Showing papers on "Alkoxide published in 2001"
TL;DR: In this article, a modified sol-gel process using different alkoxide precursors was used to obtain carbon-containing catalysts with large surface areas, capable to photodegrade p-chlorophenol (4CP) with visible light (λ>400nm).
Abstract: Photocatalysts based on titanium dioxide have been prepared by a modified sol–gel process using different alkoxide precursors. Depending on the precursor and the calcination temperature of the gels, carbon-containing catalysts with large surface areas, capable to photodegrade p-chlorophenol (4CP) with visible light (λ>400 nm), have been obtained. Photodegradation and mineralisation were confirmed by HPLC and TOC measurements. The catalysts were characterised by physisorption of argon, elemental analysis, EPR, UV/VIS, X-ray powder diffraction (XRD), FT-IR and high-resolution transmission electron microscopy (HRTEM). A highly condensed, carbonaceous species formed during calcination is responsible for the photosensitisation. When used as a photoelectrode, the appearance of a photocurrent indicated the semiconductor nature of these novel materials. The catalysts exhibit a surprisingly good long-time stability despite of the carbonaceous nature of the sensitising species. It is also shown, that commercially available TiO2 can be photosensitised by impregnation with suitable alcohols followed by pyrolysis.
554 citations
TL;DR: In this paper, the authors showed that the catalytically enhanced sodium aluminum hydride, NaAlH4, is kinetically enhanced and rendered reversible in the solid state upon doping with selected titanium compounds.
Abstract: The dehydriding of sodium aluminum hydride, NaAlH4, is kinetically enhanced and rendered reversible in the solid state upon doping with selected titanium compounds. Following the initial reports of this catalytic effect, further kinetic improvement and stabilization of the cyclable hydrogen capacity have been achieved upon variation in the method of the introduction of titanium and particle-size reduction. Rapid evolution of 4.0-wt % hydrogen at 100 °C has been consistently achieved for several dehydriding/rehydriding cycles. An improved, 4.8-wt % cyclable capacity has been observed in the material doped with a combination of Ti and Zr alkoxide complexes. Doping the hydride with Ti(OBun)4 and Fe(OEt)2 also produces a synergistic effect, resulting in materials that can be rehydrided to 4 wt % at 104 °C and 87 atm of hydrogen within 17 h. The improved kinetics allowed us to carry out constant-temperature, equilibrium-pressure studies of NaAlH4 that extended to temperatures well below the melting point of the hydride. The 37-kJ/mol value determined for enthalpy of the dehydriding of NaAlH4(s) to Na3AlH6 and Al and the hydrogen plateau pressure of 7 atm at 80 °C are in line with the predictions of earlier studies. The nature of the active catalyst and the mechanism of catalytic action are unknown. The catalytically enhanced hydrides appear to be strong candidates for development as hydrogen carriers for onboard proton exchange membran (PEM) fuel cells. However, further research and development in the areas of rehydriding catalysts, large-scale, long-term cycling, safety and adjustment of the plateau hydrogen pressure associated with dehydriding of AlH6- are required before these materials can be utilized in commercial onboard hydrogen-storage systems.
295 citations
TL;DR: The monomeric alkoxide (BDI)Mg(OtBu) and triphenylsiloxide (Zn(OSiPh3)(THF) have been shown to reversibly dissociate THF in solution on the NMR time scale as mentioned in this paper.
Abstract: The monomeric alkoxide (BDI)Mg(OtBu)(THF) and triphenylsiloxide (BDI)Zn(OSiPh3)(THF) have been prepared and characterized and shown to reversibly dissociate THF in solution on the NMR time scale; both compounds are active precursors for the ring-opening polymerization of lactide and the rate of polymerization is notably faster for the magnesium complex though in the polymerization of rac-lactide only the zinc complex shows selectivity for heterotactic tetrads.
235 citations
226 citations
TL;DR: In this article, the formation of zinc metastable complexes was followed by potentiometric and conductimetric titrations, and the existence of this matrix has been supported by FTIR, as was revealed by SEM and TEM.
