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Oxide ion conductivity in La-deficient La 2 GeO 5−δ was investigated with 18 O tracer diffusion measurement. It was found that La 1.61 GeO 4.415 exhibits a large diffusion coefficient, which is in good agreement with that estimated from electrical conductivity. Therefore, it was confirmed that La-deficient La 2 GeO 5 is a pure oxide ionic conductor. The effects of doping alkaline earth cations to the La site of La 1.8 GeO 4.7 were also investigated. Although the crystal structure was slightly changed, alkaline earth cations seem to substitute for the La site in La 2 GeO 5 . The electrical conductivity at low temperature is increased by doping alkaline earth cations, in particular, it was found that doping with Ca is the most effective for increasing the electrical conductivity. The electrical conductivity increased with increasing Ca and attained the maximum at a composition of La 1.5 Ca 0.2 GeO 4.45 . The transport number of the oxide ion, estimated by H 2 –O 2 cell, was almost 1.0. Therefore, Ca-doped La 2 GeO 5 oxide is also a pure oxide ionic conductor. Since the electrical conductivity of La 1.5 Ca 0.2 GeO 4.45 was higher than that of Zr 0.84 Y 0.15 O 2 at all temperature examined, Ca-doped La 2 GeO 5 based oxide is attractive as a new fast oxide ion conductor.

Fe doped LaGaO3 based perovskite oxide was investigated in this study as an oxygen permeating membrane for CH4 partial oxidation. La0.7Sr0.3Ga0.6Fe0.4O3 exhibits a high oxygen permeation rate from air to He as high as 102 μmol/min cm2 (2.5 cm3-std/min·cm2) at 1273 K and 0.3 mm thickness. Application of LSGF membrane for CH4 partial oxidation was further studied. Since the PO2 difference became large, oxygen permeation rate drastically increased and it attained a value of 322 μmol/min cm2 (8 cm3/min cm2) at 1273 K and 0.5 mm thickness. Catalyst for CH4 partial oxidation has a great influence on oxygen permeation rate through membrane and it became clear that Ni and Ru are highly active for CH4 partial oxidation.

Mixed electronic-oxide ionic conductivity and the cathodic property of BaCoO 3 doped with La was investigated in this study for a solid oxide fuel cell (SOFC) operating at intermediate temperature. The electrical conductivity of BaCoO 3 increases systematically with increasing amounts of La doped for Ba site. Cathodic overpotential at 1073 K decreased with increasing La content and attained a minimum at X =0.3–0.4 in Ba 1− X La X CoO 3 . Since the cathodic overpotential of Ba 0.6 La 0.4 CoO 3 was small at decreased temperature, Ba 0.6 La 0.4 CoO 3 is the optimum composition for a cathode of intermediate-temperature fuel cells among BaCoO 3 -based oxides. Mixed conductivity and surface activity for oxygen dissociation was investigated with 18 O– 16 O exchange reaction. It was found that BaCoO 3 doped with La exhibits a large oxide ion conductivity and surface activity. When La 0.8 Sr 0.2 Ga 0.8 Mg 0.115 Co 0.05 O 3 (0.4 mm in thickness) was used as electrolyte, the power density of a cell using Ba 0.6 La 0.4 CoO 3 for the cathode at 873 K attained a value of 120 mW/cm 2 , which is slightly larger than that using a conventional Sm 0.5 Sr 0.5 CoO 3 oxide for the cathode.

Electrochemical Li intercalation properties in 12-molybdophosphoric and 12-tangstophosphoric acids were investigated. It was found that both 12-molybdophosphoric and 12-tangstophosphoric acids exhibit fairly large capacity for the Li intercalation. Flat potential of 12-tangstophosphoric acids was 0.5V, which could be used for the anode of Li ion battery. 12-molybdophosphoric acid exhibits the flat potential of 1.5 V, although cycle stability is not high. XRD measurement shows the formation of Li2MoO4 after the intercalation of Li. Therefore electrochemical Li intercalation occurs by redox between Mo6+ and Mo4+ and so the theoretical Li intercalation capacity in 12-molybdophosphoric acid is 373mAh/g. Ion-exchanging H+ in 12-molybdophosphoric acid to Cs+ is effective to improve the cycle stability and capacity of ca. 200 mAh/g is sustained after 10 cycles. De-intercalation potential of 4.0V is newly appeared by substitution of Mo in 12-molybdophosphoric acid with V although the capacity is still not large. Therefore, substitution of V is effective for increasing the Li intercalation potential.

