Faculty Profiles - NAGAOKA Katsutoshi

Titania-supported cobalt and nickel bimetallic catalysts for carbon dioxide reforming of methane Reviewed

K Takanabe, K Nagaoka, K Nariai, K Aika

JOURNAL OF CATALYSIS Vol. 232 ( 2 ) page： 268 - 275 2005.6

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE

Titania-supported cobalt and nickel bimetallic catalysts were investigated for CO2 reforming of methane to synthesis gas at 1023 K under ambient pressure. Bimetallic Co-Ni/TiO2 catalysts with an appropriate Co/Ni ratio showed highly stable activities without carbon deposition. Whereas the monometallic Co/TiO2 catalyst deactivated rapidly because of the oxidation of metal, 10 mol% substitution of nickel for cobalt suppressed the oxidation of metal, providing a high catalytic stability. However, the catalysts with excess nickel content (> 80 mol%) underwent carbon formation. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses revealed that a homogeneous alloy of cobalt and nickel was formed from bulk to the surface by the H-2 reduction. and the alloy was stabte during reforming The advantages of the bimetallic catalysts are high resistance to undesirable metal oxidation and coking, through the control of reactions between CH4 and CO2. (c) 2005 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2005.03.011

Novel tough catalyst supports for reactions involving HF Reviewed

Y Takita, T Ohkuma, H Nishiguchi, K Nagaoka, T Nakajo

APPLIED CATALYSIS A-GENERAL Vol. 283 ( 1-2 ) page： 47 - 52 2005.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Metal fluorides are more stable than metals and metal oxides; therefore, no oxides can be applied as catalyst supports for the reactions in which hydrogen fluoride is involved. The authors observed that metal phosphates are not reactive to HF at higher reaction temperatures such as 973 K. Hence, the decomposition of CCIF2CCIF2 was studied over Pt-supported SiO2, Al2O3, and AlPO4-based catalysts. Hydrodehalogenation proceeded and CHF2CCIF2 and C2H6 were formed as major products, small amounts of CHF2CHF2, CH2FCCIF2, CH2FCF3. and CH4 were also formed. Pt/SiO2 was the most active; however, SiO2 reacted with HF and the SiF4 formed sublimated. Following these, Al2O3 was the most active; however, it reacted with HF to form AlF3 and was deactivated. Similar hydrodehalogenation proceeded over Pt/AlPO4 and Pt/ (CePO4-AIPO(4)). The crystal structure of these catalysts did not change during the catalytic reaction, although the reduction of specific surface areas (SSA) was observed. Therefore, AlPO4 and Ce containing AlPO4 are suitable as catalyst supports in reactions in which HF is involved. XPS showed that the electronic effects of AlPO4 lie between that of SiO2 and Al2O3. A good linear relationship is found to exist between the initial reaction rates per unit Surface area of Pt metal supported on the supports and the binding energy of supported Pt. This suggests that the more cationic the Pt. the more easily it could abstract Cl- from CCIF2CCIF2. (c) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2004.12.033

Oxidation of isobutane over complex oxides containing V, Nb, Ta, and Mo under aerobic and anaerobic reaction conditions Reviewed

