Lithium hydride purity detection method

Abstract

The invention relates to a lithium hydride purity detection method, which comprises the following steps: weighing a predetermined amount of lithium hydride particles, hydrolyzing the lithium hydride particles with deionized water to release hydrogen so as to obtain a first mixed solution containing lithium hydroxide and a substance amount for releasing gas; diluting the first mixed solution to a constant volume to form a second mixed solution, and dropwise adding 2-3 drops of a neutral red indicator solution into the second mixed solution to obtain a third mixed solution containing lithium hydroxide and a neutral red indicator; a hydrochloric acid standard solution is added into an acid burette for titration until the third mixed solution becomes yellow from red, namely the titration end point, the volume of the consumed standard hydrochloric acid titration solution is recorded, and the amount of substance of hydroxyl ions is obtained based on the volume of the consumed hydrochloric acid standard solution; and based on the amount of substance of the hydroxyl ions, the predetermined amount of the lithium hydride particles and the amount of substance of the hydrogen release gas, the purity of the lithium hydride is obtained through simultaneous calculation.

Description

Technical Field

[0001] The invention relates to the technical field of lithium hydride detection, and in particular to a method for detecting the purity of lithium hydride directly obtained by hydrogenation reaction of metallic lithium and hydrogen. Background Art

[0002] At present, the methods used to detect the purity of lithium hydride at home and abroad are water dehydrogenation method or other large-scale detection equipment detection, such as inductively coupled plasma mass spectrometer analysis, X-rav fluorescence spectrum analysis, etc. Among them, the water dehydrogenation method is to calculate the content of lithium hydride by hydrolyzing lithium hydride with deionized water and detecting the volume of gas produced. The disadvantage of this method is that it is impossible to distinguish between lithium hydride and unreacted metallic lithium in the sample. Both can release hydrogen during the water dehydrogenation process, thereby affecting the detection value of lithium hydride content and purity. Inductively coupled plasma mass spectrometry and X-ray fluorescence spectrum analysis can only give the content of elements, and it is difficult to detect light elements such as hydrogen. Therefore, it is also impossible to distinguish between lithium hydride and metallic lithium. The detection accuracy is low, and the detection conditions and detection environment are required to be high. The equipment itself is of high value, and the detection requires equipment operation training for the detection personnel. The operation is difficult and the universality is poor.

[0003] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Summary of the invention

[0004] The present invention provides a lithium hydride purity detection method, which can reduce the purity detection error of lithium hydride.

[0005] A lithium hydride purity detection method comprises:

[0006] Weighing a predetermined amount of lithium hydride particles and deionized water to dehydrate and obtain a first mixed solution containing lithium hydroxide and an amount of a substance that releases gas;

[0007] The first mixed solution is diluted to form a second mixed solution, and 2 to 3 drops of neutral red indicator solution are added to the second mixed solution to obtain a third mixed solution containing lithium hydroxide and neutral red indicator;

[0008] Add hydrochloric acid standard solution to the acid burette for titration until the third mixed solution changes from red to yellow, which is the titration endpoint, record the volume of standard hydrochloric acid titration solution consumed, and obtain the amount of hydroxide ion substance based on the volume of the consumed hydrochloric acid standard solution;

[0009] Carry out a blank experiment, titrate the same volume of deionized water with a standard hydrochloric acid solution, and record the volume of the standard hydrochloric acid solution consumed during the blank experiment to obtain the amount of hydroxide ion in the blank experiment;

[0010] Based on the amount of the substance of the hydroxide ions, the predetermined mass of the lithium hydride sample particles and the amount of the substance of the hydrogen-released gas, the purity of the lithium hydride in the sample is obtained by joint calculation.

[0011] In the lithium hydride purity detection method, before deionizing with water, a hydrogen release device is built, a double-necked flask is connected to a constant pressure separatory funnel for adding deionized water, a gas burette is connected to the double-necked flask via a valve for opening and closing, a level bottle is connected to the gas burette from the bottom, and the gas burette is provided with a thermometer for measuring temperature.

