The term dichloroethane in this document refers to 1,2-dichloroethane, also designated ethylene dichloride (EDC), CAS 107-06-2. It is a volatile chlorinated C2 liquid with molar mass 98.95 g/mol, density 1.253 g/cm³ at 20 °C, boiling point 83.5 °C at 101.325 kPa, vapour pressure 8.7 kPa at 20 °C, and closed-cup flash point 13 °C. Commercial product designations are grade-based rather than brand-based. Technical-grade EDC is supplied with minimum purity 99.5%; chemical-grade material is specified at ≥99.9%; pyrolysis-grade EDC is controlled additionally for iron and moisture because both components affect downstream cracking furnace performance. The structural difference from the isomer 1,1-dichloroethane is material: chlorine substitution on adjacent carbon atoms gives 1,2-dichloroethane different alkaline hydrolysis and dehydrochlorination behaviour.

What Limits Moisture and Acidity in Bulk Ethylene Dichloride Specifications?

Moisture and acidity are the first technical boundaries for bulk EDC. Hydrolysis consumes the product and liberates hydrogen chloride; in carbon steel storage, free water creates local acid attack at the liquid–vapour interface and at tank bottom. Representative technical-grade release limits are shown in Table 1.

A water result above 0.0050 wt% often indicates nitrogen padding failure, barge contamination, or carryover from drying columns. Acid above 0.0010 wt% is a sign of incipient hydrolysis or external contamination and should be neutralised before cracking. Iron above 0.2 mg/kg in pyrolysis-grade material is considered harmful in published VCM operating data because iron chloride species promote coking and can reduce radiant coil service intervals. Density and distillation range are used to detect higher-boiling chlorinated by-products and non-chlorinated residues; the 5–95 vol% interval of 83.0–84.5 °C under ASTM D1078-15 is a narrow purity indicator.

Industrial conversion of 1,2-dichloroethane to vinyl chloride monomer is the dominant application. Direct chlorination of ethylene proceeds in a liquid-phase bubble column or loop reactor with ferric chloride catalyst at 50–70 °C and near-atmospheric pressure; selectivity above 99% is maintained by external cooling. Oxychlorination of ethylene with hydrogen chloride and air or oxygen over a copper(II) chloride/alumina catalyst is operated at 200–250 °C in fixed-bed or fluid-bed equipment, converting the HCl coproduct back to EDC. The dried combined EDC stream enters a cracking furnace where coil outlet temperature is held at 500–550 °C, residence time ranges from 8 s to 20 s, and per-pass conversion is deliberately limited to 50–60%. Published process data from VCM units show that the radiant coil pressure drop and coke deposition increase rapidly above 60% conversion; decoking intervals are commonly 30–90 days depending on heat flux and feed purity. The furnace effluent is quenched below 150 °C before hydrogen chloride separation, preventing vinyl chloride polymerisation and secondary thermal reactions.

Managing Radiant Coil Fouling in EDC Cracking Furnaces

Radiant coil fouling is the principal process conflict in EDC cracking. The reaction is a free-radical chain in which carbon–chlorine bond cleavage followed by beta-elimination yields vinyl chloride and HCl. At coil outlet temperatures above 550 °C, secondary condensation of vinyl chloride and acetylene precursors accelerates coke formation; below 500 °C, conversion efficiency drops and unconverted EDC recycle load increases. Furnace tubes are typically centrifugally cast high-alloy steel, and published operating data indicate that tube-wall temperature must be monitored continuously because coke deposits reduce heat transfer and create local hot spots. The pressure drop across the coil is used as a fouling indicator: a rise of 0.1–0.4 MPa above clean-condition baseline typically triggers steam-air decoking. Decoking is performed by controlled oxidation at 700–800 °C, but repeated decoking cycles cause carburization and reduce tube life. Therefore feed iron, moisture, and high-boiling residues are controlled so that per-pass conversion can be maintained without excessive coil degradation.

Quench-system performance is equally material. The furnace effluent is quenched in a shell-and-tube exchanger to below 150 °C, then enters the HCl column. If the quench is insufficient, vinyl chloride can polymerise in downstream piping; if the quench is too cold, tarry residues condense and plug the exchanger. Published operating guidance therefore specifies quench temperature control in the range 120–150 °C and continuous injection of heavy tar suppressant where required. These limits are not general solvent-handling data; they are specific to continuous VCM process equipment.

