Presence Of Titanium Isopropoxide Research Articles

Ti–N coordination bonds boost Z-scheme interfacial charge transfer in TiO2/C-deficient g-C3N4 heterojunctions for enhanced photocatalytic phenolic pollutant degradation

Rational designing of chemical bond-bridged TiO2-based Z-scheme heterojunctions and deep understanding mechanism of significantly enhanced visible-light photocatalytic performance of the heterojunctions is a hotspot in photocatalysis. Herein, a defect-engineering strategy is developed to fabricate Ti–N coordination bond-bridged TiO2/C-deficient g-C3N4 heterojunctions (TiO2/VC-CN), and the preparation process includes formaldehyde-assisted preorganization of molten urea in the presence of titanium isopropoxide followed by thermal condensation. The detailed characterization results evidence the formation of a unique atomic-level heterojunction contact interface via Ti–N coordination bonds in TiO2/VC-CN, in which N atoms around the C vacancies of g-C3N4 donate electrons to unoccupied Ti 3d orbitals of TiO2. At the optimal TiO2 doping level, the TiO2/VC-CN heterojunctions exhibit remarkably high visible-light photocatalytic oxidation performance in the degradation of recalcitrant phenolic pollutants, methylparaben and acetaminophen, which outperforms commercially available P25 TiO2, as-prepared anatase TiO2 and bulk g-C3N4. The experimental results combined with theoretic calculations reveal that the outstanding interfacial Ti–N coordination bonding remarkably boosts the direct Z-scheme charge carrier transfer in the TiO2/VC-CN heterojunctions, which results in the generation of plentiful reactive oxidation species including O2−, OH and 1O2 for efficient removal of the target pollutants.

Sodium alginate‐cl‐poly (N,N‐dimethyl acryl amide‐co‐2‐acrylamino‐2‐methyl‐1‐propane sulphonic acid)/titanium dioxide nanocomposite hydrogel: An efficient dye‐removing agent

AbstractSodium alginate (SAG) crosslinked poly (N,N‐dimethyl Acrylamide‐co‐2 acrylamino‐2‐methyl‐1‐propane sulfonic acid)/Titanium dioxide [SAG‐cl‐poly(N,N‐DMA‐co‐AMPS)/TiO2] nanocomposite hydrogel (NCHG) was prepared by in situ crosslinked free radical polymerization technique using SAG, a mixture of DMA and AMPS and titanium isopropoxide in presence of methylene‐bis‐acrylamide as a cross linking agent. Different characterization techniques are used to characterize NCHG. Water swelling behavior of NCHG together with swelling kinetics is evaluated. Maximum swelling (35% at 30 min) is observed at pH 8. NCHG is used for the removal of one cationic dye methylene blue (MB) and one anionic dye carmosine‐A (CR‐A) from their aqueous solution. Adsorption dynamics, kinetics and isotherms are evaluated. Maximum dye adsorption occurs at pH 8 and 2, at time 50 min for both the cases, at temperature 60°C, 40°C for MB and CR‐A respectively. Pseudo‐second order kinetics and Langmuir isotherm model are followed for all the two cases with Qmax 403.22 mg.g−1, 106.26 mg.g−1 and the R2 value 0.9987 and 0.9950 for MB and CR‐A respectively. Evaluation of thermodynamic parameters of the adsorption indicates that the adsorption is spontaneous in nature for the two dyes.

Enhancement the photocatalytic degradation of methylene blue dye using fabricated CNTs/TiO2/AgNPs/Surfactant nanocomposites

