Makoto Inomata

Benzene-filled pore method: a method of measuring external surface areas applicable to zeolites with low-to-high Si-to-Al ratios

This study is an investigation of various adsorbates (water, hexane, and benzene) applied to several kinds of zeolites (Y, mordenite, and ZSM-5). The adsorption of water, hexane, and benzene is evaluated as a method of measuring the eternal surface areas of zeolites.

Simultaneous SO2/NOx removal by a powder-particle fluidized bed

Abstract Simultaneous dry removal of SO2 and NOx from flue gas has been investigated using a powder-particle fluidized bed. In a process of flue gas desulfurization by use of solid sorbents such as FeO (dust from a steel plant) and CuO, the smaller the particle size of sorbents, the higher the expected SO2 conversion. In a powder-particle fluidized bed (PPFB), fine particles less than 40 μm in diameter fed into the bed are fluidized with coarse particles. But only the fine particles are entrained from the bed, and their residence time in the bed is remarkably long. The reduction of NOx with NH3 in the fluidized bed is catalyzed by coarse particles or both coarse and fine particles. In this study, PPFB was applied to simultaneous dry SO2/NOx removal process, and several kinds of sorbents or catalysts were evaluated in a PPFB. Using the selected sorbents and catalysts, kinetic measurements were made in the temperature range of 300 to 600°C. SO2 removal efficiencies were affected by reaction temperature, sorbent/S ratio, and static bed height. NOx removal efficiencies in excess of 95% were achieved at NH3/NOx mole ratio of 1.0. When FeO was used as sorbent, SO2 conversion increased with increasing temperature and reached 80% at 600°C.

Activity and selectivity in the oxidation of benzene on supported vanadium oxide catalysts

The dependences of activity and selectivity in the oxidation of benzene on unsupported and supported V2O5 catalysts on the catalyst structure have been investigated. It was found that the reaction rate at various concentrations of O2 was proportional to the amount of V5+O species in the catalyst, indicating that surface VO is an active oxygen species for the reaction. The specific activity of surface VO species on unsupported V2O5 was the same as that of the fused catalyst, while the surface structures were markedly different from each other. This means that the oxidation of benzene on V2O5 is a structure-insensitive reaction. The activity of the V2O5/TiO2 and V2O5/Al2O3 catalysts was mainly determined by the number of surface VO species. The specific activity of surface VO species of V2O5/TiO2 was greater than that of unsupported V2O5 or V2O5/Al2O3, indicating the promoting effect of the TiO2 support on the activity of surface VO species. The selectivity to maleic anhydride was found to be determined only by the number of V2O5 layers on the support for both V2O5/TiO2 and V2O5/Al2O3 catalysts. When the number of V2O5 layers was 1 or 2, the selectivity to maleic anhydride was very low, while it increased markedly on increasing the number of V2O5 layers to 5 and attained a constant value above 5 layers. The change in the oxidation state of the catalyst did not affect the selectivity.

Selective exposure of the VO species on the surface of vanadium oxide supported on titania and alumina

By measuring the quantity of surface VO species on V2O5–TiO2 and V2O5–Al2O3 catalysts containing various amounts of V2O5, we have found that, for V2O5–TiO2 catalysts, the (010) face of V2O5 is selectively exposed to the surface but, for V2O5–Al2O3 and unsupported catalysts, various crystal faces of V2O5 are exposed in addition to the (010) face.

Conversion of Light Naphtha to Aromatic Hydrocarbons. Part 5. Evaluation of Catalytic Performance of Pt/KL for the Aromatization of Hexane in Pilot-scale Reactors.

Catalytic conversion of light naphtha to aromatics over platinum supported on zeolite L (Pt/KL) was studied using pilot scale units of an externally heated tubular reactor and an adiabatic reactor under operating conditions close to those used for commercial reactors, and simulated using data from laboratory experiments. Product distributions and temperature profiles in the catalyst bed of the adiabatic reactor and the externally heated tubular reactor agreed fairly well with the simulated values. The simulated performances of the adiabatic reactor and the externally heated tubular reactor were compared, suggesting that the externally heated tubular reactor is more advantageous than the adiabatic reactor, since the operating temperature at the catalyst bed can be lowered, resulting in a slower reaction rate of hydrocracking and a consequent increase in the benzene yield.

Conversion of light naphtha into aromatic hydrocarbons (part 3) ; Effects of pre-sulfiding of ZnH-ZSM-5 on catalytic performance and stability of zinc

The effects of steaming and hydrogen reduction of ZnH-ZSM-5, concerning catalytic activity in aromatization of n-hexane were examined to evaluate the stability of ZnH-ZSM-5 in commercial operating conditions, in comparison with H-ZSM-5. Steaming at high temperature resulted in greater drop in the yield of aromatics over H-ZSM-5 than that over ZnH-ZSM-5. Hydrogen reduction had little effect on the yield of aromatics over H-ZSM-5, while a remarkable drop in the yield of aromatics was observed over ZnH-ZSM-5. It was found that zinc oxide in ZnH-ZSM-5 was reduced with hydrogen to give metallic zinc, which was then vaporized from the catalyst. This vaporization led to an irreversible decline in the activity for aromatization. Pre-sulfiding of ZnH-ZSM-5 was found to be effective in preventing the vaporization of zinc, by conducting thermogravimetric measurement of vaporized zinc from the catalyst. ZnH-ZSM-5 was pre-sulfided, using thiophene, dimethylsulfide, and disulfidecarbonate, as sulfiding agents, which reduced not only the vaporization of zinc, but also the cracking activity to yield light gases, such as CH 4 and C 2 H 6 .

Conversion of Light Naphtha into Aromatic Hydrocarbons (Part 1) Kinetic Studies on Hexane Conversion on Zn/H-ZSM-5.

Conversion of light naphtha into aromatic compounds was studied on series of ZSM-5 catalysts loaded with various metal species. Among the catalysts, Zn-, Cd- and Ga-loaded ZSM-5 exhibited. high performances for aromatization of n-hexane. The mechanism of conversion of n-hexane into aromatic compounds over Zn/H-ZSM-5 catalyst was investigated. It is found that aromatization of n-hexane involves dehydrocracking of n-hexane into lower olefins, oligomerization of lower olefins, and dehydrogenation of higher olefins to aromatic compounds. In order to investigate the reaction pathway for aromatization of higher olefins, a series of conversion of n-hexane, 1-hexene, hexadiene, hexatriene, and cyclohexane over Zn/H-ZSM-5, H-ZSM-5, and Pt/H-ZSM-5 were conducted. It is suggested that aromatization proceeds in successive dehydrogenation of higher olefins, and that Zn species play a role to promote formation of hydrogen molecule. On the basis of experimental results, a general reaction model in transformation of light naphtha over Zn/H-ZSM-5 was developed. From results of the kinetic analysis, it is found that promoting the activities for dehydrocracking of n-hexane, dehydrogenation of lower paraffins, and formation of hydrogen molecules may make the catalyst more selective in aromatization of light naphtha.

Promoting effect of TiO2 and Al2O3 supports on the activity of vanadium oxide catalyst for the oxidation of benzene measured in terms of the turnover frequency

The following relationship, V2O5–TiO2 > unsupported V2O5 > V2O5–Al2O3, was found to hold for the turnover frequency for the oxidation of benzene, which indicates the promoting effect of the TiO2 support on the reaction with vanadium oxide catalyst.