CN111253281B - Preparation method of cyclohexanone oxime - Google Patents
Preparation method of cyclohexanone oxime Download PDFInfo
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- CN111253281B CN111253281B CN202010103344.0A CN202010103344A CN111253281B CN 111253281 B CN111253281 B CN 111253281B CN 202010103344 A CN202010103344 A CN 202010103344A CN 111253281 B CN111253281 B CN 111253281B
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Abstract
The invention relates to a preparation method of cyclohexanone oxime, which mainly comprises three synthesis steps of catalyzing aniline or nitrobenzene hydrogenation, cyclohexane oxidation and by-product amination, and the like: (1) Hydrogenation reaction is carried out on aniline or nitrobenzene and hydrogen under the action of a catalyst to generate cyclohexylamine and a small amount of byproduct-A, and the cyclohexylamine is obtained after the byproduct-A and the aniline which possibly is not completely converted are separated; (2) Oxidizing the cyclohexylamine obtained in the step (1) with molecular oxygen under the action of a catalyst to obtain an oxidation reaction product mainly composed of cyclohexanone oxime, a small amount of byproducts-B and possibly unconverted cyclohexylamine; (3) And (3) directly carrying out amination reaction on the oxidation reaction product obtained in the step (2) with ammonia and hydrogen under the action of a catalyst without separation, completely converting byproducts-B in the oxidation reaction product into cyclohexylamine, and separating the cyclohexylamine to obtain the cyclohexanone oxime. The invention can obviously improve the yield of the cyclohexanone oxime and obviously reduce the energy consumption and the cost of the production of the cyclohexanone oxime.
Description
Technical Field
The invention relates to preparation of cyclohexanone oxime, in particular to a preparation method of cyclohexanone oxime.
Background
Cyclohexanone oxime is an intermediate of epsilon-caprolactam which is an important raw material (the main application is that polyamide chips are further produced into nylon fibers, engineering plastics, plastic films and the like through polymerization).
The presently known processes for the production of cyclohexanone oxime have mainly two: cyclohexanone-hydroxylamine and cyclohexanone ammoximation. The two methods are most commonly applied, and benzene is used as a starting material, and cyclohexanone oxime is synthesized through intermediate cyclohexanone.
There are three methods for synthesizing cyclohexanone from benzene in the industry: phenol, cyclohexane oxidation and cyclohexene hydration. For a long time, the earliest cyclohexanone oxime production devices in the world adopt a phenol method to produce cyclohexanone: firstly, benzene is used as a raw material to produce phenol, then cyclohexanol is produced by phenol hydrogenation, and then the cyclohexanol is dehydrogenated to produce cyclohexanone. It can be seen that the key to the phenol process is how phenol is obtained. At present, the cumene method is mainly adopted to produce phenol in industry (the chlorobenzene hydrolysis method and the benzene sulfonation method are almost completely eliminated due to the problems of environment and cost): benzene and propylene are alkylated to generate isopropylbenzene, the isopropylbenzene reacts with oxygen to generate isopropylbenzene hydroperoxide, and finally the isopropylbenzene hydroperoxide is decomposed into phenol and acetone under the action of sulfuric acid or sulfonic acid resin. This method has mainly the following disadvantages: firstly, the phenol yield is low (72-75 percent) and byproducts are more; secondly, the separation and purification device of phenol and acetone is complex and has high energy consumption; thirdly, the market demand and price of a large amount of acetone byproducts influence the production cost of phenol. Thus, the process for preparing cyclohexanone from phenol has been replaced by the cyclohexane oxidation process very early.
The technology for preparing cyclohexanone by oxidizing cyclohexane is mature, and a two-step synthesis method is widely adopted in the industry at present: (i) Cyclohexane is oxidized with molecular oxygen under non-catalytic conditions to form cyclohexylhydroperoxide (while also forming a quantity of cyclohexanone and cyclohexanol and some byproducts); (ii) The cyclohexyl hydroperoxide in the oxidation product obtained in the previous step is decomposed into cyclohexanone and cyclohexanol (some byproducts are generated at the same time) by a low-temperature alkaline decomposition method, KA oil is obtained by separation, the KA oil is further separated into cyclohexanone and cyclohexanol, and finally the cyclohexanol is dehydrogenated into cyclohexanone. The method has the main advantages that the technology for preparing cyclohexane by completely hydrogenating benzene is mature, the difficulty is small, the yield is high, but three major disadvantages exist in the oxidation process of cyclohexane: (i) In order to maintain high selectivity, the conversion rate of cyclohexane in one pass through air oxidation of cyclohexane can only be controlled to be 3-5%, a large amount of unconverted cyclohexane needs to consume large energy to carry out separation circulation, and even so, the total KA oil (mixture of cyclohexanone and cyclohexanol) yield calculated as cyclohexane can only reach about 83%, and cyclohexane consumption is high and the amount of byproducts is large. (ii) The main product of the cyclohexane non-catalytic oxidation reaction is cyclohexyl hydroperoxide, naOH is consumed in the decomposition process, byproducts of the cyclohexane oxidation reaction are mainly acid, ester, ether and the like, and saponification removal is also required through an alkaline aqueous solution, so that a large amount of NaOH is consumed, a large amount of saponification waste lye is generated, the production cost is high, and the environmental pressure is high. (iii) Since the target product is cyclohexanone, KA oil is required to be further separated into cyclohexanone and cyclohexanol by rectification, and then the cyclohexanol is dehydrogenated into cyclohexanone; however, due to the limitation of thermodynamic equilibrium, the once-through conversion rate of cyclohexanol dehydrogenation is generally less than 80%, cyclohexanol and cyclohexanone are separated after dehydrogenation, the boiling points of cyclohexanone and cyclohexanol differ by only about 6 ℃, the separation difficulty can cause higher energy consumption, and the once-through conversion rate of cyclohexane oxidation is only 3-5%, so that the energy consumption of the whole process is very high.
