RU2296741C1 - Method of controlling cyclohexanol or cyclohexanone production processes - Google Patents

Abstract

FIELD: industrial organic synthesis.

SUBSTANCE: invention relates to production of cyclohexanol or cyclohexanone via hydrogenation of phenol or benzene with hydrogen in presence of catalyst and diluent followed by hydration in case of using benzene as starting material. Process is characterized by that hydrogen and benzene or hydrogen and phenol preheated in heat exchanger, provided with condensate intake control circuit, and circulation gas are supplied to vaporizer and preheater, provided with heating steam consumption control circuits, through supply lines provided with shutoff valves. Phenol or benzene and circulation gas, as well as heating steam and condensate consumptions are specified and adjusted. Preheated mix is then fed into separator to separate gas from liquid phase, which is removed, while remaining gas mixture is sent to hydrogenation reactors comprising temperature control zones and heat-extracting tube-type condensers and provided with phenol or benzene, hydrogen and condensate control circuits, temperature sensors connected to controllers to adjust consumptions of phenol or benzene, hydrogen and condensate, and wherein diluent volume level compared to that of catalyst is controlled and hydration temperature is measured. Resulting product enters cooler and then separation column provided with cyclohexanol or cyclohexanone recovery level control and adjusting, wherefrom it is directed to gas circulation line comprising cooler, separator, and compressor equipped with pipelines with circulation gas consumption control circuits.

EFFECT: increased productivity with regard to cyclohexanol or cyclohexanone.

2 dwg

Description

The invention relates to methods for producing and controlling contact devices in the presence of a cyclohexanol or cyclohexanone catalyst and may find application in the chemical industry, for example, in the production of caprolactam.

A known method of automatically controlling the catalytic process by feeding the initial mixture into the reactor depending on the flow rate, pressure drop along the length of the reactor. To improve the quality of the product, the flow rate of the initial mixture is adjusted according to the activity of the catalyst, determined by the average pressure drop along the length of the reactor. (Auth. Certificate. No. 480439, B 01 j 9/04, G 05 D 27/00, 1975). The disadvantage of this method is the low accuracy of determining the activity of the catalyst and the deterioration of the quality of the resulting product.

A known method of producing cyclohexanol / cyclohexanone in a mixture with cyclohexane and benzene, followed by isolation from the reaction products of cyclohexanol / cyclohexanone and recycling the fraction sent to the regeneration stage at elevated temperature and pressure. To simplify the process, the mixture is fed with benzene and then oxidized or hydrated, using hydrogen supplied to the hydrogenation reactor (Pat. SU No. 1833359, C 07 C 45/32, 35/05, 1993). The disadvantage is the low yield of cyclohexanol / cyclohexanone.

A known method of producing cyclohexanol electrochemically. The method includes reducing phenol in a sulfuric acid medium to cyclohexanol at a hydrogen pressure of 1.5 MPa (Pat. RF No. 2236395, IPC C 07 C 35/08, 29/20, C 25 V 3/04, 2003).

The disadvantage of this method is the low yield of cyclohexanol, in addition, the output depends on the pressure of hydrogen, and for implementation in an industrial environment, additional equipment with appropriate monitoring and control is necessary.

A known method for the isolation of cyclohexane under industrial conditions by distillation in two apparatus with condensers in which gases, water and part of unreacted cyclohexane is returned to the column, and the concentrated fraction is used in the production of caprolactam (Pat. RF No. 2226185, IPC С 07 С 13/18, 27/28, 45/82, 29/18, 2000).

The disadvantage of this method is the limited scope, as well as the non-use of gas emissions during the processing of feedstock (phenol, benzene).

The closest is the method of producing cyclohexanol by hydrogenation of phenol in the presence of a catalyst in a solvent medium, using a specific catalyst and hydrogenation is carried out in a water-alcohol medium (SU No. 1051056, C 07 C 35/08, 1983). The disadvantage of this method is the limited scope.

The objective of the invention is to expand the scope of the method and increase productivity on cyclohexanol or cyclohexanone.

