(194a) Tuning of Aminosilica Catalysts for Furfural Aldol Chemistry to Enable Production of Bio-Derived Goods

Economically viable biomass upgrading pathways are key to the sustainable production of essential goods and products. A central component of this is catalyst development. One such pathway that would benefit from catalyst design is the aldol reaction and condensation of furfural with different linear ketones. The aldol reaction and condensation is a carbon-carbon bond forming reaction that is useful for upgrading small molecules to targeted chemicals. 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 catalyst performance is investigated to establish a basis for use in the production of bio-derived chemicals such as surfactants or fuels.

Santa Barbara amorphous 15 (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, 2-heptanone and 2-undecanone) to assess regioselectivity trends. We show that amine type impacts the activity and selectivity. Counter to previous work, our kinetic results show that 1° NMP SBA-15 exhibits higher activity than 2° NMP SBA-15 for reactions involving unsymmetric ketones, as a result of solvation and steric effects. For the reaction between furfural and acetone, the observed chemoselectivity for the condensation product is higher for 2° NMP-SBA-15 than 1° NMP-SBA-15. The regioselectivity of the catalysts for the reaction with unsymmetric ketones follow a similar trend. 2° NMP-SBA-15 is highly selective for linear condensation products while 1° NMP SBA-15 shows some selectivity for branched products.

Future work will investigate catalyst recyclability, solvation, and surface environment effects to further improve catalyst performance. Overall, this work establishes a basis for aminosilica catalyst use for furfural aldol chemistry with unsymmetric ketones.