In summary, the two-step method for preparing cyclohexanone by oxidizing cyclohexane widely used in industry at present has the problems of 'three high and one big' although the technical threshold is not high and mature: namely, the problems of high cyclohexane consumption, high alkali consumption, high energy consumption, large waste alkali liquid treatment load and the like.
Therefore, in recent years, a new industrial device for cyclohexanone oxime generally adopts a route (CN 02804368.5,CN 02814607.7) for preparing cyclohexanone from cyclohexene hydration route proposed in the year 2002 by the japanese Asahi chemical industry, and the preparation process is schematically shown in FIG. 1: and (3) partially hydrogenating benzene to generate cyclohexene and cyclohexane, separating cyclohexene from the cyclohexane and unconverted benzene through extractive distillation, carrying out hydration reaction on cyclohexene and water to generate cyclohexanol, and finally dehydrogenating the cyclohexanol to generate cyclohexanone. The method has the greatest advantages that the material consumption is low: firstly, the total selectivity of the benzene partial hydrogenation to cyclohexene and cyclohexane is very high (up to 99%), and cyclohexane is also a product or intermediate with certain economic value; second, the hydration of cyclohexene to cyclohexanol is also essentially a directional conversion reaction. However, it also has the obvious disadvantage of being very energy-efficient, in that: (i) In order to obtain the highest possible single pass yield of cyclohexene, the conversion of the benzene partial hydrogenation reaction is generally controlled to be in the range of 40 to 50% (in which case the selectivity of cyclohexene is about 70 to 80%), so that the reaction product of the benzene partial hydrogenation is in fact a mixture of benzene, cyclohexene and cyclohexane having very close boiling points, which can only be separated at present by two stages of extractive distillation and vacuum distillation: the first-stage extractive distillation is to separate benzene from cyclohexene and cyclohexane by using an extractant, and separate the benzene from the extractant by vacuum distillation for recycling; the second stage of extraction rectification is to separate cyclohexene from cyclohexane by using an extractant, then separate cyclohexene from the extractant by vacuum rectification, and the separated cyclohexane can be refined and sold as a product. Thus, the separation difficulty of the benzene-cyclohexene-cyclohexane system is high and the energy consumption is high. (ii) The conversion of cyclohexene hydration to cyclohexanol is generally only 10 to 12%, so that the separation of the cyclohexene-cyclohexanol-water system and the recycling of large amounts of cyclohexene also requires relatively high energy consumption. (iii) Since the target product is cyclohexanone, the cyclohexanol obtained by hydration needs to be dehydrogenated into cyclohexanone, the dehydrogenation process for preparing cyclohexanone needs to provide energy, the conversion rate of the cyclohexanol is generally not more than 80 percent due to the limitation of reaction balance, the boiling points of the cyclohexanone and the cyclohexanol are different by only about 6 ℃, and therefore, the cyclohexanone and the cyclohexanol also need to be separated by providing larger energy (the cyclohexanol obtained by separation is used for preparing the cyclohexanone by cyclic dehydrogenation). In addition, although cyclohexane, a byproduct of the partial hydrogenation of benzene, is also economically valuable, sales and utilization problems thereof are also considered due to large yields and limited market demands.
In addition to the problems associated with the preparation of cyclohexanone described above, there are problems associated with the oximation of cyclohexanone itself. At present, two main methods are cyclohexanone hydroxylamine oximation and cyclohexanone ammoximation in industry, wherein the cyclohexanone hydroxylamine oximation method can be divided into a hydroxylamine sulfate oximation method (HSO method) and a hydroxylamine phosphate oximation method (HPO method). Either HSO or HPO requires a complex hydroxylamine salt production line, and the hydroxylamine oximation of cyclohexanone to produce cyclohexanone oxime is performed using the hydroxylamine salt produced. Therefore, the cyclohexanone-hydroxylamine oximation method has long production flow, large equipment investment, complex operation control, and higher hydrogen consumption and material consumption (the hydroxylamine salt yield based on ammonia is only about 60 percent), thus the production cost is higher.
In order to reduce the oximation cost and improve the atomic utilization rate of the oximation reaction, italian Erni company developed a cyclohexanone ammoximation method, i.e. a HAO method (U.S. Pat. No. 4,049,221 (1988)), and realized industrialization: the cyclohexanone reacts with hydrogen peroxide and ammonia under the action of titanium silicalite molecular sieve catalyst to generate cyclohexanone oxime in one step. Compared with HSO and HPO, the HAO method has the advantages of low hydrogen consumption, short production flow, simple and convenient control, low requirements on equipment and pipeline materials, small investment and small occupied area, and the like. However, the HAO method requires hydrogen peroxide consumption, so that a matched hydrogen peroxide production line is required, and water is generated in the ammoximation reaction process due to the fact that the hydrogen peroxide concentration in the hydrogen peroxide is not too high, so that the method is large in wastewater production amount and heavy in treatment burden.
