Background[1]
Meta-chlorotoluene, also known as 3-chlorotoluene, is a neutral, colorless and transparent liquid. Insoluble in water. Easily soluble in ethanol, ether, benzene, chloroform and other organic solvents. It is obtained by diazotization and replacement of m-toluidine and cuprous chloride. It can also be obtained by the isomerization of o-chlorotoluene under the action of acidic zeolite. Used as solvent and dye intermediate, also used in organic synthesis.
m-chlorotoluene
Apply[3]
It is an important organic intermediate, widely used in fine chemical industries such as medicine and pesticides, and is also a good organic solvent. Para-chlorotoluene is an important fine chemical raw material. Para-chlorotoluene with a purity of more than 95% is used to synthesize high-efficiency, low-toxicity and broad-spectrum pesticides such as chloroside (sulfamethoxazole) and fenfossil. The market demand is strong.
Preparation[2]
There are three main methods for the synthesis of m-chlorotoluene:
(a) m-Cresol method: m-chlorotoluene is produced by reacting m-cresol with phosphorus pentachloride. The raw materials used in this method are more expensive and the production cost is higher.
(b) Ortho-chlorotoluene method: Ortho-chlorotoluene is isomerized in the presence of a catalyst to obtain m-chlorotoluene and p-chlorotoluene. Since the two generated compounds have the same boiling point and basically the same properties, it is difficult to obtain high-purity m-chlorotoluene.
(c) m-nitrotoluene method: m-nitrotoluene is prepared by catalytic hydrogenation and Sandmeyer reaction.
Separation and purification
In the industrial production of p-chlorotoluene, direct chlorine chlorination of toluene has gradually replaced the traditional diazotization method of p-toluidine. However, the o-, meta- and para-isomers (o-chlorotoluene) produced in the actual production process OCT accounts for about 45%, m-chlorotoluene MCT is less than 1%, and p-chlorotoluene PC5 (about 5%) is separated and purified.
1. Sulfonation separation method: This method first sulfonates mixed chlorotoluene. OCT has greater activity and is activated first. Similarly, PCT is obtained by hydrolysis after sulfonation of p-chlorotoluene, thereby achieving separation and purification. This process involves sulfonation reaction, hydrolysis and other links, which is obviously difficult to become a suitable method for industrialization.
2. Distillation separation method: The boiling point difference of o-p-chlorotoluene is small, and distillation separation requires a considerable number of theoretical plates. French scientific researchers first proposed the distillation method to separate o-p-chlorotoluene.
Using a distillation tower to carry out single-tower and three-tower continuous distillation, it is completely possible to obtain higher-purity o-chlorotoluene and p-chlorotoluene from the mixed chlorotoluene. As the requirements for product quality increase, the number of theoretical plates required for the distillation tower increases significantly. The distillation separation process is simple, technically reliable, has less waste and is easy to industrialize. Currently, this method is expected to provide key intermediates for domestic pesticide production in the short term.
3. Crystallization separation method: As mentioned before, the rectification method separates mixed chlorotoluene and multi-tower operation requires too many fractionation plates, while the freezing crystallization method only requires a smaller number of plates. Appropriate distillation, slightly increasing the content of the paramer in the mixed solution, and then freezing, PCT crystallizes out, the mother liquor is concentrated, and then frozen, and the separation is achieved by continuous operation.
Wastewater treatment
Me-chlorotoluene is a common chemical raw material, but wastewater is easily produced during the production process. This wastewater often contains highly polluting substances such as m-cresol, dimethylbiphenyls, and formaldehyde. If the wastewater Direct discharge without treatment will cause serious environmental pollution problems. CuO nanomaterials have a narrow bandgap (2.2ev), a maximum absorption wavelength of 560nm, good photoelectrochemical response in the visible light region, and high light energy utilization in photocatalytic reactions. Fungus-shaped copper oxide nanomaterials are used as photocatalysts to degrade COD in wastewater containing m-chlorotoluene production using sunlight/CuO/H2O2 system, and the effect is remarkable.
Response to leakage
Personal Precautions, Protective Equipment and Emergency Procedures Contain spillage and collect spillage with electrical vacuum cleaner or wet brush and place in container and dispose of in accordance with local regulations. Methods and materials used to contain and clean up spills Avoid contact with skin and eyes. Avoid breathing vapor or mist. Never go near sources of fire. Fireworks are strictly prohibited and measures are taken to prevent the accumulation of static electricity.
Toxicology
Respiratory or skin sensitization: May be harmful if absorbed through skin and may cause skin irritation. There is no greater than or equal toComponents at 0.1% levels have been identified by IARC as possible or probable human carcinogens.
Main reference materials
[1] Zhang Qianping, Li Guangchao, & Zhu Yiren. (2011). Research on the treatment of m-chlorotoluene industrial wastewater by Fe_2o_3/attapulgite adsorption-photocatalysis method. Fine and Specialty Chemicals, 19(9), 14-18.
[2] Wang Shuqing, Gao Chong, & Zhu Shisheng. (2008). Synthesis of m-chlorobenzoic acid from liquid-phase oxidation of m-chlorotoluene. Chemistry World, 49(3), 161-163.
[3] An Chuyu, Cui Mifen, & Qiao Xu. (2004). Research on the photochlorination reaction process of m-chlorotoluene side chain. Proceedings of the 7th National Academic Conference on Fine Chemical Chemistry.
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