Eiji Kamio

Effects of Water Concentration on the Free Volume of Amino Acid Ionic Liquids Investigated by Molecular Dynamics Simulations

Amino acid ionic liquids (AAILs) are gaining attention because of their potential in CO2 capture technology. Molecular dynamics simulations of AAILs tetramethylammonium glycinate ([N1111][Gly]), tetrabutylammonium glycinate ([N4444][Gly]), and 1,1,1-trimethylhydrazinium glycinate ([aN111][Gly]) and their corresponding mixtures with water were performed to investigate the effect of water concentration on the cation-anion interactions. The water content significantly influenced the free volume (FV) and fractional free volume (FFV) of the AAILs that varied with the hydrophobic and hydrophilic nature of the ion pairs. Under dry conditions, the FFV increased with increasing cation molecular sizes, indicative of proportional adsorption of any inert gases, such as N2, as consistent with experimental observations. Furthermore, the polarity of the cation played an important role in FFV and hence the diffusion of the AAILs. Density functional theory calculations suggested that hydrophilic [aN111][Gly] featured stronger interactions in the presence of water, whereas the hydrophobic IL showed weaker interactions. The carboxylate group of glycinate displayed stronger interactions with water than the cation. The computational study provided qualitative insight into the role of FV of the AAILs on CO2 and N2 absorption and suggests that [aN111][Gly] has CO2 adsorption capacity in the presence of water superior to that of other studied AAILs.

Inorganic/Organic Double‐Network Gels Containing Ionic Liquids

Highly robust ion gels, termed double-network (DN) ion gels, composed of inorganic/organic interpenetrating networks and a large amount of ionic liquids (ILs), are fabricated. The DN ion gels with an 80 wt% IL content show extraordinarily high mechanical strength: more than 28 MPa of compressive fracture stress. In the DN ion gel preparation, a brittle inorganic network of physically bonded silica nanoparticles and a ductile organic network of polydimethylacrylamide (PDMAAm) are formed in the IL. Because of the different reaction mechanisms of the inorganic/organic networks, the DN ion gels can be formed by an easy and free-shapeable one-pot synthesis. They can be prepared in a controllable manner by manipulating the formation order of the inorganic and organic networks via not only multistep but also single-step processes. When silica particles form a network prior to the PDMAAm network formation, DN ion gels can be prepared. The brittle silica particle network in the DN ion gel, serving as sacrificial bonds, easily ruptures under loading to dissipate energy, while the ductile PDMAAm network maintains the shape of the material by the rubber elasticity. Given the reversible physical bonding between the silica particles, the DN ion gels exhibit a significant degree of self-recovery by annealing.

Development of facilitated transport membranes with low viscosity aprotic heterocyclic anion type ionic liquid as a CO2 carrier

ABSTRACT Low viscosity ionic liquids (ILs) composed of a cation with methoxy group and an aprotic heterocyclic anion (AHA) with highly nucleophilic amino group were synthesized and examined as a CO2 carrier of facilitated transport membranes. Due to the low viscosity of the AHA-type ILs after CO2 absorption, the AHA-type IL-based membrane showed high CO2 permeability (ca. 3900 barrer) with 200 of CO2/CH4 selectivity under dry condition at 323 K, which was much higher than that of amino acid ILs-based membrane (ca. 150 barrer with ca. 50 of CO2/CH4 selectivity).

Toluene vapor removal using an inorganic/organic double-network ion gel membrane

ABSTRACT Tough gel membrane composed of a large amount of an ionic liquid and an inorganic/organic composite double-network (inorganic/organic DN ion gel membrane) was examined to remove toluene vapor from toluene vapor/N2 mixed gas. The DN ion gel membrane with 80 wt% of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide showed higher toluene vapor permeability (more than 30,000 barrer) and toluene vapor/N2 permselectivity (690) than the supported ionic liquid membrane. The toluene vapor permeability and toluene vapor/N2 permselectivity were maintained under pressurized condition. It was confirmed that the toluene vapor permeation was limited by intramembrane diffusion of the dissolved toluene vapor.

Inorganic/organic double-network ion gels with partially developed silica-particle network

Tough inorganic/organic composite network gels consisting of a partially developed silica-particle network and a large amount of an ionic liquid, named micro-double-network (μ-DN) ion gel, are fabricated via two methods. One is a one-pot/one-step process conducted using a simultaneous network formation via sol-gel reaction of tetraethyl orthosilicate and free radical polymerization of N, N-dimethylacrylamide in an ionic liquid. When the network formation rates of the inorganic and organic networks are almost the same, the μ-DN structure is formed. The second method is simpler and involved the use of silica nanoparticles as the starting material. By controlling the dispersion state of the silica nanoparticles in an ionic liquid, the μ-DN structure is formed. In both μ-DN ion gels, silica nanoparticles partially aggregate and form network-like clusters. When a large deformation is induced in the μ-DN ion gels, the silica-particle clusters rupture and dissipate the loaded energy. The fracture stress and Youngs modulus of the μ-DN ion gel increase as the size of the silica nanoparticles decreases. The increment in the mechanical strength would have been caused by the increase in the total van der Waals attraction forces and the total number of hydrogen bonding in the silica-particle networks.

Cutting-Edge Research at the Membrane Center in Kobe University in Japan

ABSTRACT Membrane technology has been widely applied for environmental protection such as water treatment and CO2 reduction. Thus, there is increasing interest in the membrane field in Japan. The first membrane center (Center for Membrane and Film Technology, MaF Tech center) was established at Kobe University in 2007. This center is the only center focusing on membrane technology in Japan. In this paper, academic research activities and projects in Japan, and the cutting-edge research carried out at the MaF Tech center are briefly reviewed.