Tokio Iizuka

Surface properties of zirconium oxide and its catalytic activity for isomerization of 1-butene

Acidic, basic, oxidizing, and reducing properties of ZrO2 were measured by the ir spectra of adsorbed pyridine, by CO2 adsorption or the ESR of diphenylnitroxide radical formed from diphenylamine and O2, by the ESR of adsorbed triphenylamine, and by the ESR of adsorbed nitrobenzene, respectively. The variations of these properties with pretreatment temperature of ZrO2 were independent of each other. The maximum concentrations of these sites and the pretreatment temperatures at which the maxima were obtained were 3.9 × 10−8 mole/m2 and 400 °C for acidic sites, 1.7 × 10−7 mole/m2 and 700 °C for basic sites measured by diphenylamine, 1.5 × 10 mole/m2 and 700 °C for oxidizing sites, and 4.3 × 10−8 mole/m2 and 500 °C for reducing sites. Among these properties, it was the basic property with which the activity for isomerization of 1-butene correlated best. The activity was poisoned not only by CO2 but also by NH3 or triethylamine, indicating that the active sites consist of both basic and acidic sites. The results of the coisomerization of 1-butene-d0d8 showed that the reaction involved primarily an intramolecular hydrogen transfer.

Hydrogenation of carbon monoxide and carbon dioxide over supported rhodium catalysts

Abstract The formation of hydrocarbons in the reactions of CO + H2 and CO2 + H2 was studied over rhodium catalysts supported on Nb2O2, ZrO2, Al2O3, SiO2 and MgO. Among these catalysts, Rh on Nb2O5 was most active in the reaction of CO + H2 and RhMgO was least active. In the hydrogenation of CO2, RhZrO2 was more reactive than RhNb2O5 and showed measurable activity even at 50°C, in contrast to the inactivity at temperatures up to 130°C in the CO + H2 reaction. The inverse kinetic isotope effect was observed in both reactions of Co + H2(D2) and CO2 + H2(D2) over RhNb2−O5 and RhZrO2. However, the isotope effect was not observed in the CO2 reaction over RhAl2O3, whose effect in the CO reaction was still inverse. The mechanisms of the above reactions are correlated to the IR study of the adsorbed species.

Basic sites and reducing sites of calcium oxide and their catalytic activities

The amounts of basic and reducing sites of calcium oxides prepared by heat-treating the hydroxide at various temperatures were measured, respectively, by titration with benzoic acid, using bromothymol blue, etc., as indicators and by observing ESR, spectra or visible reflectance spectra of adsorbed nitrobenzene or m-dinitrobenzene. The maximum amount of basic sites was found to be 0.57 mmole/g when the hydroxide was calcined at 500 ° in air, while that of reducing sites to be 5 × 1014 and 1016 sites/g, respectively, when calcined at 700 ° in air and at 500 ° in a vacuum. It has been found that the catalytic activity of various calcium oxides for the esterification of benzaldehyde correlates well with the basicities, whereas that for the polymerization of styrene does with the amounts of reducing sites. On the basis of the above results together with infrared spectra of adsorbed benzaldehyde, isopropyl alcohol, and chloroform, the nature of basic and reducing sites was discussed, the reducing sites being shown to be entirely different from the basic sites.

Hydrogenation of carbon dioxide and carbon monoxide over supported rhodium catalysts under 10 bar pressure

Abstract The hydrogenation of carbon dioxide and carbon monoxide was carried out in a 10-atm flow reactor over supported rhodium catalysts. Rh/ZrO 2 and Rh/Nb 2 O 5 showed the highest activity for carbon dioxide and hydrogenation, the main product being methane. Methanol was formed selectively from carbon dioxide hydrogen over a Rh/TiO 2 catalyst. The products of carbon monoxide hydrogenation over supported Rh catalysts contained higher hydrocarbons and ethanol. The rate of C -C bond formation was higher in carbon monoxide hydrogenation than in carbon dioxide hydrogenation. The effect of the support on hydrogenation of carbon dioxide and carbon monoxide is discussed.

Preparation of highly acidic hydrated niobium oxide

Abstract In order to obtain a highly acidic hydrated niobium oxide, the preparation methods and conditions such as niobium precursors, precipitating reagents, treatment of precipitates, washing of precipitates, final pH in precipitation, and calcination temperature were systematically examined. Strong acidic sites of H 0 ⩽−8.2 were found to appear on hydrated niobium oxide when the oxide was prepared by boiling the precipitates, which were obtained by hydrolysis of niobium oxalate with KOH, in a diluted mild acid solution(preferably 0.1N HNO 3 ) followed by washing with hot water several times and heating in air at 300 °C. Final pH in the precipitation must be below 11.

