CN116037173B - Catalyst for selective hydrodechlorination of acetic acid chlorinated solution, preparation method and application - Google Patents
Catalyst for selective hydrodechlorination of acetic acid chlorinated solution, preparation method and application Download PDFInfo
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Abstract
The invention relates to a catalyst for selective hydrogenation dechlorination of acetic acid chloride solution, a preparation method and application thereof. The catalyst is mainly used for preparing chloroacetic acid by selective hydrodechlorination of dichloroacetic acid in acetic acid chlorination liquid, has high hydrodechlorination activity on dichloroacetic acid, and can effectively reduce further hydrodechlorination side reaction of chloroacetic acid.
Description
Technical Field
The invention belongs to the field of materials and chemical industry, and particularly relates to a catalyst for selective hydrodechlorination of acetic acid chlorinated solution, a preparation method and application thereof.
Background
Chloroacetic acid is an important intermediate of organic chemical industry and raw material of fine chemical industry, and is widely used in the fields of pesticides, medicines, fuels and organic synthesis. The acetic acid catalytic chlorination process is the main production process for producing chloroacetic acid at present, and a crude product obtained after the reaction of acetic acid and chlorine is called an acetic acid chlorination solution, and the product mainly comprises dichloroacetic acid, chloroacetic acid, acetic acid and water, and in addition, trace trichloroacetic acid may be present. In order to further obtain high-purity chloroacetic acid, it is necessary to selectively hydrodechlorinate dichloroacetic acid in the acetic acid chlorination solution while avoiding further dechlorination of chloroacetic acid. At present, a plurality of domestic and foreign patents and papers disclose a method for preparing chloroacetic acid by selective hydrogenation and dechlorination of dichloroacetic acid. Patent CN102553584A discloses a modified palladium-carbon catalyst for chloroacetic acid production and a preparation method thereof, wherein the catalyst comprises 0.5-1.25% of palladium as an active component, 0.05-1.0% of barium metal as an auxiliary agent and columnar active carbon as a carrier. Patent CN10688952A discloses a hydrodechlorination palladium-carbon catalyst and a preparation method, wherein the catalyst takes metal palladium as an active component, 0.5-2% of rhenium as an auxiliary metal, and 0.5-3% of Cl is introduced. Patent CN107413333a discloses the preparation of a modified hydrodechlorination catalyst. Wherein the active component of the catalyst is one or more selected from palladium, platinum and nickel. The metal auxiliary simple substance is selected from one or more of rhenium, zirconium, ruthenium, cadmium, barium and vanadium. The catalyst disclosed in patent CN106488903a uses palladium or platinum as an active component and one or more salts of nickel, cobalt, iron, molybdenum, tungsten, manganese or zinc as a catalyst enhancer. Patent CN108911968A discloses a method for purifying monochloroacetic acid by catalytic rectification, wherein 0.9-1.1% of noble metal palladium, platinum and silver are used as active components, and 0.3-0.5% of magnesium and aluminum are used as metal auxiliaries. In our studies on selective hydrodechlorination of acetic acid chlorides, we found that the catalysts reported in these publications had very high conversions for polychloroacetic acid, however, further hydrodechlorination of chloroacetic acid to acetic acid tended to occur. Therefore, the technical problem to be solved by the catalyst is how to inhibit the occurrence of further hydrodechlorination side reaction of chloroacetic acid while ensuring that the catalyst has high activity.
Disclosure of Invention
In order to solve the technical problems, the invention provides a catalyst for selective hydrodechlorination of acetic acid chloride, a preparation method and application thereof.
The technical scheme adopted by the invention is as follows: a preparation method of a catalyst for selective hydrodechlorination of acetic acid chloride solution comprises the steps of immersing urea phosphate aqueous solution in an equal volume into a carbon carrier, baking the carbon carrier at 500-650 ℃ for at least 3 hours, and obtaining a modified carbon carrier; the dosage of the urea phosphate accounts for 3-5% of the total mass of the carbon carrier;
dissolving palladium chloride into an ethanol water solution, adding a ligand which is an imidazole ligand or a dicarbonyl nitrogen-containing ligand after dissolving, stirring, hermetically heating the system to 70-80 ℃ and continuously stirring for 1-2h, soaking the obtained solution into the modified carbon carrier in an equal volume, and reducing the solution for at least 2h in a hydrogen atmosphere of 550-600 ℃ after drying to obtain a catalyst for selective hydrogenation and dechlorination of acetic acid chloride;
wherein, the palladium chloride consumption accounts for 1.3% -2% of the total mass of the modified carbon carrier; the molar ratio of the palladium chloride to the ligand is 1:1-2;
the imidazole ligand is one or more of 2-methylimidazole, imidazole and 4-methylimidazole; the dicarbonyl nitrogen-containing ligand is one or more of N-chlorosuccinimide, N-methyl succinimide and succinimide.
