Hydrothermal synthesis of aluminum-substituted titanosilicate, ETS-10

One of ETS-10 variants, aluminum-substituted ETAS-10 was successfully synthesized with Al/Ti molar ratio of 0.1–0.4 using different titanium sources, titanium sulfate (Ti(SO₄)₂) and titanium oxysulfate (TiOSO₄). Through the compositional study, like ETS-10, the (Na + K)/Na molar ratio significantly affects the crystallinity and phase purity depending on titanium source. The 2³ factorial designs indicate that the high alkalinity mainly by Na⁺ content is very critical to the crystallization of pure ETAS-10 while the content of K⁺ cation should be carefully controlled. It suggests that the increase in K⁺ content with smaller hydrated radius than of Na⁺ makes the formation of ETAS-10 structure difficult. The optimum composition was chosen and applied to kinetic study. The activation energies for three different stages, nucleation, transition and crystallization were calculated using the modified Avrami–Erofeev equation. This result indicates that the nucleation and transition stage proceed at the similar rate, and then the crystallization stage proceeds with lower activation energy than those of previous two stages. In addition, the temperature dependency on the crystallization was quite significant, favoring high temperature.     

水热法合成TS-1分子筛中的影响因素

有机物的选择性催化氧化是一类非常重要的化工反应。TS-1分子筛在这类反应中备受关注,其可与双氧水配合表现出优良的催化性能。本文分析了钛源、硅源、模板剂、晶化条件对TS-1分子筛纯度、结晶度及催化性能的影响,并对TS-1分子筛的发展方向提出了建议。     

Hydrothermal syntheses of ETS-10 like vanadosilicates using chiral organic molecules. Part I

Vanadosilicates with the structures of ETS-10 and AM-6 microporous materials have been hydrothermally synthesized using organic directing structures agent (SDAs) derivatives of decahydroquinoline, 3,5-dimethyl-piperidine, 2,6-dimethyl-piperidine and (S)-Sparteine. Derivatives of these chiral amines have not been explored before in the sol gel chemistry of vanadosilicates. Physicochemical characterization of the obtained vanadosilicate materials with these different chiral templates was carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and infrared (IR) spectroscopy, solid-state NMR spectroscopy, and differential thermogravimetric analysis (DTA)/thermogravimetric analysis (TGA). The results suggest that the presence of the chiral organic templates have different effects in terms of the final phase of the synthesized materials and their morphology. The products obtained using chiral template derivatives of decahydroquinoline reveal that certain products might be very enriched with chiral polymorph A while others present structures which are similar to other large-porous vanadosilicate such as AM-6 and AM-13. Derivatives of 2,6-dimethyl-piperidine and 3,5-dimethyl-piperidine have not favored any structure that resembles a chiral polymorph A, but only known vanadosilicates such as AM-6, AM-13. Derivatives of (S)-Sparteine, on the other hand, have not only favored the formation of structures enriched with a large amount of chiral polymorph A, but also their use has resulted in other unknown vanadosilicate structures whose physicochemical characterizations are in progress.     

Microwave assisted synthesis of ETS-10

Engelhard Titanium Silicate-10 (ETS-10) has attracted interest for gas adsorption, catalysis, separations and ion-exchange. The practical application of ETS-10 would benefit from improvements in the synthesis. In this paper we present a 30 h microwave assisted synthesis at 230 °C which can be compared with the 72 h required by conventional heating. The effects of different titanium precursors, pH, heating time, and organic templates on ETS-10 were also investigated.     

Rapid synthesis of high-quality ETS-10 crystals

Heating a gel consisting of briefly hydrolyzed tetraethyl orthosilicate (TEOS), 2–5-nm sized anatase, H₂SO₄, NaOH, KF, and H₂O in the mole ratio of 5.5:1:2.2:8.4:1.43:350 at 200 °C for 7 h leads to production of ETS-10 crystals in fairly uniform size (500 nm) and shape having well-developed smooth facets in the truncated tetragonal bipyramidal structure. Characterization of the crystals revealed that the titanate quantum wires are well-preserved within the produced crystals. The required reaction period under our reaction condition (7 h) is much shorter than under the previously reported conditions which use Degussa P25 (a mixture of 25 nm sized anatase and rutile) as the Ti source (>42 h at 200 °C). The marked increase in crystallization rate and uniformity of size and shape is attributed to the use of very small anatase nanoparticles and briefly hydrolyzed tetraethyl orthosilicate (TEOS) as the Ti and Si sources, respectively. This report also demonstrates for the first time that TEOS can be used as the Si source.     