Y Takita, K Kikutani, C Xia, H Takami, K Nagaoka

APPLIED CATALYSIS A-GENERAL Vol. 283 ( 1-2 ) page： 209 - 216 2005.4

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Isobutane oxidation over sin-le metal oxides of V, Nb, Ta, and Mo and over their complex oxides was studied. The most active was V2O5, while medium activity was shown by LaVO4, BiVO4, CaV2O6, Ta2O5, TaV2O6, ZnNb2O6, Nb2PO5, MgV2O6, YVO4, Cu2V2O7, MoO3 and MnNb2O5. The less active oxides were Na2MoO4 and Ag2MoO4. lsobutane was oxidized mainly to isobutene and COx. but isobutene selectivity was generally lower than 50% below 673 K. Relatively high isobutene selectivity was shown by MgTa2O6, TaV2O6, and ZnNb2O6. Methacroleine was only obtained over MoO3 and methanol was formed only over V2O5 and Cu2V2O7. Acetic acid was formed over certain V-containing oxides. No oxygen-containing products were formed over Nb- and Ta-containing oxides. On a unit surface area basis, Nb2O5 and Ta2O5 have higher oxidizing activity than V2O5 and MoO3.
Isobutane oxidation was studied in the absence of gaseous O-2 over MV2-type complex oxides. Catalytic activity was determined as follows: CuV2O6 >> CoV2O6 > MgV2O6 > ZnV2O6 >> ZrV2O7 > CaV(2)O(6)center dot MgV2O6 is the most selective for isobutene formation. Combination to easily redoxable metal ions tends to accelerate the deep oxidation process. There may be a threshold for the initial reaction rate of lattice oxygen per unit surface area for selective isobutene formation. Selective isobutene formation continued until a reduction of MgV2O6 by least 4.5%, had finished and the reduced catalyst was recovered by the calcination at 773 K. Selective formation of isobutene made it possible to combine oxidations of isobutane with MgV2O6 and with the oxidations of reduced catalysts. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apcata.2005.01.008

Methane autothermal reforming with and without ethane over mono- and bimetal catalysts prepared from hydrotalcite precursors Reviewed

Influence of reduction temperature on the catalytic behavior of Co/TiO2 catalysts for CH4/CO2 reforming and its relation with titania bulk crystal structure Reviewed

Takanabe K, Nagaoka K, Nariai K, Aika K

JOURNAL OF CATALYSIS Vol. 230 ( 1 ) page： 75 - 85 2005.2

Interaction between sulfated zirconia and alkanes: prerequisites for active sites - formation and stability of reaction intermediates Reviewed

Li XB, Nagaoka K, Simon LJ, Lercher JA, Wrabetz S, Jentoft FC, Breitkopf C, Matysik S, Papp H

JOURNAL OF CATALYSIS Vol. 230 ( 1 ) page： 214 - 225 2005.2

K Nagaoka, A Jentys, JA Lercher

JOURNAL OF CATALYSIS Vol. 229 ( 1 ) page： 185 - 196 2005.1

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE

Autothermal reforming of methane (in the presence or absence of ethane) over Ni and/or Rh catalysts prepared from hydrotalcites is reported. Surface and bulk structures of the reduced supported metal catalysts were characterized by various physicochemical techniques. XANES and EXAFS at the Ni and Rh K-edges indicate that the reduction of Ni2+ and Rh3+ in the support matrix with H-2 was incomplete for all catalysts. NiRh alloy particles are formed in NiRh/MgAl. IR spectra of adsorbed CO indicate that the surface of the NiRh alloy particles is enriched in Ni. All catalysts hardly catalyzed coke formation during CH4 autothermal reforming. The surface concentration of reduced Ni was critical for the catalytic activity, i.e., the catalytic activity decreased in the order NiRh/MgAl > Ni/MgAl-2 > Rh/MgAl-1. However, Ni/MgAl-2 lost its activity, when cycling between 1073 and 773 K at very high space velocities (1.2 x 10(4) l/(h g)) through oxidation of metallic Ni. In contrast, NiRh/MgAl was relatively stable, while Rh/MgAl-1 did not deactivate. The enhanced stability of NiRh/MgAl by Rh against oxidation is attributed to H-2 spillover from Rh in the NiRh alloy as well as to its high activity (larger fraction with reducing atmosphere). The activity of all catalysts in converting hydrocarbons increased in the presence of ethane, with ethane showing a high tendency to react preferentially. Ethane could be converted completely in the presence of partly converted methane. NiRh/MgAl and Rh/MgAl-1 showed stable activity at 1073 and 773 K, while Ni/MgAl-2 gradually deactivated at 773 K. The deactivation attributed to Ni oxidation was reduced by addition of C2H6. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2004.10.006

Labile sulfates as key components in active sulfated zirconia for n-butane isomerization at low temperatures Reviewed