Cathodic performance of six different VOPO4 phases for Li ion rechargeable battery was investigated. It was found that VOPO4 exhibits a high flat discharge potential of 3.7 V for Li ion electrochemical intercalation and de-intercalation excepting for β- and e-types. On the other hand, slightly higher flat discharge potential of 3.9 and 3.8 V was observed for β- and e-types. Capacity for Li intercalation is strongly related with the crystal structure of VOPO4. In particular, δ-phase exhibits the largest reversible capacity of ca. 130 mAh/g among the examined VOPO4. High capacity for Li intercalation in δ-phase VOPO4 hardly decreased over 30 times of charge and discharge cycles. Although the reversible capacity decreased with increasing the current density for charge and discharge, large capacity of 80 mAh/g was still sustained at 0.4 mA/cm2 for δ-type VOPO4.

The decomposition of CH4 into C and H2 over Ni/SiO2 was investigated with a Pd−Ag hydrogen-permeating membrane reactor. The CH4 decomposition reaction hardly proceeded at temperatures lower than 773 K in a conventional fixed-bed reactor because of a chemical equilibrium limit. However, the conversion of CH4 was dramatically increased by removing the formed hydrogen by the Pd−Ag membrane. Because higher CH4 decomposition conversions were achieved at higher hydrogen removal rates in the Pd−Ag membrane, the removal of the formed hydrogen seems to be the key step for CH4 decomposition reaction at decreased temperature. Because a higher hydrogen permeation rate was achieved on the Pd(77)−Ag(23) membrane than on the Pd(90)−Ag(10) membrane, the CH4 conversion was always higher in membrane reactors using Pd(77)−Ag(23) than in reactors using Pd(90)−Ag(10) for the hydrogen separation membrane. The CH4 conversion increased with increasing contact time of the reactant and/or with increasing sweep Ar flow rate, becaus...

The decomposition of CH2FCF3 over some phosphate catalysts was studied. CH2FCF3 began to react at 250, 300, and 450 °C over Zr3(PO4)4, AlPO4, and BPO4, respectively, and the conversion reached 100% at 475, 500, and 700 °C, respectively. The primary reaction over Zr3(PO4)4 was estimated to be CH2FCF3 + H2O + 1/2O2 → 2CO + 4HF, whereas the reactions over AlPO4 and BPO4 were CH2FCF3 + H2O + O2 → CO + CO2 + 4HF and CO + 1/2O2 → CO2. Complete decomposition requires both hydrolysis and oxidation. The oxidation activities of these phosphate catalysts are not high enough to accomplish complete decomposition. However, AlPO4-based catalysts can be combined with each Co3O4, Mn2O3, CuO, and Cr2O3 at a phosphate content of 1/10 by volume to make them sustainable at 550−550 °C. The addition of Ce to AlPO4 brought about a promotion effect in CH2FCF3 decomposition similar to that for CCl2F2 decomposition. This might suggest a similarity in the reaction mechanism. The primary reaction in the absence of oxygen was estimate...

Supporting extremely small concentrations of noble metals on SiO 2 and Bi 2 Mo 3 O 12 affected the catalytic activity and product distribution in iso -butane partial oxidation. Supporting Pt, Pd, and Rh onto SiO 2 by 1 atom/μm 2 enhanced the catalytic activity. Selectivity values of partial oxidation products, iso -butene, CH 3 C(CH 3 )CHO, CH 3 CHO and CH 3 COCH 3 , were increased and CO x selectivity was decreased. Rh/SiO 2 gave an EPR signal due to isolated Rh 2+ ions with g ⊥ =2.07 and g ∥ =1.95, suggesting that two valent Rh ions are well dispersed on the surface and play a role in the oxidation of iso -butane. Supporting Pd, Ir, Rh, and Au onto Bi 2 Mo 3 O 12 at a concentration of (1/9)×10 −4 atom/nm 2 increased the conversion, but supporting Pt and Ru decreased it. Selectivity values of CH 2 C(CH 3 )CHO and CO x were the same for every catalyst. Catalytic activity was increased by supporting them by (1/49)×10 −4 atom/nm 2 ; especially, supporting Rh increased the activity without changing the selectivity of CH 2 C(CH 3 )CHO. Supported noble metal will interact with active oxygen ions bridging Mo and Bi on the Bi 2 Mo 3 O 12 surface. Since a certain concentration of supported noble metals, (1/49)×10 −4 nm 2 , begins to affect the catalytic activity and selectivity, this concentration may reflect the concentration of active sites in iso -butane oxidation at 350–400 °C over Bi 2 Mo 3 O 12 .

Direct formation of methacrolein from isobutane was investigated using a combination of the catalyst effective for oxidative dehydrogenation of isobutane, Ni2P2O7, and the catalyst effective for selective oxidation of olefins, Bi1-Mo12-Fe1-Co6-Ni2-Cs0.14-Oxide. Methacrolein was formed with the selectivity as high as 65% in a reactor with two catalyst beds in series. A mixed catalyst consisting of a mixture of the powders of both catalysts was effective for isobutene formation, although the conversion was reduced, whereas a mixture of granules was less effective. Addition of water vapor to the reaction system reduced the formation of oxygenates and promoted the formation of isobutene.

