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.     

Desilication of TS-1 zeolite for the oxidation of bulky molecules

A series of modified TS-1 samples have been produced by desilication of the original TS-1 (4 wt.% Ti) using a chemical treatment with NaOH. Desilicated TS-1 zeolites exhibit a large BET surface area together with a well-developed mesoporosity. The hierarchical catalysts from desilication of TS-1 zeolite show a good catalytic activity for the oxidation of small molecules and a significantly higher activity for the oxidation of bulky molecules.     

MFI型金属硅酸盐合成、介孔改性与骨架原子脱除行为

采用无机原料合成高硅沸石ZSM-5、FeMFI、TS-1和超高硅SH-ZSM-5(摩尔比Si/Al=402.4),通过骨架Si、金属原子(M=Al、Fe、Ti)抽提对系列H-MFI沸石进行介孔改性.借助XRD、FT-IR、UV-vis、77 K N2吸附-脱附和SEM/EDX技术,研究沸石晶体结构、金属原子嵌入率、介孔率及骨架Si、M脱除行为.结果表明,与前体相比改性沸石Si/M摩尔比降低,高选择性脱硅沸石具有多级微、介孔结构和较高织构介孔率.引入附加介孔使BET比表面积和总孔体积显著增加.同构沸石介孔形成受骨架电荷密度、嵌入金属原子种类、晶体形貌与尺度等因素的影响.骨架原子脱除效率按ZSM-5、FeMFI、TS-1次序递减.聚集态TS-1、SH-ZSM-5因过度脱硅导致相对产率和介孔生成效率下降.     

Synthesis of granular zeolitic materials with high cation exchange capacity from agglomerated coal fly ash

Fly ash from coal combustion is a potential source of pollution and there is continuous interest in its recycling by converting it into products such as zeolitic materials for use in retaining pollutants. In this paper, production of granular zeolitic material from a commercially-unusable fine-fraction of a lightweight aggregate (LA) building material made from coal fly ash agglomerated with lime, by conventional alkaline activation is described. NaP1 zeolite, K-F zeolite, K-Phillipsite and K-Chabazite were synthesised. The process was optimised by combining four reaction parameters (temperature, alkali concentration, solution/fly ash ratio and reaction time). Zeolitic materials with the highest zeolite yields and cation exchange capacities were selected for future application in environmental processes. End-product zeolitic materials maintain its granular form and this could favour their use in some particular applications for environmental waste treatment (e.g. ionic exchange in column) without any further transformation stages.     

X-ray absorption spectroscopy of metal atom-substituted microporous materials

X-ray absorption spectroscopy has been applied to the characterization of metal atom-substituted microporous materials. The two spectral regions of an X-ray absorption spectrum - XANES and EXAFS - provide information about the local coordination environment of the atom investigated. Gallosilicate sodalites are shown to contain Ga in fourfold coordinated framework sites with Ga---O bond lengths of 1.83(2) Å. By contrast, in CoAPO-20, tetrahedrally and octahedrally coordinated Co atoms have been identified. In TS-1, a catalytically active titanium silicate having the structural features of the zeolite ZSM-5, Ti is octahedrally coordinated by oxygen atoms. There are indications that Ti is incorporated into the framework of the zeolitic material.     

Crosslinked TS-1 as stable catalyst for the Beckmann rearrangement of cyclohexanone oxime

Crosslinked TS-1 zeolite materials have been studied in the gas phase Beckmann rearrangement reaction of cyclohexanone oxime to ε-caprolactam. Crosslinking of the zeolite particles resulted in the formation of an additional mesoporosity leading to increased activity in the Beckmann rearrangement reaction. The increased activity can be correlated with the newly created mesopore surface. Possibly more important, together with increased catalytic activity of the materials, the deactivation behavior of the catalysts is very significantly improved.     

The co-micelle/emulsion templating route to tailor nano-engineered hierarchically porous macrospheres

Here we present a new class of nano-engineered hierarchically porous materials in which the entire framework is mesoporous. This material is engineered into macrospheres of controllable size with a highly interconnected macropore network to facilitate molecular diffusion access. To achieve this, a new co-micelle/emulsion templating (co-MET) technique was developed. In this technique a block copolymer plays the dual roles of emulsion stabilization and micelle formation within the aqueous phase of that emulsion to produce the hierarchical structures. The emulsion templating provides the macroporous structure while the mesoporous structure is formed by hydrolyzation of silica around block copolymer micelles. Increasing the copolymer concentration improves the mesoporosity up to a certain concentration where the emulsion phase behavior changes and the macroporosity is affected. Unlike other hierarchically porous materials, the walls of the co-MET macrospheres are entirely mesoporous, which provides high surface areas (>500 m² g⁻¹) and pore volumes (>1 cm³ g⁻¹) and narrow mesopore size distributions (∼10 nm). This interconnected hierarchical meso/macroporous structure combined with the controlled particle size makes this new class of materials promising for applications requiring high diffusion and throughput rates, alleviating the problems of using typical fine particle mesoporous materials.     

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.     

