Method for determining platinum content in solid superacid catalyst based on ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) and application thereof

Abstract

The invention discloses a method for determining the platinum content in a solid superacid catalyst based on ICP-OES and application of the method, and relates to the technical field of analytical chemistry, the method comprises the following steps: grinding a solid superacid catalyst sample into powder, mixing the powder with ZrO2, and digesting by adopting a microwave digestion method to obtain a digestion solution; carrying out cooling and acid removal on the digestion solution to obtain a solution to be detected; the wavelength of an analysis line of Pt is selected to be 265.945 nm, a standard solution is prepared through a matrix matching method, and a calibration curve is drawn. The method effectively overcomes spectral interference and physical interference of high-concentration ZrO2 and Al2O3 matrixes, has the characteristics of high sensitivity, good repeatability (RSD is less than or equal to 1.8%), standard recovery rate (97-101%) and high accuracy, and is suitable for industrial quality control and performance evaluation of the Pt-containing composite superacid catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and in particular to a method for determining the platinum content in solid superacid catalysts based on ICP-OES and its application. Background Art

[0002] Solid superacid catalysts, such as Pt-SO 4 2- / ZrO 2 -Al 2 O 3 , due to their unique acidity and excellent catalytic performance, are widely used in industrial fields such as alkane isomerization reactions. Such catalysts not only have high catalytic activity but also exhibit good anti-coking performance, significantly improving the reaction efficiency and product quality. However, the performance and quality of the catalysts are often closely related to their constituent elements, especially the content of noble metal elements. Platinum (Pt), as a common noble metal additive element in solid superacid catalysts, has an important influence on the catalytic activity, selectivity, and stability of the catalysts.

[0003] In the production and research and development process of solid superacid catalysts, accurately determining the platinum content in the catalysts is crucial. This can not only be used to evaluate the performance and quality of the catalysts but also provide important references for the formulation optimization and preparation process improvement of the catalysts. Traditional methods for determining platinum content include chemical analysis methods, gravimetry, titration methods, atomic absorption spectrometry, etc. Although these methods can determine the platinum content, they often have disadvantages such as cumbersome operations, long time consumption, and poor selectivity, and are difficult to meet the requirements of modern industrial production for efficient and accurate detection.

[0004] With the continuous development of analytical techniques, inductively coupled plasma optical emission spectrometry (ICP-OES), as an advanced spectroscopic analysis technique, has gradually emerged in the field of elemental analysis. ICP-OES has been widely used in the sample analysis of multiple fields such as environment, rock, mineral, metal, etc. due to its characteristics of high accuracy, high precision, low detection limit, rapid determination, and wide linear range. It can simultaneously determine multiple elements and has relatively low requirements for sample pretreatment, making it very suitable for the determination of platinum content in solid superacid catalysts.

[0005] During the ICP-OES determination process, the sample to be measured first undergoes appropriate pretreatment steps, such as crushing, dissolution, etc., to fully introduce the platinum element in the sample into the solution system. Then, the treated sample solution is introduced into the ICP-OES instrument, and characteristic spectra are generated after excitation by the inductively coupled plasma. By measuring the wavelengths and intensities of these characteristic spectra, qualitative and quantitative analysis of the platinum element in the sample can be carried out. However, although ICP-OES has the advantage of multi-element detection, high-concentration SO 42- , ZrO 2 and Al 2 O 3 matrixes are likely to cause signal suppression and spectral overlap interference. It is difficult to accurately determine Pt in complex matrixes by existing technologies.

[0006] Therefore, developing a method for determining the platinum content in solid superacid catalysts based on ICP-OES to solve the problems of spectral interference and physical interference of high-concentration ZrO 2 and Al 2 O 3 matrixes is of great significance for promoting the research, development and application of solid superacid catalysts. Summary of the Invention

[0007] To solve the above problems, the present invention provides a method for determining the platinum content in solid superacid catalysts based on ICP-OES and its application.

[0008] The present invention provides a method for determining the platinum content in solid superacid catalysts based on ICP-OES and its application. As Figure 1 shown, the method for determining the platinum content in solid superacid catalysts based on ICP-OES includes the following steps:

[0009] Grind the solid superacid catalyst sample into powder, mix it with ZrO 2 , and then perform digestion by microwave digestion method to obtain a digestion solution;

[0010] Cool and drive away the acid from the digestion solution to obtain a solution to be measured;

[0011] Select the analysis line wavelength of Pt as 265.945 nm, prepare a standard solution by matrix matching method, and draw a calibration curve;

[0012] Add matrix elements with concentrations matching those of ZrO 2 and Al 2 O 3 in the sample to the standard solution to eliminate physical interference and spectral interference;

[0013] Detect the solution to be measured by ICP-OES method and calculate the content of Pt in the sample according to the calibration curve;

[0014] Wherein, the digestion reagent during digestion consists of aqua regia and hydrofluoric acid.

