| HS Code | 111447 |
| Chemical Formula | C7H8 |
| Cas Number | 108-88-3 |
| Molecular Weight | 92.14 g/mol |
| Appearance | Clear colorless liquid |
| Purity | 99.5 wt% minimum |
| Density | 0.866-0.870 g/cm3 at 20°C |
| Boiling Point | 110.6°C |
| Melting Point | -95°C |
| Flash Point | 4.4°C (closed cup) |
| Autoignition Temperature | 480°C |
| Vapor Pressure | 28.4 mmHg at 25°C |
| Solubility In Water | 0.52 g/L at 20°C |
| Refractive Index | 1.496 at 20°C |
As an accredited Nitration Grade Toluene factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Nitration Grade Toluene is packaged in 200-litre UN-approved steel drums with secure seals and hazard labeling for safe transport. |
| Container Loading (20′ FCL) | Load 20′ FCL with Nitration Grade Toluene (UN1294, Class 3) in approved drums/IBCs; secure, ventilate, ground, and display flammable labels. |
| Shipping | Nitration Grade Toluene is a flammable, volatile liquid shipped in dedicated isotanks, drums, or railcars. Transport requires grounding, ventilation, and segregation from oxidizers. UN 1294, Class 3, Packing Group II. Temperature-controlled handling minimizes vapor risk, while strict compliance with IMDG, ADR, or DOT regulations ensures safe delivery. |
| Storage | Nitration Grade Toluene should be stored in tightly sealed, grounded containers in a cool, dry, well-ventilated area, away from direct sunlight, heat, and ignition sources. Keep separated from strong oxidizers and acids. Use explosion-proof equipment, secondary containment, and clear labeling. Ensure compliance with local regulations and inspect containers regularly for leaks or damage. |
| Shelf Life | Shelf life is indefinite when stored properly in sealed containers, away from heat, ignition sources, and oxidizing agents. |
Continuous dinitrotoluene production from nitration-grade toluene begins with a two-stage mixed-acid nitration loop. Feedstock purity controls are not incidental: benzene above 0.05 wt% co-nitrates to nitrobenzene, which complicates later TDA distillation, while non-aromatic hydrocarbons above 0.2 wt% consume mixed acid and release oxidation heat without product value. The first nitration stage is charged at a toluene-to-nitric acid molar ratio of 1:1.02–1.10 in a mixed acid containing 25–32 wt% HNO₃, 52–60 wt% H₂SO₄, and 10–18 wt% water. After phase separation, the organic phase enters a second nitration stage at 60–80 °C; the overall toluene-to-HNO₃ molar ratio reaches 1:2.05–2.25. The 2,4-dinitrotoluene/2,6-dinitrotoluene isomer ratio is maintained at approximately 76–80:20–24 through mixed-acid activity, residence time, and temperature. The washed and neutralised DNT is hydrogenated in a continuous stirred-cell reactor over supported nickel catalyst at 90–120 °C and 20–30 bar hydrogen partial pressure; reaction enthalpy is removed through an external loop heat exchanger. Toluene diamine, after solvent recovery, is phosgenated in o-dichlorobenzene at 130–180 °C and refined by vacuum distillation to TDI.
Compliance for the TDI portion of this chain is anchored to REACH Annex XVII Entry 56, which requires training prior to industrial or professional use of diisocyanates, and to EU Regulation (EU) 2020/1149. Free TDI monomer in urethane resins is determined according to ISO 10283:2007; finished flexible foam mechanical properties are assessed under ASTM D3574-17, while compression set data are generated according to ISO 3386-1:2015. In downstream slabstock foam formulation, TDI 80/20 is metered at 32–55 parts per hundred parts of polyether polyol, with water at 2.0–5.0 parts per hundred polyol and a TDI index of 100–115. Raising water from 2.0 to 5.0 pphp lowers foam density from approximately 28–32 kg/m³ to 12–18 kg/m³ while increasing urea content and hard-segment concentration; below 2.0 pphp water, processing viscosity and exotherm become difficult to control on continuous slabstock lines.
