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Difficulty: Very hardTetraoxosulfate(VI) Acid: Contact Process and Properties

In the industrial manufacture of tetraoxosulfate(VI) acid via the Contact Process, several crucial chemical and physical steps are carried out in a specific sequence to maximize yield and prevent efficiency loss. Arrange the following steps of the Contact Process in the correct sequential order from first to last.

  1. 1Combustion of elemental sulfur or roasting of sulfide ores in dry air to produce sulfur(IV) oxide gas.
  2. 2Purification and drying of the sulfur(IV) oxide and air mixture through scrubbers and electrostatic precipitators to eliminate impurities like arsenic(III) oxide.
  3. 3Reversible catalytic oxidation of sulfur(IV) oxide to sulfur(VI) oxide over vanadium(V) oxide at 450 °C and 1–2 atm.
  4. 4Absorption of sulfur(VI) oxide gas into 98% concentrated tetraoxosulfate(VI) acid to produce pyrosulfuric acid (oleum, H2S2O7H_2S_2O_7).
  5. 5Controlled dilution of pyrosulfuric acid (oleum, H2S2O7H_2S_2O_7) with water to yield desired concentrations of H2SO4H_2SO_4.

Answer

The correct sequence of the Contact Process is: Combustion/roasting to produce SO2SO_2 gas →\rightarrow Purification of SO2SO_2 gas to remove catalyst poisons →\rightarrow Catalytic conversion of SO2SO_2 to SO3SO_3 over V2O5V_2O_5 catalyst →\rightarrow Absorption of SO3SO_3 gas in concentrated H2SO4H_2SO_4 to form oleum →\rightarrow Controlled dilution of oleum with water to yield H2SO4H_2SO_4.
The Contact Process must follow a rigorous order: first generating raw SO2SO_2 gas, purifying it to prevent catalyst poisoning by impurities like As2O3As_2O_3, catalytically oxidizing SO2SO_2 to SO3SO_3 over V2O5V_2O_5, absorbing SO3SO_3 in 98% H2SO4H_2SO_4 to form oleum (H2S2O7H_2S_2O_7), and finally diluting oleum with water to produce concentrated H2SO4H_2SO_4.

Step-by-Step Solution

1
Identify the initial feedstock generation stage.
Combustion of sulfur or roasting of sulfide ores produces SO2SO_2 gas.
Sulfur(IV) oxide is the essential chemical precursor required for the process.
2
Determine the necessary gas purification stage prior to catalysis.
Passing the SO2SO_2 and air mixture through scrubbers and precipitators removes dust particles and arsenic(III) oxide (As2O3As_2O_3).
Arsenic compounds act as catalyst poisons, permanently deactivating the vanadium(V) oxide catalyst if not removed first.
3
Identify the catalytic oxidation step.
Purified SO2SO_2 reacts with O2O_2 over a V2O5V_2O_5 catalyst at 450 °C and 1–2 atm to form SO3SO_3.
This exothermic equilibrium reaction converts sulfur(IV) oxide to sulfur(VI) oxide.
4
Determine the absorption stage for sulfur(VI) oxide.
SO3SO_3 gas is absorbed into concentrated (98%) H2SO4H_2SO_4 to form oleum (H2S2O7H_2S_2O_7).
Direct hydration of SO3SO_3 with water is extremely exothermic and produces a fine acid fog that cannot be easily condensed industrially.
5
Identify the final dilution/hydration step.
Oleum (H2S2O7H_2S_2O_7) is diluted with a calculated volume of water to form concentrated H2SO4H_2SO_4.
Reacting oleum with water yields high-purity tetraoxosulfate(VI) acid safely and efficiently.

Key Concept

Sequential chemical and industrial stages of the Contact Process for tetraoxosulfate(VI) acid production
Estimated Time:2m 0s
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Topics

Tetraoxosulfate(VI) Acid: Contact Process and Properties

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