CN116496175A - A kind of preparation method of cyclohexanone cyanohydrin - Google Patents

Abstract

The invention relates to the technical field of synthesis of organic chemicals, and discloses a preparation method of cyclohexanone cyanohydrin, which comprises the following steps: step one, a raw material premixing stage: fully premixing raw material hydrocyanic acid and cyclohexanone to form a mixed solution; step two, a reaction stage: mixing the mixed solution and the catalyst, and heating for reaction to obtain a reaction solution; step three, removing impurities: and (3) regulating the pH value of the reaction solution obtained in the step (II), and removing unreacted raw material hydrocyanic acid through flash evaporation to obtain the product cyclohexanone cyanohydrin. In the production process of cyclohexanone cyanohydrin, only raw materials are required to be uniformly mixed in advance, unreacted raw materials or raw materials generated by reverse reaction in a reaction solution are removed by flash evaporation after catalytic reaction, and then the cyclohexanone cyanohydrin product can be obtained; the method can realize continuous operation, effectively avoid the steps of using and recycling the organic solvent, has simple production process, ensures that the obtained product has high quality (the purity of the obtained product is up to 99.77 percent), effectively simplifies the production flow and improves the economic benefit.

Description

A kind of preparation method of cyclohexanone cyanohydrin

technical field

The invention relates to the technical field of organic chemical synthesis, in particular to a preparation method of cyclohexanone cyanohydrin.

Background technique

Cyclohexanone cyanohydrin is an important intermediate for the synthesis of spirodiclofen. Because its molecule contains active α-hydroxyl and cyano groups, it can undergo a series of reactions such as dehydration, hydrolysis, ammonolysis, alcoholysis and cyclization, and derive many Widely used as fine chemical products such as medicine, pesticide, food and feed additives, coating additives, etc. Therefore, it is of great significance to study the synthesis of cyclohexanone cyanohydrin.

The synthesis of cyclohexanone cyanohydrin mainly contains two kinds of methods at present, and a kind of method is to be raw material with the solid state of cyclohexanone and sodium cyanide or solution and hydrochloric acid, reacts and synthesizes in water system, and this method reacts rapidly, and product quality is relatively high. Good, but the utilization rate of atoms is low, a large amount of cyanide-containing waste brine is produced in the synthesis process, and the environmental friendliness is extremely poor; another method is to use hydrocyanic acid and cyclohexanone as raw materials, with organic bases (such as: methylamine, Diethylamine and triethylamine, etc.) or inorganic bases (sodium hydroxide and potassium hydroxide, etc.) as a catalyst, after reacting in an organic solvent or water system, add acid to acidify, then remove the solvent by heating, filter or phase separation The product is obtained after dehydration and drying.

Compared with the first method, the second method greatly reduces the amount of three wastes in the synthesis process, and the operating conditions are milder. Yet the second method (using organic base or inorganic base as catalyst to produce cyclohexanone cyanohydrin) still has the following disadvantages: (1) the reaction conditions are harsh, and the pH needs to be adjusted to 7～10 in advance; The transfer of ketone cyanohydrin to increase the conversion rate of the substrate uses an organic solvent to extract the product. On the one hand, the product purification process is complicated (organic solvents, unreacted raw materials and products need to be distilled in batches), and continuous production cannot be achieved. And energy consumption is higher; On the other hand, organic solvent reclaims difficulty, causes environmental pollution easily; Form salt with acid, causing waste of resources and environmental pollution.

Therefore, the development of a preparation method of cyclohexanone cyanohydrin with mild reaction conditions, simple preparation process, continuous production, and no waste generation can not only effectively make up for the shortcomings of the existing preparation methods of cyclohexanone cyanohydrin, but also has important economic and environmental benefits.

Contents of the invention

The present invention intends to provide a method for preparing cyclohexanone cyanohydrin, so as to solve the technical problem in the existing production of cyclohexanone cyanohydrin that cannot be continuously produced due to the complexity of the preparation process.

In order to achieve the above object, the present invention adopts following technical scheme: a kind of preparation method of cyclohexanone cyanohydrin comprises the steps:

Step 1, raw material premixing stage: fully premixing the raw material hydrocyanic acid and cyclohexanone to form a mixed solution;

Step 2. Reaction stage: pump the above-mentioned mixed solution into a reactor filled with a catalyst, and heat the reaction to obtain a reaction solution;

Step 3, impurity removal: adjust the pH of the reaction solution obtained in step 2, remove the unreacted raw material hydrocyanic acid in the reaction solution by flash evaporation, and obtain the product cyclohexanone cyanohydrin.

