A preparation method of lead copper salt catalyst

Abstract

The invention discloses a preparation method of a lead copper salt catalyst, comprising the following steps: (1) preparing a deoxygenated 2,4-dihydroxybenzoic acid aqueous solution; (2) adding an initiator to the 2,4-dihydroxybenzoic acid aqueous solution to obtain a first solution; (3) dropwise adding a mixed aqueous solution of deoxygenated lead nitrate and copper nitrate to the first solution, and washing with a precipitate to obtain the lead copper salt catalyst. The lead copper 2,4-dihydroxybenzoic acid prepared by the present invention has good batch stability, effectively solving the problem that 2,4-dihydroxybenzoic acid has many types of complexes as a starting material and a complex spatial distribution. The preparation method in the present invention is simple and reliable, and has good application prospects.

Description

Technical Field

[0001] The present invention relates to a method for preparing a lead copper salt catalyst, in particular to a method for preparing 2,4-dihydroxybenzoic acid lead copper salt. Background Art

[0002] Nano-metal organic salt catalysts are different from nano-metal oxides (complexes). Their main function is to decompose metals or metal oxides in situ and evenly disperse them in the propellant components, thereby playing a better combustion catalytic role. In addition, because nano-metal organic salts contain organic groups, they exhibit a certain degree of lipophilicity, which improves their compatibility with propellant components and their dispersibility in the propellant. Currently commonly used nano-metal organic salt catalysts include: nano-lead phthalate, nano-lead gallate, nano-lead 2,4-dihydroxybenzoate, nano-lead tannate complex, copper 2,4-dihydroxybenzoate, 2,4-DNI lead salt, bismuth 2,4-dihydroxybenzoate and other organic metal salts.

[0003] During propellant combustion, lead salts primarily promote the decomposition of surface components, acting as the primary catalyst. Copper salts lower the decomposition temperature of lead salts, and the copper / copper oxide produced by their decomposition catalyzes reactions in the gas phase, acting as a co-catalyst. The combination of copper and lead salts can act as a synergistic catalyst in modified double-base propellants. Existing research has shown that copper-lead 2,4-dihydroxybenzoate can effectively modulate propellant combustion performance, significantly increasing the burning rate of modified double-base propellants containing aluminum powder and RDX, and significantly reducing their pressure exponent.

[0004] However, due to the presence of two metal central atoms, copper and lead, in the 2,4-dihydroxybenzoic acid lead copper molecule and multiple coordination groups such as carboxyl and phenol groups in 2,4-dihydroxybenzoic acid, the types of complexes that can be formed and their spatial distribution are greatly increased, such as Figure 1 As shown, compound structures (a)-(g) show the types of possible complexes and their spatial structures. This ultimately leads to problems such as unclear composition and structure of 2,4-dihydroxybenzoic acid lead copper complex salt and poor batch quality stability. Summary of the Invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for preparing a lead copper salt catalyst to solve the problem of poor batch quality stability of products in the existing preparation process.

[0006] Technical solution: The preparation method of a lead-copper salt catalyst described in the present invention comprises the following steps:

[0007] (1) preparing a deoxygenated 2,4-dihydroxybenzoic acid aqueous solution;

[0008] (2) adding an initiator to the aqueous solution of 2,4-dihydroxybenzoic acid to obtain solution 1;

[0009] (3) Add the mixed aqueous solution of deoxygenated lead nitrate and copper nitrate dropwise into solution 1, and wash the precipitate to obtain the lead-copper salt catalyst.

[0010] The present invention uses 2,4-dihydroxybenzoic acid as a starting material, and the batch quality of the 2,4-dihydroxybenzoic acid lead copper double salt prepared in a deoxygenated aqueous solution is more stable.

[0011] Preferably, the method for preparing the deoxygenated 2,4-dihydroxybenzoic acid aqueous solution in step (1) comprises: removing dissolved oxygen from water using a vacuum deoxygenation method to obtain oxygen-free water, and dissolving 2,4-dihydroxybenzoic acid in the oxygen-free water to obtain the deoxygenated 2,4-dihydroxybenzoic acid aqueous solution. Removing dissolved oxygen from the aqueous solution using a vacuum deoxygenation method prevents oxidation of the phenolic group in the 2,4-dihydroxybenzoic acid, which could affect batch stability.