[0015] Furthermore, the working condition parameters of the digestion include: the digestion temperature is 160-220 °C, the constant temperature digestion time is 30 minutes, the microwave power is 0-1200 W, preferably 500 W.

[0016] Further, the digestion temperature is 160 °C.

[0017] Further, the volume ratio of aqua regia to hydrofluoric acid in the digestion reagent is 4:1.

[0018] Further, in the matrix matching method, the matching concentration of Zr is 518 mg / L, and the matching concentration of Al is 134 mg / L.

[0019] Further, the instrument parameters of the ICP-OES are as follows: operating power 1400 W, plasma gas flow rate 12 L / min, auxiliary gas flow rate 0.4 L / min, nebulizer flow rate 0.7 L / min.

[0020] Further, the preparation of the standard solution includes Pt solutions with gradient concentrations, and Zr and Al standard solutions matching the sample matrix are added.

[0021] Further, the solid superacid catalyst sample is a Pt-SO 4 2- / ZrO 2 -Al 2 O 3 composite catalyst.

[0022] In a second aspect, the present invention provides the application of the method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to any one of the first aspect in optimizing the preparation process of the solid superacid catalyst.

[0023] The above technical solutions provided by the embodiments of the present invention have at least the following advantages compared with the prior art:

[0024] The embodiments of the present invention provide a method for determining the platinum content in a solid superacid catalyst based on ICP-OES and its application. By optimizing the microwave digestion conditions (aqua regia + hydrofluoric acid system, digestion at 160 °C), selecting the Pt analysis line (265.945 nm), and the matrix matching strategy (Zr 518 mg / L, Al 134 mg / L), the spectral interference and physical interference of the high-concentration ZrO 2 and Al 2 O 3 matrix are effectively overcome. This method has the characteristics of high sensitivity, good repeatability (RSD ≤ 1.8%), spike recovery rate (97% - 101%), and high accuracy, and is suitable for industrial quality control and performance evaluation of Pt-containing composite superacid catalysts. Brief Description of the Drawings

[0025] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present invention, and are used together with the specification to explain the principles of the present invention.

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the attached drawings required in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other attached drawings can also be obtained based on these attached drawings.

[0027] Figure 1 It is a flowchart of the method for determining the platinum content in the solid superacid catalyst based on ICP - OES in the embodiments of the present invention.

[0028] Figure 2 It is a calibration curve graph in the embodiments of the present invention. Specific Embodiments

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the attached drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0031] The technical solutions provided by the present invention are as follows:

[0032] The present invention provides a method for determining the platinum content in a solid superacid catalyst based on ICP - OES and its application. The method for determining the platinum content in the solid superacid catalyst based on ICP - OES includes the following steps:

[0033] 1. Sample pretreatment: Take 0.05 g of catalyst powder and mix it with 0.1 g of ZrO 2 Mix, add 8 mL of aqua regia and 2 mL of hydrofluoric acid, and digest at 160 °C for 30 minutes in a microwave digestion instrument;

[0034] 2. Preparation of standard solution: Add 518 mg / L of Zr and 134 mg / L of Al matrix to the gradient Pt standard solution (1 - 10 mg / L) respectively;

[0035] 3. ICP - OES analysis: Select the wavelength of 265.945 nm, and the instrument parameters are a power of 1400 W and a plasma gas flow rate of 12 L / min;

[0036] 4. Interference control: Eliminate the interference of Zr and Al through matrix matching and background correction;

[0037] 5. Result verification: The spiked recovery rate is 97% - 101%, RSD ≤ 5%, and the detection limit is 0.004 mg / L.

[0038] The core key points of the present invention at least include:

[0039] 1. Using the microwave digestion method (aqua regia + hydrofluoric acid system) to achieve the complete decomposition of the refractory ZrO 2 -Al 2 O 3 support;

[0040] 2. Eliminating physical and spectral interferences through the matrix matching method (Zr 518 mg / L, Al 134 mg / L);

[0041] 3. Optimizing the analysis line (265.945 nm) and instrument parameters to ensure high sensitivity and precision.

