Keiichi Ogasawara

Preparation of a cyclophane-bonded stationary phase and its application to separation of naphthalene derivatives

A cyclophane (CP44)-bonded silica gel stationary phase was prepared and elution behaviour of hydrophobic solutes was investigated in the reversed-phase mode. Aromatic compounds were retained on the stationary phases more strongly than the corresponding alicyclic compounds, as was expected by the complex-forming ability of the cyclophane. The stationary phases also showed isomer-selective separation for monomethyl- and dimethylnaphthalenes. The isomers having methyl groups at the α-position were eluted prior to those having methyl groups at the β-position, i.e., the retention order for methylnaphthalene was, α<β and that for dimethylnaphthalene, α,α<α,β<β,β. Moreover, some dimethylnaphthalene isomers which cannot be separated on ordinary reversed-phase stationary phases were separated finely on this stationary phase. The separation mechanism is discussed on the basis of the structure of the cyclophane-involved complex.

Simple thermodynamics of macroscopic phase separation in shrinking gels

The shrinking process induced in spherical gels by an abrupt change in temperature has been investigated qualitatively. The phase diagram of the gel system has been found to be helpful in classifying a variety of shrinking processes. When the solvent quality is lowered within the region between the volume transition and coexistence temperatures, the local swelling ratio of the inner portion, which is divided by a moving interface from the outer shrunk phase, declines in the course of the shrinking process. On the contrary, the local swelling ratio of the inner portion of the shrinking gel is enlarged when the solvent quality is lowered into the region between the coexistence and spinodal temperatures. In this latter case, owing to large local swelling of the inner portion in the vicinity of the interface, spherical symmetry will imply mechanical instability. This instability will be the origin of transient spatial patterns on the surfaces of shrinking gels.

Development of a Formation Process of CO2 Hydrate Particles for Ocean Disposal of CO2

Publisher Summary Several ocean disposal scenarios of anthropogenic CO2 have been proposed to date. Among them, disposal process in the form of CO2 hydrate would be most favorable form the viewpoint of environmental impact caused by CO2. CO2 hydrate is a clathrate compound where a CO2 molecule is included in a cage-like structure formed by the hydrogen-bonded water molecules. In the disposal process, CO2 emitted from a concentrated source of CO2—such as thermal power plant—would be collected from the flue gas and converted into CO2 hydrate particles in a hydrate formation unit. Then CO2 hydrate crystal would be released to the ocean. Two-phase mixture of water and liquid CO2 will be supplied to the reactor and fluidized under a proper flow conditions. Small particles of CO2 hydrate will be supplied to the reactor as seed particles, and CO2 hydrate particles will be fluidized with the mixture of water and CO2. During the fluidization process, CO2 would be transferred from liquid CO2 phase to the hydrate phase via dissolution in the water phase, and the hydrate particles would grow. The hydrate particles of which the size is large enough for the ocean disposal would be removed from the reactor and disposed of in the ocean. The proper size of the disposed hydrate particles would be determined by considering the behavior of the hydrate particles in the ocean: descending rate and dissolution rate, which affect the environmental impact by the CO2 released form the disposed hydrate particles.