single HAp crystal was produced. It was revealed that forced hydrolysis reaction of tpp was accelerated by HCl and aggregated secondary spherical particles with unique structure and high specific surface area were obtained.
European Journal of Organic Chemistry, Nov 15, 2005
Organic chemistry Z 0200 Synthesis and Structures of Fullerene Bromides and Chlorides-[ca. 60 ref... more Organic chemistry Z 0200 Synthesis and Structures of Fullerene Bromides and Chlorides-[ca. 60 refs.].
ABSTRACT The structural properties of vanadium doped aluminium oxyfluorides and aluminium oxides,... more ABSTRACT The structural properties of vanadium doped aluminium oxyfluorides and aluminium oxides, prepared by a modified sol–gel synthesis route, were thoroughly investigated. The influence of the preparation technique and the calcination temperature on the coordination of vanadium, aluminium and fluorine was analysed by different spectroscopic methods such as Raman, MAS NMR and ESR spectroscopy. In all samples calcined at low temperatures (350°C), vanadium coexists in two oxidation states VIV and VV, with VIV as dominating species in the vanadium doped aluminium oxyfluorides. In the fluoride containing solids aluminium as well as vanadium are coordinated by fluorine and oxygen. Thermal annealing of 800°C leads to an extensive reorganisation of the original matrices and to the oxidation of VIV to VV in both systems.
European Journal of Organic Chemistry, Oct 1, 2003
Simple bromination of a fullerene mixture allowed the separation of C 78 from other fullerenes in... more Simple bromination of a fullerene mixture allowed the separation of C 78 from other fullerenes in form of crystalline C 78 Br 18. The first X-ray single-crystal structure of a halogenated higher fullerene, C 78 Br 18 , revealed that the addition pattern of 18 bromine atoms on the C 78 cage corresponds to a partial retention of the conjugated double bond systems Since the discovery of fullerenes, their chemistry has developed very rapidly. Most experimental work was performed with C 60 , yet only a small fraction of the investigations have been devoted to the chemistry of C 70. Higher fullerenes are obtained during fullerene formation as a minor admixture with C 60 and C 70. Their separation from C 60 and C 70 is achieved by multi-step, high-pressure liquid chromatography (HPLC). This results in a mixture of higher fullerenes, [1] which makes further separation a difficult but challenging task. Limited studies on individual higher fullerenes show that the existence of several isomers complicates their investigation drastically. [2] Among halogenated fullerenes, which are important synthons for further derivatization of fullerenes, some fluorides, from C 60 F 2 to C 60 F 48 , [3] one chloride, C 60 Cl 6 , [4] and three bromides, C 60 Br 6 , C 60 Br 8 , and C 60 Br 24 , [5] were isolated. Among C 70 halides, many fluorides (from C 70 F 34 to C 70 F 44), [6] C 70 Cl 10 , [7] C 70 Br 14 , [8] and C 70 Br 10 , [9] have been reported, the latter was the only studied crystallographically. Fluorinated higher fullerenes with C 76 , C 78 , C 82 , and C 84 were isolated and characterised to varying extents by MS, NMR, and IR spectra. [10] Here, we report that bromination of fullerenes results in a separation of one of the higher fullerenes, C 78 , from its mixture with C 70 and several higher fullerenes. The X-ray single-crystal structure of C 78 Br 18 showed that a partial separation of C 78 isomers occurred even during bromination. A CS 2 solution of C 70 (94.70%, TERMUSA) containing 1.90% C 60 and 3.40% of higher fullerenes (0.24% C 76 , 0.67% C 78 , and 2.49% C 84) was brominated in a glass am-[a
Structure D 2000 Structural Study of the Dehydration of Templated Zirconium Phosphate Fluorides.-... more Structure D 2000 Structural Study of the Dehydration of Templated Zirconium Phosphate Fluorides.-The ZrPOF-1 phases (II) are prepared hydrothermally and dehydrated at 250°C for 1 h. As revealed by single crystal XRD, the dehydrated phases of (IIb) and (IIc) crystallize in space group P2 1 /c with Z = 4 and the dehydrated phase of (IId) in the triclinic space group P1 with Z = 2. The loss of water results in a new orientation of the HPO 4 tetrahedra. After the dehydration, other oxygen atoms act as new acceptors for the OH groups of the HPO 4 tetrahedra. This new orientation leads to a shift of the compact sheets connected via the HPO 4 tetrahedra.