[0042] It should be noted that for the component raw materials involved in the method for determining the platinum content in the solid superacid catalyst based on ICP - OES provided in the embodiments of the present invention, if there is no special limitation or specific description, commercially available products can be directly used or self - prepared by using existing publicly disclosed preparation methods; meanwhile, for the steps and parameters involved, if there is no special limitation or specific description, they can be carried out according to the process steps and parameters disclosed in the prior art or directly used according to the operating instructions of the existing equipment, and the present invention document will not elaborate one by one.

[0043] The following further elaborates the present invention in combination with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are usually determined according to national standards. If there is no corresponding national standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0044] Example 1

[0045] This example provides a method for determining the platinum content in the solid superacid catalyst based on ICP - OES, including the following steps:

[0046] 1.1 Experimental materials and instruments

[0047] Sample: Pt - SO 4 2- / ZrO 2 -Al 2 O 3 composite catalyst (ISO - PL, containing 0.330 wt% Pt), provided by Runhe Catalyst Co., Ltd.

[0048] Reagents: Concentrated nitric acid (GR, 64% - 67%), concentrated hydrochloric acid (AR, 34% - 38%), hydrofluoric acid (47% - 51%), aluminum chloride hexahydrate (99.999%), ZrO 2 (>97.5%).

[0049] Instruments: Microwave digestion instrument (Model M3, Shanghai Yiyao), ICP-OES (Avio 220Max, PerkinElmer), analytical balance (ES1035A, accuracy 0.0001 g).

[0050] 1.2 Experimental procedures

[0051] Sample preparation:

[0052] Grind the ISO-PL catalyst in an agate mortar to 200-mesh powder, dry it in an oven at 105 °C for 3 hours, and store it in a desiccator for later use.

[0053] Accurately weigh 0.05 g of the sample and 0.1 g of ZrO 2 (accurate to 0.0001 g), and place them in a polytetrafluoroethylene digestion tank.

[0054] Optimization of microwave digestion conditions:

[0055] Digestion reagent: 8 mL of aqua regia (concentrated hydrochloric acid: concentrated nitric acid = 3:1) + 2 mL of hydrofluoric acid.

[0056] Temperature gradient experiment: Digest at 140 °C, 160 °C, 180 °C, 200 °C, and 220 °C for 30 minutes respectively. After cooling, transfer to a polytetrafluoroethylene beaker, evaporate the acid on a hot plate until nearly dry, and make up the volume to 50 mL in a volumetric flask.

[0057] 1.3 Results and analysis

[0058] Selection of digestion method (see Table 1);

[0059] Table 1

[0060]

[0061] Conclusion: The digestion temperature is set at 180 °C, and the constant temperature digestion time is 30 min. A single strong acid cannot completely dissolve the sample. Aqua regia also cannot completely digest the sample, while the addition of hydrofluoric acid can effectively dissolve ZrO2, avoid the residual solid from wrapping the Pt active site, improve the digestion efficiency, and release the metal components. High-boiling-point acids (such as H 2 SO 4 、H 3 PO 4 ) may introduce salts or form insoluble phosphates. During volume making up, the solubility decreases due to dilution, causing turbidity and affecting the detection accuracy.

[0062] Status of digestion solution (see Table 2);

[0063] Table 2

[0064] Digestion temperature (°C) Solution state Pt content (%) 140 Partial precipitation 0.323 160～220 Clear and transparent 0.330±0.002

[0065] Conclusion: Complete dissolution of the sample can be achieved by digestion at 160°C, and Pt is released sufficiently. Select 160°C as the optimal temperature to reduce energy consumption.

[0066] Example 2

[0067] Based on Example 1, matrix matching and spectral interference elimination are carried out in this example, including the following steps:

[0068] 2.1 Preparation of standard solutions

[0069] Pt standard solution: Using a 100 mg / L Pt standard stock solution as the mother liquor, prepare Pt standard solutions with concentration gradients of 1, 2, 5, and 10 mg / L.

[0070] Matrix matching:

[0071] Zr matrix: Add 518 mg / L Zr to the Pt standard solution (simulating the ZrO 2 content in the sample).

[0072] Al matrix: Add 134 mg / L Al to the Pt standard solution (simulating the Al 2 O 3 content in the sample).

[0073] 2.2 Matrix interference experiment

[0074] Zr interference test (Table 3):

[0075] Table 3

[0076]

[0077] Al interference test (Table 4):

[0078] Table 4

[0079]

[0080] 2.3 Spectral interference analysis

[0081] Analysis line selection: By measuring the blank solution 20 times, calculate the RSD b value of each analysis line of Pt (Table 5):

[0082] Table 5

[0083]

[0084] Conclusion: Select 265.945 nm as the analysis line, with the lowest RSD b value (1.8%) and the best precision.

