Example – oxidation of manganese dioxide

Generic product activity or name
Manganese dioxide 

Synonyms
KMn0₄ and K₂CO₃, potassium permanganate, potassium carbonate 

Context and background
Manganese dioxide is an inorganic compound with the formula MnO₂ which is a precursor for KMnO₄ (Potassium permanganate) and K₂CO₃ (Potassium carbonate)(Open Chemistry Database 2015a and 2015b).

Potassium permanganate is a strong oxidizing agent and is used as an oxidizing agent in many chemical reactions. It is used as an antiseptic and as an antifungal treatment as well as to prolong the shelf life of some fruits. It is also used extensively for wastewater treatment and against certain invasive species such as the zebra mussels. Potassium carbonate is a white salt, soluble in water, where it forms a strong alkaline solution. Potassium carbonate is used in such products as soap and glass and as a corrosion inhibitor.

Presentation of example
The activity “oxidation of manganese dioxide” (present in the ecoinvent database v3.0) has two co-products: potassium permanganate and potassium carbonate. The manganese dioxide (MnO₂) is fused with potassium hydroxide and heated with a source of oxygen to give potassium manganate:
2 MnO₂ + 4 KOH + O2 → 2 K₂MnO₄ + 2 H₂O
Boiling the manganate solution in the presence of carbon dioxide then gives potassium permanganate and potassium carbonate:
3 K₂MnO₄ + 2 CO₂ → 2 KMnO₄ + 2 K₂CO₃ + MnO₂

Although there are other possible ways of production, the described activity is the only industrial production route for potassium permanganate.

For potassium carbonate, the current predominating manufacturing process is by electrolysis of potassium chloride followed by carbonation using carbon dioxide (Open Chemistry Database – PubChem 2015b, Wikipedia 2015):
2KOH + CO₂ → K₂CO₃ + H₂O

Because potassium permanganate does not have any other industrial production routes, while potassium carbonate has another production route, we can identify potassium permanganate as the determining product, while potassium carbonate is identified as a dependent by-product of the “oxidation of manganese dioxide” activity.

Information sources used
Ullmann’s Encyclopedia of Industrial Chemistry is the classic reference work related to industrial chemistry, which is also published online. Another good source is the Open Chemistry Database, which has the added benefit of being free of charge. Wikipedia is also an excellent starting place for these chemicals.

References
Open Chemistry Database – PubChem (2015a) – Potassium Permanganate. National Center for Biotechnology Information. http://pubchem.ncbi.nlm.nih.gov/compound/potassium_permanganate (accessed June 8, 2015)

Open Chemistry Database – PubChem (2015b) – Potassium carbonate. National Center for Biotechnology Information. http://pubchem.ncbi.nlm.nih.gov/compound/potassium_carbonate (accessed June 8, 2015)

Wikipedia 2015 – Potassium carbonate
http://en.wikipedia.org/wiki/Potassium_carbonate (accessed June 8, 2015)

Ullmann’s Encyclopedia of Industrial Chemistry 7th ed. (1999-2012). NY, NY: John Wiley & Sons: http://onlinelibrary.wiley.com/book/10.1002/14356007

Author of this example
Bo Weidema

Date
2014-01-30

How to reference this
Weidema B P (2014), Example –oxidation of manganese dioxide. Version: 2014-01-30 www.consequential-lca.org