(476e) Cross-Ketonization of Biomass-Derived Furans and Fatty Acids for Renewable Surfactants

The demand for linear alkyl benzene (LAB) class of anionic surfactants is at $8 billion and is projected to rise 4.5% annually. This poses a significant environmental threat as industrial methods for producing LABs utilize non-renewable petroleum based feedstocks and homogeneous acid catalysts. Therefore, it is desirable to develop a sustainable method for producing LABs. Recent work has demonstrated performance based biomass-derived oleo-furan sulfonate (OFS) surfactants. The C-C coupling reaction to form 2-alkylofuran is considered the bottleneck in this synthesis. In this context, our group developed a new synthesis of 2-alkylofurans via cross-ketonization of 2-furoic acid and lauric acid using earth-abundant, commercially-available iron oxides catalysts. The cross-ketonization strategy offers ease of separation and recyclability of solid catalysts and produces only water and carbon dioxide as byproducts. However, the iron oxide catalyzed ketonization reaction resulted in modest product yield (~41%) due to the decarboxylation of the 2-furoic acid. There is also limited understanding of the ideal catalyst properties since basic and mixed metal oxides have not been studied for this chemistry.

In this work, we investigate the activity of various alkaline earth metals and mixed metal oxides, e.g., MgO, CaO, BaO, etc. as potential catalysts for cross-ketonization. We show that MgO is a highly active catalyst, minimizes the decarboxylation side reaction and achieves ~90% yield to the desired product. Catalyst deactivation was observed but regeneration over multiple runs was possible. We studied the role of molecule structure on the cross-ketonization reaction and the role of complex formation over alkaline-earth metal oxides. Mechanistic insights will also be discussed. This research demonstrates the effectiveness of heterogeneous catalysts for cross ketonization toward the development of renewable surfactants.