1. Oxalic Acid

2. • Introduction
• Raw Materials
• Production Process & Steps
• Flow Sheet Diagram
• Unit Operations
• Unit Processes
• Applications
Contents

3. • Oxalic acid is a dicarboxylic acid with the chemical
formula H2C2O4.
• It is an important chemical compound used in various
industries such as dyes, bleaches, and pharmaceuticals.
Oxalic Acid

4. • The raw materials used in the production of oxalic acid are nitric acid,
sodium nitrate, and ethylene glycol.
• The production process involves the oxidation of ethylene glycol to
glycolic acid and the subsequent oxidation of glycolic acid to oxalic acid
using nitric acid.
• The chemical equations involved in the production process are:
2 C2H6O2 + O2 → 2 HOCH2COOH (glycolic acid)
2 HOCH2COOH + HNO3 → 2 CO2 + 2 H2O + 2 NO2 + C2H2O4 (oxalic acid)
Raw Materials

5. The production process can be divided into four main
steps:
• Glycolic acid production
• Nitric acid recovery
• Oxalic acid crystallization
• Oxalic acid drying
Production Process

6. • In the glycolic acid production step, ethylene glycol is oxidized
to glycolic acid using a catalyst and air.
• In the nitric acid recovery step, the reaction mixture is
neutralized with sodium hydroxide to recover nitric acid.
• In the oxalic acid crystallization step, oxalic acid is crystallized
out of the reaction mixture using a cooling and seeding
process.
• In the oxalic acid drying step, the oxalic acid crystals are dried
to remove any remaining water and impurities.
Production Steps

7. Flow Sheet Diagram
Flow sheet diagrams are used in chemical engineering to represent the
sequence of steps involved in a chemical process.
A typical flow sheet diagram for the production of oxalic acid is shown below:
Raw materials → Glycolic acid production → Nitric acid recovery → Oxalic
acid crystallization → Oxalic acid drying → Finished product

8. Flow Sheet Diagram
• The flow sheet diagram shows the sequence of steps involved in the
production of oxalic acid, as well as the equipment and instrumentation
used in each step.
• For example, the glycolic acid production step may involve a reactor vessel
and a cooling system, while the oxalic acid crystallization step may involve
a crystallizer vessel and a cooling tower.
• The flow sheet diagram also shows the inputs and outputs of each step, as
well as the conditions under which the process is carried out.

9. Unit Operations
• Crystallization: Used to purify oxalic acid and separate it from the
reaction mixture. Oxalic acid crystals are formed by cooling the reaction
mixture and seeding it with crystals.
• Drying: Used to remove any remaining water and impurities from the
oxalic acid crystals. The crystals are typically dried in a vacuum oven or a
fluidized bed dryer.
• Cooling: Used to control the temperature of the reaction mixture during
the production process. Cooling may be achieved using a cooling tower or
a heat exchanger.

10. • Glycolic acid production: Involves the oxidation of ethylene glycol to
glycolic acid using a catalyst and air.
• Nitric acid recovery: Involves the neutralization of the reaction mixture
with sodium hydroxide to recover nitric acid.
• Oxalic acid crystallization: Involves the cooling and seeding of the
reaction mixture to crystallize oxalic acid.
• Oxalic acid drying: Involves the drying of the oxalic acid crystals to
remove any remaining water and impurities.
Unit Processes

11. • Ethylene Glycol and Nitric Acid Mixing:
Ethylene glycol and nitric acid are mixed together in a reactor vessel to initiate the reaction. The
reaction is exothermic and releases heat, which needs to be removed by cooling.
C2H6O2 + 2HNO3 → HOCH2COOH + 2NO2 + 2H2O
• Separation:
The reaction mixture is then separated using a distillation column to obtain glycolic acid. The nitric
acid and water are removed from the reaction mixture and the remaining glycolic acid is purified by
distillation.
HOCH2COOH + HNO3 → HO2C2O2H + NO2 + H2O
Glycolic Acid Production

12. • Neutralization:
After the separation step, the reaction mixture contains unreacted nitric acid. The reaction mixture is
neutralized with sodium hydroxide to form sodium nitrate and water. The sodium nitrate can be further
processed to recover nitric acid.
HNO3 + NaOH → NaNO3 + H2O
• Crystallization:
The sodium nitrate obtained from the neutralization step is then crystallized to obtain pure sodium nitrate
crystals.
NaNO3 + H2O → NaNO3•H2O
• Decomposition:
The sodium nitrate crystals are then decomposed by heating to obtain nitric oxide gas and oxygen gas.
2NaNO3 → 2NaNO2 + O2
• Absorption:
The nitric oxide gas obtained from the decomposition step is then absorbed in water to form nitric acid.
NO + H2O → HNO3
Nitric Acid Recovery

13. • Cooling:
The oxalic acid obtained from the oxidation step is then cooled to form crystals.
HO2CCOOH → HO2CCOOH (crystals)
• Seeding:
The cooled reaction mixture is then seeded with oxalic acid crystals to promote crystallization.
HO2CCOOH (crystals) → HO2CCOOH (crystals) + HO2CCOOH (seeds)
Oxalic Acid Crystallization

14. The oxalic acid crystals obtained from the crystallization step are then dried to remove any remaining
water and obtain dry oxalic acid powder.
Oxalic Acid Drying

15. Applications
Oxalic acid has a variety of applications in different industries.
• It is commonly used as a cleaning agent for metal surfaces, textiles, and carpets.
• It is also used as a bleach for wood and paper products, as well as a chelating agent in
pharmaceuticals.
• In the textile industry, oxalic acid is used to remove rust stains from fabrics.
• In addition, oxalic acid is used as a reducing agent in the synthesis of various organic compounds.