Modified ZSM-35 molecular sieve as well as modification method and application thereof
By using a mixed solution of alkali and sodium oleate in the ZSM-35 molecular sieve for recrystallization treatment, the content of B acid in its 8-MR channel was improved, and the problem of insufficient catalytic activity of ZSM-35 molecular sieve was solved, and higher catalytic activity was achieved.
Patent Information
- Application Number
- CN202311549544.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-20
- Publication Date
- 2025-05-20
AI Technical Summary
In the prior art, the number of B acid sites in the 8-MR channel in the ZSM-35 molecular sieve is insufficient, resulting in its catalytic activity in the dimethyl ether carbonylation reaction.
By treating the ZSM-35 molecular sieve in a mixed solution including alkali and sodium oleate, the B acid content in its 8-MR pore is improved. The method includes adding a mixed solution of alkali and sodium oleate to a process, followed by calcining, ion exchange and secondary calcining to prepare a modified ZSM-35 molecular sieve.
The catalytic activity of ZSM-35 molecular sieve in dimethyl ether carbonylation reaction was improved, and the content of B acid in the 8-MR channel was enhanced, but the content of non-branch aluminum did not significantly increase.
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Figure CN120019880A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of molecular sieves, and more specifically, to a modified ZSM-35 molecular sieve, a modification method thereof, and an application thereof. Background Art
[0002] ZSM-35 molecular sieve is a mesoporous zeolite developed by Mobil Corporation of the United States in 1977. Its framework structure is formed by the perpendicular intersection of ten-membered ring channels and eight-membered ring channels. The eight-membered ring channels intersect with six-membered rings on the c-axis to form FER cages.
[0003] The gas-phase carbonylation of dimethyl ether (DME) to methyl acetate (MA) is an important catalytic reaction because the prepared MA can be easily converted into high-value-added petrochemical products, such as acetic acid or clean fuel ethanol. The 8-MR channels of mordenite (MOR) are relatively small The 12-MR channels are relatively large and it is relatively active in the dimethyl ether carbonylation reaction. However, severe coke deposition on the relatively large 12-MR channels usually leads to rapid deactivation of the catalyst. FER zeolite, which also has an 8-MR channel structure, has very good stability in the dimethyl ether carbonylation reaction, but its activity is much weaker than that of MOR. Through the study of the dimethyl ether carbonylation reaction mechanism, it is found that in acidic zeolites, the activity of dimethyl ether carbonylation is mainly related to the number of acid (B acid) sites in the 8-MR channels of the zeolite molecular sieve. Therefore, if the number of B acid sites in the 8-MR channels of the ZSM-35 molecular sieve can be increased, the catalytic activity of the ZSM-35 molecular sieve in dimethyl ether carbonylation can be well improved.
[0004] The prior art discloses improving the catalytic activity of ZSM-35 molecular sieve in the dimethyl ether carbonylation reaction by microwave alkali treatment of the ZSM-35 molecular sieve, but the use of microwave technology is complex. Therefore, it is necessary to develop a method with simple process to treat the ZSM-35 molecular sieve to improve its catalytic activity in the dimethyl ether carbonylation reaction. Summary of the Invention
[0005] The purpose of the present invention is to provide a modified ZSM-35 molecular sieve and a modification method thereof to solve the technical problem that the number of B acid sites in the 8-MR channels of the ZSM-35 molecular sieve in the prior art is insufficient and the catalytic activity is not ideal enough.
[0006] To achieve the above purpose, the technical solution adopted by the present invention is:
[0007] In a first aspect, the present invention provides a modified ZSM-35 molecular sieve, wherein the content of non-framework aluminum accounts for less than 11% of the total aluminum, and the amount of Brønsted acid in the eight-membered ring shown by pyridine infrared characterization is 0.23 to 0.27 mmol / g.
[0008] For the modified ZSM-35 molecular sieve provided by the present invention, on the basis that the content of non-framework aluminum has not increased significantly compared with the unmodified ZSM-35 molecular sieve, the content of Brønsted acid in its 8-MR channels is higher, making it have higher catalytic activity than the unmodified ZSM-35 molecular sieve in the dimethyl ether carbonylation reaction.
[0009] According to some embodiments of the present invention, in the modified ZSM-35 molecular sieve, the content of non-framework aluminum accounts for 8 to 10% of the total aluminum.
[0010] According to some embodiments of the present invention, in the modified ZSM-35 molecular sieve, the amount of Brønsted acid in the eight-membered ring shown by pyridine infrared characterization is 0.23 to 0.26 mmol / g.
