The object of this work is to investigate in detail the effects of ArF excimer laser irradiation for attaining selective and high quantum yields of methanol from a gaseous mixture of methane, O₂ and N₂O at moderate temperatures. It was found that the product distribution of oxygen-containing compounds, as well as that of hydrocarbons, varied significantly depending on the progress of the chain propagation steps subsequent to the reaction initiated by O(¹D) produced by laser photolysis of N₂O.
The experimental apparatus, as shown in Fig. 1, consisted of a pulsed laser, reaction cell, and gas chromatographs. A short ultraviolet laser pulse of the ArF excimer laser (50mJ/pulse, 193nm) was irradiated at 10Hz on the reactant gas mixture for 10min. The standard composition of the gas was kept at CH₄/N₂O=14/1 or CH₄/N₂O/O₂=14/1/3, where 50% of the laser light was absorbed almost exclusively by N₂O.
The initial elementary reaction induced by laser irradiation is considered to be the production of O(¹D) atoms by N₂O photolysis (Eq. (1)). Some of the O(¹D) radicals generated by the laser pulses react not only with CH₄ (Eqs. (2-1, 2, 3)) but also with N₂O to form N₂ and O₂, or NO (Eqs. (4-1, 2)) to a lesser extent.
With laser irradiation, the following products were obtained: carbon monoxide, carbon dioxide, ethane, propane, methanol, ethanol, and small amounts of other oxygenates such as dimethyl ether, acetaldehyde, and methyl formate. In the absence of O₂ (Table 1), the selectivity for ethane, formed by recombination of methyl radicals, is very high, while selectivities for CO and CO₂ are rather low. Taking into account the facts that (CH₃OH)^* produced by insertion of O(¹D) into the C-H bond of methane cannot be stabilized under the low pressure conditions employed (Table 3), and that the rate of reaction of methyl radicals with N₂O to form methoxy radicals (Eq. (6)) is relatively slow (Table 4); the formation of oxygen compounds such as CO, CO₂, and methanol may be attributed either to the reaction of methyl radical with O₂ formed in Eq. (4-1), or to the recombination of methyl and hydroxyl radicals.
In contrast, in the presence of O₂ (Table 2), selectivities for CO and CO₂ are relatively high, and the yields of methanol are also higher. Effects of the partial pressure of O₂ are shown in Table 3, in which it is obvious that when the partial pressure of O₂ is greater than 30 Torr, no significant change in the product selectivity takes place. Fig. 2 represents the temperature dependence of the ratio of methane consumption to N₂O consumption as a measure of the chain length. The ratio is much larger in the presence than in the absence of O₂, and it increases with increasing reaction temperature, suggesting that the chain reaction involves elementary reactions with somewhat high activation energy.
Based on these experimental results, our proposed reaction schemes in the absence of O₂ and in the presence of O₂ are shown in Figs. 4 and 5, respectively. Simulation based on these reaction schemes gives a product distribution in good agreement with the experimental results as shown in Table 5, although there are some discrepancies in terms of the temperature dependence of methanol selectivity. This is possibly due to the secondary reactions of methanol induced by absorption of the laser light to form mainly CO, as suggested by the results in Tables 6 and 7.

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In order to test the applicability of the supercritical fluid extraction technique to the separation of impurities in polymers, separation of benzene from two polymers of poly(vinyl acetate) and polystyrene was carried out using supercritical carbon dioxide.
Figure 1 shows a schematic diagram of the supercritical fluid extraction apparatus. It consists of the following sections: (1) compression of carbon dioxide, (2) extraction, and (3) control and measurement of carbon dioxide flow rates. A sample polymer disk of known dimensions which had dissolved a known quantity of benzene, was placed in the extraction cell. The concentration of benzene in the sample polymer before and after extraction was determined using a gas chromatograph. Table 1 gives the conditions used in the experiments.
Vacuum stripping (a conventional separation method) was performed along with the supercritical fluid extraction method for the benzene+poly(vinyl acetate) system. It appeared that the supercritical fluid extraction method was able at near room temperature to remove benzene more rapidly and to lower concentrations than vacuum stripping, as shown in Figures 2 and 3.
The flow rate of carbon dioxide had but slight influence, under the conditions used, on the experimental results. Hence, if the mass transfer resistance of benzene is separated into two parts, i.e., one in polymer phase and the other in the supercritical carbon dioxide phase, it is evident that the mass transfer of benzene is controlled by the polymer phase (Figs. 4, 5).
Extraction experiments were carried out varying initial concentration of benzene in poly(vinyl acetate); the results seemed but little affected by varying the initial concentration (Fig. 6).
Extraction experiments were also carried out with samples of different thicknesses in the poly(vinyl acetate) system. After 55 minutes the yield of extraction increased up to 99.8% at 313K and 7.95MPa when the sample thickness was 0.5mm. However, the yield decreased with increasing sample thickness (Figs. 7, 8).
The experimental results after 1h at temperature range of 300-373K and pressures of 7.95MPa and 14.8MPa are shown in Figure 9. The rate of extraction of poly(vinyl acetate) system was much greater than that of the polystyrene system. As for the effect of pressure, extraction at 14.8MPa could be performed with a greater rate than at 7.95MPa; on the other hand, the effect of temperature seemed rather complex. Yields of extraction of the poly(vinyl acetate) system at 7.95MPa and 14.8MPa increased with increasing temperature. The experimental results of the polystyrene system at 14.8MPa showed a tendency similar to that of the poly(vinyl acetate) system. However, the experimental results of the polystyrene system exhibited a minimum at 343K and at 7.95MPa.
The diffusion coefficient of benzene in polymers in the presence of supercritical carbon dioxide was evaluated from the experimental data by using a simple mass transfer model (Figs. 10, 12). The calculated diffusion coefficient of benzene in poly(vinyl acetate) was found to be about midway between the value in supercritical carbon dioxide and that in poly(vinyl acetate) in the absence of supercritical carbon dioxide (Fig. 11). The calculated diffusion coefficient was more than 6 orders larger than that in poly(vinyl acetate) in the absence of supercritical carbon dioxide. This was the consequence of dissolution of supercritical carbon dioxide into the polymer.