In this work, the cotton stalks waste, as a woody biomass widely produced in Egypt, was used as a carbonaceous precursor for synthesis of carbon nanotubes (CNTs) with bamboo-like structure via subsequent catalytic hydrothermal and carbonization routes. Nanocomposite of TiO2@CNTs was prepared by sol-gel of titanium isopropoxide in presence of CNTs as a support and followed by calcination at 500 °C for 180 min under flowing of N2 gas. In addition, TiO2@CNTs was wrapped by silver nanoparticles (AgNPs) individually and in presence of synthesized cationic surfactant (C10) to produce TiO2@CNTs/AgNPs and TiO2@CNTs/AgNPs/C10, respectively. The resulting nanocomposites and unadorned CNTs were characterized by transmission-electron microscope (TEM), field emission-scanningelectron microscopy (FE-SEM) combined with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman spectroscopy, N2 gas adsorption-desorption at −196 °C and UV–Vis diffuse reflectance spectroscopy (UV–vis DRS). The obtained photocatalysts were used to remediate aqueous solutions of methylene blue (MB) dye under visible light irradiation. The results affirmed that the surfactant improved the dispersion and surface interaction of AgNPs over TiO2@CNTs which formed effective photocatalytic sites. The synthesized CNTs enhanced the surface and electronic properties of TiO2 while AgNPs significantly reduced the recombination of electron–hole pairs over TiO2@CNTs/AgNPs/C10. Accordingly, TiO2@CNTs/AgNPs/C10 exhibited the superior photocatalytic degradation of MB dye and high stability as a result of good dispersion of AgNPs by the surfactant, the lower band-gap energy (2.25 eV) and the larger surface area (146 m2/g) than that of TiO2@CNTs/AgNPs.

Environmental Assessment of a Large-Scale Production of TiO2 Nanoparticles via Green Chemistry

Green chemistry concept is currently implemented in order to stimulate the development of sustainability processes and pollution prevention. However, not for all cases the use of this type of process generates an operation with good environmental performance, also in the development and evaluation of new topologies, such as the one presented in this paper, environmental assessment becomes in an important tool in order to optimize the process. In this work for developed a synthesis of titanium dioxide (TiO2) nanoparticles from titanium isopropoxide (TTIP) via green chemistry. Environmental assessment was performed using software WAR GUI, which use Waste Reduction Algorithm in order to quantify potential environmental impacts generation and output environmental impacts for this process for 4 different cases. Results show that the process doesn’t generate high potential environmental impacts (PEI) with a rate of 1.43X102 PEI/h for the case that include energy and product contributions, which represents a very low value compared to the total output rate for this case (1.21X104 PEI/h). For toxicological categories, it was obtained that for human toxicity by ingestion (HTPI) and terrestrial toxicity potential (TTP) categories exist some environmental impacts due to presence of TTIP in a high concentration, additionally these effects are increased by propanol, as a subproduct of the hydrolysis, and ethanol as solvent for the purification stage. For the aquatic matrix the potential impacts obtained was relatively low. On the other hand, it was determined for atmospheric effects that the presence of the alcohols in the process rises the potential impact related to the photochemical oxidation potential category.

Synthesis of a newly modified poly-H8-BINOL ligand and its applications in the asymmetric addition of triethylaluminium to aromatic aldehydes

A new H8-BINOL polymer was synthesized by radical polymerization and proved to be an effective catalyst in enantioselective addition of triethylaluminium to aromatic aldehydes in the presence of titanium isopropoxide. The polymer can be prepared with simple steps and reused without losing its enantioselectivity and catalytic activity.

ChemInform Abstract: Preparation of Several BINOL‐Based Polymeric Ligands for the Enantioselective Addition of Triethylaluminium to Aromatic Aldehydes.

AbstractThe title reaction is accomplished using polystyrene‐supported BINOL ligands in the presence of titanium isopropoxide as catalysts.

Preparation of several BINOL-based polymeric ligands for the enantioselective addition of triethylaluminium to aromatic aldehydes

The synthesis of several polystyrene-supported BINOL (1,1-binaphthol) ligands via radical polymerization is described. These BINOL-based polymeric ligands were applied to the enantioselective addition of triethylaluminium to aromatic aldehyde in the presence of titanium isopropoxide. The products were obtained with up to 93% enantiomeric excess (ee) in good to excellent yield. The ligands were easily recovered and reused without losing their catalytic activity as well as enantioselectivity.

