阅读说明：本技术 一种水杨酰胺连续法制备水杨腈的方法 (Method for preparing salicylamide by salicylamide continuous method ) 是由 陈群 何明阳 周维友 陈关虎 孔臻极 孙中华 钱俊峰 于 2021-01-22 设计创作，主要内容包括：本发明涉及腈类化合物的制备方法,具体涉及一种水杨酰胺连续法制备水杨腈的方法。其技术要点如下,包括如下操作步骤：将水杨酰胺溶解于有机溶剂中形成溶液,将水杨酰胺溶液经预热后进入装填有催化剂的固定床反应器,在加热条件下反应后,流出汽经冷却后收集,得到水杨腈产品的溶液。本发明采用水杨酰胺溶解于有机溶剂的方式制备水杨酰胺溶液,克服了现有技术采用熔融方式制备水杨腈反应体系,有效降低了反应能耗,且通过与其他制备工艺的改进相配合提高了最终产物的选择性和收率,具有产业价值。(The invention relates to a preparation method of nitrile compounds, in particular to a method for preparing salicylaldehyde by a salicylamide continuous method. The technical key points are as follows, comprising the following operation steps: dissolving salicylamide in an organic solvent to form a solution, preheating the salicylamide solution, then feeding the salicylamide solution into a fixed bed reactor filled with a catalyst, reacting under a heating condition, cooling effluent gas, and collecting to obtain a solution of a salicylonitrile product. The invention adopts the mode that the salicylamide is dissolved in the organic solvent to prepare the salicylamide solution, overcomes the defect that the prior art adopts a melting mode to prepare a salicylonitrile reaction system, effectively reduces the reaction energy consumption, improves the selectivity and the yield of the final product by matching with the improvement of other preparation processes, and has industrial value.)

1. A method for preparing salicylamide by a continuous method is characterized by comprising the following operation steps: dissolving salicylamide in an organic solvent to form a solution, preheating the salicylamide solution, then feeding the salicylamide solution into a fixed bed reactor filled with a catalyst, reacting under a heating condition, cooling effluent gas, and collecting to obtain a solution of a salicylonitrile product.

2. The continuous salicylamide-based salicylonitrile preparation method as claimed in claim 1, which comprises the following steps of dissolving salicylamide in an organic solvent to form a solution, preheating the salicylamide solution and ammonia gas, feeding the preheated salicylamide solution and ammonia gas into a fixed bed reactor filled with a catalyst, reacting under heating, cooling and collecting effluent gas to obtain a solution of a salicylonitrile product.

3. The continuous salicylamide process of claim 1 or 2, wherein the organic solvent is any one of aliphatic hydrocarbon, aromatic hydrocarbon, ether or nitrile compound.

4. The continuous salicylamide-based process for preparing salicylamide according to claim 3, wherein the organic solvent is any one of toluene, benzonitrile, xylene, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether or dioxane.

5. The method for continuously preparing the salicylamide nitrile according to claim 4, wherein the liquid hourly space velocity of the reaction in the catalytic reaction process is 0.1-1.5 h^-1。

6. The continuous salicylamide process of preparing salicylanitrile of claim 1 or 2, wherein the catalyst is a metal-doped supported boron phosphate catalyst comprising a support, boron phosphate and a metal-doping element.

7. The continuous salicylamide process of claim 6, wherein the metal doping element is one or more of Al, Zn or Te.

8. The continuous salicylamide process of claim 6, wherein the support is a mixture of any one or more of silica gel, molecular sieve, kaolin, alumina, or zirconia.

9. The continuous salicylamide process of claim 6, wherein the metal-doped supported boron phosphate catalyst is prepared by the following steps: weighing boric acid, phosphoric acid, a pore-forming agent and metal doped element salt with equal molar ratio, stirring and dissolving uniformly under heating conditions, adding a carrier, heating under stirring conditions to evaporate and remove water, drying, forming, and roasting for 48 hours to obtain the metal doped supported boron phosphate catalyst.

10. The continuous salicylamide-based method for preparing salicylaldehyde according to claim 9, wherein the pore-forming agent is any one of stearic acid or carboxymethyl cellulose.

Technical Field

The invention relates to a preparation method of nitrile compounds, in particular to a method for preparing salicylaldehyde by a salicylamide continuous method.

Background

The salicylonitrile is an important chemical intermediate and is widely used for synthesizing and producing medicines, pesticides, spices and liquid crystal materials. Therefore, the preparation method of the salicylonitrile with high selectivity and yield is of great significance.