Hydrothermal conversion of carbohydrate biomass to lactic acid

We investigated the hydrothermal conversion of the carbohydrates including glucose, cellulose, and starch to lactic acid using NaOH and Ca(OH)₂ as alkaline catalysts. Both catalysts significantly promoted the lactic acid formation. The highest yield of lactic acid from glucose was 27% with 2.5 M NaOH and 20% with 0.32 M Ca(OH)₂ at 300°C for 60 s. The lactic acid yields from cellulose and starch were comparable with the yield from glucose with 0.32 M Ca(OH)₂ at 300°C, but the reaction time in the case of cellulose was 90 s. The mechanism of lactic acid formation from glucose was discussed by identifying the intermediate products. Lactic acid may be formed via the formation of aldoses of two to four carbons including aldose of three carbons, which are all formed by reverse aldol condensation and double bond rule of hexose. This implies that carbon–carbon cleavage occurs at not only C₃? C₄ but also at C₂? C₃. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Effect of crystallization temperature on the synthesis of ETS-4 and ETS-10 titanosilicates

The effect of temperature on the crystallization and purity of (Na,K)-ETS-4 and (Na,K)-ETS-10 from gels with an optimized composition was examined. Microporous titano silicates (Na,K)-ETS-4 and (Na,K)-ETS-10 were obtained by hydrothermal synthesis from gels of molar composition 5x.Na₂O: 3KF: TiO₂: 6.4x.HCl: 7.45SiO₂: 197.5 H₂O where x = 2.0 for ETS-4 and x = 1.0 for ETS-10 in absence of seeds and organic template agents. The kinetics of crystallization at 160, 180 and 200 °C, respectively, by comparing gel crystallinity (%) at different times, the induction times and the apparent activation energies for nucleation and crystallization were studied. The induction time (linked to the formation of the first nuclei) suggests that the nucleation is more difficult in the case of ETS-10 and the crystal growth rates are similar at higher temperatures (>180 °C). The apparent activation energies are smaller for the (Na,K)-ETS-4 (a stable structure) crystallization than of (Na,K)-ETS-10 (a metastable structure). The characterization of these microporous materials was carried out by XRD, SEM and TGA-DSC techniques.     

ETS-10 Supported Au Nanoparticles for Solvent-Free Oxidation of 1-Phenylethanol with Oxygen

Abstract  

Au nanoparticles (NPs) were uniformly dispersed on ETS-10 titanosilicate using the cation exchange procedure and [Au(NH₃)₄](NO₃)₃ complex as the gold source. [Au(NH₃)₄]³⁺ cations were first introduced inside ETS-10 micropores, ligands were then released, Au³⁺ was reduced to Au⁺ forming electron-deficient Au clusters, and finally aggregation to Au NPs occurred. In comparison to the incipient-wetness and deposition–precipitation methods, the ion-exchange led to greater activity of the Au NPs in the oxidation of 1-phenylethanol by oxygen.     

ETS-10 Modulation to Alumina Support and its Promotion for Hydrodesulfurization

A composite support with ETS-10 stabilized in alumina, was firstly developed for hydrodesulfurization (HDS). It can impede inactive nickel spinel formation and favor more polymeric tungsten species formation, which facilitates the promotion effect of nickel on tungsten and leads to increasing activity in HDS of 4,6-DMDBT.     

Synthesis and characterisation of titanosilicate ETS-10 membranes

Titanosilicate ETS-10 membranes have been prepared on porous α-alumina and stainless steel tubular supports by seeded hydrothermal synthesis. The influence of synthesis conditions has been studied, and pure ETS-10 membranes ≈5 μm thick were synthesised, exhibiting a good intergrowth of crystals. The membranes have been characterised by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray mapping. Pervaporation experiments have been performed, yielding at 150 °C a water/ethanol separation factor up to 12 and a water flux of 1.1 kg/(m² h).     

