Tetrapropylammonium Hydroxide Research Articles

Hierarchical ZSM-5 synthesized from Bangka kaolin and Bayat natural zeolite for methane conversion catalysts

Hierarchical ZSM-5 has been successfully synthesized from Bayat natural zeolite as alumina and silica source and Bangka kaolinite as an additional silica source using tetrapropylammonium hydroxide (TPAOH) and poly(acrylamide-co-dialyldimethylammonium chloride) (PDDA-M) as a structure and pore directing agent. XRD pattern shows an evidence of MFI (Mordenite Inverted Framework) structure with peaks at 2θ = 8.01°, 8.90° and 23.15°. SEM images show that the surface of as-synthesized zeolite has coffin-like structure, while EDX analysis shows it has a Si/Al molar ratio of 8.77. The N2 isotherm adsorption exhibited a type IV H4 curve, which indicated the material has mesoporosity, although the Barrett-Joyner-Halenda analysis showed the ZSM-5 has a pore size distribution around 1.937 nm, indicated the micropore dominating its pore size. This confirms that the as-synthesized natural ZSM-5 has hierarchical properties. This as-synthesized natural ZSM-5 then was impregnated with Fe2O3 to improve its catalytic activity towards methane conversion reaction. XRD analysis shows an existence of Fe2O3 at 2θ = 41.22°. Both Fe-impregnated synthetic and natural ZSM-5 show a higher percentage of methane conversion (84.825 % and 86.958 %, respectively), but they give a lower percentage yield of formaldehyde (39.973 % and 32.2 %, respectively) than the parent synthetic and natural ZSM-5.

Hydrocracking of hexadecane to jet fuel components over hierarchical Ru-modified faujasite zeolite

Hexadecane hydrocracking was investigated over bifunctional Ru-containing micro- and mesoporous USY zeolites at 250°C under 45 bar in the presence of hydrogen in a batch reactor. A comparative study was performed using the Ru-free zeolites in the protonic form. The highest yield of jet-fuel products, C9 - C15, being 26% at 71% conversion, was obtained with 2.5 wt% Ru deposited on a hierarchical micro-mesoporous USY zeolite, e.g. a material possessing secondary porosity, where a superior combination of acidity and mesoporosity was created by treatment of the parent zeolite with aqueous sodium hydroxide and tetrapropylammonium hydroxide.

Ionic Liquid Modification of Hierarchical ZSM-5 for Solvent-Free Insertion of CO2 to Epoxides

Hierarchical H-form ZSM-5 (h-ZSM-5) was synthesized and successfully functionalized with imidazolium-based ionic liquids for solvent-free insertion of carbon dioxide to epoxides and synthesis of cyclic carbonate. Tetrapropyl ammonium hydroxide and polyurethane foam were used as soft and hard templates, respectively, to introduce mesoporosity in the structure. The synthesized hierarchical H-form ZSM-5 provided a large surface area for covalent attachment of imidazolium-based ionic liquids to produce h-ZSM-5-IL. The successful synthesis of the new catalyst was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy, the Brunauer–Emmett–Teller method, and scanning electron microscopy and utilized for the insertion of carbon dioxide to epoxides and production of cyclic carbonate under solvent-free conditions. High conversion and selectivity for the synthesis of cyclic carbonate and recovery of the catalyst for five consecutive times without loss of catalytic activity are the advantages of this newly synthesized catalyst.

