| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1989: ¥200,000 (Direct Cost: ¥200,000)
Fiscal Year 1988: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Research Abstract |
The effectiveness of rare earth intermetallics as catalysts has been examined in a number of studies. Several reactions are possible by making use of their characteristics of hydriding and dehydriding: they contain reactive. H atoms able to hydrogenate effectively unsaturated compounds as a means of extracting hydrogen, and vice versa, hydrogen produced by dehydrogenation can be intactly absorbed to form metal hydrides. The direction of the reactions is determined thermodynamically.
The vapor-phase dehydrogenation of methanol, ethanol and propan-2-ol has been studied over hydride-forming rare earth intermetallic compounds (ErFe_2, DyFe_2, Nd_2Co_7 and Sm_2CO_7) as a hydrogen acceptor. Under mild conditions methanol, ethanol and propan-2-ol were selectively dehydrogenated to carbon monoxide, acetaldehyde and acetone, respectively, forming metal hydrides simultaneously. The dehydrogenation in the presence of these hydride-forming compounds is recognized as a useful dehydrogenative method,
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in which R_2Co_7 and RFe_2 (R is rare earths) are amenable to conversion into stable metal hydrides. The dissociative chemisorption of alcohol on the activated alloy surfaces with subsequent migration of the liberated H to the underlying alloy phase is expected. The dehydrogenation of methanol and ethanol is by a rate-limited dissociation reaction. The behavior of the reaction has also been characterized by isotope techniques.
Further, the dehydrogenation of methanol has been studied in the range 356-443 K over various hydride-forming alloys (Zr_2Ni, Pr_2Co_7, Nd_2Co_7, Sm_2Co_7, DyFe_2 and ErFe_2) in detail. Because the formation of metal hydrides can change the unfavorable equilibrium in favor of dehydrogenation. Under mild conditions methanol was very selectively dehydrogenated to carbon monoxide and hydrogen in the form of hydride. However, the reaction was readily poisoned by carbon monoxide formed. The specific activity was in the order Zr_2Ni > R_2Co_7 > RFe_2, which reflected the order of relative activities of 3d-transition metals precipitated out as a result of the activation treatment. The reaction is by a rate- limited dissociation reaction of methanol on the alloy surface. Rhodium-deposited RFe_2 preparey reaction of RFe_2 in aqueous RhCl_3・3H_2O exhibited catalytic properties superior to the unpromoted alloy. Less
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