Analysis method for determining platinum content in platinum-based catalyst and application

Abstract

The invention belongs to the technical field of elemental analysis, and provides an analysis method for determining the content of platinum in a platinum-based catalyst and application. The analysis method comprises the following steps: carrying out heating program parameter setting on thermogravimetric analysis and detection equipment, and testing a platinum-based catalyst sample in the thermogravimetric analysis and detection equipment to obtain a thermogravimetric analysis curve; calculating the mass percentage content of platinum in the platinum-based catalyst sample according to the thermogravimetric analysis curve; wherein the temperature rising program is a staged temperature rising process, and the staged temperature rising process comprises a first staged temperature rising process and a second staged temperature rising process which are sequentially carried out. The analysis method provided by the invention can be used for accurately measuring the loading amount of platinum with the mass percentage content of more than 20% in the platinum-based catalyst, and has good repeatability and stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of elemental analysis, and particularly relates to an analysis method for determining the platinum content in a platinum-based catalyst and application. BACKGROUND

[0002] A hydrogen fuel cell is a key technology for converting hydrogen energy into electrical energy, and its core lies in the role of a catalyst. The catalyst is mainly responsible for promoting the occurrence of hydrogen oxidation reaction and oxygen reduction reaction in the hydrogen fuel cell, thereby generating electrical energy. Currently, the catalysts for hydrogen fuel cells are mainly divided into three categories, specifically including: platinum (Pt) -based catalysts, low platinum catalysts and non-platinum catalysts. Platinum-based catalysts are the preferred catalysts for commercial use today due to their good molecular adsorption and dispersion characteristics, but their high price and scarcity have become obstacles to large-scale commercialization. In order to effectively reduce costs, researchers are working to design catalysts with low Pt content.

[0003] The activity and stability of platinum-based catalysts are highly dependent on the loading and dispersion of Pt. In proton exchange membrane fuel cells (PEMFCs), platinum-based catalysts with high activity and good durability can accelerate the process of oxygen reduction reaction (ORR), but their high cost and limited resource reserves limit their widespread application. Therefore, developing catalysts with low Pt content and high efficiency is the focus of research. However, if the actual loading of Pt obtained by testing is not accurate, it may lead to unstable catalyst performance or low efficiency, and it is impossible to evaluate the active sites and reaction pathways of the catalytic reaction, so it is crucial to seek a method for accurately determining the Pt content for designing efficient catalysts.

[0004] The methods for measuring Pt content with a mass percentage of more than 20% in the catalyst in the prior art mainly include chemical methods and instrumental methods. For the determination of high platinum content, chemical methods such as ammonium chloroplatinate gravimetric method and current titration method can be used, while instrumental methods include atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray fluorescence spectrometry (XRF) and high performance liquid chromatography (HPLC) and the like. However, the above testing methods are relatively complex to operate and are greatly affected by human factors, making it difficult to accurately determine the Pt content in the catalyst.

[0005] Therefore, in the field, there is an urgent need to develop a simple and efficient method that can accurately determine the Pt content in platinum-based catalysts. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application aims to provide an analysis method for determining the platinum content in a platinum-based catalyst and an application thereof. The analysis method provided by the present application can accurately measure the platinum load in a platinum-based catalyst with a mass percentage of 20% or more, and has good repeatability and stability.

[0007] To achieve the object of the present application, the following technical solutions are adopted:

[0008] In a first aspect, the present application provides an analysis method for determining the platinum content in a platinum-based catalyst, which comprises:

[0009] The temperature program parameters of the thermogravimetric analysis detection equipment are set, and the platinum-based catalyst sample is set in the thermogravimetric analysis detection equipment for testing to obtain a thermogravimetric analysis curve; the mass percentage of platinum in the platinum-based catalyst sample is calculated according to the thermogravimetric analysis curve;

[0010] Preferably, the temperature program is a stage temperature process, which comprises a first stage temperature process and a second stage temperature process performed in sequence.