Preferably, the mass content of ethanol in the ethanol aqueous solution is 40% -60%.
Preferably, the carbon carrier is one or more of wood activated carbon, coconut shell carbon and coal carbon.
Preferably, the urea phosphate aqueous solution is isostatically impregnated into the carbon support, dried at 75-85 ℃, and/or the resulting solution is isostatically impregnated into the modified carbon support, dried at 75-85 ℃.
Preferably, the obtained solution is immersed in the modified carbon carrier in an equal volume, dried and reduced in a hydrogen atmosphere flowing in a tube furnace, and the solution is switched to an inert atmosphere to be cooled to room temperature after the reduction is finished; wherein the gas space velocity of the hydrogen is 180-540 h -1 The inert atmosphere is one or more of nitrogen, argon or helium.
Preferably, the modified carbon support is obtained by calcination in an air atmosphere in a muffle furnace.
A catalyst for selective hydrodechlorination of acetic acid chloride is prepared by the preparation method.
The catalyst is applied to the selective hydrodechlorination of dichloroacetic acid in acetic acid chlorination liquid to prepare chloroacetic acid.
Preferably, the method comprises the following steps:
step 1: filling the catalyst into a constant temperature zone of a continuous flow high-pressure fixed bed reactor, and acceleratingThe upper layer of the chemical agent is filled with a porcelain ring with a length of at least 20 cm as a preheating layer, the temperature is raised to 250-300 ℃ under flowing hydrogen to pretreat at least 1h, and the gas space velocity of the hydrogen is 180-540 h -1 ；
Step 2: after pretreatment is completed, the pressure of the fixed bed reactor is increased to 0.3-0.5MPa, and the reaction temperature is adjusted to 120-150 ℃;
step 3: pumping acetic acid chloride solution into a reactor by a high-pressure pump, wherein the acetic acid chloride solution comprises 40% chloroacetic acid, 10% dichloroacetic acid and 50% acetic acid by mass, and has a liquid hourly space velocity of 3.0-9.0 h –1 ；
The prepared product is acetic acid chloridizing solution after selective dechlorination.
The invention has the advantages and positive effects that: the carbon carrier is modified by urea phosphate, so that phosphate species can be uniformly distributed on the surface of the carbon carrier, and the modification effect of urea phosphate on the carrier is far greater than that of urea or phosphoric acid alone;
in the preparation process of palladium chloride solution, imidazole ligand or dicarbonyl nitrogen-containing ligand is added, so that palladium ions and organic ligand can be fully complexed, the obtained palladium complex can avoid aggregation and sintering of metal components in the subsequent processes of dipping, drying and high-temperature treatment, and palladium nano particles distributed on a carbon carrier more uniformly can be obtained;
the invention also realizes the preparation of the high-performance palladium phosphide catalyst loaded by the carbon carrier in a stepwise manner, wherein the carrier is modified by urea phosphate to uniformly load phosphate radical, then palladium complex is uniformly loaded in a coordination complexing manner, and then high-temperature hydrogen reduction is carried out to prepare the high-performance catalyst.
Drawings
FIG. 1 is a scanning electron microscope picture of the catalyst prepared in example 1.
Detailed Description
Embodiments of the present invention are described below with reference to the accompanying drawings.
The invention relates to a catalyst for selective hydrogenation dechlorination of acetic acid chloride solution, a preparation method and application thereof. The catalyst is mainly used for preparing chloroacetic acid by selective hydrodechlorination of dichloroacetic acid in acetic acid chlorination liquid, has high hydrodechlorination activity on dichloroacetic acid, and can effectively reduce further hydrodechlorination side reaction of chloroacetic acid.