Synthesis, characterization and biodegradation studies of poly(ester-urethane)s

A series of aliphatic poly(ester-urethane)s (PEUs) with different NCO/OH ratio were synthesized by a two-step bulk polymerization process from aliphatic poly(neopentyl-succinate) (PNSu), 4,4’-dicyclohexylmethane diisocyanate and 1,3-propanediol as a chain extender in the presence of dibutyltindilaurate as a catalyst. PNSu was prepared by the transesterification polycondensation from diethyl succinate and neopentyl glycol in the presence of titanium isopropoxide as a catalyst. The effect of the NCO/OH ratio on the structural, physical and thermal properties of PEUs was studied by Fourier transform infrared spectroscopy, X-ray diffraction, proton nuclear magnetic resonance, gel permeation chromatography, density measurement, differential scanning calorimetry, thermogravimetric analysis/differential thermogravimetric analysis and optical microscopy. The density (ρ) and number-average molecular weight (Mn) of PEUs are found to be in the range of 1·175–1·180 g/cm3 and 55 137–56 947 g/mol, respectively. The biodegradability of the PEUs film was investigated by hydrolytic (in 3% sodium hydroxide solution) and enzymatic degradation (Aspergilus niger lipase in phosphate buffer solution pH = 7·2) at 37°C. PEUs film shows a slower degradation rate in A. niger lipase compared with the hydrolytic process.

Optical emission spectroscopy of microwave-plasmas at atmospheric pressure applied to the growth of organosilicon and organotitanium nanopowders

An atmospheric-pressure plasma sustained by an electromagnetic surface wave (SW) in the microwave regime combined with a bubbler/flash evaporator for the injection of liquid precursors was used to produce organosilicon and organotitanium nanopowders. Following the addition of hexamethyldisiloxane (HMDSO) vapors in the nominally pure argon plasma, optical emission spectra revealed the apparition of strong C2 molecular bands along with Si and Balmer H emission lines. Such features were not observed in our atmospheric-pressure Ar/HMDSO discharges controlled by dielectric barriers, indicating that microwave plasmas are characterized by much higher fragmentation levels of the precursors due to much higher electron densities. Emission spectra from the Ar/HMDSO SW plasma further showed a high-intensity continuum, the intensity of which decreased with time as powders started to form on the discharge tube walls. In presence of titanium isopropoxide (TTIP) vapors in the nominally pure Ar plasma, the emission was dominated by Ar and Ti lines, with no trace of carbon and no continuum. Fourier-Transform Infrared (FTIR) Spectroscopy of the powders formed in Ar/HMDSO plasmas showed very strong Si-(CH3)x and O-Si-(CH3)x bands, which is consistent with the formation of silicon oxycarbide. Transmission Electron Microscopy (TEM) further showed tube and sheet-like nanofeatures as well as larger structures consisting of agglomerated primary clusters. On the other hand, introduction of O2 in Ar/HMDSO plasmas produced only round-like nanoparticles with strong Si-O-Si bands and no trace of carbon, consistent with the formation of SiOx. The average size of the silica nanoparticles was 50 nm. FTIR spectra of powders formed in Ar/TTIP plasmas showed strong Ti-O signals, even without the addition of O2 in the gas phase. Corresponding TEM analysis showed nano- and agglomerated features comparable to those obtained in Ar/HMDSO although the average size of the titanate nanoparticles was smaller (10 nm). This set of data indicates that SW plasmas represent a promising parametric tool not only to achieve nanopowders with tailored properties for applications, but also for fundamental studies of nanodusty plasmas at atmospheric-pressure.

Microwave-Assisted Synthesis and Characterization of Random Copolyesters

Synthesis and characterization of polyesters containing chalcone chromosphers were carried out and their properties were studied. Chalcones are 1,3-diphenyl-2-propene-1-one in which two aromatic rings linked by a three carbon α,β- unsaturated carbonyl system. Synthesis has been carried out using microwave. The MW-assisted synthesis of co-polyesters has been effected using from propane1, 3-diol and 1,4-cyclohexane dimethanol with various carboxylic acids in the presence of titanium isopropoxide as the catalyst. Microwave structural analysis and thermal properties of biodegradable diblock copolyesters were also performed. The synthesized polymers were characterized by solubility measurement and intrinsic viscosity methods. Results are presented and discussed.

