Method for producing cyclohexanone and cyclohexanol by cyclohexane oxidation

Abstract

The invention relates to a method for producing cyclohexanol and cyclohexanone by cyclohexane oxidation, which comprises the following steps: (1) carrying out molecular oxygen oxidation on cyclohexane under a non-catalytic condition to obtain an oxidation solution containing cyclohexyl hydrogen peroxide; (2) adding a cyclohexyl hydroperoxide decomposition catalyst and a scale inhibitor into the obtained oxidation liquid, carrying out multiple-effect reactive distillation to decompose cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone, recovering unreacted cyclohexane in the step (1), and returning to the step (1); and (3) adding alkali liquor into the decomposition liquid containing 50-70% of cyclohexane obtained after rectification, and carrying out a neutralization saponification reaction to completely convert residual cyclohexyl hydrogen peroxide into cyclohexanol and cyclohexanone so as to obtain an alcohol-ketone mixture. According to the method disclosed by the invention, cyclohexyl hydroperoxide decomposition and cyclohexane recycling are combined into one step, and a large-scale alkali liquor separation process is not needed any more, so that the production efficiency is greatly improved, and the production cost is reduced.

Description

Technical Field

[0001] The invention relates to a method for preparing cyclohexanone and cyclohexanol, an organic compound, and in particular to a method for producing cyclohexanone and cyclohexanol by taking cyclohexane as a raw material. Background Art

[0002] Cyclohexanone is an important organic chemical raw material, mainly used as an intermediate in the production of caprolactam, adipic acid and its salts. Due to its good solubility, low toxicity and relatively low price, it can also be used as an excellent solvent and a solubilizer for paints and inks.

[0003] The production methods of cyclohexanone include phenol hydrogenation, cyclohexane oxidation and cyclohexene hydration. Although cyclohexene hydration has become the method with the largest production capacity, cyclohexane oxidation still has vitality in solving the problem of cyclohexane as a by-product of cyclohexene production. It can complement the cyclohexanone unit produced by cyclohexene hydration, supply raw materials to each other, form a closed-loop circular economy chain, and participate in market competition with excellent quality and low production cost.

[0004] The existing cyclohexane oxidation process is mainly divided into a catalytic oxidation process and a non-catalytic oxidation process.

[0005] The cyclohexane catalytic oxidation process was invented by DuPont in the United States. Cobalt salt is used to catalyze the oxidation of cyclohexane. Cyclohexane oxidation reaction and decomposition reaction of the intermediate product cyclohexyl hydroperoxide occur in the oxidation reactor. After alkaline decomposition and cyclohexane recovery system, a mixture of cyclohexanone and cyclohexanol is obtained. However, since cyclohexanone produced by the decomposition of cyclohexyl hydroperoxide is more easily oxidized by molecular oxygen than cyclohexane, the cyclohexane conversion rate in the catalytic oxidation process is 5%, and the alcohol ketone yield is only 70-75%.

[0006] In recent years, a bionic catalytic process for cyclohexane has been proposed, which uses metalloporphyrins and other catalysts to oxidize cyclohexane with air. Bionic catalytic oxidation claims that the single-pass conversion rate of cyclohexane is increased to 8%, but it does not solve the core problem that the decomposition products cyclohexanol and cyclohexanone are more easily oxidized than cyclohexane, resulting in severe deep oxidation during the oxidation process and a low yield of cyclohexanone and cyclohexanol, less than 70%.

[0007] There are two main routes for the cyclohexane non-catalytic oxidation process. One is the process invented by Rhodia of France, which uses oxygen deficiency to oxidize cyclohexane without adding catalyst, and the cyclohexyl hydroperoxide in the oxidation liquid is homogeneously decomposed with tert-butyl chromate as catalyst; the other is the process invented by DSM of the Netherlands, which uses air to oxidize cyclohexane without catalysis, and the cyclohexyl hydroperoxide is heterogeneously catalyzed by cobalt acetate in an alkaline aqueous solution of sodium hydroxide. The innovation of the two processes is to separate the oxidation reaction and the decomposition reaction, and the single-pass oxidation conversion rate of cyclohexane is reduced to 3.5%, mainly generating cyclohexyl hydroperoxide, while reducing the generation of cyclohexanol and cyclohexanone in the oxidizing environment, thereby reducing deep oxidation and improving oxidation yield. However, the low oxidation conversion rate brings a larger cyclohexane circulation volume, resulting in the supporting alkali decomposition system and cyclohexane recovery system becoming the bottleneck of the entire system. At present, the production capacity of the largest single-line cyclohexane oxidation device imitating DSM is only 100,000 tons / year.

