Concentrated Sulphuric Acid Preparation

Sulfuric acid or sulphuric acid, known in antiquity as oil of vitriol, is a mineral acid composed of sulphur, oxygen, and hydrogen. It is a colourless liquid that is corrosive towards other materials if concentrated. Pure sulfuric acid does not naturally exist on Earth because it is so hygroscopic when warm and humid. Due to its strong affinity with water vapour, acid does not exist naturally on Earth; however, it can form solid compounds with many other non-volatile compounds like salt, calomel and barium, which react with it to form solid salts of barium sulphate, for example. The acid is generally manufactured using a method known as the contact process.

Physical Properties

1. Sulphuric acid is a thick and oily fluid. 
2. The acid is a colourless liquid.
3. It has a specific gravity of 1.84 at 298 K. 
4. The boiling point of the acid is 611 K. When compared to water, the higher boiling point and thickness are due to hydrogen bonding in its composition.
5.  This strong chemical reacts with water vigorously, which releases quite a lot of heat. Hence you must never add water to H2SO4 as it will result in an explosion. Instead, you should slowly add the acid to the water with proper stirring.

Chemical Properties

1. Sulfuric acid is a dibasic acid, and it is diprotic.
2.  This chemical is strong enough to act as a strong oxidising agent. 
3. When concentrated, this chemical can expel water from natural mixes like starches.
4. When the gas containing water comes in contact with Sulphuric acid, its water is expelled due to its dehydrating property. 
5. As Sulphuric acid acts as a good oxidising agent, it tends to get reduced to Sulphur dioxide, which can oxidise nonmetals and metals.

Uses of Sulphuric Acid

• Industrial Use 

1. Up to 50% of this liquid is used to make phosphate fertilisers, which help grow plants and crops. These crops include wheat, barley, fruits, and vegetables like broccoli, carrots, lettuce, and onions.
2. Use in phosphate fertiliser production helps improve overall crop health by boosting the availability of essential plant nutrients such as nitrogen and phosphorus.
3. It is also used in manufacturing metals like zinc, copper, etc.

• Domestic Use: Various uses exist for sulphuric acid in various domestic environments.

1. It is an ingredient present in many drain cleaners used to remove clogs and clear out hard-to-reach areas. 
2. In addition, it can also be used to effectively remove tissue paper from drains where kitty litter does not effectively do the trick.

• As a catalyst

1. In the manufacturing process of nylon.
2. In the Manheim process in the manufacturing of HCl.
3. In petroleum refining.

Manufacturing Process 

In general, there are two manufacturing processes for sulphuric acid. They are:

1. Contact process
2. Lead chamber process

Contact Process

The contact process for creating sulphuric acid is an industrial method of producing sulfuric acid. Creating the acidic form of sulphur primarily involves reacting both oxygen and air and water to create the needed amount for creating the material. This process has largely replaced the chamber or lead-chamber process in factories today.

Currently, the contact process is the current method of producing high concentrations of sulphuric acid. In this process, a chemical element known as platinum was originally used as a catalyst, but because it can react with arsenic impurities in the sulphur feedstock, vanadium oxide (V2O5) is now preferred.

The contact process is a chemical process that converts sulphur dioxide gas to solid sulphur.   In this method, purified sulphur dioxide and oxygen are mixed and heated at a temperature of about 450 °C over platinum or other catalysts. The reaction produces sulphur trioxide, which is then cooled and passed through two towers (the second tower is used for more material separation).

Production of Sulphuric Acid by Contact Process

The production of sulphuric acid by contact process involves three major steps:-

Step 1: Production of sulphur dioxide

This can either be done by burning sulphur in excess of air:

S+O2​→So2

or by heating sulphide ores like pyrite in excess of air:

4FeS2​+11O2→2Fe2​O3+8CO2

Step 2: Formation of Sulphur Trioxide

Then sulphur dioxide is oxidised with atmospheric oxygen to sulphur trioxide using V2O5 as a catalyst. In this process, a chemical element known as platinum was originally used as a catalyst, but because it can react with arsenic impurities in the sulphur feedstock, vanadium oxide (V2O5) is now preferred.

2SO2(Sulphur dioxide)   +   O2(Oxygen)   +   V2O5(Catalyst)   →    SO3(Sulphur trioxide)

Step 3: Conversion of Sulphur Trioxide into Sulphuric Acid

After that, the sulphur trioxide is broken into 98% sulfuric acid to give oleum. Another name for oleum is pyrosulfuric acid. Then  Oleum is diluted with water to give sulfuric acid of the desired concentration.

SO3 (Sulphur trioxide)   +  H2SO4 (Sulfuric acid-98%)    →    H2S2O7 (Pyrosulfuric acid/Oleum)

H2S2O7 (Pyrosulfuric acid/Oleum)    +  H2O(Dilution)    →     2H2SO4 (Sulfuric acid)

Lead Chamber Process

The lead chamber process, also known as the LeChambre Process, is a method typically applied to manufacturing artificial acids. In the lead chamber process, hot sulphur dioxide gas enters a Glover tower reactor, where nitrous vitriol (sulfuric acid with nitric oxide, NO and nitrogen dioxide) is used to clean the exhaust. 

2SO2   +   O2    →   2SO3

Then, sulphur trioxide is made to react with water to get H2SO4.

SO3   +   H2O   →    H2SO4

Conclusion

The article will help the new learners know about Sulphuric acid’s properties and the Contact Process. Sulphuric acid is an inorganic compound with the formula H2SO4 and a colourless, viscous liquid soluble in water. Today, sulphuric acid has become a very important commodity. It is widely used in different industries. The above article gives a comprehensive idea about Sulphuric acid, its properties, manufacturing process and a variety of uses and a detailed explanation of the preparation of sulphuric acid by contact process in which a chemical element known as platinum was originally used as a catalyst.