In the prior art: patent FR2332261 describes a process using boron phosphate as catalyst, but the starting methyl salicylate is converted to phenol, which results in a decrease in the yield of salicylanitrile and increases the difficulty of purification of the product. Patent CN102174002A discloses a method for synthesizing salicylaldehyde by using ammonium salicylate as raw material. The catalyst has complex preparation process, various solvent types and long reaction time, and is not beneficial to practical production and application. At present, salicylamide is used as a raw material in industrial production, a lot of processes for preparing the salicylaldehyde by dehydration are adopted, and patents such as CN110041229, CN104610095, CN1051111103, CN103012205 and the like all disclose methods using phosgene or sulfuryl chloride as dehydrating agents, but the dehydrating agents are extremely toxic and have strong corrosivity, so that the safety risk is seriously increased. Patent CN108863849 discloses a method for preparing salicylaldehyde in a fixed bed reactor after salicylamide is vaporized by using a supported vanadium oxide as a catalyst. The temperature of the gasification furnace is 270 ℃, and the salicylamide in the furnace inevitably generates a thermal decomposition reaction to generate a byproduct; in addition, because the salicylonitrile is solid at normal temperature, the temperature of the pipeline needs to be controlled at 150 ℃, and the complexity of equipment is increased; the yield of the final salicylonitrile is only 88.2 percent at most, the yield is low, and the difficulty of the separation and purification process is increased.

In view of the defects in the prior art, the inventor develops a method for preparing the salicylaldehyde by the salicylamide continuous method based on years of abundant experience and professional knowledge of the materials, and by matching theoretical analysis and research innovation, the method has the characteristics of simple process flow, high product selectivity and yield and the like, and has industrial value.

Disclosure of Invention

The invention aims to provide a method for preparing salicylamide by a salicylamide continuous method, which overcomes the technical defect that a salicylamide reactant is prepared by adopting a melting mode in the prior art, effectively reduces the reaction energy consumption, and improves the selectivity and yield of a final product by matching with the improvement of other preparation processes.

The technical purpose of the invention is realized by the following technical scheme:

the method for preparing the salicylamide by the continuous salicylamide method comprises the following operation steps: dissolving salicylamide in an organic solvent to form a solution, preheating the salicylamide solution, then feeding the salicylamide solution into a fixed bed reactor filled with a catalyst, reacting under a heating condition, cooling effluent gas, and collecting to obtain a solution of a salicylonitrile product.

Preferably, the method comprises the following operation steps of dissolving salicylamide in an organic solvent to form a solution, preheating the salicylamide solution and ammonia gas, then feeding the salicylamide solution and the ammonia gas into a fixed bed reactor filled with a catalyst, reacting under a heating condition, cooling effluent gas, and collecting to obtain a solution of the salicylanitrile product.

Preferably, the molar ratio of the ammonia water to the salicylamide is 1-100, the selectivity of the salicylamide can be improved by introducing ammonia gas, the product yield is improved, meanwhile, the ammonia gas can inhibit the hydrolysis of the salicylamide, the side reaction of decarboxylation of the salicylamide to generate phenol is avoided, and the yield of the salicylamide is further improved.

Preferably, the organic solvent is any one of aliphatic hydrocarbon, aromatic hydrocarbon, ether and nitrile compound.

Preferably, the organic solvent is any one of toluene, benzonitrile, xylene, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, or dioxane. The solvent is inert under the reaction condition, has better solubility for the salicylamide, the influence of the solvent on the reaction is mainly related to the polarity of the salicylamide, and the solvent with medium polarity is more favorable for the reaction in the catalytic salicylamide dehydration reaction, so the selection of the solvent can greatly improve the selectivity and the yield of the final product.

Preferably, the concentration of the salicylamide solution is greater than 0.05 g/mL. If the concentration of salicylamide is too low, the efficiency of the preparation of the salicylaldehyde is reduced.

Preferably, the reaction temperature of the heating condition is 340 to 480 ℃. The reaction temperature is too low, so that the reaction efficiency and activity are reduced, the reaction temperature is too high, the salicylamide is subjected to decarboxylation reaction, a by-product phenol is generated, the selectivity of the salicylaldehyde is influenced, and the yield of the salicylaldehyde is reduced, so that the reaction temperature is controlled within the range.

