Monday, September 22, 2008

More on Sugar to Gasoline Unique Catalysts

The platinum-rhenium catalyst devised by University of Wisconsin scientists takes solutions of sorbitol or glucose in water at high temperatures and quickly converts them into an interesting oily mix of chemicals. This mix of chemicals is then passed over various catalysts to produce hydrocarbons.
In the first reactor, a sugar-water solution is passed over a platinum-rhenium catalyst at about 500 K. This strips five out of six oxygen atoms from the sugar, creating a mixture of various hydrocarbon compounds, such as alcohols and organic acids. The compounds form an oil-like layer that floats on top of the solution.

The oil is transferred to the second reactor, where it is passed over various solid catalysts, resulting in a range of hydrocarbon molecules that make up gasoline, diesel, and jet fuel. For instance, a copper and magnesium-based catalyst produces the hydrocarbons found in diesel and jet fuel. Gasoline contains hydrocarbons in which carbon atoms are connected in branched and ring-shaped structures, while carbon atoms in diesel and jet fuel form long, linear chains. The alcohols and organic acids in the oil from the first step could also be used to make plastics and industrial chemicals, Dumesic says.

...Whether or not biogasoline competes with its petroleum counterpart, it might still make more sense than making ethanol, Regalbuto says. One of the most expensive parts of producing ethanol is the energy-intensive distillation step, in which ethanol has to be separated from water. Hydrocarbons such as gasoline and diesel, meanwhile, float to the top, so they are easier and less expensive to separate. Plus, he says, "you're getting a fuel that's 30 percent more energy dense [than ethanol]. So it's cheaper to make, and it gives you 30 percent more gas mileage." _TechnologyReview
More from PlatinumToday:
"Most of the oxygen atoms are removed, leaving an oily mixture of alcohols, ketones, carboxylic acids and some cyclic compounds.

"These compounds are monofunctional - they only have one functional group, which makes them much more adaptable for subsequent conversion.

"Petroleum has a high energy density, and not all engines currently in use are suitable for conversion to run on ethanol."

Although the finding marks a significant step forward, Mr Dumesic also explained that it may be some time before the new system can be implemented commercially on a mass scale. _PlatinumToday
The main obstacles to widespread adoption of this technique are the need for better conversion of cellulose/hemicellulose to sugars, and the need to find less expensive catalysts that will accomplish roughly the same process as the rhenium/platinum catalyst and other specialty catalysts.

Close study of the nano-energetics involved at the active catalytic sites should yield alternative catalysts to make the process more economical. And the task of breaking down cellulose/hemicellulose into simple sugars is being simplified and made more economical almost daily. This catalytic approach to making bio-petroleum may very well prove competitive to the best of LS9, Amyris, or Craig Venter.

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