An analysis of ammonia synthesis by the model of Selective Energy Transfer (SET)

Abstract

The SET theory implies that energy is transferred from the catalyst system via infrared radiation to the molecules that are supposed to react. In previous investigations it has been demonstrated that the activation of the reacting species-as long as the molecules are infrared active-can occur at low adsorption strength. However, for molecules that are IR inactive, e.g. dinitrogen, this is not possible. Hence the N 2 molecule has to be adsorbed on the catalyst surface to give rise to vibrations that can interact with IR quanta of the catalyst. By analyzing the activation energies for a series of reactions between hydrogen and nitrogen under slightly differing conditions this critical vibration has been found at wave numbers such as 374, 374 and 355cm -1 . The critical vibration is identifi ed as the degenerate bending vibration of the M-N-N unit. When this bending is activated, the N 2 triple bond is weakened and makes place for hydrogen addition. Two different routes of reaction are scheduled, of which one is the most likely one, using the metal-atomic nitrogen stretch vibration as the catalyst vibrator.For the classical Fe3O4 a perfect resonance (1:1) with the above-mentioned critical vibrations exist. This is also the case for the catalyst from Co3Mo3N, where a surface cover of, inter alia, MoO 4 2seem to act likewise in full resonance.

The Transformation by Catalysis of Prebiotic Chemical Systems to Useful Biochemicals: A Perspective Based on IR Spectroscopy of the Primary Chemicals: I. The Synthesis of Peptides by the Condensation of Amino Acids

“…In the concluding remarks on this model [15], it was reported on the decomposition of formic acid (which can react along two different lines), but also on some dehydrochlorination reactions. Recently, the SET model has been applied to the technically important dehydrogenation of propane [17], as well as to the equally important ammonia synthesis from N2 and H2 [18]. In all these cases, one can state that the SET model works well [19].…”

The Transformation by Catalysis of Prebiotic Chemical Systems to Useful Biochemicals: A Perspective Based on IR Spectroscopy of the Primary Chemicals: I. The Synthesis of Peptides by the Condensation of Amino Acids

“…In the concluding remarks on this model [15], it was reported on the decomposition of formic acid (which can react along two different lines), but also on some dehydrochlorination reactions. Recently, the SET model has been applied to the technically important dehydrogenation of propane [17], as well as to the equally important ammonia synthesis from N 2 and H 2 [18]. In all these cases, one can state that the SET model works well [19].…”