The specific preparation method of the catalyst comprises a carrier modification step and a catalyst preparation step, and specifically comprises the following steps:
and (3) carrier modification: fully dissolving urea phosphate into deionized water under the stirring state, then soaking the urea phosphate into a carbon carrier by adopting an isovolumetric soaking method, and then drying a sample at 75-85 ℃; roasting the sample in a muffle furnace at 500-650 ℃ for at least 3 hours in the air atmosphere, and cooling to room temperature to obtain a modified carbon carrier; in the modification process, the dosage of the urea phosphate accounts for 3-5% of the total mass of the carbon carrier, and the carbon carrier is one or more of wood activated carbon, coconut shell carbon and coal carbon.
The effect of urea phosphate on the carrier is far greater than that of urea or phosphoric acid alone on the carbon carrier. The carbon support is modified with urea phosphate in order to allow uniform distribution of phosphate species on the surface of the carbon support. Urea phosphate is decomposed when being roasted at 500-650 ℃ in air atmosphere, urea in urea phosphate is decomposed at high temperature to generate carbon nitride species, phosphoric acid molecules are dehydrated at high temperature, water vapor has a certain reaming effect on carbon carriers at high temperature, and generated carbon nitride species can anchor phosphoric acid molecules to prevent the phosphoric acid molecules from agglomerating and sintering in the high-temperature dehydration process. In addition, the invention also limits the usage amount of the urea phosphate to 3% -5% of the total mass of the carbon carrier, so that the pore canal of the carbon carrier is prevented from being blocked after the excessive urea phosphate is decomposed, and the too little urea phosphate cannot play a role in modifying the carbon carrier.
And (3) preparing a catalyst: dissolving palladium chloride in ethanol water solution under stirring, adding ligand after complete dissolution, stirring for 0.5h, and sealing the systemHeating to 70-80 ℃ and continuously stirring for 1-2h, then adopting an isovolumetric impregnation method to impregnate the obtained solution into a modified carbon carrier, then drying a sample at 75-85 ℃, then reducing the sample at 550-600 ℃ for at least 2h under the hydrogen atmosphere flowing in a tube furnace, then switching to the flowing inert atmosphere and cooling to room temperature to obtain the required catalyst; wherein the mass content of ethanol in the ethanol water solution is 40% -60%; the palladium chloride amount accounts for 1.3% -2% of the total mass of the modified carbon carrier; the molar ratio of the palladium chloride to the ligand is 1:1-2; the inert atmosphere is one or more of nitrogen, argon or helium; the gas space velocity of the hydrogen is 180-540 h -1 。
The ligand is imidazole ligand or dicarbonyl nitrogen-containing ligand, when the ligand is imidazole ligand, the imidazole ligand is one or more of 2-methylimidazole, imidazole and 4-methylimidazole; when the ligand is dicarbonyl nitrogen-containing ligand, the dicarbonyl nitrogen-containing ligand is one or more of N-chlorosuccinimide, N-methyl succinimide and succinimide. In the preparation process of palladium chloride solution, imidazole ligand or dicarbonyl nitrogen-containing ligand is added, so as to fully complex palladium ions with organic ligand. The palladium complex obtained in this way can avoid aggregation and sintering of metal components in the subsequent dipping, drying and high-temperature heat treatment processes, and palladium nano-particles distributed on the carbon carrier more uniformly can be obtained.
As palladium chloride is insoluble in water and soluble in dilute hydrochloric acid, the invention adopts 40 to 60 mass percent ethanol water solution to dissolve palladium chloride, and the mixed solvent can promote the dissolution of palladium chloride and organic ligand. Although noble metal palladium is easily reduced, palladium reduction can be achieved at lower temperatures, and sintering of the metal components can be avoided at low temperatures, so that palladium catalysts are reduced below 300 ℃ in many publications. Unlike the published reports, the sample is reduced for at least 2 hours at 550-600 ℃ in the hydrogen atmosphere flowing in the tube furnace, so that the reduced palladium further reacts with phosphorus species on the surface of the carbon carrier to generate palladium phosphide. In most literature reports, the hydrogenation activity of the metal component is slightly reduced due to the generation of metal phosphide, and the reduction of the hydrogenation activity can just avoid the occurrence of excessive hydrodechlorination side reaction of chloroacetic acid, so that the high-selectivity hydrodechlorination of dichloroacetic acid to chloroacetic acid can be realized.
