High purity 3,4-dimethyl benzaldehyde preparation method

Abstract

This invention relates to a method for producing high-purity 3,4-dimethylbenzaldehyde, characterizing: in the four-hole bottle, add in weighted ortho-xylene and 1,2- dichloroethane, turn on the agitator, add ice salt water to the salt water boiler, pre-cool the material in the reaction bottle to -10-0DegC, and add sequentially Lewis salt compound catalyst, with operation temperature at -10-0Deg C, and then in CO atmosphere, dropwise add concentrated sulfuric acid, when the reaction conversion rate attains up to 70%, stop the reaction, turn off the CO and HCl gas valve, continue agitation, and then pour the above reactant material into already charged ice salt water boiling flask, after agitatation, put it in the separating funnel for extraction, mix homogeneously, stewing for stratification, remove the lower acidic water, put the above oil material to the distillation bottle, turn on the vacuum pump for pressure-decreasing distillation, collect the distillant and obtain the finished product. This invention is characterized of mild reaction condition, high catalyst activity, specific catalyst effect, high product selectivity, 'clean' process and easy separation.

Description

Technical field [0001] The invention relates to a process technology for preparing dialkylbenzaldehyde compounds by a low-temperature carbonylation method, specifically using o-xylene, CO, and HCl as raw materials, 1,2-dichloroethane as a solvent, and Lewis acid as a compound The preparation method of the catalyst for formylation reaction to synthesize high-purity 3,4-dimethylbenzaldehyde. Background technique [0002] 3,4-Dimethylbenzaldehyde is a new type of fine chemical intermediate, which plays an important role in fine organic synthesis. Mainly used in the synthesis of polyolefin transparent nucleating agent DMDBS [bis(3,4-dimethyldibenzylidene)sorbitol], and also used as raw materials for medicine and daily chemicals, such as viscosity modifiers and organic pollutants Coagulant, curing agent for pharmaceuticals and cosmetics, etc. [0003] The synthesis and production processes of 3,4-dimethylbenzaldehyde mainly include incomplete oxidation method, chloromethylation method...

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Problems solved by technology

[0003] The synthesis and generation process of 3,4-dimethylbenzaldehyde mainly include incomplete oxidation method, chloromethylation method, bromination hydrolysis method and carbonylation method to synthesize 3,4-dimethylbenzaldehyde method, and the obtained product It often contains a large amount of isomers of 3,4-dimethylbenzaldehyde and 3,4-dimethylbenzoic acid. The product components are relatively complicated, and there are more than ten kinds of by-products. The boiling point of a few by-products is very close to that of 3,4-dimethylbenzaldehyde, which is difficult to separate. The overall yield of the process is relatively low. The purity of the product after distillation and separation is still low. The cost of product separation is high and the technology is very difficult.

[0008] The catalytic hydrolysis of benzylidene dichloride or substituent benzylidene dichloride has been reported (GB899953, US3087967, US3524885, US4229379, US5347054), and the hydrolysis catalyst selects soluble zinc salt, and its yield is more than 95%, but zinc salt catalyst is in Excessive water is easy to deactivate, affecting product quality, and seriously causing heavy metal pollution to the environment

The patent US4229379 uses concentrated hydrochloric acid as a catalyst, and the yield is high, but the amount of water required for hydrogen chloride gas to be absorbed and recycled through a packed tower is large, reaching 10 to 25 times the stoichiometric amount, and the utilization rate of the reactor is low

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