Titanium Silicate Molecular Sieve Research Articles

Dual effect of organic/inorganic artificial protective layer to construct high-performance zinc metal anode

Owing to their high specific capacity, low cost, environmental friendliness and safety, aqueous zinc ion batteries (AZIBs) have been one of the most popular battery systems. Nevertheless, dendrite growth, corrosion, hydrogen evolution and passivation on the anode side can seriously affect the lifetime of AZIBs. In view of this, this work constructs a protective layer compounded from inorganic (titanium silicate molecular sieve, TS) and organic (polyacrylonitrile, PAN) materials to realize the high-performance and dendrite-free zinc anode (Zn@PAN-TS). The cyano group in PAN has a coordination effect with zinc ions, which facilitates the transport of zinc ions. The porous TS can regulate the zinc ion flux through ion-confinement effect. Thus, the PAN-TS composite protective layer provides fast and orderly ion transport channels that modulate the uniform deposition of zinc through dual effect. Moreover, the experimental results show that the Zn@PAN-TS 50:1 anode has the best electrochemical performance. The corresponding MnO2 full cell maintained a high discharge capacity of 217.2 mAh·g−1 with a high retention rate of 81.1 % after 500 cycles at 0.3 A·g−1. This strategy offers fresh insight into constructing multifunctional hybrid interface for dendrite-free AZIBs.

Enhancing oxidative hydration of ethylene towards ethylene glycol over metal-modified titanosilicate catalysts

Metal-dopant modification is a promising approach to enhance the catalytic performance of titanium silicate molecular sieve. Herein, titanium silicalite-1 (TS-1) with different titanium contents and a series of metal-doping modified TS-1 are prepared, to enhance the synthesis of ethylene glycol (EG) through oxidative hydration of ethylene. The EG selectivity show a volcano relationship along with the increase of Ni addition, and reach maximum in 80.63 % at 0.13 wt % Ni loading. The Ni promoter mechanism is revealed that NiO species enhances the electropositivity of skeleton Ti and neutralizes the surface acidity of TS-1, which improves the efficient utilization of H2O2 and selectivity of EG. Furthermore, Ni-modified TS-1 shows superior stability to TS-1, as well as satisfactory reusability since the deactivation of catalyst is reversible through high-temperature calcination. This work demonstrates the feasibility and mechanism of Ni promoter and provides a promising strategy for the development of TS-1 catalysts.

Oxidation of Furfural and Furan Derivatives to Maleic Acid in the Presence of a Simple Catalyst System Based on Acetic Acid and TS-1 and Hydrogen Peroxide.

Titanium silicate molecular sieve (TS-1) and acetic acid efficiently catalyze the oxidation of furan and furan derivatives to the corresponding maleic acid (MA) in very good yields using hydrogen peroxide as an oxidizing agent. The effect of various solvents, the effect of temperature, reaction time, concentration of hydrogen peroxide, and quantities of the catalyst on the MA yield was studied. With the best conditions, MA is the sole product obtained after a fast and simple purification by filtration and evaporation. Compared to the previously reported methods, this work is a good compromise between the different reaction parameters and offers a good alternative to the production of biosourced MA.

Research on Gas-Phase Direct Epoxidation of Propylene by Nanosized Gold Catalysts

One-step synthesis of propylene oxide from propylene in gas phase in the presence of hydrogen and oxygen is an environmentally friendly and energy-saving ideal reaction, which has important research value. The gold catalyst prepared by deposition and precipitation method has the advantages of small particle size, high dispersity and good activity. It is used for epoxidation of propylene in gas phase. The selectivity meets the requirements of industrialization. However, how to improve the conversion of propylene is still the focus of research. The effect of doping on the gas phase epoxidation of propylene is obvious. The purpose of this paper is to synthesize titanium silicate molecular sieves with composite structure and corresponding nano-gold catalysts by combining the advantages of high stability, weak surface acidity, large specific surface area, large pore size and pore volume of microporous titanium cinnamon molecular sieves.