The problem is solved in that in the known method of controlling the process of producing cyclohexanol or cyclohexanone by hydrogenation of phenol or benzene with hydrogen in the presence of a catalyst and diluent, followed by hydration in the case of using benzene as the starting product, while the feed line having shut-off valves, hydrogen and benzene or hydrogen and phenol preheated in a heat exchanger with a condensate flow control loop, and the circulating gas is fed to the evaporator and heater from the loop In order to control the flow rate of heating steam, the flow rates for phenol or benzene and circulating gas, as well as heating steam and condensate are set and corrected, then the heated mixture enters the separator to separate the gas from the liquid phase that is discharged, followed by the remaining gas mixture in hydrogenation reactors containing temperature control zones and condensers with pipelines for heat removal and equipped with circuits for controlling the flow of phenol or benzene, hydrogen and condensate, temperature sensors s connected to the controllers with the correction of the flow rates of benzene or phenol, hydrogen and condensate, regulation of the volume level of the diluent in relation to the catalyst, with the determination of the hydration temperature, while the resulting product enters the refrigerator, and then into the separation column with a control loop and correction of the level of allocation cyclohexanol or cyclohexanone and into the gas circulation line, consisting of a refrigerator, a separator and a compressor, equipped with pipelines with circulating gas flow control circuits ov. A study of the production of cyclohexanol / cyclohexanone showed that it is possible to produce their joint production with the modernization of existing equipment. It was shown that for the processing of coal benzene and for the hydrogenation of petroleum benzene, the specifics of these processes are used. For the processing of coal benzene, an elevated temperature is used, and for the processing of the starting reagents (benzene or phenol), temperature limits are used to eliminate adverse reactions. In addition, methods are used to dilute the upper and middle layers of the catalyst along the height of the hydrogenation reactor with an appropriate temperature control, which increases the selectivity and speed of the processes during the conversion of phenol or benzene to cyclohexanol or cyclohexanone. To exclude explosive situations, automatic shutoffs are used that cut off the supply of initial reagents for the process. For the efficiency of the processes, stripping and circulating gases are used. When controlling, they use controllers that use standard P, PI control laws to control the costs of raw materials and products.

The essence of the invention is illustrated by the drawing, (without limiting the scope of the invention) which depicts a schematic diagram of the production control of cyclohexanol / cyclohexanone obtained from phenol or benzene. The control circuit (figure 1) includes devices 1-13.

1 - heat exchanger for heating phenol;

2 - evaporator for heating phenol / benzene, hydrogen, circulation and stripping gas;

3 - heater for phenol / benzene;

4 - a separator for separating gas from the liquid phase;

5 - hydrogenation reactor;

6 - condenser for heat removal during the hydrogenation of phenol / benzene;

7 - hydrogenation reactor;

8 - condenser for heat removal during the hydrogenation of phenol / benzene;

9 - refrigerator to remove heat after hydrogenation;

10 - separation column for the isolation of cyclohexanol / cyclohexanone.

For gas circulation are used

11 - refrigerator; 12 - separator; 13 - compressors, which form the circulation system "column 10 - refrigerator 11 - separator 12 - compressor 13" to return the circulation gas for the process (in the line of exhaust gases). The control system is based on controllers 14, which is connected to control sensors and valves 15-43, forming control loops. The electrical communication lines of the sensors and valves with the controllers 14 in the drawings are conventionally shown with a gap (Fig.1, 2). The system includes

- a phenol flow control loop 15, 16 (sensor 15, valve 16), a shut-off valve 17, and a controller 14 (which is not mentioned hereinafter);

- a benzene flow control loop 18, 19 and a shut-off valve 20;

- a circuit for controlling the flow of hydrogen 21, 22 and a shut-off valve 23;

- a loop for regulating the flow of circulating gas 15a, 15b;

- steam flow control loop (1.6 MPa) 24, 25 (sensor 24 and valve 25) for heating phenol in heat exchanger 1;

- heating steam flow control loop (1.6 MPa or 4 MPa) 26, 27 for heating phenol / benzene in evaporator 2;

- heating steam flow control circuit 28, 29 for heating phenol / benzene in heater 3;

- a condensate flow control loop 30, 31 and 32, 33 in the condensers 6, 8 for removing heat during the hydrogenation of phenol / benzene in the hydrogenation reactors 5 and 7;

- temperature sensors 34, 35, 36 in the hydrogenation reactor 5;

- temperature sensors 37, 38, 39 in the hydrogenation reactor 7;

- a flow control loop for cyclohexanol / cyclohexanone 40, 41 in the separation column 10; valves 42, 43 on the supply line of phenol and benzene to the separator 4.

