Method for preparing adipic acid by direct oxidation of cyclohexane

Abstract

The present application relates to a kind of method for preparing adipic acid by direct oxidation of cyclohexane, which comprises: contacting cyclohexane with oxygen-containing gas in the presence of solvent, catalyst and solid phase catalytic aid;The catalyst contains cobalt acetate, manganese acetate and copper acetate, and the solid phase catalytic aid contains solid carrier and titanium dioxide TiO2 loaded on the solid carrier.The present application improves the conversion rate of cyclohexane, improves the selectivity of adipic acid, reduces the occurrence of side reactions, reduces the burden of impurities in the synthesis liquid separation, and achieves good technical effect.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing adipic acid by direct oxidation of cyclohexane. BACKGROUND

[0002] Adipic acid, also known as fatty acid, is an important organic dibasic acid, and is an important raw material for preparing polyurethane and nylon 66. In the world, more than 70% of adipic acid is used in the field of nylon 66, and in China, 78% of adipic acid is used in the field of polyurethane. At present, there are four methods for producing adipic acid in the world, namely phenol method, cyclohexane method, cyclohexene method and butadiene method.

[0003] Modern industrial production mainly adopts the cyclohexane method, and the production capacity of the cyclohexane method accounts for about 93% of the total production capacity. The preparation of adipic acid by direct air / oxygen oxidation of cyclohexane is a very promising nitric acid oxidation alternative process. In 1940, US2223493 first proposed that air is used as an oxidizing agent, cobalt acetate is used as a catalyst, and acetic acid is used as a solvent to oxidize cyclohexane to prepare adipic acid in one step. This method successfully avoids the generation of nitrogen oxides and the corrosion problem of equipment caused by nitric acid in the traditional method. However, in order to prevent deep oxidation and generate a large amount of by-products, the reaction must be carried out at low temperature, and the conversion rate of cyclohexane must be controlled, so the production capacity and yield are not high.

[0004] The reaction of preparing adipic acid by air oxidation of cyclohexane is usually divided into two steps. In the first step, cyclohexane is oxidized to cyclohexanone and cyclohexanol under the action of a catalyst and oxygen at high temperature and high pressure. In the second step, cyclohexanone and cyclohexanol are continuously oxidized to adipic acid, and side reactions such as the generation of glutaric acid and succinic acid and other peroxide by-products occur. These side reactions reduce the selectivity of adipic acid on the one hand, and affect the efficiency of the catalyst on the other hand, leading to the early deactivation of the catalyst, reducing the conversion rate of cyclohexane, and further, the by-product impurities also increase the cost and difficulty of the separation of the synthesis liquid. Therefore, precise inhibition of the cyclohexane oxidation side reaction is the key to improving the selectivity of adipic acid and the conversion rate of cyclohexane. SUMMARY

[0005] The purpose of the present application is to mainly solve the problems of low conversion rate, low selectivity, and difficult purification of impurities in the synthesis liquid in the prior art of preparing adipic acid by direct oxidation of cyclohexane, and to provide a new method for preparing adipic acid by direct oxidation of cyclohexane.

[0006] In order to achieve the above-mentioned purpose, the present application provides a method for preparing adipic acid by direct oxidation of cyclohexane, which comprises:

[0007] contacting cyclohexane with an oxygen-containing gas in the presence of a solvent, a catalyst and a solid-phase catalytic additive;

[0008] The catalyst contains cobalt acetate, manganese acetate and copper acetate, and the solid-phase catalytic promoter contains a solid carrier and titanium dioxide TiO2 supported on the solid carrier.

[0009] Compared with the prior art, the present invention has the following advantages:

[0010] By using a solid-phase catalytic promoter containing a solid carrier and titanium dioxide TiO2 loaded on the solid carrier, the conversion rate of cyclohexane is improved, the selectivity of adipic acid is improved, the occurrence of side reactions is reduced, the burden of impurities in separating the target synthetic liquid is reduced, and good technical effects are achieved. DETAILED DESCRIPTION

[0011] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0012] The present invention provides a method for preparing adipic acid by direct oxidation of cyclohexane. The method comprises: contacting cyclohexane with an oxygen-containing gas in the presence of a solvent, a catalyst and a solid-phase catalyst promoter; the catalyst comprises cobalt acetate, manganese acetate and copper acetate, and the solid-phase catalyst promoter comprises a solid carrier and titanium dioxide TiO2 supported on the solid carrier.

