Method for preparing phase-stable ammonium nitrate in eutectic mode

Abstract

The invention discloses a method for preparing phase-stable ammonium nitrate in a eutectic mode, and belongs to the technical field of crystal preparation. The eutectic method specifically comprises the following steps: (1) adding ammonium nitrate into water, heating and dissolving to obtain an ammonium nitrate saturated solution; (2) adding potassium ferrocyanide into the ammonium nitrate saturated solution, and stirring for reaction to obtain an ammonium nitrate / potassium ferrocyanide mixed solution; and (3) drying and grinding the ammonium nitrate / potassium ferrocyanide mixed solution to obtain the ammonium nitrate / potassium ferrocyanide eutectic. According to the invention, the AN / KFCT eutectic with the mass ratio of 3-4% is prepared by adopting an evaporative crystallization method through a eutectic technology, the phase change problem of ammonium nitrate in storage, transportation and use temperature ranges is solved, meanwhile, the structure-activity relationship between the crystal form and thermal stability is constructed, the thermal stability of ammonium nitrate is improved through crystal form regulation and control, and the application range of ammonium nitrate is widened. The invention provides a unique idea for solving the phase change of ammonium nitrate, and has application value.

Description

Technical Field

[0001] The present invention relates to the technical field of crystal preparation, and more particularly to a method for preparing phase-stabilized ammonium nitrate by means of a eutectic. Background Art

[0002] Ammonium nitrate (AN), with the chemical formula NH4NO3, is the nitrate of ammonium cation. It is usually a white crystalline solid, non-corrosive, has clean emissions after combustion, high oxygen content and low cost. It is widely used in solid propellants, civilian and military fields.

[0003] However, the use of ammonium nitrate is limited by its hygroscopicity, agglomeration and structural instability. Although ammonium nitrate is an energetic material, it is insensitive to friction and impact and usually undergoes significant thermal decomposition reactions only after exceeding its melting point. Therefore, it is generally believed that pure AN is stable at ambient temperature. AN has five stable crystal forms, which are observed near room temperature. Transformation. The repeated phase change process of ammonium nitrate will cause changes in the crystal volume, resulting in problems such as loose product structure, moisture absorption and agglomeration, which directly affect the storage stability and blasting performance of ammonium nitrate. At the same time, the release of lattice energy during the phase change process may cause local heat accumulation, changes in crystal structure and physical and chemical properties, and bring risks of loss of control to the stability of the ammonium nitrate system. This is also one of the reasons why accidents in the storage and transportation of ammonium nitrate are common. Therefore, in order to ensure the normal function of AN-based products, it is necessary to suppress or minimize the polymorphic transformation that occurs at temperatures below 50°C. From the perspective of storage and use, preparing phase-stable ammonium nitrate to suppress the phase change of ammonium nitrate and reduce its danger within the operating temperature range is a very critical and effective measure.

[0004] Currently, the main methods for inhibiting the phase transition of ammonium nitrate include: (1) introducing inorganic salt additives (such as potassium nitrate, ammonium sulfate, etc.) to form a solid solution; (2) constructing an intermolecular hydrogen bond network with organic amine compounds (such as hexamethylenetetramine); and (3) forming a coordination complex with metal chelating agents (such as transition metal nitrates). However, since the physical addition of additives will introduce hot spots during the decomposition and detonation transition of ammonium nitrate, it may increase the explosive properties of ammonium nitrate and cannot effectively solve the explosion risk during the storage and transportation of ammonium nitrate.

[0005] Potassium ferrocyanide (K4[Fe(CN)6]·3H2O, KFCT) is a light yellow monoclinic crystal with a density of 1.85 g / cm 3It is soluble in water but insoluble in ethanol and ether. It is stable in air and begins to lose its water of crystallization upon heating to 70°C. At 100°C, it becomes a hygroscopic white powdery anhydrous substance. Its melting point is 70°C and its boiling point is 104.2°C. At 20°C, 25.4g of KFCT can be dissolved in 100mL of water. KFCT has a habit-modifying and anti-caking effect on various inorganic crystals. Due to its similar ionic radius and lattice parameters to ammonium nitrate, it exhibits excellent eutectic compatibility.

[0006] Therefore, how to use potassium ferrocyanide to regulate the crystal form of ammonium nitrate and form a stable eutectic with ammonium nitrate is a problem that those skilled in the art urgently need to solve. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide a method for preparing phase-stabilized ammonium nitrate by eutectic means to address the deficiencies in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for preparing phase-stabilized ammonium nitrate by eutectic means, comprising the following steps:

[0010] (1) adding ammonium nitrate into water and heating to dissolve it to obtain a saturated ammonium nitrate solution;

[0011] (2) adding potassium ferrocyanide to a saturated ammonium nitrate solution, stirring and reacting to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0012] (3) drying and grinding the ammonium nitrate / potassium ferrocyanide mixed solution to obtain an ammonium nitrate / potassium ferrocyanide eutectic.

