Hisao Imai

Electronic effects of alkaline carbonates in methanation over Pd/Al2O3 catalysts

Abstract Electronic effects of alkaline carbonates on the C-O bond dissociation of adsorbed CO in methanation over Pd/Al 2 O 3 catalysts were investigated by using a pulse surface reaction rate analysis (PSRA) coupled with an emissionless diffuse reflectance infrared spectroscopy (EDR). Alkaline carbonates added to the Pd/Al 2 O 3 catalyst exist mainly on the alumina support. This addition causes the IR bands of adsorbed CO to shift to lower frequencies, and markedly decreases the rate constant for the C-O bond dissociation. It was concluded that the addition of alkaline carbonates to the Pd/Al 2 O 3 catalyst increases the electron density of the Pd metal which in turn decreases the rate constant for the C-O bond dissociation of adsorbed CO. This relationship was explained in terms of a partially hydrogenated CO species which acts as intermediate for the C-O bond dissociation of adsorbed CO in methanation.

High activity of strong metal–support interaction catalysts for carbon monoxide hydrogenation revealed by pulse surface reaction rate analysis

By use of pulse surface reaction rate analysis, it was found that the active sites on titania-supported Pt and Pd catalysts for methanation were much more active in the strong metal–support interaction state than in the normal state.

Composition of Silver Deposit Collected From Waste Fixing Solution

X線写真用定着廃液中の銀は, ビス (チオスルファト) 銀 (I) 酸イオンの形で溶解している。本報では, これらの廃液から銀を回収するために, 過酸化水素法, 電解法, 銅板浸漬法により, 所定条件下における析出物を得て, それらの組成形態について比較検討した。析出物は, 過酸化水素法, 電解法では硫化銀, 銅板浸漬法では銀単体と微量の酸化銅 (I) として同定された。過酸化水素法では, 廃液中に存在するS2O32-および [Ag (S2O3) 2] 3-量に与える過酸化水素の添加量の影響を, それぞれの析出物の組成形態 (Ag/S: モル比) をもとに検討した。理論量の過酸化水素を添加して生成する析出物には, 廃液中の銀がほぼ完全に含まれ, 回収されることが見い出された。硫化銀を直接水素処理 (300～700℃, 3h) しても銀単体は得られない。硫化銀を, 硝酸溶液 (1: 1) ついで塩化ナトリウム溶液で処理をして得られた塩化銀からは, その融点 (455℃) 付近で水素処理 (400℃, 3h) すると, ほぼ純粋な銀の単体が回収された。

Adsorptive property of eggshell.

Although eggshell is partially covered by collagen film, it is sufficiently porous to adsorb a considerable amount of formic acid gas (72 cm3/g) in contrast to calcium carbonate reagent. A high temperature treatment at 700°C removed completely the collagen film, and decomposed the eggshell to calcium oxide which showed the same adsorptive property as that of the high temperature treated reagent. The eggshell can be used as the economical basic adsorbent with or without heat treatment at higher temperatures,

Rate-determining step in the methanation of carbon monoxide with a palladium on alumina catalyst

By using i.r. and pulse-dynamic measurements, it has been proved that the rate-determining step in the methanation of CO on a Pd/Al2O3 catalyst is the dissociation of the C–O bond of the adsorbed CO species while the hydrogenation of surface carbon species proceeds rapidly.