[0012] In the lithium hydride purity detection method, a predetermined amount of lithium hydride particles are weighed and placed in a two-necked flask, deionized water is added to a constant pressure separatory funnel, the valve above the gas burette is opened, and the position of the level bottle is adjusted so that the liquid level in the gas burette is consistent with the level bottle and the liquid level is at the "0" scale line. At this time, the valve is closed, the valve of the constant pressure separatory funnel is opened, and deionized water is added to the two-necked flask to hydrolyze and hydrogenate the lithium hydride sample. After the hydrogen release is completed, the solution is allowed to stand and cool until the gas temperature in the gas burette is consistent with the indoor temperature, the level bottle is moved so that the liquid level in the level bottle is consistent with the liquid level in the gas burette, and the atmospheric pressure and the indoor temperature values ​​are recorded at the same time to obtain the amount of the substance generating the gas, and at the same time, a first mixed solution containing lithium hydroxide is obtained.

[0013] In the lithium hydride purity detection method, 20 ml of deionized water is added to a constant pressure separatory funnel, and after the hydrogen release is completed, it is allowed to stand for more than 30 minutes.

[0014] In the lithium hydride purity detection method, the lithium hydride to be detected is pressed into tablets and crushed to obtain lithium hydride particles.

[0015] In the lithium hydride purity detection method, the amount of hydroxide ion substance in the titration solution is calculated according to the concentration and volume of the hydrochloric acid standard titration solution, and the amount of hydroxide ion substance in the blank experiment is calculated.

[0016] In the lithium hydride purity detection method, the amount of hydroxide ion in the titration solution is calculated by the following formula:

[0017] n OH - =c HCl V HCl ,

[0018] in:

[0019] nOH - : The amount of hydroxide ion in the titration solution, unit (mol);

[0020] c HCl : The concentration of the hydrochloric acid standard solution used for titration, unit (mol / L);

[0021] V HCl : The volume of hydrochloric acid standard solution consumed in titration, unit (L);

[0022] The amount of hydroxide ion in the blank experiment was calculated by the following formula:

[0023] n 空白 =c 空白HCl V 空白HCl ,

[0024] in:

[0025] n 空白 : The amount of hydroxide ion in the solution in the blank experiment, unit (mol);

[0026] c 空白HCl : The concentration of the standard hydrochloric acid titration solution in the blank experiment, unit (mol / L);

[0027] V 空白HCl : The volume of hydrochloric acid standard solution consumed in the blank experiment, unit (L);

[0028] After obtaining the amount of substance of hydroxide ions in the titration experiment and the blank experiment, the amount of substance of lithium hydroxide in the first solution is obtained according to the following formula:

[0029] n 氧氧化锂 =n OH - -n 空白 ;

[0030] Comprehensive hydrogen release and acid-base titration chemical reaction formula, simultaneous equation:

[0031]

[0032] The following equations are obtained:

[0033]

[0034] It can be deduced that the purity of lithium hydride in the sample is:

[0035]

[0036] The parameters are explained as follows:

[0037] ω LiH: The mass fraction of lithium hydride in the test sample;

[0038] P: The difference between the atmospheric pressure recorded after the hydrogen release reaction ends and the saturated vapor pressure of water at the temperature at that time, unit (Pa);

[0039] V: The volume of gas in the gas tube after the hydrogen release reaction is completed, unit (m1);

[0040] R: gas constant;

[0041] T: the indoor temperature value recorded after the hydrogen release reaction is completed, unit (℃);

[0042] n 氢氧化锂 : The calculated amount of lithium hydroxide in the first solution, unit (mol);

[0043] m: The mass of the lithium hydride sample weighed during the hydrolysis experiment, unit (g).

[0044] In the lithium hydride purity detection method, the gas constant is 8.314 J / (mol·K).

[0045] In the lithium hydride purity detection method, lithium hydride particles are weighed with a 1 / 10,000 balance and placed in a two-necked flask under an argon or nitrogen atmosphere.

[0046] Compared with the prior art, the present invention has the following advantages: the present invention avoids the detection error caused by the inability to distinguish between lithium hydride and unreacted metallic lithium in the existing hydrolysis hydrogenation gas volume measurement method and ion detection method, and can simultaneously determine the respective contents of lithium hydride and unreacted metallic lithium in the sample; at the same time, the device used in this method is commonly used laboratory glassware and ordinary titration equipment, which greatly reduces the operation requirements and detection costs. The concentration and volume of the standard solution used in the detection process of the present disclosure are objective readings, and the neutral red indicator selected in the present disclosure is color sensitive, with an accuracy of 1 drop before and after the titration endpoint, and is also not affected by the outside world, and the neutral red indicator color change pH range is 6.8 to 8.0, which is close to the pH value of the neutralization reaction product lithium chloride aqueous solution. For the above reasons, the results of the detection method disclosed in the present disclosure are highly accurate and stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] By reading the detailed description of the preferred specific embodiments below, various other advantages and benefits of the present invention will become clear to those of ordinary skill in the art. The drawings in the specification are only for the purpose of illustrating the preferred embodiments and are not considered to be limitations of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative work. Moreover, the same reference numerals are used to represent the same components throughout the drawings.