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In order to investigate the effect of the polarity of a supercritical fluid on the solubility of C₅-hydrocarbons, isothermal high pressure vapor-liquid equilibria for three binary systems(CHF₃-n-pentane, CHF₃-isopentane and CHF₃-isoprene) and a ternary system (CHF₃-isoprene-n-pentane) were measured at 310K and 343K by using a static type of apparatus. On the basis of the data measured in this work and reported in the literature, it was found that (1) the Peng-Robinson equation of state satisfactorily correlated the binary systems except near the critical region, but deviations for the ternary system were larger than those for the binary systems; (2) the intermolecular force between a polar supercritical fluid such as CHF₃ and a slightly polar solute such as isoprene was not strong enough to extract the solute selectively from the mixture of hydrocarbons having the same carbon number; and (3) supercritical fluids of high critical temperatures and having a chemical structure similar to that of solute exhibited greater solvent power.

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Coal-tar was found to be an effective additive for COM (coal oil mixtures) prepared from four coals (Miike-coal, Taiheiyo-coal, Saxonvale-coal, Wallarah-coal) listed in Table 1. Various COMs using coal-tar (as an additive) were prepared in a similar manner to that described in our previous paper3) (Table 2). In order to investigate the stabilization effect of coal-tar, rod penetration test, coal content test, and viscosity test were carried out.1), 3)
Table 3 summarizes the experimental results on the stability of COMs. In the absence of any additive, no stable COM was obtained. When 1-2% coal-tar was added to the COM containing 50% coal, the rod penetration ratio became 100% after 15 day storage, the rod penetration time was satisfactorily short, and the difference in the coal contents at top and bottom layers (C.D.) was small; thus, satisfactory preparation of a stable COM was realized. The COM-viscosity somewhat increased with increasing amount of additive. COMs containing 1-2% coal-tar additive had sufficiently low viscosity to be of practical use. Highly coal-loaded COMs (up to 55%) were adequately stabilized by addition of coal-tar, though their COM-viscosity increased considerably.
Figure 1 shows the changes in COM-viscosity over 25 day storage; it increased rapidly-by 0.6-1.0Pa•s-during the initial few days' storage, then it became almost constant thereafter. The rapid increase in the COM-viscosity is ascribed to the formation of a network-stabilization structure (flocculate)6) at early stage of storage.
From i.r. analysis of coal-tar in the COM oil phase, its distribution in COM was investigated. As shown in Fig. 2, about 85% of the coal-tar added in the COM was adsorbed on the coal particles during one day storage.
In order to investigate the effective chemical species within the coal-tar component responsible for the stabilization of COM, we tried to prepare COMs by addition of a variety of fractionate-oils of the coal-tar (Table 4). Creosote-oil was superior to the other fractionate-oils (carbol-oil, naphthalene-oil, anthraceneoil), since it exhibited a higher degree of aromatic ring condensation and had higher contents of hetero-atoms. These results suggest that stabilization of the COM using coal-tar (as an additive) is due to the effect of polycyclic aromatics possessing hetero-atom functional groups which are adsorbed on the coal surface.

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The rate of dehydrogenation of cumene over Fe₂O₃-Cr₂O₃-K₂CO₃ catalyst to derive α-methylstyrene has been studied. The reaction rate has been interpreted on the basis of a reaction model taking account of competitive adsorption of cumene, α-methylstyrene, styrene and CO₂. The kinetic parameters were compared with those of dehydrogenation of ethylbenzene. The dehydrogenation of cumene proceeded more rapidly than that of ethylbenzene because the effect of product retardation was less serious.

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A new modification for the three-parameter pseudo-cubic equation of state is proposed to improve the accuracy on the performance of the saturated properties of polar substances. All temperature coefficients of the parameters in the equation of state are correlated with the acentric factor and reduced dipole moment. To better improve the accuracy on the performance of vapor pressures, the individual values of one particular coefficient among the others are recommended. The equation of state modified in the present study is applicable not only to polar substances but also to nonpolar components. The present equation of state completely satisfies the critical point requirements.

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Ca²⁺ ions loaded on MgO surface markedly promoted catalytic activities of MgO for isomerization of 1-butene, hydrocarbon gasification with CO₂ or O₂, and the reverse water-gas shift reaction, although MgO itself was almost inactive after treatment at 1273K in air. Ca²⁺ ions also increased the basicity and basic strength of MgO. Strong basic sites catalyzed isomerization of 1-butene. In the course of impregnation with Ca(NO₃)₂, MgO (periclase) was completely transformed into hydrate (brucite) by the action of nitrate ions. It is considered that Ca²⁺ ions interfere with the transformation of surface arrangements accompanied with structural transformation from brucite (hcp) to periclase (fcc). It was found that most of Ca²⁺ ions aggregated to form particles of CaO on the surface of MgO while Ca²⁺ ions were highly dispersed on the surface of MgO when the MgO was prepared from basic carbonate salt involving calcium as an impurity.

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