TW201331165A - Process for the production of a mixture comprising cyclohexanol and cyclohexanone - Google Patents

Abstract

A continuous process for the preparation of a mixture of cyclohexanone and cyclohexanol, said process comprising: (a) oxidizing, in an oxidation section, cyclohexane in the presence of an oxygen-containing gas, without a transition metal-containing catalyst to form an oxidized reaction mixture; (b) cooling, in a cooling section, the oxidized reaction mixture from a temperature T1 to a temperature T3; (c) decomposing, in a decomposition section, the oxidized reaction mixture to form a decomposed reaction mixture, which decomposed reaction mixture has a temperature T4; and (d) removing cyclohexane from the decomposed reaction mixture; characterized in that step (b) comprises (i) cooling the oxidized reaction mixture from a temperature T1 to a temperature T2 by means of an in-process heat exchanger configured to heat the decomposed reaction mixture obtained in step (c) from a temperature T4 to a temperature T5; and (ii) cooling the oxidized reaction mixture from a temperature T2 to a temperature T3 by means of a cooling unit; and apparatus for carrying out the same.

Description

Method for producing a mixture comprising cyclohexanol and cyclohexanone (1)

This invention relates to a process for the preparation of a mixture comprising cyclohexanol and cyclohexanone.

Cyclohexanol and cyclohexanone are commercially available from cyclohexane in a two-step process. The first step is to oxidize cyclohexane by an oxygen-containing gas to produce a mixture comprising cyclohexanol, cyclohexanone, and cyclohexyl hydroperoxide. Conventionally, in this first step, cyclohexane is oxidized in a liquid phase having air. In the case of industrial grade processes, this oxidation reaction is usually carried out in one or more reactors in the range of 130 to 200 ° C, and it is not catalyzed or is a soluble cobalt catalyst. To catalyze. The evaporated cyclohexane and other products in the gaseous effluent are concentrated and recovered, and the off-gas leaves the system. The product mixture is recovered from the liquid effluent from one or more reactors, while the unreacted cyclohexane is recycled (Kirk-Othmer, Encyclopedia of Chemical Technology, John Wiley & Sons, New York, 1979, 3rd Edition, Vol. 7, pp. 410-416; and Ullmanns, Encyklopädie der Technischen Chemie, Verlag Chemie, Weinheim, 1975, 4th Edition, Vol. 9, pp. 689-698).

In the known method, the first step (oxidation reaction) occurs substantially in an oxidation zone, where the reaction (I) occurs. The prepared oxidized reaction mixture is composed of cyclohexanol, cyclohexanone, cyclohexyl hydroperoxide, unreacted cyclohexane, and some minor by-products. In the second step, the oxidized reaction mixture is decomposed in the presence of the hydroxyl ion-containing phase and the cobalt catalyst in accordance with the reaction (II) in the decomposition zone to form a decomposed reaction mixture. Hydroxyl ions also have the effect of neutralizing acidic by-products (not described). For the sake of simplicity, reactions (I) and (II) are described herein as unbalanced reaction formulas. The by-products obtained in the reactions (I) and (II), respectively, are generally different in terms of composition, concentration, and amount.

(I) C ₆ H ₁₂ +O ₂ → C ₆ H ₁₀ O+C ₆ H ₁₁ OH+C ₆ H ₁₁ OOH+ by-product

The decomposed reaction mixture is then sent to the distillation zone where cyclohexane is distilled. The next step is to produce a mixture of cyclohexanone and cyclohexanol.

EP 0 579 932 describes a process in which the oxidized reaction mixture leaving the oxidation zone is cooled to at least 10 ° C, preferably at least 30 ° C, before allowing the cyclohexyl hydroperoxide to be decomposed. After cooling, the decomposition of cyclohexyl hydroperoxide is produced by the influence of the catalyst containing a transition metal. Cooling can be achieved by a plurality of heat exchange devices or by expansion.

However, the conventional method has a problem, that is, when cooling When the procedure is applied to the oxidized reaction mixture, for example with water cooling, the energy is removed from the system.