[0013] The present invention uses a solid-phase catalyst promoter containing a solid carrier and titanium dioxide TiO2 loaded on the solid carrier, thereby improving the conversion rate of cyclohexane, improving the selectivity of adipic acid, reducing the occurrence of side reactions, and alleviating the burden of impurities in the separation of the synthetic liquid, thereby achieving good technical effects.

[0014] In the present invention, as long as the purpose of the present invention can be achieved, the solid carrier can be a conventional choice in the field. According to a preferred embodiment of the present invention, the solid carrier is solid glass microspheres and / or solid alumina microspheres, and the size of the microspheres is preferably 0.1 to 10 mm, more preferably 1.5 to 5 mm.

[0015] The above technical solution can further improve the conversion rate of cyclohexane, increase the selectivity of adipic acid, and reduce the occurrence of side reactions.

[0016] In the present application, the weight content of titanium dioxide TiO2 in the solid phase catalytic aid has no particular requirement as long as the purpose of the present application can be achieved, according to a preferred embodiment of the present application, the weight content of titanium dioxide TiO2 in the solid phase catalytic aid is 0.1-5%, preferably 0.5-2%. Through the above technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid is improved, and the occurrence of side reactions is reduced.

[0017] In the present application, the weight ratio of the solid phase catalytic aid to the reaction liquid has no particular requirement as long as the purpose of the present application can be achieved, according to a preferred embodiment of the present application, the weight ratio of the solid phase catalytic aid to the reaction liquid is 1.0-10.0:100, preferably 5.0-7.0:100; the reaction liquid is a mixed liquid of solvent and cyclohexane. Through the above technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid is improved, and the occurrence of side reactions is reduced.

[0018] In the present application, the solvent can be a conventional selection in the art as long as the purpose of the present application can be achieved, according to a preferred embodiment of the present application, the solvent is one or more of acetic acid, acetonitrile and acetone.

[0019] According to a preferred embodiment of the present application, the concentration of cobalt acetate in the solvent is 10-600 mg / L in terms of cobalt, preferably 60-300 mg / L, the concentration of manganese acetate is 6-400 mg / L in terms of manganese, preferably 120-200 mg / L, and the concentration of copper acetate is 40-1000 mg / L in terms of copper, preferably 300-500 mg / L. Through the above technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid is improved, and the occurrence of side reactions is reduced.

[0020] In the present application, the weight ratio of the catalyst to the reaction liquid has no particular requirement as long as the purpose of the present application can be achieved, according to a preferred embodiment of the present application, the weight ratio of the catalyst to the reaction liquid is 0.001-0.2:100, and the reaction liquid is a mixed liquid of solvent and cyclohexane. Through the above technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid is improved, and the occurrence of side reactions is reduced.

[0021] In the present application, the content of cyclohexane in the reaction liquid has no particular requirement as long as the purpose of the present application can be achieved, according to a preferred embodiment of the present application, the content of cyclohexane in the reaction liquid is 10.0-50.0% by weight, preferably 20-40% by weight, and the reaction liquid is a mixed liquid of solvent and cyclohexane. Through the above technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid is improved, and the occurrence of side reactions is reduced.

[0022] In order to further improve the conversion rate of cyclohexane, increase the selectivity of adipic acid, and reduce the occurrence of side reactions, according to a preferred embodiment of the present invention, the molar ratio of the oxygen-containing gas to cyclohexane is 0.5-2.5, preferably 0.8-1.6, calculated as oxygen.

[0023] According to a preferred embodiment of the present invention, the oxygen content in the oxygen-containing gas is 12-21% by volume, preferably 16-21% by volume. Through the above technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid can be increased, and the occurrence of side reactions can be reduced.

[0024] According to a preferred embodiment of the present invention, the oxygen-containing gas is air and / or oxygen-depleted gas.

[0025] In the present invention, the contact conditions can be conventionally selected in the art. According to a preferred embodiment of the present invention, the contact conditions include a temperature of 85-105°C, preferably 90-100°C. This can further improve the conversion of cyclohexane, increase the selectivity of adipic acid, and reduce the occurrence of side reactions.