Esterification of acrylic acid with methanol over niobic acid catalyst

Abstract The esterification of acrylic acid with methanol and the hydrolysis of the ester were examined over niobic acid preheated at different temperatures. Niobic acid pretreated at 200 – 400°C showed a high activity and selectivity (⋍100%) for both reactions. In the reaction of acrylic acid with excess methanol, niobic acid could maintain the conversion of more than 90% for 6 h or more.

Infrared spectroscopic study of CO and CO2 adsorption on Rh–ZrO2, Rh–Al2O3 and Rh–MgO

The adsorption states of CO and CO2 on Rh catalysts supported on ZrO2, Al2O3 and MgO were studied using i.r. spectroscopy. Upon adsorption of CO on reduced Rh–ZrO2, the carbonate bands due to the reaction 2CO →C + CO2, together with the bands of twin, linear and bridge CO species were observed at moderate temperatures, whereas Rh–MgO gave no appreciable formation of CO2 even at higher temperatures (> 100 °C) and Rh–Al2O3 showed intermediate behaviour. On the adsorption of CO2, the linear CO band was formed at lower frequency than that on CO adsorption. The linear CO species formed from CO2 showed higher reactivity toward hydrogen compared with that from CO adsorption.

Effect of supports on the acitivity of Mo and Fe catalysts for the reduction of NO with H2

In the reduction of NO with H2, MoO3−ZrO2 and Fe2O3−SiO2 were found to be the most active among each ten kinds of a series of Mo and Fe catalysts. On the basis of an IR study, the high catalytic activities were conclued, to be caused by the ability of the catalysts to the formation of adsorbed NO− species.AbstractБыло установлено, что при восстановлении NO с помощью H2, MoO3−ZrO2 и Fe2O3−SiO2 являются наиболее активными среди всех десяти типов серий катализаторов Mo и Fe. На основе ИК-исследований было заключено, что высокая каталитическая активность вызвана способностью этих катализаторов образовывать адсорбированные частицы NO−.

Function of metal oxide and complex oxide catalysts for hydrocracking of coal

Abstract The catalytic activity and selectivity of metal oxides and complex oxides for the liquefaction of bituminous coal and lignite are reviewed first and discussed in connection with surface properties of catalysts. However, it has been realized that the functions of catalysts are not fully understood. Thus, in the present work, the hydrocracking of diphenylmethane, diphenyl ether, and benzyl phenyl ether as model compounds of coal, the dehydration of 2-propanol as a test reaction for cracking ability (acidity) of a catalyst, and the hydrogenation of naphthalene as a test reaction for hydrogenation ability of a catalyst were studied by employing various metal oxide and complex metal oxide catalysts. It has been concluded that the acidic property of a catalyst plays an important role for CC bond cleavage, while the hydrogenation ability of a catalyst is important for CO bond cleavage. This conclusion was found to be in agreement with the results of liquefaction of Akabira coal (carbon content: 83.0%) and Big Brown lignite (carbon content: 72.3%). That is, the highly acidic catalysts exhibited high activities for liquefaction of bituminous coals with high carbon content, whereas catalysts possessing high hydrogenation ability showed high activities for liquefaction of lignite containing a large amount of oxygen. The best three catalysts for Akabira coal were MoO 3 Fe 2 O 3 SnO 2 , MoO 3 TiO 2 , and Fe 2 O 3 SO 4 2- , whose activities were almost comparable to a well known MoO 3 CoOAl 2 O 3 catalyst, though they did not contain expensive cobalt. For Big Brown lignite, MoO 3 TiO 2 was the best among the various catalysts.

The support effect of CuO catalyst for the reduction of nitric oxide with hydrogen or ammonia

The reduction of nitric oxide (NO) with H2 or NH3 over CuOx catalysts supported on ZrO2 or TiO2 has been investigated. The activity and selectivity of NO reduction were very sensitive to the types of support oxide. A gradual increase in activity of CuO/ZrO2 for the reduction of NO with NH3 was observed in the course of the reaction, while the activity of CuO/TiO2 was rapidly reduced as the reaction proceeded under the same reaction conditions. For the reaction of NO + NH3 in the presence of oxygen, however, CuO/ZrO2 was less active than CuO/TiO2. Several states of Cu2+ on the surfaces of ZrO2 or TiO2 were detected by means of e.s.r. spectroscopy. Cu2+ ions on ZrO2 were reduced more easily than those on TiO2 and hence this catalyst was concluded to show a high activity in NO + NH3 or NO + H2 reactions.