Preparation method of rare earth metal exchange molecular sieve XRF standard sample

Abstract

The invention discloses a rare earth metal exchange molecular sieve XRF standard sample preparation method, which comprises: drying a molecular sieve in a drying oven, cooling, weighing the dried molecular sieve and a rare earth metal salt or oxide, adding a reagent, and carrying out grinding mixing; carrying out vacuum rapid drying on the mixed sample, and carrying out secondary drying in a drying oven; and tabletting the dried sample by using a tablet press to obtain the rare earth metal exchange molecular sieve XRF standard sample. The invention provides a preparation method of a rare earth metal exchange molecular sieve XRF standard sample. The rare earth metal exchange molecular sieve XRF standard sample can be rapidly obtained through the preparation method. The method solves the problem of rare earth metal content characterization in the rare earth metal modified molecular sieve, and can be used in the fields of catalyst structure and performance research, catalyst formula optimization, inactivation reason analysis and the like.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalyst sample detection methods, and relates to a method for preparing XRF standard samples of rare earth metal exchange molecular sieves. Background Technology

[0002] Molecular sieves function as both "molecule sieving" and "shape-selective catalysis," primarily acting as adsorbents and molecular sieves themselves. Molecular sieve adsorbents have the highest demand, while molecular sieve catalysts offer higher added value. The global molecular sieve market was valued at approximately US$6.4 billion in 2020 and is projected to reach US$8.49 billion by 2028, representing a CAGR of 3.8%. With increasingly stringent environmental regulations and the development of industries such as steel metallurgy, coal chemicals, and power generation, the domestic demand for molecular sieves will continue to grow. In oil refining catalysts, rare earth molecular sieve catalysts are among the most widely used catalytic materials. Compared to amorphous aluminosilicate catalysts, rare earth molecular sieves offer advantages such as higher gasoline yield and stronger resistance to coking. In the petrochemical field, rare earth-based molecular sieve catalysts exhibit high activity, good selectivity, and strong resistance to heavy metal poisoning. The addition of rare earth elements or rare earth oxides, whether as additives, carriers, or co-catalysts, plays a positive role in improving catalyst activity and low-temperature performance, increasing the dispersion of active components, preventing high-temperature aggregation or sintering of active components, and enhancing resistance to poisoning. As an important source for molecular sieve modification, the rapid quantification of rare earth element content is crucial for catalyst research in this field. X-ray fluorescence spectrometry (XRF) is widely used due to its simplicity, speed, accuracy, and non-destructive nature; however, establishing an XRF spectrum requires setting a standard curve for each element. For powder compression methods, preparing standard samples for quantitative analysis is critical. Current methods include mechanical grinding, equal-volume impregnation, and fusion methods; mechanical grinding is widely used due to its short processing time and simple operation. However, achieving homogeneous mixing and preparing standard samples remains a common challenge for this method.

[0003] Chinese patent CN101799437A discloses a method for determining the phosphorus and iron content in co-catalysts using X-ray fluorescence spectrometry. This method involves adding standard solutions of phosphorus and iron of a specific concentration to a molecular sieve, then loading these solutions onto a silicon-aluminum support containing mixed rare earth elements. The mixture is then mixed, evaporated, and dried to prepare a standard sample. A working curve for phosphorus and iron is established on an X-ray fluorescence analyzer. By measuring the X-ray fluorescence intensity of phosphorus and iron in the sample, the apparent content of phosphorus and iron in the sample is determined from the working curve. An empirical equation is then used to correct the apparent content for the matrix to obtain the true content of phosphorus and iron. However, this technique primarily targets the detection of iron and phosphorus content in catalysts supported on aluminum-silicon substrates and does not include the analysis of rare earth element content.