[0026] According to a preferred embodiment of the present invention, the contacting conditions include: a pressure of 1-1.5 MPa, preferably a pressure of 1.2-1.4 MPa, thereby further improving the conversion rate of cyclohexane, increasing the selectivity of adipic acid, and reducing the occurrence of side reactions.

[0027] According to a preferred embodiment of the present invention, the contacting conditions include: a time of 1-2 hours, preferably a time of 1.2-1.5 hours.

[0028] According to a preferred embodiment of the present invention, the contact is carried out in a reactor, and an oxygen-containing gas is continuously introduced into the reactor containing the solvent, cyclohexane, the catalyst and the solid-phase catalytic promoter and continuously discharged from the reactor. The discharge method is overflow, and the liquid level of the reactor is kept stable. The outlet of the reactor is equipped with a filter screen with a pore size of 0.1 to 10 mm, which is smaller than the size of the added solid-phase catalytic promoter.

[0029] According to a preferred embodiment of the present invention, the method comprises:

[0030] a) adding catalyst, solvent, cyclohexane and solid-phase catalyst promoter into a reactor;

[0031] b) continuously introducing oxygen-containing gas under working pressure into the reactor, and heating the reactor to the reaction temperature and reaction pressure to carry out contact reaction;

[0032] c) stopping the feeding to terminate the reaction and obtain adipic acid synthesis liquid.

[0033] The above technical solution can further improve the conversion rate of cyclohexane, increase the selectivity of adipic acid, and reduce the occurrence of side reactions.

[0034] In the present invention, as long as the purpose of the present invention can be achieved, the solid-phase catalyst promoter can be obtained according to conventional technical means in the art. According to a preferred embodiment of the present invention, the preparation method of the solid-phase catalyst promoter comprises: (1) soaking a solid support in an alkaline solution, filtering and washing to obtain a first filter cake; (2) soaking the first filter cake in an acid solution, filtering and washing to obtain a second filter cake; (3) stirring and contacting the second filter cake with an aqueous solution of urea and an aqueous solution of a titanium-containing compound, filtering, washing, drying, and roasting. This can further improve the conversion rate of cyclohexane, improve the selectivity of adipic acid, and reduce the occurrence of side reactions.

[0035] In the present invention, as long as the purpose of the present invention can be achieved, there is no special requirement for the usage ratio of the alkali solution to the solid carrier. According to a preferred embodiment of the present invention, in step (1), the usage ratio of the alkali solution to the solid carrier is 5-20:1, preferably 8-12:1.

[0036] In the present invention, the alkali solution in step (1) can be a conventional choice in the art. According to a preferred embodiment of the present invention, in step (1), the alkali solution is an alkali metal hydroxide aqueous solution with a concentration of 10-40 weight %, preferably an alkali metal hydroxide aqueous solution with a concentration of 20-30 weight %. More preferably, the alkali metal hydroxide is one or both of NaOH and KOH.

[0037] In the present invention, the soaking temperature and time in step (1) can be conventional choices in the art. According to a preferred embodiment of the present invention, in step (1), the soaking temperature is 20-40°C, preferably 25-30°C, and the soaking time is 0.5-2h, preferably 1-1.5h.

[0038] By adopting the above preferred technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid can be increased, and the occurrence of side reactions can be reduced.

[0039] In the present invention, as long as the purpose of the present invention can be achieved, there is no special requirement for the usage ratio of the acid solution to the solid carrier. According to a preferred embodiment of the present invention, in step (2), the usage ratio of the acid solution to the solid carrier is 5-20:1, preferably 8-12:1.

[0040] In the present invention, the acid solution can be a conventional choice in the art. According to a preferred embodiment of the present invention, in step (2), the acid solution is an inorganic acid aqueous solution with a concentration of 10-40 weight %, preferably an inorganic acid aqueous solution with a concentration of 20-30 weight %. More preferably, the inorganic acid is at least one of hydrochloric acid, sulfuric acid and nitric acid.

[0041] In the present invention, the soaking temperature and time in step (2) can be conventional choices in the art. According to a preferred embodiment of the present invention, in step (2), the soaking temperature is 20-40°C, preferably 25-30°C, and the soaking time is 0.5-2h, preferably 1-1.5h.