Preferably, the liquid hourly space velocity of the reaction in the catalytic reaction process is 0.1-1.5 h^-1. If the liquid hourly space velocity is too low, the reaction efficiency and the reaction selectivity are reduced; too high a liquid hourly space velocity can reduce the conversion of the feedstock and increase the difficulty of subsequent separation.

Preferably, the catalyst used in the invention is a metal-doped supported boron phosphate catalyst, which comprises a carrier, boron phosphate and a metal-doping element. According to the preparation method, the carrier is adopted to load the boron phosphate, and the distribution of acid sites with different strengths is changed by compounding the carrier and the boron phosphate, so that the catalytic activity of the boron phosphate is improved, and the selectivity and the preparation efficiency of the salicylonitrile are improved.

Preferably, the boron phosphate loading amount is 5-80% of the total mass of the supported boron phosphate catalyst.

Preferably, the metal doping element is any one or a mixture of more of Al, Zn or Te. The doping of the three elements can make up for crystal defects, adjust the distribution of acid sites on the surface of the catalyst and further improve the catalytic performance of the catalyst.

Preferably, the doping amount of the metal doping element is 0.1-5% of the total mass of the supported boron phosphate catalyst.

Preferably, the carrier is any one or a mixture of silica gel, molecular sieve, kaolin, alumina or zirconia.

Preferably, the metal doping element is any one or a mixture of more of Al salt, Zn salt or Te salt, and the content is 0.1-5%.

Preferably, the preparation method of the metal-doped supported boron phosphate catalyst comprises the following operation steps: weighing boric acid, phosphoric acid, a pore-forming agent and metal salt of a doping element in equal molar ratio, stirring and dissolving uniformly under heating conditions, adding a carrier, heating under stirring conditions to evaporate and remove water, drying, forming, and roasting for 48 hours to obtain the metal-doped supported boron phosphate catalyst.

Preferably, the pore-forming agent is either stearic acid or carboxymethyl cellulose. The pore-forming agent can improve the specific surface area of the catalytic material, adjust the pore structure parameters and further improve the catalytic reaction performance.

Preferably, the addition amount of the pore-forming agent is 0.5-5% of the total mass of the supported boron phosphate catalyst.

Preferably, in the preparation process of the metal-doped supported boron phosphate catalyst, the roasting temperature is 350-800 ℃, and preferably 380-500 ℃; the roasting temperature plays an important role in generating acid sites on the surface of the catalyst, the acid sites can be more uniformly arranged through high-temperature roasting, but the framework of the catalyst collapses due to overhigh temperature, and the effect cannot be achieved due to overlow temperature, so that the catalyst has excellent catalytic performance when the roasting temperature of the catalyst is 350-500 ℃ in the reaction.

In conclusion, the invention has the following beneficial effects:

(1) the method for preparing the salicylamide solution by dissolving the salicylamide in the organic solvent overcomes the defect that a salicylonitrile reaction system is prepared by adopting a melting mode in the prior art, effectively reduces the reaction energy consumption, and improves the selectivity and the yield of a final product by matching with the improvement of other preparation processes.

(2) The salicylamide solution is used as a raw material, so that the process equipment is simplified, and the selectivity of the salicylamide is improved; the salicylonitrile solution collected by the reaction can separate out a high-purity salicylonitrile solid after being cooled, and the separation process is simplified.

(3) The metal modified supported boron phosphate catalyst is adopted, so that the selectivity and the yield of the product, namely the salicylonitrile, are improved.

(4) During the reaction process, ammonia gas is introduced, so that the selectivity and the yield of the product, namely the salicylaldehyde are improved.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description will be provided for the specific embodiments, features and effects of a continuous process for preparing salicylamide from salicylamide according to the present invention.

Example 1

The metal-doped supported boron phosphate catalyst comprises the following operation steps:

20g of boric acid, 37.3g of phosphoric acid, 0.54g of telluric acid dihydrate, 1.2g of stearic acid and 140mL of water are sequentially added into a reactor, heated and stirred uniformly. 77.8g of an acidic silica sol having a silica content of 25% were then added to the system. Heating and evaporating to dryness under the stirring condition to be colloidal, drying and forming, and then roasting at 400 ℃ for 5h to obtain the catalyst 1. The load of boron phosphate is 67.3%, the tellurium content is 0.5%, and the addition of stearic acid is 2%, so that the target catalyst is obtained.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 1 and N was added₂Preheating to 370 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 20, after reaction at 370 ℃, effluent gas is cooled and collected to obtain a target product water solution, and the conversion rate of the salicylamide is detected to be 99 percent, and the selectivity of the salicylamide is 96 percent.

