Preparation method of zirconium pyrophosphate

Abstract

In order to solve the technical problem that zirconium pyrophosphate with relatively high purity cannot be industrially prepared by an existing preparation method of zirconium pyrophosphate, the invention provides a preparation method of zirconium pyrophosphate. The preparation method comprises the following steps: reacting zirconium dioxide with hydrofluoric acid to prepare a hexafluorozirconic acid solution, and filtering to obtain a refined hexafluorozirconic acid solution; adding the hexafluorozirconic acid solution fine product into phosphoric acid, heating and evaporating to dryness to obtain an evaporation-dried substance, crushing the evaporation-dried substance, sieving, and boiling and washing with high-purity water to obtain a zirconium pyrophosphate crude product; and drying the zirconium pyrophosphate crude product to obtain the target product zirconium pyrophosphate. According to the method, zirconium pyrophosphate with the purity of 99.5% or above can be prepared, wet production can be achieved, and large-scale production can be carried out.

Description

Technical Field

[0001] The invention relates to a method for preparing zirconium pyrophosphate. Background Art

[0002] Zirconium pyrophosphate is an important inorganic compound with good catalytic properties, excellent electrical properties, high temperature stability, high temperature flame retardant properties, antibacterial properties and biocompatibility. It is widely used in various fields, for example, as a catalyst in the decarbonylation reaction of lactic acid, in electrical equipment such as capacitors and fuses, in kitchen supplies such as non-stick pans and high-temperature plastic tableware, in the field of medical devices, and in building materials.

[0003] At present, there are documents that disclose the preparation of zirconium pyrophosphate by dry calcination of ammonium dihydrogen phosphate and zirconium dioxide. Through analysis, we found that this preparation method is not feasible for industrial mass production. Even if it is feasible, it still has the disadvantage of not being able to completely react to prepare zirconium pyrophosphate with higher purity. Summary of the invention

[0004] In order to solve the technical problem that the existing method for preparing zirconium pyrophosphate cannot industrially prepare zirconium pyrophosphate with higher purity, the present invention provides a method for preparing zirconium pyrophosphate.

[0005] The technical solution of the present invention is:

[0006] A method for preparing zirconium phosphate, which is special in that it comprises the following steps:

[0007] Step 1, preparing a fluorozirconic acid solution;

[0008] Zirconium dioxide is fully reacted with hydrofluoric acid and then filtered to obtain a fine fluorozirconic acid solution. Under normal circumstances, zirconium dioxide cannot be dissolved in high concentrations in acids other than hydrofluoric acid, and cannot directly react with phosphoric acid. Therefore, the present invention uses hydrofluoric acid to dissolve zirconium dioxide first.

[0009] Step 2, preparing crude zirconium pyrophosphate;

[0010] The fine fluorozirconic acid solution is slowly added to phosphoric acid, and heated to react at 150-180° C. until evaporated to dryness to obtain an evaporation product; the evaporation product is crushed, sieved, and washed with high-purity water to obtain a crude zirconium pyrophosphate product; in this step, hydrofluoric acid is a low-boiling acid, and most of the fluoride ions will be evaporated by heating reaction, but they cannot be completely removed.

[0011] Step 3, preparing zirconium pyrophosphate;

[0012] The crude zirconium pyrophosphate is dried at 500-600°C for 2-3 hours. When the loss on ignition at 500°C is less than 0.5%, the drying is completed to obtain the target product. The product is characterized as zirconium pyrophosphate by XRD. Using icp-oes control, phosphorus pentoxide is 53-54%, and zirconium oxide is 46-47%, which meets the required range. The control in this step is a detection step. When the loss on ignition at 500°C is detected to be less than 0.5%, it means that the drying is completed.

[0013] Further, step 1 is specifically as follows: step 1.1 dissolves zirconium dioxide with a mass fraction of 40-50% hydrofluoric acid, keeps the temperature at 80-100°C (the reaction is slow below 80°C, and it is difficult to achieve above 100°C in the solution), stirs and dissolves until transparent, and obtains a crude fluorozirconic acid solution; the molar ratio of hydrofluoric acid to zirconium dioxide is 6:1; in this step, the mass fraction of hydrofluoric acid is limited to 40-50% because the mass fraction of hydrofluoric acid greater than 50% is considered to be easy to volatilize, which is not conducive to operation; the mass fraction of hydrofluoric acid less than 40% will result in a slow reaction rate and incomplete reaction.

