Titanium Silicate Research Articles

Environmentally Benign Oxidation of Alkylphenols to p-Benzoquinones: A Comparative Study of Various Ti-Containing Catalysts

Catalytic properties of Ti-containing porous solids were compared in the oxidation of 2,3,6-trimethylphenol (TMP) with H2O2 to produce 2,3,5-trimethyl-1,4-benzoquinone (TMBQ, vitamin E key intermediate). Mesoporous titanium–silicates with di(oligo)nuclear Ti centers, metal–organic framework MIL-125 and amorphous TiO2 demonstrated 100 % selectivity toward TMBQ. Titanium–silicates prepared by evaporation-induced self-assembly revealed superior performance in terms of product yield and catalyst reusability.

Photocatalytic Oxidation of Phenolic Pollutants and Hydrophobic Organic Compounds in Industrial Wastewater Using Modified Nonosize Titanium Silicate-1 Thin Film Technology

Nanocrystalline Titanium Silicate-1 (TS-1) with attractive physical and chemical properties is being explored for the degradation of phenol. A fully dispersible nanocrystalline zeolite TS-1 was prepared. The catalyst was characterized by DLS, XRD, TEM and BET analyses. XRD analysis confirmed that the diffraction pattern of the NPs (CP-0) was very similar to that of amorphous silica and the aged concentrated precursor sample CP-48 showed peaks characteristic of MFI. TEM analysis confirmed that the size of the crystal is about 30 nm. The photocatalytic oxidation of phenol was studied over nanocrystalline Titanium silicate-1 thin film flow reactor. The experimental parameters such as aeration, flow rate, solution pH and phenol concentration were optimized. The degradation efficiency of choro-substituted phenols are compared at optimum conditions. In addition, photocatalytic degradation efficiency of simulated phenolic waste water was studied. The results are significant, as the method adopted here can be extended for the treatment and purification of waste water and air using nanocrystalline Titanium silicate-1 thin film flow reactor.

EXAFS studies of the metal coordination environments in mixed Ti/Zr silicates

Microporous materials have a wide range of commercial uses from ion-exchangers to catalysts and have been used in the treatment of nuclear waste. The acidity associated with legacy waste pools often limits the effectiveness of these zeolites due to a loss of crystallinity. Microporous titanium silicates display different structural characteristics compared to conventional zeolites. Sitinakite, KNa2Ti4Si2O13(OH)·4H2O and the synthetic niobium doped analogue are being used as ion-exchange materials for the removal of Cs+and Sr2+from nuclear waste . Natisite is a layered titanium silicate with titanium in an unusual 5 coordinate square pyramidal environment. Natisite, Na2TiSiO5, crystallises in the tetragonal space group P4/nmm. [1, 2] A series of samples have been prepared with varying levels of zirconium doping ranging from 10% to 50%. Powder x-ray diffraction (PXRD) showed no obvious impurities attributed to zirconium containing phase. X-Ray Fluorescence (XRF) was carried out and showed the presence of zirconium indicating that doping had been successful. Ion-exchange experiments were carried out on the doped and undoped natiste samples using Cs and Co containing solutions. It was found that increasing the levels of zirconium increased the affinity towards Cs with the undoped materials taking up very little Cs. The rate of exchange with Co seemed to increase as the zirconium level was increased within the sample. This suggests that the presence of zirconium in the framework has a considerable effect on the ion-exchange properties of natisite. EXAFS has been useful in determining the coordination environment of titanium and zirconium in order to help fully understand the chemistry of this material. Also it has helped with determining if the exchanged Cs and Co have a preference for the sites close to Zr rather than Ti. It is therefore believed that the inclusion of zirconium in the natisite framework has potential use as an ion-exchanger in the nuclear industry.

