Recently, applications of the carbon nanohorn (CNH) have become of great interest in various industrial fields. The load carrying capacity and wear resistance of lithium soap grease containing CNH and heat-treated CNH (HT-CNH) were studied using a Falex friction tester, and compared with those of grease containing reference carbon materials such as graphite, cluster diamond (CD), and graphite cluster diamond (GCD). The load carrying capacity of the greases with carbon materials was always higher than that of the base grease. The greases with CNH and HT-CNH had the same or higher seizure load than those with CD and GCD. In particular, the grease with HT-CNH exhibited good load carrying capacity even at a low concentration of 1 mass%. The grease with 3 or more mass% graphite had the highest seizure load of all greases in this study. The grease with HT-CNH showed the best wear resistance of all greases in this study. The wear resistance of the grease with other solid lubricants was the same or inferior to that of the base grease.
Hydrodechlorination of monochlorobenzene (MCB), 1,4-dichlorobenzene (DCB), and 1,3,5-trichlorobenzene (TCB) was carried out on palladium-supported γ-alumina and alumina Lewis superacid catalysts at 298 K and ambient pressure in a stream of hydrogen, using a fixed bed flow reactor for the gas-phase reaction and a fixed bed semi-batch reactor for the liquid-phase reaction. Both catalysts showed higher activity for hydrodechlorination in the gas-phase reactions than the platinum catalysts supported on the same carriers. The completely hydrodechlorinated products consisted only of benzene and cyclohexane. Hydrodechlorination of MCB and DCB at 3900 g·h·mol−1 resulted in conversions and cyclohexane yields of 100%, and for TCB the cyclohexane yield was also over 95% with a conversion of 90%. Slight activity decrease of the Pd catalysts due to chlorine accumulation on the catalyst was observed, but the chlorine amount was about one-fourth at 353 K compared to 298 K in spite of the remarkable increase in the number of reacted (dechlorinated) molecules, so catalyst deactivation was effectively reduced at higher reaction temperatures. Furthermore, even in the liquid-phase reactions at ambient temperature, which was lower than the reaction temperatures previously used, the palladium-supported catalysts had moderate activity for hydrodechlorination and formed benzene and cyclohexane. The hydrodechlorination of chlorobenzenes probably proceeded through reactions between the hydrogen atoms spilling over from the Pd surface to the alumina carrier surface and the chlorobenzenes adsorbed and activated on the Lewis acid sites of the alumina surface.
The catalytic precursors of alumina-supported molybdenum dithiocarbamate (Mo-DTC) and molybdenum dithiophosphate (Mo-DTP) were assessed as catalysts for hydrodesulfurizastion (HDS). The effect of the activation method on catalytic activity was evaluated for the HDS of dibenzothiophene (DBT). Catalysts derived from alumina-supported Mo-DTC or Mo-DTP after activation with H2S or H2 showed HDS activity comparable to that of conventional Mo catalyst prepared with ammonium heptamolybdate. Various activation procedures for the Mo complex precursors were investigated. Mo-DTC and Mo-DTP precursors activated with N2 and H2O showed much higher catalytic activity. Moreover, the selectivity for biphenyl of the Mo-DTC and Mo-DTP catalysts, which indicates the capacity of direct desulfurization, was higher than that of the sulfided conventional Mo catalyst.
The activity of Cu-Zn oxide catalysts for methanol synthesis from syngas varies depending on the additives to the oxide, and optimum composition is sensitive to the reaction conditions. An artificial neural network (ANN) was applied to identify the most effective additives based on the experimental results already reported. The physicochemical characters of element X, such as ionic radii and ionization energy, and the activity of Cu-Zn-X oxide catalyst were correlated using the ANN. Twenty-two types of X were supplied for the training of the ANN, and 29 activities of Cu-Zn-X, the X of which was not included in the training data, were predicted. Beryllium was predicted as the most effective additive, which was verified experimentally.
Focusing on sunlight that has severe effects on the degradation of asphalt pavement during service, this study examined the relationships between the film thickness of asphalt and the states of photodegradation. The results confirmed that thinner films had a higher modulus of elasticity, lower viscosity, and increased production of carbonyl groups, which is an indicator of oxidative degradation. The degree of degradation rapidly increased especially at thicknesses below 200 μm. The wavelength dependence of spectral photodegradation was also examined. Visual observations and the carbonyl index confirmed that ultraviolet irradiation in the range of 300 to 400 nm caused severe photodegradation of asphalt. Carbon black blocked light near the surface of the asphalt layer, where the damage caused by light is most severe. Addition of carbon black helps to prevent photodegradation by ultraviolet irradiation in the wavelength range of 300 to 400 nm.