[0014] Step 1.2: Filter the crude fluorozirconic acid solution using a precision filter with a filtration accuracy of less than or equal to 2 microns to obtain a fine fluorozirconic acid solution. The finer the filter screen of the precision filter, the better the filtering and impurity removal effect.

[0015] Furthermore, step 2 is specifically as follows:

[0016] Step 2.1: add phosphoric acid with a mass fraction of less than or equal to 85% to a tetrafluoro beaker, place the tetrafluoro beaker containing phosphoric acid in an oil bath, heat it to 150-180°C, and slowly add the fluorozirconic acid solution therein; the molar ratio of zirconium to phosphorus is 1:2; the mass fraction of phosphoric acid in this step only affects the preparation efficiency to a certain extent, and has no substantial effect on the subsequent preparation process. If the mass fraction of phosphoric acid is small, excess water can be evaporated in the subsequent reaction process. If the mass fraction of phosphoric acid is high, the process of evaporating water will be shortened accordingly; the reason for heating to 150-180°C is that at this temperature, hydrofluoric acid can be prepared from phosphoric acid using the method of preparing weak acid with strong acid, and the low-boiling hydrofluoric acid can be evaporated at this temperature;

[0017] Step 2.2: The solution obtained in step 2.1 is kept at 150-180° C. for further heating reaction and evaporation until it is evaporated to dryness to obtain an evaporated product;

[0018] Step 2.3: The evaporated product is crushed, sieved, and washed several times with high-purity water at 80-90° C., with the fluoride ion content being controlled to be less than 0.05%, to obtain a crude zirconium pyrophosphate product. In theory, the finer the sieve, the better, but it will be difficult to crush, so it is recommended to sieve through a 100-mesh sieve.

[0019] The present invention also provides zirconium pyrophosphate, which is characterized in that it is prepared by the above-mentioned preparation method.

[0020] The advantages of the present invention are:

[0021] 1. The method of the present invention can prepare zirconium pyrophosphate with a purity of more than 99.5%.

[0022] 2. The present invention can be realized by wet production and can be produced on a larger scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the XRD diagram of the zirconium pyrophosphate prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention is conceived as follows:

[0025] Zirconium dioxide is very stable and cannot fully react with acids other than hydrofluoric acid under normal conditions. The method of using strong acid to produce weak acid is adopted to evaporate the hydrofluoric acid with phosphoric acid. Taking advantage of the fact that hydrofluoric acid is a low-boiling acid, most of the hydrofluoric acid is volatilized at a relatively high temperature. Finally, the very small amount of hydrofluoric acid remaining in the evaporated product is washed with high-purity water to obtain crude zirconium pyrophosphate.

[0026] The reaction equation involved in the present invention is:

[0027] ZrO2+6HF====H2ZrF6+2H2O

[0028] H2ZrF6+2H3PO4====ZrP2O7+6HF

[0029] Example 1

[0030] In this embodiment, zirconium pyrophosphate is prepared by the following steps:

[0031] Step 1, preparing a fluorozirconic acid solution;

[0032] Step 1.1: add 50% hydrofluoric acid by mass into a tetrafluoroethylene beaker, add zirconium dioxide thereto for dissolution, the molar ratio of hydrofluoric acid to zirconium dioxide being 6:1, keep warm at 80°C, stir and dissolve until transparent, and obtain a crude fluorozirconic acid solution;

[0033] Step 1.2: Filter the crude fluorozirconic acid solution obtained in step 1.1 through a 1-micron precision filter to obtain a fine fluorozirconic acid solution.

[0034] Step 2, preparing crude zirconium pyrophosphate;

[0035] Step 2.1: add 85% phosphoric acid by mass into a tetrafluoro beaker, place the tetrafluoro beaker containing phosphoric acid into an oil bath, heat it to 150°C, and slowly add the fluorozirconic acid solution obtained in step 1.2, wherein the molar ratio of zirconium to phosphorus is 1:2;

[0036] Step 2.2: The solution obtained in step 2.1 is kept at 150°C for further heating reaction and evaporation. As the hydrofluoric acid is continuously evaporated, a white precipitate begins to appear in the solution. The heating reaction and evaporation are continued until the solution is evaporated to dryness to obtain an evaporation product.

