| HS Code | |
| Product Name | Ethylbenzene |
| Iupac Name | Ethylbenzene |
| Cas Number | 100-41-4 |
| Molecular Formula | C8H10 |
| Molecular Weight | 106.165 g/mol |
| Appearance | Colorless liquid |
| Odor | Aromatic gasoline-like odor |
| Boiling Point | 136.2 °C |
| Melting Point | -95 °C |
| Density | 0.8665 g/cm³ at 20 °C |
| Solubility In Water | 0.015 g/100 mL at 20 °C |
| Vapor Pressure | 0.93 kPa at 20 °C |
| Flash Point | 15 °C closed cup |
| Autoignition Temperature | 432 °C |
| Refractive Index | 1.4952 at 20 °C |
| Viscosity | 0.64 mPa·s at 20 °C |
| Logp | 3.15 |
| Un Number | UN 1175 |
| Hazard Class | 3 Flammable liquid |
| Explosive Limits | 0.8–6.7% by volume in air |
As an accredited Ethylbenzene factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Ethylbenzene is packaged in 1 L amber glass bottles with secure caps, flammability labels, and UN 1175 markings for safe transport. |
| Container Loading (20′ FCL) | Ethylbenzene (UN 1175, Class 3) in a 20′ FCL: approved drums or ISO tanks, properly secured, sealed, labeled, and IMDG-compliant. |
| Shipping | Ethylbenzene is transported as UN 1175, Ethylbenzene, Class 3 flammable liquid, Packing Group II. Shipments require approved UN packaging, flammable-liquid labels/placards, dangerous goods documentation, and trained personnel. Keep containers closed, away from ignition sources, heat, and oxidizers; follow applicable DOT, IMDG, IATA, or ADR regulations. |
| Storage | Store ethylbenzene in a cool, dry, well-ventilated area away from heat, sparks, flames, and strong oxidizers. Keep containers tightly closed, properly labeled, grounded, and inside approved flammable-liquid safety cabinets. Use secondary containment to control leaks and separate from incompatible materials. Protect from sunlight and physical damage; avoid inhaling vapors. Follow local fire-code and SDS storage requirements. |
| Shelf Life | Stable under recommended storage conditions; kept sealed, cool, dry, away from ignition sources, ethylbenzene's shelf life is typically indefinite. |
Ethylbenzene entering catalytic dehydrogenation is held to a tighter specification than solvent-grade material because polar and olefinic impurities poison the iron-oxide/potassium-oxide catalyst and accelerate coke formation. Bulk assay by ASTM D5060 gas chromatography normally requires ethylbenzene purity at or above 99.0 wt%, benzene below 0.05 wt%, total C8 aromatics and non-aromatics combined below 0.1 wt%, and carbonyl-containing impurities controlled to trace levels that do not consume the potassium promoter. The upstream ethylbenzene unit is usually integrated with a zeolite-catalysed liquid-phase alkylation of benzene with ethylene; the resulting aromatic stream is treated for water removal and trace chloride before dehydrogenation because chloride accelerates potassium migration from the iron-oxide catalyst and shortens cycle length. The dehydrogenation reaction itself operates in a radial-flow fixed-bed reactor loaded with promoted iron oxide/potassium oxide catalyst pellets, with inlet temperatures between 600°C and 640°C and outlet temperatures declining by 60–90°C as the endothermic transformation consumes heat. Steam is injected at a steam-to-ethylbenzene mass ratio between 1.0 and 2.0; this steam serves as a heat carrier, partial-pressure diluent, and coke suppressor, while steam partial pressure shifts equilibrium toward styrene. Reactor outlet pressure is held in the range 40–70 kPa absolute, typically by vacuum equipment downstream of the quench cooler, because the reaction produces two moles of gas per mole of ethylbenzene and is favoured by low pressure. Single-pass conversion is routinely held at 60–70 mol%; higher conversion in an adiabatic bed without isothermal interstage reheating accelerates thermal cracking to benzene, toluene, and fuel oil, and depresses styrene selectivity below 90 mol%. The condensed organic phase from the reactor effluent is sent to a three-column vacuum distillation train operating under polymerisation-suppressing conditions: styrene-rich streams are inhibited with 4-tert-butylcatechol or 2,4-dinitro-6-sec-butylphenol, and column bottom temperatures are kept below 110°C to prevent thermal styrene polymerisation. Recycle ethylbenzene is returned to the reactor after the styrene column; heavy ends and tar are purged continuously.