[0011] In a second aspect, the present invention provides a method for modifying a ZSM-35 molecular sieve, comprising:
[0012] S1. Adding the ZSM-35 molecular sieve raw powder to a mixed solution comprising an alkali and sodium oleate, and treating at 110 to 170 °C for 8 to 12 h;
[0013] S2. Subjecting the ZSM-35 molecular sieve raw powder treated in step S1 to primary calcination, ion exchange, and secondary calcination in sequence to obtain a modified ZSM-35 molecular sieve;
[0014] And optionally S3. Shaping the modified ZSM-35 molecular sieve.
[0015] By recrystallizing the ZSM-35 molecular sieve with an alkali and sodium oleate, the present invention makes the content of Brønsted acid in the 8-MR channels of the obtained modified ZSM-35 molecular sieve higher, and the content of non-framework aluminum does not increase significantly. It has higher catalytic activity than the ZSM-35 molecular sieve treated solely with an alkali and the ZSM-35 molecular sieve without post-treatment in the dimethyl ether carbonylation reaction.
[0016] According to some embodiments of the present invention, the concentration of the alkali in the mixed solution is 0.2 to 0.6 mol / L, and for example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, etc.
[0017] According to some embodiments of the present invention, the concentration of sodium oleate in the mixed solution is 0.1 - 0.3 mol / L, and for example, it can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.3 mol / L, etc.
[0018] According to some embodiments of the present invention, the base includes at least one of sodium hydroxide, potassium hydroxide, and ammonia water.
[0019] According to some embodiments of the present invention, the solvent of the mixed solution includes water.
[0020] According to some embodiments of the present invention, the temperature of the first calcination is 400 - 600 °C, and the time is 3 - 12 h.
[0021] According to some embodiments of the present invention, the temperature of the second calcination is 400 - 600 °C, and the time is 3 - 12 h.
[0022] According to some embodiments of the present invention, before the first calcination, washing, filtration, and drying treatments are sequentially performed.
[0023] According to some embodiments of the present invention, before the second calcination, washing, filtration, and drying treatments are sequentially performed.
[0024] According to some embodiments of the present invention, the temperature of the drying is 90 - 120 °C.
[0025] According to some embodiments of the present invention, the ion exchange includes ammonium exchange.
[0026] According to some embodiments of the present invention, the ammonium exchange reagent includes at least one of ammonium acetate, ammonium nitrate, ammonium sulfate, and ammonium chloride.
[0027] According to some embodiments of the present invention, the ammonium exchange is performed for 1 - 5 h under the condition that the temperature is 30 - 90 °C.
[0028] According to some embodiments of the present invention, the concentration of the aqueous solution of the ammonium exchange reagent is 5 - 15 wt%.
[0029] According to some embodiments of the present invention, the solid-liquid ratio of the ammonium exchange is 1 g: 10 - 20 mL.
[0030] In the third aspect, the present invention provides a modified ZSM-35 molecular sieve prepared by using the modification method described in the second aspect.
[0031] In the fourth aspect, the present invention provides the application of the modified ZSM-35 molecular sieve described in the first aspect or the modified ZSM-35 molecular sieve described in the third aspect in the gas-phase carbonylation reaction of dimethyl ether.
[0032] The beneficial effects of the present invention are at least as follows:
[0033] By treating the ZSM-35 molecular sieve with alkali and sodium oleate, the obtained modified ZSM-35 molecular sieve has good crystallinity, a higher content of Bronsted acid in the 8-MR channels, and the content of non-framework aluminum does not increase significantly, which can effectively improve its catalytic activity in the dimethyl ether carbonylation reaction. Description of the Drawings
[0034] Figure 1 X-ray diffraction patterns (XRD) of molecular sieves FER-Re, FER-C, and FER-AT.
[0035] Figure 2 Scanning electron microscope images (SEM) and transmission electron microscope images (TEM) of molecular sieves FER-Re, FER-C, and FER-AT.
[0036] Figure 3 For the NH 3 -TPD curve of molecular sieves FER-Re, FER-C, and FER-AT.
[0037] Figure 4 Py-IR spectra of molecular sieves FER-Re, FER-C, and FER-AT.
[0038] Figure 5 Graph showing the change in the conversion rate of raw material dimethyl ether with reaction time during the dimethyl ether carbonylation reaction using molecular sieves FER-Re, FER-C, and FER-AT.
