Preparation of Pd / C catalyst and application of Pd / C catalyst in synthesis of phenylacetic acid from benzyl chloride

Abstract

The invention belongs to the field of catalyst preparation technology and application, and relates to preparation of a Pd / C catalyst and a method for synthesizing phenylacetic acid from benzyl chloride by using the Pd / C catalyst. The method comprises the following steps: S1, preparation of a Pd / C catalyst: preparing a high-dispersity, high-activity and stable catalyst by improving the process, obtaining a high conversion rate by only using 0.2% of the catalyst, and having excellent reusability; and S2, synthesizing phenylacetic acid: taking benzyl chloride and CO as raw materials, adding the prepared high-activity Pd / C catalyst, and optimizing a reaction process to obtain high-yield and high-purity phenylacetic acid. The prepared catalyst shows an excellent catalytic effect, the production method is simple in step and mild in reaction condition, the yield of the obtained phenylacetic acid is relatively high, the used solvent can be recycled, the cost is greatly saved, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of phenylacetic acid production, and particularly relates to a Pd / C catalyst and a preparation method thereof, and application of the catalyst in carbonylation of benzyl chloride to produce phenylacetic acid. Background Art

[0002] Phenylacetic acid is an important intermediate for synthesizing many drug molecules and agricultural chemicals. It can be used as a starting material for organic synthesis and for preparing other compounds. It is mainly used to manufacture products such as medicines, pesticides and spices. In medicine, phenylacetic acid is mainly used to produce penicillin, prepare dibacil for the treatment of hypertension, and naproxen for the treatment of rheumatoid arthritis. In pesticides, phenylacetic acid is often used to prepare fungicides such as bensulfuron, herbicides such as trichlorophenylacetic acid and rodenticides such as styrene. In addition, phenylacetic acid has a sweet honey flavor at low concentrations and still has a sweet taste below 1ppm. It is an important flavor ingredient used in food, cosmetics, etc. Phenylacetic acid can also be used as a component of industrial cleaners, with bactericidal and preservative effects.

[0003] There are many methods for synthesizing phenylacetic acid, and the main synthesis methods currently include benzyl cyanide hydrolysis, carbonylation synthesis, styrene method, acetophenone method, and ethyl phenylacetate hydrolysis. However, the ethyl phenylacetate hydrolysis method has little industrial significance due to the high price of the raw materials themselves, and the sulfur-containing byproducts produced by the styrene method and acetophenone method are too polluting to the environment, so it is difficult to industrialize. Currently, the benzyl cyanide hydrolysis method and carbonylation synthesis method are used in industry. However, the benzyl cyanide hydrolysis method has low reaction yield, produces highly toxic substances that harm the environment and operators, and harms downstream products, so this method has low economic value, while the carbonyl synthesis method has mild reaction conditions, high production efficiency, and low toxicity, and is currently one of the more popular methods in industry.

[0004] Patent CN 1039241 A uses Co2(CO)8 as a catalyst, benzyl chloride and CO as raw materials, sodium hydroxide, methanol and water as reaction media, and the yield of phenylacetic acid produced can reach more than 85%, but the catalyst preparation process used in this method is complicated, and the amount of catalyst used in the reaction is large, which is not conducive to the recycling of the catalyst, so the production application value is not high. Patent CN 114956983 A adds a supported catalyst and manganese-iron alloy powder to a mixed solution of benzyl chloride methanol water, and passes CO to synthesize phenylacetic acid. The catalyst used in this method contains multiple metals, making the catalyst preparation procedure complicated and difficult to control, and the conversion rate of phenylacetic acid needs to be improved. Patent CN 113461516 A mentions a carbonylation reaction through a multi-stage reaction tower, which can realize the recycling of CO, but it is difficult to industrialize due to its low yield and poor economic efficiency. Summary of the invention

[0005] To solve the above problems, the present invention aims to provide a novel Pd / C catalyst, which has a simple preparation method, good catalytic activity and stability, and is applied to the synthesis of phenylacetic acid from benzyl chloride, with high yield, high purity and good selectivity, and the catalyst has good recycling performance, and can obtain phenylacetic acid with higher yield and higher purity through treatment, and is suitable for industrial production.