[0004] Chinese patent CN1601261A discloses a method for analyzing metal elements in catalytic cracking catalysts using X-ray fluorescence spectrometry. The method involves preparing 8-14 standard samples with different metal contents. The standard samples are metal oxides supported on a support, which consists of 60-80% by mass alumina and 20-40% by mass silicon oxide. The metals are iron, sodium, mixed rare earth elements, nickel, copper, vanadium, antimony, and calcium. These are then pressed into sheets to form standard samples. An empirical formula for determining the metal content is established, and the content of each metal in the sample is calculated by measuring the X-ray fluorescence intensity of each metal element using the empirical formula. However, this technique relies on the self-evaporation of anhydrous ethanol as a lubricant during standard sample preparation. This can lead to secondary migration and uneven dispersion of metal ions on the support during evaporation, resulting in a high failure rate of the standard samples and poor linearity of the standard curve, making it unsuitable for quantitative analysis. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing XRF standard samples of rare earth metal exchange molecular sieves, which can solve the problem of uneven distribution of trace rare earth elements in rare earth metal exchange molecular sieves and obtain XRF standard samples of rare earth metal exchange molecular sieves.

[0006] To achieve this objective, the present invention provides a method for preparing rare earth metal exchange molecular sieve XRF standard samples, the method comprising the following steps:

[0007] (1) Sample mixing: Dry the molecular sieve in an oven, cool it, weigh the dried molecular sieve and rare earth metal salt or oxide, add reagents and grind and mix them.

[0008] (2) Sample drying: After mixing, the sample is first dried quickly under vacuum, and then placed in an oven for secondary drying;

[0009] (3) Preparation of standard samples: The dried sample is pressed into tablets using a tablet press to obtain rare earth metal exchange molecular sieve XRF standard samples.

[0010] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes rare earth metal salts or oxides being at least one of rare earth metal nitrates, rare earth metal sulfates, rare earth metal chlorides, and rare earth metal oxides, more preferably rare earth metal nitrates.

[0011] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes at least one of deionized water, anhydrous ethanol, petroleum ether, and n-hexane, more preferably anhydrous ethanol.

[0012] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes at least one of manual grinding, ball milling, and cryogenic ball milling, with manual grinding being more preferred.

[0013] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes step (1) in which the drying temperature is 105-150℃ and the time is 1-2h.

[0014] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes a grinding and mixing time of 5-20 min in step (1).

[0015] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes step (2) in which the secondary drying temperature is 105-250℃ and the time is 1-2h.

[0016] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably involves a vacuum degree of less than or equal to 800 Pa during rapid vacuum drying in step (2).

[0017] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably involves step (2) in which the vacuum degree is less than or equal to 400 Pa during rapid vacuum drying.

[0018] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes step (2) in which the vacuum degree is less than or equal to 1 Pa during rapid vacuum drying.

[0019] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes step (2) in which the vacuum rapid drying temperature is 20-30℃ and the time is 5-10min.

[0020] The method for preparing rare earth metal exchange molecular sieve XRF standard samples of the present invention preferably includes step (1) in which the content of rare earth metal accounts for 0-1.5 wt% of the total mass of the dried molecular sieve and rare earth metal salt or oxide.

[0021] The rare earth metal exchange molecular sieve XRF standard sample of the present invention refers to a standard sample using at least one rare earth element selected from La, Ce, Nd, Eu, etc. as the main metal and a molecular sieve as the carrier for X-ray fluorescence spectroscopy.

[0022] The preparation method of the present invention is applicable to a variety of molecular sieves, including but not limited to at least one of MCM22 molecular sieve, ZSM5 molecular sieve, ZSM23 molecular sieve, β molecular sieve, SAPO11 molecular sieve, ZSM12 molecular sieve, ZSM48 molecular sieve, type A molecular sieve, and octahedral zeolite molecular sieve.

[0023] This invention provides a method for preparing XRF standard samples of rare earth metal exchange molecular sieves. This method allows for the rapid acquisition of XRF standard samples of rare earth metal exchange molecular sieves. The invention employs a staged drying process during standard sample preparation, reducing the migration of rare earth metals during conventional drying processes, significantly improving sample homogeneity. Furthermore, the method is simple and reliable, solving the problem of characterizing the rare earth metal content in rare earth metal-modified molecular sieves. It can be used in fields such as catalyst structure and performance research, catalyst formulation optimization, and deactivation analysis. Attached Figure Description

[0024] Figure 1 This is the standard curve graph for Example 1.

