Editing Haber process (section)

==== Ruthenium ====
[[Ruthenium]] forms highly active catalysts. Allowing milder operating pressures and temperatures, Ru-based materials are referred to as second-generation catalysts. Such catalysts are prepared by the decomposition of [[triruthenium dodecacarbonyl]] on [[graphite]].<ref name="Appl" /> A drawback of activated-carbon-supported ruthenium-based catalysts is the methanation of the support in the presence of hydrogen. Their activity is strongly dependent on the catalyst carrier and the promoters. A wide range of substances can be used as carriers, including [[carbon]], [[magnesium oxide]], [[aluminium oxide]], [[zeolite]]s, [[spinel]]s, and [[boron nitride]].<ref name="YouZhixiong">{{Cite journal |last1=You |first1=Zhixiong |last2=Inazu |first2=Koji |last3=Aika |first3=Ken-ichi |last4=Baba |first4=Toshihide |date=October 2007 |title=Electronic and structural promotion of barium hexaaluminate as a ruthenium catalyst support for ammonia synthesis |journal=Journal of Catalysis |volume=251 |issue=2 |pages=321–331 |doi=10.1016/j.jcat.2007.08.006}}</ref>

Ruthenium-activated carbon-based catalysts have been used industrially in the KBR Advanced Ammonia Process (KAAP) since 1992.<ref name="rosowski">{{Cite journal |last1=Rosowski |first1=F. |last2=Hornung |first2=A. |last3=Hinrichsen |first3=O. |last4=Herein |first4=D. |last5=Muhler |first5=M. |date=April 1997 |title=Ruthenium catalysts for ammonia synthesis at high pressures: Preparation, characterization, and power-law kinetics |journal=Applied Catalysis A: General |volume=151 |issue=2 |pages=443–460 |doi=10.1016/S0926-860X(96)00304-3|bibcode=1997AppCA.151..443R }}</ref> The carbon carrier is partially degraded to [[methane]]; however, this can be mitigated by a special treatment of the carbon at 1500&nbsp;°C, thus prolonging the catalyst lifetime. In addition, the finely dispersed carbon poses a risk of explosion. For these reasons and due to its low [[acid]]ity, magnesium oxide has proven to be a good choice of carrier. Carriers with acidic properties extract electrons from ruthenium, make it less reactive, and have the undesirable effect of binding ammonia to the surface.<ref name="YouZhixiong" />