CN112920018A - Method for producing mixture of cyclohexanol and cyclohexanone by cyclohexane oxidation - Google Patents
Method for producing mixture of cyclohexanol and cyclohexanone by cyclohexane oxidation Download PDFInfo
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Abstract
A process for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane, comprising the steps of: heating cyclohexane, and oxidizing with molecular oxygen under a non-catalytic condition to obtain an oxidation solution; the oxidation liquid is cooled through two-step indirect heat exchange, wherein in the first step, pure anhydrous recovered hot alkane is used for heat exchange to reduce the temperature of the oxidation liquid to 150 ℃, in the second step, heterogeneous decomposition liquid is used for heat exchange to reduce the temperature of the oxidation liquid to 115-125 ℃, so that the heat-sensitive substances in the heterogeneous decomposition liquid are prevented from undergoing polymerization reaction at high temperature to scale and block a heat exchanger; decomposing the oxidation liquid after the two-step temperature reduction by sequentially passing through a homogeneous decomposition system and a heterogeneous decomposition system to obtain a heterogeneous decomposition liquid; and (3) heating the heterogeneous decomposition liquid to 145 ℃ through indirect heat exchange with the oxidation liquid subjected to the first-step cooling, and directly entering a lower end socket distributor of a reboiler of the first alkane tower to perform cyclohexane rectification and recovery to obtain a mixture of cyclohexanol and cyclohexanone, so that scaling blockage of the reboiler of the first alkane tower is avoided.
Description
Technical Field
The invention relates to a method for producing a cyclohexanol and cyclohexanone mixture, in particular to a method for producing a cyclohexanol and cyclohexanone mixture by oxidizing cyclohexane.
Background
The process for the oxidation of cyclohexane to produce cyclohexanol and cyclohexanone is generally divided into three main sections: a cyclohexane oxidation section, a cyclohexyl hydroperoxide decomposition section and a cyclohexane recovery section. The cyclohexane oxidation section adopts two main methods: 1) the cyclohexane cobalt salt is catalyzed and oxidized, the reaction temperature is controlled to be 150-160 ℃, and the pressure is controlled to be 0.9-1.0 MpaG. However, in this method, most of the cyclohexyl hydroperoxide generated by cyclohexane oxidation is decomposed in the oxidation kettle to generate cyclohexanol and cyclohexanone, and then alcohol ketone is further deeply oxidized to acids and esters, resulting in the final oxidation product containing 40 wt% of cyclohexanol, 25 wt% of cyclohexanone, less than 15 wt% of cyclohexyl hydroperoxide, and up to 20 wt% of impurities such as acids and esters, so the catalytic oxidation conversion rate of this method is 5%, but the yield is very low, and the slagging of the oxidation kettle is relatively serious due to the high content of acids and esters in the product (see "Yangxi, progress of cyclohexane liquid phase air catalytic oxidation to cyclohexanone and cyclohexanol, synthetic fiber industry, 1992, 15 (1): 9-13" and CN 1011203B); 2) cyclohexane is not subjected to catalytic oxidation, the reaction temperature is increased to 160-180 ℃, the pressure is controlled to be 1.1-1.3 MpaG, and an oxidation system does not contain a transition metal catalyst. The cyclohexane oxidation product obtained by the method contains cyclohexyl hydrogen peroxide accounting for 68 wt%, cyclohexanol accounting for 15 wt%, cyclohexanone accounting for 8 wt%, and acid, ester and other impurities accounting for 9 wt%, so that the oxidation yield is improved, and the problem of slagging and blockage of the oxidation kettle is basically solved (see 'technical improvement and prospects of cyclohexanone preparation by Yangchun and cyclohexane oxidation method, energy and chemical engineering, 2016, 37 (6): 17-27' and CN 1621398A).
The oxidation process is controlled to be carried out under low conversion rate, otherwise, cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone generated by oxidation are more active than the chemical property of cyclohexane, and are easy to be continuously deeply oxidized into acids, esters and the like, so that the oxidation yield is reduced. However, the lower the conversion in the cyclohexane oxidation process, the more steam is consumed to recover the large amount of unreacted cyclohexane in the oxidation liquid. Thus, the conventional cyclohexane non-catalytic oxidation process sets the conversion of cyclohexane oxidation at 3.5% and then recovers cyclohexane by means of a series of oxidative heat recovery and multi-effect distillation recovery of cyclohexane.
