CN112920018B - Method for producing mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane - Google Patents
Method for producing mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane Download PDFInfo
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- C07C29/48—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by oxidation reactions with formation of hydroxy groups
- C07C29/50—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by oxidation reactions with formation of hydroxy groups with molecular oxygen only
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
- C07C45/27—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
- C07C45/32—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with molecular oxygen
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Abstract
A process for the production of a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane comprising the steps of: heating cyclohexane and oxidizing with molecular oxygen under the condition of no catalysis to obtain an oxidation solution; the oxidation liquid is cooled through two-step indirect heat exchange, wherein the first step is to adopt pure anhydrous recovered hot alkane for heat exchange, so that the temperature of the oxidation liquid is reduced to 150 ℃, and the second step is to adopt heterogeneous decomposition liquid for heat exchange, so that the temperature of the oxidation liquid is reduced to 115-125 ℃, thereby avoiding the polymerization reaction of heat-sensitive substances in the heterogeneous decomposition liquid at high temperature and fouling the heat exchanger; decomposing the oxidation solution subjected to the two-step cooling sequentially through a homogeneous decomposition system and a heterogeneous decomposition system to obtain a heterogeneous decomposition solution; and (3) indirectly exchanging heat between the heterogeneous decomposition liquid and the oxidation liquid cooled in the first step to 145 ℃, directly entering a distributor of a lower end enclosure of the alkane-tower reboiler, and rectifying and recovering cyclohexane to obtain a cyclohexanol and cyclohexanone mixture, thereby avoiding scaling and blocking of the alkane-tower reboiler.
Description
Technical Field
0001 the present invention relates to a method for producing a mixture of cyclohexanol and cyclohexanone, and more particularly to a method for producing a mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane.
Background
The process for producing cyclohexanol and cyclohexanone by oxidation of 0002 cyclohexane generally falls into three main stages: a cyclohexane oxidation section, a cyclohexyl hydroperoxide decomposition section and a cyclohexane recovery section. The methods adopted in the cyclohexane oxidation section mainly comprise two 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 the method, due to the existence of a transition metal catalyst, most of cyclohexyl hydroperoxide generated by cyclohexane oxidation is decomposed in an oxidation kettle to generate cyclohexanol and cyclohexanone, then alcohol ketone is further deeply oxidized into acids and esters, so that the final oxidation product of cyclohexanol accounts for 40wt%, cyclohexanone accounts for 25wt%, the cyclohexyl hydroperoxide is lower than 15wt%, and the content of impurities such as acids and esters is up to 20wt%, so that the catalytic oxidation conversion rate of the method is 5 percent, but the yield is very low, and the oxidation kettle slag is serious due to the high content of the acids and esters in the product (see 'Yang Xuqing, the progress of the cyclohexane liquid phase air catalytic oxidation to prepare cyclohexanone and cyclohexanol, the synthetic fiber industry, 1992, 15 (1): 9-13', and CN 1011203B); 2) Cyclohexane is not catalyzed and oxidized, the reaction temperature is increased to 160-180 ℃, the pressure is controlled to be 1.1-1.3 MpaG, and the oxidation system does not contain transition metal catalyst. The cyclohexane oxidation product obtained by the method comprises about 68wt% of cyclohexyl hydroperoxide, 15wt% of cyclohexanol, 8wt% of cyclohexanone, and 9wt% of acid and ester impurities, so that the oxidation yield is improved, and the problem of slag formation and blockage of an oxidation kettle is basically solved (see 'Yang Chun and improvement and prospect of cyclohexane oxidation method cyclohexanone technology, energy chemical industry, 2016, 37 (6): 17-27' and CN 1621398A).
0003 the traditional cyclohexane catalytic oxidation method and the non-catalytic oxidation method adopt free radical chain reaction mechanism in the oxidation process, the oxidation must be controlled to be carried out under low conversion rate, otherwise, the cyclohexyl hydroperoxide, cyclohexanol and cyclohexanone generated by the oxidation are more active than the chemical property of cyclohexane, and are easily continuously oxidized into acids, esters and the like deeply, so that the oxidation yield is reduced. However, the lower the conversion of cyclohexane oxidation process, the more steam is required to recover the large amount of unreacted cyclohexane in the oxidation liquor. Therefore, the conventional cyclohexane non-catalytic oxidation process sets the conversion rate of cyclohexane oxidation at 3.5%, and then cyclohexane is recovered by a series of means of oxidation heat recovery and cyclohexane multi-effect rectification recovery.
