Mechanism of Selective Metal Ion Removal from Methanol Carbonylation Acetic Acid Reaction Solution by Ion Exchange Resin

The demand for acetic acid is rising, with the methanol-based method as the main production process. However, impurity metal ions (Fe, Cr, Ni, and K) hinder catalyst activity and product purity. While ion exchange resins are used for impurity removal, their adsorption mechanisms and influencing factors are not well understood, restricting technological advancements. This study systematically examined nine types of commercial ion exchange resins, including strong acid cation, strong alkaline anion, and chelating resins, for the methanol-based circulation liquid. The type 001*7 strong acid cation exchange resin showed excellent selective adsorption for impurity ions. Static adsorption experiments examined the impact of resin dosage and contact time. Kinetic analysis using PFO, PSO, and IPD models indicated that the process is mainly chemisorption. Optimal conditions (70 g/L resin, 120 min) achieved removal efficiencies of 90.61% for Fe, 13.47% for Cr, 92.35% for Ni, and 66.46% for K, with iridium loss under 3%. Using techniques like FTIR, XPS, and zeta potential analysis, we demonstrated that the 001*7 resin effectively removes impurity ions through a combination of adsorption, electrostatic interactions, and ion exchange.