Zeolite
Zeolite membranes
Zeolites are widely used as catalysts, adsorbents and membrane materials because they have ordered micropores and a large pore volume. Zeolite membranes can separate molecules by pore size as molecular sieving. Particularly, we focus on the separation of carbon dioxide, methane and hydrogen to solve issues of environmental or energy security.
- Sepr. Purif. Technol. 199 (2018) 298-303
- Micropor. Mesepor. Mater. 292 (2020) 109798
- J. Jpn. Petro. Inst. 61 (2018) 263-271
Zeolite Synthesis and adsorption
To prepare zeolite membranes, understanding of zeolite growth process is required. We study about not only the application of zeolite membranes but also basic research. Permeation through a membrane involves adsorption, diffusion and desorption processes. Adsorption properties is affected by the difference of adsorbate molecular size and pore size, and the affinity between adsorbate and membrane. To clarify the permeation mechanism, adsorption properties will be evaluate in detail with a view to using zeolite as an adsorbent.
- Mesopor. Macropor. Mater 273 (2019) 243-248
- J. Colloid. Inter. Sci. 388 (2012) 185-190
Organo-silica
Pervoporation
Pore size of amorphous silica can be easily controlled from several micrometer to several tens of nanometer by the molecular template such as surfactants. In addition, hydrophobic functional groups can be added to silica by using silane coupling agents.
We develop the hydrophobic silica membrane to separate volatile organic compounds from aqueous solutions, which assume to be waste water from pharmaceutical and chemical manufacturing process, by pervaporation.
- Desalination and Water Treatment 143 (2019) 17-23
- J. Membr. Sci. 548 (2018) 66-72
- J. Membr. Sci. 514 (2016) 458-466
Nanofiltration
Filtration, which is one of the simplest separation process, has been around us for a long time. Among filtration processes, nanofiltration, which can be separate substances with several nanometer, has been attracting attention to recycle or reuse solvents in pharmaceutical and chemical manufacturing process.
We are trying to apply the hydrophobic silica membranes to organic solvent nanofiltration, which was generally difficult to apply with conventional polymer membranes due to their chemical stability.
We are also trying to create a new type of nanofiltration membranes such as the composite hydrophobic silica and graphene membranes.
Hollow fibre
Ceramic hollow fibre
We have succeeded in synthesizing porous hollow fibers using various ceramics such as zinc oxide, yttria-stabilized zirconia, and silica, as well as typical alumina. The cross-sectional shape can be prepared to various shapes. In addition to ceramics, stainless steel porous hollow fibers can also be synthesized. This stainless steel hollow fiber can also be bent.
Ceramic hollow fibers can also be applied to microfiltration and ultrafiltration by themselves. It can be expected to be applied not only as a support for membranes such as gas separation and nanofiltration, but also as an adsorbent and catalyst.
Convert to Functional Materials
Ceramic hollow fibers are generally prepared by sintering at high temperature over 1000 °C. The crystal structure of porous materials such as mesoporous silica and zeolite would be broken during the sintering process. To solve this issue, mixed matrix membranes, containing a continuous polymer phase and a dispersed inorganic filler (zeolite etc.) phase, have been studied. However, the mixed matrix membrane cannot fully utilized the characteristics of zeolites, which have high chemical and heat resistance. We have succeeded in synthesizing an all-ceramic zeolite porous hollow fiber using silica as an inorganic binder.
We are also trying to directly convert ceramic hollow fibers to functional materials. For example, the conversion of amorphous silica to zeolite has been reported, and we have also succeeded in synthesizing CHA-type zeolite hollow fibers from amorphous silica hollow fibers. Currently, we are also trying to convert various metal oxide hollow fibers to functional materials.