Method for increasing proportion of paradichlorobenzene in benzene chlorination product

Abstract

The invention discloses a method for increasing a proportion of paradichlorobenzene in a benzene chlorination product. The method comprises the steps: adding a combined catalyst in benzene, introducing chlorine under a stirring condition, to obtain the chlorination product with high paradichlorobenzene content, wherein the temperature of the whole process is controlled to be 50-80 DEG C, and the amount of the introduced chlorine is controlled to ensure that the conversion rate of the benzene is more than 99 percent and the conversion rate of chlorobenzene is more than 93 percent, and in addition, the combined catalyst comprises a main catalyst and a co-catalyst, the main catalyst is one of iron powder, ferric trichloride, aluminum trichloride, antimony trichloride, antimony pentachloride or tin tetrachloride, the co-catalyst is a dibenzo thiazepine organic matter, and the weight ratio of the main catalyst to the co-catalyst is 1:1. According to the method, the proportion of the paradichlorobenzene in the product is effectively increased, the ratio of the paradichlorobenzene to orthodichlorobenzene can reach 4.8, the content of the orthodichlorobenzene is less than 0.4 percent, and the content of phenyl polychloride is less than 1 percent.

Description

technical field [0001] The invention relates to a method for increasing the ratio of p-dichlorobenzene in benzene chlorination products. Belong to the technical field of benzene chlorination, Background technique [0002] p-dichlorobenzene (1,4-dichlorobenzene) is an important organic chlorinated product. It is a colorless or white crystal at room temperature. It is easy to sublimate at room temperature and has a special aromatic smell. In the past 30 years, p-dichlorobenzene has been widely used in medicine, pesticides, engineering plastics, dyes, catalysts, etc. [China Chlor-Alkali 2009, 7:1-4]. Since the traditionally used naphthalene-made sanitary balls are potential carcinogens, naphthalene-made sanitary balls have been banned abroad since the 1980s. In terms of pesticides, p-dichlorobenzene can be used to manufacture insecticides and fungicides, such as the intermediate 2,5-chloroacetophenone for the preparation of the organophosphorus insecticide carfecarb, and the ...

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Problems solved by technology

Moreover, the selectivity of p-dichlorobenzene in mixed dichlorobenzene is good, and the ratio (p / o) of p-dichlorobenzene to o-dichlorobenzene can reach more than 8. The disadvantage is that after the use of zeolite catalysts, due to the The generated strong acid HCl destroys the zeolite lattice, resulting in a greatly reduced catalytic activity, which is expensive, easy to be poisoned and deactivated, and difficult to regenerate, which limits its industrial application

[0004] Iron powder and other Lewis such as FeCl 3 , AlCl 3 , ZnCl 2 , SbCl 5 etc. are commonly used catalysts in the aromatics chlorination industry. The main disadvantage is that when benzene is chlorinated, the para-selectivity of the chlorination product mixed with dichlorobenzene is low, and the p / o is only about 1.5. Usually, it is necessary to add some Co-catalysts improve the selectivity of para-products. MANDAL et al. synthesized a series of diphenylamine co-catalysts with substituted aromatic rings, which were used in combination with Lewis acid catalysts. The experimental results show that the p / o in dichlorobenzene is close to 3.0 [PTCNO0600185]

However, the auxiliary catalyst has a complex structure and is difficult to synthesize, resulting in high cost.

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