| Parameter | Typical range | Measured by / equipment |
|---|---|---|
| Ethylbenzene purity | 99.0–99.9 wt% | ASTM D5060 GC |
| Reactor inlet temperature | 600–640°C | Multipoint thermowell, radial bed |
| Reactor outlet pressure | 40–70 kPa abs | Vacuum jet/condenser |
| Steam/ethylbenzene mass ratio | 1.0–2.0 | Flow ratio controller |
| Single-pass conversion | 60–70 mol% | Online GC |
| Styrene selectivity | 90–95 mol% | Online GC |
After quench and condensation, the organic phase contains unconverted ethylbenzene, styrene, benzene, toluene, and heavy residue. The three-column vacuum distillation train separates benzene-toluene overhead, recycle ethylbenzene, and polymer-grade styrene. Because styrene polymerises rapidly above 100°C, the styrene recovery column is operated below 90–110°C bottom temperature and injected with inhibitor at concentrations typically 10–15 ppm relative to styrene. Production-scale failure modes include maldistribution from radial flow due to top-bed coking, potassium chloride fouling on quench exchangers, and polymer deposition in reboiler tubes during inhibitor pump trips. Such deposits reduce heat-transfer coefficients by more than 50% within days if the column is not shut down for hot toluene circulation. Batch-to-batch variation in ethylene feed quality maps directly to reactor pressure drop and catalyst cycle length; ethylbenzene producers monitor spent catalyst fines and reactor pressure differential continuously to schedule regeneration before the radial bed loses flow uniformity.
In propylene oxide/styrene monomer co-production, ethylbenzene is not dehydrogenated directly. It is first oxidised with air to ethylbenzene hydroperoxide, the oxidant later used to epoxidise propylene. The oxidation loop is deliberately run at low per-pass conversion, commonly 10–20 mol%, and at temperatures between 130°C and 160°C. The liquid-phase air-oxidation route is protected by a weak alkaline buffer such as sodium carbonate or sodium bicarbonate to prevent acid-catalysed decomposition of ethylbenzene hydroperoxide into acetophenone and methyl phenyl carbinol. Reactor pressure is maintained between 0.2 MPa and 0.5 MPa to keep oxygen partial pressure within a narrow band; excess oxygen accelerates byproduct formation and creates vent-stream flammability issues. Ethylbenzene hydroperoxide concentration in the oxidate is kept below roughly 25 wt% because the hydroperoxide is thermally unstable and decomposes exothermically at elevated temperature or in contact with iron and copper ions. Selectivity to ethylbenzene hydroperoxide relative to converted ethylbenzene typically sits in the 80–90 mol% range under commercial oxidation conditions, with acetophenone and methyl phenyl carbinol as the main byproducts. The epoxidation step that follows reacts ethylbenzene hydroperoxide with propylene in the presence of a transition-metal catalyst, usually a molybdenum-based complex, at propylene-to-ethylbenzene hydroperoxide molar ratios between 4:1 and 10:1, temperatures near 100–120°C, and pressures sufficient to keep propylene in liquid phase, typically 3–5 MPa. The co-product methyl phenyl carbinol is subsequently dehydrated to styrene, and the residual ethylbenzene is recycled to the oxidation section. The controlling operational boundaries are trace-metal exclusion, hydroperoxide concentration, and oxygen-to-hydrocarbon ratio; published data for catalyst-specific yield under all commercial configurations is limited because licensors keep the epoxidation catalyst formulation and aging profile restricted under license. Chemical incompatibilities include strong acids, amines, and equipment with heavy-metal contamination, which can trigger rapid hydroperoxide decomposition and pressure excursions.
