How is benzene refined and how is toluene made?

Refining method: Benzene extraction from petroleum products is the most widely used preparation method. at 500-525 ° C, 8-50 atmospheres.

Under various aliphatic hydrocarbons with boiling points between 60-200 °C.

It is converted into benzene and other aromatic hydrocarbons by dehydrogenation and cyclization through a platinum-rhenium catalyst.

Benzene is extracted from the mixture and then distilled.

Benzene: Benzene is a highly flammable, fragrant colorless liquid at room temperature, an organic compound, and an aromatic hydrocarbon with the simplest composition. Benzene is highly toxic and is also a carcinogen.

It is insoluble in water, soluble in organic solvents, and can also be used as an organic solvent in itself. Benzene is also the basic raw material of petrochemical industry, and the output and technical level of benzene production are one of the indicators of the development level of a country's petrochemical industry.

Uses of benzene: solvents for fats, resins, iodine, etc. Determination of the mineral refractive index.

Organic synthesis. Optically pure solvents. High-pressure liquid chromatography solvents, used as synthetic dyes, pharmaceuticals, pesticides, photographic films, and raw materials for petrochemicals, varnishes, nitrocellulose paints, paint removers, lubricating oils, greases, waxes, celluloids.

Solvents such as resin, artificial leather, etc.

Benzyl chloride hydrolysis method: benzyl alcohol is obtained by azeotropic hydrolysis of benzyl chloride and alkali aqueous solution, and the product benzyl ether is generated at the same time, up to 10%. Pressurization, high temperatures, and increased alkali concentrations are all conducive to the formation of by-products.

Batch method: add water, soda ash and benzyl chloride to a steel reactor equipped with a reflux condenser and a jacket, stir and heat, reflux until there is no longer carbon dioxide escape, cool the reactants, add salt to saturation and stratification, carefully separate the upper layer to obtain crude alcohol, and the crude alcohol can be distilled under vacuum pressure to obtain industrial-grade benzyl alcohol, with a yield of 70% 72%.

Precautions for storage of benzyl alcohol.

Storage: Store in an airtight container in a cool, dry place.

Packing: Packing Material: Packed in galvanized drums or steel drums or ton drums as per customer's requirements.

Net weight specification: 200kg drum, 210kg drum. 1000kg drum, 1050kg drum.

Transportation: Strong vibration, exposure to the sun, high temperature and fireworks should be avoided during transportation.

Benzene can be converted into benzyl chloride by chloromethylation reaction, and benzyl rechlorination hydrolysis is prepared, and the synthesis steps and reaction formula are expressed as follows

C6H6 HCO HCl (anhydrous ZnCl2 as catalyst) C6H5CH2Cl

C6H5CH2Cl H2O (NaOH aqueous solution) C6H5CH2OH

Laboratory Preparation of Toluene:

1. Use benzene and chloromethane to carry out the reaction under the heating catalysis of anhydrous aluminum trichloride (Friedel-Crafts reaction), note that all drugs must be anhydrous, all instruments must be dry, and the reaction must be carried out in an anhydrous state, otherwise the yield will be reduced.

C H + C H C C H + HCl (catalyst AlCl).

2. Chloromethylation of benzene and reduction of the product to prepare toluene.

c₆h₆+ hcl + hcho → c₆h₅ch₂cl + h₂o

c₆h₅ch₂cl + lialh₄ →c₆h₅ch₃

Test method: toluene is prepared from benzene, and the alkylation reaction is used.

In the presence of the catalyst ALCL3, benzene and CH3Cl are used for reverse osmosis, that is, benzene and chloromethane undergo substitution reaction, and aluminum chloride is used as a catalyst. Also, all materials must be made to be dry, otherwise the yield will be very low.

Industrial method: There are two main production routes for the production of petroleum-grade toluene in China:

1. Extracted by the refinery, the raw material is catalytic reforming gasoline.

2. Extracted by petrochemical plants, the raw material is hydrocracking gasoline (py gas).

In addition, toluene disproportionation technology can also be used to produce toluene by switching the start-up mode, and the corresponding production device is called TDP device. There are two production modes for this device:

Toluene > pure benzene isomeric grade xylene.

Pure benzene > toluene isomeric grade xylene.

The above process produces petroleum-grade products, in addition, coking crude benzene as a by-product of coking can also produce benzene, toluene, xylene, but the grade of the product is coking grade, and its accuracy is lower than that of petroleum-grade products, and it can only be partially replaced in a few industries. For (petroleum-grade) toluene and (petroleum-grade) xylene, the market share of coking grade products is negligible.