Takao Ohmori

Internally Heat-Integrated Distillation Columns: A Review

The heat-integrated distillation column to be addressed in this paper is a special distillation column that involves internal heat integration between the whole rectifying and the whole stripping sections. An overview of the research on this process is presented in this work. It covers from the thermodynamic development and evaluations to the practical design and operation investigations for the process. Comparative studies against conventional distillation columns are introduced and the results obtained show distinctively the substantial advantages in energy efficiency of the process over its conventional counterparts. Some relevant issues of process design and operation are to be stressed and the results of the first of its kind bench-scale plant experimentation are given in great detail. The application of internal heat integration principle to other distillation-related processes is also discussed in depth. These include heat integration within batch distillation columns, pressure-swing distillation columns that are used for the separation of pressure-sensitive binary azeotropes, and different distillation columns that have no connections at all. The prospects of the HIDiC and our future research work are then highlighted.

The structure of glutaraldehyde in aqueous solution determined by ultraviolet absorption and light scattering

The structure of glutaraldehyde (GA) in aqueous solutions has been the subject of much debate. Since there were fundamental problems in the experiments in the preceding studies, in this article, the structure of GA was investigated with uv absorption and light scattering to avoid those problems. It was discovered that 70% glutaraldehyde solution contains a large quantity of polymeric species with cyclic hemiacetal structure. On dilution, the polymerized glutaraldehyde slowly converted to monomers. In dilute solution, glutaraldehyde is almost monomeric at pH 3-8, the major portion taking the cyclic hemiacetal structure. The structure of GA in 20% solution is similar to that in more dilute solution. alpha, beta-Unsaturated structure does not exist in aqueous solution regardless of the concentration of glutaraldehyde.

Evaluation of pore size distribution in boundary region of micropore and mesopore using gas adsorption method

This paper discusses an accurate method of pore size distribution evaluation in boundary regions of micropores and mesopores using the gas adsorption process on the basis of the capillary condensation theory, which is liable to be underestimated with the existing BJH and DH methods. A typical nitrogen adsorption isotherm for highly ordered mesoporous silica, which has cylindrical pores with diameter smaller than 4 nm, is considered to be type IV and it is well known for the steep increase of the amount adsorbed through capillary condensation in the region of the relative pressure P/P0 smaller than 0.4. In calculating the distribution of the pore size from the change of the amount adsorbed due to capillary condensation, it is important to accurately predict both the multilayer thickness t of the adsorbed nitrogen molecules and the critical radius rc where capillary condensation occurs. It is necessary to consider the curvature of the adsorption layer-gas phase interface when predicting the multilayer thickness t of nitrogen adsorbed within the pore of highly ordered mesoporous silica. Revision of the Kelvin equation is also required when rc is to be predicted. While the predicted value of t based on the Broekhoff and de Boer theory is matched well with the value of t which is actually measured using highly ordered mesoporous silica, and the predicted value of rc based on the GTKB-Kelvin-cylindrical equation that has been revised considering the effect of the interfacial curvature on the interfacial tension of the adsorption layer-gas phase interface is matched with the value of rc which is actually measured using highly ordered mesoporous silica. A combination method of the Broekhoff and de Boer equation and the GTKB-Kelvin-cylindrical equation is proposed as a means of accurately evaluating, from the nitrogen adsorption isotherm, the pore size distribution in the highly ordered mesoporous silica in boundary region of micropore and mesopore. The proposed new method of pore size evaluation features high accuracy and offers the convenience of obtaining the pore size distribution without repeated calculations by employing the same algorithm as DH method. The pore size predicted by the Halsey equation and the Kelvin equation of the conventional DH method is about 20% smaller than the pore size predicted by the newly proposed evaluation method.

Nonlinear effects of electrolyte diodes and transistors in a polymer gel medium

The polarization curve of an acid-base interface in a hydrogel medium has a diode characteristic. Two of each such electrolyte diodes can be combined to give an electrolyte transistor. When a salt is added to the alkaline or to the acidic part of a reverse biased electrolyte diode, the current response is highly nonlinear. If the salt is added to the acidic side, even bistability can be observed. This bistability can generate complex oscillations in a base-acid-base electrolyte transistor. These nonlinear effects are studied experimentally and theoretically. While the nonlinear salt effect can be explained with the Nernst-Planck equations, to understand the bistable behavior further investigations are necessary. (c) 1999 American Institute of Physics.