One main heat source for recycling the cyclohexane oxidation heat is heat released by cooling the 160-170 ℃ cyclohexane oxidation liquid from the oxidation reaction kettle to the temperature of 90-100 ℃ required by the decomposition reaction of the cyclohexyl hydroperoxide. The non-catalytic oxidation method disclosed by the French Longboli company is followed by an acid homogeneous decomposition process, and the heat recovery method comprises the following steps: the high-temperature and high-pressure cyclohexane oxidation solution is directly flashed to normal pressure and the temperature of 90-100 ℃ required by homogeneous decomposition, partial cyclohexane is continuously vaporized by utilizing the decomposition heat of cyclohexyl hydroperoxide, and then the cyclohexane is removed from a cyclohexane recovery rectifying tower to recover cyclohexane by utilizing steam rectification, wherein the steam consumption of the process is 7.0 ton/ton of crude alcohol ketone (see 'caprolactam production and application compiling group, caprolactam production and application, Beijing: hydrocarbon processing publisher, 1988: 23-99'). The cyclohexane non-catalytic oxidation method disclosed by the Dutch DSM company is followed by a heterogeneous decomposition method of an alkaline aqueous solution, and the heat recovery method comprises the following steps: the method comprises the following steps of (1) indirectly exchanging heat between 160-170 ℃ cyclohexane oxidation liquid and 90-100 ℃ decomposition liquid in the subsequent process through a heat exchanger to reduce the temperature of the oxidation liquid to about 120 ℃, and continuously cooling the oxidation liquid to 60-70 ℃ by using circulating water; then decomposing cyclohexyl hydrogen peroxide, wherein the decomposition temperature of the cyclohexyl hydrogen peroxide is increased by the decomposition heat of the cyclohexyl hydrogen peroxide, and then cooling by circulating water is carried out to ensure that the decomposition temperature is 90-100 ℃; and returning the decomposition liquid to the front, indirectly exchanging heat with 160-170 ℃ oxidation liquid, raising the temperature to 145-150 ℃, and entering a triple-effect cyclohexane recovery distillation tower to recover cyclohexane by using steam. Since Dutch DSM uses sensible heat of the oxidation liquid to heat the decomposition liquid and effect triple-effect alkane distillation, while France Longboli uses sensible heat of the oxidation liquid for single-effect cyclohexane flash distillation, the steam consumption of the process disclosed by Dutch DSM is 6.0 tons/crude ketol, which is slightly lower than that disclosed by Fanguage Longboli (see "caprolactam production and application authoring group, caprolactam production and application, Beijing: Hydrocarbon processing Press, 1988: 23-99").
In 2007, the first 10 million ton/year cyclohexane oxidation device in China was developed by Xiaozaocheng, and in addition to adopting new cyclohexane oxidation and cyclohexyl hydrogen peroxide decomposition technologies, in the aspect of cyclohexane recovery, on the basis of an indirect heat exchange method of an oxidation liquid and a decomposition liquid disclosed by the Dutch DSM company, a four-effect alkane distillation technology is adopted to recover cyclohexane, so that the steam consumption is reduced to 5.5 tons/ton crude alcohol ketone.
CN102627525B discloses a three-step decomposition process of cyclohexyl hydroperoxide, wherein homogeneous decomposition with high decomposition yield and heterogeneous decomposition with high decomposition conversion rate are connected in series, the consumption of cyclohexane in the system is reduced, and a part of heat of oxidizing liquid cooled from 120 ℃ to 60-70 ℃ by circulating water in the method disclosed by DSM company in the Netherlands is used for flash evaporation and recovery of cyclohexane in homogeneous decomposition, and the decomposition heat of cyclohexyl hydroperoxide is also used for evaporation and recovery of cyclohexane, so that the heat of the oxidizing liquid is utilized to a greater extent, and the steam consumption of the process is reduced to 5.0 ton/ton of crude alcohol ketone.
However, the cyclohexane oxidation heat exchange and cyclohexane recovery processes disclosed by DSM, the netherlands and CN102627525B have the following two problems: 1) when the high-temperature oxidation liquid and the low-temperature decomposition liquid are subjected to indirect heat exchange through the oxidation decomposition heat exchanger, the tube pass scaling phenomenon of the decomposition liquid flowing in the heat exchanger is obvious, so that the thermal resistance of the oxidation decomposition heat exchanger is increased, and the heat exchange effect is continuously reduced; 2) fouling of the reboiler of the cyclohexane-distillation column causes an increase in the heat transfer resistance of the reboiler of the cyclohexane-distillation column. These two problems severely reduce the cyclohexane recovery efficiency, greatly shorten the operation period of the device, and cause the device to be forced to operate under the condition of high oxidation conversion rate all the time, thereby causing a great deal of raw material and energy waste.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art, firstly provides a fouling mechanism of a heat exchanger and a reboiler, and then provides a method for producing a mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane, which reduces the fouling speed of an oxidative decomposition heat exchanger and a reboiler of a cyclohexane distillation tower and prolongs the continuous operation period of a device under the condition of keeping the original main equipment of the device unchanged greatly.
The fouling mechanism of the heat exchanger and the reboiler provided by the invention is as follows:
in the process of non-catalytic oxidation of cyclohexane, cyclohexanone with a certain concentration is always kept in oxidation feed cyclohexane as an initiator of free radicals and is used for increasing the concentration of the free radicals in an oxidation liquid at the initial stage of oxidation reaction, so that the reaction speed of cyclohexane oxidation is improved, and the safety level that the oxygen content in oxidation tail gas is less than 2 wt% is ensured, as shown in formula I.