Activities for the hydrolysis of CCl 2 F 2 (CFC-12) on various metal sulfates were investigated in this study. It was found that Zr(SO 4 ) 2 exhibits a high activity for CFC-12 decomposition and a high selectivity to CO 2 . On the other hand, the metal sulfates Al 2 (SO 4 ) 3 , La 2 (SO 4 ) 3 , Ce 2 (SO 4 ) 3 , and Cr 2 (SO 4 ) 3 were also active for the hydrolysis of CFC-12. However, the activities for CFC-12 decomposition of MnSO 4 , CoSO 4 , and MgSO 4 were low, and decomposition of CFC-12 hardly occurred on the metal sulfates CaSO 4 , SrSO 4 , and BaSO 4 . Among the investigated metal sulfates, Zr(SO 4 ) 2 was the most active, and the complete decomposition of CFC-12 was achieved at 598 K. The CFC-12 decomposition rate monotonically increased with increasing CFC-12 partial pressure. On the other hand, CFC-12 conversion became highest at an oxygen content of 18.9 mol% and a H 2 O content of 5 mol%. Therefore, the main reaction on Zr(SO 4 ) 2 for CFC-12 decomposition into CO 2 and HCl and HF is the hydrolysis reaction. The high activity to CFC-12 decomposition on Zr(SO 4 ) 2 was stably sustained over the 40-h period examined. Therefore, the metal sulfate Zr(SO 4 ) 2 is highly active for the hydrolysis of CFC-12 and has sufficient stability against fluorination and/or chlorination.

Effects preparation condition of multiwall carbon nanotube on Li intercalation were investigated in this study. Both Li intercalation and reversible capacities increased with increasing contact time of CH 4 on Ni catalyst when the multiwall carbon nanotube was prepared. Raman spectroscopy suggested that the content of graphitic carbon tube increased with increasing the contact time of CH 4 upon synthesis. Therefore, in case of tubular carbon, graphitic carbon also exhibited a larger capacity for Li intercalation comparing with that of amorphous one. Intercalation and reversible capacity for Li insertion at first cycle were attained to a value of 430 and 320 mAh/g, respectively, on the carbon nanotube obtained at the contact time higher than 100 g-cat h/mol.

Although hole conduction was present, it was found that doping with Ni was effective in improving the oxide ion conductivity in La0.8Sr0.2Ga0.8Mg0.2O3 based perovskite oxides. Considering the ionic transport number and the electrical conductivity, the optimized composition for Ni doped samples was La0.8Sr0.2Ga0.8Mg0.13Ni0.07O3 (LSGMN). In this composition, electrical conductivity was found to be virtually independent of the oxygen partial pressure from 1 to 10−21 atm. Consequently, the oxide ion conductivity was still dominant in this optimized composition. In agreement with the improved oxide ionic conductivity, the power density of the solid oxide fuel cell using LaGaO3 as an electrolyte increased by doping with a small amount of Ni on the Ga site. In particular, the power density of 224 mW/cm2 at 873 K, which is the maximum power density in the cells using LaGaO3 based oxide as the electrolyte, was attained using LSGMN in spite of the use of electrolyte plates with a thickness of 0.5 mm. Therefore, LSGMN is highly attractive for the electrolyte material of low temperature operating SOFCs.

種々の貴金属を担持したCo3(PO4)2についてCH4を用いたNOの選択還元反応を検討し，Ptを担持したCo3(PO4)2はCH4によるNO選択還元に高い活性を示すことを見出した．N0転化率はPt担持量とともに増加し，1wt%Pt担持で最大となった．同一条件ではN0の還元活性は常にNO2還元活性より高くなった．これは反応がNO2やNO3−を中間体とするのではなく，NO直接分解から開始することを示唆している．酸素分圧の低下とともにNO転化率は向上し，酸素の非共存下では50%程度の高いNO転化率が最高SVまで維持されることがわかった．昇温脱離法による吸着種の反応性，およびNO，O2，CH4分圧依存性を検討したところ，Pt担持はNOの解離吸着を促進し，O2の吸着を弱めることがわかった．Pt/Co3(PO4)2上ではNOが解離的に吸着し，直接分解でN2を生成し，触媒上に残った酸素をメタンによって除去する機構でNoの還元反応が進行していると推定された．本研究によりPt/Co3(PO4)2はCH4によるNO還元に高い活性を有する触媒であることがわかった．

