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A New Chemical Recipe Raises Prospect of Inexpensive Fuel

The views expressed are those of the author and are not necessarily those of Scientific American.


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metal-organic framework

This tubelike molecule, called a MOF, can transform ethane (small structures with light blue dots) into ethanol (structures with added red dots). Credit: NIST

Cheap fuel: A lot of people would like to bring down the cost of gas, and not just for running car engines. Natural gas derivatives like liquid methanol can become the basis for chemicals that make everything from paint to plywood. Methanol, however, often gets its start from the gas component methane, and moving the gas safely and storing it costs a lot of money.

The liquid form would be a lot easier, safer, and less expensive to use. But transforming methane to methanol, on an industrial scale, drives up the cost, because the reaction requires a lot of added energy, in the form of heat. About 1560 degrees Fahrenheit of heat, in fact. When nature does the conversion it is more efficient: It happens at room temperature.

Some honeycomb-shaped molecules created in a lab are coming closer to that bit of alchemy. They have not done it yet, but they have recently pulled off a related feat, turning ethane, another natural gas component, into liquid ethanol. “Chemists have been trying to do things like this for a long time,” says Jeffrey Long from the University of California at Berkeley, who is one of those chemists.

The molecules are called metal-organic frameworks, or MOFs. They are laboratory-built, formed from metal atoms that are linked together by organic, carbon-based molecules. The result does look something like a honeycomb, or a box of drinking straws built on a microscopic scale. Long and his colleagues built one around iron atoms, called it Fe-MOF-74, and patented it.

When the scientists ran ethane through the frameworks, they learned that a lot of it was converted to ethanol at the end of the process, they reported two weeks ago in Nature Chemistry. The iron catalyzed the reaction, by but the rigid framework was key to keeping the iron exposed so it could do that job. The entire structure holds the iron open, free to react with the substances flowing by it.

The goal, chemists say, is not to turn natural gas into whiskey—ethanol is the alcohol we drink—or any other beverage. MOFs are “tunable,” meaning chemists can slightly alter their properties to react with other gas components. The hope is that deliberate tuning will eventually let them move on to methane and move it to liquid methanol at close to room temperature, and that is an intoxicating prospect.

Josh Fischman About the Author: Josh is a senior editor at Scientific American, covering biology, chemistry, and earth science. On Twitter, he is @jfischman, and you can email him story ideas at jfischman@sciam.com Follow on Twitter @jfischman.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. Pragmatist 7:27 pm 06/2/2014

    1. Since it’s a partial oxidation couldn’t the process
    be managed to be exothermic in spite of the high activation temperature?

    2. Wouldn’t the more calorie dense ethanol be preferable
    as a fuel assuming the feedstock is a renewable?

    Link to this
  2. 2. Dr. Strangelove 11:45 pm 06/2/2014

    Methanol is not a good fuel because it is corrosive. It will destroy your engine. You can convert natural gas to diesel via Fischer-Tropsch process. Shell is doing this commercially in Malaysia.

    Link to this
  3. 3. jimmybo 12:28 am 06/3/2014

    booze from nat gas interesting

    Link to this
  4. 4. sjn 2:03 am 06/3/2014

    And methane is 20X more efficient greenhouse gas than CO2, so where does this exactly get us????

    Another cheap carbon based fuel – not exactly what is needed right now.

    Can we have a slight amount of consistency here – you can’t one day put out articles about the reality of climate change, and the next swoon over another shot at continued burning of carbon based fuels for energy.

    Link to this
  5. 5. singing flea 2:40 am 06/3/2014

    One of the positive feedback loops in global warming is release of frozen methane hydrates in the arctic and antarctic regions. Considering it is 20 times more effective as a green house gas, it makes sense to convert it to CO2 with the process of combustion in heat engines rather then let it evaporate into the atmosphere. The key to proper utilization of this fuel is developing ways to capture and convert CO2 back into carbon and oxygen. We need to work on that. The company that can come up with an economical way to do that is going to be the darling of the worlds wealthiest investors.