Synthesis of Azoxybenzenes by Selective Oxidation of Anilines on Titanium Silicate Molecular Sieves

Synthesis of Azoxybenzenes by Selective Oxidation of Anilines on Titanium Silicate Molecular Sieves

Adsorption of carbon dioxide and water vapor on fly-ash based ETS-10

CO2 capture from humid flue gas is always costly due to the irreplaceable pretreatment of dehydration in current processes, which creates an urgent demand for moisture-insensitive adsorbents with considerable CO2 uptakes as well as remarkable H2O tolerances. In the present work, the microporous titanium silicate molecular sieve ETS-10 was synthesized with coal fly ash as the only silica source. The as-synthesized ETS-10 was characterized by X-ray diffraction, scanning electronic microscopy and infrared spectroscopy to verify its crystal morphology, in which neither impurity nor aggregation was observed. The following CO2 adsorption experiments on the thermal gravimetric analyzer demonstrated its similar CO2 adsorption capacity yet dramatical adsorption kinetics among some other microporous materials, e.g., potassium chabazite. These specific properties consequently guaranteed its favorable CO2 adsorption capacity even at high temperatures (1.35 mmol/g at 393 K) and shortened the breakthrough time of single CO2 flow to less than 20 s. In CO2/H2O binary breakthrough experiments, the as-obtained ETS-10 still maintained excellent CO2 uptake of 0.81 mmol/g at 323 K, regardless of the presence of water vapor, making it a promising substitute for direct CO2 separation from humid flue gases at practical conditions of post-combustion adsorption.

Heterogeneous photocatalytic degradation of organic contaminant in water over high-activity Fe-TS-1 under the radiation of solar light

The Fe-supported titanium silicate molecular sieve (Fe-TS-1) was synthesized and its solar light responsive activity was evaluated by the degradation of acid orange 7 (AO7) in the heterogeneous photo-Fenton system. The vital operational parameters as mass ratio of the iron and the TS-1 (Q (m (Fe): m (TS-1)), concentration of H2O2 and the initial solution pH value have been extensively studied. The obtained results showed that the solar light radiation could to enhance the catalytic efficiency of the Fe-TS-1 catalyst and there was a synergistic effect of the solar light and the Fe-TS-1 catalyst. The decoloration of AO7 in the photo-Fenton system followed the pseudo-first-order kinetics model and the optimal conditions for the degradation of AO7 of a concentration of 100 mg/L were obtained under the condition of 0.2 Q, 10 mL/L H2O2 addition and 3.0 solution initial pH value. The achieved decoloration of AO7 was 97.7% and corresponding TOC removal was 52.7%. The degradation pathway of AO7 was also inferred by the change of pH, and UV–vis spectrum in the process of reaction in the paper and the possible catalytic degradation mechanism of the Fe-TS-1 was proposed. The high-efficiency degradation of AO7 in the photo-Fenton system was the result of interaction of photosensitivity of dye, adsorption and photocatalysis of TS-1 and Fenton reaction. The whole process of degradation proceeded as follow: “adsorption-degradation-regeneration”.

Preparation of photo-Fenton heterogeneous catalyst (Fe-TS-1 zeolite) and its application in typical azo dye decoloration

The titanium silicate (TS-1) molecular sieve and Fe-loading TS-1 (Fe-TS-1) with various mass ratios of Fe and TS-1 (Q = m (Fe): m (TS-1)) were prepared successfully. The X-ray fluorescence (XRF), ultraviolet-visible (UV–vis), X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR), BET specific surface area analyzer and scanning electron microscopy (SEM) techniques were used to characterize the prepared catalysts. The catalytic activity of the Fe-TS-1 for the acid orange 7 (AO7) decoloration under radiation of different light sources and the vital operational parameters as Q, additive amount of the catalyst and the initial solution pH value have been extensively studied. The obtained results showed that there was a synergistic catalysis of the Fe-TS-1 catalyst, the optimum values of the Q and the initial solution pH value was 0.15 and 3, respectively. The degradation of the AO7 was positive correlation with the additive amount of the Fe-TS-1 catalyst. The Fe-TS-1 catalyst also had better visible light response in the photocatalytic system. Furthermore, the process of mineralization was also evaluated by analyzing total organic carbon (TOC) values and the results indicated that 99.9% TOC removal could be achieved at the optimal condition after 40 min reaction.