It is well known that for supported metal catalysts, the smaller the size of the active sites, the higher the catalyst activity tends to be. In the preparation process of metal phosphide, phosphate radical is easy to complex with metal ions and is crosslinked through metal particles, so that metal phosphate is easy to sinter metal components in the processes of dipping, drying and roasting reduction, and the particle size of the metal phosphide in the prepared supported catalyst is far larger than that of individual metal particles. According to the invention, the preparation of the carbon-supported high-performance palladium phosphide catalyst is realized in a stepwise manner, phosphate groups are uniformly loaded by modifying the carrier through urea phosphate, then palladium complexes are uniformly loaded in a coordination complexing manner, and then the high-performance catalyst is prepared through high-temperature hydrogen reduction.
In addition, in the preparation method, the second metal is not added as an auxiliary agent, so that the recovery of noble metal palladium in the subsequent waste catalyst is more convenient.
The following description of the present invention is made with reference to the accompanying drawings, wherein the experimental methods without specific description of the operation steps are performed according to the corresponding commodity specifications, and the instruments, reagents and consumables used in the embodiments can be purchased from commercial companies without specific description.
Example 1
(1) And (3) carrier modification: fully dissolving urea phosphate into deionized water under the stirring state, then soaking the urea phosphate into a carbon carrier by adopting an isovolumetric soaking method, and then drying a sample at 80 ℃; roasting the sample in a muffle furnace at 650 ℃ for 3 hours in the air atmosphere, and cooling to room temperature to obtain a modified carbon carrier; the dosage of the urea phosphate accounts for 3% of the total mass of the carbon carrier, and the carbon carrier is coconut shell carbon;
(2) And (3) preparing a catalyst: dissolving palladium chloride in ethanol water solution under stirring, adding imidazole ligand after complete dissolution, stirring for 0.5 hrHeating the system to 70 ℃ in a closed manner and continuously stirring for 1h, then soaking the obtained solution into a modified carbon carrier by adopting an isovolumetric soaking method, then drying a sample at 80 ℃, then reducing the sample for 2h at 600 ℃ in a hydrogen atmosphere flowing in a tube furnace, then switching to a flowing inert atmosphere and cooling to room temperature to obtain the required catalyst; wherein the mass content of ethanol in the ethanol water solution is 40%; the palladium chloride amount is 1.3 percent of the total mass of the modified carbon carrier; the molar ratio of palladium chloride to imidazole ligand is 1:1; the imidazole ligand is 2-methylimidazole; the inert atmosphere is nitrogen; the gas space velocity of the hydrogen was 180 h -1 . The catalyst obtained was numbered CAT-1. The morphology of the CAT-1 obtained by the preparation is observed by a scanning electron microscope and is shown in figure 1.
Example 2
The procedure of example 2 was the same as in example 1, except that the amount of urea phosphate in step (1) was changed to 5% by weight based on the total mass of the carbon support, and the catalyst was CAT-2.
Example 3
The procedure of example 3 was the same as in example 1, except that the sample in step (1) was calcined at 650℃for 3 hours in a muffle furnace atmosphere to 500℃and the resulting catalyst was CAT-3.
Example 4
The procedure of example 4 was the same as in example 1, except that the coconut shell charcoal in step (1) was changed to coal-based charcoal, and the catalyst number was CAT-4.
Example 5
The procedure of example 5 was the same as in example 1 except that the palladium chloride amount in step (2) was changed to 2% by weight based on the total mass of the modified carbon support, and the catalyst was CAT-5.
Example 6
The procedure for the preparation of example 6 was the same as in example 1, except that 2-methylimidazole in step (2) was changed to imidazole, and the catalyst obtained was designated CAT-6.
Example 7
The procedure of example 7 was the same as in example 1 except that the sample in step (2) was reduced at 600℃for 2 hours under a hydrogen atmosphere flowing in a tube furnace to 550℃and the resulting catalyst was No. CAT-7.
Example 8
The procedure of example 8 was the same as in example 1 except that the mass content of ethanol in the aqueous ethanol solution in step (2) was changed to 60%, and the obtained catalyst was CAT-8.