The principle and advantages of this scheme are:

1. Compared with the complex production process of the existing cyclohexanone cyanohydrin, in the production process of cyclohexanone cyanohydrin in this scheme, only the raw materials need to be mixed in advance, and the unreacted raw materials or The raw material that reverse reaction produces can obtain cyclohexanone cyanohydrin product; This scheme can realize continuous production, and its production process is simple, and the product quality of gained is high (as shown in Figure 2, the purity of the resulting product produced by this scheme is as high as 99.77%) ), effectively simplify the production process and improve economic efficiency.

2. The preparation method of cyclohexanone cyanohydrin provided by the present invention effectively avoids the use of organic solvents. On the one hand, it reduces the cost and energy consumption of organic solvent utilization and recycling plates; The pollution to the environment caused by the difficulty in recovering the organic solvent improves the environmental protection benefits of production.

3. In the preparation method of cyclohexanone cyanohydrin provided by the present invention, the catalyst is loaded in the reactor and does not enter the subsequent impurity removal process with the reaction solution, which facilitates the recycling of the catalyst on the one hand; on the other hand, effectively avoids the traditional preparation method The use of catalysts such as organic acids, organic bases and inorganic bases reduces the generation of waste water and solid waste; and the operation is simple, the product yield is high, and large-scale industrial production is easy to realize.

Preferably, in step 1, the molar ratio of the raw material hydrocyanic acid to cyclohexanone is 1-10:1.

Beneficial effects: By adopting the molar ratio of the above-mentioned raw materials, this scheme facilitates the positive progress of the synthesis reaction with redundant raw materials and improves the product yield. The applicant found through experiments that the molar ratio of raw materials hydrocyanic acid and cyclohexanone is preferably 1-3:1, which can further promote the conversion rate of raw materials and product yield in the production process, reduce the amount of raw materials used, and improve production efficiency. And when adopting too little hydrocyanic acid (as adopting hydrocyanic acid and cyclohexanone mol ratio in comparative example 2 is 0.5:1), even slow down the flow velocity of raw material mixed solution, prolong the contact time of raw material and catalyzer, raw material ring The conversion rate of hexanone is still significantly reduced (the conversion rate of cyclohexane in Comparative Example 2 is only 20.1%), thereby significantly reducing the raw material utilization rate and product yield.

Preferably, in step 2, the reactor is a static mixing heat exchange reactor, and the mixed solution is pumped into the static mixing heat exchange reactor at a speed of 1.4-2.8 g/min to react for 3-6 hours.

Beneficial effects: This scheme adopts the above-mentioned pumping speed to effectively ensure sufficient mixing between raw materials, sufficient contact between raw materials and catalysts, and promote the conversion of substrates into products; and this scheme effectively promotes The reaction is carried out continuously, thereby improving production efficiency. This scheme is carried out continuously, and the reaction time is inversely proportional to the flow rate of the mixed solution, that is, when a higher flow rate is selected, the reaction time is correspondingly shortened; when a lower flow rate is selected, the reaction time is relatively prolonged. This program is specifically carried out in a static mixing heat exchange reactor (reactor C in Figure 1). The non-stirring reaction is realized through the high-efficiency heat exchange function of the reactor, and the unreacted reaction is realized through the flash tank F connected in series with the reactor C. Thorough separation of the raw material hydrocyanic acid and the product, so as to realize the continuous process of the entire reaction stage and post-treatment stage, and by fixing the catalyst in the interior of the reactor C, the efficient utilization and continuous application of the catalyst can be realized. When the applicant adopts too fast flow rate (as selecting 8.3g/min in comparative example 1), the mixed solution causes the reaction time too short (reaction time is 1h among the comparative example 1) because of flowing too fast, causes the incomplete reaction of substrate and Reduced conversion of the substrate cyclohexanone.

Preferably, in step 2, the reaction is at a temperature of 60-80°C.

Beneficial effect: this scheme carries out the reaction under the above-mentioned condition parameters, and can obtain higher substrate conversion rate and product yield. The applicant has found through long-term experiments that the reaction conditions of this scheme are milder and the product yield is higher. However, if the reaction temperature is too high (such as the reaction at 120°C for use in Comparative Example 6 and the reaction at 130°C for use in Comparative Example 7), the special stable structure of the six-membered ring of the substrate cyclohexanone will result. More inclined to enol formula in the interconversion of formula; And then make cyclohexanone ring-opening and produce by-product, reduce product selectivity, influence product purity and yield; reaction), then the conversion rate of the substrate will be reduced (the conversion rate of cyclohexanone is only 43.8% in comparative example 5) because the reaction speed drops.

Preferably, in step 2, the catalyst is used in an amount of 2-4% of the mass of cyclohexanone.

Beneficial effect, this scheme adopts the catalyst of the above quality, which can efficiently and quickly catalyze the synthesis of cyclohexanone cyanohydrin from hydrocyanic acid and cyclohexanone, effectively reducing the amount and cost of the catalyst. The applicant finds through long-term experiment, if adopt lower catalyst consumption (select the catalyst of quality 0.5% of cyclohexanone as comparative example 3, select the catalyst of 0.3% of quality of cyclohexanone as comparative example 4), then because catalyst consumption is too low And reduce the reaction efficiency, thereby reducing the substrate conversion rate and product yield.