[0008] In the technical solutions reported in CN201210085933.6 and CN201210091366.5, the homogeneous decomposition technology of Rhodia of France and the alkaline decomposition technology of DSM of the Netherlands are combined, and the high selectivity of homogeneous decomposition and the high conversion rate of alkaline decomposition are fully utilized, so that the process of preparing cyclohexanol and cyclohexanone by oxidation of cyclohexane has developed to a new stage, and the unit consumption of cyclohexane and caustic soda has been greatly reduced, forming the most competitive technology for preparing cyclohexanol and cyclohexanone by oxidation of cyclohexane. Although this technology recovers part of the cyclohexane in the homogeneous decomposition process, the organic phase flow rate in the alkaline decomposition process is still too large, and the alkaline separation load still becomes a difficulty for the device to continue to expand its capacity; secondly, the cyclohexane recovery tower still needs to consume a large amount of steam to recover cyclohexane. At present, the production capacity of the largest single-line cyclohexane oxidation device using this technology can only reach 120,000 tons / year, which cannot be further expanded. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a method for producing cyclohexanone and cyclohexanol by cyclohexane oxidation, which has a shorter process, lower steam consumption and lower material consumption cost, and a larger production capacity of a single-line cyclohexane oxidation device.

[0010] The technical solution adopted by the present invention to solve the technical problem is: a method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane, comprising the following steps:

[0011] (1) oxidizing cyclohexane with molecular oxygen under non-catalytic conditions to obtain an oxidation liquid containing cyclohexyl hydroperoxide;

[0012] The non-catalytic oxidation refers to the oxidation reaction of liquid cyclohexane with molecular oxygen in an oxidation reaction device without adding a catalyst to generate an oxidation liquid with the intermediate cyclohexyl hydroperoxide as the main component;

[0013] (2) adding a cyclohexyl hydroperoxide decomposition catalyst and a scale inhibitor to the oxidation liquid obtained in step (1), and performing multiple-effect reaction distillation to decompose more than 95% of the cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone, and during the distillation process, simultaneously recovering the unreacted cyclohexane in step (1) and returning it to step (1) as a raw material for the oxidation reaction in step (1);

[0014] The multi-effect reaction distillation of the oxidation liquid refers to that the oxidation liquid containing cyclohexyl hydroperoxide is subjected to a decomposition reaction in a distillation tower under the action of a decomposition catalyst and a scale inhibitor, and at the same time, the sensible heat, decomposition heat and auxiliary heat of the oxidation liquid are used to condense most of the cyclohexane that is not oxidized in step (1) from the top of the distillation tower and then circulate back to the oxidation reactor of step (1) through multi-effect distillation, and a small amount of acid water is discharged at the same time. After the distillation, the output from the bottom of the tower is a decomposition liquid containing cyclohexanone, cyclohexanol and a trace amount of cyclohexyl hydroperoxide containing 50-70% of cyclohexane;

[0015] (3) adding alkali solution and water to the decomposition liquid containing 50-70% of cyclohexane obtained in step (2) to carry out a neutralization and saponification reaction so that the residual cyclohexyl hydroperoxide is completely converted into cyclohexanol and cyclohexanone to obtain an alcohol-ketone mixture;

[0016] The neutralization saponification means that after the decomposition liquid containing 50-70% cyclohexane is washed with water to remove most of the acid, the acid water is separated, and the organic phase is then neutralized with alkali solution to remove the acid and ester in the saponified crude alcohol ketone liquid, and the residual cyclohexyl hydroperoxide is completely converted into cyclohexanol and cyclohexanone. After the aqueous phase of the saponified liquid is separated, the organic phase is dried to remove cyclohexane and water to obtain a mixture of cyclohexanone and cyclohexanol; the cyclohexane removed by drying the organic phase is returned to step (1) as a raw material for the oxidation reaction in step (1).

[0017] Furthermore, in step (1), the oxidation reaction device is an oxidation reaction device composed of ≥3 oxidation reactors connected in series; the reaction temperature is controlled at 160-170° C., and the molar conversion rate of cyclohexane is controlled at 2.5-4.0%, preferably 3.0-3.5%. The oxidation reaction device composed of ≥3 oxidation reactors connected in series is used to carry out molecular oxygen oxidation of cyclohexane under non-catalytic conditions in order to achieve a reaction form similar to plug flow and improve the reaction efficiency.