In the same process, the decomposed reaction mixture is sent to a distillation zone where heat must be applied to remove cyclohexane by distillation of the decomposed reaction mixture. Therefore energy is applied to the system.

The inventors of the present invention have realized that at least some of the energy removed from the system upon cooling the oxidized reaction mixture can be transferred back to the system via the decomposed reaction mixture prior to evaporation prior to the decomposition reaction. .

It is an object of the present invention to provide an improved process for the manufacture of a mixture comprising cyclohexanone and cyclohexanol. More specifically, the present invention provides a process for making a mixture comprising cyclohexanone and cyclohexanol; this process requires less energy to perform than is known.

The above object can be attained by introducing a heat exchanger into the process such that the thermal self-oxidation reaction mixture can be transferred to the decomposed reaction mixture. The heat exchanger must be arranged on the one hand between the oxidation zone and the decomposition zone and on the other hand between the decomposition zone and the distillation zone.

Accordingly, the present invention provides a continuous process for the preparation of a mixture comprising cyclohexanone and cyclohexanol, the process comprising: a) in the oxidation zone, the cyclohexane is in the presence of an oxygen-containing gas but not The transition metal-containing catalyst is oxidized and forms an oxidized reaction mixture; b) the oxidized reaction mixture is cooled from temperature T ₁ to temperature T ₃ in a cooling zone; c) decomposed in a decomposition zone The oxidized reaction mixture is oxidized to form a decomposed reaction mixture, and the decomposed reaction mixture has a temperature T ₄ ; and d) the cyclohexane is removed from the decomposed reaction mixture; characterized in that step b) comprises: i) oxidizing the reaction mixture from temperature by means of an in-process heat exchanger in a process for heating the decomposed reaction mixture obtained in step c) from temperature T ₄ to temperature T ₅ T _{1 is} cooled to temperature T ₂ ; and ii) the oxidized reaction mixture is cooled from temperature T ₂ to temperature T ₃ by a cooling unit.

The invention further provides an apparatus suitable for carrying out the above method, the apparatus comprising: a) an oxidation zone; b) a cooling zone; c) a decomposition zone; and d) a cyclohexane recovery zone; characterized in that the cooling zone Including: i) a heat exchange device in a process; and ii) a cooling unit; and wherein the device is installed such that a reaction mixture passes through i), ii), c) sequentially, and i) Go back to d).

The invention has particular advantages because it is used to cool the oxidation The oxidized reaction mixture between the zone and the decomposition zone requires less cooling water. In addition, less heat is required from the outside of the system to separate cyclohexane from the reaction mixture obtained in the decomposition zone and the distillation zone.

The method of the invention additionally has the unpredictable advantages described below.

As is well known in the art, cooling the water to cool the reaction zone of the oxidation zone and the decomposition zone results in the formation of, for example, adipic acid and hydroxycaproic acid in the oxidation unit. The problem of contamination caused by the crystallization of organic acids as by-products. This is caused by the local low surface temperature in the heat exchanger and the relatively low temperature of the cooling water. In the claimed method, the first cooling step is accomplished with a reaction mixture derived from the decomposition zone. This reaction mixture has a temperature higher than that of the cooling water, so that the range of local cooling is reduced, thus causing contamination of the organic acid crystals.

Conversely, in the conventional method, heat is introduced substantially by steam into the reaction mixture located after the decomposition zone and/or in the distillation zone. The vapor can cause localized hot spots in the heat exchanger which can result in the formation of by-products (i.e., known "heavies" such as cyclohexanone oligopolymers. Reducing the use of steam to heat the reaction mixture results in less contact time of the reaction mixture with any such hot spots. Further, when the reaction mixture has been preheated, the temperature difference between the reaction mixture and the hot spot will be small, and therefore, the yield of by-products becomes lower, and the yield of the reaction is increased.

Therefore, the method of the present invention has the advantage of not only the heat exchange between the two reaction mixtures, but also the temperature difference to avoid Side effects that occur in conventional methods.