ABSTRACT Magnesium fluoride sols for the wet chemical processing of porous MgF2 antireflective co... more ABSTRACT Magnesium fluoride sols for the wet chemical processing of porous MgF2 antireflective coatings were prepared by the reaction of MgCl2 with HF. The formation and crystallisation of MgF2 nanoparticles were followed by 19F NMR spectroscopy, X-ray diffraction (XRD) and dynamic light scattering (DLS) in the liquid phase. The crystallization of the resulting films was monitored by XRD experiments. At temperatures exceeding 550 °C the film material and glass substrates undergo a chemical reaction, MgO is formed and SiF4 evaporates as a volatile product. Microstructure and optical properties were characterized as a function of the annealing temperature. The mechanical stability of MgF2 films was evaluated by the Crockmeter test using both felt and steel wool. It is shown that porous MgF2 films prepared by this synthesis have a vast potential for the large-area processing of antireflective coatings.
C 60 F 18 single crystals were grown by vacuum sublimation from the product of reaction of C 60 w... more C 60 F 18 single crystals were grown by vacuum sublimation from the product of reaction of C 60 with K 2 PtF 6 at 460 K in vacuo. Solvent free C 60 F 18 containing only a few percent of C 60 F 18 O crystallizes in monoclinic lattice. The molecular structure of C 60 F 18 is very close to that found in the C 60 F 18 solvates with aromatic hydrocarbons. Two C.. .C distances are slightly elongated in the statistically averaged structure due to the presence of C 60 F 18 O.
Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.
Nano metal fluorides are appropriate materials for different applications e.g. heterogeneous cata... more Nano metal fluorides are appropriate materials for different applications e.g. heterogeneous catalysis, ceramic materials for laser applications and antireflective layers on glass, respectively. An easy way to synthesize such nano metal fluorides is the fluorolytic sol-gel synthesis which was developed some few years ago for HS-AlF3 [1] and MgF2.[2] CaF2 exhibits similar optical properties as MgF2, and thus, is a promising candidate for antireflective (AR) coatings. That means, CaF2 exhibits a lower refractive index (n500 = 1.44) as compared to common soda lime glass (n500 = 1.53). Hence, we present an easy synthesis approach toward nanoscaled CaF2 sols to fabricate finally AR-CaF2 films by dip coating. Irrespective of the choice of the calcium precursor, the CaF2 films are porous in comparison to thin dense CaF2 films which are generated by physical vapor deposition. The characterization of CaF2 films was performed by different analytical methods like HR-SEM, XPS, EDX, EP (ellipsometric porosimetry), DLS (dynamic light scattering) and CA (contact angle measurement). Beside the good optical and mechanical properties, we have investigated the surface properties of CaF2 films on glass and silicon wafer e.g. surface morphology with elemental composition, open porosity, zeta potentials at the surfaces as well as the free energy of interaction between water and the CaF2 film.
Conventional simultaneous thermal analysis, capillary-coupled TG–MS, in situ and ex situ Raman an... more Conventional simultaneous thermal analysis, capillary-coupled TG–MS, in situ and ex situ Raman and Mössbauer spectroscopy, as well as chemical analysis have been used for the investigation of the first decomposition step of the mixed valence chloroferrate (dmpipzH2)6[Fe(II)Cl4]2[Fe(III)Cl4]2[Fe(II)Cl5][Fe(III)Cl6]. Under argon at ca. 200°C, an almost complete reduction proceeds in a solid state reaction forming Fe(II). It is accompanied by the release of HCl and, to a minor degree, carbon containing species. A multi-phase product with at least two chloroferrate species, coke, and C,H,N-containing polymers is formed. Binuclear iron complexes, such as (dmpipzH)2[Fe(II)2Cl6], and small amounts of (dmpipzH)[Fe(III)Cl4] have been proposed to be the major and minor component of the product mixture, respectively.