Adsorption of ethane and ethylene on modified ETS-10

Ethylene and ethane adsorption isotherms were measured for Engelhard Titanosilicate (ETS-10) both as made in the sodium form and ion exchanged with different mono-, di-, and trivalent cations. Isotherms for Na-, K-, and Ag-ETS-10 were found to be nearly rectangular indicating very strong adsorption. In contrast, isotherms for Li-, Ba-, and Cu-ETS-10 show substantial curvature. Isotherms for some mixed cation forms (such as Ba/H and La/H) demonstrate the weakest adsorption with substantial adsorption swing capacity between 1 and 200 kPa. Using the ideal adsorption solution theory (IAST), it was determined that ethylene/ethane adsorption selectivity decreases in the order Na>K>Li>Cu≈Ba>Ba/H>La/H, while the adsorption swing capacity (from 1 to 200 kPa) shows an exactly reversed trend. It is thus probable to find the right balance between selectivity and swing capacity in order to design appropriate pressure swing adsorption (PSA) processes for the separation of ethylene and ethane under a wide range of conditions.     

Hydrothermal synthesis, structural, and spectroscopic studies of vanadium substituted ETS-4

Titano-vanadium silicate with the structure of ETS-4 has been hydrothermally synthesized to produce V-ETS-4. Direct comparison between ETS-4 and V-ETS-4 showed successful isomorphous substitution of titanium by vanadium. The existence of vanadium is confirmed by energy dispersive X-ray spectrometry (EDS). ⁵¹V and ²⁹Si magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy revealed that the vanadium is present as V⁴⁺ and prefers the octahedral site in the ETS-4 structure. Diffuse reflectance ultraviolet–visible (DR UV–Vis) and Raman spectroscopy analyses showed the existence of five- and six-coordinated V⁴⁺, which partly substitute TiO₅ square-pyramids and interrupts the chains of TiO₆ octahedra in the ETS-4 structure. This isomorphous substitution also impacts the thermal stability of V-ETS-4 and it was observed by differential scanning calorimetry (DSC).     

The strong basicity of the microporous titanosilicate ETS-10

Base-catalysed reactions in general are of great importance. In zeolite chemistry, alkali-metal-exchanged zeolites, such as zeolite X, display very strong basicity coupled with high catalytic activity. However, in order to achieve this strong basicity, considerable post-synthesis modification is necessary. In this report, it is shown that strong basicity is exhibited by the microporous titanosilicate ETS-10 in the as-prepared form which is superior to the presently known suite of zeolite catalysts. This opens up a new class of material for heterogeneous base catalysis. This revised version was published online in August 2006 with corrections to the Cover Date.     

钛硅分子筛ETS-10的合成和表征

以硅酸钠溶胶、硫酸钛为起始原料,在含KF碱性水热体系中制备出ETS-10钛硅酸盐分子筛;考察了原料的配比、晶化时间与温度对ETS-10合成的影响。应用XRD、SEM、EDX、FTIR和N2吸附技术表征了合成的ETS-10的结构和物性。结果表明,用组成为n(SiO2)∶n(TiO2)∶n(Na2O)∶n(KF)∶n(H2O)=7.5∶1.0∶5.0∶3.0∶198的凝胶,在463K(48h)和无模板剂的条件下,合成出结晶度良好的ETS-10。ETS-10晶体具有规则的四方切角锥形晶貌和微孔性质,比表面积和孔容分别为383.75cm2/g和0.16cm3/g;典型样品的化学组成接近已知的ETS-10组成表达式(Na,K)2TiSi5O13.4H2O。     