Preferably, in step 2, the catalyst is a solid base catalyst M/N, the solid base catalyst M/N is composed of an active component M and a carrier N, and the amount of the active component M is 10% of the mass of the carrier N ~50%.

Beneficial effects: Compared with the prior art when organic base (liquid) and inorganic base (powder solid) are used, the catalyst and reaction solution cannot be quickly separated and the catalyst cannot be recovered, this scheme uses a solid base catalyst, which is convenient for fixing the solid base catalyst Packed in the reactor, so as to effectively prevent the catalyst from being mixed in the reaction solution during the reaction process, which will cause the catalyst to be unrecoverable and increase the cost; in addition, the solid base catalyst of this scheme can be recovered quickly, and it can also effectively avoid acid-base neutralization when adjusting the pH. Salt , thereby effectively reducing the amount of wastewater.

Preferably, the active ingredient M is any one of metal salts of Ca, K, Mg, Na, Zn and Ni, and the metal salts are hydroxides, nitrates, hydrochlorides or carbonates Any one; the carrier N is any one of γ-Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SBA-15, activated carbon, HY-5 and HZSM-5.

Beneficial effect: This scheme uses the above-mentioned active component M and carrier N to produce a "supported" solid base catalyst, and can obtain a solid base catalyst with good catalytic effect. The applicant has found through long-term experiments that the solid base catalyst M/N prepared by this scheme has a higher substrate conversion rate (up to 98.9%) and product selection when catalyzing hydrocyanic acid and cyclohexanone to synthesize cyclohexanone cyanic acid. (up to 98.9%), not only can effectively improve the reaction efficiency, but also reduce the formation of by-products in the reaction, and improve the product yield.

Preferably, the preparation method of the solid base catalyst M/N is as follows:

S1. Carrier pretreatment: Disperse the carrier N in water, boil it at 50-100°C for 4 hours, then filter it with suction, dry it in vacuum at 120°C for 4 hours, then place it in a muffle furnace and bake it at 550°C for 3 hours to obtain the pretreated carrier ;

S2. Prepare the metal salt solution of the active ingredient M: mix the metal salt of the active ingredient M with a solvent to prepare a metal salt solution; the solvent is any one of 5-10% dilute hydrochloric acid solution, water or ethanol;

S3. Mix the pretreated carrier obtained in step S1 with the metal salt solution prepared in S2, heat up to 60° C. and stir for 8 hours, and then vacuum-dry at 105° C. for 15 hours to obtain a catalyst precursor;

S4. Put the catalyst precursor prepared in S3 in a muffle furnace, and calcinate at 500° C. for 5 hours to obtain a solid base catalyst M/N.

Beneficial effects: the preparation method of the supported solid base catalyst M/N provided by the present invention is a common impregnation method in the field of catalysis. The activity can be restored by high-temperature roasting, which greatly reduces the cost of raw materials for the production of cyclohexanone cyanohydrin. The applicant found through long-term experiments that the solid base catalyst M/N prepared by this scheme (such as the 10% loading CaO/γ-Al ₂ O ₃ obtained in Example 10) still has a relatively high cyclohexene concentration after 24 hours of continuous production. Ketone conversion (84.5%) and cyclohexanone cyanohydrin selectivity (99%); And after this part of catalyst is reclaimed and roasted again, it still can have higher catalytic efficiency (after putting into production 4h again as regenerated catalyst, The conversion rate of cyclohexanone is as high as 97.1%, and the selectivity of cyclohexanone cyanohydrin is also as high as 96.5%; after 24 hours of continuous production of the regenerated catalyst, the conversion rate of cyclohexanone is still as high as 98.8%, and the selectivity of cyclohexanone cyanohydrin is also as high as 96.8%) .

Preferably, in step three, the pH of the reaction solution is adjusted to 2-3 by a stabilizer, and the stabilizer is 98% concentrated sulfuric acid or 20% concentrated hydrochloric acid.

Beneficial effects: the solution improves the stability of the product cyclohexanone cyanohydrin by adjusting the pH of the reaction solution to the above-mentioned range, and is convenient for obtaining a high-concentration and stable cyclohexanone cyanohydrin product. The applicant has found through long-term experiments that when the pH of the reaction solution is too high or too low, it will not affect the front-end reaction (such as comparative example 8 and comparative example 9 still have higher cyclohexanone conversion and cyclohexanone cyanohydrin selection However, when the pH is too low, it consumes too much acid and increases the production cost; and when the pH is too high, the neutralization of the alkali in the reaction solution is not complete, resulting in a decrease in the stability of the product cyclohexanone cyanohydrin and affecting the product yield. Rate.

