Method for increasing flash point of ethanol aqueous solution serving as frozen impregnation liquid

Abstract

The invention relates to the field of freezing impregnation liquid and the field of environmental protection, in particular to a method for increasing the flash point of an ethanol aqueous solution for impregnation freezing, and the method specifically comprises the steps that ethanol and water are mixed to form an ethanol-water mixed solution, and in the ethanol-water mixed solution, the mass concentration of ethanol is 39-41%; the method comprises the following steps: adding nano silver chloride particles into an ethanol-water mixed solution, and stirring, wherein the mass ratio of the nano silver chloride particles to the ethanol-water mixed solution is 9.5-10.5%. Under the condition that the freezing point of the mixed solution of ethanol and water is basically kept unchanged (the temperature change is less than 3 DEG C), the flash point of the mixed solution of ethanol and water is greatly improved; therefore, the method has the advantage of higher safety.

Description

Technical Field

[0001] The invention relates to the field of freezing impregnation liquid and environmental protection, and in particular to a method for improving the flash point of an ethanol aqueous solution used for impregnation freezing. Background Art

[0002] A mixture of ethanol and water is a common antifreeze that can be used as a heat exchanger in immersion freezing equipment. It can maintain liquid properties (no freezing) at temperatures below freezing. Due to its higher specific heat capacity, the temperature fluctuation of the ethanol and water mixture is smaller when immersion freezing the same sample, making it easier to achieve better results.

[0003] The freezing point of a mixture of ethanol and water decreases as the ethanol content increases; however, the temperature safety (flash point) of the mixture increases as the ethanol content increases; large-scale production of the mixture of ethanol and water requires an increase in the level of safety equipment due to the change in its flash point.

[0004] How to ensure that the freezing point of the mixture of ethanol and water is low while lowering its flash point temperature (thereby ensuring safety) is an urgent problem to be solved in the industry. That is, it is necessary to improve the mixture of ethanol and water so as to increase its flash point without changing its freezing point depression property. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving the flash point of an ethanol-water solution used as a freezing impregnation liquid. The present invention can significantly improve the flash point of the solution while basically keeping the freezing point of the ethanol-water mixture unchanged (temperature change is less than 3°C).

[0006] In order to solve the above technical problems, the present invention provides a method for improving the flash point of an ethanol aqueous solution used as a freezing impregnation liquid:

[0007] Mixing ethanol and water to form an ethanol-water mixed solution, wherein the mass concentration of ethanol in the ethanol-water mixed solution is 39-41%;

[0008] Add nano silver chloride particles into the ethanol-water mixture and stir the mixture, wherein the mass ratio of the nano silver chloride particles to the ethanol-water mixture is 9.5-10.5%.

[0009] That is, ethanol and water are mixed in a mass ratio of 39-41:61-59 to form an ethanol-water mixed liquid.

[0010] As an improvement of the method for increasing the flash point of the ethanol aqueous solution used as the freezing impregnation liquid of the present invention: the particle size of the nano silver chloride particles is 10±1 nm.

[0011] As a further improvement of the method of raising the flash point of the ethanol aqueous solution as the freezing impregnation liquid of the present invention:

[0012] The mass ratio of the nano silver chloride particles to the ethanol-water mixture is 10%;

[0013] The particle size of the nano silver chloride particles is 10 nm.

[0014] The present invention finds that adding nano silver chloride particles of a specific diameter and a specific dosage ratio into a binary solution of a specific ratio of ethanol and water can form a uniform and stable metastable state, that is, the flash point of the solution is greatly increased while the freezing point of the ethanol-water mixture is basically kept unchanged (temperature change is less than 3° C.).

[0015] Note: A uniformly stable metastable state refers to a state in which a system remains relatively stable under certain conditions, but it is not the lowest energy state of the system. Although this state can be maintained for a period of time, it may turn into a stable state with lower energy if it is disturbed by external factors or changes in conditions.

[0016] The present invention has been found in the process of invention that, relative to the technical solution of the present invention, under the premise that the nano silver chloride particles keep the same dosage ratio, if the particle diameter of the nano silver chloride particles is changed, for example, to 5nm, 15nm, 20nm, 50nm, it is impossible to achieve that the flash point of the solution can be significantly improved while the freezing point of the ethanol water mixture is basically kept unchanged. Similarly, relative to the technical solution of the present invention, under the premise that the nano silver chloride particles keep the same particle diameter, if the consumption of the nano silver chloride particles is changed, it is also impossible to achieve that the flash point of the solution can be significantly improved while the freezing point of the ethanol water mixture is basically kept unchanged.

[0017] It is speculated that under the specific technical scheme set by the present invention, a layer of ethanol molecules is tightly surrounded by the nano silver chloride particles, and then a layer of water molecules is surrounded by the outer layer, forming a multi-layer dynamic structure with the nano silver chloride particles as the core, and maintaining relative dynamic stability. This dynamic metastable structure can basically not change the chemical potential of water in the ethanol-water mixture, and thus does not change the freezing point of the mixture.