[0048] In the attached picture:

[0049] Figure 1 It is a schematic diagram of a hydrogen release device in the required hydrogen release stage of a preferred embodiment of the present invention.

[0050] The present invention is further explained below in conjunction with the accompanying drawings and embodiments. DETAILED DESCRIPTION

[0051] The specific embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the specific embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0052] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present invention, but the description is based on the general principles of the specification and is not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the attached claims.

[0053] To facilitate understanding of the embodiments of the present invention, further explanation will be given below by taking specific embodiments as examples in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention.

[0054] like Figure 1 As shown, the lithium hydride purity detection method comprises the following steps:

[0055] Weighing a predetermined amount of lithium hydride particles and deionized water to dehydrate and obtain a first mixed solution containing lithium hydroxide and an amount of a substance that releases gas;

[0056] The first mixed solution is diluted to form a second mixed solution, and 2 to 3 drops of neutral red indicator solution are added to the second mixed solution to obtain a third mixed solution containing lithium hydroxide and neutral red indicator;

[0057] Add hydrochloric acid standard solution to the acid burette for titration until the third mixed solution changes from red to yellow, which is the titration endpoint, record the volume of standard hydrochloric acid titration solution consumed, and obtain the amount of hydroxide ion substance based on the volume of the consumed hydrochloric acid standard solution;

[0058] Conduct a blank experiment, titrate the same volume of deionized water with a standard hydrochloric acid solution, and record the volume of the standard hydrochloric acid solution consumed during the blank experiment to obtain the amount of hydroxyl ion in the blank experiment. The blank experiment is to eliminate the interference of hydroxyl ions in deionized water and ensure the objectivity of the test results. Because the indicator in deionized water with a general pH of 7 may consume a small part of the titration solution due to different color change ranges, this factor must be excluded.

[0059] Based on the amount of the substance of the hydroxide ions, the predetermined mass of the lithium hydride sample particles and the amount of the substance of the hydrogen-released gas, the purity of the lithium hydride in the sample is obtained by joint calculation.

[0060] In a preferred embodiment of the lithium hydride purity detection method, before deionizing with water, a hydrogen release device is built, a double-necked flask is connected to a constant pressure separatory funnel for adding deionized water, a gas burette is connected to the double-necked flask via a valve for opening and closing, a level bottle is connected to the gas burette from the bottom, and the gas burette is provided with a thermometer for measuring temperature.

[0061] In a preferred embodiment of the lithium hydride purity detection method, a predetermined amount of lithium hydride particles is weighed and placed in a two-necked flask, deionized water is added to a constant pressure separatory funnel, the valve above the gas tube is opened, and the position of the level bottle is adjusted so that the liquid level in the gas tube is consistent with the level bottle and the liquid level is at the "0" scale line. At this time, the valve is closed, and the valve of the constant pressure separatory funnel is opened, and deionized water is added to the two-necked flask to hydrolyze the lithium hydride sample to hydrogen. After the hydrogen release is completed, it is allowed to stand and cool until the gas temperature in the gas tube is consistent with the room temperature, and the level bottle is moved so that the liquid level of the level bottle is consistent with the liquid level in the gas tube. At the same time, the atmospheric pressure and the room temperature values ​​are recorded to obtain the amount of the substance generating the gas, and at the same time, a first mixed solution containing lithium hydroxide is obtained.

[0062] In a preferred embodiment of the lithium hydride purity detection method, 20 ml of deionized water is added to the constant pressure separatory funnel, and after the hydrogen release is completed, it is allowed to stand for more than 30 minutes.

[0063] In a preferred embodiment of the lithium hydride purity detection method, the lithium hydride to be detected is pressed into tablets and crushed to obtain lithium hydride particles.

[0064] In a preferred embodiment of the lithium hydride purity detection method, the amount of hydroxide ion in the titration solution is calculated based on the concentration and volume of the hydrochloric acid standard titration solution, and the amount of hydroxide ion in the blank experiment is calculated.