Development of mesoporous ZSM-5 zeolite with microporosity preservation through induced desilication

Alkali treatment is a widely used strategy to create mesopores for microporous zeolites to decrease the diffusion limitation in micropores. However, many of the micropore losses existed due to the uncontrollable destruction of framework. In this paper, a series of mesoporous ZSM-5 with well-maintained micropores was synthesized through induced desilication strategy. To induce the diffusion of alkali solution for the homogenizing desilication and mesopore formation, abundant and uniform small mesopores were firstly built for ZSM-5 by protective desilication in tetrapropylammonium hydroxide solution. The pore structure and acidity of the obtained ZSM-5 were characterized by XRD, TEM, N2 physisorption, NH3-TPD and Py-IR. Through induced desilication, the external surface area of obtained ZSM-5 increased from 42 m2 g−1 of parent ZSM-5 to 148 m2 g−1 and only 17% of micropore surface area was sacrificed, which was far lower than 37% of the loss in traditional NaOH treatment. Meanwhile, the strong acid sites were well preserved and the external acid sites were reduced. Compared with the sample treated by NaOH solution, the obtained catalyst exhibited higher catalytic stability and aromatics, especially PX selectivity. Good regenerated performance with long catalytic lifetime and high liquid hydrocarbon yield could also be found for the obtained catalyst. The strategy proposed in this paper is simple and ingenious in tailoring the porosity since it only relies on the desilication method, which is different from the usual coupling of dealumination and desilication.

Hydrothermal synthesis of tungsten-tin bimetallic MFI type zeolites and their catalytic properties for cyclohexene epoxidation

Abstract A series of tungsten-tin bimetallic MFI type zeolites (WSn-MFI) with different Sn and W contents were hydrothermally synthesized using tetrapropyl ammonium hydroxide (TPAOH) as a template and polypyrrolidone as a co-surfactant. Tetraethylorthosilicate (TEOS), ammonium tungstate hydrate and tin (IV) chloride pentahydrate were used as the Si, W and Sn sources, respectively. The resultant samples were characterized by various techniques, and were evaluated as catalysts for the epoxidation of cyclohexene with hydrogen peroxide. The results reveal that all the W–Sn bimetallic zeolites have the typical MFI structure, and their relative crystallinities and morphologies change somewhat with the variety of W and Sn contents. Both the isolated framework SnO4 species and the extra-framework SnO2 species could be detected in all WSn-MFI samples, while only trace amount of extra-framework W species are present inside the channels/cages of the bimetallic zeolites. Compared with the monometallic zeolites of W-MFI and Sn-MFI, the bimetallic WSn-MFI zeolites exhibit much higher catalytic activity for the epoxidation of cyclohexene. Of these, the sample named WSn-MFI-a could efficiently convert cyclohexene to the corresponding epoxide with a high yield of 79% under an optimized reaction condition. A synergistic effect between the W and Sn species should play critical role in improving the catalytic activity and the epoxide selectivity of the bimetallic zeolite catalysts.

Synthesis Strategy of Hierarchical Alumiosilicates from Low Grade Indonesian Kaolin with Adjusted Activity in Acetalization Reaction

Synthesis strategy of hierarchical aluminosilicates was carried out by varying the starting material, type of a basic solution, and the hydrothermal condition. Aluminosilicate was synthesized using pre-treated low-quality kaolin by three kinds of basic solution, such as sodium hydroxide, sodium fluoride, and tetrapropyl ammonium hydroxide. The hydrothermal condition was carried out by gradual temperature and constant temperature. The desired mole ratio of Si/Al achieved by dealumination or by addition of silica. Products were characterized by X-ray diffraction, FTIR spectrometry, and nitrogen physisorption. Cation exchange was carried out on the product to obtain an acid catalyst. The acidity test of the catalyst was carried out by FTIR-pyridine spectrometry. The catalyst activity test was carried out to the acetalization reaction of 3,4-dimethoxybenzaldehyde with propylene glycol. The results showed that the catalyst synthesized with the basic solution of tetrapropyl ammonium hydroxide had the highest acid site number and the highest conversion of 3,4-dimethoxybenzaldehyde to acetal.

