Preparation method and application of catalyst for hydrogenation of dimethyl 1, 6-adipate

Abstract

The invention relates to the technical field of catalysts, and particularly discloses a preparation method and application of a catalyst for hydrogenation of dimethyl 1, 6-adipate, and the preparation method of the catalyst comprises the following steps: S1, crushing and sieving montmorillonite, carrying out acid treatment, and washing and drying after treatment; s2, dissolving szaibelyite in hot nitric acid under stirring, filtering after dissolving is completed, adding a barium hydroxide solution into filtrate, mixing and stirring, adjusting the pH value to 9.5-10.5, and aging at 50-80 DEG C; s3, uniformly mixing the montmorillonite obtained in the S1 with the material obtained in the S2 for reaction, and then filtering, washing, drying and roasting to obtain a modified montmorillonite carrier; and S4, uniformly mixing the modified montmorillonite carrier, a metal salt solution and a precipitant, standing, aging, filtering, washing, drying and calcining to obtain the modified montmorillonite catalyst. The catalyst has good catalytic performance in the reaction process of preparing 1, 6-hexanediol through hydrogenation of dimethyl 1, 6-adipate, the conversion rate of dimethyl 1, 6-adipate and the selectivity of 1, 6-hexanediol are both higher than 99%, impurities are few, the catalyst is not prone to loss, and the catalyst is green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a method for preparing a catalyst for the hydrogenation of dimethyl 1,6-adipic acid and its application. Background Technology

[0002] 1,6-Hexanediol, abbreviated as HDO, is an important chemical raw material, mainly used in the production of polyurethane, unsaturated polyester, plasticizers, hardeners for gelling agents, heat stability improvers for lubricating oils, etc. It is also used in the production of pesticides such as pyrethroids, organic peroxides, cyclic musk, polyethylene plastic crosslinking agents, and polyether rubber.

[0003] Currently, the mainstream process for preparing 1,6-hexanediol is the adipic acid esterification hydrogenation method, which involves two steps. First, adipic acid undergoes an esterification reaction to obtain an adipic acid ester derivative, which is then hydrogenated to obtain 1,6-hexanediol. This process uses readily available raw materials and has a simple production flow, but its challenges lie in the high reaction pressure, high hydrogen-to-ester ratio, low liquid hourly space velocity, and the high toxicity and environmental pollution of traditional catalysts, leading to excessively high actual production costs. CN102380389A discloses a catalyst for the hydrogenation of dialkyl adipic acid esters to prepare 1,6-hexanediol. The catalyst has a weight composition of Cu: 5-30%, Ni: 2-10%, B: 5-20%, M: 0-5%, with the balance being a porous support. The prepared catalyst, after reduction, was applied to the hydrogenation of 1,6-dialkyl adipate to 1,6-hexanediol, requiring a reaction system pressure higher than 10 MPa. CN101531568A discloses a method for preparing a hydrogenation catalyst for dimethyl adipate. The preparation process involves stirring a silica support and an aqueous copper salt solution, followed by evaporation, drying, and calcination to obtain the hydrogenation catalyst. This method uses microwave treatment of the catalyst, making large-scale industrial application difficult. In the hydrogenation reaction of dimethyl adipate, the catalyst exhibits a feed conversion rate of approximately 90% and a product selectivity of <90%, indicating a generally poor catalytic effect. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing a catalyst for the hydrogenation of dimethyl 1,6-adipic acid and its application. The catalyst prepared by this method exhibits high activity, stable performance, environmental friendliness, and low production cost.

[0005] The technical solution of the present invention is a method for preparing a catalyst for the hydrogenation of dimethyl 1,6-adipate, comprising the following steps: S1. After crushing and sieving montmorillonite, acid treatment is carried out, followed by washing and drying. S2. Dissolve boromagnesia in hot nitric acid while stirring. After dissolution is complete, filter the solution. Add barium hydroxide solution to the filtrate, mix and stir, adjust the pH to 9.5-10.5, and age at 50-80℃. S3. Mix the montmorillonite obtained in S1 with the material obtained in S2, then filter, wash, dry and calcine to obtain the modified montmorillonite carrier. S4. After mixing the modified montmorillonite carrier, metal salt solution, and precipitant, the mixture is allowed to stand for aging, filtered, washed, dried, and then calcined to obtain the modified montmorillonite catalyst.

[0006] Optionally, the acid mentioned in S1 is one or more of acetic acid, propionic acid, oxalic acid, citric acid, and benzenesulfonic acid. Preferably, the mass ratio of montmorillonite to the acid treatment agent is 1:(1-25).

