2-Methylnaphthalene Methylation over Aluminosilicate and Ferrisilicate with MTW-type Zeolite Structure and Their Kinetic Analysis

Aluminosilicate and ferrisilicate with the MTW-type zeolite structure were hydrothermally prepared and used to catalyze the methylation of 2-methylnaphthalene (2-MN) under supercritical conditions in a batch-type reactor. Dimethylnaphthalene (DMN) and 1-methylnaphthalene (1-MN) yields increased with decreasing Si/Al ratio of the zeolite. In contrast, ferrisilicate with the MTW-type zeolite structure (Si/Fe = 100) exhibited higher DMN selectivity and the beta,beta-DMN fraction in total DMNs was higher than that over aluminosilicate with MTW structure (Si/Al = 100). Kinetic analysis of 2-MN methylation over MTW zeolites was conducted, to obtain the reaction rate constants and apparent activation energies. The activation energy for the methylation of 2-MN over aluminosilicate with MTW structure was 176 kJ mol(-1), which was almost the same as that for the ferrisilicate with MTW structure. This indicates that the mechanism for methylation is independent of hetero-atoms species in the MTW zeolite framework. The introduction of Fe atoms into the framework significantly decreased the rate constant for the isomerization of 2-MN compared with that for the methylation of 2-MN. Therefore, ferrisilicate with MTW structure is effective for 2-MN methylation due to the decrease of the isomerization rate

Size-Controlled Synthesis of Nano-Zeolites and Their Application to Light Olefin Synthesis

For the application of zeolites as heterogeneous catalysts, low diffusion resistance for hydrocarbons within the micropore is essential for improving product selectivity and catalyst lifetime. This problem has been overcome by reducing the crystal size. This review introduces size-controlled preparation of nano-sized zeolites via hydrothermal synthesis in water/surfactant/organic solvent (emulsion method) and their application to heterogeneous catalysts. The ionicity of the hydrophilic group in surfactant molecules and the concentration of the Si source affected the crystallinity and morphology of zeolites prepared using the emulsion method. When using a non-ionic surfactant, mono-dispersed silicalite-1 nanocrystals approximately 60 nm in diameter were successfully prepared. Nano- and macro-ZSM-5 zeolites with crystal sizes of approximately 150-200 nm and 1.5 μm, respectively, were prepared and applied to n-hexane cracking and acetone-to-olefin reactions to investigate the effect of zeolite crystal size on catalytic stability and light olefin yield. Application of nano-zeolite to light olefin production was effective in achieving faster mass transfer of hydrocarbon molecules within the micropore, which led to improvements in olefin yields and catalyst lifetime

Preparation of hydrophilic silicalite-1 nanocrystal-layered membranes and their application to separating water from water–acetone solution

Separation of water from a water-acetone solution was carried out by a pervaporation method using a hydrophilic silicalite-1 membrane. Silicalite-1 nanocrystals were piled up on the outer surface of cylindrical alumina ceramic filters, followed by a hydrothermal synthesis to form a silicalite-1 protection layer oil the nanocrystal layer. In other words, the membrane consisted of a silicalite-1 nanocrystal layer and a silicalite-1 protection layer (the nanocrystal-layered membrane). In order to achieve high hydrophilic properties of the membrane with the remaining silanol group, the liquid-phase oxidation technique was applied to remove the template. From the SEM observation, the nanocrystal layer and the protection layer were clearly observed, and the silicalitc-1 protection layer was uniformly formed on the nanocrystal layer. Pervaporation experiments to separate water from the water-acetone solution were conducted using the nanocrystal-layered membrane. It was considered that the secondary growth of the nanocrystals around the interface between the nanocrystal and protection layers affected the separation properties. The effects of the nanocrystal size oil the separation properties were examined. The membrane exhibited selective permeation as well as a high flux of water, and these properties were improved with a decrease in the size of the nanocrystals. Moreover, the layered membrane exhibited high hydrophilic properties regardless of the acetone concentrations. (C) 2008 Elsevier Inc. All rights reserved