[0018] Furthermore, in step (2), the cyclohexyl hydroperoxide decomposition catalyst is an oil-soluble transition metal catalyst; preferably a transition metal salt catalyst such as chromium, cobalt, iron, manganese, molybdenum or vanadium, or an ester compound of a transition metal acid.

[0019] Furthermore, the oil-soluble transition metal acid ester compound is tert-butyl chromate.

[0020] Furthermore, in step (2), cyclohexyl hydroperoxide is subjected to catalytic decomposition reaction while distilling, and the reaction heat is used to evaporate cyclohexane, and the decomposition rate of cyclohexyl hydroperoxide is controlled between 93-98%, preferably between 95-97%.

[0021] Furthermore, in step (2), the scale inhibitor is HEDP ester, i.e., 1-hydroxyethylidene-1,1-diphosphonate. The function of the scale inhibitor is to prevent the precipitation of organic acid transition metal salts from clogging the reactor and the pipeline. The HEDP ester also has the function of a dispersant, i.e., HEDP ester is both a scale inhibitor and a dispersant, having both scale inhibition and dispersing functions.

[0022] Further, in step (2), the multi-effect reaction distillation of the oxidizing liquid is carried out in a multi-stage distillation tower, and the multi-stage distillation tower is preferably a three-stage distillation tower; the top operating pressure of the first distillation tower is 0.20-0.35MpaA (A represents absolute pressure in the pressure unit of chemical literature), the top operating temperature is 105-130°C, the bottom operating pressure is 0.22-0.4MPaA, and the bottom operating temperature is 110-135°C; the top operating pressure of the second distillation tower is 0.10-0.24MPaA, and the operating temperature is 110-135°C. The temperature is 85-110°C, the operating pressure of the tower bottom is 0.12-0.25MPaA, and the operating temperature is 90-105°C; the top operating pressure of the three-stage distillation tower is 0.04-0.06MPaA, the top operating temperature is 55-70°C, the tower bottom operating pressure is 0.05-0.07MPaA, the tower bottom operating temperature is 65-80°C, and the decomposition liquid discharged from the tower bottom enters the second tower of the three-stage distillation to use a small amount of steam to fine-tune the cyclohexane content of the decomposition liquid to 50-70%, wherein 60-65% is preferred.

[0023] Furthermore, the specific process of the three-stage distillation is as follows: the oxidizing liquid from the cyclohexane non-catalytic oxidation reaction device is heat-exchanged with cyclohexane, and then mixed with a scale inhibitor and a decomposition catalyst and enters the kettle of the first cyclohexane distillation tower. The lower part of the first distillation tower is provided with an inner guide tube. While the decomposition reaction of cyclohexyl hydroperoxide occurs, the cyclohexane is evaporated by using pressure-reducing flash evaporation, reaction heat and a steam reboiler as the heat source of the first distillation tower. The gaseous cyclohexane in the first distillation tower enters the reboiler of the second distillation tower, and the kettle liquid of the first distillation tower enters the kettle of the second distillation tower; the cyclohexane condensed in the reboiler of the second distillation tower enters the cyclohexane condensate tank, is pressurized by a cyclohexane pump, and then exchanges heat with the oxidizing liquid, and is then sent to the oxidation tower. Reaction process: the gaseous cyclohexane from the second distillation tower enters the reboiler of the third distillation tower for heat exchange, the condensed cyclohexane enters the condensate tank, the cyclohexane condensate is pressurized by a cyclohexane pump and enters the cyclohexane water separator; the bottom liquid of the second distillation tower enters the bottom of the third distillation tower, the gaseous cyclohexane from the third distillation tower enters the condenser, the bottom liquid of the third distillation tower enters the third distillation tower II, the bottom liquid of the third distillation tower II is pressurized by a decomposition liquid discharge pump and sent to the neutralization and saponification process; the non-condensable gas at the outlet of the vacuum pump enters the tail gas absorption device, and the cyclohexane condensate enters the cyclohexane water separator; the cyclohexane part of the cyclohexane water separator is refluxed, and the remaining cyclohexane is pressurized by a cold alkane pump and sent to the oxidation heat recovery section, and the separated acid water is deacidified water treatment process.

