Delicate oxidation can transform greenhouse gas into useful chemicals

Sep 16, 2013 by Lisa Zyga feature
Illustration of one methane molecule adsorbing on positively charged gold molecules ranging in size from 2 to 201 atoms. Credit: Mowbray, et al. ©2013 American Chemical Society

(Phys.org) —Methane is the main component of natural gas, as well as a potent greenhouse gas whose levels in the atmosphere have been rising. In a new study, scientists have investigated a way to transform methane into more valuable and useful chemicals by partially oxidizing methane in a "delicate" way—that is, at low temperatures, low pressures, and by controlled means. This ability requires understanding how the catalytic activity of nanoparticles can be controlled and manipulated, which is currently a major challenge in nanoscience.

The researchers, led by Dr. Duncan J. Mowbray, Dr. Annapaola Migani, and Professor Angel Rubio at the University of País Vasco in San Sebastián, Spain, have published their paper on the delicate oxidation of methane on gold nanoparticles in a recent issue of The Journal of Physical Chemistry Letters.

"The partial oxidation of methane is important for a number of reasons," Mowbray told Phys.org. "Methane is one of the worst . For example, one cubic meter of methane has the same environmental impact as 30 cubic meters of carbon dioxide.[1] Methane is also produced in large quantities, both naturally through within humans and animals, and as a by-product of . In fact, as methane is so environmentally unfriendly and requires specialized infrastructure to transport, tens of billions of cubic meters are flared by the into carbon dioxide each year.[2] If one could instead produce something useful from the methane, e.g. through its partial oxidation, it would have an exceedingly positive environmental and economic impact."

So far, only a few studies have investigated the interaction between methane and gold. These studies have experimentally demonstrated that methane can adsorb (or adhere) to gold nanoparticles, but the underlying mechanism is not well understood. Since methane is a noble gas, its adsorption on metals is usually weak. For this reason, previous studies assumed that methane adsorption is dissociative, meaning that the methane molecules (CH4) split into two molecules (e.g,, CH3 and H) when adsorbing on the gold nanoparticles.

As the charge of the gold molecules increases, the adsorption energy of (a) oxygen stays the same while that of (b) methane decreases, indicating that less energy is required for methane to adsorb to gold when gold is strongly charged. This relationship allows researchers to tune methane adsorption independently of oxygen adsorption. Credit: Mowbray, et al. ©2013 American Chemical Society

But the scientists in the current study have found that such a reaction would require too much energy to overcome the energy barrier for methane to adsorb on gold nanoparticles.

Instead, the scientists show that methane adsorbs on gold nanoparticles only when the gold nanoparticles are positively charged, and that the adsorption can be explained by charge transfer. Even more interestingly, they found that as the total charge of the gold nanoparticles increases, the more strongly the methane binds to the gold nanoparticles. Specifically, the researchers observed a linear relation between the gold charge and the methane adsorption.

While methane adsorption depends on the gold charge, oxygen adsorption does not, so tuning the gold charge provides a way for researchers to independently tune the methane absorption. By making the methane adsorb approximately three orders of magnitude more strongly than the oxygen, the researchers could perform delicate methane oxidation on gold at low temperatures and pressures, which is a requirement for many environmental and economic applications such as producing useful chemicals.

"Methanol, ethylene, and formaldehyde are just some of the important chemicals that can be produced directly by partially oxidizing methane," Mowbray said. "Methanol is especially important, as it is a green fuel alternative for motor vehicles.[2] However, almost all methanol produced is used to make formaldehyde. So a direct pathway from methane to methanol or formaldehyde is environmentally and economically vital."

The researchers also formulated two models to predict energies on charged gold nanoparticles, which show that the mechanism holds for with sizes ranging from two atoms to 200 atoms. In the future, the scientists hope that these models will guide further research in this area. The next step for the researchers is to demonstrate these ideas experimentally.

Explore further: DNA-based method enables the identification of a bacterium as an indicator that obstructs methane fermentation

More information: Duncan J. Mowbray, et al. "Gold and Methane: A Noble Combination for Delicate Oxidation." The Journal of Physical Chemistry Letters." DOI: 10.1021/jz401553p

[1] Vladimir S. Arutyunov "Recent Results on Fast Flow Gas-Phase Partial Oxidation of Lower Alkanes", J. Nat. Gas Chem. 13(1) 10-22 (2004).

[2] V. S. Arutyunov, V. I. Savchenko, V. M. Rudakov, V. N. Blinichev, and A. M. Kutepov "Methanol Synthesis by Direct Oxidation of Natural Gas at Thermal Power Plants", Theor. Found. Chem. Eng. 36(4) 382-388 (2002).

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NikFromNYC
2.1 / 5 (15) Sep 16, 2013
Exhibit A: "Lisa graduated...with a Bachelor of Arts degree in rhetoric in 2004. She subsequently completed a science writing internship at Fermilab, followed by a communications internship at Caterpillar.... Lisa's stimulating and accurate science and technology articles...."

Exhibit B: "Since methane is a noble gas...."

Bacteria eat it, it readily explodes, is heated by sunlight, is attacked by photochemical radicals, forms solid hydrates, and exists as methyl groups but it's now a "noble gas."

Exhibit C: Daily Phys.org doses of CO₂ being called the main greenhouse gas when every insider knows that all climate alarm is based on H₂O amplification of any warming since *water* vapor is in fact the dominant greenhouse gas, not CO₂ or highly unstable trace gas CH₄.