Mixed electronic–oxide ionic conductivity in LaGaO 3 -based oxide doped with Fe, Co or Ni was investigated in this study. The electric conductivity was greatly increased by doping Fe, Co, or Ni for the Ga site of La 0.8 Sr 0.2 GaO 3 . Compared to the conventional mixed electronic–ionic conductors such as LaCoO 3 , these LaGaO 3 -based oxides exhibited a lower electronic conductivity but a higher oxide ion conductivity. In particular, Fe-doped LaGaO 3 exhibited a high oxygen permeation rate and a stability against reduction. Consequently, higher CH 4 conversion in the partial oxidation of CH 4 was attained by using La 0.8 Sr 0.2 Ga 0.6 Fe 0.4 O 3 in the place of the conventional candidate material of La 0.6 Sr 0.4 Fe 0.8 Co 0.2 O 3 for the oxygen permeation membrane. As a result, this study revealed that LaGaO 3 -based oxide doped with Fe, Co or Ni for Ga site is a new family of mixed electronic–oxide ionic conductors.

Oxide ion conductivity in La 10 Si 6 O 27 and La 10 Ge 6 O 27 -based apatite oxides was investigated in this study. In spite of the low symmetry of the crystal lattice, both oxides exhibited high oxide ion conductivity over a wide range of oxygen partial pressures. Oxide ion conductivity of La 10 Si 6 O 27 was increased by doping Sr for La sites. On the other hand, it was found that La 10 Ge 6 O 27 also exhibited high oxide ion conductivity which is comparable with that of La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3 perovskite oxide. Arrhenius plots of the oxide ion conductivity in La 10 Ge 6 O 27 show a knee around 1000 K. However, the knee in the Arrhenius plot of conductivity disappeared by doping Sr for La sites. Thus, the conductivity at low temperature was greatly enhanced by doping Sr for La sites in La 10 Ge 6 O 26 . This may be due to stabilization of the high temperature crystal phase. The electrical conductivities of Sr-doped La 10 Si 6 O 27 and La 10 Ge 6 O 27 were almost independent of the oxygen partial pressure from P O 2 =1 to 10 −21 atm. This suggests that these materials are ionic over a wide P O 2 range. This study revealed that apatite oxide of La 10 M 6 O 27 (M=Si, Ge) is a new class of the fast oxide ion conductors.

Ni–CeO2 doped with 20 mol.% Gd3+ (GDC) cermet was investigated as the anode of an intermediate temperature operating solid oxide fuel cell using LaGaO3-based oxide electrolyte. It was found that the anodic overpotential decreased by mixing Ni with mixed electronic-ionic conductor, in particular, mixing with doped CeO2 is the most effective for decreasing the overpotential of the anode. Anodic overpotential became a minimum at 10 vol.% GDC to NiO. Using Ni–GDC cermet is also effective for improving the stability of the power density at the constant current output. Impedance analysis suggests that the improvement of anodic activity by mixing Ni with GDC was brought about by decreasing the diffusion overpotential, which was a result of the enlarged effective electrode area.

Capacitive-type NO sensor, which is operable at high temperature, was investigated in this study for monitoring NO in flue gases from a gasoline engine. Oxide capacitor consisting of BaSnO3 or SrSnO3 mixed with WO3 exhibits high sensitivity at temperature higher than 773 K. In particular, mixed oxide capacitor of SrSnO3–WO3 exhibited high sensitivity to NO and stable response at high temperatures. Furthermore, the capacitance of SrSnO3–WO3 is less sensitive to CO2, H2O, and CO compared to NO. Addition of small amount of Pt was effective for improving the response characteristics. Consequently, mixed oxide of SrSnO3–WO3 is as promising as the capacitive-type NO sensor operable at high temperatures. The NO adsorption state was further investigated with TPD measurement. It became clear that NO adsorbed on SrSnO3 was undissociative and two adsorption species exist. In contrast, NO adsorption on WO3 is dissociative. Addition of Pt was effective for decreasing the desorption temperature of oxygen from WO3 which was formed by the dissociative adsorption of NO.

Aluminum-phosphate catalysts prepared from aqueous solution of Al(NO 3 ) 3 6H 2 O and H 3 PO 4 in acidic condition are effective for hydrolysis of CCl 2 F 2 . Active species of the AlPO 4 catalysts were studied and it was found that not Al(PO 3 ) 3 but pure AlPO 4 was active. AlPO 4 was amorphous when calcined at 1000°C for 5 h. But a slight crystallization of AlPO 4 took place after the reaction at 400°C for 1000 h. Crystallization of AlPO 4 proceeded only in the presence of both CCl 2 F 2 and water vapor. Replacement of 5–10 at.% of Al in AlPO 4 by Ce increased the catalytic activity without changing the selectivity. The Ce-promoted catalysts were composed of the mixture of AlPO 4 and CePO 4 . The compositions of the catalysts were the same as those of parent liquor in preparation and it was almost uniform in the surface and the bulk. AlPO 4 in the Ce-promoted AlPO 4 catalyst was partially crystallized after the calcination at 1000°C for 5 h.

