Editing Ostwald process (section)

=== Initial oxidation of ammonia===
The Ostwald process begins with burning [[ammonia]]. Ammonia burns in [[oxygen]] at temperature about {{convert|900|°C}} and pressure up to {{convert|8|atm}}<ref>{{Cite book |editor=Considine, Douglas M. |title=Chemical and process technology encyclopedia |year=1974 |publisher=McGraw-Hill |location=New York |isbn=978-0-07-012423-3 |pages=[https://archive.org/details/chemicalprocesst00newy/page/769 769–72] |url=https://archive.org/details/chemicalprocesst00newy/page/769 }}</ref> in the presence of a [[catalysis|catalyst]] such as [[platinum]] gauze, alloyed with 10% [[rhodium]] to increase its strength and nitric oxide yield, platinum metal on fused silica wool, copper or nickel to form [[nitric oxide]] (nitrogen(II) oxide) and [[water]] (as steam). This reaction is strongly [[exothermic reaction|exothermic]], making it a useful heat source once initiated:<ref name="jones1">{{cite book
| title = Access to chemistry
| url = https://archive.org/details/accesstochemistr00jone
| url-access = limited
| author1 = Alan V. Jones
| author2 = M. Clemmet
| author3 = A. Higton
| author4 = E. Golding
| editor = Alan V. Jones
| publisher = Royal Society of Chemistry
| year = 1999
| isbn = 0-85404-564-3
| page = [https://archive.org/details/accesstochemistr00jone/page/n273 250]
}}</ref>
:{{chem2|4NH3 + 5O2 -> 4NO  + 6H2O}}  (Δ''H'' = −905.2 kJ/mol)

====Side reactions====
A number of side reactions compete with the formation of nitric oxide. Some reactions convert the ammonia to N<sub>2</sub>, such as:
:{{chem2|4NH3 + 6NO -> 5N2 + 6H2O}}
This is a secondary reaction that is minimised by reducing the time the gas mixtures are in contact with the catalyst.<ref>{{cite book
| title = Inorganic Colloid Chemistry -: The Colloidal Elements
| author = Harry Boyer Weiser
| publisher = Read Books
| year = 2007
| isbn = 978-1-4067-1303-9
| page = 254
}}</ref>
Another side reaction produces [[nitrous oxide]]:
:{{chem2|4NH3 + 4O2 -> 2N2O + 6H2O}}  (Δ''H'' = −1105 kJ/mol)

==== Platinum-rhodium catalyst ====
The platinum and rhodium catalyst is frequently replaced due to decomposition as a result of the extreme conditions which it operates under, leading to a form of degradation called [[cauliflowering]].<ref name=":02">{{Cite journal |last1=Hannevold |first1=Lenka |last2=Nilsen |first2=Ola |last3=Kjekshus |first3=Arne |last4=Fjellvåg |first4=Helmer |date=2005-04-28 |title=Reconstruction of platinum–rhodium catalysts during oxidation of ammonia |url=https://www.sciencedirect.com/science/article/pii/S0926860X05000669 |journal=Applied Catalysis A: General |volume=284 |issue=1 |pages=163–176 |doi=10.1016/j.apcata.2005.01.033 |bibcode=2005AppCA.284..163H |issn=0926-860X}}</ref> The exact mechanism of this process is unknown, the main theories being physical degradation by hydrogen atoms penetrating the platinum-rhodium lattice, or by metal atom transport from the centre of the metal to the surface.<ref name=":02" />