Method for producing cyclohexanone and cyclohexanol by cyclohexane oxidation
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-07
- Publication Date
- 2026-08-13
Smart Images
Figure CN2025081187_13082026_PF_FP_ABST
Abstract
Description
A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane Technical Field
[0001] This invention relates to a method for preparing the organic compounds cyclohexanone and cyclohexanol, and more particularly to a method for producing cyclohexanone and cyclohexanol from cyclohexane. Background Technology
[0002] Cyclohexanone is an important organic chemical raw material, mainly used as an intermediate in the production of caprolactam and adipic acid and their 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] Cyclohexanone can be produced through three methods: phenol hydrogenation, cyclohexane oxidation, and cyclohexene hydration. While cyclohexene hydration has become the method with the highest production capacity, cyclohexane oxidation remains viable in addressing the issue of cyclohexane as a byproduct. It can complement cyclohexene hydration cyclohexanone production, allowing for mutual raw material supply and forming a closed-loop circular economy chain. This enables the production of cyclohexanone with superior quality and lower production costs, thus competing in the market.
[0004] Existing cyclohexane oxidation processes are mainly divided into catalytic oxidation processes and non-catalytic oxidation processes.
[0005] The catalytic oxidation process for cyclohexane, invented by DuPont, uses cobalt salts to catalyze the oxidation of cyclohexane. Within the oxidation reactor, the cyclohexane oxidation reaction and the decomposition of the intermediate cyclohexyl hydroperoxide occur. After alkaline decomposition and a cyclohexane recovery system, a mixture of cyclohexanone and cyclohexanol is obtained. However, because cyclohexanone, produced by the decomposition of cyclohexyl hydroperoxide, is more easily oxidized by molecular oxygen than cyclohexane, the cyclohexane conversion rate in this catalytic oxidation process is only 5%, and the alcohol-ketone yield is only 70-75%.
[0006] In recent years, some people have proposed a biomimetic catalytic process for cyclohexane, which uses metalloporphyrins and other catalysts to oxidize cyclohexane in air. The biomimetic catalytic oxidation claims to increase the single-pass conversion rate of cyclohexane to 8%. However, it has not solved the core problem that the decomposition products cyclohexanol and cyclohexanone are more easily oxidized than cyclohexane. This results in severe deep oxidation during the oxidation process, and the yield of cyclohexanone and cyclohexanol is low, less than 70%.
[0007] There are two main routes for the non-catalytic oxidation of cyclohexane. One route, invented by Rhodia of France, uses oxygen-deficient oxidation of cyclohexane without the addition of a catalyst, with cyclohexyl hydrogen peroxide in the oxidation liquid undergoing homogeneous decomposition using tert-butyl chromate as a catalyst. The other route, invented by DSM of the Netherlands, uses air for non-catalytic oxidation of cyclohexane, with cyclohexyl hydrogen peroxide undergoing heterogeneous catalytic decomposition using cobalt acetate in an alkaline sodium hydroxide aqueous solution. The innovation of both processes lies in separating the oxidation and decomposition reactions, reducing the single-pass oxidation conversion rate of cyclohexane to 3.5%, mainly producing cyclohexyl hydrogen peroxide, while reducing the formation of cyclohexanol and cyclohexanone in the oxidation environment, thereby reducing deep oxidation and increasing the oxidation yield. However, the low oxidation conversion rate leads to a larger cyclohexane recycling volume, making the supporting alkaline decomposition system and cyclohexane recovery system the bottleneck of the entire system. Currently, the largest single-line cyclohexane oxidation unit, modeled after DSM, has a production capacity of only 100,000 tons / year.