Preferably, in step 3, the flash evaporation is under the conditions of temperature 25°C and pressure -0.09Mpa for 0.5-1h.

Beneficial effects: this scheme performs flash evaporation under the above parameter conditions, which facilitates the rapid removal of unreacted raw material hydrocyanic acid in the reaction solution, thereby obtaining a high-concentration cyclohexanone cyanohydrin product.

Description of drawings

Fig. 1 is the schematic diagram of the reaction device for producing cyclohexanone cyanohydrin in the embodiment of the present invention.

Fig. 2 is the gas chromatogram of the present invention to produce gained cyclohexanone cyanohydrin finished product.

Fig. 3 is the result of the stability test (reaction time, cyclohexanone hydroalcohol selectivity and cyclohexanone conversion rate relationship diagram) of the catalyst (10% loaded CaO/γ-Al ₂ O ₃ catalyst) produced in Example 10 of the present invention. ).

Detailed ways

The following will be further described in detail through specific embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following examples and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial sources. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art.

The reference signs in the drawings of the description include: reactor A, pump B, static mixing heat exchange reactor C, sampler D, preheating device E, flash tank F.

Example 1

This scheme provides a kind of preparation method of cyclohexanone cyanohydrin, and it is finished in the equipment as shown in Figure 1, specifically comprises the steps:

Step 1, raw material premixing stage: fully premixing the raw material hydrocyanic acid and cyclohexanone to form a mixed solution;

Specifically, hydrocyanic acid and cyclohexanone with a molar ratio of 1 to 10:1 (preferably 1 to 3:1) are sequentially added to the reactor A, stirred and mixed evenly to form a mixed solution for later use;

Step 2, reaction stage: mix the above-mentioned mixed solution and catalyst, heat and react to obtain a reaction solution; the reaction of this scheme is as follows:

Specifically, the total mass of the mixed solution formed by the raw materials hydrocyanic acid and cyclohexanone in this program is about 500g, and the mixed solution in the reactor A is pumped at a speed of 1.4 to 2.8g/min under the action of the pump B to the loaded solid In the static mixing heat exchange reactor C of alkali catalyst M/N, the amount of catalyst in this scheme is 0.5-4% of the mass of cyclohexanone; the temperature in the static mixing heat exchange reactor C is heated to 20-120°C in advance, and the mixed solution After 1-5 hours of reaction, the raw material hydrocyanic acid and cyclohexanone react under the catalysis of the loaded solid base catalyst to generate cyclohexanone cyanohydrin, and the released heat is taken away by the cooling water in the heat exchange tube inside the reactor, forming a high temperature Cooling water.

The pumping speed of the mixed solution in this solution can ensure that the materials are fully mixed and reacted, and the conversion rate of raw materials and the yield of products are improved.

Step 3, impurity removal: adjust the pH of the reaction solution obtained in step 2, and remove the unreacted raw material hydrocyanic acid by flash evaporation to obtain cyclohexanone cyanohydrin;

Specifically, after the reaction solution obtained in step 2 flows out of the static mixing heat exchange reactor C, a stabilizer is added to the reaction solution through the sampler D to adjust the Ph of the reaction solution to 2-3. In this scheme, the stabilizer is specifically 98% concentrated Sulfuric acid or 20% concentrated hydrochloric acid, then the reaction solution is preheated to 25°C by the preheating device E and then enters the flash tank F, and is removed by flashing for 0.5-1h at a temperature of 25°C and a pressure of -0.09Mpa The unreacted hydrocyanic acid of the raw material is used to obtain the finished product cyclohexanone cyanohydrin.

The supported solid base catalyst M/N (also referred to as "catalyst") used in the present invention is composed of an active component and a carrier, and the amount of the active component accounts for 10-50% of the mass of the carrier. Among them, the active component M is selected from any one of metal salts of Ca, K, Mg, Na, Zn and Ni, and the carrier N is selected from γ-Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SBA- 15. Any one of activated carbon, HY-5 and HZSM-5. Further, the active component M is preferably any one of metal salts of Ca, K, and Na, and the carrier N is preferably any one of γ-Al ₂ O ₃ , activated carbon and SBA-15; the appearance of the carrier in the present invention is spherical , with a diameter of 3-5 mm, a bulk density of 0.6-0.8 g/cm ³ , a specific surface area of 200-500 m ² /g, and a pore volume of 0.4-0.5 cm ³ /g.