[0011] Compared with the complex measurement method disclosed in the prior art, the present application provides a thermogravimetric analysis method for accurately measuring platinum in a platinum-based catalyst. Specifically, the mass percentage of platinum in the platinum-based catalyst sample is determined by monitoring the mass change of the sample in the specific two-stage temperature process. In addition, the thermogravimetric analysis method provided by the present application is simple and fast, and is particularly suitable for application scenarios that require fast and accurate measurement of platinum load.

[0012] Preferably, the first stage temperature process comprises a first temperature process and a first holding process.

[0013] Preferably, the starting temperature of the first temperature process is 25-30℃, for example, it can be 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc.

[0014] Preferably, the ending temperature of the first temperature process is 200-300℃, for example, it can be 200℃, 220℃, 250℃, 280℃, 300℃, etc.

[0015] Preferably, the heating rate of the first temperature process is 5-20℃ / min, for example, it can be 5℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 15℃ / min, 18℃ / min, 20℃ / min, etc.

[0016] Preferably, the temperature of the first insulation process is 200°C to 300°C, for example, 200°C, 220°C, 250°C, 280°C, 300°C, etc.

[0017] Preferably, the time of the first insulation process is 30 min to 50 min, for example, it can be 30 min, 32 min, 35 min, 38 min, 40 min, 42 min, 45 min, 48 min, 50 min, etc.

[0018] Preferably, the first stage heating process is carried out under an inert atmosphere.

[0019] Preferably, the second stage heating process includes a second heating process and a second heat preservation process.

[0020] Preferably, the starting temperature of the second heating process is 200°C to 300°C, for example, 200°C, 220°C, 250°C, 280°C, 300°C, etc.

[0021] Preferably, the termination temperature of the second heating process is 800°C to 1000°C, for example, it can be 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, 1000°C, etc.

[0022] Preferably, the heating rate of the second heating process is 5°C / min to 20°C / min, for example, it can be 5°C / min, 8°C / min, 10°C / min, 12°C / min, 15°C / min, 18°C / min, 20°C / min, etc.

[0023] Preferably, the temperature of the second insulation process is 800°C to 1000°C, for example, it can be 800°C, 820°C, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, 1000°C, etc.

[0024] Preferably, the second insulation process lasts for 5 to 15 minutes, for example, 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, etc.

[0025] Preferably, the second stage temperature rising process is carried out in an oxygen-containing atmosphere.

[0026] Further preferably, the termination temperature of the first heating process is 200°C to 250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0027] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0028] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0029] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0030] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0031] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0032] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0033] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0034] Further preferably, the temperature of the first temperature-increasing process is 200-250°C, for example, it can be 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, etc.

[0035] Preferably, the inert atmosphere is helium.

[0036] For example, (1) the carbon carrier will interfere with the thermogravimetric analysis test process. In an oxygen-containing environment, the carbon carrier will burn violently and release gas during heating, affecting the stability of the balance and thus the accurate determination of Pt mass; (2) the test conditions and atmosphere types of thermogravimetric analysis have a significant impact on the test results. Thermogravimetric analysis is usually carried out in an air atmosphere, but the oxygen in the air will cause the sample to oxidize and form an oxidized Pt, thereby affecting the measurement results; (3) the test results obtained under the test conditions disclosed in the prior art have poor stability, and the test deviation is also high.

[0037] Based on this, the present application effectively improves the above-mentioned problems existing in the measurement process of the thermogravimetric analysis method by selecting a suitable atmosphere and optimizing the temperature programming process and its parameters, thereby improving the accuracy, reproducibility and stability of the test results. Specifically, the present application uses helium as the purge gas and selects to add a lower concentration of oxygen during the high-temperature stage for continuous heating. This not only enables the rapid combustion of amorphous carbon to generate carbon dioxide, thereby effectively improving the combustion efficiency, but also avoids the adverse effects of carbon content release on Pt content weighing. Compared with directly using a nitrogen atmosphere, using helium as the purge gas can displace smaller gas molecules (such as nitrogen, methane, etc.) adsorbed on the surface of amorphous carbon, thereby achieving full combustion of amorphous carbon. This not only improves the accuracy of carbon mass, but also reduces the impact on Pt content measurement.

