Study on Active Site Leaching of K₂O/Al₂O₃ Catalysts in Ethyl 3-Ethoxypropionate Synthesis

Solid alkaline catalysts K₂O/Al₂O₃ with different loading ratios were prepared using γ-alumina as a support and KNO₃ as a precursor, which were used in ethyl 3-ethoxypropionate synthesis. XRD, FT-IR, N₂ adsorption-desorption and CO₂-TPD results reveal that the catalyst has two alkaline sites. The strong alkaline site (K₂O) is derived from KNO₃ decomposition while the weak one (K-O-Al) is from the interaction between γ-alumina and KNO₃. The increase of KNO₃ enhances overall basicity of the catalyst, but it breaks the support by decreasing its specific surface area and pore volume. When K₂O loading is 30%(wt), reaction temperature is 70℃, mole ratio of ethanol/ethyl acrylate is 6:1 and catalyst usage is 10%(wt) of ethyl acrylate, 53.6% of ethyl acrylate can be converted to EEP with selectivity of 98.8%. However, recycling tests reveal that K₂O can irreversibly react with ethanol to form potassium ethoxide that subsequently dissolves in the reaction solution, which results in deterioration of catalytic performance in the following cycles. Reloading of equimolar K₂O onto the used catalyst can effectively regenerate the deactivated catalyst. Therefore, solid alkaline catalysts with permanently immobilized potassium ethoxide are of great interests.