CS257204B1 - A method of performing a Beckmann cyclohexanone oxime rearrangement and a method for performing the same - Google Patents

Abstract

The solution relates to a method of carrying out the Beckmann rearrangement and a device for carrying out this method. The device consists of a reaction and aftercooling loop, wherein the reaction loop includes a mixer, a tubular reactor, an intermediate reservoir, a circulation pump and a heat exchanger, and the aftercooling loop includes an intermediate reservoir, a circulation pump and a heat exchanger. The flow rate in the reaction loop is in the range of 60 to 100 wt. % of the flow rate calculated by the solution of the adiabatic tubular reactor, and the flow rate in the aftercooling loop differs by no more than 30% of the flow rate determined by the control calculation of the included exchangers.

Description

The present invention relates to a process for carrying out a Beckmann cyclohexanone oxime rearrangement in an oleate and to an apparatus for carrying out the process.

Cyclohexanone oxime rearrangement apparatuses in the production of caprolactam are usually solved in a circulation loop consisting of

- a mixer of circulating lactamsulphuric acid and injected cyclohexanone oxime (usually of the ejector, hydrocyclone, etc.) type.

- tubular reactor

- intermediate storage

- circulating medium pump

- heat exchanger with filtered water cooling, heated filtered water, possibly with circulation cooling

The disadvantage of these devices is the necessity to operate them in a narrow power range. It is known that the capacity decreases as the capacity of the tubular reactor decreases. Due to the reduction of the oxime concentration at the inlet to the tubular reactor, and thus the adiabatic temperature rise, which has a decisive influence on the reaction rate, the conversion rate at the exit from the tubular reactor decreases. .

Conversely, as the capacity increases and the cooling capacity is exceeded, the temperature rises along the entire circulation loop, resulting in an increase in the by-products content. In addition, cooling water warming decreases and water consumption increases disproportionately.

The above-mentioned disadvantages are eliminated by the method of carrying out the Beckmann cyclohexanone oxime rearrangement in an oleate, wherein the flow in the reaction loop is in the range of 60 to 100 wt. The flow rate calculated by the adiabatic tubular reactor solution at the required cyclohexanone oxine conversion and the flow rate in the after-cooling loop differ by 30% of the flow rate determined by the control calculation of the heat exchangers under conditions. The process is carried out at temperatures of 70 to 150 ° C, acidity of 54 to 61% by weight. (content of I ₂ SO ₄ and SO ₂ as H ₂ SO ₄ in the reaction mixture in%) in a tubular reactor circulation device, which consists in that it consists of a reaction and a cooling loop, with a mixer in series in the reaction loop, a tubular reactor, an intermediate stack, a circulation pump and a heat exchanger, and an intermediate stack, a circulation pump and a heat exchanger are arranged in succession in the after-cooling loop, the common for both loops being an intermediate stack or even a pump or even a heat exchanger.

Figures 1 and 2 show a solution according to the invention, wherein:

reaction loop

II aftercooling loop mixer tubular reactor intermediate stack 4 a, b circulation pumps a, b heat exchangers

6 ^ a, b circulating loop control valves

A pipe for injected oxime

B pipe for sprayed oleum

C pipe for product

D cooling water pipes

E line for circulating reaction mixture

Technical cyclohexanone oxime with a water content of 3.5 to 4.5% by weight. % and cyclohexanone 0.4 to 0.8 wt. is injected via line A into the mixer 31. Oleum having a free sulfur trioxide content of 23 to 26 wt. is sprayed into the circulation behind the intermediate stack 3, preferably into the suction of the circulation pump 4 a, b of the reaction loop via line B.

The product - lactamsulphuric acid - with a caprolactam concentration of 39 to 56% by weight, an acidity of 54 to 61% by weight. and a free sulfur trioxide content of 3.0 to 6.0 wt. The ratio of the cyclohexanone oxime-olea feed is controlled according to the desired acidity of the lactamsulphuric acid produced. In the process according to the invention, the flow of the reaction mixture through the reaction loop is determined by the desired degree of conversion of cyclohexanone oxime at the outlet of the tubular reactor 2. The flow of the reaction mixture in the after-cooling loop is determined by the desired warming of the cooling water. It is desirable to include a regulating element, such as an orifice with a pneumatically or electrically controlled control valve 2 a, b, between the circulation pump and the mixer in the reaction loop and / or between the circulation pump and the intermediate tank in the after-cooling loop.

It is advisable to regulate the flow of cooling water in line D according to the temperature in the storage tank 2.