As the oxidation reaction proceeds, the cyclohexyl hydroperoxide which is the intermediate product of the oxidation is partially decomposed by heat or catalyzed by a metal wall, and the concentration of cyclohexanone in the system is gradually increased; since the hydrogen in the alpha position of cyclohexanone is chemically more reactive than that of cyclohexane and is more prone to form free radicals, cyclohexanone is more prone to be oxidized by air by forming free radicals relative to cyclohexane, and the oxidized product is a cyclohexanone-based hydrogen peroxide intermediate, as shown in formula II.
The cyclohexanone-based hydrogen peroxide is thermally decomposed or catalytically decomposed to generate hydroxycyclohexanone, and a part of the hydroxycyclohexanone is subjected to intramolecular rearrangement to generate caprolactone which is shown as a formula III.
And the other part of the hydroxycyclohexanone is subjected to ring opening reaction at high temperature and is continuously deeply oxidized by air or subjected to decarburization reaction to generate a series of acid and ester byproducts with five carbon atoms and six carbon atoms, as shown in a formula IV.
The cyclohexane oxidation liquid containing the byproducts mainly undergoes three types of reactions through the heterogeneous decomposition process of NaOH aqueous solution: 1) cyclohexyl hydroperoxide is catalytically decomposed to cyclohexanol and cyclohexanone; 2) the acidic by-products are neutralized into salts which are dissolved in an alkaline water phase; 3) the esters are saponified and hydrolyzed and extracted into an aqueous alkaline phase. Wherein caprolactone can be partially saponified into hydroxycaproic acid salt (shown in formula V), amphiphilic molecules (one end is hydrophilic, the other end is lipophilic) such as caprolactone and carbonyl caproic acid salt are distributed between the alkaline phase and the cyclohexane phase, and even form a third phase on the oil-water interface. Therefore, after the heterogeneous decomposition liquid is washed by water, a part of carbonyl caproic acid and hydroxycaproic acid and unsaponified caprolactone are dissolved in the heterogeneous decomposition liquid of the oil phase.
When the heterogeneous decomposition liquid is heated, the carbonyl caproic acid can generate aldol condensation reaction, the hydroxycaproic acid is dehydrated and generates polymerization reaction to generate polyester, and the caprolactone can also generate polyester through ring-opening polymerization, and the caprolactone can be collectively called as a heat-sensitive polymerization monomer as shown in a formula VI. When the temperature is lower, the polymerization reaction is slow, mainly a polymer with low molecular weight is formed, and part of the polymer can be dissolved in a cyclohexane phase, so that the system equipment cannot be quickly influenced; however, when the temperature is increased, the dehydration polymerization reaction is accelerated, and a large amount of a high molecular weight polymer is formed, and the polymer is insoluble in cyclohexane to form scale on the wall of the apparatus.
The rate of the polymerization is related to the concentration of the heat-sensitive polymerizable monomer, the acidity or basicity of the material, and the temperature at which the material is exposed, as can be seen from the law of mass action and the mechanism of polymerization.
Thus, the fouling rate of the oxidative decomposition heat exchanger or the reboiler of the cyclohexane-distillation alkane-one column is increased by the following reasons in the prior art:
(1) when the design of the alkane tower of the prior device is smaller, the concentration of cyclohexanone in the recovered cyclohexane is high, or the oxidation conversion rate is improved due to pursuit of yield, the content of cyclohexanone-based hydrogen peroxide generated by oxidizing cyclohexanone in an oxidation solution is increased, and the concentration of thermosensitive polymerization monomers as oxidation byproducts is increased, so that the scaling speed of an oxidative decomposition heat exchanger and an alkane-tower reboiler is higher; (2) when the decomposition liquid is acidic (method disclosed by French Longboli corporation) or alkaline (method disclosed by Dutch DSM corporation), the polymerization reaction is catalyzed and accelerated due to the existence of acid or alkali, and the scaling speed of the oxidative decomposition heat exchanger and the reboiler of the alkane-one tower is also accelerated; (3) when the alkaline condition is weak or the reaction temperature is not high enough in the heterogeneous decomposition process, the saponification reaction of caprolactone and the like is incomplete, so that the thermosensitive polymerized monomers carried away by waste alkali liquor are reduced, the thermosensitive polymerized monomers in the decomposition liquid are high in content, and the scaling speed of an oxidative decomposition heat exchanger and an alkane-tower reboiler is also increased; (4) when the low-temperature decomposition liquid directly exchanges heat with the high-temperature oxidation liquid at 160-170 ℃ in the oxidative decomposition heat exchanger indirectly, and the temperature of the decomposition liquid contacting with the wall of the metal heat exchange tube is more than 165 ℃, the polymerization scaling speed of the tube side of the oxidative decomposition heat exchanger can be accelerated; (5) when the decomposition liquid enters the alkane tower system from the alkane tower body, the water contained in the decomposition liquid is evaporated on a tower tray, the material entering the reboiler of the alkane tower is very dry, and the heating temperature of the reboiler of the alkane tower of the four-effect alkane tower is higher than that of the reboiler of the three-effect alkane tower, so that the dehydration polymerization reaction is promoted, and the scaling speed of the tube pass of the reboiler of the alkane tower is accelerated.
