Papers by Atsushi Ishihara
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.
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
Applied Catalysis A-general, Jun 1, 1998
In the present part of the group study on the preparation of 13wt% MoO3/Al2O3, the effects of dry... more In the present part of the group study on the preparation of 13wt% MoO3/Al2O3, the effects of drying processes were investigated on the physicochemical and catalytic properties. Two series of catalysts were prepared by a conventional impregnation technique and by an equilibrium adsorption method using a common extrudate support. XPS and EPMA results demonstrated that the distribution of Mo oxide species in extrudates was strongly affected by drying processes. A rapid drying, in particular at a reduced pressure, was found to induce a strong segregation of Mo oxides on the outer surface of the extrudates, forming a sharp egg shell type distribution of Mo. On the other hand, drying under static conditions produced a moderate egg shell type distribution, suggesting that a slow drying rate is favorable for a homogeneous distribution of Mo. The equilibrium adsorption technique was found to provide considerably flat Mo profiles inside the extrudates except for the utmost surfaces where Mo concentrations increased steeply.
Applied Catalysis A-general, Jun 1, 1998
In the present part of the group study on the preparation of 13wt% MoO3/Al2O3, the effects of dry... more In the present part of the group study on the preparation of 13wt% MoO3/Al2O3, the effects of drying processes were investigated on the physicochemical and catalytic properties. Two series of catalysts were prepared by a conventional impregnation technique and by an equilibrium adsorption method using a common extrudate support. XPS and EPMA results demonstrated that the distribution of Mo oxide species in extrudates was strongly affected by drying processes. A rapid drying, in particular at a reduced pressure, was found to induce a strong segregation of Mo oxides on the outer surface of the extrudates, forming a sharp egg shell type distribution of Mo. On the other hand, drying under static conditions produced a moderate egg shell type distribution, suggesting that a slow drying rate is favorable for a homogeneous distribution of Mo. The equilibrium adsorption technique was found to provide considerably flat Mo profiles inside the extrudates except for the utmost surfaces where Mo concentrations increased steeply.
Applied Catalysis A-general, Jun 1, 1998
The effects of the volume and pH of the impregnation solution and of the calcination conditions w... more The effects of the volume and pH of the impregnation solution and of the calcination conditions were examined on the physicochemical and catalytic properties of a 13wt% MoO3/Al2O3 extrudate catalyst. The Al2O3 support and drying procedures (static conditions without flowing air) were fixed in the preparations. In the present series of catalysts, the amount of crystalline MoO3 was marginally small.
Applied Catalysis A-general, Jun 1, 1998
The effects of the volume and pH of the impregnation solution and of the calcination conditions w... more The effects of the volume and pH of the impregnation solution and of the calcination conditions were examined on the physicochemical and catalytic properties of a 13wt% MoO3/Al2O3 extrudate catalyst. The Al2O3 support and drying procedures (static conditions without flowing air) were fixed in the preparations. In the present series of catalysts, the amount of crystalline MoO3 was marginally small.
Journal of the Japan Petroleum Institute
The two-layered and three-layered hierarchical catalysts with micropore-small mesopore-large meso... more The two-layered and three-layered hierarchical catalysts with micropore-small mesopore-large mesopore (micro-meso-meso) structures were prepared using the gel skeletal reinforcement (GSR) method. A Curie point pyrolyzer method was used to evaluate their properties in the catalytic cracking of low density polyethylene (LDPE) and the effects of their pore structure and zeolite type were investigated. The two-layered catalyst prepared with malic acid, TEOS and β-zeolite achieved conversion of 78 % and was more active than similar Y-zeolite-based catalysts. The three-layered catalyst, in which the two-layered catalyst was dispersed in silica made by the GSR method, maintained the conversion despite lower zeolite content. Evaluation of conversion against the XRD integrated intensity and the number of acid sites of the zeolite as a measure of the relative activity of the catalyst found that the relative activity was higher for the hierarchical structured catalyst than for single zeolite and kaolin-mixed catalysts.
Journal of the Japan Petroleum Institute
The two-layered and three-layered hierarchical catalysts with micropore-small mesopore-large meso... more The two-layered and three-layered hierarchical catalysts with micropore-small mesopore-large mesopore (micro-meso-meso) structures were prepared using the gel skeletal reinforcement (GSR) method. A Curie point pyrolyzer method was used to evaluate their properties in the catalytic cracking of low density polyethylene (LDPE) and the effects of their pore structure and zeolite type were investigated. The two-layered catalyst prepared with malic acid, TEOS and β-zeolite achieved conversion of 78 % and was more active than similar Y-zeolite-based catalysts. The three-layered catalyst, in which the two-layered catalyst was dispersed in silica made by the GSR method, maintained the conversion despite lower zeolite content. Evaluation of conversion against the XRD integrated intensity and the number of acid sites of the zeolite as a measure of the relative activity of the catalyst found that the relative activity was higher for the hierarchical structured catalyst than for single zeolite and kaolin-mixed catalysts.