Abstract: Zinc oxide nano-particles with different morphologies have been obtained by controlling different parameters of the precipitation process: solution concentration, pH and washing medium. The reactions leading to the formation of zinc metastable complexes were followed by potentiometric and conductimetric titrations. During the ethanol washing step the intermediate zinc complexes have been modified by weathering and solution processes which drived both the phase transformation reactions and the particles recrystallization. The nucleation of zinc alkoxides during this process is an “organic matrix-mediated” process, where the matrix is formed on the intermediate zinc complexes surface during the NH 4 OH addition to the solution of the zinc precursor. The existence of this matrix has been supported by FTIR. The transformation of the zinc metastable complexes during the washing with ethanol was followed with XRD. Through this process it is possible to obtain agglomerates of zinc oxide nanoparticles from a random network, as was revealed by SEM and TEM.
179 citations
TL;DR: In this paper, the β-galactosidase activity of E. coli, trapped in sol-gel silica matrices, was analyzed and two routes, using alkoxide and aqueous precursors, have been used and compared.
Abstract: The viability of bacteria in the presence of sol–gel reagents has been studied in order to define the best experimental conditions for the sol–gel encapsulation of E. coli. The β-galactosidase activity of these bacteria, trapped in sol–gel silica matrices, was then analyzed. Two routes, using alkoxide and aqueous precursors, have been used and compared. It appears that the aqueous route is less damaging than the alkoxide one. Moreover the aqueous silica matrix appears to slow down the lysis of cell membranes when bacteria are aged without nutrient.
152 citations
TL;DR: Incorporation of an alkoxide functional group into an N-heterocyclic carbene (NHC) ligand allows the synthesis of the first anionic NHC chelating ligands, which react to give the first neutral, molecular silver-I alkoxide carbene complex, and a copper(I) derivative containing the first nonmacrocyclic, square planar Cu(I), centres.
152 citations
TL;DR: In this paper, a mimic alkoxide method was used to synthesize nanocrystalline CeO 2 powders of high sinterability, which employed alcohols as solvent, cerium nitrate hexahydrate as source and diethylamine (DEA) as precipitant.
115 citations
TL;DR: Titania was prepared by the sol-gel method from titanium alkoxide, and specific surface areas between 88 and 10 m2/g were obtained as discussed by the authors, where the band gap (Eg) of the samples was found between 3.05 and 3.32 eV.
Abstract: Titania was prepared by the sol-gel method from titanium alkoxide. Depending on the pH of the gelling solution, specific surface areas between 88 and 10 m2/g were obtained. The band gap (Eg) of the samples was found between 3.05 and 3.32 eV. In samples gelled at pH5 and 9 and calcined at 400°C only anatase phase is observed, while for pH3 and pH7 brookite, anatase and rutile or anatase-rutile phases coexist. It was found that the photoactivity in the 2,4-dinitroanailine decomposition depends on the Eg and on the crystalline phases. The highest activity corresponds to the catalysts having the lowest Eg and more than one crystalline phases co-existing.
81 citations
TL;DR: In this paper, the primary hydroxyl groups introduced by 2-mercaptoethanol as a capping agent used for preparation of the CdS nanoparticles are considered to play an important role for successful adhesion and growth of the TiO2 layer on the cdS surfaces.
Abstract: Hydrolysis of Ti alkoxide in the presence of inverse micelles containing CdS nanoparticles in their hydrophilic interior results in formation of TiO2/CdS nanocomposites in which the CdS nanoparticles are embedded in a TiO2 matrix with a thickness of ≤10 nm at the surface of the particles. The primary hydroxyl groups introduced by 2-mercaptoethanol as a capping agent used for preparation of the CdS nanoparticles are considered to play an important role for successful adhesion and growth of the TiO2 layer on the CdS surfaces. TEM observation strongly supports formation of semiconductor-in-semiconductor heteronanostructure by compartmentalized hydrolysis of Ti alkoxide within the inverse micelles in which the surface-capped CdS nanoparticles coexist.
