Noriyoshi Kakuta

Thermal and chemical recycle of waste polymers

Abstract Catalytic degradations of polyethylene into fuel oils and of polystyrene into styrene monomer have been studied using solid acids and bases as catalysts. Solid acids such as silica-aluminas and ZSM-5 zeolite were found to be effective to degrade waste polyethylene into fuel oils, and solid bases such as BaO and K 2 O were concluded to be effective to convert waste polystyrene into styrene monomer. A design of recyclable polystyrene films will be briefly mentioned.

Effect of SO2 on NOx reduction by ethanol over Ag/Al2O3 catalyst

A new Ag/Al2O3 catalyst for removing NOx in diesel engine exhaust gas was developed. The influence of SO2 on the reduction of lean NOx by ethanol over the Ag/Al2O3 catalyst was evaluated in simulated diesel exhaust and characterized using TPD, XRD, XPS, SEM and BET measurements. The Ag/Al2O3 catalyst was highly active for the reduction of NOx with ethanol in the presence of SO2 although the reduction of NOx is suppressed at lower temperatures. The activity for NOx reduction is high even on the Ag/Al2O3 catalyst exposed to a SO2 (200 ppm)/O2 (10%)/H2O (10%) flow for 20 h at 723 K and comparable to that on the fresh Ag/Al2O3 catalyst. No crystallized Ag metal and Ag compounds were formed by the SO2/O2/H2O exposure. On the other hand, crystallized Ag2SO4 was easily formed when the Ag/Al2O3 catalyst was exposed to a SO2 (200 ppm)/O2 (10%)/NO (800 ppm)/H2O (10%) flow for 10 h at 723 K. XRD, SEM and XPS studies showed that the formation of crystallized Ag2SO4 results in growing of Ag particles in larger size and lowering the surface content of Ag particles. In addition, the specific surface area of the Ag/Al2O3 catalyst decreases from 221 to 193 m2/g. Although the dispersion of Ag particles was decreased by the formation of Ag2SO4, the activity for the reduction of lean NOx was, remarkably, not affected. This suggests that the Ag–alumina sites created by the Ag2SO4 formation are still active for the lean catalytic reduction of NOx.

Generation of acid sites on finely divided TiO2

Caracterisation du catalyseur par microscopie electronique a transmission et distributions de la taille des particules

Thermally stabilized transitional alumina prepared by fume pyrolysis of boehmite sols

Abstract Alumina prepared by fume pyrolysis of sols consisting of fibrillar boehmite, 100 nm in length and 10 nm in diameter, was subjected to the thermal resistant tests. Even after calcination at 1473 K for 30 h, the alumina still consisted of fibrils and possessed a surface area as high as 50 m2/g. This was ascribed to the suppression of the rate of phase transformation to α-alumina, caused by the fact that the alumina particles are of crude structures assembled by fibrils.

Characterisation and activity evaluation of silica supported cobalt and ruthenium catalysts

Abstract We prepared Co/SiO 2 , Co–Ru/SiO 2 and Ru/SiO 2 catalysts by ion-exchange method in an attempt to obtain well dispersed active sites. The catalysts were characterised by chemisorption, oxygen titration, TPD and XPS, and their activity was evaluated in CO hydrogenation. The results showed that the Co/SiO 2 catalyst exhibited a very low extent of reduction, and consequently its hydrogen uptake and activity were very low. In case of CoRu/SiO 2 , the hydrogen and CO uptake was far much higher than for the physical mixture or for the sum of Co/SiO 2 and Ru/SiO 2 . Evidently, ruthenium acted as a reduction aid to cobalt in the bimetallic system. Yet, irrespective of the highest uptakes of the CoRu/SiO 2 system, the highest activity in CO hydrogenation was obtained with the Ru/SiO 2 catalyst. The synergistic performance of the CoRu catalyst was, however, evidenced by the unusually high formation of methanol – a novel finding which indicates that neither of the metals was present as a pure entity in the bimetallic system.

