1. Lecture Outline - Sulfuric Acid
- History of Manufacture Development
- Manufacture
- Oleum Production
- Heat Integration Issues / By-products
- Markets
- Usage in Caprolactam Manufacture

2. History of Manufacture of Sulfuric Acid
One of the oldest industrially applied processes. Discovered by a Persian alchemist in the tenth century.
Saltpeter and sulfur were mixed in a glass container and burned in a moist atmosphere. Acid was collected from the condensed vapors.
In England, 1746, the lead chamber reactor was invented. This invention allowed for higher production rates (<78%).
In England, 1831, a patent was filed that described the oxidation of sulfur dioxide over a platinum catalyst, the Contact Process. This new process increased yields of reaction from 70 to above 95%.
In 1913, BASF was granted a patent for the use of vanadium pentoxide as a catalyst for the Contact Process
By the 1930’s, vanadium pentoxide was becoming the dominate catalyst used because of insensitivities to poisons and lower cost.
In 1960 a patent application was filed by Bayer using the so called double-catalyst process (double absorption).

3. Manufacture
Manufacture

4. Oxidation of Sulfur Oxidation of Sulfur Process:
Air
93% H2SO4
Sulfur
10-12% SO2
Steam
Water
Process:
- Air drying tower with acid
- Sulfur is injected into burner
- Reaction Temperature 2000°F
- Exothermic reaction must be cooled
- Steam recovered
Primary Generation of SO2
79% Combustion of Sulfur
9% Recovery from Metallurgic Processes
- 5% Regeneration of Spent Acids

5. Oxidation of Sulfur Dioxide
Gas
Cooling
SO3 Gas
SO2 Gas
Contact Process:
-Vanadium pentoxide
catalyst
- Exothermic Reaction
- Multiple Steps with
cooling in between
- Double absorption
- Heat integration

6. Oxidation of Sulfur Dioxide
Because of the large effect temperature plays on the reaction, multiple catalyst layers are used, with cooling between each step.
Additionally, as the partial pressure of SO3 increases, further reaction is limited.
This is overcome by removing the SO3 after the third stage to drive the reaction to completion.
Gas
Cooling
SO3 Gas
SO2 Gas
93% H2SO4

7. Oxidation of Sulfur Dioxide
Kinetic Effects
- Oxidation of sulfur dioxide is slow and reversible
- The reaction requires a catalyst and 426.7°C temperatures
The reaction is exothermic and sensitive to excessive heat
Equilibrium Constant (The degree at which the reaction proceeds is temp. dependent)
log Kp = T
T = absolute temp. in kelvin
Kp = equilibrium constant as a function of partial pressure of gases
Kp = ( PSO3 )
PSO2 PO2
0.5

8. Oxidation of Sulfur Dioxide
Temperature Profile
Gas
Cooling
SO3 Gas
SO2 Gas
93% H2SO4
510 C
75 C
430 C
200 C
125 C

9. Oxidation of Sulfur Dioxide
Temperature Profile

10. Oxidation of Sulfur Dioxide
Typical Catalyst Distribution

11. Overall Production Scheme

12. Oleum Production Oleum Production
Sulfuric acid with additional SO3 absorbed
20% Oleum contains 20% SO3 by weight in the oleum
Common strengths of oleum are 20, 30, 40, 65 percent.
To produce 20 and 30 percent oleum, only requires an additional absorption tower.
Oleum is used in reactions where water is excluded
SO3 + H2SO H2S2O7 (disulfuric acid)

13. Reaction By-products / Heat Integration
57 to 64% of the energy input generates steam
Steam energy is used to drive the turbine that supplies power to the main air blower
Additional steam remaining is tolled internally for other plant operations
SO2/SO3 is vented in small amounts and is federally regulated.
Heat Integration
Steam is used to pre-heat and vapor from the absorption towers used to cool
Minimizes the cost of manufacturing to maximize the profit.

14. Production Considerations
Metal corrosion is a big issue in the manufacture of sulfuric acid.
Special alloy metals must be used to guard against excessive corrosion.
Nickel, chromium, molybdenum, copper, an silicon are the most important elements that enhance corrosion resistance of alloys.
Important variables for corrosion
Concentration of the acid
Temperature of service
Speed of flow in pipes and
equipment
Alloy element make-up

15. World Production of Sulfuric Acid

16. World Supply / Demand for Sulfuric Acid (thousands of metric tons, 100% H2SO4)

17. Markets for Sulfuric Acid
The fertilizer market is the largest U.S. single use for sulfuric acid and consumes percent of all produced.
Second is the organic chemical industry. Production of plastics and synthetic fibers are examples.
Production of TiO2 consumes large quantities of sulfuric acid. TiO2 is a white pigment used in paints and plastics.
In the metal industry, sulfuric acid is used for pickling ferrous and non-ferrous materials and in the recovery of copper, nickel, and zinc from low-grade ores.
Finally, the petroleum industry uses acid as a catalyst for various reactions.

18. Acid Strengths Associated End Uses

19. Usage in Caprolactam Manufacture
Production and consumption figures for caprolactam manufacture