Papers by Atsushi Ishihara
Nihon Enerugī Gakkaishi, 1996
RSC Advances, 2021
Novel carbon-Al 2 O 3 and carbon-ZrO 2 composite-supported Co catalysts were prepared using the s... more Novel carbon-Al 2 O 3 and carbon-ZrO 2 composite-supported Co catalysts were prepared using the sol-gel method with polyethylene glycol (PEG) as a carbon source, and the effects of the addition of CeO 2 to catalysts on the steam reforming of ethanol were investigated. The reactions were carried out in a fixed bed reactor with H 2 O/EtOH ¼ 12 (mol/mol) and a temperature range of 300 C to 600 C. The catalyst characterization was performed by XRD, nitrogen adsorption and desorption isotherms, TG-DTA, XRF and TEM. Although the carbon-Al 2 O 3 composite-supported Co catalysts exhibited a higher conversion of ethanol than the carbon-ZrO 2 composite-supported Co catalysts, the effect of the addition of CeO 2 was hardly observed for catalysts with Al 2 O 3 . In contrast to the case of catalysts with Al 2 O 3 , the effect of the addition of CeO 2 to catalysts with ZrO 2 on the conversion and the hydrogen yield was observed, and the hydrogen yield at 600 C exceeded that of catalysts with Al 2 O 3 . 16Co42C31.5Ce10.5Zr exhibited the highest hydrogen yield of 89% at 600 C. Fine Co metal species were observed for the used ZrO 2 -based catalysts, while Co 3 O 4 peaks were observed for the used Al 2 O 3 -based catalysts. The development of the carbon nanotube-like structure with a diameter of 50 nm was observed with particles having diameters of 30 nm to 50 nm, suggesting that the carbon deposition might occur so as not to deactivate the catalyst.
Journal of The Japan Petroleum Institute, Mar 1, 2018
Global industrial progress has rapidly increased the mass consumption of resources. In particular... more Global industrial progress has rapidly increased the mass consumption of resources. In particular, carbonbased fuel reserves are declining, resulting in potential shortages. In addition, consumption of carbon-based fuels causes environmental degradation including global warming, and the emission of harmful particles has severe effects on organisms including humans. Consequently, drastic increases in the price of crude oil and increasing demand for clean alternative fuels have occurred 1) . Hydrogenation of carbon monoxide, the so-called Fischer-Tropsch synthesis (FTS), converts synthesis gas produced by the gasification of biomass into completely sulfur-free fuels. Biomass is regarded as a carbon neutral renewable source. The FTS has been widely investigated in both the academic community and in the industrial world. This method of gas to liquid (GTL) conversion depends on the development of effective catalysts. Various heterogeneous transition metal catalysts containing Fe, Co, Ni and Ru have been developed, and Co-based catalysts are particularly advantageous for practical applications due to the high activity, selectivity for long chain linear hydrocarbons, high resistance toward deactivation, and lower cost than Ru. Generally, Co and Fe catalysts are deposited on supports with high surface area (e.g., SiO2, Al2O3, TiO2 and ZrO2) to increase the number of active Co, Fe metal species, and silica-supported cobalt is an especially promising catalyst 2),3) . Alumina is one of the most effective support materials for Co or Fe based FT catalysts due to the high resistance to attrition and stabilization of small clusters. Most transition metal-supported catalysts are made by the impregnation method, but preparation of catalysts using the sol-gel method has become common. Our research to prepare catalysts using the sol-gel 51
RSC Advances, 2021
The dehydrocyclization-cracking of methyl oleate was performed by ZnZSM-5-Al 2 O 3 hierarchical c... more The dehydrocyclization-cracking of methyl oleate was performed by ZnZSM-5-Al 2 O 3 hierarchical composite-supported Pt catalysts in the range of 450-550 C under 0.5 MPa hydrogen pressure. Most catalysts converted methyl oleate completely and produced aromatics with more than 10 wt% yield as well as valuable fuels even at 450 C. The reactivity of catalysts changed remarkably depending on the addition method of Pt, while supporting Pt of 0-0.16 wt% did not affect the pore structure of each catalyst. When Pt was introduced into the composite support by the conventional impregnation method, remarkable hydrocracking proceeded through the decarboxylation and decarbonylation of methyl oleate and the successive conversion of C17 fragments and gave the significant amounts of gaseous products. Nevertheless, the selectivity for the aromatics of the gasoline fraction was relatively high and the yields of aromatics reached maximum 19% at 500 C under 0.5 MPa, suggesting that gaseous olefins would be cyclized through the Diels-Alder reaction on ZnZSM-5 in the composite support. In contrast, when Pt was introduced into catalysts by ion-exchange with ZnZSM-5, the significant conversion of methyl oleate was inhibited and produced liquid fuels in a wide range.