Solvent-grade ethylbenzene is used in industrial coating formulations and as a component of mixed C8 aromatic solvents where its solvent strength and evaporation profile fall between toluene and xylene. The material is accepted for dilution only when the formulation's flash point remains above the site permit threshold, because ethylbenzene has a closed-cup flash point of approximately 18–23°C by ASTM D56, a boiling point of 136.2°C, and a lower explosive limit below 1 vol%. High-solids alkyd and alkyd-urethane coatings use ethylbenzene at limited addition levels, commonly 5–15 wt% of the solvent blend, to reduce brushing viscosity without shifting the evaporation rate too far into the fast-evaporation zone that causes orange peel and dry spray. Compliance with volatile organic compound limits under 40 CFR Part 59 or national equivalents requires that the ethylbenzene portion be counted as a VOC; no exemption is available for this aromatic solvent in architectural and industrial maintenance coatings. The operational boundary in practice is hazardous air pollutant content: ethylbenzene is listed in many jurisdictions as a hazardous air pollutant, and coating plants with major-source permits frequently substitute higher-flash aromatic or oxygenated solvents when total hazardous air pollutant emissions approach the permit cap. No separate polymerisation or viscosity modifier chemistry is required; addition is constrained by flash point and volatile organic compound accounting rather than resin compatibility.
In fine-chemical oxidation, ethylbenzene is converted to acetophenone and 1-phenylethanol by air or oxygen in acetic acid or benzoic acid media using soluble cobalt, manganese, and bromide catalyst systems at temperatures between 80°C and 120°C. The reaction is stopped at low ethylbenzene conversion, generally below 20 mol%, because over-oxidation produces benzoic acid, formic acid, and ring-hydroxylated species that are difficult to reject from the ketone product. The industrial separation train relies on a vacuum distillation column and an aqueous wash to remove metal salts; unconverted ethylbenzene and 1-phenylethanol are recycled or separately purified. Acetophenone from this route is used in the synthesis of photoinitiators for UV-curable coatings, pharmaceutical intermediates, and fragrance chemicals. Quality requirements for such downstream uses are tighter than solvent-grade ethylbenzene: acetophenone assay by GC is typically specified at 99.0 wt% minimum, with ethylbenzene and 1-phenylethanol each limited to 0.5 wt% maximum to avoid undesirable odour and polymerisation side-reactions. This segment is small in volume but is one of the few non-styrene merchant uses of ethylbenzene that justifies dedicated purification and peroxide-limited storage.
Where a C8 aromatic solvent is specified for resin cleanout or closed-loop heat-transfer flushing, ethylbenzene enters as a natural component of mixed xylene grades rather than as a separate addition. The limiting specifications are aromatic content by ASTM D7504, distillation range by ASTM D850 or ISO 4626, and flash point by ASTM D56. In these cleaning operations, the primary risks are vapour accumulation in confined vessels and elastomer seal swelling; use requires bonded grounding, local exhaust ventilation, and verification that tank-stripping temperatures stay below the autoignition temperature of 432°C. No fixed addition level is applied because the ethylbenzene fraction is determined by the C8 aromatic cut composition, not by formulation.
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Ethylbenzene is a monoalkyl aromatic hydrocarbon derived from benzene and ethylene; CAS registry number 100-41-4 and molecular formula C8H10 correspond to a molar mass of 106.16 g/mol. The substance appears in the EC inventory as 202-849-4 and is produced commercially by liquid-phase alkylation of benzene with polymer-grade ethylene over a zeolite-beta catalyst, followed by transalkylation of diethylbenzene and heavier polyalkylbenzenes. At 20 °C the density measured by ASTM D4052 is 0.867 g/cm³, normal boiling point is 136.2 °C, and closed-cup flash point is 15 °C under ASTM D56. Vapour pressure at 20 °C is approximately 0.93 kPa; lower and upper explosion limits in air are 0.8 vol% and 6.7 vol%. Autoignition temperature is approximately 432 °C. The compound is an aromatic solvent with log Kow of 3.15 and low aqueous solubility of about 0.015 g/100 mL at 20 °C.
Under EC 1272/2008 the harmonised classification is Flam. Liq. 2 (H225), Acute Tox. 4 (H332), Skin Irrit. 2 (H315), Eye Irrit. 2 (H319), STOT SE 3 (H335), STOT RE 2 (H373), and Asp. Tox. 1 (H304). Storage and transfer installations therefore use closed piping, nitrogen blanketing, and fixed-roof tanks with internal floating screens; filling lines are bottom-fed or dip-leg equipped to limit static charge generation. Vent streams must be controlled because the vapour space at ambient temperature can lie within the flammable range.
Analytical laboratories use certified reference material grade ethylbenzene for calibration of gas chromatographic methods under ISO 17034; this grade is supplied with certified purity values, uncertainty budgets, and traceability to SI units. Such material is distinct from industrial styrene-grade and is not used as feedstock.
