Method for testing the precious metal content in silicon-based precious metal catalysts
By using a mixture of silicon-based noble metal catalysts and hydrofluoric acid and aqua regia to generate a solid phase, and combining this with nitric acid contact and inductively coupled plasma atomic emission spectrometry, the problem of large testing errors in the noble metal content of silicon-based catalysts was solved, achieving high-precision analysis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-18
- Publication Date
- 2026-06-19
AI Technical Summary
Existing technologies have large errors in testing the content of precious metals in silicon-based catalysts, which cannot meet analytical requirements. In particular, the stability of silica makes digestion difficult.
A mixture containing a silicon-based noble metal catalyst, water, hydrofluoric acid, and aqua regia was used as the solvent to generate a solid phase, which was then contacted with nitric acid. The response signal of the noble metal was measured by inductively coupled plasma atomic emission spectrometry, and the content was calculated by combining the standard curve.
It improves testing accuracy and stability, reduces the impact of silica on testing accuracy, and achieves high-precision precious metal content analysis.
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Figure CN122238041A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical technology, and more specifically to a method for testing the noble metal content in silicon-based noble metal catalysts. Background Technology
[0002] Silica, as a representative of silicon-based supports, is widely used in catalyst preparation. Due to its excellent chemical stability, silica is often used as a support for strongly acidic raw materials such as chloroauric acid and chloropalladic acid to produce silicon-based noble metal catalysts. Because of the high price of gold and palladium, it is essential to accurately measure their content in silicon-based catalysts. Generally, the metal content in silicon-based catalysts is tested using XRF or spectrophotometry. XRF can directly test the metal elements in the catalyst, but X-ray methods are generally "semi-quantitative" and have relatively large testing errors, often failing to meet the requirements for gold and palladium content analysis. Spectrophotometry has more limitations; the catalyst must first be digested into a colorless solution, otherwise the elemental content cannot be accurately measured. However, due to its stable chemical properties, silica is difficult to digest into a colorless solution.
[0003] Therefore, developing a highly accurate and stable method and system for analyzing the gold and palladium content is of great significance for the preparation of silicon-based catalysts containing precious metals. Summary of the Invention
[0004] The purpose of this invention is to overcome the problem that the existing technology has large testing errors in the noble metal content of silicon-based catalysts and cannot meet the analytical requirements, and to provide a method for testing the noble metal content in silicon-based noble metal catalysts. This method has high testing accuracy and good stability.
[0005] To achieve the above objectives, the present invention provides a method for testing the noble metal content in a silicon-based noble metal catalyst, characterized in that the method comprises: (1) A step of evaporating the solvent in a mixture containing a silicon-based noble metal catalyst, water, hydrofluoric acid and aqua regia to obtain a solid phase; (2) The step of contacting the solid phase obtained in step (1) with nitric acid to obtain the sample digest solution; (3) The intensity of the response signal of noble metals in the sample digestion solution was tested by inductively coupled plasma atomic emission spectrometry; (4) Prepare a precious metal standard solution, test the precious metal response signal intensity of the precious metal standard solution according to the method in step (3), fit the standard curve, and substitute the response signal intensity in step (3) into the standard curve to calculate the precious metal content.
[0006] Preferably, the silicon-based noble metal catalyst is a silicon-based noble metal catalyst powder.
[0007] Preferably, the silicon-based noble metal catalyst powder is prepared by grinding and drying a silicon-based noble metal catalyst.
[0008] Preferably, the average particle size of the silicon-based noble metal catalyst powder is less than 10 μm, and more preferably 0.1-5 μm.
[0009] Preferably, the drying conditions include: a drying temperature of 100-120℃ and a drying time of 4-6 hours.
[0010] Preferably, the method further includes a step of pretreating the silicon-based noble metal catalyst before step (1).
[0011] Preferably, the pretreatment conditions include: under a hydrogen-containing atmosphere, a pretreatment temperature of 300-500℃, a heating rate of 1-10℃ / min, a pretreatment pressure of 0.1-0.5MPa, and a pretreatment time of 10-30min.
