Change of Process

[Mihit Parekh]

Initial, before Contact process to produce H2SO4, method used was Lead Chamber Process.In Lead Chamber Process, Sulphuric Acid was prepared using Lead Beds. These beds where cheap, robust and could be made larger compared to glass. This process used homogeneous catalyst and process was so good that it was used to manufacture Sulfuric acid for more than 175 years and was used almost upto 1948 during when it used to provide almost 31 % of world total production. What was so innovative, profitability about Contact process that made the Lead Chamber process outdated ??

[Vishwanath Dalvi]

Great question.  Anybody care to have a go?

[Utkarsh Shah]

The inability to produce concentrated sulfuric acid at a cheaper cost and contamination of environment due to lead.

[Chetan Patil 11CHE1031]

• The lead-chamber process is the older process, and its product is aqueous sulfuric acid containing 62% to 78% H2SO4. The contact process yields pure sulfuric acid. 
• In both processes, sulfur dioxide, SO2, is oxidized to sulfur trioxide, SO3, and the SO3 is dissolved in water.
• In the old lead-chamber process, the catalyst is nitrogen dioxide gas, which doesn't give better conversion.
• The sulfur dioxide and nitrogen dioxide dissolve and over a period of approximately 30 minutes the sulfur dioxide is oxidized to sulfuric acid.
  
• The process is highly exothermic
  
• The internal lead sheathing served to contain the corrosive sulfuric acid and to render the wooden chambers waterproof.
• The major disadvantage includes the limitations in throughput, quality and concentration of the acid produced.

[Vishwanath Dalvi]

@Mihit

 

The reason is actually really simple.  We will go over this in greater detail soon. :)