Products
Products
Products
| HS Code | 815210 |
| Chemical Name | Paraxylene |
| Cas Number | 106-42-3 |
| Chemical Formula | C8H10 |
| Appearance | Colorless liquid |
| Odor | Sweet aromatic odor |
| Solubility In Water | Slightly soluble |
As an accredited Paraxylene factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Paraxylene supplied in 20-metric-ton ISO tank containers, ensuring safe and efficient bulk transport. |
| Container Loading (20′ FCL) | Load 20′ FCL with approved UN drums/IBCs of Paraxylene, upright, secure, ventilated, segregated from oxidizers, per hazardous chemical regulations. |
| Shipping | Paraxylene, a flammable liquid, ships in dedicated ISO tank containers or heated tankers. Transport requires UN 1307, Class 3 hazard labeling, and strict moisture exclusion to prevent contamination. Proper grounding and ventilation are essential during loading, discharge, and transit to manage vapor risks and ensure safe, compliant delivery. |
| Storage | Paraxylene should be stored in tightly sealed, grounded containers or stainless steel/carbon steel tanks under a nitrogen blanket. Keep in a cool, dry, well-ventilated area away from heat, sparks, and open flames. Use proper bonding and spill containment. Avoid contact with strong oxidizers. Monitor temperatures and ensure compliance with hazardous material regulations. |
| Shelf Life | Paraxylene has a shelf life of 24 months when stored properly in sealed containers, away from heat, ignition sources, and oxidizers. |
Continuous air oxidation of paraxylene in acetic acid at 150–205 °C and total pressure between 0.9 MPa and 2.5 MPa remains the dominant downstream route to purified terephthalic acid (PTA) for polyester staple fibre and filament spinning. Incoming merchant paraxylene is assessed under ASTM D5211; typical supply specifications require 99.7 wt% minimum p-xylene with ethylbenzene and m-xylene held below 0.25 wt% because C8 impurities contribute to colour bodies and 4-carboxybenzaldehyde precursors during oxidation. The p-xylene-to-acetic acid mass ratio is maintained between 1:3 and 1:5, while the Co/Mn/Br catalyst package is charged as cobalt acetate, manganese acetate, and sodium bromide at a cobalt-to-manganese weight ratio of 0.5:1 to 3:1 and a bromide-to-metals molar ratio of 1:1 to 3:1. Published data for the line-specific optimum under varying solvent dehydration rates is limited; start-up relies on off-gas CO₂-to-CO ratio trending rather than a single fixed catalyst composition. The oxidation train typically consists of a titanium-lined continuous stirred tank reactor, air sparger ring, external heat exchanger, and overhead reflux condenser; residence time is held between 60 min and 120 min. Exothermic heat removal depends on acetic acid vaporisation, and temperature excursions above 210 °C accelerate p-xylene combustion and raise 4-CBA in crude terephthalic acid. Crude terephthalic acid is then hydrogenated over a Pd/C fixed bed at 250–290 °C and 0.3–1.0 MPa to reduce 4-CBA below 25 ppm, followed by crystallisation, centrifugation, and rotary vacuum drying. Finished staple and filament are classified under ISO 2076 and are routinely tested against OEKO-TEX Standard 100 Class I for skin-contact apparel. Terminal product types cover polyester staple fibre, continuous filament, high-tenacity tyre cord yarn, and thermal-bond bicomponent fibre; fibre-grade PTA must meet bulk density, 4-CBA, and particle size requirements prescribed by the receiving polyester polymerisation unit.
When paraxylene-derived PTA is fed to a continuous esterification train, the PTA-to-ethylene glycol molar ratio is controlled between 1:1.15 and 1:1.40, with isophthalic acid blended at 1.0–3.0 wt% to suppress crystallisation and diethylene glycol present at 1.0–1.5 wt% in the final copolymer. Melt-phase polycondensation uses antimony trioxide at 190–250 ppm Sb, a cobalt acetate toner at 10–50 ppm Co, and a phosphoric acid stabiliser to raise intrinsic viscosity to 0.60–0.65 dL/g before pelletising; final bottle-grade intrinsic viscosity of 0.80–0.85 dL/g is obtained by solid-state polymerisation at 170–210 °C under nitrogen dew point below -40 °C. Food-contact compliance is governed by FDA 21 CFR 177.1630 and EU 10/2011, with residual acetaldehyde below 3 mg/kg in the blown preform, as measured by headspace gas chromatography. The production line includes continuous esterification at 240–270 °C and 0.2–0.4 MPa, followed by pre-polycondensation and finisher reactors at vacuum below 1 mbar. The solid-state polymerisation reactor typically uses a cylindrical moving-bed vessel with nitrogen residence time of 8–16 h; pellet size 2.5–3.5 mm and fines content below 0.1 wt% are controlled to prevent channelling. Terminal products include carbonated soft drink bottles, still water containers, aseptic liquid packaging, and hot-fill containers, with preform injection pressures between 80 MPa and 120 MPa on reciprocating screw injection moulding machines.