[0012] Preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to water is 1:0.1-1, more preferably 1:0.2-0.8.
[0013] Preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to hydrofluoric acid is 1:2-15, more preferably 1:4-10.
[0014] Preferably, the mass concentration of the hydrofluoric acid is ≥30wt%, and more preferably 40-50wt%.
[0015] Preferably, step (1) further includes: mixing the silicon-based noble metal catalyst, water and hydrofluoric acid, and then mixing them with aqua regia to obtain a mixture.
[0016] Preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to aqua regia is 1:2-15, more preferably 1:5-10.
[0017] Preferably, in step (1), the step of obtaining a solid phase from the volatile solvent is carried out under an oxygen-containing atmosphere.
[0018] Preferably, the pressure of the oxygen-containing atmosphere in step (1) is 0.1-0.5 MPa, more preferably 0.2-0.4 MPa.
[0019] Preferably, step (1) includes: (1-1) Heat the mixture until white mist is produced, then stop heating and maintain the temperature to obtain a mixed solution; (1-2) Heat the mixed solution to volatilize until the solid content is ≥99wt%, then stop heating to obtain the solid phase.
[0020] Preferably, the heating rate is 2-15℃ / min, and more preferably 4-10℃ / min.
[0021] Preferably, in step (1-2), the temperature for heating and volatilization is 200-330℃, more preferably 250-300℃.
[0022] Preferably, in step (2), the nitric acid is added in the form of a nitric acid solution.
[0023] Preferably, the volume ratio of the silicon-based noble metal catalyst to the nitric acid solution is 1:2-15, more preferably 1:4-10.
[0024] Preferably, in step (2), the volume concentration of nitric acid in the nitric acid solution is ≥40%, preferably 50-80%.
[0025] Preferably, in step (2), the contact is carried out under heating conditions, and the heating temperature is 200-330℃, preferably 250-300℃.
[0026] Preferably, step (2) includes: heating at a rate of 2-15℃ / min until the liquid produces white mist, then stopping the heating and adjusting the volume to obtain the sample digest solution.
[0027] Preferably, the noble metal in the silicon-based noble metal catalyst is selected from at least one of Au, Pd, Pt, Ru, Rh, Os, Ag and Ir.
[0028] Preferably, the content of noble metal in the silicon-based noble metal catalyst is 0.01-2 wt%, more preferably 0.05-1 wt%.
[0029] Preferably, in step (4), the noble metal content in the silicon-based noble metal catalyst is calculated using the following formula:
[0030] In the formula, C 贵 V represents the concentration of noble metal elements (μg / mL) obtained from the standard curve, V is the volume of the sample digestion solution (mL), and m is the mass of the silicon-based noble metal catalyst powder (g).
[0031] The beneficial effects achieved through the above technical solution are as follows: The testing method provided by this invention is simple, has high accuracy and good stability, and can reduce the impact of silica on the accuracy of precious metal content testing. Attached Figure Description
[0032] Figure 1 This is the standard curve of Embodiment 1 of the present invention; Figure 2This is the standard curve of Embodiment 2 of the present invention. Detailed Implementation
[0033] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0034] This invention provides a method for testing the noble metal content in a silicon-based noble metal catalyst, wherein the method includes: (1) A step of evaporating the solvent in a mixture containing a silicon-based noble metal catalyst, water, hydrofluoric acid and aqua regia to obtain a solid phase; (2) The step of contacting the solid phase obtained in step (1) with nitric acid to obtain the sample digest solution; (3) The intensity of the response signal of noble metals in the sample digestion solution was tested by inductively coupled plasma atomic emission spectrometry; (4) Prepare a precious metal standard solution, test the precious metal response signal intensity of the precious metal standard solution according to the method in step (3), fit the standard curve, and substitute the response signal intensity in step (3) into the standard curve to calculate the precious metal content.
[0035] The testing method provided by this invention is simple, has high accuracy and good stability, and can reduce the impact of silica on the accuracy of precious metal content testing.