ACS omega, Feb 18, 2021
Zn-exchanged ZSM-5-Al 2 O 3 (ZA) composite-supported Pt/ NiMo (NM) sulfided catalysts were prepar... more Zn-exchanged ZSM-5-Al 2 O 3 (ZA) composite-supported Pt/ NiMo (NM) sulfided catalysts were prepared using the conventional kneading method and were tested for dehydrocyclization-cracking of soybean oil. The effects of Zn addition on the activity and selectivity of products were investigated under moderate-pressure conditions of 0.5 and 1.0 MPa H 2 in the temperature range of 420-580 °C. At the temperature 500 °C and higher, most of the sample soybean oil was converted at both the pressures of 0.5 and 1.0 MPa. At 1.0 MPa and 500 °C, the effects of Zn addition appeared and increased the yields of aromatics, while the catalyst without Zn produced larger amounts of products with more than C18. Further, at 0.5 MPa and 580 °C, the gas formation was inhibited in comparison to the cases of 1.0 MPa and the effects of the Zn addition also appeared and increased the yields of aromatics, while the catalyst without Zn produced larger amounts of products with more than C18. The Pt/NM/Zn(122)ZA test catalyst produced more than 63% of liquid fuels in the range C5-C18, and the yield of aromatics was 13%, the maximum value in the present study. The following reaction routes were proposed. The structure of triglyceride is converted by hydrocracking to three molecules of aliphatic acids and propane on the surface PtNiMo sulfide on Al 2 O 3 support. The converted aliphatic acids are decomposed through decarboxylation to hydrocarbon fragments, which are further decomposed by cracking on the acid sites of the catalyst, the surface of NiMo sulfide, Al 2 O 3 , or ZSM-5. Finally, the formed C3 and C4 olefins are transformed to aromatics through the Diels-Alder reaction on the Zn species of ZnZSM-5. On the other hand, although gases were relatively small in amount, aromatic compounds were formed significantly, suggesting that cyclization might directly occur without conversion to gaseous hydrocarbons to some extent.
ACS omega, May 11, 2020
In this study, the effects of the combination of a mesoporous material and Zn-exchanged ZSM-5 on ... more In this study, the effects of the combination of a mesoporous material and Zn-exchanged ZSM-5 on the activity and selectivity of aromatic compounds in dehydrocyclization of npentane were investigated. A total of 65-85 wt % of ZnZSM-5 was mixed with 0-20 wt % of Al 2 O 3 and 15 wt % of the alumina-sol binder using a conventional kneading method. Dehydrocyclization of n-pentane was performed using a fixed-bed reactor under the conditions of a H 2 atmosphere and the temperature range of 450-550 °C. Conversions of n-pentane tended to increase upon increasing the amounts of zeolite content and ZnZSM/0A (85 wt % ZnZSM-5, 0 wt % Al 2 O 3 , and 15 wt % binder) exhibited the highest value. The selectivity for toluene and benzene increased with increasing temperature, while it decreased in the order ZnZSM/10A > ZnZSM/0A > ZnZSM/20A in comparison at the same temperature. Upon changing the carrier gas, the conversion decreased in the order CH 4 > H 2 > H 2 + N 2 > N 2 . Although the selectivity for aromatics was higher under CH 4 and N 2 atmospheres, the conversions decreased at 550 °C with time, suggesting that the deactivation would proceed by coke formation. Furthermore, the selectivity for aromatics of ZnZSM/10A was higher than that of ZnZSM/0A, indicating that the use of mesoporous Al 2 O 3 as a matrix would be very effective for this reaction and draw the maximum catalytic functions. When the reaction route was estimated from the amounts of methane and C2 and C3 fractions formed, it was proposed that active Zn species would catalyze the aromatization of olefins where benzene is formed from ethene and butene, toluene from propene and butene, and xylene from 2 molecules of butene.