[0065] In a preferred embodiment of the lithium hydride purity detection method, the amount of hydroxide ion in the titration solution is calculated by the following formula:

[0066] n OH - =c HCl V HCl ,

[0067] in:

[0068] n OH - : The amount of hydroxide ion in the titration solution, unit (mol);

[0069] C HCl : The concentration of the hydrochloric acid standard solution used for titration, unit (mol / L);

[0070] V HCl : The volume of hydrochloric acid standard solution consumed in titration, unit (L);

[0071] The amount of hydroxide ion in the blank experiment was calculated by the following formula:

[0072] n 空白 =c 空白HCl V 空白HC1 ,

[0073] in:

[0074] n 空白 : The amount of hydroxide ion in the solution in the blank experiment, unit (mol);

[0075] c 空白HCl : The concentration of the standard hydrochloric acid titration solution in the blank experiment, unit (mol / L);

[0076] V 空白HCl : The volume of hydrochloric acid standard solution consumed in the blank experiment, unit (L);

[0077] After obtaining the amount of substance of hydroxide ions in the titration experiment and the blank experiment, the amount of substance of lithium hydroxide in the first solution is obtained according to the following formula:

[0078] n 氢氧化锂 =nOH - -n 空白 ;

[0079] Comprehensive hydrogen release and acid-base titration chemical reaction formula, simultaneous equation:

[0080]

[0081] The following equations are obtained:

[0082]

[0083] It can be deduced that the purity of lithium hydride in the sample is:

[0084]

[0085] The parameters are explained as follows:

[0086] ω LiH : The mass fraction of lithium hydride in the test sample;

[0087] P: The difference between the atmospheric pressure recorded after the hydrogen release reaction ends and the saturated vapor pressure of water at the temperature at that time, unit (Pa);

[0088] V: The volume of gas in the gas tube after the hydrogen release reaction is completed, unit (m1);

[0089] R: gas constant;

[0090] T: the indoor temperature value recorded after the hydrogen release reaction is completed, unit (℃);

[0091] n 氢氧化锂 : The calculated amount of lithium hydroxide in the first solution, unit (mol);

[0092] m: The mass of the lithium hydride sample weighed during the hydrolysis experiment, unit (g).

[0093] In a preferred implementation of the lithium hydride purity detection method, the gas constant is 8.314 J / (rmol·K).

[0094] In a preferred embodiment of the lithium hydride purity detection method, in step S6, the second mixed solution is placed on a magnetic stirrer for stirring and shaking to obtain a third mixed solution.

[0095] In a preferred embodiment of the lithium hydride purity detection method, lithium hydride particles are weighed with a 1 / 10,000 balance and placed in a two-necked flask under an argon or nitrogen atmosphere.

[0096] In one embodiment, a method for detecting the purity of lithium hydride comprises the following steps:

[0097] 1. Under argon or nitrogen atmosphere, weigh 0.0510g of lithium hydride particles using a 1 / 10,000 balance and place in a two-necked flask.

[0098] In this step, by pressing the lithium hydride powder into tablets and then crushing it into particles, the flying powder and wall sticking phenomenon that occur when the lithium hydride powder is loaded into the double-necked flask can be avoided, thereby minimizing the detection error caused by the sample powder in the bottle mouth part that cannot be hydrolyzed.

[0099] 2. Add a certain amount of deionized water (for example, 20 ml, which can meet the hydrolysis requirements) to the constant pressure separatory funnel, adjust the hydrogen release device to allow the deionized water to hydrolyze the lithium hydride sample. After the reaction is completed, let it stand for more than 30 minutes (30 minutes is a reference value here, and the actual test can be carried out according to the change of ambient temperature. Take a suitable time) until the temperature in the gas collecting pipe is consistent with the indoor temperature, move the level bottle so that the liquid level of the level bottle is flush with the liquid level in the gas collecting pipe, and read the corresponding atmospheric pressure, indoor temperature, and gas volume readings. At the same time, obtain the first mixed solution containing lithium hydroxide;

[0100] 3. After the hydrolysis reaction is completed, the first mixed solution containing lithium hydroxide is added with deionized water to a 100 ml volumetric flask, and 2 to 3 drops of neutral red indicator solution are added to 5 ml of the second mixed solution after the dilution to obtain a third mixed solution containing lithium hydroxide and neutral red indicator;

[0101] In this step, after adding the neutral red indicator solution to the second mixed solution, the first mixed solution appears red.