As used herein, the term "oxidized reaction mixture" means a reaction mixture that has been oxidized in the oxidation zone but has not yet been decomposed in the decomposition zone. "Oxidized" means that the reaction (I) as described above has occurred. It will be understood that this term does not mean that the reaction mixture is completely oxidized.

The oxidation zone is essentially a system in which the plurality of reactors are arranged in series, or is arranged in a pipe-reactor and divides the zones. Usually oxygen or oxygen-containing gas is supplied to each reactor or reactor component. The oxidation reaction can be catalyzed or uncatalyzed. Preferably, it is uncatalyzed. The oxidation reaction that is not catalyzed is substantially carried out in a relatively warm environment compared to the catalyst. Therefore, in the case of a method involving an uncatalyzed reaction, the magnitude of the temperature drop from the oxidation reaction to the decomposition reaction is substantially large. The process of the invention is therefore more advantageous for processes which contain such an uncatalyzed organic reaction.

Oxygen-containing gas is basically oxygen; and air with high oxygen content or low oxygen content, or oxygen mixed with nitrogen or other inert gas, can be selected. Air is preferred, but the air can be mixed with additional inert gas to eliminate the risk of explosion. Under such circumstances, a large amount of oxygen-containing gas is usually delivered to the reactor, but in this manner, the oxygen concentration of the exhaust gas is maintained below the explosion limit.

As used herein, the term "catalyst without transition metal" means that such an effective amount of such catalyst is not included. A trace amount of transition metal-containing catalyst can be present in the reaction mixture without significant effect fruit. Thus, the amount of transition metal-containing catalyst that is substantially ineffective for fractional distillation of the cyclohexyl hydroperoxide may be present.

The decomposition zone contains one or more decomposition units arranged in series. The decomposition unit is a reactor, and the above reaction (II) is carried out therein. As used herein, the term "decomposed reaction mixture" means the reaction mixture that has been decomposed in the decomposition zone. "Decomposed" means that the reaction (II) as described above has occurred. It will be understood that this term does not mean that the reaction mixture is completely decomposed. By definition, the decomposed reaction mixture has been subjected to an oxidation reaction as described above.

The temperature in each of the decomposition units is substantially between 20 ° C and 50 ° C, preferably between 50 ° C and 130 ° C. The use of a transition metal-containing catalyst such as cobalt or chromium or a mixture thereof or the like substantially produces a cyclohexyl hydroperoxide decomposition product. In terms of efficiency, the decomposition reaction can occur substantially at a lower temperature than the oxidation reaction. Preferably, the decomposition reaction is carried out as described in EP-A-004105 or EP-A-092867.

The decomposition zone may comprise one or more cleaning units. The decomposition zone may comprise one or more heat exchangers. One specific example of the decomposition zone includes a cleaning unit followed by a heat exchanger and a cleaning unit.

Cyclohexane can be isolated from the decomposed reaction mixture by techniques known to those skilled in the art. Essentially cyclohexane is distilled from the reaction mixture in a distillation zone. The distillation zone essentially comprises a number of distillation columns arranged in series. The distillation zone can be removed from the reaction mixture to remove a partial flash of cyclohexane as a precursor. The presence of a local flash operation has the advantage of removing the fractionated low boiling component, which is a low boiling component Including inert materials that hinder heat transfer in the condenser/reboiler. This is important if the various distillation columns are operated in series. The presence of partial flashing is arbitrarily limited for the effect of the heat required to be distilled into the decomposed reaction mixture to distill out the cyclohexane.

A heat exchanger is a device that transfers heat from one fluid stream to another. The heat exchanger can be direct (when the fluid flow is mixed) or indirect (when the fluid flow is still separated by the partition). The heat exchange device in the process is an indirect heat exchanger in which process fluid from a portion of the process delivers heat to another portion of the process fluid. The temperature of the oxidized reaction mixture is higher than that of the decomposed reaction mixture before the oxidized reaction mixture and the decomposed reaction mixture enter the heat exchange unit in the process. Thus, in the present invention, the oxidized reaction mixture is used to heat the decomposed reaction mixture. In other words, the heat exchange means in the process is arranged to heat the oxidized reaction mixture to the decomposed reaction mixture and to cool the oxidized reaction mixture.