In addition to the above-described process for producing cyclohexanone oxime by oximation of cyclohexanone, there is also a process for producing cyclohexanone oxime not using cyclohexanone as an intermediate, which may be referred to as "cyclohexane photonitrosation process": process for the photochemical reaction of cyclohexane with nitrosyl chloride to cyclohexanone oxime hydrochloride, wherein nitrosyl chloride is prepared from nitrososulfuric acid (NOHSO) 4 ) Is reacted with HCl to obtain the product. The method has the advantages of few reaction steps and short flow, but has very high electricity consumption (used for generating the light source), high cost of the light source equipment, troublesome maintenance and long production stoppage.
Furthermore, U.S. Pat. nos. 2967200a (1959) and 3255261a (1964) also propose a process for the preparation of cyclohexanone oxime which does not use cyclohexanone as an intermediate: cyclohexane and nitric acid react to obtain nitrocyclohexane, and then partial hydrogenation is carried out to obtain cyclohexanone oxime. This method, although simple in steps, still has many problems such as: cyclohexane nitrate nitration reaction conditions are harsh (the temperature is 150-200 ℃ and the pressure is 3-4 MPa), equipment corrosion is serious, the environmental impact is relatively large, the cyclohexane conversion is only about 20%, and the selectivity of nitrocyclohexane based on cyclohexane and nitric acid is less than 80%; the selectivity of the nitrocyclohexane partially hydrogenated cyclohexanone oxime is also less than 60%. Because of these limitations, this method has not been reported industrially since the advent of more than half a century ago.
In fact, there is also a process for the preparation of cyclohexanone oxime which has been attracting attention since the 50 th century: the cyclohexylamine is subjected to partial oxidation to produce cyclohexanone oxime (J.of Molecular Catalysis A:chemical,2000, 160:393-402). Early studies focused mainly on the use of hydrogen peroxide or alkyl hydrogen peroxide as the oxidizing agent, as suggested by U.S. Pat. No. 4,975,954 (1955) and U.S. Pat. No. 3,976 (1976). In view of the cost of the oxidizing agent, research is gradually focused on the use of molecular oxygen as the oxidizing agent, for example, in 1982, a silica gel catalyst and a solid-gas catalytic oxidation of cyclohexylamine at 150 ℃ with a cyclohexanone oxime selectivity of 60% at 18% is proposed by united states corporation (US 4337358). In 1985, the company also proposed to use gamma-alumina to carry tungsten oxide as a catalyst and molecular oxygen as an oxidant, and perform gas-solid phase catalytic oxidation at 159 ℃, wherein the conversion rate of cyclohexane can reach 28%, and the selectivity of cyclohexanone oxime can reach 54% (US 4504681); if molybdenum oxide is supported on gamma-alumina, the conversion rate of cyclohexylamine can reach 33%, and the selectivity of cyclohexanone oxime can reach 64% (J. Of Catalysis,1983, 83:487-490). However, until the present century, there has been no great progress in the research results on the production of cyclohexanone oxime by partial oxidation of cyclohexylamine with molecular oxygen. For example, CN 103641740a (2013) discloses a gas-phase catalytic oxidation method using supported mesoporous silicon as a catalyst, and when the conversion rate of cyclohexane is 20-30%, the selectivity of cyclohexanone oxime can reach more than 85%; CN 109206339a (2017) discloses a liquid phase catalytic oxidation method using supported titanium dioxide as a catalyst, and when the conversion rate of cyclohexane reaches more than 50%, the selectivity of cyclohexanone oxime can reach more than 90%.
In 2002, a new process for producing cyclohexanone oxime by partial oxidation based on cyclohexylamine and molecular oxygen was proposed by the japanese Asahi chemical industry (CN 02804368.5, CN 02814607.7): the cyclohexanol obtained by cyclohexene hydration method is used as raw material, first undergoes amination reaction with ammonia to generate cyclohexane, and then undergoes partial oxidation reaction with molecular oxygen under the action of a catalyst to generate cyclohexanone oxime. In order to be able to obtain a higher cyclohexanone oxime yield, the byproducts (referred to as byproduct-a and byproduct- β, respectively) produced in both steps of the reaction need to be separated off and recycled back to the amination system for amination to form cyclohexylamine. The advantages of this method are very obvious: firstly, cyclohexanol is not required to be dehydrogenated to prepare cyclohexanone, so that energy consumption is reduced; and secondly, as the oximation of cyclohexanone is not needed, hydroxylamine salt or hydrogen peroxide is not needed to be consumed, and a matched hydroxylamine salt or hydrogen peroxide production line is not needed, so that the production cost of the cyclohexanone-hydroxylamine method and the cyclohexanone-ammoximation method can be obviously reduced, and the method has the advantages of short flow, investment saving and simple and convenient operation control. However, this method still has the following drawbacks: firstly, the cyclohexanol is still prepared by adopting a cyclohexene hydration route, so that the problem of high energy consumption is not avoided; secondly, both the cyclohexanol amination and the cyclohexylamine oxidation reactions involved produce by-products having boiling points close to or higher than the boiling point of cyclohexanone oxime, for example, where the boiling point of nitrocyclohexane is 205 ℃ to 206 ℃, very close to the boiling point of cyclohexanone oxime, 206 ℃ to 210 ℃, and both dicyclohexylamine and N-cyclohexylimine have boiling points higher than the boiling point of cyclohexanone oxime. Thus, separating cyclohexanone oxime from these close boiling or higher boiling byproducts is not only very difficult, but also the energy required may be very large.
