Katsuhiko Muroyama

Preparation of activated carbon from lignin by chemical activation

Activated carbons were prepared from lignin by chemical activation with ZnCl2, H3PO4 and some alkali metal compounds. The influence of carbonization and activating reagent on the pore structure of the activated carbon was investigated. It was found that the maximum surface areas were obtained at the carbonization temperature of 600°C in both ZnCl2 and H3PO4 activation, and that the surface areas were as large as those of the commercial activated carbons. On the other hand, in alkali metal activation it was found that the maximum surface areas were obtained at the carbonization temperature of 800°C. Except for Na2CO3 maximum surface areas were much larger than those of the commercial activated carbons. The activated carbon prepared by K2CO3 activation showed a surface area of nearly 2000 m2/g. It was shown that ZnCl2 works effectively as dehydration reagent below 600°C. On the other hand, K2CO3 works effectively in two temperature ranges, below 500°C and above 600°C. Below 500°C, the carbonization behavior was modified by impregnation with K2CO3, but the pore structure changes little. Above 600°C, carbon was consumed by K2CO3 reduction and then the surface area was increased.

Preparing activated carbon from various nutshells by chemical activation with K2CO3

We have prepared activated carbons by chemical activation with K2CO3 from five kinds of nutshells: almond shell (AM), coconut shell (CN), oil palm shell (OP), pistachio shell (PT) and walnut shell (WN). When prepared at 1073 K, the activated carbons from all the nutshells had the maximum specific surface areas. According to the maximum values of specific surface areas, the activated carbons prepared were classified into two groups: Group-L and Group-S; the former group included activated carbons with high specific surface area and the latter included those with lower specific surface area, respectively. It was found that K2CO3 effectively worked as an activation reagent, but differently in the temperature ranges below 800 and above 900 K. Due to impregnation, cellulose and hemi-cellulose were modified by K2CO3 and accordingly the weight loss behaviors of the nutshells were changed in the temperature range below 800 K. In the temperature range above 900 K, carbon in the chars was removed as CO gas by the reduction of K2CO3 to increase the specific surface area and the pore volume. It was deduced that the difference between the specific surface areas of Group-L and those of Group-S correspond to the difference between weight loss behaviors in the temperature range above 900 K.

Activated carbon from chickpea husk by chemical activation with K2CO3: preparation and characterization

Activated carbon was prepared from chickpea husk by chemical activation with K2CO3. At 1073 K, the specific surface area of activated carbon prepared with an impregnation ratio of 1.0 yielded the maximum value of 1778 m2/g. From the results of the yield of the activated carbon and the reagent recovery ratio, it was concluded that the carbon involved in the husk char was removed as CO by reduction of K2CO3 above 1000 K. The fractal dimension changed slightly between 773 and 973 K, and it decreased rapidly between 973 and 1173 K. It was deduced that this decrease of the fractal dimension was due to the decomposition of the cross-linked structure and the small crystallite structure. The micropore volume and the specific surface area increased by the release of plugged pore due to the decomposition of the cross-linked structure. It was further deduced that the mesopore volume increased and the micropore volume decreased by combination of micropores due to the decomposition of small crystallites.

Synthesizing activated carbons from resins by chemical activation with K2CO3

We prepared activated carbons from phenol–formaldehyde (PF) and urea–formaldehyde (UF) resins by chemical activation with K2CO3 with impregnation during the synthesis of the resins. The influence of carbonization temperature (773–1173 K) on the pore structure (specific surface area and pore volume) and the temperature range at which K2CO3 worked effectively as an activation reagent, were investigated. The specific surface area and micropore volume of PF–AC and UF–AC increased with an increase of carbonization temperature in the range of 773–1173 K. We prepared activated carbon with well-developed micropores from PF, and activated carbon with high specific surface area (>3000 m2/g) and large meso-pore volume from UF. We deduced the activation mechanism with thermogravimetry and X-ray diffraction. In preparing activated carbon from PF, K2CO3 was reduced by carbon in the PF char. The carbon was removed as CO gas resulting in increased specific surface area and pore volume above 1000 K. In preparing AC from UF, above 900 K the carbon in UF char was consumed during the K2CO3 reduction step.

