TS-1 Zeolite Research Articles

Nitrogen-incorporated TS-1 zeolite: Synthesis, characterization and application in the epoxidation of propylene

A novel nitrogen-incorporated TS-1 zeolite (N-TS-1) was successfully synthesized by direct calcinating the as-synthesized TS-1 powder in NH 3 flow at high temperature. The samples were characterized by XRD, FTIR, UV–Vis, NH 3-TPD, ICP-AES, CHN, XPS and 29Si MAS NMR techniques. The results showed that nitrogen was incorporated into the framework of TS-1, and N-TS-1 preserved the MFI structure well. The fresh N-TS-1 samples showed low H 2O 2 conversion in the epoxidation of propylene with dilute H 2O 2, which was due to the coverage of the active titanium sites by unstable nitrogen species. By refluxing the fresh N-TS-1 samples with methanol, the unstable nitrogen species were washed out and the conversion of H 2O 2 increased markedly. The stable nitrogen species incorporated into the zeolite framework could effectively decrease the acidity of TS-1 zeolite and inhibit the side reactions, thereby improving the propylene oxide (PO) selectivity. After the 20th run, the N-TS-1-850-5 catalyst gave a H 2O 2 conversion of 91.5%, a H 2O 2 selectivity of 92.0%, and a PO selectivity of 90.9%. Finally, a model for nitridation of the as-synthesized TS-1 powder at high temperature was proposed.

Mesoporous zirconosilicate doughnuts with high performance in liquid oxidative dehydrogenation of hydroquinone to quinone

Unusual partially crystalline ordered mesoporous zirconosilicate doughnuts with Si/Zr ratio as low as 1.5 were synthesized from the aqueous polymerisation of a single source molecular precursor Zr[OSi(Ot-BuO)3]4 without the use of any templating agent. A radial homogenous mesoporosity (4nm) was observed inside these very regular sub-micrometric (600nm) doughnuts. These structures were partially crystallized in hydrothermal conditions (100°C) into an analogous zircon (ZrSiO4) framework. The formation mechanism has been investigated. It is evidenced that chlorine anions Cl− concentration and pH value are essential to achieve the process, even if their role is still a matter of investigations. The obtained materials demonstrated even higher catalytic activity, selectivity and stability in the liquid oxidative dehydrogenation of hydroquinone to 1,4-benzoquinone compared to TS-1 zeolite catalysts and amorphous highly ordered mesoporous zirconosilicate materials.

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.

Formation of a Ti-siliceous trimodal material with macroholes, mesopores and zeolitic features via a one-pot templating synthesis

Based on a facile one-pot templating synthesis, using a TS-1 zeolite recipe whereby part of the zeolite structure directing agent is replaced by a mesopore templating agent, a trimodal material is formed. The resulting meso-TSM material combines mesoporosity (Ti-MCM-41) with zeolitic features (TS-1) and a unique sheet-like morphology with uniform macroporous voids (macroholes). Moreover, the macrohole formation, mesoporosity and zeolitic properties of the meso-TSM material can be controlled in a straightforward way by adjusting the length of the hydrothermal treatment. This newly developed material may imply great potential for catalytic redox applications and diffusion limitated processes because of its highly tunable character in all three dimensions (micro-, meso- and macroporous scale).

Hierarchical TS-1 zeolite synthesized from SiO 2 TiO 2 xerogels imprinted with silanized protozeolitic units

A new method is reported for the synthesis of TS-1 zeolite with hierarchical porosity based on the crystallization of SiO 2–TiO 2 xerogels that have been previously imprinted with silanized protozeolitic units. The organic functionalization of the latter disrupts the growth and aggregation of the zeolitic crystals during the hydrothermal crystallization, causing the formation of a hierarchical porosity. The TS-1 materials so obtained exhibit enhanced textural properties, due to the formation of an additional porosity within the supermicro/mesoporous range, and present less diffusion restrictions than TS-1 samples prepared by conventional methods. The development of this additional porosity depends both on the molecular size of the organosilane compound and on the TPAOH/xerogel ratio employed in the synthesis. However, these changes are accompanied by a higher hydrophilic character of TS-1 zeolite, reducing its potential application in oxidation reactions using hydrogen peroxide as oxidant, since water molecules adsorbed on the zeolite surface prevent the access of the substrates to the titanium active sites. In contrast, these hierarchical TS-1 zeolites present remarkable catalytic activity in olefin epoxidation reactions using alkyl hydroperoxides as oxidant. This fact is ascribed to the enhanced accessibility to the Ti active sites originated by the presence of the secondary porosity.