Nihon Enerugī Gakkaishi, 2018
Pt/TiO2-Bi2O3 test catalysts were prepared by impregnating Pt on the sol-gel derived TiO2-Bi2O3 t... more Pt/TiO2-Bi2O3 test catalysts were prepared by impregnating Pt on the sol-gel derived TiO2-Bi2O3 to give these testpieces high photocatalytic activity under visible light irradiation. The optimum Pt support content and TiO2 content were observed in the ranges 0.05-0.3 wt% and 17-28 wt%, respectively in the photocatalytic activity for Methylene Blue (MB) degradation on Pt/TiO2-Bi2O3. Specifically, those 0.1Pt/17TiO2-83Bi2O3, 0.2Pt/23TiO2-77Bi2O3 and 0.3Pt/28TiO2-72Bi2O3 samples showed relatively higher photocatalytic activity for the MB degradation. The results were closely related to (1) the restriction of recombination of the photo-induced electron and hole pairs by Pt, and (2) the presence of bismuth titanate with such high Ti content as built up by Pt.
Sekiyu Gakkaishi, 1993
(HDS) of dibenzothiophene (DBT) catalyzed by alumina-supported metal carbonyl complexes (Mo(CO)6,... more (HDS) of dibenzothiophene (DBT) catalyzed by alumina-supported metal carbonyl complexes (Mo(CO)6, Cr(CO)6, W(CO)6) was investigated in a pressurized flow system. Catalysts prepared by activation of metal carbonyl complexes-triethylamine(NEt3)-ethanethiol(EtSH)/ Al2O3 systems where metal carbonyls were reacted with NEt3 and EtSH to give anionic complexes with metal-sulfur bonds were found to be active in HDS of DBT. When a Mo(CO)6-NEt3-EtSH/Al2O3 system was activated by H2 or H2S, the catalytic activity was the highest among catalysts derived from supported-metal carbonyls and the conversion of DBT at 300℃ was 43%, which was higher than that over a conventional molybdena-alumina. From NO chemisorption and XPS measurement, it was deduced that hydrogenation of a Mo(CO)6-NEt3-EtSH/Al2O3 system would give alumina-supported MoS2-x species which was active in HDS of DBT.
Journal of The Japan Petroleum Institute, Sep 1, 2016
Zeolite-containing catalysts with hierarchical structures were prepared by combining microporous ... more Zeolite-containing catalysts with hierarchical structures were prepared by combining microporous zeolites (beta and Y zeolite) with mesoporous matrices (silicas and silica _ aluminas with large mesopores) prepared by the gel skeletal reinforcement method and a binder. Morphology of the prepared catalysts was characterized by X-ray diffraction, nitrogen adsorption-desorption, ammonia adsorption-desorption, and thermogravimetric-differential thermal analysis. Catalytic cracking of soybean oil was performed with these mixed catalysts to observe the effect of the pore size on the catalytic activity and the selectivity of products using the convenient Curie point pyrolyzer. Zeolite-containing mixed catalysts exhibited great improvements in all aspects such as maximum increase of 31 % conversion, about 10 % higher gasoline yields, and maximum decrease of 36 % coke formation in comparison with single zeolite, indicating that the presence of the matrices greatly influenced the catalytic cracking. The yields of gasoline, single branched and multi-branched hydrocarbons increased with higher conversion, indicating that increased conversion was necessary to obtain higher yields of products. In comparison of product yields at the same conversion, Y zeolite-containing catalysts exhibited the higher yields than beta (β) zeolite-containing catalysts, indicating that the larger micropore diameter of Y zeolite in the catalysts induced the increase in the gasoline fraction and promoted the isomerization to produce the bulkier products. The conversion of soybean oil increased with increasing the pore diameter for β series catalysts and the conversions were maximum for MAT(200S)-β and MAT(200SA)-β with relatively larger mesopores, indicating that the diffusion of reactants and products affected the catalytic performance. In contrast to this phenomenon, MAT(0S)-Y and MAT(0SA)-Y with relatively smaller mesopores exhibited the maximum conversions for Y series catalysts.
