Professor Alan Goldman and his Rutgers team in collaboration with researchers at the University of North Carolina have invented a new catalytic process that could increase the yield of a clean form of diesel fuel made from coal. The method uses a pair of catalysts to improve the yield of diesel fuel from Fischer-Tropsch (F-T) synthesis.
The F-T process produces a mixture of hydrocarbons -- many of which are not useful as fuel. The low-weight and the high-weight Fischer-Tropsch products are useful – the light as gas and the medium-heavy as diesel fuel. The medium-weight products are not useful for much of anything.
Their method uses a pair of catalysts to convert the undesirable hydrocarbons into diesel. The catalysts work by rearranging the carbon atoms, transforming six-carbon atom hydrocarbons, for example, into two- and ten-carbon atom hydrocarbons. The ten-carbon version can be used to power diesel engines. The first catalyst removes hydrogen atoms, which allows the second catalyst to rearrange the carbon atoms. Then the first catalyst restores the hydrogen, to form fuel.
“The problem – the greatest inefficiency of the process – is that you also wind up with a substantial quantity of medium-weight products that are not useful and you are stuck with them,” Goldman said. “What we are now able to do with our new catalysts is something no one else has done before. We take all these undesirable medium-weight substances and convert them to the useful higher- and lower-weight products.”
Diesel fuel produced in this way would have several advantages. Conventional diesel contains aromatics, that, when combusted produce particulates, but the diesel formed by the new catalysts does not include aromatics, so it burns much cleaner. This could lead to more vehicles using diesel engines, which are about 30 percent more efficient than gasoline engines.
The biggest advantage may be that the United States has huge amounts of coal, enough to last us the next hundred years or so. Thus, a more efficient, and so less expensive method of converting coal to diesel could significantly cut U.S. dependence on foreign oil, and do so for a long time. Diesel engines provide the power to move 94 percent of all freight in the U.S. and 95 percent of all transit buses and heavy construction machinery, consuming approximately 56 billion gallons of diesel fuel per year.
At this time, the method is still under development, and not ready for commercial use. The second catalyst tends to break down, but this problem should be solvable.
This method sounds like it has a great potential if it is needed. I have never heard of this limitation of Fischer-Tropsch diesel, I wonder if it is as big a deal as they make it out to be. Maybe that is why F-T diesel hasn't been tried on a bigger scale.
Resource: Coal-to-diesel Breakthrough Could Drastically Cut Oil Imports, Rutgers Research Highlights