One of the main heat sources for the heat recovery of 0004 cyclohexane oxidation is the heat released by cooling the cyclohexane oxidation solution at 160-170 ℃ from the oxidation reactor to the temperature required for the decomposition reaction of cyclohexyl hydroperoxide at 90-100 ℃. The method for catalytic oxidation free disclosed by French Long Bo company adopts an acidic homogeneous decomposition process, and the method for heat recovery comprises the following steps: the cyclohexane oxidation solution with high temperature and high pressure is directly flash evaporated to normal pressure and 90-100 ℃ which are required by homogeneous decomposition, part of cyclohexane is continuously vaporized by utilizing the decomposition heat of cyclohexyl hydroperoxide, then the cyclohexane is recovered by utilizing steam distillation in a cyclohexane recovery rectifying tower, and the steam consumption of the process is 7.0 tons/ton of crude alcohol ketone (see 'caprolactam production and application writing group, caprolactam production and application, beijing: hydrocarbon processing press, 1988: 23-99'). The cyclohexane non-catalytic oxidation method disclosed by the Dutch DSM company adopts a heterogeneous decomposition method of alkaline aqueous solution, and the heat recovery method comprises the following steps: the cyclohexane oxidizing solution with 160-170 ℃ and the decomposing solution with 90-100 ℃ in the subsequent working procedure are subjected to indirect heat exchange through a heat exchanger, so that the temperature of the oxidizing solution is reduced to about 120 ℃, and then the oxidizing solution is continuously cooled to 60-70 ℃ by circulating water; then, carrying out cyclohexyl hydroperoxide decomposition, wherein the decomposition heat of the cyclohexyl hydroperoxide can raise the temperature of the decomposition liquid, and then, using circulating water to cool the decomposition liquid to ensure that the decomposition temperature is between 90 and 100 ℃; the decomposed liquid is returned to the front to indirectly exchange heat with the oxidizing liquid at 160-170 ℃, the temperature is raised to 145-150 ℃, and the decomposed liquid enters a three-effect cyclohexane recovery distillation tower to recover cyclohexane by utilizing steam. Since the sensible heat of the oxidizing liquid is used by the company DSM in the netherlands to heat the decomposition liquid and act on the triple-effect alkane distillation, while the sensible heat of the oxidizing liquid is used by the company Long Bo in the france to flash the cyclohexane in a single effect, the steam consumption of the process disclosed by the company DSM in the netherlands is 6.0 tons per crude ketone alcohol, which is slightly lower than the process disclosed by the company Long Bo in the france (see "caprolactam production and application writing group, caprolactam production and application, beijing: hydrocarbon processing press, 1988: 23-99").
0005 In 2007, the first set of 10 ten thousand tons/year cyclohexane oxidation equipment in China was developed, and besides the new cyclohexane oxidation and cyclohexyl hydroperoxide decomposition technologies, on the basis of the indirect heat exchange method of oxidation solution and decomposition solution disclosed by Dutch DSM company, the four-effect alkane distillation technology was adopted to recover cyclohexane, so that the steam consumption is reduced to 5.5 tons/ton of crude alcohol ketone.
0006CN102627525B discloses a three-step process for decomposing cyclohexylhydroperoxide, which connects in series a homogeneous decomposition with high decomposition yield and a heterogeneous decomposition with high decomposition conversion, while reducing the cyclohexane consumption of the system, uses circulating water to cool a part of heat of an oxidation solution from 120 ℃ to 60-70 ℃ in the method disclosed by the netherlands DSM company, for flash evaporation to recover cyclohexane in the homogeneous decomposition, and uses the heat of decomposition of cyclohexylhydroperoxide for evaporation to recover cyclohexane, so that the heat of the oxidation solution is utilized to a greater extent, and the steam consumption of the process is reduced to 5.0 tons/ton of crude alcohol ketone.
0007 however, the cyclohexane oxidation heat exchange and cyclohexane recovery processes disclosed by the company DSM, the netherlands and CN102627525B both have the following two problems: 1) When the high-temperature oxidizing liquid and the low-temperature decomposing liquid exchange heat indirectly through the oxidative decomposition heat exchanger, the tube side scaling phenomenon of the decomposing liquid running in the heat exchanger is obvious, so that the thermal resistance of the oxidative decomposition heat exchanger is increased, and the heat exchange effect is continuously reduced; 2) Cyclohexane distills the fouling of the alkane-to-column reboiler, resulting in increased heat transfer resistance of the alkane-to-column reboiler. These two problems severely reduce cyclohexane recovery efficiency, greatly shorten the plant operating cycle, and force the plant to operate at high oxidative conversion at all times, resulting in significant raw material and energy waste.
Disclosure of Invention
0008 the present invention solves the above-mentioned drawbacks of the prior art by first providing a mechanism for fouling the heat exchanger and reboiler, and then providing a method for producing a mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane that slows down the fouling rate of the oxidative decomposition heat exchanger and the cyclohexane distillation alkane-tower reboiler, and extends the continuous operation cycle of the apparatus, without significantly modifying the original main equipment of the apparatus according to the mechanism.
