Acid-functionalized PVA composite membranes for pervaporation-assisted esterification.

Area of Science:

• Chemical Engineering
• Materials Science
• Catalysis

Background:

• Esterification reactions are crucial in chemical synthesis.
• Developing efficient and reusable catalysts is essential for sustainable chemical processes.
• Membrane technology offers advantages for reaction separation and integration.

Purpose of the Study:

• To develop composite membranes functionalized with ionic liquids (ILs) for enhanced esterification.
• To investigate the catalytic activity of IL-functionalized membranes in the esterification of n-butanol and acetic acid.
• To compare the performance of ILs with different anions (hydrogen sulfate and bromide) for catalytic esterification and membrane separation.

Main Methods:

• Composite flat-sheet membranes were prepared via dip-coating commercial pervaporation membranes.
• Imidazolium-based ionic liquids with hydrogen sulfate [HSO4]- or bromide [Br]- anions were grafted onto a poly(vinyl alcohol)/glutaraldehyde layer.
• The catalytic activity and membrane performance were evaluated through esterification experiments and water separation tests.

Main Results:

• Compact, defect-free catalytic layers (12 μm thick) were successfully formed on the membrane supports.
• Both IL-functionalized membranes promoted esterification, with the [HSO4]- based IL achieving higher butyl acetate yields (up to 50% in 15 h).
• The coated membranes showed improved water separation factors due to reduced swelling and wettability.

Conclusions:

• Imidazolium-based ionic liquids grafted onto composite membranes serve as effective catalysts for esterification.
• The choice of anion significantly impacts catalytic efficiency, with hydrogen sulfate being more effective.
• The functionalized membranes offer a promising approach for integrated reaction and separation processes.