Postsynthesis of hierarchical TS-1 and its unique catalytic performance in the direct hydroxylation of toluene

Hierarchical TS-1 (PTS-1) with intracrystalline mesopores have been synthesized through post-treatment with tetrapropyl ammonium hydroxide (TPAOH). The changes in physical and chemical properties of PTS-1 were studied in detail. The results showed that abundant mesopores were introduced via TPAOH treatment. Moreover, more silanol groups were generated, which enhanced the hydrophilicity of PTS-1. The hierarchical TS-1 with abundant mesopores showed higher catalytic activity than microporous TS-1 in the direct hydroxylation of toluene. In addition to powerfully enhanced the mesoporosity, the hydrophilicity of PTS-1 was also enhanced. The enhancement of hydrophilicity led to the adsorption capacity of toluene reduced, thus reducing the catalytic activity of PTS-1. The highest conversion of toluene and the yield of cresol could be reached 69.5 % and 67.2 %, respectively over the optimal catalyst and the regenerated catalyst exhibited excellent reusability. These findings provide a facile method to construct high active TS-1 catalysts for the direct hydroxylation of toluene.

Hydrothermal synthesis of H-ZSM-5 catalysts employing the mixed template method and their application in the conversion of methanol to light olefins

A hydrothermal procedure was utilized to synthesize high silica H-ZSM-5 catalysts for application in methanol to olefin (MTO) reaction by partial and total substitution of tetrapropyl ammonium hydroxide (TPAOH) with equivalent amount of the less expensive tetrapropyl ammonium bromide (TPABr) template. Five H-ZSM-5 zeolites with a similar Si/Al ratio (200) were synthesized using various proportions of TPAOH and TPABr. The TPA+ concentration (0.04 M) and initial gel pH (10.5) were constant. The catalysts were characterized by TG–DTA, XRD, ICP, FE-SEM, BET, FT-IR and NH3-TPD techniques. The samples showed cubic morphology, but their particle sizes and shapes were different. The highest crystallinity were obtained by single template synthesis for MFI structure whereas using mixed template synthesis led to lower crystallinity and larger crystallite sizes. Increasing molar ratio of TPAOH in initial gel from 0.33 to 3 decreased the purity of H-ZSM-5, and also affected its crystallinity and particle size. The NH3-TPD results indicated that both TPAOH and TPABr templates exhibited almost the same effect on the acidity of the as-synthesized catalysts, whereas mixing the two templates increased the total acidity and decreased the content of strong acid site. The catalytic performance of all samples was evaluated in MTO reaction in a fixed-bed reactor at 480 °C and atmospheric pressure using feed containing a mixture of 50 wt% methanol in water with methanol WHSV of 0.9 h−1. All the catalysts exhibited approximately similar methanol conversion though their propylene selectivities and products distributions were greatly dependent on the template composition. This work verified that despite providing the same TPA+ and OH− concentrations in the initial gel, the H-ZSM5 samples with different properties could form using diverse template combinations.

A strategy for fast and facile embedding platinum nanoparticles in silicalite‑1 crystallites with a stable and catalytic active structure

A strategy for embedding ultrasmall Pt nanoparticles in silicalite-1 (S-1) was proposed. It consists of treating the zeolite with tetrapropylammonium hydroxide (TPAOH) solution, loading Pt, and recrystallizing the resultant composite in a silicon-containing Na+-free TPAOH solution at 170 °C for 6 h. Complementary characterizations confirm that, the first step is facile and effective for creating plenty of mesopores in the zeolite, and the last step is fast and favorable for embedding ultrasmall Pt nanoparticles in S-1 yielding the Pt@S-1 hybrid. This material displayed excellent resistance to sintering and much higher activity for ethylene hydrogenation and CO oxidation than conventional Pt-loading catalyst.