Through the analysis of the scale-forming mechanism, the technical scheme adopted by the invention for solving the technical problem is that the method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane comprises the following steps: heating cyclohexane, and oxidizing with molecular oxygen under a non-catalytic condition to obtain an oxidation solution; cooling the oxidation liquid through a two-step indirect heat exchange process, and then sequentially decomposing through a homogeneous decomposition system and a heterogeneous decomposition system to obtain a heterogeneous decomposition liquid; heating the heterogeneous decomposition liquid through a one-step indirect heat exchange process, then directly entering a lower end socket distributor of an alkane-first tower reboiler, and performing cyclohexane rectification recovery to obtain a mixture of cyclohexanol and cyclohexanone;
the oxidizing solution is cooled through a two-step indirect heat exchange process, namely, the oxidizing solution and hot cyclohexane recovered by a cyclohexane distillation system are subjected to first-step indirect heat exchange cooling to obtain the oxidizing solution subjected to first-step cooling; carrying out second-step indirect heat exchange cooling on the oxidized liquid subjected to the first-step cooling and the heterogeneous decomposition liquid to obtain a second-step cooled oxidized liquid;
the step of heating the heterogeneous decomposition liquid through one-step indirect heat exchange refers to the step of heating the heterogeneous decomposition liquid and the oxidation liquid subjected to the first step of cooling through indirect heat exchange to obtain the heated decomposition liquid.
Further, the pressure of an oxidation reactor used for oxidizing cyclohexane is 1.1-1.3 MpaG, the temperature of an oxidizing liquid at the outlet of the oxidation reactor is 165-170 ℃, and the oxidation conversion rate is controlled to be 3.3-3.5%.
Further, the temperature of the oxidation liquid after the first step of temperature reduction is 150-155 ℃; and the temperature of the oxidizing liquid after the temperature reduction in the second step is 110-120 ℃.
Further, the temperature of the recovered hot cyclohexane is 110-120 ℃; the temperature of the recovered hot cyclohexane after the first-step indirect heat exchange is 150-155 ℃.
Because the cyclohexane recovered by the cyclohexane distillation system is pure, the temperature of the oxidizing liquid is reduced to 150-155 ℃ by utilizing the pure cyclohexane, and then the oxidizing liquid is subjected to indirect heat exchange with the heterogeneous decomposition liquid at 95-105 ℃, so that the phenomenon that the heterogeneous decomposition liquid containing the thermosensitive polymerization monomer is contacted with the heat exchange tube wall at too high temperature is avoided, the phenomenon of organic matter dehydration polymerization scaling in the tube pass of the decomposition heat exchanger is relieved, and the operation period of the decomposition heat exchanger is prolonged.
The cyclohexane recovered by the multi-effect cyclohexane distillation system is divided into two types, wherein one type is high-temperature cyclohexane which is condensed by using cyclohexane steam of the first three effects to heat and concentrate the bottom liquid of the rectifying tower and is called hot alkane, the temperature is 110-120 ℃, the other type is low-temperature cyclohexane which is generated by condensing the cyclohexane steam of the last effect by using circulating water and is called cold alkane, and the temperature is 60-70 ℃; the temperature of the recovered hot alkane after indirect heat exchange with the oxidation liquid is raised to 150-155 ℃, the recovered hot alkane directly enters an oxidation heater, and the recovered hot alkane can be used as a raw material for cyclohexane oxidation reaction after being heated to 175-185 ℃ by steam; and the cold methane returns to the oxidation tail gas recovery system according to the old process, and cyclohexane steam in the oxidation tail gas is recovered by direct heat exchange and then is removed from the oxidation heater by the oxidation feed pump. The process can greatly reduce the operation load of the oxidation feed pump, and is favorable for improving the feeding amount of cyclohexane oxidation in the original device.
Further, sending the oxidized liquid subjected to the second step of cooling to a homogeneous decomposition system, flashing to 90-100 ℃, and simultaneously adding a homogeneous catalyst tert-butyl chromate and a scale inhibitor 1-hydroxy-ethylidene-diphosphonic acid octyl ester for homogeneous decomposition to obtain a homogeneous decomposition liquid; and carrying out heterogeneous decomposition, saponification, water washing and separation on the homogeneous decomposition and decomposition liquid in a NaOH aqueous solution to obtain a waste alkali liquid and a heterogeneous decomposition liquid.
Further, the temperature of the heterogeneous decomposition is 95-105 ℃, the pH value of the heterogeneous decomposition liquid is 6-8, and OH in the waste alkali liquor-The concentration is 0.5 to 1.0 mol/L.
And (3) directly removing the 110-120 ℃ oxidation liquid subjected to temperature reduction in the second step from circulating water cooling, performing flash evaporation in a homogeneous decomposition system, continuously evaporating and recovering a part of cyclohexane by using decomposition heat generated in the homogeneous decomposition process, greatly utilizing heat brought by the decomposition process, improving the recovery amount of the cyclohexane on the premise of not increasing steam consumption, and reducing the conversion rate of cyclohexane oxidation.