Improvement of Pt/ZrO2 by CeO2 for high pressure CH4/CO2 reforming Reviewed

Nagaoka K, Seshan K, Takanabe K, Aika K

CATALYSIS LETTERS Vol. 99 ( 1-2 ) page： 97 - 100 2005.1

XB Li, K Nagaoka, JA Lercher

JOURNAL OF CATALYSIS Vol. 227 ( 1 ) page： 130 - 137 2004.10

Language：English Publishing type：Research paper (scientific journal) Publisher：ACADEMIC PRESS INC ELSEVIER SCIENCE

A wide variety of sulfate species exists on sulfated zirconia and many of these species have been connected to the catalytic performance. Some of these groups show strong interactions with polar molecules, indicating that they may play a role for the catalytic properties. In order to differentiate between these groups and to explore the role of labile soluble sulfate for n-butane skeletal isomerization, active sulfated zirconia was washed with water. Water washing removed around 40% of the sulfate species and led to a catalyst inactive for the alkane isomerization. This indicates that the labile sulfate plays a key role for the catalysis. The water-soluble fraction of the sulfate exists as highly covalent sulfate species characterized by an S=O vibration between 1390 and 1410 cm(-1) on the activated sulfated zirconia. Bronsted acid sites related to the sulfate groups are shown to be indispensable for activating n-butane, while Lewis acid sites do not directly participate in the alkane conversion catalysis. (C) 2004 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.jcat.2004.07.003

Modification of Co/TiO2 for dry reforming of methane at 2 MPa by Pt, Ru or Ni Reviewed

K Nagaoka, K Takanabe, K Aika

APPLIED CATALYSIS A-GENERAL Vol. 268 ( 1-2 ) page： 151 - 158 2004.8

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Influences of an addition of trace amounts of Pt (Pt/Co = 0.005-0.05 in atomic ratio) or Ru (Ru/Co = 0.01-0.05) and of replacement of Co by Ni (Ni:Co = 1:99-100:0) to 0.5 wt.% Co/TiO2 have been investigated for the dry reforming of methane at 2MPa. Co/TiO2 reduced at 1123 K showed slow deactivation due to oxidation of Co. The addition of noble metals improved the catalytic stability of Co/TiO, drastically. The strong resistant nature of Co/TiO, to coke deposition was also retained by the catalysts. TPR revealed that noble metals improved the reducibility of cobalt oxide. The replacement of Co by a small amount of Ni also enhanced the catalytic stability of Co/TiO2, but replacement by an excess of Ni resulted in the decrease of catalytic stability because of coking. CoNi/TiO2 with an optimum Co:Ni ratio of 90:10 presented high stability with only an insignificant amount of coke deposition under 2 MPa, where coke deposition is highly favorable. (C) 2004 Published by Elsevier B.V.

DOI： 10.1016/j.apcata.2004.03.029

Co/TiO<inf>2</inf>catalyst for high pressure dry reforming of methane and its modification by other metals Reviewed

Katsutoshi Nagaoka, Kazuhiro Takanabe, Ken Ichi Aika, Ken Ichi Aika

Studies in Surface Science and Catalysis Vol. 147 page： 187-192 2004.1

Language：English Publishing type：Research paper (scientific journal)

Catalytic behaviour of 0.5wt%Co/TiO2, prepared from TiO2containing only anatase phase, in CH4/CO2reforming at 2 MPa was strongly affected by reduction temperature. Co/TiO2reduced at relatively lower temperatures (<1123 K) lost all of its activity at the beginning of the reaction, whereas the catalyst reduced at higher temperatures (1123 K) showed relatively stable activity with only a slight amount of deposited coke. However, the latter catalyst lost all of activities at a higher space velocity after the reaction for 20 h, mainly due to oxidation of metallic Co. The addition of trace amounts of noble metals (Pt or Ru) improved the catalytic stability drastically by retarding the oxidation. It was confirmed that the strong resistant nature of Co/TiO2to coke deposition was retained after the addition of the noble metals.