[0039] Figure 6 Graph showing the change in the selectivity of methyl acetate as a product with reaction time during the dimethyl ether carbonylation reaction using molecular sieves FER-Re, FER-C, and FER-AT (reaction conditions: P = 2.0 MPa, T = 200 °C, DME feed flow rate 4 mL / h, CO feed 200 mL / min). Detailed Embodiments
[0040] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present invention clearer, the following further details the present invention with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent in detail and do not limit the protection scope of the present invention in any way.
[0041] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. The reagents used in the following examples are all conventional biochemical reagents unless otherwise specified; the raw materials, instruments, and equipment used in the following examples can all be obtained through market purchase or by existing methods; the reagent dosages are all the dosages used in conventional experimental operations unless otherwise specified; the experimental methods are all conventional methods unless otherwise specified.
[0042] In the examples and comparative examples of the present invention, the following test methods were used for testing the various test results:
[0043] (1) X-ray diffraction pattern: Measured using a D8 Advance SS X-ray diffractometer with Cu Kα radiation at 40 kV and 40 mA. By observing the scan in the region of 2θ = 5 - 50°, the X-ray diffraction spectrum of the molecular sieve can be obtained.
[0044] (2) Scanning electron microscope image: Measured using a Hitachi S-4800 microscope (Scanning Electron Microscopy) at an acceleration voltage of 3.0 kV. When preparing the sample, first, the dried sample was calcined and evenly prepared on the conductive adhesive.
[0045] (3) Transmission electron microscope image: Observed and studied the shape, particle size, and lattice parameters of the molecular sieve using a JEOL-LEM-2100F field emission transmission electron microscope. The sample preparation method includes: First, hydrolyze the molecular sieve powder in an ethanol solution, then perform ultrasonic treatment for 30 min, and finally drop the suspension after the treatment process onto the surface of a copper mesh carbon film. The test voltage is 200 kV.
[0046] (4) NH 3 -TPD: Measured using an AMI-3300 produced by Altamira Instruments. Before the test, the molecular sieve sample needs to be dried at 550 °C for 1 h, and the heating rate during temperature-programmed desorption is 10 °C·min -1 , and the temperature is raised from 100 °C to 550 °C.
[0047] (5) Py-IR: Detected using a Nicolet NEXUS 670FT-IR spectrometer.
[0048] Example 1
[0049] (1) Sodium hydroxide and sodium oleate were added to water to prepare a mixed solution with a sodium hydroxide concentration of 0.3 mol / L and a sodium oleate concentration of 0.1 mol / L. The as-synthesized ZSM-35 zeolite powder was added to the mixed solution and stirred with a magnetic stirrer for 2 h until the solution was homogeneous. Then it was transferred to a high-temperature and high-pressure autoclave and treated at 170 °C for 10 h.
[0050] (2) The sample treated in step (1) was washed, filtered, dried at 110 °C for 12 h, and then the dried sample was calcined at 550 °C for 4 h. It was exchanged three times in a 10 wt% ammonium acetate solution for 2 h each time, with a solid-liquid ratio (g:mL) of 1:10. The sample after ion exchange was washed, filtered, dried at 110 °C for 12 h, and then calcined at 550 °C for 4 h to obtain the modified ZSM-35 zeolite (FER-Re).
[0051] Example 2
[0052] (1) Sodium hydroxide and sodium oleate were added to water to prepare a mixed solution with a sodium hydroxide concentration of 0.6 mol / L and a sodium oleate concentration of 0.3 mol / L. The as-synthesized ZSM-35 zeolite powder was added to the mixed solution and stirred with a magnetic stirrer for 2 h until the solution was homogeneous. Then it was transferred to a high-temperature and high-pressure autoclave and treated at 110 °C for 10 h.
[0053] (2) The sample treated in step (1) was washed, filtered, dried at 110 °C for 12 h, and then the dried sample was calcined at 550 °C for 4 h. It was exchanged three times in a 10 wt% ammonium acetate solution for 2 h each time, with a solid-liquid ratio (g:mL) of 1:10. The sample after ion exchange was washed, filtered, dried at 110 °C for 12 h, and then calcined at 550 °C for 4 h to obtain the modified ZSM-35 zeolite.
[0054] Example 3
[0055] (1) Sodium hydroxide and sodium oleate were added to water to prepare a mixed solution with a sodium hydroxide concentration of 0.2 mol / L and a sodium oleate concentration of 0.2 mol / L. The as-synthesized ZSM-35 zeolite powder was added to the mixed solution and stirred with a magnetic stirrer for 2 h until the solution was homogeneous. Then it was transferred to a high-temperature and high-pressure autoclave and treated at 150 °C for 10 h.