高结晶度ETS-10分子筛的合成与表征

采用水热合成法成功合成出高结晶度ETS-10分子筛。通过XRD、N2吸附-脱附、FTIR、SEM和NMR等方法对样品进行了表征,并考察了不同合成条件对ETS-10分子筛结晶度的影响。结果表明,碱度、硅钛比、晶化时间对分子筛结晶度影响显著。在分子筛制备过程中,钛溶解分散于凝胶体系,并在晶化过程中完全进入分子筛形成Si-O-Ti骨架结构,是合成高结晶度ETS-10分子筛的关键。制备的ETS-10分子筛晶粒形状规整,比表面积高,无杂晶相,具有高的结晶度。     

Kinetic and thermodynamic effects during the adsorption of heavy metals on ETS-4 and ETS-10 microporous materials

ETS-10 and ETS-4 microporous materials were synthesized in presence of tetralkylammonium (TAA) ions from gels of molar composition w Na₂O–0.10 TAABr–1 SiO₂–z TiO₂–0.6 KF–1.28 w HCl–39.5 H₂O with TAA = tetramethyl-, tetraethyl-, tetrapropyl- and tetrabutyl-ammonium in hydrothermal conditions at 190 °C. The TAA ions enter the microporous channel of ETS-10, while they cannot penetrate the void spaces of ETS-4. The ETS-10 microcrystals are all cubic, while the ETS-4 crystals are laminar and irregular. The microporous volume of ETS-10 is equal to 0.11–0.13 cm³ g^?1, the microporous volume of ETS-4 is very small, 0.002–0.008 cm³ g^?1. The ion exchange of Cs⁺, Cd⁺⁺, Pb⁺⁺ and Hg⁺⁺ ions using their corresponding nitrates show kinetic effects, i.e. the efficiency of ion exchange is higher at 1 than 2 h, the thermodynamic equilibrium. For ETS-10, partially dehydrated cations intervene in the ion exchange, while for ETS-4 well dehydrated ions can only penetrate the available pores.     

Bactericidal activity of silver nanoparticles supported on microporous titanosilicate ETS-10

The bactericidal activity of Ag nanoparticles supported on microporous titanosilicate ETS-10 was investigated. The nanoparticles were prepared by ion exchange followed by in situ reduction with NaBH₄ and characterized using XRD, XPS, HRTEM, and UV techniques. The Ag nanoparticles immobilized on ETS-10 were found to be stable against leaching with a concentration in an aqueous phase of less than the World Health Organization (WHO) specified secondary minimum concentration level. In comparison with the as-synthesized ETS-10 and Ag-exchanged ETS-10 materials, the ETS-10 materials containing an optimum amount of Ag nanoparticles were observed to exhibit a significantly enhanced bactericidal activity and a longer lifetime towards microorganisms, such as Escherichia coli.     

Fischer-Tropsch synthesis on ruthenium supported ETS-10 titanium silicate catalysts

Titanium silicate ETS-10 was found to be a suitable metal catalyst support, having high surface area, high ion exchange capacity and no acidic functions. In this work, ETS-10 was used as a support in preparing ruthenium supported catalyst for Fischer-Tropsch synthesis. Ru/METS-10 catalytic systems (M standing for Na or K) showed some important characteristics, as good metal dispersion and shape selectivity. Moreover, no side reactions due to acidic functions were evidenced; indeed readsorption of olefins on active metal centers was found to control the activity of the catalysts.In part presented at 10th IZC, Garmisch-Partenkirchen, July 1994.     

Hydrothermal conversion of rice husk ash to faujasite-types and NaA-type of zeolites

The faujasite-type of zeolites (NaX and NaY) and NaA-type of zeolite were synthesized from rice husk ash (RHA) via the hydrothermal conditions. The combustion of rice husk at controlled temperature of 600 °C for an hour in open air produce more than 90% of amorphous silica in the ash which was reactive towards the synthesis of zeolites. The formation of zeolite NaY from RHA is metastable and thus, the seeding and ageing effects in the synthesis of zeolite NaY were investigated to avoid the formation of zeolite A or P as the impurities in zeolite NaY. Zeolites NaX and NaA were also successfully synthesized with high purity, absence of impurities and other phases, and high reproducibility. Thus, the amorphous forms of silica in RHA can be used as a source of silica for the synthesis of faujasite-types and NaA-type of zeolites.