The loaded solid base catalyst M/N used in the present invention is prepared by impregnation, and the specific preparation method is as follows:

S1. Carrier pretreatment: Add the spherical carrier N to an appropriate amount of water, boil it at 50-100°C for 4 hours, and wash away the impurities in the pores of the carrier; after the cleaned carrier is suction-filtered and vacuum-dried at 120°C for 4 hours, put it in a muffle furnace Calcined at 550°C for 3 hours to obtain the pretreated carrier;

S2. Configure the metal salt solution of the active ingredient M: calculate the amount of the active ingredient according to the active ingredient M accounting for 10-50% of the mass of the carrier, mix the metal salt of the active ingredient M with a solvent, and prepare a metal salt solution with a certain concentration, the active ingredient The metal salt of M is any one of oxide, hydroxide, nitrate, hydrochloride or carbonate, and the solvent for dissolving the metal salt of M is one of 5-10% dilute hydrochloric acid solution, water or ethanol Kind, specifically should be selected according to the solubility of the metal salt of M in it;

S3. Prepare catalyst precursor: mix the pretreated carrier obtained in step S1 with the metal salt solution obtained in step (2), heat up to 60° C. and stir for 8 hours, then vacuum dry at 105° C. for 15 hours to obtain a catalyst precursor;

S4. Preparation of the finished catalyst: the catalyst precursor prepared in S3 was placed in a muffle furnace, and calcined at 500° C. for 5 hours to obtain a solid base catalyst M/N.

The preparation method of the loaded solid base catalyst M/N that the present invention adopts, concrete implementation is as follows:

(1) Carrier pretreatment: take 10g of HZSM-5 carrier, add 100g of water, heat up to 80°C and cook for 4h, after suction filtration, vacuum-dry the filter cake at 120°C for 4h, and finally place it in a muffle furnace and roast at 550°C for 3h to obtain Pretreated carrier HZSM-5;

(2) Prepare the metal salt solution of the active ingredient M: accurately weigh 4.2g Ca(NO ₃ ) ₂ ·4H ₂ O and dissolve it in 20g deionized water to prepare a calcium nitrate aqueous solution;

(3) Preparation of catalyst precursor: mix the pretreated HZSM-5 carrier obtained in step (1) with the calcium nitrate solution obtained in step (2), heat up to 60°C and stir for 8h, then vacuum dry at 105°C for 15h to obtain a catalyst precursor Bulk Ca(NO ₃ ) ₂ /HZSM-5;

(4) Prepare the finished catalyst: put the Ca(NO ₃ ) ₂ /HZSM-5 precursor prepared in (3) in a muffle furnace, and roast at 500°C for 5 hours to obtain the solid base catalyst CaO/HZSM-5.

Examples 2-11 are basically the same as Example 1, the difference is that Examples 2-11 show the supported solid base catalyst M/N prepared by loading different active components M on different carriers N, and the carrier N and active components of Examples 1-11 The difference between M is shown in Table 1.

The composition of catalyst in table 1 embodiment 1～11

Example Metal salt of active ingredient M Solvents for metal salt solutions Carrier N Supported solid base catalyst Example 1 Ca(NO ₃ ) ₂ 4H ₂ O water HZSM-5 CaO/HZSM-5 Example 2 KOH water SBA-15 KOH/SBA-15 Example 3 Mg(NO ₃ ) ₂ 6H ₂ O water γ-Al ₂ O ₃ MgO/γ-Al ₂ O ₃ Example 4 KOH water C KOH/C Example 5 _NaNO3 water SiO ₂ Na ₂ O/SiO ₂ Example 6 Zn(NO ₃ ) ₂ 6H ₂ O water γ-Al ₂ O ₃ ZnO/γ-Al ₂ O ₃ Example 7 Ni(NO ₃ ) ₂ 6H ₂ O water _ZrO2 NiO/ _ZrO2 Example 8 KNO ₃ water TiO ₂ K ₂ O/TiO ₂ Example 9 Ca(NO ₃ ) ₂ 4H ₂ O water HY-5 CaO/HY-5 Example 10 Ca(NO ₃ ) ₂ 4H ₂ O water γ-Al ₂ O ₃ CaO/γ-Al ₂ O ₃ Example 11 _NaNO3 water γ-Al ₂ O ₃ Na ₂ O/γ-Al ₂ O ₃

Experimental Example 1: Catalytic Activity of Different Catalysts

Catalyst is used to produce cyclohexanone cyanohydrin in the embodiment 1～11, and concrete parameter is controlled as follows: loading in the catalyst is 10% (active component accounts for the mass ratio of carrier), catalyst consumption is 2%, hydrocyanic acid and The mol ratio of cyclohexanone is 3:1 (concrete, the consumption 228g (about 8.5mol) of hydrocyanic acid, the mol ratio of cyclohexanone consumption 276g (about 2.8mol), the mol ratio of hydrocyanic acid and cyclohexanone is 3: 1), the reaction temperature is 80° C., the reaction is 3 hours, and the pH of the reaction solution is 2.

Calculate the conversion rate of cyclohexanone and the selectivity of cyclohexanone cyanohydrin during the reaction, and show the catalytic effect of the catalyst, the results are shown in table 2; the obtained cyclohexanone cyanohydrin product produced by the catalyst in Example 10 is used for gas chromatography Detection, the resulting gas chromatogram as shown in Figure 2.

