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Atsushi Ishihara

Bio: Atsushi Ishihara is an academic researcher from Mie University. The author has contributed to research in topics: Catalysis & Hydrodesulfurization. The author has an hindex of 35, co-authored 262 publications receiving 6078 citations. Previous affiliations of Atsushi Ishihara include Kyoto University & Tokyo University of Agriculture and Technology.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the authors showed that a mixture of hydrogen peroxide and formic acid can oxidize model sulfur compounds to detectable levels (c.a., 0.01 wt % S) by GC-FPD analysis.
Abstract: The oxidation of model sulfur compounds (thiophene derivatives, benzothiophene derivatives, and dibenzothiophene derivatives), straight run-light gas oil (SR-LGO, S: 1.35 wt %), and vacuum gas oil (VGO, S: 2.17 wt %) were conducted with a mixture of hydrogen peroxide and formic acid. The thiophene derivatives with 5.696 to 5.716 electron densities on the sulfur atoms could not be oxidized at 50 °C. Benzo[b]thiophene with 5.739 electron density and other benzothiophene and dibenzothiophenes with higher electron densities could be oxidized. The sulfur compounds in SR-LGO and VGO appeared to be oxidized to a detectable levels (c.a., 0.01 wt % S) by GC-FPD analysis. The IR spectra of oxidized SR-LGO and VGO showed that sulfones were formed by oxidation. The removal of sulfur compounds by extraction became more effective for the oxidized samples than for the original samples. Lighter sulfur compounds were preferentially extracted. The extraction efficiencies of solvents, i.e., N,N‘-dimethylformamide (DMF), a...

894 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the oxidation properties of dibenzothiophene (DBT) in kerosene for a series of Mo catalysts supported on Al2O3 with various Mo contents.
Abstract: The oxidation of sulfur compounds in kerosene was conducted with tert-butyl hydroperoxide (t-BuOOH) in the presence of various catalysts. The oxidation activities of dibenzothiophene (DBT) in kerosene for a series of Mo catalysts supported on Al2O3 with various Mo contents were estimated. The results show that the oxidation activity of DBT increased with increasing Mo content up to about 16 wt.% and decreased when Mo content was beyond this value. The oxidation of benzothiophene (BT), dibenzothiophene (DBT), 4-methyl dibenzothiophene (4-MDBT), and 4,6-dimethyl dibenzothiophene (4,6-DMDBT) dissolved in decalin was also carried out on 16 wt.% Mo/Al2O3 catalyst with t-BuOOH to investigate the oxidation reactivities of these sulfur compounds. The results indicated that the oxidation reactivities of these sulfur compounds decreased in the order of DBT>4-MDBT>4,6-DMDBT⪢BT. Analyses of the oxidative reactions of the sulfur compounds suggested that the oxidative reaction of each sulfur compound can be treated as a first-order reaction. The oxidation mechanism is then discussed.

341 citations

Journal ArticleDOI
TL;DR: In this article, the authors compared the oxidation reactivity of dibenzothiophene (DBT), 4,6-dimethyldibenzethiophene and trimethy-ldibenothiophena (C 3 -DBT) in light gas oil.
Abstract: The oxidation of undesirable sulfur compounds present in a desulfurized light gas oil (LGO; sulfur content: 39 ppm) was performed with tert -butyl hydroperoxide ( t -BuOOH) as the oxidant in the presence of a 16 wt.% MoO 3 /Al 2 O 3 catalyst. The oxidation activity of the sulfur compounds in the light gas oil increased when the O/S molar ratio increased up to 15; the activity slightly decreased for higher ratios. This optimal ratio was significantly higher that the stoichiometric one (=2) due to parallel oxidation reactions of olefins, etc., in the LGO. Further, we compared the oxidation reactivity of dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (4,6-DMDBT), and trimethyldibenzothiophene (C 3 -DBT), which are refractory compounds present in the light gas oil. The reactivity decreased in the order DBT ≫ 4,6-DMDBT > C 3 -DBT, irrespective of the WHSV and the temperature. Subsequent mathematical treatment revealed that the oxidative reaction of each sulfur compound follows a first-order kinetics. We found an activation energy of 32 ± 2 kJ mol −1 , whatever the compound, suggesting that the oxidation mechanism was the same for these compounds. Then, according to the proposed global process, the previously oxidized molecules in the treated light gas oil were further removed by adsorption over a silica gel at ambient temperature. As a result, the total sulfur content could be decreased after oxidation/adsorption to less than 5 ppm. Further, N-containing model compounds were also treated according to the same procedure and the denitrogenation performance decreased in the order indole > quinoline > acridine > carbazole. Subsequently, the same process allowed decreasing the N content in the LGO from an initial value of 13.5 ppm to a value of 0.8 ppm, which is a remarkable result.