[0038] Preferably, the flow rate of the inert atmosphere is 20 mL / min to 100 mL / min, further preferably 50 mL / min to 100 mL / min, for example, it can be 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, etc. The present application adjusts the flow rate of the inert atmosphere so that helium molecules can fully displace smaller gas molecules (such as nitrogen, methane, etc.) adsorbed on the surface of amorphous carbon.

[0039] Preferably, the oxygen-containing atmosphere comprises a combination of oxygen and helium.

[0040] Preferably, the volume ratio of oxygen and helium is (4-10):(90-96), further preferably (4-7):(93-96), for example, it can be 4:96, 5:95, 6:94, 7:93, 8:92, 9:91, 10:90, etc. By adjusting the volume ratio of oxygen and helium, the amorphous carbon can be quickly combusted to generate carbon dioxide, thereby effectively improving the combustion efficiency and avoiding the adverse effects of carbon content release on the weighing of Pt content. If a higher content of oxygen is used, it will affect the release of carbon content, thereby affecting the accuracy of the balance.

[0041] Preferably, the mass of the platinum-based catalyst sample is 5mg-10mg, for example, it can be 5mg, 6mg, 7mg, 8mg, 9mg, 10mg, etc. In the analysis method of the present application, the sample size of the platinum-based catalyst sample is not particularly limited, and can be selected according to the accuracy and range of the thermobalance, especially to use as little sample as possible to reduce the analysis cost under the condition of meeting the accurate weighing of the remaining mass by the thermobalance.

[0042] Preferably, the analysis method comprises the following steps:

[0043] S1. Weigh the platinum-based catalyst sample into a crucible, and put the crucible containing the platinum-based catalyst sample into the thermogravimetric analyzer;

[0044] S2. Set the temperature rising program parameters in the thermogravimetric analyzer, so that the platinum-based catalyst sample is first heated from 25-30℃ to 200-300℃ at a heating rate of 5-20℃ / min under an inert atmosphere, and kept at a constant temperature of 200-300℃ for 30-50min; then switched to an oxygen-containing atmosphere to heat from 200-300℃ to 800-1000℃ at a heating rate of 5-20℃ / min, and kept at a constant temperature of 800-1000℃ for 5-15min;

[0045] S3. After heating is completed, stop heating, so that the platinum-based catalyst sample automatically cools down to a constant temperature, and a thermogravimetric analysis curve is obtained, and the mass percentage of platinum in the platinum-based catalyst sample is calculated according to the thermogravimetric analysis curve.

[0046] Preferably, after the heating is stopped in step S3, the platinum-based catalyst sample is naturally cooled to room temperature.

[0047] As a preferred technical solution of the present application, the analysis method comprises the following steps:

[0048] S1. Put a platinum-based catalyst sample with a mass of 5 mg to 10 mg into a crucible, and put the crucible containing the platinum-based catalyst sample into a thermogravimetric analyzer, which records the mass of the platinum-based catalyst sample at present, denoted as M1;

[0049] S2. Set the helium flow rate in the thermogravimetric analyzer so that the surface of the platinum-based catalyst sample is blown by helium;

[0050] S3. Set the temperature rising program parameters in the thermogravimetric analyzer so that the platinum-based catalyst sample is first heated from 25℃ to 30℃ to 200℃ to 250℃ at a heating rate of 10℃ / min to 20℃ / min under a helium flow rate of 20mL / min to 100mL / min, and kept at a constant temperature of 200℃ to 250℃ for 40min to 50min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of (4-10):(90-96) to heat from 200℃ to 250℃ to 900℃ to 1000℃ at a heating rate of 10℃ / min to 20℃ / min, and kept at a constant temperature of 900℃ to 1000℃ for 5min to 10min;

[0051] S4. After heating is completed, stop heating so that the platinum-based catalyst sample naturally cools to room temperature, and the thermogravimetric analyzer records the mass of the platinum-based catalyst sample at present, denoted as M2, and the mass percentage of platinum in the platinum-based catalyst sample is calculated according to the thermogravimetric analysis curve, denoted as X, X=M2 / M1*100%.

[0052] In a second aspect, the application provides an application of the analysis method for determining the content of platinum in a platinum-based catalyst according to the first aspect, and the application is to test the content of platinum in a catalyst sample.

