What Exactly is The Andrussow Process?

 The Andrussow Process 

The Andrussow process is a type of industrial process used in the production of hydrogen cyanide from methane and ammonia in the presence of oxygen and a platinum catalyst. This process is based on a reaction that was discovered by Leonid Andrussow in 1927. He further developed the BMA Process also known as the Degussa Process. Hydrogen Cyanide (HCN) is also produced in the BMA process.

Leonid Andrussow

Leonid Andrussow was born on the 28th of  November in 1896 in Riga and he died on the 15th of December 1988 near Paris.

He was a well known German chemical engineer who developed the process for the production of hydrogen cyanide based on the oxidation of ammonia and methane, which today, is named after him Andrussow oxidation.

Hydrogen Cyanide

Hydrogen cyanide also called prussic acid, is a chemical compound with the formula of HCN and a structure of H−C≡N. It is an extremely poisonous, colorless and flammable liquid that boils slightly above room temperature, at 25.6 °C (78.1 °F). 

It has a bitter, almond-like odor. Hydrogen cyanide interferes with the body’s use of oxygen and causes harm to the brain, blood vessels, heart, and even lungs. Hydrogen cyanide is the chemical responsible for causing tissue hypoxia and chronic exposure to HCN may cause neurological, respiratory, cardiovascular diseases.

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Uses of Hydrogen Cyanide 

  1. Hydrogen cyanide is used as a chemical intermediate in the concentration of ores.
  2. It is used as a pharmaceutical intermediate.
  3. It is used as a fumigant.
  4. It is used in hardening of iron and steel, and in electroplating.
  5. HCN is used in the preparation acrylonitrile, used in production of acrylic fibers, synthetic rubber, and plastics. 
  6. Hydrogen Cyanide is used in the production of dyes.

Hydrogen Cyanide Preparation Via Andrussow Process

Approximately, half of the Hydrogen Cyanide produced globally is produced on purpose by ammoxidation using the Andrussow process from ammonia, natural gas, and oxygen. 

A significant amount of HCN is produced as a byproduct of the ammoxidation of propylene during the manufacture of acrylonitrile, particularly in the United States. 

Smaller amounts of HCN are produced on purpose from ammonia and natural gas using the BMA (Blausäure, Methan, Ammoniak) process, and from propane or butane using the Fluohmic (Shawinigan) process.

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This PEP review focuses on the traditional Andrussow process and the newer BMA process, with the primary difference being that the former uses oxygen (from air) and the latter does not. 

Both processes rely on platinum-based catalysis and coproduce hydrogen. The Andrussow process benefits from thermodynamic favorability, whereas the BMA process benefits from higher HCN yield and a relatively pure H2 offgas stream.

Note:

Both the Andrussow and the BMA processes use platinum-based catalysis, and both processes coproduce hydrogen. The Andrussow process has alot of advantages inherent to thermodynamic favorability, while the BMA process has the advantages of a higher HCN yield and a relatively pure H2 offgas stream.

Reactions That Take Place In The Andrussow Process

The reaction involving the Andrussow Process is very exothermic. The enthalpy change of this reaction is equal to -481.06 kJ.The heat produced by the main reaction serves as a catalyst for other side reactions.

CH4 + H2O → CO + 3H2

2CH4 + 3 O2 → 2 CO + 4H2O

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4 NH3 + 3 O2 → 2 N2 + 6H2O

The side reactions can only be reduced by only short exposures to the catalyst of the order of 0.0003s.

First Reaction

CH4 + H2O → CO + 3H2

In this reaction, methane reacts with water to produce carbon monoxide and hydrogen. This reaction usually takes place at a temperature of (750-870°C) or (760-880°C ). In this reaction, the catalyst is can be nickel on a oxide aluminum.

Reactants

CH4 – Methane

H2O – Water

Products

CO – Carbon

3H2 – Hydrogen 

Second Reaction

2CH4 + 3O2 → 2CO + 4H2O

In this reaction, methane reacts with oxygen to produce carbon dioxide and water. This reaction is an oxidation-reduction (redox) reaction.

Reactants

2CH4 – Methane

3O2 – Oxygen

Products

2CO – Carbon

4H2O – Water

Third Reaction

4NH3 + 3O2 → 2N2 + 6H2O

In this reaction ammonia reacts with oxygen to produce nitrogen and water. It is also an oxidation-reduction (redox) reaction.

Reactants

4NH3 – Ammonia

3O2 – Oxygen

Products 

2N2 – Nitrogen

6H2O – Oxygen