New evidence supports 19th century idea on formation of oil and gas

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An oil pump taps deposits of petroleum deep beneath the Earth. Scientists are reporting new evidence that oil may have originated from processes other that the decay of prehistoric plants. Credit: Wikimedia Commons

Scientists in Washington, D.C. are reporting laboratory evidence supporting the possibility that some of Earth's oil and natural gas may have formed in a way much different than the traditional process described in science textbooks.

Their study is scheduled for Nov./Dec. issue of ACS' Energy & Fuels, a bi-monthly publication. Anurag Sharma and colleagues note that the traditional process involves biology: Prehistoric plants died and changed into oil and gas while sandwiched between layers of rock in the hot, high-pressure environment deep below Earth's surface. Some scientists, however, believe that oil and gas originated in other ways, including chemical reactions between carbon dioxide and hydrogen below Earth' surface.

The new study describes a test of that idea, which dates to at least 1877 and famous Russian chemist Dimitri Mendeelev.

They combined ingredients for this so-called abiotic synthesis of methane, the main ingredient in natural gas, in a diamond-anvil cell and monitored in-situ the progress of the reaction. The diamond anvils can generate high pressures and temperatures similar to those that occur deep below Earth's surface and allow for in-situ optical spectroscopy at the extreme environments.

The results "strongly suggest" that some methane could form strictly from chemical reactions in a variety of chemical environments.

This study further highlights the role of reaction pathways and fluid immiscibility in the extent of hydrocarbon formation at extreme conditions simulating deep subsurface.

More information: "In Situ Diamond-Anvil Cell Observations of Methanogenesis at High Pressures and Temperatures", Energy & Fuels, http://pubs.acs.org/stoken/presspac/presspac/full/10.1021/ef9006017

Source: American Chemical Society (news : web)

   

• thermodynamics - Nov 04, 2009
  • Rank: 5 / 5 (2)
  Abiotic synthesis of lighter hydrocarbons is almost certain to take place. However, crude oil is made up of much more complicated molecules. Part of the argument for a biotic origin is the close resemblance of some of the larger molecules to those in plants that exist today. Specifically, there are porphyrin compounds and asphaltanes that would present challenges for abiotic syntheses but are very similar to chlorophyll and molecules forming structural sections of living plants. It is easy to form small molecules abiotically by squeezing hydrogen and CO2 at high temperatures and that can produce methane, ethane, and other materials that make natural gas. However, you need complex methods to synthesize something much larger or containing complex rings. They are going to have to have some new arguments to convince very many chemists that chlorophyll will be produced by CO2, H2, and pressure and temperature. ;-)
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