[0042] By adopting the above preferred technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid can be increased, and the occurrence of side reactions can be reduced.

[0043] In the present invention, as long as the purpose of the present invention can be achieved, there is no special requirement for the usage ratio of the urea aqueous solution, the titanium-containing compound aqueous solution and the solid carrier in the step (3). According to a preferred embodiment of the present invention, in the step (3), the usage ratio of the urea aqueous solution, the titanium-containing compound aqueous solution and the solid carrier is 10-30:10-30:1, preferably 20-25:20-25:1.

[0044] In the present invention, the contact conditions in step (3) can be conventionally selected in the art. According to a preferred embodiment of the present invention, in step (3), the contact conditions include: a temperature of 60-80°C, preferably 65-75°C, and / or a time of 4-10h, preferably 5-8h.

[0045] In the present invention, as long as the purpose of the present invention can be achieved, there is no special requirement for the concentration of the urea aqueous solution. According to a preferred embodiment of the present invention, in step (3), the concentration of the urea aqueous solution is 0.1-1 mol / L, preferably 0.3-0.6 mol / L.

[0046] In the present invention, as long as the purpose of the present invention can be achieved, there is no special requirement for the concentration of the titanium-containing compound aqueous solution. According to a preferred embodiment of the present invention, in step (3), the concentration of the titanium-containing compound aqueous solution is 0.1-1.5 mol / L, preferably 0.2-1.1 mol / L.

[0047] In the present invention, the calcination conditions can be conventionally selected in the art. According to a preferred embodiment of the present invention, in step (3), the calcination conditions include: a temperature of 400-500°C, preferably 450-500°C, and a time of 1-3h, preferably 1.5-2.5h.

[0048] By adopting the above preferred technical solution, the conversion rate of cyclohexane can be further improved, the selectivity of adipic acid can be increased, and the occurrence of side reactions can be reduced.

[0049] The TiO2 content in the present invention is determined by ICP (Inductively Coupled Plasma Spectrometer) instrumentation.

[0050] The present invention is further described below by way of specific examples, but the scope of the present invention is not limited to the scope covered by the examples. The specific calculation method of cyclohexane conversion and adipic acid selectivity is as follows:

[0051] Cyclohexane conversion rate = (molar amount of cyclohexane before reaction - molar amount of cyclohexane after reaction) / molar amount of cyclohexane before reaction

[0052] Adipic acid selectivity = molar amount of adipic acid produced by the reaction / (molar amount of cyclohexane before the reaction - molar amount of cyclohexane after the reaction)

[0053] Example 1

[0054] 1) Select 70g of solid glass microspheres with a diameter of 1.5mm, first soak them in 1000g of 30% NaOH solution at 25℃ for 0.6h, filter, wash the filter cake with 1000ml of water, soak the obtained filter cake with 1000g of 30% hydrochloric acid solution at 25℃ for 0.6h, filter, add the filter cake into 1000g of 0.2mol / L TiCl4 aqueous solution, then add 1000g of 0.5mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / solid glass microspheres. It was determined that the content of titanium dioxide in TiO2 / solid glass microspheres was 1.52%.

[0055] The reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder of the solvent, acetic acid solution. The concentration of cobalt acetate in the acetic acid solution was 60 mg / L (cobalt), 120 mg / L (manganese), and 300 mg / L (copper). The initial weight concentration of cyclohexane in the reaction solution was 40%. 50 g of the TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 5:100.

[0056] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate converted to oxygen of 1.5 mol / h, the reaction temperature was 90° C., the reaction pressure was 1.2 MPa, and after 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 h was calculated to be 0.63:1, the cyclohexane conversion was calculated to be 17.9%, and the adipic acid selectivity was calculated to be 98.1%.

[0057] Comparative Example 1

[0058] The difference from Example 1 is that TiO2 / solid glass microspheres are not added. Specifically:

[0059] 1) A reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder was an acetic acid solution as solvent. The acetic acid solution contained 60 mg / L of cobalt acetate, 120 mg / L of manganese acetate, and 300 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 40%.

[0060] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate of 1.5 mol / h (equivalent to oxygen), the reaction temperature was 90° C., and the reaction pressure was 1.2 MPa. After 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthesis liquid collection tank for composition analysis. The cyclohexane conversion was calculated to be 12.8%, and the adipic acid selectivity was 78.7%.

