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Ionic liquid pretreatment developed for cellulosic biofuel production

Ionic liquid pretreatment developed for cellulosic biofuel production
A new ionic liquid pretreatment of cellulosic biomass yields a biphasic solution, a lower phase rich in sugar and an upper phases rich in ionic liquid. (Courtesy of Simmons/JBEI)

A recyclable liquid for the pre-treatment of cellulosic biomass could bring down the cost of biofuel production.

Researchers at the United States Department of Energy’s Joint BioEnergy Institute have developed the new treatment using ionic liquids – salts that are liquids at room temperature.

This new liquid pre-treatment does not require the expensive enzymes that many other pretreatments depend on to help break down the cell walls in plant matter to release fermentable sugars for biofuels.

“Most of our ionic liquid efforts at J.B.E.I. have focused on using enzymes to liberate fermentable sugars from lignocellulosic biomass after pretreatment, but with this new enzyme-free approach we use an acid as the catalyst for hydrolyzing biomass polysaccharides into a solution containing fermentable sugars,” said Blake Simmons, a chemical engineer who heads J.B.E.I.’s Deconstruction Division and was the leader of this research.

Previous attempts using acid catalysts to replace enzymes have run into a snag because it is difficult and expensive to separate the freed sugars and ionic liquids. These processes also used a lot of water, further increasing the cost.

Mr. Simmons and his colleagues solved this problem by deploying the ionic liquid imidazolium chloride in tandem with an acid catalyst. They then added a solution of sodium hydroxide.

The result is a biphasic solution in which a lower phase contains most of the sugar and the upper phase contains most of the ionic liquids. The sugar can be extracted for biofuel production, while the ionic liquid can then be recovered and reused.

Currently, the optimal amount of fermentable sugar that can be extracted by the solution is 15-percent, with yields of 54 percent glucose and 88 percent xylose. The researchers believe that these yields can be increased by optimizing the process conditions and using more advanced methods of phase separation and sugar recovery.

“After optimizing the process conditions, our next step will be to scale the process up to 100 liters,” said Mr. Simmons.

Cellulosic biofuels are considered crucial for a lower-carbon future as they could displace gasoline, diesel and jet fuel on a gallon-for gallon basis, being able to be directly dropped into today’s existing engines and infrastructures without impacting performance. – EcoSeed Staff

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