Decomposition of CCl 4 , CCl 2 F 2 , CClF 3 , and CF 4 was studied in the presence of water vapor over AlPO 4 . They began to decompose at about 300, 330, 450, and 550°C, respectively. A good linear relationship between the reactivity of CFCs and the bond dissociation energy of the C–Cl bond suggests that the C–Cl bond cleavage is the rate-determining step. The lattice structure of AlPO 4 before reaction was slightly distorted but the environment of Al and P ions became uniform after the reaction, consistent with a slight progress of crystallization of AlPO 4 . Supporting AlPO 4 onto active charcoal is not preferable to the support because of its reactivity to water vapor. ALPO-5 was less active than that AlPO 4 because the inside of the pores of ALPO-5 is hydrophobic and not effective for the CCl 2 F 2 decomposition. Meso-porous AlPO 4 showed almost the same activity with AlPO 4 , but the destruction of the meso-porous structure brought about a loss of activity at 400°C.

Preparation of CuO-BaTiO3 mixed oxide thin film by the decomposition of a self-assembled multibilayer film as a molecular template was investigated in this study. Furthermore, CO2 sensing property of the resultant thin film was investigated as a capacitive type sensor. The self-assembled bilayer film of few 1000 layers thickness can be obtained easily by casting an aqueous suspension consisting of dimethyldihexadecylammoiun bromide (DC1-16), Cu(ClO4)2, Ba(TiO(C2H4)2), 2,6-dimetyle-3,5heptadione (DHP), and polyvinyl alcohol. Divalent copper ion (Cu2+)) which is associated with 2 DHP molecules was incorporated into the molecular bilayer film and BaTiO3 precursor exists at the interspace of molecular bilayer film by coordinating with polyvinyl alcohol. Upquenching the organic-inorganic film at 1173 K leads to the uniform film of CuO-BaTiO3 oxide mixture. Although operating temperature shifted to higher temperature, the resultant film exhibits the capacitance change upon exposure to CO2. Consequently, it is concluded that the mixed oxide film of CuO-BaTiO3 prepared by the decomposition of multibilayer film was also an appropriate capacitive type CO2 sensor.

種々の金属リン酸についてC3H6を用いたNOの選択還元反応を検討したところ, Co3(PO4)2およびGaPO4において高いNO還元活性が得られることを見い出した。検討した金属リン酸塩の中ではCo3(PO4)2はNOの選択還元に最も高い活性を示し, その結晶構造の安定性から排ガス浄化に高い活性を長時間にわたって維持すると期待された。また, 金属リン酸塩は還元剤のC3H6の単純酸化反応が進行しにくく, 炭化水素が選択還元に有効に利用されることがわかった。一方, 還元剤にCH4を用いたところCo3(PO4)2ではNOの還元反応はほとんど進行しなかったが, Ptなどの貴金属を添加することによりCH4の燃焼活性を向上させると, CH4を用いてもO2共存下でNOの選択還元が進行できることがわかった。昇温脱離法による吸着種の反応性を検討したところ, Co3(PO4)2上ではNOが解離的に吸着し, まず直接分解でN2を生成すると推定された。一方, O2は触媒上に強く吸着し, 脱離しにくい。Co3(PO4)2によるNOの直接分解を検討したところ, NOの直接分解反応が比較的高い転化率で進行し, N2が生成したが, O2は生成しなかった。以上より, Co3(PO4)2によるNOの選択還元は, まずCo3(PO4)2上へのNOの解離的吸着によるN2生成で開始され, C3H6またはCH4は共存する気相酸素との反応で活性化され, 触媒上に残った酸素を除去する機構で反応は進行する推定された。

In the decomposition of chlorofluorocarbons (CFCs), HF produced in the decomposition reacts with and deactivates the catalyst. Metal phosphates were chosen as the catalyst from ΔG calculations. Zr–P–O and AlPO4 showed high catalytic activity for the decomposition of CCl2F2 above 350°C. The essential reaction of the decomposition is hydrolysis. On increasing the CCl2F2 concentration in the feed, the formation of CClF3 as a by-product is promoted. AlPO4 has both weak acid sites and those of intermediate strength and these acid sites may participate in the hydrolysis of CCl2F2. No reaction between AlPO4 and formed HF was observed during 1000 h reaction at 400°C, AlPO4 promises to be of practical use.

Oxidative reforming of n-butane is triggered over a Rh/CeO2−x at ambient temperature and at 273 K without heating the catalyst. The n-butane autoignition is enabled by the heat produced by spontane...