Indirect heat exchangers are well known to those skilled in the art. Examples of inter-connected heat exchangers suitable for use in the present invention are shell & tube, flat plate, and thin tube. Basically, the indirect heat exchanger comprises a shell-and-tube type inter-connected heat exchanger. Shell-and-tube type inter-connected heat exchange devices are preferred because they can handle fluids with large flow rates.

The composition of the oxidized reaction mixture and the decomposed reaction mixture are each mainly cyclohexane. Therefore, the specific heat of each reaction mixture is roughly the same Wait. Due to the removal of by-products of the oxidation reaction and the decomposition reaction (and optionally because of the expansion of the oxidized reaction mixture before entering the decomposition zone), the flow rate of the decomposed reaction mixture may be less than the flow rate of the oxidized reaction mixture. .

A cooling unit is used to lower the temperature of the oxidized reaction mixture. The cooling unit is preferably cooled by expansion, but can also be cooled by a heat exchanger, such as adding cooling water to an indirect heat exchanger. If by the expansion, the part will cyclohexane (basically with some components C ₁ -C ₆₎ is evaporated. The evaporated cyclohexane is preferably fed back to the oxidation zone. This is due to the concentration of cyclohexyl hydroperoxide to be decomposed at the same time as expansion.

In a specific embodiment, the invention provides a method, further comprising: purifying the mixture of cyclohexanone and cyclohexanol after e) after step d). Substantial purification is carried out by methods well known in the art. In general, a purified mixture of cyclohexanone and cyclohexanol is obtained by distillation. By distillation, components having boiling points above and below the boiling point of cyclohexanone and cyclohexanol can be removed. In addition, cyclohexanol can be converted to cyclohexanone.

Basically T ₂ T ₄ ; basically T ₁ T ₅ . In the method of the invention, preferably T ₂ T ₄ and T ₁ T ₅ .

Basically T ₁ is from 130 ° C to 180 ° C. Preferably, T ₁ is from 140 ° C to 170 ° C, for example 160 ° C.

Basically T ₃ is from 40 ° C to 80 ° C. Preferably, the T ₃ is from 50 ° C to 70 ° C.

Basically T ₄ is from 80 ° C to 130 ° C. Preferably, the T ₄ is from 90 ° C to 110 ° C.

The temperature difference between the two X and Y, can be used △ _T, in the form of _{x y} is represented, in which case _{△ T x, y = T x} -T y. In the process of the present invention, substantially ΔT _1,2 is from 40 ° C to 70 ° C, wherein ΔT _1,2 = T ₁ -T ₂ . Preferably, ΔT _1,2 is from 50 ° C to 65 ° C, more preferably ΔT _{1,2 is} about 60 ° C.

A heat exchange device in a process having a complete benefit refers to a device in which the temperature of the heated reaction mixture that is being removed from the heat recovery unit is equivalent to the process being entered into the process. The temperature of the hot reaction mixture in the heat exchange unit. The advantage of this fully efficient system is that it reduces the cost of heating and cooling the system. What is craving in practice is that these temperatures should be as close as possible. In other words, in the present invention, T ₅ is as close as possible to T ₁ . In one embodiment, the invention provides a method wherein ΔT _{1,5 is} less than 20 ° C; and ΔT _1,5 = T ₁ -T ₅ . Preferably, ΔT _1,5 is less than 10 ° C, more preferably ΔT _1,5 is less than 5 ° C.

Basically step d) comprises distillation. By distillation, cyclohexane is removed from the top of one or more distillation columns. Preferably, step d) optionally comprises partial flashing followed by distillation in one or more distillation columns.

In the apparatus of the present invention, the cyclohexane recovery zone, i.e., d), substantially comprises a partial flash evaporator which is subsequently followed by one or more distillation columns. The partial flasher is used to remove a portion of the low boiling component (eg, dissolved inert material) by evaporation.