Styrene-grade material is a low-olefin, low-sulfur aromatic stream intended for catalytic dehydrogenation; solvent-grade material may contain higher levels of xylenes and non-aromatics and is directed to coatings, adhesives, or chemical intermediate use. A representative styrene-grade specification requires ethylbenzene purity not less than 99.5 wt%, benzene not more than 0.05 wt%, toluene not more than 0.05 wt%, total xylenes not more than 0.10 wt%, cumene not more than 0.02 wt%, non-aromatic hydrocarbons not more than 0.10 wt%, sulfur not more than 1 mg/kg, and water not more than 150 mg/kg.
| Property | Method | Limit |
|---|---|---|
| Ethylbenzene purity | ASTM D7504 | ≥ 99.5 wt% |
| Benzene | ASTM D7504 | ≤ 0.05 wt% |
| Toluene | ASTM D7504 | ≤ 0.05 wt% |
| Total xylenes | ASTM D7504 | ≤ 0.10 wt% |
| Cumene | ASTM D7504 | ≤ 0.02 wt% |
| Non-aromatic hydrocarbons | ASTM D7504 | ≤ 0.10 wt% |
| Total sulfur | ASTM D5453 | ≤ 1 mg/kg |
| Water | ASTM E1064 | ≤ 150 mg/kg |
| Bromine index | ASTM D1492 | ≤ 10 mg Br/100 g |
Solvent-grade material may contain higher total xylenes and C9 aromatics, giving a wider distillation range under ASTM D850. These components are tolerated in coatings but can condense on dehydrogenation catalyst surfaces and increase pressure drop if the material is misdirected to styrene service. Published data for low-purity ethylbenzene cuts from pyrolysis gasoline or reformate is variable; olefinic content measured as bromine index can exceed 50 mg Br/100 g unless the stream is hydrotreated. For styrene producers, the practical effect of the specification is catalyst life. Olefins and heavy aromatics are oligomerised to coke on the dehydrogenation catalyst; sulfur and nitrogen compounds shift selectivity. Regular feed analysis by gas chromatography is therefore a production control requirement, not a regulatory formality.
Most ethylbenzene is consumed in adiabatic catalytic dehydrogenation to styrene. The reaction is equilibrium-limited and strongly endothermic. Commercial units use two or three radial-flow fixed beds loaded with iron oxide–potassium oxide catalyst promoted with cerium, molybdenum, and magnesium oxides. Inlet temperatures are held between 600 °C and 650 °C; steam-to-ethylbenzene molar ratios range from 6:1 to 12:1; absolute pressure at the reactor outlet is commonly 40–80 kPa. Single-pass conversion is typically 55–65% with styrene selectivity of 90–95 mol%. The cycle length of the catalyst is 12–24 months; potassium migration from the inlet zone reduces activity, requiring progressive inlet temperature increase. Reactor effluent is quenched and separated in a benzene-toluene recovery column, an ethylbenzene recycle column, and a styrene finishing column under vacuum. The finishing column is operated with polymerisation inhibitors such as 4-tert-butylcatechol because thermally initiated styrene polymerisation accelerates above 90 °C.
Pressure drop across each radial-flow bed is kept below 30 kPa; higher pressure drop from catalyst attrition or coke maldistributes gas flow and lowers selectivity. The dilution steam is condensed, stripped, and reused; dissolved hydrocarbons are recovered in a steam condensate stripper. Feed benzene to the alkylation unit is typically dried by azeotropic distillation or molecular sieve to below 50 mg/kg water before entering the reactor. Ethylene feed is supplied at 99.9 mol% minimum purity with acetylene and dienes removed to avoid acid-catalysed polymerisation.
In the propylene oxide/styrene monomer route, ethylbenzene is oxidized to ethylbenzene hydroperoxide at 100–150 °C and 0.2–0.5 MPa with air or oxygen. The hydroperoxide is then used to epoxidize propylene over a molybdenum-based or titanium-containing catalyst, yielding propylene oxide and 1-phenylethanol; dehydration of the alcohol produces styrene. This integrated route avoids the high steam consumption of direct dehydrogenation but imposes additional constraints on iron and copper ions, which catalyse hydroperoxide decomposition. Process piping and reactors are fabricated from passivated stainless steel, and organic acid formation is controlled by pH adjustment with sodium or calcium salts. The structural distinction from cumene is critical: cumene forms a tertiary hydroperoxide used in phenol/acetone manufacture, while ethylbenzene forms a secondary hydroperoxide that is less stable and must be held at lower conversion per pass to maintain selectivity.