[0102] 4. Add 0.1026 mol / L hydrochloric acid standard titration solution to a 5 ml micro-acid burette, and add 0.1026 mol / L hydrochloric acid standard titration solution dropwise to the third mixed solution containing lithium hydroxide and neutral red indicator solution. The concentration and dosage of the hydrochloric acid standard titration solution described here are also exemplary and can be adjusted according to actual conditions. Titrate until the solution changes from red to yellow, which is the titration endpoint, and record the volume of the standard hydrochloric acid titration solution consumed;

[0103] In this step, a standard hydrochloric acid titration solution is added to the third mixture, so that the lithium hydroxide in the solution reacts with the hydrochloric acid to undergo a neutralization reaction. The specific reaction is shown in the following formula:

[0104] OH - +H + →H 2 O

[0105] 5. Take 5 ml of deionized water and put it in a duckbill bottle. Add a 0.1026 mol / 1 hydrochloric acid standard titration solution into a 5 ml micro-acid burette (the concentration and dosage of the hydrochloric acid standard solution described here are also exemplary and can be adjusted according to actual conditions). Titrate the deionized water and record the end point when the deionized water changes from red to yellow. The volume of the hydrochloric acid standard titration solution consumed is the blank experiment consumption.

[0106] After completing the above experiment, the amount of hydroxide ion in the titration solution can be calculated based on the concentration and volume of the hydrochloric acid standard titration solution; at the same time, the amount of hydroxide ion in the blank experiment can be calculated. Specifically,

[0107] The amount of hydroxide ion in the titration solution is calculated by the following formula:

[0108] n OH - =c HCl V HCl

[0109] in:

[0110] n OH - : The amount of hydroxide ion in the titration solution, unit (mol);

[0111] C HCl : The concentration of the hydrochloric acid standard solution used for titration, unit (mol / L);

[0112] V HCl : The volume of hydrochloric acid standard solution consumed in titration, unit (L);

[0113] The amount of hydroxide ion in the blank experiment was calculated by the following formula:

[0114] n 空白 =c 空白HCl V 空白HCl ,

[0115] in:

[0116] n 空白 : The amount of hydroxide ion in the solution in the blank experiment, unit (mol);

[0117] c 空白HCl : The concentration of the standard hydrochloric acid titration solution in the blank experiment, unit (mol / L);

[0118] V 空白HCl : The volume of hydrochloric acid standard solution consumed in the blank experiment, unit (L);

[0119] After obtaining the amount of substance of hydroxide ions in the titration experiment and the blank experiment, the amount of substance of lithium hydroxide in the first solution can be obtained according to the following formula:

[0120] n 氢氧化锂 =n oH - -n 空白 ;

[0121] Comprehensive hydrogen release and acid-base titration chemical reaction formula, simultaneous equation:

[0122]

[0123] The following equations are obtained:

[0124]

[0125] It can be deduced that the purity of lithium hydride in the sample is:

[0126]

[0127] The parameters shown in the above formula are explained as follows:

[0128] ω LiH : The mass fraction (purity) of lithium hydride in the test sample;

[0129] P: The difference between the atmospheric pressure recorded after the hydrogen release reaction ends and the saturated vapor pressure of water at the temperature at that time, unit (Pa);

[0130] V: The volume of gas in the gas tube after the hydrogen release reaction is completed, unit (ml);

[0131] R: gas constant, 8.314 J / (mol·K);

[0132] T: the indoor temperature value recorded after the hydrogen release reaction is completed, unit (℃);

[0133] n 氢氧化锂 : The calculated amount of lithium hydroxide in the first solution, unit (mol);

[0134] m: The mass of the lithium hydride sample weighed during the hydrolysis experiment, unit (g).

[0135] According to the above formula, the purity of lithium hydride in 0.0510 g of lithium hydride particle sample is 98.104%.

[0136] In another embodiment, the present disclosure proposes a method for detecting the purity of lithium hydride. Different from the above embodiment, the lithium hydride particles weighed in this embodiment are 0.0282 g, and the purity of the lithium hydride calculated based on the above formula is 98.116%, which is 0.012% different from the purity of the above embodiment.

