Studies of solid base catalysis performed in our group are summarized. Strongly basic sites for most solid base catalysts are generated by removal of water and carbon dioxide by pretreatment at high temperatures from the surfaces. The nature of the surface basic sites varies with the severity of the pretreatment conditions. Rearrangement of surface and bulk atoms occurs, in addition to the removal of water and carbon dioxide, during the pretreatment. The optimum pretreatment temperature varies with the type of reaction. Characterization of basic sites by the indicator method, TPD of CO₂, O exchange between adsorbed CO₂ and MgO surface, NMR of ¹³³Cs and ¹⁹F are described. The catalytic behaviors of solid base catalysts are described for the following reactions; (1) double bond migration, (2) hydrogenation, (3) amination, (4) aldol addition, (5) nitroaldol reaction, (6) Michael addition, (7) conjugate addition of alcohol, (8) cyanoethylation, (9) transesterification of ethyl acetate and alcoholysis of propylene oxide, and (10) the Tishchenko reaction. The strength of basic sites relevant to different reactions is discussed based on the activity order among alkaline earth oxides, and the optimum pretreatment temperatures of MgO for different reactions. Reactions with hydrocarbons need strongly basic sites, whereas reactions with compounds containing functional groups proceed even on weakly basic sites. Finally, important issues to be investigated for the development of solid base catalysis are pointed out.

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Styrene were extracted from mixtures of styrene and ethylbenzene using Cu(NO₃)₂ methanol solutions and metallic copper as extraction reagents. Extraction rates and extraction equilibria were measured. For the extraction experiments, oxygen dissolved in the methanol solution had to be removed. The effects on extraction ratios of ionic strength, mole fraction of water in the methanol solutions and the mole fraction of styrene in the feed oil phases were investigated. ¹³C NMR analysis showed the chemical shift caused by the complex formation between copper(I) ion and the vinyl group of styrene. Slope analysis suggested a styrene to copper(I) ion ratio of 1 : 1 in the complex.

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The formation of internal cracks in asphalt mixtures in the wheel tracking test at high temperature was investigated in dense graded (13F) and drainage asphalt mixtures prepared outside. Such cracks are caused by movement of aggregates in asphalt mixtures with distance separation in the crossing direction under passes of the testing wheel.
The movement of aggregates during the wheel tracking test (1 h, 2500 passes) at 0 passes, 600 passes, 1900 passes and 2500 passes was analyzed by photography. Greater deformation of aggregates in asphalt mixtures occurred at 50-60 mm from both tire ends in the case of dense graded asphalt mixture (13F) and at both tire ends in the case of drainage asphalt mixture. Local strain in those areas exceeded the maximum failure strain of the mixtures in the tensile test. Internal cracking may occur under passes of the wheel at high temperature, and cracks may appear in the surface with time, which has not been considered until now.

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The most efficient process and conditions for the preparation of mesophase pitch and carbon fiber from decant oil were examined. Mesophase pitch yield was extremely low (4.6%) when prepared directly by one step. A preparation method combining heat-treatment under pressure and heating under nitrogen flow improved the mesophase pitch yield to 19.0%. The optimum raw material was aromatic rich decant oil with a density of 1.05 g/cm³ or more. The pressurizing heat-treatment temperature of the first step was optimum at about 400°C based on reaction time and solid carbonaceous formation. Carbon fiber thinner than 10 μm could be spun from mesophase pitch with lower content of quinoline-insoluble material. Carbon fiber spun from mesophase pitch with higher quinoline-insoluble content showed higher Young's modulus and tensile strength. Stabilization in air with 2% NO₂ improved the tensile strength.

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Water was added to extend the continuous run of the atmospheric residue hydrotreatment process in bench plant and autoclave tests for improvement of catalyst life. Addition of water increased the catalytic activities for both hydrodesulfurization (HDS) and hydrodemetallization, and suppressed catalyst deactivation by reducing coke deposition on the catalyst surface. The effects disappeared after water addition was stopped resulting in increased coke formation. The remarkable effects of water addition were observed with both new and spent catalysts, but the amounts of deposited metals and coke were different. Effects of water addition are considered as follows. The addition of water is considered to accelerate the desorption of asphaltene in the feed and coke precursor produced during the reaction on the catalyst surface to extend the catalyst life. Water addition also increases the catalytic activity by accelerating the cycle of asphaltene adsorption and product desorption, resulting in increased catalytic turnover of HDS reactions on the active sites. The stripping roles of water are considered to reflect the high dissolving activity of high temperature, high pressure steam under HDS conditions.