[0025] Figure 2 This is the standard curve graph for Example 2.

[0026] Figure 3 This is the standard curve graph for Example 3.

[0027] Figure 4 This is the standard curve graph for Example 4.

[0028] Figure 5 This is the standard curve graph for Example 5.

[0029] Figure 6 This is the standard curve graph for Example 6.

[0030] Figure 7 This is the standard curve for Comparative Example 1.

[0031] Figure 8 This is the standard curve for Comparative Example 2.

[0032] Figure 9 This is the standard curve for Comparative Example 3.

[0033] Figure 10 This is the standard curve for Comparative Example 4.

[0034] Figure 11 This is the standard curve for Comparative Example 5. Detailed Implementation

[0035] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0036] Example 1

[0037] Approximately 5g of MCM22 molecular sieve was weighed and dried in an oven at 105℃ for 1 hour, then cooled in a desiccator for 2 hours. Five portions of the dried molecular sieve and lanthanum nitrate hexahydrate were weighed out according to lanthanum mass fractions of 0.2%, 0.4%, 0.6%, 1%, and 1.5%, respectively. These five samples were ball-milled in a mortar with anhydrous ethanol for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 20℃, and a drying time of 5 minutes. The five samples were then dried in an oven at 105℃ for 1 hour, and then compressed into tablets using a tablet press to obtain five XRF standard samples. A standard curve was established. The fitting results are as follows: Figure 1 As shown, the R-value can reach 2 nines, indicating good linearity, and it can be used for quantitative analysis.

[0038] Example 2

[0039] Approximately 5g of ZSM23 molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. Five portions of the dried molecular sieve and cerium nitrate hexahydrate were weighed out according to cerium mass fractions of 0.4%, 0.5%, 0.6%, 1%, and 1.5%, respectively. These five samples were manually ground and mixed in a mortar with anhydrous ethanol for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 25℃, and a drying time of 10 minutes. The five samples were then dried in an oven at 120℃ for 2 hours, and then compressed into tablets using a tablet press to obtain five XRF standard samples. A standard curve was established. The fitting results are as follows: Figure 2 As shown, the R-value can reach 2 nines, indicating good linearity, and it can be used for quantitative analysis.

[0040] Example 3

[0041] Approximately 5g of SAPO11 molecular sieve was weighed and dried in an oven at 150℃ for 2 hours, then cooled in a desiccator for 2 hours. Five portions of the dried molecular sieve and lanthanum nitrate hexahydrate were weighed out according to lanthanum mass fractions of 0.2%, 0.4%, 0.8%, 1%, and 1.2%, respectively. These five samples were then separately mixed in a mortar with n-hexane and cryogenically ball-milled for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 30℃, and a drying time of 7 minutes. The five samples were then dried in an oven at 250℃ for 2 hours, and then compressed into tablets using a tablet press to obtain five XRF standard samples. A standard curve was established. The fitting results are as follows: Figure 3As shown, the R-value can reach 2 nines, indicating good linearity, and it can be used for quantitative analysis.

[0042] Example 4

[0043] Approximately 5g of ZSM5 molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. Europium was added at mass fractions of 0.2%, 0.4%, 0.8%, 1%, and 1.5% respectively. These five samples were manually ground and mixed in a mortar with anhydrous ethanol for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 25℃, and a drying time of 10 minutes. The five samples were then dried in an oven at 120℃ for 2 hours, and then compressed into tablets using a tablet press to obtain five XRF standard samples. A standard curve was established. The fitting results are as follows: Figure 4 As shown, the R-value can reach three nines, indicating good linearity, and it can be used for quantitative analysis.

