Probing the reactivity of lattice nitrogen in transition metal nitrides

Alexander, Anne-Marie C. (2011) Probing the reactivity of lattice nitrogen in transition metal nitrides. PhD thesis, University of Glasgow.

Abstract

Reactions involving nitrogen transfer are of great industrial interest. Utilizing nitrides in this manner, in principle, could help industries overcome the increasing challenges which they face to meet economic and environmental targets. An example of this is the possible application of metal nitrides in the direct synthesis of aniline from benzene, which could potentially remove the need for the lengthy, uneconomical, and environmentally unfriendly process which is currently employed.

In the work presented in this thesis a screening study has been undertaken which explores the reactivity of lattice nitrogen within bulk and supported transition metal nitride catalysts. The experimental work has been conducted with the aim of developing a potential nitrogen transfer reagent in order to synthesise aniline via the direct conversion of benzene and has focused on three main objectives: determining the most active transition metal nitride catalyst for ammonia synthesis, in the absence of N2 to determine the reactivity of “lattice” nitrogen. It was necessary at this point to establish which materials were reactive and lost nitrogen from the metal lattice at or below 400oC, the maximum temperature for the envisaged process. Materials which demonstrated a subsequent loss of lattice nitrogen upon reaction with H2/Ar were then screened to establish whether it was possible to restore the original nitrogen content in the materials in order for the nitrides to function in a Mars-van Krevelen type capacity. Finally the reaction of benzene and hydrogen over bulk binary nitrides was conducted in an attempt to trap reactive NHx species for the production of aniline. It was found that no aniline was produced in these reactions. However, some interesting results were obtained over a selection of nitride materials, namely Co3Mo3N,
Cu3N, Zn3N2, Re3N and a metallic Co-4Re compound where low quantities of, as yet unidentified, reaction products were formed.

To the author’s knowledge, this is the largest systematic study of bulk nitrides and related materials which has been investigated on this scale and which has been directed towards this specific, novel, target process.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Nitrides, Ammonia Synthesis, Aniline
• Subjects: Q Science > QD Chemistry
• Colleges/Schools: College of Science and Engineering > School of Chemistry
• Supervisor's Name: Hargreaves, Dr. Justin
• Date of Award: 2011
• Depositing User: Miss Anne-Marie C Alexadner
• Unique ID: glathesis:2011-2796
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 Aug 2011
• Last Modified: 25 Jul 2017 15:27
• URI: https://theses.gla.ac.uk/id/eprint/2796