High-temperature chlorination of C 100 fullerene followed by X-ray structure determination of the... more High-temperature chlorination of C 100 fullerene followed by X-ray structure determination of the chloro derivatives enabled the identification of three isomers of C 100 from the fullerene soot, specifically numbers 18, 425, and 417, which obey the isolated pentagon rule (IPR). Among them, isomers C 1-C 100 (425) and C 2-C 100 (18) afforded C 1-C 100 (425)Cl 22 and C 2-C 100 (18)Cl 28/30 compounds,r espectively,w hichr etain their IPR cage connectivities.Incontrast, isomer C 2v-C 100 (417) gives C s-C 100 (417)Cl 28 whichu ndergoes as keletal transformation by the loss of aC 2 fragment, resulting in the formation of an onclassical (NC) C 1-C 98 (NC)Cl 26 with ah eptagon in the carbon cage.M ost probably,t wo nonclassical C 1-C 100 (NC)-Cl 18/22 chloro derivatives originate from the IPR isomer C 1-C 100 (382), although both C 1-C 100 (344) and even nonclassical C 1-C 100 (NC) can be also considered as the starting isomers.
Sc(3)N@D(5h)-C(80) and Sc(3)N@I(h)-C(80) were trifluoromethylated with CF(3)I at 400 °C, affordin... more Sc(3)N@D(5h)-C(80) and Sc(3)N@I(h)-C(80) were trifluoromethylated with CF(3)I at 400 °C, affording mixtures of CF(3) derivatives. After separation with HPLC, the first multi-CF(3) derivative of Sc(3)N@D(5h)-C(80), Sc(3)N@D(5h)-C(80)(CF(3))(18), and three new isomers of Sc(3)N@I(h)-C(80)(CF(3))(14) were investigated by X-ray crystallography. The Sc(3)N@D(5h)-C(80)(CF(3))(18) molecule is characterized by a large number of double C-C bonds and benzenoid rings within the D(5h)-C(80) cage and a fully different position of the Sc(3)N unit compared to that in the pristine Sc(3)N@D(5h)-C(80). A detailed comparison of five Sc(3)N@I(h)-C(80)(CF(3))(14) isomers reveals a strong influence of the exohedral additions on the behavior of the Sc(3)N cluster inside the I(h)-C(80) cage.
ABSTRACT A new sol–gel technique was developed for preparing vanadium-containing aluminium fluori... more ABSTRACT A new sol–gel technique was developed for preparing vanadium-containing aluminium fluoride catalysts for selective oxidation reactions. With this new synthesis, highly dispersed vanadium species can be obtained in the metal fluoride host lattice. The X-ray amorphous solids were investigated by conventional and advanced analytical methods such as for instance N2 adsorption experiments, FTIR spectroscopy, pyridine adsorption and NH3-TPD. The surface properties, acidity and catalytic performance were all dependent on the vanadium content of the samples. EDX, FTIR and Raman spectroscopy confirmed the high degree of dispersion of vanadium (oxidation state: III or IV or both) species in the aluminium fluoride matrix. The samples had relatively high BET surface areas and medium strength Lewis acid sites. Additional Brønsted acid sites were observed on samples with higher vanadium contents only. The catalytic performance of the vanadium-containing aluminium fluorides was investigated for the oxidative dehydrogenation (ODH) of propane. Depending on the vanadium content, the new catalyst system offers a surprisingly high catalytic activity and selectivity towards the desired product, propylene. The high degree of dispersion of the active vanadium species in the aluminium fluoride matrix and the type of the acid sites on the solid surface are crucial to the selectivity of the catalyst in the selective oxidation reaction.
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