[0012] Preferably, the initiator is an inorganic base, and the inorganic base is preferably at least one of sodium hydroxide, sodium carbonate or sodium bicarbonate.

[0013] Preferably, the molar ratio of 2,4-dihydroxybenzoic acid to the initiator in the solution 1 in step (2) is 1:2-2.5.

[0014] Preferably, the pH of the solution 1 in step (3) is 7.5-8.5.

[0015] Preferably, the temperature of the solution 1 in step (3) is 60-70°C.

[0016] Preferably, the molar ratio of lead nitrate to copper nitrate in the mixed aqueous solution of lead nitrate and copper nitrate in step (3) is 1:1-1.5.

[0017] Preferably, the concentration of 2,4-dihydroxybenzoic acid in the 2,4-dihydroxybenzoic acid aqueous solution in step (1) is 0.4-1 mol / L; the concentration of lead nitrate in the mixed aqueous solution of lead nitrate and copper nitrate in step (3) is 0.2-0.5 mol / L.

[0018] Preferably, the precipitate washing method in step (3) is: repeatedly washing the precipitate with deionized water until it becomes neutral and then drying it in a vacuum at 50-60°C.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the batch quality stability of 2,4-dihydroxybenzoic acid lead copper prepared by the present invention effectively solves the batch instability problem caused by the large variety of complexes and complex spatial distribution of 2,4-dihydroxybenzoic acid as a starting material. The preparation method of the present invention is simple and reliable and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The possible structures of different lead copper 2,4-dihydroxybenzoate;

[0021] Figure 2 Characterization diagrams of 2,4-dihydroxybenzoate lead copper synthesized in Example 1; wherein (a) is a Fourier transform infrared spectrum; (b) is a SEM; (c) is an XRD curve; and (d) is an XPS full spectrum.

[0022] Figure 3 Characterization diagrams of 2,4-dihydroxybenzoate lead copper synthesized in Example 2; wherein (a) is a Fourier transform infrared spectrum; (b) is a SEM; (c) is an XRD curve; and (d) is an XPS full spectrum.

[0023] Figure 4 These are characterization diagrams of 2,4-dihydroxybenzoate lead copper synthesized in Example 3; wherein, (a) is a Fourier infrared spectrum; (b) is a SEM; (c) is an XRD curve; and (d) is a full XPS spectrum. DETAILED DESCRIPTION

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Example 1: The preparation method of 2,4-dihydroxybenzoic acid lead copper is as follows:

[0026] Step 1: Remove dissolved oxygen in water by vacuum deoxygenation method;

[0027] Step 2: preparing a 0.4 mol / L 2,4-dihydroxybenzoic acid aqueous solution using the deoxygenated water obtained in step 1;

[0028] Step 3: Add an appropriate amount of sodium bicarbonate as an initiator to the 2,4-dihydroxybenzoic acid solution in step 2, wherein the molar ratio of 2,4-dihydroxybenzoic acid to sodium bicarbonate is 1:2, and stir evenly;

[0029] Step 4: Adjust the pH value of the solution obtained in step 3 to 7.5 and the temperature to 60° C.;

[0030] Step 5: Prepare a mixed solution of lead nitrate and copper nitrate using the deoxygenated water obtained in step 1, wherein the concentration of lead nitrate in the mixed solution is 0.2 mol / L, and the molar ratio of lead nitrate to copper nitrate is 1:1.

[0031] Step 6: Add the mixed solution of lead nitrate and copper nitrate in step 5 dropwise to the solution in step 4 until a yellow-green precipitate is obtained, wash repeatedly with deionized water until the pH reaches 7, and dry under vacuum at 50° C. for later use.

