Benzene Manufacturing Methods
Benzene is an important raw material for chemical production, widely used in pharmaceuticals, pesticides, dyes, spices and other fields. The main manufacturing methods of benzene are catalytic reforming method, cracked gasoline method and coking method. This article will introduce these three manufacturing methods in detail.
I. Catalytic Reforming Method
Catalytic reforming method is a method to rearrange the hydrocarbon molecules in naphtha through catalyst to generate benzene, toluene and other aromatic hydrocarbons. This method has the advantages of high product purity and high yield, so it is widely used in the manufacture of benzene.
1. Raw material preparation
Naphtha is the main raw material for the catalytic reforming method, which contains alkanes, cycloalkanes and a small amount of aromatic hydrocarbons. In order to make the reaction run more smoothly, the naphtha needs to be pretreated to remove impurities such as sulfur and nitrogen.
2. Catalytic Reforming
Under the action of catalyst, the hydrocarbon molecules in naphtha are rearranged to produce aromatic hydrocarbons such as benzene and toluene. Commonly used catalysts are platinum, rhodium and other precious metal catalysts. The reaction temperature is generally 450-550°C and the pressure is 1-3 MPa.
3. Product separation
After the reaction product is cooled and condensed, the aromatic hydrocarbons, such as benzene and toluene, are separated from the unreacted hydrocarbons by distillation and other methods. The purity of the benzene product obtained is generally above 99.5%.
II. Cracked gasoline method
Cracked gasoline method is a method of generating olefins and aromatics by cracking naphtha or heavy hydrocarbons at high temperature. The product yield of this method is high, but the purity is relatively low.
1. Raw material preparation
Naphtha or heavy hydrocarbons are the main raw materials for the cracked gasoline method. In order to improve the cracking effect, the feedstock needs to be pretreated, such as desulfurization and denitrogenation.
2. High-temperature cracking
Under high temperature conditions, hydrocarbon molecules in the feedstock undergo cracking reactions to produce olefins and aromatics. Cracking temperature is generally 700-800 ℃, atmospheric pressure or slightly negative pressure conditions.
3. Product Separation
After the cracking products are cooled and condensed, the olefins and aromatics are separated by distillation and other methods. The purity of the benzene product obtained is generally 95%-98%.
Third, coking method
The coking method is a method of generating benzene, toluene and other aromatic hydrocarbons by heating coal tar at a high temperature so that it undergoes pyrolysis and condensation reactions. This method has a wide source of raw materials, but the purity of the product is low.
1. Raw material preparation
Coal tar is the main raw material of the coking method, which contains a large amount of aromatic hydrocarbons. In order to improve the quality of the product, it is necessary to pre-treat the coal tar, such as dewatering, removing impurities and so on.
2. High temperature heating
Under high temperature conditions, the aromatic hydrocarbons in coal tar undergo pyrolysis and condensation reactions to produce benzene, toluene and other aromatic hydrocarbons. The heating temperature is generally 450-550℃.
3. Product Separation
After the reaction products are cooled and condensed, the aromatic hydrocarbons such as benzene, toluene and other hydrocarbons are separated from the unreacted coal tar by methods such as distillation. The purity of the benzene product obtained is generally 90%-95%.
The above three methods can be used in the manufacture of benzene, but different methods are suitable for different production scenarios based on considerations of raw material source, product purity and yield. In actual production, the appropriate method for benzene manufacturing can be selected according to the specific situation.
