A catalyst for the gas phase hydrogenation of acetone to isopropanol and a method for its preparation

Abstract

The application discloses a preparation method of a catalyst for preparing isopropyl alcohol by gas-phase hydrogenation of acetone, and comprises the following steps: (1) adding a zinc salt solution and a copper salt solution into a weak alkaline solution simultaneously, stirring, neutralizing and aging; (2) adding the zinc salt solution, an aluminum salt solution and the weak alkaline solution into the slurry obtained in the step (1) simultaneously, stirring, neutralizing and aging to form a coprecipitate; (3) washing, filtering, drying and calcining the coprecipitate, and tabletting and forming. In the application, Al2O3 is selected as an additive component, the proportion of each component is reasonably controlled, and the Zn element is formed in the catalyst in steps, so that the acid sites and hydrogenation active sites of the catalyst can be reasonably matched, thereby reducing the occurrence of side reactions such as etherification, and realizing high acetone conversion rate and isopropyl alcohol selectivity.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a catalyst for the gas-phase hydrogenation of acetone to isopropanol and its preparation method. Background Technology

[0002] Currently, acetone is mainly obtained industrially through the peroxidation of cumene, and is co-produced with phenol. Due to the increasing demand for phenol, a large amount of acetone is produced, often leading to a surplus due to the imbalance between demand and supply, thus raising the issue of acetone utilization.

[0003] Industrially, the hydrogenation of acetone to isopropanol is one of the effective and economical ways to utilize acetone. Currently, the catalysts used for acetone hydrogenation mainly include supported metal catalysts, alloy catalysts, and metal oxide catalysts. Supported catalysts generally involve supporting metals such as Ni and Pt on supports such as TiO2 and Al2O3, with acetone conversion and isopropanol selectivity not exceeding 97%. Alloy catalysts mainly combine metals such as Ni, Cu, and Ru with other catalysts, exhibiting good stability and long lifespan, but suffer from low conversion rates and difficulties in industrial scale-up. Metal oxide catalysts are mainly copper oxide and chromium oxide catalysts. Since the mid-1990s, catalysts with Cu-Zn as the active component have gradually replaced Cu-Cr catalysts. Compared to Cu-Cr catalysts, Cu-Zn catalysts have the advantages of lower pollution, longer lifespan, and higher mechanical strength.

[0004] Japanese patent Hei 3-141235 uses a Raney Ni catalyst for acetone hydrogenation, achieving a conversion rate and selectivity of 99.9% for isopropanol production. Hei 2-278643 uses a Ru / Al₂O₃ catalyst with isopropanol as the solvent, achieving a maximum conversion rate and selectivity of 99.9% at a hydrogen pressure of 9.0 MPa. Both catalysts are characterized by high cost and demanding reaction conditions.

[0005] Soviet patents SU1051055A and SU1118632A used Cu-Cr catalysts for acetone hydrogenation. With this type of catalyst, both the acetone conversion and isopropanol selectivity were below 99.5%. The Cr compounds used in this catalyst caused severe environmental pollution.

[0006] Chinese patent CN1255482A describes a method for the hydrogenation of acetone to isopropanol, using a CuO-ZnO oxide mixture catalyst in a pressed form. The catalyst is then placed in a fixed-bed reactor to hydrogenate acetone to isopropanol. Under certain temperature and pressure conditions, the conversion rate of acetone and the selectivity of isopropanol can reach 99%. However, this method involves the addition of organic additives such as polyvinyl alcohol during catalyst preparation, and a high copper oxide content, leading to increased costs. Furthermore, the hydrogenation of acetone to isopropanol requires relatively high pressure.

[0007] Chinese patent CN103030526A discloses a method for preparing isopropanol by gas-phase hydrogenation of acetone. This method uses acetone and hydrogen as raw materials, with a hydrogen / acetone molar ratio of 1–20:1, at a reaction temperature of 100–200℃, a reaction pressure of 0.1–5 MPa, and a total liquid hourly space velocity of 0.5–6.0 h⁻¹. -1 Under these conditions, the reaction produces isopropanol, and the conversion rate of acetone and the selectivity of isopropanol can reach 99%. This method incorporates 75% isopropanol as a solvent in the raw materials, and requires relatively high reaction temperature and pressure. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a catalyst for the gas-phase hydrogenation of acetone to isopropanol, so as to solve the defects of relatively harsh process conditions, expensive catalysts and environmentally unfriendly process when using existing catalysts for the gas-phase hydrogenation of isopropanol.

[0009] Another objective of this invention is to provide a catalyst for the gas-phase hydrogenation of acetone to isopropanol.

