abstracts - Институт катализа им. Г.К. Борескова

OP-III-21and selective oxidation of NH 3 to N 2 . Thereis practically neither NO nor N 2 O formation.N 2 is the main N-containing product. TPRand kinetic results show a large shift in thetemperature at which the reaction starts (550-650 K) depending on the O 2 /NH 3 ratio. Wesuggest that the influence of oxygen isrelated to its effect on the NH 3decomposition.Rh(100). It was very surprising to finddecomposition of ammonia on Rh(100), as itwas reported [2], that ammonia does notdecompose over Rh(111). TD-spectra showthe presence of NH 2 -species on the surface.In coadsorption NH 3 + O 2 experiments nosignificant shift of the desorption peak ofnitrogen was observed as was found forruthenium surface. We suppose, that unlikefor ruthenium, all the oxygen consumed inreaction with hydrogen. And at highertemperatures ~ 700 K only nitrogen atomsare present on the surface. Under oxidationconditions, nitrogen desorption is the limitingprocess. The main products are N 2, H 2 O, anda small amount of NO. NO forms only athigh temperature. We suppose, that attemperatures lower than the desorptiontemperature of nitrogen, only nitrogen atomsare on the surface. When nitrogen begins todesorb, oxygen reacts with nitrogen, formingNO. At R>1 after nitrogen desorption onlyNO, water and no N 2 or a significant amountof N 2 O were observed. At R=10 a small shiftof nitrogen desorption temperature wasfound, but not as large as for ruthenium.Fig. 1. (a) N 2 formation during heating of an O ads(10 L) saturated Pt(410) surface with differentamounts of NH 3 . (b) NO formation during heating ofan O ads saturated surface (10 L) with different amountsof NH 3 . (c) N1s spectra obtained during heating of acoadsorbed NH 3ads /O ads layer in the presence of 5×10 -8mbar O 2 .Hydrogen intensity (arb. un.)380 KNH 3/Ru(0001)T ads= 300 KNH 3exposure:16.0 L8.0 L4.0 L3.0 L2.0 L1.0 L0.5 L0.25 L300 400 500 600 700Temperature (K)Fig. 2. TPR spectra of dissociative ammoniadecomposition on Ru(0001).362