Shipments declared as “ethanolamine” without the six-digit Harmonized System code are routinely selected for laboratory examination. Monoethanolamine is classified under 2922.11 at the World Customs Organization Harmonized System subheading level, where the legal description is “monoethanolamine and its salts.” The tariff decision is based on molecular identity under General Interpretative Rule 1, not on downstream use; the same bulk substance supplied to a gas-treating plant or a detergent blender remains 2922.11 as a separate chemically defined compound. Correct use of MEA HS Code 2922.11: Correct Classification to Avoid Customs Delays therefore requires the invoice, packing list, and safety data sheet to cross-reference CAS 141-43-5, EC 205-483-3, and UN 2491. A declaration containing only the proprietary name “alkanolamine activator” creates a verification loop that can hold cargo at the port.

What Does Subheading 2922.11 Actually Cover for Bulk Monoethanolamine?

Under heading 2922, the World Customs Organization Harmonized System covers oxygen-function amino-compounds. Subheading 2922.11 is the six-digit basket for monoethanolamine and its salts; diethanolamine is assigned to 2922.12, triethanolamine to 2922.13, and other amino-alcohols to 2922.19. A pure monoethanolamine shipment should not be declared under 2922.19 because the product is not an “other” amino-alcohol. That misclassification triggers requests for a formal ruling and can expose the importer to penalty interest on any duty difference. General Interpretative Rule 1 establishes heading 2922, and General Interpretative Rule 6 establishes subheading 2922.11.

The legal text of subheading 2922.11 does not impose a purity threshold at the World Customs Organization six-digit level, but national ten-digit lines may include documentation requirements. In the European Union, the Combined Nomenclature line is 2922 11 00; in the United States, the Harmonized Tariff Schedule line is 2922.11.00. In tank container trade, the cargo description should state “monoethanolamine (CAS 141-43-5)” rather than “ethanolamine blend,” because the term “blend” suggests a mixture classifiable outside Chapter 29 if the product is not a separate chemically defined compound.

Physical verification at the receiving terminal begins with density and water content. Bulk monoethanolamine has a molar mass of 61.08 g/mol, a normal boiling point of 170.5 °C at 101.3 kPa, and a freezing point near 10.5 °C. Because the freezing point is high relative to ambient storage in temperate ports, 80 m³ stainless steel storage tanks are often specified with external steam tracing or recirculation loops to maintain product temperature above 15 °C. Density at 20 °C is 1.016 g/cm³, measured by ASTM D4052. Water content above 0.3 wt% lowers density and can alter downstream stoichiometry; it is measured by ASTM E203 Karl Fischer titration. Color is reported against the platinum-cobalt scale using ASTM D1209; a Pt-Co value above 30 at receiving often indicates oxidative degradation, iron contamination, or heating coil leakage.

Commercial specification sheets typically report assay at 99.0–99.7 wt% monoethanolamine, diethanolamine below 0.5 wt%, and triethanolamine below 0.1 wt%. The homolog profile is not only a quality indicator; it is the primary analytical evidence used to defend the 2922.11 subheading during a customs challenge. Assay by GC-FID with internal standard is not governed globally by a single ISO method; producer certificates should state the calibration basis because area percent alone can overstate purity if water and non-volatiles are not subtracted.

Lean/Rich Loading and Corrosion Boundaries in Gas-Treating Columns

Post-combustion CO₂ capture and natural gas sweetening use aqueous monoethanolamine at concentrations between 15 wt% and 30 wt%. In carbon steel absorber/regenerator circuits, the conventional operating window is constrained by corrosion rather than equilibrium capacity. Lean solvent loading is maintained between 0.10 mol CO₂/mol MEA and 0.15 mol CO₂/mol MEA. Rich solvent loading is normally not permitted to exceed 0.40–0.45 mol CO₂/mol MEA in carbon steel because acid-gas loading lowers pH and increases the concentration of corrosive carbamate and bicarbonate species. At lean loads below 0.08 mol CO₂/mol MEA, free MEA concentration can exceed 12 wt%, producing alkaline pH above 11 in the absorber sump; stress corrosion cracking in weld heat-affected zones has been observed in carbon steel lines when no inhibitor or stainless steel upgrade is used.

Regenerator bottoms are held at 120–125 °C. Operation above 126 °C accelerates thermal degradation of MEA carbamate and promotes formation of heat stable salts. Heat stable salt anions—formate, acetate, and oxalate—accumulate in closed loops and reduce CO₂ capacity. In licensed reclaiming operations, total heat stable salts are typically controlled below 1.0 wt% as formate to limit absorber foaming and carryover. Oxygen ingress above 1 vol% in flue-gas systems increases oxidative degradation to ammonia and organic acids; therefore air ingress into the lean solvent storage tank is minimized by nitrogen blanketing at 0.5–1.0 kPa gauge. Packed columns with structured packing are operated at liquid loads of 20–80 m³/m²·h depending on solvent viscosity. Monoethanolamine also forms copper-amine complexes with copper alloys; brass or copper trim in pumps and valves is replaced with stainless steel or carbon steel with inhibitor packages. Published data for low-pressure post-combustion towers at 20 wt% MEA show that the rich loading limit and regeneration temperature, not the packing surface area, govern the practical capture rate.

