Any of several gaseous mixtures used for synthesizing a wide range of compounds, both organic and inorganic, especially ammonia. Such mixtures result from reacting carbon-rich substances with steam (steam reforming) or steam and oxygen (partial oxidation); they contain chiefly carbon monoxide and hydrogen, plus low percentages of carbon dioxide and usually less than 2.0% nitrogen. The organic source materials may be biomass, natural gas, methane, naphtha, heavy petroleum oils, or coke (coal). The reactions are nickel-catalyzed steam-cracking (reforming) of methane or natural gas(CH4 + H2O → CO + 3H2); partial oxidation of methane, naphtha, or heavy oils; and the water-gas reaction with coke (C + H2O → CO + H2). With transition-metal catalysts synthesis gas yields alcohols, aldehydes, acrylic acid, etc., and has many useful reactions with acetylene; it is the basis of the Oxo and Fischer-Tropsch reactions. Synthesis gas from that the carbon monoxide has been removed and which has been adjusted to a ratio of 3 parts hydrogen and 1 part nitrogen is used for ammonia synthesis (nitrogen fixation). Processing with a catalyst at high temperatures and pressures yields ammonia.See Ammonia, Anhydrous; Oxo Process; Haber, Fritz; Water Gas; Gasification; Fischer-Tropsch Process.