On production-scale continuous nitration units, the most frequent failure mode occurs in the second-stage reactor when spent acid entrainment from the first-stage settler carries residual mononitrotoluene at more than 0.5 wt%. The resulting uncontrolled exotherm can exceed 10 K/min, requiring automatic quench and pressure relief; settler residence time is therefore specified at 30–45 min and mixed-acid recycle flow is interlocked with reactor temperature. DNT hydrogenation catalyst is poisoned by sulfur-bearing impurities above 5 ppm; nitration-grade toluene with a sulfur content at or below 1 ppm is preferred for this derivative chain. Premature contact between TDI and tertiary amine catalyst at high concentration must also be avoided because uncontrolled polyurea formation raises local viscosity and can plug mixing heads.
Terminal products derived from this route include flexible slabstock foams for bedding and furniture, high-resilience moulded foams for automotive seating, viscoelastic foams for damping and mattress cores, and CASE systems such as two-component polyurethane adhesives, sealants, and cast elastomers.
In civil blasting service, nitration-grade toluene is carried through a three-stage mixed-acid sequence to 2,4,6-trinitrotoluene. The processing window is narrower than DNT manufacture because the final nitration requires very low water activity and higher sulfuric acid strength, while overall heat release per mole of nitric acid consumed increases. Stage one mononitration is run at 30–40 °C with a mixed acid containing 25–30 wt% HNO₃ and 52–60 wt% H₂SO₄. Stage two dinitration is run at 60–80 °C, and stage three trinitration is run at 90–110 °C in a mixed acid containing 35–40 wt% HNO₃ and 60–70 wt% H₂SO₄. The overall toluene-to-nitric acid molar ratio is maintained at 1:3.10–3.25. Each stage includes independent phase separation vessels; spent acid from stage three is concentrated and blended into earlier stages. Crude TNT is purified by sulfitation with sodium sulfite at 80–90 °C, which converts unsymmetrical TNT isomers into water-soluble sulfonates, then flaked on a water-jacketed drum flaker.
| Stage | HNO₃ wt% | H₂SO₄ wt% | H₂O wt% | Temperature |
|---|---|---|---|---|
| Mononitration | 25–30 | 52–60 | 12–18 | 30–40 °C |
| Dinitration | 30–35 | 58–65 | 5–10 | 60–80 °C |
| Trinitration | 35–40 | 60–70 | 0–5 | 90–110 °C |
Regulatory compliance for civil TNT-based explosives is defined by UN Model Regulations classification as UN 0209, Class 1.1D, and by EU Directive 2014/28/EU for making civil explosives available on the market. Major hazard plant siting is controlled under Directive 2012/18/EU (Seveso III). In downstream booster manufacture, TNT is compounded at 40–100 wt% depending on product class; Amatol-grade castings use 50–60 wt% TNT with 40–50 wt% ammonium nitrate. Crude TNT congealing point is monitored because residual unsymmetrical TNT isomers above 0.2 wt% depress the congealing point below 80.2 °C and cause exudation in finished castings. Batch-to-batch variance is commonly traced to sulfitation inefficiency or spent-acid recycle containing nitrous acid above 0.1 wt%, which also increases nitrobenzoic acid by-product carryover.
Terminal product types include cast boosters for ANFO and emulsion columns, detonating cord cores, seismic exploration charges, and underwater blasting charges used in quarrying, road construction, and mine development.
Continuous mononitration of nitration-grade toluene at 30–40 °C with a toluene-to-nitric acid molar ratio of 1:1.02–1.08 produces an isomer mixture consisting of 56–60% ortho-nitrotoluene, 38–40% para-nitrotoluene, and 2–5% meta-nitrotoluene. Ortho-nitrotoluene is separated by vacuum distillation because its boiling point differential from the para isomer is approximately 16–18 K at reduced pressure; the meta/para pair is separated by fractional crystallisation after an initial distillation cut. The ortho stream is hydrogenated to o-toluidine in a continuous fixed-bed reactor over copper or palladium catalyst at 150–250 °C and 5–25 bar hydrogen partial pressure; the para stream is reduced to p-toluidine under similar conditions. Diazo coupling of o-toluidine or p-toluidine derivatives with β-naphthol or acetoacetarylide components proceeds at a stoichiometric ratio of 1:1 based on free amine; residual free amine in the product press cake is typically controlled below 500 ppm to meet dye purity specifications.