[0008] The technical solutions reported in CN201210085933.6 and CN201210091366.5 combine the homogeneous decomposition technology of Rhodia (France) and the alkaline decomposition technology of DSM (Netherlands). By fully utilizing the high selectivity of homogeneous decomposition and the high conversion rate of alkaline decomposition, the process of cyclohexane oxidation to produce cyclohexanol and cyclohexanone has reached a new stage. The unit consumption of cyclohexane and caustic soda has been significantly reduced, forming the most competitive technology for cyclohexane oxidation to produce cyclohexanol and cyclohexanone. Although this technology recovers some cyclohexane during the homogeneous decomposition process, the organic phase flow rate in the alkaline decomposition process is still too large, and the alkali separation load remains a challenge for further capacity expansion. Secondly, the cyclohexane recovery tower still requires a large amount of steam to recover cyclohexane, and the current maximum single-line cyclohexane oxidation unit using this technology can only reach a production capacity of 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 cyclohexane ketone and cyclohexanol from cyclohexane oxidation with a shorter process, lower steam consumption and material costs, and greater production capacity of a single-line cyclohexane oxidation unit.
[0010] The technical solution adopted by this invention to solve its technical problem is: a method for producing cyclohexanone and cyclohexanol by cyclohexane oxidation, comprising the following steps:
[0011] (1) Cyclohexane is subjected to molecular oxygen oxidation under non-catalytic conditions to obtain an oxidizing solution containing cyclohexyl hydrogen peroxide;
[0012] The aforementioned non-catalytic oxidation refers to the oxidation reaction of liquid cyclohexane with molecular oxygen in an oxidation reactor without the addition of a catalyst, to generate an oxidizing liquid with the intermediate cyclohexyl hydrogen peroxide as the main component.
[0013] (2) Add cyclohexyl hydrogen peroxide decomposition catalyst and scale inhibitor to the oxidizing liquid obtained in step (1) and carry out multi-effect reactive distillation to decompose more than 95% of cyclohexyl hydrogen peroxide into cyclohexanol and cyclohexanone. During the distillation process, the unreacted cyclohexane in step (1) is recovered and returned to step (1) as the raw material for the oxidation reaction in step (1).
[0014] The multi-effect reactive distillation of the oxidizing liquid refers to the decomposition reaction of the oxidizing liquid containing cyclohexyl hydrogen peroxide in a distillation column under the action of a decomposition catalyst and a scale inhibitor. At the same time, the sensible heat, decomposition heat and auxiliary heat of the oxidizing liquid are used to condense most of the cyclohexane that was not oxidized in step (1) and return it to the oxidation reactor in step (1) after condensation at the top of the distillation column. At the same time, a small amount of acid water is discharged. The output of the column bottom after distillation is a decomposition liquid containing 50-70% cyclohexane, cyclohexanone, cyclohexanol and trace amounts of cyclohexyl hydrogen peroxide.
[0015] (3) In the decomposition solution containing 50-70% cyclohexane obtained in step (2), add alkali and water to carry out neutralization and saponification reaction, so that the residual cyclohexyl hydrogen peroxide is completely converted into cyclohexanol and cyclohexanone, and a mixture of alcohol and ketone is obtained.
[0016] The neutralization saponification refers to the process of washing the decomposition liquid containing 50-70% cyclohexane with water to remove most of the acid, separating the acid water, and then using alkali solution to neutralize the acid and ester in the crude alcohol and ketone liquid of the organic phase, and converting all the residual cyclohexyl hydrogen peroxide into cyclohexanol and cyclohexanone. After separating the aqueous phase of the saponification liquid, the organic phase is dried to remove cyclohexane and water, resulting in a mixture of cyclohexanone and cyclohexanol. The cyclohexane removed by drying the organic phase is returned to step (1) as the 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. o C, the molar conversion rate of cyclohexane is controlled at 2.5-4.0%, preferably 3.0-3.5%. The molecular oxygen oxidation of cyclohexane under catalytic-free conditions is carried out using an oxidation reactor consisting of ≥3 oxidation reactors connected in series to achieve a plug flow-like reaction pattern and improve reaction efficiency.
[0018] Furthermore, in step (2), the cyclohexyl hydroperoxide decomposition catalyst is an oil-soluble transition metal catalyst; preferably, it is a transition metal salt catalyst such as chromium, cobalt, iron, manganese, molybdenum or vanadium, or an ester compound of transition metal acid.
[0019] Furthermore, the oil-soluble transition metal acid ester compound is tert-butyl chromate.
