1,4-Butanediol purification commonly uses vacuum distillation because BDO is high boiling and excessive thermal exposure can promote decomposition, including formation of tetrahydrofuran and water. The column must remove water and lower-boiling impurities overhead while rejecting heavy diols, tars and salts toward the bottom. High-purity BDO can be recovered from an intermediate product zone, making side-draw location and bed staging important. Modern industrial BDO technology directly uses high-efficiency structured packing such as Sulzer BXPlus under deep vacuum. Packing selection should therefore balance theoretical-stage efficiency, pressure drop, impurity profile, heavy-end tolerance and product side-draw location rather than HETP alone.

Isopropyl alcohol and water form a minimum-boiling azeotrope near 87–88 wt% IPA at atmospheric pressure, so conventional distillation cannot directly produce anhydrous IPA simply by adding more theoretical stages. Industrial purification may use extractive distillation, pervaporation, adsorption or other dehydration technologies to move beyond the azeotropic limitation. Structured packing becomes particularly valuable in high-efficiency and final polishing sections, where low pressure drop, high stage density and uniform liquid distribution help remove residual water and trace organic impurities. For semiconductor-grade IPA, packing cleanliness and contamination control become part of the equipment specification alongside normal hydraulic performance.

Tetrahydrofuran purification is complicated by the THF-water minimum-boiling azeotrope, so ordinary single-pressure distillation cannot directly produce dry THF from an azeotropic mixture simply by adding more stages. Industrial processes use pressure changes, extractive solvents or other dehydration methods before final high-purity polishing. Structured packing is particularly valuable in the polishing stage, where many effective stages and low pressure drop may be required to remove trace impurities such as methanol and other ethers. Packing selection should therefore follow the exact column duty, pressure level, extractive-solvent circulation and trace impurity specification rather than THF concentration alone.

Acetonitrile recovery often involves much more than removing water. Industrial crude ACN may contain HCN, acrylonitrile and other organics, while ACN and water form a pressure-sensitive minimum-boiling azeotrope. Modern recovery processes can use water-assisted impurity removal, pressure-swing distillation and intermediate side-draw product recovery, with structured packing used in multiple columns to provide high stage density and low pressure drop. Packing selection should be based on the exact feed source, pressure level, internal reflux, impurity targets and product withdrawal location rather than ACN purity alone.

Formic acid and water form a maximum-boiling azeotrope containing about 77.6 wt% formic acid at atmospheric pressure, so conventional single-pressure distillation cannot directly produce essentially anhydrous formic acid simply by adding more packing. Industrial purification may use pressure-swing, extraction, amine-based separation or other processes before final vacuum purification. Structured packing becomes especially valuable in deep-vacuum sections because low pressure drop preserves low bottom pressure, while highly corrosive service may require fluoropolymer packing and specialty vessel materials. A recent CO₂-to-formic-acid process used a Zr702 purification column with PTFE structured packing at about 35 mbar.