[0013] In the present invention, potassium ferrocyanide can also be replaced by potassium nitrate (as in Example 6); the evaporative crystallization method can also be replaced by recrystallization (as in Example 4) or mechanical ball milling (as in Example 5).

[0014] Furthermore, in the above step (1), the temperature for heating and dissolving is 40-80°C, preferably 80°C.

[0015] Furthermore, in the above step (2), the amount of potassium ferrocyanide added is 0.5%-5% of the mass of ammonium nitrate, preferably 3%-4%, and more preferably 3%.

[0016] Furthermore, in the above step (2), the stirring reaction time is 30-60 min, preferably 60 min.

[0017] Furthermore, in the above step (3), the drying temperature is 70° C. and the drying time is 2-3 h, preferably 3 h.

[0018] Furthermore, in the above step (3), a crystal growth step is also included before drying. Furthermore, the crystal growth time is 12-48 hours, preferably 12 hours, 24 hours or 48 hours, and more preferably 48 hours.

[0019] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. In the ammonium nitrate / potassium ferrocyanide eutectic of the present invention, the radius of potassium ions and ammonium ions between ammonium nitrate and KFCT is close, which replaces the ammonium ions in the crystal lattice. By adjusting the KFCT content, the hydrogen bonds between ammonium ions and nitrate ions are broken, and the ammonium ions are redirected, thereby forming an ammonium nitrate / KFCT eutectic, eliminating the ammonium nitrate at 32.1 ° C. phase transition and increased the thermal conductivity of ammonium nitrate at 84 °C. Phase transition temperature, while suppressing phase transition without generating new endothermic processes.

[0021] 2. The present invention realizes the eutectic technology of ammonium nitrate and KFCT through orthogonal experiments, and prepares AN / KFCT eutectic with a mass ratio of 3%-4% by mass using evaporation crystallization method, which solves the phase change problem of ammonium nitrate in the storage, transportation and use temperature ranges. At the same time, by regulating the structure-activity relationship between crystal phase transition and thermal stability, the thermal stability of ammonium nitrate is improved, providing a unique idea for solving the phase transition of ammonium nitrate and having application value.

[0022] 3. The eutectic method of the present invention is simple to operate and easy to form a stable eutectic. At the same time, the amount of additive (potassium ferrocyanide) added is small and is coated in the crystal lattice, which does not affect the use of ammonium nitrate-based compounds and does not pose additional explosion risks. Compared with other ammonium nitrate phase change materials, ammonium nitrate / potassium ferrocyanide has significant advantages. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The microstructure of ammonium nitrate (AN) used in Example 1 and the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 1;

[0024] Figure 2 TG-DSC curve of ammonium nitrate (AN) used in Example 1;

[0025] Figure 3 TG-DSC curve of potassium ferrocyanide (KFCT) used in Example 1;

[0026] Figure 4 The DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 1;

[0027] Figure 5This is the DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 2;

[0028] Figure 6 This is the DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 3;

[0029] Figure 7 This is the DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 4;

[0030] Figure 8 This is the DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 5;

[0031] Figure 9 This is the DSC curve of the ammonium nitrate / potassium nitrate eutectic (AN / KNO3) prepared in Example 6;

[0032] Figure 10 The DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Comparative Example 1 is shown;

[0033] Figure 11 The DSC curve of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Comparative Example 2;

[0034] Figure 12 This is the DSC curve of the ammonium nitrate / copper oxide eutectic (AN / CuO) prepared in Comparative Example 3;

[0035] Figure 13 This is the DSC curve of the ammonium nitrate / manganese dioxide eutectic (AN / MnO2) prepared in Comparative Example 4. DETAILED DESCRIPTION

[0036] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0037] Example 1

[0038] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0039] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0040] (2) adding 3 g of potassium ferrocyanide to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0041] (3) The ammonium nitrate / potassium ferrocyanide mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0042] Example 2

[0043] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0044] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0045] (2) adding 4 g of potassium ferrocyanide to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0046] (3) The ammonium nitrate / potassium ferrocyanide mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0047] Example 3

[0048] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0049] (1) Add 100 g of ammonium nitrate to water and heat to 40° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0050] (2) adding 3 g of potassium ferrocyanide to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0051] (3) The ammonium nitrate / potassium ferrocyanide mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0052] Example 4

[0053] The method for preparing phase-stabilized ammonium nitrate by eutectic mode (recrystallization) specifically comprises the following steps:

[0054] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0055] (2) adding 3 g of potassium ferrocyanide to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0056] (3) The ammonium nitrate / potassium ferrocyanide mixed solution was cooled to room temperature to allow crystals to precipitate. The crystals were grown for 48 h, filtered, washed with ethanol, and dried in a 70°C oven for 2 h to constant weight to obtain ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0057] Example 5

[0058] The method for preparing phase-stabilized ammonium nitrate by eutectic method (mechanical ball milling method) specifically comprises the following steps:

[0059] (1) Place 100 g of ammonium nitrate and 3 g of potassium ferrocyanide in a dry ball mill, add the same volume of ball mill beads, place the ball mill filled with materials in a ball mill and grind at a speed of 240 r / min for 15 min to obtain an ammonium nitrate / potassium ferrocyanide mixture;

[0060] (2) The ammonium nitrate / potassium ferrocyanide mixture was placed in an oven at 70°C and dried for 2 h to constant weight to obtain an ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0061] Example 6

[0062] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0063] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0064] (2) adding 3 g of potassium nitrate to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium nitrate mixed solution;

[0065] (3) The ammonium nitrate / potassium nitrate mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain an ammonium nitrate / potassium nitrate eutectic (AN / KNO3), which was then stored in a desiccator.

[0066] Comparative Example 1

[0067] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0068] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0069] (2) adding 2 g of potassium ferrocyanide to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0070] (3) The ammonium nitrate / potassium ferrocyanide mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0071] Comparative Example 2

[0072] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0073] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0074] (2) adding 3 g of potassium ferrocyanide to the saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / potassium ferrocyanide mixed solution;

[0075] (3) The ammonium nitrate / potassium ferrocyanide mixed solution was placed in a 40°C oven and dried for 3 h to constant weight, then ground and mixed to obtain ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT), which was then stored in a desiccator.

[0076] Comparative Example 3

[0077] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0078] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0079] (2) adding 3 g of copper oxide to a saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / copper oxide mixed solution;

[0080] (3) The ammonium nitrate / copper oxide mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain an ammonium nitrate / copper oxide eutectic (AN / CuO), which was then stored in a desiccator.

[0081] Comparative Example 4

[0082] The method for preparing phase-stabilized ammonium nitrate by eutectic method specifically comprises the following steps:

[0083] (1) Add 100 g of ammonium nitrate to water and heat to 80° C. to dissolve the water to obtain a saturated ammonium nitrate solution;

[0084] (2) adding 3 g of manganese dioxide to a saturated ammonium nitrate solution and stirring for 60 min to obtain an ammonium nitrate / manganese dioxide mixed solution;

[0085] (3) The ammonium nitrate / manganese dioxide mixed solution was placed in an oven at 70°C and dried for 3 h to constant weight, then ground and mixed to obtain an ammonium nitrate / manganese dioxide eutectic (AN / MnO2), which was then stored in a desiccator.

[0086] Performance Testing

[0087] 1. Microstructure

[0088] The microstructures of ammonium nitrate (AN) used in Example 1 and ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 1 are as follows: Figure 1 shown.

[0089] Depend on Figure 1 Pure AN exhibits a needle-like structure with surface irregularities and accumulation. This is primarily due to the strong hygroscopicity of ammonium nitrate, which leads to salting out and salt bridges between particles. However, the AN / KFCT eutectic no longer exhibits a needle-like structure, but rather a rhombus-like structure, which is also an outward characteristic of its eutectic formation. Its particles are larger than pure AN and possess numerous pores on the surface, which increases the specific surface area of ​​the ammonium nitrate.

[0090] TG-DSC data

[0091] In order to understand the phase behavior of the AN / KFCT eutectic sample, the TG-DSC data of ammonium nitrate (AN) and potassium ferrocyanide (KFCT) used in Example 1 were measured using a Mettler 1600HT synchronous thermal analyzer. The test conditions were heating from 30°C to 800°C in a nitrogen atmosphere at a heating rate of 10°C / min.

[0092] See the results Figure 2 and Figure 3 .

[0093] Depend on Figure 2 It can be seen that ammonium nitrate has a mass loss step on the TG curve and 5 endothermic peaks on the DSC curve. The first three peaks are generated by phase transition of non-chemical reaction. The phase transition peak temperatures are 61℃, 96.5℃ and 136.5℃, corresponding to and Phase transition, the fourth endothermic peak temperature of 177.3 ° C corresponds to the melting process of ammonium nitrate, and the last peak is the peak produced by thermal decomposition. The thermal decomposition peak starts at 185 ° C, the decomposition peak temperature is 267.6 ° C, and the end temperature is 293.5 ° C.