[0018] The currently known theories cannot deduce the above results of the present invention, and even more cannot deduce that the nano silver chloride particles with a specific particle diameter (10 nm) of the present invention can produce the above special experimental phenomenon.

[0019] The beneficial effects of the present invention are mainly reflected in:

[0020] 1. Forming a uniform and stable metastable state, the mixed liquid of ethanol and water exhibits the characteristic of greatly increasing the flash point, thus having the advantage of higher safety;

[0021] 2. While keeping the freezing point of the mixture of ethanol and water basically unchanged (temperature change is less than 3°C), the flash point of the mixture of ethanol and water is greatly improved; therefore, it has the advantage of higher safety. DETAILED DESCRIPTION

[0022] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0023] 1. The flash point and freezing point of ethanol-water mixtures with different ratios are shown in Table 1 below.

[0024] Table 1: Flash point and freezing point of ethanol-water mixtures with different ratios

[0025]

[0026]

[0027] Example 1 series, a method for increasing the flash point of ethanol aqueous solution as a freezing impregnation liquid:

[0028] Ethanol and water are mixed to form an ethanol-water mixture, in which the mass fractions (mass concentrations) of ethanol and water are as shown in Table 2 below;

[0029] Add nano silver chloride particles with a particle size of 10 nm into the ethanol-water mixture and stir for about 45 minutes; the resulting solution is named frozen impregnation solution. The mass ratio of the nano silver chloride particles to the ethanol-water mixture is 10%.

[0030] Note: Only Examples 1-6, 1-7, and 1-8 can achieve complete dissolution of the nano-silver chloride particles. Even if the stirring time is extended in the remaining cases, the complete dissolution of the nano-silver chloride particles cannot be achieved.

[0031] The flash point, freezing point and precipitation of the frozen impregnation solution (i.e., the ethanol-water mixture after adding nano silver chloride particles) are shown in Table 2 below.

[0032] Table 2: Flash point, freezing point and precipitation of the mixed solution after adding 10% mass fraction of 10nm diameter nano silver chloride to different ratios of ethanol and water

[0033]

[0034]

[0035] According to Table 2, it can be learned that only when nano silver chloride (diameter 10 nm) is added to a mixture of ethanol and water in a specific ratio (Example 1-6, Example 1-7, Example 1-8), precipitation will not occur.

[0036] Explanation: The precipitation means that the nano silver chloride particles cannot be well and evenly distributed in the liquid phase and cannot form a metastable state.

[0037] In addition, the ethanol-water mixture obtained in Examples 1-6, 1-7, and 1-8 after adding nano silver chloride particles was stored at -20°C and protected from light for 7 days and found that no precipitation occurred. Therefore, it is shown that these three solutions have good stability.

[0038] In the second embodiment, the particle size of the nano silver chloride particles in the first embodiment was changed from 10 nm to 5 nm, and the rest was the same as the first embodiment. The results are shown in Table 3 below.

[0039] Table 3: Flash point, freezing point and precipitation of the mixed solution after adding 10% mass fraction of 5nm diameter nano silver chloride to different ratios of ethanol and water

[0040]

[0041] According to Table 3, it can be learned that when the diameter of the nano silver chloride is 5 nm, no matter how the ratio of the ethanol-water mixture is adjusted, even if the stirring time is extended, precipitation will occur.

[0042] In the third embodiment, the particle size of the nano silver chloride particles in the first embodiment was changed from 10 nm to 15 nm, and the rest was the same as the first embodiment; the results are shown in Table 4 below.

[0043] Table 4: Flash point, freezing point and precipitation of the mixed solution after adding 10% mass fraction of 15nm diameter nano silver chloride to different ratios of ethanol and water

[0044]

[0045]

[0046] According to Table 4, it can be learned that when the diameter of the nano silver chloride is 15 nm, no matter how the ratio of the ethanol-water mixture is adjusted, even if the stirring time is extended, precipitation will occur.

[0047] In Example 4, the particle size of the nano silver chloride particles in Example 1 was changed from 10 nm to 20 nm, and the rest was the same as in Example 1. The results are shown in Table 5 below.

[0048] Table 5: Flash point, freezing point and precipitation of the mixed solution after adding 10% mass fraction of 20nm diameter nano silver chloride to different ratios of ethanol and water

[0049]

[0050] According to Table 5, it can be learned that when the diameter of the nano silver chloride is 20 nm, no matter how the ratio of the ethanol-water mixture is adjusted, even if the stirring time is extended, precipitation will occur.

[0051] In Example 5, the particle size of the nano silver chloride particles in Example 1 was changed from 10 nm to 50 nm, and the rest was the same as in Example 1. The results are shown in Table 6 below.

[0052] Table 6: Flash point, freezing point and precipitation of the mixed solution after adding 10% mass fraction of 50nm diameter nano silver chloride to different ratios of ethanol and water

[0053]

[0054] According to Table 6, it can be learned that when the diameter of the nano silver chloride is 50nm, no matter how the ratio of the ethanol-water mixture is adjusted, even if the stirring time is extended, precipitation will occur.