[0006] In order to achieve the above-mentioned invention object, the present invention adopts the following technical solutions:

[0007] The present invention provides a Pd / C catalyst for carbonylation of benzyl chloride to produce phenylacetic acid. The preparation method of the catalyst comprises the following steps:

[0008] (1) dissolving a Pd source precursor in a hydrochloric acid solution, adding water and methanol in a certain volume ratio, adjusting the pH value to between 4 and 6, and forming an impregnation solution A under magnetic stirring conditions; and subjecting the carrier to an activation treatment to obtain a carrier B;

[0009] (2) Pour the carrier B into the impregnation solution A, perform ultrasonic treatment, then add a reducing agent and stir at a constant temperature under an inert atmosphere, then filter, wash and dry the reaction product to obtain a Pd / C catalyst.

[0010] In the above technical solution, further, the Pd source described in step (1) is PdCl2, the concentration of the hydrochloric acid solution used is 5%, and the volume ratio of water to methanol is 1:1 to 1:4. Preferably, the volume ratio of water to methanol is 1:2.

[0011] In the above technical solution, further, the carrier in step (1) is activated carbon, and the activated carbon carrier is made from coconut shell and has a specific surface area of ​​500 to 1100 m 2 / g. The activation method is: the activated carbon is washed with 8% HCl solution, then oxidized with 30% H2O2 solution, and dried at 80°C to obtain carrier B; the activation method can also be: the activated carbon is placed in a vacuum tube furnace and calcined at 300-1500°C for 24h to obtain carrier B.

[0012] In the above technical scheme, further, the ultrasonic treatment time in step (2) is 30 minutes; the reducing agent is formaldehyde, and the amount used is 4 to 8 times the Pd content. Preferably, the amount of formaldehyde used is 6 times the Pd content; the constant temperature is 50°C, the reduction time is 4 hours, deionized water is used for washing 3 to 5 times, and a forced air drying oven is used for drying, the drying temperature is 80°C, and the drying time is 2 to 4 hours.

[0013] The second aspect of the present invention provides the use of the above-mentioned Pd / C catalyst, wherein the catalyst is used for carbonylation of benzyl chloride to produce phenylacetic acid. Specifically, the above-mentioned application method comprises the following steps:

[0014] (1) The reaction is carried out in an autoclave, a solvent and benzyl chloride are added, a base, the above-mentioned Pd / C catalyst and a ligand are added in sequence under stirring, N2 is replaced three times, and then CO gas is introduced, and the temperature and reaction time are set;

[0015] (2) detecting the reaction conditions, treating the reaction solution to obtain a crude product, and recovering the reaction solvent and the catalyst; extracting the crude product three times with dichloromethane, and concentrating the organic phase to obtain the product.

[0016] In the above technical scheme, further, in step (1), the stirring speed of the high-pressure reactor is 600-800RPM, the solvent is toluene and water, the base is sodium carbonate, the ligand is triphenyl phosphate (TPP), the CO pressure is 1.5-2.0MPa, the temperature is 100-120°C, and the reaction time is 12-24h.

[0017] In the above technical scheme, further, the detection method in step (2) is LC analysis, and the reaction liquid treatment method is: the reaction liquid is filtered, the filter cake is washed with water, the filtrate is evaporated to 1.5 times the volume at 60-80°C, the solvent toluene is evaporated, 80% is recovered by GC, the filter cake is washed with water and dried to recover the catalyst, and the concentrated product is placed at 60°C for drying.

