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SuttichaiAssabumrungrat,Tomohiko Tagawa,Piyasan Praserthdam,Garun Tanarungsun,Worapon Kiatkittipong,Suttichai Assabumrungrat,Hiroshi Yamada 한국공업화학회 2007 Journal of Industrial and Engineering Chemistry Vol.13 No.3
of CHD (Eq. 3). In addi-tion, CHD can easily collapse to benzene when the Fe(II) content increased (Eq. 4) and also phenol can be further reacted with excess hydroxyl radicals to yield catechol, hydroquinone, and benzoquinone, resulting in the de-crease of selectivity.It is should be noted that ascorbic acid was highly solu-ble in the aqueous phase, but not in the organic phase. The addition of solvent was necessary to promote the re-action in this system by dissolving H2O2, ascorbic acid, and benzene into one phase. ConclusionThe liquid phase hydroxylation of benzene to phenol with hydrogen peroxide catalyzed by Fe(III)/TiO2 cata-lysts was investigated. The most suitable Fe(III) pre-cursor and %Fe(III) loading were iron(III) acetylaceto-nate and 5 wt%, respectively. Among the solvents stud-ied (acetone, dichloromethane, acetronitrile, pyridine, tert-butyl alcohol, 1-butyl alcohol, and ethyl alcohol), acetone showed the highest conversion and yield, but low selectivity. However, acetronitrile may be an attrac-tive solvent because of its high selectivity. Biphasic op-eration was not attractive compared to triphasic operation because of the dilution effect. Benzene conversion in-creased with increasing the amount of ascorbic acid; however, to much ascorbic acid retarded the yield im-provement because of lower phenol selectivity.AcknowledgmentFinancial support from the Thailand Research Fund and Commission on Higher Education are gratefully acknowledged.
Ultrasound-assisted capillary microreactor for aqueous–organic multiphase reactions
Salah Aljbour,Tomohiko Tagawa,Hiroshi Yamada 한국공업화학회 2009 Journal of Industrial and Engineering Chemistry Vol.15 No.6
A simple capillary microreactor was tested as a potential reactor to carry out a multiphase reaction. The hydrolysis of benzyl chloride in a biphasic system was investigated. The capillary microreactor was irradiated by 28 kHz ultrasound at different temperatures, capillary lengths and phase flow rates. It was found that the combination of microreactor technique and the ultrasound irradiation provides a promising protocol for process intensification. Under sonication conditions, higher conversions were obtained compared to silent conditions. The presence of ultrasound has affected the multiphase slug size and promoted better internal circulation within these slugs. Similar reactivities were noticed at higher temperature for both sonication and silent conditions.
Gas diffusion in an automotive catalyst in an unsteady state
Hiroshi Yamada,Tomohiko Tagawa,Satoru Kato,Naoki Takahashi 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.119 No.-
The influence of gas diffusion is often ignored because the washcoat layer is thin. Therefore, in addition todeveloping new catalytic materials, modifying the washcoat pores is important for improving effectivegas diffusivity. The gas diffusion phenomena in an unsteady state in an experimentally simulated washcoatlayer were evaluated by the pulse injection method. Wicke–Kallenbach diffusion cell was used. Effective diffusion coefficients obtained in an unsteady state were compared to those obtained in a steadystate. The effective diffusion coefficients were similar to the values obtained under a steady state, exceptfor low-molecular-weight gasses, due to the difference in mean molar speed between the evaluating gasand atmospheric gas.
CO2 reforming of waste plastics
Hiroshi Yamada,Hiromasa Mori,Tomohiko Tagawa 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.1
Carbon dioxide reforming of polyethylene was carried out. Pyrolysis and catalytic carbon dioxide reforming were combined. Polyethylene was packed at the bottom of the reactor and the catalyst, Pd/Al2O3, was packed at the top of the reactor. The pyrolysis of the polyethylene occurred at the bottom of the reactor, and the pyrolysis products reacted with carbon dioxide on the catalyst bed. Carbon dioxide reforming occurred on the catalyst bed zone. Hydrogen, carbonmonoxide,methane, ethane, ethene were produced at 910 and 720 K which were the catalyst and polyethylene temperature, respectively. Polyethylene was completely reformed to carbon monoxide and hydrogen when catalyst temperature was increased or polyethylene temperature was decreased.
Satoru Kato,Hironobu Ozeki,Hiroshi Yamada,Tomohiko Tagawa,Naoki Takahashi,Hirofumi Shinjoh 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.3
A method for directly measuring gas diffusivity in a washcoat layer was established by preparing a simulated washcoat layer and modifying a Wicke–Kallenbach type counter-current diffusion cell. Three pairs of gases, N2–Ar, CO2–Ar and C3H8–Ar, were used in the measurements. It was found to be possible to evaluate the pore-transport parameters of the washcoat layer based on the mean transport pore model and the modified Stefan–Maxwell equation. Analysis of the gas diffusion mechanism in the washcoat layer showed that bulk and Knudsen diffusion took place simultaneously, and the percentage value of the contribution by Knudsen transport to net diffusion transport was evaluated.
Ternary metal oxide catalysts for selective oxidation of benzene to phenol
Garun Tanarungsun,Worapon Kiatkittipong,Piyasan Praserthdam,Hiroshi Yamada,Tomohiko Tagawa,Suttichai Assabumrungrat 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.5
This paper studied the liquid phase hydroxylation of benzene to phenol with hydrogen peroxide catalyzed by ternary metal oxide catalysts (Fe(III), V(V) and Cu(II)) supported on TiO2 at room temperature. The effects of V(V) and Cu(II) metal oxide loading were investigated. The catalysts were prepared by co-impregnation method and characterized by BET, XRD, XRF, SEM-EDX, NH3-TPD techniques. It was reported that the presence of V(V) and Cu(II) influenced the acid property on the catalyst. The increase of the metal loading increased the acidity of the catalyst. TiO2 loaded with Fe, Vand Cu of 5, 2.5 and 2.5 wt%, respectively offered the highest yield of phenol. Although the increase of the metal loading improved the yield of phenol, the TOF reduced due to the reduction of dispersion of the catalyst metal. The optimum condition for the system is a reaction time of 4 h, catalyst weight of 0.2 g, the H2O2:benzene molar ratio of 2 and 6.25 g of ascorbic acid per mole of benzene.