[0056] (2) The sample treated in step (1) was washed, filtered, dried at 110 °C for 12 h, and then the dried sample was calcined at 550 °C for 4 h. It was exchanged three times in a 10 wt% ammonium acetate solution for 2 h each time, with a solid-liquid ratio (g:mL) of 1:10. The sample after ion exchange was washed, filtered, dried at 110 °C for 12 h, and then calcined at 550 °C for 4 h to obtain the modified ZSM-35 zeolite.
[0057] Example 4
[0058] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that the alkali concentration is 0.1 mol / L.
[0059] Example 5
[0060] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that the alkali concentration is 1.0 mol / L.
[0061] Due to the too high alkali concentration, most of the molecular sieve was dissolved.
[0062] Example 6
[0063] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that the sodium oleate concentration is 0.05 mol / L.
[0064] Example 7
[0065] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that the sodium oleate concentration is 0.4 mol / L.
[0066] Comparative Example 1
[0067] The ZSM-35 molecular sieve raw powder was exchanged 3 times in 10 wt% ammonium acetate solution for 2 h each time, with the solid-liquid ratio (g:mL) being 1:10; the sample after ion exchange was washed, filtered, dried at 110 °C for 12 h, and then calcined at 550 °C for 4 h to obtain ZSM-35 molecular sieve (FER-C).
[0068] Comparative Example 2
[0069] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that sodium oleate was not added to the mixed solution.
[0070] The obtained modified ZSM-35 molecular sieve was denoted as FER-AT.
[0071] Comparative Example 3
[0072] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that sodium oleate was replaced with sodium dodecyl sulfate.
[0073] Comparative Example 4
[0074] The modification method of ZSM-35 molecular sieve refers to Example 1, with the only difference being that sodium oleate was replaced with sodium lauryl polyoxyethylene ether sulfate.
[0075] Comparative Example 5
[0076] The modification method of ZSM-35 molecular sieve refers to Example 1, except that sodium oleate is replaced by cetyltrimethylammonium bromide (CTAB).
[0077] Comparative Example 6
[0078] The modification method of ZSM-35 molecular sieve refers to Example 1, except that the treatment temperature is changed from 170 °C to 100 °C.
[0079] Comparative Example 7
[0080] The modification method of ZSM-35 molecular sieve refers to Example 1, except that the treatment temperature is changed from 170 °C to 200 °C.
[0081] Comparative Example 8
[0082] The modification method of ZSM-35 molecular sieve refers to Example 1, except that the treatment time is changed from 10 h to 4 h.
[0083] Comparative Example 9
[0084] The modification method of ZSM-35 molecular sieve refers to Example 1, except that the treatment time is changed from 10 h to 24 h.
[0085] Catalyst performance evaluation
[0086] (1) The X-ray diffraction patterns of the molecular sieves of Example 1 and Comparative Examples 1-2 are as Figure 1 shown. It can be seen from Figure 1 that the molecular sieves of Example 1 and Comparative Examples 1-2 are all ZSM-35 molecular sieves with a FER topological structure.
[0087] According to Figure 1 , taking FER-C as the reference standard and defining its relative crystallinity as 100%, by calculating the ratio of the sum of the peak areas of the characteristic peaks (2θ = 9.4°, 25.1°, 25.6°) of the sample to that corresponding to FER-C, the crystallinity of FER-Re is calculated to be about 98%, proving that the modified ZSM-35 molecular sieve provided by the present invention still has good crystallinity.
[0088] (2) The scanning electron microscope images (SEM) and transmission electron microscope images (TEM) of the molecular sieves of Example 1 and Comparative Examples 1-2 are as Figure 2 shown. It can be seen from Figure 2 that the molecular sieves of Example 1 and Comparative Examples 1-2 all have typical FER sheet structures. It shows that after the ZSM-35 molecular sieve is modified by the modification method provided by the present invention, the structure of the molecular sieve is not damaged, and it is still ZSM-35 molecular sieve, which also corroborates the test results of XRD. And throughFigure 2 It can also be seen that FER-Re has good crystallinity.
[0089] (3) The NH 3 -TPD curves and Py-IR spectra of the molecular sieves of Example 1 and Comparative Examples 1-2 are shown in Figure 3 and Figure 4 respectively. Figure 4 Combined with TPD, the number of Brønsted acid sites in the 8-membered ring of ZSM-35 molecular sieve was calculated.