TS-1分子筛催化剂的制备和表征

以四丙基氢氧化铵为模板剂,正硅酸乙酯为硅源,钛酸四丁酯为钛源,异丙醇为络合剂,碳酸铵为晶化调节剂,对经典水热法进行改进,制备出形貌规则且粒径约为200 nm的TS-1分子筛,考察晶化时间、正硅酸乙酯水解时间及络合剂种类对骨架Ti含量的影响,并采用XRD、SEM、FTIR和UV-Vis等对合成的样品进行表征。结果表明,当正硅酸乙酯水解2 h和晶化时间3天时,异丙醇的加入可有效阻止TiO_2沉淀的产生,同时加入(NH_4)_2CO_3能够促进钛物种进入TS-1分子筛骨架,提高骨架中的Ti含量。     

Controllable synthesis of a large TS-1 catalyst for clean epoxidation of a C=C double bond under mild conditions

Development of a titanium silicalite-1 (TS-1) catalyst with good crystallinity and a four-coordinate Ti framework is critical for efficient catalytic oxidation reaction under mild conditions. Herein, a size-controlled TS-1 zeolite (TS-1 0.1ACh (acetylcholine)) was synthesized via steam-assisted crystallization by introducing acetylcholine as a crystal growth modifier in the preparation process, and TS-1 0.1ACh was also employed in epoxidations of different substrates containing C=C double bonds. The crystalline sizes of the as-synthesized TS-1 0.1ACh catalysts were controlled with the acetylcholine content, and characterization results showed that the particle sizes of highly crystalline TS-1 0.1ACh zeolite reached 3.0 μm with a good Ti framework. Throughout the synthetic process, the growth rate of the crystals was accelerated by electrostatic interactions between the connected hydroxyl groups of the acetylcholine modifier and the negatively charged skeleton of the pre-zeolites. Furthermore, the TS-1 0.1ACh catalyst demonstrated maximum catalytic activity, good selectivity and high stability during epoxidation of allyl chloride. Importantly, the TS-1 0.1ACh catalyst was also highly versatile and effective with different unsaturated substrates. These findings may provide novel, easily separable and large TS-1 catalysts for efficient and clean industrial epoxidations of C=C double bonds.     

无机方法制TS-1催化剂上的环己酮氨氧化反应

用无机方法合成了钛硅分子筛催化剂TS-1,并优化了TS-1催化环己酮氨氧化反应的条件。结果表明,无机催化剂可以取代有机催化剂。同时,物料比、溶剂以及温度都对氨氧化反应有很大影响。适当调整反应条件,可得到较好的结果。其最优的反应条件为：n(氨)∶n(酮)＝2,n(H₂O₂)∶n(酮)＝1.5,溶剂用蒸馏水,n(水)∶n(酮)＝7.5,反应温度为74 ℃。     

Synthesis and characterization of TS-48, a titanium containing silica analog of ZSM-48

Crystalline titanium containing silica analog of ZSM-48 (TS-48) samples were synthesized using soluble peroxytitanate, fumed silica and diamino octane. All samples were characterized using a variety of techniques including XRD, IR, AAS, SEM, UV-Vis, XANES and catalytic testing in hydroxylation of phenol. Data suggest that titanium in these materials is linked to the framework. However, it was impossible to incorporate more than about 2 wt% Ti in the zeolite lattice. TS-48 samples prepared by this method had no activity for hydroxylation of phenol in the presence of hydrogen peroxide. The lack of activity of this material even though it showed all of the regular characteristics of other catalytically active titanium silicalites (i.e., TS-1 and TS-2) could be due either to diffusional limitations or to subtle differences in titanium environment.     

Titanium silicalite-1 macrostructures for photocatalytic removal of organic pollutants from aqueous media

Titanium silicalite-1 (TS-1) structures in the form of macroscopic beads with hierarchical porosity were prepared by the resin templating method. The Ti content within the samples was varied between 1 and 7 wt%, with corresponding surface areas ranging from 725 to 350 m² g^?1, respectively. The samples contained a large amount of amorphous material, which was necessary to achieve high mechanical stability of the beads. The TS-1 macrostructures were used as catalysts for the photocatalytic degradation of methylene blue (MB), and results were compared to the results for a commercial anatase nanopowder (CristalACTiV? PC500). All TS-1 beads showed similar MB degradation rates independently of their Ti content, which was linked to variations in the surface areas and structure. The macroscopic shape of the TS-1 beads allowed easy recovery from the mother liquor upon decolouration of the MB solutions, which was highly beneficial compared to the reference anatase nanopowder. The TS-1 beads could be reused in subsequent photocatalytic cycles after decanting exhausted solutions and replacing with fresh MB solutions without any energy-consuming regeneration steps involved. The samples were tested in five consecutive cycles and MB degradation rates remained broadly unchanged during all tests.     

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.     

