CN111517984B - Method for synthesizing cyclohexanone oxime by catalyzing cyclohexanone with titanium ammonium phosphotungstate - Google Patents

Abstract

The invention relates to a method for synthesizing cyclohexanone oxime from cyclohexanone catalyzed by ammonium phosphotungstate titanium salt. The method comprises the following steps: adding cyclohexanone, ammonia water, hydrogen peroxide and ammonium phosphotungstate titanium salt into the reactor, and reacting under normal pressure at 20-60°C under stirring in the presence of a solvent or without a solvent 3-7 hours, after the reaction is completed, wait until the temperature drops to room temperature to obtain the product cyclohexanone oxime; wherein, the molar ratio of the materials is cyclohexanone: ammonia water: hydrogen peroxide: ammonium phosphotungstate titanium salt = 1:0.5-2.5:0.5 ‑2.5: 0.1‑1; when there is a solvent, the volume ratio is: cyclohexanone: solvent = 1: 3 ~ 8. The invention has the advantages of high efficiency, environmental protection, mild reaction conditions, easy catalyst separation and the like.

Description

A kind of method that catalyzed cyclohexanone synthesizes cyclohexanone oxime by ammonium phosphotungstate titanium salt

technical field

The invention relates to the synthesis of organic chemical products, in particular to a process for synthesizing cyclohexanone oxime by using an ammonium phosphotungstate titanium salt as a catalyst to catalyze cyclohexanone liquid-phase ammoximation.

Background technique

Cyclohexanone oxime (abbreviated as CHO) is an important organic intermediate for the synthesis of ε-caprolactam, and caprolactam is one of the important organic raw materials. It has been widely used in various industries such as synthetic fibers, nylon-6, plastics and resins. field (Li Dawei, Synthetic Fiber Industry, 2016(4):61-64). In recent years, with the increasing demand for cyclohexanone oxime, researchers have begun to try to use different catalysts to synthesize cyclohexanone oxime in order to reduce the cost of catalyst preparation and optimize the production process.

A series of catalysts for catalyzing the synthesis of cyclohexanone oxime from cyclohexanone have been developed at home and abroad, such as silicides, heteropolyacids, heteropoly compounds, etc. The study found that heteropolyacids showed high catalytic activity in catalytic oxidation reactions. Heteropolyacids have the characteristics of green, non-toxic, high activity and selectivity, but there are also problems such as easy loss of active components and difficulty in separating the catalyst from the reaction system after the reaction. In order to solve the above problems, methods such as loading the heteropolyacid on a porous carrier or converting it into an insoluble heteropolyacid salt catalyst have been adopted. Compared with supported heteropolyacids, heteropolyacid salt catalysts are easy to prepare and widely used in ammoximation reactions. Such as sodium phosphotungstate, potassium phosphotungstate and ammonium phosphotungstate (Zeng Xiang et al., Journal of Petroleum (Petroleum Processing), 2010 (5): 779-784), single transition metal substituted ammonium zirconium phosphotungstate Salt, ammonium phosphotungstate cobalt salt, ammonium phosphotungstate nickel salt and ammonium phosphotungstate copper salt (Liu Biyu et al., Molecular Catalysis, 2018, 28(2):140-147), and quaternary ammonium phosphotungstate, Pyridinium phosphotungstate, imidazolium phosphotungstate and a series of new organic-inorganic compound heteropolyacid salts (Zeng Yuanhui, master thesis, Xiangtan University, 2010) and other catalysts can catalyze the synthesis of cyclohexanone oxime from cyclohexanone ammoximide . However, the above-mentioned single-type heteropolyacid salt catalysts still have defects such as low catalytic activity, easy loss of active components, or difficulty in catalyst recovery.

Therefore, it is still an urgent problem to be solved by researchers in this field to develop a green, efficient, stable and easy-to-separate catalyst from the reaction system, and to use it in the ammoximation reaction of cyclohexanone and to optimize the production process.