[0024] Furthermore, in step (3), the alkali solution is a NaOH aqueous solution; the neutralization saponification process includes washing the decomposition liquid with water, neutralization saponification reaction with the NaOH aqueous solution in a reactor, separation of the saponified liquid, and removal of cyclohexane and water in a drying tower to obtain an alcohol-ketone mixture with a purity of more than 97%.

[0025] Further, in step (3), during the neutralization and saponification process, the OH in the alkali solution - The ion concentration is 0.3-1.5 Mol / L, preferably 0.5-1.0 Mol / L.

[0026] Furthermore, in step (3), the reaction temperature of neutralization and saponification is controlled at 80-110°C, preferably 90-100°C.

[0027] Compared with the existing process, the present invention creatively combines the steps of cyclohexyl hydroperoxide decomposition and cyclohexane recovery into one, the load of alkali solution separation is reduced by 10 times, and it is no longer necessary to build a large-scale cyclohexane recovery device, so that the generation capacity of a single cyclohexane oxidation device can be increased to 300,000 tons / year; at the same time, most of the cyclohexyl hydroperoxide is decomposed under homogeneous conditions, so that the system yield is higher, the unit consumption of cyclohexane and caustic soda (sodium hydroxide) and steam of the product reaches the lowest level, the production efficiency is greatly improved, and the production cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1The present invention is a schematic diagram of a process flow diagram of a method for preparing cyclohexanone and cyclohexanol by oxidizing cyclohexane.

[0029] Figure 2 The structure and working process diagram of the oxidation liquid three-effect reaction distillation system used in the method embodiment of the present invention.

[0030] Figure 2 In: 01-cyclohexane first distillation tower, 02-steam reboiler of the first distillation tower, 03-cyclohexane second distillation tower, 04-reboiler of the second distillation tower, 05-condensate tank of the second distillation tower reboiler, 06-first cyclohexane pump, 07-third cyclohexane distillation tower, 08-reboiler of the third distillation tower, 09-condensate tank of the third distillation tower reboiler, 10-third cyclohexane distillation second tower, 11-steam reboiler of the third cyclohexane distillation second tower, 12-decomposition liquid discharge pump, 13-second cyclohexane pump, 14-condenser, 15-vacuum pump, 16-cyclohexane water separator, 17-cold alkane pump;

[0031] 010-oxidizing liquid, 011-scaling inhibitor, 012-decomposition catalyst, 013-gas phase cyclohexane in the first distillation tower, 014-bottom liquid of the first distillation tower, 015-reflux liquid of the first distillation tower, 030-gas phase cyclohexane in the second distillation tower, 031-reflux liquid of the second distillation tower, 032-bottom liquid of the second distillation tower, 040-cyclohexane condensate in the first distillation tower, 060-cyclohexane condensate in the second distillation tower, 070-reflux liquid of the third distillation tower, 071-gas phase cyclohexane in the third distillation tower, 072-bottom liquid of the third distillation tower, 100-bottom liquid of the second tower of the third cyclohexane distillation, 120-de-neutralized and saponified decomposition liquid, 140-cyclohexane condensate in the third distillation tower, 150-non-condensable gas, 160-acid water, 170-cold alkane deoxidation section. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the embodiments and drawings.

[0033] Example

[0034] Reference Figure 1 and 2 The method for producing cyclohexanone and cyclohexanol by cyclohexane oxidation according to the present invention comprises the following steps (the material quantity is taken as an example of a 120,000 tons / year cyclohexane oxidation production line):

[0035] (1) Cyclohexane is oxidized with molecular oxygen in the absence of a catalyst to obtain an oxidation solution containing cyclohexyl hydroperoxide:

[0036] Fresh cyclohexane 14550kg / h and recycled cyclohexane 509582kg / h and compressed air with an oxygen mole fraction of 21% 20388Nm 3 / h enters the oxidation reaction device for non-catalytic oxidation, controls the reaction temperature at 163-170°C, the reaction pressure at 1.32MPaA, discharges 108418kg / h of gas phase from the top of the oxidation reaction device, and discharges 421111kg / h of cyclohexane oxidation liquid from the bottom, wherein the concentrations of cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, cyclohexane and other acid ester impurities in the oxidation liquid are 3.2%wt, 0.68%wt, 0.34%wt, 95.36%wt and 0.42%wt, respectively;