74 citations
TL;DR: The protonation of ethene, propene, 1-butene, and isobutene by acidic theta-1 zeolite to give covalent alkoxide intermediates has been theoretically investigated by means of cluster and periodic c...
Abstract: The protonation of ethene, propene, 1-butene, and iso-butene by acidic theta-1 zeolite to give covalent alkoxide intermediates has been theoretically investigated by means of cluster and periodic c...
TL;DR: In this paper, a self-standing films of titanium-containing (Ti/Si ratio of 1/50) silica−surfactant mesostructured materials, having a thickness of ca. 50 μm and a lateral size of a few centimeters, were synthesized by the solvent evaporation method from tetramethoxysilane, vinyltrimethoxylane, titanium tetraisopropoxide, and octadecyltrimethylammonium chloride.
Abstract: Transparent self-standing films of titanium-containing (Ti/Si ratio of 1/50) silica−surfactant mesostructured materials, having a thickness of ca. 50 μm and a lateral size of a few centimeters, were synthesized by the solvent evaporation method from tetramethoxysilane, vinyltrimethoxysilane, titanium tetraisopropoxide, and octadecyltrimethylammonium chloride. The films were converted to titanium-containing nanoporous silica films by subsequent calcination in air at 550 °C, while their highly ordered mesostructures and macroscopic morphology were retained after the surfactant removal. Titanium-containing nanoporous silica films with hexagonal and cubic symmetry were obtained by changing the composition of the starting mixtures. The resulting materials possess a large surface area (ca. 900 m2/g) as evidenced by nitrogen adsorption/desorption isotherms. The titanium ions exist in the silica network as a tetrahedrally coordinated species. UV irradiation of the titanium-containing nanoporous silica film in the...
TL;DR: In this paper, the differences in the network structures of the hybrid materials with different curing processes were characterized with Fourier transform infrared (FTIR) and showed that the difference in the interactions between the organic and inorganic phases significantly affect the properties and microstructures of the resultant composites.
Abstract: Several kinds of organic–inorganic hybrids were synthesized from an epoxy resin and a silane alkoxide with a primary amine-type curing agent or tertiary amine curing catalyst. In the hybrid systems cured with the primary amine-type curing agent, the storage modulus in the high-temperature region increased, and the peak area of the tan δ curve decreased. Moreover, the mechanical properties were improved by the hybridization of small amounts of the silica network. However, these phenomena were not observed in the hybrid systems cured with the tertiary amine catalyst. The differences in the network structures of the hybrid materials with the different curing processes were characterized with Fourier transform infrared (FTIR). In the hybrid systems cured with the primary amine-type curing agent, FTIR results showed the formation of a covalent bond between silanol and hydroxyl groups that were generated by the reaction of an epoxy group with an active hydrogen of the primary amine. However, this phenomenon was not observed in the hybrids cured with the tertiary amine. The hybrids with the primary amine showed a homogeneous microstructure in transmission electron microscopy observations, although the hybrids cured with the tertiary amine showed a heterogeneous structure. These results mean that the differences in the interactions between the organic and inorganic phases significantly affect the properties and microstructures of the resultant composites. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1071–1084, 2001
TL;DR: The ring-opening polymerization of l-lactide with calcium alkoxides generated in-situ from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and 2-propanol is presented in this article.
Abstract: The ring-opening polymerization of l-lactide with calcium alkoxides generated in-situ from bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] and 2-propanol are presented. The polymerization in THF at room temperature proceeds rapidly and in a living manner, giving poly(l-lactide)s of controlled molecular weight, low polydispersity, and tailored end-functionalities. Kinetic studies show the absence of an induction period and a pseudo-first order rate constant of 6.41 L mol−1 min−1, which is significantly higher than for related Y5(μ-O)(O
i
Pr)13− or aluminum alkoxide-initiated polymerizations. The initiation involves a two-step process: (1) alcoholysis of bis(tetrahydrofuran)calcium bis[bis(trimethylsilyl)amide] to give the corresponding calcium alkoxide and (2) ring-opening of l-lactide via acyl-oxygen cleavage and insertion into the calcium-alkoxide bond. In the presence of excess alcohol, fast and reversible exchange between free alcohol molecules and coordinated alkoxide ligands takes place. This allows tuning of the poly(l-lactide) molecular weight over a wide range.