In-situ high-temperature diffraction studies of ion-exchanged umbite

Microporous materials such as zirconium silicates have the potential to be of importance in the nuclear industry for the selective uptake of cationic radionuclides and environmental pollutants. The structural behaviour of these materials at elevated temperatures is of interest for two reasons, the first is the densification of the exchanged materials prior to long term storage and the second is the formation of new porous phases which may have increased ion exchanged affinity for certain cations. The work presented here focuses on the umbite system. Umbite is a naturally occurring microporous zirconium titanium silicate found in northern Russia and synthetic analogues, K2ZrSi3O9·H2O, can be prepared using hydrothermal methods. It has an orthorhombic cell with a = 10.2977(2)Å, b = 13.3207(3)Å and c = 7.1956(1)Å. The ion-exchange of umbite with cations such as rubidium, caesium and strontium and the structures of the resulting exchanged materials have been studied. Exchanges with certain cations were found to cause a change in crystal system to a monoclinic cell. Recently Rocha and co-workers found that synthetic umbite will undergo a topotactic transformation when heated 9100C to form a new microporous zirconium silicate (AV-15) with the formula K2ZrSi3O9·2H2O, but to date no in-situ work has been carried out on this phase transition. In this work the high temperature structural behaviour of five umbite samples with different exchanged cations (K+, Na+, Mg2+Ca2+and Cu2+) was studied up to a temperature of 10000C. All samples behaved very differently, indicating that the nature and location of the charge balancing cation plays an important part in determining which high temperature phases are formed. Certain general trends were observed, with group 1 cations the samples remain crystalline to high temperatures. With group 2 cations dense phases are formed at high temperatures and with transition metal cations there is a loss of crystallinity at low temperature.

Why was the structure of the niobium silicate AM-11 so difficult to solve?

The synthesis of the polycrystalline niobium silicate catalyst AM-11 was first reported in 1998 [1], but its structure proved to be elusive. In 2007 we received two samples from the Aveiro group. At the time, we were looking for a material suitable for the application of the texture method of structure solution, and AM-11 seemed to be ideal for this purpose. One of the samples had needle and the other platelet morphology, and textured samples could be prepared in both cases. The conventional powder diffraction pattern could be indexed on a hexagonal, an orthorhombic or a monoclinic unit cell, so this was the first issue to be resolved. The texture measurements quickly revealed that the crystal system was orthorhombic, but the structure resisted solution. We then tried applying the precession electron diffraction technique in combination with high-resolution powder diffraction data, but beyond confirming the orthorhombic symmetry, these data did not help us to solve the structure. Another attempt was made with a new sample and an improved texture setup, but to no avail. Rotation electron diffraction data and high-resolution transmission electron microscopy images showed that some disorder was present and helped to define the space group, but the structure remained a mystery. The powder charge-flipping routine in Superflip [2], yielded tantalizingly clear electron density maps, but they could not be interpreted sensibly. The unit cell parameters were seen to be related to those of the titanium silicate zorite [3] (one axis doubled in AM-11), so the problem was taken up once again last year. By starting with a simplified zorite framework structure with Nb in place of Ti, and performing what amounts to manual Fourier recycling, the surprisingly simple structure (1Nb, 3 Si, 9 O), which is significantly different from zorite, finally revealed itself. There is some stacking disorder, but the structure is otherwise innocuous. What made it so difficult to solve?

CO2 selective NaMg-CTS-1 and its structural formation from the titanium silicate based molecule sieve NaMg-ETS-4

A range of titanium silicates (ETS-4 and CTS-1) with interesting gas separation properties were studied as CO2 adsorbents. Some of these adsorbents, in particular NaMg-CTS-1, showed the ability to selectively adsorb CO2-over-N2. Partially exchanged NaM-ETS-4 (M=Mg, Ca, Sr and Ba) were synthesised in the Na+ form and ion exchanged with group 2 cations. All but NaBa-ETS-4 transformed into their CTS-1 counterparts, when these partially exchanged Na-ETS-4 were dehydrated. The transformation from ETS-4 to CTS-1 was monitored and studied extensively using diffraction and spectroscopic techniques. Powder X-ray diffraction allowed us to follow the changes of the unit cell parameters occurred at different temperatures. We combined high energy X-ray total scattering (analysed by pair distribution functions – PDF analysis), electron diffraction, infrared, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy to study the transformation of ETS-4 to CTS-1. We understood that under dehydration steps, there was significant disruption to the Ti–O–Ti chain along the b-axis, which occurred concurrently with the distortion of the double 3-rings alongside of these chains. These changes were partly responsible for the contraction of the ETS-4 framework (and successive transformation to CTS-1). The new information allowed us to understand the interesting structures and sorption properties of these adsorbents.