[0053] The analysis method for determining the content of platinum in a platinum-based catalyst provided by the application has excellent precision and accuracy.

[0054] Compared with the prior art, the application has the following beneficial effects:

[0055] The application provides an analysis method for determining the content of platinum in a platinum-based catalyst, which specifically determines the mass percentage of platinum in a platinum-based catalyst sample by monitoring the mass change of the sample in a specific two-stage temperature rising process. In addition, the thermogravimetric analysis method provided by the application is simple and fast, and is especially suitable for application scenarios that require fast and accurate measurement of platinum loading.

[0056] The test method provided by the present application can solve the following technical problems existing in the prior art thermogravimetric analysis method: (1) the adverse effect of the release of carbon content in the platinum-based catalyst on the test of Pt content; (2) the change of the oxidation state of Pt during the test; (3) the influence of small molecule gas adsorbed on the surface of the platinum-based catalyst on the test result; (4) the test result has poor repeatability and stability, thereby improving the accuracy and reliability of the thermogravimetric analysis method of the platinum-based catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 The thermogravimetric analysis curve of the platinum-based catalyst sample provided in Example 1 of the present application is obtained after testing.

[0058] Figure 2 The thermogravimetric analysis curve of the platinum-based catalyst sample provided in Example 2 of the present application is obtained after testing.

[0059] Figure 3 The thermogravimetric analysis curve of the platinum-based catalyst sample provided in Comparative Example 1 of the present application is obtained after testing.

[0060] Figure 4 The thermogravimetric analysis curve of the platinum-based catalyst sample provided in Comparative Example 2 of the present application is obtained after testing. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be further described below by combining the drawings and specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations of the present application.

[0062] Example 1

[0063] The present embodiment provides an analysis method for determining the platinum content in a platinum-based catalyst, which comprises the following steps:

[0064] S1. A platinum-based catalyst sample with a mass of 5.44 mg is weighed and placed in an alumina crucible, and the alumina crucible is placed in a thermogravimetric analyzer, and the thermogravimetric analyzer records the mass of the current platinum-based catalyst sample;

[0065] S2. The helium flow rate in the thermogravimetric analyzer is set to 100 mL / min, so that the surface of the platinum-based catalyst sample is swept by helium;

[0066] S3. Set the temperature rising program parameters in the thermal gravimetric analyzer, so that the platinum-based catalyst sample is first heated from 30°C to 200°C at a temperature rising rate of 20°C / min under helium gas blowing, and kept at a constant temperature of 200°C for 50 min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of 4:96 to heat from 200°C to 900°C at a temperature rising rate of 20°C / min, and kept at a constant temperature of 900°C for 10 min;

[0067] S4. After heating is completed, stop heating, so that the platinum-based catalyst sample is naturally cooled to room temperature, and then the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample to obtain a thermal gravimetric analysis curve, and the mass percentage content of platinum in the platinum-based catalyst sample is calculated according to the thermal gravimetric analysis curve.

[0068] As shown in Figure 1 the weight loss rate of the platinum-based catalyst sample in the whole thermal gravimetric analysis test process is 47.25%, and the residual substance content is 52.75%, that is, the mass percentage content of platinum in the platinum-based catalyst sample is 52.75%, which is compared with the loading amount of platinum in the commercial platinum-based catalyst, which is 55%, and the error is only 2.25%.

[0069] Example 2

[0070] The embodiment provides an analysis method for determining the content of platinum in a platinum-based catalyst, and the analysis method comprises the following steps:

[0071] S1. A platinum-based catalyst sample with a mass of 7.02 mg is weighed in an alumina crucible, and the alumina crucible is placed in a thermal gravimetric analyzer, and the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample;

[0072] S2. Set the helium gas flow rate in the thermal gravimetric analyzer to 100 mL / min, so that the surface of the platinum-based catalyst sample is blown by helium gas;

[0073] S3. Set the temperature rising program parameters in the thermal gravimetric analyzer, so that the platinum-based catalyst sample is first heated from 30°C to 200°C at a temperature rising rate of 20°C / min under helium gas blowing, and kept at a constant temperature of 200°C for 50 min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of 4:96 to heat from 200°C to 900°C at a temperature rising rate of 20°C / min, and kept at a constant temperature of 900°C for 10 min;

[0074] S4. After heating is completed, stop heating, so that the platinum-based catalyst sample is naturally cooled to room temperature, and then the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample to obtain a thermal gravimetric analysis curve, and the mass percentage content of platinum in the platinum-based catalyst sample is calculated according to the thermal gravimetric analysis curve.

