A One-Step Process for Converting Biomass and Biomass-Derived Carbohydrates into DMTHF for Liquid Fuels

A team at the University of Pennsylvania has developed a one-step process for converting hexose from a wide range of biomass-derived carbohydrates, cellulose and even raw lignocellulose (e.g., corn stover) into 2,5-dimethyltetrahydrofuran (DMTHF) in good yields and under mild conditions in water. A paper on the work by Weiran Yang and Ayusman Sen was published online 30 April in the journal ChemSusChem.

DMTHF is similar to DMF (2,5-dimethylfuran, earlier post) in terms of energy density
(31.8 MJ L^-1), volatility (bp 90–92 °C), and solubility (immiscible in water). However, because DMTHF is a saturated molecule
it has good storage and transportation stability and is a
better candidate for liquid fuel, Yang and Sen note.

Under the same reaction conditions, 2-methyltetrahydrofuran (MTHF) is formed from pentose.

The reaction uses a multifunctional catalyst system composed of rhodium salt, dihydrogen, and HI/HCl+NaI. The catalytic system is
robust and can be recycled repeatedly without loss of activity.

A one-step process generally requires less energy than processes
that involve multiple steps, and the use of water as reaction
medium is attractive, the authors note. In addition, a variety of feedstocks,
including raw lignocellulosic biomass such as corn stover, can
be directly used without any chemical pretreatment.

The optimized yields of tetrahydrofuran derivatives from cellulose and corn stover appear to be the highest reported, and the purity of DMTHF from hexose and that of MTHF from pentose are relatively high. Finally, the catalyst system has been shown to be robust and can be recycled
repeatedly without loss of activity.

Although the use of an expensive rhodium salt, the potentially corrosive acid, and dihydrogen clearly make the process
uneconomical, we do show that in principle it is possible to
“devise a simple, one-step or one-pot process that directly converts
agricultural and municipal plant waste and other forms
of raw biomass to valuable products.” A one-step, high-yield
chemical process also compares favorably with typical bioconversions
of lignocellulose that require three steps: lignocellulosic
pretreatment, enzymatic hydrolysis of cellulose, and fermentation
of sugars to make ethanol or other bio-based chemicals.

—Yang and Sen

Resources

• Weiran Yang, Ayusman Sen (2010) One-Step Catalytic Transformation of Carbohydrates and Cellulosic Biomass to 2,5-Dimethyltetrahydrofuran for Liquid Fuels. ChemSusChem doi: 10.1002/cssc.200900285