The advantage of the device according to the invention is its great variability in terms of performance due to the possibility of independent flow control in both the reaction and aftercooling loop. By reducing the performance of the apparatus, it is possible to continuously reduce the circulation in the reaction loop, thereby ensuring an optimal concentration of cyclohexanone oxime in the lactamic acid at the inlet of the tubular reactor necessary to achieve the desired conversion. Reducing the circulation in the reaction loop contributes favorably to the conversion growth also due to the prolonged residence time of the reaction mixture in the tubular reactor. On the other hand, by increasing the circulation, the cooling loop ensures optimum cooling capacity by increasing circulation in the after-cooling loop, which allows the desired temperatures to be maintained throughout the plant and thus avoids the formation of by-products (and thus caprolactam losses) to a minimum. This is achieved by achieving a higher temperature gradient on the cooling water and thus reducing its consumption, as well as the possibility of using the dissipated heat in the power plant operation.

He did

A device containing only the reaction loop was used. The mixer was constructed as a hydrocyclone, the dimensions of the tubular reactor were: length 1 = 5 m, diameter d = 0.263 m 3 2 and volume V = 0.270 m. Heat exchanger surface 150 m. The acidity of the reaction mixture (given the relative amounts of oleate and cyclohexanone oxime injected) was 59 wt. The achieved technological parameters are given in Table II.

Example2

The apparatus shown in Example 1 was supplemented with a cooling loop (Fig. 1) with a 150 m heat exchanger. The acidity of the reaction mixture was again 59% mot., The achieved technological parameters are shown in Table XI.

Example3

Based on mathematical modeling we were collected cyclohexanone oxime concentration profiles in the tube reactor mentioned in Example 1 at reducing circulation _c m in the reaction loop.

The parameters remained constant:

hm. cyclohexanone oxime feed F = 5.3 t / h acidity A = 58 wt.

temperature in the reaction loop downstream of the cooler 5a t = 80 ° C

The following Table I shows the resulting reactor volume values V _{r of} the cyclohexanone oxime C inlet concentration, the reactor length l _r, and the reaction time (ζ. Necessary to achieve the oxime concentration in the reaction mixture at the outlet of the tubular reactor).

C _r = Ο, βΐ kg / m ³

Further, the temperature at the end of the tubular reactor t _r and the thermal gradient on the tubular reactor Tt are given.

Table I r

t / h kg / m ³ m ³ m

325 300 275 250 225 200 23.0 24.9 27.1 29.8 33.1 37.3 0.268 0.224 0.181 0.142 0,108 0,079 4.93 4,11 3.32 2.61 1.98 1.44 4.23 3.81 3.36 2.91 2.45 2.01 101.6 103.3 105.5 108.8 111.1 115.0 21.6 23.3 25.5 28.8 31.1 35.0

II

Units

Example 1

Example 3 wt., Cyclohexynonoxime spray w / w wt. flow - reaction loop t / h mass flow - cooling loop t / h lactamsulphuric acid temperature

- intermediate tank ° C

- reaction loop (at 5a) ° C

- cooling loop (after 5b) ° C

- at the end of the tubular reactor ° C

- adiabatic temperature increase ° C

4.7

330

114

114

5.3

330

180

105 cooling water temperature

- input ° C

- output ° C

- warming of cooling water ° C oxime concentration at the end of the tubular reactor loss kg / m ³ % 0.80

0.01

1.05

Claims (3)

Process for carrying out a Beckmann cyclohexanone oxime rearrangement in an oleate at 70 to 150 ° C, an acidity of 54 to 61% by weight. characterized in that the flow rate in the reaction loop is in the range of 60 to 100 wt. The flow rate calculated by the adiabatic tubular reactor solution at the desired cyclohexanone oxime conversion and that the flow rate in the after-cooling loop differs by no more than 30% of the flow rate determined by the control calculation of the heat exchangers under conditions. 2. Apparatus for carrying out the method according to claim 1, characterized in that it comprises a reaction and a quench loop, wherein the mixer, the tubular reactor, the intermediate storage tank, the circulation pump and the heat exchanger are arranged in the reaction loop and a circulation pump and a heat exchanger, the common for both loops being an intermediate storage tank or even a circulation pump or even a heat exchanger. 3. Apparatus according to claim 2, characterized in that a regulating member, preferably an orifice with a pneumatically or electrically controlled regulating valve, is arranged between the circulation pump and the mixer in the reaction loop and / or the circulation pump and the intermediate storage tank in the after-cooling loop. 2 drawings