    Link to this
  6. 6. Anonymous 9:16 am 06/3/2014

    sjn and singing flea: You make a good point about methane as greenhouse gas. But if you convert leaky methane gas to non-leaky methanol, isn’t that an improvement? Easier to move and store methanol without losing gas into the air.

    Link to this
  7. 7. jafrates 12:29 am 06/4/2014

    @Pragmatist: The advantage of methane -> methanol over ethane -> ethanol here is that we have far more methane than ethane.

    @Dr. Strangelove: You can’t use E85 in older gasoline engines, either, for similar reasons. New engines to take advantage of methanol would have to be introduced.

    As for the Fischer-Tropsch process, there’s the question of energy efficiency compared to this process.

    Link to this
  8. 8. Dr. Strangelove 10:04 pm 06/4/2014

    @jafrates: Yeah the new engines must be made of noble metals like silver or gold to prevent corrosion.

    As for energy efficiency of FT process, Shell Malaysia has been commercially producing jet fuel and clean diesel from natural gas for over 15 years. The Berkley chemists in this article are still trying to figure out how to make liquid fuels from natural gas. Shell has done it 40 years ago.

    Link to this
  9. 9. jafrates 1:45 am 06/5/2014

    The FT process usually runs around a 60% efficiency process, perhaps up to 80% in near-perfect conditions. The Berkley chemists are looking for alternatives that may provide higher efficiency or greater simplicity, or both.

    I checked on the diesel pump prices in Malaysia. They’re running about US$0.58 per liter compared to an average US cost of about US$1.06 per liter in the United States. Malaysia has extremely low taxes (if any) and very high subsidies on diesel fuel.

    I also checked on the volume produced. Shell manufactures about 12,000 barrels per day in Malaysia using the FT process. Malaysia consumed some 173,000 barrels of distillate per day in 2010, and that number is likely higher now. That means that the FT process would make up less than 7% of daily consumption. I’m sure Shell sees a financial benefit from it, but there are probably other significant factors at play. At best, it’s probably a wash, or even a hedge against oil supply disruptions.

    Link to this
  10. 10. Chrmngblly 4:13 pm 06/5/2014

    All this basic science is worth discovering, no doubt, considering all the methane temporarily trapped in methane ices in the artic and on the sea floor. We really do need to find something else to do with all that before it ends up in the atmosphere.

    Still, I take note of the basic truth of the notion that all these compounds are nature’s way of sequestering carbon. We ought to figure out a way to lock this stuff up more permanently and get our energy somewhere else.

    Link to this
  11. 11. kebowers47 7:19 pm 06/5/2014

    P resent technology requires very high temperatures to achieve reasonable rates of reaction. This is capital cost intensive and thermally inefficient. Converting natural gas to LNG for shipping is almost twice as efficient as making methanol from it. A new approach that does not require high temperatures would substantially lower the capital and energy cost.

    F-T processing is well developed, and has very poor energy efficiency. Both of the two main chemical reactions are highly exothermic (generate heat)which is almost all dumped to the air and water. Integrating FT with another chemical process that can utilize that waste heat is possible, but very costly and complicated, suffering from poor operability.

    Link to this
  12. 12. Gopher63 9:42 am 06/6/2014

    Any alcohol fuel is less efficient as an energy source when burned than the parent hydrocarbon. In both cases described here, the practicality is that a liquid fuel is produced. The thermochemistry of partial oxidations is complicated since the tendency is to proceed to complete oxidation. There has been a commercial process for decades the prepares food grade ethanol from the oxidation/hydration of ethylene. There tends to be more ethylene available than ethane.

    Link to this
  13. 13. BMattsson 3:49 pm 06/6/2014

    Ethanol is hydroscopic and thus absorb moisture. Alcoholester of fatty acids behaves more like diesel and has also higher latent energy than ethanol and methanol.

    Link to this
  14. 14. GreatWhiteSnark 4:54 pm 06/8/2014

    “Integrating FT with another chemical process that can utilize that waste heat is possible, but very costly and complicated, suffering from poor operability.”

    It does not need to be integrated with another chemical process to be useful. Waste heat can generate power, as with the device describe here:
    http://phys.org/news/2014-06-power.html#nRlv

    Link to this

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