Silicalite-1 synthesized with geothermal and Ludox colloidal silica and corresponding TiO2/silicalite-1 hybrid photocatalysts for VOC oxidation

Abstract Silicalite-1 samples of uniform sub-micron size with two distinct morphologies were prepared using colloidal silica extracted from geothermal fluids. The colloidal silica used was provided by a New Zealand Company, GEO40 Ltd, and was produced by them using their patented process for recovering colloidal silica from geothermal brine. Spherical crystals with an average size of ca. 250 nm (S1N) as well as typical MFI-type coffin-shaped crystals with a size of ca. 900 nm (S1M) were prepared from clear synthesis solutions made from colloidal silica and aqueous tetrapropylammonium hydroxide of different concentration. The silicalite-1 samples prepared showed very similar characteristics to samples prepared using a conventional silica sol, Ludox SM, as a silica source. Silicalite-1 samples prepared with geothermal and conventional silica sols were used as supports for TiO2 nanoparticles. The hybrid TiO2/silicalite-1 materials were tested as photocatalysts for the photocatalytic degradation of trichloroethylene for air pollution control. The hybrid samples reduced the formation rates of non-desirable reaction products, promoting the mineralization process in comparison with a reference TiO2 xerogel and high Si/Al ratio ZSM-5-based hybrid materials.

A green route for the synthesis of nano-sized hierarchical ZSM-5 zeolite with excellent DTO catalytic performance

Nano-sized hierarchical ZSM-5 zeolite with high crystallization was prepared by a novel green strategy, that is, the consecutive freezing and vacuum drying route. In comparison with the traditional synthesis process, only 1/5 amount of TPAOH (tetrapropylammonium hydroxide) template was involved. Moreover, hierarchical structured zeolites can be formed even in the absence of mesoporous template (e. g. cetyltrimethylammonium bromide, CTAB). Moreover, the hierarchical ZSM-5 with a wide range of SiO2/Al2O3 ratio (25–200) can be modulated. The effects of the consecutive freezing and vacuum drying methods on the formation process, pore characteristics, crystallinity, morphology and acidity of the ZSM-5 zeolites were explored. It is noted that the abundant intra-crystal mesopores and nanoparticles structure were generated from the porous structure on the surface of the freeze-dried powder. The constructed nano-sized and hierarchical ZSM-5 catalyst exhibits a prolonged lifetime of 110 h in dimethyl ether-to-olefin (DTO) reaction, which is around 3.7-fold lifetime compared to the conventional microporous ZSM-5.

Bangka Kaolin and Bayat Zeolite-based ZSM-5 zeolite as heterogeneous catalyst for hexadecane cracking reaction

Microporous ZSM-5 material was synthesized using natural aluminosilicate minerals, i.e. Bayat zeolite and Bangka kaolin as silica and alumina sources. Prior to use, Bayat zeolite was treated with several treatments, i.e. purification, fragmentation and dealumination. While Bangka Kaolin was used as the source of additional silica, in which the silica was extracted using aqua regia. After that, ZSM-5 zeolite was synthesized using tetrapropylammonium hydroxide (TPAOH) as template. Then, it was characterized using Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy-Energy Dispersive X-Ray (SEM-EDX). Based on XRD pattern, mordenite inverted framework (MFI) structure was obtained. SEM-EDX images showed that the natural aluminosilicate-based ZSM-5, so called ZSM-5 MA, has a coffin-like shape with average crystal size and Si/Al ratio are 1.6 μm and 14.26, respectively. As reference, another as-synthesized ZSM-5 was prepared from pro-analysis reagents, and labelled as ZSM-5MS. It also has mordenite inverted framework (MFI) structure, Si/Al ratio of 21.45 and average crystal size of 0.8 μm. ZSM-5 was tested with micro activity test (MAT) method for hexadecane cracking reaction at 500 °C. Prior to be used, the ZSM-5 was subjected to NH4− exchanged followed by calcination at 550 °C to obtain H/ZSM-5. The products that obtained from hexadecane cracking reaction are gas (H2, C1–C4) and gasoline (C5–C12) fractions. The catalytic test shows that both H/ZSM-5MA and H/ZSM-5MS gave similar results, despite their differences in Si/Al ratio and particle sizes. Therefore, zeolite synthesis using natural minerals as Si and Al sources is promising to be explored further.

Selective Monoacylation of Mesitylene Using Hierarchical Nanocrystalline ZSM-5 Catalyst.