Selective adsorption of N2 over CH4 in flexible Sr2+- and Ba2+-UPRM-5 (TEA) titanium silicates: Effect of activation temperature

Removal of N2 from CH4 continues to be a challenging endeavor due to the similar properties of both molecules and, particularly, from the process energy consumption point of view. Although adsorption separation processes offer an attractive platform to address the latter, working capacity and selectivity are usually limiting factors. In this work, porous Sr2+- and Ba2+-UPRM-5 titanium silicates adsorbents exhibiting flexible structures were studied to elucidate their applicability for the separation of N2 from CH4 at ambient temperature. These materials showcase surface areas that are an order of magnitude larger than other flexible titanium silicates as a result of the incorporation of tetraethylammonium (TEA) as a structure-directing agent during the hydrothermal synthesis. The adsorbents were fully characterized to consider their response to thermal treatment and its relationship to adsorption selectivity. For Sr2+-UPRM-5 (TEA), the selectivity reversal in favor of N2 at 25 °C occurred upon pre-activation of the adsorbent at 180 °C. However, for Ba2+-UPRM-5 (TEA) this happens at a pre-activation temperature of 320 °C most likely due to its structural thermal stability. Both materials did not exhibit N2 adsorption saturation within a 10 atm range and 25 °C, a reflection of the availability of larger surface areas and a feature suitable for natural gas upgrading at higher pressures. At 25 °C, the maximum observed kinetic selectivity value in favor of N2 and estimated at CH4 and N2 pressures of 0.95 and 0.05 atm was 25, which matches results reported for the commercially available ETS-4 type titanium silicate. However, the UPRM-5 (TEA) adsorbent can be fully activated at a much lower temperature.

Rubidium and Cesium Ion Adsorption by a Potassium Titanium Silicate-Calcium Alginate Composite Adsorbent

In this work, a composite spherical adsorbent, which employs potassium titanium silicate as an adsorption active component, and calcium alginate as a carrier, was successfully prepared. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the adsorbent. The kinetics and thermodynamics of rubidium and cesium ions adsorption were investigated comprehensively, by considering the effects of initial concentration, temperature, solution pH, and coexisting NaCl. According to the determination coefficients, the pseudo second-order kinetic model provided an impressive and comparable correlation, and the second-order rate constant and the initial adsorption rate increase with increasing temperature. In general, the equilibrium adsorption amount increases with the increasing initial metal ion concentration, but decreases with increasing coexisting NaCl. The adsorption capacity keeps constant in the pH value range 3-12 and slightly fades when the temperature increases from 25 to 55°C. Under similar conditions, rubidium and cesium show the similar adsorption amount. The adsorbent has a fast adsorption rate and an adsorption capacity of about 1.55 mmol g−1 for rubidium and 1.47 mmol g−1 for cesium when the initial metal ion concentration is 0.10 mol L−1. The composite adsorbent is effective for the adsorption of rubidium or cesium ions from simulated brines.

Determination of the Apparent Crystal Structure of a Highly Faulted UPRM-5 Type Flexible Porous Titanium Silicate via a Polymorph Based Superposition Model, a Rietveld Refinement and a Pair Distribution Function

The crystal structure of a UPRM-5 titanium silicate prepared using tetraethylammonium (TEA+) has been approximated using a superposition model product of a polymorph stacking and a dual-phase Rietveld refinement method. Na+-UPRM-5 polymorphs were employed to elucidate the level of polymorphism or faulting in the crystal structure. DIFFaX simulations revealed that it was impossible to match the experimental diffraction data based solely on “pure” polymorphs. Instead, an intergrowth of combinations of polymorphs in the a and c directions resulted in the best faulting simulation scenario. The most suitable model combined two (2) orthorhombic polymorphs with faulting of 90 and 10% in the a and c directions, respectively. A refinement using this model did not yield a reliable structure, but an approximation was possible after employing a combination of orthorhombic and faulted triclinic phases. The superposition model, however, was not able to predict the final configuration of the TiO5 plausibly due to the un...

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.

Investigations on the ion exchange process of Cs+ and Sr2+ cations by ETS materials

Ion exchange experiments were carried out for evaluation the removal capability of cesium and strontium ions by the microporous Engelhard Titanium Silicates – 4 and 10 (ETS-4 and ETS-10, respectively) synthesized from alkaline gels. Ionic selectivities were estimated from the ion exchange isotherms, Kielland and Langmuir plots. It is shown that both microporous titanosilicates perform under a similar ion exchange profile against Cs+ cations and the selectivity of ETS-4 for Sr2+ is highly depended on temperature. ETS-10 is unselective for Sr2+ over a wide range of equivalent ionic fraction of strontium in solution. The Langmuir isotherms indicate that in the absence of ionic competition both titanosilicates retain Cs+ and Sr2+ cations, as much as their ion exchange capacities. These positive results promote ETS materials as very good candidates for the removal of both cesium and strontium from nuclear waste solutions.