The homogeneous decomposition liquid is subjected to high-temperature heterogeneous decomposition in NaOH aqueous solution, cyclohexyl hydrogen peroxide is fully decomposed into cyclohexanol and cyclohexanone through saponification and water washing, most of thermosensitive impurities such as acids and esters are neutralized and saponified by alkali, and are converted into sodium salts which are dissolved in an alkali waste aqueous phase and taken out of a system, so that the content of thermosensitive polymerization monomers which are easy to scale at high temperature in the heterogeneous decomposition liquid is reduced. In addition, the heterogeneous decomposition liquid is kept neutral by water washing, so that the catalytic action of acid and alkali on polymerization reaction can be greatly reduced, and the operation period of a decomposition heat exchanger and an alkane-tower reboiler is prolonged.
Further, the temperature of the heated decomposition liquid is 140-145 ℃.
Further, the heated decomposition liquid is directly led into a reboiler tube side from the lower head of the reboiler of the alkane-first tower through a distributor, rectification is carried out to recover cyclohexane, and the total concentration of a mixture of cyclohexanol and cyclohexanone in the recovered cyclohexane is less than or equal to 500 ppm.
The neutral heterogeneous decomposition liquid with the reduced content of heat-sensitive impurities and the oxidation liquid (150-155 ℃) subjected to the first-step temperature reduction are subjected to indirect heat exchange to raise the temperature to 140-145 ℃, so that the heterogeneous decomposition liquid is prevented from contacting a heat exchange pipe wall with a high temperature of more than 165 ℃, the heat-sensitive polymerization reaction in the heterogeneous decomposition liquid is greatly reduced, and the operation period of a decomposition heat exchanger and an alkane-tower reboiler is prolonged.
The heated heterogeneous decomposition liquid is not introduced into the tower body section of the rectifying tower, but is directly introduced from the lower end socket of the reboiler of the alkane-one tower, so that the phenomenon that water in the heterogeneous decomposition liquid is evaporated and dried in the tower body and then introduced into the tube pass of the reboiler of the alkane-one tower can be avoided. Therefore, the method can keep a certain amount of water partial pressure in the tube pass of the reboiler and inhibit the continuous dehydration and polycondensation of the oligomer on the premise of not increasing the water inlet of a cyclohexane rectification system; meanwhile, the material flow rate in the tube pass tube array is greatly improved, so that the scouring force can reduce the scaling speed of the reboiler.
Compared with the prior art, the invention has the beneficial effects that:
(1) on the premise of not changing the flow rate of a cyclohexane oxidation feeding pump and the distillation load of cyclohexane, the feeding amount of cyclohexane oxide is increased, the conversion rate of cyclohexane oxidation is reduced, and the raw material consumption is reduced;
(2) the scaling speed of the oxidative decomposition heat exchanger and a reboiler of the cyclohexane distillation first tower is slowed down, the continuous operation period of the device is prolonged to more than 12 months from 3-4 months, and the safety of the device is improved.
Drawings
FIG. 1 is a schematic diagram of the equipment and process flow used in the embodiment of the method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane.
In the figure: 01-oxidation tail gas recovery system, 02-oxidation feed pump, 03-oxidation heater, 04-oxidation reactor group, 05-oxidation cyclohexane heat exchanger, 06-oxidation decomposition heat exchanger, 07-homogeneous decomposition reaction system, 08-heterogeneous decomposition reaction system, 09-alkane-tower reboiler and 10-cyclohexane distillation recovery system;
011-cyclohexane liquid, 012-oxidized tail gas noncondensable gas, 013-acid water, 021-cyclohexane is sent out by an oxidation feed pump, 031-cyclohexane heated by an oxidation heater, 040-air entering an oxidation reactor, 041-cyclohexane oxidizing liquid, 042-oxidized tail gas, 051-oxidizing liquid cooled in the first step, 052-hot alkane heated in temperature rise, 061-oxidizing liquid cooled in the second step, 062-temperature rise decomposition liquid, 071-homogeneous decomposition liquid, 072-homogeneous decomposition liquid for recycling cold alkane, 073-homogeneous decomposition tail gas, 080-new alkali entering a heterogeneous decomposition system, 081-heterogeneous decomposition liquid, 082-waste alkali liquid, 083-process washing water, 091-cyclohexane gas and liquid mixed fluid, 100-system supplemented new cyclohexane, 101-alkane tower for recycling hot alkane, 102-alkane recycling tower for recycling cold alkane, 103-alkane-tower self-circulating cyclohexane liquid between a first kettle and a reboiler, 104-crude alcohol ketone.
FIG. 2 is a schematic diagram of a conventional process for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane using the Dutch DSM scheme as a comparative example.