[0137] In another embodiment, the present disclosure provides a method for detecting the purity of lithium hydride. Different from the above embodiment, the lithium hydride powder weighed in this embodiment is 0.0202 g, and the purity of the lithium hydride calculated based on the above formula is 98.202%.

[0138] In another embodiment, the present disclosure proposes a method for detecting the purity of lithium hydride. Different from the above embodiment, the lithium hydride powder weighed in this embodiment is 0.0575 g. Based on the above formula, the purity of the lithium hydride is 98.024%, which is 0.178% different from the purity of the above embodiment, and the detection result is stable.

[0139] As described above, the present disclosure has detected and calculated the purity of lithium hydride samples by weighing lithium hydride particles and lithium hydride powder of different masses. According to the final test results, it can be concluded that for samples of different masses (when the mass increases or decreases), the detection method given in this article will not affect the stability of the results.

[0140] Next, the present disclosure uses a simple aqueous hydrogenation method to test the purity of lithium hydride powder of the same mass for comparison with the embodiments described in the present disclosure.

[0141] In one embodiment, lithium hydride powder of different masses is weighed, and further, a hydrolysis hydrogenation device is used to add water to the gas burette, and the excess gas in the burette is first removed by adjusting the position of the level bottle, and the height of the level bottle is adjusted again so that the page in the gas burette is located at the "0" scale line. At this time, the entire device is connected to prepare for hydrolysis; 20 ml of deionized water is added to the separatory funnel, the upper cover is plugged, and the flask is slowly added to the two-necked flask, and the two-necked flask is slowly shaken to promote the complete reaction. After the reaction is complete, it is allowed to stand for 30 minutes, and the gas in the gas burette is cooled to room temperature (based on the judgment that the volume no longer shrinks), and the level bottle is moved so that the liquid level of the level bottle is parallel to the liquid level of the gas burette, and the gas volume in the gas burette is recorded. At the same time, the atmospheric pressure and temperature are recorded.

[0142] Calculation results: The purity of 0.0214g lithium hydride powder sample is: 99.13%;

[0143] The purity of 0.052lg lithium hydride powder sample is: 99.84%;

[0144] The difference between the two results is 0.71%, and the stability of the result is poor. In this embodiment, the same lithium hydride sample as mentioned above is used. Through the test results, it is found that the test result of using the hydrogen release method alone is about 1.6% larger than the method given in the present disclosure. The reason is that the hydrogen release method cannot distinguish the metallic lithium part in the lithium hydride sample, which makes the test value larger.

[0145] In another embodiment, lithium hydride particles of different masses are weighed, and further, a water-hydrogenation device is used to add water to the gas burette, and the excess gas in the burette is first removed by adjusting the position of the level bottle, and the height of the level bottle is adjusted again so that the page in the gas burette is located at the "0" scale line. At this time, the entire device is connected to prepare for hydrolysis; 20 ml of deionized water is added to the separatory funnel, the upper cover is plugged, and the flask is slowly added to the two-necked flask, and the two-necked flask is slowly shaken to promote the complete reaction. After the reaction is complete, it is allowed to stand for 30 minutes, and the gas in the gas burette is cooled to room temperature (based on the judgment that the volume no longer shrinks), and the level bottle is moved so that the liquid level of the level bottle is parallel to the liquid level of the gas burette, and the gas volume in the gas burette is recorded. At the same time, the atmospheric pressure and temperature are recorded.

[0146] Calculation results: The purity of 0.0513g lithium hydride powder sample is: 99.79%;

[0147] 0.0221g lithium hydride powder sample purity: 99.10%;

[0148] The difference between the two results is 0.69%, and the result is also less stable.

[0149] By testing and calculating the purity of lithium hydride particle samples of different masses, it can be concluded that for samples of different masses (when the mass increases), when the water dehydrogenation method is used alone for testing, the test results are still quite different, and the error of the test results is larger than that of the test method given in the present disclosure.

[0150] Next, the present disclosure uses an inductively coupled plasma mass spectrometer to perform purity detection on lithium hydride powder of the same mass for comparison with the embodiments described in the present disclosure.

[0151] In one embodiment, lithium hydride powder of different masses is weighed, and further, a hydrolysis and acidification solution is performed using a standard hydrochloric acid solution to obtain a solution, and then a sample is taken for sample detection according to an ICP-MS (inductively coupled plasma mass spectrometer) operating method.