[0036] In this invention, the type and source of the silicon-based noble metal catalyst are not particularly limited. It can be commercially available or prepared using existing methods. The testing method provided by this invention can determine the noble metal content in conventional silicon-based catalysts loaded with noble metal elements. The silicon-based noble metal catalyst is digested to effectively dissolve silicon dioxide and prepare a sample digestion solution that meets the testing conditions of inductively coupled plasma atomic emission spectrometry.
[0037] According to the present invention, preferably, the silicon-based noble metal catalyst is a silicon-based noble metal catalyst powder.
[0038] According to the present invention, preferably, the silicon-based noble metal catalyst powder is prepared by grinding and drying the silicon-based noble metal catalyst. In the present invention, the grinding method is not particularly limited, and conventional grinding methods can be used by those skilled in the art. According to a preferred embodiment of the present invention, the silicon-based noble metal catalyst is ball-milled. The ball-milling conditions are not particularly limited, as long as the average particle size of the silicon-based noble metal catalyst powder meets the requirements. Preferably, the ball milling is performed in a ball mill.
[0039] According to the present invention, preferably, the average particle size of the silicon-based noble metal catalyst powder is less than 10 μm, and more preferably 0.1-5 μm. In the present invention, the average particle size of the silicon-based noble metal catalyst powder is obtained by laser particle size analyzer.
[0040] According to the present invention, the drying conditions are not particularly limited. Preferably, the drying conditions include: a drying temperature of 100-120°C and a drying time of 4-6 hours.
[0041] In this invention, preferably, the silicon-based noble metal catalyst powder is cooled to room temperature after drying. The drying equipment used in this invention is not particularly limited; those skilled in the art can choose conventional drying equipment, but preferably, the drying is carried out in a drying oven.
[0042] In this invention, the room temperature is 10-30℃.
[0043] According to the present invention, preferably, the method further includes a step of pretreating the silicon-based noble metal catalyst before step (1). According to a preferred embodiment of the present invention, pretreating the silicon-based noble metal catalyst before step (1) can weaken the interaction between the noble metal component and the silicon-based support, which is beneficial to the separation of the noble metal from the silicon-based support during the subsequent digestion process; at the same time, it can reduce the noble metal to its elemental form, making it easier to digest and further improving the test accuracy.
[0044] According to the present invention, preferably, the pretreatment conditions include: a pretreatment temperature of 300-500°C under a hydrogen-containing atmosphere, a heating rate of 1-10°C / min, a pretreatment pressure of 0.1-0.5 MPa, and a pretreatment time of 10-30 min. In this invention, the equipment for performing the pretreatment is not particularly limited, but it is preferably carried out in a reactor, more preferably in a polytetrafluoroethylene reactor. In this invention, the pretreatment time refers to the pretreatment time started after the pretreatment temperature is reached.
[0045] In this invention, the hydrogen-containing atmosphere has the conventional meaning in the art, referring to an atmosphere containing hydrogen, preferably hydrogen gas.
[0046] According to the present invention, preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to water is 1:0.1-1, for example 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:1, or any range between the two, preferably 1:0.2-0.8.
[0047] In this invention, the addition of hydrofluoric acid helps to dissolve silicon dioxide in silicon-based noble metal catalysts. Hydrofluoric acid has a good dissolving effect on silicon dioxide, preferentially dissolving silicon dioxide in the catalyst and reducing the impact of silicon dioxide on the accuracy of test results.
[0048] According to the present invention, preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to hydrofluoric acid is 1:2-15, for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:15, or any range between the two, preferably 1:4-10.
[0049] According to the present invention, the mass concentration of the hydrofluoric acid is not particularly limited, but preferably, the mass concentration of the hydrofluoric acid is ≥30wt%, and more preferably 40-50wt%.
[0050] According to the present invention, preferably, step (1) further includes: mixing the silicon-based noble metal catalyst, water and hydrofluoric acid, and then mixing them with aqua regia to obtain a mixture.
[0051] According to the present invention, preferably, in the mixture of step (1), the volume ratio of the silicon-based noble metal catalyst to aqua regia is 1:2-15, for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:15, or any range between the two, preferably 1:5-10. In the present invention, the addition of aqua regia helps to dissolve the noble metal and enhances the digestion of substances other than the silicon-based support.