In biaxially oriented film extrusion, film-grade PET from paraxylene-sourced PTA is polymerised at a PTA-to-EG molar ratio of 1:1.15 to 1:1.35 and an intrinsic viscosity limited to 0.60–0.68 dL/g, because higher IV raises melt viscosity and draw stress in the transverse direction. Compliance for flexible food packaging is governed by FDA 21 CFR 177.1630 and EU 10/2011 overall migration limits; mechanical properties are tested under ASTM D882 and haze under ASTM D1003. The melt extrusion is conducted through a T-die onto a chill roll at 15–30 °C to produce an amorphous cast sheet with thickness 180–300 µm before sequential stretching; machine-direction draw ratio is 2.5–4.0 at 85–105 °C, and transverse-direction draw ratio is 3.0–4.5 at 105–125 °C. Silica antiblock particles are added at 0.05–0.5 wt% to control roll blocking and winding friction, while heat setting at 180–230 °C with 1–5% relaxation crystallises the film and locks orientation. Production-scale issues include die-line build-up from degraded PET gel and non-uniform transverse thickness exceeding ±2%, which creates wrinkles in the winder. Terminal product types include flexible packaging, lidding film, photovoltaic backsheet core layers, release liner, and optical-grade display film.
Adoption of non-phthalate plasticiser production routes has moved paraxylene-sourced PTA into direct esterification with 2-ethylhexanol to form dioctyl terephthalate. The molar feed ratio of 2-ethylhexanol to PTA is held between 2.05:1 and 2.30:1, with titanium tetrabutoxide added at 50–200 ppm Ti based on PTA to accelerate esterification; excess alcohol is recovered by stripping at 180–220 °C under vacuum below 10 mbar. Esterification is run at 180–230 °C in a stainless-steel or glass-lined reactor with nitrogen sparge and a distillation column for water removal, continuing until the acid value falls below 0.1 mg KOH/g. The crude ester is neutralised with 3–5 wt% sodium carbonate solution, washed to remove titanium residues, steam-stripped, and polished through a plate-and-frame filter to a moisture content below 0.05 wt%. Dioctyl terephthalate is not classified under REACH phthalate restrictions and meets EU 10/2011 overall migration testing for flexible food-contact PVC; final product is assayed by gas chromatography for 2-ethylhexanol below 100 mg/kg. Terminal finished product types include PVC wire and cable compounds, automotive interior skins, artificial leather, flooring, and plastisol formulations where phthalate-free labelling is required.
During the transesterification of paraxylene-derived dimethyl terephthalate with 1,4-butanediol, the DMT-to-BDO molar ratio is maintained between 1:1.4 and 1:1.8, using tetrabutyl titanate at 50–150 ppm Ti. The transesterification stage is operated at 150–200 °C under atmospheric pressure to strip methanol, with formation of tetrahydrofuran controlled below 0.8 wt% of reactor mass by maintaining a slight BDO excess and limiting residence time above 200 °C. Polycondensation follows at 245–255 °C under vacuum below 0.5 mbar in a horizontal disc-ring finisher, raising intrinsic viscosity to 0.80–1.20 dL/g for injection moulding grades. Compliance for electrical and electronic parts invokes UL 94 V-0 in glass-filled compounds and ISO 1133-1:2022 for melt flow rate; mechanical data are generated under ASTM D638 and ISO 527. Production bottlenecks on twin-screw compounding lines with L/D 40:1 and side feeding arise when undried PBT pellets above 0.03 wt% moisture hydrolyse the polymer, producing a melt flow shift; therefore pre-drying at 120–130 °C for 4–6 h is required. Glass fibre reinforcement at 30 wt% raises tensile strength to the range of 110–140 MPa depending on coupling agent, while unfilled PBT remains below 60 MPa. Terminal product types include automotive connectors, relay housings, sensor brackets, electronic control unit enclosures, and industrial fibre applications.