[0037] (2) adding a cyclohexyl hydroperoxide decomposition catalyst and a scale inhibitor to the oxidation liquid obtained in step (1), and performing three-effect reactive distillation to decompose the cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone, and in the distillation process, simultaneously recovering the unreacted cyclohexane in step (1) and recycling it back to step (1) as a raw material for the oxidation reaction in step (1):

[0038] The 163℃ oxidation liquid 421111kg / h from the cyclohexane non-catalytic oxidation reactor is heat exchanged with 105℃ cyclohexane 060 to cool down to 155℃, and then mixed with the decomposition catalyst tert-butyl chromate 012 (2.2kg / h) and the scale inhibitor 1-hydroxyethylidene-1,1-diphosphonate 011 (4.5kg / h) and then enters the kettle of the cyclohexane first distillation tower 01; the operating pressure at the top of the cyclohexane first distillation tower 01 is 0.23MPaA, and the operating pressure is 1.25kg / h. The temperature is 110°C, the operating pressure at the bottom of the tower is 0.26MPaA, and the operating temperature is 115°C. An inner draft tube is provided at the bottom of the first distillation tower. While the decomposition reaction of cyclohexyl hydroperoxide occurs, the cyclohexane is evaporated by using the pressure reduction flash evaporation, the reaction heat and the steam reboiler 02 as the heat source of the first distillation tower 01. The gas phase cyclohexane 013 of the first distillation tower is used as the heat source to enter the reboiler 04 of the second distillation tower 07, and the bottom liquid 014 of the first distillation tower enters the bottom of the second distillation tower 07.

[0039] 178518kg / h of cyclohexane cooled to 105°C in the reboiler 04 of the second distillation tower enters the cyclohexane condensate tank 05, is pressurized by the cyclohexane pump 06 and heat-exchanged with the oxidizing liquid to 120°C, and then is sent to the oxidation reaction process; the top operating pressure of the second cyclohexane distillation tower is 0.11MPaA, the operating temperature is 85°C, and the tower bottom operating pressure is 0.13MPaA, and the operating temperature is 90°C. The bottom liquid 014 of the first distillation tower enters the draft tube in the bottom of the second distillation tower 03, and while the decomposition reaction of cyclohexyl hydroperoxide occurs, the cyclohexane is evaporated by using the pressure reduction flash evaporation, the reaction heat and the reboiler 04 as the heat source of the second distillation tower 03. The gas phase cyclohexane 030 of the second distillation tower is used as a heat source to enter the reboiler 08 of the third distillation tower for heat exchange, and the cyclohexane cooled to 75°C enters the condensate tank 09. The cyclohexane condensate is pressurized by the cyclohexane pump 13 and enters the cyclohexane water separator 16;

[0040] The bottom liquid 032 of the second distillation tower enters the draft tube in the bottom of the third distillation tower 07, and the decomposition reaction of cyclohexyl hydroperoxide occurs; the top operating pressure of the cyclohexane third distillation tower is 0.05MPaA, the operating temperature is 59°C, the bottom operating pressure is 0.06MPaA, the operating temperature is 68°C, and the bottom temperature of the cyclohexane third distillation tower is 70°C; the pressure-reducing flash evaporation, reaction heat and material heat exchange reboiler 08 are used as the heat source of the third distillation tower 07 to evaporate cyclohexane; the gas phase cyclohexane 071 of the third distillation tower enters the condenser 14, the bottom liquid 072 of the third distillation tower enters the third distillation tower 10, and the steam reboiler 11 is used as the heat source of the third distillation tower 10 to evaporate cyclohexane, 95% of the cyclohexyl hydroperoxide in the 38660kg / h bottom liquid 100 of the third distillation tower has been decomposed, and it also contains about 60% of cyclohexane, which is pressurized by the decomposition liquid discharge pump 12 and sent to the neutralization and saponification process;

[0041] The non-condensable gas 150 at the outlet of the vacuum pump 15 enters the tail gas absorption device, and the cyclohexane condensate 140 enters the cyclohexane water separator 16;

[0042] The cyclohexane in the cyclohexane water separator 16 is partially refluxed, and the remaining 215320 kg / h cyclohexane 170 is pressurized by the cold alkane pump 17 and sent to the oxidation heat recovery section to recover the cyclohexane in the tail gas, and the separated 1500 kg / h acid water 160 is removed from the acid water treatment process;