Example 9
(1) And (3) carrier modification: fully dissolving urea phosphate into deionized water under the stirring state, then soaking the urea phosphate into a carbon carrier by adopting an isovolumetric soaking method, and then drying a sample at 80 ℃; roasting the sample in a muffle furnace at 650 ℃ for 3 hours in the air atmosphere, and cooling to room temperature to obtain a modified carbon carrier; the dosage of the urea phosphate accounts for 3% of the total mass of the carbon carrier, and the carbon carrier is coconut shell carbon;
(2) And (3) preparing a catalyst: dissolving palladium chloride into ethanol water solution under a stirring state, adding dicarbonyl nitrogen-containing ligand after complete dissolution, stirring for 0.5h, sealing the system, heating to 70 ℃ and continuing stirring for 1h, then adopting an isovolumetric impregnation method to impregnate the obtained solution into a modified carbon carrier, drying a sample at 80 ℃, reducing the sample at 600 ℃ for 2h under a hydrogen atmosphere flowing in a tube furnace, switching to a flowing inert atmosphere, and cooling to room temperature to obtain the required catalyst; wherein the mass content of ethanol in the ethanol water solution is 40%; the palladium chloride amount is 1.3 percent of the total mass of the modified carbon carrier; the molar ratio of palladium chloride to dicarbonyl nitrogen-containing ligand is 1:1; the dicarbonyl nitrogen-containing ligand is succinimide; the inert atmosphere is nitrogen; the gas space velocity of the hydrogen was 180 h -1 . The catalyst obtained was designated CAT-9.
Example 10
The procedure of example 10 was the same as in example 9, except that the succinimide in step (2) was changed to N-methylsuccinimide, and the catalyst was designated CAT-10.
Comparative example 1
The firing temperature in the muffle furnace was lowered in order to explain the importance of the firing temperature in step (1) as compared with example 1.
The procedure of comparative example 1 was the same as in example 1 except that the sample in step (1) was calcined at 650℃for 3 hours in a muffle furnace atmosphere to 450℃and the resulting catalyst was designated CAT-11.
Comparative example 2
The firing temperature in the muffle furnace was increased in order to explain the importance of the firing temperature in step (1) as compared with example 1.
The procedure of comparative example 2 was the same as in example 1 except that the sample in step (1) was calcined at 650℃for 3 hours in a muffle furnace atmosphere to 700℃and the resulting catalyst was numbered CAT-12.
Comparative example 3
The inert atmosphere firing was used in the muffle furnace for the purpose of illustrating the importance of the firing atmosphere in step (1) as compared with example 1.
The procedure for preparation of comparative example 3 was the same as in example 1 except that the sample in step (1) was calcined at 650℃for 3 hours in a muffle furnace atmosphere, and the resultant catalyst was numbered CAT-13, instead of calcined at 650℃for 3 hours in a tube furnace atmosphere.
Comparative example 4
The carbon support was not modified with urea phosphate in order to demonstrate the importance of urea phosphate modification in step (1) as compared to example 1.
Preparation procedure of comparative example 4: dissolving palladium chloride into ethanol water solution under a stirring state, adding imidazole ligand after complete dissolution, stirring for 0.5h, sealing the system, heating to 70 ℃ and continuing stirring for 1h, then adopting an isovolumetric impregnation method to impregnate the obtained solution into coconut shell carbon, drying a sample at 80 ℃, reducing the sample at 600 ℃ for 2h under a hydrogen atmosphere flowing in a tube furnace, switching to a flowing inert atmosphere and cooling to room temperature to obtain the required catalyst; wherein the mass content of ethanol in the ethanol water solution is 40%; the palladium chloride amount accounts for 1.3% of the total mass of the coconut shell carbon; the molar ratio of palladium chloride to imidazole ligand is 1:1; the imidazole ligand is 2-methylimidazole; the inert atmosphere is nitrogen; the gas space velocity of the hydrogen was 180 h -1 . The catalyst obtained was designated CAT-14.
Comparative example 5
The amount of urea phosphate was increased in order to explain the importance of the amount of urea phosphate in step (1) as compared with example 1.
The procedure of comparative example 5 was the same as in example 1 except that the amount of urea phosphate in step (1) was changed to 8% by weight based on the total mass of the carbon support, and the catalyst was designated CAT-15.