Kinetics of the acid orange 7 degradation in the photocatalytic system of UV/H2O2/TS-1

In this paper, the titanium silicate (TS-1) molecular sieve was prepared through a rapid synthesis process, in which the tetrabutyl titanate used as titanium source, the tetraethyl orthosilicate used as silicon source and the tetrapropylammonium hydroxides used as template. A UV/H2O2/TS-1 photocatalytic system, including the light source of the high pressure mercury lamp (300W, main wavelength of 365nm), the oxidant of H2O2 and the photocatalyst of the prepared TS-1, was then built to investigate the kinetics of acid orange 7 (AO7) degradation. The effect of the mass concentration of TS-1, H2O2 volume fraction, initial pH value of the solution and initial concentration of the AO7 solution on the degradation rate constant (k) of the AO7 degradation was investigated. The obtained results showed that the AO7 degradation in the UV/H2O2/TS-1 photocatalytic system obeyed the first order kinetics equation. 0.2g/L TS-1 addition, 10mL/L H2O2 addition, 6.18pH value was the optimal conditions for the AO7 degradation in the reaction system and the corresponding k value (0.11879min−1) of the AO7 degradation was the highest. The azo group, the hydrogenated azo and the naphthalene of the AO7 molecules could be damaged under the optimal reaction conditions.

Adsorption separation performance of H2/CH4 on ETS-4 by concentration pulse chromatography

To exploit an effective adsorbent to separate hydrogen and methane, microporous titanium silicate molecular sieve NaETS-4 was synthesized and modified by strontium. The adsorption characteristics and diffusion behaviors of the prepared titanosilicate molecular sieve were studied by concentration pulse chromatography. And the effects of ion-exchange and dehydration temperature on adsorbent structure and gas diffusion were also discussed. The results showed that the thermal stability and Henry's Law constants were enhanced and micropore diffusivity decreased after exchanging Na+ with Sr2+. With the increase of dehydration temperature, Henry's Law constant and micropore diffusivity of CH4 decreased in both NaETS-4 and SrETS-4. While for H2 in SrETS-4, the increase of Henry's Law constant and the decrease of diffusion rate can be attributed to the shrinks of pore diameter resulting from the relocation of Sr2+. Correspondingly, the kinetic selectivity of H2/CH4 reached 8.91 indicating its potentiality in separating H2 and CH4.

Titanium silicates as efficient catalyst for alkylation and acylation of silyl enol ethers under liquid-phase conditions

The activity of titanium- and tin-silicate samples such as TS-1, TS-2, Ti-β and Sn-MFI has been investigated for acylation and alkylation of silyl enol ethers under mild liquid-phase conditions. Silyl enol ethers successfully react with acetyl chloride and tert-butyl chloride under dry conditions in the presence of above catalysts to produce the corresponding acylated and alkylated products, respectively. In the case of acetylation reaction, two different nucleophiles with carbon-center (C-atom) and oxygen-center (O-atom) in silyloxy group of silyl enol ether reacts with acetyl chloride to give 1,3-diketone and ketene-ester, respectively. The selectivity for alkylation is always ca. 100% and no side products are formed. Among the various solvents investigated, anhydrous THF was found to be the suitable solvent for alkylation; whereas dichloromethane exhibited high selectivity for diketones for acylation. The formation of nucleophiles from silyl enol ethers appears to be the key step for successful acetylation and tert-butylation by nucleophilic reaction mechanism. Sn-MFI showed less activity than that observed over the titanosilicates. The observed catalytic activity is explained on the basis of “oxophilic Lewis acidity” of titanium silicate molecular sieves in the absence of H 2O under dry reaction conditions.

Silanized Titanium Silicate (TS-1) Molecular Sieve for Promoting the Homogeneously Catalyzed Oxidation of Cyclohexane

