A team of chemical and biological engineers at the University of Wisconsin–Madison has developed a new chemical pathway a way to produce from biomass a valuable compound—1,5-pentanediol, a plastic precursor primarily used to make polyurethanes and polyester plastics—that they estimate could lower the cost of cellulosic ethanol by more than two dollars per gallon.
The highly efficient approach devised by Professor George Huber and collaborators is much cheaper than a previously reported method—direct hydrogenolysis of tetrahydrofurfuryl alcohol (THFA)—and represents the first economically viable way of producing 1,5-pentanediol from biomass. A paper on their work is published in the journal ChemSusChem.
A process for the synthesis of 1,5-pentanediol (1,5-PD) with 84% yield from furfural is developed, utilizing dehydration/hydration, ring-opening tautomerization, and hydrogenation reactions. Although this process has more reaction steps than the traditional direct hydrogenolysis of tetrahydrofurfuryl alcohol (THFA), techno-economic analyses demonstrate that this process is the economically preferred route for the synthesis of biorenewable 1,5-PD.
2-Hydroxytetrahydropyran (2-HY-THP) is the key reaction pathway intermediate that allows for a decrease in the minimum selling price of 1,5-PD. The reactivity of 2-HY-THP is 80 times greater than that of THFA over a bimetallic hydrogenolysis catalyst. This enhanced reactivity is a result of the ring-opening tautomerization to 5-hydoxyvaleraldehyde and subsequent hydrogenation to 1,5-PD.—Brentzel et al.
Furfural is first hydrogenated into THFA, which is then dehydrated in the gas phase to produce dihydropyran (DHP) with 87% yield. The DHP is then hydrated to 2-HY-THP and 2-HY-THP dimers in yields up to 100 % in the aqueous phase (20 wt % DHP in water) without a catalyst at temperatures from 343 to 403 K (70 to 130 ˚C). 2-HY-THP is a cyclic hemiacetal that undergoes ring-opening tautomerization in the aqueous phase to form 5-HY-Val.
The hydrogenation of 5-HY-Val in the presence of the 2-HY-THP monomers and dimers with a Ru catalyst results in 97% overall yield of 1,5-PD from DHP.The researchers refer to this routeas the dehydration, hydration, and hydrogenation (DHH) pathway.
|Comparison of costs and MSPs for the DHH pathway with the direct hydrogenolysis pathway. Source: Click to enlarge.|
Plant biomass is typically about 40% oxygen by weight, while petroleum oil is less than 0.1% oxygen. Huber’s approach uses the oxygen already inherent in the biomass to produce high value oxygenated commodity chemicals that can be used to make performance polymer materials such as polyurethanes and polyesters.
The study’s foundational discovery, its new pathway for chemical production, also provides fundamental chemistry that could be applicable to a wide cross-section of products. For example, the same pathway could be used to produce two other plastic precursors—1,4 butanediol and 1,6-hexanediol—currently derived from petroleum and which together represent an annual market of more than $6 billion.
The team will continue to refine their work, collecting the data needed to scale their process up to pilot plant testing. The Wisconsin Alumni Research Foundation (WARF) is in charge of licensing the technology.
Huber was joined in the collaborative study by UW–Madison engineering professors James Dumesic and Christos Maravelias, experts in a catalysis and techno-economic modeling, respectively, graduate students Zachary Bentzel (the paper’s first author) and Kevin Barnett, and postdoctoral researcher Kefeng Huang.
The development is the latest in an ongoing effort at UW–Madison to create commodity chemicals currently derived from petroleum out of biomass. These bio-derived chemicals could serve as high value co-products of the biofuels manufacturing process, improving the economics of the cellulosic bio-refinery.
Zachary J. Brentzel, Kevin J. Barnett, Dr. Kefeng Huang, Prof. Christos T. Maravelias, Prof. James A. Dumesic and Prof. George W. Huber (2017) “Chemicals from Biomass: Combining Ring-Opening Tautomerization and Hydrogenation Reactions to Produce 1,5-Pentanediol from Furfural” ChemSusChem doi: 10.1002/cssc.201700178