[0044] Example 5

[0045] Approximately 5g of β-molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. The dried molecular sieve and lanthanum nitrate hexahydrate were weighed out according to lanthanum mass fractions of 0.1%, 0.2%, 0.4%, 0.8%, and 1.5%, respectively. These five samples were manually ground and mixed in a mortar with petroleum ether for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 25℃, and a drying time of 10 minutes. The five samples were then dried in an oven at 120℃ for 2 hours, and then compressed into tablets using a tablet press to obtain five XRF standard samples. A standard curve was established. The fitting results are as follows: Figure 5 As shown, the R-value can reach 2 nines, indicating good linearity, and it can be used for quantitative analysis.

[0046] Example 6

[0047] Approximately 5g of octahedral zeolite molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. Five samples were weighed with anhydrous neodymium chloride at neodymium mass fractions of 0.2%, 0.4%, 0.8%, 1.2%, and 1.5%, respectively. Anhydrous ethanol was added to each of these five samples and they were manually ground and mixed in a mortar for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 25℃, and a drying time of 10 minutes. The five samples were then dried in an oven at 120℃ for 2 hours, and then compressed into tablets using a tablet press to obtain five XRF standard samples. A standard curve was established. The fitting results are as follows: Figure 6 As shown, the R-value can reach 2 nines, indicating good linearity, and it can be used for quantitative analysis.

[0048] Comparative Example 1

[0049] The difference from Example 4 is that vacuum rapid drying is not performed; otherwise, it is the same as Example 4.

[0050] Approximately 5g of ZSM5 molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. The dried molecular sieve and europium oxide were weighed out according to europium mass fractions of 0.2%, 0.4%, 0.8%, 1%, and 1.5%, respectively. These five samples were manually ground and mixed in a mortar with anhydrous ethanol for 10 minutes. The mixed samples were then dried in an oven at 120℃ for 2 hours. Five XRF standard samples were prepared by tableting using a tablet press. A standard curve was established. The fitting results are shown below. Figure 7 As shown, the R value is 0.9558, indicating poor linearity, making it unsuitable for quantitative analysis.

[0051] Comparative Example 2

[0052] The difference from Example 5 is that infrared lamp drying is used instead of vacuum rapid drying; otherwise, it is the same as Example 5.

[0053] Approximately 5g of β-molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. The dried molecular sieve and lanthanum nitrate hexahydrate were weighed out according to lanthanum mass fractions of 0.1%, 0.2%, 0.4%, 0.8%, and 1.5%, respectively. These five samples were manually ground and mixed in a mortar with petroleum ether for 10 minutes. The mixed samples were then dried under an infrared lamp at 25℃ for 10 minutes. After drying in an oven at 120℃ for 2 hours, the samples were compressed into tablets to obtain five XRF standard samples, and a standard curve was established. The fitting results are as follows: Figure 8 As shown, the R value is 0.8299, indicating poor linearity, making it unsuitable for quantitative analysis.

[0054] Comparative Example 3

[0055] The difference from Example 6 is that no drying is performed during the sample mixing process; otherwise, it is the same as Example 6.

[0056] Approximately 5g of octahedral zeolite molecular sieve was weighed. Five samples were then weighed with anhydrous neodymium chloride at neodymium mass fractions of 0.2%, 0.4%, 0.8%, 1.2%, and 1.5%, respectively. Anhydrous ethanol was added to each of these five samples, and they were manually ground and mixed in a mortar for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 25℃, and a drying time of 10 minutes. Finally, the five samples were dried in an oven at 120℃ for 2 hours. Five XRF standard samples were prepared by pressing each sample into tablets using a tablet press, and a standard curve was established. The fitting results are as follows: Figure 9As shown, the R value is 0.8707, indicating poor linearity, making it unsuitable for quantitative analysis.

[0057] Comparative Example 4

[0058] The difference from Example 2 is that an electric heating plate is used instead of vacuum rapid drying; otherwise, they are the same as in Example 2.