[0061] This indicates that there are many side reactions in the blank test and the selectivity of adipic acid is not high.

[0062] Comparative Example 2

[0063] The difference from Example 1 is that TiO2 powder is added instead of TiO2 / solid glass microspheres, but the amount of TiO2 used in both is the same, specifically:

[0064] 1) A reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder was acetic acid solution. The cobalt acetate concentration in the acetic acid solution was 60 mg / L (cobalt), 120 mg / L (manganese), and 300 mg / L (copper). The initial weight concentration of cyclohexane in the reaction solution was 40%. 0.76 g of titanium dioxide powder was added to the reactor.

[0065] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate of 1.5 mol / h converted to oxygen, the reaction temperature was 90° C., and the reaction pressure was 1.2 MPa. After 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthesis liquid collection tank for composition analysis. The cyclohexane conversion was calculated to be 12.9%, and the adipic acid selectivity was 79.1%.

[0066] Comparative Example 3

[0067] 1) Select porous glass microspheres with a diameter of 1.5 mm (specific surface area 56.9 m 2 / g, pore volume 0.5146cm 3 / g)70g, first soaked in 1000g mass fraction 30% NaOH solution at 25℃ for 0.6h, filtered, and the filter cake was washed with 1000ml water. The resulting filter cake was soaked in 1000g mass fraction 30% hydrochloric acid solution at 25℃ for 0.6h, filtered, and the filter cake was added to 1000g of 0.1mol / L TiCl4 aqueous solution, and then 1000g of 0.5mol / L urea aqueous solution was added, stirred at 70℃ for 5h, filtered, washed with running pure water for 12h, dried, and calcined at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / porous glass microspheres. It was determined that the content of titanium dioxide in the TiO2 / porous glass microspheres was 1.51%.

[0068] The reactor is filled with 1 kg of reactor liquid, of which the amount of cyclohexane is 0.4 kg, and the rest is solvent acetic acid solution, in which the concentration of cobalt acetate is 60 mg / L in terms of cobalt, the concentration of manganese acetate is 120 mg / L in terms of manganese, and the concentration of copper acetate is 300 mg / L in terms of copper. 50 g of the above-mentioned TiO2 / porous glass microspheres are taken and added to the oxidation reactor, that is, the ratio of TiO2 / porous glass microspheres to reaction liquid is 5:100.

[0069] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate of 1.5 mol / h converted to oxygen, the reaction temperature was 90° C., and the reaction pressure was 1.2 MPa. After 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthesis liquid collection tank for composition analysis. The cyclohexane conversion was calculated to be 14.8%, and the adipic acid selectivity was 72.3%.

[0070] Example 2

[0071] 1) Select 70g of solid glass microspheres with a diameter of 5mm, first soak them in 350g of 35% NaOH solution at 30℃ for 1h, filter, wash the filter cake with 1000ml of water, soak the obtained filter cake with 350g of 35% hydrochloric acid solution at 30℃ for 1h, filter, add the filter cake into 1000g of 0.3mol / L TiCl4 aqueous solution, then add 1000g of 0.6mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / solid glass microspheres. It was determined that the content of titanium dioxide in TiO2 / solid glass microspheres was 0.98%.

[0072] The reactor was charged with 1 kg of liquid, including 0.5 kg of cyclohexane, and the remainder was an acetic acid solution containing 300 mg / L of cobalt acetate, 200 mg / L of manganese acetate, and 500 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 50%. 70 g of the aforementioned TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 7:100.

[0073] 2) Oxygen was continuously introduced into the oxidation reactor, wherein the oxygen content was 18% by volume, which was converted into a molar flow rate of oxygen of 4 mol / h. The reaction temperature was 100° C. and the reaction pressure was 1.5 MPa. After the reaction was continued for 1 hour, a sample of the adipic acid oxidation reaction liquid was taken from the synthesis liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 1 hour was calculated to be 0.67:1. The cyclohexane conversion was calculated to be 17.5%, and the adipic acid selectivity was 98.0%.

