There are many ways that can be used to produced sulfuric acid in industrial scale.
The most popular method is the process named the contact process. In this process sulfur is burned to produce sulfur dioxide and then sulfur dioxide is further oxidized to sulfur trioxide in the presence of vanadium pentoxide.
`S_((s)) + O_(2(g)) -------gt SO_(2(g))`
`2SO_2(g) + O_(2(g)) -------gt 2SO_3(g)`
Then this sulfur trioxide is absorbed in 97% percent `H_2SO_4 ` (previously made) to produce oleum.
`SO_3(g) +H_2SO_4_(l) ------gt H_2S_2O_7_(l)`
Then this oleum is dissolved in water to produce sulfuric acid. If we dissolve `SO_3` direclty in water, it will produce highly corrsive mist not a solution.
`H_2S_2O_7_(l) +H_2O_((l)) ------------gt 2H_2SO_4_(l)`
The other method is the wet sulfur method in which `SO_3` is dissolved in water and `H_2SO_4_(g)` is formed. Then this mist is condensed to produce `H_2SO_4_(l) `
There is also an outdated method called the lead chamber process which is very complex than above two.