Vapour Degreaser Solvency and Co-Solvent Boundary Conditions

Use of EDC in controlled vapour degreasing is narrower than the higher-boiling chlorinated solvents because of its flash point and regulatory status. Its solvency is exploited mainly for low-polarity resins, chlorinated rubber, and certain bituminous binders. Published data for specific coating systems is limited, so laboratory immersion tests are required before substitution. Mass-change and dimensional-stability testing of elastomers and plastics is commonly run under ASTM D543-21; metallic coupon corrosion is evaluated by weight-loss panels in sealed cells. Process equipment must be sealed and nitrogen-blanketed when EDC vapour is generated: the lower explosive limit is 6.2 vol%, and the upper explosive limit is 16.2 vol%. Continuous photoionization detection is used to keep vapour concentrations below 25% LEL. Unlike trichloroethylene or perchloroethylene, EDC is not suitable for open-top degreasers under NFPA 30 area-classification logic because it forms flammable vapour at ambient temperatures.

Differences from other chlorinated products are summarised in Table 2. Dichloromethane has a much lower boiling point and higher vapour pressure, producing faster evaporation but higher emission load and different vapour density. Trichloroethylene has a similar boiling point to EDC but higher density and lower vapour pressure, and perchloroethylene is far less volatile. 1,1-Dichloroethane, the isomeric ethylidene chloride, has the same molecular mass but a boiling point of 57.3 °C and a density of 1.174 g/cm³ at 20 °C. In alkaline hydrolysis, 1,2-dichloroethane converts to ethylene glycol, while the 1,1-isomer yields acetaldehyde; the two isomers are therefore not interchangeable in closed process syntheses or in solvent recovery streams where the azeotrope behaviour differs.

When Ethylene Dichloride Replaces Methylene Chloride in Immersion Stripping

In enclosed immersion stripping, the EDC–methylene chloride comparison is governed by evaporation rate, blanketing requirement, and waste classification. The vapour pressure ratio is 8.7 kPa versus 47.0 kPa at 20 °C, so EDC drag-out remains longer on the part surface unless counter-current rinsing and hot-air drying are adjusted. Sealed strippers with carbon adsorption can handle EDC, but the adsorption bed regeneration temperature must consider EDC dehydrochlorination; bed regeneration is held below 200 °C unless stabilised. Materials of construction for continuous immersion service include 316L stainless steel for wetted parts where water may be present; carbon steel is limited to dry, low-acid conditions. EDC is incompatible with strong oxidisers, aluminium in wet service, active metals such as sodium and magnesium, and strong bases. Hot caustic contact above 80 °C hydrolyses EDC rapidly to ethylene glycol and sodium chloride; amine-based additives are avoided because they accelerate dehydrochlorination to vinyl chloride at elevated temperature. The replacement of methylene chloride in coating removal therefore requires a closed, electrically grounded vessel, nitrogen blanketing, and a lower operating temperature in the immersion bath.

Regulatory status modifies application scope. 1,2-Dichloroethane is classified as Carcinogen Category 1B under Regulation (EC) No 1272/2008 and is listed as a Substance of Very High Concern under REACH. OSHA 29 CFR 1910.1000 Table Z-1 retains an 8-hour TWA of 50 ppm for ethylene dichloride. Air sampling is performed by charcoal tube sampling with gas chromatography under NIOSH Method 1003. The US EPA drinking water maximum contaminant level for 1,2-dichloroethane is 0.005 mg/L. Thermal decomposition in oxygen-starved combustion generates hydrogen chloride, vinyl chloride, and trace phosgene, requiring positive-pressure respiratory protection. Bulk transfer uses nitrogen padding and closed-loop sampling; transfer hoses are conductive PTFE-lined stainless steel braid. Carbon steel tanks are acceptable only when water and acidity remain below the Table 1 limits; otherwise coated or 316L stainless steel linings are used. Waste streams containing EDC are classified as chlorinated hazardous waste and are incinerated at temperatures above 1100 °C with HCl scrubbing.