Chemists Closing In On Commercial Potential Of Alkanes

February 02, 1998

BERKELEY, CA -- The elusive goal of harnessing the vast potential of one of the earth's most plentiful materials is another step closer to realization. Using ultrafast spectroscopic techniques that provide "stop-action" images within a trillionth of a second, scientists at the U.S. Deparment of Energy's Lawrence Berkeley National Laboratory have obtained the first detailed picture of an alkane-activation reaction at room temperature.

Alkanes are compounds of carbon and hydrogen atoms held together by single bonds. The simplest and most abundant is methane, the primary constituent of natural gas. Chemists have long coveted the use of alkanes as environmentally benign feedstock for clean-burning fuels and a host of petrochemicals, including plastics, solvents, synthetic fibers, and pharmaceutical drugs. The problem has been that the bonds between an alkane's carbon and hydrogen atoms are strong enough to render alkanes generally unreactive.

In the early 1980s, Robert Bergman, a chemist in Berkeley Lab's Chemical Sciences Division (CSD) and with the University of California at Berkeley, led the discovery of a group of organometallic complexes --compounds of metal atoms, such as iridium or rhodium, sandwiched between organic molecules with a unique property. Upon irradiation with ultraviolet light, these organometallics were shown to generate a reaction that is able to break the carbon-hydrogen bonds in alkanes and insert metal atoms into the mix, creating new, much more reactive carbon-metal-hydrogen compounds.

Since discovering this alkane-activating reaction, Bergman has been working to better understand it with the ultimate aim of designing a catalytic process that could be used in commercial operations. An obstacle has been that the reaction takes place within 230 nanoseconds (billionths of a second). To slow it down for detailed study, Bergman and Bradley Moore, another chemist who also holds a joint Berkeley Lab-UC Berkeley appointment, conducted experiments in liquefied noble gas solvents under extremely low temperatures.

Since these conditions are far removed from those that might be used in a commercial process, Bergman sought a means of studying the alkane-activating reaction under more realistic conditions. A new collaboration was established with Berkeley Lab scientists Charles Harris and Heinz Frei.

Harris provided a special time-resolved infra-red flash kinetics spectrometer that operates on a femtosecond (millionths of a billionth) time-scale. This enabled the researchers to irradiate alkanes and the organometallic complexes with ultraviolet light and measure the kinetics at room temperature with the compounds dissolved in a hydrocarbon solvent. Frei supplied a Fourier transform infrared spectrometer (FTIR) that allowed the researchers to monitor the carbon-hydrogen activation reaction in the nanosecond regime. These powerul tools made it possible for the scientists to directly establish the time-scale for alkane bond-activation in a room-temperature solution.

Says Bergman, "We now have a detailed picture of the activation reaction. Structures of all the intermediates involved have been identified and assigned, and energy barriers for each reaction step from solvation to formation of the final alkyl hydride product have been estimated."

Says Harris, an expert in femtosecond studies, "The femtosecond technique used in this alkane reaction study in combination with step-scan infra-red spectroscopy should be applicable to many other problems associated with the reactions of complex molecules."

While the results of this study do not represent a quantum leap toward the goal of converting alkanes into chemically useful products, a good "mechanistic understanding" of the alkane activation reaction brings science closer to that goal.

Collaborating with Bergman, Harris, and Frei on this project were Matthew Asplund, Steven Bromberg, Tianquan Lian, Kenneth Kotz, Bruce McNamara, Haw Yang, Jake Yeston, and M. Wilkens.

The research was reported as the cover story in a recent issue of the journal Science.

The Berkeley Lab is a U.S. Department of Energy national laboratory located in Berkeley, California. It conducts unclassified scientific research and is managed by the University of California.
-end-


DOE/Lawrence Berkeley National Laboratory

Related Ultraviolet Light Articles from Brightsurf:

NRL researchers evaluate ultraviolet sources, combat COVID-19
NRL researchers evaluated commercial ultraviolet (UV) sources for viral disinfection to combat COVID-19 on land and at sea, and established a dedicated UV characterization lab in five days.

Ultraviolet shines light on origins of the solar system
In the search to discover the origins of our solar system, an international team of researchers, including planetary scientist and cosmochemist James Lyons of Arizona State University, has compared the composition of the sun to the composition of the most ancient materials that formed in our solar system: refractory inclusions in unmetamorphosed meteorites.

New extreme ultraviolet facility opens for use
Researchers have established a novel high-frequency laser facility at the University of Tokyo.

Astronomers find the first galaxy whose ultraviolet luminosity is comparable to that of a quasar
An international scientific team, led by researchers at the Centre for Astrobiology (CAB, CSIC-INTA) and with participation by the Instituto de Astrofísica de Canarias (IAC), have found the galaxy BOSS-EUVLG1.

Comet Chury's ultraviolet aurora
On Earth, auroras, also called northern lights, have always fascinated people.

SwRI instruments aboard Rosetta help detect unexpected ultraviolet aurora at a comet
Data from Southwest Research Institute-led instruments aboard ESA's Rosetta spacecraft have helped reveal auroral emissions in the far ultraviolet around a comet for the first time.

Ultraviolet B exposure expands proenkephalin+ regulatory T cells with a healing function
Skin exposure to ultraviolet B (UVB) induces expansion of regulatory T (Treg) cells with immunosuppressive activity.

Ultraviolet communication to transform Army networks
Of ever-increasing concern for operating a tactical communications network is the possibility that a sophisticated adversary may detect friendly transmissions.

NASA's Maven observes martian night sky pulsing in ultraviolet light
Vast areas of the Martian night sky pulse in ultraviolet light, according to images from NASA's MAVEN spacecraft.

A new look at Mars' eerie, ultraviolet nighttime glow
An astronaut standing on Mars couldn't see the planet's ultraviolet ''nightglow.'' But this phenomenon could help scientists to better predict the churn of Mars' surprisingly complex atmosphere.

Read More: Ultraviolet Light News and Ultraviolet Light Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.