[0090] The acid property data of some examples and comparative examples, as well as 27 the 27Al NMR results are shown in Table 1.
[0091] Table 1
[0092]
[0093]
[0094] As can be seen from Table 1, for the modified ZSM-35 molecular sieve provided by the present invention compared with the unmodified ZSM-35 molecular sieve (FER-C prepared in Comparative Example 1), the number of Brønsted acids in the 8-membered ring increases significantly, and the proportion of non-framework aluminum does not increase significantly.
[0095] (4) Catalyst reaction performance:
[0096] The evaluation of the catalyst reaction performance was carried out in a fixed-bed reactor. The radius of the reaction tube was 8 mm, the length was 33 cm, and the catalyst loading was 8 g. The catalyst was pretreated at 400 °C for 2 h in an N 2 atmosphere, and then cooled to the reaction temperature (200 °C) in an N 2 atmosphere.
[0097] A mixture of dimethyl ether and carbon monoxide was passed through the catalyst bed from top to bottom to produce the target product methyl acetate. The products after the reaction were analyzed online by Aglient-8890 gas chromatography. The results are shown in Table 2 and Figures 5-6 respectively.
[0098] Dimethyl ether conversion rate: Methyl acetate selectivity:
[0099] Table 2
[0100]
[0101]
[0102] Among them, since most of the molecular sieves were dissolved during the modification process of Example 5, the catalyst reaction performance of the product obtained in Example 5 was not tested.
[0103] As Figure 5 shown, the conversion rate of dimethyl ether of FER-Re was stable during the 30-hour fluidization time test, while the conversion rate of dimethyl ether of FER-C and FER-AT increased in the first 6 hours and then decreased in the next 24 hours. After 30 hours, the conversion rate gap between FER-Re and FER-C, FER-AT still remained more than 3%.
[0104] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present invention within the scope of the claims of the present invention as provided, and the present invention can be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.
Claims
1. A modified ZSM-35 molecular sieve, characterized in that: In the modified ZSM-35 molecular sieve, the content of non-framework aluminum accounts for less than 11% of the total aluminum, and the pyridine infrared characterization result shows that the amount of B acid in the eight-membered ring is 0.23-0.27 mmol / g.
2. A method for modifying a ZSM-35 molecular sieve, characterized in that: include: S1. Add ZSM-35 molecular sieve powder to a mixed solution including alkali and sodium oleate, and treat at 110-170°C for 8-12h; S2. The ZSM-35 molecular sieve powder treated in step S1 is subjected to primary calcination, ion exchange, and secondary calcination to obtain a modified ZSM-35 molecular sieve; And optionally S3. forming the modified ZSM-35 molecular sieve.
3. The modification method according to claim 2, characterized in that: The concentration of the alkali in the mixed solution is 0.2-0.6 mol / L.
4. The modification method according to claim 2 or 3, characterized in that: The concentration of sodium oleate in the mixed solution is 0.1-0.3 mol / L.
5. The modification method according to any one of claims 2 to 4, characterized in that: The alkali includes at least one of sodium hydroxide, potassium hydroxide and ammonia water.
6. The modification method according to any one of claims 2 to 5, characterized in that: The primary calcination temperature is 400-600°C and the time is 3-12h; And / or, the secondary calcination is carried out at a temperature of 400 to 600° C. and for a time of 3 to 12 hours.
7. The modification method according to any one of claims 2 to 6, characterized in that: Before the primary roasting, washing, filtering and drying are sequentially performed; And / or, washing, filtering and drying are sequentially performed before the secondary roasting.
8. The modification method according to any one of claims 2 to 7, characterized in that: The ion exchange comprises ammonium exchange; Preferably, The ammonium exchange reagent includes at least one of ammonium acetate, ammonium nitrate, ammonium sulfate, and ammonium chloride; And / or, the ammonium exchange is carried out at a temperature of 30 to 90° C. for 1 to 5 hours; and / or, the concentration of the aqueous solution of the ammonium exchange reagent is 5 to 15 wt %; And / or, the solid-liquid ratio of the ammonium exchange is 1 g: 10-20 mL.
9. A modified ZSM-35 molecular sieve prepared by the modification method according to any one of claims 2 to 8.
10. Use of the modified ZSM-35 molecular sieve according to claim 1 or the modified ZSM-35 molecular sieve according to claim 9 in a gas-phase carbonylation reaction of dimethyl ether.