[0020] Furthermore, in step (2), the cyclohexyl hydrogen peroxide catalytic decomposition reaction is carried out simultaneously with distillation, and the cyclohexane is evaporated using its reaction heat. The decomposition rate of cyclohexyl hydrogen peroxide is controlled between 93-98%, preferably 95-97%.
[0021] Furthermore, in step (2), the scale inhibitor is HEDP ester, namely 1-hydroxyethylidene-1,1-diphosphonate. The function of the scale inhibitor is to prevent organic acid transition metal salts from precipitating and clogging the reactor and pipelines. The HEDP ester also functions as a dispersant, that is, HEDP ester is both a scale inhibitor and a dispersant, possessing both scale inhibition and dispersing functions.
[0022] Further, in step (2), the multi-effect reactive distillation of the oxidizing liquid is carried out in a multi-stage distillation column, preferably a three-stage distillation column; the top operating pressure of the first-stage distillation column is 0.20-0.35 MPaA (A represents absolute pressure in chemical engineering literature), the top operating temperature is 105-130℃, the bottom operating pressure is 0.22-0.4 MPaA, and the bottom operating temperature is 110-135℃; the top operating pressure of the second-stage distillation column is 0.10-0.24 MPaA, and the operating temperature is... The operating temperature is 85-110℃, the bottom pressure is 0.12-0.25MPaA, and the operating temperature is 90-105℃; the top operating pressure of the three-stage distillation column is 0.04-0.06MPaA, the top operating temperature is 55-70℃, the bottom operating pressure is 0.05-0.07MPaA, and the bottom operating temperature is 65-80℃. The decomposition liquid discharged from the bottom column enters the second column of the three-stage distillation, where a small amount of steam is used to fine-tune the cyclohexane content of the decomposition liquid to 50-70%, preferably 60-65%.
[0023] Furthermore, the specific process of the three-stage distillation is as follows: the oxidant from the cyclohexane non-catalytic oxidation reactor exchanges heat with cyclohexane, then mixes with scale inhibitor and decomposition catalyst before entering the bottom of the first cyclohexane distillation column. The lower part of the first distillation column is equipped with an internal guide tube. Simultaneously with the decomposition reaction of cyclohexyl hydrogen peroxide, cyclohexane is evaporated using pressure-reducing flash evaporation, reaction heat, and a steam reboiler as heat sources. The vaporous cyclohexane from the first distillation column enters the reboiler of the second distillation column, and the bottom liquid from the first distillation column enters the bottom of the second distillation column; the third... The cyclohexane condensed in the reboiler of the second distillation column enters the cyclohexane condensate tank, is pressurized by the cyclohexane pump, exchanges heat with the oxidation liquid, and is then sent to the oxidation reaction process. The gaseous cyclohexane from the second distillation column enters the reboiler of the third distillation column for heat exchange, and the condensed cyclohexane enters the condensate tank. The cyclohexane condensate is pressurized by the cyclohexane pump and then enters the cyclohexane-water separator. The bottom liquid of the second distillation column enters the bottom of the third distillation column, the gaseous cyclohexane from the third distillation column enters the condenser, and the bottom liquid of the third distillation column enters the second third distillation column. The bottom liquid of the second third distillation column is pressurized by the decomposition liquid discharge pump and sent to the neutralization and saponification process. The non-condensable gas from the vacuum pump outlet enters the tail gas absorption unit, and the cyclohexane condensate enters the cyclohexane-water separator. The cyclohexane portion of the cyclohexane in the cyclohexane-water separator is refluxed, and the remaining cyclohexane is pressurized by the cold cyclohexane pump and sent to the oxidation heat recovery section. The separated acid water is sent to the acid water treatment process.
[0024] Furthermore, in step (3), the alkaline solution is an aqueous solution of NaOH; the neutralization and saponification process includes washing the decomposition solution with water, neutralization and saponification reaction with the aqueous solution of NaOH in a reactor, separation of the saponification solution, and removal of cyclohexane and water in a drying tower to obtain an alcohol-ketone mixture with a purity of over 97%.