In the figure: 01-oxidation tail gas recovery system, 02-oxidation feed pump, 03-oxidation heater, 04-oxidation reactor group, 06-oxidative decomposition heat exchanger, 07-circulating water cooler, 08-heterogeneous decomposition reaction system, 09-one-alkane tower reboiler and 10-three-effect cyclohexane distillation system;
011-cyclohexane liquid, 012-oxidation tail gas non-condensable gas, 021-cyclohexane is sent out by an oxidation feed pump, 031-cyclohexane heated by an oxidation heater, 040-air entering an oxidation reactor, 041-cyclohexane oxidation liquid, 042-oxidation tail gas, 061-oxidation liquid after heat exchange by an oxidative decomposition heat exchanger, 062-temperature-raising decomposition liquid, 071-oxidation liquid cooled by a circulating water cooler, 080 new alkali, 081-heterogeneous decomposition liquid, 082-waste alkali liquid, 083-process washing water, 091-cyclohexane gas evaporated by an alkane-tower reboiler and liquid mixed fluid such as cyclohexane, 100-new cyclohexane supplemented to a system, hot alkane distilled by 101-cyclohexane, 102-cold alkane, 103-cyclohexane liquid self-circulating between the alkane-tower kettle and the reboiler, and 104-crude alcohol ketone.
Detailed Description
The invention is further illustrated by the following examples and figures.
Examples
Referring to fig. 1, the method for producing a mixture of cyclohexanol and cyclohexanone by cyclohexane oxidation according to the embodiment of the present invention uses a set of 10 ten thousand tons/year cyclohexane oxidation apparatus according to the present invention, which comprises the following operation steps:
(1) liquid cold alkane (containing supplemented 12.5t/h new cyclohexane 100)102 and 130t/h cold alkane 072 recovered by cyclohexane distillation at 157.5t/h are subjected to direct heat exchange with 170-172 ℃ oxidation tail gas 042, most of cyclohexane condensed from the oxidation tail gas is recovered, the total flow of the cyclohexane is increased to 390t/h, the temperature is increased to 155 ℃, and the oxidation tail gas noncondensable gas 012 is subjected to tail gas absorption treatment continuously;
390t/h cyclohexane liquid 011 is pressurized by an oxidation feed pump 02 from a direct heat exchange tower kettle, and enters an oxidation heater 03 together with 160t/h hot alkane 052 (the temperature is 155 ℃) after heat exchange with an oxidation cyclohexane heat exchanger 05; 550t/h cyclohexane 031 (the temperature is 183 ℃) heated by the oxidation heater 03 sequentially enters the oxidation reactor group 04 connected in series to perform non-catalytic oxidation reaction with air, the conversion rate of cyclohexane oxidation is controlled to be 3.4%, and the working conditions of the oxidation cyclohexane oxidation reactor are as follows: the pressure P is 1.25MpaG, and the temperature t is 168-180 ℃; total flow rate of air 040 to oxidation reactor 20000Nm3Obtaining 455t/h cyclohexane oxidation liquid 041 (the temperature is 168 ℃);
(2) enabling 455t/h cyclohexane oxidation liquid 041 obtained in the step (1) (the temperature is 168 ℃) to enter a cyclohexane oxide heat exchanger 05, and carrying out first-step indirect heat exchange cooling on the oxidation liquid 041 and 160t/h hot alkane 101 (the temperature is 113 ℃) which does not contain heat-sensitive polymerization monomers and is obtained through cyclohexane recovery distillation to obtain oxidation liquid 051 (the temperature is 155 ℃) cooled in the first step and hot alkane 052 (the temperature is 155 ℃);
the heated thermal alkane 052 deoxidation heater 03 is heated by steam, the oxidation solution 051 subjected to temperature reduction in the first step is subjected to secondary indirect heat exchange with 313t/h heterogeneous decomposition solution 081 (the temperature is 100 ℃) from the heterogeneous decomposition reactor 08 for temperature reduction, and after heat exchange in the oxidation decomposition heat exchanger 06, 455t/h oxidation solution 061 subjected to secondary heat reduction (the temperature is 120 ℃) is obtained;
(3) enabling 455t/h oxidized liquid 061 obtained in the step (2) after being cooled in the second step (at the temperature of 120 ℃) to enter a normal-pressure homogeneous decomposition reaction system 07 for flash evaporation, carrying out a homogeneous decomposition reaction of cyclohexyl hydrogen peroxide under the action of a homogeneous catalyst 100L/h 3 wt% tert-butyl chromate cyclohexane solution and a scale inhibitor 150L/h 3 wt% 1-hydroxy-ethylidene-diphosphonic acid octyl ester cyclohexane solution to obtain a homogeneous decomposition solution 071, continuing evaporating cyclohexane through decomposition reaction heat, recovering 130t/h cold alkane 072 through homogeneous decomposition to remove an oxidized tail gas recovery system 01 as an oxidized feed, compressing the tail gas of homogeneous decomposition tail gas 073, and then sending the compressed tail gas to an oxidized tail gas absorption treatment;