[0052] In this invention, the aqua regia has the conventional meaning in the art, referring to a mixture of concentrated hydrochloric acid and concentrated nitric acid in a volume ratio of 3:1.
[0053] According to the present invention, preferably, in step (1), the step of obtaining a solid phase from the volatile solvent is carried out under an oxygen-containing atmosphere. In the present invention, the oxygen-containing atmosphere refers to an atmosphere capable of providing oxygen at the temperature at which the solvent evaporates, preferably oxygen and / or ozone.
[0054] According to the present invention, preferably, the pressure of the oxygen-containing atmosphere in step (1) is 0.1-0.5 MPa, for example 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or any range between the two, preferably 0.2-0.4 MPa. In the present invention, evaporating the solvent in an oxygen-containing atmosphere can enhance the oxidation reaction in the digestion process, accelerate the digestion rate, improve the digestion effect, reduce undigested substances, and improve the testing accuracy.
[0055] According to the present invention, preferably, step (1) includes: (1-1) Heat the mixture until white mist is produced, then stop heating and maintain the temperature to obtain a mixed solution; (1-2) Heat the mixed solution to volatilize until the solid content is ≥99wt%, then stop heating to obtain the solid phase.
[0056] In this invention, heating is stopped when white mist is observed to form in the liquid. The temperature is maintained and heated until the silicon-based noble metal catalyst dissolves to the point where no obvious solid remains. Heating continues to evaporate the solvent until the solid content is ≥99wt%, at which point heating is stopped.
[0057] In this invention, the solid content = 1 - (total mass before heating - total mass after heating) / (total mass before heating - container mass) × 100%. There is no particular limitation on the heating time. Heating is stopped when the solid content value is ≥ 99wt%.
[0058] In this invention, heating the mixture helps dissolve the silicon-based noble metal catalyst to obtain a mixed solution.
[0059] According to the present invention, preferably, the heating rate is 2-15℃ / min, more preferably 4-10℃ / min.
[0060] According to the present invention, preferably, in step (1-2), the evaporation temperature is 200-330°C, for example 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, or any range between the two, preferably 250-300°C.
[0061] In this invention, the solvent evaporation method described above can remove acid and eliminate acid radicals introduced to promote silica dissolution, thereby reducing the impact of acid radical ions on the accuracy of precious metal content testing.
[0062] In this invention, the containers used in steps (1) and (2) are not particularly limited; they can be carried out in the same container or in different containers, but preferably in the same container. The container can be used as a container for heating and evaporating hydrofluoric acid and aqua regia, and is preferably a polytetrafluoroethylene beaker.
[0063] According to the present invention, preferably, in step (2), the nitric acid is added in the form of a nitric acid solution.
[0064] According to the present invention, preferably, the volume ratio of the silicon-based noble metal catalyst to the nitric acid solution is 1:2-15, for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:15, or any range between the two, preferably 1:4-10.
[0065] According to the present invention, preferably, in step (2), the volume concentration of nitric acid in the nitric acid solution is ≥40%, preferably 50-80%.
[0066] According to the present invention, preferably, in step (2), the contact is carried out under heating conditions, and the heating temperature is 200-330°C, preferably 250-300°C.
[0067] According to the present invention, preferably, step (2) includes: heating at a heating rate of 2-15℃ / min until the liquid produces white mist, then stopping the heating, and finally obtaining the sample digestion solution after adjusting the volume.
[0068] In this invention, heating in step (2) helps the precious metal dissolve in the nitric acid solution. There is no particular limit to the heating rate. The heating can be stopped when white mist is produced and the temperature is maintained.
[0069] In this invention, preferably, after heating in step (2), the liquid is cooled to room temperature and the volume is adjusted to obtain a sample digest. The intensity of the response signal of the noble metal in the sample digest is then tested using an inductively coupled plasma atomic emission spectrometer. In this invention, preferably, the volume is adjusted in a volumetric flask.