[0007] Optionally, the acid treatment temperature in S1 is 40-90℃, and the acid treatment time is 8-12h.

[0008] Optionally, the reaction temperature in S3 is 30-65℃, and the reaction time is 12-24h.

[0009] Optionally, the mass ratio of montmorillonite in S3 to the material obtained in S2 is 1:(8-25).

[0010] Optionally, the metal salt solution in S4 is a mixed aqueous solution composed of copper salt and palladium salt, with a mass concentration of 2-20%, and the molar ratio of copper salt to palladium salt is 1:(0.01-0.1).

[0011] Optionally, the copper salt is one or more of copper nitrate, copper sulfate, and copper chloride, and the palladium salt is one or more of sodium chloropalladate, potassium chloropalladate, palladium nitrate, palladium sulfate, and tetraamminepalladium chloride.

[0012] Optionally, the precipitant is an aqueous solution of one or more of sodium carbonate, sodium hydroxide, potassium hydroxide, potassium carbonate and potassium bicarbonate, and the mass concentration of the precipitant is 1-15%.

[0013] Optionally, the mass ratio of modified montmorillonite carrier, metal salt solution, and precipitant in S4 is 1:(1-10):(10-50), the reaction temperature is 50-80℃, and the reaction time is 1.5-4.5h.

[0014] The present invention also relates to the application of the catalyst obtained by the preparation method described above in the hydrogenation of dimethyl 1,6-adipate to prepare 1,6-hexanediol.

[0015] The present invention has the following beneficial effects: (1) After acid hydrolysis, borosilicate will generate a large amount of tetrahydroxyborate in a strongly alkaline solution. The tetrahydroxyborate then reacts with a large number of silanol groups in montmorillonite to form a stable complex structure. This structure has three advantages: first, it makes the pore structure of the support less prone to collapse, and the catalyst structure is more stable; second, it changes the electron cloud density of the montmorillonite support structure by reacting with silanol groups, thereby adjusting the acidity and alkalinity of the support and improving the product selectivity; and third, it can load some magnesium and barium auxiliary components onto the support, increasing the catalyst activity.

[0016] (2) Copper has a strong hydrogen absorption capacity, which can improve the conversion rate of raw materials, while palladium has a good selectivity for 1,6-hexanediol products. In this invention, copper and palladium are used as active components of catalysts, and combined with magnesium and barium auxiliary components on montmorillonite support, so that the catalyst has high activity. Using low concentration metal salt solution and precipitant can make the precipitation reaction slower and more thorough, and increase the loading of active components. At the same time, long-term static residence can make the active components crystallize better and improve the dispersion of active components.

[0017] (3) Furthermore, the hydrogenation catalyst of this invention uses natural montmorillonite as the support component and natural boromagnesia as the support modification component. These natural materials are environmentally friendly raw materials, pollution-free, and in line with the principles of green chemistry. Moreover, these substances are widely available and inexpensive, which can greatly reduce the cost of the catalyst. When used in the hydrogenation of dimethyl 1,6-adipate to prepare 1,6-hexanediol, it can reduce the reaction pressure and hydrogen-ester ratio, and improve the conversion rate of dimethyl 1,6-adipate and the selectivity of 1,6-hexanediol. Attached Figure Description

[0018] Figure 1 The image shows a typical gas chromatogram of the product from the hydrogenation of dimethyl 1,6-adipate to 1,6-hexanediol in Example 6, with the peak elution time of 8.038 min for dimethyl 1,6-adipate and 11.358 min for 1,6-hexanediol. Detailed Implementation

[0019] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the raw materials or reagents used are commercially available. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention.

[0020] Example 1 A: Crush 30.5g of montmorillonite, sieve it into powder, add it to 100g of acetic acid, stir vigorously at 60℃ for 10h, filter after completion, wash the filter cake with ethanol and water until neutral, and dry at 80℃. B: Dissolve 85.2g of boromagnesite powder in 200g of hot concentrated nitric acid at 50℃ under vigorous stirring. After filtration, add 0.16mol / L barium hydroxide solution dropwise to the filtrate while stirring until the pH of the filtrate is 10. After the addition is complete, let it stand in a constant temperature water bath at 60℃ for 18h for aging. C: Add 15g of the montmorillonite treated in step A to 150g of the filtrate treated in step B, stir vigorously at 60℃ for 18h, let stand for 5h after completion, then filter, wash the filter cake until neutral, dry, grind finely, and calcine to obtain the modified montmorillonite carrier. D: Mix 5g of modified montmorillonite support, 10g of 10% (w / w) metal salt aqueous solution (where the copper salt is copper nitrate, the palladium salt is sodium chloropalladate, and the molar ratio of copper salt to palladium salt is 1:0.03), and 60g of 5% (w / w) sodium carbonate aqueous solution. Stir at 60℃ for 3h, allow to stand and age for 18h after reaction, filter, wash the filter cake, dry at 80℃, and calcine at 450℃ for 6h to obtain the modified montmorillonite catalyst.