‐based perovskite oxides doped with Sr and Mg exhibit high ionic conductivity over a wide range of oxygen partial pressure. In this study, the stability of ‐based oxide was investigated. The ‐based oxide was found to be very stable in reducing, oxidizing, and atmospheres. Solid oxide fuel cells (SOFCs) using ‐based perovskite‐type oxide as the electrolyte were studied for use in intermediate‐temperature SOFCs. The power‐generation characteristics of cells were strongly affected by the electrodes. Both Ni and (Ln:rare earth) were suitable for use as anode and cathode, respectively. Rare‐earth cations in the Ln site of the Co‐based perovskite cathode also had a significant effect on the power‐generation characteristics. In particular, a high power density could be attained in the temperature range 973–1273 K by using a doped for the cathode. Among the examined alkaline earth cations, Sr‐doped exhibits the smallest cathodic overpotential resulting in the highest power density. The electrical conductivity of increased with increasing Sr doped into the Sm site and attained a maximum at . The cathodic overpotential and internal resistance of the cell exhibited almost the opposite dependence on the amount of doped Sr. Consequently, the power density of the cell was a maximum when was used as the cathode. For this cell, the maximum power density was as high as 0.58 W/cm2 at 1073 K, even though a 0.5 mm thick electrolyte was used. This study revealed that a ‐based oxide for electrolyte and a ‐based oxide for the cathode are promising components for SOFCs operating at intermediate temperature.

Among various rare earth phosphates, CePO4 and LaPO4 were found to catalyze the oxidative dehydrogenation of iso-butane to iso-butene at 450–550°C using a feed gas of 75 mol% iso-butane and 5 mol% O2. As for the phosphates of Y, Pr, Nd, Gd, Er, and Yb, iso-butene was formed with a limited selectivity of 20–40% selectivity, and C3H6 formation and deep oxidation into CO and CO2 were promoted over the same temperature range. Temperature-programmed-desorption spectra of NH3 for CePO4 and LaPO4 consisted of two large desorption peaks with maxima at 100°C and 270°C suggesting that these phosphates have strong acid sites. But the rest of the phosphates have only weak acid sites. Rare earth phosphates have no adsorbed oxygen which can be desorbed up to 550°C. The lattice oxygen of CePO4 and PrPO4 can be reduced at 200°C and that of the rest of the phosphates at about 400°C. The amount of oxygen removed up to 550°C in TPR was smaller than the amount corresponding to a monolayer for all phosphates. Oxygen isotope equilibration experiments over CePO4 and LaPO4 revealed that only surface lattice oxygen can participate in the equilibration at 500°C and 550°C. It can be concluded that acidic character is a key factor in the selective oxidative dehydrogenation of iso-butane over the rare earth phosphate catalysts.

Cu ion-exchanged SAPO-34 which is a highly active catalyst for selective reduction of NO with C3H6, was synthesized and the Cu ion was characterized in the SAPO-34 by ESR, XPS, IR, and XAFS. ESR study indicated that two kinds of Cu(II) with different environments exist in SAPO-34. The Cu(II) species disappeared immediately by C3H6 treatment and recovered by oxygen treatment. XAFS study indicated that most of the Cu(II) was reduced to Cu(I) under the presence of C3H6. These studies revealed that a selective NO reduction by C3H6 over SAPO-34 should proceed by the redox reaction of a copper ion between Cu(I) and Cu(II).

Metal pyrophosphates catalyse the oxidative dehydrogenation of iso-butane to iso-butene at 450–550°C using a feed gas of 75 mol% iso-butane and 5% O 2 . Ni 2 P 2 O 7 is the most selective catalyst with the iso-butene selectivity reaching to a maximum value of 82.2% at 550°C. Ag 4 P 2 O 7 and Zn 2 P 2 O 7 are also effective, but the iso-butene selectivities were slightly lower than that of Ni 2 P 2 O 7 . Pyrophosphates of Mg, Cr, Co, Mn, and Sn catalyse the oxidative dehydrogenation, but the iso-butene selectivity was 43.8–65.7% at the temperature where the maximum iso-butene yield is observed. The optimum oxygen concentration for iso-butene formation was 5–15 mol%, but the increase in O 2 concentration did not increase the iso-butene selectivity. No adsorbed oxygen species was found by means of TPD. The lattice oxygen of the pyrophosphates began to react with H 2 at 200–400°C. Reactivity of the lattice oxygen of pyrophosphates can be estimated from the value of ΔH f 0 for the corresponding oxide. More than 2 desorption peaks were observed in the TPD spectra of NH 3 adsorbed on the pyrophosphates, and a linear correlation was found between the concentration of acid amount of the catalysts and the specific rate of iso-butene formation. This strongly suggests that the acidic sites play a key role in the iso-butene formation.

