Activation of nitrogen by alkali metal-promoted transition metal. VI. Hydrogen effect on isotopic equilibration of nitrogen and rate-determining step of ammonia synthesis on potassium-promoted ruthenium catalysts

Journal Article · Sat May 01 00:00:00 EDT 1976 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(76)90253-0· OSTI ID:7322566

Urabe, K; Aika, K I; Ozaki, A

The effect of hydrogen on isotopic equilibration of nitrogen was studied on ruthenium catalysts with and without potassium at P/sub N/sub 2// = 40 to 150 mm Hg, P/sub H/sub 2// = 7 to 180 mm Hg and 300 to 450/sup 0/C. The equilibration rate is increased on pure Ru but is decreased on Ru--K by the addition of hydrogen. The rate of ammonia synthesis is correspondingly faster than equilibration on pure Ru but is slower on Ru--K. The equilibration rate on Ru--K is decreased by condensing the ammonia produced in the presence of hydrogen and by increasing the H/sub 2//N/sub 2/ ratio and approaches negligible value at H/sub 2//N/sub 2/ = 3, demonstrating that the rate-determining step of ammonia synthesis is the dissociation of nitrogen molecule. The equilibration rate on Ru--K in the presence of ammonia also decreases as hydrogen pressure increases, whereas the reaction order with respect to nitrogen pressure is higher than that in the absence of hydrogen, suggesting that the adsorbed hydrogen exhibits a retarding effect on the adsorption of nitrogen. The surface area of Ru--K was found to increase on hydrogen treatment of nitrogen covered surface, suggesting a corrosive adsorption of nitrogen to form a nitride on Ru--K.

• Research Organization: Tokyo Inst. of Tech., Ohokayama, Japan
• OSTI ID: 7322566
• Journal Information: J. Catal.; (United States), Vol. 42:2
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMMONIA
SYNTHESIS
POTASSIUM
CATALYTIC EFFECTS
RUTHENIUM
CHEMICAL ACTIVATION
CHEMICAL REACTION KINETICS
EQUILIBRIUM
HIGH TEMPERATURE
HYDROGEN
ISOTOPE RATIO
NITROGEN
PROMOTERS
ALKALI METALS
CRYOGENIC FLUIDS
ELEMENTS
FLUIDS
HYDRIDES
HYDROGEN COMPOUNDS
KINETICS
METALS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
PLATINUM METALS
REACTION KINETICS
REFRACTORY METALS
TRANSITION ELEMENTS
090320* - Inorganic Hydrogen Compound Fuels- Preparation- (1976-1989)
400201 - Chemical & Physicochemical Properties