The method for producing cyclohexanol or cyclohexanone in contact apparatuses is as follows.

Set the cost of the load:

phenol up to 7000 t / h (including at start-up no more than 0.2 t / h);

for benzene up to 7000 t / h (including at start-up no more than 0.5 t / h);

hydrogen up to 65 t / t;

the costs of the circulation circuit "column 10-refrigerator 11 - separator 12 - compressor 13" - 3000 - 4000 nm ³ / h;

diluent volume level with respect to the catalyst 0.44 (determined when the reactor is started),

temperature control zones in reactors 7, 5:

for phenol no more than 210 ° С with an alarm of 210 ° С and blocking of 230 ° С in a reactor 7 and 160-200 ° С in a reactor 5 with an alarm of 200 ° С and a blocking of 220 ° С; (1a)

benzene no more than 240 ° C with an alarm of 240 ° C and a lock of 250 ° C in a reactor 7 and 170-230 ° C in a reactor 5 with an alarm of 230 ° C and a lock of 240 ° C. (1b)

Enter information on the current values of the processes into the controllers 14. When working on phenol, the heated phenol enters the tube space of the heat exchanger 1, where it is heated by condensate supplied to the annulus, and then goes to the evaporator 2, where circulating gas and fresh hydrogen are added, where the components are heated, and then the mixture enters the steam heater 3, where it is heated to a temperature due to the supply of heating steam. Then, the initial mixture enters the separator 4 (the valve 42 is open and the valve 43 is closed) to separate the gas from the liquid phase, which then, if necessary, is discharged into the drainage tank. Next, the mixture is sent to the tube space of the reactors 5, 7, equipped with capacitors 6, 8 to remove heat during the hydrogenation of the phenolic mixture.

After the hydrogenation reaction, the crude cyclohexanol is sent to the refrigerator 9 and the separation column 10 to isolate the cyclohexanol. From the top of the column 10, the exhaust gases are sent to the refrigerator 11, the separator 12 and to the compressor 13, where they are compressed, and returned to the process, forming a circulation system "column 10 - refrigerator 11 - separator 12 - compressor 13". Then, the circulation gases enter the exhaust gas line for supplying hydrogen to the process.

When working on benzene, the heated benzene enters the tube space of the evaporator 2, where stripping and circulating gases and hydrogen are added. The components are heated due to the condensation heat supplied to the evaporator 2, then the mixture enters the steam heater 3, where it is heated. Then the heated mixture is sent to heat exchanger 1, where it is heated to 155 ° C using petroleum benzene, and when using coal benzene, the mixture is heated to 230 ° C by supply of heating steam (3.9 MPa) and then sent to separator 4 and then according to the scheme through reactors 5, 7, a refrigerator 9 and a separator 10.

Consider examples of obtaining cyclohexanol and cyclohexanone.