Monoacylated mesitylene is an important precursor used in fine chemical industries In the present work, acylation of mesitylene was carried out using hierarchical ZSM-5 catalyst to prepare 2',4',6'-trimethyl acetophenone (monoacylated Mesitylene). The catalyst hierarchical ZSM-5 possessing three generations of micro-, meso-, and macroporosities was fabricated through a dual-template approach using tetrapropylammonium hydroxide (TPAOH) and poly(methyl methacrylate) (PMMA) latex particles as micropore and macropore templates, respectively. The catalyst is well characterized by XRD, FTIR and SEM. The liquid phase reactions were carried out in the temperature range of 30-50 #x00B0;C. The effect of various parameters such as mole ratio of reactants, catalyst loading, and temperature on the rates of reaction has been investigated. The result shows that the present process gives 100% selective towards the desired product, that is, 2',4',6'-trimethyl acetophenone, because hierarchical ZSM-5 allows faster diffusion of the products out of the catalyst provide an important increase in the activity and selectivity.

Synthesis of metal oxide-hierarchical ZSM-5 (CO3O4/ZSM-5 and Fe2O3/ZSM-5) as catalysts for partial oxidation of biomethane to methanol

This study presents a partial oxidation of biomethane from anaerobic organic waste of cow dung (83.7 % of methane and 16.3 % of oxygen) to methanol using modified cobalt and iron metal oxide-hierarchical ZSM-5 catalysts. Hierarchical ZSM-5 was synthesized using double template methods with tetrapropylammonium hydroxide (TPAOH) and dimethyl diallyl ammonium chloride acrylamide copolymer (PDDAM) as the first and secondary templates, respectively. The as-synthesized ZSM-5 materials were characterized with Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), and the results show the similarities of physicochemical properties with standard ZSM-5 materials. The hierarchical ZSM-5 was then modified with cobalt or iron oxides through impregnation with incipient wetness. The results of XPS analysis show that the impregnated cobalt and iron metal oxide are Co3O4 and Fe2O3, respectively. While the AAS analysis indicates that the metal content in Co3O4/ZSM-5 and Fe2O3/ZSM-5 are 2.1 % (Co) and 2.4 % (Fe), respectively. The partial oxidation of bio-methane to methanol was carried out in an atmospheric fixed batch reactor, c.a. 200 mL, with biomethane to N2 ratio of 0,2:2 (in bar). The results of application using biomethane show the hierarchical Fe2O3/ZSM-5 catalyst has higher methanol yield (17.61 %), compared to the yield by using hierarchical Co3O4/ZSM-5 (10.99 %). In addition, no side product is detected after reaction. Thus, it can be concluded that Fe2O3 is more active than Co3O4 as catalyst and biomethane can be utilized as source in this partial oxidation reaction.

Floating Adsorbent for Organic Removal Fabricated Through Crystallization of Silicalite-1 on Hollow Glass Microspheres

MFI-type zeolite is a crystalline microporous aluminosilicate with an intersecting two-dimensional pore structure and well-defined windows of approximately 0.55 nm. It generally crystallizes in high silica to alumina ratios, leading to a rather hydrophobic character. This makes it an attractive adsorbent for removing organic pollutants from wastewater. However, separating the conventional powdery-zeolites from the media after treatment is difficult because they require considerable time to settle. They also trigger filter clogging. In this work, high silica MFI-type zeolite, namely, silicalite-1, was synthesized on the surfaces of hollow glass microspheres to develop a floating adsorbent with high hydrophobicity. Tetraethylorthosilicate and tetrapropylammonium hydroxide were used as the additional silica source and structure directing agent, respectively. The crystallization of silicalite-1 on hollow glass microspheres was performed using hydrothermal synthesis at 180 °C or 150 °C for 40 h using a precursor sol with a molar composition of 3SiO2:1TPA:14EtOH:286H2O. The surface coverage and crystallinity of the as-prepared samples were optimized, and the floatability and adsorption performance of the optimized sample were investigated. Well-covered microspheres were obtained when hydrothermal synthesis was conducted at 180 °C using 0.5 g of hollow glass microspheres and 15 g of a precursor sol adjusted to pH 12.5. The balance between the dissolution rate of the hollow glass microspheres and the crystallization rate of silicalite-1 appeared to be the key factor in the successful synthesis.