In view of the above, with the continuous development and progress of society, it is demanded to develop a simpler, efficient and more environmentally friendly cyclohexanone oxime production process.
Disclosure of Invention
According to the deep understanding and analysis of the prior art, in order to realize the simpler, more efficient and environment-friendly production of cyclohexanone oxime, the invention provides a novel method for preparing cyclohexanone oxime, which mainly comprises three synthetic steps of catalyzing aniline or nitrobenzene hydrogenation, oxidizing cyclohexane and aminating oxidation products: (1) And (3) carrying out hydrogenation reaction on aniline or nitrobenzene and hydrogen under the action of a solid catalyst to generate cyclohexylamine and a small amount of byproduct-A (namely byproduct-A), and separating the byproduct-A and the aniline which is possibly not completely converted to obtain cyclohexylamine. (2) Oxidizing the cyclohexylamine obtained in the step (1) with molecular oxygen under the action of a solid catalyst to obtain an oxidation reaction product mainly composed of cyclohexanone oxime, a small amount of byproducts (named as byproducts-B) and possibly unconverted cyclohexylamine; (3) And (3) directly carrying out amination reaction on the oxidation reaction product obtained in the step (2) with ammonia and hydrogen under the action of a solid catalyst without separation, completely converting byproducts-B in the reaction product into cyclohexylamine, and separating the cyclohexylamine to obtain the cyclohexanone oxime.
The method of the invention has the following three main characteristics: (i) The cyclohexanone is not used as an intermediate for preparing cyclohexanone oxime, so that the production of the cyclohexanone is not needed, and all the defects of the existing cyclohexanone production technology, such as high material consumption of a cyclohexane oxidation method or high energy consumption of a cyclohexene hydration method, are avoided, thereby greatly saving energy and reducing consumption. (ii) As the oxidation of the cyclohexane and the molecular oxygen is adopted instead of the oximation of the cyclohexanone, the consumption of hydroxylamine salt or hydrogen peroxide is avoided, and a production line for matching the hydroxylamine salt or the hydrogen peroxide is not needed, so that the material consumption and the energy consumption can be greatly reduced, and the occupied area and the investment can be greatly reduced. (iii) Since the oxidation reaction of cyclohexylamine with molecular oxygen also produces some by-products in an amount which is not negligible, namely the above-mentioned by-product-B, it will have a large influence on the yield of cyclohexanone oxime if not used. However, some of these by-products have boiling points very close to or higher than those of cyclohexanone oxime, such as nitrocyclohexane, dicyclohexylamine, N-cyclohexylcyclohexylamine, etc., and thus, it is very difficult in practice to separate them from cyclohexanone oxime, and the energy consumption may be very high. The invention provides an oxidation reaction product of cyclohexane and molecular oxygen, which is directly subjected to amination reaction with ammonia and hydrogen under the action of a solid catalyst, and the separation of the cyclohexane and the cyclohexanone oxime is carried out after all oxidation byproducts are converted into the cyclohexane, so that the problems of difficult separation of the cyclohexanone oxime from the oxidation byproducts and high energy consumption are solved.
Therefore, the novel method for preparing cyclohexanone oxime by using benzene as a starting material through hydrogenation of aniline or nitrobenzene, molecular oxygen oxidation of cyclohexylamine and amination of ammonia and hydrogen has the remarkable advantages of short process flow, less construction investment, low material consumption, simple and convenient operation, safety, environmental friendliness and the like compared with the prior art.
For a clearer understanding of the present invention, the above steps of the present invention will be described in detail with reference to fig. 2:
(1) Amination of aniline or nitrobenzene: aniline or nitrobenzene and hydrogen are subjected to hydrogenation reaction under the action of a solid catalyst to generate cyclohexylamine, and a small amount of byproduct-A is generated; the nitrobenzene is easy to be converted into the aniline, so that when the nitrobenzene is taken as a raw material, the nitrobenzene can be completely converted, but the conversion rate of the aniline into the cyclohexylamine is not necessarily or not necessarily required to be complete, and the conversion rate can be adjusted according to the needs; the boiling points of cyclohexylamine, aniline and byproduct-A are quite different, the cyclohexylamine, the aniline and the byproduct-A can be separated through vacuum rectification, and the aniline obtained through separation is circularly hydrogenated;
the hydrogenation of aniline or nitrobenzene mainly comprises the following reactions:
(a)C 6 H 5 NO 2 +3H 2 →C 6 H 5 NH 2 +2H 2 O
(b)C 6 H 5 NH 2 +3H 2 →C 6 H 11 NH 2 +2H 2 O
(d)
(e)
(f)
(g)
the reaction (a) is hydrogenation of nitrobenzene to generate cyclohexylamine, the reaction (b) is hydrogenation of aniline to generate cyclohexylamine, and the other four reactions are main side reactions: (d) Side reactions of respectively generating the diphenylamine, the dicyclohexylamine and the N-cyclohexylaniline, and (f) and (g) are reactions of respectively further hydrogenating the diphenylamine and the N-cyclohexylaniline to generate the dicyclohexylamine. However, the rate of nitrobenzene hydrogenation reaction (a) is much faster than the other six reactions. Therefore, when hydrogenation is carried out using nitrobenzene as a raw material, it can be considered that hydrogenation is actually carried out using aniline as a raw material.
