Steady-state kinetics of the CON 2O reaction over an alumina-supported rhodium catalyst

Abstract

Kinetics of the rhodium-catalyzed reaction between carbon monoxide (CO) and nitrous oxide (N 2O) were measured in a laboratory plug-flow reactor at temperatures between 550 and 700 K, space times between 0.06 and 0.26 s, and CO and N 2O partial pressures between 0.6 and 7 Torr. A brief comparison was also made between the CON 2O kinetics and kinetics of the CONO and COO 2 reactions. The comparison showed that the CON 2O reaction is an important subreaction of the CONO reaction (i.e., CO reacts initially with NO to produce N 2O which undergoes further reaction is much lower than rates of the CONO and COO 2 reactions (ratio of turnover frequencies at 475 K estimated as 1 (CON 2O) vs 7.1 × 10 2 (CONO) vs 4.4 × 10 5 (COO 2). CON 2O rate measurements under differential conversion conditions at temperatures of 564 and 583 K yielded reaction orders of −1.0 ± 0.15 in CO pressure, 0.65 ± 0.1 in N 2O pressure, and −0.30 ± 0.1 in total (CO + N 2O) pressure. The reaction orders and apparent activation energy (40 ± 2 kcal/gmol) are consistent with a mechanism involving reaction between adsorbed CO and adsorbed N 2O dissociation products. The low rate of the CON 2O reaction compared to the COO 2 and CONO reactions suggests that, under reaction conditions characterized by high CO coverages, the rate of dissociative N 2O adsorption is slow compared to the rates of dissociative O 2 or NO adsorption.