[0074] Example 3

[0075] 1) Select 70g of solid glass microspheres with a diameter of 3mm, first soak them in 1400g of 10% NaOH solution at 30℃ for 1h, filter, wash the filter cake with 1000ml of water, soak the obtained filter cake with 1400g of 10% hydrochloric acid solution at 30℃ for 1h, filter, add the filter cake into 2100g of 0.1mol / L TiCl4 aqueous solution, then add 2100g of 0.1mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / solid glass microspheres. It was determined that the content of titanium dioxide in TiO2 / solid glass microspheres was 1.53%.

[0076] The reactor was charged with 1 kg of liquid, including 0.3 kg of cyclohexane, and the remainder was an acetic acid solution containing 300 mg / L of cobalt acetate, 200 mg / L of manganese acetate, and 500 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 30%. 60 g of the TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 6:100.

[0077] 2) Oxygen was continuously introduced into the oxidation reactor, wherein the oxygen content was 16% by volume, which was converted into a molar flow rate of oxygen of 3 mol / h. The reaction temperature was 105° C. and the reaction pressure was 1 MPa. After 1.5 hours of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 hours was calculated to be 1.26:1. The cyclohexane conversion was calculated to be 17.8%, and the adipic acid selectivity was 97.8%.

[0078] Example 4

[0079] 1) Select 70g of solid glass microspheres with a diameter of 0.1mm, first soak them in 1000g of 30% KOH solution at 25℃ for 0.6h, filter, wash the filter cake with 1000ml of water, soak the obtained filter cake with 1000g of 30% nitric acid solution at 25℃ for 0.6h, filter, add the filter cake into 700g of 1.1mol / L TiCl4 aqueous solution, then add 700g of 0.3mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / solid glass microspheres. It was determined that the content of titanium dioxide in TiO2 / solid glass microspheres was 4.77%.

[0080] The reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder was an acetone solution containing 60 mg / L of cobalt acetate, 120 mg / L of manganese acetate, and 300 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 40%. 50 g of the TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 5:100.

[0081] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate converted to oxygen of 1.5 mol / h, the reaction temperature was 90° C., the reaction pressure was 1.2 MPa, and after 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 h was calculated to be 0.63:1, the cyclohexane conversion was calculated to be 17.4%, and the adipic acid selectivity was calculated to be 95.3%.

[0082] Example 5

[0083] 1) Select 210g of solid alumina microspheres with a diameter of 1.5mm, first soak them in 2100g of 20% NaOH solution at 25℃ for 0.6h, filter, wash the filter cake with 3000ml of water, soak the obtained filter cake with 1050g of 40% sulfuric acid solution at 25℃ for 0.6h, filter, add the filter cake to 3000g of 0.1mol / L TiCl4 aqueous solution, then add 3000g of 0.1mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 400℃ for 2h to obtain solid alumina microspheres loaded with TiO2 - TiO2 / solid alumina microspheres. It was determined that the content of titanium dioxide in TiO2 / solid alumina microspheres was 1.56%.

[0084] The reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder was an acetonitrile solvent solution containing 60 mg / L of cobalt acetate, 120 mg / L of manganese acetate, and 300 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 40%. 150 g of the aforementioned TiO2 / solid alumina microspheres were added to the oxidation reactor, resulting in a ratio of 15:100 between the TiO2 / solid alumina microspheres and the reaction solution.

[0085] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate converted to oxygen of 6 mol / h, the reaction temperature was 90° C., the reaction pressure was 1.2 MPa, and after 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 h was calculated to be 2.5:1, the cyclohexane conversion was calculated to be 17.5%, and the adipic acid selectivity was calculated to be 94.9%.

[0086] Example 6

[0087] 1) 70 g of solid glass microspheres with a diameter of 1.5 mm were selected and directly added to 100 g of a 2 mol / L TiCl4 aqueous solution, followed by the addition of 100 g of a 5 mol / L urea aqueous solution. The mixture was stirred at 70°C for 5 h, filtered, washed with running pure water for 12 h, and then dried to obtain TiO2-loaded solid glass microspheres - TiO2 / solid glass microspheres. The titanium dioxide content in the TiO2 / solid glass microspheres was determined to be 2.22%.

[0088] The reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder was an acetic acid solution containing 60 mg / L of cobalt acetate, 120 mg / L of manganese acetate, and 300 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 40%. 50 g of the TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 5:100.

