Epichlorohydrin downstream map: epoxy resin vs synthetic glycerol demand split is an operational variable in chlor-alkali and C3 derivative planning. Epichlorohydrin, CAS 106-89-8, is manufactured by dehydrochlorination of dichloropropanol. In the dominant allyl chloride route, dichloropropanol is obtained from propylene via allyl chloride hypochlorination; in the glycerin route, it is obtained from crude glycerol and hydrogen chloride. The downstream map is not static. Integrated producers with liquid epoxy resin units consume the largest share, while synthetic glycerol production by ECH hydrolysis occupies a smaller, price-sensitive niche. Trade-flow analyses and producer disclosures commonly place epoxy resin consumption at 70% to 80% of global ECH demand, while synthetic glycerol from direct ECH hydrolysis remains below 5% except in specific integrated assets where propylene shortage or glycerin surplus economics temporarily shift allocation. The remainder is consumed in water treatment quaternary ammonium monomers, epichlorohydrin elastomers, wet-strength resins, and glycidyl derivatives. The epoxy resin versus synthetic glycerol split is the most sensitive allocation variable because the two routes require different purity thresholds and different reaction economics.

What Determines the Epoxy Resin Versus Synthetic Glycerol Allocation?

The allocation depends on reaction stoichiometry and downstream purification boundaries. In epoxy resin synthesis, ECH is reacted with bisphenol A in the presence of sodium hydroxide. The nominal ECH consumption is 0.55 t to 0.58 t per tonne of liquid DGEBA after recovery. In synthetic glycerol hydrolysis, ECH reacts with water in the presence of dilute sodium hydroxide or acid catalyst; the nominal conversion factor is 1.05 t to 1.10 t ECH per tonne of glycerol because the molecular weights of ECH and glycerol are nearly identical but yield losses and purification reduce mass efficiency. When epoxy resin demand is high, the larger volume and lower ECH unit intensity reinforce epoxy resin’s position. Synthetic glycerol is rarely the primary destination unless glycerol market prices exceed the epoxy resin variable margin or a producer has excess ECH capacity without integrated bisphenol A supply.

At reactor level, the split is also affected by chloride speciation. Epoxy resin production tolerates ionic chloride in the waste brine but requires low hydrolyzable chloride in the resin, typically 300 ppm maximum. Synthetic glycerol requires near-complete removal of ionic chloride to satisfy USP or EP monographs, often below 10 ppm. ECH contaminated with residual dichloropropanol is therefore more easily directed to epoxy resin than to synthetic glycerol, because dichloropropanol in glycerol hydrolysis produces chlorinated propanediols that are difficult to separate.

These ratios are not fixed; published data for specific configurations is limited, particularly for integrated glycerin-to-ECH complexes where the same C3 backbone can be shifted between ECH export, epoxy resin, or synthetic glycerol depending on port-level netback pricing.

When Synthetic Glycerol Units Compete for ECH Supply in Aqueous Hydrolysis Networks

When synthetic glycerol demand increases from pharmaceutical or personal care buyers, ECH that would otherwise be condensed into liquid epoxy resin can be diverted to a hydrolysis unit. The hydrolysis section is usually a continuous stirred-tank cascade with 2 h to 6 h residence time and a dilute sodium hydroxide addition of 1.0 mol to 1.2 mol NaOH per mol ECH. Temperature is maintained between 80°C and 150°C to balance selectivity and byproduct formation. Selectivity to glycerol is typically 88% to 95%; the remainder is glycidol, diglycerol, and chloride-terminated oligomers. A wiped-film evaporator recovers unreacted ECH and water before ion-exchange polishing. When the NaOH:ECH molar ratio exceeds 1.2, glycidol formation increases; below 1.0, unreacted ECH carryover increases distillation load.

Production-scale failure modes associated with this configuration include accelerated corrosion of carbon steel pump casings when hot brine carries dissolved chloride. Plants therefore use 316L stainless steel or rubber-lined equipment in the hydrolysis loop. Brine recycle integration also drives the split. Epoxy resin brine can be recovered for chlor-alkali cells if total organic carbon is below 10 ppm. Synthetic glycerol brine contains glycerin and glycidol residues that can foul membranes; therefore an additional oxidation step is often required. This cost reduces synthetic glycerol’s share when chlor-alkali integration is tight.

The synthetic glycerol route is not a pure downstream sink in all contexts. In glycerin-to-ECH plants, crude glycerol is the feedstock, so synthetic glycerol from the ECH produced downstream is an economic round trip that only occurs during unusual price inversions. This circularity does not alter the technical map but explains why the synthetic glycerol demand share is comparatively small in the global ECH balance.

