Researchers discover new way to deoxygenize biomass

University of California Berkeley and Berkeley Lab researchers have discovered a relatively inexpensive way to remove oxygen from biomass, which could pave the way for producing many of today's petrochemical products from biomass.

The one-step deoxygenation technique is based on an existing formic acid treatment. Formic acid, a chemical found in bee venom, converts glycerol (a byproduct of biodiesel production) into allyl alcohol, which is used as a starting material in the production of polymers, drugs, organic compounds, herbicides and other chemical products. Today, allyl alcohol is produced from the oxidation of petroleum.

"Right now, about 5 percent of the world's supply of petroleum is used to make feedstocks that are synthesized into commodity chemicals," said Jonathan Ellman, UC Berkeley chemistry professor and a principal investigator in the research. "If these feedstocks can instead be made from biomass, they become renewable and their production will no longer be a detriment to the environment." The process also can convert erythritol, obtained by the fermentation of glucose, to dihydrofuran, according to Ellman.

The formic acid removes the oxygen from the glycerol, creating the alcohol. In its original conception, the reaction was low-yielding because of charring, an unselective combustion that leads to an intractable mixture under high heat. Ellman and his fellow principal investigator, Robert Bergman, who holds a joint appointment with Berkeley Lab's Chemical Sciences Division and the UC Berkley chemistry department, used labeling experiments and a unique distillation system on the old process. They found that protecting the reaction from air provided a much improved process for the deoxygenation of glycerol.

Treating the glycerol with formic acid while directing a stream of nitrogen through the reaction mixture completely eliminates charring, Bergman said. The nitrogen also facilitates distillation of the alcohol and the final product shows substantially improved yield-80 percent-and higher selectivity.

Bergman and Ellman's technique could be used to convert carbohydrates in biomass, along with other polyhydroxy compounds, into the chemical feedstocks that are now derived from petroleum, according to Berkeley. It also could prove useful in converting biomass into liquid transportation fuels. Scaling up the process to industrial levels, however, will be a challenge, the researchers say.

"We continue to investigate the application of this deoxygenation method to other biomass derived materials," Ellman said.

"But it will not necessarily be applicable to all types of biomass material."