Regulatory compliance for o-toluidine operation requires closed-loop handling under CLP (EC) No 1272/2008 Carcinogen 1B classification; workplace exposure monitoring plans are aligned with Directive 98/24/EC and national occupational exposure limit frameworks. For p-toluidine-derived dye intermediates, compliance with EU Regulation (EC) No 1907/2006 (REACH) is required, and finished azo pigments are tested for aromatic amine release under EN 14362-1:2017 for textile applications. A rise of 5 °C above the mono-stage setpoint increases meta-isomer production and reduces ortho/para yield, which depresses distillation capacity and alters downstream diazonium salt stoichiometry.
Terminal product categories include azo pigments for printing inks, industrial coatings, plastics, and textile dyestuffs, as well as p-toluidine-based intermediates for agrochemical active substances and pharmaceutical building blocks.
At the para-enriched distillate cut from mononitrotoluene separation, air oxidation under cobalt-manganese acetate catalysis converts p-nitrotoluene to p-nitrobenzoic acid. This oxidation is performed in a bubble column reactor at 120–160 °C and 0.5–1.0 MPa air partial pressure in acetic acid; the cobalt/manganese catalyst system is typically charged at 0.5–1.5 wt% total metal acetate relative to p-nitrotoluene, with a bromide promoter concentration below 0.5 wt%. Off-gas oxygen concentration is maintained below 8 vol% to avoid flammable vapour-air mixtures. The product is crystallised by water dilution and filtered; selectivity to p-nitrobenzoic acid can exceed 90% under optimised residence time, with p-nitrobenzaldehyde as the principal intermediate impurity.
Residual solvent control in subsequent p-aminobenzoic acid and ester-type active pharmaceutical ingredients follows ICH Q3C (R8), where acetic acid is assigned to Class 3. Reduction of p-nitrobenzoic acid to p-aminobenzoic acid is carried out via catalytic hydrogenation over palladium or via iron-acid reduction; the choice of route affects residual metal limits that are monitored under ICH Q3D. Esterification consumes p-aminobenzoic acid on a 1:1 molar basis with ethanol or 2-diethylaminoethanol to yield benzocaine or procaine; the alcohol component is charged at a molar excess of 5–15 mol% to drive conversion. Acetic acid recovery must keep water below 5 wt%, otherwise catalyst metal segregation and reactor wall deposition reduce conversion and increase p-nitrobenzaldehyde carryover.
Terminal product categories include topical local anesthetics, injectable local anesthetics, veterinary pharmaceutical formulations, and p-aminobenzoic acid-derived dye and polymer additives.
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Nitration-grade toluene is the low-benzene, low-nonaromatic, low-sulfur aromatic feedstock qualified under ASTM D841-21 for mixed-acid nitration. The substance is toluene, CAS 108-88-3, EC 203-625-9, C₇H₈, molecular weight 92.14 g/mol. Supplier-specific model identifiers are not harmonized; representative product codes include TOL-NG-99.5, Nitration Grade Toluene 99.5%, and TDI Feedstock Toluene, but each designation refers to the same aromatic cut controlled for benzene, sulfur, and close-boiling nonaromatic hydrocarbons. The grade is produced from reformate or pyrolysis gasoline by extractive distillation or selective hydrogenation, followed by distillation to a narrow boiling range. Unlike solvent-grade toluene, which may be released with comparatively broad aromatic purity, the nitration-grade material is specified so that impurities cannot enter the nitrator, consume nitric acid, or degrade isomer separation.
Release testing on production-scale storage tanks routinely includes toluene assay by ASTM D6526, benzene by ASTM D7504, trace nonaromatic hydrocarbons by ASTM D2360, total sulfur by ASTM D5453, acid wash color by ASTM D848, density by ASTM D4052, and distillation range by ASTM D1078. Water in bulk shipments is controlled below 0.03 wt% by Karl Fischer titration, typically ASTM D1364, because water entering the mixed-acid system dilutes the sulfuric acid dehydration strength. The product is stored as a flammable liquid in fixed-roof or internal floating-roof tanks under nitrogen blanketing where air permit conditions require it. Transfer pumps and loading arms are bonded and grounded, and the material is segregated from nitric acid and mixed-acid charging systems until the feed tank is positively released.
