Lecture Outline - Sulfuric Acid

Lecture Outline - Sulfuric Acid
- History of Manufacture Development

- Manufacture
- Oleum Production
- Heat Integration Issues / By-products
- Markets
- Usage in Caprolactam Manufacture
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).
World Supply / Demand for Sulfuric Acid
(thousands of metric tons, 100% H2SO4)
250,000
200,000
150,000
100,000
50,000
0
1985
1988
1991
1994
1997
2000
Annual Capacity Production
World Production of Sulfuric Acid
Canada
Mexico
Others
Japan
Latin
F-USSR
Europe
Africa
U.S.
Asia
0.0 5.0 10.0 15.0 20.0 25.0 30.0

Share (percent)
Manufacture
Three Step Process
1) S + O2 SO2
2) SO2 + 1/2O2 SO3
3) SO3 + H2O H2SO4

Oxidation of Sulfur
1) S + O2 SO2
Sulfur
Steam
10-12% SO2
Water
Air
93% H2SO4
Process:
- Air drying tower with acid
Primary Generation of SO2 - Sulfur is injected into burner
-79% Combustion of Sulfur
- Reaction Temperature 2000°F
-9% Recovery from Metallurgic Processes
- Exothermic reaction must be cooled
- 5% Regeneration of Spent Acids
- Steam recovered
Oxidation of Sulfur Dioxide
SO2 Gas
Contact Process:
-Vanadium pentoxide
Gas
catalyst Cooling
- Exothermic Rxn
- Multiple Steps with
cooling in between
- Double absorption
- Heat integration
SO3 Gas
 Because of the large effect temperature plays on the reaction, multiple catalyst
layers had to be used with cooling between each step.
 Additionally, as the partial pressure of SO3 increases further reaction is limited.
 This was overcome by removing the SO3 after the third stage to drive the
reaction to completion.
SO2 Gas SO2 Gas
Gas
Cooling
SO3 Gas
SO3 Gas 93% H2SO4

• 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 = 4.956 - 4.678

T
T = absolute temp. in kelvin

Kp = equilibrium constant as a function of partial pressure of gases
0.5
Kp = ( PSO3 )
PSO2 PO2
Temperature Profile
SO2 Gas SO2 Gas
Gas
Cooling
SO3 Gas
510 C
75 C
430 C
200 C
SO3 Gas 93% H2SO4

125 C
Temperature Profile
Typical Catalyst Distribution
Catalyst % Catalyst Conversion %

Bed
1 19.4 56
2 25.0 87
3 26.7 99.1
4 28.9 99.7
Overall Production Scheme
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 + H2SO4 H2S2O7 (disulfuric acid)

Reaction By-products / Heat Integration
By-products
 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.
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
Markets for Sulfuric Acid
 The fertilizer market is the largest U.S. single use for sulfuric acid and
consumes 50-65 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.
Acid Strengths
Associated End Uses
Percent
H2SO4 Uses
35.67 Storage batteries, electric utilities
62.18
Normal superphosphate and other fertilizers
69.65
Normal superphosphate and other fertilizers,
77.67
isopropyl and sec-butyl alcohols
80.00 Copper leaching
Phosphoric acid, tianium dioxide, steel pickling,
93.19
regenerating ion exchange resins of utilities
98-99 Chlorine drying, alkylation, boric acid
104.50
Surfactants, nitrations, hydrofluoric acid
106.75
109.00 Explosives
111.25
Reagent manufacture, organic sulfonations,
113.50
blending with weaker acids
114.63
Usage in Caprolactam Manufacture
Production and consumption figures for caprolactam manufacture

Caprolactam Production Rate 120,000 ton/yr
H2SO4 Consumption (100% Acid) 636 kg per ton of CPL
Oleum Consumption 1300kg per ton of CPL
Ammonium Sulfate Production 312,000 ton/yr

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Lecture Outline - Sulfuric Acid

- History of Manufacture Development

• One of the oldest industrially applied processes. Discovered by a

0.0 5.0 10.0 15.0 20.0 25.0 30.0

Three Step Process

2) SO2 + 1/2O2 SO3

3) SO3 + H2O H2SO4

SO3 Gas 93% H2SO4

log Kp = 4.956 - 4.678

T = absolute temp. in kelvin

SO2 Gas SO2 Gas

SO3 Gas 93% H2SO4

Typical Catalyst Distribution

Catalyst % Catalyst Conversion %

 Sulfuric acid with additional SO3 absorbed

 Oleum is used in reactions where water is excluded

SO3 + H2SO4 H2S2O7 (disulfuric acid)

 Metal corrosion is a big issue in the manufacture of sulfuric acid.

 Important variables for corrosion

Production and consumption figures for caprolactam manufacture

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