[0070] According to the present invention, preferably, the noble metal in the silicon-based noble metal catalyst is selected from at least one of Au, Pd, Pt, Ru, Rh, Os, Ag, and Ir. In this invention, the type of noble metal element is not particularly limited, and the method provided by this invention can determine the content of common noble metals with high accuracy.
[0071] According to the present invention, preferably, the content of noble metal in the silicon-based noble metal catalyst is 0.01-2 wt%, for example, 0.01 wt%, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.2 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, or any range between the two, preferably 0.05-1 wt%. In the present invention, the range of measurable noble metal content is relatively wide, and the noble metal content in conventional silicon-based catalysts supported on noble metals can be determined by the method of the present invention.
[0072] In this invention, the testing conditions of the inductively coupled plasma atomic emission spectrometer are not particularly limited. Those skilled in the art can use conventional testing conditions to measure the response signal intensity of the noble metal.
[0073] According to the present invention, preferably, in step (4), the noble metal content in the silicon-based noble metal catalyst is calculated by the following formula:
[0074] In the formula, C 贵 V represents the concentration of noble metal elements (μg / mL) obtained from the standard working curve, V is the volume of the sample digestion solution (mL), and m is the mass of the silicon-based noble metal catalyst (g).
[0075] In this invention, the determination of the standard curve includes: preparing standard solutions according to different concentration gradients; measuring the signal intensity of the noble metal element in the standard solution of known concentration according to the analytical spectral wavelength of the noble metal element; and fitting the standard curve with the concentration of the standard solution as the abscissa and the response signal intensity of the corresponding noble metal element as the ordinate. For example, to determine the concentration of gold, standard solutions with concentrations of 1 μg / mL, 2 μg / mL, 3 μg / mL, 4 μg / mL, and 5 μg / mL are prepared, and the elemental response signal intensity is measured according to the analytical spectral wavelength of gold at 242.7 nm, and a standard curve is plotted.
[0076] In this invention, the order of performing step (4) is not particularly limited. Step (4) can be performed before step (1), or simultaneously with steps (1)-(3), or after step (3) is completed, as long as a standard curve can be obtained.
[0077] According to a particularly preferred embodiment of the present invention, a method for testing the noble metal content in a silicon-based noble metal catalyst, the method comprising: (1) A step of evaporating the solvent in a mixture containing a silicon-based noble metal catalyst, water, hydrofluoric acid and aqua regia to obtain a solid phase; (2) The step of contacting the solid phase obtained in step (1) with nitric acid to obtain the sample digest solution; (3) The intensity of the response signal of noble metals in the sample digestion solution was tested by inductively coupled plasma atomic emission spectrometry; (4) Prepare a precious metal standard solution, test the precious metal response signal intensity of the precious metal standard solution according to the method in step (3), fit the standard curve, and substitute the response signal intensity in step (3) into the standard curve to calculate the precious metal content. The method further includes a step of pretreating the silicon-based noble metal catalyst before step (1); The pretreatment conditions include: under a hydrogen-containing atmosphere, a pretreatment temperature of 300-500℃, a heating rate of 1-10℃ / min, a pretreatment pressure of 0.1-0.5MPa, and a pretreatment time of 10-30min; In step (1), the step of obtaining a solid phase from the volatile solvent is carried out under an oxygen-containing atmosphere; The pressure of the oxygen-containing atmosphere in step (1) is 0.2-0.4 MPa.
[0078] The present invention will be described in detail below through examples and comparative examples. Unless otherwise specified, all reagents used in the following examples and comparative examples are commercially available.
[0079] Example 1 In this embodiment, the silicon-based noble metal catalyst is a silicon-based gold catalyst, wherein the gold content is 0.2 wt%.
[0080] (1) The catalyst was ball-milled to a powder with an average particle size of 2 μm, dried at 110°C for 5 h in a drying oven, and then cooled to room temperature in the drying oven to obtain silicon-based noble metal catalyst powder. The silicon-based noble metal catalyst was pretreated in a polytetrafluoroethylene reactor under a hydrogen atmosphere at a heating rate of 5°C / min to 400°C, with the pressure maintained at 0.2 MPa for 15 min.