Effects of TS-1 zeolite structures on physical properties and enzymatic degradation of Poly (butylene succinate) (PBS)/TS-1 zeolite hybrid composites

The objective of this study was to investigate how the water uptake features and carrier characteristics of the TS-1 zeolite affected the physical and rheological properties, morphological parameters, and enzymatic hydrolysis of Poly (butylene succinate) (PBS). The introduction of TS-1 zeolite as catalyst was developed for the preparation of PBS/TS-1 zeolite hybrid composites (PTHC) without heavy metal toxic substance in the context on clean technology. The TS-1 zeolite can act as a catalyst as well as a reinforcement filler with the result that PTHC can show marked increases in tensile properties and elongation at breakage in the solid state. The rheological properties of PTHC with high zeolite contents showed low values of complex viscosity, as compared with PTHC with low TS-1 zeolite contents, due to the volatilization of water released from the zeolite pores during esterification. The introduction of the TS-1 zeolite in the PBS matrix was not significantly affected by changes in the size of the long period, lamella thickness, or the amorphous region, indicating that PBS chains do not penetrate into zeolite pores, as confirmed by SAXS profiles. In enzymatic hydrolysis over 90 days, the enzymatic hydrolysis rates of PTHC significantly accelerated with increasing TS-1 zeolite contents, compared with Homo PBS. This result indicated that TS-1 zeolite can act as a carrier for enzyme activation, resulting in enzymatic hydrolysis, occurring from the amorphous area on the surface into the inside of the film.

Density Functional Calculations on the Distribution, Acidity, and Catalysis of TiIV and TiIII Ions in MCM‐22 Zeolite

Isolated Ti species in zeolites show unique catalytic activities for a variety of chemical reactions. In this work, density functional calculations were used to explore three current concerns: 1) the distributions of Ti(IV) and Ti(III) ions in the MCM-22 zeolite; 2) the Lewis acidity of the Ti(IV) and Ti(III) sites; and 3) activation of alkane C-H bonds by photocatalysis with Ti-doped zeolites. Neither the Ti(IV) nor Ti(III) ions are randomly distributed in the MCM-22 zeolite. The orders of relative stability are very close for the eight Ti(IV) and Ti(III) sites, and the T3 site is the most probable in both cases. The wavelengths for Ti(IV)-Ti(III) excitations were calculated to lie in the range λ=246.9-290.2 nm. The Ti3(IV) site shows Lewis acidity toward NH(3) in two different modes, and these two modes can coexist with each other. The calculated Ti(IV) coordination numbers, Ti(IV)-O bond elongations, and charge transfers caused by NH(3) adsorption are in good agreement with previous results. Similarly, two different NH(3) adsorption modes exist for the Ti3(III) site; the site that exhibits radical transfer from the lattice O to N atoms is preferred due to the higher adsorption energy. This indicates that the Ti3(III) site does not show Lewis acidity, in contrast to the Ti3(IV) site. At the Ti3(III) site, the energy barrier for activating the methane C-H bond was calculated to be 33.3 kJ mol(-1) and is greatly reduced by replacing the hydrogen atoms with methyl groups. In addition, the reactivity is improved when switching from MCM-22 to TS-1 zeolite. The studies on the various Ti species reveal that lattice O atoms rather than Ti(III) radicals are crucial to the activation of alkane C-H bonds. This work provides new insights into and aids understanding of the catalysis by isolated Ti species in zeolites.

Core/shell-structured TS-1@mesoporous silica-supported Au nanoparticles for selective epoxidation of propylene with H2 and O2

Hierarchically ordered materials with core/shell structures were synthesized through a layer-by-layer approach. The novel microporous/mesoporous hybrid materials were composed of a TS-1 zeolite particle for the core and mesoporous silica for the shell. The as-synthesized TS-1 crystals were modified with polydiallyldimethylammonium chloride to make their external surface positively charged, which induced an oriented self-assembly of tetraethoxysilane (TEOS) with cetyltrimethyl ammonium bromide on the TS-1 particle surface to form a shell of mesophase silica. The thickness of the mesoporous silica shell was controlled to be in the range 30–55 nm by changing the amount of TEOS added in the synthesis. The mesoporous channels in the shell were perpendicular to the zeolite core, which made the micropores inside the core accessible from the outside through the mesopores. Taking advantage of the confining effect of the mesopores, Au nanoparticles were incorporated into the shell, resulting in bifunctional catalysts which were more selective than conventional Au/TS-1 catalysts in the direct epoxidation of propylene to propylene oxide with H2 and O2.