Terephthaloyl chloride derived from paraxylene is polymerised with p-phenylenediamine in N-methyl-2-pyrrolidone containing calcium chloride at 5–10 wt% to produce poly(p-phenylene terephthalamide) for high-performance fibre. The PPD-to-TPC stoichiometry is maintained at 1:1.000 within a tolerance of ±0.001 mol%; deviations of 0.2 mol% or more reduce inherent viscosity below the required 5.5 dL/g for spinning. Polymerisation is carried out under nitrogen at 0–5 °C in a high-shear mixer, with polymer solids content between 10 wt% and 18 wt%. The resulting anisotropic dope is spun through a dry-jet wet spinning die into a water coagulation bath at 5–15 °C, followed by washing, neutralisation, and hot drawing at 450–550 °C. Filament tensile properties are tested under ASTM D7269 and ballistic performance under NIJ 0101.06; workplace exposure is controlled under national occupational exposure limits for NMP and TPC. Finished product types include para-aramid yarn for ballistic vests, cut-resistant gloves, optical fibre strength members, automotive friction linings, and composite reinforcement. The process is constrained by NMP recovery and the need to exclude moisture from TPC storage; TPC is stored in nitrogen-blanketed vessels to prevent hydrolysis to terephthalic acid, which would disrupt stoichiometry.
Competitive Paraxylene prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615365186327 or mail to sales3@ascent-chem.com.
We will respond to you as soon as possible.
Tel: +8615365186327
Email: sales3@ascent-chem.com
Flexible payment, competitive price, premium service - Inquire now!
Paraxylene, systematically 1,4-dimethylbenzene (CAS 106-42-3), is a C8 aromatic hydrocarbon with a molecular formula C8H10, molar mass 106.17 g/mol, normal boiling point 138.35°C at 101.325 kPa, freezing point 13.26°C, and liquid density 0.861 g/cm³ at 20°C. The material is produced in integrated aromatics complexes from catalytic reformate, pyrolysis gasoline, toluene disproportionation, transalkylation, and xylene isomerization. Because the boiling-point separation between paraxylene and meta-xylene is only 0.75°C, commercial isolation relies on selective adsorption or fractional crystallization rather than ordinary distillation. The dominant derivative application is catalytic oxidation to purified terephthalic acid for polyester resin and fiber; dimethyl terephthalate is a smaller-volume esterification route. Paraxylene does not carry a discrete “model” designation in the manner of formulated products; instead, commercial supply is defined by grade names such as polymer-grade paraxylene or technical-grade paraxylene, with impurity ceilings referenced to standards such as ASTM D5136. At 20°C the vapor pressure is approximately 1.2 kPa, and the closed-cup flash point is approximately 27°C, placing the liquid in GHS flammable liquid category 3. Production-scale PTA-aromatics complexes often operate single-train paraxylene units above 1,000,000 tonnes/year, with adsorption separation and xylene isomerization integrated to maximize para-xylene yield.
Integrated production of paraxylene begins with removal of ethylbenzene and ortho-xylene by superfractionation, followed by isomerization of the meta-xylene-rich stream toward the thermodynamic para-xylene equilibrium. At typical xylene isomerization temperatures, the para-xylene fraction at equilibrium is approximately 22–24 mol% of the C8 aromatic pool; therefore, the separation and recycle loop must process several times the net paraxylene production. Toluene disproportionation over shape-selective ZSM-5 type catalyst can produce a para-enriched mixed xylene stream, but it also co-produces benzene and must be balanced with transalkylation of C9 aromatics. This integration determines the impurity profile entering the separation unit and explains why ethylbenzene is removed before adsorption rather than allowed to accumulate in the recycle loop.
