Name | p-Xylene |
Synonyms | p-Xylene C6H4(CH3)2 1,4-xylene Dibencoside para-xylene p-Xylene (1.4- 1,4-Dimethylbenzene P-XYLENE FOR SYNTHESIS 1 L P-XYLENE FOR ANALYSIS EMSURE p-Xylene in Dimethyl Sulfoxide, USP 467 Standard |
CAS | 106-42-3 |
EINECS | 203-396-5 |
InChI | InChI:1S/C8H10/c1-7-3-5-8(2)6-4-7/h3-6H,1-2H3 |
InChIKey | URLKBWYHVLBVBO-UHFFFAOYSA-N |
Molecular Formula | C8H10 |
Molar Mass | 106.17 |
Density | 0.861 g/mL at 20 °C (lit.) |
Melting Point | 12-13 °C (lit.) |
Boling Point | 138 °C (lit.) |
Flash Point | 77°F |
Water Solubility | Miscible with alcohol, ether, acetone, benzene and chloroform. Immiscible with water. |
Solubility | water: soluble0.2g/L |
Vapor Presure | 9 mm Hg ( 20 °C) |
Vapor Density | 3.7 (vs air) |
Appearance | Liquid |
Color | Colorless |
Odor | Like benzene; characteristic aromatic. |
Exposure Limit | TLV-TWA100 ppm (~434 mg/m3) (ACGIH,MSHA, and OSHA); STEL 150 ppm(~651 mg/m3) (ACGIH); ceiling 200 ppm/10 min (NIOSH); IDLH 1000 ppm (NIOSH). |
Maximum wavelength(λmax) | ['λ: 294 nm Amax: 1.00', , 'λ: 320 nm Amax: 0.10', , 'λ: 350 nm Amax: 0.05', , 'λ: 38 |
Merck | 14,10081 |
BRN | 1901563 |
pKa | >15 (Christensen et al., 1975) |
Storage Condition | Store at +5°C to +30°C. |
Stability | Stable. Incompatible with oxidizing agents. Hygroscopic. Flammable. |
Explosive Limit | 1.1-7%(V) |
Refractive Index | n20/D 1.495(lit.) |
Physical and Chemical Properties | Characteristics of colorless liquid, crystallization at low temperature. melting point 13.263 ℃ boiling point 138.37 ℃ relative density 0.8611 refractive index 1.5004 flash point 27.2 ℃ solubility, benzene, acetone miscible, insoluble in water. |
Use | Solvents for rubber, paint and additives for aviation power fuels |
Risk Codes | R10 - Flammable R20/21 - Harmful by inhalation and in contact with skin. R38 - Irritating to the skin R39/23/24/25 - R23/24/25 - Toxic by inhalation, in contact with skin and if swallowed. R11 - Highly Flammable |
Safety Description | S25 - Avoid contact with eyes. S45 - In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.) S36/37 - Wear suitable protective clothing and gloves. S16 - Keep away from sources of ignition. S7 - Keep container tightly closed. |
UN IDs | UN 1307 3/PG 3 |
WGK Germany | 2 |
RTECS | ZE2625000 |
TSCA | Yes |
HS Code | 29024300 |
Hazard Class | 3 |
Packing Group | III |
Toxicity | LD50 orally in Rabbit: 3910 mg/kg |
Raw Materials | Sulfuric acid Sodium hydroxide |
Downstream Products | Terephthaldicarboxaldehyde Terephthaloyl chloride p-Toluic acid |
colorless liquid, crystallized at low temperature, relative density 0.8611,o.8610. Melting point 263 °c. Boiling point 138. 37 °c. The refractive index was 5004,(7z ~ 5) 4958. Flash point 27.2 °c. With ethanol, ether, benzene, acetone miscible, insoluble in water. Explosion limit of 1% to 6% (volume).
The raw material toluene is subjected to a transalkylation reaction in a transalkylation reactor to produce xylene and benzene. Mixing xylene in the isomerization reactor, part of the M-Xylene is isomerized to generate p-xylene, and the reactant is mixed with the xylene from the transalkylation section after removing the light fraction in the stabilization tower and entering the decarbon9 distillation column, mixed Xylenes with high p-xylene content were obtained at the top of the column, and C9 or more components were obtained in the column.
The mixed xylene obtained from the top of the stabilization Tower enters the adsorption separation section, and the non-molecular sieve solid adsorbent is used to adsorb p-xylene, and the p-xylene product with a purity of 99.9% is obtained by desorption, and the by-product is m-xylene.
mainly used as polyester (polyester) fiber and resin, paint, dyes and pesticides and other raw materials.