Example 2

The metal-doped supported boron phosphate catalyst comprises the following operation steps:

5g of boric acid, 9.3g of phosphoric acid, 0.18g of telluric acid dihydrate, 1.0g of hydroxymethyl cellulose and 50mL of water are sequentially added into a reactor, heated and uniformly stirred. 442.9g of an ammonia-type alkaline silica sol having a silica content of 40% were then added to the system. Heating and evaporating to dryness under the condition of stirring to be colloidal, drying and forming, and then roasting for 4 hours at the temperature of 400 ℃ to obtain the catalyst 2. The boron phosphate loading was 5%, the tellurium content was 0.1%, and the stearic acid addition was 0.5%.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 2 and N was added₂Pre-heating to 480 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.1h^-1The mol ratio of ammonia gas and salicylamide is 20, after reaction at 480 ℃, effluent gas is cooled and collected to obtain a target product water solution, and the conversion rate of the salicylamide is 89% and the selectivity of the salicylamide is 88%.

Example 3

The metal-doped supported boron phosphate catalyst comprises the following operation steps:

to the reactor were added 20g of boric acid, 37.3g of phosphoric acid, 17.0g of aluminum nitrate nonahydrate, 1.3g of stearic acid, and 140mL of water in this order, followed by heating and stirring. Then 9.7g of 3A molecular sieve was added to the system. Heating and evaporating to dryness under the stirring condition to be colloidal, drying and forming, and then roasting at 300 ℃ for 4h to obtain the catalyst 3. The boron phosphate loading is 80%, the aluminum content is 5%, and the carboxymethyl cellulose addition is 5%.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 3, and N was passed through₂Pre-heating to 340 ℃. Preheating a p-xylene solution of salicylamide with the concentration of 1.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 1, after reaction at 340 ℃, effluent gas is cooled and collected to obtain a target product aqueous solution, and the conversion rate of the salicylamide is 99 percent and the selectivity of the salicylamide is 90 percent through detection.

Example 4

The metal-doped supported boron phosphate catalyst comprises the following operation steps:

to the reactor were added 20g of boric acid, 37.3g of phosphoric acid, 1.3g of zinc nitrate hexahydrate, 1.2g of stearic acid and 140mL of water in this order, followed by heating and stirring. Then, 19.5g of alumina was added to the system. Heating and evaporating to dryness under the condition of stirring to be colloidal, drying and forming, and then roasting at 350 ℃ for 8h to obtain the catalyst 4. The boron phosphate loading was 67.3%, the zinc content was 0.5%, and the carboxymethyl cellulose addition was 2%.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 4 and N was passed through₂Preheating to 370 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.05g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 1.5h^-1The mol ratio of ammonia gas and salicylamide is 100, after reaction at 370 ℃, effluent gas is cooled and collected to obtain a target product water solution, and the conversion rate of the salicylamide is 92% and the selectivity of the salicylamide is 93% by detection.

Example 5

The metal-doped supported boron phosphate catalyst comprises the following operation steps:

20g of boric acid, 37.3g of phosphoric acid, 0.54g of telluric acid dihydrate, 1.2g of stearic acid and 140mL of water are sequentially added into a reactor, heated and stirred uniformly. 77.8g of an acidic silica sol having a silica content of 25% were then added to the system. Heating and evaporating to dryness under stirring to obtain colloid, drying, molding, and roasting at 800 deg.C for 4h to obtain catalyst 5. The boron phosphate loading was 67.3%, the tellurium content was 0.5%, and the stearic acid addition was 2%.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 5 and N was passed through₂Preheating to 370 ℃. Preheating a salicylamide diethylene glycol dimethyl ether solution with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution and the ammonia gas into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 20, after reaction at 370 ℃, the effluent gas is cooled and collected to obtain the water solution of the target product, and the conversion rate of the salicylamide is detected92% and the selectivity to salicylonitrile is 98%.

Example 6

A metal-doped supported boron phosphate catalyst 1 was prepared according to the procedure of example 1.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 1 and N was added₂Preheating to 370 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 50, after the reaction at 370 ℃, effluent gas is cooled and collected to obtain the water solution of the target product, and the conversion rate of the salicylamide is 99 percent and the selectivity of the salicylamide is 98 percent through detection.

