Name | m-Xylene |
Synonyms | m-Xylol m-Xylene 3-xylene ai3-08916 2,4-Xylene 1,3-xylene meta-xylene META-XYLENE 3-methyltoluene m-Dimethylbenzene 1,3-dimethyl-benzen 1,3-Dimethylbenzene Benzene,1,3-dimethyl- |
CAS | 108-38-3 |
EINECS | 203-576-3 |
InChI | InChI=1/C8H10/c1-7-4-3-5-8(2)6-7/h3-6H,1-2H3 |
InChIKey | IVSZLXZYQVIEFR-UHFFFAOYSA-N |
Molecular Formula | C8H10 |
Molar Mass | 106.17 |
Density | 0.868 g/mL at 25 °C (lit.) |
Melting Point | -48 °C (lit.) |
Boling Point | 138-139 °C (lit.) |
Flash Point | 77°F |
Water Solubility | Miscible with organic solvents. Immiscible with water. |
Solubility | Miscible with many organic solvents, including alcohol and ether |
Vapor Presure | 16 mm Hg ( 37.7 °C) |
Vapor Density | 3.7 (vs air) |
Appearance | Liquid |
Color | Colorless |
Odor | Like benzene; characteristic aromatic. |
Exposure Limit | NIOSH REL: 100 ppm (435 mg/m3), STEL 150 ppm (655 mg/m3), IDLH 900ppm; OSHA PEL: TWA 100 ppm; ACGIH TLV: TWA 100 ppm, STEL 150 ppm (adopted). |
Merck | 14,10081 |
BRN | 605441 |
pKa | >15 (Christensen et al., 1975) |
Storage Condition | 2-8°C |
Explosive Limit | 1.1-7%(V) |
Refractive Index | n20/D 1.497(lit.) |
Physical and Chemical Properties | Character: colorless transparent liquid with strong aromatic odor. melting point -47.872 ℃ boiling point 139.1 ℃ relative density 0.8684 refractive index 1.4972 flash point 29.44 ℃ solubility insoluble in water, soluble in ethanol and ether. |
Use | Used as raw materials of spices, pesticides, medicines |
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 R36/38 - Irritating to eyes and skin. |
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 | ZE2275000 |
TSCA | Yes |
HS Code | 29024200 |
Hazard Class | 3 |
Packing Group | II |
Toxicity | LD50 orally in rats: 7.71 ml/kg (Smyth) |
Downstream Products | Isophthalic acid 2,4-Dimethylaniline m-Toluic acid 2,6-Dimethylaniline chlorothalonil |
colorless transparent liquid with strong aromatic odor. Relative density 0.8684,(d20) 0.642. Melting Point -872 °c. Boiling point 139.1 °c. Refractive index 4972,(,z) 4971. Flash point 29. 44 °c. Spontaneous ignition point was 527. 78 ℃. Insoluble in water, soluble in ethanol and ether.
This product is a by-product of the production of p-xylene, and the preparation method is shown in p-xylene.
mainly used as solvent for the manufacture of isophthalic acid, M-methyl benzoic acid, isophthalonitrile, etc. It can also be used as raw materials and dye intermediates for oil-soluble couplers of medicines, spices and color film.
see xylene. The lethal concentration of the product to mice was 50mg/L.
olfactory Threshold | 0.041ppm |
Henry's Law Constant | 14.80 at 45.00 °C, 17.26.4 at 50.00 °C, 19.90 at 55.00 °C, 23.01.3 at 60.00 °C, 27.46.3 at 70.00 °C(static headspace-GC, Park et al., 2004) |
LogP | 3.16 at 20℃ |
NIST chemical information | information provided by: webbook.nist.gov (external link) |
EPA chemical substance information | information provided by: ofmpeb.epa.gov (external link) |
xylene | xylene is an aromatic hydrocarbon in which two hydrogen atoms on the benzene ring are substituted by two methyl groups. It has three isomers: O-xylene, M-xylene, P-xylene. Industrial product is a mixture of three isomers, Ortho-10%, meta-70%, para-20%. In the coking industry, it is one of the refined products of crude benzene. xylene is a colorless flammable liquid; The melting points of O-, m-and p-xylene are -25.2 ℃,-47.9 ℃ and 13.3 ℃, and the boiling points are 144.4 ℃,139.1 ℃ and 138.3 ℃, the relative density were 0.8802,0.8642 and 0.8611; Insoluble in water, can be miscible with many organic solvents. Phthalic anhydride, isophthalic acid and terephthalic acid were produced by catalytic oxidation. xylene is also one of the important raw materials of organic chemical industry. It is naturally found in coal tar and some petroleum, and can be obtained by fractionation of light oil part of coal tar or catalytic reforming light gasoline. The extraction of the C8 fraction in the naphtha reformate is industrially the main one. Can also be derived from toluene in the catalyst and high temperature, high pressure, through the differentiation. At present, freeze crystallization, adsorption, complex formation or molecular sieve are used in the industry to separate them. The boiling point of O-Xylene is relatively high, which can be separated by distillation. The melting point of p-xylene is relatively high, and the purification is carried out by fractional crystallization. Mixed xylene without separation can be directly used as a solvent, and can be added to gasoline to improve the Antiknock, which is a component of aviation gasoline. O-Xylene is mainly used for the preparation of phthalic anhydride, which is an important raw material for the manufacture of a variety of dyes and indicators (such as phenolphthalein). In addition, O-xylene can also be used to prepare polyester resins, insect repellents, plasticizers and dyes. 4, 6-dimethyl-1, 3-phenylenediamine produced by nitration and reduction of M-Xylene is an intermediate for the synthesis of dyes, and M-xylene can also be used as a raw material for the synthesis of fragrances (such as Musk xylene). P-xylene is mainly used in the manufacture of terephthalic acid, which is a synthetic polyester fiber (Polyester) an important raw material. |
