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Abstract The efficient modification of zeolites for improving their catalytic properties is a significant subject of microporous materials chemistry. H-ZSM-5 zeolite is a potent catalyst of the production of propylene as an important start material of a variety of chemical products, which is mainly obtained from fossil resources. Recently, the production of propylene using non-fossil carbon resources are desired because of the depletion risk of fossil fuels and global warming problem. Dimethyl ether (DME) conversion to propylene is actively studied using acid catalysts as an alternative synthetic route of propylene. This paper reports the propylene production from DME using H-ZSM-5 catalyst whose surface was modified with an organo-disilane compound, 1,4-bis(hydroxydimethylsilyl)benzene. An H-ZSM-5 catalyst surfacely modified with the disilane compound produced propylene from DME in higher yield than original (non-modified) H-ZSM-5. Air flow treatment at 480 °C effectively regenerated the modified H-ZSM-5 that was deactivated by coke formation during the reaction, and this regenerated catalyst had a nearly equivalent activity of the propylene production to the catalyst before deactivation. The polycyclic aromatic compounds formed from the benzene ring of the disilane compound that covered the exterior surface of H-ZSM-5 controlled the catalytic activity to increase the yield of propylene. Graphical abstract Image 1 Highlights • 10% of 1,4‒bis(hydroxydimethylsilyl)benzene was modified on H-ZSM-5 zeolite. • The modified H-ZSM-5 was effective for propylene synthesis from dimethyl ether. • Propylene yield by the modified H-ZSM-5 was more than double of that by H-ZSM-5. • Polycyclic aromatics was formed of the disilane compound on the surface of H-ZSM-5. • Restricting the reaction at exterior surface of H-ZSM-5 improved propylene synthesis. [ABSTRACT FROM AUTHOR]

Highlights: [•] Hydrogen was stored into ZSM-5 in the ambient atmosphere for a few months. [•] The sealing of the micropores outlet is essential for the hydrogen storage. [•] Remarkable hysteresis between the sorption branches showed narrowed micropore. [•] The amount of hydrogen stored was calculated to 0.015wt% from the released hydrogen over 150°C. [ABSTRACT FROM AUTHOR]

Abstract: The controls of oxygen permeation including oxygen delivery to the circumstances without sufficient oxygen supply from the atmosphere are important technologies for chemical and environmental engineering. The combination of the storage of molecular oxygen into the small pore voids and the appropriate discharge to the outside is a promising technique for a new method of oxygen supply. We recently showed that the surface modification of mordenite with organo-disilane compounds blocked the permeation of molecular nitrogen into the micropores. This result suggested that the grafting of the organo-disilane compounds on zeolite surface is also available for controlling oxygen permeations. In this paper, the oxygen storage in the pore void of mordenite was attempted by the modification method under pressurized oxygen atmosphere. A proton type of mordenite with impregnated 1,4-bis(hydroxydimethylsilyl)benzene was heated at 150°C under pressurized oxygen flow of 10bar. When this oxygen-filled mordenite sample was heated at 230°C under argon flow after sufficient deaeration of residual oxygen in dead space, clear decreases of oxygen releasing to the flow were found. A partial oxidation of the organo-disilane compound took place by the oxygen discharged from the micropore, which was supported by the formation of a partially oxidized benzene species of the organo-disilane compound in the treated sample. Although the direct extract of free oxygen was still unsuccessful, this might be the first example that the molecular oxygen is stored in the micropore of mordenite by the effective sealing of the micropore. [Copyright &y& Elsevier]

Abstract: Although the versatilities of zeolitic materials are widely known to chemists and materials scientists, their exclusive microporosity sometimes causes various defections especially in the diffusion of reactant and product molecules in catalytic reactions. Silica–alumina/epoxy-resin composite materials were obtained from TMOS (tetramethoxysilane), aluminum acetylacetonate and bisphenol A diglycidyl ether with a cyclic acid anhydride as both condensation and curing reagents. Hydrothermal treatment of the composite materials with TPAOH (tetra-n-propylammonium hydroxide) crystallized the amorphous silica–alumina part to the MFI zeolite crystalline phase and induced the phase separation of epoxy-resin domain from the zeolite phase at the same time, forming both zeolite microporosity and mesoporosity in the solid catalyst after calcination. The mesoporous MFI zeolite thus prepared had a good catalytic activity in liquid phase Friedel–Crafts benzylation reaction. The mesoporous channels fabricated in the MFI zeolite material enhanced the diffusion of reactants and products in the solid matrix, and thus it showed a better catalytic activity in the benzylation of toluene together with the high selectivity of the mono-substituted para-isomer. The new methodology reported in this paper to produce the mesoporous zeolite materials will promote the chemistry and the applications of zeolite catalysts and related materials. [Copyright &y& Elsevier]

Abstract: Regularly arranged pore structures are effective for regulating molecular permeation processes. Microporous zeolite materials are advantageous to manipulate the diffusion of gaseous molecules. Especially, zeolitic membranes are actively utilized in a number of membrane separation processes. Recently, we have reported that some disilylbenzene compounds grafted onto the surfaces of mordenite and ZSM-5 zeolites sealed their micropores to restrict the penetrations of molecular nitrogen, and that the calcination and heated HCl treatment reopened the sealed micropores. This paper reports that the micropores of mordenite and ZSM-5 zeolites were also sealed with the surface modification using benzene-1,4-diboronic acid, and molecular nitrogen cannot permeate into the micropores thus closed. This modification process provided some milder reopening of the sealed micropores such as diluted HCl treatment at room temperature. The reopening process was also successful by the UV irradiation to the solid zeolite samples after the impregnation of photo-acid generator (PAG). The pore reopening of the micropores with photo-irradiation in solid phase is a unique technique that will be applicable for some manipulation technologies of gaseous molecules. [Copyright &y& Elsevier]

Abstract: Regularly-structured solid matrices are potent materials for regulating molecular permeation and diffusion. Zeolite materials bearing ordered micropores are very advantageous to control the diffusion of molecules. When some disilylbenzene compounds were grafted on mordenite and ZSM-5 zeolites, the penetrations of small molecules such as α-methylstyrene (AMS) and molecular nitrogen were prevented by the direct formation of the crosslinking with two grafting sites on the exterior surfaces of those zeolites. The dimerization reaction of α-methylstyrene effectively promoted by mordenite was not catalyzed by these grafted mordenite samples. No adsorptions of molecular nitrogen were observed in the grafted mordenite and ZSM-5 samples. When these grafted samples were calcined, both the catalytic activity for the dimerization and the permeation of molecular nitrogen were recovered. The reopening of the micropores of zeolites was also achieved by the treatment with HCl acidic solutions. Thus, the diffusion and the permeation of various small molecules can be perfectly and reversely controlled by the sealing and the reopening of the micropores of zeolites by the disilylbenzene compounds. [Copyright &y& Elsevier]