[0085] Example 3

[0086] Based on the above Examples 1 and 2, this example conducts calibration curve and precision verification, including the following steps:

[0087] 3.1 Plotting the calibration curve

[0088] Standard series: The Pt concentration gradient is 0, 1, 2, 5, 10 mg / L, matrix-matched with Zr (518 mg / L) and Al (134 mg / L), as Figure 2 shown.

[0089] Linear equation: y = 38611.66x + 4843.87, the correlation coefficient R is 0.999995, indicating excellent precision in measuring the Pt content within the standard curve using ICP-OES. Using the above curve, the standard deviation of the Pt content in the blank solution was determined 20 times in parallel to be 1.8%, and the final detection limit (LOD) was 0.004 mg / L.

[0090] 3.2 Precision test

[0091] Repeatability experiment: The same catalyst sample (ISO-PL) was determined 6 times in parallel (Table 6):

[0092] Table 6

[0093]

[0094]

[0095] Conclusion: The sample was determined 6 times in parallel, with an RSD of 0.37% (n = 6), indicating a high degree of precision in the measurement results.

[0096] 3.3 Spiked recovery experiment

[0097] Sample spiking: 3.0, 5.0, 7.0 mg / L Pt standard solutions were added to the ISO-PL sample, and the recovery rates were measured (Table 7):

[0098] Table 7

[0099]

[0100] It was found from the table that the spiked recovery rates of Pt were between 97% and 101%, and the RSD values of the three determinations were within 5%. This indicates that the samples had good spiked recovery rates and repeat stability, and the method was stable, reliable, and had good applicability.

[0101] Verified by the above embodiments, the method of the present invention can efficiently and accurately determine the platinum content in the solid superacid catalyst under microwave digestion (160 °C, aqua regia + hydrofluoric acid system), matrix matching (Zr 518 mg / L, Al 134 mg / L), and analysis line optimization (265.945 nm). The precision (RSD≤1.8%), spiked recovery rate (97% - 101%), and the test results of actual samples all indicate that this method has the reliability and universality for industrial applications.

[0102] In summary, the embodiments of the present invention provide a method and its application for determining the platinum content in a solid superacid catalyst based on ICP-OES. The present invention effectively overcomes the spectral interference and physical interference of the high-concentration ZrO 2 and Al 2 O 3 matrix. Moreover, this method has the characteristics of high sensitivity, good repeatability (RSD≤1.8%), spiked recovery rate (97% - 101%), and high accuracy, and is applicable to the industrial quality control and performance evaluation of Pt-containing composite superacid catalysts.

[0103] The various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the description of the range has specifically disclosed all possible sub-ranges and the single values within that range. For example, it should be considered that the description of the range from 1 to 6 has 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., and the single numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0104] The above description is only the specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for determining the platinum content in a solid superacid catalyst based on ICP-OES, characterized in that: The method comprises the following steps: The solid superacid catalyst sample is ground into powder and then mixed with ZrO2, and then digested by microwave digestion to obtain a digestion solution; Cooling the digestion solution and removing acid to obtain a solution to be tested; The analytical line wavelength of Pt was selected as 265.945 nm, and the standard solution was prepared by the matrix matching method to draw the calibration curve; Add matrix elements that match the concentrations of ZrO2 and Al2O3 in the sample to the standard solution to eliminate physical and spectral interferences; The ICP-OES method is used to detect the solution to be tested and the content of Pt in the sample is calculated according to the calibration curve; Wherein, the digestion reagent during the digestion is composed of aqua regia and hydrofluoric acid.

2. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: The working condition parameters of the digestion include: a digestion temperature of 160-220° C., a constant temperature digestion time of 30 minutes, and a microwave power of 0-1200W.

3. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: The digestion temperature was 160°C.

4. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: The volume ratio of aqua regia to hydrofluoric acid in the digestion reagent is 4:

1.

5. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: In the matrix matching method, the matching concentration of Zr is 518 mg / L, and the matching concentration of Al is 134 mg / L.

6. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: The instrument parameters of the ICP-OES are: operating power 1400 W, plasma gas flow rate 12 L / min, auxiliary gas flow rate 0.4 L / min, and nebulizer flow rate 0.7 L / min.

7. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: The preparation of the standard solution includes a Pt solution with gradient concentrations, and Zr and Al standard solutions matching the sample matrix are added.

8. The method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to claim 1, characterized in that: The solid superacid catalyst sample is Pt-SO4 2- / ZrO2-Al2O3 composite catalyst.

9. Use of the method for determining the platinum content in a solid superacid catalyst based on ICP-OES according to any one of claims 1 to 8 in optimizing the preparation process of a solid superacid catalyst.

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