[0055] In Example 6, the mass ratio of the nano silver chloride particles: ethanol water mixture in Example 1 was changed from 10% to 5%, and the rest was the same as in Example 1. The results are shown in Table 7 below.

[0056] Table 7: Flash point, freezing point and precipitation of the mixed solution after adding 5% mass fraction of 10nm diameter nano silver chloride to different ratios of ethanol and water

[0057]

[0058] According to Table 7, it can be learned that when the dosage of nano silver chloride (diameter 10nm) is 5%, no matter how the ratio of the ethanol-water mixture is adjusted, even if the stirring time is extended, precipitation will be generated.

[0059] In Example 7 series, the mass ratio of the nano silver chloride particles: ethanol water mixture in Example 1 series was changed from 10% to 15%, and the rest was the same as in Example 1 series; the results are shown in Table 8 below.

[0060] Table 8: Flash point, freezing point and precipitation of the mixed solution after adding 15% mass fraction of 10nm diameter nano silver chloride to different ratios of ethanol and water

[0061]

[0062] According to Table 8, it can be learned that when the dosage of nano silver chloride (diameter 10nm) is 15%, no matter how the ratio of the ethanol-water mixture is adjusted, even if the stirring time is extended, precipitation will occur.

[0063] Experiment 1: Fresh snakehead (average weight 1.5±0.2kg) were purchased from Sanding Farmers Market in Xihu District, Hangzhou. After knocking the snakehead unconscious, the head, skin, bones and internal organs were removed and the fish meat was transferred to the laboratory within half an hour. After rinsing the snakehead meat with cold water, the back muscle was taken and cut into 3×3×1.5cm 3 Fish fillets of about 13 g were placed in polyethylene ziplock bags, the air in the bags was exhausted, and the bags were precooled at 4°C as samples.

[0064] In this experiment, a K-type thermocouple (OMEGA, USA) was used to detect the center temperature of the sample during the freezing process. The K-type thermocouple was inserted into the center of the sample, and then the sample was placed in the freezing immersion liquid already in the freezing chamber for freezing. The K-type thermocouple collected data once per second, and the temperature during the freezing process was recorded by a data logger.

[0065] The freezing process of snakehead fish fillets is divided into three stages: pre-cooling stage (4℃~0℃), phase change stage (0℃~-5℃) and deep freezing stage (-5℃~-18℃).

[0066] The phase change stage is also known as the maximum ice crystal formation zone. Most of the water in the sample undergoes phase change in this process. Therefore, the length of this stage is the main factor determining the duration of the freezing process.

[0067] The fish fillets precooled at 4°C were used as samples. The temperature of the freezer was -18°C.

[0068] Set up the following 4 groups:

[0069] The samples were directly placed in the freezer for freezing as the control group;

[0070] The frozen impregnation liquid obtained in Examples 1-6 was placed in a freezing chamber and balanced to a temperature of -18°C, and then the samples were placed in the frozen impregnation liquid in the freezing chamber for freezing, as Experimental Group 1;

[0071] The frozen impregnation liquid obtained in Examples 1-7 was placed in a freezing chamber and balanced to a temperature of -18°C, and then the samples were placed in the frozen impregnation liquid in the freezing chamber for freezing, as Experimental Group 2;

[0072] The frozen impregnation liquid obtained in Examples 1-8 was placed in a freezing chamber and balanced to a temperature of -18°C, and then the samples were placed in the frozen impregnation liquid in the freezing chamber for freezing, as Experimental Group 3;

[0073] The time required for the center of the sample to drop from 0°C to -5°C is shown in Table 9 below.

[0074] Note: Set 4 replicates for each group and take the average value.

[0075] Table 9

[0076]

[0077] The present invention also provides the following comparison:

[0078] The freezing immersion solution was changed to 41% ethanol aqueous solution, 40% ethanol aqueous solution, and 39% ethanol aqueous solution respectively; the rest was the same as the above experiment 1. The time required for the center of the sample to drop from 0°C to -5°C was not significantly different from the above experimental groups 1 to 3.

[0079] Finally, it should be noted that the above examples are only some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many variations. All variations that can be directly derived or associated with the content disclosed by a person skilled in the art should be considered as the protection scope of the present invention.

Claims

1. A method for improving the flash point of an ethanol aqueous solution as a freezing impregnation liquid, characterized in that: Mixing ethanol and water to form an ethanol-water mixed solution, wherein the mass concentration of ethanol in the ethanol-water mixed solution is 39-41%; Add nano silver chloride particles into the ethanol-water mixture and stir the mixture, wherein the mass ratio of the nano silver chloride particles to the ethanol-water mixture is 9.5-10.5%.

2. The method for improving the flash point of an ethanol-water solution as a freezing impregnation liquid according to claim 1, characterized in that: The particle size of the nano silver chloride particles is 9.5 to 10.5 nm.

3. The method for improving the flash point of an ethanol-water solution as a freezing impregnation liquid according to claim 2, characterized in that: The mass ratio of the nano silver chloride particles to the ethanol-water mixture is 10%; The particle size of the nano silver chloride particles is 10 nm.

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