The promoting effect of titanium silicate (TS-1) molecular sieve and silanized TS-1 (TS-1-S) on the homogeneous liquid oxidation of cyclohexane catalyzed by cobalt naphthenate (Co-nap) with oxygen as oxidant was investigated. Both TS-1 zeolites were efficient promoters. The conversion of cyclohexane was 7.9% with a selectivity of 83.7% when it was catalyzed by Co-nap/TS-1-S, and the reaction time was reduced to 130 min as compared to 300 min with Co-nap as the catalyst. The adsorption of Co-nap on TS-1-S, which transformed a homogeneous reaction into a “quasi-heterogeneous” reaction, was the reason for the better catalytic performance. 摘要：考察了钛硅分子筛 (TS-1) 以及硅烷化钛硅分子筛 (TS-1-S) 上环烷酸钴 (Co-nap) 催化环己烷氧化反应性能. 结果表明, TS-1 和 TS-1-S 对该反应均具有显著的促进作用, 环己烷转化率由无 TS-1 时的 3.6% 分别提高至 6.4% 和 7.9%, 产物选择性保持在 80% 左右, 反应时间由 300 min 可缩短为 130 min. 进一步的研究表明, 随着 TS-1 的加入, Co-nap 在其表面发生了吸附, 使得均相反应变成了“类多相催化反应”, 这是反应性能显著提高的主要原因. Titanium silicate (TS-1) molecular sieve was used to promote the oxidation of cyclohexane catalyzed by cobalt naphthenate. The adsorption of cobalt naphthenate on TS-1-S was the reason for the better activity.

Separation of a binary mixture of ethylene and ethane by adsorption on Na-ETS-10

Ethylene produced by steam cracking and thermal decomposition of ethane must be purified prior to use in the production of plastics, rubber and films. Ethane–ethylene separation is generally achieved by cryodistillation. The energy and equipment costs associated with ethylene purification could be significantly reduced by the development of alternative separation methods. Both modelling predictions for the binary adsorption of ethylene and ethane, and recent work investigating the adsorption of ethane and ethylene on the surface of Engelhard Titanosilicate-10 (ETS-10), a large-pored, mixed octahedral/tetrahedral titanium silicate molecular sieve, indicate that this molecular sieve might be an adsorbent capable of ethylene/ethane separations. However, the actual separation of a binary mixture of ethylene and ethane on ETS-10 has yet to be demonstrated. In this work, Na-ETS-10 was used to separate a mixture of ethylene and ethane (59% C 2H 4, 41% C 2H 6) from an industrial process stream with a measured binary bed selectivity for ethylene over ethane of approximately 5 at 25 °C and 1 atm. In a laboratory-scale demonstration, both high purity ethane and significantly enriched ethylene were produced, and the Na-ETS-10 adsorbent was regenerated for further separation cycles by both steam and microwave desorption, without degradation of the adsorbent or products.

Anion-Controlled Pore Size of Titanium Silicate Molecular Sieves

Titanium silicate molecular sieves contain structural units that are fundamentally different from classical aluminosilicates. In addition to ordered octahedral titanium chains, members of the zorite family contain pentagonal titanium units which project into the main adsorption channels of the framework. We report that the effective pore size of these materials can be controlled by substituting halogens at the O7 sites that cap the pentagonal pyramids projecting into the channel. The quantity and type of halogen used determines the adsorptive properties of the molecular sieve. Barium exchange stabilizes these materials over a wide temperature range (nominally 200-400 degrees C). The barium-exchanged materials do not contract appreciably with calcination, as is observed in related Molecular Gate materials, and thus halogen content can control the pore size of the materials. This new approach to pore size control may have important implications for the purification of multiple classes of compounds, including light hydrocarbons and permanent gases.

Eco-friendly, Selective Hydroxylation of C-7 Aromatic Compounds Catalyzed by TS-1/H2O2System under Solvent-free Solid−Liquid−Liquid-Type Triphase Conditions

Direct ring hydroxylation of aromatics, namely, anisole, toluene, and benzylchloride, using TS-1 catalyst, a MFI-type titanium silicate molecular sieve, dilute H2O2 as oxidizing agent, and water as reaction medium, was investigated under solid−liquid−liquid (SLL)-type triphase conditions. The aim was to study the relative influence of commonly used organic solvents, under solid−liquid (SL)-type biphase reaction conditions, as compared to that of water, on the conversion and product selectivity. Under solvent-free triphase conditions, the ring hydroxylation of anisole, toluene, and benzylchloride leads to significant enhancement in the conversion, turn-over frequency, and para-selectivity. However, in the case of benzyl chloride, no ring hydroxylation took place under biphase conditions (using acetone as solvent) contrary to significant ring hydroxylation (ca. 60% H2O2 efficiency) under triphase aqueous medium conditions. The simple product recovery (phase separation of organic and aqueous layers) and use ...