Oxygen storage capacity (OSC) of aged Pt/CeO2/Al2O3 catalysts : roles of Pt and CeO2 supported on Al2O3

Abstract In order to investigate the behavior of Pt and CeO2 on the Pt/CeO2/Al2O3 catalyst after aging at 1273 K, the oxygen storage capacity(OSC) has been measured and physically mixed catalysts such as Pt Al 2 O 3 + CeO 2 Al 2 O 3 , Pt Al 2 O 3 + CeO 2 , Pt CeO 2 + Al 2 O 3 and Pt CeO 2 + Pt Al 2 O 3 catalysts have been employed for comparison. After the aging, the OSC of the physically mixed catalysts whose CeO2 was not supported on Al2O3 became poor because of the large-sized CeO2 and the deactivation of Pt, although those catalysts provided large OSC assisted by the PtCeO2 interaction before the aging. The OSC increment calculated by subtraction of the OSC of Pt Al 2 O 3 + CeO 2 Al 2 O 3 from that of Pt/CeO2/Al2O3 indicated that both the PtCeO2 interaction and the dispersed CeO2 on Al2O3 are essential for the generation of OSC, even after the aging.

Characterization of iron oxide thin film prepared by the sol-gel method

Thin films consisting of γ-Fe2O3 particles were prepared by a spin-on process using a solution of iron (III) nitrate dissolved in ethylene glycol. Film thickness was observed to be controlled by the solution viscosity as well as the revolution of a spinner. Local structures around iron ions in the solution were studied by extended X-ray absorption fine structure spectroscopy and the formation of an (FeOx)n cluster was deduced. A film thus prepared was confirmed to consist of finely divided γ-Fe2O3 particles by TEM observation. Magnetic and optical properties of the films are briefly discussed.

Promoting effects of metals for NO reduction over potassium doped carbon

Reduction of NO to N2O or N2 was studied over activated carbons using thermal desorption technique. The addition of other metals such as Zn, Cu, Fe, Ni, Sn, Mn or Ce, to potassium doped carbon remarkably enhanced direct NO reduction or NO reduction by carbon. The high activity might be ascribed to the synergism between potassium-metal on the carbon surface.

Characterization of alumina prepared by sol-gel methods and its application to MoO3CoOAl2O3 catalyst

Abstract Alumina powder was prepared by hydrolysis of aluminum isopropoxide (AIP) by two different methods: (1) AIP was poured directly into hot water to form fibrillar sols of aluminum hydroxide; (2) AIP was dissolved in butanol and then hydrolyzed with a small amount of water. The physical properties of these two alumina powders were compared. Alumina-supported molybdenum-cobalt catalysts were prepared by these two different hydrolysis methods and the catalytic activities for the desulfurization of thiophene were studied and discussed in terms of the surface concentrations of Mo and Co in the catalyst particles.

Preparation of niobium oxide films as a humidity sensor

Abstract Niobium oxide films were prepared over a quartz plate by withdrawing it from a solution of niobium penta-isopropoxide (NIP) dissolved in sec-propyl alcohol. The films calcined at 673 K were well controlled in the film thickness either by NIP concentration in the solution or by the withdrawing rate of the quartz plate from the solution. BET surface area of the calcined films was as huge as around 400 m2g−1 and was not reduced by cyclic adsorption/desorption of water vapor. A rapid decrease and increase in the electrical resistivity of the calcined films was well associated with the cyclic adsorption/desorption of water vapor. The decrease in the electrical resistivity of the films by water vapor adsorption was more than 10 times sensitive than the decrease caused by the adsorption of ethanol, hydrocarbons, carbon monoxide and carbon dioxide. These results suggest an application of the niobium oxide films as an element of a humidity sensor. The calcined films were proved by SEM observation to consist of tiny particles possessing a lotofmicropores sized less than 20 A. The decrease in the electrical resistivity of the films, or the increase in the electrical conductivity, was attributed to the water vapor adsorbed in these micropores. In order to identify the charge carriers during water vapor adsorption on the films, changes in the impedance and the phase shift caused by water vapor adsorption were measured using an LCR meter in AC frequency range of 10 Hz to 100 kHz. From a complex impedance plotting, single semicircule was obtained for water vapor adsorption onto the films, suggesting single adsorbed species as a charge carrier. Assuming an equivalent electric circuit for the films adsorbing water vapor, a constant capacitance was calculated under various partial pressures of water vapor, probably suggesting that the charge carriers will be H3O+ on the films.