Preparation method of copper-based hydrogenation catalyst and application thereof

Abstract

This invention discloses a method for preparing a copper-based hydrogenation catalyst and its application. The method for preparing the copper-based hydrogenation catalyst includes the following steps: (1) preparing a mixed aqueous solution A of soluble salts of Cu, Zn, and Al, with a Cu:Zn:Al molar ratio of 2:(0.3~3):(0~3); preparing an aqueous solution B of a precipitant; (2) pre-filling a reaction vessel with pure water, and adding solutions A and B concurrently to the reaction vessel to generate a precursor precipitate; and obtaining the copper-based hydrogenation catalyst after post-treatment. This invention uses a co-precipitation method to prepare a copper-based hydrogenation catalyst, which shows significant effect in the catalytic hydrogenation of diisobutyl ketone (DIBK) to DIBC, with a diisobutyl ketone conversion rate greater than 95% and a diisobutyl methanol selectivity greater than 99%. Under relatively mild reaction conditions, the excellent hydrogenation conversion rate and selectivity reduce the difficulty of product purification, giving this invention good prospects for industrialization.

Description

Technical Field

[0001] This invention relates to a method for preparing a copper-based catalyst, namely, a co-precipitation method for preparing a copper-based catalyst, and its application in the preparation of diisobutylmethanol. Background Technology

[0002] 2,6-Dimethyl-4-heptanol, commonly known as diisobutylcarbinol (DIBC), is a colorless, transparent liquid with a sweet taste. It is insoluble in water but miscible with most organic solvents. It is primarily used as a solvent in the anthraquinone process for producing hydrogen peroxide. It can also be used as an antifoaming agent, fabric softener, paint film-forming agent, coating thinner, coupling solvent for resin synthesis, mineral flotation agent, chemical extractant, additive in plastics, rubber, lubricants, and petroleum products, as well as a raw material or intermediate in the synthesis of pharmaceuticals and fragrances.

[0003] With the rapid growth in domestic demand for hydrogen peroxide, the capacity and scale of industrial hydrogen peroxide plants have also expanded accordingly. Therefore, there is an urgent need for a more efficient working carrier, 2-pentylanthraquinone, to increase unit capacity. Diisobutylmethanol, with its low density and high partition coefficient, is a good solvent for 2-pentylanthraquinone, and market demand for it is pressing.

[0004] Industrially, DIBC production primarily involves the catalytic hydrogenation of diisobutyl ketone (DIBK) to diisobutyl methanol, a widely adopted method. CN104355965A uses Raney nickel as a catalyst, achieving a hydrogenation yield of over 99%. However, the hydrogen source used is high-purity hydrogen, and the temperature and pressure in the examples cannot simultaneously achieve milder process conditions. Furthermore, there is a risk of spontaneous combustion of Raney nickel. CN1325837A uses a copper-based catalyst for ketone hydrogenation, but the prepared copper-based catalyst is more suitable for the catalytic hydrogenation of acetone. In the examples, the conversion rate of catalytic hydrogenation of DIBK is low (75.4%), and the pressure is high, requiring 2 MPa. CN105107487A discloses a method for preparing diisobutyl methanol by catalytic hydrogenation of DIBK using a supported nickel-based catalyst. The conditions are relatively mild, but the conversion rate of DIBK is not high (91%). Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a copper-based hydrogenation catalyst and its application. The preparation method uses copper nitrate, zinc nitrate, and aluminum nitrate as raw materials, and ammonium bicarbonate as a precipitant, to prepare the copper-based hydrogenation catalyst through precipitation. The preparation method is simple and convenient to operate. The copper-based hydrogenation catalyst is used to prepare diisobutylmethanol, achieving a diisobutyl ketone conversion rate greater than 95% and a diisobutylmethanol selectivity greater than 99%.

[0006] The first aspect of this invention provides a method for preparing a copper-based hydrogenation catalyst, comprising the following steps: (1) Prepare a mixed aqueous solution A of soluble salts of Cu, Zn and Al, with a Cu:Zn:Al molar ratio of 2:(0.3~3):(0~3); prepare an aqueous solution B of precipitant; (2) Pure water is pre-placed in the reactor, and solutions A and B are added to the reactor in parallel to generate a precursor precipitate; after post-treatment, a copper-based hydrogenation catalyst is obtained.