Journal of The Japan Petroleum Institute, 2008
Bacteria were screened to identify strains that could degrade carbazole, a model compound for the... more Bacteria were screened to identify strains that could degrade carbazole, a model compound for the N-containing compounds present in fossil fuels which could be removed by biodenitrogenation instead of hydrotreatment. Enrichment cultures from 6 different habitats were examined with carbazole as a source of nitrogen. Bacterium strain NIY3 was isolated, which efficiently metabolized very low concentrations of carbazole. Strain NIY3 is a bright yellow Gram-negative immotile bacterium with a rod shape (0.7×0.7-1.0 μm). DNA base sequence anal ysis revealed that strain NIY3 belongs to genus Novosphingobium sp., most closely related to Novosphingobium subarcticum (98.3％ similarity). Novosphingobium sp. strain NIY3 could degrade 95％ of 100 ppm of carbazole in a culture within 3 days.
Sekiyu Gakkaishi, 1992
The effects of organometallic complexes (Fe3(CO)12, Mo(CO)6, Ru3(CO)12, and Ru(acac)3) on the hyd... more The effects of organometallic complexes (Fe3(CO)12, Mo(CO)6, Ru3(CO)12, and Ru(acac)3) on the hydrogenation of coal tar pitch for high performance carbon fiber were investigated, and their activities were compared with those of commercial molybdenum-based supported catalysts. The hydrogenation was carried out with tritium-labelled gaseous hydrogen using a 350ml autoclave. The catalysts derived from the organometallic complexes were found to be more active for the hydrogen transfer from the gas phase to pitch than the molybdenum-based supported catalysts. Especially, the ruthenium complexes were most active for hydrogen transfer, and could effectively catalyze the hydrogenation of not only low molecular weight aromatics but also high molecular weight polycondensed ones in pitch. The results from XPS analyses of the used organometallic complexes suggest that the fine metal particles with a reduced state formed at the initial stage of hydrogenation may be the active form for the activation of molecular hydrogen or pitch molecules.
Catalysts, Sep 13, 2012
Tetraethoxy orthosilicate (TEOS) was used not only as a precursor of silica, but also as an agent... more Tetraethoxy orthosilicate (TEOS) was used not only as a precursor of silica, but also as an agent which reinforces the skeleton of silica-gel to prepare an aerogel and resultant silica and silica-alumina with large pore size and pore volume. In this gel skeletal reinforcement, the strength of silica aerogel skeleton was enhanced by aging with TEOS/2-propanol mixed solution to prevent the shrink of the pores. When silica aerogel was reinforced by TEOS solution, the pore diameter and pore volume of calcined silica could be controlled by the amount of TEOS solution and reached 30 nm and 3.1 cm 3 /g. The results from N 2 adsorption measurement indicated that most of pores for this silica consisted of mesopores. Silica-alumina was prepared by the impregnation of an aluminum tri-sec-butoxide/2-butanol solution with obtained silica. Mixed catalysts were prepared by the combination of β-zeolite (26 wt%) and prepared silica-aluminas with large mesopore (58 wt%) and subsequently the effects of their pore sizes on the catalytic activity and the product selectivity were investigated in catalytic cracking of n-dodecane at 500 °C. The mixed catalysts exhibited not only comparable activity to that for single zeolite, but also unique selectivity where larger amounts of branched products were formed.