(4)325t/h homogeneous decompositionContinuing to remove the decomposition liquid 071 from the heterogeneous decomposition reaction system 08 to perform a heterogeneous decomposition reaction of the NaOH aqueous solution to obtain a heterogeneous decomposition liquid, wherein the temperature of the heterogeneous decomposition is set to be 100 ℃; the caprolactone in the decomposition liquid is saponified to hydroxy caproic acid sodium salt, and most of the caprolactone is carried out of the system by waste alkali solution 082; continuously adding new alkali 080 into the heterogeneous decomposition system 08 to ensure that OH in the waste alkali liquor-The concentration of (2) is maintained at 0.6 mol/L; then washing with process washing water 083 to obtain 318t/h neutral heterogeneous decomposition liquid (the temperature is 100 ℃); 12.5t/h of waste alkali solution 082 (the temperature is 100 ℃) is sent to waste alkali evaporation treatment; then, the 318t/h neutral heterogeneous decomposition liquid (the temperature is 100 ℃) enters an oxidation decomposition heat exchanger 06 for indirect heat exchange heating to obtain 318t/h heated heterogeneous decomposition liquid 062 (the temperature is 143 ℃);
(5) after the temperature is increased by 318t/h, the heterogeneous decomposition liquid 062 (the temperature is 143 ℃) enters the tube side of the alkane-first tower reboiler 09 through the lower end enclosure of the alkane-first tower reboiler 09 together with the alkane-first tower bottom liquid under the water-containing environment to obtain a liquid mixed fluid 091 of cyclohexane gas, cyclohexane and the like, then the mixed fluid enters the alkane-first tower body section of the cyclohexane distillation and recovery system 10 to carry out four-effect cyclohexane recovery and rectification, 145t/h of cold alkane and 160t/h of hot alkane are recovered to obtain 13t/h of crude alcohol ketone 104, and the total concentration of cyclohexanol and cyclohexanone in the cold and hot alkane is 500 ppm.
Through detection, the embodiment fully utilizes the heat of the oxidation solution to realize lower oxidation conversion rate, and adopts four-effect cyclohexane distillation recovery, the unit consumption of cyclohexane of the device is 960 Kg/ton of crude alcohol ketone, and the unit consumption of steam is 5.0 ton/ton of crude alcohol ketone; because the heat exchange process is optimized, the stable operation period of the oxidation decomposition heat exchanger and the reboiler of the first tower of the cyclohexane recovery rectification alkane is 12 months.
Comparative example
Referring to fig. 2, the method for producing a mixture of cyclohexanol and cyclohexanone by cyclohexane oxidation of the comparative example uses a set of cyclohexane oxidation apparatus of 10 ten thousand tons per year of conventional process, comprising the following operation steps:
(1)150t/h of liquid cold alkane 102 (containing supplemented 12.5t/h of new cyclohexane 100) and 220t/h of hot alkane 101 are subjected to direct heat exchange with 165-170 ℃ oxidation tail gas 042 in an oxidation tail gas recovery system 01, most of cyclohexane condensed from the oxidation tail gas is recovered, the flow rate of cyclohexane liquid 011 is increased to 480t/h, the temperature is increased to 155 ℃, and oxidation tail gas noncondensable gas 012 is subjected to tail gas absorption treatment continuously;
the 480t/h cyclohexane liquid 011 is pressurized by an oxidation feed pump 02, heated by an oxidation heater 03 to obtain cyclohexane 031 (with the temperature of 178 ℃), and then enters an oxidation reactor group 04 connected in series to perform a non-catalytic oxidation reaction with air, the conversion rate of cyclohexane oxidation is controlled to be 3.5%, and the working conditions of the oxidation cyclohexane oxidation reactor are as follows: the pressure P is 1.10MpaG, and the temperature t is 160-170 ℃; total flow rate of air 040 to oxidation reactor 20000Nm3H; obtaining 375t/h cyclohexane oxidation liquid 041 (the temperature is 165 ℃);
(2) feeding 375t/h cyclohexane oxidation liquid 041 obtained in the step (1) (the temperature is 165 ℃) into an oxidation decomposition heat exchanger 06, carrying out indirect heat exchange with 369.5t/h heterogeneous decomposition liquid 081 (the temperature is 95 ℃) decomposed by a heterogeneous decomposition system 08 to obtain oxidation liquid 061 at 120 ℃, and cooling the oxidation liquid 061 to 60 ℃ through a circulating water cooler 07 to obtain oxidation liquid 071;
(3) the oxidation liquid 071 enters a heterogeneous decomposition system 08 for carrying out a heterogeneous decomposition reaction of a NaOH aqueous solution, wherein the temperature of the heterogeneous decomposition is 95 ℃, so as to obtain a heterogeneous decomposition liquid; adding new alkali 080 continuously to make OH in waste alkali-The concentration of the obtained product is maintained at 1.2mol/L, and the obtained product is washed by process washing water 083 to make the heterogeneous decomposition solution neutral, so that 369.5t/h decomposition solution (the temperature is 95 ℃) is obtained; 17.5t/h of waste alkali solution 082 (the temperature is 95 ℃) is sent to waste alkali evaporation treatment;
(4)369.5t/h decomposition liquid (the temperature is 95 ℃) enters an oxidative decomposition heat exchanger 06 to exchange heat with high-temperature oxidation liquid at 165 ℃ to obtain 369.5t/h heated decomposition liquid 062 (the temperature is 143 ℃); and then the heated decomposition liquid enters an alkane-first tower body of a cyclohexane distillation system 10, the decomposition liquid and tower bottom liquid enter an alkane-first tower reboiler 09 after being dried, the decomposition liquid and the tower bottom liquid are vaporized to obtain a mixed liquid 091 of cyclohexane vapor, the mixed liquid is returned to the alkane-first tower body to be subjected to cyclohexane recovery rectification, 137.5t/h of cold alkane and 220t/h of hot alkane are recovered, 12t/h of crude alcohol ketone 104 is obtained, and the total concentration of cyclohexanone and cyclohexanol in the cold and hot alkane is 1000 ppm.
