Ostwald process 22830 214798005 2008-05-25T09:22:49Z Da monster under your bed 2040962 Reverted edits by [[Special:Contributions/221.120.210.41|221.120.210.41]] ([[User talk:221.120.210.41|talk]]) to last version by 59.176.90.249 The '''Ostwald process''' is [[chemistry|chemical]] [[process(science)|process]] for producing [[nitric acid]], which was developed by [[Wilhelm Ostwald]] (patented 1902). It is a mainstay of the modern [[chemical industry]]. Historically and practically it is closely associated with the [[Haber process]], which provides the requisite raw material, [[ammonia]]. ==Description== Ammonia is converted to nitric acid in two stages. It is [[redox|oxidized]] (in a sense "burnt") by heating with [[oxygen]] in the presence of a [[catalyst]] such as [[platinum]] with 10% [[rhodium]], to form [[nitric oxide]] and [[water]]. This step is strongly exothermic, making it a useful heat source once initiated (ΔH = -950 kJ): :4NH<sub>3(g)</sub> + 5O<sub>2(g)</sub> → 4NO<sub>(g)</sub> + 6H<sub>2</sub>O<sub>(g)</sub> Stage two (combining two reaction steps) is carried out in the presence of water in an [[absorption (chemistry)|absorption]] apparatus. Initially nitric oxide is oxidized again to yield [[nitrogen dioxide]]: :2NO<sub>(g)</sub> + O<sub>2(g)</sub> → 2NO<sub>2(g)</sub> This gas is then readily absorbed by the water, yielding the desired product (nitric acid, albeit in a dilute form), while [[redox|reducing]] a portion of it back to nitric oxide: :3NO<sub>2(g)</sub> + H<sub>2</sub>O<sub>(l)</sub> → 2HNO<sub>3(aq)</sub> + NO<sub>(g)</sub> The NO is recycled, and the acid is concentrated to the required strength by [[distillation]]. Alternatively, if the last step is carried out in air: :4NO<sub>2(g)</sub> + O<sub>2(g)</sub> + 2H<sub>2</sub>O<sub>(l)</sub> → 4HNO<sub>3(aq)</sub> Typical conditions for the first stage, which contribute to an overall [[Yield (chemical)|yield]] of about 96%, are: * [[pressure]] between 4 and 10 [[atmosphere (unit)|atmospheres]] (approx. 400-1010 kPa or 60-145 psig) and * [[temperature]] is about 1173 [[Kelvin|K]] (approx. 900°C or 1652°F.). ==History== An earlier patent (Kuhlmann, 1838) described the basic chemistry, but ammonia (from animal sources) was scarce at the time, so it was probably of only academic interest, either then or when Ostwald patented his version in 1902. A later date is frequently given for the development of the process (1908), and it may be that by then [[Fritz Haber]]'s [[Haber process|method]] of making ammonia was known, which would have changed the outlook entirely. Ostwald's primary contributions seem to have been practical ones concerning the catalyst and operating conditions, a matter perhaps more of [[chemical engineering]] than of basic [[science]]. Prior to this the source of most industrial nitrogen were [[sodium nitrate|nitrate ores]], primarily imported [[Chile saltpeter]], from which nitric acid was produced by treatment with [[sulfuric acid]]. The Ostwald process gained prominence as an adjunct to the [[nitrogen fixation|fixing of nitrogen]] ([[Haber Process]]).The combined processes undoubtedly prolonged [[World War I]], when [[Germany]]'s overseas sources were cut off and [[explosives]] production was threatened. Subsequently their use of widely available raw materials (and the resulting low cost) led to their general adoption, resulting in vastly increased nitrogen consumption, mostly as [[fertilizer]]s. Initially the process was carried out in low pressure [[stoneware]] vessels, but the introduction of [[stainless steel]] made higher pressures practical, leading to higher yields. == External links == * [http://www.physicsdaily.com/physics/Ostwald_process Physics Daily] * [http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch10/group5.php Nitrogen & Phosphorus] (General Chemistry course), [http://chemed.chem.purdue.edu Purdue University] * Drake, G; [http://www.fertiliser-society.org/Proceedings/UK/Prc78.HTM "Processes for the Manufacture of Nitric Acid"] (1963), [http://www.fertiliser-society.org International Fertiliser Society] * [http://www.carlton.paschools.pa.sk.ca/chemical/mtom/contents/chapter3/fritzhaber_2.htm Manufacturing Nitrates: the Ostwald process] Carlton Comprehensive High School; Prince Albert; Saskatchewan, Canada. [[Category:Chemical processes]] [[Category:Industrial processes]] [[de:Ostwaldverfahren]] [[es:Método de Ostwald]] [[io:Ostwald-procedo]] [[nl:Ostwaldproces]] [[pt:Processo Ostwald]] [[sv:Ostwald-metoden]]