(109a) Economically Competitive Production of Oleo-Furan Sulfonate Detergents from Furfural and Fatty Alcohols

Oleo-furan sulfonates (OFS) are superior detergents derived from the combination of fatty acids and furanic derivatives, rather than petrochemicals, and exhibit improved properties compared to their legacy counterparts. The traditional pathway to their production is via the acylation of furan by fatty acid anhydrides. However, this pathway is limited thermodynamically by the low equilibrium constant of the acid dehydration to the anhydride. We propose instead to leverage dehydrogenative aldol condensation of fatty alcohols with furfural, combined with transfer hydrodeoxygenation using isopropanol as a hydrogen donor.

The first step of this process takes place over hydrotalcite catalysts, in which basic sites catalyze the transfer dehydrogenation and aldol condensation reactions. The liquid-phase batch reaction yields an α,β-unsaturated furanic aldehyde at 70% yield and no significant catalyst degradation over 5 recycles.

In the second synthesis step, the obtained aldehyde undergoes hydrodeoxygenation (HDO) to yield the desired oleo-furan molecules. The synthesis is performed over a ruthenium-based catalyst (a mixture of Ru/C, catalyzing localized hydrogen production, and RuO₂ hydrate, catalyzing the reverse Mars-van Krevelen HDO step) at 180°C under both inert nitrogen (N₂) and hydrogen gas (H₂) conditions. At short reaction times, the oleo-furan yield during H₂-HDO is observed to be consistently higher than under N₂. Remarkably, however, at longer reaction times, oleo-furans production under an inert atmosphere exceeds that of the H₂ atmosphere, providing a promising pathway to achieve high oleo-furan yields via hydrodeoxygenation without involving H₂. We attribute this observation to the reduction of the RuO₂ catalyst to Ru during reaction, which renders it inactive for the HDO reaction.

The subsequent sulfonation of the oleo-furan intermediates yields oleo-furan sulfonate surfactants with good detergency properties. Importantly, technoeconomic analysis of the oleo-furan sulfonate production process suggests improved economic potential compared to the legacy process.