Akinori Yasutake

Removal of SOx and NOx over activated carbon fibers

Abstract The recent development of de-SOx and de-NOx using activated carbon fibers (ACF) in Japan is introduced in this review comparing it with the conventional commercialized system. Pitch-based ACFs showed higher de-SOx activity than other ACFs from different precursors. De-SOx activity can be further modified by the heat-treatment, continuous and complete removal of SOx. ACF is also effective for removing NOx in the presence of NH4. The mechanisms of de-SOx and de-NOx on the surface of ACFs are proposed and discussed. Based on fundamental research results de-SOx, de-NOx and their combined processes are designed and proposed.

Technology for removing carbon dioxide from power plant flue gas by the physical adsorption method

Abstract Research into technology for removal of CO 2 considered to be the major cause of global warming, was applied to electric power plant flue gas. Our method was to use zeolite as adsorbent for physical adsorption, progressing from the previously used PSA (Pressure Swing Adsorption) method to the more advanced PTSA (Pressure and Temperature Swing Adsorption) method. We have been conducting basic research since the 1980s, and in 1991 built a 1000m 3 N/h scale pilot plant, where we are continuing research through trial operation. Trial operation of the pilot plant has been mainly for acquisition of scale up data, as well as improvement in the decrease in the power consumption of PTSA units. As a result, we have seen a better than 20% improvement in that area. In addition, the pilot plant completed 2000 hours of continuous operation without incident between October and December, 1994. The total hours of operation of the plant have topped 4000 hours, but we have seen no decrease in the effectiveness of the CO 2 adsorbent. The SOx in the flue gas was trapped in the lower part of desiccant in PSA-H 2 O before the process. Some of desiccant reacts to that, but we have prevented any ill effects on the process that might be caused by main units. At this point we would like to report on the results of our research, as well as outline our plants for the future.

Rapid Room Temperature Synthesis of Hexagonal Mesoporous Silica Using Inorganic Silicate Sources and Cationic Surfactants under Highly Acidic Conditions

The room-temperature synthesis of mesoporous silica was investigated by using cationic surfactants and inorganic Si sources, like sodium silicate and colloidal silica. Mesoporous silica analogous to the hexagonal MCM-41 could be obtained over a wide range of pH below ca. 11 within short synthesis time (3 h), when the Q4-state Si was absent in the Si source solution prior to mixing with an aqueous solution of cationic surfactants. It was suggested that the strongly acidic conditions (pH < 1) were favorable to give mesoporous silica materials with higher surface area and larger mesopore volume.

Synthesis and characterization of tin oxide-modified mesoporous silica by the repeated post-grafting of tin chloride

Abstract Modification of mesoporous silica with tin oxide was investigated by the repeated post-grafting method, which consisted of the repetition of the cycle of hydroxylation of the surface, grafting of tin(IV) chloride through the reaction with surface hydroxyl groups and calcination in air. The singly SnO2-modified material showed extremely high thermal stability up to 950°C as well as the stability against the treatment in basic solution (pH=10). With increasing the number of cycles, XRD peak intensity characteristic to the hexagonal mesophase decreased gradually, but the mesoporous structure was maintained up to the third modification. The optical absorption due to tin oxide was emerged by the modification and its absorbance increased with an increase in the modification cycles. The repeated modification with tin oxide caused progressive decreases in specific surface area, mesopore volume and diameter, while no significant change of the hexagonal cell parameter was observed. It was suggested from the enhanced stabilities and the pore-structure change that inner wall and outer surfaces of the mesoporous silica was progressively coated with the tin oxide layer.

Adsorption of sulfur dioxide on Y-type zeolites

The adsorption of SO2 on Y-type zeolites exchanged with H+, alkali (A+) and alkali earth (AE2+) metal cations has been studied. Y-type zeolites adsorbed more amount of SO2 than MFI and mordenite zeolites as well as SiO2 due to the larger pore volume. The SO2 adsorption is likely to be physical, because the isosteric heat of adsorption on NaY was estimated to be about 32 kJ·mol−1. The adsorption of SO2 on HY was reversible at 298 K, while the strongly adsorbed species, which did not desorb by evacuation, was observed on A- and AE-Y. The adsorption capacity, the affinity of SO2 with zeolites and the apparent diffusion coefficient of SO2 molecules in zeolite channels depended almost exclusively on the type of exchanged ions as H-Y

Improvement of Tribological Properties of C/C Composites at High Temperatures

Tribological properties of carbon/carbon (C/C) composites at high temperatures were investigated. Dry friction tests of C/C composites up to 1000° C were performed to evaluate the effects of the temperature relating to the evaporation of adsorbed water vapor and oxidation of carbon on the friction and wear properties. Observations of sliding surfaces which compared their friction and wear properties, were also made. The friction and wear of C/C composites sliding against themselves increased suddenly at about 200°C, at which temperature the adsorbed water vapor is released. Although the sliding surface at 25° C was flat and smooth, that of 200°C was rough and covered with wear particles. The transition temperature increased with the incorporation of high-carbon-number hydrocarbons and further increased with water-soluble inorganic compounds with a high melting point. The friction and wear of oxide-incorporated C/C composites with the high adsorbing capacity of water vapor was low and stable at all tempera...

Molecular sieve effect of chemically modified Na-A type zeolite and its molecular dynamic simulation

Summary In this study, the precise window shrinkage of Na-A type zeolite (Na-A) in the order of 0.1by calcination after rehydration, a partial K exchange and low temperature adsorption was evaluated[1],[2],[3]. It was understood that the precise window shrinkage of thermally and chemically modified Na-A was related to the behavior of Na located in the center of 8 oxygen members ring. Following the adsorption evaluation of oxygen selectivity based on an oxygen/nitrogen binary system and CO2 selectivity based on CO2/nitrogen binary system, a more precise relationship between the window shrinkage and the behavior of Na located at the center of 8 oxygen members ring was studied with an MAS-NMR, a single crystal X-ray diffraction (SCXD) and a molecular dynamic simulation (MD).

An Evaluation of Advanced Material Modified with Amine for Environmental Control Systems

Energy saving and miniaturization of equipment are important subjects in Space. Therefore, development of a new adsorbent which is able to adsorb CO2 in the presence of water vapor and eliminate the dehumidification process is required. We report on the application possibility of TA/MSU-H in space.