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.

Reference:
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): http://www.ausetute.com.au/lewisstr.html
2-Dimensional Structural Formula: http://www.ausetute.com.au/structural2D.html
Molecular Formula: http://www.ausetute.com.au/molecularformula.html
Halogenation of Hydrocarbons: http://www.ausetute.com.au/halogalk.html
Energy Profiles: http://www.ausetute.com.au/enerprof.html
Reaction Rates: http://www.ausetute.com.au/reactrate.html
Redox Reaction Concepts: http://www.ausetute.com.au/redoxreactions.html

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.

CGS and the Solvay Process

Coal seam gas (CSG) is any naturally occurring gas, such as methane, that is trapped in underground coal seams by water and pressure. Methane, often called natural gas, is a commercially valuable resource, so mining companies drill into the coal seam, pump the water out, which releases the pressure and forces the gases to the surface. Queensland is believed to have about 98% of Australia's coal seam gas reserve. More than 4,000 CSG wells in Queensland account for about 17% of that state's electricity. NSW has about 500 CSG wells.

The water that is produced in coal seam gas mining is not suitable for human consumption. The water is most often very salty and can contain heavy metals and toxic compounds.
A new drilling project in the Pilliga Forest in the north-west of NSW is expected to produce an average of 3 tonnes of salt a day over three years!

(http://www.smh.com.au/environment/coal-seam-gas-industry-faces-salt-overload-20131204-2yqx8.html#ixzz2mYw2aSQc)

That's a lot of salt! Left to itself, lying around near the mine, it will poison land and waterways. So what can you do with all this salt?

Salt, sodium chloride, is an important commercial chemical. It is used to produce chlorine and sodium hydroxide, and is used in other industrial process, it is used directly for snow and ice control, as a mineral in animal diets, as a preservative, as a flavouring agent, and as a reagent for water softening. The total (deliberate) production of sodium chloride world-wide is about 250 million tonnes per year.

One way to get rid of the salt produced in coal seam gas mining is to turn it into something else, sodium carbonate for instance.
In Australia, the Penrice Soda Products company in Osborne, South Australia, operates a plant using the Solvay Process to turn sodium chloride into sodium carbonate.
The overall chemical equation for the Solvay Process is
CaCO₃(s)   +   2NaCl (aq)      Na₂CO₃(aq)   +   CaCl₂(aq)
 CaCO₃(s) is present in limestone and the NaCl is the by-product of the CGS mining.
The company currently produces about 325,000 tonnes of sodium carbonate every year.

Further Reading:
density
yield

Solvay Process

Suggested Study Questions:

1. How much NaCl will the Pilliga Forest mining project produce in one year?
2. Assume that there are 4,500 CSG mines in Australia and they each produce 3 tonnes of salt a day. How much salt will be produced in one year in Australia from CSG mines?
3. The density of sodium chloride is about 2.2 g/cm³. Calculate the volume of salt produced each day by the Pilliga Forest CSG mine.
4. Assume a single truck can carry 100 tonnes of salt. How many truck loads of salt will be produced at the Pilliga Forest CSG mine each year?
5. Give one environmental issue that would be raised in trucking salt over large distances. Explain how the problem could be reduced.
6. Give one commercial problem associated with trucking salt over large distance using the same truck. Explain how the problem could be reduced.
7. What is the maximum amount, in tonnes, of sodium carbonate that could be produced using 1 truck load of sodium chloride?
8. What is the maximum amount, in tonnes, of calcium carbonate required to completely convert 1 tonne of sodium chloride to  sodium carbonate?
9. If the actual yield of sodium carbonate is 86.2%, what mass of sodium carbonate would be produced from the complete reaction of 1 tonne of sodium chloride?
10. Assuming the solvay process was used to convert all the salt from all Australia's CSG mines into sodium carbonate, how much sodium carbonate would be be produced?
11. World production of sodium carbonate is currently about 42 million tonnes per year. If Australia began production of sodium carbonate using all the salt produced in the CSG mines, what percentage increase would there be in world production of sodium carbonate?
12. What would you suggest Australia do with the salt produced as a by-product of coal seam gas mining?

Methane Reactions

By using gold dimer cations as catalysts, Georgia Institute of Technology and the University of Ulm scientists have converted methane into ethene at room temperature, and into methanal at temperatures below 250K (-9^o F). In both the room temperature reaction-producing ethene, and the methanal generation colder reaction, the gold dimer catalyst is freed at the end of the reaction, thus enabling the catalytic cycle to repeat again and again.

The temperature-tuned catalyzed methane partial combustion process involves activating the methane carbon-to-hydrogen bond to react with molecular oxygen.
In the first step of the reaction process, methane and oxygen molecules coadsorb on the gold dimer cation at low temperature.
Subsequently, water is released and the remaining oxygen atom binds with the methane molecule to form methanal.
If done at higher temperatures, the oxygen molecule comes off the gold catalyst, and the adsorbed methane molecules combine to form ethene through the elimination of hydrogen molecules.