[0043] (3) The decomposed liquid obtained in step (2) is washed with water, and then an aqueous sodium hydroxide solution is added to carry out a neutralization and saponification reaction, so that the residual cyclohexyl hydroperoxide is completely converted into cyclohexanol and cyclohexanone:

[0044] The decomposition liquid of 38660 kg / h obtained from the oxidation liquid three-effect reaction distillation process in step (2) and 2000 kg / h of process water are mixed and washed with water to separate the acid water phase, and then an aqueous sodium hydroxide solution is added to carry out a neutralization saponification reaction in a neutralization saponification reactor. After the reaction is completed, the saponification liquid aqueous phase and the organic phase are separated by a saponification liquid separator. The saponification liquid aqueous phase is discharged from the system, and the organic phase is sent to a washing tower to wash away the entrained alkaline water, and then sent to a drying tower to dry and remove cyclohexane and water, so as to obtain 15464 kg / h of alcohol-ketone mixed liquid with a purity of more than 97%; the cyclohexane removed by drying the organic phase is recycled to the non-catalytic oxidation process in step (1) as the non-catalytic oxidation reaction raw material in step (1).

[0045] The embodiment of the present invention effectively utilizes the heat of decomposition reaction to carry out multi-effect reaction distillation, cyclohexane oxidation produces more than 97% alcohol-ketone mixed liquid, steam consumption is 35.8 t / h, and the unit consumption of alcohol-ketone liquid steam is 2.39 t / t alcohol-ketone liquid. Since the alkali decomposition process is eliminated and water is used to wash away most of the acid generated by the reaction, only the new alkali is used in the neutralization and saponification process, the unit consumption of 32% alkali is reduced to 150 kg / t alcohol-ketone liquid, and the unit consumption of cyclohexane is 970 kg / t alcohol-ketone liquid.

[0046] Comparative Example 1

[0047] The currently operating 120,000 tons / year cyclohexane oxidation unit production line combining homogeneous decomposition and heterogeneous decomposition includes the following operating steps:

[0048] Fresh cyclohexane 14700kg / h and recycled cyclohexane 511912kg / h and compressed air with an oxygen mole fraction of 21% 20600Nm 3 / h enters the oxidation reactor for non-catalytic oxidation, the reaction temperature is controlled at 165-170°C, the reaction pressure is 1.32MPaA, the gas phase discharge from the top of the oxidation reactor is 110954kg / h, and the bottom discharge is cyclohexane oxidation liquid 421111kg / h, and the concentrations of cyclohexyl hydroperoxide, cyclohexanol, cyclohexanone, cyclohexane and other acid ester impurities in the oxidation liquid are 3.2%wt, 0.68%wt, 0.34%wt, 95.36%wt and 0.42%wt, respectively.

[0049] 421111 kg / h of 165°C oxidation liquid from the cyclohexane non-catalytic oxidation reactor is heat exchanged with the decomposition liquid to 130°C, and then mixed with the decomposition catalyst tert-butyl chromate (1.8 kg / h) and the scale inhibitor 1-hydroxyethylidene-1,1-diphosphonate (3.6 kg / h) and enters the homogeneous decomposition reactor to decompose about 80% of the cyclohexyl hydroperoxide. At the same time, about 150,000 kg / h of cyclohexane is circulated to the non-catalytic oxidation reactor by pressure reduction flash evaporation, reaction heat and steam-assisted evaporation. 269,711 kg / h of homogeneous decomposition liquid enters the heterogeneous decomposition process, decomposes the remaining 20% ​​of the cyclohexyl hydroperoxide in a sodium hydroxide aqueous solution, and then enters the waste alkali liquid separation process for two-phase separation. 269711 kg / h of organic phase enters the cyclohexane recovery process after heat exchange with the oxidizing liquid to 155°C. 245338 kg / h of cyclohexane is recovered in the multi-effect evaporation process by steam and circulated to the non-catalytic oxidation reactor. 23080 kg / h of crude ketone containing 33% of cyclohexane enters the crude ketone refining process.

[0050] 23080kg / h crude alcohol ketone containing 33% alkane from the cyclohexane recovery process reacts with a sodium hydroxide aqueous solution in a refining reactor, and then the organic phase is separated by a saponification liquid separator. The organic phase goes to a water washing tower to wash away the entrained alkaline water, and then goes to a drying tower to remove cyclohexane and water, to obtain 15464kg / h alcohol ketone liquid with a purity of more than 97%.