[0025] Furthermore, 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℃, preferably 90-100℃.
[0027] Compared with existing processes, this invention creatively combines the decomposition of cyclohexyl hydrogen peroxide and the recovery of cyclohexane into one step, reducing the load on alkali separation by 10 times and eliminating the need to construct large-scale cyclohexane recovery units. This makes it possible to increase the production capacity of a single cyclohexane oxidation unit to 300,000 tons / year. At the same time, most of the cyclohexyl hydrogen peroxide decomposes under homogeneous conditions, resulting in higher system yield and minimizing the consumption of cyclohexane, caustic soda (sodium hydroxide), and steam. This significantly improves production efficiency and reduces production costs. Attached Figure Description
[0028] Figure 1 is a schematic diagram of the process flow of an embodiment of the method for preparing cyclohexanone and cyclohexanol by cyclohexane oxidation according to the present invention.
[0029] Figure 2 is a schematic diagram of the structure and working process of the three-effect reactive distillation system for oxidizing liquid used in the embodiment of the method of the present invention.
[0030] In Figure 2: 01-Cyclohexane first distillation column, 02-First distillation column steam reboiler, 03-Cyclohexane second distillation column, 04-Second distillation column reboiler, 05-Second distillation column reboiler condensate tank, 06-First cyclohexane pump, 07-Third cyclohexane distillation column, 08-Third distillation column reboiler, 09-Third distillation column reboiler condensate tank, 10-Third cyclohexane second distillation column, 11-Third cyclohexane second distillation column steam reboiler, 12-Decomposition liquid discharge pump, 13-Second cyclohexane pump, 14-Condenser, 15-Vacuum pump, 16-Cyclohexane water separator, 17-Cold cyclohexane pump;
[0031] 010-Oxidizing liquid, 011-Scale inhibitor, 012-Decomposition catalyst, 013-Cyclohexane vapor from the first distillation column, 014-Bottom liquid from the first distillation column, 015-Reflux liquid from the first distillation column, 030-Cyclohexane vapor from the second distillation column, 031-Reflux liquid from the second distillation column, 032-Bottom liquid from the second distillation column, 040-Cyclohexane condensate from the first distillation column, 060-Cyclohexane condensate from the second distillation column, 070-Reflux liquid from the third distillation column, 071-Cyclohexane vapor from the third distillation column, 072-Bottom liquid from the third distillation column, 100-Bottom liquid from the second distillation column of the third cyclohexane distillation column, 120-Decomposition liquid from neutralization and saponification, 140-Cyclohexane condensate from the third distillation column, 150-Non-condensable gas, 160-Acid water, 170-Cold alkane deoxidation section. Detailed Implementation
[0032] The present invention will be further described below with reference to the embodiments and accompanying drawings.
[0033] Example
[0034] Referring to Figures 1 and 2, an embodiment of the method for producing cyclohexanone and cyclohexanol by cyclohexane oxidation of the present invention includes the following operational steps (the material quantities are taken as an example of a 120,000-ton / year cyclohexane oxidation unit production line):
[0035] (1) Cyclohexane was subjected to molecular oxygen oxidation under non-catalytic conditions to obtain an oxidized solution containing cyclohexyl hydrogen peroxide:
[0036] Fresh cyclohexane (14550 kg / h), recycled cyclohexane (509582 kg / h), and compressed air (20388 Nm³ / h) with an oxygen molar fraction of 21% are fed into the oxidation reactor for non-catalytic oxidation. The reaction temperature is controlled at 163-170℃ and the reaction pressure at 1.32 MPaA. The top gaseous output of the oxidation reactor is 108418 kg / h, and the bottom output is cyclohexane oxidation liquid (421111 kg / h). The concentrations of cyclohexyl hydrogen peroxide, 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) Add cyclohexyl hydrogen peroxide decomposition catalyst and scale inhibitor to the oxidizing liquid obtained in step (1) and carry out triple-effect reactive distillation to decompose cyclohexyl hydrogen peroxide into cyclohexanol and cyclohexanone. During the distillation process, the unreacted cyclohexane in step (1) is recovered and recycled back to step (1) as the raw material for the oxidation reaction in step (1):
[0038] The 163℃ oxidant liquid (421111 kg / h) from the cyclohexane non-catalytic oxidation reactor was cooled to 155℃ by heat exchange with cyclohexane 060 at 105℃. Then, it was mixed with the decomposition catalyst tert-butyl chromate 012 (2.2 kg / h) and the scale inhibitor 1-hydroxyethylidene-1,1-diphosphonate 011 (4.5 kg / h) and fed into the bottom of the first cyclohexane distillation column 01. The operating pressure at the top of the first cyclohexane distillation column 01 was 0.23 MPaA. The temperature is 110℃, the bottom operating pressure is 0.26MPaA, and the operating temperature is 115℃. The lower part of the first distillation column is equipped with an internal guide tube. While the decomposition reaction of cyclohexyl hydrogen peroxide occurs, the pressure reduction flash evaporation, reaction heat, and steam reboiler 02 are used as the heat source for evaporating cyclohexane in the first distillation column 01. The gaseous cyclohexane 013 in the first distillation column enters the reboiler 04 of the second distillation column 07 as a heat source. The bottom liquid 014 of the first distillation column enters the bottom of the second distillation column 07.