Preferably, the cyclohexane recovery zone, step d), comprises a set of distillation columns connected in series. More preferably, there are three or four distillation columns. The steaming The distillation column is preferably capable of being operated-in-effect. In other words, the vapor of the first distillation column is used to heat the second distillation column, and the vapor of the second distillation column is used to heat the third distillation column, and selectively, the third distillation The vapor of the column is used to heat the fourth distillation column. Preferably, the cyclohexane recovery zone d) comprises a plurality of distillation columns connected in series and which have been integrated such that an overhead stream of the first distillation column is used as a heat source for the second distillation column.

One of the conventional methods is shown in Figure 1, in which the present invention has not been implemented. Fresh cyclohexane is supplied via the feed tube (11), while cyclohexane removed in the cyclohexane recovery zone (F) is supplied via the feed tube (16) to contain one or more Oxidation zone (A) of a plurality of oxidation reactors. The oxygen containing system is fed to (A) via a feed tube (12). The oxidized reaction mixture comprising cyclohexanone, cyclohexanol, cyclohexyl hydroperoxide, by-products, and unreacted cyclohexane is passed through the feed tube (1) to contain one or more A plurality of indirect heat exchangers in the cooling unit (C). The oxidized reaction mixture which has been cooled is then fed to a decomposition zone (D) comprising one or more decomposition reactors and one or more liquid/liquid phase separators. An aqueous caustic solution containing a transition metal-containing catalyst is introduced into the decomposition zone (D) through a feed pipe (13); the separated aqueous phase passes through the feed pipe (14) Was removed. The decomposed reaction mixture is fed through a feed pipe (4) to a cyclohexane recovery zone (F) containing a distillation column of one or more seats. The removed cyclohexane is fed to the oxidation zone (A) through a feed pipe (16). A mixture mainly comprising cyclohexanone, cyclohexanol, and cyclohexane is discharged through a feed tube (15).

Figure 2 shows a specific example of the method according to the invention. Fresh cyclohexane is supplied to the oxidation zone (A) containing one or more oxidation reactors through the feed pipe (11), and cyclohexane removed in the cyclohexane recovery zone (F), It is then supplied to the oxidation zone (A) through the feed pipe (16). The oxygen-containing gas is fed into the (A) through the feed pipe (12). The oxidized reaction mixture comprising cyclohexanone, cyclohexanol, cyclohexyl hydroperoxide, by-products, and unreacted cyclohexane, passed through the feed tube (1) to contain one or more The heat exchange unit (B) in the process of the heat exchange device in the process; here, the reaction mixture is cooled. The oxidized reaction mixture which has been cooled is then fed through a feed pipe (2) to a cooling unit (C) containing one or more inter-connected heat exchangers, where it is further cooled. The oxidized reaction mixture, which has been further cooled, is then fed to a decomposition zone (D) comprising one or more decomposition reactors and one or more liquid/liquid phase separators. An aqueous sodium hydroxide solution containing a catalyst containing a transition metal is introduced into the decomposition zone (D) through a feed pipe (13); the separated aqueous phase is removed through the feed pipe (14). The decomposed reaction mixture is fed through a feed pipe (4) to a heat exchange unit (B) in the process and heated there. The heated decomposed reaction mixture is fed through a feed tube (5) to a partial flash zone (E) containing one or more flashers; here, a portion of the low boiling component is Flashed and removed. The rapidly processed reaction mixture which has been decomposed is then passed through a feed line (6) to a cyclohexane recovery zone (F) containing a distillation column of one or more seats. The removed cyclohexane is fed into the oxidation zone (A) through a feed tube (16). Alternatively (not shown in Figure 2), the partial flash zone (E) may only be It is bypassed and the heated decomposed reaction mixture is passed through the feed tube (5) and directly fed to the cyclohexane recovery zone (F). A mixture mainly comprising cyclohexanone, cyclohexanol, and cyclohexane is discharged through a feed tube (15).