[0007] Preferably, in step (1), the soluble salts of Cu, Zn, and Al are nitrates; the Cu in the reaction solution 2+ and Zn 2+ And Al 3+ The molar ratio can be 6:6:1.2, 6:6:2, 6:3:1, or 6:1:3; the molar ratio of the sum of the added nitrate moles to the precipitant is 1:1 to 1.1:1. The precipitant is selected from one or more of ammonia, urea, sodium carbonate, and ammonium bicarbonate.

[0008] Preferably, in step (2), the post-processing includes: heat preservation aging, washing, filtration, drying and crushing of the filter cake to obtain a powdered catalyst precursor, and calcination to obtain a copper-based hydrogenation catalyst.

[0009] Preferably, in step (2), the volume of pure water pre-placed in the reactor is 0-10% of the total volume of solution A, preferably 3-6%; the pH value of the system during the precipitation process is controlled between 5.0 and 7.0, preferably 5.5-6.5; and the precipitation temperature is 50-90℃.

[0010] Preferably, in step (2), after precipitation, the pH of the system is controlled between 6.0 and 7.0 by controlling the amount of precipitant, and aged at a constant temperature for 0 to 24 hours. The filtrate is washed until the pH is neutral to obtain a filter cake. The filter cake is dried at 120 ℃ for 8 to 12 hours. The filter cake can be pulverized using a pulverizer or a grinder.

[0011] Preferably, in step (2), the roasting process is as follows: roasting at 220℃~270℃ for 0.5~3 hours, preferably 1~2 hours, in an air atmosphere; then roasting at 350~500℃, preferably 400~450℃ for 2~6 hours, preferably 3~5 hours.

[0012] A second aspect of the present invention provides an application of a copper-based hydrogenation catalyst, wherein the copper-based hydrogenation catalyst is used for the hydrogenation of diisobutyl ketone to prepare diisobutyl methanol.

[0013] Preferably, the hydrogenation of diisobutyl ketone to prepare diisobutyl methanol includes the following steps: (1) Diisobutyl ketone and the copper-based hydrogenation catalyst are added to a batch reactor. Under rapid stirring, the reaction temperature is raised to 140~160℃, and hydrogen is continuously introduced to carry out the catalytic hydrogenation reaction. (2) During the reaction, the pressure should not exceed 1.4~1.5MPa, the temperature should be 150~180℃, and the reaction time should be 3~4.5h; (3) After the reaction is complete, stop the hydrogen gas supply, maintain the temperature and stir, and let the reaction proceed under pressure for a period of time; then cool down and separate the crude diisobutylmethanol through a membrane.

[0014] Preferably, the mass of the copper-based hydrogenation catalyst is 1.0 times the sum of the masses of the copper-based hydrogenation catalyst and diisobutylmethanol. wt. % ~ 10.0 wt. %, preferably 5.0 wt. Preferably, after separating the crude diisobutylmethanol, the copper-based hydrogenation catalyst is left in the reactor for reuse.

[0015] Preferably, the conversion rate of diisobutyl ketone is greater than 95%, and the selectivity of diisobutyl methanol is greater than 99%.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) The catalyst prepared by the present invention can be reused multiple times and is easy to recycle. The increase in catalyst life can effectively reduce the cost of catalyst preparation and reduce the wastewater and spent catalyst solids generated during the catalyst preparation process; (2) In the copper-zinc-aluminum catalyst provided by the present invention, Cu exists in the form of CuO, and ZnO and Al2O3 serve as supports and promoters, which can separate the copper species, thereby improving the dispersion of copper species and the stability of the pore structure. Catalysts with better dispersion of copper species have more contactable active centers on their surface, which is beneficial to improving the hydrogenation activity of the catalyst; on the other hand, the introduction of ZnO and Al2O3 is beneficial to improving the thermal stability of the catalyst during hydrogenation and activation, avoiding large temperature fluctuations, thus helping to obtain a catalyst with stable hydrogenation performance; (3) In the preparation method of copper-zinc-aluminum catalyst provided by the present invention, ammonium bicarbonate solution is used instead of sodium carbonate solution, the traditional precipitant. The reason is that sodium ions are not easy to be completely removed during the washing process. The residual sodium ions will hinder the dispersion of copper crystals on the support, affect the surface properties of copper-zinc-aluminum catalyst, and thus reduce the hydrogenation activity of the catalyst. (4) In the method for preparing copper-zinc-aluminum catalyst provided by the present invention, the increase of precipitation temperature will change the precipitation characteristics of copper ions, zinc ions and aluminum ions, so that the precipitation reaction can start under lower pH conditions. However, the precipitation temperature should not be too high, otherwise large CuO particles will appear on the catalyst surface too early, affecting the dispersion of copper species on the catalyst surface, thereby affecting the hydrogenation activity of the catalyst. (5) The method for preparing copper-zinc-aluminum catalyst provided by the present invention does not generate toxic waste liquid, which meets the requirements of environmentally friendly chemistry. Detailed Implementation