Eco-friendly synthesis of epichlorohydrin catalyzed by titanium silicate (TS-1) molecular sieve and hydrogen peroxide

In a mixed solvent system of acetonitrile and methanol, titanium silicate molecular sieve, TS-1, having MFI topology, efficiently catalyses the epoxidation of allyl chloride to the corresponding epichlorohydrin in excellent yields using dilute hydrogen peroxide (45%) as an oxidizing agent.

Photocatalytic activity of CdS nanoparticles incorporated in titanium silicate molecular sieves of ETS-4 and ETS-10

Nanoscopic CdS particles were encapsulated into microchannels of Engelhard titanosilicates, ETS-4 as well as ETS-10, with the photocatalytically active –Ti–O–Ti– quantum wires in their frameworks. The photocatalytic activities for hydrogen production from water under visible light irradiation ( λ > 420 nm) were investigated in the CdS/ETS system. A stable photocatalytic activity under visible light irradiation was found in an aqueous solution containing Na 2S and Na 2SO 3 as electron donors. The results suggest that the encapsulation of CdS in ETS-zeolites is effective for separating charge-carriers photogenerated in CdS and for improving the activity as well as the stability.

Active Sites and Reactive Intermediates in Titanium Silicate Molecular Sieves

AbstractFor Abstract see ChemInform Abstract in Full Text.

Alkali effect and kinetic studies on the crystallization of a small pored titanium silicate molecular sieve, ETS-4 using different sources of silica and titanium under stirring

A small pored variety of titanium silicate, ETS-4 was synthesized to investigate the effect of alkali content on the crystallization and phase purity using different sources of silica and titanium under stirring at 200 rpm and to calculate activation energy. The results showed that the alkali content significantly affects the crystallization and phase purity depending on titanium source. In addition, regardless of silica and titanium sources, the morphology of ETS-4 is quite different from that synthesized under static condition showing a thin plate-like shape and seems to be significantly affected by stirring. The composition with the shortest reaction time to reach the 100% crystallinity and the purity for different silica and titanium source was chosen and applied to the kinetic study. All the experiments for kinetic study were conducted at 423, 443 and 463 K, respectively. The activation energies for three different stages, nucleation, transition and crystallization were calculated using the modified Avrami–Erofeev equation. The results of kinetic study suggest that the effect of titanium source is more significant than that of silica source; that is, Ludox AS-40 and fumed silica show the most significant temperature dependency on the crystallization for titanium oxysulfate and titanium trichloride as the titanium sources, respectively. The modified Avrami–Erofeev equation to three different stages, nucleation, transition and crystallization for rapid crystallization seems to be an excellent tool to predict the crystallization of ETS-4.

Titanium silicates for carbon–carbon bond formation reactions

The activity of titanium silicate molecular sieves, TS-1 and aluminum-free Ti- β, has been studied for carbon–carbon bond formation reactions such as Mukaiyama-type aldol condensation and Michael addition under mild liquid-phase conditions. All the reactions were efficiently carried out in the absence of water by using dry solvents in the temperature range of 313–333 K. In the case of Mukaiyama aldol condensation, a variety of aldehydes successfully react with silyl enol ethers to give β-hydroxy esters/aldols in high yields under heterogeneous reaction conditions. Similarly in the case of Michael addition, silyl enol ethers undergo addition reactions with Michael acceptors such as acrylates and α, β-unsaturated ketones to give 1,4-addition products. The selectivity for aldol as well as Michael addition product is always 100%, regardless of conversion level, and no side products are formed. The facile formation of nucleophiles from silyl enol ethers appears to be the key step for successful carbon–carbon bond formation reactions over titanium silicates. The activity of other isomorphously substituted zeolites such as V-, Sn-, and Al-ZSM-5 as well as modified zeolites by ion exchange exhibits less activity than that observed over TS-1 and Ti- β in the aldol condensation. Among the various solvents investigated tetrahydrofuran (THF) shows the best activity. The observed catalytic activity is explained on the basis of “oxophilic Lewis acidity” of titanium silicate molecular sieves in the absence of H 2O 2 and H 2O.