[0152] Test results: 0.0274g lithium hydride powder sample purity: 99.27%;

[0153] The purity of 0.0511g lithium hydride powder sample is: 99.62%;

[0154] The difference between the two results is 0.35%, and the stability of the result is poor. In this embodiment, the same lithium hydride sample as mentioned above is used. Through the test results, it is found that the test result using the inductively coupled plasma mass spectrometer is about 1.3% larger than the method given in the present disclosure. The reason is that the inductively coupled plasma mass spectrometer detects the content of lithium ions in the solution after the lithium hydride sample is dissolved, and cannot distinguish the metallic lithium part in the lithium hydride sample, which makes the test value larger.

[0155] In another embodiment, lithium hydride particles of different masses are weighed, and further, hydrolyzed, acidified and dissolved with a standard hydrochloric acid solution to obtain a solution, and then samples are taken for sample detection according to the operating method of an ICP-MS (inductively coupled plasma mass spectrometer) instrument.

[0156] Calculation results: The purity of 0.0533g lithium hydride powder sample is: 99.69%;

[0157] The purity of 0.0271g lithium hydride powder sample is: 99.18%;

[0158] The difference between the two results is 0.51%, and the result is also less stable.

[0159] By testing and calculating the purity of lithium hydride particle samples of different masses, it can be concluded that for samples of different masses (when the mass increases), when the inductively coupled plasma mass spectrometer is used alone for testing, the test results are still quite different, and the error of the test results is larger than that of the test method given in the present invention.

[0160] In one embodiment, a method for detecting the purity of lithium hydride includes: tableting and crushing the lithium hydride powder to be tested to obtain lithium hydride particles; weighing a certain amount of lithium hydride particles for hydrolysis and hydrogenation, recording the volume of released gas and the corresponding gas temperature and atmospheric pressure, and hydrolyzing to obtain a mixed solution; adding a neutral red indicator to the mixed solution, titrating with a standard hydrochloric acid solution, and recording the consumed volume of the standard hydrochloric acid solution; obtaining the molar mass of hydroxide ions in the solution based on the consumed volume of the standard hydrochloric acid solution; performing a blank experiment, and recording the consumed volume of the standard hydrochloric acid solution during the blank experiment, and obtaining the molar mass of hydroxide ions in the blank experiment; based on the volume of gas released by hydrolysis and hydrogenation and the volume of the standard hydrochloric acid solution consumed in the titration, the chemical equation of the two-step reaction is combined to calculate the mass of the incompletely reacted metallic lithium and the synthesized lithium hydride in the sample, and further calculate the purity of the lithium hydride.

[0161] Although the embodiments of the present invention are described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific embodiments and application fields, and the above specific embodiments are only illustrative and instructive, rather than restrictive. A person of ordinary skill in the art can also make many forms under the guidance of this specification and without departing from the scope of protection of the claims of the present invention, all of which belong to the protection of the present invention.

Claims

1. A method for detecting the purity of lithium hydride, suitable for detecting the lithium hydride product obtained by direct hydrogenation of metallic lithium and hydrogen, characterized in that: The steps include: Weighing a predetermined amount of lithium hydride particles and deionized water to dehydrate and obtain a first mixed solution containing lithium hydroxide and an amount of a substance that releases gas; The first mixed solution is diluted to form a second mixed solution, and 2 to 3 drops of neutral red indicator solution are added to the second mixed solution to obtain a third mixed solution containing lithium hydroxide and neutral red indicator; Add hydrochloric acid standard solution to the acid burette for titration until the third mixed solution changes from red to yellow, which is the titration endpoint, record the volume of standard hydrochloric acid titration solution consumed, and obtain the amount of hydroxide ion substance based on the volume of the consumed hydrochloric acid standard solution; Carry out a blank experiment, titrate the same volume of deionized water with a standard hydrochloric acid solution, and record the volume of the standard hydrochloric acid solution consumed during the blank experiment to obtain the amount of hydroxide ion in the blank experiment; The difference between the amount of hydroxide ions calculated by acid-base titration of the third mixed solution and the amount of hydroxide ions obtained in the blank experiment is the amount of lithium hydroxide in the solution after the lithium hydride sample is hydrolyzed; Based on the calculated amount of lithium hydroxide, the predetermined mass of the lithium hydride sample particles and the amount of the substance that releases hydrogen and releases gas, the purity of the lithium hydride in the sample is obtained by joint calculation.

