Friedel Crafts acylation is an important C-C coupling reaction with the potential to create high value fuels and chemicals from renewable biomass streams. Recent efforts have been made by our group and others to reduce the environmental footprint of these reactions by utilizing carboxylic acids directly (rather than halogenated species) and using zeolites as non-sacrificial catalysts. While we have learned a great deal over the past 5 years regarding the nature of mechanism of this reaction over Brønsted zeolites, much less is known regarding the role of common additives that influence the local environment and acidity on rates and stability for this reaction. Here we report the acylation of 2-methylfuran (2-MF) with acetic acid (AA) over Phosphorus (P) modified MFI zeolites with a Si/Al ratio of 140 spanning a wide range of P loadings. Isopropylamine temperature programmed reaction (IPA-TPRx) measurement shows the loss of BAS upon the addition of P indicating FAL. We show that at lower reaction temperatures (160°C), only the sites that are not titrated by P exhibit activity for acylation. However, when increasing the reaction temperature to 240°C the weaker P modified sites begin to exhibit activity for acylation. Interestingly, the P loaded samples exhibited significantly slower coke formation, and therefore deactivation, due to diminished side AA coupling reactions. Additionally, P promoted MFI zeolites can recover its major activity after mild treatment compared to parent zeolite. Findings were consolidated with FTIR spectroscopy revealing significantly lower coke observed on the surface of P zeolites.

Consequence of altering acid strength in MFI zeolites via phosphorus modification and their effects on acylation reaction

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