separation of m-and p-xylenes by crystallization | xylene is present in coked crude benzene and petroleum cracked oil. Crude benzene by preliminary distillation, sulfuric acid washing and distillation, separation of benzene and toluene, and then by distillation can be obtained xylene, also known as coking xylene. The quality of coking xylene depends on the separation capacity, overhead temperature and reflux ratio of the rectification column. China will be coking xylene products are divided into three levels. Coking xylene generally contains O-xylene 16%, M-xylene 50%, p-xylene 21%, ethylbenzene 7%. In xylene produced by petroleum industry, the content of M-Xylene is lower and the content of ethylbenzene is higher. Industrial xylene is a solvent and additive for the rubber and coating industries, as well as for aviation and power fuels. O-xylene, M-xylene and p-xylene separated from industrial xylene are raw materials of phthalic acid, isophthalic acid and terephthalic acid, respectively. Phthalic acid and terephthalic acid are used in the production of plasticizers, polyester resins and polyester fibers. M-xylene can be used alone as solvent and fuel additive. The boiling point difference between O-xylene and other isomers in industrial xylene is greater than 5.2 ℃. O-xylene with a purity of more than 95% can be separated by precise distillation, and then purified by sulfonation and distillation, higher purity of O-xylene can also be obtained. The separation methods of M-xylene and p-xylene include sulfonation method, crystallization method, adsorption method and complex method. A mixed xylene fraction containing m-xylene and p-xylene is eutectic CRYSTALLIZED (crystallization temperature is -53.1 ℃) to obtain a eutectic containing 12.5% of p-xylene and 87.5% of M-xylene, the two products were separated by secondary crystallization. The crystals obtained by the first crystallization and filtration are industrial M-xylene. When the filtrate is crystallized for the second time, an appropriate amount of carbon tetrachloride is added, which can form a solid complex with p-xylene at an initial crystallization temperature of -40 °c, A solid complex with an initial crystallization temperature of -78 °c is formed with M-xylene. The crystallization temperature was controlled to crystallize only carbon tetrachloride and p-xylene. The crystals obtained by filtration were melted, and carbon tetrachloride was separated by distillation to obtain p-xylene. After carbon tetrachloride was recovered from the filtrate by distillation, M-xylene was obtained. The carbon tetrachloride in the process is recycled. |
Use | M-Xylene is the bactericide metalaxyl, furaxyl, benzoxaose, chlorothalonil, as well as intermediates of the insecticidal and acaricidal agents Amitraz, monoformamidine, chlormeform, and the herbicides clachlor, isobutachlor, and the like. M-Xylene is mainly used as a solvent for the production of isophthalic acid and then the production of Unsaturated Polyester Resin and coatings, and also used for the production of M-methyl benzoic acid, isophthalonitrile, medical lidocaine, oxymetazoline, new diatria, etc. It can also be used as raw materials and dye intermediates for perfume, oil-soluble color former of color film, etc. Due to the technical difficulty in the production of M-xylene, China's output is very small, and neither the output nor the quality can meet the market demand. |
production method | 1. Rectification of mixed xylene, cut off the fraction at 130-140 ℃, then sulfonated with sulfuric acid at 80-90 ℃ for 3.5h. Then unsulfonated xylene was separated, hydrolyzed and distilled, the 140-150 °c fraction was cut to obtain a finished product. 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. The preparation method is the use of petroleum xylene or coal tar xylene separation, separation method can use low temperature crystallization method, coordination method, adsorption method and sulfonation hydrolysis method. In the past, the sulfonated hydrolysis method was used to produce m-xylene in China, and now the adsorption method has been used to separate M-xylene. The molecular sieve is used as the adsorbent for the adsorption method, and the gas phase adsorption or the liquid phase adsorption can be carried out, and the process is as follows. (1) the mixed xylene is cut into 130~140 ℃ fraction by the method of sulfonation and hydrolysis, and then sulfonated with sulfuric acid, The reaction temperature is 80 to 90 ° C., and the reaction time is 3.5h. Then the sulfonated xylene is separated out, and then the 140 to 150 ° C. Fraction is cut through hydrolysis and distillation to obtain a finished product. The method is serious to the equipment corrosion, and there are more three wastes, can only be small-scale production, and therefore is replaced by the adsorption method. (2) adsorption method using molecular sieve liquid phase adsorption or gas phase adsorption, liquid phase adsorption with K-Ba-Y type as adsorbent, toluene as desorption agent, in the moving bed for Continuous adsorption separation, operating temperature 65~85 degrees C, the ratio of adsorbent and raw material is not more than 10, the ratio of desorption agent and raw material is greater than 5. Gas phase adsorption also uses K-Ba-Y type molecular sieve as adsorbent, adsorption temperature 170~180 deg C, the operating pressure of atmospheric pressure. Adsorption separation is a new method for the separation of xylene. |
category | relatively flammable liquid |
toxicity grade | poisoning |
Acute toxicity | oral-rat LD50: 5000 mg/kg |
stimulation data | Skin-rabbits 20 mg/24 h moderate; eye-rabbit 5 mg/24 h mild |
explosive hazard characteristics | explosive when mixed with air |
flammability hazard characteristics | flammable in case of open flame, high temperature and oxidant; combustion-induced smoke |
storage and transportation characteristics | The warehouse is ventilated and dried at low temperature; It is stored separately from the oxidant |
extinguishing agent | dry powder, dry sand, carbon dioxide, foam, 1211 extinguishing agent |
Occupational Standard | TWA 435 mg/m3 |
spontaneous combustion temperature | 982 ° F. |
toxic substance data | information provided by: pubchem.ncbi.nlm.nih.gov (external link) |