TL;DR: FTIR and UV/Vis spectroscopy of solid and dissolved samples showed that the solid-state structure changes at least to some extent on dissolution in toluene/MOEH, and the continuous decrease of (chiM)T with decreasing temperature below 150 K in the magnetic susceptibility measurements is probably due to antiferromagnetic interactions.
Abstract: Alkoxides are of great interest as precursors for sol-gel processing of advanced ceramic materials, but there is very little general knowledge about the low-valent 3d-element alkoxides. The novel oxo-alkoxide, [Mn19O12(moe)14(moeH)10]⋅MOEH (MOE=OC2H2OCH3), was prepared, by metathesis and auto-decomposition, from MnCl2 and potassium methoxyethoxide in toluene/MOEH, and the solid-state structure was determined from single-crystal X-ray diffraction data: trigonal cell, space group R (no. 148), a=27.560(3), c=19.294(2) A, Z=3, R1=0.0737, wR2=0.1609. The individual molecules are shaped as flat discs and all Mn atoms are divalent and octahedrally coordinated by oxygen atoms in a CdI2-type layer structure. The central Mn atom is coordinated by six μ3-oxo atoms, the six middle ring Mn-atoms by two μ3-oxo atoms and four MOE(H) groups, while the peripheral ring contains twelve Mn atoms coordinated by one μ3-oxo atom and five MOE(H) groups. Differential scanning calorimetry studies showed that the first and irreversible changes start at about 100 °C. The continuous decrease of χMT with decreasing temperature below 150 K in the magnetic susceptibility measurements is probably due to antiferromagnetic interactions. FTIR and UV/Vis spectroscopy of solid and dissolved samples showed that the solid-state structure changes at least to some extent on dissolution in toluene/MOEH.
TL;DR: In this paper, the authors showed that at low H 2 O 2 /Ti ratio the contribution of the direct mechanism of epoxidation is important, around 40% of the productive H 2 o 2 conversion and 60 % of the reaction reaction.
TL;DR: In this article, the authors used SAXS curves analysis in the range of scattering vector values s = 0.07−4.26 nm−1 for O(OBu)4 hydrolysis products to suggest their multilevel nature.
Abstract: Hydrolysis of Ti(OR)4 (R = Et, iPr, nBu) at various concentrations of titanium alkoxides and ratios h = [H2O] /[Ti(OR)4] is studied in alcoholic medium by means of calorimetry, electron microscopy, SAXS, and chemical analysis. The measured values for heat of hydrolysis of Ti(OR)4 by excess water (−Δ Hh) at 298.15 K comprise 14.2, 64.9, 19.3 kJ/mol for R = Et, R = Et, iPr, nBu respectively. −Δ Hh increases drastically in the region of 0
TL;DR: In this article, a new heterobimetallic catalysts possessing lithium alkoxide as Bronsted base have been developed for the direct asymmetric aldol reaction of less acidic dialkyl ketones as well as aromatic ketones.
TL;DR: In this article, the epoxide ring-opening, the formation of ethyl ether groups, and the condensation degree of RSi(O0.5)3 units in sols and gels of the system 3-glycidoxypropyltrimethoxysilane (GPTS)-1.5H2O-0.1/1.
