A method for determining poorly soluble metal oxide impurities using ionic liquids

Abstract

The application discloses a method for determining insoluble metal oxide impurities by using ionic liquids, and belongs to the technical field of quantitative analysis. The method is combined with the method of ionic liquids and low-temperature heating, wherein the ionic liquids have large solubility, can dissolve a large amount of substances, and can dissolve metals at room temperature without high-temperature heating, and steam pressure is not generated. In combination with low-temperature microwave heating, complete dissolution of the oxides can be realized, and the method is a low-pollution and low-energy-consumption method for dissolving insoluble metal oxides.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of quantitative analysis, and particularly relates to a method for determining insoluble metal oxide impurities by using ionic liquids. BACKGROUND

[0002] Metal oxides often serve as various functional materials or basic raw materials for synthesizing specific materials, and their physical and chemical properties such as particle size, specific surface area, valence, etc. will affect the synthesis of materials. In addition, the purity of the oxides is also a key factor for measuring the performance of the materials. For example, in the field of catalysis, alumina is widely used as a catalyst carrier, and excessive impurity content often affects the selectivity of catalytic reactions, and even causes the deactivation of the catalyst. Therefore, the determination of the content of the oxides is an indispensable part in the synthesis of materials. The current methods for determining the content of elements include titration, X-ray fluorescence spectroscopy analysis, atomic absorption spectroscopy analysis, and plasma emission spectroscopy analysis. Among them, the titration method needs to select the corresponding titration reaction due to excessive impurity elements, and it is difficult to accurately determine trace or micro amounts of metal oxides; the X-ray fluorescence analysis can analyze various forms of oxides, but is easily affected by mutual element interference and superimposed peaks, and it is difficult to accurately determine trace elements; and when using atomic absorption spectroscopy and inductively coupled plasma emission spectroscopy to determine insoluble metal impurities, a digestion process is required, i.e. converting the solid to be measured into a liquid.

[0003] The current commonly used method for determining alumina is high-temperature acid digestion and high-temperature alkali fusion. The high-temperature acid digestion includes microwave high-temperature digestion and hydrothermal kettle high-temperature high-pressure digestion, i.e. adding acid in a digestion tank or a hydrothermal kettle and then heating the sample by microwave or an oven. The high-temperature alkali fusion uses sodium hydroxide or sodium carbonate as a solvent, and after melting the oxides at 900-1100℃, the sample is dissolved with acid, and finally the test solution is detected by atomic absorption or ICP.

[0004] Both the acid digestion and alkali digestion methods have problems such as high acid consumption, high energy consumption for heating, high pressure safety hazards, and environmental pollution caused by waste liquid. In addition, alkali fusion may also introduce impurity elements to affect the measurement results. SUMMARY

[0005] The present application provides a method for determining insoluble metal oxide impurities by using ionic liquids, to solve the problems of high energy consumption, high pollution, and high risk caused by the traditional high-temperature digestion method in the prior art, and to improve the accuracy of the determination.

[0006] In a first aspect, the present application provides a method for determining insoluble metal oxide impurities by using ionic liquids, comprising the following steps:

[0007] Take the ionic liquid, mix with two known samples after adding acid to adjust the pH value, get sample solution A and sample solution B; take the ionic liquid, without sample, get blank solution C, blank solution D and blank solution E;

[0008] Heat the sample solution A, sample solution B, blank solution C, blank solution D and blank solution E after fully oscillation;

[0009] After the reaction, the sample solution A and sample solution B are diluted and constant volume;

[0010] After the reaction, the blank solution C is added to the standard solution as the internal standard solution;

[0011] After the reaction, the blank solution D and blank solution E are added to the measured element standard solution, constant volume and shake well;

[0012] The treated sample solution A, sample solution B, blank solution C, blank solution D and blank solution E are measured on the plasma emission spectrum by internal standard method to determine the content of the insoluble metal oxide impurities.

[0013] Further, the ionic liquid is trialkylammonium propyl sulfonic acid di(trifluoromethyl sulfonyl) imide, and the molecular formula is [NRRRC3SO3H][Tf2N].

[0014] Further, the structure of [NRRRC3SO3H][Tf2N] is shown as formula I,

[0015]

[0016] In which, R = methyl, ethyl, propyl, butyl, hexyl, octyl or phenyl.

[0017] Further, the mixing ratio of the ionic liquid and the sample is 10-20 mL:0.05-0.1 g.

[0018] Further, the acid is sulfuric acid, and the end point of adjusting the pH value is 0-0.2.

[0019] Further, the heating method is water bath heating or microwave digestion, the temperature of water bath heating is 50-75℃, and the time of water bath heating is 1-3h.

