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Sawdust to gasoline, in just 2 steps

By JW Dowey - 25 Nov 2014 18:5:0 GMT
Sawdust to gasoline, in just 2 steps

The authors have this cute cartoon which illustrates the softwood sawdust being converted in a single 2-pahase container to more than 3 final products, via the liquid hexanes that are manufactured so efficiently by the catalysis. Cartoon image; Credit: © Royal Society of Chemistry

A year ago in the US, switchgrass, Panicum virgatum, was being used in the production of sugars. More progress on this use of biofuel material has now been made.

The murky depths of laboratories have solved many of our problems. In the case of the researchers writing this paper, one of the problems is the lack of gasoline in the future, so there may be no need, for various reasons! However, we need to be prepared to construct alkanes, which is what they do, for many other reasons too. The gasoline product can be replaced with ethylene (and plastics) and benzene. Beau Op de Beeck and his 7 fellow chemists from the KU Leuven Center for Surface Chemistry and Catalysis, in Belgium, Dresden’s Leibniz Institute for Solid State and Materials Research, in Germany, and the California Institute of Technology solved the problem of converting cellulose by catalysis.

They publish their work in the journal, Energy and Environmental Science under the name, Direct catalytic conversion of cellulose to liquid straight-chain alkanes. They have a high yield, a lengthy process and sawdust as a raw material.

Two phases are involved within the one container. Tungstosilicic acid in aqueous phase causes the cellulose to hydrolyse and dehydrate, after which hydrogenation creates the liquid alkanes, which are saturated hydrocarbons. The high yield consists of 82% n-decane-soluble products, mainly hexanes, known as light nafta. There is only a small amount of charring and a low percentage of gaseous products. And the length of time this takes is a mere few hours. Although not instant, this is catalytic and therefore able to convert more and more cellulose to glucose, especially with gradual heating of the reaction.

The second phase consists of a Ru/C (ruthenium) catalyst that is hydrothermally modified (ie. tuned) to make it chemo-selectively suitable. More rapid hydrogenation of the correct substrate is therefore possible, while for the whole set of reactions, subsequent batches of softwood cellulose can be introduced. The liquid alkanes can then accumulate over several runs.

The thought of biofuel plants being used for a more focussed, and non-combustible future set of plastics seems irresistible. Even lignin (wood) might be convertible one day, if this cellulose from soft wood industry becomes a major player in our fuel and other technologies. Areas that have few fossil fuel resources and no shale gas can apply straight away for technical help to begin processing their plant waste. We don’t want any more of these fuels in our future anyway guys.