Under the condition of the catalytic reaction, the total amount of the byproduct-A (the main component is one or more than two of dicyclohexylamine, N-cyclohexylaniline, diphenylamine and the like) is very small, and the dicyclohexylamine is a product with better economic value, and can be used for preparing intermediates for dyes, rubber accelerators, nitrocellulose lacquer, pesticides, catalysts, preservatives, gas-phase corrosion inhibitors, fuel antioxidation additives and the like. Therefore, the byproduct-A can be collected, hydrogenation reactions such as (f) and (g) are further carried out under the action of a catalyst, N-cyclohexylaniline and diphenylamine in the product-A are converted into dicyclohexylamine, and the dicyclohexylamine serving as a byproduct can be obtained through separation and purification.
(2) Oxidation of cyclohexylamine with molecular oxygen: oxidation of cyclohexylamine with molecular oxygen: partially oxidizing the cyclohexylamine obtained in the step (1) and molecular oxygen under the action of a solid catalyst to generate cyclohexanone oxime; compared with the current industrial technology for preparing cyclohexanone oxime by oximation of cyclohexanone, the partial oxidation of cyclohexane and molecular oxygen does not need to consume hydroxylamine salt or hydrogen peroxide, and the production cost can be greatly reduced. However, at the same time of producing cyclohexanone oxime by partial oxidation of cyclohexane and molecular oxygen, a certain amount of by-products-B, namely one or more than two of cyclohexanone, nitrocyclohexane, dicyclohexylamine, cyclohexylimine (CAS: 22554-30-9), N-cyclohexylcyclohexylimine (CAS: 10468-40-3) and the like, are also produced.
In general, the selectivity of the byproduct-B may reach about 6% -12%, and if the byproduct-B is not recycled, the selectivity is a great problem from the aspects of economy and environment. Thus, japanese Asahi chemical (CN 02814607.7) proposes separating them from cyclohexanone oxime, and subjecting them to amination with ammonia and hydrogen to regenerate cyclohexylamine (see FIG. 1). However, in the by-product-B, the boiling points of other substances except cyclohexanone and cyclohexylimine are very close to or higher than that of cyclohexanone oxime, for example, the boiling point of nitrocyclohexane is 205 to 206 ℃ and very close to 206 to 210 ℃ of cyclohexanone oxime, and the boiling points of dicyclohexylamine and N-cyclohexylimine are both above 255 ℃, and it is found that it is practically difficult to separate them from cyclohexanone oxime by a conventional method and that the separation energy consumption may be very high.
The reaction of cyclohexylamine with molecular oxygen is mainly:
(a)C 6 H 11 NH 2 +O 2 →C 6 H 10 NOH+H 2 O
(b)C 6 H 11 NH 2 +1.5O 2 →C 6 H 11 NO 2 +H 2 O
(c)C 6 H 11 NH 2 +0.5O 2 →C 6 H 10 NH+H 2 O
(d)2C 6 H 11 NH 2 +3.5O 2 →2C 6 H 10 O+3H 2 O+2NO
(e)C 6 H 10 O+C 6 H 11 NH 2 →C 6 H 10 ＝N-C 6 H 11 +H 2 O
(f)2C 6 H 11 NH 2 +2.5O 2 →2C 6 H 11 OH+H 2 O+2NO
(g)C 6 H 11 OH+C 6 H 11 NH 2 →(C 6 H 11 ) 2 NH+H 2 O
as can be seen from the above reaction scheme, the side reactions (d) and (f) for the production of cyclohexanone should be strictly controlled, which bring not only N or NH by themselves 3 And the cyclohexanone and cyclohexanol produced further consume cyclohexylamine to produce N-cyclohexylcyclohexylimine and dicyclohexylamine. Since the rate of reaction (f) is relatively slow and the rate of reaction (g) is fast, cyclohexanol is rarely found in byproduct-B.
(3) Amination of the oxidation product: in order to solve the difficult problem of separating cyclohexanone oxime from byproduct-B in the oxidation reaction product, the invention provides that: firstly, the oxidation reaction product is not subjected to any separation, but is directly subjected to amination reaction with ammonia and hydrogen under the action of a solid catalyst. Under the catalytic reaction conditions of the present invention, the byproduct-B in the oxidation reaction product may be completely converted into cyclohexylamine, while cyclohexanone oxime does not react with ammonia and hydrogen. Since the boiling points of cyclohexanone oxime and cyclohexanone oxime are very different, the separation of cyclohexanone oxime and cyclohexanone oxime by rectification is easy.