Journal of the Japan Petroleum Institute
NIPPON KAGAKU KAISHI, 1991
Fuel Processing Technology, 2004
Roles of mineral matters and oxygen functional groups of coal on hydrogen transfer reaction with ... more Roles of mineral matters and oxygen functional groups of coal on hydrogen transfer reaction with gaseous hydrogen were investigated by using a tritium tracer technique in a fixed-bed reactor system. Mineral matters in coal were removed by HCl or HCl/HF treatments. Alkali metals and a part of pyrite were removed by HCl treatment. SiO 2 and Al 2 O 3 were removed only by HCl/HF treatment. A large part of pyrite was removed by HCl/HF treatment but about 20% of them still remained even after the treatment. It was observed that the efficiency of hydrogen transfer of coal decreased to some extent when cations and mineral matters were removed by HCl treatment. Further decrease in hydrogen transfer was observed after HCl/HF treatment. These results suggested that iron species from pyrite may catalyze the hydrogen transfer reaction with H 2 gas. Mineral matters assist the Htransfer to the carbon network of coal but does not promote hydrogen transfer to hydroxy groups.
Catalysis Today, 1998
Composite types of TiO 2 ±Al 2 O 3 supports, which are g-aluminas coated by titania, have been pr... more Composite types of TiO 2 ±Al 2 O 3 supports, which are g-aluminas coated by titania, have been prepared by chemical vapor deposition (CVD), using TiCl 4 as a precursor. Then supported molybdenum catalysts have been prepared by an impregnation method. As supports, we employed g-alumina, anatase types of titania, and composite types of TiO 2 ±Al 2 O 3 with different loadings of TiO 2. We studied the conversion of Mo from oxidic to sul®dic state through sulfurization by X-ray photoelectron spectroscopy (XPS). The obtained spectra unambiguously revealed the higher reducibility from oxidic to sul®dic molybdenum species on the TiO 2 and TiO 2 ±Al 2 O 3 supports compared to that on the Al 2 O 3 support. Higher TiO 2 loadings of the TiO 2 ±Al 2 O 3 composite support led to higher reducibility for molybdenum species. Furthermore, the catalytic behavior of supported molybdenum catalysts has been investigated for hydrodesulfurization (HDS) of dibenzothiophene (DBT) and methylsubstituted DBT derivatives. The conversion over the TiO 2 ±Al 2 O 3 supported Mo catalysts, in particular for the 4,6-dimethyl-DBT, is much higher than that obtained over Al 2 O 3 supported Mo catalyst. The ratio of the corresponding cyclohexylbenzene (CHB)/biphenyl (BP) derivatives is increased over the Mo/TiO 2 ±Al 2 O 3. This indicates that the prehydrogenation of an aromatic ring plays an important role in the HDS of DBT derivatives over TiO 2 ±Al 2 O 3 supported catalysts.
Journal of the Japan Institute of Energy
Recently, we have reported that the needle-like crystals appeared under the different heat treatm... more Recently, we have reported that the needle-like crystals appeared under the different heat treatments between Upper Freeport (UF) and Illinoi#6 bituminous coals. In this study, we investigated the change in the behavior of ash components of UF bituminous coal, Wyodak-Anderson (WD) sub-bituminous coal, and Beulah-Zap (BZ) brown coal with treatment temperature and atmosphere by XRD, TG-DTA, and TEM measurements. Anhydrite, quartz, and hematite were observed for WD heat-treated up to 1000 °C under air atmosphere. The peak of anhydrite for WD was stronger than others at all temperatures. This can be attributed to the difference in the SO3 content in the ash. A part of anhydrite in WD and BZ changed to gehlenite by heat treatment up to 1200 °C, while anhydrite was observed for UF heat-treated. It seems that this would be due to the difference in Ca content. Troilite formed by the reduction of pyrite was observed under argon treatment for coals other than WD. The cubic shape crystals observed in the TEM image in WD and BZ heat-treated at 1200 °C under air atmosphere could be gehlenite from the XRD data.
Applied Catalysis A: General, 2005
We systematically monitored the hydrodesulfurization (HDS) activity of dibenzothiophene (DBT) and... more We systematically monitored the hydrodesulfurization (HDS) activity of dibenzothiophene (DBT) and groups of substituted DBTs present in a SR-LGO over various noble metal catalysts (Ru, Rh, Ru-Rh, Pt, Pd and Pt-Pd) supported on alumina. The catalytic performances were compared to those obtained over a conventional CoMo catalyst. The Pd-based catalysts exhibited excellent HDS performances, especially for desulfurizing the refractory compounds. In particular, the 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS activity over the Pd or the Pd-Pt catalyst was equivalent to that over the CoMo catalyst. This was attributed to the exceptional hydrogenation (HYD) properties of the Pd-based catalysts, which enable desulfurization of the refractory compounds by considerably minimizing the effect of the steric hindrance due to their substituents. The synergetic effect observed on the bimetallic Pt-Pd system at low temperature for all the sulfur compounds was largely attenuated in the high temperature range, probably due to shifting of the HYD/dehydrogenation equilibrium to dehydrogenation. Despite a much lower metal loading (0.25 wt.%), the performances of the Rh catalyst were superior to those of the optimized 16 wt.% Ru catalyst. A synergetic effect was observed on the Ru-Rh catalyst, on which the DBT HDS activity was significantly enhanced compared to the activity of each corresponding monometallic catalyst. Further, we recently showed that the use of SiO 2 or SiO 2-Al 2 O 3 as a support allows higher optimal Rh contents, making the Rh-based HDS catalysts even more promising. In brief, we obtained encouraging results, which showed for instance that the excellent properties of the noble metal catalysts in model HDS reactions are still observed during the HDS treatment of real feeds.
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Papers by Atsushi Ishihara