(140d) Zeolite-Catalyzed Conversion of Lactates for Production of Sustainable Acrylates: Alcohol-Water Solvent Systems and Their Effects on Selectivity and Product Distribution

Acrylic acid (AA) and its alkyl ester derivatives are high-value, fossil fuel-derived platform chemicals used in the production of sealants, textiles, and superabsorbent polymers. Alternatively, lactic acid and lactate esters are bio-derived chemicals that can be dehydrated to form AA, thus presenting attractive replacement feedstocks. When lactate esters are used, the presence of exchangeable alkoxy groups allows for the formation of both alkyl acrylate esters and acrylic acid, adding complexity to the product stream.

In this work, the solvent dependence of the zeolite-catalyzed lactate-to-acrylate reaction was investigated. Feeds containing methyl or ethyl lactate in a solvent of water and/or alcohol were vaporized and fed into a fixed-bed reactor containing sodium-exchanged Zeolite Y. Adding a small amount (< 10 mol %) of methanol or ethanol to an aqueous reaction feed of methyl or ethyl lactate resulted in a 10-15 percentage point increase in molar selectivity to the desired acrylate products as compared to the purely aqueous feed. The exception to this pattern was the ethyl lactate/methanol system, in which the addition of methanol in any amount did not cause any change in selectivity. In all four cases studied, higher concentrations of alcohol did not result in further improvements in selectivity. Among the acrylate products, the acid was preferentially formed independent of feed alcohol concentration, representing a non-equilibrium composition of the acid-ester system. When ethanol was added to a mixture of water and methyl lactate, the methyl ester of the acrylate was always more favored than the ethyl ester, as predicted by thermodynamic equilibrium. These results indicate a mixture of thermodynamic and kinetic control, presenting both challenges and opportunities for tuning product distributions.