Exhibit D this week: "As the researchers explain, the results provide more evidence to support the supposedly controversial theory of human-induced global warming." - Lisa

-=NikFromNYC=-, Ph.D. In C chemistry (Columbia)
NikFromNYC
1.7 / 5 (12) Sep 16, 2013
Exhibit E about Lisa's promotion of quackery: http://lofi.forum...375.html

"Physorg, have recently published Amrit's ga-ga, crank poppycock.

Far worse (if that's conceivably possible) this (unfit for flushing into a 3rd world cholera pit) material was reported only last year!

See links for beyond-belief confirmation..."

"ps;- What next? ..... Headlining Mazulu's extraordinary (Flashing Lights - Warp Drive) insanity?"

"Is Phys.org affiliated with this forum? I seem to remember something about that.

Yeah, it was Physorg's official forum, until me and a few equally unsavoury types made it so 'embarrassing';- they shamefully brushed us away, uncoupling the forum from their news site ..... how most brainsplatteringly ironic!"

"As f*****d-up as this forum clearly is;- perhaps PhysOrg will re-unite with us again;- purely to increase its now unfathomably dire credibility by a factor of no less than one-trillion fold."
Humpty
2.3 / 5 (12) Sep 16, 2013
Methane is a noble gas.

She says it comes from Uranus.
NikFromNYC
1.9 / 5 (14) Sep 16, 2013
This sort of theoretical study is rock solid hard science with great relevance for the vast net of hydrocarbon processing that affords us all materials and medicines, which now must sadly compete with activist charlatans for funding. Wrapping basic R&D news with climate alarm does make methane stink of indole since it severely detracts from the ability of scientists to follow intuition into arcane areas unrelated to modern fads and it especially punishes honesty in all scientific fields, nearly all of which have now loudly and quite publicly tied their reputations to a highly speculative supercomputer models that the recent lack of warming now bluntly falsifies (as a leak of even the latest IPCC report confirms).

"The next step for the researchers is to demonstrate these ideas experimentally."

No, the next step is to *test* their hypothesis, not "demonstrate" it, in fact to try to falsify their ideas, vigorously, from every angle, hoping it will be wrong so they will learn more.
djr
2.4 / 5 (8) Sep 16, 2013
No, the next step is to *test* their hypothesis, not "demonstrate" it, in fact to try to falsify their ideas, vigorously, from every angle, hoping it will be wrong so they will learn more.

Nick - you are truly ignorant. It is perfectly valid to develop an idea theoretically, and then to put it in to practice - to see if the theory hits any road blocks. Let's say for example that I theorize that doping the material being used for solar panels will increase their efficiency. The next step is to demonstrate my idea experimentally. I do not try to falsify my idea from every angle - hoping that it will be wrong. I simply build the thing - and measure the performance.
MikeBowler
1.6 / 5 (8) Sep 16, 2013
Exhibit A: "blah blah blah"

...

Exhibit E: "blah blah blah"

-- NikFromNYC
you're supposed to present you case beforehand
tadchem
3.7 / 5 (6) Sep 16, 2013
Speaking as a chemist, the factual errors in this article deny it any credibility.
Restrider
2.5 / 5 (8) Sep 17, 2013
"Since methane is a noble gas, its adsorption on metals is usually weak."

Their definition of noble gas is peculiar.
Restrider
2.4 / 5 (8) Sep 17, 2013
Speaking as a chemist, the factual errors in this article deny it any credibility.

Which is a sad thing. Only because the author of this article seems to have no qualification when it comes to basic chemistry, it should not reduce the validity of the research.
In the end, you have to read the actual paper and judge on the research on that instead.

In any case, this is a perfect example how "scientific" journalism that lacks proper proof reading warps the public's perception of science in one way or the other.
alfie_null
2 / 5 (4) Sep 17, 2013
In any case, this is a perfect example how "scientific" journalism that lacks proper proof reading warps the public's perception of science in one way or the other.

In Nik's case, the warping is some time in the past. Not the first time he's vented ire at those who make grants. Bearing his PhD (which he delights in reminding us of), he now seems to be working as a lab technician, third shift (could be wrong, maybe he'll elaborate). You can draw your own conclusions.
NikFromNYC
1.4 / 5 (10) Sep 17, 2013
...he now seems to be working as a lab technician, third shift (could be wrong, maybe he'll elaborate). You can draw your own conclusions.


In my 15 year old company on Broadway near Columbia, I sleep ~4 hours at a time in order to sleep twice a day along with regular naps. Creative work is more effective when you sleep on a problem several times. The citing of my degree is in direct response to the hoards of newly minted "Climate Communicators" from Evangelical activist John Cook's site and divinity major Al Gore's workshops who have been brainwashed into thinking that the information flow is from Fox News to skeptics which is a silly idea since it's quite obviously the other way around. Thanks for being so creepy alfie, in public, as you irefully commiserate with those who round out my my original post.

In today's "warped" news, antibiotic resistance is now killing 23K a year in the US as chemists etc. tragically lose funding to Climatology and green boondoggles.
scotto
3 / 5 (2) Oct 01, 2013
Nik,

Your unhinged ramblings do more harm to your cause than any article or comment could. You could have a point, but no one would see it.