Preparation of CuO thin films by decomposition of self-assembled multibilayer films as a molecular template was investigated. Furthermore, the CO2 sensing property of the resultant CuO thin films on a porous BaTiO3 was investigated as a capacitive type sensor. Self-assembled bilayer films of a few 1000 layers thickness can be readily obtained by casting an aqueous suspension composed of dimethyldihexadecylammoniun bromide (DC1–16), Cu(CH3CO2)2 , hexadecylethylenediamine and poly(vinyl alcohol). Divalent copper ions (Cu2+) which are associated with two hexadecylethylenediamine molecules were arranged in the hydrophobic layer of the multibilayer film. Rapid heating to the combustion temperature of DC1–16 was desirable for removing organic molecules in the multibilayer template. Thin films of CuO can be obtained by calcination at temperatures higher than 573 K. The resultant CuO thin films were porous and consisted of fine particles. The capacitance of CuO thin films prepared from self-assembled multibilayer films as a molecular template on the BaTiO3 porous substrate exhibited a high sensitivity to CO2 , which is twice that of a conventional mixed oxide capacitor of CuO–BaTiO3 . The capacitance of CuO thin films on BaTiO3 increases with increasing CO2 concentration in the range from 100 ppm to 50% at 873 K. Consequently, it is concluded that CuO thin films on BaTiO3 were appropriate capacitive type CO2 sensors.

Redox properties of CeO2 and Pt-Rh/CeO2 were studied by temporal analysis of products (TAP) method using alternative pulses of CO and O2. A portion of pulsed CO was oxidized to CO2 and a portion of CO was adsorbed on the surface. Pulsing 18O2 onto the catalyst which has surface species derived from CO, evolved CO2 contained no 18O suggesting that the surface species will be carbonate ions.

Oxygen sensors are important for combustion control, in particular, for vehicles. A perovskite-type oxide of LaGaO{sub 3} doped with Sr and Mg exhibits a high oxide ion conductivity over a wide range of oxygen partial pressures. In this study, the application of LaGaO{sub 3}-based oxide as the electrolyte of a potentiometric oxygen sensor was investigated. It became clear that silver is the most effective electrode for decreasing the operating temperature. Although a temperature higher than 800 K is required when a conventional Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} electrolyte is used, an operating temperature as low as 600 K is adequate when La{sub 1{minus}x}Sr{sub x}Ga{sub 0.8}Mg{sub 0.2}O{sub 3} at X = 0.1 and 0.2 is used. The open-circuit potential was slightly smaller than that estimated with the Nernst equation. There was agreement with the Nernst equation down to 673 K when Nd-doped LaGaO{sub 3}-based oxide was used. Moreover, 90% of the response was attained within 15 s at 673 K for the sensor with Nd-doped LaGaO{sub 3}-based oxide.

Selective reduction of NO with C{sub 3}H{sub 6} under an oxidizing atmosphere was studied over various Cu ion-exchanged molecular sieves. All examined Cu ion-exchanged catalysts are active for NO reduction with C{sub 3}H{sub 6} in a large excess of O{sub 2}; however, the temperature at the maximum NO conversion depends on the kind of molecular sieves. In particular, it was found that Cu-SAPO-34 is sometimes more active than Cu-ZSM-5. Thermal stability of SAPO-34 was extremely high, and consequently, decrease in the activity to NO selective reduction on Cu-SAPO-34 was negligible over 60 h at 673 K in an atmosphere containing 15 vol % H{sub 2}O. After thermal treatment at 1,073 K in a humidified atmosphere, decrease in the activity to NO reduction was also small. Although the activity of Cu-SAPO-34 to NO reduction was decreased slightly with the coexistence of SO{sub 2}, it is expected that the activity of Cu-SAPO-34 is sustained over a long period.

In order to clarify the effect of the microenvironment of the host adsorbents on the photophysical and photochemical properties of the guest molecules in restricted void spaces, the characteristic properties of the phosphorescence of xanthone and photolysis of 2-pentanone included within alkali metal cation-exchanged zeolites were investigated. An enhancement of the phosphorescence yield of xanthone included within the zeolite cavities and a reduction in the phosphorescence lifetime were ovserved on changing the exchangeable alkali metal cation from Li+ to Cs+. These results suggest an external heavy-atom effect derived from the alkali metal cation on the singlet-triplet transitions of xanthone molecules within the zeolite cavities. During the photolysis of 2-pentanone included within the zeolite cavities, the selectivity of the Norrish type II reaction was found to decrease remarkably due to the steric hindrance caused by the restricted void space of the zeolite cavities. IR and photoluminescence investigations indicated that 2-pentanone consists of two different adsorption types: one is adsorbed on the surface OH group by hydrogen bonding and the other is directly adsorbed onto the alkali metal cations. On changing the cation from Li+ to Cs+, a decrease in the strength of the interaction between the alkali metal cation and 2-pentanone caused an increase in the yield of photolysis of 2-pentanone. Thus changes in the zeolite cavities, modified by the exchange of cations, have a significant effect on the excited states and chemical reactions of ketones.