[0032] Example 2: The preparation method of 2,4-dihydroxybenzoic acid lead copper is as follows:

[0033] Step 1: Remove dissolved oxygen in water by vacuum deoxygenation method;

[0034] Step 2: Prepare a 0.8 mol / L 2,4-dihydroxybenzoic acid solution using the deoxygenated water obtained in step 1;

[0035] Step 3: Add an appropriate amount of sodium carbonate as an initiator to the 2,4-dihydroxybenzoic acid solution of step 2, wherein the molar ratio of 2,4-dihydroxybenzoic acid to sodium carbonate is 1:2, and stir evenly;

[0036] Step 4: Adjust the pH value of the solution obtained in step 3 to 8 and the temperature to 65° C.

[0037] Step 5: Prepare a mixed solution of lead nitrate and copper nitrate using the deoxygenated water obtained in step 1, wherein the concentration of lead nitrate in the mixed solution is 0.4 mol / L, and the molar ratio of lead nitrate to copper nitrate is 1:1.25.

[0038] Step 6: Add the mixed solution of lead nitrate and copper nitrate in step 5 dropwise to the solution in step 4 until a yellow-green precipitate is obtained, wash repeatedly with deionized water until the pH reaches 7, and dry under vacuum at 60° C. for later use.

[0039] Example 3: The preparation method of 2,4-dihydroxybenzoic acid lead copper is as follows:

[0040] Step 1: Remove dissolved oxygen in water by vacuum deoxygenation method;

[0041] Step 2: Prepare a 1 mol / L 2,4-dihydroxybenzoic acid solution using the deoxygenated water obtained in step 1;

[0042] Step 3: Add an appropriate amount of sodium hydroxide as an initiator to the 2,4-dihydroxybenzoic acid solution of step 2, wherein the molar ratio of 2,4-dihydroxybenzoic acid to sodium hydroxide is 1:2.5, and stir evenly;

[0043] Step 4: adjusting the pH value of the solution obtained in step 3 to 8.5 and the temperature to 70° C.;

[0044] Step 5: preparing a mixed solution of lead nitrate and copper nitrate using the deoxygenated water obtained in step 1, wherein the concentration of lead nitrate in the mixed solution is 0.5 mol / L, and the molar ratio of lead nitrate to copper nitrate is 1:1.5.

[0045] Step 6: Add the mixed solution of lead nitrate and copper nitrate in step 5 dropwise to the solution in step 4 until a yellow-green precipitate is obtained, wash repeatedly with deionized water until the pH reaches 7, and dry under vacuum at 50° C. for later use.

[0046] Comparative Example 1: All other aspects are the same as Example 2, except that: step 1 is not performed, and undeoxygenated water is used to prepare the 2,4-dihydroxybenzoic acid solution and the mixed solution of lead nitrate and copper nitrate.

[0047] Comparative Example 2: The rest is the same as Example 2, except that 2,4-dihydroxybenzoic acid is replaced by 3,4-dihydroxybenzoic acid.

[0048] Comparative Example 3: The rest is the same as Example 2, except that 2,4-dihydroxybenzoic acid is replaced by 2,3-dihydroxybenzoic acid.

[0049] Comparative Example 4: The rest is the same as Example 2, except that 2,4-dihydroxybenzoic acid is replaced by 3,5-dihydroxybenzoic acid.

[0050] Currently, most of the existing technologies focus on the preparation and catalytic performance characterization of 2,4-dihydroxybenzoic acid lead salt or 2,4-dihydroxybenzoic acid copper salt. In addition, the characterization of the structure of 2,4-dihydroxybenzoic acid lead salt or 2,4-dihydroxybenzoic acid copper salt is limited to X-ray diffraction to characterize its crystallization properties, infrared spectroscopy to study the presence of certain chemical groups in its molecules, thermal analysis to study its thermal stability, SEM to study its morphology and agglomeration state, etc., while there are almost no reports on the research of structural details such as its metal coordination mode, element content, metal element valence, metal ratio, chelation mode, etc. The present invention intends to use X-ray single crystal diffraction to characterize its single crystal structure (including structural details such as metal coordination mode and element ratio), and combine XPS, XRD and SEM to comprehensively test and verify the structural characteristics of different batches of 2,4-dihydroxybenzoic acid lead copper complex salt from the aspects of metal element valence, element content, etc. At the same time, the structure-activity relationship between 2,4-dihydroxybenzoic acid lead copper double salt and propellant burning rate was studied to obtain the optimal preparation process and its catalytic mechanism for propellant burning rate. Figure 2-Figure 4 shown.