[0089] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate converted to oxygen of 1.5 mol / h, the reaction temperature was 90° C., the reaction pressure was 1.2 MPa, and after 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 h was calculated to be 0.63:1, the cyclohexane conversion was calculated to be 17.1%, and the adipic acid selectivity was calculated to be 91.7%.

[0090] Example 7

[0091] 1) Select 70g of solid glass microspheres with a diameter of 1.5mm, first soak them in 1000g of 30% NaOH solution at 25℃ for 0.6h, filter, wash the filter cake with 1000ml of water, soak the obtained filter cake with 1000g of 30% hydrochloric acid solution at 25℃ for 0.6h, filter, add the filter cake into 1000g of 0.2mol / L TiCl4 aqueous solution, then add 1000g of 0.5mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / solid glass microspheres. It was determined that the content of titanium dioxide in TiO2 / solid glass microspheres was 1.52%.

[0092] The reactor was charged with 1 kg of liquid, including 0.1 kg of cyclohexane, and the remainder was an acetic acid solution containing 10 mg / L of cobalt acetate, 6 mg / L of manganese acetate, and 40 mg / L of copper acetate. The initial weight concentration of cyclohexane in the reaction solution was 10%. 10 g of the TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 1:100.

[0093] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate converted into oxygen of 0.3 mol / h, the reaction temperature was 90° C., the reaction pressure was 1.2 MPa, and after 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 h was calculated to be 0.5:1, the cyclohexane conversion was calculated to be 15.0%, and the adipic acid selectivity was calculated to be 93.3%.

[0094] Example 8

[0095] 1) Select 70g of solid glass microspheres with a diameter of 10mm, first soak them in 1000g of 30% NaOH solution at 25℃ for 0.6h, filter, wash the filter cake with 1000ml of water, soak the obtained filter cake with 1000g of 30% hydrochloric acid solution at 25℃ for 0.6h, filter, add the filter cake into 1000g of 0.2mol / L TiCl4 aqueous solution, then add 1000g of 0.5mol / L urea aqueous solution, stir at 70℃ for 5h, filter, wash with running pure water for 12h, dry and calcine at 500℃ for 2h to obtain solid glass microspheres loaded with TiO2 - TiO2 / solid glass microspheres. It was determined that the content of titanium dioxide in TiO2 / solid glass microspheres was 1.49%.

[0096] The reactor was charged with 1 kg of liquid, including 0.4 kg of cyclohexane, and the remainder was acetic acid solution. The cobalt acetate concentration in the acetic acid solution was 600 mg / L (cobalt), the manganese acetate concentration was 400 mg / L (manganese), and the copper acetate concentration was 1000 mg / L (copper). The initial weight concentration of cyclohexane in the reaction solution was 40%. 30 g of the TiO2 / solid glass microspheres were added to the oxidation reactor, resulting in a TiO2 / solid glass microsphere to reaction solution ratio of 3:100.

[0097] 2) Air was continuously introduced into the oxidation reactor at a molar flow rate converted into oxygen of 0.3 mol / h, the reaction temperature was 90° C., the reaction pressure was 1.2 MPa, and after 2 h of continuous reaction, a sample of the adipic acid oxidation reaction liquid was taken from the synthetic liquid collection tank for composition analysis. The molar ratio of the total oxygen to cyclohexane in 2 h was calculated to be 0.5:1, the cyclohexane conversion was calculated to be 17.6%, and the adipic acid selectivity was calculated to be 92.5%.

[0098] As can be seen from Table 1, the method for preparing adipic acid by direct oxidation of cyclohexane according to the present invention improves the conversion rate of cyclohexane and the selectivity of adipic acid.

[0099] Table 1

[0100]

[0101] If the data in the table are inconsistent with the examples, the examples shall prevail.

[0102] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for preparing adipic acid by direct oxidation of cyclohexane, characterized in that: The method includes: contacting cyclohexane with an oxygen-containing gas in the presence of a solvent, a catalyst and a solid-phase catalyst promoter; The catalyst is composed of cobalt acetate, manganese acetate and copper acetate, and the solid-phase catalyst promoter contains a solid carrier and titanium dioxide TiO2 supported on the solid carrier; The solid carrier is a solid glass microsphere and / or a solid alumina microsphere, and the size of the microsphere is 0.1 to 10 mm; The weight content of titanium dioxide TiO2 in the solid-phase catalyst promoter is 0.1-5%; The weight ratio of the solid-phase catalyst promoter to the reaction liquid is 1.0-10.0:100; and the reaction liquid is a mixture of the solvent and cyclohexane.

