Biomass Depolymerization projects
Catalytic Carbon-Oxygen Bond Cleavage for Upgrading Cellulose
The team developed a process that couples petrochemically derived arenes from the BTX stream and sugar dehydration product for the production of diesel-like fuel precursors. Petroleum-derived diesel is a mixture of C11-C15 alkanes, cycloalkanes, and aromatic compounds. To convert the C5, C6 units into diesel-range fuel, CC-bond formation is necessary. Researchers also developed a biphasic reaction system that could produce diesel precursors even from cellulose and glucose. A key component was formic acid, which not only acts as a solvent but catalyzes the C-C coupling reaction.
Intense interest is focused on lignocellulosic biomass as a potential source of liquid fuels and chemicals, replacing petroleum-derived products. Work on saccharide components of lignocellulose is rather advanced, but the utilization of the lignin is still in its formative stages, despite the fact that this fraction accounts for up to 40 percent of the energy content of typical plant matter. The main challenge in upgrading lignin is scission of C-O bonds without using external hydrogen which would be prohibitively expensive in the biorefinery. In this project, we demonstrated the cleavage of C-O bonds in lignin model compounds without H2 using the commercially available Pd/C. Hydrogen donor solvents are helpful for this reaction through transfer hydrogenation, but not necessary. A redox neutral process that utilizes the internal hydrogen source for the cleavage is also possible. Mechanistic study indicates that b-benzylic-hydrogen centers in the substrates play a critical role. Preliminary studies showed that this system also induced partial depolymerization of lignin.
We developed a process that couples petrochemically derived arenes from the BTX stream and sugar dehydration product, 5-(hydroxymethyl)furfural (HMF), for the production of diesel-like fuel precursors. Petroleum-derived diesel is a mixture of C11-C15 alkanes, cycloalkanes, and aromatic compounds. To convert the C5, C6 units composed in lignocellulosic biomass into diesel-range fuel, C-C bond formation is necessary. And the hybrid fuel concept we conceived is a step along this direction. We also developed a biphasic reaction system that could produce diesel precursors even from glucose and cellulose with fairly good yields. And a key component of this system is formic acid, which not only acts as a solvent but also catalyzes the C-C coupling reaction.
Studies investigated the formation mechanism of humins, a by-product of the acid-catalyzed conversion of sugars into HMF. Formation of this polymeric material prevents the efficient generation of HMF from sugars, and thus understanding its formation mechanism would be of significant help for the synthesis of HMF. We found that, in our system, the major pathway to humins is the cooligomerization of sugars and their furan derivatives. Finally, we discovered that palladium catalyzed dehydrogenation of benzyl alcohol. This reaction could potentially be applied to the degradation of lignin that bears benzylic-like hydroxyl groups.