[0010] To achieve the above objectives, the present invention provides a method for preparing a catalyst for the gas-phase hydrogenation of acetone to isopropanol, comprising the following steps:

[0011] (1) Add zinc salt solution and copper salt solution to a weak alkaline solution at the same time, stir, neutralize and age;

[0012] (2) Add zinc salt solution, aluminum salt solution and weak alkaline solution to the slurry obtained in step (1) at the same time, stir, neutralize and age to form a co-precipitate;

[0013] (3) Co-precipitate, wash, filter, dry, calcinate, and compress into tablets.

[0014] In the preparation method of the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to the present invention, the mass ratio of zinc salt in step (1) to zinc salt in step (2) is 1.5 to 3.3:1.

[0015] In the preparation method of the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to the present invention, the molar ratio of the total amount of zinc salt and copper salt to the weakly basic substance in step (1) is 1 to 1.5:1, and the molar ratio of the total amount of zinc salt and aluminum salt to the weakly basic substance in step (2) is 1 to 1.5:1.

[0016] The method for preparing the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to the present invention uses a weakly alkaline solution, which is a sodium carbonate or sodium bicarbonate solution.

[0017] The method for preparing the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to the present invention, wherein the pH value is controlled between 6 and 8, the temperature is controlled between 35 and 65°C, the neutralization reaction time is 20 to 50 min, and the aging time is 20 to 40 min during the reaction process of steps (1) and (2).

[0018] The method for preparing the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to the present invention involves adding graphite during the tableting process.

[0019] To achieve the above objectives, the present invention also provides a catalyst prepared by the above method, which, by mass percentage, contains 28% to 40% copper oxide, 50% to 70% zinc oxide, 0.1% to 10% aluminum oxide, and 1% to 3% graphite.

[0020] The catalyst of this invention has a BET specific surface area of ​​30–80 m². 2 / g, pore volume 0.1~0.35cm 3 / g, with an average pore size of 6–25 nm and a compressive strength greater than 200 N / cm.

[0021] The beneficial effects of this invention are:

[0022] This invention selects Al2O3 as the auxiliary component and rationally controls the proportion of each component. By stepwise shaping Zn element into the catalyst, the acidic sites and hydrogenation active sites of the catalyst can be reasonably matched, thereby reducing the occurrence of side reactions such as etherification and achieving high acetone conversion and isopropanol selectivity. Simultaneously, the co-catalyst component acts as a support for the main active component, elemental copper. Through the method described in this invention, copper grains are uniformly dispersed on the support, avoiding aggregation and ensuring the activity and stability of the catalyst.

[0023] Using the catalyst provided by this invention, after reduction and activation by H2, the reaction can proceed at a temperature of 100–180°C, a pressure of 0.4–0.8 MPa, and a volume hourly space velocity (VHSV) ≤1.0 h⁻¹. -1 Under conditions where the hydrogen-to-acetone volume ratio is 1–5:1 and the circulating hydrogen volume concentration is ≥70%, the acetone feedstock does not require dilution with isopropanol. Both the conversion rate and isopropanol selectivity are above 99.0%. Long-term operation results after 1000 hours show good catalyst activity and stability. Furthermore, the catalyst has a low Cu content, reducing costs, and does not contain precious metals such as Ru or environmentally harmful species such as Cr. Detailed Implementation

[0024] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0025] Example 1

[0026] (1) Add zinc nitrate solution and copper nitrate solution to sodium carbonate solution at the same time. The total amount of zinc nitrate and copper nitrate is 1 molar ratio to sodium carbonate. React at 35-40℃ for 20 min and age for 30 min. During the process, control the pH of the system to 6-6.5 with sodium carbonate to obtain slurry.

[0027] (2) Add zinc nitrate solution, aluminum nitrate solution and sodium carbonate solution to the slurry obtained in step (1) at the same time. The total amount of zinc nitrate and aluminum nitrate is 1.2 molar ratio of sodium carbonate to 1.2. React at 35-40℃ for 20 min and age for 30 min to form a coprecipitate. During this period, the pH of the system is controlled to be 6-6.5 by sodium carbonate.

[0028] (3) The obtained coprecipitate was washed, filtered, dried, and calcined, and then added to graphite to form tablets. The composition and physical properties of the obtained catalyst are shown in Table 1 and Table 2.

[0029] Example 2

[0030] The catalyst was prepared according to the steps in Example 1, except that the total amount of zinc nitrate and copper nitrate in step (1) was 1.5 molar ratio to sodium carbonate, and the content of catalyst components was different. The composition and physical properties of the resulting catalyst are shown in Table 1 and Table 2.

[0031] Example 3

[0032] The catalyst was prepared according to the steps in Example 1, except that the pH of the system in steps (1) and (2) was 6.5 to 7.5 and the content of catalyst components was different. The composition and physical properties of the obtained catalyst are shown in Table 1 and Table 2.

