Takaji Kanazuka

Degradation of polyethylene to aromatic hydrocarbons over metal-supported activated carbon catalysts

Abstract The degradation of polyethylene to aromatic hydrocarbons on metal-supported activated carbon catalysts has been studied. The effect of the added metals was investigated in detail. Activated carbon impregnated with Pt, Fe, Mo, Zn, Co, Ni or Cu showed a higher catalytic activity for the formation of aromatics than that of the metal-free catalyst. The first three metals were the most effective. It was also found that the catalytic effects of Pt and Fe on the aromatic yield depended strongly on the support: activated carbon was most efficient, and silica-alumina and alumina were much less effective. Two active sites with different functions seemed to take part in the dehydrocyclization step involved in the degradation reaction. One was activated carbon surface sites, on which the abstraction of hydrogen atoms occurred predominantly. The other was metal sites which catalyzed the desorption of the hydrogen atoms. The desorption was a slow step of the dehydrocyclization on activated carbon, but was enhanced by the added metals, resulting in an increase in the yield of aromatics.

Degradation of polypropylene to aromatic hydrocarbons over Pt- and Fe-containing activated carbon catalysts

Abstract The degradation of polypropylene to aromatic hydrocarbons over activated carbon catalysts containing Pt and Fe has been investigated. The results obtained were compared with those for the degradation of polyethylene. The addition of Pt or Fe to activated carbon resulted in an increase in the yield of aromatics from polypropylene. However, the increase was less than that from polyethylene. Pt metal was more effective than Fe only when the reaction conditions involved a longer contact time. The formation of aromatics was explained by essentially the same mechanism as the case of polyethylene, in which an influence of methyl branching of polypropylene on the aromatization yield and a difference in catalytic activity of the catalysts containing Pt and Fe for a ring expansion reaction were considered.

Promotive effect of H2S for hydrocarbon conversions over Na zeolites

H2S promotes remarkably the catalytic cracking of n-butane and the isomerization of cyclopropane over various Na zeolites, presumably because of the formation of new Brönsted acid sites on catalyst surface.AbstractH2S сильно промотирует каталитический крекинг н-бутана и изомеризацию циклопропана на различных Na-цеолитах, вероятно, вследствие образования новых брёнстэдовских кислых центров на поверхности катализатора.

Catalytic gasification of carbon: method for the determination of the activity of alkali metal catalysts in the gasification of highly pure amorphous and graphitic carbons with steam

Abstract Gasifications of highly pure carbons in an amorphous state and graphite were studied in the presence of alkali metal catalysts and water. A detailed investigation was made with respect to the dispersion processes of the catalysts. It was found that (i) evaporation of the metal, (ii) condensation of the metal vapour into the amorphous carbon and (iii) dissolution of alkali metal into glass-wool occurred under the conditions of the gasification. Under certain conditions that minimized such dispersion phenomena during the gasification, both the gasification ratt and the amount of the effective catalyst were measured simultaneously. The order of the catalytic activity per unit catalyst composition and unit surface area of carbon was determined as follows: Li>Cs>Rb≥K>Na. A mechanism controlling such catalytic activity is discussed on the basis of the mediator action and the role of the carbon activator of the catalyst.

High activity and selectivity of sulfided CoNaA zeolite for isomerization of 1-butene.

The effect of sulfiding with H2S on the catalytic activity and selectivity of CoNaA zeolite in the isomerization of 1-butene was investigated. High activity and selectivity to trans-2-butene were obtained by sulfiding of CoNaA zeolite with H2S.