From Simple English Wikipedia, the free encyclopedia
Stuctural formula of ammonia. N isnitrogen and H ishydrogen. The lines show that theatoms are joined bychemical bonds.A picture to show simply how the atoms may fill space. The blue is nitrogen and the white is hydrogen.
Many organicnitrogen compounds are in animal waste, includingurine andguano. In the 19th century theDistillation (boiling for separation) of nitrogenous vegetable and animal waste was the main source of ammonia. During the 20th century theHaber process using high temperature and pressure withcatalysts (things that make reactions faster) became the main source.
Ammonia istoxic. If a goldfishtank is dirty from their waste, the fish can suffer from ammonia burns which cause black spots or patches on their body. The tank must be large enough and have afilter.
Because of its many uses, ammonia is one of the most often produced inorganic chemicals. Dozens ofchemical plants worldwide produce ammonia. The worldwideammonia production in 2004 was 109 millionmetric tonnes.[2]China produced 28.4% of the worldwide production (increasingly from coal as part ofurea synthesis)[3] followed byIndia with 8.6%,Russia with 8.4%, and theUnited States with 8.2%.[2] About 80% or more of the ammonia produced is used for fertilizing agricultural crops.[2]
Before the start ofWorld War I, most ammonia was obtained by thedry distillation[4] of nitrogenous vegetable and animal waste products, includingcameldung, where it wasdistilled by the reduction ofnitrous acid andnitrites with hydrogen; in addition, it was produced by the distillation ofcoal, and also by the decomposition of ammonium salts byalkaline hydroxides[5] such asquicklime, the salt most generally used being the chloride (sal-ammoniac) thus:
2 NH4Cl + 2 CaO → CaCl2 + Ca(OH)2 + 2 NH3
Today, the typical modern ammonia-producing plant first convertsnatural gas (i.e., methane) orliquefied petroleum gas (such gases arepropane andbutane) or petroleumnaphtha into gaseous hydrogen. The process used in producing the hydrogen begins with removal ofsulfur compounds from the natural gas (because sulfur deactivates thecatalysts used in subsequent steps). Catalytichydrogenation converts organosulfur compounds into gaseoushydrogen sulfide:
H2 + RSH → RH + H2S (g)
The hydrogen sulfide is then removed by passing the gas through beds ofzinc oxide where it is adsorbed and converted to solidzinc sulfide:
The final step in producing the hydrogen is to use catalytic methanation to remove any small residual amounts of carbon monoxide or carbon dioxide from the hydrogen:
CO + 3 H2 → CH4 + H2O
CO2 + 4 H2 → CH4 + 2 H2O
To produce ammonia, the hydrogen then reacts with nitrogen (derived from process air) using amagnetitecatalyst under high pressure to form anhydrous liquid ammonia. This step is known as the ammonia synthesis loop (also referred to as theHaber-Bosch process):
3 H2 + N2 → 2 NH3
Hydrogen required for ammonia synthesis could also be produced economically using other sources like coal or coke gasification, less economically from the electrolysis of water into oxygen + hydrogen and other alternatives that are presently impractical for large scale production.At one time, most of Europe's ammonia was produced from the Hydro plant atVemork, using electrolysis.
