Norikazu Nishiyama

Synthesis of ordered mesoporous carbons with channel structure from an organic–organic nanocomposite

Mesoporous carbons with ordered channel structure (COU-1) have been successfully fabricated via a direct carbonization of an organic-organic nanocomposite.

Synthesis of defect-free zeolite-alumina composite membranes by a vapor-phase transport method

Abstract The value of pH for gel preparation has a significant influence on the compactness of a dry gel. A compact gel was prepared at high pH of ca. 12. An amorphous dry gel on a porous alumina support was crystallized by a vapor-phase transport (VPT) method. Membranes of low silica zeolites, analcime (ANA) and mordenite (MOR), were formed because alumina was partly dissolved and incorporated into the framework of zeolite. Coating of the alumina support with colloidal silica depressed the dissolution of alumina. On the alumina support coated with colloidal silica, ferrierite (FER) and ZSM-5 (MFI) membranes were obtained. Compactness of the MOR membrane was examined by a permeation test of 1,3,5-triisopropylbenzene (TIPB) at room temperature. Since no permeation of TIPB was detected, it was concluded that there existed no pinholes and cracks in the MOR membrane. The pervaporation test of a benzene/ p -xylene mixture of which the molar ratio was 0.860, was carriee out. The separation factor ((benzene/ p -xylene)permeate/(benzene/ p -xylene)feed) exceeded 160. Thus some shape selectivity appeared at the pore mouths of MOR. The formation process of the MOR membrane was studied by using SEM and XRD. The gel which penetrated in the alumina pores crystallized to MOR and formed a defect-free MOR-alumina composite layer.

Synthesis of zeolites under vapor atmosphere: Effect of synthetic conditions on zeolite structure

Abstract The present study found that aluminosilicate gels were crystallized to ZSM-5, ferrierite, KZ-2 or analcime under a vapor atmosphere. The structure and crystallinity of the resultant zeolite significantly depended on the composition of the organic vapor as well as that of the parent gel.

Crystallization of FER and MFI zeolites by a vapor-phase transport method

Abstract Dry aluminosilicate gels were crystallized to MFI and FER by a vapor-phase transport (VPT) method using ethylenediamine (EDA), triethylamine (Et3N) and water as vapor sources. The roles of water and amines in this crystallization were investigated. While Et3N and water encouraged crystallization, EDA acted as a structure-directing agent. A dry gel was crystallized to FER when no water was added. The 27Al and the 29SiNMR spectra indicated that all Al atoms were incorporated into the zeolitic framework in the early stage of crystallization and that the rest of the Si-rich phase gradually crystallized. Full crystallization of Si and Al atoms in dry gel was possible by selecting optimum synthetic conditions. FER was transformed to MFI with prolonged crystallization. The structure and crystallinity of zeolite significantly depended on the sort of support on which the dry gel was placed.

FER membrane synthesized by a vapor-phase transport method: Its structure and separation characteristics

Abstract The mechanism of formation of ferrierite (FER) membrane on an alumina support by a vapor-phase transport (VPT) method was studied using XRD, SEM, FE-SEM and EDX. The XRD measurement for a FER membrane after the removal of FER particles formed on the support showed that FER was formed in the pores of the alumina support, namely, a FER-alumina composite layer was formed. The FE-SEM image for the cross-sectional view of the FER-alumina composite layer showed that FER nanocrystals of about 50 nm diameter grew in the pores of the alumina support. Pervaporation tests for benzene/p-xylene mixtures were performed at 303 K. Even when the concentration of benzene in the feed solution was extremely small (0.5 mol%), the flux of benzene through the FER membrane was still greater than that of p-xylene. Therefore, a separation factor as high as 600 was obtained in the low feed concentration of benzene. Such a high selectivity for the benzene/p-xylene mixture suggested that the selectivity for the benzene/p-xylene mixture appears at the pore mouths of FER on the feed side of the FER-alumina composite layer.