Abstract: The extent of the epoxide ring-opening, the formation of ethyl ether groups as one reaction product of the ring-opening and the condensation degree of RSi(O0.5)3 units in sols and gels of the system 3-glycidoxypropyltrimethoxysilane (GPTS)-1.5H2O-0.01/0.1/1.0 metal alkoxide [Si(OEt)4, Sn(OBut)4, Al(OBus)3, Al(OEtOBu)3, Ta(OEt)5, Ti(OEt)4, Zr(OBun)4] in ethanol has been examined by means of liquid- and solid-state 13C and 29Si NMR spectroscopies. The results reveal a strong epoxide ring-opening effect of Al-alkoxides in hybrid sols after 24 h reaction time and of Zr-, Ta-, Al- and Sn-alkoxides in corresponding hybrid gels already at low concentration (1 mole%). The ring-opening rate increases in sols with higher metal alkoxide concentration (10 mole%) but decreases at 50 mole% concentration of Al-, Ti- and Zr-alkoxides. The ring-opening activity of metal alkoxides in 10 mole% hybrid sols increases after 24 h reaction time in the order Si(OEt)4 < Ti(OEt)4 < Zr(OBun)4 < Ta(OEt)5, Sn(OBut)4, Al(OBus)3, Al(OEtOBu)3. The 24 h hybrid sols and gels contain considerable amounts (up to 90%) of ethyl ether groups as reaction product of the ring-opening reaction which lowers the formation of polyether bonds. The condensation degree (c.d.) of RSi(O0.5)3 units of GPTS-1.5H2O sols with 10 mole% of metal alkoxides increases up to 80% after 7 h reaction time in the order: Si(OEt)4 ≪ Sn(OBut)4 < Zr(OBun)4 < Al(OBus)3 < Al(OEtOBu)3 < Ta(OEt)5 < Ti(OEt)4. An additional increase in c.d. up to 90% follows after the thermal sol-gel transformation. Generally, maximum activity of metal alkoxides in ring-opening and condensation reactions was found in sols and gels with 10 mole% additives. The effect of water on the epoxide ring-opening and on c.d. is discussed. Furthermore, the activity of metal alkoxides is compared with corresponding nanoscaled metal oxides.
Patent•
29 May 2001
TL;DR: In this article, a new transition group IV or V complex was provided for forming an improved precursor combination for use in chemical vapor deposition (CVD), which dispenses with an alkoxide ligand having an α proton.
Abstract: A new complex of an element of transition group IV or V is provided for forming an improved precursor combination for use in chemical vapor deposition (CVD). This complex dispenses with an alkoxide ligand having an α proton, so that hydrolysis of the complex no longer liberates a reducing agent.
TL;DR: In this paper, three different vanadium oxide catalysts, containing comparable amounts of vanadium, have been studied for the OHD of propane, and a pseudo-first order kinetic law has been used to interpret the results.
Abstract: The oxidative dehydrogenation (ODH) of propane have been studied on three different vanadium oxide catalysts, containing comparable amounts of vanadium. All the proven catalysts have been prepared by grafting but following different procedures. One has been prepared by grafting vanadyl tri-isopropoxide, dissolved in n-hexane on a support of silica coated with a multi-layer of TiO2. The support has been prepared by grafting in three different steps titanium alkoxide on silica. Another catalyst has been prepared by partially hydrolysing vanadyl tri-isopropoxide, dissolved in isopropanol, before grafting the obtained product on the same support. The third catalyst has been prepared by reacting partially hydrolysed vanadyl tri-isopropoxide with titanium alkoxide in isopropanol and anchoring then the reaction product, a vanadium–titanium bimetallic alkoxide, directly on silica. The first and second catalysts have similar activities and selectivities, while the third catalyst is less active but more selective than the other two ones. A kinetic approach has been made and a pseudo-first order kinetic law has been used to interpret the results. All the observed catalytic phenomena have been interpreted also with the aid of the several used characterisation techniques. © 2002 Elsevier Science B.V. All rights reserved.
TL;DR: In this article, four binucleating ligands which potentially could provide bimetallic complexes bearing 5-and 6-coordinate sites have been prepared, which can be regarded as more elaborate binuclear ligands with tridentate chelates on each side of the alkoxy bridge.
Abstract: Four binucleating ligands which potentially could provide bimetallic complexes bearing 5- and 6-coordinate sites have been prepared. These ligands, which have alkoxide bridging groups, can be regarded as more elaborate versions of binucleating ligands which have tridentate chelates on each side of the alkoxy bridge. Unlike these previous, less complex ligands, the present series of binucleating ligands have a strong tendency to form oligomers. This has been demonstrated with a series of crystal structures of copper(II) complexes of these ligands. It is probable that oligomers are formed because of the high flexibility of the present ligands. The work serves to illustrate the limits of binuclear ligand design and suggests that, with alkoxide ligand bridges, rigidity is necessary in order to obtain bimetallic complexes with extended multidentate binucleating ligands. One of the ligands gives a mixed valence Mn(II)–Mn(IV) complex
after O2 oxidation of a di-Mn(II) precursor.