The reaction scheme associated with amination of byproduct-B with ammonia and hydrogen is as follows:
(a)C 6 H 10 O+NH 3 +H 2 →C 6 H 11 NH 2 +H 2 O
(b)
(c)C 6 H 11 NO 2 +3H 2 →→C 6 H 11 NH 2 +2H 2 O
(d)C 6 H 10 ＝N-C 6 H 11 +NH 3 +H 2 →→2C 6 H 11 NH 2
(e)C 6 H 11 -NH-C 6 H 11 +NH 3 →→2C 6 H 11 NH 2
further, in the step (1), the active component of the solid catalyst is selected from one or more of transition metals of group VIII of the periodic table, preferably nickel, cobalt, copper, ruthenium, rhodium, palladium, etc. For example, when a cobalt-supported catalyst is adopted and the conversion rate is close to 100%, the selectivity of the cyclohexylamine can reach more than 90%; when the conversion rate is controlled to be about 90%, the selectivity of the cyclohexylamine can reach more than 97%.
Further, in the step (2), the solid catalyst is a surface hydroxyl-rich catalyst containing an active component, preferably titanium dioxide, silica gel, alumina, titanium phosphorus oxide composite oxide, meta-titanic acid, meta-silicic acid, tungsten trioxide and the like. For example, tiO with rich hydroxyl groups on the surface is prepared under the condition of the reaction temperature of 100 ℃ and the oxygen pressure of 1.2MPa 2 Or supported TiO 2 The MCM-41 is used as a catalyst, the conversion rate of the cyclohexane can reach more than 40%, the selectivity of the cyclohexanone oxime can reach 90%, and the balance is cyclohexanone, nitrocyclohexane, cyclohexane imine and N-cyclohexylcyclohexane imine.
Further, in the step (3), the solid catalyst is a catalyst formed by hydrotalcite or hydrotalcite-like compound transition metal simple substance active components, wherein the transition metal simple substance active components comprise a main active component and a auxiliary active component, and the main active component is one or more than two selected from VIII group transition metals in the periodic table of elements, preferably nickel, platinum and the like; the auxiliary active component is one or more than two transition metals selected from IB-VIIB groups in the periodic table of elements, preferably copper, iron and the like. For example, cyclohexanone, nitrocyclohexane, cyclohexylimine, N-cyclohexylimine and the like are almost completely converted into cyclohexylamine under the pressure conditions of hydrogen and ammonia at a reaction temperature of 100℃and 1.0MPa with hydrotalcite-based NiCu/MgAlO as a catalyst.
Further, in the step (1), the aniline is obtained by catalytic hydrogenation of nitrobenzene or by direct catalytic amination of benzene; the nitrobenzene is obtained by benzene catalytic nitration.
Compared with the prior art such as the method for industrially producing cyclohexanone oxime, the method proposed by the Japanese Asahi chemical industry (shown in figure 1), and the like, the invention (shown in figure 2) has the following beneficial effects:
(i) The new route for preparing the cyclohexanone oxime by oxidizing the cyclohexane from the aniline or the nitrobenzene not only avoids the problems of high cost and the like of hydrogen peroxide or hydroxylamine salt in the cyclohexanone oxime process, but also avoids the problems of high material and energy consumption and the like of preparing the cyclohexanone by oxidizing the cyclohexane and hydrating the cyclohexene, can obviously improve the yield of the cyclohexanone oxime, and obviously reduces the energy consumption and the cost of the cyclohexanone oxime production.
(ii) The oxidation reaction product of the cyclohexane and the molecular oxygen is not separated, and is directly subjected to amination reaction with ammonia and hydrogen under the action of a solid catalyst, so that all byproducts in the reaction product are converted into the cyclohexane, and then the separation of the cyclohexanone oxime and the cyclohexane is performed, thereby obviously reducing the separation difficulty and the separation energy consumption.
(iii) The production flow of the new route is shortened, and the equipment investment, the production land and the like are obviously reduced.
Drawings
FIG. 1 is a schematic view of a process for producing cyclohexanone oxime as described in the following.
FIG. 2 is a schematic view of a process for producing cyclohexanone oxime according to the present invention.
Detailed Description
The following examples are intended to illustrate the invention, but not to limit it.
Example 1
Benzene nitration to prepare nitrobenzene: 23.4 g of benzene (analytically pure > 99.8%) and 27.6 g of NO were weighed out 2 (purity > 99.8%) and 0.5 g AlCl 3 -SiO 2 The acid catalyst was added to a 100 ml reactor together, then 0.6Ma hydrogen was introduced, and the reaction was carried out at 25 ℃ for 2 hours, after the completion of the reaction, the solid catalyst was separated by filtration, and 39.7 g of a mixed solution was obtained. The solution is qualitatively determined by a gas chromatograph-mass spectrometer, and accurately quantified by a gas chromatograph-internal standard method (chlorobenzene is used as an internal standard), 0.11 g of benzene, 36.6 g of nitrobenzene and 0.012 g of by-product dinitrobenzene are measured, the conversion rate of benzene in the process is 99.5%, and the selectivity of nitrobenzene is 99.76%. And (3) rectifying and separating the filtrate obtained after the reaction to obtain high-purity nitrobenzene.
