SCOT tail-gas absorbers use selective amines such as MDEA to recover H₂S while deliberately allowing much of the CO₂ to pass through the absorber. The selectivity comes from reaction kinetics: H₂S reacts rapidly with MDEA, while CO₂ absorption proceeds through a much slower bicarbonate pathway. Structured packing can provide efficient H₂S removal with low pressure drop, but adding excessive contacting height, overly aggressive packing or unnecessary solvent circulation can increase unwanted CO₂ co-absorption. That CO₂ travels through the regenerator and back to the Claus sulfur-recovery unit, where excessive recycle CO₂ can reduce H₂S concentration and lower furnace temperature. SCOT packing design should therefore optimize H₂S removal and CO₂ slip together rather than maximizing total acid-gas absorption.

Electronic-grade hydrofluoric acid purification demonstrates an important limit of structured packing: some impurities cannot be removed effectively simply by increasing bed height or reflux. Trivalent arsenic can form volatile AsF₃ with boiling behavior too close to HF for efficient rectification alone. Industrial electronic-grade processes therefore oxidize arsenic into pentavalent, less-volatile chemistry before distillation. Structured packing then becomes valuable for efficient light- and heavy-impurity separation with low pressure drop and potentially lower reflux demand. Material selection must address both HF corrosion and ultra-high-purity contamination requirements, while downstream filtration or other polishing technologies handle impurities not governed by useful volatility differences. The purification flowsheet should therefore identify which impurity mechanism belongs to pretreatment, structured-packed rectification or final polishing before the packing itself is specified.

DMSO is thermally unstable, so conventional purification commonly uses vacuum distillation to reduce boiling temperature. A published Toray process uses a different additional strategy: sodium carbonate is controlled in the tower-bottom liquid to suppress DMSO decomposition and widen the usable operating-temperature range. The same process prefers regular structured packing because shorter residence time reduces heat deterioration and stabilizes operation. Water and other light components leave overhead, heavy impurities are rejected at the bottom, and purified DMSO is withdrawn through an intermediate side cut, with structured packing below the side draw helping prevent heavy-end contamination. For electronic-grade DMSO, distillation may be followed by ion-exchange polishing to reach ultra-low metal-ion levels. Packing selection should therefore consider thermal residence time, side-draw stage location, stabilizer-related crystallization risk and downstream purity requirements—not pressure drop alone.

Chlorine purification towers can use structured packing in the upper separation section to improve vapor-liquid contact and remove less-volatile bromine-containing impurities from purified chlorine. The same separation causes heavy contaminants, including nitrogen trichloride, to become enriched in the descending liquid. Because NCl₃ is an unstable chlorine impurity, the lower tower must be designed around controlled liquid inventory as well as normal mass-transfer performance. Published BASF technology combines upper structured packing with a smaller lower tower section specifically to reduce retained liquid chlorine and NCl₃ inventory. Packing selection should therefore consider reflux distribution, pressure drop, drainage, approved metallurgy and the plant's process-safety basis rather than treating the tower as a conventional chlorine scrubber or ordinary distillation column.

Formaldehyde-water-methanol distillation cannot always be predicted from a conventional structured-packing HETP alone because dissolved formaldehyde participates in reversible liquid-phase reactions. Formaldehyde forms methylene glycol and poly(oxymethylene) glycols with water and hemiformal species with methanol, so the concentration of volatile free formaldehyde changes with temperature and composition. BASF laboratory experiments used 3.5 m of Montz A3-500 structured packing, while pilot-scale studies used 2 m of Sulzer BX wire-gauze packing. These studies showed that equilibrium-stage models using normal packing-efficiency data matched only part of the experimental behavior and that reaction kinetics can need explicit treatment. Formaldehyde packing design should therefore combine validated reactive VLE modeling, real hydraulic data and liquid-distribution analysis rather than treating catalogue HETP as a universal bed-height predictor.