The Contact Process & Making Sulphuric acid H 2 SO 4

Sulphuric Acid H 2 SO 4 commercially important raw material

Sulphuric Acid H 2 SO 4 commercially important raw material

Sulphuric Acid H 2 SO 4 commercially important raw material more sulphuric acid made than any other compound

Sulphuric Acid H 2 SO 4 commercially important raw material more sulphuric acid made than any other compound fertilisers, paints and pigments, detergents, car batteries, laboratory acid

Sulphuric Acid H 2 SO 4 manufacture properties properties uses uses

Sulphuric Acid H 2 SO 4 manufacture properties properties uses uses H2OH2OAirSulphur

Sulphuric Acid H 2 SO 4 manufacture H2OH2OAirSulphur Step 1: Formation of SO 2 either S + O 2 SO 2 or 2ZnS + 3O 2 2SO 2 + 2ZnO

Sulphuric Acid H 2 SO 4 manufacture H2OH2OAirSulphur Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 Δ H = -197 kJ mol – 1 exothermic

Sulphuric Acid H 2 SO 4 manufacture H2OH2OAirSulphur Step 3: Formation of Oleum SO 3 + conc H 2 SO 4 H 2 S 2 O 7 [the direct combination of SO 3 with water is too exothermic and forms a fine mist of acid]

Sulphuric Acid H 2 SO 4 manufacture H2OH2OAirSulphur Step 4: Dilution of Oleum H 2 O + H 2 S 2 O 7 2H 2 SO 4 the oleum is diluted to give the desired concentration of sulphuric acid

Sulphuric Acid H 2 SO 4 manufacture H2OH2OAirSulphur Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Let’s look at this equilibrium more closely….

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process Factors: Catalyst Temperature Temperature Pressure Pressure 2SO 2 + O 2 2SO 3 exothermic

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Factors: Catalyst V 2 O 5 Temperature Temperature Pressure Pressure

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Factors: Catalyst V 2 O 5 Temperature 450 o C Temperature 450 o C Pressure Pressure

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Factors: Catalyst V 2 O 5 Temperature 450 o C Temperature 450 o C Pressure 1-2 atmospheres Pressure 1-2 atmospheres ***These are compromise conditions***

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Factors: Catalyst V 2 O 5 ***These are compromise conditions*** The catalyst works best as the temperature increases Provides an alternative path with a lower E act Speeds up time taken to achieve equilibrium Several catalyst beds used to achieve high yield

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Factors: Temperature 450 o C ***These are compromise conditions*** The yield of SO 3 increases as T is decreased However Catalyst does not work if T is too low Rate of attainment of equilibrium is slow if T is too low

Sulphuric Acid Step 2: Formation of SO 3 the Contact Process 2SO 2 + O 2 2SO 3 exothermic Factors: Pressure 1-2 atmospheres ***These are compromise conditions*** The yield of SO 3 increases as P is increased High pressure is costly £££

Sulphuric Acid H 2 SO 4 manufacture properties properties uses uses

Sulphuric Acid H 2 SO 4 manufacture properties properties uses uses Dehydrating agent Viscous liquid

Sulphuric Acid H 2 SO 4 manufacture properties properties uses uses Dehydrating agent Conc H 2 SO 4 will dehydrate hydrated copper sulphate and carbohydrates (e.g. sugar)