Synthesis, characterization and catalytic performance of hierarchical TS-1 with carbon template from sucrose carbonization

A series of hierarchical porous TS-1 zeolites had been successfully synthesized using cheap tetrapropylammonium bromide as microporous template and carbon material from sucrose carbonization as mesoporous template. The samples were characterized by powder X-ray diffraction, UV–Vis spectroscopy, FT-infrared spectroscopy, N 2 physical adsorption–desorption, scanning and transmission electron microscopy techniques. The catalytic performances of the obtained materials were investigated via the oxidation of both small and bulky molecular sulfur compounds (thiophene and benzothiophene) using H 2O 2 as oxidant. The mesopores or macropores system is clearly demonstrated by N 2 adsorption–desorption isotherm, scanning and transmission electron microscopy images. Moreover, the hierarchical pores correspond well with the framework structure of the carbon template trapped in TS-1 crystals, which confirms the template effect of the carbon material from sucrose carbonization. The reaction results show that hierarchical porous TS-1 zeolites not only give high removal rates of small molecular thiophene, but also exhibit high activities in oxidation of bulky benzothiophene, which are superior to TS-1.

Synthesis and catalytic properties of hierarchical TS-1 in the presence of cationic organosilane surfactant

Hierarchical TS-1 has been synthesized in the presence of cationic organosilane surfactant. The material is characterized with XRD, TEM, N2 adsorption isotherm. The results show that the hierarchical TS-1 aggregates consist of small primary units with sizes of 20–30 nm. The BET surface area increases from 420 to 513 m2/g compared to conventional TS-1 zeolite. The sample is shown to be more active in epoxidation of cyclohexene than conventional TS-1.

Nitrogen‐Incorporated TS‐1 Zeolite Obtained by Post‐Synthetic Nitridation

Nitrogen, Inc.: A novel nitrogen-incorporated TS-1 zeolite is prepared by direct calcination of the as-synthesized TS-1 powder in NH3 flow at high temperature. By introducing nitrogen into the framework of TS-1 zeolite, the acidic sites of TS-1 are reduced effectively and the material shows high catalytic activity and stability for epoxidation of propylene with dilute hydrogen peroxide.

Synthesis of Hierarchical TS-1 Zeolite from Silanized Seeds

Hierarchical TS-1 zeolites with a bimodal pore architecture, consisting of the typical MFI micropores and an additional mesoporosity, have been synthesized by grafting an organosilane compound to the zeolitic seeds previously prepared from two different raw materials: a liquid gel and an amorphous SiO2–TiO2 xerogel. These hierarchical TS-1 zeolites show an excellent catalytic behavior in olefin epoxidation reactions employing organic hydroperoxides as oxidants due to the presence of the secondary mesoporosity, which makes possible the access and interaction of bulky molecules with the Ti active sites.

Template-free synthesis of TS-1 zeolite film on tubular mullite support

The TS-1 film on tubular mullite support was prepared by secondary growth via template-free route using tetraethyl orthosilicate (TEOS) and tetrabutyl orthotitanate (TBOT) as silica and titanium sources. The as-made films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and ultraviolet–visible spectroscopy (UV–vis). Continuous TS-1 seed layer was bonded tightly to the mullite substrates. After secondary growth in the template-free synthesis solution, intergrown TS-1 zeolite film with the typical MFI-type structure was formed on the outer surface of support. The Si atoms in zeolitic lattice were found to be isomorphously substituted by Ti atoms which existed only in tetrahedral coordination. The thickness of the obtained TS-1 zeolite film was less than 20 μm.

Preparation of Ti incorporated Y zeolites by a post-synthesis method under acidic conditions and their catalytic properties

Ti incorporated Y zeolites were prepared by post-synthesis treatment of a dealuminated USY zeolite with an aqueous solution of (NH 4) 2TiF 6, and characterized by XRD, 27Al MAS NMR, FT-IR, SEM, TEM, UV–vis, and XANES techniques. The results showed that Ti species were tetrahedrally incorporated into the hydroxyl nests in the zeolite framework under acidic conditions. Furthermore, the catalytic performance of Ti incorporated Y zeolites in epoxidation of cycloalkenes using an aqueous solution of hydrogen peroxide was higher than that of TS-1 zeolite.