Titanium alkoxide induced BiOBr–Bi2WO6 mesoporous nanosheet composites with much enhanced photocatalytic activity

Here we report a facile hydrothermal route for the preparation of BiOBr–Bi2WO6 mesoporous nanosheet composites (MNCs) in the presence of titanium isopropoxide, Ti(OiPr)4. High resolution transmission electron microscopy, X-ray diffraction, nitrogen adsorption/desorption analysis and X-ray photoelectron spectroscopy were employed for structural and composition analyses of the MNCs. The photogenerated charge transfer and photocatalytic activity of BiOBr–Bi2WO6 MNCs were investigated by Kelvin probe force microscopy and UV-vis spectroscopy. We propose mechanisms to illustrate how titanium alkoxide induces the formation of mesoporous nanosheet heterostructures and the enhanced photodecomposition efficiency of the dye under low light intensity illumination. Overall, our results suggest that titanium alkoxide is not only strongly involved in the growth of BiOBr (001) facets, but also plays a critical role in the pore evolution of the product. Kelvin probe force microscopy analysis allows us to conclude that the resulting nanocomposites demonstrate high photogenerated charge mobility and a long lifetime. Dye molecules can be rapidly and thoroughly decomposed with the photocatalyst under very low light intensity illumination. The enhanced photocatalytic activity is attributed to well matched band edge positions of BiOBr and Bi2WO6 and the large specific surface area of the MNCs in view of the incorporation of mesopores and the highly exposed BiOBr (001) facet due to the use of Ti(OiPr)4 during the synthesis. The results presented here are expected to make a contribution toward the development of delicate nanocomposites for photocatalytic water purification and solar energy utilization.

Reductive amination using ammonia borane

Abstract A variety of primary, secondary, and tertiary amines were prepared in 84–95% yields using ammonia borane for the reductive amination of aldehydes and ketones in the presence of titanium isopropoxide.

1‐Aryl‐3,3‐diisopropyltriazenes: An Easily Accessible and Particularly Stable Class of Triazenes Towards Strong Basic and Lewis Acid Conditions

AbstractThe stability of various substituted aryl‐3,3‐dialkyltriazenes, valuable synthetic intermediates, under several reaction conditions has been evaluated. To do so, anthranilonitrile and 2‐amino‐6‐(trifluoromethyl)benzonitrile have been reacted in the presence of different secondary amines to the corresponding 1‐(2‐R‐phenyl)‐3,3‐dialkyltriazenes. These compounds have been submitted to a series of different reaction conditions with special emphasis on strong basic and metal/acid reductive conditions in order to test the stability of the triazene moiety under these circumstances. Generally, triazenes are unstable in metal/acid reducing conditions. A lot of 1‐aryl‐3,3‐dialkyltriazenes are known to undergo deprotonation in α‐position of N‐3 in the presence of strong bases, thus limiting the scope of action of this class of compounds. Among the tested substances, most triazenes were stable in the presence of titanium isopropoxide and/or strong nucleophiles. 1‐(2‐R‐phenyl)‐3,3‐diisopropyltriazenes turned out to be particularly stable under strong basic conditions. 1,2‐addition reactions in the presence of Grignard reagents or lithiated compounds, showed in most cases no side products resulting from a degradation of the triazene function. The same was true for the titanium‐catalyzed Kulinkovich–de Meijere cyclopropanation or for reductive amination. In both cases, no triazene degradation products could be detected. 1‐(2‐R‐phenyl)‐3,3‐diisopropyltriazenes were even stable in the presence of strong Lewis acids like trimethylaluminium. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Unexpected Vinyl Transfer in the Titanium-Mediated Cyclopropanation Reaction

Simple cyclopropanols are obtained on addition of ethylmagnesium halides to esters in the presence of titanium isoprop-oxide. Alternatively, we have found that they may also be prepared in moderate to good yields through unexpected vinyl transfer from vinyl ethers via a titanium-promoted inter- or intramolecular reaction. On the basis of deuterium labeling experiments, a mechanism has been proposed.

