Oxidation method for cyclohexane

Abstract

The invention provides an oxidation method for cyclohexane. The method comprises the step of subjecting a liquid mixture containing cyclohexane and an oxidant to passing through catalyst beds under the condition of oxidation reaction, wherein the catalyst beds comprise a first catalyst bed and a second catalyst bed; on the basis of the flow direction of the liquid mixture, the first catalyst bed is located at the upper stream of the second catalyst bed; a titanium-silicon molecular sieve filled in the first catalyst bed is a hollow titanium-silicon molecular sieve; and the titanium-silicon molecular sieve filled in the second catalyst bed is the titanium-silicon molecular sieve different from the hollow titanium-silicon molecular sieve. The method provided by the invention can effectively prolong the single-way service life of the titanium-silicon molecular sieve used as a catalyst, reduce regeneration frequency of the catalyst, improve production efficiency, and enhance operation stability and prolong the total service life of the catalyst at the same time.

Description

technical field [0001] The invention relates to a cyclohexane oxidation method. Background technique [0002] Cyclohexanone is an important chemical raw material, widely used in fiber, synthetic rubber, industrial coating, medicine, pesticide, organic solvent industry. Cyclohexanol is also an important chemical raw material, used to make adipic acid, plasticizers and detergents, as well as solvents and emulsifiers. Especially due to the rapid development of the polyamide industry, the demand for cyclohexanone (alcohol) as an intermediate for the preparation of nylon-6 and nylon-66 is more than 1,000,000 tons per year all over the world. Today, there are three main production process routes for cyclohexanone: cyclohexane liquid-phase oxidation, phenol hydrogenation and benzene partial hydrogenation, while cyclohexane oxidation is the main process for industrial production of cyclohexanone, accounting for 90% of the production process. %above. However, this production proce...

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Problems solved by technology

[0003] Industrially, there are generally three methods for producing cyclohexanone by oxidation of cyclohexane: one is the catalytic oxidation using cobalt salt as a catalyst. Fouling has been basically eliminated

The second is the boric acid catalytic oxidation method. This method requires high infrastructure investment, high energy consumption, very complicated process, difficult operation, and it is easy to cause serious blockage of equipment and pipelines.

The third is the non-catalytic oxidation of direct oxidation with air. This method effectively avoids the problem of reactor fouling and is widely used in industry. Large, high energy consumption, and relatively large pollution, especially in the decomposition process of cyclohexyl hydroperoxide, cyclohexanone (alcohol) has poor selectivity and low yield

However, there are still common problems such as low cyclohexane conversion rate and low effective utilization rate of hydrogen peroxide. At the same time, the catalyst is not easy to separate, which increases the cost of product and catalyst separation.

[0005] When titanium-silicon molecular sieves are used as catalysts to oxidize cyclohexane, the common problem is that with the prolongation of the reaction time, the catalytic activity of titanium-silicon molecular sieves will show a downward trend, resulting in the conversion rate of oxidant, the effective utilization rate of oxidant and the selectivity of target oxidation products. reduce

[0007] However, when the regenerated catalyst is put into operation again, especially after being regenerated in the device, the activity and selectivity of the catalyst fluctuate greatly, and it takes a long time to stabilize; at the same time, it is necessary to combine operations such as increasing the reaction temperature To achieve the smooth operation of the reaction, but this will further accelerate the deactivation of the catalyst and reduce the selectivity of the target oxidation product, which will affect the refining and separation of subsequent products, and is also not conducive to safe production

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