Catalyst Deactivation in Pyridine-Assisted Selective Dehydration of Methyl Lactate on NaY

Abstract

Acrylic acid is a major commodity chemical currently produced almost entirely from petroleum-derived sources. The catalytic dehydration of methyl lactate is a promising renewable route to producing this vital chemical feedstock; however, enhancing the selectivity toward the dehydration pathway and catalyst stability remain challenging. We demonstrate a selectivity for dehydration products of ∼90% over a period of 30 h on NaY by introducing a small amount of pyridine in the reactant feed (pyridine/methyl lactate = 1:10). This increase in selectivity is attributed to the inhibition of side pathways, i.e., decarbonylation and coking, both of which are catalyzed by surface Bronsted acid sites generated in situ, rather than the acceleration of the dehydration pathway. Catalyst deactivation is shown to proceed through a drastically different mechanism in the absence and presence of pyridine in the feed via a combination of activity tests, thermogravimetric analysis, N2, and transmission FTIR spectroscopic inves...