[0075] AsFigure 2 As shown, the weight loss rate during the whole thermal gravimetric analysis test of this embodiment is 43.85%, and the remaining substance content is 56.15%, i.e. the mass percentage content of platinum in the platinum-based catalyst sample is 56.15%, which has an error of only 1.15% compared with the platinum loading of 55% in the commercial platinum-based catalyst.

[0076] Example 3

[0077] The difference between this embodiment and Example 1 is that the temperature rising program parameters in the thermal gravimetric analyzer in step S3 are set as follows: the platinum-based catalyst sample is first raised from 30°C to 200°C at a temperature rising rate of 10°C / min under helium purging, and kept at a constant temperature of 200°C for 50 min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of 5:95 to raise the temperature from 200°C to 900°C at a temperature rising rate of 10°C / min, and kept at a constant temperature of 900°C for 10 min, and the others are the same as in Example 1.

[0078] Example 4

[0079] The difference between this embodiment and Example 1 is that the temperature rising program parameters in the thermal gravimetric analyzer in step S3 are set as follows: the platinum-based catalyst sample is first raised from 30°C to 250°C at a temperature rising rate of 20°C / min under helium purging, and kept at a constant temperature of 250°C for 40 min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of 7:93 to raise the temperature from 250°C to 950°C at a temperature rising rate of 20°C / min, and kept at a constant temperature of 950°C for 10 min, and the others are the same as in Example 1.

[0080] Example 5

[0081] The difference between this embodiment and Example 1 is that the temperature rising program parameters in the thermal gravimetric analyzer in step S3 are set as follows: the platinum-based catalyst sample is first raised from 30°C to 150°C at a temperature rising rate of 20°C / min under helium purging, and kept at a constant temperature of 150°C for 60 min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of 4:96 to raise the temperature from 150°C to 900°C at a temperature rising rate of 20°C / min, and kept at a constant temperature of 900°C for 10 min, and the others are the same as in Example 1.

[0082] Example 6

[0083] The difference between this embodiment and embodiment 1 is that the temperature rising program parameters in the thermal gravimetric analyzer in step S3 are set as follows: the platinum-based catalyst sample is first heated from 30℃ to 350℃ at a temperature rising rate of 20℃ / min under helium purging, and kept at a constant temperature of 350℃ for 20min; then switched to a mixed gas atmosphere composed of oxygen and helium with a volume ratio of 4:96 to heat from 350℃ to 900℃ at a temperature rising rate of 20℃ / min, and kept at a constant temperature of 900℃ for 10min, and the others are the same as in embodiment 1.

[0084] Embodiment 7

[0085] The difference between this embodiment and embodiment 1 is that the helium is replaced by an equal volume content of carbon dioxide in step S3, and the others are the same as in embodiment 1.

[0086] Embodiment 8

[0087] The difference between this embodiment and embodiment 1 is that the volume ratio of oxygen and helium in step S3 is 2:98, and the others are the same as in embodiment 1.

[0088] Embodiment 9

[0089] The difference between this embodiment and embodiment 1 is that the volume ratio of oxygen and helium in step S3 is 15:85, and the others are the same as in embodiment 1.

[0090] Comparative Example 1

[0091] This comparative example provides an analysis method for determining the platinum content in a platinum-based catalyst, which comprises the following steps:

[0092] S1. A platinum-based catalyst sample with a mass of 7.90mg is weighed in an alumina crucible, and the alumina crucible is placed in a thermal gravimetric analyzer, and the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample;

[0093] S2. The helium flow rate in the thermal gravimetric analyzer is set to 100mL / min, so that the surface of the platinum-based catalyst sample is purged by helium;

[0094] S3. The temperature rising program parameters in the thermal gravimetric analyzer are set so that the platinum-based catalyst sample is heated from 30℃ to 800℃ at a temperature rising rate of 10℃ / min under purging by a mixed gas atmosphere composed of nitrogen and oxygen with a volume ratio of 8:2;

[0095] S4. After heating is completed, heating is stopped, and after the platinum-based catalyst sample naturally cools to room temperature, the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample, and a thermal gravimetric analysis curve is obtained, and the mass percentage content of platinum in the platinum-based catalyst sample is calculated according to the thermal gravimetric analysis curve.