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A series of Ni-Mo-P/Al₂O₃ catalysts with phosphorus added by different methods were prepared. The hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was carried out using the catalysts. The catalysts were also characterized using magic angle spinning nuclear magnetic resonance (MAS NMR).
The hydrodesulfurization activities of phosphorized catalysts were changed from that of NiMo/Al₂O₃ catalyst. Furthermore, the method for phosphorus addition affected their hydrodesulfurization activities. However, the activation energy and product selectivity for the hydrodesulfurization of 4,6-DMDBT were almost the same for all catalysts. It was indicated that the phosphorus content and the addition method did not change the mechanism of hydrodesulfurization of 4,6-DMDBT.
MAS NMR showed that the phosphorus addition method affected the dispersion of phosphorus on alumina. Catalyst with higher dispersion of phosphorus on alumina showed higher activity for hydrodesulfurization. Phosphorus addition may affect the structure of the molybdenum cluster and the degree of sulfidation of active metal.

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Hydrodesulfurization (HDS) of atmospheric residue (AR) over Ni-Co-Mo catalysts supported on γ-alumina was carried out to examine the effect of alumina pore size on HDS activity, hydrodemetallization (HDM) activity and initial catalyst deactivation under deep hydrodesulfurization conditions.
HDM activity slightly increased with alumina pore size, but HDS activity decreased due to the decrease in the surface area of the support. Deactivation of the HDS catalyst was greater on large pore size supports than on medium pore size supports. The combination of HDS catalyst with large pore size supports (40%) and medium pore size supports (60%) did not improve the catalyst life. HDS was carried out with the large pore size support catalyst at the upstream side in the first reactor and the medium pore size support catalyst at the upstream side in another reactor. Catalyst deactivation was greater in the former than in the latter reactor. These results suggest that HDS catalyst supported on alumina with medium pore size has a higher performance than HDS catalyst supported on alumina with large pore size for deep HDS.
To examine the behavior of asphaltene (ASP) at the reaction temperature, adsorption of ASP was investigated on catalyst supports with different pore size. ASP was a large molecule at low temperatures, but the molecular size decreased at HDS reaction temperature caused by the dissociation of the molecular structure. Furthermore, ASP containing sulfur was preferentially adsorbed on the catalyst support. The chemical interaction between ASP and alumina indicates that alumina is a good support for the HDS reaction.

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Many kinds of additives are used to prevent the degradation of organic chemicals, including macromolecular materials. Tocopherols are natural products known to be effective antioxidants. Now, on the basis of the anti-oxidation mechanism of tocopherols proposed by us, we have studied amines as promoters, which may enhance the antioxidant activity of a tocopherol, and studied 4-n-butoxyphenol, too, as model compounds as tocopherols. It was found that amines exhibit an antagonism to 4-alkylphenols, such as 2,6-di-t-butyl-4-methylphenol, whereas they exhibit certain synergism to 4-alkoxyphenols. In addition, it is clarified that an amine having a low ionization potential improves the antioxidant activity of α-tocopherol.

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The applicability of supercritical methanol was investigated to the selective para methylation of 4-methylbiphenyl to produce 4,4'-dimethylbiphenyl, which has recently attracted much attention as a valuable monomer of thermotropic liquid crystals, engineering plastics and others. The effects of the catalysts, temperature, pressure, reaction time, initial molar ratio of methanol to 4-methylbiphenyl and initial weight ratio of catalyst to 4-methylbiphenyl were evaluated using a batch-type reactor. The combination of supercritical methanol with SAPO-11 catalyst gave an excellent product selectivity of 70-85% of 4,4'-dimethylbiphenyl at 300°C, 14-16 MPa, 0.5 h reaction time, 15-20 initial molar ratio of methanol to 4-methylbiphenyl and 0.4-0.6 initial weight ratio of catalyst to 4-methylbiphenyl. Comparing with supercritical and gaseous methanol, the selectivity of 4,4'-dimethylbiphenyl in the supercritical phase was 1.5-3.4 times higher than that in the gas phase at the same conversion of 20-50% of 4-methylbiphenyl. The methylation almost stopped around 1 h due to coke deposition on the catalyst surface.

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Isomerization of organic sulfur containing light naphtha was studied over metal sulfated zirconium catalyst. Even in the presence of sulfur compounds, Pd/SO₄²⁻/Zr0₂-Al₂O₃ catalyst indicated the high isomerization activity without catalyst deactivation. We supposed that isomerization activity was kept by continuous regeneration of the dehydrogenation active site through the desulfurization of sulfur compounds deposited on catalyst by Pd.

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