0009 the heat exchanger and reboiler fouling mechanism proposed by the present invention is as follows:
0010 in the cyclohexane non-catalytic oxidation process, cyclohexanone with a certain concentration is always kept in the oxidation feed cyclohexane as an initiator of free radicals, and is used for increasing the concentration of the free radicals in the oxidation solution in the initial stage of the oxidation reaction, so that the reaction speed of cyclohexane oxidation is improved, and the oxygen content in oxidation tail gas is ensured to be at a safe level of less than 2wt%, as shown in a formula I.
As the oxidation reaction proceeds, the concentration of cyclohexanone in the oxidation intermediate product cyclohexyl hydroperoxide is gradually increased through thermal decomposition or catalytic decomposition of metal walls; since the hydrogen at the alpha position of cyclohexanone is more reactive than the hydrogen chemistry of cyclohexane and forms radicals more readily, cyclohexanone is more readily oxidized by air than cyclohexane by forming radicals, and the oxidized product is a cyclohexanone-based hydrogen peroxide intermediate, as shown in formula II.
Cyclohexanone-based hydrogen peroxide is thermally decomposed or catalytically decomposed to form hydroxycyclohexanone, and a portion of the hydroxycyclohexanone undergoes intramolecular rearrangement to form caprolactone, as shown in formula III.
The other part of the hydroxy cyclohexanone is subjected to ring opening reaction at high temperature and is continuously subjected to deep oxidation by air, or decarburization reaction is carried out, so that a series of acid and ester byproducts with five carbon atoms and six carbon atoms are generated, as shown in a formula IV.
The cyclohexane oxidation solution containing these byproducts is decomposed by heterogeneous phase of NaOH aqueous solution, three types of reactions mainly occur: 1) The cyclohexyl hydroperoxide is catalytically decomposed into cyclohexanol and cyclohexanone; 2) The acidic byproducts are neutralized into salts and dissolved in the alkaline water phase; 3) The esters are hydrolyzed by saponification and extracted to the aqueous alkaline phase. Wherein caprolactone is partially saponified into hydroxy caproate (shown in formula V), and amphiphilic molecules (one end is hydrophilic and the other end is oleophylic) such as caprolactone and carbonyl caproate are distributed between alkali water phase and cyclohexane phase, and even form a third phase on oil-water interface. Thus, after washing the heterogeneous decomposition liquid with water, the heterogeneous decomposition liquid of the oil phase will dissolve a part of the carbonyl hexanoic acid and the hydroxycaproic acid, and the caprolactone which is not saponified.
When the heterogeneous decomposition solution is heated, the carbonyl caproic acid undergoes aldol condensation reaction, the hydroxyl caproic acid undergoes dehydration polymerization reaction to produce polyester, and caprolactone undergoes ring-opening polymerization to produce polyester, which is called as a heat-sensitive polymerization monomer by the inventor, and is shown as a formula VI. When the temperature is low, the polymerization reaction is slow, mainly a polymer with low molecular weight is formed, and part of the polymer can be dissolved in cyclohexane phase, so that the influence on system equipment can not be quickly caused; however, when the temperature is increased, the dehydration polymerization reaction is accelerated, a large amount of polymer with high molecular weight is generated, and the polymer is insoluble in cyclohexane to form scale on the pipe wall of the equipment.
The speed of the polymerization reaction is related to the concentration of the heat-sensitive polymerized monomer, the acid-base property of the material and the temperature of the material through the law of mass action and the polymerization reaction mechanism.
Thus, the fouling rate of oxidative decomposition heat exchangers or cyclohexane distillation alkane-column reboilers is increased for the following reasons in the prior art:
(1) When the design of the alkane tower of the existing device is smaller, the concentration of cyclohexanone in the recovered cyclohexane is high, or the oxidation conversion rate is improved due to the pursuit of yield, the content of cyclohexanone-based hydrogen peroxide generated by oxidation of cyclohexanone in the oxidation liquid is increased, the concentration of heat-sensitive polymerization monomers of the oxidation byproducts is increased, and the scaling speed of an oxidative decomposition heat exchanger and an alkane-tower reboiler is higher; (2) When the decomposition liquid becomes acidic (method disclosed by French Boril) or the decomposition liquid becomes alkaline (method disclosed by Dutch DSM), the polymerization reaction is catalyzed and accelerated due to the existence of the acid or the alkali, and the scaling speed of an oxidative decomposition heat exchanger and an alkane-tower reboiler is also accelerated; (3) In the heterogeneous decomposition process, when the alkaline condition is weaker or the reaction temperature is not high enough, the saponification reaction of caprolactone and the like is incomplete, so that the heat-sensitive polymerized monomer carried away by waste alkali liquor is reduced, the content of the heat-sensitive polymerized monomer in the decomposition solution is high, and the scaling speed of an oxidative decomposition heat exchanger and an alkane-tower reboiler is also accelerated; (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, and the temperature of the decomposition liquid contacting the metal heat exchanger tube wall is more than 165 ℃, the polymerization scaling speed of the tube side of the oxidative decomposition heat exchanger is also 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 the tray, the materials entering the alkane-tower reboiler are very dry, and the heating temperature of the alkane-tower reboiler of the four-effect alkane tower is higher than that of the three-effect alkane tower, so that the dehydration polymerization reaction is promoted, and the scaling speed of the tube side of the alkane-tower reboiler is accelerated.