[0017] The purity of crude DIBC was analyzed by gas chromatography, and the detection conditions are listed in Table 1.

[0018] Table 1. Gas Chromatography Detection Conditions

[0019] Example 1 109.94 g of copper nitrate trihydrate, 135.36 g of zinc nitrate hexahydrate, and 34.15 g of aluminum nitrate nonahydrate were weighed and dissolved in 1.4 L of deionized water to prepare an acidic salt solution with a copper-zinc-aluminum concentration ratio of 5:5:1. 155.64 g of ammonium bicarbonate was weighed and dissolved in 1.4 L of deionized water to prepare an alkaline precipitant solution with a concentration of 1.4 mol / L. 0.09 L of pure water was pre-placed in the reactor, and the temperature was raised to 80°C. Under rapid stirring, the acidic salt solution and precipitant solution were added to the reactor in a parallel flow to generate the precursor precipitate. The pH of the precipitation process was maintained at approximately 6.5 by controlling the rate of material addition. After precipitation, the precursor was kept at a constant temperature for 2 hours, washed three times with water, and dried at 120℃ for 12 hours to obtain 97.89 g of precursor. After pulverization, it was calcined at 250℃~270℃ for 2 hours in air atmosphere, then calcined at 400~450℃ for 3 hours, and then cooled to obtain 70.5 g of catalyst A.

[0020] Example 2

[0021] 103.69 g of copper nitrate trihydrate, 127.67 g of zinc nitrate hexahydrate, and 53.70 g of aluminum nitrate nonahydrate were weighed and dissolved in 1.4 L of deionized water to prepare an acidic salt solution with a copper-zinc-aluminum concentration ratio of 6:6:2. 159.7 g of ammonium bicarbonate was weighed and dissolved in 1.4 L of deionized water to prepare an alkaline precipitant solution with a concentration of 1.4 mol / L. 0.09 L of pure water was pre-placed in a reactor, and the temperature was raised to 80°C. Under rapid stirring, the acidic salt solution and precipitant solution were added to the reactor in a parallel flow to generate the precursor precipitate. The pH was controlled at approximately 6.5 during the precipitation process. After aging at this temperature for 2 hours, the precursor was washed three times with water and dried at 120°C to obtain 98.53 g of precursor. This precursor was then pulverized and calcined in air at 250°C–270°C for 2 hours, followed by calcination at 400–450°C for 3 hours. After cooling, 70.7 g of catalyst B was obtained.

[0022] Example 3

[0023] 144.98 g of copper nitrate trihydrate, 89.3 g of zinc nitrate hexahydrate, and 37.59 g of aluminum nitrate nonahydrate were weighed and dissolved in 1.4 L of deionized water to prepare an acidic salt solution with a copper-zinc-aluminum concentration ratio of 6:3:1. 154.32 g of ammonium bicarbonate was weighed and dissolved in 1.4 L of deionized water to prepare an alkaline precipitant solution with a concentration of 1.4 mol / L. 0.09 L of pure water was pre-placed in a reactor, and the temperature was raised to 80°C. Under rapid stirring, the acidic salt solution and precipitant solution were added to the reactor in a parallel flow to generate the precursor precipitate. The pH was controlled at approximately 6.5 during the precipitation process. After aging at this temperature for 2 hours, the precursor was washed three times with water and dried at 120°C to obtain 98.63 g of precursor. This precursor was then pulverized and calcined in air at 250°C–270°C for 2 hours, followed by calcination at 400–450°C for 3 hours. After cooling, 69.56 g of catalyst C was obtained.