Patent•
21 Aug 2001TL;DR: In this paper, a polyester can be prepared with a higher catalytic activity as compared with a case of using a conventional catalyst, and polyester having better transparency, better hue and lower acetaldehyde content can be obtained as compared to a process using an antimony compound as a polycondensation catalyst.
Abstract: By the present invention, there are provided a catalyst for polyester preparation, which comprises a solid titanium compound containing titanium, oxygen, carbon and hydrogen and having a Ti—O bond and which has a maximum solubility in ethylene glycol, as measured when the catalyst is dissolved in ethylene glycol under heating at 150° C., of not less than 3,000 ppm in terms of a titanium atom, a catalyst for polyester preparation, which comprises a titanium-containing solution wherein a contact product of a hydrolyzate of a titanium halide or a hydrolyzate of a titanium alkoxide with a polyhydric alcohol is dissolved in ethylene glycol in an amount of 3,000 to 100,000 ppm in terms of a titanium atom, a process for preparing a polyester using the catalyst, and a polyester prepared by the process. According to the present invention, a polyester can be prepared with a higher catalytic activity as compared with a case of using a conventional catalyst, and a polyester having better transparency, better hue and lower acetaldehyde content can be obtained as compared with a process using an antimony compound as a polycondensation catalyst.
TL;DR: In this paper, a thin film photocatalysts were obtained by thermal decomposition of tetraisopropyl orthotitanate with a dip coating process using α-terpineol as a highly viscous solvent.
TL;DR: In this paper, the metallorganic precursor Fe(OBut)2(THF)2 followed by ultrasound and thermal treatment yielded either nanoparticles of γ-Fe2O3 or Fe3O4, depending on the process conditions.
Abstract: Hydrolysis of the new metallorganic precursor Fe(OBut)2(THF)2 followed by ultrasound and thermal treatment yielded either nanoparticles of γ-Fe2O3 or Fe3O4, depending on the process conditions. The samples have been characterised by X-ray powder diffraction, TEM, SEM, Mossbauer spectroscopy and magnetization measurements. The maghemite nanoparticles (9 ± 2 nm) are superparamagnetic and form unique needle-like assemblies of nanoparticle arrays. The nanoparticles of Fe3O4
(19 ± 2 nm) form plate-like aggregates about 10 µm thick.
TL;DR: At long last an experimentally utilized superbase has been crystallographically characterized, and this landmark compound adopts a novel sixteen-vertex "carousel" arrangement stabilized by two distinct types of benzene ligation.
Abstract: It has long been known that mixtures of organolithium derivatives (e.g., alkyls, amides, or enolates) and heavier alkali metal alkoxides (e.g. tert-butoxides or tert-pentoxides) can exhibit special proton-abstracting powers well beyond the capability of the lithium compounds on their own.[1] A forest of literature has grown around this superbasicity focussing mainly on its exploitation in organic synthesis[2] and, to a lesser extent in polymerization.[3] Yet for all this accumulated knowledge, there is still much uncertainty about the precise identities and structures of these superbasic reagents, which seems remarkable given that in general their two separate components (e.g. nBuLi[4] and tBuOK[5]) have themselves been fully characterized both in solution and in the solid state.
TL;DR: The rheological properties of two different sol compositions prepared from a mixture of TEOS, phosphorous alkoxide and calcium nitrate, or calcium chloride in a water-ethanol solution, are reported.