By analyzing a scale formation 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 the condition of no catalysis to obtain an oxidation solution; cooling the oxidation liquid through a two-step indirect heat exchange process, and then decomposing the oxidation liquid sequentially 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, and then directly entering a distributor of a lower end enclosure of an alkane-tower reboiler for cyclohexane rectification recovery to obtain a cyclohexanol and cyclohexanone mixture;
the step of cooling the oxidation liquid through a two-step indirect heat exchange process means that the oxidation liquid is subjected to a first-step indirect heat exchange cooling with hot cyclohexane recovered by a cyclohexane distillation system to obtain the oxidation liquid after the first-step cooling; then the oxidation liquid after the first step of cooling is subjected to the second step of indirect heat exchange cooling with the heterogeneous decomposition liquid to obtain the oxidation liquid after the second step of cooling;
the heating of the heterogeneous decomposition liquid through the one-step indirect heat exchange process means that the heterogeneous decomposition liquid and the oxidation liquid cooled in the first step are subjected to indirect heat exchange and heated, and the heated decomposition liquid is obtained.
Further, 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%.
Further, the temperature of the oxidation liquid after the first step of cooling is 150-155 ℃; the temperature of the oxidation liquid after the second step of cooling 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 of indirect heat exchange is 150-155 ℃.
The cyclohexane recovered by the cyclohexane distillation system is purer, the pure cyclohexane is firstly utilized to reduce the temperature of the oxidation liquid to 150-155 ℃, and then the oxidation liquid is subjected to indirect heat exchange with the heterogeneous decomposition liquid of 95-105 ℃, so that the heterogeneous decomposition liquid containing the thermosensitive polymerization monomer is prevented from contacting the wall of a heat exchange tube at too high temperature, the phenomenon of organic matter dehydration polymerization scaling in the tube side of the decomposition heat exchanger is relieved, and the operation period of the decomposition heat exchanger is prolonged.
Cyclohexane recovered by a multi-effect cyclohexane distillation system is divided into two types, wherein one type is high-temperature cyclohexane condensed by heating and concentrating rectifying tower kettle liquid by using first three-effect cyclohexane steam, namely hot cyclohexane, the temperature is 110-120 ℃, and the other type is low-temperature cyclohexane generated by condensing last-effect cyclohexane steam by circulating water, namely cold cyclohexane, and the temperature is 60-70 ℃; the temperature of the recovered hot alkane after indirect heat exchange with the oxidizing liquid is increased 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; the cold alkane returns to the oxidation tail gas recovery system according to the old flow, and is subjected to direct heat exchange to recover cyclohexane steam in the oxidation tail gas, and then the oxidation tail gas is subjected to oxidation by an oxidation feeding pump to oxidize the heater. The flow can greatly reduce the operation load of the oxidation feed pump, and is beneficial to improving the feed amount of cyclohexane oxidation in the original device.
Further, sending the oxidation solution cooled in the second step into a homogeneous decomposition system, flashing to 90-100 ℃, and simultaneously adding a homogeneous catalyst tert-butyl chromate and a scale inhibitor 1-hydroxy-ethylidene-octyl bisphosphonate for homogeneous decomposition to obtain a homogeneous decomposition solution; and (3) carrying out heterogeneous decomposition, saponification and water washing on the homogeneously decomposed solution in an NaOH aqueous solution, and separating to obtain waste alkali liquid and the heterogeneously decomposed solution.
Further, the heterogeneous decomposition temperature is 95-105 ℃, the pH value of the heterogeneous decomposition solution is 6-8, and OH in the waste alkali solution - The concentration is 0.5-1.0 mol/L.
The 110-120 ℃ oxidizing solution cooled in the second step is not cooled by circulating water, but is directly subjected to flash evaporation by a homogeneous decomposition system, and part of cyclohexane is continuously evaporated and recovered by utilizing decomposition heat generated in the homogeneous decomposition process, so that the heat brought by the decomposition process is utilized to the greatest extent, the recovery amount of cyclohexane is improved on the premise of not increasing steam consumption, and the method is used for reducing the conversion rate of cyclohexane oxidation.