The effect of cobalt addition on Mo/Al2O3 hydrodesulfurization catalyst was investigated by 129Xe NMR. Both the amount of adsorbed xenon and the peak width of 129Xe NMR were almost constant at various cobalt loadings. This result indicates that the cobalt species on the catalyst surface had little effect on the motion of xenon in the micropores. The chemical shift δ of the 129Xe NMR peak varied nonlinearly with the amount of adsorbed xenon. Presumably this is due to a strong interaction between xenon and coordinatively unsaturated anion vacancy sites. The curvature of δ increased further at cobalt loadings of more than 2.2 mass%, which suggests that the electrons of xenon were strongly attracted by the cobalt species. Moreover, the parameter δ0 calculated from fitting of the theoretical equation gradually increased with Co/Mo ratio and reached the maximum value at Co/Mo = 0.71. This is caused by an increase in the term δM that depends on the magnetic susceptibility and strongly suggests that antiferromagnetic Co-Mo-S phases were formed. On the other hand, a small decrease in δ0 at Co/Mo = 0.99 originated from a decline in the magnetic susceptibility of the whole sample due to the formation of diamagnetic Co9S8. 129Xe NMR is useful for analysis of the formation of the Co-Mo-S phase on CoMo/Al2O3 hydrodesulfurization catalyst.
The catalytic activity of Rh/CeO2/SiO2 was assessed for the partial oxidation of tar derived from spent malt. This catalyst was developed for the gasification of cedar wood at lower temperatures than conventional methods, such as steam reforming using Ni catalyst and or without catalyst. Partial oxidation of spent malt in the absence of catalyst yielded tar with a carbon based yield almost the same as that from cedar wood. Partial oxidation of the tar from cedar wood pyrolysis over Rh/CeO2/SiO2 and Ni catalyst converted the tar almost completely. On the other hand, tar from the pyrolysis of spent malt had lower reactivity than that of cedar wood. Higher temperatures such as 923 K were needed for tar conversion to the similar level to tar from cedar wood even over Rh/CeO2/SiO2. The nitrogen content in spent malt was much higher than that in cedar wood. The effect of NH3 addition on the partial oxidation of cedar wood was investigated. Furthermore, tar derived from cedar wood and spent malt was analyzed by GC-MS. Various nitrogen-containing hydrocarbons were observed in the tar derived from spent malt, although oxygenates were observed in the tar from cedar. Nitrogen-containing tar is only removed with difficulty.
In order to establish a CO adsorption method for rapid measurement of metal dispersion of catalysts containing CeO2 that disturbs the measurement due to the adsorption of H2 or CO, the effect of reduction conditions on CO adsorption over Pt/CeO2 catalyst was examined on the basis of the standardized manual of CO-pulse method established by the Committee on Reference Catalyst, the Catalysis Society of Japan. Reduction of the catalysts under the standardized condition (673 K, 15 min) showed that Pt catalysts supported on low surface area CeO2 (12.6 m2·g−1) gave reasonable ratios of adsorbed CO to total Pt. However, the CO/Pt ratio exceeded unity on high surface area CeO2 support (66.7 m2·g−1), suggesting adsorption of CO on the CeO2 surface. Reduction of the catalyst under milder conditions at 373 to 573 K for 15 min to 5 h gave constant CO/Pt ratio of 0.40 within a reasonable experimental error. The mean particle diameter estimated from this CO/Pt ratio on the assumption of spherical particles closely agreed with a volume-area mean diameter measured by TEM. It was concluded that the dispersion of Pt supported on CeO2 can be measured by lowering the reduction temperature to suppress the effect of the CeO2 support.
Needle-like crystals of ruthenium-molybdenum polyoxometalate having a composition of Na4(NH4)[RuMo7O25]•8H2O (RuMo7) were synthesized with high reproducibility. With cetylpyridinium cation, RuMo7 was modified and its catalytic features were evaluated using oxidation of cyclohexanol to cyclohexanone with t -butyl hydroperoxide or hydrogenperoxide (H2O2). The results indicated that RuMo7 exhibits high rate for the former reaction and that RuMo7 has high potential for H2O2 decomposition.