[0018] Beneficial effects of the present invention

[0019] (1) The modified activated carbon carrier obtained by calcination in the present invention has a larger specific surface area, which is beneficial to increase the loading amount of the active component and improve the dispersion of the active component;

[0020] (2) The carrier modification method of the present invention is simple and has low cost; the catalyst is prepared by an impregnation method, the preparation process is simple, and it is easy to industrialize;

[0021] (3) The catalyst of the present invention is used for synthesizing phenylacetic acid from benzyl chloride under mild reaction conditions. When reacting at 120° C., the conversion rate of benzyl chloride can reach more than 95%, and the selectivity of phenylacetic acid is 98% to 99%. The selectivity of phenylacetic acid is improved while the conversion rate of benzyl chloride is improved;

[0022] (4) The catalyst of the present invention is a mercury-free catalyst, which is green and environmentally friendly, and the preparation method is simple and easy to repeat. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0024] Figure 1 For application example products 1 H NMR spectrum. DETAILED DESCRIPTION

[0025] For a better understanding of the present invention, the present invention is illustrated by the following examples. It should be clear to those skilled in the art that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0026] Examples 1 and 2 mainly compare the effects of different activation methods of the carrier activated carbon on the catalyst, wherein the activation method of the activated carbon in Example 1 is to wash and activate it with chemical reagents for standby use; the activation method of the activated carbon in Example 2 is vacuum high-temperature calcination to increase its surface area and surface activity. Application Examples 1 and 2 use catalysts 1# and 2# to conduct catalytic experiments, respectively, to compare their catalytic effects; Application Examples 3 and 4 correspond to the application of recovered catalysts in Examples 1 and 2, respectively, to compare the stability of the two catalysts. Application Examples 5 and 6 conduct pilot experiments on catalysts 1# and 2#, respectively, to compare their scaled-up production effects, while Application Examples 7 and 8 test the stability of the pilot experiment catalysts. This comparison can accurately reflect the catalytic activity of different catalysts, while it can also show the stability of the catalysts and the possibility of production.

[0027] Embodiment 1:

[0028] Weigh 0.83g PdCl2 (0.5g Pd) and dissolve it in 20mL 5% HCl solution, adjust the pH to between 4 and 6, and then add 2 times the volume of methanol to form impregnation solution A; take a certain amount of activated carbon and place it in 200mL 8% HCl solution, stir it at 50℃ for 2h, filter it, and wash it with deionized water for 3 to 5 times, then place the activated carbon in 200mL 30% The H2O2 solution was stirred at 50°C for 5 hours and then filtered. The solution was washed with deionized water for 3 to 5 times and then dried in a forced air drying oven at 80°C for 2 to 4 hours to obtain a carrier B. 9.5 g of the activated carrier B was added to the prepared impregnation solution A, and after ultrasonic treatment for 30 minutes, it was transferred to a 250 mL single-necked flask, and then 7 g of 38% formaldehyde solution was added. The solution was stirred at 60°C for 4 hours under a N2 atmosphere, and the solid was filtered after being fully reduced. The solid was washed with deionized water for 3 to 5 times and then dried at 80°C for 2 to 4 hours to obtain a Pd / C catalyst with a loading of 5 wt%, which was marked as catalyst #1.

[0029] Embodiment 2:

[0030] Weigh 0.83g PdCl2 (0.5g Pd) and dissolve it in 20mL 5% HCl solution, adjust the pH between 4 and 6, and then add an equal volume of methanol to form impregnation solution A; take a certain amount of activated carbon and place it in a vacuum tube furnace, heat it to 800℃ at a rate of 5℃ / min, and calcine it at high temperature for 24h as carrier B, and take it out after vacuum recovery to room temperature for use; weigh 9.5g activated carrier B and add it to the prepared impregnation solution A, ultrasonically treat it for 30min, then transfer it to a 250mL single-necked flask, add 7g 38% formaldehyde solution, and stir it at 60℃ under N2 atmosphere for 4h, filter it after sufficient reduction, wash it with deionized water 3 to 5 times, and dry the solid at 80℃ for 2 to 4h to obtain a Pd / C catalyst with a loading of 5wt%, marked as catalyst 2#.