Influence of the reduction temperature on catalytic activity of Co/TiO2 (anatase-type) for high pressure dry reforming of methane Reviewed

Co/TiO2 catalyst for high pressure dry reforming of methane and its modification by other metals Reviewed

Nagaoka K, Takanabe K, Aika KI

NATURAL GAS CONVERSION VII Vol. 147 page： 187 - 192 2004

K Nagaoka, K Takanabe, K Aika

APPLIED CATALYSIS A-GENERAL Vol. 255 ( 1 ) page： 13 - 21 2003.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

0.5 wt.% Co/TiO2 was prepared by incipient wetness impregnation with Co(NO3)(2)(.)6H(2)O and TiO2, which contains only anatase as crystal structure. The influence of reduction temperature (973-1223 K) on the catalytic activity of the 0.5 wt.% Co/TiO2 was investigated for the CH4/CO2 reaction under 2.0 MPa mainly at a space velocity (SV) of 6000 ml g(-1) h(-1). Co/TiO2 reduced below 1123 K lost its activity completely at the beginning of the reaction. The results of TPO revealed that large amounts of coke (greater than or equal to2.9 wt.% carbon for 24 h) were deposited on the catalysts during the CH4/CO2 reaction. On the other hand, Co/TiO2 reduced at and above 1123 K kept relatively stable activity for 24 h and did not show significant amounts of deposited coke (less than or equal to0.25 wt.% carbon). The natures causing different catalytic behavior among the catalysts were discussed with the results of TEM, XRD, and TPR. In addition, slow deactivation of the Co/TiO2 reduced at 1123 K, probably due to the oxidation of the metallic cobalt, was inhibited by the addition of small amount of ruthenium (Ru/Co = 0.05) and it was found that the strong resistance to the coking of the Co/TiO2 reduced at 1123 K was retained after the addition of ruthenium. (C) 2003 Elsevier B.V. All rights reserved.

DOI： 10.1016/S0926-860X(03)00631-8

Influence of the phase composition of titania on catalytic behavior of Co/TiO2 for the dry reforming of methane Reviewed

K Nagaoka, K Takanabe, K Aika

CHEMICAL COMMUNICATIONS ( 9 ) page： 1006 - 1007 2002

Language：English Publishing type：Research paper (scientific journal) Publisher：ROYAL SOC CHEMISTRY

The phase transfer of TiO2 from anatase to rutile for a 10wt% Co/TiO2 catalyst during the reduction causes serious disappearance of activity at 0.1 MPa during CH4/CO2 reforming, whereas the transfer for 0.5wt% Co/TiO2 brings about relatively stable activity at 2 MPa.

DOI： 10.1039/b201717m

Mechanism of carbon deposit/removal in methane dry reforming on supported metal catalysts Reviewed

Effect of additives on the stability of Pd/Al2O3 for carbon dioxide reforming of methane Reviewed

Nagaoka K, Aika K

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN Vol. 74 ( 10 ) page： 1841 - 1846 2001.10

Nagaoka K, Seshan K, Lercher J.A, Aika K

Studies in Surface Science and Catalysis Vol. 136 page： 129 - 134 2001

Titania supported ruthenium as a coking-resistant catalyst for high pressure dry reforming of methane Reviewed

Katsutoshi Nagaoka, Masato Okamura, Ken-Ichi Aika

Catalysis Communications Vol. 2 ( 8 ) page： 255 - 260 2001

Language：English Publishing type：Research paper (scientific journal)

Support (SiO2, Al2O3, MgO, and TiO2) effects on catalytic behavior of Ru catalysts for the CH4/CO2 reforming were investigated under 2 (industrial condition) and 0.1 MPa at 1023 K. The order of the catalytic activity of the four catalysts investigated was dependent on the reaction pressure. High coking rate was observed at high pressure. 2 wt% Ru/TiO2, showing a low coking extent, is a promising candidate for industrial use. © 2001 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S1566-7367(01)00043-7