Researchers are trying to find a simple and affordable way to convert the sugars, including glucose and fructose, in plants into compounds that can replace petroleum feedstocks. If successful, such technology could use a chemical made from corn, potatoes, and even grass to substitute for ones derived from oil.

Now scientists at the Pacific Northwest National Laboratory have come up with a process for transforming cellulose directly into 5-hydroxymethylfurfural (HMF), a chemical that can be converted into biofuels and chemical feedstocks.  Previously they had only been able to turn cellulose into HMF via the intermediate sugar stage.

If this new process works at larger than lab scale the cellulose issue has changed in another way.

To carry out the conversion, the Pacific Northwest researchers used an ionic solvent to dissolve the cellulose, in combination with copper chloride and chromium chloride at 120° C to act as catalysts. The team found that this system worked 10 times faster than using acid to break down cellulose and at much lower temperatures. The paired metal-chloride catalysts also avoided the use of a mineral acid that is known to degrade the HMF product.

The method converted about 57% of the sugar in the cellulose feedstock into HMF in one step. The team recovered more than 90% of the HMF formed and the final product was 96% pure. The metal chlorides and ionic liquids could be reused many times and this recycling should lower the cost of HMF production.

Jim Amonette of Pacific Northwest National Laboratory said, “By combining the cellulose-breakdown and sugar-conversion steps, we are very close to a single-step method of converting raw biomass into a new platform chemical – a chemical you can readily turn into a transportation fuel or for synthesis of plastics and other useful materials.  Advances like this can help reduce our dependence on fossil fuels.”

The ability to use cellulosic biomass as feedstock for the large-scale production of liquid fuels and chemicals critically depends upon the development of effective low temperature processes.  As HMF can currently be made from fructose and glucose, the ability to synthesize HMF directly from raw natural cellulose would remove a major barrier to the development of a sustainable HMF platform and solve in another way the direct use of cellulosic materials to make fuels and feedstocks.

The technical explanation is pair of metal chlorides (CuCl2 and CrCl2) dissolved in 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl) at temperatures of 80–120° C collectively catalyze the single-step process of converting cellulose to HMF with an unrefined 96% purity among the recoverable products at a 55.4 ± 4.0% HMF yield.

Product selectivity can be tuned by simply varying the metal chloride ratio as shown in the chart that follows:

PNL's Cellulose to HMF Products Chart

PNL's Cellulose to HMF Products Chart

HMF has been around for about one hundred years and is a handy and effective precursor to a wide range of chemical feedstocks. HMF can be converted to 2,5-dimethylfuran, which is a liquid biofuel that some believe in certain ways is superior to ethanol.  That might be an error as it’s a more complex molecule that might pose some difficult challenges if carbon based fuel cells gain market traction.  The HMF molecule layout, which has certain advantages in chemical construction, has the oxygen located differently from alcohols.

Good stuff from good research and innovation.  The paper is published at Applied Catalysts A.

But there is a bunch of unused sugar, nearly half left over.  That could prove to be a project breaker or another opportunity.  More likely it’s an opportunity.  But it seems that the new process is a step in a series of processes at this time.  Just what those steps are and the practicality might be – is yet to be determined.

I find the research quite encouraging.  But it does depend on a chemical process path to get from raw biomass to a useful fuel that is yet to be figured for its economic potential.  With so much sugar left over, and its condition not discussed, there is nearly as much to do as done.

But it’s a “big” organic molecule with 6 carbon atoms, 6 hydrogen atoms and 3 oxygen atoms and is really handy stuff.  It’s a sure breakthrough, although barely noticed.  But with oil heading back up, if only briefly one hopes, this kind of research has legs and should get more development soon.  Just what happens to that remaining 43% or so of the sugars is a question begging another answer.


1 Comment so far

  1. Rufor on June 4, 2009 3:54 AM

    Thank you! I would now go on this blog every day!

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