Abstract: Bioactive fibers were produced using a sol-gel method. The rheological properties of two different sol compositions prepared from a mixture of TEOS, phosphorous alkoxide and calcium nitrate, or calcium chloride in a water–ethanol solution, are reported. The sols were extruded through a spinneret to produce continuous 10 μm-diameter fibers. Discontinuous fibers and fibrous mats were prepared by air-spraying the multicomponent sols. The sol-gel fibers were converted to the bioactive fibers by three different thermal treatments at either 600°, 700°, or 900°C for 3 h. SEM, BET, EDX, and FTIR were used to characterize the morphology and structure of the fibers. The BET measured surface area of the fibers sintered at 900°C was 0 m2/gm compared to a value of 200 m2/gm for a typical sol-gel-derived particle of similar composition. Both the continuous and discontinuous fibers exhibited in vitro bioactivity in a simulated body fluid. © 2001 John Wiley & Sons, Inc. J Biomed Mater Res 55: 460–467, 2001
TL;DR: In this paper, a V2O5-based catalyst obtained by grafting vanadyl tri-isopropoxide on a TiO2-SiO2 support was studied as to the selective catalytic reduction (SCR) of NO with ammonia.
Abstract: A V2O5-based catalyst obtained by grafting vanadyl tri-isopropoxide on a TiO2-SiO2 support obtained by grafting titanium alkoxide on silica has been studied as to the selective catalytic reduction (SCR) of NO with ammonia. The performances obtained have been compared with those of other catalysts in which V2O5 was supported, respectively, on the same support by impregnating it with ammonium vanadate and on TiO2 both by grafting vanadyl tri-isopropoxide and by impregnating it with ammonium vanadate. The first mentioned catalyst turned out to be the best as to activities and selectivities. All the used catalysts and supports have been characterised using many techniques in order to explain the different performances observed. As it will be seen, activities and selectivities, in the mentioned reaction, are mainly affected by three factors that are: (i) V2O5 dispersion largely favoured by the grafting technique; (ii) the morphological properties of TiO2 surfaces that cannot be foreseen but only investigated when TiO2 is obtained by grafting titanium alkoxide on the surface of another oxide and (iii) the type of surface acidity, retaining ammonia reagent.
TL;DR: In this paper, the possibility of using amide complexes, in the presence of alcohol, to produce alkoxides was investigated in homogeneous and heterogeneous media, and the polymerization of e-caprolactone with alkoxide formed in situ was performed with and without excess alcohol.
Abstract: The synthesis of lanthanide(III) alkoxides has been described as a series of reactions for which the control of product purity is difficult. The possibility of using amide complexes, in the presence of alcohol, to produce alkoxides was investigated in homogeneous and heterogeneous media. The polymerization of e-caprolactone with alkoxides formed in situ was performed with and without excess alcohol. The latter system was efficient since the polymers were obtained in a short time period, with a well-controlled molecular weight and low polydispersity. The alcohol functionalized all the polymer chains.
TL;DR: In this paper, a refined sol-gel method using titanium butoxide and copper-loaded titania was used to synthesize nanoparticles of titania and copper loaded titania by adding copper chloride to titania sol.
Abstract: Nanoparticles of titania and copper-loaded titania were synthesized by a refined sol-gel method using titanium butoxide. Unlike the conventional sol-gel procedure of adding water directly, the esterification of anhydrous butanol and glacial acetic acid provided the hydrolyzing water. In addition, acetic acid also served as a chelating ligand to stabilize the hydrolysis-condensation process and minimize the agglomeration of titania. Following the hydrolysis, Cu/TiO2 was prepared by adding copper chloride to titania sol. The sol was dried, then calcined at 500°C to remove organics and transformed to anatase titania which was verified by XRD. Cu/TiO2 was further hydrogen-reduced at 300°C. The recovery of Ti was exceeded by an average of 95% from titanium butoxide. TEM micrographs show that the Cu/TiO2 particles are near uniform. The average crystallite sizes are 17–20 nm estimated from the peak broadening of XRD spectra. The bandgaps of TiO2 and reduced Cu/TiO2 range from 2.70 to 3.15 eV estimated from the diffusive reflective UV-Vis spectra. XPS analysis shows that Cu 2p3/2 is 933.4 eV indicating primary Cu2O form on the TiO2 supports. The binding energy of Ti does not exhibit chemical shift suggesting negligible interaction of Cu cluster and TiO2 support.