[0094] Depend on Figure 3As shown, potassium ferrocyanide (KFCT) exhibits two steps in its TG curve as the temperature rises from room temperature to 800°C. At 110.5°C, the weight loss is approximately 12%, indicating the loss of three molecules of water. A strong endothermic peak due to this loss of water appears on the DSC curve. From 574°C to 800°C, the mass decreases dramatically, driven by the thermal decomposition of KFCT. The weight loss during this stage is approximately 22%.

[0095] 3.DSC data

[0096] The DSC data of the eutectic products prepared in Examples 1-6 and Comparative Examples 1-4 were measured using a Mettler 1600HT synchronous thermal analyzer. The test conditions were heating from 30° C. to 800° C. at a heating rate of 10° C. / min under a nitrogen atmosphere.

[0097] See the results Figure 4-13 .

[0098] Depend on Figure 4 It can be seen that the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 1 has no phase change in the range of 30-100°C, indicating that KFCT effectively inhibits the formation of ammonium nitrate. Phase change.

[0099] Depend on Figure 5 It can be seen that the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Example 2 eliminates the phase transition, The phase transition temperature moves toward higher temperature.

[0100] Depend on Figure 6 It can be seen that when the melting temperature is 40℃, there is no endothermic peak in the DSC curve in the range of 30-100℃, indicating that the AN / KFCT eutectic prepared under this condition has a strong effect on the AN Phase transition has an inhibitory effect.

[0101] Depend on Figure 7 and Figure 8 It can be seen that when KFCT is added by recrystallization and mechanical ball milling, there is no endothermic peak in the range of 30-100 °C for AN, indicating that the AN / KFCT eutectic prepared under this condition has a good effect on the thermal conductivity of AN. Phase transition has an inhibitory effect.

[0102] Depend on Figure 9 It can be seen that when potassium ferrocyanide is replaced by potassium nitrate while keeping the experimental conditions unchanged, no endothermic peak appears at a lower temperature, which has an inhibitory effect on the phase change of ammonium nitrate.

[0103] Depend on Figure 10It can be seen that the endothermic peak of the ammonium nitrate / potassium ferrocyanide eutectic (AN / KFCT) prepared in Comparative Example 1 in the range of 30-100°C is consistent with the phase transition peak of pure AN, indicating that KFCT with a mass fraction of 2% has no phase stabilizing effect on AN.

[0104] Depend on Figure 11 It can be seen that when the oven temperature is 40°C, the DSC curve has three endothermic peaks in the range of 30-140°C, indicating that the AN / KFCT eutectic prepared under this condition has no phase stabilizing effect on AN.

[0105] Depend on Figure 12 It can be seen that when potassium ferrocyanide is replaced by copper oxide while keeping the experimental conditions unchanged, no eutectic is formed and there is no inhibitory effect on the phase change of ammonium nitrate.

[0106] Depend on Figure 13 It can be seen that when potassium ferrocyanide is replaced by manganese dioxide while keeping the experimental conditions unchanged, no eutectic is formed and there is no inhibitory effect on the phase transition of ammonium nitrate.

[0107] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing phase-stabilized ammonium nitrate by eutectic method, characterized in that: The specific steps include: (1) adding ammonium nitrate into water and heating to dissolve it to obtain a saturated ammonium nitrate solution; (2) adding potassium ferrocyanide to a saturated ammonium nitrate solution, stirring and reacting to obtain an ammonium nitrate / potassium ferrocyanide mixed solution; (3) drying and grinding the ammonium nitrate / potassium ferrocyanide mixed solution to obtain an ammonium nitrate / potassium ferrocyanide eutectic.

2. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 1, characterized in that: In step (1), the temperature for heating and dissolving is 40-80°C.

3. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 2, characterized in that: In step (1), the temperature for heating and dissolving is 80°C.

4. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 1, characterized in that: In step (2), the amount of potassium ferrocyanide added is 0.5%-5% of the mass of ammonium nitrate.

5. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 4, characterized in that: In step (2), the amount of potassium ferrocyanide added is 3%-4% of the mass of ammonium nitrate.

6. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 5, characterized in that: In step (2), the amount of potassium ferrocyanide added is 3% of the mass of ammonium nitrate.

7. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 1, characterized in that: In step (2), the stirring reaction time is 30-60 minutes.

8. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 1, characterized in that: In step (3), the drying temperature is 70° C. and the drying time is 2-3 h.

9. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 1, characterized in that: In step (3), a crystal growing step is also included before drying.

10. The method for preparing phase-stabilized ammonium nitrate by eutectic method according to claim 9, characterized in that: In step (3), the crystal growing time is 12-48 hours.

Images