Polymer-grade paraxylene is specified by the concentrations of isomeric and nonaromatic impurities rather than by a single boiling-point or density value. Under ASTM D5136, high-purity p-xylene is commonly controlled to a minimum p-xylene content of 99.7 wt%; producer certificates of analysis often report 99.8–99.9 wt% p-xylene, total C8 aromatic impurities below 0.20 wt%, nonaromatics below 0.10 wt%, and C9+ aromatics below 0.05 wt%. Technical-grade paraxylene may be offered at 99.0 wt% minimum p-xylene for applications in which the downstream unit includes additional purification or where the solvent-use specification tolerates higher impurity levels.
| Parameter | Reference basis | Polymer-grade limit | Technical-grade limit |
|---|---|---|---|
| p-Xylene content | ASTM D5136 | ≥99.7 wt% | ≥99.0 wt% |
| Total C8 aromatic impurities | Producer certificate | ≤0.30 wt% | ≤1.0 wt% |
| Ethylbenzene | Producer certificate | ≤0.10 wt% | ≤0.30 wt% |
| Nonaromatics | Producer certificate | ≤0.10 wt% | ≤0.20 wt% |
| C9+ aromatics | Producer certificate | ≤0.05 wt% | ≤0.10 wt% |
| Color, Pt-Co | ASTM D1209 | ≤10 | ≤20 |
The distinction between polymer-grade and technical-grade material is not merely commercial; it determines the oxidation reactor’s steady-state impurity inventory. In a continuous PTA oxidation train using acetic acid solvent, air as the oxidant, and a Co/Mn/Br homogeneous catalyst at 150–205°C and 1.5–3.0 MPa, ethylbenzene and nonaromatic hydrocarbons can raise the demand for oxygen and increase the rate of acetic acid combustion to carbon oxides. Heavy C9+ aromatics may accumulate in the solvent-recovery loop and deposit on column reboilers. Free water is specified as absent because it accelerates corrosion in carbon steel storage and transfer systems. Because supplier certificates are not uniform globally, the purchase specification must state the test method for each limit; ASTM D5136 provides a consensus reference for high-purity material but not for all technical-grade solvent applications.
Commercial paraxylene separation does not use conventional distillation for p-xylene/meta-xylene splitting. The two dominant production-scale routes are simulated moving-bed adsorption and fractional crystallization. Adsorption units, such as the UOP Parex process and the Axens Eluxyl process, use a zeolitic adsorbent with a rotary valve or sequential manifold to simulate countercurrent movement of the C8 aromatic feed and desorbent. A typical Parex unit may sequence feed, desorbent, extract, and raffinate streams through 24 adsorbent beds; the extract side contains a p-xylene-rich stream that is fractionated to remove desorbent and yield polymer-grade p-xylene. Recovery in a well-optimized adsorption unit can exceed 97% of the p-xylene in the feed, and the extract purity can be held above 99.7 wt% if the feed has been properly distilled to remove lighter and heavier hydrocarbons. The rotary valve must maintain hydraulic sequencing within a few seconds, because flow irregularities result in extract and raffinate cross-contamination. Desorbent recovery is performed in separate extract and raffinate distillation columns, and vacuum or low-pressure operation limits thermal stress on the desorbent.
Fractional crystallization exploits the freezing-point difference between p-xylene (13.26°C) and meta-xylene (−47.9°C) by chilling the mixed xylene stream to selectively solidify p-xylene. Single-stage crystallization is insufficient for polymer-grade product because meta-xylene and ortho-xylene can be occluded in the crystal mass; multi-stage crystallizers with countercurrent washing and partial remelting are therefore used. Crystallization is less sensitive to ethylbenzene content than some adsorption systems, but it is more energy-intensive at low p-xylene concentration and may require scraped-surface exchangers to manage solid-liquid separation. Integrated aromatics complexes often combine selective adsorption with crystallization to debottleneck capacity or to recover p-xylene from isomerate streams that have an unfavorable para-xylene equilibrium concentration. The process technology, not the chemical product, functions as the “model” in licensing agreements; licensors provide performance guarantees around purity, recovery, and utilities.
Unlike ortho-xylene, which is converted mainly to phthalic anhydride for plasticizers and unsaturated polyester resins, paraxylene is withdrawn from the C8 aromatic pool almost exclusively as a polyester-chain monomer feedstock. The isomeric differences are not limited to downstream chemistry; they also determine physical separation options. Ethylbenzene boils at 136.2°C, meta-xylene at 139.1°C, paraxylene at 138.35°C, and ortho-xylene at 144.4°C, so only ethylbenzene and ortho-xylene can be separated by efficient superfractionation from the mixed xylene fraction. Paraxylene and meta-xylene differ by only 0.75°C in boiling point, which is below the economic stage count for industrial distillation. Meta-xylene is primarily oxidized to isophthalic acid for copolymerized PET and alkyd resins; ortho-xylene is oxidized to phthalic anhydride; ethylbenzene is dehydrogenated to styrene for polystyrene and ABS. Paraxylene therefore occupies the highest-volume C8 aromatic derivative route, because its oxidation product terephthalic acid is one of the two acid monomers in polyethylene terephthalate. Mixed xylenes used as solvent do not require this isomeric purity; separation of p-xylene from the pool simultaneously upgrades the remaining raffinate for gasoline blending or hydrodealkylation to benzene, which changes the product specification requirements for each stream.
