Kinetics of Friedel Crafts Acylation of 2-Methylfuran with Octanoic Anhydride and Al-MCM-41.

Friedel Crafts acylation reaction of aromatic substrates with different acylating agents produces ‘aryl alkyl ketones’. The acylation reaction of biomass derived furans and long-carbon chain (C₁₂-C₂₀) fatty carboxylic acids or anhydrides obtained by hydrolysis of plant -oil based triglycerides produces ‘alkyl furan ketones’. These ketone molecules are important precursors for the synthesis of renewable oleo-furan sulphonate (OFS) surfactants as demonstrated by Park et al. [1]. The exceptional stability of these OFS surfactants for use as detergents in hard water as well as other comparable detergent characteristics makes them a useful alternative to the petroleum-based surfactants. In this work, we elucidate the reaction kinetics of Friedel Crafts acylation reaction of 2-methylfuran and n-octanoic anhydride as a model system with Al-MCM-41 as a solid Brønsted acid catalyst in the presence of a non-protic solvent heptane. The apparent activation energy and the reaction rate orders are obtained in a flow reactor set-up. The experimental observations are explained using a potential mechanism and a kinetic model. The understanding of this C-C coupling reaction using long chain fatty acid derivatives will contribute to the scale-up of OFS surfactants as well as to the design of heterogeneous Friedel Crafts acylation catalysts.

Reference:

1. Park, D. S., Joseph, K. E., Koehle, M., Krumm, C., Ren, L., Damen, J. N., Shete, M. H., Lee, H. S., Zuo, X., Lee, B., Fan, W., Vlachos, D. G., Lobo, R. F., Tsapatsis, M. and Dauenhauer, P. J. ACS Cent. Sci. 2, 820–824 (2016).