Hierarchical macroporous epoxy resin templated from single semi-fluorinated surfactant

A hierarchical macroporous epoxy resin monolith has been successfully synthesized via a single semi-fluorinated surfactant (FSO-100) templating approach. The hierarchical macroporous material is characterized by variety of techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric (TG), infrared (IR) and X-ray diffraction (XRD). The results show that this material features a hierarchical macropore distribution with pore sizes at 0.4–2 μm and 20–100 nm, respectively. Additionally, the semi-fluorinated surfactant (FSO-100) disperses homogenerously in the epoxy resin, which imparts mesoscopic features.     

纳米TS-1分子筛的合成及环己酮肟化反应性能

采用预晶化后补充硅源的合成方法,在模硅物质的量比0.15条件下,合成晶粒尺寸300 nm的TS-1分子筛。考察模板剂用量和预晶化时间对分子筛合成的影响,并采用XRD、SEM、TEM、UV-vis和N2吸附-脱附对分子筛进行表征,通过环己酮肟化反应考察分子筛催化性能。结果表明,相对于传统法合成的TS-1分子筛,采用预晶化补硅法合成的TS-1分子筛具有较大的比表面积和介孔体积,而且其非骨架钛含量减少,能够有效地提高环己酮肟化反应的转化率、选择性和催化剂寿命。     

Phenol Hydroxylation over Alkaline Treated TS-1 Catalysts

Alkaline treatment on TS-1 can selective remove silica from the framework while MFI zeolitic framework remains intact, which creates new large micropores or even mesopores and increases Si/Ti ratio in the alkaline treated TS-1. Among various alkaline hydroxide, CsOH treatment leads to partial destruction of MFI structure. All the desilicated TS-1 samples show enhanced phenol conversion and dihydroxylbenzene (DHB) yield in acetone solvent by two folds, which can be attributed to the higher Ti/Si ratio and improved diffusivity. Pore structure modified with alkaline treatment affects significantly reaction pathway and product selectivity. The initial product over the parent TS-1 and NaOH treated TS-1 is mainly 4-hydroxycyclohexa-2,5-dienone and catechol enriched DHB, respectively.     

Organosilane surfactant-assisted synthesis of mesoporous SSZ-39 zeolite with enhanced catalytic performance in the methanol-to-olefins reaction

SSZ-39 zeolite with AEI framework structure is a good catalyst candidate for the methanol-to-olefins (MTO) reaction. However, the diffusion limitation and coke formation often results in fast deactivation of the SSZ-39 zeolite catalyst. One solution for this challenge is to introduce mesoporosity in the SSZ-39 zeolite. Herein, we report the synthesis of mesoporous SSZ-39 zeolite using an organosilane surfactant, N,N-dimethyl-N-(3-(trimethoxysilyl)propyl)octan-1-aminium chloride, as a mesopore template and N,N-dimethyl-cis-2,6-dimethylpiperidinium as a micropore template. The obtained zeolites were characterized by X-ray diffraction, N₂ sorption, scanning electron microscopy, temperature programmed desorption of ammonia, and magic angle spinning nuclear magnetic resonance of ²⁷Al. The results show that the mesoporous SSZ-39 zeolite has high crystallinity, meso/microporosity, high surface area, cuboid morphology, and abundant acidic sites. More importantly, this mesoporous SSZ-39 zeolite exhibits enhanced catalyst lifetime in the MTO reaction due to the presence of mesoporosity for fast mass transfer, compared with a conventional SSZ-39 zeolite without mesoporosity.     

Zeolite Beta with hierarchical porosity prepared from organofunctionalized seeds

Beta zeolite with hierarchical porosity has been obtained by a new synthesis strategy, based on perturbing the growth of the zeolite crystals by functionalization of the zeolitic seeds with organosilanes in order to hinder and prevent their further aggregation and agglomeration. As a consequence, a secondary porosity in the supermicropore region has been generated in zeolite Beta, leading to a considerable increase in both the total surface area and the pore volume of the material. The enhancement of the textural properties can be controlled by changing the silanization agent molecular size and its quantity added to the synthesis medium. This type of hierarchical Beta zeolites presents interesting applications as catalysts in reactions involving bulky molecules. Thus, their catalytic activity in the catalytic cracking of LDPE has been found to be strongly enhanced compared to a standard Beta zeolite sample, due to the higher accessibility to the acid sites caused by the presence of the secondary porosity.     

A titanium containing micro/mesoporous composite and its catalytic performance in oxidative desulfurization

A novel Ti-containing meso–microporous composite molecular sieve, namely Ti-HMS/TS-1, has been successfully synthesized through a two-step crystallization process. The products were characterized by X-ray diffraction, transmission electron microscopy, FT-infrared, UV–visible and N₂ physical adsorption–desorption techniques. The catalytic performances of the composite materials were investigated by means of sulfur compounds oxidation. It has been shown that the Ti-HMS/TS-1 simultaneously possesses a disordered mesoporous phase and a crystalline zeolitic phase and the two phases are composite rather than the physical mixture. UV–visible analysis indicates the existence of framework tetracoordination titanium species (Ti⁴⁺). Composite Ti-HMS/TS-1 exhibits excellent activities in the oxidation of both small and bulky molecular sulfur compounds, which is superior to the pure materials of TS-1 and Ti-HMS.