Contents of the invention

The present invention aims at the current complex production process of cyclohexanone oxime and the problems of low catalytic activity, easy loss of active components or difficulty in catalyst recovery when using a single heteropoly salt catalyst, and provides a titanium ammonium phosphotungstate The invention discloses a method for synthesizing cyclohexanone oxime from cyclohexanone. The method realizes the synthesis of cyclohexanone oxime under mild conditions by using cyclohexanone as a raw material and using ammonium phosphotungstate titanium salt as a catalyst for the first time. The invention has the advantages of high efficiency, environmental protection, mild reaction conditions, easy catalyst separation and the like.

Concrete technical scheme of the present invention is as follows:

A method for catalyzing cyclohexanone to synthesize cyclohexanone oxime by ammonium phosphotungstate titanium salt, the method comprises the following steps:

Add cyclohexanone, ammonia water, hydrogen peroxide and ammonium phosphotungstate titanium salt into the reactor, and react under normal pressure 20-60°C under stirring for 3-7 hours in the presence of solvent or without solvent, and the reaction is completed After the temperature drops to room temperature, the product cyclohexanone oxime is obtained;

Among them, the material molar ratio is cyclohexanone: ammonia water: hydrogen peroxide: ammonium phosphotungstate titanium salt = 1: 0.5-2.5: 0.5-2.5: 0.1-1; when there is a solvent, the volume ratio is, ring Hexanone: solvent = 1: 3 ~ 8;

Described solvent is specifically ethanol, acetonitrile, tert-butanol, cyclohexane or water;

The method also includes the recovery of the ammonium phosphotungstate titanium salt catalyst, including the following steps: after the reaction is completed, adding an extractant for extraction, the reaction solution is divided into two layers, the upper layer is an organic phase containing the product cyclohexanone oxime, and the lower layer is an organic phase containing cyclohexanone oxime. Contains ammonium phosphotungstate titanium salt phase; the lower liquid is distilled under reduced pressure to remove water and dried for the next round of reaction;

Wherein, the volume ratio is cyclohexanone:extractant=1:1-3.

The extractant is toluene.

Beneficial effects of the present invention:

(1) This method realizes for the first time that ammonium phosphotungstate titanium salt is used as a catalyst for the synthesis of cyclohexanone oxime from cyclohexanone amidoxime. The ammonium phosphotungstate titanium salt catalyst involved in the invention has a better keggin structure, excellent catalytic performance, can effectively catalyze the ammoximation reaction of cyclohexanone, and has high selectivity of the product cyclohexanone oxime.

(2) The raw materials required for the catalyst are easy to obtain, cheap, simple in the preparation process, and high in catalytic efficiency. After the reaction, the reaction solution is divided into two layers, the catalyst and the product are easy to separate, and can be recycled, so it has a good application prospect.

(3) Compared with the existing preparation of cyclohexanone oxime with cyclohexanone as raw material and titanium silicon molecular sieve as catalyst, the reaction uses ammonium phosphotungstate titanium salt as catalyst, and the reaction is carried out at normal pressure and low temperature of 20-60°C The target product cyclohexanone oxime can be obtained after 3-7 hours of reaction. The reaction conditions are mild (compared with the reaction using titanium silicon molecular sieve as catalyst, the temperature can be reduced from 80 ° C to 20 ° C), which can effectively avoid the decomposition of hydrogen peroxide. And then improve the utilization rate of hydrogen peroxide. This method realizes for the first time that ammonium phosphotungstate titanium salt is used as a catalyst for the synthesis of cyclohexanone oxime from cyclohexanone amidoxime. The ammonium phosphotungstate titanium salt catalyst involved in the invention has a better keggin structure, excellent catalytic performance, can effectively catalyze the ammoximation reaction of cyclohexanone, and has high selectivity of the product cyclohexanone oxime. The conversion rate of cyclohexanone was 92.5%, and the selectivity of cyclohexanone oxime was 91.0%.

Detailed ways

The essential features and remarkable effects of the present invention can be manifested from the following examples, but they do not limit the present invention in any way, and those skilled in the art can make some non-essential improvements and adjustments according to the contents of the present invention. The present invention will be further described below through specific embodiments.