[0039] 178518 kg / h of cyclohexane cooled to 105°C in the reboiler 04 of the second distillation column enters the cyclohexane condensate tank 05. After being pressurized by the cyclohexane pump 06 and heat-exchanged with the oxidizing liquid to 120°C, it is sent to the oxidation reaction process. The operating pressure at the top of the second cyclohexane distillation column is 0.11 MPaA and the operating temperature is 85°C. The operating pressure at the bottom of the column is 0.13 MPaA and the operating temperature is 90°C. The bottom liquid 014 of the first distillation column enters the guide tube inside the bottom of the second distillation column 03. While the cyclohexyl hydrogen peroxide decomposition reaction occurs, the cyclohexane is evaporated using the pressure reduction flash evaporation, the heat of reaction, and the reboiler 04 as heat sources for the second distillation column 03. The vapor cyclohexane 030 from the second distillation column enters the reboiler 08 of the third distillation column for heat exchange. The cyclohexane cooled to 75°C enters the condensate tank 09. The cyclohexane condensate is pressurized by the cyclohexane pump 13 and then enters the cyclohexane water separator 16.
[0040] The second distillation column bottom liquid 032 enters the guide tube inside the bottom of the third distillation column 07, where the decomposition reaction of cyclohexyl hydrogen peroxide occurs. The operating pressure at the top of the cyclohexane third distillation column is 0.05 MPaA, the operating temperature is 59℃, the bottom pressure is 0.06 MPaA, the operating temperature is 68℃, and the bottom temperature of the cyclohexane third distillation column is 70℃. The cyclohexane is evaporated using the pressure-reducing flash evaporation, reaction heat, and material heat exchange reboiler 08 as the heat source for the third distillation column 07. The vapor phase cyclohexane 071 from the third distillation column enters the condenser 14, and the bottom liquid 072 from the third distillation column enters the third distillation column 10. The steam reboiler 11 serves as the heat source for the third distillation column 10 to evaporate the cyclohexane. 95% of the cyclohexyl hydrogen peroxide in the 38660 kg / h bottom liquid 100 of the third distillation column has been decomposed, and it still contains about 60% cyclohexane. After being pressurized by the decomposition liquid discharge pump 12, it is sent to the neutralization and saponification process.
[0041] The non-condensable gas 150 from the outlet of vacuum pump 15 enters the tail gas absorption device, and the cyclohexane condensate 140 enters the cyclohexane water separator 16.
[0042] The cyclohexane portion of the cyclohexane water separator 16 is refluxed, and the remaining 215320 kg / h cyclohexane 170 is boosted by the cold cyclohexane pump 17 and sent to the oxidation heat recovery section to recover the cyclohexane in the tail gas. The separated 1500 kg / h acid water 160 is sent to the acid water treatment process.