2. The method according to claim 1, wherein The size of the microspheres is 1.5 to 5 mm; and / or The weight content of titanium dioxide TiO2 in the solid-phase catalyst promoter is 0.5-2%; and / or The weight ratio of the solid-phase catalyst promoter to the reaction liquid is 5.0-7.0:100; and the reaction liquid is a mixture of the solvent and cyclohexane.

3. The method according to claim 1 or 2, wherein: The solvent is one or more of acetic acid, acetone and acetonitrile; and / or The concentration of cobalt acetate in the solvent is 10-600 mg / L as cobalt, the concentration of manganese acetate is 6-400 mg / L as manganese, and the concentration of copper acetate is 40-1000 mg / L as copper; and / or The weight ratio of the catalyst to the reaction liquid is 0.001-0.2:100, and the reaction liquid is a mixture of the solvent and cyclohexane.

4. The method according to claim 3, wherein: The concentration of cobalt acetate in the solvent is 60-300 mg / L in terms of cobalt, the concentration of manganese acetate is 120-200 mg / L in terms of manganese, and the concentration of copper acetate is 300-500 mg / L in terms of copper.

5. The method according to claim 1 or 2, wherein: The reaction solution contains cyclohexane at a content of 10.0 to 50.0% by weight, and the reaction solution is a mixture of the solvent and cyclohexane; and / or The molar ratio of the oxygen-containing gas to cyclohexane is 0.5-2.5 as oxygen; and / or The oxygen content of the oxygen-containing gas is 12-21% by volume; and / or The oxygen-containing gas is air and / or oxygen.

6. The method according to claim 5, wherein: The oxygen content in the oxygen-containing gas is 16-21% by volume.

7. The method according to claim 1 or 2, wherein: The contact conditions include: a temperature of 85-105° C., and / or a pressure of 1-1.5 MPa, and / or a time of 1-2 h.

8. The method according to claim 1 or 2, wherein: The method includes: a) adding catalyst, solvent, cyclohexane and solid-phase catalyst promoter into a reactor; b) continuously introducing oxygen-containing gas under working pressure into the reactor, and heating the reactor to the reaction temperature and reaction pressure to carry out contact reaction; c) stopping the feeding to terminate the reaction and obtain adipic acid synthesis liquid.

9. The method according to claim 1 or 2, wherein: The preparation method of the solid-phase catalyst promoter comprises: (1) soaking the solid carrier in alkali solution, filtering and washing to obtain a first filter cake; (2) soaking the first filter cake in acid solution, filtering and washing to obtain a second filter cake; (3) The second filter cake is stirred and contacted with a urea aqueous solution and a titanium compound aqueous solution, filtered, washed, dried, and calcined.

10. The method according to claim 9, wherein: In step (1), The ratio of alkali solution to solid carrier is 5-20:1; and / or The alkali solution is an aqueous solution of alkali metal hydroxide with a concentration of 10-40% by weight, and the alkali metal hydroxide is one or both of NaOH and KOH; and / or The soaking temperature is 20-40°C and the soaking time is 0.5-2h.

11. The method according to claim 9, wherein In step (2), The ratio of acid solution to solid carrier is 5-20:1; and / or The acid solution is an inorganic acid aqueous solution with a concentration of 10-40% by weight, and the inorganic acid is at least one of hydrochloric acid, sulfuric acid and nitric acid; and / or The soaking temperature is 20-40°C and the soaking time is 0.5-2h.

12. The method according to claim 9, wherein In step (3), The ratio of urea aqueous solution, titanium compound aqueous solution and solid carrier is 10-30:10-30:1; and / or The contact conditions include: a temperature of 60-80°C, and / or a time of 4-10 hours; and / or The concentration of the urea aqueous solution is 0.1-1 mol / L; and / or The concentration of the titanium compound aqueous solution is 0.1-1.5 mol / L; and / or The calcination conditions include: temperature of 400-500° C. and time of 1-3 hours.

13. The method according to claim 12, wherein: In step (3), The concentration of the titanium compound aqueous solution is 0.2-1.1 mol / L.

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