Shimio Sato

Control of pore size distribution of silica gel through sol-gel process using water soluble polymers as additives

To control the pore size distribution of silica gel, several kinds of water soluble polymers were added in the sol-gel process starting from tetraethyl orthosilicate. The polymers employed here were classified into three groups. The first group comprised uncharged polymers such as polyvinyl alcohol and polyethylene glycol, which affected only the amount of micropores and small mesopores (<20 nm). The second group comprised charged polymers (polyelectrolyte) such as polyacrylic acid (anionic) and a quaternary salt of polyethylene imine (cationic), which significantly increased the number of larger mesopores (>20nm). The third group comprised proteins such as lipase and albumin and decreased the number of micropore and mesopores and greatly increased the number of macropores. The results could almost be explained in terms of the principal effects of the polymers on a process of sol particle growth.

Control of pore size distribution of silica gel through sol-gel process using inorganic salts and surfactants as additives

For control of the pore size distribution of silica gel, the gel was prepared using the sol-gel process modified by adding several kinds of inorganic salts and surfactants. The addition of any inorganic salt decreased the gel surface area and depressed the formation of mesopores. The surface area and the volume occupied by mesopores changed with the valency of the cation of the salt used. When surfactants were employed as additives, the surface area and the pore size distribution were greatly dependent on the kind of head group of the surfactant: non-ionic surfactant addition monotonously increased the surface area owing to the formation of larger mesopores; anionic surfactant addition significantly decreased the surface area because of the decrease in the volume of mesopores; cationic surfactants caused the surface area to decrease with small additions as anionic surfactants did, while further addition raised the surface area. The rise in the surface area was due to a marked formation of smaller mesopores. These results are discussed on the basis of the interfacial properties of the additives.

Solvent effect on thermal degradation of polystyrene and poly-α-methylstyrene

Abstract Polystyrene (PS) and poly-α-methylstyrene (PMS) in various kinds of solvents such as 1-methylnaphthalene, tetralin and phenol were thermally degraded in the temperature range from 250 to 450°C. The conversion of PS to low molecular weight products depended on the kinds of solvents and the polymer concentration, whereas the conversion of PMS was independent of both of these. The difference in degradation behaviour between the polymers was explained in terms of a mechanism which involves hydrogen transfer steps from solvents to intermediate polymer radicals.

Hydrothermal synthesis of fine perovskite PbTiO3 powders with a simple mode of size distribution

Perovskite phase PbTiO3 powders were hydrothermally synthesized so as to be fine and homogeneous in physico-chemical properties. Such powders are currently used in the fabrication of electronic ceramic components. The powders were successfully synthesized using a strong alkali as catalyst. Borderline synthesizing conditions, such as temperature and time, were established and their effects on geometrical properties, like mean particle size were determined. Polyacrylamide as an additive was found to be effective for the synthesis of the powders with a simple mode of particle-size distribution.

Effect of solvent on thermal degradation of poly (p-methylstyrene)

Abstract The thermal degradation of poly(p-methylstyrene) (P-pMS) was studied in several solvents, such as 1-methylnaphthalene, tetralin and phenol, in the temperature range 300–400°C. No undesirable by-products, such as gels and cross-linked high molecular weight products, were formed, in contrast to the significant yield of these products with conventional polymer pyrolyses without solvents. The conversion of P-pMS to low molecular weight products, and the molecular weight of the residual polymer after pyrolysis, depended markedly on the kind of solvent used. Such degradation behaviour is explained well by a proposed mechanism including hydrogen transfer from solvents to intermediate polymer radicals.

Activity enhancement of iron ores as a catalyst for direct coal liquefaction

Abstract Several ion ores for possible use as disposable catalysts for direct coal liquefaction were pretreated to enhance their catalytic activity. The pretreatment consisted of immersion in boiling water for 3 h or calcination for 1 h at around 500 °C. This broght about a 10% increase in oil yields compared with the use of non-pretreated ores and also brought about a slight improvement in overall coal conversion. The pretreatment resulted in significant changes in the specific surface area and pore volume distribution of the ores. These changes attributed to pores having radii greater than 5 nm correlated well with oil yields.

Coal liquefaction using indene-tetralin and indene-decalin mixtures as solvent

Abstract Indene-tetralin and indene-decalin mixtures were used as the solvent for coal liquefaction. The effect of mixing on conversion for Yallourn coal was observed under nitrogen pressure at 400 and 440 °C. Conversion to benzene-soluble material in an indene-decalin mixture (50:50, wt) at 440 °C for 1 h was 73.0% and was only 9% lower than that in 100% tetralin. The reaction of indene with tetralin or decalin may provide the active species for coal dissolution. Simultaneously, coal radicals may be scavenged by indene.

Selective pyrolysis of polystyrene to that with a desired low polymeric degree

To obtain low polymeric polystyrene (PS), pyrolysis of high polymeric PS in solution was studied in the temperature range from 290 to 400°C by using additives or acid catalysts. The low polymeric PS targeted here was that with average molecular weight of 104. When the feed PS was pyrolyzed in tetralin by adding sulfur or diphenyl disulfide, the molecular weight of PS decreased greatly, even at lower temperatures, and the desired low polymeric PS was formed in a relatively large amount at the temperatures below 350°C. The degradation behavior was able to be explained in terms of a random polymer chain scission mechanism initiated by sulfur radicals formed from the additives.

CATALYTIC ACTIVITIES AND THEIR ENHANCEMENTS OF IRON ORES IN DIRECT LIQUEFACTION OF COAL

Publisher Summary This chapter discusses a study to determine how iron ores mixed with sulfur are active for the direct coal liquefaction as a disposable catalyst and how they can become more active. Taiheiyo coal (Japan), Minamiohyubari coal (Japan), and Bukit Asam coal (Indonesia) were used. The liquefaction was carried out with a 300 ml shaking autoclave under the liquefaction condition of 20.3 MPa at 420°C and nominal liquefaction times (NRT) from 0–60 min. To elucidate the catalytic role of ores during coal liquefaction, coal hydrogenation in the presence of ores was analyzed with high pressure differential thermography (HPDT) and then ores after the reaction were characterized with X-ray diffraction spectrometry (XDP). To find a simple method for enhancing the catalytic activity of the ores, some pretreatments of ores were carried out. Most of the iron ores mixed with sulfur were as active as red mud mixed with sulfur, which has been regarded as a typical disposable catalyst for the liquefaction, and they gave the liquefaction products rich in oils.

Non-Isothermal Analysis of Hydrogenation Rate of Coal

Many investigations of coal hydrogenation have heen carried out with batch autoclaves operated under non-isothermal conditions. Kinetics of the reaction, however, has been analyzed in a way similar to that for isothermal reaction.1) This report points out that there are some cases where such analysis can not give us correct values of rate constants.2) Therefore, theexperimental rgsults of the hydrogenation with batch autoclaves must be regarded as non-isothermal data, and should be analyzed as such. An analytical method, which can treat non-isothermal data, is proposed. Results so far studied by the conventional way were analyzed by the new one to obtain the values of the kinetic parameters in rate equations. Simulation of the reaction by these values gave good agreement with the experimental results.3) Reaction characteristics under the experimental condition in the reports discussed can be explained by the following mechanism: (1) Coal1→Oil (2) Coal2→Asphaltene→Oil. Thus far it has been unknown what kind of component in starting coal would contribute to the individual reactions. According to the analyzed results obtained here, the former and the latter reactions seem to correspond mainly to the oil formations from volatile matter and fixed carbon components, respectively.