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Ti-containing zeolites showed extremely high activity and selectivity in numerous friendly environmental oxidation reactions with hydrogen peroxide as a green oxidant. It will be in high demand to synthesize Ti-containing crystalline extra-large-pore zeolites due to the severe restrictions of medium-pore and/or large-pore zeolites for bulky reactant oxidations. However, the direct synthesis of extra-large-pore Ti-zeolites was still challengeable. Here, we firstly report a strategy to directly synthesize high-performance Ti-containing CFI-type extra-large-pore (Ti-CFI) zeolites assisted with fluorides. The well-crystallized Ti-CFI zeolites with framework titanium species could be synthesized in the hydrofluoric acid system with seed or in the ammonium fluoride system without seed, which showed higher catalytic activity for cyclohexene oxidation than that synthesized from the traditional LiOH system.

Catalytic cracking of n-hexane to selectively produce propylene on Beta zeolite was carried out. The H-Beta (HB) (Si/Al = 77) zeolite showed higher catalytic stability and propylene selectivity than the Al-rich HB (Si/Al = 12), due to its smaller number of acid sites, especially Lewis acid sites (LAS). However, catalytic stability and propylene selectivity in high n-hexane conversions were still not satisfactory. After dealumination with HNO3 treatment, catalytic stability was improved and propylene selectivity during high n-hexane conversions was increased. On the other hand, catalytic stability was not improved after desilication with NaOH treatment, although mesopores were formed. This may be related to the partially destroyed structure. However, propylene selectivity in high n-hexane conversions was increased after alkali treatment. We successfully found that the catalytic stability was improved and the propylene selectivity in high n-hexane conversions was further increased after the NaOH treatment followed by HNO3 treatment. This is due to the decrease in the number of acid sites and the increase in mesopores which are beneficial to the diffusion of coke precursor.

The presence of fluorine would be harmful to the catalytic activity of Ti-beta(F) is proved. The catalytic activity of Ti-beta(F) was effectively improved by defluorination through the treatment with NMe4OH.

The article discusses a recently developed methodology, which utilizes the molecular alkoxysilylation of zeolitic lamellar precursors for the synthesis of crystalline metallosilicates with expanded pore windows. The expanded structures are shown to exhibit extremely high thermal, as well as hydrothermal stability.

Carbon replica constructed of three-dimensional, ordered mesopores was employed as the conductive framework for the composite electrode in Li-sulfur all-solid-state batteries. Using a gas-phase mixing method under various conditions, elemental sulfur was introduced into the mesopores with an average diameter of 12 nm. The all-solid-state cells consisted of the sulfur-carbon replica composite cathode, thio-LISICON solid electrolyte, and Li-Al alloy anode. The cells produced discharge capacities of approximately 1500 mAh g-1 in the 1st cycle, which is comparable to the theoretical capacity of sulfur. Thermogravimetric and X-ray diffraction analyses revealed that sulfur deposited inside the mesopores is the main contributor to the excellent performance of the battery. However, sulfur strongly interacted with the carbon replica, reducing the thickness of the carbon wall from 7 to 4 nm. This structural change in the carbon matrix triggered the deterioration of battery performance, especially the cycling capability. Optimizing the sulfur deposition conditions could therefore enhance the performance of batteries using such composite electrodes. [ABSTRACT FROM AUTHOR]

The use of pentaerythritol in combination with the Na cation in the synthesis of ZSM-5 led to a unique Al distribution in the MFI framework; Al atoms were preferentially located at straight and sinusoidal channels, not the intersection. [ABSTRACT FROM AUTHOR]

Treatment of the zeolitic layered precursor of Al-MWW, so-called Al-MWW(P), with diethoxydimethylsilane (DEDMS) in acidic media leads to the formation of an aluminosilicate-type interlayer-expanded zeolite MWW (Al-IEZ-MWW) with expanded 12-membered ring (12-MR) micropores. However, the silylation process under acidic conditions simultaneously causes dealumination from the MWW framework, resulting in a decrease in the acid amount. We have developed a method for preparing Al-IEZ-MWW without leaching of the Al species. The strategy is to conduct the silylation under weakly acidic conditions; the silylation was conducted in an aqueous solution of an ammonium salt, e.g., NH4Cl, instead of HNO3. Subsequent additional acid treatment led to the formation of Al-IEZ-MWW that shows a high catalytic performance in the acylation of anisole compared to typical Al-MWWas well as Al-IEZ-MWW directly prepared under acidic conditions. The change in the state of Al atoms during the preparation process was investigated by high-resolution solid-state 27Al MAS NMR and 27Al MQMAS NMR techniques. [ABSTRACT FROM AUTHOR]

A novel type of organic–inorganic hybrid zeolite material ZOL (zeolite with organic group as lattice) is reviewed. ZOL materials are synthesized from an organosilane in which a methylene group bridges two silicon atoms to supersede an oxygen atom in the zeolite framework. ZOLs of various structures with the LTA, MFI, and *BEA topologies can be synthesized under synthesis conditions similar to those for conventional zeolites. The presence of framework methylene is demonstrated through the 13C MAS NMR analyses, although the presence of Si−CH 3formed through the hydrolysis of Si−CH 2−Si linkage is also observed. Although ZOL has physical properties similar to those of its inorganic counterpart, it shows higher hydrophobicity because of the presence of the framework organic group. The organic moieties in ZOL materials are thermally stable enough to be retained after the combustion of occluded organic structure directing agents. [ABSTRACT FROM AUTHOR]