Performance study of extraction and oxidation–extraction coupling processes in the removal of thiophenic compounds

Thiophenic sulfur removal was attempted in three different modes of operation, such as extraction, oxidation and simultaneous oxidation–extraction for a model fuel. Extraction was done using different solvents, viz., acetonitrile, dimethyl sulfoxide and 1-ethyl 3-methyl imidazolium ethyl sulfate at near ambient condition. The sulfur compounds tested were thiophene, benzothiophene and dibenzothiophene in iso-octane. Titanium silicate-1 and titanium-beta catalysts were used for oxidation of the compounds. A detailed parametric study was performed varying stirring time, extraction temperature and amount of solvent, to investigate their effects on the extraction of the three sulfur compounds. Simultaneous oxidation–extraction process showed a significant amount of sulfur removal. Dimethyl sulfoxide was found to be the best solvent for extraction.

Selective oxidation of benzene to phenol by Fe-CN/TS-1 catalysts under visible light irradiation

Fe-g-C3N4 (denoted as Fe-CN) and titanium silicate zeolite (TS-1) hybrid materials were fabricated by a facial thermal polymerization approach using dicyandiamide, metal chloride as precursors and TS-1 zeolite as a support. The structure and textural properties of the resulting hybrid materials were thoroughly characterized by X-ray diffraction, UV–Vis spectrophotometry, nitrogen adsorption–desorption isotherm, Fourier transform infrared spectroscopy, scanning transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical measurement. The as-synthesized Fe-CN/TS-1 composites could be used as heterogeneous catalysts for the photocatalytic selective oxidation of benzene to phenol using H2O2 as benign oxidant under ambient conditions. It is found that the Fe-CN/TS-1 hybrid materials show superior photocatalytic performance for the phenol production from benzene to sole Fe-CN and TS-1 catalysts. Under the optimal conditions, up to 10.0% phenol yield (based on benzene) is achieved over the hybrid materials, with 18.4% phenol selectivity (based on H2O2).

Oxidation of Catechol using Titanium Silicate (TS-1) Catalyst: Modeling and Optimization

The oxidation of catechol was studied in an eco-friendly process with commercial titanium silicate-1 (TS-1) catalyst and hydrogen peroxide as oxidant in absence of all mass transfer effects. The process was opti-mized by Box-Behnken design in terms of three independent process variables such as reaction tempera-ture, moles of hydrogen peroxide per mole of catechol and catalyst amount whose optimum values of the process variables were found to be 60 °C, 13.2 and 1.24 g respectively for maximum conversion of 75.8 %. The effects of different process parameters such as mole ratio of hydrogen peroxide to catechol, catalyst par-ticle size, catalyst amount, temperature and reaction time were studied. A pseudo first order kinetic model was fitted with the experimental rate data. The apparent activation energy for the reaction was found to be 11.37 kJ/mole. © 2013 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

KOLSKYITE, (Ca□)Na2Ti4(Si2O7)2O4(H2O)7, A GROUP-IV Ti-DISILICATE MINERAL FROM THE KHIBINY ALKALINE MASSIF, KOLA PENINSULA, RUSSIA: DESCRIPTION AND CRYSTAL STRUCTURE