[0081] Take 0.2 g of pretreated silicon-based noble metal catalyst powder and place it in a polytetrafluoroethylene beaker. Add pure water and hydrofluoric acid (45 wt%), with a powder-to-pure water volume ratio of 1:0.5 and a powder-to-hydrofluoric acid volume ratio of 1:6. Add aqua regia at a powder-to-aqua regia volume ratio of 1:6, seal the container, inject oxygen to a pressure of 0.2 MPa, and begin heating slowly at a rate of 10 °C / min. Once the temperature reaches 200 °C, remove the seal from the container. When the liquid produces a noticeable white mist at 260 °C, stop heating and maintain this temperature until the powder is completely dissolved. Continue heating until the solid content in the beaker is ≥99 wt%, and then cool the beaker to room temperature.
[0082] (2) Add nitric acid solution (nitric acid volume concentration of 60%) according to the volume ratio of catalyst powder to nitric acid solution of 1:6. Heat to 260℃ and the liquid produces obvious white mist. Stop heating and cool the beaker to room temperature. Transfer the liquid in the beaker to a 100mL volumetric flask and make up to volume to obtain the sample digestion solution.
[0083] (3) The intensity of the response signal of noble metal in the sample digestion solution was tested by inductively coupled plasma atomic emission spectrometry. The wavelength of the gold element analysis spectrum was 242.7 nm.
[0084] (4) Take 6 volumetric flasks, one as a blank, and the other 5 are prepared into a series of standard solutions as shown in Table 1. The response signal intensity of the standard solutions is tested by inductively coupled plasma atomic emission spectrometry. The standard curve is plotted with the concentration of the standard solution as the abscissa and the response signal intensity of the gold element as the ordinate. The response signal intensity of the gold in the sample digestion solution obtained in step (3) is substituted into the standard curve to calculate the gold content in the silicon-based noble metal catalyst.
[0085]
[0086] In the formula, C 贵 V represents the concentration of noble metal elements (μg / mL) obtained from the standard curve, V is the volume of the sample digestion solution (mL), and m is the mass of the silicon-based noble metal catalyst powder (g).
[0087] Figure 1 The standard curve for Example 1 shows that the concentration of the noble metal element is 3.97 μg / mL. Substituting this into the formula, the Au content in the catalyst is calculated to be 0.1985 wt%.
[0088] Table 1
[0089] Example 2 In this embodiment, the silicon-based noble metal catalyst is a silicon-based palladium catalyst, wherein the palladium content is 0.52 wt%. (1) The catalyst was ball-milled to a powder with an average particle size of 4 μm, dried at 100 °C for 6 h in a drying oven, and then cooled to room temperature in the drying oven to obtain silicon-based noble metal catalyst powder. The silicon-based noble metal catalyst was pretreated in a polytetrafluoroethylene reactor under a hydrogen atmosphere at a heating rate of 8 °C / min to 350 °C, with the pressure maintained at 0.3 MPa for 12 min.
[0090] Take 0.3 g of pretreated silicon-based noble metal catalyst powder and place it in a polytetrafluoroethylene beaker. Add pure water and hydrofluoric acid (40 wt%), with a powder-to-pure water volume ratio of 1:0.5 and a powder-to-hydrofluoric acid volume ratio of 1:9. Add aqua regia at a powder-to-aqua regia volume ratio of 1:9, seal the container, inject oxygen to a pressure of 0.3 MPa, and begin slow heating at a rate of 5 °C / min. Once the temperature reaches 200 °C, remove the seal from the container. When the liquid produces obvious white fumes at 290 °C, stop heating and maintain this temperature until the powder is completely dissolved. Continue heating until the solid content in the beaker is ≥99 wt%, and then cool the beaker to room temperature.
[0091] (2) Add nitric acid solution (nitric acid volume concentration of 50%) according to the volume ratio of catalyst powder to nitric acid solution of 1:9. Heat to 290℃ and the liquid produces obvious white mist. Stop heating and cool the beaker to room temperature. Transfer the liquid in the beaker to a 250 mL volumetric flask and make up to volume to obtain the sample digestion solution.