Liquid-phase diffusivity of benzene within mesoporous materials measured by a laser Raman technique

The intracrystalline diffusivities of benzene within a series of porous materials in the liquid phase (cyclohexane was used as solvent) were measured by a constant volumetric method using Raman spectroscopy at a temperature range from 323 to 393 K. Silicalite-1, mono-dispersed mesoporous silica spheres (MMSS), Silica Gel, γ-Al2O3, and SiO2-Al2O3 were used as adsorbents. The intracrystalline diffusivity was calculated by parameter fitting using theoretical equations and the experimental transient change of benzene concentrations with time in response to the adsorption. The intracrystalline diffusivities of benzene within mesoporous silicas were almost the same as that within the micropore of silicalite-1, though the pore diameters of silicalite-1 and mesoporous silicas were different from each other. It is considered that the pore walls as well as the solvent molecules of cyclohexane affect the diffusion of benzene molecules in the meso pore region

Preparation of nano-crystalline MFI zeolite via hydrothermal synthesis in water/surfactant/organic solvent using fumed silica as the Si source

The preparation of nano-crystalline MFI zeolites (Silicalite-1 and ZSM-5) was carried out by hydrothermal synthesis in a water/surfactant/organic solvent using fumed silica and aluminum sulfate as the Si and Al source, respectively. It was confirmed that the surfactant in the solution affected the nucleation rate of the MFI zeolite. Moreover, the crystal size of the MFI zeolite decreased with increasing surfactant concentration, and nanometer-sized MFI zeolites was obtained at a surfactant concentration of 0.25～0.5 mol/L. The successful preparation of MFI zeolite nanocrystals was ascribed to the stabilization of the MFI zeolite precursors and/or crystals by the adsorbed surfactant on their surface. This method was applied to the preparation of nano-crystalline ZSM-5 zeolite. ZSM-5 zeolite with a crystal size of approximately 50 nm was obtained. The nano-crystalline ZSM-5 zeolite was well-crystallized without octahedral Al atoms in the external framework, and exhibited almost the same acidity as a reference ZSM-5 zeolite

酸化鉄系触媒によるグリセロールからの有用化学物質合成

Catalytic conversion of glycerol with iron oxide-based catalysts was investigated for the production of useful chemicals. The catalytic reaction was carried out in a fixed-bed flow reactor at 623 K under atmospheric pressure. Useful chemicals such as allyl-alcohol, propylene and ketones were produced from glycerol through two main pathways: formation of allyl alcohol and propylene (Pathway I), and formation of hydroxyacetone and acrolein (Pathway II). Hydroxyacetone in Pathway II is easily converted into carboxylic acids followed by ketonization to form acetone, methyl ethyl ketone and pentanone. An increase in the W/F (weight ratio of catalyst to feedstock) value allowed the consecutive reactions to progress and the final products were mol%-carbon of propylene and 25 mol%-carbon of ketones. Moreover, addition of alkaline metals to the catalyst increased the yield of allyl alcohol. This study demonstrates the production of useful chemicals from glycerol (crude glycerol and reagent glycerol). The effects of catalyst composition and experimental conditions on these yields are discussed, based on investigations of the reaction pathways and mechanisms.酸化鉄系触媒によるグリセロールからの有用化学物質合成を実施した。反応実験は反応温度623 K，常圧下，固定床流通式反応器にて実施した。グリセロールからの有用化学物質転換反応では，主にアリルアルコール，プロピレン，ケトン類が得られた。これらの有用化学物質は反応経路I（アリルアルコール，プロピレン）と反応経路II（ヒドロキシアセトン，アクロレイン）に従って生成し，経路IIに含まれるヒドロキシアセトンは容易にカルボン酸へと転化し，カルボン酸のケトン化反応によりケトンへと転化された。W/F値（触媒量／供給原料比）を増加させると，アリルアルコールからのプロピレン生成，およびカルボン酸からのケトン生成の各逐次反応が進行し，生成物はプロピレン（収率約24 mol%-Carbon）とケトン類（収率約25 mol%-Carbon）に収束した。また，アルカリ金属を触媒に添加することにより，アリルアルコールの収率が効果的に向上することを見出した。本論文では，試薬グリセリン，および粗製グリセリンからの有用化学物質合成を報告するとともに，触媒組成と反応条件が生成物収率に及ぼす影響を反応機構の観点から議論する