[0031] Application Example 1:

[0032] A 1L autoclave was purged with N2, and 300mL toluene and 100mL water were first added to the autoclave, and then 80g benzyl chloride was added. Under stirring at 600-800RPM, 33.6g anhydrous sodium carbonate was added, and finally 0.16g (dry basis) 1# catalyst and 0.16g TPP were added. The autoclave was replaced with N2 three times, and then replaced with CO three times. The CO was pressurized to 1.5-2.0MPa, the temperature was 120°C, and the reaction was stirred for 12h-24h to obtain the product. The reaction was cooled to room temperature and sampled for LC analysis to detect the reaction. The catalytic results are shown in Table 1; the reaction solution was filtered, the filter cake was washed with water, the filtrate was evaporated to 1.5 times the volume at 60-80°C, the solvent toluene was evaporated, 80% was recovered by GC at a fixed ratio, and the filter cake was washed with water and dried to recover the catalyst; the concentrated filtrate was extracted with dichloromethane three times, the organic phase was concentrated to obtain the product, and the concentrated product was dried at 60°C to obtain the product. The purification results are shown in Table 2.

[0033] Application Example 2:

[0034] This application example is basically the same as application example 1, the only difference being that the catalyst used is catalyst 2#. The catalytic results are shown in Table 1, and the purification results are shown in Table 2.

[0035] Application Example 3:

[0036] This application example is basically the same as application example 1, except that the catalyst used is the 1# catalyst recovered from application example 1 and 0.016 g (dry basis) of unused 1# catalyst is added. The catalytic results are shown in Table 1, and the purification results are shown in Table 2.

[0037] Application example 4:

[0038] This application example is basically the same as application example 2, except that the catalyst used is the 2# catalyst recovered from application example 2 and 0.016 g (dry basis) of unused 2# catalyst is added. The catalytic results are shown in Table 1, and the purification results are shown in Table 2.

[0039] Application Example 5:

[0040] After purging the 10L autoclave with N2, 3L toluene, 1L water, 800g benzyl chloride were added successively, stirring was started at 300RPM, and then 336g sodium carbonate, 1.6g (dry basis) 1# catalyst, 1.6g TPP were added. After CO was replaced three times, CO was pressurized to 1.5MPa-2.0MPa, the temperature was raised to 120℃, and the reaction was kept warm for 24 hours. LC monitoring was performed, and the reaction was stopped after the raw material was less than 5%, and the product was obtained. The catalytic results are shown in Table 1; the reaction solution was cooled to room temperature for filtration, the filter cake was washed with water, and the filtrate was evaporated to 2 times the volume at 80℃, the solvent toluene was evaporated, and the GC was used to determine the proportion of recovery; the filter cake was washed with water and dried to recover the catalyst. The concentrated filtrate was transferred to a 100L glass kettle in batches, and then extracted with dichloromethane, and the dichloromethane was recovered and applied. The organic phase was spin-dried to obtain a crude product, which was dried and weighed at 60℃. The crude product was quantified by the standard curve, and the purification results are shown in Table 2.

[0041] Application Example 6:

[0042] This application example is basically the same as application example 5, the only difference being that the catalyst used is catalyst 2#. The catalytic results are shown in Table 1, and the purification results are shown in Table 2.

[0043] Application Example 7:

[0044] This application example is basically the same as application example 5, the only difference being that the catalyst used is the 1# catalyst recovered from application example 5 and 0.32 g (dry basis) of unused 1# catalyst is added. The catalytic results are shown in Table 1, and the purification results are shown in Table 2.

[0045] Application Example 8:

[0046] This application example is basically the same as application example 6, except that the catalyst used is the 2# catalyst recovered from application example 6 and 0.32 g (dry basis) of unused 2# catalyst is added. The catalytic results are shown in Table 1, and the purification results are shown in Table 2.

[0047] Table 1: Catalytic results of preferred application examples

[0048]

[0049] Table 2: Purification results of preferred application examples

[0050]

[0051]

[0052] It can be seen from Table 1 and Table 2 that the Pd / C catalyst prepared by the present invention has excellent catalytic performance and excellent recycling performance. The yield of purified phenylacetic acid can reach more than 95%, which exceeds the yield of 60% to 80% in the prior art, and has the same stability in the scaled-up production; at the same time, in the phenylacetic acid preparation method of the present application, the solvents (toluene and dichloromethane) used in the reaction can be recycled and reused, and the present application has obvious effects both in terms of process innovation and final practicality. The present invention greatly reduces the production cost of phenylacetic acid and provides a green and efficient new synthesis process for the industrial manufacture of phenylacetic acid.