Example 2
Hydrogenation of nitrobenzene to prepare aniline: 30 g of nitrobenzene prepared as described in example 1 (purity: 99.8%) and 0.5 g of Pd/C catalyst were weighed and put into a 100 ml reaction vessel together, and then 30 g of ethylenediamine was added as a solvent, and hydrogen gas was introduced (pressure was maintained at 1.0 MPa) to react at 120℃for 4 hours, after the completion of the reaction, the solid catalyst was separated by filtration to obtain 61.38 g of a mixed solution. The solution is accurately quantified by adopting a gas chromatography internal standard method (chlorobenzene is used as an internal standard substance), the content of nitrobenzene and reaction products in the solution is analyzed, the solution is qualitatively analyzed by adopting a gas chromatograph-mass spectrometer, and 0.36 g of residual nitrobenzene is measured to obtain 22.25 g of aniline and 0.179 g of byproduct diphenylamine, wherein the conversion rate of nitrobenzene in the process is 98.8%, and the selectivity of aniline is 99.12%. The resulting solution after the reaction was subjected to rectification separation to obtain 21.5 g of aniline, the purity of which was 99.5%.
Example 3
Hydrogenation of nitrobenzene to prepare cyclohexane: 30 g of nitrobenzene (purity: 99.8%) prepared as described in example 1 and 0.5 g of Pt/C catalyst were weighed and put into a 100 ml reaction vessel together, and then 30 g of ethylenediamine was added as a solvent, and hydrogen gas (pressure: 1.2MPa was maintained) was introduced, and reacted at 140℃for 5 hours, after the completion of the reaction, the solid catalyst was separated by filtration to obtain 62.91 g of a mixed solution. The solution is qualitatively characterized by adopting a gas chromatograph-mass spectrometer, and accurately quantified by adopting a gas chromatography internal standard method (chlorobenzene is used as an internal standard), and 0.06 g of residual nitrobenzene, 23.95 g of cyclohexane, 0.05 g of byproduct aniline, 0.04 g of diphenylamine and 0.02 g of N-cyclohexylaniline are measured. The conversion of nitrobenzene in this process was 99.8% and the selectivity to cyclohexylamine was 99.5%. And (3) rectifying and separating the solution obtained after the reaction to obtain the high-purity cyclohexylamine.
Example 4
Hydrogenation of aniline to produce cyclohexylamine: 20 g of aniline prepared as described in example 2 (purity: 99.5%) and 0.5 g of Ni/C catalyst were weighed and put into a 100 ml reaction vessel together, 20 g of ethylenediamine was then added as a solvent, hydrogen gas was introduced (pressure was maintained at 1.2 MPa), the reaction was carried out at 140℃for 4 hours, and after the completion of the reaction, the solid catalyst was separated by filtration to obtain 42.48 g of a mixed solution. The solution is qualitatively determined by a gas chromatograph-mass spectrometer, and accurately quantified by a gas chromatography internal standard method (chlorobenzene is used as an internal standard), and 0.46 g of aniline, 20.5 g of cyclohexane, 0.28 g of byproduct dicyclohexylamine and 0.15 g of N-cyclohexylaniline are measured. The aniline conversion of this procedure was 97.7% and the selectivity to cyclohexylamine was 98.2%. And (3) rectifying and separating the solution obtained after the reaction to obtain the high-purity cyclohexylamine.
Example 5
Partial oxidation of cyclohexylamine: 15 g (purity 99.9%) of cyclohexylamine and TiO were weighed out as described in example 3 or example 4 2 0.5 g of MCM-41 catalyst is added into a 100 ml reaction kettle together, oxygen is introduced (the pressure is maintained at 1.0 megaPa), the reaction is carried out for 4 hours at 100 ℃, after the reaction is finished, the solid catalyst is filtered and separated, and 16.25 g of oxidation reaction liquid is obtained. The solution is qualitatively determined by a gas chromatograph-mass spectrometer and accurately quantified by a gas chromatograph-internal standard method (chlorobenzene is used as an internal standard), 8.78 g of cyclohexane, 6.42 g of cyclohexanone oxime, 0.45 g of byproduct nitrocyclohexane, 0.15 g of cyclohexanone, 0.07 g of cyclohexane imine and 0.03 g of N-cyclohexylcyclohexane, the conversion rate of the cyclohexane in the process is 41.6%, the selectivity of cyclohexanone oxime is 90.2%, the selectivity of nitrocyclohexane is 5.5%, the selectivity of cyclohexanone is 2.5%, the selectivity of cyclohexane imine is 1.2%, and the selectivity of N-cyclohexylcyclohexane imine is 0.6%.