Comparative example 6
The amount of urea phosphate was reduced in order to demonstrate the importance of the amount of urea phosphate in step (1) as compared to example 1.
Comparative example 6 was prepared in the same manner as in example 1 except that the amount of urea phosphate in step (1) was changed to 1% by weight of the total mass of the carbon support, and the catalyst was designated CAT-16.
Comparative example 7
The hydrogen reduction temperature was lowered in order to explain the importance of the hydrogen reduction temperature in step (2) as compared with example 1.
Comparative example 7 was prepared in the same manner as in example 1 except that the sample in step (2) was reduced at 600℃for 2 hours under a hydrogen atmosphere flowing in a tube furnace to 500℃and the resulting catalyst was No. CAT-17.
Comparative example 8
The organic ligand was not added in order to demonstrate the importance of adding the ligand in step (2) as compared to example 1.
(1) And (3) carrier modification: fully dissolving urea phosphate into deionized water under the stirring state, then soaking the urea phosphate into a carbon carrier by adopting an isovolumetric soaking method, and then drying a sample at 80 ℃; roasting the sample in a muffle furnace at 650 ℃ for 3 hours in the air atmosphere, and cooling to room temperature to obtain a modified carbon carrier; the dosage of the urea phosphate accounts for 3% of the total mass of the carbon carrier, and the carbon carrier is coconut shell carbon;
(2) And (3) preparing a catalyst: dissolving palladium chloride in ethanol water solution under stirring, soaking the obtained solution in modified carbon carrier by isovolumetric soaking method, oven drying sample at 80deg.C, reducing sample in hydrogen gas atmosphere flowing in tubular furnace at 600deg.C for 2 hr, switching to flowing inert atmosphere, and reducingThe catalyst is heated to room temperature to obtain the required catalyst; wherein the mass content of ethanol in the ethanol water solution is 40%; the palladium chloride amount is 1.3 percent of the total mass of the modified carbon carrier; the inert atmosphere is nitrogen; the gas space velocity of the hydrogen was 180 h -1 . The catalyst obtained was numbered CAT-18.
Comparative example 9
The carbon support was modified with phosphoric acid in order to illustrate the importance of urea phosphate modification in step (1) as compared to example 1.
Comparative example 9 was prepared in the same manner as in example 1 except that urea phosphate in step (1) was changed to phosphoric acid, and the catalyst number obtained was CAT-19.
Comparative example 10
The carbon support was modified with urea in order to demonstrate the importance of urea phosphate modification in step (1) as compared to example 1.
Comparative example 10 was prepared in the same manner as in example 1 except that urea phosphate in step (1) was changed to urea, and the catalyst number was CAT-20.
Comparative example 11
The urea phosphate and palladium chloride were loaded in a one-step process with the aim of illustrating the importance of the stepwise preparation of the catalyst in comparison with example 1.
Preparation procedure of comparative example 11: dissolving palladium chloride into ethanol water solution under a stirring state, adding urea phosphate and imidazole ligand after the palladium chloride is completely dissolved, stirring for 0.5h, sealing the system, heating to 70 ℃ and continuously stirring for 1h, then soaking the obtained solution into coconut shell carbon by adopting an isovolumetric soaking method, drying a sample at 80 ℃, reducing the sample at 600 ℃ for 2h under a hydrogen atmosphere flowing in a tube furnace, switching to a flowing inert atmosphere, and cooling to room temperature to obtain the required catalyst; wherein the mass content of ethanol in the ethanol water solution is 40%; the dosage of the urea phosphate accounts for 3% of the total mass of the coconut shell carbon; the palladium chloride amount accounts for 1.3% of the total mass of the coconut shell carbon; the molar ratio of palladium chloride to imidazole ligand is 1:1; the imidazole ligand is 2-methylimidazole; the inert atmosphere is nitrogen; the gas space velocity of the hydrogen was 180 h -1 . The catalyst obtained was designated CAT-21.