Reference
Sandra M. Lang, Thorsten M. Bernhardt, Robert N. Barnett, Uzi Landman. Temperature-Tunable Selective Methane Catalysis on Au2 : From Cryogenic Partial Oxidation Yielding Formaldehyde to Cold Ethylene Production. The Journal of Physical Chemistry C, 2011; 115 (14): 6788 DOI: 10.1021/jp200160r

Further Reading
Balancing Chemical Equations
Nomenclature
Combustion of Hydrocarbons
Oxidation and Reduction
Oxidation States (Numbers)

Study Questions

1. Write the molecular formula for each of the following:
   
   • methane
   • methanal
   • ethene
2. Draw the structural formula for each of the following:
   
   • methane
   • methanal
   • ethene
3. On the structural formula above, identify the functional groups present in methanal and ethene.
   
4. The following molecules are known by other names. Give atleast one other name used for each of the following:
   
   • methane
   • methanal
   • ethene
5. Write a balanced chemical equation for each of the following reactions involving the gold dimer cation catalyst:
   
   • methane and oxygen react to form methanal and water
     
   • methane and oxygen react to form ethene and water
6. Classify each reaction above as an oxidation or a reduction reaction. Justify your answer.
   
7. Write balanced chemical equations to represent the combustion of methane at high temperature, without the aid of a catalyst, under each of the following conditions:
   
   • excess oxygen
   • excess methane
8. Compare the chemical equations in question 7 to those in question 5. In what ways are the reactions similar? In what ways are the reactions different?
   

Sweeter Natural Gas

Natural gas extracted from the coal beds and methane-rich geologic features must first be purged of hydrogen sulfide before it can be used as fuel in a process called "sweetening".

Thermal Swing Regeneration, a common industry process used for sweetening natural gas, uses chemical sponges called sorbents to remove toxic and flammable gases, such as rotten-egg smelling hydrogen sulfide from natural gas. The gas must first be treated with a solution of chemical sorbents that are dissolved in water. That solution must then be heated up and boiled to remove the hydrogen sulfide, in order to prepare the sorbent for future use. Once the hydrogen sulfide is boiled off, the sorbent is then cooled and ready for use again. The repeated heating and cooling requires a lot of energy and markedly reduces the efficiency of the process.

A new process called Antisolvent Swing Regeneration takes advantage of hydrogen sulfide's ability to dissolve better in some liquids than others at room temperatures. In this process, the hydrogen sulfide "swings" between different liquids during the processing at nearly room temperature, resulting in its removal, in just a few steps, from liquids that can be reused again and again.

First hydrogen sulfide is dissolved in a substance known as a DMEA which is a recyclable binding organic liquid, a substance that can hold onto hydrogen sulfide without the addition of water. DMEA forms a salt with hydrogen sulfide. The salty DMEA is then mixed with hexane (or hexadecane and a small amount of heat) which returns most of the hydrogen sulfide back to the gaseous state which is then bubbled out of the mixture. Separating the hexane from the DMEA allows these substances to be re-used.

Scientists estimate that the Antisolvent Swing Regeneration method could reduce the amount of energy needed to complete the sweetening process by at least 10%.

Reference
Phillip K. Koech, James E. Rainbolt, Mark D. Bearden, Feng Zheng, David J. Heldebrant. Chemically selective gas sweetening without thermal-swing regeneration. Energy & Environmental Science, 2011; DOI: 10.1039/c0ee00839g

Further Reading:
Writing Ionic Formulae
Naming Straight Chain Alkanes
Intermolecular Forces

Study Questions:

1. Write the chemical formula for each of the following:
   
   • methane
   • hydrogen sulfide
   • hexane
2. In a sample of each of the following pure substances, what type of forces would you expect to attract molecules to each other?
   
   • methane
   • hydrogen sulfide
   • hexane
3. Describe what would happen if each of these pure substances was mixed with water.
4. Describe what would happen if each of these substances were mixed with a petroleum-based oil.
5. Use the description of the Thermal Swing Regeneration process to draw a flow chart for this method of sweetening natural gas.
   
6. Use the description of the Antisolvent Swing Regeneration process to draw a flow chart for this method of sweetening natural gas.
   

Dry Water

Discovered in 1968, "dry water" consists of 95% water, yet it is a dry powder which resembles powdered sugar at room temperature and pressure. Each powder particle contains a water droplet surrounded by modified silica. The silica coating prevents the water droplets from combining and turning back into liquid water. The result is a fine powder that can slurp up gases which combine with the water molecules to form hydrates.

Dry water can absorb over three times as much carbon dioxide gas as ordinary uncombined water and silica in the same length of time. This ability to absorb large amounts of carbon dioxide gas as a hydrate could make it useful in helping to reduce global warming since carbon dioxide gas is a major contributor to global warming.

Dry water can also be used to store methane, a component of natural gas. This could provide a safer, more convenient way to store methane fuel for use in vehicles powered by natural gas.

Reference:
American Chemical Society (2010, August 25). 'Dry water' could make a big splash commercially. ScienceDaily. Retrieved August 26, 2010, from http://www.sciencedaily.com­ /releases/2010/08/100825174102.htm

Study Questions

1. Write the chemical formula for each of the following compounds:


• water


• silica


• carbon dioxide


• methane




2. Draw a diagram to represent the molecular structure of dry water powder.
3. Draw a diagram to represent the structure of hydrated carbon dioxide.
4. Explain how water can absorb carbon dioxide.
5. Explain how silica can absorb carbon dioxide.
6. Explain why dry water is so much better at absorbing carbon dioxide than either pure water or silica.
7. Write a chemical equation to represent the production of hydrated methane.
8. Using the equation above, discuss how dry water could be used to store and release methane for use in vehicles powered by natural gas.