Preparation of a thin zeolitic membrane

The synthesis method to obtain a tight and thin zeolitic membrane was investigated. It was found that the most important factor to prepare a zeolitic membrane in a compact form was the pH to prepare the parent aluminosilicate gel. The aluminosilicate gel was supported on a porous alumina plate and treated in the vapor of templating reagents. It was found that a thin layer of ferrierite was formed on the surface of the plate. The rates of permeation of H 2 , He, CH 4 , O 2 , N 2 and CO 2 through the ferrierite membrane were measured. Permeation results indicated that the ferrierite membrane is formed in a compact form.

A DEFECT-FREE MORDENITE MEMBRANE SYNTHESIZED BY VAPOUR-PHASE TRANSPORT METHOD

A defect-free MOR membrane is synthesized on a porous alumina plate by a vapour phase transport method: shape selectivity is apparent in the pervaporation of a benzene–p-xylene mixture (the separation factor exceeded 160).

Evaluation of reproducible high flux silicalite-1 membranes: gas permeation and separation characterization

The permeation of helium, ethane, propane, n-butane, i-butane through a newly developed silicalite-1 membrane was performed using by a batch method and a Wicke–Kallenbach (WK) method. This membrane exhibits high flux properties and maintains a good separation selectivity. A procedure is outlined to interpret measured fluxes and estimate the various contributions of transport modes. The experimental fluxes of helium, ethane, propane and n-butane in the batch method could be divided into different parallel contributions, such as surface diffusion, activated gaseous diffusion and viscous flow. The permeation of helium was mostly governed by activated gaseous diffusion at 303–573 K. For adsorbing gases such as ethane, propane and n-butane, surface diffusion was dominant at temperatures up to 393 K. Their permeation mechanism shifted to activated gaseous diffusion with increasing temperature. In the WK method, both single component measurements and binary mixture separations using n-butane and i-butane were performed in the temperature range of 303–573 K. The selectivity for n-butane in a 1:1 mixture n-butane/i-butane was about 28 up to 400 K, which was higher than the ideal selectivity calculated from the single component measurements because of the competitive adsorption of the butanes. The selectivity of the membrane for n-butane/i-butane mixtures was highly dependent on feed composition and feed pressure.

Synthesis of FER membrane on an alumina support and its separation properties

Preparation method was established to synthesize a defect-free FER membrane by a vapor-phase transport (VPT) method. In preparing FER membrane a porous alumina support was dipped in a gel to coat with the gel. After drying, the gel on the alumina support was crystallized to FER under vapors of ethylenediamine, triethylamine and water. Two types of dipping methods were examined. First, the porous alumina support was dipped in a gel for 1 day. In the second method, after dipping the support in the gel for 1 day we forced the gel to penetrate into the pores of the alumina support by evacuating the support from one side. A permeation test of 1,3,5-triisopropylbenzene (TIPB) through FER membrane was carried out at room temperature to check the compactness of the FER membrane. The permeation of 1,3,5-triisopropylbenzene (TIPB) through FER membrane synthesized using the second dipping method was not detected, indicating that in the FER membrane there was no pinhole as large as the molecular dimension of TIPB. The pervaporation tests for cyclohexane, benzene, p-xylene and o-xylene were carried out at room temperature. The separation factor for a benzene/p-xylene mixture using the FER membrane was 100, which was much greater than 10.3 predicted from the gas-liquid equilibrium. The FER membrane showed a promising potential to separate organic compounds such as aromatic hydrocarbons.

Synthesis and permeation studies of ferrierite/alumina composite membranes

Abstract Polycrystalline ferrierite/alumina composite membranes were prepared by a vapor-phase transport method. Pervaporation of m -xylene and 1,3,5-triisopropylbenzene was then used to evaluate the compactness of the membranes. Permeation measurements were carried out for hydrogen, helium, methane, n -butane, i -butane and sulfur hexafluoride at 300–375 K. Ideal selectivities and the mixed gas separation factors were compared. The separation factor of butane isomers depended on the compactness of the membrane. The separation factor of n -butane/ i -butane was as high as 40–70 at 375 K, and no detectable permeation flux of m -xylene was observed at 303 K. Separation of a 25/75 p -xylene/ m -xylene mixture was also performed at 303 K using pervaporation. The permeation of p -xylene was detectable, whereas that of m -xylene was below the detection limit of the experiment. The separation factor of p -xylene to m -xylene was greater than 16, which is much higher than the value of 1.0 expected from the vapor–liquid equilibrium.