In these figures, temperatures such as T ₁ to T ₅ correspond to the following points. T ₁ is the temperature of the oxidized reaction mixture leaving the oxidation zone (A); T ₂ is the temperature of the cooled oxidized reaction mixture leaving the heat exchange device (B) in the process; T ₃ is leaving the cooling The temperature of the cooled oxidation reaction mixture of unit (C); T ₄ is the temperature of the decomposed reaction mixture leaving the decomposition zone (D); and T ₅ is the heat exchange device (B) leaving the process. The temperature at which the reaction mixture has been decomposed by heating.

1, 2, 4, 5, 6, 11, 12, 13, 14, 16‧‧‧ feed tubes

A‧‧‧Oxidation zone

B‧‧‧Heat exchange unit in the process

C‧‧‧Cooling unit

D‧‧‧decomposition zone

E‧‧‧Local flash zone

F‧‧‧Recycling area

One of the conventional methods is shown in Figure 1; and Figure 2 shows a specific example of the method in accordance with the present invention.

example Comparative example

The invention is illustrated by the following examples, but the invention is not limited thereto.

This example was implemented in a working cyclohexanone plant. For comparison with the examples according to the present invention, the data of this comparative example was calculated by emulating a cyclohexanone plant having the same productivity as the factory of the example.

As described above and together with reference to Figure 1, an uncatalyzed cyclohexane a cyclohexanone plant consisting of an alkoxylation reaction zone, a cooling unit, a decomposition zone, a cyclohexane recovery zone, and a cyclohexanone purification zone, directly cleaned and included in the cyclohexane recovery zone After the entire plant of the reboiler of a distillation column, the cyclohexanone plant was operated under the decomposition zone with a mass flow of 500 metric tons per hour of the decomposed reaction mixture. The sum of the weight fractions of cyclohexanol and cyclohexanone in the organic fluid obtained after the decomposition was maintained at 3.4%. In this comparative example, the oxidized zone composed of five oxidation reactors connected in series was air as a source of oxygen. The cooling zone is composed of a set of six shell-tube indirect heat exchangers connected in series. The oxidized reaction mixture exiting the uncatalyzed cyclohexane oxidation reaction zone has a temperature of about 165 ° C and a pressure of about 1.2 MPa and passes through the inside of the line of the heat exchanger. Water is used as a coolant and flows on the outside of the piping of the heat exchanger of the cooling zone. The cooled, oxidized reaction mixture leaving the cooling zone is fed to the decomposition zone.

The decomposition zone is composed of a pre-neutralization zone and a two-phase decomposition zone. In the pre-neutral zone, the subsequently oxidized reaction mixture has been recovered from the used aqueous sodium hydroxide solution in the decomposition zone. In the two-phase decomposition zone, the washed organic phase is decomposed by an aqueous sodium hydroxide solution in the presence of a homogeneous catalyst containing Co, and then the obtained organic phase is combined with the used aqueous sodium hydroxide solution. Phase separation. The recovered sodium hydroxide aqueous stream is discarded after the pre-neutral cleaning. In this decomposition zone, the temperature of the organic phase increases due to the neutralization reaction and the release heat of the decomposition reaction of the cyclohexyl hydroperoxide. The organic stream leaving the decomposition zone (ie, the decomposed reaction mixture) The temperature is maintained at about 94 ° C by adjusting the flow of water in the cooling zone. The decomposed reaction mixture is then fed to the cyclohexane recovery zone.

The cyclohexane recovery zone is comprised of three distillation columns that are effectively manipulated. In other words, the vapor of the first distillation column is used to heat the second distillation column, and the vapor of the second distillation column is used to heat the third distillation column. The decomposed reaction mixture is fed to the first cyclohexane distillation column, which is equipped with a vapor driven reboiler. The head pressures of the three distillation columns were about 0.5 MPa, 0.3 MPa, and 0.1 MPa, respectively. All of these distillation columns are operated with reflux to recover the overhead fluid, which primarily contains cyclohexane, as well as low concentrations of cyclohexanone and cyclohexanol. The recovered overhead stream is reused in the oxidation zone. The bottom stream of the last distillation column contained approximately 66 weight percent cyclohexane, while the residue was primarily cyclohexanone, cyclohexanol, light fractions, and heavy ends. The bottom stream of the last distillation column is sent to the cyclohexanone purification zone for further purification and conversion of cyclohexanol to cyclohexanone.