Reaction mechanism of the present invention is:

The method realizes the one-step clean synthesis of cyclohexanone oxime by using cyclohexanone as a raw material and ammonium phosphotungstate titanium salt as a catalyst.

The ammonium phosphotungstate titanium salt described in the present invention is a known substance, and its simplified structure is: (NH ₄ ) ₅ PW ₁₁ TiO ₃₉ . Its preparation process comprises the following steps:

(1) dissolving titanium sulfate, ammonium salt and sodium phosphotungstate in water to form a solution;

(2) After the reaction, filter and recrystallize to obtain the ammonium phosphotungstate titanium salt.

Example 1

The preparation process of the ammonium phosphotungstate titanium salt catalyst involved in the present invention is as follows:

Dissolve titanium sulfate solution (6mmol) in 1mL sulfuric acid (2M), add it to the aqueous solution containing 6mmol sodium phosphotungstate, and use 1mol L ^-1 NaHCO ₃ solution to adjust the pH value to 4.0–5.0.60 Stir at ℃ for 30 minutes, add 0.01mol of NH ₄ Cl and continue stirring for 2 hours to stop the reaction, filter the obtained reaction product, and recrystallize with water for 3 times to obtain phosphotungstic acid with the molecular formula (NH ₄ ) ₅ PW ₁₁ TiO ₃₉ ammonium titanium salt.

Example 2

Add cyclohexanone (0.05mol), ammonium phosphotungstate titanium salt (0.0125mol), ammonia water (0.075mol-the concentration of ammonia water is 25%) and hydrogen peroxide (0.025mol-the concentration of hydrogen peroxide is 30%) into the flask , magnetically stirred, reacted at normal pressure and 30° C. for 3 hours, then stopped the reaction. The reaction solution was cooled to room temperature, and the reaction solution was extracted with toluene (5ml-15ml); the reaction solution was divided into two layers, the upper layer was an organic phase containing the product cyclohexanone oxime, and the lower layer was a phase containing ammonium phosphotungstate titanium salt; the lower layer liquid After vacuum distillation to remove water and drying, it was used for the next round of reaction; the supernatant was taken as an internal standard with n-heptanol, and analyzed on gas chromatography. The reaction result was that the conversion rate of cyclohexanone was 72.49%, and the The selectivity of oxime is 60.58%.

Example 3

Other steps are the same as in Example 2, except that before the reaction, 4 times the volume of solvent ethanol of cyclohexanone is added to the system. The reaction result is that the conversion rate of cyclohexanone is 56.39%, and the selectivity of cyclohexanone oxime is 39.53%. .

Example 4

Other steps are the same as in Example 3, except that the added solvent is changed to acetonitrile, the reaction result is that the conversion rate of cyclohexanone is 48.86%, and the selectivity of cyclohexanone oxime is 36.23%.

Example 5

Other steps are the same as in Example 3, except that the added solvent is changed to cyclohexane, and the reaction result is that the conversion rate of cyclohexanone is 43.56%, and the selectivity of cyclohexanone oxime is 34.78%.

Example 6

Other steps are the same as in Example 3, except that the added solvent is changed to tert-butanol, the reaction result is that the conversion rate of cyclohexanone is 60.35%, and the selectivity of cyclohexanone oxime is 40.26%.

Example 7

Other steps are the same as in Example 3, except that the added solvent is changed to water, and the reaction result is that the conversion rate of cyclohexanone is 69.29%, and the selectivity of cyclohexanone oxime is 54.86%.

Example 8

Other steps are the same as in Example 2, except that the added ammonium phosphotungstate titanium salt is 0.005 mol, and the reaction result is that the conversion rate of cyclohexanone is 68.34%, and the selectivity of cyclohexanone oxime is 56.23%.

Example 9

Other steps are the same as in Example 2, except that the added ammonium phosphotungstate titanium salt is 0.025 mol, and the reaction result is that the conversion rate of cyclohexanone is 78.61%, and the selectivity of cyclohexanone oxime is 72.78%.