[0092] (3) The intensity of the response signal of noble metals in the sample digestion solution was tested by inductively coupled plasma atomic emission spectrometry. The wavelength of the palladium element analysis spectrum was 340.4 nm.
[0093] (4) Take 6 volumetric flasks, one as a blank, and the other 5 to prepare a series of standard solutions as shown in Table 2. Test the response signal intensity of the standard solutions using an inductively coupled plasma atomic emission spectrometer. Plot a standard curve with the concentration of the standard solutions as the x-axis and the response signal intensity of palladium as the y-axis. Substitute the response signal intensity of palladium in the sample digestion solution obtained in step (3) into the standard curve and calculate the palladium content in the silicon-based noble metal catalyst according to the following formula.
[0094]
[0095] In the formula, C 贵 V represents the concentration of noble metal elements (μg / mL) obtained from the standard curve, V is the volume of the sample digestion solution (mL), and m is the mass of the silicon-based noble metal catalyst powder (g).
[0096] Figure 2The standard curve for Example 2 shows a concentration of 6.21 μg / mL for the noble metal element. Substituting this into the formula, the Pd content in the catalyst is calculated to be 0.5175 wt%.
[0097] Table 2
[0098] Example 3 The method of Example 1 is the same as in Example 1, except that H2 is not used to pretreat the silicon-based noble metal catalyst. Instead, the dried silicon-based noble metal catalyst powder is directly contacted with pure water and hydrofluoric acid. Other conditions are the same as in Example 1.
[0099] Example 4 The method of Example 1 is the same as that in Example 1, oxygen is not introduced during the digestion process in step (1). After the silicon-based noble metal catalyst powder comes into contact with aqua regia, it is slowly heated in air at a heating rate of 10°C / min until the temperature reaches 260°C to dissolve the powder. Other conditions are the same as in Example 1.
[0100] Comparative Example 1 In this embodiment, the silicon-based noble metal catalyst is a silicon-based gold catalyst, wherein the gold content is 0.2 wt%.
[0101] (1) The catalyst was ball-milled to a powder with an average particle size of 2 μm, dried at 110°C for 5 h in a drying oven, and then cooled to room temperature in a drying oven to obtain silicon-based noble metal catalyst powder.
[0102] Take 0.2 g of pretreated silicon-based noble metal catalyst powder and place it in a polytetrafluoroethylene beaker. Add pure water and hydrofluoric acid (45 wt%), with a powder-to-pure water volume ratio of 1:0.5 and a powder-to-hydrofluoric acid volume ratio of 1:6. Slowly heat the beaker in air at a rate of 10 °C / min. Stop heating when the liquid produces obvious white fumes at 260 °C, and maintain this temperature until the powder is completely dissolved. Continue heating until the solid content in the beaker is ≥99 wt%. Cool the beaker to room temperature.
[0103] (2) Add hydrofluoric acid (45wt%) at a ratio of catalyst powder to hydrofluoric acid solution of 1:6. Heat to 260°C and the liquid will produce obvious white mist. Stop heating and cool the beaker to room temperature. Transfer the liquid in the beaker to a 100mL volumetric flask and make up to volume to obtain the sample digestion solution.
[0104] Steps (3) and (4) are the same as in Example 1.
[0105] Table 3 shows a comparison between the precious metal content obtained from the examples and comparative tests and the actual precious metal content.
[0106] Accuracy = (Tested precious metal content / Actual precious metal content in catalyst) × 100%.
[0107] Table 3
[0108] As can be seen from the results in Table 3, the method provided in the embodiments of the present invention for testing the content of noble metals in silicon-based noble metal catalysts has significantly higher accuracy.