According to the detection, the comparative example does not fully utilize the heat of the oxidizing solution, the oxidation conversion rate is higher, and only three-effect cyclohexane distillation is adopted, the unit consumption of cyclohexane in the device is 1040 Kg/ton of crude alcohol ketone, and the steam consumption is 6.0 ton/ton of crude alcohol ketone. The stable operation period of the oxidative decomposition heat exchanger and the reboiler of the first tower of the cyclohexane recovery rectification alkane is 5 months.
Claims (8)
1. A method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane, comprising the steps of: heating cyclohexane, and oxidizing with molecular oxygen under a non-catalytic condition to obtain an oxidation solution; cooling the oxidation liquid through a two-step indirect heat exchange process, and then sequentially decomposing through a homogeneous decomposition system and a heterogeneous decomposition system to obtain a heterogeneous decomposition liquid; heating the heterogeneous decomposition liquid through a one-step indirect heat exchange process, then directly entering a lower end socket distributor of an alkane-first tower reboiler, and performing cyclohexane rectification recovery to obtain a mixture of cyclohexanol and cyclohexanone;
the oxidizing solution is cooled through a two-step indirect heat exchange process, namely, the oxidizing solution and hot cyclohexane recovered by a cyclohexane distillation system are subjected to first-step indirect heat exchange cooling to obtain the oxidizing solution subjected to first-step cooling; carrying out second-step indirect heat exchange cooling on the oxidized liquid subjected to the first-step cooling and the heterogeneous decomposition liquid to obtain a second-step cooled oxidized liquid;
the step of heating the heterogeneous decomposition liquid through one-step indirect heat exchange refers to the step of heating the heterogeneous decomposition liquid and the oxidation liquid subjected to the first step of cooling through indirect heat exchange to obtain the heated decomposition liquid.
2. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to claim 1, wherein the pressure of the oxidation reactor used for oxidizing cyclohexane is 1.1-1.3 MpaG, the temperature of the oxidation liquid at the outlet of the oxidation reactor is 165-170 ℃, and the oxidation conversion rate is controlled to be 3.3-3.5%.
3. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to claim 1 or 2, wherein the temperature of the oxidizing solution after the first step of cooling is 150-155 ℃; and the temperature of the oxidation liquid after the temperature reduction in the second step is 110-120 ℃.
4. The method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to any one of claims 1 to 3, wherein the temperature of the recovered hot cyclohexane is 110 to 120 ℃; the temperature of the recovered hot cyclohexane after the first-step indirect heat exchange is 150-155 ℃.
5. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to any one of claims 1 to 4, wherein the oxidized liquid obtained by cooling in the second step is sent to a homogeneous decomposition system, flashed to 90 to 100 ℃, and then added with homogeneous catalysts of tert-butyl chromate and 1-hydroxy-ethylidene-octyl diphosphonate for homogeneous decomposition to obtain a homogeneous decomposition solution; and carrying out heterogeneous decomposition, saponification, water washing and separation on the homogeneous decomposition and decomposition liquid in a NaOH aqueous solution to obtain a waste alkali liquid and a heterogeneous decomposition liquid.
6. The method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane as claimed in any one of claims 1 to 5, wherein the temperature of the heterogeneous decomposition is 95-105 ℃, the pH of the heterogeneous decomposition solution is 6-8, and OH in the waste lye is-The concentration is 0.5 to 1.0 mol/L.
7. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to any one of claims 1 to 6, wherein the temperature of the decomposition liquid after temperature rise is 140 to 145 ℃.
8. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to any one of claims 1 to 7, wherein the heated decomposition solution is directly introduced into a reboiler tube side from a reboiler lower head of an alkane-first column through a distributor, and is rectified to recover cyclohexane, wherein the total concentration of the mixture of cyclohexanol and cyclohexanone in the recovered cyclohexane is less than or equal to 500 ppm.
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| CN116396001A (en) * | 2022-11-25 | 2023-07-07 | 湖南聚仁化工新材料科技有限公司 | Cement grinding aid, application thereof and caprolactone rectification byproduct-based manufacturing method |
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