The homogeneous decomposition solution is subjected to heterogeneous decomposition at a higher temperature in NaOH aqueous solution, cyclohexyl hydroperoxide is fully decomposed into cyclohexanol and cyclohexanone by saponification and water washing, most of thermosensitive impurities such as acids and esters are neutralized and saponified by alkali, and are converted into sodium salt to be dissolved in waste alkaline water phase, and the sodium salt is taken out of the system, so that the content of thermosensitive polymerized monomers in the heterogeneous decomposition solution, which are easy to scale at a high temperature, is reduced. In addition, the heterogeneous decomposition liquid is kept neutral by water washing, so that the catalysis of acid and alkali to polymerization reaction can be greatly reduced, and the operation period of the decomposition heat exchanger and the alkane-tower reboiler is prolonged.
Further, the temperature of the decomposed solution after the temperature rise is 140 to 145 ℃.
And further, the heated decomposition liquid is directly led into a reboiler tube side from the lower end socket of the alkane-tower reboiler through a distributor, and is rectified to recover cyclohexane, wherein the total concentration of the mixture of the cyclohexane and the cyclohexanone in the recovered cyclohexane is less than or equal to 500ppm.
The neutral heterogeneous decomposition liquid with reduced heat-sensitive impurity content is indirectly heat-exchanged with the oxidation liquid (150-155 ℃) which is subjected to the first step of temperature reduction to be heated to 140-145 ℃, so that the heterogeneous decomposition liquid is prevented from contacting the heat exchange pipe wall with the high temperature of more than 165 ℃, the heat-sensitive polymerization reaction in the heterogeneous decomposition liquid is greatly reduced, and the operation period of the decomposition heat exchanger and the alkane-first tower reboiler is prolonged.
The heterogeneous decomposition liquid after temperature rising is not led into the tower section of the rectifying tower, but is directly led from the lower end socket of the alkane-tower reboiler, so that the situation that the water in the heterogeneous decomposition liquid is evaporated and dried in the tower body and then led into the alkane-tower reboiler tube side can be avoided. Therefore, the method can keep a certain amount of water partial pressure in the tube side of the reboiler and inhibit the oligomer from continuously dehydrating and polycondensing under the premise of not increasing the water inflow of the cyclohexane rectifying system; meanwhile, the flow rate of materials in the tube side tube is greatly improved, and the scale forming speed of the reboiler is slowed down by scouring force.
Compared with the prior art, the invention has the beneficial effects that:
(1) On the premise of not changing the flow of a cyclohexane oxidation feeding pump and the cyclohexane distillation load, the feeding amount of cyclohexane oxidation cyclohexane is improved, 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 the cyclohexane distillation alkane-tower reboiler is slowed down, the continuous operation period of the device is prolonged from 3-4 months to more than 12 months, and the safety of the device is improved.
Drawings
FIG. 1 is a schematic diagram of equipment and process flow used in an example of a process for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to the present invention.
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-oxidation tail gas noncondensable gas, 013-acid water, 021-cyclohexane pumped 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, 051-oxidation liquid cooled in a first step, 052-heated hot alkane, 061-oxidation liquid cooled in a second step, 062-heating decomposition liquid, 071-homogeneous decomposition liquid, 072-homogeneous decomposition recovery cold alkane, 073-homogeneous decomposition tail gas, 080-neoalkali entering a heterogeneous decomposition system, 081-heterogeneous decomposition liquid, 082-waste alkali liquid, 083-process washing water, 091-cyclohexane vapor and liquid mixed fluid, 100-system-supplemented new cyclohexane, 101-alkane tower recovery cold alkane, 102-alkane tower recovery cold alkane, 103-alkane one tower self-circulating cyclohexane liquid and 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 procedure of DSM company, netherlands, 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-alkane-tower reboiler and 10-triple-effect cyclohexane distillation system;
011-cyclohexane liquid, 012-oxidation tail gas noncondensable gas, 021-cyclohexane pumped 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 subjected to heat exchange by an oxidative decomposition heat exchanger, 062-heating decomposition liquid, 071-oxidation liquid cooled by a circulating water cooler, 080-neo-alkali, 081-heterogeneous decomposition liquid, 082-waste alkali liquid, 083-process washing water, 091-cyclohexane vapor evaporated by an alkane-tower reboiler, cyclohexane and other liquid mixed fluid, 100-new cyclohexane supplemented to a system, 101-cyclohexane distilled hot alkane, 102-cold alkane, 103-cyclohexane liquid self-circulated between an alkane-tower kettle and the reboiler, 104-crude alcohol ketone and 105-alkane tower.
Detailed Description
The invention will be further described with reference to specific examples and figures.