Example 6
By-product amination: 12.98 g of the oxidation reaction solution prepared as described in example 5 (wherein 7 g of cyclohexane, 5.14 g of cyclohexanone oxime, 0.12 g of cyclohexanone, 0.36 g of nitrocyclohexane, 0.06 g of cyclohexylimine and 0.1 g of N-cyclohexylcyclohexylimine) was weighed and charged into a 50 ml reaction vessel together with 0.1 g of hydrotalcite-based Ni-Cu/MgAlO catalyst, and in a hydrogen-critical state, 0.1 MPa of ammonia gas (reaction pressure: maintained at 1.0 MPa) was introduced, and after the reaction was completed, the solid catalyst was separated by filtration to obtain 13.05 g of a mixed solution, which was subjected to qualitative analysis by a gas chromatograph and accurately quantified by a gas chromatography internal standard method (chlorobenzene as an internal standard), and 7.40 g of cyclohexylamine, 5.22 g of cyclohexanone oxime and 0.001 g of N-cyclohexylimine were measured. Finally, 7.3 g of cyclohexane is obtained through rectification separation, the purity is 99.9%, the cyclohexanone oxime is 5.2 g, and the purity is 99.8%.
Example 7
2 g of by-product diphenylamine obtained by repeating example 2 for 15 times and 2 g of N-cyclohexylaniline obtained by repeating example 3 for 15 times were taken as reaction raw materials, and 0.1 g of Ni-Co/gamma-Al was taken 2 O 3 As a catalyst, added into a 50 ml reaction kettle together, added with 20 g of ethylenediamine as a solvent, introduced with hydrogen (the pressure is maintained at 1.0 megapascal), reacted for 3 hours at 160 ℃, and after the reaction is finished, the solid catalyst is filtered and separated to obtain 24.21 g of mixed solution. The solution adopts a gas chromatography internal standard method (chlorobenzene is used as an internal standard) to accurately quantify, the contents of diphenylamine, N-cyclohexylaniline and reaction products in the solution are analyzed,and the obtained product is qualitatively characterized by adopting a gas chromatograph-mass spectrometer, and the residual diphenylamine is 0.01 g and the N-cyclohexylaniline is 0.005 g, so that the dicyclohexylamine is 4.18 g. The conversion of diphenylamine in this process was 99.5%, the conversion of N-cyclohexylaniline was 99.75%, and the selectivity to dicyclohexylamine was 99.76%. The solution obtained after the reaction was subjected to rectification separation to obtain 3.98 g of dicyclohexylamine, whose purity was 99.9%.
Claims (6)
1. A method for preparing cyclohexanone oxime, comprising the steps of:
(1) Hydrogenation of aniline or nitrobenzene: carrying out hydrogenation reaction on aniline or nitrobenzene and hydrogen under the action of a solid catalyst to generate cyclohexylamine and a small amount of byproducts, namely byproduct-A, and separating the byproduct-A and the aniline which is possibly not completely converted to obtain cyclohexylamine;
(2) Oxidation of cyclohexylamine: carrying out oxidation reaction on the cyclohexylamine obtained in the step (1) and molecular oxygen under the action of a solid catalyst, wherein the obtained oxidation reaction product mainly contains cyclohexanone oxime, and also contains a small amount of byproducts, namely byproduct-B and possibly unconverted cyclohexylamine;
(3) Amination of the oxidation product: directly carrying out amination reaction on the oxidation reaction product obtained in the step (2) with ammonia and hydrogen under the action of a solid catalyst without separation, completely converting byproducts-B in the oxidation reaction product into cyclohexylamine, and separating the cyclohexylamine to obtain cyclohexanone oxime;
the byproduct-A in the step (1) is one or more than two of dicyclohexylamine, N-cyclohexylaniline and diphenylamine;
the byproduct-B in the step (2) is one or more than two of cyclohexanone, nitrocyclohexane, cyclohexylimine, dicyclohexylamine and N-cyclohexylimine;
in the step (3), rectification is adopted for separation, and the separated cyclohexylamine is recycled for oxidation reaction in the step (2);
the solid catalyst in the step (3) is a catalyst formed by hydrotalcite or hydrotalcite-like compound transition metal simple substance active components, wherein the transition metal simple substance active components comprise main active components and auxiliary active components, and the main active components are one or more than two selected from VIII group transition metals in the periodic table of elements; the auxiliary active component is one or more than two transition metals selected from IB-VIIB groups in the periodic table of elements.
2. The process of claim 1, wherein in step (1), the aniline obtained by separation is recycled for hydrogenation by distillation, and the by-product-A obtained by separation can be directly used as a by-product.
3. The process of claim 1 or 2, wherein the active component of the solid catalyst of step (1) is selected from one or more of transition metals of group VIII of the periodic table of elements.
4. A process according to claim 3, wherein the solid catalyst of step (2) is a surface hydroxyl rich catalyst containing an active component.
5. The process of claim 1, wherein the active component of the solid catalyst of step (1) is selected from one or more of nickel, cobalt, copper, ruthenium, rhodium and palladium; the solid catalyst in the step (2) is one or more than two of titanium dioxide, silica gel, alumina, titanium phosphorus oxide composite oxide, meta-titanic acid, meta-silicic acid and tungsten trioxide; the solid catalyst in the step (3) is characterized in that the main active component is platinum or/and nickel, and the auxiliary active component is copper or/and iron.
6. The process of claim 1, wherein the aniline of step (1) is obtained by catalytic hydrogenation of nitrobenzene or by direct catalytic amination of benzene; the nitrobenzene is obtained by benzene catalytic nitration.
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