Example 10

The other steps are the same as in Example 2, except that the added ammonium phosphotungstate titanium salt is 0.0375 mol, the reaction result is that the conversion rate of cyclohexanone is 78.82%, and the selectivity of cyclohexanone oxime is 73.12%.

Example 11

The other steps are the same as in Example 2, except that the added ammonium phosphotungstate titanium salt is 0.05 mol, the reaction result is that the conversion rate of cyclohexanone is 79.03%, and the selectivity of cyclohexanone oxime is 73.83%.

Example 12

Other steps are the same as in Example 9, except that the added ammonia water is 0.025 mol, the reaction result is that the conversion rate of cyclohexanone is 62.26%, and the selectivity of cyclohexanone oxime is 46.38%.

Example 13

The other steps were the same as in Example 9, except that the amount of ammonia water added was 0.05 mol. The reaction result showed that the conversion rate of cyclohexanone was 69.31%, and the selectivity of cyclohexanone oxime was 54.23%.

Example 14

The other steps were the same as in Example 9, except that the amount of ammonia water added was 0.1 mol. The reaction result showed that the conversion rate of cyclohexanone was 73.47%, and the selectivity of cyclohexanone oxime was 64.22%.

Example 15

The other steps are the same as in Example 9, except that the amount of ammonia water added is 0.125 mol, the reaction result is that the conversion rate of cyclohexanone is 69.92%, and the selectivity of cyclohexanone oxime is 62.24%.

Example 16

Other steps are the same as in Example 9, except that the added hydrogen peroxide is 0.025 mol, the reaction result is that the conversion rate of cyclohexanone is 80.35%, and the selectivity of cyclohexanone oxime is 76.28%.

Example 17

Other steps are the same as in Example 9, except that the added hydrogen peroxide is 0.075 mol, the reaction result is that the conversion rate of cyclohexanone is 85.39%, and the selectivity of cyclohexanone oxime is 80.34%.

Example 18

The other steps were the same as in Example 9, except that the added hydrogen peroxide was 0.1 mol, and the reaction result was that the conversion rate of cyclohexanone was 80.02%, and the selectivity of cyclohexanone oxime was 78.36%.

Example 19

Other steps are the same as in Example 9, except that the added hydrogen peroxide is 0.125 mol, the reaction result is that the conversion rate of cyclohexanone is 72.03%, and the selectivity of cyclohexanone oxime is 73.32%.

Example 20

Other steps were the same as in Example 17, except that the reaction temperature was 20° C., and the reaction result was that the conversion rate of cyclohexanone was 75.32%, and the selectivity of cyclohexanone oxime was 63.25%.

Example 21

Other steps were the same as in Example 17, except that the reaction temperature was 40° C., and the reaction result was that the conversion rate of cyclohexanone was 83.25%, and the selectivity of cyclohexanone oxime was 79.96%.

Example 22

Other steps were the same as in Example 17, except that the reaction temperature was 50° C., the reaction result was that the conversion rate of cyclohexanone was 73.01%, and the selectivity of cyclohexanone oxime was 68.20%.

Example 23

Other steps are the same as in Example 17, except that the reaction temperature is 60° C., the reaction result is that the conversion rate of cyclohexanone is 60.13%, and the selectivity of cyclohexanone oxime is 53.68%.

Example 24

The other steps were the same as in Example 17, except that the reaction time was 4 hours. The reaction result showed that the conversion rate of cyclohexanone was 86.35%, and the selectivity of cyclohexanone oxime was 83.28%.

Example 25

The other steps were the same as in Example 17, except that the reaction time was 5 hours. The reaction result showed that the conversion rate of cyclohexanone was 90.36%, and the selectivity of cyclohexanone oxime was 89.44%.

Example 26

The other steps are the same as in Example 17, except that the reaction time is 6 hours. The reaction result is that the conversion rate of cyclohexanone is 91.17%, and the selectivity of cyclohexanone oxime is 89.13%.

Example 27

The other steps are the same as in Example 17, except that the reaction time is 7 hours. The reaction result is that the conversion rate of cyclohexanone is 92.5%, and the selectivity of cyclohexanone oxime is 91.0%.

