Phthalic anhydride purification removes lower-boiling impurities such as maleic anhydride and benzoic-acid-related components and separates PA from higher-boiling compounds such as phthalide and heavy residues. Industrial PA purification has used structured packing under vacuum, where low pressure drop helps reduce required boiling temperature. The application is unusual because PA melts at about 131°C, so liquid distribution, drainage, insulation and avoidance of cold spots are critical to prevent crystallization inside packing and other tower internals. Packing selection should therefore balance stage efficiency, vacuum pressure drop, heavy-end tolerance and temperature uniformity rather than HETP alone.

Dimethyl carbonate and methanol form an azeotropic system that limits conventional distillation, so industrial DMC purification commonly requires extractive distillation or another azeotrope-breaking process. Structured packing has been directly applied in DMC water-removal, extractive and final rectification columns because it provides high separation efficiency with relatively low pressure drop. Packing selection should account for extractant circulation, water removal, methanol recycle, DMC recovery, liquid distribution and the hydraulic trade-off between high surface area and solvent-loaded capacity.

Structured packing can be used in epichlorohydrin purification columns to separate water and light impurities from ECH while rejecting dichlorohydrins and heavier components. A high-purity design can withdraw finished ECH as a liquid side stream rather than directly from the overhead, allowing water and lighter impurities to continue concentrating above the product withdrawal point. Low-pressure-drop structured packing also supports vacuum operation and lower tower temperatures. Packing grade, side-draw elevation, collectors, redistribution and corrosion-resistant materials should therefore be designed as one complete purification system.

Aniline produced by nitrobenzene hydrogenation contains reaction water together with low-boiling impurities such as benzene, cyclohexylamine and cyclohexanone and high-boiling contaminants such as phenol, diphenylamine and other aromatic compounds. Industrial purification therefore uses separate dewatering/light-boiler and high-boiler separation duties, often under reduced pressure. Structured packing can provide high stage density with low pressure drop, but packing grade, bed arrangement, side draws and liquid distribution should be selected according to the specific impurity being removed rather than bulk aniline purity alone.

Methanol carbonylation produces crude acetic acid containing water, methyl iodide, methyl acetate and trace carbonyl and heavy impurities. The purification train must remove these contaminants while recovering valuable iodide promoter and recycle components. Structured packing can be used in drying, finishing and selected trace-impurity columns because its high stage density and low pressure drop can reduce tower size, improve separation and support energy-integrated revamps. Packing selection must nevertheless follow the exact impurity target, recycle duty, corrosion environment and fouling risk of each column section.