[0096] As shown in Figure 3 The weight loss rate of the entire thermal gravimetric analysis test process of the present embodiment is 77.22%, and the remaining substance content is 22.78%, that is, the mass percentage content of platinum in the platinum-based catalyst sample is 22.78%. Compared with the platinum load of 55% in the commercial platinum-based catalyst, the error is 32.22%. After inspection, it was found that due to the high sample mass of the platinum-based catalyst, the heat released during carbon combustion was large, causing the sample to fly and the error of the test to be large. Compared with Example 1, the present comparative example uses a mixed gas atmosphere composed of nitrogen and oxygen in a volume ratio of 8:2. Nitrogen can only displace oxygen molecules adsorbed by amorphous carbon, and nitrogen molecules occupy the carbon surface, so that oxygen molecules cannot fully contact the carbon surface, so that the carbon cannot be fully burned. In addition, oxygen participates in the reaction during the entire temperature rise process, and the unstable heat release causes the mass measured by the balance to fluctuate greatly, and the unbalanced heat release causes the sample to fly, finally resulting in a large test error of the method.

[0097] Comparative Example 2

[0098] The present comparative example provides an analysis method for determining the platinum content in a platinum-based catalyst, which comprises the following steps:

[0099] S1. Weigh a platinum-based catalyst sample with a mass of 3.62 mg into an alumina crucible, and place the alumina crucible into a thermal gravimetric analyzer, and the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample;

[0100] S2. Set the helium flow rate in the thermal gravimetric analyzer to 100 mL / min, so that the surface of the platinum-based catalyst sample is swept by helium;

[0101] S3. Set the temperature rise program parameters in the thermal gravimetric analyzer, so that the platinum-based catalyst sample is heated at a temperature rise rate of 10°C / min from 30°C to 800°C under the sweeping of a mixed gas atmosphere composed of nitrogen and oxygen in a volume ratio of 8:2;

[0102] S4. After heating is completed, stop heating, so that the platinum-based catalyst sample automatically cools to room temperature, and the thermal gravimetric analyzer records the mass of the current platinum-based catalyst sample, obtains a thermogravimetric analysis curve, and calculates the mass percentage content of platinum in the platinum-based catalyst sample according to the thermogravimetric analysis curve.

[0103] As shown in Figure 4As shown, the weight loss rate of the whole thermal gravimetric analysis test process in the embodiment is 59.29%, and the remaining substance content is 40.71%, that is, the mass percentage content of platinum in the platinum-based catalyst sample is 40.71%, which has an error of 14.29% compared with the loading amount of platinum in the commercial platinum-based catalyst which is 55%. Compared with Comparative Example 1, although Comparative Example 2 reduces the sample amount of the platinum-based catalyst sample and reduces the error value to a certain extent, there is still a large test error compared with the analysis method provided by the present application. Compared with Example 1, since the mixed gas atmosphere composed of nitrogen and oxygen in a volume ratio of 8:2 is used in the present comparative example, nitrogen can only displace oxygen molecules adsorbed by amorphous carbon, and nitrogen molecules occupy the carbon surface, so that oxygen molecules cannot fully contact the carbon surface, so that the carbon cannot be fully burned. In addition, oxygen participates in the reaction during the whole temperature rise process, and the unbalanced heat release causes the mass fluctuation measured by the balance to be large, and the unbalanced heat release causes the sample to fly and finally makes the test error of the method large. Although the sample amount is reduced in the present comparative example, the test error is still unavoidable.