Under these conditions, the following performance of the cyclohexanone plant was calculated:

Based on these conditions, the reboiler of the first cyclohexane distillation column The steam consumption is 121.5 GJ/hr. However, it is expected that the fouling of the reboiler will cause the energy transfer to deteriorate. In order to maintain proper operation of the plant, it is expected that the plant will need to stop for three weeks each year to remove these dirt from the reboiler. The consequence of downtime in order to remove dirt is the substantial annual loss of the cyclohexanone plant, which can be calculated to be approximately 8,250 metric tons per year. The amount of heat transferred to the cooling water in the cooling zone was 133.2 GJ/hr.

Example

As described above and referring to FIG. 2, a ring composed of an uncatalyzed cyclohexane oxidation reaction zone, a heat exchange device in a process, a cooling unit, a decomposition zone, and a cyclohexane recovery zone a hexanone plant; wherein the flash unit (E) is bypassed directly after cleaning the entire plant of the reboiler contained in the first distillation column in the cyclohexane recovery zone, where the plant is decomposed The reaction mixture was operated under a mass flow of 500 metric tons per hour leaving the decomposition zone. The sum of the weight fractions of cyclohexanol and cyclohexanone in the organic stream obtained after decomposition was maintained at 3.4%.

In this embodiment, the heat exchange means and the cooling zone in each process are formed by a set of shell-and-tube indirect heat exchangers connected in series. The oxidized reaction mixture exiting the uncatalyzed oxidation zone of cyclohexane has a temperature of about 165 ° C and a pressure of about 1.2 MPa. The oxidized reaction mixture leaving the uncatalyzed cyclohexane oxidation reaction zone flows around the outside of the line of the heat exchanger in the heat exchange unit in the process. The decomposed reaction mixture leaving the decomposition zone passes through the inside of the line of the heat exchanger of the heat exchange unit in the process. In the cooling unit, water is used as a coolant and outside the pipeline of the heat exchanger in the cooling zone The Ministry flows. The oxidized reaction mixture leaving the heat recovery zone passes through the inside of the line of the heat exchanger.

The decomposition zone is composed of a pre-neutralization zone and a two-phase decomposition zone; in the pre-neutralization zone, the subsequently oxidized reaction mixture has been recovered from the used hydrogen of the decomposition zone. The sodium oxide aqueous solution was washed. In the two-phase decomposition zone, the washed organic phase is decomposed by an aqueous sodium hydroxide solution in the presence of a homogeneous catalyst containing Co, and then the obtained organic phase is combined with the used aqueous sodium hydroxide solution. Phase separation. The recovered sodium hydroxide aqueous stream is discarded after the pre-neutral cleaning. In this decomposition zone, the temperature of the organic phase increases due to the neutralization reaction and the release heat of the decomposition reaction of the cyclohexyl hydroperoxide. The temperature of the organic stream (i.e., the decomposed reaction mixture) leaving the decomposition zone is maintained constant by adjusting the flow of water in the cooling zone. The decomposed reaction mixture is then fed to the cyclohexane recovery zone.

The cyclohexane recovery zone is comprised of three distillation columns that are effectively manipulated; in other words, the vapor of the first distillation column is used to heat the second distillation column, and the second distillation column The vapor is used to heat the third distillation column. The decomposed reaction mixture is fed to the first cyclohexane distillation column equipped with a vapor driven reboiler. The top pressures of the three distillation columns are approximately 0.5 MPa, 0.3 MPa, and 0.1 MPa, respectively. All of these distillation columns are operated by reflux to recover overhead overhead, which primarily contains cyclohexane, and low concentrations of cyclohexanone and cyclohexanol. The recovered overhead stream is reused in the oxidation zone. The bottom stream of the last distillation column contains approximately 66% by weight of cyclohexane, and the residue is mainly cyclohexanone, ring Hexanol, light ends, and heavy ends. The bottom stream of the last distillation column is then transported or further purified and the cyclohexanol is converted to cyclohexanone.