[0043] (3) The decomposition solution obtained in step (2) is washed with water, and then an aqueous solution of sodium hydroxide is added to carry out a neutralization and saponification reaction, so that all the residual cyclohexyl hydrogen peroxide is converted into cyclohexanol and cyclohexanone:
[0044] The decomposition liquid obtained from the three-effect reactive distillation process of the oxidizing liquid in step (2) is mixed with 38660 kg / h of process water and washed with water to separate the acidic aqueous phase. Then, sodium hydroxide aqueous solution is added and neutralization and saponification reaction is carried out in the neutralization saponification reactor. After the reaction is completed, the saponification liquid aqueous phase and organic phase are separated by the saponification liquid separator. The saponification liquid aqueous phase is discharged from the system, and the organic phase is sent to the water washing tower to wash away the entrained alkaline water. Then, it is sent to the drying tower to dry and remove cyclohexane and water to obtain a 15464 kg / h alcohol-ketone mixture with a purity of more than 97%. The cyclohexane removed by drying the organic phase is recycled back to the non-catalytic oxidation process in step (1) as the raw material for the non-catalytic oxidation reaction in step (1).
[0045] This invention effectively utilizes the heat of decomposition reaction for multi-effect reactive distillation, oxidizing cyclohexane to obtain an alcohol-ketone mixture with a purity of over 97%. The steam consumption is 35.8 t / h, resulting in a steam consumption of 2.39 t / t alcohol-ketone solution. By eliminating the alkali decomposition step and using water to wash away most of the acid generated in the reaction, with only the neutralization and saponification process using fresh alkali, the alkali consumption is reduced to 150 kg / t alcohol-ketone solution, and the cyclohexane consumption is 970 kg / t alcohol-ketone solution.
[0046] Comparative Example 1
[0047] A currently operating 120,000-ton / year cyclohexane oxidation production line combining homogeneous and heterogeneous decomposition includes the following operating steps:
[0048] Fresh cyclohexane (14700 kg / h), recycled cyclohexane (511912 kg / h), and compressed air (20600 Nm³ / h, 21% oxygen molar fraction) are fed into an oxidation reactor for non-catalytic oxidation. The reaction temperature is controlled at 165-170℃ and the reaction pressure at 1.32 MPaA. The top gaseous discharge from the oxidation reactor is 110954 kg / h, and the bottom discharge is cyclohexane oxidation liquid (421111 kg / h). The concentrations of cyclohexyl hydrogen peroxide, 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] The 165℃ oxidant liquid (421,111 kg / h) from the cyclohexane non-catalytic oxidation reactor is cooled to 130℃ by heat exchange with the decomposition liquid. It is 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 hydrogen peroxide. At the same time, about 150,000 kg / h of cyclohexane is recycled to the non-catalytic oxidation reactor by pressure reduction flash evaporation, reaction heat and steam-assisted evaporation. The 269,711 kg / h of homogeneous decomposition liquid enters the heterogeneous decomposition process, where the remaining 20% of the cyclohexyl hydrogen peroxide is decomposed in sodium hydroxide aqueous solution. After that, it enters the waste alkali separation process for two-phase separation. The organic phase of 269,711 kg / h is heated to 155°C by heat exchange with the oxidizing liquid and then enters the cyclohexane recovery process. 245,338 kg / h of cyclohexane is recovered by steam in the multi-effect evaporation process and recycled to the non-catalytic oxidation reactor. The crude alcohol ketone containing 33% cyclohexane, 23,080 kg / h, enters the crude alcohol ketone refining process.
[0050] The crude alcohol-ketone solution with a capacity of 23,080 kg / h, containing 33% alkane from the cyclohexane recovery process, reacts with an aqueous sodium hydroxide solution in a refining reactor. The organic phase is then separated by a saponification liquid separator. The organic phase is then washed in a water washing tower to remove entrained alkaline water, and then sent to a drying tower to remove cyclohexane and water, yielding an alcohol-ketone solution with a purity of over 97%.