Kolskyite, (Ca□)Na2Ti4(Si2O7)2O4(H2O)7, is a Group-IV TS-block mineral from the Kirovskii mine, Mount Kukisvumchorr, Khibiny alkaline massif, Kola Peninsula, Russia. The mineral occurs as single, platy crystals 2–40 μm thick and up to 500 μm across. It is pinkish yellow, with a white streak and a vitreous luster. The mineral formed in a pegmatite as a result of hydrothermal activity. Associated minerals are natrolite, nechelyustovite, kazanskyite, barytolamprophyllite, hydroxylapatite, belovite-(La), belovite-(Ce), gaidonnayite, nenadkevichite, epididymite, apophyllite-(KF), and sphalerite. Kolskyite has perfect cleavage on {001}, splintery fracture, and a Mohs hardness of 3. Its calculated density is 2.509 g/cm3. Kolskyite is biaxial negative with α 1.669, β 1.701, γ 1.720 (λ 590 nm), 2 V meas. = 73.6(5)°, 2 V calc. = 74.0°, with no discernible dispersion. It is nonpleochroic. Kolskyite is triclinic, space group P 1, a 5.387(1), b 7.091(1), c 15.473(3) A, α 96.580(4), β 93.948(4), γ 89.818(3)°, V 585.8(3) A3. The strongest lines in the X-ray powder-diffraction pattern [ d (A)(I)( hkl )] are: 15.161(100)(001), 2.810(19)(121, 122), 3.069(12) (005), 2.938(10)(121,120,121), 2.680(9)(123, 200,114, 201), 1.771(9) (041,040), 2.618(8)(123,122), 2.062(7)(221,222,223,222), and 1.600(7)(321,320,320). Chemical analysis by electron microprobe gave Nb2O5 6.96, ZrO2 0.12, TiO2 26.38, SiO2 27.08, FeO 0.83, MnO 2.95, MgO 0.76, BaO 3.20, SrO 5.21, CaO 4.41, K2O 0.79, Na2O 6.75, H2O 13.81, F 0.70, O = F –0.29, sum 99.66 wt.%; H2O was determined from structure solution and refinement. The empirical formula was calculated on 25 (O + F) apfu : (Na1.93Mn0.04Ca0.03)∑2(Ca0.67Sr0.45Ba0.19K0.15)∑1.46(Ti2.93Nb0.46Mn0.33Mg0.17Fe2+0.10Zr0.01)∑4Si4.00O24.67H13.60F0.33, Z = 1. Simplified and ideal formulae are as follows: (Ca,□)2Na2Ti4(Si2O7)2O4(H2O)7 and (Ca□)Na2Ti4(Si2O7)2O4(H2O)7. The FTIR spectrum of the mineral contains the following bands: ~3300 cm−1 (very broad) and ~1600 cm−1 (sharp). The crystal structure was solved by direct methods and refined to an R 1 index of 8.8%. The crystal structure of kolskyite is a combination of a TS (titanium-silicate) block and an I (intermediate) block. The TS block consists of HOH sheets (H-heteropolyhedral, O-octahedral). The TS block exhibits linkage and stereochemistry typical for Group IV [Ti (+ Mg + Mn) = 4 apfu ] of Ti-disilicate minerals. In the H sheet in kolskyite, Si2O7 groups link to [6]-coordinated Ti octahedra. In the O sheet, Ti-dominant and Na octahedra each form brookite-like chains. There is one peripheral A P site occupied mainly by Ca (less Sr, Ba, and K) at 68%. The I block consists of H2O groups and A P atoms. The I block is topologically identical to those in the kazanskyite and nechelyustovite structures. The mineral is named after the Kola Peninsula ( Kolskyi Poluostrov in Russian). The chemical formula and structure of kolskyite were predicted by [Sokolova & Camara (2010)][1]; this is the first correct prediction of a TS-block mineral. [1]: #ref-11

FROM STRUCTURE TOPOLOGY TO CHEMICAL COMPOSITION. XVI. NEW DEVELOPMENTS IN THE CRYSTAL CHEMISTRY AND PREDICTION OF NEW STRUCTURE TOPOLOGIES FOR TITANIUM DISILICATE MINERALS WITH THE TS BLOCK

New developments in crystal chemistry have been considered for 34 titanium disilicate minerals that contain the TS (Titanium-Silicate) block, a central trioctahedral (O) sheet, and two adjacent heteropolyhedral (H) sheets of [5–7]-coordinated polyhedra and Si 2 O 7 groups. The general formula of the TS block is A P 2 B P 2 M H 2 M O 4 (Si 2 O 7 ) 2 X 4+n , where M H 2 and M O 4 = cations of the H and O sheets; M H = Ti, Nb, Zr, Mn, Ca + REE, Ca; M O = Ti, Zr, Nb, Fe 2+ , Mg, Mn, Ca, Na; A P and B P = cations at the peripheral ( P ) sites = Na, Ca + REE, Ca, Ba, Sr, K; X = anions, O, OH, F, and H 2 O groups; X 4+n = X O 4 + X P n , n = 0, 1, 1.5, 2, 4. There are three topologically distinct TS blocks based on three types of linkage of H and O sheets. In the crystal structures of TS-block minerals, TS blocks either link directly or alternate with intermediate ( I ) blocks. The I block consists of alkali and alkaline-earth cations, oxyanions (PO 4 ), (SO 4 ) and (CO 3 ), and H 2 O groups. There are four groups of TS-block structures, based on the topology and stereochemistry of the TS block: Groups I, II, III, and IV, where Ti (+ Nb + Zr + Mg + Mn) = 1, 2, 3, and 4 apfu , respectively. In a TS-block structure, four types of self-linkage between adjacent TS blocks occur. The concept of basic and derivative structures has been introduced for TS-block minerals. A basic structure has the following four characteristics: (1) there is only one type of TS block; (2) the two H sheets of the TS block are identical; (3) there is only one type of I block, or it is absent; and (4) there is only one type of self-linkage of TS blocks. Basic structures obey the general structural principles of Sokolova (2006). A derivative structure has one or more of the three following characteristics: (1) there is more than one type of TS block; (2) there is more than one type of I block; (3) there is more than one type of self-linkage of TS blocks. A derivative structure is related to two or more basic structures of the same Group: it can be derived by adding these structures via sharing the central O sheet of the TS blocks of adjacent structural fragments which represent basic structures . There are 30 basic TS-block structures and four derivative TS-block structures. Based on established relations between basic and derivative structures, possible atomic arrangements and chemical formulae have been predicted for 12 derivative structures and two basic structures.

