Biomass can serve as a renewable source for both energy and carbon. ABE (acetone, n-butanol, and ethanol) fermentation broth as a biomass-derived source of fuels and chemicals has received a lot of attention for several decades. However, the crude fermentation broth contains low concentrations of oxygenates, limiting its practical applications.
Thus, it is pivotal to develop a highly efficient water-resistant catalyst to directly and selectively convert crude aqueous oxygenate mixtures to value-added chemicals; water-immiscible ones (easy separation after reaction) are especially of great importance. However, the efficiency and selectivity of the transformation process for biomass-derived intermediates remains a major techno-economic challenge.
Prof. WANG Feng and his colleagues from Peking University, recently reported an efficient and novel catalytic method for the conversion of aqueous biomass fermentation broth to a water-immiscible product. Their finding is published in Nature Communications.
They developed a strategy capable of transforming ~70% of carbon in an aqueous ABE fermentation mixture to 4-heptanone (4-HPO), catalyzed by tin-doped ceria (Sn-ceria) with a selectivity as high as 86%. While Sn-ceria is a versatile catalyst for dehydrogenation, the Guerbet alcohol reaction, condensation, and esterification reactions, all these reactions, involving acid-base catalysis and redox ones, relay and generate 4-HPO with high selectivity(Fig.(A)). 4-HPO is a value-added intermediate and can be used to produce jet fuel and fine chemicals (Fig. (B)).
(A) Proposed reaction pathways leading to 4-HPO. (B) 4-HPO utilization.(Image by WANG Yehong)
Furthermore, water, which is detrimental to the reported catalysts for ABE conversion, was beneficial for producing 4-HPO. The excellent catalytic performance of tin-doped ceria is due to the highly dispersed tin species and oxygen vacancies of ceria.
"This strategy offers a route for highly efficient organic carbon utilization," said WANG. "It can potentially integrate biological and chemical catalysis platforms for the robust and highly selective production of value-added chemicals."
The research was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences, the National Key R&D Program of China, and the Natural Science Foundation of China. This work is also dedicated to the 70th anniversary of Dalian Institute of Chemical Physics, CAS. (Text by WANG Yehong)