Enhanced Catalytic Oxidation by Hierarchically Structured TS-1 Zeolite

A TS-1 zeolite with a disordered network of mesopores penetrating the microporous crystalline zeolite framework was successfully synthesized by a one-pot carbon hard-templating synthesis approach. Besides conventional methods to characterize the mesoporosity, the use of variable-temperature 129Xe NMR spectroscopy was explored. At low temperature, a new resonance of 129Xe adsorbed in the mesopores could be distinguished from the signal of Xe in the micropores. The similarity of UV−vis and UV resonance Raman spectra of this mesoporous TS-1 zeolite with a conventional microporous TS-1 zeolite shows that the local coordination environment of Ti in these samples is identical. Further characterization (TEM, XRD) indicates that phase separation of titanium oxide is absent. The mesoporous TS-1 zeolite exhibits improved catalytic activity in the hydroxylation of phenol and ammoxidation of methyl ethyl ketone. The catalytic activity is substantially improved by introducing mesoporosity in TS-1, whereas the selectiv...

Hierarchical mesoporous TS-1 zeolite: a highly active and extraordinarily stable catalyst for the selective oxidation of 2,3,6-trimethylphenol

We report the synthesis of a new hierarchical mesoporous TS-1 type zeolite by a simple steam-assisted crystallization method. This novel product exhibits high catalytic activity and a strongly prolonged lifetime in the selective oxidation of 2,3,6-trimethylphenol to trimethyl-p-benzoquinone.

Photocatalytic efficiency of nanocrystalline zeolite TS-1 for the degradation of methyl orange

The photocatalytic properties of nanocrystalline TS-1 were confirmed via the degradation of an aqueous solution of the model compound methyl orange (MO). The light intensity and quantum yield were measured by ferrioxalate actinometry and the values are 1.7 × 10−5 einstein l−1 s−1 and 0.71, respectively. The experimental parameters such as catalyst loading, pH and initial concentration of MO were optimized at 1.5 g/L, 10 and 300 μM, in order. The results showed that the dye molecules are completely degraded to CO2, H2O and simple inorganic ions.

In-situ13C MAS NMR investigation of solvent effect on the formation of phenylacetaldehyde over TS-1 zeolite

In-situ 13C MAS NMR techniques were used to investigate the effects of different solvent systems on the formation of phenylacetaldehyde (PADH) over TS-1 zeolite. Protic solvents such as water and methanol provide acidic centers during the reaction. These acidic species catalyzed the transformation of the intermediates to PADH. Whereas in the presence of aprotic solvents such as acetone, the precursor of PADH remains stable on the framework of TS-1 and accordingly there is no PADH formation.

Turning TS-1 zeolite into a highly active catalyst for olefin epoxidation with organic hydroperoxides

A new synthesis route, based on the silanization of zeolitic seeds, has been applied to prepare nanocrystalline TS-1 zeolite with hierarchical porosity, leading to materials exhibiting high catalytic activity in 1-octene epoxidation with organic hydroperoxides as oxidizing agents.

Epoxidation of Linear Olefins over Stacked TS-1 Zeolite Catalysts

Stacked TS-1 [NSTS-1(MW)] has been prepared by microwave synthesis and applied to the epoxidation of linear olefins with H2O2 under mild conditions, and the epoxidation activities were compared with the non-stacked TS-1 and the conventional TS-1, which were also synthesized by microwave and by typical hydrothermal method, respectively. Stacking of TS-1 crystals was accomplished by using microwave which facilitated the dehydration of hydroxyl groups on the external surface of crystallites through the selective absorption of microwave onto Ti species. The stacked crystallites seemed to allow the running pore structure in the b-axis orientation through the crystallites in the stacked morphology. Besides this unique pore structure, the stacked TS-1 showed peculiar features like higher hydrophobicity and enhanced catalytic property than typical TS-1. Moreover, the NSTS-1(MW) showed the highest activity in the epoxidation of linear olefins among three catalysts, and also coincided with the differences in the adsorption of linear aliphatics due to strong interaction with the straight channel in the stacked morphology, which gave larger Henry’s constants, obtained by the tracer chromatographic analysis, as the increase in the carbon chain length.