[0020] Further, the temperature rising rate of microwave digestion is 4-6℃ / min, the temperature of microwave digestion is 95-100℃, and the holding time of microwave digestion is 8-15min.

[0021] Further, the dilution multiple of the sample solution A and sample solution B is 10-15 times.

[0022] The technical scheme provided by the embodiments of the present application has at least the following advantages compared with the prior art.

[0023] The application discloses a method for determining a difficult-to-dissolve metal oxide impurity by using an ionic liquid. BRIEF DESCRIPTION OF DRAWINGS

[0024] The drawings incorporated in the specification and forming a part thereof demonstrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required to be used in the embodiments or the prior art description will be briefly introduced as follows, and obviously, other drawings can be obtained by those skilled in the art without any creative labor on the basis of these drawings.

[0026] Figure 1 The synthesis method of the [NRRRC3SO3H][Tf2N] ionic liquid used in the present application. DETAILED DESCRIPTION

[0027] In order to make the purposes, technical schemes and advantages of the embodiments of the present application more clear, the technical schemes in the embodiments of the present application will be clearly and completely described in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without any creative labor are within the protection scope of the present application.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment and the like used in the present application can be purchased from the market or can be prepared by the existing method.

[0029] In a first aspect, the present application provides a method for determining a difficult-to-dissolve metal oxide impurity by using an ionic liquid, comprising the following steps:

[0030] The ionic liquid is taken, mixed with two known samples, and then acid is added to adjust the pH value, to obtain sample solution A and sample solution B; the ionic liquid is taken without adding samples, to obtain blank solution C, blank solution D and blank solution E;

[0031] After heating, the sample solution A, sample solution B, blank solution C, blank solution D and blank solution E are fully shaken;

[0032] After the reaction, the sample solution A and sample solution B are diluted and constant volume is added;

[0033] After the reaction, the blank solution C is added to the standard solution as an internal standard solution;

[0034] After the reaction, the blank solution D and blank solution E are added to the standard solution of the element to be measured, constant volume is added and shaken uniformly;

[0035] After treatment, the sample solution A, sample solution B, blank solution C, blank solution D and blank solution E are measured by internal standard method on plasma emission spectrum to determine the content of the insoluble metal oxide impurities.

[0036] In the present application, the ionic liquid is the abbreviation of room temperature ionic liquid, which is a molten salt system composed of specific organic cation and anion, and is in liquid state at room temperature or near room temperature.

[0037] In the preferred embodiment of the present application, the ionic liquid is trialkylammonium propyl sulfonic acid di(trifluoromethyl sulfonimide), the molecular formula is [NRRRC3SO3H][Tf2N], and the structural formula is shown as formula I,

[0038]

[0039] In the formula, R = methyl, ethyl, propyl, butyl, hexyl, octyl or phenyl.

[0040] The principle of the present application is that under acidic conditions, in a hydrophobic ionic liquid, metal cations exchange with acidic protons of the ionic liquid:

[0041] M n+ (aq) +n[RSO3H][Tf2N] (IL) →[(RSO3) n M][Tf2N]n (IL) +nH + (aq) ,

[0042] For example, when detecting aluminum element, the following chemical reaction is generated: Al2O3+6[RSO3H][Tf2N]→2[Al(RSO3)3][Tf2N]6+3H2O.

[0043] Preferably, in the present application, the structure formula of the ionic liquid is shown as formula II:

[0044]

[0045] The above ion liquid is synthesized from 1,3-propane sulfolane (CAS: 1120-71-4) and trihexylamine (CAS: 102-86-3) to obtain product A, and then Tf2N (CAS: 82113-65-3) is added to obtain the product A. The structure of product A is shown in the following formula III:

[0046]

[0047] Preferably, the mixing ratio of the ion liquid and the standard sample is 10-20 mL: 0.05-0.1 g.

[0048] More preferably, the mixing ratio of the ion liquid and the standard sample is 10 mL: 0.1 g.

[0049] Preferably, the acid is sulfuric acid, and the end point of pH adjustment is 0-0.2.

[0050] Preferably, the heating method is water bath heating or microwave digestion, the temperature of the water bath heating is 50-75℃, and the time of the water bath heating is 1-3 h.

[0051] More preferably, the present application selects the method of microwave heating digestion to assist the ion liquid in determination, wherein the heating rate of the microwave digestion is 4-6℃ / min, the temperature of the microwave digestion is 95-100℃, and the holding time of the microwave digestion is 8-15 min.

[0052] Preferably, the dilution multiple of the sample solution A and the sample solution B is 10-15 times.