[0024] Example 4

[0025] 132.72 g of copper nitrate trihydrate, 27.24 g of zinc nitrate hexahydrate, and 103.1 g of aluminum nitrate nonahydrate were weighed and dissolved in 1.4 L of deionized water to prepare an acidic salt solution with a copper-zinc-aluminum concentration ratio of 6:1:3. 154.3 g of ammonium bicarbonate was weighed and dissolved in 1.4 L of deionized water to prepare an alkaline precipitant solution with a concentration of 1.39 mol / L. 0.09 L of pure water was pre-placed in the reactor, and the temperature was raised to 80°C. Under rapid stirring, the acidic salt solution and precipitant solution were added to the reactor in a parallel flow to generate the precursor precipitate. The pH of the precipitation process was maintained at approximately 6.5 by controlling the rate of material addition. After precipitation, the precursor was kept at a constant temperature for 2 hours, washed three times with water, and dried at 120℃ for 12 hours to obtain 95.13 g of precursor. After pulverization, it was calcined at 250℃~270℃ for 2 hours in air atmosphere, then calcined at 400~450℃ for 3 hours, and then cooled to obtain 69.91 g of catalyst D.

[0026] Example 5

[0027] The pH was controlled at around 6.0 during the precipitation process, and the remaining operations were the same as in Example 1. The resulting catalyst was denoted as Catalyst E.

[0028] Example 6

[0029] The pH was controlled at around 7.0 during the precipitation process, and the remaining operations were the same as in Example 1. The resulting catalyst was denoted as catalyst F.

[0030] Example 7

[0031] 169.12 g of copper nitrate trihydrate and 104.12 g of zinc nitrate hexahydrate were weighed and dissolved in 1.4 L of deionized water to prepare an acidic salt solution with a copper-zinc concentration ratio of 2:1. The remaining operations were the same as in Example 1 to obtain 103.55 g of precursor, which was calcined at 450 °C for 4 h to obtain 70.32 g of catalyst G.

[0032] Example 8

[0033] 147.83 g of copper nitrate trihydrate and 120.03 g of zinc nitrate hexahydrate were weighed and dissolved in 1.4 L of deionized water to prepare an acidic salt solution with a copper-zinc concentration ratio of 1:1. The remaining operations were the same as in Example 1, and 69.21 g of catalyst H was obtained.

[0034] Comparative Example 1 The industrial nickel catalyst used is the IPAOS-1 type nickel catalyst from Liaoning Haitai Technology Development Co., Ltd.

[0035] Comparative Example 2 The noble metal hydrogenation catalyst Pd / Al2O3 was used, specifically the LDHA-1 type Pd / Al2O3 catalyst from Liming Chemical Research and Design Institute Co., Ltd.

[0036] Catalyst evaluation: 1200g of diisobutyl ketone and 66g of the catalyst prepared in the examples and comparative examples were added to a stirred tank reactor. Under rapid stirring at 300 RPM, the temperature was raised to 150°C, and hydrogen gas was continuously introduced to initiate the catalytic hydrogenation reaction. During the reaction, the pressure was controlled at 1.4–1.5 MPa, the temperature at 160–165°C, and the reaction time was 4 hours. After the reaction was completed, the hydrogen supply was stopped, but the temperature and stirring were maintained, and the reaction was allowed to proceed under reduced pressure for a period of time. Subsequently, the temperature was lowered, and the crude diisobutyl methanol was separated by membrane separation. The conversion rate and selectivity were calculated.

[0037] Table 2. Catalyst performance evaluation results

[0038] The results in Table 2 show that the copper-zinc-aluminum hydrogenation catalyst provided by this invention can achieve high diisobutyl ketone conversion and diisobutyl methanol selectivity when used for the hydrogenation of diisobutyl ketone to diisobutyl methanol.