296 citations

Journal ArticleDOI
TL;DR: In this paper, deep hydrodesulfurization of polyaromatic sulfur-containing compounds (PASC) in light oil was carried out by using Co-Mo/Al 2 O 3 under experimental conditions representative of industrial practice.
Abstract: Deep hydrodesulfurization of polyaromatic sulfur-containing compounds (PASC) in light oil was carried out by using Co-Mo/Al 2 O 3 under experimental conditions representative of industrial practice. PASC were determined by gas chromatography-atomic emission detection (GC-AED) and gas chromatography-mass spectroscopy (GC-MS). Alkyl-substituted dibenzothiophenes among sulfur-containing compounds in light oil were most difficult to desulfurize

268 citations


Cited by
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Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the problems of sulfur reduction in highway and non-road fuels and present an overview of new approaches and emerging technologies for ultra-deep desulfurization of refinery streams for ultra clean (ultra-low-sulfur) gasoline, diesel fuels and jet fuels.

1,874 citations

Journal ArticleDOI
TL;DR: Progress made on several aspects of elicitor signal transduction leading to production of plant secondary metabolites are summarized, including the integration of multiple signaling pathways into or by transcription factors, as well as the linkage of the above signal components in eliciting network through protein phosphorylation and dephosphorylation.

1,649 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the recent advancement on ultra low sulfur diesel (ULSD) production from both scientific and applied point of view, highlighting the importance of catalyst selection and hydrogen consumption issues.

1,074 citations

Journal ArticleDOI
TL;DR: In this paper, a selective review on design approaches and associated catalysis and chemistry for deep desulfurization and deep dearomatization (hydrogenation) of hydrocarbon fuels, particularly diesel fuels, is presented.
Abstract: This paper is a selective review on design approaches and associated catalysis and chemistry for deep desulfurization and deep dearomatization (hydrogenation) of hydrocarbon fuels, particularly diesel fuels. The challenge for deep desulfurization of diesel fuels is the difficulty of removing the refractory sulfur compounds, particularly 4,6-dimethyldibenzothiophene, with conventional hydrodesulfurization processes. The problem is exacerbated by the inhibiting effect of polyaromatics and nitrogen compounds, which exist in some diesel blend stocks on deep HDS. With the new Environmental Protection Agency (EPA) Tier II regulations to cut the diesel sulfur from current 500 ppmw down to 15 ppmw by June 2006, refineries are facing major challenges to meet the fuel sulfur specification along with the required reduction of aromatics contents. The principles and problems for the existing hydrodesulfurization processes, and the concepts, advantages and disadvantages of various new approaches will be discussed. Specifically, the following new design approaches for sulfur removal will be discussed: (1) novel catalysts for ultra-deep hydrodesulfurization under conventional HDS process conditions; (2) new design concept for sulfur-tolerant noble metal catalysts for low-temperature hydrogenation; (3) new desulfurization process by sulfur adsorption and capture under H2; (4) new desulfurization process by selective adsorption at ambient temperature without H2 and a related integrated process concept; (5) oxidative desulfurization in liquid-phase; and (6) biodesulfurization.

1,045 citations