Example 28

Other steps are the same as in Example 25, except that after the reaction liquid is cooled to room temperature, the ammonium phosphotungstate titanium salt is recovered, and the recovered ammonium phosphotungstate titanium salt and the newly produced Ammonium phosphotungstate titanium salt for comparison. The conversion rate of cyclohexanone and the selectivity of cyclohexanone oxime are basically unchanged, indicating that after the reaction, the ammonium phosphotungstate titanium salt still has a keggin structure, and the catalyst can be recycled and reused, thus realizing the environmentally friendly cyclohexanone Oxime synthesis process.

Summary table of 28 implementation examples

The influence of table 1 solvent on cyclohexanone ammoximation reaction

Table 1 Influence ofsolvent on ammoximation of cyclohexanone

The impact of table 2 catalyst dosage on cyclohexanone ammoximation reaction

Table2 Influence of the amount of catalyst on ammoximation of cyclohexanone

The influence of table 3 ammoniacal liquor addition amount on cyclohexanone ammoximation reaction

Table 3 Influence of the addition of ammonia on ammoximation of cyclohexanone

The influence of table 4 hydrogen peroxide addition amount on cyclohexanone ammoximation reaction

Table4 Influence of the addition of hydrogen peroxide on ammoximation of cyclohexanone

The influence of table 5 reaction temperature on cyclohexanone ammoximation reaction

Table 5Influence of the reaction temperature on ammoximation of cyclohexanone

The impact of table 6 reaction time on cyclohexanone ammoximation reaction

Table 6Influence of the reaction time on ammoximation of cyclohexanone

As can be seen from the examples, the ammonium phosphotungstate titanium salt has higher catalytic activity as a catalyst to catalyze the ammoximation reaction of cyclohexanone, and the reaction conditions such as material ratio, reaction temperature, and reaction time have certain effects on the ammoximation reaction of cyclohexanone. Larger impact, suitable reaction conditions can significantly improve the yield of cyclohexanone oxime. In addition, for the reaction solvent, the catalytic effect is better under the condition of no solvent, and at the same time, the use of solvent and subsequent separation are avoided when there is no solvent, which saves cost.

Matters not covered in the present invention are known technologies. It should be understood that although the present invention has been clearly described through the above embodiments, those skilled in the art can make various corresponding changes and modifications according to the present invention without departing from the spirit and essence of the present invention. But these corresponding changes and amendments should all belong to the protection scope of the claims of the present invention.

Claims (2)

1. A method for synthesizing cyclohexanone oxime by catalyzing cyclohexanone with titanium ammonium phosphotungstate is characterized by comprising the following steps:

adding cyclohexanone, ammonia water, hydrogen peroxide and ammonium titanium phosphotungstate into a reactor, reacting for 3-7h under the condition of no solvent and under the condition of normal pressure of 20-60 ℃ and stirring, and cooling to room temperature after the reaction is finished to obtain a product cyclohexanone-oxime;

wherein the molar ratio of materials is cyclohexanone: ammonia water: hydrogen peroxide: ammonium titanium phosphotungstate =1:0.5-2.5:0.5-2.5:0.1 to 1;

the structural formula of the ammonium titanium phosphotungstate is as follows: (NH) ₄ ) ₅ PW ₁₁ TiO ₃₉ 。

2. The method for synthesizing cyclohexanone oxime by catalyzing cyclohexanone with titanium ammonium phosphotungstate according to claim 1, wherein the method further comprises recovering the titanium ammonium phosphotungstate catalyst, and comprises the following steps: after the reaction is finished, adding an extracting agent for extraction, and dividing the reaction liquid into two layers, wherein the upper layer is an organic phase containing the product cyclohexanone oxime, and the lower layer is a titanium salt phase containing ammonium phosphotungstate; distilling the lower layer liquid under reduced pressure to remove water, drying, and using for the next reaction;

wherein, the volume ratio is cyclohexanone: extractant =1:1 to 3; the extractant is toluene.