[0037] Step 2.3: The evaporated product obtained in step 2.2 is crushed, passed through a 100-mesh sieve, added with high-purity water and heated to 80°C for 40 minutes, wherein the mass ratio of high-purity water to the evaporated product is 5:1, and then filtered and washed with water. The boiling and washing operation is repeated twice, and the fluoride ion is controlled to be less than 0.046%, thereby obtaining a crude zirconium pyrophosphate product.

[0038] Step 3, preparing zirconium pyrophosphate;

[0039] Step 3.1 Add the crude zirconium pyrophosphate obtained in step 2.3 into an alumina crucible, heat to 500°C and dry for 3 hours, control the ignition loss at 500°C to be less than 0.5%, complete the drying, and obtain the target product, whose XRD pattern is as follows: Figure 1 As shown. It is zirconium pyrophosphate identified by XRD, and the iron is controlled by ICP-OES less than 10ppm, and the transition metal impurities such as cobalt, nickel, copper, titanium, vanadium, cadmium, chromium, etc. are all less than 3ppm, phosphorus pentoxide is 53.3%, and zirconium oxide is 46.3%, which meet the required range.

[0040] Example 2

[0041] In this embodiment, zirconium pyrophosphate is prepared by the following steps:

[0042] Step 1, preparing a fluorozirconic acid solution;

[0043] Step 1.1: add 40% hydrofluoric acid by mass into a tetrafluoroethylene beaker, add zirconium dioxide thereto for dissolution, the molar ratio of hydrofluoric acid to zirconium dioxide being 6:1, keep warm at 90°C, stir and dissolve until transparent, and obtain a crude fluorozirconic acid solution;

[0044] Step 1.2: Filter the crude fluorozirconic acid solution obtained in step 1.1 through a 2-micron precision filter to obtain a fine fluorozirconic acid solution.

[0045] Step 2, preparing crude zirconium pyrophosphate;

[0046] Step 2.1: add 85% phosphoric acid by mass into a tetrafluoro beaker, place the tetrafluoro beaker containing phosphoric acid into an oil bath, heat it to 170°C, and slowly add the fluorozirconic acid solution obtained in step 1.2, wherein the molar ratio of zirconium to phosphorus is 1:2;

[0047] Step 2.2: The solution obtained in step 2.1 is kept at 170°C for further heating reaction and evaporation. As the hydrofluoric acid is continuously evaporated, a white precipitate begins to appear in the solution. The heating reaction and evaporation are continued until the solution is evaporated to dryness to obtain an evaporation product.

[0048] Step 2.3: The evaporated product obtained in step 2.2 is crushed, passed through a 100-mesh sieve, added with high-purity water and heated to 90°C for 30 minutes, wherein the mass ratio of high-purity water to the evaporated product is 5:1, and then filtered and washed with water. The boiling and washing operation is repeated twice, and the fluoride ion is controlled to be less than 0.037%, thereby obtaining a crude zirconium pyrophosphate.

[0049] Step 3, preparing zirconium pyrophosphate;

[0050] Step 3.1 Add the crude zirconium pyrophosphate obtained in step 2.3 into an alumina crucible, heat to 550°C and dry for 2.5 hours, control the ignition loss at 500°C to be less than 0.5%, complete drying, and obtain a zirconium pyrophosphate product. XRD characterization is zirconium pyrophosphate, and the iron is controlled to be less than 10ppm by icp-oes, and the transition metal impurities such as cobalt, nickel, copper, titanium, vanadium, cadmium, and chromium are all less than 3ppm, phosphorus pentoxide is 53.4%, and zirconium oxide is 46.3%, which meets the required range.

[0051] Example 3

[0052] Step 1, preparing a fluorozirconic acid solution;

[0053] Step 1.1: add 45% hydrofluoric acid by mass into a tetrafluoroethylene beaker, add zirconium dioxide thereto for dissolution, the molar ratio of hydrofluoric acid to zirconium dioxide being 6:1, keep warm at 100°C, stir and dissolve until transparent, and obtain a crude fluorozirconic acid solution;

[0054] Step 1.2: Filter the crude fluorozirconic acid solution obtained in step 1.1 through a 2-micron precision filter to obtain a fine fluorozirconic acid solution.