In the PTA oxidation train, p-xylene is oxidized by air in acetic acid at 150–205°C and 1.5–3.0 MPa using a homogeneous cobalt/manganese/bromine catalyst. The conversion proceeds stepwise through p-toluic acid and 4-carboxybenzaldehyde (4-CBA); residual 4-CBA in crude terephthalic acid is the principal impurity that must be eliminated in the hydrogenation purification section. If the paraxylene feed contains ethylbenzene, the ethyl side chain introduces side-chain oxidation products and can shift the oxygen-to-product stoichiometry; this increases the carbon oxide yield in the off-gas and raises the purification hydrogen requirement per tonne of PTA. Meta-xylene impurity oxidizes to isophthalic acid, which can remain in the PTA product and modify the melting and crystallization behavior of the polyester; ortho-xylene yields phthalic acid, which similarly becomes a chain stopper or copolymer impurity in PET. Nonaromatic hydrocarbons are largely converted to carbon oxides and water, but their presence reduces the partial pressure of oxygen in the reactor and can lower the effective oxidation rate. These impurity pathways explain why polymer-grade paraxylene limits are set at the sub-one-percent level: the PTA process cannot economically purge isophthalic, phthalic, and benzoic-type impurities at the same rate as the main oxidation product without large solvent-recovery and hydrogenation penalties. Published data for exact impurity-to-byproduct yields on commercial PTA lines are limited, but the operating constraint is visible in the differential specifications for polymer-grade and technical-grade paraxylene. Production-scale PTA oxidation reactors are typically titanium-lined bubble columns with air spargers; off-gas containing unconverted acetic acid, water, carbon oxides, and methyl bromide is directed to scrubbing and catalytic oxidation.
For dimethyl terephthalate production, paraxylene is oxidized and esterified with methanol; the resulting crude DMT is purified by crystallization and/or distillation. The route is used where a distillable monomer is preferred or where PET producers operate older ester-exchange polymerization lines. The specification may relax ethylbenzene and color limits if the DMT purification train includes a high-reflux dimethyl ester column capable of removing methyl benzoate and methyl toluate, but solvent recovery and methanol handling add fixed costs. Compared with the PTA route, DMT units tend to be smaller and less integrated with refinery aromatics complexes, and they may accept off-spec paraxylene only after a documented feed-trial demonstrates that ester-column fouling and product color remain within limits.
Bulk storage and transfer of paraxylene require freeze protection and vapor control. Because the freezing point is 13.26°C, storage tanks in temperate or cold climates must be heat-traced or insulated to maintain a minimum liquid temperature typically above 18°C; pipelines and transfer hoses may require external steam tracing or electric heat tracing to prevent solidification during low-flow or shutdown conditions. The closed-cup flash point of approximately 27°C places paraxylene in GHS flammable liquid category 3; the vapor is heavier than air and can accumulate in pits or containment dikes. Fixed-roof tanks with inert-gas padding, usually nitrogen, are used to exclude oxygen and moisture; floating-roof tanks are less common for this service because of the material’s low vapor pressure and the need to maintain inert-gas blanketing. Marine transfer to coastal PTA plants uses stainless steel or coated carbon steel tanks with vapor return to the terminal; loading arms are fitted with dry-break couplings and the vessel’s inert-gas system is kept positive during unloading. Water must be excluded from the product because free water can accelerate corrosion and cause operational upset in downstream oxidation units. Paraxylene is incompatible with strong oxidizers, nitric acid, and sulfonating agents; rubber gaskets and seals must be selected from fluoropolymer or other aromatic-resistant materials because the solvent can swell and degrade common elastomers. Transport classification under UN 1307 for xylenes includes flammable liquid and harmful by inhalation; exposure controls are referenced to national OELs for xylenes, with vapor monitoring near transfer pumps and sampling points because the methyl-substituted aromatic has acute inhalation and dermal absorption toxicity.