[0021] Example 2 Based on Example 1, the acid treatment agent acetic acid in step A was changed to oxalic acid, and the rest was the same as in Example 1.

[0022] Example 3 Based on Example 1, the reaction temperature in step C was changed from 60°C to 50°C, while other aspects remained the same as in Example 1.

[0023] Example 4 Based on Example 1, the copper salt in step D was changed to copper chloride, and the rest was the same as in Example 1.

[0024] Example 5 Based on Example 1, the palladium salt in step D was changed to palladium tetraammine chloride, and the rest was the same as in Example 1.

[0025] Example 6 Based on Example 1, the molar ratio of copper salt to palladium salt in step D was changed to 1:0.05, while other aspects remained the same as in Example 1.

[0026] Example 7 Based on Example 1, the reaction temperature in step D was changed from 60°C to 75°C, while other aspects remained the same as in Example 1.

[0027] Comparative Example 1 Based on Example 1, the acid treatment agent acetic acid in step A was removed, and everything else was the same as in Example 1.

[0028] Comparative Example 2 Based on Example 1, the reaction temperature in step C was changed from 60°C to 80°C, while other aspects remained the same as in Example 1.

[0029] Comparative Example 3 Based on Example 1, the palladium salt in step D was removed, and everything else was the same as in Example 1.

[0030] Comparative Example 4 Based on Example 1, the molar ratio of copper salt to palladium salt in step D was changed to 1:10, and the rest was the same as in Example 1.

[0031] Comparative Example 5 Based on Example 1, the alkaline treatment process of barium hydroxide solution in step B is removed, and the filtrate is directly used in step C, otherwise the same as in Example 1.

[0032] Comparative Example 6 Based on Example 1, the boromagnesia stone in step B was replaced with borax, while the rest remained the same as in Example 1.

[0033] The above catalyst was ground and sieved to form catalyst particles of 20-40 mesh size. 1 g of these particles was mixed with 2 g of quartz sand and then packed into a fixed-bed reactor. A 10% (w / w) methanol solution of dimethyl 1,6-adipate was used as the raw material, flowing downwards through the catalyst bed along with high-purity hydrogen gas. The reaction was carried out at a temperature of 220°C, a pressure of 3 MPa, a hydrogen-to-ester ratio of 25, and a liquid hourly space velocity (LISH) of 0.95 h⁻¹. -1 The hydrogenation reaction was carried out under certain conditions to obtain 1,6-hexanediol. The results of the analysis are shown in Table 1 below.

[0034] Table 1: Comparison of feed conversion and product selectivity in the hydrogenation of dimethyl 1,6-adipate to 1,6-hexanediol.

[0035] As can be seen from the comparison of experimental data in Table 1, Comparative Example 1, without the acid treatment agent in step A, effectively removes the acid treatment agent. The role of the acid treatment agent is to dissolve and react away a large number of impurities in natural montmorillonite, including inorganic metal salts and a small amount of organic matter. Without the action of the acid treatment agent, these impurities would usually block the pores of the support and form complex crystal forms with the aluminosilicate structure of the support itself, making subsequent support modification difficult. The resulting catalyst would have unsatisfactory pore structure and active component loading, resulting in poor catalytic performance.

[0036] As can be seen from the comparison of experimental data in Table 1, in Comparative Example 2, the reaction temperature in step C was changed from 60℃ to 80℃. The purpose of step C is to induce a complexation reaction between montmorillonite and the tetrahydroxyborate active species to form a modified montmorillonite support. Increasing the reaction temperature will cause the montmorillonite component itself to decompose and generate side reactions, inhibiting the interaction between silanol groups and active species, resulting in incomplete modification of the catalyst support and a poorer catalytic effect.

[0037] As can be seen from the comparison of experimental data in Table 1, Comparative Example 3, which removes the palladium salt in step D, utilizes the palladium component to activate the carbon-oxygen double bond in dimethyl 1,6-adipic acid, making the ester group more likely to react with hydrogen to form an alcohol and improving the selectivity of the product 1,6-hexanediol. Removing the palladium active component reduces the product selectivity and deteriorates the catalytic activity.