The result of catalyst catalytic production cyclohexanone cyanohydrin in the embodiment 1～11 of table 2

Experimental data shows, the catalyst prepared by this scheme has higher cyclohexanone cyanohydrin selectivity when catalyzing hydrocyanic acid and cyclohexanone to synthesize cyclohexanone cyanohydrin (cyclohexanone cyanohydrin selectivity in embodiments 1～11 properties are all higher than 92.1%), indicating that the resulting catalyst prepared by this scheme can effectively promote the raw material to the direction of synthesizing a single product when catalyzing the synthesis of cyclohexanone cyanohydrin, and improve the product purity (as shown in Figure 2, this scheme produces The purity of the obtained cyclohexanone cyanohydrin is as high as 99.77%), thereby effectively reducing the energy consumption required for product purification when there are many by-products, and improving production efficiency.

In addition, the cyclohexanone conversion rate of the catalyst prepared by this scheme is quite different. Among them, the active component M is selected from any of Ca, K, and Na, and the carrier N is selected from γ-Al ₂ O ₃ , activated carbon and SBA-15. When any one of them is used, the prepared carrier has a more excellent catalytic effect. Specifically as embodiment 2, embodiment 4, the conversion rate of the substrate cyclohexanone of catalyst in embodiment 10-11 is all higher than 90%, and embodiment 10 prepares gained catalyst CaO/γ-Al ₂ O ₃ in catalyzing hydrocyanic acid In the reaction of synthesizing cyclohexanone cyanohydrin with cyclohexanone, the conversion rate of the substrate cyclohexanone is as high as 98.9%, which has a very excellent catalytic effect.

Experimental example 2: Stability experiment of catalyst

The catalyst in Example 10 (specifically, 10% loaded CaO/γ-Al ₂ O ₃ ) was selected to conduct a catalyst stability test experiment. The specific steps are, the catalyst obtained in Example 10 (also called "fresh catalyst") is loaded in the static mixing heat exchange reactor C, and the loading amount is 2% of the quality of the raw material cyclohexanone. After continuous reaction for 24h, the catalyst is recovered and The catalyst was put back into the muffle furnace and calcined at 500°C for 5 hours to obtain a "regenerated catalyst". The "regenerated catalyst" was filled in the static mixing heat exchange reactor C again and continued to be used for the production of cyclohexanone cyanohydrin for 24 hours. During the reaction, the "cyclohexanone conversion rate" and "cyclohexanone cyanohydrin selectivity" were calculated every 4 hours, and the results are shown in Table 3 and Figure 3.

Catalyst (10% loaded CaO/γ-Al ₂ O ₃ ) stability test result in the embodiment 10 of table 3

According to Table 3, it can be seen that the activity of the 10% loaded CaO/γ-Al ₂ O ₃ catalyst has been reduced for 24 hours after continuous reaction, but the catalyst can recover its activity after re-calcining, and the recovery catalyst (also called "regenerated catalyst") ) catalytic efficiency after continuous production for 24 hours is not much different from that of the fresh catalyst, indicating that the catalyst prepared by this scheme has better stability.

Experimental example 3: Production results of cyclohexanone cyanohydrin under different parameter conditions

The catalyst in Example 10 was selected to catalyze the reaction of cyclohexanone and hydrocyanic acid to produce cyclohexanone cyanohydrin. Wherein, embodiment 12～19 shows and selects the parameter production cyclohexanone cyanohydrin within the protection scope of this scheme, comparative example 1～9 shows that selects the parameter production cyclohexanone cyanohydrin outside the protection scope of this scheme; Embodiment 12～19, See Table 4 for the differences in the condition parameters for the production of cyclohexanone cyanohydrin in Comparative Examples 1-9.

Table 4 Example 12～19, comparative example 1～9 in the condition parameter difference of producing cyclohexanone cyanohydrin

Experimental data shows that adopting the preparation method of cyclohexanone cyanohydrin provided by this scheme to produce cyclohexanone cyanohydrin can obtain high-purity products, and in the continuous production process, the substrate conversion rate is high, the product selectivity is high, and the by-product In the case of effectively reducing the production cost, the production efficiency of cyclohexanone cyanohydrin is improved.

The inventor encountered the following technical difficulties when synthesizing cyclohexanone cyanohydrin: a large amount of three wastes pollutes the environment, low product purity reduces product quality, low substrate conversion rate leads to waste of raw materials, and continuous production cannot be achieved.

