Process method of adipic acid by cyclohexane oxidation

Abstract

The invention discloses a process method of adipic acid by cyclohexane oxidation. The process method comprises the following steps: a step (a) of oxidation, namely introducing cyclohexane, solvent, catalyst and oxygen-containing gas continuously into an oxidation reactor to react, so as to obtain a oxidation reaction solution containing adipic acid and six-carbon oxygen-containing compound; a step (b) of liquid-liquid stratification, namely stratifying the oxidation reaction solution obtained in the step (a) at the temperature of 50-160 DEG C and the pressure of 0.1-1.2MPa, so that an upper oil-phase containing cyclohexane and six-carbon oxygen-containing compound and a lower solvent-phase containing adipic acid and six-carbon oxygen-containing compound are obtained; step (c) of separation of adipic acid, namely cooling, crystallizing and filtrating the lower solvent-phase obtained in the step (b), so that the filtrate and the adipic acid product are obtained. The process method has the advantages of simple technology, low cost, high efficiency, high raw material conversion rate and good target product selectivity; the conversion rate of the cyclohexane is higher than 99% and the selectivity of the adipic acid is higher than 91%.

Description

technical field [0001] The invention relates to a method for preparing adipic acid, in particular to a process for preparing adipic acid by oxidation of cyclohexane. Background technique [0002] Adipic acid is an important basic raw material for the nylon and polyurethane industries, as well as an intermediate for many lubricating oil additives. At present, the industrial production of adipic acid mainly uses cyclohexane as the starting material, and produces adipic acid through a two-step process. Among them, the first step uses air to oxidize cyclohexane to cyclohexanol and cyclohexanone (KA oil), and the second step uses nitric acid to oxidize KA oil to adipic acid. This route accounts for about 93% of the global total production capacity. Its reaction process is as follows: [0003] [0004] The first step process of the above route often uses a homogeneous cobalt-based catalyst or does not add a catalyst. During the reaction, an intermediate product cyclohexyl hyd...

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Problems solved by technology

[0011] (1) A large amount of cyclohexyl hydroperoxide will be generated during the oxidation process. This substance is easily decomposed by heating, and there is a high risk of explosion. There are major safety hazards in the actual production process

[0012] (2) The low boiling point components are mainly cyclohexanone, cyclohexanol, etc. During the distillation process, cyclohexanone is easy to polymerize, and cyclohexanol is easy to form an ester with the acid in the system, which also leads to considerable loss of cyclohexanone and cyclohexanone in the distillation process. Cyclohexanol, while more high-boiling point six-carbon oxygenated compounds, such as caprolactone, epoxy cyclohexane, cyclohexenone, etc., are easily polymerized and lost when heated, resulting in a decrease in the utilization rate of cyclohexane and low economic efficiency. good

[0013] (3) The distillation process cannot recover more six-carbon oxygenated compounds such as cyclohexanedione, cyclohexanolone, and cyclohexenone with high boiling points, which also leads to a decrease in the utilization rate of cyclohexane

[0015] (1) The six-carbon oxygen-containing compound required for the reaction needs to be added outside the system, and the price of the six-carbon oxygen-containing compound is higher than the target product adipic acid, resulting in an increase in production costs;

[0016] (2) The conversion rate of raw material cyclohexane is only 12.4~19.9%, and the production efficiency is low;

Since water is generated during the reaction process, water is a reaction poison, and staying in the reaction system for a long time will reduce the main reaction speed, so that the deep oxidation reaction speed of adipic acid will increase relatively, resulting in a decrease in the selectivity of the product

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