Journal of The Japan Petroleum Institute, 2014
Hierarchical Y zeolite-containing mesoporous silica _ aluminas were prepared by the one pot sol-g... more Hierarchical Y zeolite-containing mesoporous silica _ aluminas were prepared by the one pot sol-gel method using malic acid. Properties for the catalytic cracking of vacuum gas oil (VGO) were estimated using a Curie point pyrolyzer, to establish a novel and very simple estimation method for the catalytic cracking of VGO. Prepared catalysts showed higher conversions and selectivities for gasoline than zeolite single, indicating that yields of gasoline for zeolite-containing catalysts increased compared with that of zeolite single. Higher content of aluminum species in the catalysts resulted in decreased olefin/paraffin ratios and increased iso-/n-ratios (ratio of branched products to straight-chained ones), indicating that hydrogen transfer and isomerization were promoted by the addition of acid sites into the matrix. Catalysts with mesopores tended to form larger amounts of multibranched products, which are very important in modern petroleum refining. When the yields of gasoline, singlebranched products and multi-branched products were plotted against the conversion of VGO, the linear relationships were observed and the effect of kinds of zeolite was rather small, indicating that the activity and the selectivity were largely affected by the presence of matrices. Comparison of the yields of gasoline, single-branched products and multi-branched products at the same conversions showed that Y zeolite-containing catalysts always showed the highest yields and ZSM-5-containing catalysts showed the lowest yields although the differences were small. Pore size of the zeolite probably also affected the yields in the treatment of large molecules such as VGO. The present findings suggest that the appropriate combination of zeolite and matrix is the most important factor to obtain high catalytic activity and high yields of gasoline and branched products.
Journal of The Japan Petroleum Institute, 2002
A series of CoMo catalysts supported on TiO2 with various Co/Mo molar ratios were prepared to inv... more A series of CoMo catalysts supported on TiO2 with various Co/Mo molar ratios were prepared to investigate the relationship between the support and the promoting effect of cobalt. The catalytic activities of these catalysts were measured for the hydrodesulfurization (HDS) of dibenzothiophene (DBT). The HDS activity of Mo/TiO2 catalysts increased remarkably with increased addition of cobalt up to Co/Mo ratio of 0.2 and then increased slightly above this value. The HYD activity of these catalysts remained almost constant with increasing Co/Mo ratio. Sulfur mobility on the sulfided CoMo/TiO2 catalysts under the reaction conditions was investigated by a 35S radioisotope tracer method using 35S-labeled DBT. The rate constants of H2S release (kRE) for Co-promoted catalysts were approximately the same as those for non-promoted Mo catalysts at a given temperature, indicating that the addition of cobalt did not affect the mobility of sulfur over Mo/TiO2 catalysts. In contrast, the amount of labile sulfur (S0) increased remarkably with the addition of cobalt up to Co/Mo ratio of 0.2 and then increased slightly above this value. The increase in the catalytic activity with the addition of cobalt is probably due to an increase in the number of active sites.
Journal of the Japan Institute of Energy