[0104] The present application carries out comparison experiments on Examples 1-9 and Comparative Examples 1-2, specifically adopts double parallel determination, and the results are shown in Table 1:

[0105] Table 1

[0106] Content of platinum Factory index Example 1 52.75％ 55％* Example 2 56.15％ 55％* Example 3 56.2 55％* Example 4 54.6 55％* Example 5 51.25 55％* Example 6 57.6 55％* Example 7 58.85 55％* Example 8 59.25 55％* Example 9 57.95 55％* Comparative Example 1 22.78％ 55％* Comparative Example 2 40.71％ 55％*

[0107] Note: * is the data provided by the manufacturer

[0108] As can be seen from Table 1, compared with the thermal gravimetric analysis test method disclosed in the prior art, the analysis method for determining the platinum content in the platinum-based catalyst provided by the present application has higher accuracy.

[0109] In order to further evaluate the accuracy and repeatability of the analysis method for determining the platinum content in the platinum-based catalyst provided by the present application, the precision and accuracy of the analysis method provided by the present application are evaluated as follows.

[0110] (1) Precision test

[0111] The platinum-based catalyst samples with different platinum loading content levels and the platinum-based catalyst samples with different sample weight levels are respectively tested for 6 times independently, and the sample weight is accurate to 0.1 mg. The precision test results are shown in Table 2:

[0112] Table 2

[0113]

[0114] As can be seen from Table 2, the analysis method for determining the platinum content in the platinum-based catalyst provided by the application has high precision, the standard deviation is not higher than 2%, the method repeatability limit is not higher than 5%, and meets the requirements of element analysis.

[0115] (2) Accuracy test

[0116] First, 4 samples of platinum-based catalyst with a mass of 7 mg are weighed and are respectively recorded as S1, S2, S3 and S4; then, 4 samples of platinum powder with a mass of 1 mg, 2 mg, 3 mg and 3 mg are weighed in turn and are respectively recorded as P1, P2, P3 and P4; then, P1 is added to the S2 sample, P2 is added to the S3 sample, and P3 is added to the S4 sample to obtain different spiked samples; finally, the weight loss rates of the different spiked samples, the S1 sample and the P4 platinum powder are respectively tested, and the results are shown in Table 3:

[0117] Table 3

[0118]

[0119] Note: The recovery rate of spiking * = (mass after spiking x weight loss rate determination value of spiking - sample mass x sample weight loss rate determination value) / spiking mass x weight loss rate determination value of spiking x 100%.

[0120] As can be seen from the results of the spiking recovery test in Table 3, the analysis method for determining the platinum content in the platinum-based catalyst provided by the application has a spiking recovery rate greater than 95%, and the recovery rate meets the requirements of element detection.

[0121] In summary, the analysis method for determining the platinum content in the platinum-based catalyst provided by the application has good accuracy and reproducibility.

[0122] The process method of the application is illustrated by the above examples, but the application is not limited to the above process steps, that is, it does not mean that the application must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvement on the application, equivalent replacement of the materials selected by the application, addition of auxiliary ingredients, selection of specific methods, etc. fall within the protection scope and disclosure scope of the application.

Claims

1. An analytical method for determining the platinum content in a platinum-based catalyst, characterized in that, The analysis method comprises the following steps: The temperature program parameter setting is performed on the thermal gravimetric analysis detection equipment, and the platinum-based catalyst sample is set in the thermal gravimetric analysis detection equipment for testing to obtain a thermal gravimetric analysis curve; and the mass percentage content of platinum in the platinum-based catalyst sample is calculated according to the thermal gravimetric analysis curve. The temperature program is a stage temperature process, and the stage temperature process comprises a first stage temperature process and a second stage temperature process performed in sequence.

2. The analysis method according to claim 1, characterized in that, The first stage temperature process comprises a first temperature process and a first holding process. The starting temperature of the first temperature process is 25-30°C. The ending temperature of the first temperature process is 200-300°C. The heating rate of the first temperature process is 5-20°C / min. The temperature of the first holding process is 200-300°C. The time of the first holding process is 30-50 min. The first stage temperature process is performed in an inert atmosphere. The second stage temperature process comprises a second temperature process and a second holding process. The starting temperature of the second temperature process is 200-300°C. The ending temperature of the second temperature process is 800-1000°C. The heating rate of the second temperature process is 5-20°C / min. The temperature of the second holding process is 800-1000°C. The time of the second holding process is 5-15 min. The second stage temperature process is performed in an oxygen-containing atmosphere.