[0053] The principles and characteristics of the present application are described below in combination with examples, and the examples are only used to explain the present application and are not used to limit the scope of the present application. The specific conditions not noted in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments not noted by the manufacturer are all conventional products that can be purchased on the market.

[0054] Example 1

[0055] The present embodiment provides a method for determining a difficultly soluble metal oxide impurity by using an ion liquid, which comprises the following steps:

[0056] (1) Respectively take 0.05 g of alumina standard samples with known metal loadings in A, B beakers, and then add 20 mL of [N 666 C3SO3H][Tf2N] ion liquid, add sulfuric acid to adjust the pH to 0.2, and mix and shake. C, D, and E beakers are used as blank samples, no sample is added, only the ion liquid is added, and the blank experiment is carried out after shaking.

[0057] (2) Respectively, A, B, C, D, E, beaker in water bath 60 ℃ heating 2h to chase acid, and fully oscillation.

[0058] (3) Reaction end, A, B sample dilution 10 times, shake uniform constant volume. C, add appropriate amount of organic Y standard solution, as internal standard solution. D, F corresponding volumetric flask, add appropriate concentration of the measured element standard solution. Constant volume, shake uniform.

[0059] (4) The resulting solution in plasma emission spectrometry using internal standard method for determination of aluminum oxide impurities. The experimental data are shown in table 3.

[0060] A, B sample shows the last solution is clear, but there are still a small amount of solid particles left, ICP test before centrifugation and take the supernatant filtration.

[0061] Example 2

[0062] The present embodiment provides a kind of method for determining insoluble metal oxide impurities using ionic liquid, comprising the following steps:

[0063] (1) respectively, 0.1 g of alumina standard sample with known each load metal content is taken in a, b digestion tank, then 10 mL of [N 666 C3SO3H][Tf2N] ionic liquid is added, sulfuric acid is added to adjust the pH to 0.2, mixed and shaken up, c, d, e digestion tank is blank sample, no sample is added, only ionic liquid is added, and blank experiment is carried out by shaking up.

[0064] (2) a, b, c, d, e number of digestion tank is placed in batches in microwave digestion instrument, and the temperature rising program is set to 5 min to 100 DEG C, and the temperature is kept for 10 min.

[0065] (3) Reaction end, A, B sample dilution 10 times, shake uniform constant volume. C, add appropriate amount of organic Y standard solution, as internal standard solution. D, F corresponding volumetric flask, add appropriate concentration of the measured element standard solution. Constant volume, shake uniform.

[0066] a, b sample shows that the solution is clear, and there is no solid residue, indicating that the sample is completely dissolved.

[0067] The ionic liquid in the present embodiment is:

[0068] Comparative example 1

[0069] The present comparative example provides a kind of method for determining alumina by traditional microwave high temperature digestion, comprising the following steps:

[0070] (1) Respectively take 0.05g of alumina sample in 1,2 digestion tank, add 9mL of hydrochloric acid, 3mL of nitric acid, 1mL of hydrofluoric acid, shake carefully. Take 3,4,5 digestion tank as blank experiment, do not add sample, only add the same amount of acid.

[0071] (2) 1,2,3,4,5 digestion tank is placed in microwave digestion instrument, the temperature rising program is 10min to 200℃, and keeps for 30min.

[0072] (3) After the reaction, the above digestion tank is chased on the electric heating plate, and the solution is left about 1mL. 1,2 sample solution is moved to a volumetric flask and diluted with pure water, 3 is added with appropriate Y standard solution as internal standard, and 5,6 corresponding volumetric flask is added with appropriate concentration of standard solution of the element to be measured.

[0073] (4) The obtained solution is determined by internal standard method on plasma emission spectrometer. The test results are shown in Table 2.

[0074] 1,2 sample solution is turbid, indicating that the sample is not completely dissolved, and needs to be centrifuged and the upper clear liquid is filtered before ICP test.

[0075] Comparative example 2

[0076] This comparative example provides a method for detecting impurities in alumina assisted by protonated betaine bis(trifluoromethylsulfonyl) imide ([Hbet][NTf2] ionic liquid) microwave digestion, comprising the following steps:

[0077] (1) Respectively take 0.1g of alumina standard sample with known metal content in ①①①①① digestion tank, add 10mL of [Hbet][NTf2] ionic liquid, adjust pH to 0.2 with sulfuric acid, and mix and shake. ①①① digestion tank is used as blank sample, without sample, only ionic liquid is added, and shake to carry out blank experiment.

[0078] (2) Put ①①①①① digestion tank into microwave digestion instrument in batches, set the temperature rising program to 5min to 100℃, and keep for 10min.