Hierarchical ZSM-5-Al2O3-TiO2-composite supported Pt, Ni and Mo sulfides catalysts were used for ... more Hierarchical ZSM-5-Al2O3-TiO2-composite supported Pt, Ni and Mo sulfides catalysts were used for the dehydrocyclization-cracking of soybean oil at 1.0 MPa of hydrogen in the range 420-580 °C. Pt/NM/Z(24)75Ti(500sg) (N=Ni, M=Mo, Z=ZSM-5, 24=SiO2/Al2O3, 75=weight ratio, Ti=TiO2, 500=cal-cination temp. °C, sg=sol-gel method) and Pt/NM/Z(24)75Ti(600sg) prepared by the sol-gel method exhibited the higher activity in this reaction and the higher aromatics yields than the catalysts with single use of Al 2O3 and TiO2 prepared by the kneading method. Further, Pt/NM/Z(24)30Al30Ti prepared by the kneading method and Pt/NM/Z(24)75Al(600sg) prepared by the sol-gel method exhibited the highest aromatics yield of 15% among the catalysts tested. The result indicated that the addition of TiO 2 to the composite support would promote the interaction between molybdenum sulfide and TiO2, activate hydrogen and lead to enhanced cracking of ester group of triglyceride and cyclization of hydrocarbon fragments. When the sol-gel method was used, the catalysts with not only TiO2 but also Al2O3 exhibited the higher aromatics yields. Pt/NM/Z(24)75Ti(500sg) and Pt/NM/Z(24)75Ti(600sg) inhibited the formation of gaseous products while Pt/NM/Z(24)30Al30Ti and Pt/NM/Z(24)75Al(600sg) increased gaseous products, suggesting that the mechanism of aromatics formation might be different, and that the former would produce aromatics through the direct cyclization of longer-chained hydrocarbon fragments while the latter would produce them through gasification to C2-C4 olefins and the successive cyclization by the Diels-Alder reaction of olefins. ZSM-5-Al2O3-TiO2 複合担体をゾル-ゲル法および混錬法で作製し，Pt，Ni および Mo を含浸担持した触媒を作製した。予 備硫化後，大豆油の環化脱水素化分解反応を1.0 MPa および 420-580 °C の条件で行った。ゾル-ゲル法で調製した Pt/NM/ Z(24)75Ti(500sg) (N=Ni, M=Mo, Z=ZSM-5, 24= SiO2/Al2O3, 75=weight ratio, Ti=TiO2, 500=calcination temp. °C, sg=solgel method)と Pt/NM/Z(24)75Ti(600sg) 触媒は，混錬法で Al2O3 および TiO2 を用いて作製した触媒よりも高活性と高芳香族
Journal of the Japan Institute of Energy
Hierarchical ZSM-5-Al2O3-TiO2-composite supported Pt, Ni and Mo sulfides catalysts were used for ... more Hierarchical ZSM-5-Al2O3-TiO2-composite supported Pt, Ni and Mo sulfides catalysts were used for the dehydrocyclization-cracking of soybean oil at 1.0 MPa of hydrogen in the range 420-580 °C. Pt/NM/Z(24)75Ti(500sg) (N=Ni, M=Mo, Z=ZSM-5, 24=SiO2/Al2O3, 75=weight ratio, Ti=TiO2, 500=cal-cination temp. °C, sg=sol-gel method) and Pt/NM/Z(24)75Ti(600sg) prepared by the sol-gel method exhibited the higher activity in this reaction and the higher aromatics yields than the catalysts with single use of Al 2O3 and TiO2 prepared by the kneading method. Further, Pt/NM/Z(24)30Al30Ti prepared by the kneading method and Pt/NM/Z(24)75Al(600sg) prepared by the sol-gel method exhibited the highest aromatics yield of 15% among the catalysts tested. The result indicated that the addition of TiO 2 to the composite support would promote the interaction between molybdenum sulfide and TiO2, activate hydrogen and lead to enhanced cracking of ester group of triglyceride and cyclization of hydrocarbon fragments. When the sol-gel method was used, the catalysts with not only TiO2 but also Al2O3 exhibited the higher aromatics yields. Pt/NM/Z(24)75Ti(500sg) and Pt/NM/Z(24)75Ti(600sg) inhibited the formation of gaseous products while Pt/NM/Z(24)30Al30Ti and Pt/NM/Z(24)75Al(600sg) increased gaseous products, suggesting that the mechanism of aromatics formation might be different, and that the former would produce aromatics through the direct cyclization of longer-chained hydrocarbon fragments while the latter would produce them through gasification to C2-C4 olefins and the successive cyclization by the Diels-Alder reaction of olefins. ZSM-5-Al2O3-TiO2 複合担体をゾル-ゲル法および混錬法で作製し，Pt，Ni および Mo を含浸担持した触媒を作製した。予 備硫化後，大豆油の環化脱水素化分解反応を1.0 MPa および 420-580 °C の条件で行った。ゾル-ゲル法で調製した Pt/NM/ Z(24)75Ti(500sg) (N=Ni, M=Mo, Z=ZSM-5, 24= SiO2/Al2O3, 75=weight ratio, Ti=TiO2, 500=calcination temp. °C, sg=solgel method)と Pt/NM/Z(24)75Ti(600sg) 触媒は，混錬法で Al2O3 および TiO2 を用いて作製した触媒よりも高活性と高芳香族
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Papers by Atsushi Ishihara