3. The analysis method according to claim 2, characterized in that, The ending temperature of the first temperature process is 200-250°C. The heating rate of the first temperature process is 10-20°C / min. The temperature of the first holding process is 200-250°C. The time of the first holding process is 40-50 min. The starting temperature of the second temperature process is 200-250°C. The ending temperature of the second temperature process is 900-1000°C. The heating rate of the second temperature process is 10-20°C / min. The temperature of the second holding process is 900-1000°C. The time of the second holding process is 5-10 min.

4. The analysis method according to claim 2, characterized in that, The inert atmosphere is helium. The flow rate of the inert atmosphere is 20-100 mL / min.

5. The analysis method according to claim 2, characterized in that, The oxygen-containing atmosphere comprises a combination of oxygen and helium. The volume ratio of the oxygen and helium is (4-10):(90-96).

6. The analysis method of claim 1, wherein, The mass of the platinum-based catalyst sample is 5-10 mg.

7. The analysis method of claim 1, wherein, The analysis method comprises the following steps: S1. A platinum-based catalyst sample is weighed and placed in a crucible, and the crucible containing the platinum-based catalyst sample is placed in a thermal gravimetric analyzer; S2. The temperature program parameters in the thermogravimetric analyzer are set so that the platinum-based catalyst sample is first heated from 25°C to 30°C to 200°C to 300°C at a heating rate of 5°C / min to 20°C / min under an inert atmosphere, and is kept at a constant temperature of 200°C to 300°C for 30min to 50min; then switched to an oxygen-containing atmosphere and heated from 200°C to 300°C to 800°C to 1000°C at a heating rate of 5°C / min to 20°C / min, and is kept at a constant temperature of 800°C to 1000°C for 5min to 15min; S3. After the heating is completed, the heating is stopped, and the platinum-based catalyst sample is automatically cooled to a constant temperature, and a thermogravimetric analysis curve is obtained. The mass percentage of platinum in the platinum-based catalyst sample is calculated according to the thermogravimetric analysis curve.

8. The analysis method according to claim 7, characterized in that, After stopping the heating in step S3, the platinum-based catalyst sample is allowed to cool naturally to room temperature.

9. The analysis method of claim 1, wherein, The analytical method comprises the following steps: S1. Weigh 5 mg to 10 mg of a platinum-based catalyst sample and place it in a crucible. Place the crucible containing the platinum-based catalyst sample into a thermogravimetric analyzer. The thermogravimetric analyzer records the mass of the platinum-based catalyst sample, which is recorded as M1. S2. Setting the helium flow rate in the thermogravimetric analyzer so that the surface of the platinum-based catalyst sample is purged with helium; S3. the temperature program parameters in the thermogravimetric analyzer are set so that the platinum-based catalyst sample is first heated from 25 ° C to 30 ° C to 200 ° C to 250 ° C at a heating rate of 10 ° C / min to 20 ° C / min under helium with a flow rate of 20 mL / min to 100 mL / min, and is kept at a constant temperature of 200 ° C to 250 ° C for 40 min to 50 min; then switched to a mixed atmosphere consisting of oxygen and helium in a volume ratio of (4 to 10): (90 to 96) and heated from 200 ° C to 250 ° C to 900 ° C to 1000 ° C at a heating rate of 10 ° C / min to 20 ° C / min, and is kept at a constant temperature of 900 ° C to 1000 ° C for 5 min to 10 min; S4. After the heating is completed, the heating is stopped and the platinum-based catalyst sample is allowed to cool naturally to room temperature. The thermogravimetric analyzer records the current mass of the platinum-based catalyst sample, which is recorded as M2. The mass percentage of platinum in the platinum-based catalyst sample is calculated according to the thermogravimetric analysis curve, which is recorded as X, X = M2 / M1×100%.

10. Use of the analytical method for determining the platinum content in a platinum-based catalyst according to any one of claims 1 to 9, characterized in that, The application is testing the platinum content in catalyst samples.

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