Chimica industriale/Zolfo: differenze tra le versioni
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==Processi industriali==
===Processo delle camere di piombo===
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The '''lead chamber process''' was an industrial process used to produce relatively strong concentrations of [[sulfuric acid]] in large quantities.
In [[1746]], [[John Roebuck]] began producing sulfuric acid in [[lead]]-lined chambers, which were stronger, less expensive, and could be made larger than the [[glass]] containers which had been used previously. This allowed the effective industrialization of sulfuric acid production, and with several refinements remained the standard method of production for almost two centuries.
[[Concentration]]s ranged from 35%-40%, and after numerous refinements up to 78%. This is not a strong enough concentration for some industrial applications, and thus this method was eventually replaced by the [[contact process]].
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===Processo a contatto===
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The '''contact process''' is the current method of producing [[sulfuric acid]] in the high concentrations needed for industrial processes. [[Vanadium(V) oxide]] is the [[catalyst]] employed.
This process was patented in 1831 by the British [[vinegar]] merchant Peregrine Phillips, as a far more economical process for producing [[sulfur trioxide]] and concentrated [[sulfuric acid]] than the previous [[lead chamber process]] method used for producing sulfuric acid.
==Manufacturing sulfuric acid by the contact process==
The process can be divided into three stages:
#Preparation and purification of [[sulphur dioxide]]
#[[Catalytic oxidation]] (using Vandium catalyst) of [[sulphur dioxide]] to [[sulphur trioxide]]
#Conversion of [[sulphur trioxide]] to sulphuric acid
Purification of air and [[sulfur dioxide|SO<sub>2</sub>]] is necessary to avoid [[catalyst]] ''poisoning'' (ie. removing catalytic activities). The gas is then washed with [[water_(molecule)|water]] and dried by H<sub>2</sub>SO<sub>4</sub>.
To conserve energy, the mixture is heated by exhaust gases from the catalytic converter by heat exchangers.
[[Sulphur dioxide]] and [[oxygen]] then react in the manner as follows:
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2 [[sulphur dioxide|SO<sub>2</sub>]]''([[gas|g]])'' + O<sub>2</sub>''(g)'' ↔ 2 [[sulphur trioxide|SO<sub>3</sub>]]''(g)'' <br>
Δ''H'' = -197 kJ/mol
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To increase the reaction rate, high temperatures (450 °C), high pressures (200 kPa or 2 [[atmosphere (unit)|atm]]), and [[vanadium(V) oxide]] (V<sub>2</sub>O<sub>5</sub>) are used to ensure a '''95% conversion'''.
Hot [[sulphur trioxide]] passes through the heat exchanger and is dissolved in concentrated H<sub>2</sub>SO<sub>4</sub> in the absorption tower to form [[oleum]]:
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H<sub>2</sub>SO<sub>4</sub>''([[liquid|l]])'' + SO<sub>3</sub> → H<sub>2</sub>S<sub>2</sub>O<sub>7</sub>''(l)''
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Note that directly dissolving [[sulphur trioxide|SO<sub>3</sub>]] in [[water_(molecule)|water]] is impractical due to the highly [[exothermic_reaction|exothermic]] nature of the reaction. Mists are formed instead of a liquid.
Oleum is reacted with water to form concentrated H<sub>2</sub>SO<sub>4</sub>.
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H<sub>2</sub>S<sub>2</sub>O<sub>7</sub>''(l)'' + H<sub>2</sub>O''(l)'' → 2 H<sub>2</sub>SO<sub>4</sub>''(l)''
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Note: Sulfur is the American spelling of the UK spelling sulphur; they are synonymous and interchangeable.
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==Usi==
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