C6 - the contact process

what is the contact process used for?

what is the contact process used for?

to make sulphuric acid

what are the first 3 stages of the contact process?

1) to make sulfur dioxide (SO2) - usually by burning sulphur in air

2) the sulfur dioxide is then oxidised to make sulphur trioxide (SO3)

3) the sulphur trioxide is used to make sulphuric acid (H2SO4)

is the reaction reversible?

yes

what are the 3 conditions needed to form sulphur trioxide?

temperature

pressure

catalyst

TEMPERATURE

oxidising sulfuric acid to form sulphur trioxide is exothermic

a compromise temp. of 450 degrees is used

PRESSURE

there are 2 moles of gas on the products side compared to 3 moles on the reactants side

increasing the pressure is expensive so the reaction is carried out at just above atmospheric pressure

CATALYST

to increase the rate of reaction a vanadium pentoxide catalyst (V2O5) is used

it DOESN’T change the position of equilibrium