[0051] A cyclohexane oxidation process combining homogeneous and heterogeneous decomposition was used to produce an alcohol-ketone liquor with a purity of over 97%. The steam consumption was 51.8 t / h, equivalent to a steam consumption of 3.45 t / t alcohol-ketone liquor, and a 32% alkali consumption of 260 kg / t alcohol-ketone liquor. The cyclohexane consumption was 980 kg / t alcohol-ketone liquor.
[0052] Comparative Example 2
[0053] The currently operating 100,000-ton / year cyclohexane oxidation unit, which only uses heterogeneous alkaline decomposition, includes the following operating steps:
[0054] Fresh cyclohexane (12750 kg / h), recycled cyclohexane (441884 kg / h), and compressed air (17166 Nm³ / h) with an oxygen molar fraction of 21% are fed into the oxidation reactor for non-catalytic oxidation. The reaction temperature is controlled at 165-170℃ and the reaction pressure at 1.32 MPaA. The top gaseous discharge from the oxidation reactor is 90348 kg / h, and the bottom discharge is cyclohexane oxidized liquid (368830 kg / h).
[0055] The 165℃ oxidant liquid (368830 kg / h) from the cyclohexane non-catalytic oxidation reactor is heated with the decomposition liquid, then cooled to 60℃ by circulating water before entering the alkaline decomposition reactor. There, cyclohexyl hydrogen peroxide decomposition occurs in a sodium hydroxide aqueous solution, followed by two-phase separation in the waste alkaline liquid separation process. The organic phase (368830 kg / h) enters the multi-effect evaporation cyclohexane recovery process, where 350420 kg / h of cyclohexane is evaporated using steam auxiliary heating and recycled back to the non-catalytic oxidation reactor. The crude alcohol ketone (19234 kg / h) containing 33% cyclohexane enters the crude alcohol ketone purification process.
[0056] 19234 kg / h of crude alcohol ketone containing 33% alkane from the cyclohexane recovery process is reacted with sodium hydroxide aqueous solution in a refining reactor. The organic phase is then separated by a saponification liquid separator. The organic phase is washed in a water washing tower to remove entrained alkaline water, and then sent to a drying tower to remove cyclohexane and water, yielding an alcohol ketone solution with a purity of over 97%.
[0057] The cyclohexane oxidation process using only heterogeneous alkaline decomposition produces alcohol-ketone liquid with a steam consumption of 56.3 t / h, which translates to a steam consumption of 4.50 t / t alcohol-ketone liquid, an alkaline consumption of 450 kg / t alcohol-ketone liquid, and a cyclohexane consumption of 1020 kg / t alcohol-ketone liquid.
[0058] .
Claims
1. A method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane, characterized in that, Includes the following steps: (1) Cyclohexane is subjected to molecular oxygen oxidation under non-catalytic conditions to obtain an oxidizing solution containing cyclohexyl hydrogen peroxide; The aforementioned non-catalytic oxidation refers to the oxidation reaction of liquid cyclohexane with molecular oxygen in an oxidation reactor without the addition of a catalyst, to generate an oxidizing liquid with the intermediate cyclohexyl hydrogen peroxide as the main component. (2) Add cyclohexyl hydrogen peroxide decomposition catalyst and scale inhibitor to the oxidizing liquid obtained in step (1) and carry out multi-effect reactive distillation to decompose more than 95% of cyclohexyl hydrogen peroxide into cyclohexanol and cyclohexanone. During the distillation process, the unreacted cyclohexane in step (1) is recovered and returned to step (1) as the raw material for the oxidation reaction in step (1). The multi-effect reactive distillation of the oxidizing liquid refers to the decomposition reaction of the oxidizing liquid containing cyclohexyl hydrogen peroxide in a distillation column under the action of a decomposition catalyst and a scale inhibitor. At the same time, the sensible heat, decomposition heat and auxiliary heat of the oxidizing liquid are used to condense most of the cyclohexane that was not oxidized in step (1) and return it to the oxidation reactor in step (1) after condensation at the top of the distillation column. At the same time, a small amount of acid water is discharged. The output of the column bottom after distillation is a decomposition liquid containing 50-70% cyclohexane, cyclohexanone, cyclohexanol and trace amounts of cyclohexyl hydrogen peroxide. (3) In the decomposition solution containing 50-70% cyclohexane obtained in step (2), add alkali and water to carry out neutralization and saponification reaction, so that the residual cyclohexyl hydrogen peroxide is completely converted into cyclohexanol and cyclohexanone, and a mixture of alcohol and ketone is obtained. The neutralization saponification refers to the process of washing the decomposition liquid containing 50-70% cyclohexane with water to remove most of the acid, separating the acid water, and then using alkali solution to neutralize the acid and ester in the crude alcohol and ketone liquid of the organic phase, and converting all the residual cyclohexyl hydrogen peroxide into cyclohexanol and cyclohexanone. After separating the aqueous phase of the saponification liquid, the organic phase is dried to remove cyclohexane and water, resulting in a mixture of cyclohexanone and cyclohexanol. The cyclohexane removed by drying the organic phase is returned to step (1) as the raw material for the oxidation reaction in step (1).