[0051] By using the cyclohexane oxidation process combining homogeneous decomposition and heterogeneous decomposition, more than 97% alcohol ketone liquid is obtained, the steam consumption is 51.8t / h, the unit consumption of alcohol ketone liquid steam is 3.45t / t alcohol ketone liquid, the unit consumption of 32% alkali is 260kg / t alcohol ketone liquid, and the unit consumption of cyclohexane is 980kg / t alcohol ketone liquid.

[0052] Comparative Example 2

[0053] The currently operating 100,000 t / a cyclohexane oxidation unit with only heterogeneous alkaline decomposition includes the following operating steps:

[0054] Fresh cyclohexane 12750kg / h and recycled cyclohexane 441884kg / h and compressed air with an oxygen mole fraction of 21% 17166Nm 3 / h enters the oxidation reactor for non-catalytic oxidation, the reaction temperature is controlled at 165-170°C, the reaction pressure is 1.32MPaA, the gas phase discharge from the top of the oxidation reactor is 90348kg / h, and the bottom discharge is 368830kg / h of cyclohexane oxidation liquid.

[0055] 368,830 kg / h of 165°C oxidation liquid from the cyclohexane non-catalytic oxidation reactor is heat exchanged with the decomposition liquid, cooled to 60°C by circulating water, and then enters the alkali decomposition reactor, where cyclohexyl hydroperoxide decomposition reaction occurs in sodium hydroxide aqueous solution, and then enters the waste alkali liquid separation process for two-phase separation. 368,830 kg / h of organic phase enters the multi-effect evaporation cyclohexane recovery process, and 350,420 kg / h of cyclohexane is evaporated by steam auxiliary heat and circulated to the non-catalytic oxidation reactor, and 19,234 kg / h of crude alcohol ketone containing 33% cyclohexane enters the crude alcohol ketone refining process.

[0056] 19234 kg / h crude alcohol ketone containing 33% alkane from the cyclohexane recovery process reacts with a sodium hydroxide aqueous solution in a refining reactor, and then the organic phase is separated by a saponification liquid separator. The organic phase goes to a water washing tower to wash away the entrained alkaline water, and then goes to a drying tower to remove cyclohexane and water, to obtain 12887 kg / h alcohol ketone liquid with a purity of more than 97%.

[0057] The cyclohexane oxidation process with only heterogeneous alkali decomposition produces more than 97% of the alcohol ketone liquid with a steam consumption of 56.3t / h, which is equivalent to a unit consumption of 4.50t / t of alcohol ketone liquid for alcohol ketone liquid steam, 450kg / t of alcohol ketone liquid for 32% alkali, and 1020kg / t of alcohol ketone liquid for cyclohexane.

[0058] Production equipment category Embodiments of the present invention Comparative Example 1 Comparative Example 2 Unit consumption of alcohol ketone liquid steam t / t 2.39 3.45 4.50 Alkali consumption of 32% alcohol-ketone solution kg / t 150 260 450 Unit consumption of cyclohexane per ketone liquid kg / t 970 980 1020

Claims

1. A method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane, characterized in that: The following steps are involved: (1) oxidizing cyclohexane with molecular oxygen under non-catalytic conditions to obtain an oxidation liquid containing cyclohexyl hydroperoxide; The non-catalytic oxidation refers to the oxidation reaction of liquid cyclohexane with molecular oxygen in an oxidation reaction device without adding a catalyst to generate an oxidation liquid with the intermediate cyclohexyl hydroperoxide as the main component; (2) adding a cyclohexyl hydroperoxide decomposition catalyst and a scale inhibitor to the oxidation liquid obtained in step (1), and performing multiple-effect reaction distillation to decompose more than 95% of the cyclohexyl hydroperoxide into cyclohexanol and cyclohexanone, and in the distillation process, simultaneously recovering the unreacted cyclohexane in step (1) and returning it to step (1) as a raw material for the oxidation reaction in step (1); The multi-effect reaction distillation of the oxidation liquid refers to the step of subjecting the oxidation liquid containing cyclohexyl hydroperoxide to a decomposition reaction in a distillation tower under the action of a decomposition catalyst and a scale inhibitor, and simultaneously utilizing the sensible heat, decomposition heat and auxiliary heat of the oxidation liquid to cause most of the cyclohexane that is not oxidized in step (1) to be condensed from the top of the distillation tower and then circulated back to the oxidation reactor in step (1) through multi-effect distillation, and simultaneously discharging a small amount of acid water, and the output from the bottom of the tower after distillation is a decomposition liquid containing cyclohexanone, cyclohexanol and a trace amount of cyclohexyl hydroperoxide in an amount of 50-70% of cyclohexane; (3) adding alkali solution and water to the decomposition liquid containing 50-70% of cyclohexane obtained in step (2) to carry out neutralization and saponification reaction, so that the residual cyclohexyl hydroperoxide is completely converted into cyclohexanol and cyclohexanone to obtain an alcohol-ketone mixture; The neutralization saponification means that the decomposition liquid containing 50-70% cyclohexane is washed with water to remove most of the acid, and then the acid water is separated. The organic phase is then neutralized with alkali solution to remove the acid and ester in the saponified crude alcohol ketone liquid, and the residual cyclohexyl hydroperoxide is completely converted into cyclohexanol and cyclohexanone. After the aqueous phase of the saponified liquid is separated, the organic phase is dried to remove cyclohexane and water to obtain a mixture of cyclohexanone and cyclohexanol; the cyclohexane removed by drying the organic phase is returned to step (1) as a raw material for the oxidation reaction in step (1).