Biodegradable and photostable Nb2C MXene quantum dots as promising nanofluorophores for metal ions sensing and fluorescence imaging

Conventional fluorescent probes are either easily photobleached or non-biodegradable, which often leads to the unstable fluorescence signal output and long-term biological toxicity. Therefore, the development of novel fluorescent materials with both excellent photostability and biodegradability is of great significance for further broadening their application in numerous research fields. In this work, Nb2C quantum dots (Nb2C QDs) with pristine crystallographic structures of Nb2C MXene phases and surface oxygen-containing species are synthesized by an ultrasound assisted physicochemical exfoliation in tetrapropylammonium hydroxide. Detailed analyses indicate that the Nb2C QDs not only possess excellent chemical- and photo-stable fluorescence emission but also achieve successful application in fluorescence sensing of heavy metal ions and fluorescence imaging. More importantly, it is confirmed that the Nb2C QDs present high biocompatibility and unique biodegradation property responsive to human myeloperoxidase, implying the application safety of Nb2C QDs in vivo. Under the background of ever-growing and stringent requirements for biosafety and technical stability, the chemical- and photo-stability, biocompatibility, biodegradability, and most importantly the promising fluorescence sensing/imaging characteristic of the obtained Nb2C QDs may argue well for their future applications in environmental monitoring, biomedical diagnosis, visual display, and anti-counterfeiting.

Dissolution–Recrystallization Formation of Huge Thin 2D Silicalite Lamella for Promoted Sorption

AbstractAn all silica MEL‐type silicalite‐2 nanocrystal is hydrothermally treated in coexistence with cetyltrimethylammonium bromide (CTAB) and tetrapropylammonium hydroxide (TPAOH) at ordinary and elevated temperatures. From monitoring its structural transition process by various physico‐chemical methodologies, it is found that, instead of simple delamination, silicalite‐2 nanocrystal changes with a dissolution and recrystallization mechanism by treatment at an elevated temperature and for a long time, that is, it is first dissolved and then reorganized to huge 2D platelets via an intermediate step forming periodic mesoporous material. The newly formed nanoplatelets (h‐nanoplatelets) from in‐plane growth along a (or b)‐, c‐directions (normal to b (or a)‐axis) are of silicalite (either MEL or MEL/MFI intergrowth)‐type framework topology with a thickness of 3.3 nm (the equivalent of ≈1.6 unit cell) and interspersed with a minor part of small square‐like MFI‐type nanoplatelets (s‐nanoplatelets). The h‐nanoplatelets have expanded lattice parameters and a larger micropore size compared to the parent silicalite‐2 nanocrystal and s‐nanoplatelets, whose micropore structure are modified so as to benefit from both equilibrium adsorption and desorption‐recovering ability of organic contaminants particularly at a low vapor pressure range. This is the first report regarding the dissolution–recrystallization formation of 2D lamella‐type silicalites mediated by popular types of surfactant and base species.

Dissolution of kraft lignin in alkaline solutions

Lignins are among the most abundant renewable resources on the planet. However, their application is limited by the lack of efficient dissolution and extraction methodologies. In this work, a systematic and quantitative analysis of the dissolution efficiency of different alkaline-based aqueous systems (i.e. lithium hydroxide, LiOH; sodium hydroxide, NaOH; potassium hydroxide, KOH; cuprammonium hydroxide, CuAOH; tetrapropylammonium hydroxide, TPAOH and tetrabutylammonium hydroxide, TBAOH) is reported, for the first time, for kraft lignin. Phase maps were determined for all systems and lignin solubility was found to decrease in the following order: LiOH > NaOH > KOH > CuAOH > TPAOH > TBAOH, thus suggesting that the size of the cation plays an important role on its solubility. The π∗ parameter has an opposite trend to the solubility, supporting the idea that cations of smaller size favor lignin solubility. Dissolution was observed to increase exponentially above pH 9–10 being the LiOH system the most efficient. The soluble and insoluble fractions of lignin in 0.1 M NaOH were collected and analyzed by several techniques. Overall, data suggests a greater amount of simple aromatic compounds, preferentially containing sulfur, in the soluble fraction while the insoluble fraction is very similar to the native kraft lignin.