Distillation behaviour is the principal physical distinction. The narrow boiling interval around the toluene normal boiling point of 110.6°C excludes co-boiling paraffins and naphthenes that otherwise remain in solvent-grade material. In a continuous nitration train, methylcyclohexane and dimethylhexane species absorb heat of dilution and can undergo oxidative side reactions with mixed acid; their removal reduces spent-acid organic loading. The 1.0°C max range in ASTM D841-21 is therefore not a routine purity marker but a process-control limit that prevents accumulation of nonaromatic diluents in the recycle acid loop. Table 1 cross-references the standard limit, method, and typical release envelope for tank-car quantities.
| Property | ASTM D841-21 limit | Test method | Typical release range |
|---|---|---|---|
| Toluene assay | ≥ 99.0 wt% | ASTM D6526 | 99.5–99.8 wt% |
| Benzene | ≤ 0.05 wt% | ASTM D7504 | 0.01–0.04 wt% |
| Nonaromatic hydrocarbons | ≤ 1.5 wt% | ASTM D2360 | 0.3–1.0 wt% |
| Total sulfur | ≤ 1 mg/kg | ASTM D5453 | <0.5 mg/kg |
| Acid wash color | ≤ 2 | ASTM D848 | ≤ 1 |
| Density at 20°C | 0.869–0.873 g/cm³ | ASTM D4052 | 0.870–0.872 g/cm³ |
| Distillation range | max 1.0°C, including 110.6°C | ASTM D1078 | 0.7–0.9°C |
In a production-scale continuous mononitrotoluene unit, nitration-grade toluene is metered into a recirculated mixed-acid stream. The reactor is typically a loop nitrator with external heat removal; the toluene feed nozzle is placed at the suction side of the recirculation pump to generate high-shear dispersion. Mixed acid contains nitric acid, sulfuric acid, and water, with sulfuric acid acting as the dehydrating agent and nitronium-ion activity regulator. Operating temperature is held between 30°C and 45°C because reaction rate, isomer distribution, and by-product formation are sharply temperature-sensitive. The resulting mononitrotoluene distribution is approximately 56–58% ortho, 38–40% para, and 2–4% meta. Spent acid is separated, extracted with fresh toluene to recover organics, and reconcentrated for recycle.
The ortho isomer is the precursor for 2,4-dinitrotoluene and 2,6-dinitrotoluene after second-stage nitration; the para isomer is used for dyes, agrochemicals, and specialty amines, while the meta isomer is processed as a minor co-product. The nitration-grade feedstock has a direct influence on the distillation train because benzene entering the feed is nitrated to nitrobenzene. The downstream separation of o-nitrotoluene must then remove a low-boiling impurity that can co-distill at the top of the ortho column.
In the subsequent dinitration stage, purified ortho-mononitrotoluene is contacted with a second mixed-acid system to produce the 80:20 2,4-/2,6-dinitrotoluene isomer mixture typical for TDI. This second nitration operates at higher acid strength and slightly higher temperature. Impurities from the first stage, including nitrobenzene or incomplete removal of para-MNT, can influence the isomer ratio and become embedded in the DNT product. Hydrogenation of DNT to toluene diamine uses supported nickel or palladium catalysts in slurry or fixed-bed reactors. Feed sulfur is controlled below 1 mg/kg because sulfur compounds can persist through nitration and contribute to catalyst poisoning if not removed in DNT washing.
Batch-to-batch variance in nitration-grade feed is normally observed in nonaromatic content rather than toluene assay. A shift of 0.5 wt% in nonaromatics can alter emulsion settling rates and increase organic carryover into spent acid. The nonaromatic limit in ASTM D841-21 is therefore enforced at the feed tank rather than at the nitrator. This is the main production-scale penalty for using solvent-grade material: the unit may still operate, but heater cleaning, exchanger tube replacement, and acid bleed become more frequent. The documented control point is not only toluene purity but also the absence of low-level contaminants that survive neutralization and wash steps.