[0038] As can be seen from the comparison of experimental data in Table 1, in Comparative Example 4, changing the molar ratio of copper salt to palladium salt in step D to 1:10 is beneficial. The role of the copper active component in the catalyst is to adsorb hydrogen gas. It has a strong ability to capture hydrogen, which allows the raw material dimethyl 1,6-adipate to have sufficient contact with hydrogen gas, thereby increasing the degree of hydrogenation reaction. Changing the molar ratio of copper salt to palladium salt to 1:10 will greatly reduce the amount of copper in the active component of the catalyst, resulting in a decrease in the degree of hydrogenation reaction, a decrease in the conversion rate of raw materials, and a deterioration in catalytic activity.

[0039] As can be seen from the experimental data comparison in Table 1, Comparative Example 5, without the alkaline treatment of barium hydroxide solution in step B, shows that under strongly alkaline conditions, the large amount of boric acid present in the boromagnesite solution after nitric acid dissolution will combine with hydroxide ions to transform into the active species tetrahydroxyborate. Without the alkaline treatment in step B, the boron in the solution mainly exists in the form of boric acid under acidic conditions, resulting in a significant reduction in the amount of the active species tetrahydroxyborate. This leads to fewer complex structures formed by the reaction with the silanol groups in montmorillonite, and a reduction in the auxiliary components magnesium and barium, resulting in a decrease in the selectivity of the hydrogenation reaction products and a deterioration in catalytic activity.

[0040] As can be seen from the comparison of experimental data in Table 1, in Comparative Example 6, boromagnesia was replaced with borax in step B. Boromagnesia contains magnesium, an additive component. The presence of this additive can improve the dispersion of the active components copper and palladium on the catalyst support, prevent catalyst agglomeration and sintering, and support the pore structure of the catalyst support, thereby greatly improving product selectivity. However, by replacing boromagnesia with borax in step B, the catalyst lacks magnesium additives, resulting in decreased product selectivity and poorer catalytic activity.

[0041] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for preparing a catalyst for the hydrogenation of dimethyl 1,6-adipate, characterized in that, Includes the following steps: S1. After crushing and sieving montmorillonite, acid treatment is carried out, followed by washing and drying. S2. Dissolve boromagnesia in hot nitric acid while stirring. After dissolution is complete, filter the solution. Add barium hydroxide solution to the filtrate and mix and stir. Adjust the pH to 9.5-10.5 and age the solution at 50-80℃ for later use. S3. Mix the montmorillonite obtained in S1 with the material obtained in S2, then filter, wash, dry and calcine to obtain the modified montmorillonite carrier. S4. After mixing the modified montmorillonite carrier, metal salt solution, and precipitant, the mixture is allowed to stand for aging, filtered, washed, dried, and then calcined to obtain the modified montmorillonite catalyst.

2. The preparation method according to claim 1, characterized in that: The acid mentioned in S1 is one or more of acetic acid, propionic acid, oxalic acid, citric acid, and benzenesulfonic acid.

3. The preparation method according to claim 1, characterized in that: The acid treatment temperature in S1 is 40-90℃, and the acid treatment time is 8-12h.

4. The preparation method according to claim 1, characterized in that: The reaction temperature in S3 is 30-65℃, and the reaction time is 12-24h.

5. The preparation method according to claim 1, characterized in that: The mass ratio of montmorillonite in S3 to the material obtained in S2 is 1:(8-25).

6. The preparation method according to claim 1, characterized in that: The metal salt solution in S4 is a mixed aqueous solution composed of copper and palladium salts with a mass concentration of 2-20% and a molar ratio of copper salt to palladium salt of 1:(0.01-0.1).

7. The preparation method according to claim 6, characterized in that: The copper salt is one or more of copper nitrate, copper sulfate, and copper chloride, and the palladium salt is one or more of sodium chloropalladate, potassium chloropalladate, palladium nitrate, palladium sulfate, and tetraamminepalladium chloride.

8. The preparation method according to claim 1, characterized in that: The precipitant is an aqueous solution of one or more of sodium carbonate, sodium hydroxide, potassium hydroxide, potassium carbonate and potassium bicarbonate, with a mass concentration of 1-15%.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The mass ratio of modified montmorillonite carrier, metal salt solution, and precipitant in S4 is 1:(1-10):(10-50), the reaction temperature is 50-80℃, and the reaction time is 1.5-4.5h.

10. The use of the catalyst obtained by the preparation method according to any one of claims 1 to 9 in the hydrogenation of dimethyl 1,6-adipate to prepare 1,6-hexanediol.

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