Examples
Referring to fig. 1, the method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to an embodiment of the present invention uses a set of 10 ten thousand tons/year cyclohexane oxidation unit according to the present invention, comprising the following operation steps:
(1) Liquid cold alkane (containing new cyclohexane 100 of supplementary 12.5 t/h) 102 and cold alkane 072 of homogeneous decomposition recovery 130t/h of 157.5t/h cyclohexane, through carrying on the direct heat exchange with oxidation tail gas 042 of 170-172 deg.C, have recovered the cyclohexane condensed in most oxidation tail gas, the total flowrate of cyclohexane increases to 390t/h, the temperature rises to 155 deg.C, oxidation tail gas does not condense 012 and continues to carry on the tail gas absorption treatment;
390t/h cyclohexane liquid 011 from the direct heat exchange tower kettle is pressurized by an oxidation feed pump 02 and enters an oxidation heater 03 together with 160t/h hot alkane 052 (the temperature is 155 ℃) after heat exchange from an oxidation cyclohexane heat exchanger 05; 550t/h cyclohexane 031 (the temperature is 183 ℃) heated by the oxidation heater 03 sequentially enters the series-connected oxidation reactor group 04 to carry out 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=1.25 MpaG and the temperature t=168-180 ℃; air 040 total flow 20000Nm into oxidation reactor 3 Obtaining 455t/h cyclohexane oxidation solution 041 (temperature is 168 ℃);
(2) Introducing 455t/h cyclohexane oxidation solution 041 (temperature is 168 ℃) obtained in the step (1) into a cyclohexane oxidation heat exchanger 05, and performing first-step indirect heat exchange cooling on the oxidation solution 041 and 160t/h hot alkane 101 (temperature is 113 ℃) which is obtained from cyclohexane recovery distillation and does not contain heat-sensitive polymerization monomers, so as to obtain oxidation solution 051 (temperature is 155 ℃) which is subjected to first-step cooling and hot alkane 052 (temperature is 155 ℃);
the heated hot alkane 052 deoxidization heater 03 is heated by steam, the oxidation liquid 051 of the first step is deoxidized and decomposed heat exchanger 06, the second step indirect heat exchange cooling is continuously carried out with 313t/h heterogeneous decomposition liquid 081 (the temperature is 100 ℃) from the heterogeneous decomposition reactor 08, and 455t/h oxidation liquid 061 of the second step (the temperature is 120 ℃) is obtained after heat exchange in the oxidation and decomposition heat exchanger 06;
(3) Introducing 455t/h of the oxidation solution 061 (the temperature is 120 ℃) obtained in the step (2) cooled in the second step into a normal-pressure homogeneous decomposition reaction system 07, then flashing, carrying out a homogeneous decomposition reaction of cyclohexyl hydrogen peroxide under the action of 100L/h 3wt% of a tert-butyl chromate cyclohexane solution and 150L/h 3wt% of a scale inhibitor 1-hydroxy-ethylidene-bisphosphonate octyl cyclohexane solution to obtain a homogeneous decomposition solution 071, continuously evaporating cyclohexane by using the decomposition reaction heat, carrying out oxidation feeding by using a homogeneous decomposition recovery 130t/h cold alkane 072 deoxidization tail gas recovery system 01, compressing tail gas of the homogeneous decomposition 073, and then delivering the tail gas to an oxidation tail gas absorption treatment;
(4) Continuously removing the 325t/h homogeneous decomposition solution 071 to a heterogeneous decomposition reaction system 08 to carry out heterogeneous decomposition reaction of the NaOH aqueous solution to obtain a heterogeneous decomposition solution, wherein the heterogeneous decomposition temperature is set to be 100 ℃; the caprolactone in the decomposing liquid is saponified to hydroxycaproic acid sodium salt, and most of the caprolactone is carried out of the system by waste lye 082; continuously adding neo-alkali 080 into the heterogeneous decomposition system 08 to enable OH in the waste alkali solution - Is maintained at a concentration of 0.6mol/L; washing with process washing water 083 to obtain 318t/h neutral heterogeneous decomposition liquid (at 100 ℃); delivering 12.5t/h waste alkali liquor 082 (the temperature is 100 ℃) to waste alkali evaporation treatment; then, the neutral heterogeneous decomposition liquid (with the temperature of 100 ℃) of 318t/h enters an oxidative decomposition heat exchanger 06 to carry out indirect heat exchange and heating, so as to obtain heterogeneous decomposition liquid 062 (with the temperature of 143 ℃) after 318t/h heating;
(5) The heterogeneous decomposition liquid 062 (the temperature is 143 ℃) after the temperature is increased by 318t/h passes through the lower end enclosure of the alkane-tower reboiler 09, and enters the tube side of the alkane-tower reboiler 09 together with alkane-tower kettle liquid under the water-containing environment to obtain liquid mixed fluid 091 such as cyclohexane vapor and cyclohexane, and then enters the alkane-tower section of the cyclohexane distillation 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, and the crude alcohol ketone 104 of 13t/h is obtained, and the total concentration of the cyclohexane alcohol and the cyclohexanone in the cold alkane is 500ppm.