The characteristics properties of xanthone phosphorescence and of 2-pentanone photolysis in alkali metal cation-exchanged zeolites have been investigated to clarify the effect of the micro-environment of host-adsorbents on the photophysical and photochemical properties of guest-molecules in restricted void spaces. The enhancement of the phosphorescence yields of xanthone included in zeolites is observed by changing the exchangeablealkali metal cation from Li+ to Cs+. Simultaneously, the phosphorescence lifetimes were observed to continuously shorten by changing the cation from Li+ to Cs+. These results suggest that the external heavy-atom effect deriving from the alkali metal cations on the singlet-triplet transitions of xanthone molecules stabilized on alkali metal cations in the order of Li+, Na+, K+, Rb+, and Cs+. The yields for the photolysis of 2-pentanone included in zeolites increase with changing the alkali metal cation from Li+ to Cs+. IR investigations of the adsorption state of 2-pentanone indicate that strength of the interaction between the alkali metal cations and 2-pentanones decreases by changing the cation from Li+ to Cs+, which results in a longer lifetime of 2-pentanone. The selectivity of propylene formation is dramatically increased by changing the cation from Li+ to Cs+. The enhanced formation of propylene is asociated with the hydrogen absorption from propyl radicals by lattice oxygen, their basicity increasing by changing the cation from Li+ to Cs+. Thus, these changes in the zeolite cavities modified by exchanging cations caused significant effects not only on the excited state but also on the following chemical reactions of ketones.

The phosphorescence properties of xanthone included in alkali-cation-exchanged zeolites have been investigated to determine the effect of the microenvironment of the host adsorbent on the electronic excited states of the guest molecules included in the restricted void spaces. An enhancement of the phosphorescence yield is observed on changing the exchangeable alkali cation from Li + to Cs + . Simultaneously, the phosphorescence lifetimes are continuously reduced by changing the cation from Li + to Cs + . IR investigation of xanthone included in alkali-cation-exchanged Y-zeolite shows that xanthone molecules are stabilized in zeolite cavities by the diret interaction between the molecules and the alkali cations anchored in the cavity. These results are well explained in terms of the external heavy-atom effect, derived from the alkali cations Li + , Na + , K + , Rb + and Cs + , on the singlet-triplet transitions of xanthone molecules included in the alkali-cation-exchanged zeolites.

Photoinduced reduction of CO2 by H2O to produce CH4 and CH3OH has been investigated on wellcharacterized standard TiO2 catalysts and on a Cu2+ loaded TiO2 catalyst. The efficiency of this photoreaction depends strongly on the kind of catalyst and the ratio of H2O to CO2. Anatase TiO2, which has a large band gap and numerous surface OH groups, shows high efficiency for photocatalytic CH4 formation. Photogenerated Ti3+ ions, H and CH3 radicals are observed as reactive intermediates, by ESR at 77 K. Cu-loading of the small, powdered TiO2 catalyst (Cu/TiO2) brings about additional formation of CH3OH. XPS studies suggest that Cu+ plays a significant role in CH3OH formation.

Although TiO 2 exhibits a small fluoride ion exchange capacity, it was found that titanium hydroxide, Ti(OH) 4 , can exchange fluoride ion with large saturation capacity of 1.60 m . mol/g. Although the H 2 PO 4 - interferes with the F - exchange, the amount of F - exchange of Ti(OH) 4 was hardly changed by the coexistence of Cl - , NO 3 - , and SO 4 2- . The capacity for F - exchange was almost unchanged over 4 times repetition of ion-exchange and desorption and furthermore, the elution of Ti was negligibly small. Consequently, Ti(OH) 4 is expected to be a new inorganic F - exchanger for the removal of fluoride ion from wastewater.

Application of the new oxide ion conductor of composition La0.9Sr0.1Ga0.8Mg0.2O3 as electrolyte in solid oxide fuel cells is effective in enabling a decrease in the operating temperature.

Power generation characteristics of fuel cells was greatly improved by using La0.8Sr0.2Ga0.8Mg0.115Co0.085O3 as electrolyte. In particular, the maximum power density attained a value of 1.53 and 0.50 W cm–2 at 1073 and 873 K, respectively, in an H2–O2 cell when the thickness of electrolyte was 0.18 mm.

Photocatalytic decomposition of pure water on NiO supporting KTaO3 partially substituted with acceptor was investigated. Formation rate of H2 and O2 increased by partially substituting Ta with group 4 element. The increased photocatalytic decomposition activity by additives might be caused by a charge carrier annihilation.

It was found that LaGaO3 perovskite oxide doped with Ni for Ga site exhibits a high mixed electronic-oxide ionic conduction. Oxygen permeation rate was increased with increasing Ni content and it attained to a maximum value of 2.15 cm3/min cm2 at 1273 K when 25 mol% Ni was doped.