Wednesday, May 25, 2016

Vanadium Phosphate Catalyst

Methane, CH4, in natural gas can be used as a raw material to produce bromomethane, CH3Br. Bromomethane (methyl bromide) can then be used in the chemical industry to produce fuels, chemicals, polymers and pharmaceuticals. When  bromomethane is converted into fuels and other chemicals, bromine is released in the form of hydrogen bromide, HBr. Using oxygen and a suitable catalyst, bromine from the hydrogen bromide by-product is embedded back into bromomethane so that no bromine is lost from the system.
Researchers at ETH, Zurich, have identified vanadium phosphate as an ideal catalyst for this reaction.
Vanadium(III) phosphate (vanadium(3+) phosphate), has the structure shown below:
It is a relatively mild oxidising catalyst.
It is a strong enough oxidising catalyst to allow hydrogen bromide to react with oxygen at the surface of the catalyst, but, it is not strong enough to oxidise the methane and brominated reaction products.
It is therefore possible to brominate methane in a single step at atmospheric pressure and at a temperature below 500°C.  The catalyst is also stable, able to resist the corrosive reaction environment.
This makes it an attractive catalyst for this important, industrial, chemical reaction.

Vladimir Paunović, Guido Zichittella, Maximilian Moser, Amol P. Amrute, Javier Pérez-Ramírez. Catalyst design for natural-gas upgrading through oxybromination chemistry. Nature Chemistry, 2016; DOI:10.1038/nchem.2522

Further Reading:
Lewis Structures (electron dot diagrams):
2-Dimensional Structural Formula:
Molecular Formula:
Halogenation of Hydrocarbons:
Energy Profiles:
Reaction Rates:
Redox Reaction Concepts:

Suggested Study Questions:

  1. Draw the Lewis Structures (electron dot diagrams) for each of the following molecules:
    • methane
    • bromomethane
    • hydrogen bromide
  2. Draw the 2-dimensional structural formula for each of the following molecules:
    • methane
    • bromomethane
    • hydrogen bromide
  3. Give the molecular formula for each of the following molecules:
    • methane
    • bromomethane
    • hydrogen bromide
  4. Write a chemical equation to represent the reaction between methane and bromine to produce bromomethane
  5. Name the type of reaction given in question 4.
  6. Give the reaction conditions necessary for this reaction in question 5 to occur at room temperature and pressure in your laboratory.
  7. Why do you think a catalyst is required for this reaction above in order to produce commercial quantities of bromomethane?
  8. Which organic compound, methane or bromomethane, do you expect to be the most chemically reactive? Explain your answer.
  9. What is meant by the term "oxidising agent"?
  10. Is the bromination of methane using bromine a redox reaction? Explain your answer.
  11. Refer to the structure of vanadium(III) phosphate given in the article. Give the oxidation state (oxidation number) for each of the following:
    • vanadium
    • oxygen
    • phosphorus
  12. Why do you think vanadium phosphate is talked about as being an "oxidising catalyst" rather than as an "oxidising agent"? Explain your answer.

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