The inventor has explored the reasons for the above phenomenon, and tried various means to solve the above problems, and finally found that the reasons for the above problems are as follows: catalyst type, catalyst service life, cyclohexanone cyanohydrin production process; especially prior art When using a solvent to extract the cyclohexanone cyanohydrin synthesized by the reaction, the solvent removal process is complicated, which leads to great difficulty in product purification, the existing production process has poor catalyst effect and reduces product selectivity, and the organic base reacts with acid to form salt discharge and pollute the environment .

Referring to the experimental results of the examples and comparative examples in Table 1-4, in terms of catalyst type, the resulting catalyst prepared by this scheme, especially the solid base catalyst M/N prepared in Example 2, Example 4, and Example 10-11, its In the production of catalyzing cyclohexanone and hydrocyanic acid to synthesize cyclohexanone cyanohydrin, it has higher substrate conversion rate (cyclohexanone conversion rate is higher than 90%) and product selectivity (cyclohexanone cyanohydrin selectivity higher than 97.8%); it can be seen that in the solid base catalyst M/N produced by this scheme, the active component M is preferably any one of the metal salts of Ca, K, and Na, and the carrier N is preferably γ-Al ₂ O _3. Any one of activated carbon and SBA-15. And the carrier N is spherical in appearance, with a diameter of 3-5mm, a bulk density of 0.6-0.8g/cm ³ , a specific surface area of 200-500m ² /g, and a pore volume of 0.4-0.5cm ³ /g, which is convenient for production and acquisition The solid base catalyst M/N with good catalytic effect can reduce the environmental pollution in the process of synthesizing cyclohexanone cyanohydrin.

In addition, compared with the prior art when organic base (liquid) and inorganic base (powder solid) are used, the catalyst and reaction solution cannot be quickly separated and the catalyst cannot be recovered, this scheme adopts a solid base catalyst, which is convenient for fixed loading of the solid base catalyst In the reactor, it can effectively prevent the catalyst from being mixed in the reaction solution during the reaction process, which will cause the catalyst to be unrecoverable and increase the cost; in addition, the solid base catalyst of this scheme can be recovered quickly, and it can also effectively avoid the acid-base neutralization to produce salt when adjusting the pH. Thereby effectively reducing the amount of waste water.

In terms of the service life of the catalyst, the catalyst of this scheme can not only be recovered, but the "regenerated catalyst" obtained by recovery and roasting has the same catalytic effect as the "fresh catalyst", and it still has a high substrate conversion rate and product after 24 hours of continuous production. selective.

In terms of the production process of cyclohexanone cyanohydrin, the inventor has obtained the process parameters of the high-efficiency continuous production of cyclohexanone cyanohydrin through long-term experimental optimization: the mol ratio of raw material hydrocyanic acid to cyclohexanone is preferably 1 to 3 1. The amount of solid base catalyst is preferably 2-4% of the amount of cyclohexanone, the flow rate of the mixed solution is preferably 1.4-2.8g/min (corresponding to the reaction time of 3-6h), the reaction temperature is preferably 60-80°C, and the pH of the reaction solution 2 to 3 etc. are preferable. The conversion rate of the substrate in the reaction is as high as 99.4%, the selectivity of the cyclohexanone cyanohydrin is as high as 99.1%, and the purity of the obtained cyclohexanone cyanohydrin is higher than 99.77%, which significantly improves the product quality.

Concrete, at first, when prussic acid consumption is too low in the raw material (as adopting prussic acid and cyclohexanone mol ratio in comparative example 2 is 0.5:1), even slow down the flow velocity of raw material mixed solution, prolong the contact between raw material and catalyzer During the contact time, the conversion rate of raw material cyclohexanone is still obviously reduced (the conversion rate of cyclohexane in Comparative Example 2 is only 20.1%), thereby significantly reducing the raw material utilization rate and product yield. Secondly, when the applicant adopts too fast flow rate (select 8.3g/min as in comparative example 1), the mixed solution causes reaction time too short (reaction time is 1h in comparative example 1) because of flowing too fast, causes the reaction of substrate Incompletely reducing the conversion rate of the substrate cyclohexanone. Then, if the reaction temperature is too high (such as comparative example 6 selects 120 DEG C for reaction, comparative example 7 selects 130 DEG C for reaction), it will lead to the special stable structure of the six-membered ring of substrate cyclohexanone, in enol formula and ketone More inclined to enol formula in the interconversion of formula; And then make cyclohexanone ring-opening and produce by-product, reduce product selectivity, influence product purity and yield; reaction), then the conversion rate of the substrate will be reduced (the conversion rate of cyclohexanone is only 43.8% in comparative example 5) because the reaction speed drops. Furthermore, if adopt lower catalyst consumption (select the catalyst of quality 0.5% of cyclohexanone as comparative example 3, select the catalyst of 0.3% of quality of cyclohexanone as comparative example 4), then can reduce reaction efficiency because catalyst consumption is too low , thereby reducing the substrate conversion and product yield. Finally, when the pH of the reaction solution is too high or too low, it will not affect the front-end reaction and carry out (as comparative example 8 and comparative example 9 still have higher cyclohexanone conversion rate and cyclohexanone cyanohydrin selectivity); When the pH is too low, it consumes too much acid and increases the production cost; and when the pH is too high, the neutralization of the alkali in the reaction solution is not complete, resulting in a decrease in the stability of the product cyclohexanone cyanohydrin and affecting the product yield.