According to detection, in the embodiment, the lower oxidation conversion rate is realized by fully utilizing the heat of the oxidation liquid, four-effect cyclohexane distillation recovery is adopted, the cyclohexane unit consumption of the device is 960 Kg/ton of crude alcohol ketone, and the steam unit consumption is 5.0 tons/ton of crude alcohol ketone; the stable operation period of the oxidative decomposition heat exchanger and the cyclohexane recovery rectifying alkane-tower reboiler is 12 months due to the optimization of the heat exchange flow.
Comparative example
Referring to fig. 2, the method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to the present comparative example uses a cyclohexane oxidation unit of 10 ten thousand tons/year of conventional technology, comprising the following operation steps:
(1) 150t/h of liquid cold alkane 102 (containing 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 in 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 the oxidation tail gas noncondensable gas 012 is subjected to continuous tail gas absorption treatment;
the cyclohexane liquid 011 at 480t/h is pressurized by an oxidation feeding pump 02, and is heated by an oxidation heater 03 to obtain cyclohexane 031 (the temperature is 178 ℃), and then enters a series-connected oxidation reactor group 04 to perform 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 reactor for oxidizing cyclohexane are as follows: the pressure P=1.10 MpaG and the temperature t=160-170 ℃; air 040 total flow 20000Nm into oxidation reactor 3 /h; obtaining 375t/h cyclohexane oxidation solution 041 (the temperature is 165 ℃);
(2) Feeding 375t/h cyclohexane oxidation solution 041 (temperature is 165 ℃) obtained in the step (1) into an oxidative decomposition heat exchanger 06, performing indirect heat exchange with a 369.5t/h heterogeneous decomposition solution 081 (temperature is 95 ℃) decomposed by a heterogeneous decomposition system 08 to obtain an oxidation solution 061 with the temperature of 120 ℃, and cooling to 60 ℃ through a circulating water cooler 07 to obtain an oxidation solution 071;
(3) Introducing the oxidizing solution 071 into a heterogeneous decomposition system 08 for heterogeneous decomposition reaction of NaOH aqueous solution, wherein the heterogeneous decomposition temperature is 95 ℃, so as to obtain a heterogeneous decomposition solution; continuously adding new alkali 080 into the system to enable OH in the waste alkali - The concentration of (2) is maintained at 1.2mol/L, and the solution is washed by process washing water 083 to make the heterogeneous decomposition solution neutral, thus obtaining 369.5t/h decomposition solution (the temperature is 95 ℃); 17.5t/h of waste alkali 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 165 ℃ high-temperature oxidation liquid to obtain 369.5t/h decomposition liquid 062 (the temperature is 143 ℃); then the heated decomposition liquid enters an alkane-tower body of a cyclohexane distillation system 10, and enters an alkane-tower reboiler 09 together with tower bottom liquid after drying, so as to obtain liquid mixed fluid 091 of cyclohexane gas, cyclohexane and the like through vaporization, and then the liquid mixed fluid returns to the alkane-tower body to carry out cyclohexane recovery rectification, 137.5t/h of cold alkane and 220t/h of hot alkane are recovered, and the crude alcohol ketone 104 with the total concentration of cyclohexanone and cyclohexanol in the cold alkane of 12t/h is 1000ppm; the alkane tower tail gas 105 is sent to the oxidation tail gas absorption treatment after being compressed.
According to detection, the heat of the oxidation liquid is not fully utilized in the comparative example, the oxidation conversion rate is high, only three-effect cyclohexane distillation is adopted, the cyclohexane unit consumption of 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 cyclohexane recovery rectifying alkane-tower reboiler is 5 months.
Claims (12)
1. A process for the production of a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane, comprising the steps of: heating cyclohexane and oxidizing with molecular oxygen under the condition of no catalysis to obtain an oxidation solution; cooling the oxidation liquid through a two-step indirect heat exchange process, and then decomposing the oxidation liquid sequentially 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, and then directly entering a distributor of a lower end enclosure of an alkane-tower reboiler for cyclohexane rectification recovery to obtain a cyclohexanol and cyclohexanone mixture;
the step of cooling the oxidation liquid through a two-step indirect heat exchange process means that the oxidation liquid is subjected to a first-step indirect heat exchange cooling with hot cyclohexane recovered by a cyclohexane distillation system to obtain the oxidation liquid after the first-step cooling; then the oxidation liquid after the first step of cooling is subjected to the second step of indirect heat exchange cooling with the heterogeneous decomposition liquid to obtain the oxidation liquid after the second step of cooling;
the heating of the heterogeneous decomposition liquid through the one-step indirect heat exchange process means that the heterogeneous decomposition liquid and the oxidation liquid cooled in the first step are subjected to indirect heat exchange and heated to obtain the heated decomposition liquid;
the step of sequentially carrying out decomposition through a homogeneous decomposition system and a heterogeneous decomposition system is that the oxidation solution after the second step of cooling is sent into the homogeneous decomposition system, is flashed to 90-100 ℃, and is simultaneously added with a homogeneous catalyst of tert-butyl chromate and 1-hydroxy-ethylidene-octyl biphosphonate for homogeneous decomposition to obtain a homogeneous decomposition solution; carrying out heterogeneous decomposition, saponification and water washing on the homogeneous decomposition solution in NaOH aqueous solution, and separating to obtain waste alkali solution and heterogeneous decomposition solution; the heterogeneous decomposition temperature is 95-105 ℃, the pH value of the heterogeneous decomposition solution is 6-8, and OH in the waste alkali solution - The concentration is 0.5-1.0 mol/L.
