Tadao Shiba

The nature of the acid sites on cationized zeolites: Characterization by infrared study of adsorbed pyridine and water

Abstract Infrared spectral studies of pyridine adsorbed on cationized zeolites prepared from Linde 13-X by ion exchange with salt solutions of K, NH4, Mg, Ca, Sr, Zn, La(III), Ce(III), and Mn are presented in this paper. The OH stretching frequency was studied in connection with the adsorption of water and pyridine. NH4X, LaX, and CeX have both Bronsted and Lewis acid sites, and the larger portion of the Lewis acid is strong enough to be converted into Bronsted acid by the addition of water. On CaX and SrX, only Lewis acid is present after evacuation at 450 °C and it can be converted into Bronsted acid by water. On ZnX, MgX, and MnX, the larger portion of acid is of a weak Lewis type and not all of the Lewis acid can be converted into Bronsted acid by water. Only weak Lewis acid is present on NaX. More than three OH stretching frequencies were observed on all of the zeolites and the nature of each OH group is discussed.

Mutual influence of adsorption of hydrogen and carbon monoxide on a methanol synthesis catalyst

Abstract The mutual influence of the chemisorption of hydrogen and carbon monoxide on a three-component methanol synthesis catalyst has been studied. The rate as well as the equilibrium amounts of the chemisorption of hydrogen and carbon monoxide are mutually enhanced by the presence of the other gas. The mutual enhancement of the adsorption is explained in terms of the complex formation. It is also suggested that the complex formed is the intermediate of the methanol synthesis reaction, and that the rate-determining step of the over-all reaction is the reaction between hydrogen gas and the surface complex.

Adsorption measurement during the decomposition of methanol on a methanol synthesis catalyst

The adsorption as well as the rate during the course of the methanol decomposition on a methanol synthesis catalyst with three components have been investigated. The amounts of adsorption of both hydrogen and carbon monoxide or any complex formed from them during the decomposition were greater than those from the mixture of 2H2:1CO. No decrease in the ambient pressure of hydrogen was observed at the sudden removal of methanol from the gas phase during the course of the decomposition reaction by means of a dry ice trap. The rate-determining step of the decomposition of methanol is suggested to be the process of dissociation of the adsorbed methanol into the adsorbed intermediate and hydrogen. The initial amount of adsorption of methanol during the reaction was the saturation value expected from vm in the BET equation. The empirical zero order kinetics is explained on the basis of the saturated adsorption of methanol on the catalyst surface.