[0053] For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention should still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a Pd / C catalyst for carbonylation of benzyl chloride to produce phenylacetic acid, characterized in that: The method comprises the following steps: (1) dissolving a Pd source precursor in a hydrochloric acid solution, adding water and methanol in a certain volume ratio, adjusting the pH value to between 4 and 6, and forming an impregnation solution A under magnetic stirring conditions; and subjecting the carrier to an activation treatment to obtain a carrier B; (2) pouring the carrier B into the impregnation solution A, performing ultrasonic treatment, then adding the reducing agent formaldehyde and stirring at a constant temperature under an inert atmosphere, and then filtering, washing and drying the reaction product to obtain the Pd / C catalyst; Wherein, the carrier in step (1) is selected from activated carbon.

2. The preparation method according to claim 1, characterized in that: The Pd source precursor described in step (1) is PdCl2, the mass fraction of the hydrochloric acid solution used is 5%, and the volume ratio of water to methanol is 1:1 to 1:

4.

3. The preparation method according to claim 2, wherein the volume ratio of water to methanol in step (1) is preferably 1:

2.

4. The preparation method according to claim 1, characterized in that: The carrier described in step (1) is an activated carbon carrier made from coconut shell, and its specific surface area is 500-1100m 2 / g.

5. The preparation method according to claim 4, characterized in that: The carrier activation method in step (1) is: the activated carbon is washed with 8% HCl solution, then oxidized with 30% H2O2 solution, and dried at 80°C to obtain carrier B; or, the activated carbon is placed in a vacuum tube furnace and calcined at 300-1500°C for 24 hours to obtain carrier B.

6. The preparation method according to claim 1, characterized in that: The ultrasonic treatment time in step (2) is 30 minutes; the reducing agent is formaldehyde, and the amount used is 4 to 8 times the Pd content; the constant temperature is 50° C., the reduction time is 4 hours, deionized water is used for washing 3 to 5 times, and the mixture is dried in a blast drying oven at a drying temperature of 80° C. for a drying time of 2 to 4 hours.

7. The preparation method according to claim 6, characterized in that: The amount of formaldehyde used in step (2) is preferably 6 times the Pd content.

8. Use of the Pd / C catalyst obtained by the preparation method according to any one of claims 1 to 7 for carbonylation of benzyl chloride to synthesize phenylacetic acid, characterized in that: The use of the Pd / C catalyst for carbonylation of benzyl chloride to synthesize phenylacetic acid comprises the following steps: (1) The synthesis reaction is carried out in a high-pressure reactor, a solvent and benzyl chloride are added, and a base, the Pd / C catalyst and a ligand triphenyl phosphate (TPP) are added in sequence under stirring, N2 is replaced three times, and then CO gas is introduced, and the temperature and reaction time are set; (2) LC analysis is used to detect the reaction conditions, and the reaction solution is treated to obtain a crude product, and the reaction solvent and catalyst are recovered; the crude product is extracted three times with dichloromethane, and the organic phase is concentrated to obtain the product phenylacetic acid.

9. The use according to claim 8, characterized in that The stirring speed of the reactor is 600-800RPM, the solvent is toluene and water, the base is sodium carbonate, the CO pressure is 1.5-2.0MPa, the temperature is 100-120°C, and the reaction time is 12-24h.

10. The use according to claim 8, characterized in that: The reaction liquid treatment method is as follows: the reaction liquid is filtered, the filter cake is washed with water, the filtrate is evaporated to 1.5 times the volume at 60-80° C., the solvent toluene is evaporated, 80% is recovered by GC, the filter cake is washed with water and dried to recover the catalyst, and the concentrated product is dried at 60° C.

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