NUMERICAL STUDY ON TIME DELAY FOR CHEMICAL WAVE TRANSMISSION VIA AN INACTIVE GAP

Abstract The time delay for transmission of chemical waves via a geometrically asymmetric gap is studied based on the Rovinsky-Zhabotinsky model of the Belousov-Zhabotinsky reaction. It decreases with acidity and increases with the gap width. The time delay is assumed to be the sum of two components: the diffusion process within the gap and the reaction process at the receiving boundary. The latter accounts for the presence of the critical gap width above which no transmission occurs, and consequently, for switching of unidirectional transmission. An equation for the time delay is proposed as a function of the gap width.

Characterization of carbon cryogel microspheres as adsorbents for VOC.

Adsorption characteristics of carbon cryogel microspheres (CC microspheres) with controlled porous structure composed of mesopores (2 nm<d(p)<50 nm; d(p) is pore diameter) and micropores (d(p)<2 nm) were studied to examine their suitability as adsorbents for a volatile organic compound (VOC). The amount of toluene, as a model VOC, adsorbed on the CC microspheres could be changed by varying either the size of the mesopores or the volume of the micropores. The peak temperature of the temperature-programmed desorption profiles of toluene from the CC microspheres was higher than that from granular activated carbon (GAC) with numerous micropores, indicating that toluene is adsorbed more strongly on CC microspheres than on GAC. To permit the practical use of CC microspheres, the adsorption characteristic of moisture on CC microspheres and GAC were evaluated. The effect of adsorption of moisture on the gas permeation property of an adsorption module prepared from the CC microspheres was also examined.

Bromomalonic acid as a source of photochemically produced Br− ion in the Ru(bpy)32+-catalyzed Belousov-Zhabotinsky reaction

Abstract Experimental observation shows that bromomalonic acid (BrMA) is one of the sources of photo-induced Br− ion in the photosensitive Belousov-Zhabotinsky reaction. The rate of Br− production by visible light was measured using a Br−-ion-selective electrode in a solution containing BrMA, H2SO4 and Ru(bpy)3SO4 but no oxybromine species. The order of reaction was 1 for [BrMA] and [H+], and about 1 2 for the light intensity and [Ru(bpy)32+]. Two types of probable photocyclic mechanisms are proposed.

Enhancement effect of carbon adsorbent on ozonation of aqueous phenol

Removal of aqueous phenol was examined by the simultaneous use of ozone and porous carbon adsorbents possessing different porous structures and surface properties. The removal efficiency of aqueous phenol was higher with the simultaneous use of ozone and carbon adsorbents than the use of ozone alone, due to the adsorptive-concentration effect of the adsorbents. The enhancement effect of macroporous carbon cryogel beads (CCB) on the ozonation of aqueous phenol was confirmed to be greater than in microporous activated carbon beads. Introduction of acidic functional groups to CCB by liquid-phase oxidation significantly diminished the adsorptive-concentration effect of CCB, since the interaction of aqueous phenol with the surface of CCB decreased.

Chemical waves in mesoporous media

Abstract Chemical waves in the Belousov-Zhabotinsky (BZ) reaction were investigated in mesoporous glass (vycor 7930). Some characteristics such as wavelengths or pattern sizes, periods and velocities of chemical waves have been found in the glass systems. The velocity of the waves in the vycor glass (pore diameter ∼40 A, ca. 10 times larger than the reacting molecules) was about 1 3 of that in aqueous systems. A microscopic model for the wave propagation in mesoporous glass is presented. The reduced velocity of the chemical waves is explained in terms of the reaction and diffusion in a fractal-like network of narrow channels. Porous glass has been found to be a useful heterogeneous medium for studying chemical patterns under open conditions.

Effect of drying method on gas adsorption characteristics of carbon gel microspheres

Abstract The effect of drying method used in the preparation of carbon gel microspheres was studied by comparing the porous properties of carbon cryogel microspheres (CCM) and carbon xerogel microspheres (CXM), which were respectively obtained using freeze drying and hot air drying. CCM were found to possess higher mesoporosity than CXM because freeze drying was effective to suppress the shrinkage of the mesopores during drying. On the other hand, the microporosity of the carbon gel microspheres was hardly influenced by not only the drying method but also the synthesis condition. Although the amounts of nitrogen and oxygen adsorbed were almost the same, the adsorption rate of nitrogen on both CCM and CXM possessing ultramicroporous surfaces was much larger than that of oxygen, which indicated the applicability of the carbon gel microspheres to adsorbents for pressure swing adsorption (PSA) of air. The relations between the temperature and the amount of oxygen adsorbed showed the adsorption characteristics of CCM and CXM as adsorbents for temperature swing adsorption (TSA) were almost the same.