Fractal dimensions of activated carbons prepared from lignin by chemical activation

the form of adsorbents, catalysts and catalyst supports. In was mixed with one of the activating reagent and water,principle, there are two methods for preparing activated and was kneaded. An impregnation ratio [(the weight ofcarbons: physical activation and chemical activation. The activating reagent)/(the weight of lignin)] of 1.0 was usedphysical activation method comprises two steps: a carboni- in this work. The mixture was then dried at 383 K tozation step and an activation step. In chemical activation, a prepare the impregnated sample. The impregnated sampleraw material is impregnated with an activating reagent and was heated up to the carbonization temperature under N

Preparation and characterization of the carbonized material of phenol–formaldehyde resin with addition of various organic substances

Abstract We prepared carbonized materials of phenol–formaldehyde resins (PF) synthesized with the addition of organic substances such as ethylene glycol (EG), 1,6-hexanediol (1,6HD), polyethylene glycol (PEG), etc. We investigated the influence of the carbonization temperature, the organic additive species, and the additive ratio in synthesizing the PF resins on the pore structure of the carbonized PFs. Variation in the length of the added organic substance caused differences in the pore sizes of the carbonized PFs; when the length was short, the pore size of the carbonized PF became gradually smaller with increasing carbonization temperature, but when the length was long, the pore size gradually increased with increasing carbonization temperature. The difference in the additive organic species gave different pore sizes in the carbonized PFs such that the longer the length of the organic additive the greater the pore size in the carbonized PF. The additive ratio of EG did not give a large change in the pore size of the carbonized PF, but the variance in the average pore sizes were sharper than that of the carbonized PF without any additives. On the other hand, the pore sizes of the carbonized PFs with a high additive ratio of PEG20K were greater, and the carbonized PFs had mesopores. The BET surface area of the carbonized PFs with a 50% additive ratio of PEG20K was about 500 m2/g.

Hydrodynamics and computer simulation of an ozone oxidation reactor for treating drinking water

Numerical calculations were conducted to analyze the ozone absorption behavior and removal of odorous materials in the U-Tube® reactor, which is a bubble column fitted with a concentric down-flow diffuser. A novel calculation model was developed to simulate the reactor by assuming that it is composed of a plug flow section (inner tube) followed by a tanks-in-series section (outer bubble column). The bubble size distribution and gas holdup were measured in the downflow diffuser to obtain correlations for the gas holdup and the Sauter mean bubble diameter. It is found that the ozone absorption efficiency increases with decreasing gas/liquid ratio but is almost independent of the gas-phase ozone concentration. It is also found that the removal efficiency of odorous compounds (2-methylisoborneol (2-MIB)) significantly increases with both increasing gas-phase ozone concentration and gas/liquid ratio. In order to achieve a high 2-MIB removal efficiency a ozone loading value (=gas-phase ozone conc. x gas/liquid ratio) greater than 0.003 kg/m 3 is required. The numerical calculation well explains the experimental data on the ozone absorption efficiency and the 2-MIB removal efficiency of a pilot plant, showing usefulness of the simulation model proposed.

Mass transfer from an immersed cylinder in three-phase systems with fine suspended particles

The film mass transfer coefficient k W was measured on the surface of a cylindrical electrode immersed vertically in three-phase systems with fine suspended particles with an average diameter ranging from 0.10 to 1.1 mm. A 50 to 75% enhancement in the values of k W in the three-phase systems suspended with fine particles was observed in comparison with those in the beds with coarser particles otherwise operated under similar hydrodynamic conditions. This enhancement was due to erosion of liquid film caused by penetration of particles into the mass transfer film. The values of the mass transfer coefficient were correlated well by a unified dimensionless equation in terms of the energy dissipation rate per unit mass of liquid to cover the liquid-solid and gas-liquid-solid fluidized systems.

Preparation of Activated Carbon with High Specific Surface Area from Beer Lees by Chemical Activation with KOH.

ビール粕を原料とし, 賦活剤に水酸化カリウムを用いた薬品賦活法による高比表面積活性炭の製造を試みた. そして, 製造条件が細孔構造に及ぼす影響について検討した. また, ベンゼン, アセトンの吸着性能についても検討した.比表面積は800℃まで炭化・賦活温度の上昇とともに増加し, 900℃では過度の賦活のために減少した. また, 含浸率は2.0で比表面積は最大となった. 含浸率2.0, 炭化・賦活温度800℃の製造条件で, 2, 440mm2/gという高比表面積を有する活性炭を製造することができた.また, 活性炭の炭化・賦活過程で水酸化カリウムは500℃までと600℃を越えてからの2段階で賦活剤として有効に作用することが明らかとなった.得られた活性炭に対するベンゼン, アセトンの吸着量は, 市販の活性炭に対する吸着量を大きく上回ることがわかった.

Preparation of mesoporous material having a hydrophobic surface by combining silica xerogel with resin using sol-gel method

Abstract We tried to prepare a mesoporous material with a hydrophobic surface by combining the silica xerogel with the phenol–formaldehyde resin using the sol–gel method. During the procedure, the formation of the silica xerogel and the formation of phenol–formaldehyde resin simultaneously occurred in the liquid phase. Then, the pore structure of the xerogel was different from the simple mixture of silica xerogel and phenol–formaldehyde resin. It is found that the pore size can be tailored by changing the phenol–formaldehyde resin ratio.