The catalysts CAT-1 to CAT-21 were evaluated respectively, and the activity test methods and conditions for the catalysts were as follows:
(1) Filling the catalyst into a constant temperature zone of a continuous flow high-pressure fixed bed reactor, filling a ceramic ring with the length of 20 cm on the upper layer of the catalyst as a preheating layer, heating to 250 ℃ under flowing hydrogen to pretreat 1h, wherein the gas space velocity of the hydrogen is 180 h -1 ；
(2) After pretreatment is completed, the pressure of the fixed bed reactor is increased to 0.5MPa, and the reaction temperature is adjusted to 130 ℃;
(3) Pumping acetic acid chloride solution into a reactor by a high-pressure pump, wherein the acetic acid chloride solution comprises 40% chloroacetic acid, 10% dichloroacetic acid and 50% acetic acid by mass, and has a liquid hourly space velocity of 3.0 h –1 ；
(4) Collecting a liquid phase product, and then carrying out qualitative and quantitative analysis on the reacted product by using gas chromatography;
(5) After the reaction is finished, stopping feeding, then continuing to purge with nitrogen for 1h, cooling, and closing the nitrogen after the temperature is reduced to below 80 ℃.
The results of evaluating the activities of the CAT-1 to CAT-21 catalysts are shown in Table 1:
TABLE 1
| Catalyst numbering | Dichloroacetic acid conversion (%) | Chloroacetic acid selectivity (%) |
| CAT-1 | 99.2 | 79.6 |
| CAT-2 | 99.3 | 78.9 |
| CAT-3 | 99.1 | 79.1 |
| CAT-4 | 98.0 | 75.7 |
| CAT-5 | 99.6 | 81.9 |
| CAT-6 | 99.2 | 79.3 |
| CAT-7 | 99.2 | 78.8 |
| CAT-8 | 99.2 | 79.8 |
| CAT-9 | 99.2 | 80.3 |
| CAT-10 | 99.3 | 81.7 |
| CAT-11 | 94.2 | 66.7 |
| CAT-12 | 90.0 | 49.8 |
| CAT-13 | 84.3 | 52.4 |
| CAT-14 | 89.1 | 49.7 |
| CAT-15 | 97.2 | 64.3 |
| CAT-16 | 99.7 | 48.1 |
| CAT-17 | 98.3 | 59.2 |
| CAT-18 | 94.4 | 61.8 |
| CAT-19 | 93.0 | 64.9 |
| CAT-20 | 92.2 | 47.4 |
| CAT-21 | 80.7 | 48.1 |
As can be seen from the data in Table 1, the conversion rate of the dichloroacetic acid in the evaluation process of CAT-1 to CAT-10 prepared by the embodiments 1 to 10 of the scheme of the invention is higher, the conversion rate of the dichloroacetic acid can reach more than 98%, the selectivity of the chloroacetic acid in the product is higher, and the selectivity of the chloroacetic acid can reach more than 75%, which indicates that the side reaction is less. The prepared catalyst was compared with each comparative example by changing a certain experimental condition, and it can be seen from the data in table 1 that the change of a certain condition during the preparation process has some influence on the conversion rate of dichloroacetic acid, the conversion rate is reduced, and the change of a certain condition does not reduce the conversion rate of dichloroacetic acid, but the change of any condition has a great influence on the selectivity of chloroacetic acid. The catalyst prepared by the method provided by the invention can be used for efficiently converting dichloroacetic acid, and the ratio of chloroacetic acid in the product is improved, so that the catalyst is especially suitable for preparing chloroacetic acid by selective hydrodechlorination of dichloroacetic acid.
The foregoing describes the embodiments of the present invention in detail, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.
Claims (8)
1. A preparation method of a catalyst for selective hydrodechlorination of acetic acid chlorinated solution is characterized by comprising the following steps: immersing urea phosphate aqueous solution in an equal volume into a carbon carrier, and roasting the carbon carrier for at least 3 hours at 500-650 ℃ in the air atmosphere in a muffle furnace after drying to obtain a modified carbon carrier; the dosage of the urea phosphate accounts for 3-5% of the total mass of the carbon carrier;
dissolving palladium chloride into an ethanol water solution, adding a ligand which is an imidazole ligand or a dicarbonyl nitrogen-containing ligand after dissolving, stirring, hermetically heating the system to 70-80 ℃ and continuously stirring for 1-2h, soaking the obtained solution into the modified carbon carrier in an equal volume, and reducing the solution for at least 2h in a hydrogen atmosphere of 550-600 ℃ after drying to obtain a catalyst for selective hydrogenation and dechlorination of acetic acid chloride;
wherein, the palladium chloride consumption accounts for 1.3% -2% of the total mass of the modified carbon carrier; the molar ratio of the palladium chloride to the ligand is 1:1-2; the imidazole ligand is one or more of 2-methylimidazole, imidazole and 4-methylimidazole; the dicarbonyl nitrogen-containing ligand is one or more of N-chlorosuccinimide, N-methyl succinimide and succinimide.