2. The method for producing a 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 oxidizing liquid at the outlet of the oxidation reactor is 165-170 ℃, and the oxidation conversion is controlled to be 3.3-3.5%.
3. The method for producing a 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 ℃; the temperature of the oxidation liquid after the second step of cooling is 110-120 ℃.
4. The process for the production of a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to claim 1 or 2, wherein the temperature of the recovered hot cyclohexane is 110-120 ℃; the temperature of the recovered hot cyclohexane after the first step of indirect heat exchange is 150-155 ℃.
5. A process for the production of a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to claim 3, wherein the temperature of the recovered hot cyclohexane is 110-120 ℃; the temperature of the recovered hot cyclohexane after the first step of indirect heat exchange is 150-155 ℃.
6. The method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to claim 1 or 2, wherein the temperature of the decomposition liquid after temperature increase is 140-145 ℃.
7. A method for producing a mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to claim 3, wherein the temperature of the decomposition liquid after temperature rise is 140-145 ℃.
8. The method for producing a mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to claim 4, wherein the temperature of the decomposed solution after heating is 140 to 145 ℃.
9. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to claim 1 or 2, wherein the decomposed solution after temperature rise is directly led into a reboiler tube side from a lower end socket of an alkane-tower reboiler through a distributor, cyclohexane is recovered by rectification, and the total concentration of the mixture of cyclohexanol and cyclohexanone in the recovered cyclohexane is less than or equal to 500ppm.
10. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to claim 3, wherein the decomposed solution after temperature rise is directly led into a reboiler tube side from a lower end socket of an alkane-tower reboiler through a distributor, cyclohexane is recovered by rectification, and the total concentration of the mixture of cyclohexanol and cyclohexanone in the recovered cyclohexane is less than or equal to 500ppm.
11. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidizing cyclohexane according to claim 4, wherein the decomposed solution after temperature rise is directly led into a reboiler tube side from a lower end socket of an alkane-tower reboiler through a distributor, cyclohexane is recovered by rectification, and the total concentration of the mixture of cyclohexanol and cyclohexanone in the recovered cyclohexane is less than or equal to 500ppm.
12. The method for producing the mixture of cyclohexanol and cyclohexanone by oxidation of cyclohexane according to claim 6, wherein the decomposed solution after temperature rise is directly led into a reboiler tube side from a lower end socket of an alkane-tower reboiler through a distributor, cyclohexane is recovered by rectification, and the total concentration of the mixture of cyclohexanol and cyclohexanone in the recovered cyclohexane is less than or equal to 500ppm.
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| CN202170313U (en) * | 2011-06-07 | 2012-03-21 | 南京德力菲技术咨询有限公司 | Device for recovering heat of oxidant solution in process of preparing cyclohexanone by oxidizing cyclohexane |
| CN102627525A (en) * | 2012-03-31 | 2012-08-08 | 肖藻生 | Preparation process for preparing hexamethylene and cyclohexanone by cyclohexane oxidation |
| CN102627541A (en) * | 2012-03-28 | 2012-08-08 | 肖藻生 | Technology for preparing hexanaphthene and cyclohexanone through cyclohexane oxidation and device thereof |
| WO2013083512A1 (en) * | 2011-12-07 | 2013-06-13 | Dsm Ip Assets B.V. | Process for the production of a mixture comprising cyclohexanol and cyclohexanone |
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| CN202170313U (en) * | 2011-06-07 | 2012-03-21 | 南京德力菲技术咨询有限公司 | Device for recovering heat of oxidant solution in process of preparing cyclohexanone by oxidizing cyclohexane |
| WO2013083512A1 (en) * | 2011-12-07 | 2013-06-13 | Dsm Ip Assets B.V. | Process for the production of a mixture comprising cyclohexanol and cyclohexanone |
| CN103987452A (en) * | 2011-12-07 | 2014-08-13 | 帝斯曼知识产权资产管理有限公司 | Process for the production of a mixture comprising cyclohexanol and cyclohexanone |
| CN102627541A (en) * | 2012-03-28 | 2012-08-08 | 肖藻生 | Technology for preparing hexanaphthene and cyclohexanone through cyclohexane oxidation and device thereof |
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