[0051] The effects of the products obtained in Examples 1-3 and Comparative Examples 1-4 on the burning rate of double-base propellants were measured, and the results are as follows:

[0052] Table 1 Effects of different 2,4-dihydroxybenzoic acid lead copper complex salts on the burning rate of double-base propellants

[0053]

[0054] The results in Table 1 show that the product prepared by the present invention exhibits a good catalytic combustion-promoting effect. However, when dissolved oxygen is present in the solution environment during the preparation reaction, the product contains a wide variety of complexes, and the types and amounts of these complexes are uncertain. These complexes act as impurities, affecting the catalytic combustion-promoting effect of the target product, 2,4-dihydroxylead copper benzoate. Similarly, altering the position of the hydroxyl groups in the starting material can also reduce the catalytic combustion-promoting effect of the target product.

[0055] Three batches of lead copper 2,4-dihydroxybenzoate were prepared according to the method of Example 2, and the stability data of different batches of products were measured. The results are shown in Table 2:

[0056] Table 2 Effect of different batches on product stability

[0057]

[0058] As shown in Table 2, the effects of the target product on the propellant burning rate in the three different batches of Example 2 showed minimal fluctuation. Therefore, the product prepared in the present invention exhibits good batch stability and is significantly superior to the prior art. This may be closely related to the selection of starting materials and the deoxygenation step of the aqueous solution.

Claims

1. A method for preparing a lead copper salt catalyst, characterized in that: The following steps are included: (1) Preparing a deoxygenated 2,4-dihydroxybenzoic acid aqueous solution; (2) adding an inorganic base to the aqueous solution of 2,4-dihydroxybenzoic acid to obtain solution 1; (3) Add the mixed aqueous solution of deoxygenated lead nitrate and copper nitrate dropwise into solution 1, and wash the precipitate to obtain the lead-copper salt catalyst.

2. The method for preparing a lead copper salt catalyst according to claim 1, wherein The method for preparing the deoxygenated 2,4-dihydroxybenzoic acid aqueous solution in step (1) is: using a vacuum deoxygenation method to remove dissolved oxygen in water to obtain oxygen-free water, and dissolving 2,4-dihydroxybenzoic acid in the oxygen-free water to obtain the deoxygenated 2,4-dihydroxybenzoic acid aqueous solution.

3. The method for preparing a lead copper salt catalyst according to claim 1, wherein The inorganic base is at least one of sodium hydroxide, sodium carbonate or sodium bicarbonate.

4. The method for preparing a lead copper salt catalyst according to claim 1, wherein The molar ratio of 2,4-dihydroxybenzoic acid to the inorganic base in the solution 1 in step (2) is 1:2-2.

5.

5. The method for preparing a lead copper salt catalyst according to claim 1, wherein The pH of the solution 1 in step (3) is 7.5-8.

5.

6. The method for preparing a lead copper salt catalyst according to claim 1, wherein The temperature of the solution 1 in step (3) is 60-70°C.

7. The method for preparing a lead copper salt catalyst according to claim 1, wherein The molar ratio of lead nitrate to copper nitrate in the mixed aqueous solution of lead nitrate and copper nitrate in step (3) is 1:1-1.

5.

8. The method for preparing a lead copper salt catalyst according to claim 1, wherein The concentration of 2,4-dihydroxybenzoic acid in the 2,4-dihydroxybenzoic acid aqueous solution in step (1) is 0.4-1 mol / L; the concentration of lead nitrate in the mixed aqueous solution of lead nitrate and copper nitrate in step (3) is 0.2-0.5 mol / L.

9. The method for preparing a lead copper salt catalyst according to claim 1, wherein The precipitate washing method in step (3) is: the precipitate is repeatedly washed with deionized water until it becomes neutral and then vacuum dried at 50-60°C.

Images