In liquid detergent compounding, monoethanolamine neutralizes linear alkylbenzene sulfonic acid to form the monoethanolamine sulfonate salt; the addition rate is determined by acid number and target pH of 8.0–9.0 in the finished concentrate. For cement grinding, MEA is metered at 0.02–0.05 wt% of clinker mass into the mill inlet to reduce agglomeration on grinding media. At mill exit temperatures above 90 °C, residual amine can decompose to ammonia and carbonaceous residues; therefore injection is often placed in the second compartment of a ball mill or into a mill ventilation stream where gas temperature is below 80 °C. Storage for these dose rates is not trivial: MEA solidifies near 10.5 °C, so bulk tanks in unheated warehouses require electric trace heating and insulated piping above 15 °C. Aqueous blends below 70 wt% MEA are sometimes used to depress freezing point, but the dilution does not change the 2922.11 classification of the separate chemically defined compound.

In metalworking fluid concentrates used for synthetic coolants, monoethanolamine addition of 5–15 wt% provides reserve alkalinity and helps maintain pH between 9.0 and 9.8 in diluted sump fluid. At this concentration, it is not a lubricant additive; it is a separate chemical intermediate and should be declared as 2922.11 on the raw material entry. The same substance used to manufacture ethyleneamines in a reactor train with a nickel or cobalt catalyst is consumed in molar excess to control homolog distribution; reactor design with a fixed-bed adiabatic catalyst and ammonia-to-ethylene oxide molar ratio above 5:1 favors monoethanolamine selectivity above 85 mol%. Published data for this specific configuration is limited, but process licensors typically report that uncontrolled adiabatic temperature rise above 150 °C reduces selectivity and increases diethanolamine formation.

When a National Ten-Digit Tariff Line Demands a Purity Certificate

A customs hold frequently occurs when the gas chromatogram shows more than one ethanolamine homolog and the declarant has not attached a batch certificate. At the six-digit level, the presence of 0.5–2.0 wt% diethanolamine as a manufacturing impurity does not move the product out of 2922.11, provided the principal component remains monoethanolamine. The risk arises at national ten-digit subdivisions where customs may require proof that the impurity is not a deliberate co-product. A shipment described as “diethanolamine/monoethanolamine mixture” with 20 wt% diethanolamine would not be classified under 2922.11 because the product is no longer a single ethanolamine; the correct subheading would be determined by the principal component or, if no single component predominates, by the appropriate residual provision for mixtures.

To avoid delays, the batch production record should show reactor charge molar ratios, ammonia/ethylene oxide reaction conditions, and GC-FID area percent results for monoethanolamine, diethanolamine, and triethanolamine. The safety data sheet should list CAS 141-43-5 and the UN 2491 proper shipping name. A missing C-14 certificate may be less significant than a homolog profile that contradicts the declared 2922.11 subheading.

Under transport regulations, monoethanolamine is assigned to UN 2491, ethanolamine or ethanolamine solutions, Class 8, Packing Group III. The CLP harmonized classification for monoethanolamine includes H314 for severe skin burns and eye damage and H302/H312/H332 for acute oral, dermal, and inhalation toxicity. A tank container placarded with Class 8 and declared under HS 2922.11 should carry a dangerous goods declaration that matches the invoice product name; mismatch between DGD and tariff description is a common source of examination. For packed cargo, the packing list line item should read “monoethanolamine (CAS 141-43-5), UN 2491, Class 8, PG III.” The description “amine activator” or “gas treating agent” is not sufficient for customs entry because it omits chemical identity and forces the inspector to request a laboratory sample.

Tariff engineering by dilution is not effective. Aqueous monoethanolamine solutions in which monoethanolamine remains a separate chemically defined compound are classified under 2922.11 at the six-digit level, even if water is added at 30–50 wt% to lower viscosity and reduce storage freezing risk. General Interpretative Rule 1 looks to the chemical identity of the solute, not the concentration. However, a formulated detergent containing monoethanolamine plus surfactants is not a separate chemically defined compound; it falls outside heading 2922 and is generally classified under a formulation heading such as Chapter 34. The boundary between raw material and formulation should be documented through the batch ticket, because customs officials may reclassify a product described as “cleaning agent” under Chapter 34 even if the invoice states 2922.11.