Example 7

A metal-doped supported boron phosphate catalyst 1 was prepared according to the procedure of example 1.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 1 and N was added₂Preheating to 400 ℃. Preheating dioxane solution of salicylamide with the concentration of 0.2g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of reaction liquid to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 20, after reaction at 400 ℃, effluent gas is cooled and collected to obtain a target product water solution, and the conversion rate of the salicylamide is 99 percent and the selectivity of the salicylamide is 92 percent by detection.

Example 8

A metal-doped supported boron phosphate catalyst 3 was prepared according to the procedure of example 3.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 3, and N was passed through₂Preheating to 380 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor,controlling the liquid hourly space velocity of the reaction liquid to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 20, after reaction at 380 ℃, effluent gas is cooled and collected to obtain a target product aqueous solution, and the conversion rate of the salicylamide is 99 percent and the selectivity of the salicylamide is 97 percent through detection.

Example 9

A metal-doped supported boron phosphate catalyst 3 was prepared according to the procedure of example 3.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 3, and N was passed through₂Preheating to 380 ℃. Preheating dioxane solution of salicylamide with the concentration of 0.2g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of reaction liquid to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 50, after reaction at 380 ℃, effluent gas is cooled and collected to obtain a target product aqueous solution, and the conversion rate of the salicylamide is 99 percent and the selectivity of the salicylamide is 94 percent through detection.

Comparative example 10

A metal-doped supported boron phosphate catalyst 1 was prepared according to the procedure of example 1.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 1 and N was added₂Preheating to 370 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1And (3) reacting at 370 ℃ without introducing ammonia gas, cooling effluent gas, and collecting to obtain a target product water solution, wherein the conversion rate of the salicylamide is 88% and the selectivity of the salicylanitrile is 76%.

Comparative example 11

The metal-free doped supported boron phosphate catalyst comprises the following operation steps:

to the reactor were added 20g of boric acid, 37.3g of phosphoric acid, 1.2g of stearic acid, and 140mL of water in this order, heated, and stirred uniformly. 77.8g of an acidic silica sol having a silica content of 25% were then added to the system. Heating and evaporating to dryness under stirring to obtain colloid, drying, molding, and roasting at 400 deg.C for 5h to obtain catalyst 6. The load of boron phosphate is 67.6%, and the adding amount of stearic acid is 2%, so as to obtain the target catalyst.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 1 and N was added₂Preheating to 370 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 20, after the reaction at 370 ℃, effluent gas is cooled and collected to obtain a target product water solution, and the conversion rate of the salicylamide is detected to be 92%, and the selectivity of the salicylamide is detected to be 90%.

Comparative example 12

The metal-doped boron phosphate catalyst comprises the following operation steps:

20g of boric acid, 37.3g of phosphoric acid, 0.36g of telluric acid dihydrate, 1.2g of stearic acid and 140mL of water are sequentially added into a reactor, the mixture is heated and uniformly stirred, and is further heated and evaporated to dryness to be colloidal, the colloidal mixture is dried and formed, and then the mixture is roasted for 5 hours at the temperature of 400 ℃ to obtain a catalyst 7. The tellurium content is 0.5%, and the stearic acid addition amount is 2%, so as to obtain the target catalyst.

The method for preparing the salicylaldehyde by the salicylamide continuous method by adopting the catalyst comprises the following operation steps:

the fixed bed reactor was charged with 10mL of catalyst 1 and N was added₂Preheating to 370 ℃. Preheating a cyanobenzene solution of salicylamide with the concentration of 0.1g/mL and ammonia gas to 150 ℃, introducing the solution into a reactor, and controlling the liquid hourly space velocity of a reaction solution to be 0.3h^-1The mol ratio of ammonia gas and salicylamide is 20, after the reaction at 370 ℃, effluent gas is cooled and collected to obtain a target product water solution, and the conversion rate of the salicylamide is 89% and the selectivity of the salicylamide is 91% by detection.

As can be seen from the results of example 1 and comparative example 10, the conversion rate of salicylamide and the selectivity of salicylaldehyde are obviously lower than those of the technical scheme of introducing ammonia under the same conditions under the condition of not introducing ammonia; as can be seen from example 1 and comparative example 11, the conversion of salicylamide and the selectivity of salicylanitrile are greatly reduced when no metal is doped; it can be seen from example 1 and comparative example 12 that the conversion of salicylamide and the selectivity of salicylanitrile are also greatly reduced when the catalyst is supported. In conclusion, the metal-doped supported boron phosphate catalyst provided by the invention greatly improves the conversion rate of salicylamide and the yield of salicylanitrile.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.