(703e) Tuning the Selectivity of Aminosilica Catalysts for Aldol Reaction and Condensation to Produce Bio-Derived Surfactants

Designing catalysts to produce biomass-derived products is vital to society’s transition away from fossil fuels. One intriguing target class of compounds is surfactants, including the recently discovered oleo-furan sulfonates (OFSs). OFSs are a bio-derived class of surfactants that are highly tunable compared to their conventional counterparts. Whereas synthesis methods to produce OFS have been identified, these tend to be costly. A potential low-cost synthesis route for OFSs is the aldol reaction and condensation between bio-derived furfural and linear ketones. A promising catalyst for aldol chemistry is aminosilica, which is highly active because of acid-base cooperativity. However, a key challenge for aldol chemistry is product selectivity, including both chemoselectivity (reaction vs. condensation product) and regioselectivity (linear vs. branched products). Here, aminosilica catalysts are tuned for OFS surfactant production to improve the selectivity for the linear condensation product.

SBA-15 is post-synthetically grafted with a primary (1°) or secondary (2°) aminosilane. The catalysts are tested with a symmetric ketone (i.e., acetone) to study chemoselectivity and unsymmetric ketones (i.e., 2-butanone and 2-undecanone) to assess regioselectivity trends. We show that amine type impacts the activity and selectivity. For the reaction between furfural and acetone, the observed chemoselectivity for the condensation product is higher for 2° SBA-15 than 1° SBA-15. The regioselectivity of the catalysts for the reaction with butanone follows a similar trend. Counter to previous work, our kinetic results show that 1° SBA-15 exhibits higher activity for reactions involving unsymmetric ketones, which is unexpected and will be investigated further. Ongoing work will elucidate the regioselectivity for the reaction with 2-undecanone and investigate temperature effects. Future work will leverage solvation and surface environment effects to improve the selectivity. Overall, this work develops a novel synthesis method for OFSs and establishes reactivity trends for aldol chemistry with unsymmetric ketones.