[0079] (3) After the reaction, dilute ① sample by 10 times, shake and dilute to volume. ① is added with appropriate amount of organic Y standard solution as internal standard solution. ① corresponds to the volumetric flask, and appropriate concentration of standard solution of the element to be measured is added. Dilute to volume, shake and dilute to volume.

[0080] ① sample shows turbid solution, and there is still solid residue, indicating that the sample is not completely dissolved, and needs to be centrifuged and the upper clear liquid is filtered before ICP test.

[0081] Table 1. Metal content in alumina standard sample

[0082]

[0083] Table 2. ICP analysis results for hydrothermal dissolution of Example 1 ionic liquid

[0084]

[0085] Table 3. Deviation of measured data from standard sample for hydrothermal dissolution of Example 1 ionic liquid

[0086]

[0087] Table 4. ICP analysis results for microwave digestion of Example 2 ionic liquid

[0088]

[0089] Table 5. Deviation of measured data from standard sample for microwave digestion of Example 2 ionic liquid

[0090]

[0091] Table 6. ICP analysis results for microwave digestion of Comparative Example 1 acid

[0092]

[0093] Table 7. Deviation of measured data from standard sample for microwave digestion of Comparative Example 1 acid

[0094]

[0095] Table 8. ICP analysis results for microwave digestion of Comparative Example 2 ionic liquid

[0096]

[0097] Table 9. Deviation of measured data from standard sample for microwave digestion of Comparative Example 2 ionic liquid

[0098]

[0099] Various embodiments of the application can exist in a range of forms; it should be understood that a range format is used herein only for convenience and brevity, and should not be construed as limiting the scope of the application to a broadest form; therefore, the description of a range format should be considered to have specifically disclosed sub-ranges within the range and individual numerical values within that range. For example, a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within the range, for example 1, 2, 3, 4, 5, and 6, and this applies regardless of the breadth of the range.

[0100] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to the embodiments in light of the above detailed description without departing from the spirit and intended scope of the application. It is to be understood that the application can be practiced otherwise than as specifically described without altering its spirit or essential characteristics. Accordingly, the scope of the application should be judged in terms of the broadest allowable principles and features described herein, and not according to the above detailed description, which is to be viewed in all its novel aspects with the scope and spirit of the application.

Claims

1. A method for determining sparingly soluble metal oxide impurities using ionic liquids, characterized in that, Includes the following steps: Take an ionic liquid, mix it with two known standard samples, and then add acid to adjust the pH value to obtain sample solution A and sample solution B. Take an ionic liquid and, without adding a sample, obtain blank solution C, blank solution D, and blank solution E; Sample solution A, sample solution B, blank solution C, blank solution D, and blank solution E are heated and then shaken thoroughly. After the reaction was completed, sample solution A and sample solution B were diluted and brought to a final volume. After the reaction was completed, blank solution C was added to the standard solution to serve as an internal standard solution. After the reaction is complete, add blank solution D and blank solution E to the standard solution of the element to be tested, and make up to volume and shake well; The contents of sparingly soluble metal oxide impurities were determined by internal standard method using inductively coupled plasma atomic emission spectrometry (ICP-AES) on the processed sample solutions A, B, C, D, and E. The ionic liquid is trialkylaminopropanesulfonic acid di(trifluoromethylsulfonyl)imine, with the molecular formula [NRRRC3SO3H][Tf2N]; The structural formula of [NRRRC3SO3H][Tf2N] is shown in Formula I. Equation I; Where R = methyl, ethyl, propyl, butyl, hexyl, octyl, or phenyl.

2. The method for determining sparingly soluble metal oxide impurities using ionic liquids according to claim 1, characterized in that, The mixing ratio of the ionic liquid to the standard is 10~20 mL: 0.05~0.1 g.

3. The method for determining sparingly soluble metal oxide impurities using ionic liquids according to claim 1, characterized in that, The acid is sulfuric acid, and the pH value is adjusted to a final value of 0-0.

2.

4. The method for determining sparingly soluble metal oxide impurities using ionic liquids according to claim 1, characterized in that, The heating method is water bath heating or microwave digestion, wherein the water bath heating temperature is 50~75 ℃ and the water bath heating time is 1~3 h.

5. The method for determining sparingly soluble metal oxide impurities using ionic liquids according to claim 4, characterized in that, The microwave digestion heating rate is 4~6 ℃ / min, the microwave digestion temperature is 95~100 ℃, and the microwave digestion holding time is 8~15 min.

6. The method for determining sparingly soluble metal oxide impurities using ionic liquids according to claim 1, characterized in that, The sample solution A and sample solution B are diluted by a factor of 10 to 15.

Images