Heterogeneity in the microstructure and dynamics of tetraalkylammonium hydroxide ionic liquids: insight from classical molecular dynamics simulations and Voronoi tessellation analysis.

Microscopic structural and dynamic heterogeneities were investigated for three ionic liquids (ILs), namely tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide (TPAH), and tetrabutylammonium hydroxide (TBAH), by employing classical molecular dynamics (MD) simulations. Structural heterogeneity was explored through radial distribution functions, domain analysis from Voronoi tessellation, spatial distribution functions, combined distribution functions, and structure factors. Radial distribution functions reveal that TEAH has a slightly different structure than TPAH and TBAH. The domain analysis shows that the three ILs have structural heterogeneity. The cations form continuous domains and the anions form discreet domains. The anions are trapped in the voids formed by the cationic domains. When the cation has sufficiently longer alkyl chains, the polar domains become discontinuous. The total structure factor reveals that a pre-peak is absent in TEAH due to a short alkyl chain. The cation head-anion partial structure factor further confirms this phenomenon. Polar and non-polar domains can be better distinguished in the ILs with longer alkyl chains. This distinctive structural behaviour leads to dynamic heterogeneity, which plays an important role in the applications related to ion transportation. To shed light on dynamic heterogeneity, we have calculated the mean square displacements, vibrational density of states, van Hove correlation, and non-Gaussian parameter. The diffusion of ions is lowest in TPAH among all the ILs. The dynamics are highly sluggish in these ILs. The peaks in the low frequency vibrational density of states undergo redshift with an increase in the alkyl chain length. The van Hove correlation functions and non-Gaussian parameter suggest the presence of dynamic heterogeneity in all three ILs. Dynamic heterogeneity is discussed through van Hove correlation functions and the non-Gaussian (NG) parameter was calculated to account for the deviation from Gaussian behaviour. The NG parameter suggests that TEAH has different dynamics than TPAH and TBAH.

The Synthesis of Mesoporous TS-1 and Its Performance for Oxidation of Diphenyl Sulfide and Dibenzyl Sulfide

TS-1 zeolite has outstanding performance in the catalytic reactions with hydrogen peroxide as catalytic promoter. However, the narrow pore size (< 1.0 nm) of traditional TS-1 makes it difficult for bulky organic compounds to contact with the active sites in the pores, which seriously limits application of TS-1. Recently, the introduction of mesoporous structure into microporous TS-1 becomes a hot research topic. Meanwhile, the huge synthesis cost of TS-1 is another main reason hindering its industrial application. In this paper, mesoporous TS-1 was successfully synthesized using sodium silicate as silicon source and titanium trichloride as titanium source under the template conditions of tetrapropylammonium hydroxide (TPAOH) and cationic polymer. The mesoporous TS-1 was characterized by X-ray diffraction (XRD), N2 adsorption, scanning electric microscopy (SEM), transmitting electric microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis Spectrum spectra (UV-Vis). Results show that the synthesized TS-1 zeolites have good crystallinity and tetra-coordinated framework Ti atoms, and there are abundant mesoporous structures in the zeolite crystals. The results of oxidation experiments show that conversion of diphenyl sulfide and dibenzyl sulfide with mesoporous TS-1 are 97.3 % and 85.3 % respectively, while that conversion with microporous TS-1 are 75.7 % and 63.5 respectively.