Vapor-phase silylation of Al-MWW layered precursor with SiMe2Cl2and following calcination produced an interlayer-expanded MWW structure with 12-membered ring micropores without delamination as a result of the formation of silica puncheons between the MWW sheets; strong acidity of zeolitic nature was retained. [ABSTRACT FROM AUTHOR]

Microporous titanosilicate Ti-MCM-68 (Ti-MSE) was successfully synthesized by post-synthetic isomorphous substitution of Ti for Al and proved to be a high-performance catalyst, in particular showing superior performance to TS-1, Ti-BEA, and Ti-MWW for phenol oxidation using H2O2as an oxidant. [ABSTRACT FROM AUTHOR]

The study of methylation of ethene with methanol to propene over MFI zeolites with different heteroatoms has found that an efficient catalyst with weak acidities prevented the side reactions related with the formation of ethene oligomers from occurring, as evidenced by in situ IR spectroscopy, leading to superior propene selectivity in the product distribution. [ABSTRACT FROM AUTHOR]

The all-silica zeolite RUB-41, containing 8- and 10-membered rings, is able to separate trans-2-butene and cis-2-butene from 1-butene and represents a possible improvement in isolating pure 1-butene from a butene mixture. [ABSTRACT FROM AUTHOR]

The interlayer silylation of pure silica PLS-1 with dichlorodimethylsilane gave a novel organic–inorganic hybrid zeolite IEZ-1, of which the micropores are able to adsorb benzene molecules, in contrast to its purely inorganic analogue IEZ-2. [ABSTRACT FROM AUTHOR]

Single crystals of mesoporous silica SBA-16 with the shape of rhombododecahedron consisting of 12 flat crystal faces can be obtained by the addition of fluorinated surfactants with short carbon chains. [ABSTRACT FROM AUTHOR]

This study is the first report on synthesis, characterization and catalytic application of propylsulfonic acid-functionalized mesoporous composites based on natural rubber (NR) and hexagonal mesoporous silica (HMS). In comparison with propylsulfonic acid-functionalized HMS (HMS-SO3H), a series of NR/HMS-SO3H composites were prepared via an in situ sol-gel process using tetrahydrofuran as the synthesis media. Tetraethylorthosilicate as the silica source, was simultaneously condensed with 3-mercaptopropyltrimethoxysilane in a solution of NR followed by oxidation with hydrogen peroxide to achieve the mesoporous composites containing propylsulfonic acid groups. Fourier-transform infrared spectroscopy and 29Si MAS nuclear magnetic resonance spectroscopy results verified that the silica surfaces of the NR/HMS-SO3H composites were functionalized with propylsulfonic acid groups and covered with NR molecules. After the incorporation of NR and organo-functional group into HMS, the hexagonal mesostructure remained intact concomitantly with an increased framework wall thickness and unit cell size, as evidenced by the X-ray powder diffraction analysis. Scanning electron microscopy analysis indicated a high interparticle porosity of NR/HMS-SO3H composites. The textural properties of NR/HMS-SO3H were affected by the amount of MPTMS loading to a smaller extent than that of HMS-SO3H. NR/HMS-SO3H exhibited higher hydrophobicity than HMS-SO3H, as revealed by H2O adsorption-desorption measurements. Moreover, the NR/HMS-SO3H catalysts possessed a superior specific activity to HMS-SO3H in the esterification of lauric acid with ethanol, resulting in a higher conversion level. [ABSTRACT FROM AUTHOR]

Highly crystalline CHA -type aluminosilicate zeolites with the Si/Al ratio of around 4-5 were successfully synthesized by a seed-assisted method in the absence of organic-structure-directing agents (OSDAs); a method for so-called "OSDA-free synthesis" of the CHA zeolite has been newly developed. In this OSDA-free system, in addition to the seeds with the CHA topology, a judicious use of potassium or cesium cations together with sodium cations is a crucial key to the crystallization of the amorphous aluminosilicate gel into the CHA structure. The Si/Al ratio of the CHA zeolite was increased by decreasing the total amount of alkali cations added and/or the use of cesium cations in place of potassium ones. Furthermore, the employment of the amorphous aluminosilicate gel containing boron species led to the formation of the CHA zeolite with a high Si/Al ratio of 6.1 compared with the synthetic chabazite crystallized through the interzeolite conversion of the FAU zeolite (Si/Al: 2.0). The catalytic performance of the prepared CHA zeolites was also evaluated. In the methanol-to-olefins reaction, the catalyst life was improved by increasing the Si/Al ratio of the CHA zeolite. [ABSTRACT FROM AUTHOR]

Structural stability of mesoporous molecular sieves synthesized under various conditions were investigated. The effect of synthesis temperature, compositions, and silica source was examined. The MCM-41 synthesized from fumed silica and FSM-16 synthesized from kanemite was the most stable towards water, retaining the regularity for more than 90 days; the sample synthesized from TEOS at room temperature was less structurally stable. It is considered that the regularity loss involves the adsorption of water onto the surface silanol groups, which causes the nearby Si–O–Si bond cleavage, eventually resulting in the structural collapse. The X-ray powder diffraction, N2 adsorption, and NMR study revealed that the structural stability has a strong correlation with the ratio of pore wall thickness t to the amount of SiOH, while such stability is weakly correlated with each parameter. [Copyright &y& Elsevier]