[0109] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for testing the noble metal content in a silicon-based noble metal catalyst, characterized in that, The method includes: (1) A step of evaporating the solvent from a mixture containing a silicon-based noble metal catalyst, water, hydrofluoric acid and aqua regia to obtain a solid phase; (2) The step of contacting the solid phase obtained in step (1) with nitric acid to obtain the sample digestion solution; (3) The intensity of the response signal of noble metals in the sample digestion solution was tested by inductively coupled plasma atomic emission spectrometry; (4) Prepare a precious metal standard solution, test the precious metal response signal intensity of the precious metal standard solution according to the method in step (3), fit the standard curve, and substitute the response signal intensity in step (3) into the standard curve to calculate the precious metal content.
2. The method according to claim 1, wherein, The silicon-based noble metal catalyst is a silicon-based noble metal catalyst powder; Preferably, the silicon-based noble metal catalyst powder is prepared by grinding and drying a silicon-based noble metal catalyst. Preferably, the average particle size of the silicon-based noble metal catalyst powder is less than 10 μm, and more preferably 0.1-5 μm; Preferably, the drying conditions include: a drying temperature of 100-120℃ and a drying time of 4-6 hours.
3. The method according to claim 1 or 2, wherein, The method further includes a step of pretreating the silicon-based noble metal catalyst before step (1); Preferably, the pretreatment conditions include: under a hydrogen-containing atmosphere, a pretreatment temperature of 300-500℃, a heating rate of 1-10℃ / min, a pretreatment pressure of 0.1-0.5MPa, and a pretreatment time of 10-30min.
4. The method according to any one of claims 1-3, wherein, In the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to water is 1:0.1-1, preferably 1:0.2-0.8; Preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to hydrofluoric acid is 1:2-15, more preferably 1:4-10; Preferably, the hydrofluoric acid has a mass concentration of ≥30wt%, and more preferably 40-50wt%.
5. The method according to any one of claims 1-4, wherein, Step (1) also includes: mixing the silicon-based noble metal catalyst, water and hydrofluoric acid, and then mixing the mixture with aqua regia to obtain a mixture; Preferably, in the mixture of step (1), the volume ratio of silicon-based noble metal catalyst to aqua regia is 1:2-15, more preferably 1:5-10; Preferably, in step (1), the step of obtaining a solid phase from the volatile solvent is carried out under an oxygen-containing atmosphere; Preferably, the pressure of the oxygen-containing atmosphere in step (1) is 0.1-0.5 MPa, more preferably 0.2-0.4 MPa.
6. The method according to any one of claims 1-5, wherein, Step (1) includes: (1-1) Heat the mixture until white mist is produced, then stop heating and maintain the temperature to obtain a mixed solution; (1-2) Heat the mixed solution to volatilize until the solid content is ≥99wt%, then stop heating to obtain the solid phase; Preferably, the heating rate is 2-15℃ / min, and more preferably 4-10℃ / min; Preferably, in step (1-2), the temperature for heating and volatilization is 200-330℃, more preferably 250-300℃.
7. The method according to any one of claims 1-6, wherein, In step (2), the nitric acid is added in the form of a nitric acid solution; Preferably, the volume ratio of the silicon-based noble metal catalyst to the nitric acid solution is 1:2-15, more preferably 1:4-10; Preferably, in step (2), the volume concentration of nitric acid in the nitric acid solution is ≥40%, preferably 50-80%.
8. The method according to any one of claims 1-7, wherein, In step (2), the contact is carried out under heating conditions, and the heating temperature is 200-330℃, preferably 250-300℃; Preferably, step (2) includes: heating at a rate of 2-15℃ / min until the liquid produces white mist, then stopping the heating and adjusting the volume to obtain the sample digest solution.
9. The method according to any one of claims 1-8, wherein, The noble metal in the silicon-based noble metal catalyst is selected from at least one of Au, Pd, Pt, Ru, Rh, Os, Ag and Ir; Preferably, the content of noble metal in the silicon-based noble metal catalyst is 0.01-2 wt%, more preferably 0.05-1 wt%.
10. The method according to any one of claims 1-9, wherein, In step (4), the noble metal content in the silicon-based noble metal catalyst is calculated using the following formula: In the formula, C 贵 V represents the concentration of noble metal elements (μg / mL) obtained from the standard curve, V is the volume of the sample digestion solution (mL), and m is the mass of the silicon-based noble metal catalyst powder (g).