relative polarity | 0.074 |
olfactory Threshold | 0.058ppm |
Henry's Law Constant | 16.1 at 45.00 °C, 18.6 at 50.00 °C, 20.3 at 55.00 °C, 23.4 at 60.00 °C, 30.5 at 70.00 °C (staticheadspace-GC, Park et al., 2004) |
LogP | 3.16 at 20℃ |
EPA chemical substance information | information provided by: ofmpeb.epa.gov (external link) |
important organic chemical raw materials | p-xylene is an important organic chemical raw materials, mainly used for the production of p-dibenzoic acid (PTA) dimethyl terephthalate (DMT) and ethylene Terephthalate (PET), and then the production of polyethylene terephthalate (polyester), can also be used as a solvent and pharmaceutical, perfume, ink and other industries production of raw materials. At present, China has become the world's largest production and consumption of p-xylene, p-xylene is initially obtained from the catalytic reforming of petroleum aromatics, later, with the development of petrochemical industry and coal coking industry, the conversion of aromatic hydrocarbons has become the most direct and effective means of production for the preparation of p-xylene. In industry, toluene and C9 aromatics are usually used as raw materials, and p-xylene is produced by toluene disproportionation and alkyl transfer, xylene isomerization, toluene-methanol alkylation and adsorption separation. In the xylene isomerization process, C8 aromatics without p-xylene are used as raw materials, and the isomerization reaction takes place under the action of catalyst so that the concentration of p-xylene in mixed C8 aromatics reaches equilibrium concentration, thus improving the production of p-xylene. There are about 10 kinds of xylene isomerization technologies in industrialization, and the main ones that are competitive in the production of aromatic hydrocarbons are the Isomer process of UOP company, the octaining process of Axens company and the MHA I process of the United States Mobil company. The Isomar process uses a dual-function catalyst (MgAPSO/ZSM-5) to generate ethylbenzene in the presence of hydrogen to form xylene, which overcomes the corrosion problem caused by a catalyst. The process is used in the second-stage aromatics joint unit of PetroChina Liaoyang Petrochemical Company. Axens octahining process adopts ethylbenzene isomerization catalyst, which can increase the yield of p-xylene from 88% to 92%, and the single-pass yield loss of p-xylene can be reduced by 40% ~ 50% compared with the conventional catalyst, The activity is increased by 20% to 30%, and the high activity enables it to adopt a higher space velocity under mild conditions. The process is suitable for feeds with high ethylbenzene content. In 2001, the company introduced the XyMax process to maximize the production of xylene to the market. The concentration of p-xylene is higher than the equilibrium value, and the ethylbenzene and non-aromatic hydrocarbons in the raw materials can also be converted into benzene and light alkanes respectively. The conversion of ethylbenzene can be as high as 60% to 80%. FIG. 1 is a chemical reaction equation for preparing p-xylene by disproportionation and isomerization of toluene. |
Application | p-xylene can be used to produce terephthalic acid, and then produce polyester resins such as ethylene terephthalate and butylene glycol. Polyester resin is the raw material for the production of polyester fiber, polyester sheet, polyester hollow container. |
Use | used in the production of polyester fibers and resins, coatings, raw materials of dyes and pesticides used as standard substance and solvent for chromatographic analysis, also used in organic synthesis used in rubber, paint solvent and aviation power fuel additives for the production of terephthalic acid, and then the production of ethylene terephthalate, butylene glycol Ester and other polyester resin. Polyester resin is the raw material for the production of polyester fiber, polyester sheet, polyester hollow container. Taenia fiber is the largest synthetic fiber in China. It is also used as a raw material for coatings, dyes and pesticides. solvent. Organic Synthesis. Standard for gas chromatographic analysis. |
production method | 1. Petroleum xylene, coal tar xylene, contains a considerable amount of p-xylene. Since the boiling point difference between p-xylene and M-Xylene is only 0.75 ℃, distillation separation method cannot be used. At present, the research and development methods at home and abroad are low temperature crystallization separation method, adsorption separation method and complexation separation method. The low temperature crystallization separation method uses the difference of melting point of xylene isomers for separation, the main method is cryogenic fractional crystallization, the technology is mature, and it is dominant in xylene separation at present. But this method equipment is huge, p-xylene by the limitations of the co-melting point, the recovery rate is low, only 60-70%. The adsorption separation method is a new method developed in the 70 s. This method has less investment, lower total cost of production, high yield of p-xylene and high purity, and may replace the cryogenic crystallization method. 2. The raw material toluene is subjected to a transalkylation reaction in a transalkylation reactor to produce xylene and benzene. Mixing xylene in the isomerization reactor, part of the M-Xylene is isomerized to generate p-xylene, and the reactant is mixed with the xylene from the transalkylation section after removing the light fraction in the stabilization tower and entering the decarbon9 distillation column, mixed Xylenes with high p-xylene content were obtained at the top of the column, and C9 or more components were obtained in the column. The mixed xylene obtained from the top of the stabilization Tower enters the adsorption separation section, and the non-molecular sieve solid adsorbent is used to adsorb p-xylene, and the p-xylene product with a purity of 99.9% is obtained by desorption, and the by-product is m-xylene. In addition, a hydrogen fluoride-boron trifluoride extraction method is also used. |
category | flammable liquid |
toxicity grade | poisoning |
Acute toxicity | oral-rat LD50: 5000 mg/kg; Abdominal injection-mouse LD50: 2110 mg/kg |
explosive hazard characteristics | explosive when mixed with air |
flammability hazard characteristics | open flame, combustible heat and oxidant; Combustion emission stimulus smoke |
storage and transportation characteristics | The warehouse is ventilated and dried at low temperature, separate from oxidants and acids |
extinguishing agent | water mist, foam, sand, carbon dioxide, 1211 extinguishing agent |
Occupational Standards | TLV-TWA 100 PPM (440 mg/m3); Tel 150 PPM(655 mg/m3) |
spontaneous combustion temperature | 984 ° F. |
toxic substance data | information provided by: pubchem.ncbi.nlm.nih.gov (external link) |