Under these conditions, the following performance of the cyclohexanone plant was calculated:

Based on these conditions, the reboiler of the first cyclohexane distillation column had a vapor consumption of 49.9 GJ/hr. The fouling of the reboiler is expected to be significantly reduced. Due to the reduced fouling of the reboiler, the plant was expected to be operational for more than 12 months without any downtime to clean the reboiler. This has resulted in a substantial increase in the actual annual production of the cyclohexanone plant, which is calculated to be more than 8,250 metric tons per year, which is superior to the comparative example. The amount of heat transferred to the cooling water in the cooling zone was 55.7 GJ/hr.

1, 2, 4, 5, 6, 11, 12, 13, 14, 16‧‧‧ feed tubes

A‧‧‧Oxidation zone

B‧‧‧Heat exchange unit in the process

C‧‧‧Cooling unit

D‧‧‧decomposition zone

E‧‧‧Local flash zone

F‧‧‧Recycling area

Claims (15)

A continuous process for preparing a mixture comprising cyclohexanone and cyclohexanol, the process comprising: a) reacting cyclohexane in the presence of an oxygen-containing gas in the oxidation zone but without a transition metal-containing catalyst In the case of being oxidized to form an oxidized reaction mixture; b) cooling the oxidized reaction mixture from temperature T ₁ to temperature T ₃ in a cooling zone; c) decomposing the oxidized reaction mixture in a decomposition zone Forming a decomposed reaction mixture, and the decomposed reaction mixture has a temperature T ₄ ; and d) removing cyclohexane from the decomposed reaction mixture; the method is characterized in that step b) comprises: i) An in-process heat exchanger installed in a process for heating the decomposed reaction mixture obtained in step c) from temperature T ₄ to temperature T ₅ to oxidize the reaction mixture from temperature T ₁ cooling to temperature T ₂ ; and ii) cooling the oxidized reaction mixture from temperature T ₂ to temperature T ₃ in a cooling unit. The method of claim 1, wherein, after the step d), further comprises e) purifying the mixture of cyclohexanone and cyclohexanol. For example, the method of claim 1 or 2, wherein T ₂ T ₄ and T ₁ T ₅ . The method of any one of claims 1 to 3 wherein T ₁ is from 130 ° C to 180 ° C. The method of any one of claims 1 to 4, wherein the T ₃ is from 40 ° C to 80 ° C. The method of any one of claims 1 to 5, wherein the T ₄ is from 80 ° C to 130 ° C. The method of any one of claims 1 to 6, wherein ΔT _1,2 is from 40 ° C to 70 ° C, and ΔT _1,2 = T ₁ -T ₂ . The method of any one of claims 1 to 7, wherein ΔT _{1,5 is} less than 20 ° C, wherein ΔT _1,5 = T ₁ -T ₅ . The method of claim 8, wherein ΔT _{1, 5 is} less than 5 °C. The method of any one of claims 1 to 9, wherein the heat exchange device in the process comprises a shell & tube inter-connected heat exchanger. The method of any one of claims 1 to 10, wherein the step d) comprises distillation. The method of claim 11, wherein step d) comprises partial flash distillation and thereafter is distilled in one or more distillation columns. A device suitable for carrying out the method of any one of claims 1 to 12, comprising: a) an oxidation zone; b) a cooling zone; c) a decomposition zone; and d) a cyclohexane Recycling area The apparatus is characterized in that the cooling zone comprises: i) a heat exchange device in a process; and ii) a cooling unit; wherein the device is installed to sequentially pass a reaction mixture from a) to i), Ii), c), and back to d) via i). The apparatus of claim 13, wherein the cyclohexane recovery zone d) comprises a partial flasher and is followed by one or more distillation columns. The apparatus of any one of claims 13 or 14, wherein the cyclohexane recovery zone d) comprises a set of distillation columns connected in series and integrated so that the overhead stream of the first distillation column (overhead stream) ) is used as a heat source for the second distillation column.