Preparation of magnetic core/shell structured γ-Fe2O3@Ti-tmSiO2 and its application for the adsorption and degradation of dyes

A core/shell structured γ-Fe2O3@Ti-tmSiO2 nanocomposite with enhanced activity for the degradation of dyes that is capable of fast magnetic separation has been successfully prepared by a sol–gel process followed with calcination. The obtained core/shell structure is composed of a superparamagnetic core with a strong response to external fields, and an outer layer of porous titanium silicate with a tunable porous sizes. The convenient control over the pore size and the thickness of porous silica containing titanium species may make it possible to adsorb and catalyze molecules with different sizes. The presence of porous SiO2 helps to enhance the chemical and thermal stability of γ-Fe2O3 core. It is demonstrated that the core γ-Fe2O3 as a Fenton-like catalyst exhibits good performance, while the Ti4+ existing in the porous shell also gives obvious activity in the degradation of dyes. The composite γ-Fe2O3@Ti-tmSiO2 possesses enhanced activity for the treatment of pollutants in water.

High pressure tuning of whispering gallery mode resonances in a neodymium-doped glass microsphere

The effects of pressure on the behavior of optical microspherical resonators, prepared from Nd3+ doped, barium titanium silicate glass, have been studied up to 5 GPa inside a diamond anvil cell using silicone oil as the hydrostatic transmission medium and ruby emission lines as the pressure gauge. The optical resonances, known as whispering gallery modes, were observed within the broad emission band of the Nd3+ ions, and the resonances were identified as a function of pressure. By means of simulations, it was found that the average wavelength position of both transverse electric and magnetic modes depended on the radius and refractive index of the sphere, but not on the refractive index of the pressure transmitting medium under the experimental conditions. This was used to define the average sensitivity of the resonant modes with the pressure. Therefore, a value of 6.5×10−4 GPa−1 has been obtained for this sensitivity, which is higher than the value for ruby, the most conventional pressure sensor.

Synthesis, characterization of hierarchical TS-1 and its catalytic performance for cyclohexanone ammoximation

A hierarchical titanium silicate (TS-1) that possesses large open voids has been prepared by using a dissolution/re-crystallization process. Carbon black was introduced as a hard template during the synthesis process to generate defects both inside and on the surface of crystals, then TPAOH post-treatment was applied, as a result, a novel TS-1 zeolite crystal with large open voids was successfully synthesized. The synthesized hierarchical TS-1 was characterized by XRD, FTIR, SEM, TEM and N2 physisorption. Compared with the traditional TS-1 and hollow TS-1, the activity of hierarchical TS-1 in cyclohexanone ammoximation was improved and attributed to the macropores that linked the voids inside the zeolite directly to the outer surface.

Hydrogen-oxidizing hydrogenases 1 and 2 ofEscherichia coliregulate the onset of hydrogen evolution and ATPase activity, respectively, during glucose fermentation at alkaline pH

Simultaneous measurement of redox potential (Eh ) and determination of H2 evolution kinetics using a pair of titanium silicate and platinum redox electrodes in fermenting cultures of Escherichia coli wild type and different mutants lacking hydrogenases 1 (Hyd-1) or 2 (Hyd-2) revealed that Hyd-1 controls the onset of H2 evolution at slightly alkaline pH (pH 7.5) and under oxidizing Eh . In addition, Hyd-2 influences the N,N'-dicyclohexylcarbodiimide-inhibited ATPase activity in fermenting cells and thus regulates the proton F0 F1 -ATPase at the alkaline pH but under reducing Eh .