In high-solids alkyd and epoxy coatings, ethylbenzene is used as a tail solvent because its evaporation rate is lower than toluene and its aromatic solvency assists wet film formation. Replacement of toluene by ethylbenzene reduces dry-spray and solvent popping at comparable thinner addition, but increases dry-to-handle time due to the 136.2 °C normal boiling point. The vapour pressure of 0.93 kPa at 20 °C places the material between toluene and xylene in evaporation profile. Formulations containing ethylbenzene are treated as volatile organic compounds under EU Directive 2004/42/EC and as hazardous air pollutants under the US Clean Air Act 42 U.S.C. §7412(b)(1). Ventilation design in coating application booths must keep vapour concentration below 20% of the lower explosion limit, corresponding to approximately 1600 ppm by volume.
| Solvent | Normal boiling point (°C) | Density at 20 °C (g/cm³) | Vapour pressure at 20 °C (kPa) | Closed-cup flash point (°C) |
|---|---|---|---|---|
| Ethylbenzene | 136.2 | 0.867 | 0.93 | 15 |
| Toluene | 110.6 | 0.867 | 2.9 | 4 |
| para-Xylene | 138.4 | 0.861 | 0.8 | 27 |
| Cumene | 152.4 | 0.862 | 0.4 | 44 |
Ethylbenzene is also used as a component in mixed xylene solvent blends for agricultural formulations and specialty adhesives, but its hazardous air pollutant status restricts formulation in architectural coatings sold in regulated jurisdictions. The low flash point requires explosion-proof pumps and electrical classification in storage areas; transfer hoses must be conductive and bonded. Unlike cumene, which is oxidized to cumene hydroperoxide for phenol and acetone, ethylbenzene has no tertiary benzylic C-H bond; its primary industrial chemistry is side-chain dehydrogenation to styrene or hydroperoxide-mediated epoxidation in the POSM process. This difference makes ethylbenzene unsuitable as a direct replacement for cumene in phenol units and cumene unsuitable for styrene units without carbon-chain rearrangement.
Ethylbenzene obtained from catalytic reforming or pyrolysis gasoline is present in mixed C8 aromatic streams. The boiling point gap between ethylbenzene and para-xylene is only 2.2 °C; the relative volatility at typical C8 splitter conditions is approximately 1.06. Commercial recovery by distillation requires 300–400 theoretical stages and reflux ratios between 50:1 and 100:1. This energy load is among the highest in a petrochemical complex. When the plant objective is para-xylene purification rather than ethylbenzene recovery, ethylbenzene is removed in the isomerization loop by catalysts that either dealkylate it to benzene or convert it to xylenes. Adsorptive separation on BaX or BaKX zeolites in simulated moving-bed units can also separate ethylbenzene from mixed xylenes by side-chain selectivity. Oxygen ingress must be excluded from the C8 splitter to prevent gum formation on tray surfaces; units are operated with nitrogen blanketing or under slight vacuum in the overhead receiver.
In liquid-phase alkylation, the zeolite-beta catalyst is sensitive to water, oxygenates, nitriles, and heavy olefins. Water above 200 mg/kg in the benzene feed hydrolyses framework aluminium and reduces acid-site density. Oxygenates such as methanol and ethanol dehydrate to light olefins, which alkylate benzene to cumene and other propylbenzene impurities. Nitrogen compounds are neutral-site poisons; feed nitrogen is controlled below 0.5 mg/kg. Amine-based corrosion inhibitors should not be injected upstream of the reactor because they neutralise acid sites. The transalkylation reactor operates at 180–230 °C and converts diethylbenzene and triethylbenzene with benzene to additional ethylbenzene. Reactor pressure is maintained at 3.5–4.0 MPa to keep the mixture in the liquid phase and retain ethylene in solution. On commercial units, feed quality excursions are first indicated by a rising cumene-to-ethylbenzene ratio in the reactor effluent and by an increase in pressure drop across the guard bed. If guard-bed pressure drop exceeds 50 kPa, the bed is bypassed and replaced to prevent flow maldistribution.