2. The method for preparing the catalyst for selective hydrodechlorination of acetic acid chloride according to claim 1, wherein the method comprises the following steps: the mass content of the ethanol in the ethanol water solution is 40-60%.
3. The method for preparing the catalyst for selective hydrodechlorination of acetic acid chloride according to claim 1, wherein the method comprises the following steps: the carbon carrier is one or more of wood activated carbon, coconut shell carbon and coal carbon.
4. A method for preparing a catalyst for selective hydrodechlorination of acetic acid chloride according to any one of claims 1 to 3, wherein: immersing urea phosphate aqueous solution in equal volume into a carbon carrier, drying at 75-85 ℃, and/or immersing the obtained solution in equal volume into the modified carbon carrier, and drying at 75-85 ℃.
5. A method for preparing a catalyst for selective hydrodechlorination of acetic acid chloride according to any one of claims 1 to 3, wherein: immersing the obtained solution in the modified carbon carrier in an equal volume, drying, reducing in a hydrogen atmosphere flowing in a tube furnace, switching to an inert atmosphere after the reduction is finished, and cooling to room temperature; wherein the gas space velocity of the hydrogen is 180-540 h -1 The inert atmosphere is one or more of nitrogen, argon or helium.
6. A catalyst for selective hydrodechlorination of acetic acid chloride, characterized in that: prepared by the preparation method of any one of claims 1 to 5.
7. The use of the catalyst of claim 6 in the selective hydrodechlorination of dichloroacetic acid in acetic acid chloride to produce chloroacetic acid.
8. The use according to claim 7, characterized in that: the method comprises the following steps:
step 1: filling the catalyst into a constant temperature zone of a continuous flow high-pressure fixed bed reactor, filling a ceramic ring with a thickness of at least 20 cm on the upper layer of the catalyst as a preheating layer, heating to 250-300 ℃ under flowing hydrogen to pretreat at least 1h, and controlling the gas space velocity of the hydrogen to be 180-540 h -1 ；
Step 2: after pretreatment is completed, the pressure of the fixed bed reactor is increased to 0.3-0.5MPa, and the reaction temperature is adjusted to 120-150 ℃;
step 3: pumping acetic acid chloride solution into a reactor by a high-pressure pump, wherein the acetic acid chloride solution comprises 40% chloroacetic acid, 10% dichloroacetic acid and 50% acetic acid by mass, and has a liquid hourly space velocity of 3.0-9.0 h –1 ；
The liquid phase product obtained by the preparation is acetic acid chloridizing solution after selective dechlorination.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5462651A (en) * | 1994-08-09 | 1995-10-31 | Texaco Inc. | Hydrodearomatization of hydrocarbon oils using novel "phosphorus treated carbon" supported metal sulfide catalysts |
| CN102553584A (en) * | 2011-12-26 | 2012-07-11 | 西安凯立化工有限公司 | Modified palladium-carbon catalyst for producing chloroacetic acid and preparation method for catalyst |
| CN106241806A (en) * | 2016-08-29 | 2016-12-21 | 山东大学 | The technique that a kind of urea phosphate activation method prepares high nitrogen-containing functional group microporous activated carbon |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5462651A (en) * | 1994-08-09 | 1995-10-31 | Texaco Inc. | Hydrodearomatization of hydrocarbon oils using novel "phosphorus treated carbon" supported metal sulfide catalysts |
| CN102553584A (en) * | 2011-12-26 | 2012-07-11 | 西安凯立化工有限公司 | Modified palladium-carbon catalyst for producing chloroacetic acid and preparation method for catalyst |
| CN106241806A (en) * | 2016-08-29 | 2016-12-21 | 山东大学 | The technique that a kind of urea phosphate activation method prepares high nitrogen-containing functional group microporous activated carbon |
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