EDC 1,2-Dichloroethane

Commercial 1,2-dichloroethane (EDC; ethylene dichloride) is a chlorinated aliphatic hydrocarbon supplied as a clear, low-viscosity liquid with CAS 107-06-2, EC 203-458-1, and transport classification UN 1184. Industrial shipments are not defined by a single “model” but by specification-controlled grades that differ principally in assay, water content, acidity, non-volatile residue, colour, and trace oxygenates. A representative receiving specification matrix for two common commercial grades is shown below. The limits are typical industrial receiving criteria rather than universal guarantees.

Independent physical property data used for receiving inspection and equipment sizing include a boiling point of 83.5 °C at 101.3 kPa, density of 1.253 g/cm³ at 20 °C, vapour pressure of approximately 85 hPa at 20 °C, refractive index of 1.4448 at 20 °C, melting point of -35.3 °C, and water solubility of 8.7 g/L at 25 °C. The closed-cup flash point is near 13 °C, and the explosion limits are approximately 6.2–16.0 vol% in air. These flammability values distinguish EDC from non-flammable chlorinated solvents such as trichloroethylene and perchloroethylene and are the basis for explosion-proof specification in storage and processing areas.

What Limits Direct Substitution of 1,2-Dichloroethane for Methylene Chloride in Coating Removal?

Compared with dichloromethane, EDC has a higher boiling point by 43.9 °C and a lower vapour pressure by more than 380 hPa at 20 °C. The comparative data below summarise the main single-point solvent properties used in substitution studies. Values are reported at 20 °C unless otherwise indicated.

Direct substitution in immersion coating-removal equipment is constrained by the vapour-phase flammability of EDC. Vessels previously designed for dichloromethane, trichloroethylene, or 1,1,1-trichloroethane may be fitted with non-explosion-proof immersion heaters, standard fan motors, and open drainage; EDC requires an inertisation regime, explosion-proof electrical classification, and continuous lower-explosion-limit monitoring. The boiling point of EDC is close to that of trichloroethylene, but its solvent action on heavy paraffinic and bituminous coating films is generally lower; process trials on production-scale immersion tanks are used to set contact time because published comparative soil-removal data for complex aged coatings are limited. EDC also attacks polycarbonate and acrylic sight glasses, so borosilicate glass or PTFE sight tubes are required in retrofit installations.

In vinyl chloride monomer production, the largest integrated use of EDC is as the primary intermediate. Direct chlorination of ethene is carried out in a boiling EDC loop where dissolved iron(III) chloride provides catalytic activity. Typical reactor conditions are 50–70 °C and 0.2–0.5 MPa(g); unreacted ethene is recovered from the off-gas and returned to the reactor. Oxychlorination uses ethene, hydrogen chloride, and oxygen over a copper chloride on alumina catalyst in fixed-bed or fluid-bed reactors at approximately 200–240 °C and 0.3–0.6 MPa(g). The combined crude EDC streams are dehydrated, distilled, and routed to thermal cracking. Thermal dehydrochlorination is performed in fired tubular coils near 500 °C with per-pass conversion deliberately held at 50–60% to limit coking and heavy by-product formation. Specific coil outlet temperatures, steam-to-EDC ratios, and quench configurations vary by licensor, and published data for operator-specific coking rates are limited. The cracked gas is quenched rapidly to stop secondary reactions, then distilled to separate hydrogen chloride, vinyl chloride, unreacted EDC, and heavy residues. In this application, low-water EDC reduces hydrochloric acid corrosion in the quench and distillation overhead systems; receiving specifications below 0.010 wt% water are therefore common.

Stabilizer Chemistry and Moisture Limits in Downstream Ammonolysis

Ammonolysis of EDC is a high-pressure route to ethylenediamine and higher ethyleneamines such as diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. Ammonia-to-EDC molar ratios above 20:1 are used to favour primary amine selectivity, while lower ratios increase higher oligomer formation. The reaction is performed at approximately 120–180 °C and pressures up to 15 MPa in high-pressure tubular or autoclave reactors constructed from nickel-chromium-molybdenum alloys such as Hastelloy C-276 to resist chloride-induced stress corrosion cracking. Moisture is kept below 0.005 wt% in anhydrous EDC feed because water accelerates undesirable hydrolysis and generates acid. Amine-based stabiliser packages are excluded from EDC destined for ammonolysis because the stabiliser consumes feedstock and can form quaternary ammonium chloride precipitates that foul reactor preheaters and downstream salt separation equipment. Trace oxygenates are controlled by dedicated gas chromatography with flame ionisation detection after cryofocusing; area-normalisation assay alone is insufficient for this grade because oxygenates with low response factors can affect colour and product distribution in amine distillation.

Storage of low-water EDC is normally carried out in carbon steel cone-roof tanks with nitrogen blanketing and vent driers containing molecular sieve 4A to maintain a tank vapour dew point below -40 °C. Moisture ingress above specification initiates gradual hydrolysis and acid formation, which increases corrosion at liquid-vapour interfaces and at weld heat-affected zones. Transfer loops generally employ canned motor pumps or centrifugal pumps with tandem mechanical seals to control fugitive emissions. Storage temperature is maintained below 35 °C to limit vapour loading and to reduce degradation reactions. EDC is incompatible with aluminium, zinc, magnesium, strong alkalis, and finely divided metals; gasket materials should be selected from PTFE, PVDF, or other fluoropolymer grades. Occupational exposure and use restrictions apply. Harmonised classification under Regulation (EC) No 1272/2008 includes Flam. Liq. 2 and Carc. 1B with hazard statement H350; industrial handling is therefore conducted in closed systems with vapour recovery in many jurisdictions.

When EDC Replaces 1,1,1-Trichloroethane in Vapour Degreasing Equipment

Conversion of an existing vapour degreaser from 1,1,1-trichloroethane to EDC requires recalculating immersion heater watt density because the boiling point is 9.4 °C higher and the latent heat of vaporisation is different. Heater sheath temperatures should remain below the threshold where EDC degradation can accelerate, and the condenser coil area must be checked against the lower vapour pressure of EDC relative to 1,1,1-trichloroethane. A freeboard ratio above 0.75 is commonly applied to reduce vapour escape, and an emergency safety shutoff interlocked with lower-explosion-limit monitors is required because EDC is flammable. Published data for specific retrofit performance on older open-top degreasing equipment are limited, so equipment manufacturers generally revalidate the heater sheaths, cooling capacity, and vent scrubber before placement into service.