[0033] Example 4

[0034] The catalyst was prepared according to the steps in Example 1, except that the pH of the system in steps (1) and (2) was 7-8 and the content of catalyst components was different. The composition and physical properties of the obtained catalyst are shown in Table 1 and Table 2.

[0035] Example 5

[0036] The catalyst was prepared according to the steps in Example 1, except that the reaction temperature was controlled at 55-60°C in steps (1) and (2), and the content of catalyst components was different. The composition and physical properties of the resulting catalyst are shown in Table 1 and Table 2.

[0037] Comparative Example 1

[0038] A comparative catalyst was prepared using the method described in Chinese patent CN1255482A.

[0039] The catalyst is prepared by co-precipitating soluble copper and zinc salts in an aqueous solution with an alkaline solution. The precipitate is dried and calcined to obtain an oxide mixture, which is then pressed into tablets with the addition of an inorganic or organic binder. The catalyst composition, by weight, is: 50% CuO, 45% ZnO, 5% polyvinyl alcohol, and graphite carbon.

[0040] Comparative Example 2

[0041] This example demonstrates the preparation of a comparative catalyst using the method described in Chinese patent CN103030526A.

[0042] The required amount of alumina powder was mixed with water to obtain slurry I. The required mixed solution of ketone nitrate, nickel nitrate and magnesium nitrate and sodium carbonate aqueous solution were simultaneously added dropwise to slurry I to carry out the reaction. The reaction temperature was 70℃ and the pH value of the solution was controlled at 7.5. After precipitation, the solution was aged at 70℃ for 2 hours, washed and filtered, dried at 120℃ for 12 hours, calcined at 400℃ and then pressed into tablets to obtain the comparative catalyst.

[0043] The compositional analysis of the catalysts prepared in the above examples is listed in Table 1.

[0044] Table 1 Catalyst Composition for Each Example

[0045]

[0046] Table 2 Physical properties of catalysts in various examples

[0047]

[0048] The reduction conditions for Examples 1-5 and Comparative Examples 1-3 were evaluated using a 200 mL fixed-bed hydrogenation evaluation apparatus: nitrogen as the carrier gas and hydrogen as the reducing gas, hydrogen volume concentration 2%, reduction temperature 190 °C, reduction pressure 0.45 MPa, and reduction time 10 hours. Industrial acetone was used as the feedstock, with a reactor hotspot temperature of 140 °C and a volume hourly space velocity (VHSV) of 0.6 h⁻¹. -1 The volume ratio of hydrogen to acetone is 3:1, the purity of the circulating hydrogen is 70%, and the reaction pressure is 0.4 MPa.

[0049] Table 3. Acetone hydrogenation performance of each example.

[0050]

[0051]

[0052] Catalyst 2 from Example 2 was used to investigate the hydrogenation performance under different process conditions. The results are shown in Table 4.

[0053] Table 4 Catalyst performance under different process conditions in Example 2

[0054]

[0055] As shown in Tables 2 and 3, this technology, when used to prepare isopropanol, exhibits good hydrogenation activity under more moderate operating conditions. The catalyst has a low copper content and is free of Ni and Cr, making it environmentally friendly.

[0056] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a catalyst for the gas-phase hydrogenation of acetone to isopropanol, characterized in that, Includes the following steps: (1) Add zinc salt solution and copper salt solution to a weak alkaline solution at the same time, stir, neutralize and age; (2) Add zinc salt solution, aluminum salt solution and weak alkaline solution to the slurry obtained in step (1) at the same time, stir, neutralize and age to form a co-precipitate; (3) Co-precipitation, washing, filtering, drying, calcining, and tableting; The weakly alkaline solution is a sodium carbonate or sodium bicarbonate solution; The mass ratio of zinc salt in step (1) to zinc salt in step (2) is 1.5 to 3.3:1; Graphite is added during the tableting process in step (3); the catalyst contains 28% to 40% copper oxide, 50% to 70% zinc oxide, 0.1% to 10% aluminum oxide, and 1% to 3% graphite.

2. The method for preparing the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to claim 1, characterized in that, In step (1), the total amount of zinc salt and copper salt and the molar ratio of the weak alkaline substance are 1 to 1.5:

1. In step (2), the total amount of zinc salt and aluminum salt and the molar ratio of the weak alkaline substance are 1 to 1.5:

1.

3. The method for preparing the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to claim 1, characterized in that, During the reaction process of steps (1) and (2), the pH value is controlled between 6 and 8, the temperature is controlled between 35 and 65°C, the neutralization reaction time is 20 to 50 minutes, and the aging time is 20 to 40 minutes.

4. The method for preparing the catalyst for the gas-phase hydrogenation of acetone to isopropanol according to claim 1, characterized in that, BET has a specific surface area of ​​30–80 m². 2 / g, pore volume 0.1~0.35cm 3 / g, with an average pore size of 6–25 nm and a compressive strength greater than 200 N / cm.

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