Method for combined production of benzyl alcohol, benzaldehyde and benzoic acid through oxidizing toluene

Abstract

The invention discloses a method for combined production of benzyl alcohol, benzaldehyde and benzoic acid through oxidizing toluene. The method comprises the following steps: 1, oxidizing: continuously introducing toluene, a catalyst and an oxygen-containing gas to an oxidation reactor, and reacting to obtain an oxidation reaction solution; 2, hydrolyzing: continuously introducing the oxidation reaction solution to a hydrolysis reactor, continuously adding water to the hydrolysis reactor, and reacting to obtain a hydrolysis reaction mixture; 3, carrying out liquid-liquid layering: continuously adding the hydrolysis reaction mixture to a liquid-liquid layering device to obtain an upper layer oil phase containing toluene, benzyl alcohol and benzaldehyde and a lower layer water phase containing benzyl alcohol, benzaldehyde and benzoic acid; and 4, carrying out product separation: rectifying the upper layer oil phase to obtain incompletely reacted toluene, benzyl alcohol and benzaldehyde products, and cooling and crystallizing the lower layer water phase, and filtering the cooled and crystallized lower layer water phase to obtain a filtrate and a benzoic acid product. The method has the advantages of high raw material conversion rate, few byproducts, good selectivity of target products, and environmental protection.

Description

technical field [0001] The invention relates to a method for preparing aromatic compounds, in particular to a method for co-producing benzyl alcohol, benzaldehyde and benzoic acid by oxidation of toluene. Background technique [0002] Benzoic acid, benzyl alcohol and benzaldehyde are important fine chemical products. Benzoic acid is one of the important raw materials in the organic synthesis industry. It can be used as dye intermediates, mordants, plasticizers, diuretics, food preservatives, etc., and has very considerable market prospects. Benzaldehyde and benzyl alcohol are the most important aromatic aldols in industry, widely used in medicine, pesticide, food and other fields. Industrially, benzoic acid is produced by the direct oxidation of toluene, as described in EP0036233, CN101613269A, etc., and a small amount of byproducts such as benzaldehyde and benzyl alcohol are also generated. However, the selectivity of benzyl alcohol and benzaldehyde is very low, and the p...

AI Technical Summary

Problems solved by technology

When the conversion rate of toluene was 4.83%, the selectivity of benzaldehyde and benzyl alcohol was 38.8% and 20.5% respectively, and the total selectivity was 59.3%. The disadvantage was that the reaction conversion rate was low, so that the production efficiency was low. There is still a large room for improvement in the selectivity, and more importantly, 10.5% of other unknown by-products are generated during the reaction

This method relies on the oxygen-containing gas to disperse through the small holes on the tower-shaped sieve plate for many times to react with the raw material. The principle that oxygen can be absorbed with high efficiency improves the production efficiency, but the selectivity of benzaldehyde and benzyl alcohol in the product is generally lower than that of 30%, and there are nearly 10% unknown heavy component by-products

CN1522996A has further developed the disclosed method of CN1296937A. After adding benzaldehyde as initiator and optimizing the reaction conditions, from the effects of its examples, the selectivity of benzaldehyde and benzyl alcohol can reach nearly 90%, but there are still nearly 10% selectivity. % of unknown heavy component by-products

This method is the same as the shortcoming of US6495726, has used solvent and bromide or chloride, makes equipment corrode seriously, simultaneously bromide or chloride is difficult to separate from product, has polluted the quality of product

The common post-treatment process of the prior art is to adopt rectification to carry out rectification and separation of unreacted raw materials and products, which not only consumes a large amount of heat energy, but also benzaldehyde is easily heated to cause aldol condensation reaction and loss, benzyl alcohol, etc. It is easy to be heated and lost due to esterification of benzoic acid in the system, resulting in a large amount of residue in the distillation tower and low product yield, generally not more than 90%.

[0014] Toluene oxidation products benzaldehyde and benzyl alcohol are high value-added products, and benzoic acid has relatively low economic value. How to increase the total selectivity of benzoic acid, benzyl alcohol and benzaldehyde while increasing the conversion rate of toluene, especially high The selectivity and yield of the value-added target products benzaldehyde and benzyl alcohol, reducing the generation of other by-products and improving the economy are urgent problems to be solved

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