Epoxy Resin Chain Architecture and ECH Consumption Factors

Liquid DGEBA produced from ECH and bisphenol A is the largest demand block. The condensation is carried out with an initial ECH to bisphenol A molar ratio of 5:1 to 10:1 for liquid grades. After reaction, excess ECH is recovered by vacuum distillation at 60°C to 80°C under reduced pressure. The recovered ECH is recycled to the epoxidation reactor; a 1% loss of ECH to the brine stream represents a direct increase in ECH consumption factor and changes the downstream map by consuming supply that might otherwise be available for synthetic glycerol. Liquid standard BPA epoxy resin produced under these conditions has an epoxide equivalent weight of 182 g/eq to 192 g/eq per ASTM D1652-11 and a dynamic viscosity of 12 Pa·s to 14 Pa·s at 25°C per ISO 3219. Hydrolyzable chlorine is determined by ASTM D1726-11 and is typically held below 300 ppm for electrical and electronic grades. Solid epoxy resins are produced by chain extension with bisphenol A at lower ECH ratios, and their molecular weight is controlled by melt viscosity rather than epoxide equivalent weight.

Compounding of solid epoxy resin with mineral fillers or curing agents on twin-screw extruders with an L/D ratio of 40:1 shows that free ECH residuals above 50 ppm in the base resin contribute to surface defects in coatings because residual chlorohydrin groups initiate localized curing during storage. To avoid this, resin producers specify a maximum residual ECH of 5 ppm to 10 ppm in high-end electrical encapsulants. This constraint is separate from the synthetic glycerol boundary and reinforces the preference for integrating ECH with epoxy resin units rather than diverting to hydrolysis, because epoxy resin assets can tolerate a wider chloride input while the product is still within specification. The exact free ECH limit depends on customer-specific coating approval under 21 CFR 175.300 for indirect food contact; published data for this specific configuration is limited.

In the water treatment sector, ECH reacts with trimethylamine to form 3-chloro-2-hydroxypropyltrimethylammonium chloride, a cationic monomer that is subsequently grafted onto polyacrylamide. The process requires strict temperature control because trimethylamine addition is highly exothermic. The final monomer specification limits free ECH to 10 ppm by high-performance liquid chromatography with UV detection. This derivative consumes a smaller share of ECH than synthetic glycerol in some regions, but it can draw on inventory during municipal water treatment demand peaks. In epichlorohydrin rubber production, ECH is copolymerized with propylene oxide or allyl glycidyl ether in a solution or slurry process. Vulcanization uses thiadiazole or thiourea accelerators; the Mooney viscosity of the resulting elastomer is controlled between 30 MU and 80 MU per ISO 289-1:2015. This segment is stable but small, and it is not typically the swing destination for ECH because the polymer requires high-purity ECH with low water content.

The upstream route also shapes the downstream map. In the propylene-based allyl chloride process, the chlorination section operates with propylene to chlorine molar ratios below 5:1 to minimize diallyl ether byproducts; this yields allyl chloride that is then hypochlorinated to dichloropropanol. The resulting ECH contains traces of allyl chloride and chlorinated C3 hydrocarbons. If the ECH is sent to synthetic glycerol, these impurities are removed in the distillation train; if sent to epoxy resin, they are largely consumed or vented. In the glycerin-to-ECH process, the feedstock is crude glycerol from biodiesel, which contains methanol and fatty acid residues. The hydrogen chloride-catalyzed hydrochlorination of glycerol to dichloropropanol takes place at 90°C to 120°C with a catalyst such as adipic acid or glutaric acid. The crude ECH from this route may contain residual glycerol and glycidol, which are easier to remove in synthetic glycerol production than in epoxy resin because the hydrolysis route already includes aqueous separation of polyols. This impurity tolerance difference can shift the split toward synthetic glycerol when a glycerin-to-ECH unit is not fully integrated with bisphenol A supplies.

Storage and transfer of ECH before the downstream split impose a common set of constraints. ECH is sensitive to both acids and strong bases, which can open the epoxide ring and generate oligomeric chlorinated polyethers; this is an incompatibility with amine-based additives because residual amines initiate premature polymerization. ECH storage tanks are typically 316L stainless steel or phenolic-lined carbon steel, and nitrogen blanketing is used to exclude moisture. Water content is maintained below 500 ppm to avoid hydrolysis to 3-chloro-1,2-propanediol in storage. These constraints do not favor epoxy resin over synthetic glycerol, but they explain why downstream conversion is often integrated within the same production fence to reduce holding time and limit water ingress.