2. The method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane according to claim 1, characterized in that: In step (1), the oxidation reaction device is an oxidation reaction device consisting of ≥3 oxidation reactors connected in series; the reaction temperature is controlled at 160-170° C., and the molar conversion rate of cyclohexane is controlled at 2.5-4.0%, preferably 3.0-3.5%.

3. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to claim 1 or 2, characterized in that: In step (2), the cyclohexyl hydroperoxide decomposition catalyst is an oil-soluble transition metal catalyst; preferably a transition metal salt catalyst such as chromium, cobalt, iron, manganese, molybdenum or vanadium, or an ester compound of a transition metal acid.

4. The method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane according to claim 3, characterized in that: The oil-soluble ester compound of transition metal acid is tert-butyl chromate.

5. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to any one of claims 1 to 4, characterized in that: In step (2), a catalytic decomposition reaction of cyclohexyl hydroperoxide is carried out simultaneously with distillation, and the reaction heat is used to evaporate cyclohexane. The decomposition rate of cyclohexyl hydroperoxide is controlled between 90-98%, preferably between 95-97%.

6. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to any one of claims 1 to 5, characterized in that: In step (2), the scale inhibitor is HEDP ester, i.e. 1-hydroxyethylidene-1,1-diphosphonate.

7. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to any one of claims 1 to 6, characterized in that: In step (2), the multi-effect reaction distillation of the oxidizing liquid is carried out in a multi-stage distillation tower, wherein three-stage distillation is preferred, the top operating pressure of the first distillation tower is 0.20-0.35MpaA, the top operating temperature is 105-130°C, the bottom operating pressure is 0.22-0.4MPaA, and the bottom operating temperature is 110-135°C; the top operating pressure of the second distillation tower is 0.10-0.24MPaA, the operating temperature is 85-110°C, and the bottom operating pressure is 0.22-0.4MPaA. The operating pressure is 0.12-0.25MPaA, and the operating temperature is 90-105°C; the top operating pressure of the three-stage distillation tower is 0.04-0.06MPaA, the top operating temperature is 55-70°C, the bottom operating pressure is 0.05-0.07MPaA, the bottom operating temperature is 65-80°C, and the decomposition liquid discharged from the bottom enters the second tower of the three-stage distillation to use a small amount of steam to fine-tune the cyclohexane content of the decomposition liquid to 50-70%, wherein 60-65% is preferred.

8. The method for producing cyclohexanone and cyclohexanol by oxidizing cyclohexane according to claim 1, characterized in that: In step (3), the alkali solution is a NaOH aqueous solution; the neutralization saponification process includes washing the decomposition liquid with water, neutralization saponification reaction with the NaOH aqueous solution in a reactor, separation of the saponified liquid, and removal of cyclohexane and water in a drying tower to obtain an alcohol ketone liquid with a purity of more than 97%.

9. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to any one of claims 1 to 8, characterized in that: During the neutralization and saponification process, the OH in the alkali solution - The ion concentration is 0.3-1.5 Mol / L, preferably 0.5-1.0 Mol / L.

10. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to any one of claims 1 to 9, characterized in that: In step (3), the reaction temperature of neutralization and saponification is controlled at 80-110°C, preferably 90-100°C.

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