Efficient multimetallic catalytic systems for the selective hydrogenation of nitric acid

Hara, Takuma; Nakamura, Yosuke; Nishimura, Jun

doi:10.1016/j.apcata.2008.02.008

Cited by 3 publications

(1 citation statement)

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“…Information on the catalytic properties of GeO 2 is scarce and is mainly limited e.g. to the use of GeO 2 as a promoter in the selective hydrogenation of nitric acid or the use of bimetallic Pt and Rh-Ge particles in hydrogenation reactions [9]. On the basis of the structural results of the thin film model preparation discussed in a separate publication [10], the present contribution therefore is focussed on the structural changes of the SnO 2 and GeO 2 thin films upon reduction and the subsequent correlation to catalytic activity and selectivity in methanol steam reforming.…”

Section: +mentioning

confidence: 99%

Catalytic characterization of pure SnO2 and GeO2 in methanol steam reforming

Zhao

Lorenz

Turner

et al. 2010

Applied Catalysis A: General

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Structural changes of a variety of different SnO, SnO2 and GeO2 catalysts upon reduction in hydrogen were correlated with associated catalytic changes in methanol steam reforming. Studied systems include SnO, SnO2 and GeO2 thin film model catalysts prepared by vapour phase deposition and growth on polycrystalline NaCl surfaces and, for comparison, the corresponding pure oxide powder catalysts. Reduction of both the SnO2 thin film and powder at around 673 K in 1 bar hydrogen leads to a substantial reduction of the bulk structure and yields a mixture of SnO2 and metallic β-Sn. On the powder catalyst this transformation is fully reversible upon oxidation in 1 bar O2 at 673 K. Strongly reduced thin films, however, can only be re-transformed to SnO2 if the reduction temperature did not exceed 573 K. For GeO2, the situation is more complex due to its polymorphism. Whereas the tetragonal phase is structurally stable during reduction, oxidation or catalytic reaction, a small part of the hexagonal phase is always transformed into the tetragonal at 673 K independent of the gas phase used. SnO2 is highly active and CO2-selective in methanol steam reforming, but the initial high activity drops considerably upon reduction between 373 and 573 K and almost complete catalyst deactivation is observed after reduction at 673 K, which is associated with the parallel formation of β-Sn. In close correlation to the structural results, the catalytic activity and selectivity can be restored upon an oxidative catalyst regeneration at 673 K. Tetragonal GeO2 exhibits only a small activity and no pronounced selectivity to either CO or CO2, at least after reduction. In its fully oxidized state release of surface/lattice oxygen results in a non-catalytic formation of CO2 by oxidation of CO originating from catalytic dehydrogenation.

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Section: +mentioning

confidence: 99%