Benzene in toluene feed is nitrated to nitrobenzene under the same mixed-acid conditions. The boiling point of nitrobenzene is 210.9°C, compared with 222.0°C for o-nitrotoluene, 232.6°C for m-nitrotoluene, and 238.3°C for p-nitrotoluene. In the o-MNT column, nitrobenzene appears as a front-end contaminant rather than a heavy impurity, so it does not simply leave as bottom residue. Full removal requires additional rectification stages, increased reflux, and a dedicated light-ends draw. When benzene in feedstock exceeds 0.05 wt%, the accumulated nitrobenzene load in the MNT fractionation train rises rapidly because the feed impurity is quantitatively nitrated at high conversion.
The same nitrobenzene contaminant is carried into dinitration if the MNT cut is not tightly distilled. During DNT hydrogenation to toluene diamine, residual nitrobenzene can be hydrogenated to aniline, adding an amine impurity that is difficult to separate before phosgenation. The practical limit is therefore an upstream raw-material specification, not only an analytical preference. Production-scale MNT isomer columns are typically operated under vacuum to keep reboiler temperatures low; the relative volatility between nitrobenzene and o-MNT is small enough that even 0.1 wt% benzene in feed shifts column profiles and reduces ortho product recovery at the same production rate.
Mixed-acid nitration of toluene releases substantial heat and is sensitive to local mixing. Continuous reactors use external coolers, recirculation loops, and tube-and-shell exchangers with defined heat-transfer area per unit volume. Below 30°C, the reaction rate is low and phase transfer may limit conversion; above 45°C, the rate of dinitrotoluene formation and oxidative side reactions increases sufficiently to change product distribution and spent-acid colour. The temperature ceiling is not an arbitrary shelf-life matter. In an adiabatic stirred cell, a loss of cooling at high acid strength can generate a self-heating excursion, leading to polynitration, NOx evolution, and organic phase decomposition.
Continuous nitrators are fitted with external circulation pumps rated for strong acid service, typically high-silicon stainless steel or lined carbon steel. The heat exchanger is commonly designed for a temperature approach of 10–15°C between process acid and cooling water to maintain the nitration temperature below 45°C. At feed rates above design, the limiting unit operation is often the acid cooler rather than the reactor itself. Spent acid from the nitrator is passed to a vacuum concentrator to restore sulfuric acid strength to 70 wt% or higher. If the toluene feed contains excessive nonaromatic hydrocarbons, oxidation products accumulate in the acid recycle loop and increase the fouling rate of heat exchangers and column trays.
The differences between nitration-grade and solvent-grade material are best evaluated by specification overlap. Solvent-grade toluene may show a high toluene assay while still failing nitration because the measured high purity does not distinguish benzene and sulfur at levels that are tolerable in coatings but harmful in mixed-acid nitration. Reagent-grade material may meet or exceed the purity test, but its drummed logistics, small batch scale, and cost structure do not support continuous TDI-scale operations. Table 2 presents representative grade profiles for comparison; solvent-grade limits vary by supplier and are not governed by the same ASTM D841 requirements.
| Parameter | Nitration Grade ASTM D841-21 | Industrial/Solvent Grade | Reagent Grade |
|---|---|---|---|
| Toluene assay | ≥ 99.0 wt% | 98.0–99.0 wt% | ≥ 99.5 wt% |
| Benzene | ≤ 0.05 wt% | 0.05–0.10 wt% | ≤ 0.05 wt% |
| Nonaromatic hydrocarbons | ≤ 1.5 wt% | 1.0–2.5 wt% | ≤ 0.5 wt% |
| Total sulfur | ≤ 1 mg/kg | 2–5 mg/kg | ≤ 1 mg/kg |
| Water | ≤ 0.03 wt% | ≤ 0.05 wt% typical | ≤ 0.03 wt% |
| Primary use | Mixed-acid nitration to MNT/DNT/TDI | Coatings, cleaning, blending | Analytical reference, specialty synthesis |
The critical substitution risk is benzene carryover. A solvent-grade tank with 99.0 wt% toluene assay and 0.10 wt% benzene can appear equivalent by simple GC purity but will double the nitrobenzene load in the MNT unit. Nonaromatic hydrocarbons above 1.5 wt% also reduce nitrator throughput by occupying reactor volume and increasing acid-phase organic loading. Thus the product specification for nitration-grade toluene is defined by the negative potential of trace impurities, not by the toluene assay alone.
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