Example 1

According to the information of the sensor 15, phenol with a pressure of 0.8 MPa and a flow rate of 2.3 t / h (at start-up no more than 0.2 t / h) is fed into the tube space of the heat exchanger 1, where it is heated to a temperature of 130-150 ° C due to heat condensation of steam with a pressure of 1.6 MPa supplied through valve 25 (control loop 15, 16,) to the annulus of heat exchanger 1. Steam is supplied by temperature (not shown conditionally) and pressure of the sensor 24 (control loop 24, 25). Phenol heated to 150 ° C enters through evaporator 2 through a nozzle, to which circulating gas and stripping gas in the amount of 3300 nm ³ (control loop 15a, 15b) and fresh hydrogen, according to sensor 21, with a pressure of 2.1-2.4 MPa at flow rate 62 t / t (control loop 21, 22). The evaporation of phenol in a mixture with gas and hydrogen occurs due to the heat of condensation of steam with a pressure of 1.6 MPa supplied through valve 27 to the annulus of evaporator 2. The steam is supplied by temperature (not shown conditionally) and pressure of the sensor 26 (control loop 26, 27 ) Then, the initial mixture enters heater 3, where it is heated to 175-180 ° C due to the supply of heating steam with a pressure of 1.6 MPa supplied through valve 29 to the annulus of heater 3. Steam is supplied by temperature (not shown conditionally) and pressure sensor 28 (control loop 28, 29). From the heater 3, the reaction mixture enters the separator 4 (valve 42 is open, and valve 43 is closed), from where it is sent to the hydrogenation reactor 5, which is filled with catalyst. The process temperature significantly affects the selectivity and speed of the hydrogenation reaction. The phenol hydrogenation process proceeds with the release of heat. The optimum range is 170-180 ° C, the higher the phenol-hydrogen ratio, the lower the temperature in the reactor is 5 and 7. In addition, with an increase in temperature, the proportion of side reactions of formation of cyclohexane, methane, water and other organic compounds increases, which is necessary consider when controlling the process, taking into account the temperature limit with phenol. For a stable reaction, the catalyst is diluted (before starting the reactors) with non-hydrogenating material, which can be adjusted depending on the activity of the catalyst. In this case, temperature sensors 34, 35, 36 are used for monitoring, as the average measured by sensors ((175 + 176 + 180) / 3 = 177 ° С) located along the height of the catalyst. A condenser 6 is used to maintain a temperature of 177 ° C in the reaction zone. The condensate level is maintained by a level sensor 30 and valve 31 (control loop 30, 31). Then the reaction mixture is sent to a hydrogenation reactor 7, which is also filled with a catalyst and non-hydrogenating material, as a reactor 5. To control the temperature (activity of the catalyst), sensors 37, 38, 39 are used, as the average measured by sensors, for example 179 ° C. Heat is removed by a condenser 8 with a level sensor 32 and a valve 33 (control circuit 32, 33). From the reactor 7, the reaction mixture enters the refrigerator 9 (where it is cooled with circulating water) and is sent to the separation column 10 (the level is maintained by the control loop 40, 41), where the liquid cyclohexanol is separated from the circulating gas and sent in an amount of 2.1 t / h to obtain caprolactam. Circulation gas (3000-4000 nm ³ / h) is sent along the “column 10 - refrigerator 11 - separator 12 - compressor 13” circuit to compression to a pressure of 1 MPa and returned to the process through the gas circulation line (control loop 15a, 15b) and together with hydrogen is used to obtain another batch of cyclohexanol. If the process is interrupted, the operator, on command from the controller 14, acts on the shut-off valve 17 at the phenol supply (for example, at 0.1 t / h) and the shut-off valve 23 at the hydrogen supply. In addition, control the restrictions on signaling and blocking by temperature (1a) upon receipt of cyclohexanol in reactors 5, 7, which in this case did not go beyond the specified limits (177 ° and 179 ° C).

Example 2

According to the sensor 18, benzene in the amount of 2.8 t / h with a pressure of 0.75 MPa (when starting up the unit is not more than 0.5 t / h) is fed into the tube space of the evaporator 2, where it is heated to a temperature of 125-145 ° С due to steam condensation heat with a pressure of 1.6 MPa or 0.8 MPa supplied through valve 27 (control circuit 18, 19) to the annulus of evaporator 2. Steam is supplied by temperature (not shown conditionally) and pressure 26 (control circuit 26, 27 ) supplied to the same circulation and stripping gas in an amount of 3700 nm ³ (control circuit 15a, 15b) and fresh odorod 64 m / g by the sensor information 21 (control circuit 21, 22). Then the benzene mixture enters heater 3, where it is heated to a temperature of 150 ° C due to the supply of 1.6 MPa (or 0.8 MPa) of steam to the annular space supplied through valve 29. The steam is supplied by temperature and pressure of the sensor 28 Next, the heated mixture enters the heat exchanger 1 (valve 42 is closed and valve 43 is open), where it is heated to 160 ° C using petroleum benzene with a pressure of 1.6 MPa, and when cleaning coal benzene to a temperature of 230 ° C due to the supply of heating 3.9 MPa steam supplied through the valve 25 (control loop 24, 25).