2. The method for producing cyclohexanone and cyclohexanol by oxidation of 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℃, and the molar conversion rate of cyclohexane is controlled at 2.5-4.0%, preferably 3.0-3.5%.
3. The 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, it is a transition metal salt catalyst such as chromium, cobalt, iron, manganese, molybdenum or vanadium, or an ester compound of transition metal acid.
4. The method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to claim 3, characterized in that, The oil-soluble transition metal acid ester compound is tert-butyl chromate.
5. A method for producing cyclohexane oxidatively and cyclohexanone and cyclohexanol according to any one of claims 1-4, characterized in that, In step (2), the cyclohexyl hydrogen peroxide catalytic decomposition reaction is carried out simultaneously with distillation, and the cyclohexane is evaporated using its reaction heat. The decomposition rate of cyclohexyl hydrogen peroxide is controlled between 90-98%, preferably 95-97%.
6. A method for producing cyclohexane oxidatively and cyclohexanone and cyclohexanol according to any one of claims 1-5, characterized in that, In step (2), the scale inhibitor is HEDP ester, namely 1-hydroxyethylidene-1,1-diphosphonate.
7. A method for producing cyclohexane oxidatively and cyclohexanone and cyclohexanol according to any one of claims 1-6, characterized in that, In step (2), the multi-effect reactive distillation of the oxidizing liquid is carried out in a multi-stage distillation column, preferably a three-stage distillation. The operating pressure at the top of the first-stage distillation column is 0.20–0.35 MPaA, the operating temperature at the top is 105–130℃, the operating pressure at the bottom is 0.22–0.4 MPaA, and the operating temperature at the bottom is 110–135℃. The operating pressure at the top of the second-stage distillation column is 0.10–0.24 MPaA, the operating temperature is 85–110℃, and the operating temperature at the bottom is 110–135℃. The operating pressure is 0.12-0.25 MPaA, and the operating temperature is 90-105℃. The top operating pressure of the three-stage distillation column is 0.04-0.06 MPaA, and the top operating temperature is 55-70℃. The bottom operating pressure is 0.05-0.07 MPaA, and the bottom operating temperature is 65-80℃. The decomposition liquid discharged from the bottom enters the second column of the three-stage distillation, where a small amount of steam is used to fine-tune the cyclohexane content of the decomposition liquid to 50-70%, preferably 60-65%.
8. The method for producing cyclohexanone and cyclohexanol by oxidation of cyclohexane according to claim 1, characterized in that, In step (3), the alkaline solution is an aqueous solution of NaOH; the neutralization and saponification process includes washing the decomposition solution with water, neutralization and saponification reaction with the aqueous solution of NaOH in a reactor, separation of the saponification solution, and removal of cyclohexane and water in a drying tower to obtain an alcohol-ketone solution with a purity of more than 97%.
9. A method for producing cyclohexane oxidatively and cyclohexanone and cyclohexanol according to any one of claims 1-8, 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 cyclohexane oxidatively and cyclohexanone and cyclohexanol according to any one of claims 1-9, characterized in that, In step (3), the reaction temperature for neutralization and saponification is controlled at 80-110℃, preferably 90-100℃.