[0055] Step 2, preparing crude zirconium pyrophosphate;

[0056] Step 2.1: add 50% by mass phosphoric acid into a tetrafluoro beaker, place the tetrafluoro beaker containing phosphoric acid into an oil bath, heat it to 180°C, and slowly add the fluorozirconic acid solution obtained in step 1.2, wherein the molar ratio of zirconium to phosphorus is 1:2;

[0057] Step 2.2: The solution obtained in step 2.1 is kept at 180°C for further heating reaction and evaporation. As the hydrofluoric acid is continuously evaporated, a white precipitate begins to appear in the solution. The heating reaction and evaporation are continued until the solution is evaporated to dryness to obtain an evaporated product.

[0058] Step 2.3: The evaporated product obtained in step 2.2 is crushed, passed through a 100-mesh sieve, added with high-purity water and heated to 90°C for 40 minutes, wherein the mass ratio of high-purity water to the evaporated product is 5:1, and then filtered and washed with water. The boiling and washing operation is repeated twice, and the fluoride ion is controlled to be less than 0.031%, thereby obtaining a crude zirconium pyrophosphate.

[0059] Step 3, preparing zirconium pyrophosphate;

[0060] Step 3.1 Add the crude zirconium pyrophosphate obtained in step 2.3 into an alumina crucible, heat to 600°C and dry for 2 hours, control the ignition loss at 500°C to be less than 0.5%, complete drying, and obtain a zirconium pyrophosphate product. XRD characterization is zirconium pyrophosphate, and the iron is controlled to be less than 10ppm by icp-oes, and the transition metal impurities such as cobalt, nickel, copper, titanium, vanadium, cadmium, and chromium are all less than 3ppm, phosphorus pentoxide is 53.4%, and zirconium oxide is 46.4%, which meets the required range.

Claims

1. A method for preparing zirconium pyrophosphate, characterized in that: The following steps are involved: Step 1, preparing a fluorozirconic acid solution; Zirconium dioxide and hydrofluoric acid are fully reacted and then filtered to obtain a fine fluorozirconic acid solution; Step 2, preparing crude zirconium pyrophosphate; Slowly adding the fine fluorozirconic acid solution into phosphoric acid, heating at 150-180° C. for reaction until evaporated to dryness, thereby obtaining an evaporation product; crushing the evaporation product, sieving it, and washing it with high-purity water to obtain a crude zirconium pyrophosphate product; Step 3, preparing zirconium pyrophosphate; The crude zirconium pyrophosphate product is dried at 500-600° C. for 2-3 hours. When the weight loss on ignition at 500° C. is less than 0.5%, the drying is completed to obtain a zirconium pyrophosphate product.

2. The method for preparing zirconium pyrophosphate according to claim 1, characterized in that: Step 1 is as follows: Step 1.1: dissolving zirconium dioxide with hydrofluoric acid having a mass fraction of 40-50%, maintaining the temperature at 80-100° C., stirring and dissolving until transparent, to obtain a crude fluorozirconic acid solution; the molar ratio of hydrofluoric acid to zirconium dioxide is 6:1; Step 1.2: Filter the crude fluorozirconic acid solution using a precision filter with a filtration accuracy of 1 micron or less to obtain a fine fluorozirconic acid solution.

3. The method for preparing zirconium pyrophosphate according to claim 1 or 2, characterized in that: Step 2 is as follows: Step 2.1 Take phosphoric acid with a mass fraction of less than or equal to 85% and add it to a tetrafluoro beaker, put the tetrafluoro beaker containing phosphoric acid into an oil bath, heat it to 150-180°C, and slowly add the fluorozirconic acid solution therein; the molar ratio of zirconium to phosphorus is 1:2; Step 2.2: The solution obtained in step 2.1 is kept at 150-180° C. for further heating reaction and evaporation until it is evaporated to dryness to obtain an evaporated product; Step 2.3: The evaporated product is crushed, sieved, and high-purity water with a mass at least 5 times that of the evaporated product is added to perform boiling and washing for multiple times at 80-90° C., and the fluoride ion is controlled to be less than 0.05%, thereby obtaining a crude zirconium pyrophosphate product.

4. A zirconium pyrophosphate, characterized in that The invention is prepared by the preparation method described in any one of claims 1 to 3.

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