From the heat exchanger 1, the mixture enters the separator 4 and then into the hydrogenation reactor 5, which is filled with a catalyst with a diluent (the reaction of benzene with hydrogen is exothermic). The technological process of purification of benzene from thiophene and other compounds is reduced to the absorption of sulfur compounds and hydrogenation with hydrogen at a temperature of 200-230 ° C. For a stable reaction, temperature is measured by sensors 34, 35, and 36 (and as the average measured by sensors, for example, 215 ° C). A condenser 6 is used to maintain a temperature of 215 ° C in the reaction zone. The condensate level is maintained by a level sensor 30 and valve 31 (control loop 30, 31) .3 Then the reaction mixture is sent to a hydrogenation reactor 7. Temperature sensors 37, 38 and 39 are used to control the temperature. (average measured by sensors, for example 220 ° C). A temperature of 220 ° C is maintained by a capacitor 8 with level sensors 32 and a valve 33 (control loop 32, 33). From the reactor 7, cyclohexanone enters the refrigerator 9 in the amount of 2.6 t / h and is sent to the separation column 10, which maintains the level of 40%, using the sensor 40 and valve 41 (control loop 40, 41) and then to the finished goods warehouse . If the process is violated, the controller 14 uses the shut-off valve 20 to supply benzene (for example, 0.3 t / h) and valve 23 to prevent the supply of hydrogen to the process. In addition, the temperature and signaling blocking restrictions are monitored (1b) upon receipt of cyclohexanone in reactors 5, 7, which in this case did not go beyond the specified limits of 215 ° and 220 ° C.

Thus, modernization with appropriate re-equipment of equipment and control loops allows the use of petroleum and coal benzene in the production of cyclohexanone to produce caprolactam in comparison with other industries. To eliminate adverse reactions, the temperature is controlled by the height of the catalyst — its activity and, if necessary, catalyst dilution methods are used, which increases the selectivity and speed of phenol and benzene reactions to produce cyclohexanol or cyclohexanone. To exclude explosive situations, cutoff devices are used and circulating gases are used to increase the efficiency of processes, which ultimately increases production efficiency.

The implementation of the method for managing the production of cyclohexanol and cyclohexanone is scheduled for 4 square meters. 2005 in Togliatti, Kuibyshevazot.

Claims (1)

A method of controlling the process of producing cyclohexanol or cyclohexanone by hydrogenating phenol or benzene with hydrogen in the presence of a catalyst and diluent, followed by hydration in the case of using benzene as a starting product, characterized in that in the supply lines having shut-off valves, hydrogen and benzene or hydrogen and phenol preheated in a heat exchanger with a condensate flow control loop, and the circulating gas is fed to the evaporator and heater with flow control loops steam, at the same time, the costs of phenol or benzene and circulating gas, as well as heating steam and condensate, are set and corrected, then the heated mixture enters the separator to separate the gas from the liquid phase, which is discharged, followed by the remaining gas mixture into hydrogenation reactors, containing temperature control zones and condensers with pipelines for heat removal and equipped with control circuits for the consumption of phenol or benzene, hydrogen and condensate, temperature sensors connected to the controller frames with the correction of the flow rates of benzene or phenol, hydrogen and condensate, the regulation of the volume level of the diluent in relation to the catalyst with the determination of the hydration temperature, while the resulting product is sent to the refrigerator, and then to the separation column with a control loop and correction of the level of release of cyclohexanol or cyclohexanone and a gas circulation line consisting of a refrigerator, a separator and a compressor, equipped with pipelines with circulating gas flow control circuits.

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