Hydrogen Affinity of Silica-based Nanocomposite for High Temperature Hydrogen Separation Membranes
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1098-HH03-40
Hydrogen Affinity of Silica-based Nanocomposite for High Temperature Hydrogen Separation Membranes Yumi H Ikuhara, Tomohiro Saito, Koji Hataya, Yuji Iwamoto, and Seiji Takahashi Japan Fine Ceramics Center, Nagoya, 456-8587, Japan ABSTRACT Ni nanoparticles-dispersed amorphous silica (Si-O) membrane materials were synthesized through chemical solution method. Ni nanoparticles were homogeneously dispersed in the amorphous Si-O matrix, and the Ni nanoparticles reached to saturate in the Si-O matrix with Ni /(Si+Ni) ratio of about 0.2. There was appreciable pressure dependence of the reversible hydrogen adsorption on the composite. By analyzing the surface area of Ni nanoparticle in the composite, the adsorbed hydrogen on the Ni particles was evaluated. Reversible hydrogen adsorption sites in Ni nanoparticle-dispersed amorphous Si-O were determined at the Ni/Si-O interface in the composite. These reversible hydrogen adsorption sites play a role in the selective enhancement in the hydrogen permeance of the nanocomposite membrane.
INTRODUCTION Because of concerns about global warming, increasing attention is being directed to find an alternative to fossil hydrocarbon fuels and hydrogen is rapidly becoming one of the leading candidates. For hydrogen production, high temperature membrane reactor is applicable by simplify the process of producing hydrogen from natural gas and purifying it by combining these process into single step. Among the materials, ceramic membranes with molecular sieve-like properties have been expected for application in membrane reactors for conversion enhancement in dehydrogenation and methane reforming reactions[1-6]. Amorphous silica (Si-O) membranes prepared by sol-gel method have been intensively studied as molecular sieve membranes for gas separation at 773K. To enhance the hydrogen permselectivity, we have developed Ni nanoparticle-dispersed amorphous Si-O based composite membrane through the precursor solution method and achieved higher hydrogen permeance compared to helium and nitrogen at 573K to 773K[7]. In order to understand the phenomenon of the high hydrogen permeance of the novel nanocomposite membrane, it is important to clarify the expected high temperature hydrogen affinity, i.e., hydrogen adsorption properties. Here, the relationship between microstructure and hydrogen affinity of the nanocomposite was intensively studied from the view point of concentration of Ni nanoparticle in the amorphous Si-O matrix and reversible hydrogen adsorption property.
EXPERIMENT The Ni nanoparticle-dispersed amorphous Si-O powder was synthesized by precursor solution method. A stable metal-organic precursor solution for the ternary Si-Ni-O system was prepared by mixing tetraethoxysilane (Si(OC2H5)4, TEOS) in distilled ethanol and nickel nitrate
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hexahydrate (Ni (NO3) 2·6H2O) dissolved in 30 H2O2 aqueous solution with vigorous stirring for 120 min under an ice-cooled bath. The hydrolysis and polycondensation reaction of the precursor solution result in the Si-Ni-O composites[7]. The
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