The reduction of 15N14NO by CO and by H2 over Rh/SiO2: A test of a mechanistic proposal

A literature proposal that the reduction of nitrous oxide by carbon monoxide over rhodium catalysts proceeds by cleavage of the NN bond has been tested through the use of 15N14NO as the reactant. The results disprove the suggestion in that 14N15N is the dominant product at temperatures from 336 °C to 356 °C with nitrous oxide conversions from 26% to >99%. Little, if any, 14N2 and 15N2 is formed, in contrast with the 25% of each expected for the model. Results for the corresponding reaction of 15N14NO with H2 are even more clear-cut in demonstrating the absence of NN bond cleavage. The activity of the Rh/SiO2 used here for the N2O/CO system fell within the rather wide of values reported in the literature for other Rh catalysts. However, activity for the reduction of N2O by H2 was approximately five times higher than the only previous result in the literature, that for a Rh/Al2O3 catalyst.

The reduction of 15N14NO by carbon monoxide, and also by hydrogen, over a Rh/SiO2 catalyst yields 15N14N as the exclusive nitrogen-containing product. The result rules out a suggestion in the literature that the reduction using carbon monoxide proceeds through cleavage of the nitrogennitrogen bond.Figure optionsDownload high-quality image (26 K)Download as PowerPoint slideResearch highlights
► Rh/SiO2 catalyses reduction of 15N14NO by CO to 14N15N with near zero 14N2 or 15N2.
► The isotopic result rules out a literature suggestion that the NN bond is cleaved.
► Reduction of 15N14NO by H2 also yields 14N15N alone.
► The reduction by H2 over Rh/SiO2 is much faster than reported for Rh/Al2O3.