In summary, this program adopts the method of "premixing the reaction raw materials first, and then passing them through a reactor filled with a solid alkali catalyst to complete the synthesis reaction of cyclohexanone cyanohydrin", and optimizes the parameters in the production process, not only Realized the continuous production of cyclohexanone cyanohydrin; and in the process of continuous production, by increasing the amount of hydrocyanic acid when mixing the raw materials to promote the positive progress of the synthesis reaction, the conversion rate of the raw material cyclohexanone and cyclohexanone cyanide Alcohol selectivity and product purity.

Compared with the prior art, this scheme effectively avoids the use of organic solvents; on the one hand, it reduces the impurity removal link and energy consumption of the product cyclohexanone cyanohydrin, and simplifies the production process; Environmental pollution caused by the use of organic solvents.

What is described above is only an embodiment of the present invention, and common knowledge such as specific technical solutions and/or characteristics known in the solutions are not described here too much. It should be pointed out that for those skilled in the art, without departing from the technical solutions of the present invention, some modifications and improvements can also be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation of the present invention effect and utility of the patent. The scope of protection required by this application shall be based on the content of the claims, and the specific implementation methods and other records in the specification may be used to interpret the content of the claims.

Claims (10)

1. a preparation method of cyclohexanone cyanohydrin, is characterized in that: comprise the steps: Step 1, raw material premixing stage: fully premixing the raw material hydrocyanic acid and cyclohexanone to form a mixed solution; Step 2. Reaction stage: pump the above-mentioned mixed solution into a reactor filled with a catalyst, and heat the reaction to obtain a reaction solution; Step 3, impurity removal: adjust the pH of the reaction solution obtained in step 2, remove the unreacted raw material hydrocyanic acid in the reaction solution by flash evaporation, and obtain the product cyclohexanone cyanohydrin. 2. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 1 is characterized in that: in step 1, the molar ratio of described raw material hydrocyanic acid and cyclohexanone is 1～10:1. 3. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 2 is characterized in that: in step 2, described reactor is a static mixing heat exchange reactor, and described mixed solution is mixed with 1.4～2.8g /min speed pumped into the static mixing heat exchange reactor. 4 . The method for preparing cyclohexanone cyanohydrin according to claim 3 , characterized in that: in step 2, the reaction is carried out at a temperature of 60-80° C. for 3-6 hours. 5. The preparation method of a kind of cyclohexanone cyanohydrin according to claim 4, characterized in that: in step 2, the catalyst consumption is 2 to 4% of the quality of cyclohexanone. 6. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 5 is characterized in that: in step 2, described catalyzer is solid base catalyst M/N, and described solid base catalyst M/N is by active The component M and the carrier N are composed, and the dosage of the active ingredient M is 10-50% of the mass of the carrier N. 7. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 6 is characterized in that: described active ingredient M is any one in the metal salt of Ca, K, Mg, Na, Zn and Ni, The metal salt is any one of hydroxide, nitrate, hydrochloride or carbonate; the carrier N is γ-Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , SBA-15, Any one of activated carbon, HY-5 and HZSM-5. 8. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 7, is characterized in that: the preparation method of described solid base catalyst M/N is as follows: S1. Carrier pretreatment: Disperse the carrier N in water, boil it at 50-100°C for 4 hours, then filter it with suction, dry it in vacuum at 120°C for 4 hours, then place it in a muffle furnace and bake it at 550°C for 3 hours to obtain the pretreated carrier ; S2. Prepare the metal salt solution of the active ingredient M: mix the metal salt of the active ingredient M with a solvent to prepare a metal salt solution; the solvent is any one of 5-10% dilute hydrochloric acid solution, water or ethanol; S3. Mix the pretreated carrier obtained in step S1 with the metal salt solution prepared in S2, heat up to 60° C. and stir for 8 hours, and then vacuum-dry at 105° C. for 15 hours to obtain a catalyst precursor; S4. Put the catalyst precursor prepared in S3 in a muffle furnace, and calcinate at 500° C. for 5 hours to obtain a solid base catalyst M/N. 9. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 8 is characterized in that: in step 3, the pH of described reaction solution is adjusted to 2～3 by stabilizer, and described stabilizer is 98 % concentrated sulfuric acid or 20% concentrated hydrochloric acid. 10. the preparation method of a kind of cyclohexanone cyanohydrin according to claim 9 is characterized in that: in step 3, described flashing is flashing 0.5 ~ 1h.