Effects of annealing treatment on the properties of MEH-PPV/titania hybrids prepared via in situ sol–gel reaction

A uniform poly[2-methoxy-5-(2′-ethylhexyloxy)- p-phenylenevinylene] (MEH-PPV)/titania hybrid film was successfully prepared by an in situ sol–gel reaction of titanium isopropoxide (TIP) in the presence of MEH-PPV/2-chlorophenol solution. The annealing treatment increased the conversion of TIP to titania as determined from evidence of the formation of Ti–O–Ti bonds in the Fourier transform infrared (FTIR) spectrum. Scanning electronic microscope (SEM) photographs showed that the morphology and distribution of titania in the hybrid film were strongly related to the amount of water in the in situ sol–gel reaction. The thermal stability of MEH-PPV/titania hybrids was enhanced by the annealing treatment. Small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) analyses indicated that annealing treatment promoted the ordered aggregation of the MEH-PPV chains and crystallization of titania to a certain extent. The blue shift in Ultraviolet–visible (UV–vis) absorption of pure MEH-PPV after annealing was ascribed to the small extent of decomposition and coil conformation which occurred at high temperature. A more-obvious blue shift for the hybrids was observed, which resulted from irregular aggregation and coil conformation of the MEH-PPV chains induced by heterogeneous point, TIP (titania). The red shift in the photoluminescent (PL) emission for pure MEH-PPV resulted from a certain extent of ordered aggregation after annealing. However, only a slight red shift in the PL emission peak for the hybrids was found due to the hindrance of ordered aggregation of MEH-PPV chains in the presence of TIP (titania).

An Efficient, One-Pot Synthesis of Fosfomycin Dialkyl Esters from (R)-2-Tosyloxypropanal

(R)-2-Tosyloxypropanal (4) was prepared from D-mannitol in a 7-step sequence (51% overall yield). Addition of dialkyl phosphonates to 4 in the presence of titanium isopropoxide and the subsequent treatment with DBU stereoselectively afforded, in one-pot, fosfomycin dimethyl (5a) and dibenzyl (5b) esters both in 58% isolated yield.

Polymer-Titanium hybrids obtained by radical polymerization and Sol-Gel process

AbstractThe possibility to prepare hybrids made by poly(vinyl acetate) (PVAc), poly(methyl methacrylate) (PMMA) and/or poly(ethyl acrylate) (PEtA) with TiO2 was studied. The processes of polymer formation-radical polymerization and sol-gel process for inorganic network —were achieved simultaneously. Due to a high reactivity of titanium isopropoxide (TIP) in the sol-gel process, a complexant comonomer, allyl acetoacetate (AlAcAc), was used. Covalent bonds between polymer and inorganic chains were obtained by addition of trialkoxysilane derivates with vinyl (VTES) or methacryloyl (MPTS) groups. The presence of TIP inhibits the radical polymerization of vinyl acetate (VAc). The PVAc-TiO2 hybrids were produced by the sol-gel process of TIP in the presence of pre-obtained PVAc. Except for VTES and MPTS, trialkoxysilane derivates with methyl (MeTES), octyl (OTES) and phenyl (PTES) groups were used. The thermal stability of hybrids is strongly affected by TiO2 presence and by the type of trialkoxysilane derivates. The thermal stability of PVAc hybrids decreases in the presence of TiO2 inorganic network. The glass transition temperature of polymers increases in the presence of the inorganic network.

Asymmetric syntheses of new functionalized beta-amino alcohols via diastereoselective addition of organometallic reagents onto oxazolidines.

Diastereoselective reactions between (S)-phenylglycinol-derived oxazolidines and two unsaturated organolithium reagents afforded chiral beta-amino alcohols having vinyl and alkynylsilane moieties. When the same reactions were performed in the presence of titanium isopropoxide, a dramatic change of regioselectivity was observed, from the alpha- to the gamma-position, thus producing beta-amino alcohols with allyl or allenylsilane functions. A rationalization of the observed diastereoselectivity was suggested for each case.

A novel one-pot conversion of aldehydes to trifluoromethylated bromoallylic alcohols.

[reaction: see text]. One-pot conversion of aldehydes to trifluoromethylated bromoallylic alcohols in the presence of titanium isopropoxide and triphenylphosphine is described.

Dramatic change of regioselectivity in the addition of silylated organolithium reagents with oxazolidines induced by the presence of a titanium salt

Diastereoselective reactions between oxazolidines and organolithium reagents afford β-amino alcohols having chiral vinyl and alkynylsilane moieties. A meaningful change of regioselectivity, from the α- to the γ-position, occurred when these reactions were performed in the presence of titanium isopropoxide, since allyl and allenylsilane derivatives were thus produced.