MFI型，MTW型ゼオライト構造を有するメタロシリケートを用いた含酸素有機物からの低級オレフィン合成

Selective production of light olefins over zeolite catalyst requires control of consecutive reactions because the objective products are intermediates. In catalytic reactions using zeolite, the diffusion resistance of both the raw material and products within the crystal, and acid site strength of the zeolite, strongly affect the catalyst activity and selectivity. This review describes the preparation of macro, and nano-sized ferrisilicate and ferroalumino-silicate with MFI and MTW-type zeolite structures and their application to the production of light olefins from oxygenated organic compounds such as acetone and methanol. Nano-sized ferrisilicate with MFI-type zeolite structure showed more stable activity compared to macro-sized zeolite in the acetone to olefin and methanol to olefin reactions. Moreover, metallosilicates containing Fe atoms in the zeolite framework had higher selectivity for light compared to aluminosilicate due to suppression of the consecutive reactions forming aromatics and coke. Ferroaluminosilicate containing two types of Bronsted acid sites, derived from both Fe and Al atoms in the framework, was the most effective catalyst for the production of light olefins from methanol.低級オレフィンは逐次反応の中間体生成物であるため，ゼオライト触媒を用いた選択合成において逐次反応の制御が必須である。ゼオライトを触媒に用いる際，ゼオライト結晶内における反応原料，反応生成物の拡散抵抗およびゼオライト酸点の強度が触媒活性や生成物選択性に強く影響を及ぼす。本稿では，粒径の異なるMFI，MTW型の構造を有するフェリシリケートおよびフェロアルミノシリケートの合成と，含酸素有機物であるアセトン，メタノールからの低級オレフィン合成について解説する。アセトンおよびメタノールからの低級オレフィン合成において，MFI型構造を有するフェリシリケートナノ結晶はマクロ結晶に比べ安定な触媒活性を示した。さらに，両反応に対し骨格中にFeを有するメタロシリケートは芳香族やコーク生成の抑制によりアルミノシリケートに比べ高い低級オレフィン選択性を示した。メタノールからの低級オレフィン合成において，ゼオライト骨格中のFeおよびAlに由来する二種類のブレンステッド酸点を有するフェロアルミノシリケートが低級オレフィン合成に有効であった

Characterization and catalytic performance of modified nano-scale ZSM-5 for the acetone-to-olefins reaction

In the acetone to olefins (ATO) reaction using ZSM-5 zeolites, isobutylene is initially produced via decomposition of an acetone dimer, followed by dimerization of the isobutylene and its cracking to form ethylene and propylene. Nano-scale ZSM-5 zeolite exhibited stable activity during the ATO reaction compared with that of macro-scale ZSM-5.1n order to further improve the catalytic stability of the nano-scale ZSM-5, control of the acidity of nano-scale ZSM-5 zeolites through SiO2 unit formation was examined using phenyl silane and triphenyl silane as new deactivators. This modification led to an increase in the olefins yield and an improvement in the catalyst lifetime. In particular, the regioselective deactivation of acid sites located on the external surface of the zeolite inhibits the formation of aromatics. Moreover, the acidity control within the pores significantly improved the catalyst lifetime. Notably, the modified nano-scale ZSM-5 zeolite exhibited a stable olefins yield above 55C-mol% for 180h