The Indus Valley Civilization

Industrial preparation of Sulphuric acid by Contact process

## Industrial preparation of Sulphuric acid by Contact process:

The Contact process is the dominant method for industrial production of sulfuric acid due to its efficiency and environmental friendliness compared to the older Chamber process. Here's a breakdown of the key steps involved:

1. Preparation of Sulphur dioxide (SO2):

* Sulfur, in various forms like elemental sulfur, pyrite (FeS2), or other sulfides, is burned in air to produce SO2:

* S(s) + O2(g) → SO2(g)

* 4FeS2(s) + 11O2(g) → 8SO2(g) + 2Fe2O3(s)

* The SO2 gas is then purified to remove impurities like dust, arsenic, and other harmful metals. This is crucial for the catalyst's efficiency in the next step.

2. Conversion of SO2 to Sulphur trioxide (SO3):

* The purified SO2 gas is mixed with excess air and passed through a converter containing a vanadium pentoxide (V2O5) catalyst at around 450°C.

* The exothermic reaction converts SO2 to SO3:

* 2SO2(g) + O2(g) ↔ 2SO3(g) ΔH < 0

* The equilibrium favors SO2 at high temperatures and SO3 at low temperatures. The optimal temperature balances conversion efficiency with catalyst longevity.

3. Conversion of SO3 to Sulfuric acid (H2SO4):

* SO3 cannot be directly absorbed in water due to its exothermic reaction forming a mist. It's first absorbed in concentrated sulfuric acid to form oleum (H2SO4•SO3):

* SO3(g) + H2SO4(l) → H2S2O7(l) (oleum)

* Oleum is then diluted with water in a controlled manner to produce sulfuric acid of the desired concentration:

* H2S2O7(l) + H2O(l) → 2H2SO4(l)

Additional points:

* The Contact process is a multi-stage process with heat recovery and multiple converters to improve efficiency and yield.

* The process also produces a small amount of nitrogen oxides (NOx) as a byproduct, which require control measures to minimize environmental impact.

* Sulfuric acid is a vital industrial chemical used in various applications, including fertilizers, batteries, detergents, and many others.

I hope this explanation provides a clear overview of the industrial preparation of sulfuric acid by the Contact process. Feel free to ask if you have any further questions!

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