[0059] Approximately 5g of ZSM23 molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. Five portions of the dried molecular sieve and cerium nitrate hexahydrate were weighed out according to cerium mass fractions of 0.4%, 0.5%, 0.6%, 1%, and 1.5%, respectively. These five samples were manually ground and mixed in a mortar with anhydrous ethanol for 10 minutes. The mixed samples were then dried on an electric heating plate at 25℃ for 1 hour. After drying in an oven at 120℃ for 2 hours, the samples were compressed into tablets using a tablet press to obtain five XRF standard samples, and a standard curve was established. The fitting results are as follows: Figure 10 As shown, the R value is 0.7457, indicating poor linearity, making it unsuitable for quantitative analysis.

[0060] Comparative Example 5

[0061] The difference from Example 2 is that no secondary drying is performed; otherwise, it is the same as Example 2.

[0062] Approximately 5g of ZSM23 molecular sieve was weighed and dried in an oven at 120℃ for 2 hours, then cooled in a desiccator for 2 hours. Five portions of the dried molecular sieve and cerium nitrate hexahydrate were weighed out according to cerium mass fractions of 0.4%, 0.5%, 0.6%, 1%, and 1.5%, respectively. These five samples were manually ground and mixed in a mortar with anhydrous ethanol for 10 minutes. The mixed samples were then rapidly dried in a vacuum chamber at a vacuum degree of 1 Pa, a drying temperature of 25℃, and a drying time of 10 minutes. Five XRF standard samples were prepared by tableting using a tablet press, and a standard curve was established. The fitting results are as follows: Figure 11 As shown, the R value is 0.8852, indicating poor linearity, making it unsuitable for quantitative analysis.

[0063] The results from the examples and comparative examples show that the preparation method of this invention improves the uniformity of the samples, solves the problem of characterizing the rare earth metal content in rare earth metal modified molecular sieves, and the obtained XRF standard samples can be used for the study of catalyst structure and performance.

[0064] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing rare earth metal exchange molecular sieve XRF standard samples, characterized in that, Includes the following steps: (1) Sample mixing: Dry the molecular sieve in an oven, cool it, weigh the dried molecular sieve and rare earth metal salt or oxide, add reagents and grind and mix them. (2) Sample drying: After mixing, the sample is first dried quickly under vacuum, and then placed in an oven for secondary drying; (3) Preparation of standard samples: The dried sample is pressed into tablets using a tablet press to obtain rare earth metal exchange molecular sieve XRF standard samples.

2. The preparation method according to claim 1, characterized in that, The rare earth metal salt or oxide is at least one of rare earth metal nitrate, rare earth metal sulfate, rare earth metal chloride, and rare earth metal oxide.

3. The preparation method according to claim 1, characterized in that, The reagent is at least one of deionized water, anhydrous ethanol, petroleum ether, and n-hexane.

4. The preparation method according to claim 1, characterized in that, The grinding method is at least one of manual grinding, ball milling, and cryogenic ball milling.

5. The preparation method according to claim 1, characterized in that, In step (1), the drying temperature is 105-150℃ and the time is 1-2h.

6. The preparation method according to claim 1, characterized in that, In step (1), the grinding and mixing time is 5-20 min.

7. The preparation method according to claim 1, characterized in that, In step (2), the temperature of the secondary drying is 105-250℃ and the time is 1-2h.

8. The preparation method according to claim 1, characterized in that, In step (2), during vacuum rapid drying, the vacuum degree is less than or equal to 800 Pa; preferably, the vacuum degree is less than or equal to 400 Pa; more preferably, the vacuum degree is less than or equal to 1 Pa.

9. The preparation method according to claim 1, characterized in that, In step (2), the temperature of the vacuum rapid drying is 20-30℃ and the time is 5-10 min.

10. The preparation method according to claim 1, characterized in that, In step (1), the content of rare earth metals accounts for 0-1.5 wt% of the total mass of the dried molecular sieve and rare earth metal salts or oxides.

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