C&EN
news of the week JUNE 2 5 , 2 0 0 7 EDITED BY WILLIAM G. SCHULZ & STEPHEN TRZASKA
SWEET ROUTES TO SUSTAINABILITY BIOFUELS: Catalytic reactions convert sugars from biomass into renewable fuel and feedstock
Zhang
Wisconsin researchers Dumesic (right) and Yuriy RomdnLeshkov work to produce chemicals from biomass.
icals but are rarely used in industry due to high costs. The PNNL researchers obtained a moderate yield (70%) of HMF, using a chromium chloride catalyst in i-ethyl-3-methylimidazolium chloride, an ionic liquid solvent. By using fructose instead of glucose, they were able to produce HMF in higher yield (90%). The mechanism for glucose conversion remains unclear, but the researchers have preliminary ideas about what might be happening. The Wisconsin group has taken its sugar-transformation process a step beyond HMF. James A. Dumesic and colleagues report selective conversion of fructose to HMF and then to 2,5-dimethylfuran (DMF). Fruc-
I ANY SCIENTISTS expect that the fuels of the future will be made from carbohydrates found I in plant material (biomass), but the fuels of choice and how they will be OH produced remain big question marks. HO .0. Offering another potential production opHO OH HO tion, two research groups—one at Pacific OH Northwest National Laboratory (PNNL) and one at the University of Wisconsin, 5-Hydroxymethylfurfural Glucose Madison—have independently reported two catalytic methods to convert biomass-derived sugars into renewable fuel 0. -OH HO and feedstock (Science 2007,316,1597; HO/ OH Nature 2007,447,982). "These two papers clearly advance the OH field of biomass conversion to liquid fuel 2,5-Dimethylfuran Fructose by offering innovative solutions to steps of the overall process," says Harold H. S W E E T E N E R S T O F U E L S Simple sugars can be conKung, a professor of chemical and biologiverted into compounds of interest for biofuel development. cal engineering at Northwestern University. "Their work helps clarify the vision and bring the possibility of large-scale biofuel introduction tose can be prepared from glucose or produced directly one step closer to reality." from biomass. DMF has potential for use as a transportation fuel and could be better than ethanol because it The new catalytic methods do not rely on ferhas a 40% higher energy density and is less volatile. mentation, which is currently used to manufacture Dumesic and colleagues used a biphasic reactor for bioethanol. acid-catalyzed dehydration of fructose. HMF was exPNNL'sZ. Conrad tracted from the reactor with butanol. Over a copperZhang and colleagues ruthenium catalyst, HMF underwent hydrogenolysis, convert glucose to 5where hydrogen is used to remove two oxygen atoms hydroxymethylfurfural. in the form of water, to produce a moderate yield of HMF itself is not a good DMF. candidate for a transportation fuel because its Although several experts commend the new catalytboiling point is too high. ic reactions, Joseph J. Bozell, a biomass chemist at the But HMF and its derivaUniversity of Tennessee, Knoxville, says, "there's still tives are multipurpose quite a bit of work to be done before these approaches intermediates that could show up in a commercial biorefinery." serve as fuel precursors In addition, Pierre Gallezot, a research director or replace petroleumat France's National Center for Scientific Research < based building blocks (CNRS), points out some economic and environmental z that are used to make drawbacks. Processes that use ionic liquids can be ex§ some plastics, pharmapensive, and some acids and chromium catalysts are far Q ceuticals, and fine chem- from green chemistry, he says.—RACHEL PETKEWICH WWW.CEN-0NLINE.ORG
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JUNE 25. 2007