2. A lithium hydride purity detection method according to claim 1, characterized in that: Preferably, before deionizing hydrogen with water, a hydrogen release device is built, the double-necked flask is connected to a constant pressure separatory funnel for adding deionized water, a gas burette is connected to the double-necked flask via a valve for opening and closing, a level bottle is connected to the gas burette from the bottom, and the gas burette is provided with a thermometer for measuring temperature.

3. A lithium hydride purity detection method according to claim 2, characterized in that: A predetermined amount of lithium hydride particles is weighed and placed in a two-necked flask, deionized water is added to a constant-pressure separatory funnel, the valve above the burette is opened, and the position of the level bottle is adjusted so that the liquid level in the burette is consistent with the level bottle and the liquid level is at the "0" scale line. At this time, the valve is closed, and the valve of the constant-pressure separatory funnel is opened, and deionized water is added to the two-necked flask to hydrolyze and hydrogenate the lithium hydride sample. After the hydrogen release is completed, the flask is allowed to stand and cool until the gas temperature in the burette is consistent with the room temperature, and the level bottle is moved so that the liquid level of the level bottle is consistent with the liquid level in the burette. At the same time, the atmospheric pressure and the room temperature are recorded to obtain the amount of the substance generating the gas, and at the same time, a first mixed solution containing lithium hydroxide is obtained.

4. A lithium hydride purity detection method according to claim 2, characterized in that: Add 20 ml of deionized water to the constant pressure separatory funnel and let it stand for more than 30 minutes after the hydrogen release is completed.

5. A lithium hydride purity detection method according to claim 1, characterized in that: The lithium hydride tablet to be tested is crushed to obtain lithium hydride particles.

6. A lithium hydride purity detection method according to claim 1, characterized in that: The amount of hydroxide ion in the titration solution is calculated based on the concentration and volume of the hydrochloric acid standard titration solution, and the amount of hydroxide ion in the blank experiment is also calculated.

7. A lithium hydride purity detection method according to claim 1, characterized in that: The amount of hydroxide ion in the titration solution is calculated by the following formula: n OH - =c HCl V HCl , in: n OH - : The amount of hydroxide ion in the titration solution, unit (mol); C HCl : The concentration of the hydrochloric acid standard solution used for titration, unit (mol / L); V HCl : The volume of hydrochloric acid standard solution consumed in titration, unit (L); The amount of hydroxide ion in the blank experiment was calculated by the following formula: n 空白 =c 空白HCl V 空白HCl , in: n 空白 : The amount of hydroxide ion in the solution in the blank experiment, unit (mol); c 空白HCl : The concentration of the standard hydrochloric acid titration solution in the blank experiment, unit (mol / L); V 空白HCl : The volume of hydrochloric acid standard solution consumed in the blank experiment, unit (L); After obtaining the amount of substance of hydroxide ions in the titration experiment and the blank experiment, the amount of substance of lithium hydroxide in the first solution is obtained according to the following formula: n 氢氧化锂 =n OH - -n 空白 ; Comprehensive hydrogen release and acid-base titration chemical reaction formula, simultaneous equation: The following equations are obtained: It can be deduced that the purity of lithium hydride in the sample is: The parameters are explained as follows: ω LiH : The mass fraction of lithium hydride in the test sample; P: The difference between the atmospheric pressure recorded after the hydrogen release reaction and the saturated vapor pressure of water at the temperature at that time, unit (Pa); V: The volume of gas in the gas tube after the hydrogen release reaction is completed, unit (m1); R: gas constant; T: the indoor temperature value recorded after the hydrogen release reaction is completed, unit (℃); n 氢氧化锂 : The calculated amount of lithium hydroxide in the first solution, unit (mol); m: The mass of the lithium hydride sample weighed during the hydrolysis experiment, unit (g).

8. A lithium hydride purity detection method according to claim 7, characterized in that: The gas constant is 8.314 J / (mol·K).

9. A lithium hydride purity detection method according to claim 1, characterized in that: In step S6, the second mixed solution is placed on a magnetic stirrer for stirring and shaking to obtain a third mixed solution.

10. A lithium hydride purity detection method according to claim 1, characterized in that: Under an argon or nitrogen atmosphere, weigh the lithium hydride particles using a 1 / 10,000 balance and place them in a two-necked flask.

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