[0039] Catalyst lifetime assessment: Catalyst lifetime investigation experiments were conducted using a 3-liter evaluation apparatus. 66.03 g of catalyst A from Example 1 was selected for the experiment, and the results are shown in Table 3. The experimental conditions were as follows: diisobutyl ketone catalyst was added to a batch reactor, stirred rapidly at 300 RPM, and the temperature was raised to 150°C. Hydrogen gas was then continuously introduced to initiate the catalytic hydrogenation reaction. During the reaction, the pressure was controlled at 1.4–1.5 MPa, the temperature at 160–165°C, and the reaction time was 4 hours. After the reaction, the hydrogen supply was stopped, and the temperature and stirring were maintained while allowing the pressure to decrease for a period of time. Subsequently, the temperature was lowered, and the crude diisobutyl methanol was separated by membrane separation. The conversion rate and selectivity were calculated.

[0040] Table 3. Results of catalyst lifetime investigation experiments

[0041] Table 3 shows that the copper-zinc-aluminum catalyst can be reused up to 12 times, with an average hydrogenation activity of 96.53% and an average selectivity of 99.8%. After the 12th use, the catalyst activity remains at 96.22% and the selectivity at 99.18%, and it still has the potential for continued use. The amount of catalyst added for reuses 2-12 times represents the mass of catalyst added, and the catalyst mass ratio consumed per unit product will be less than 6.5 g / kg. Therefore, the copper-based catalyst of this invention not only has a high conversion rate of diisobutyl ketone and a high selectivity for diisobutyl methanol, but also a long service life.

Claims

1. A method for preparing a copper-based hydrogenation catalyst, comprising the following steps: (1) Prepare a mixed aqueous solution A of soluble salts of Cu, Zn and Al, with a Cu:Zn:Al molar ratio of 2:(0.3~3):(0~3); prepare an aqueous solution B of precipitant; (2) Pure water is pre-placed in the reactor. Solution A and solution B are added to the reactor in parallel to generate a precursor precipitate. The copper-based hydrogenation catalyst was obtained after post-processing.

2. The preparation method according to claim 1, characterized in that, In step (1), the soluble salts of Cu, Zn, and Al are nitrates.

3. The preparation method according to claim 1, characterized in that, In step (1), the sum of the molar numbers of added nitrates and the molar ratio of the precipitant is 1:1 to 1.1:

1.

4. The preparation method according to claim 1, characterized in that, In step (1), the precipitant is selected from one or more of ammonia, urea, sodium carbonate, and ammonium bicarbonate.

5. The preparation method according to claim 1, characterized in that, In step (1), preferably, in step (2), the post-processing includes: heat preservation aging, washing, filtration, drying and crushing the filter cake to obtain a powdered catalyst precursor, and calcining to obtain a copper-based hydrogenation catalyst.

6. The preparation method according to claim 1, characterized in that, In step (1), preferably, in step (2), the volume of pre-placed pure water in the reactor is 0 to 10% of the total volume of solution A, preferably 3 to 6%.

7. The preparation method according to claim 1, characterized in that, In step (1), the pH value of the precipitation process system is controlled between 5.0 and 7.0, preferably between 5.5 and 6.5; the precipitation temperature is 50 to 90°C.

8. The application of a copper-based hydrogenation catalyst according to any one of claims 1 to 7, wherein the copper-based hydrogenation catalyst is used for the hydrogenation of diisobutyl ketone to prepare diisobutyl methanol.

9. The application according to claim 8, characterized in that, The preparation of diisobutylmethanol by hydrogenation of diisobutyl ketone includes the following steps: (1) Diisobutyl ketone and the copper-based hydrogenation catalyst are added to a batch reactor. Under rapid stirring, the reaction temperature is raised to 140~160℃, and hydrogen is continuously introduced to carry out the catalytic hydrogenation reaction. (2) During the reaction, the pressure should not exceed 1.4~1.5MPa, the temperature should be 150~180℃, and the reaction time should be 3~4.5h; (3) After the reaction is complete, stop the hydrogen gas supply, maintain the temperature and stir, and let the reaction proceed under pressure for a period of time; then cool down and separate the crude diisobutylmethanol through a membrane.

10. The application according to claim 8, characterized in that, The conversion rate of diisobutyl ketone is greater than 95%, and the selectivity of diisobutyl methanol is greater than 99%.

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