A method for regenerating a metal-modified mordenite catalyst used in a methanol amination reaction

Abstract

The application discloses a regeneration method of a metal-modified mordenite catalyst used in a methanol amination reaction, and belongs to the technical field of catalyst regeneration. The catalyst regeneration method comprises the following steps: firstly, removing non-framework aluminum in the catalyst by using an organic acid solution; then, removing residual organic acid and part of carbon deposition after acid treatment by washing with an organic solvent; subsequently, oxidizing carbon deposition on the surface of the catalyst by using a hydrogen peroxide solution and inert mixed gas containing ozone; and finally, reducing active metal components in the catalyst by using hydrogen. The regeneration method can effectively remove carbon deposition on the surface of the catalyst at low temperature and reduce the generation of non-framework aluminum on the surface of the mordenite during the regeneration process, effectively prolongs the service life of the catalyst, and the regenerated catalyst can maintain good reaction performance in the methanol amination reaction.

Description

Technical Field

[0001] This invention belongs to the field of catalyst regeneration technology, specifically relating to a method for regenerating a metal-modified mordenite catalyst used in methanol amination reactions. Background Technology

[0002] Methylamine is an important fine chemical product, commonly used as an intermediate in water treatment, pesticides, pharmaceuticals, surfactants, and solvents. The methanol amination route for methylamine production has become the main method for industrial production due to its readily available and inexpensive raw materials and environmentally friendly process. However, due to thermodynamic equilibrium limitations, the proportions of monomethylamine (MMA), dimethylamine (DMA), and trimethylamine (TMA) produced by equilibrium catalysts such as zirconium oxide and tungsten oxide in the methanol amination reaction can no longer meet market demands. Therefore, zeolites with shape-selective catalytic functions, such as mordenite (MOR) and ZSM-5, have become research hotspots in recent years.

[0003] The alcohol amination reaction mechanism generally includes three consecutive steps: 1) alcohol dehydrogenation to aldehyde / ketone; 2) CN coupling of aldehyde / ketone with ammonia to form imine; 3) hydrogenation of imine to form amine. In alcohol amination, the dehydrogenation step is considered the rate-determining step. Modifying mordenite zeolite catalysts with alkaline earth metals and transition metals can improve the reaction performance of methanol amination by modifying the pore structure, controlling acid properties, and increasing dehydrogenation active sites. However, with increasing reaction time, the selectivity of trimethylamine and the conversion rate of methanol gradually decrease. The main reasons for catalyst deactivation are as follows: 1) Coke formation: Organic matter adsorbed on the catalyst surface will coke, leading to blockage of the catalyst's pore structure and coverage of reactive sites; 2) Sintering of metal elements: High temperature and high pressure reaction conditions cause metal particles to agglomerate, reducing active sites; 3) Dealuminization of the zeolite framework: Although the water vapor generated in the reaction system can vaporize some of the coke, it will cause dealuminization of the zeolite framework and the formation of amorphous aluminum species.

[0004] The commonly used industrial method for removing coke from catalyst surfaces is high-temperature oxidation with controlled oxygen concentration. While this avoids localized overheating caused by coke oxidation during regeneration, the high temperature conditions still exacerbate zeolite dealumination and metal sintering. Therefore, the ideal regeneration method for metal-modified mordenite zeolite catalysts used in methanol amination reactions combines low-temperature controlled combustion of coke, removal of non-framework aluminum, and reduction of transition metal elements. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a method for regenerating a metal-modified mordenite catalyst for use in a methanol amination reaction.

[0006] This invention is achieved using the following technical solution:

[0007] The regeneration method of the metal-modified mordenite catalyst used in the methanol amination reaction described in this invention involves first removing the non-skeletal aluminum from the metal-modified mordenite with an organic acid solution, then washing, filtering and drying it with an organic solvent, and finally loading the dried catalyst into a fixed bed and subjecting it to low-temperature oxidation and hydrogen reduction treatment by passing hydrogen peroxide solution and an inert gas mixture containing ozone through it, ultimately obtaining the regenerated catalyst.

[0008] A method for regenerating a metal-modified mordenite zeolite catalyst used in a methanol amination reaction includes the following steps:

[0009] 1) The metal-modified mordenite catalyst with reduced activity was sequentially immersed in an organic acid solution, then filtered and dried;

[0010] 2) The dried catalyst was washed with an organic solvent, then filtered and dried.

[0011] 3) The dried and cooled catalyst is loaded into a fixed-bed reactor. The reactor temperature is first raised to 70-90°C under an inert atmosphere. After the temperature stabilizes, hydrogen peroxide solution is introduced for treatment for 10-16 hours.

[0012] 4) Purge the pipeline with inert gas and raise the reactor temperature to 105-115°C. After the temperature stabilizes for 2 hours, continuously introduce an inert gas mixture containing ozone for 6-24 hours.

[0013] 5) Purge the pipeline with inert gas and raise the reactor temperature to 400-550℃. After the temperature stabilizes for 0.5-1 h, continuously introduce hydrogen gas for 6-20 h to obtain the regenerated catalyst.

[0014] Based on the above technical solution, further, the mass of alkaline earth metal elements accounts for 20% to 60% of the mass of mordenite; the mass of transition metal elements accounts for 1% to 5% of the mass of mordenite; the silicon-to-aluminum ratio of the mordenite is 5 to 60; the alkaline earth metal elements are selected from one or more of barium and calcium, and the transition metal elements are selected from one or more of nickel, cobalt, copper, and zinc.

[0015] Based on the above technical solution, the organic acid solution is further selected from one or more of 4-chloro-3-nitrobenzoic acid, p-nitrotoluene-o-sulfonic acid, 4-bromophthalic acid, and 2,2'-dithiodibenzoic acid, and the pH range of the organic acid solution is 4 to 6.

[0016] Based on the above technical solution, the organic solvent is further selected from one or more of ethanol, diethyl ether, and chloroform.

[0017] Based on the above technical solution, the concentration of the hydrogen peroxide solution is further 5% to 20%.

[0018] Based on the above technical solution, further, the concentration of oxidizing gas in the ozone-containing inert atmosphere is 3% to 50%, preferably 20% to 30%. The inert atmosphere is one or a combination of two or more of argon, nitrogen, and helium.

[0019] Based on the above technical solution, the hydrogen peroxide treatment temperature is further set at 70–90°C.

[0020] Based on the above technical solution, the hydrogen peroxide treatment time is further 10–16 h.

[0021] Based on the above technical solution, the treatment temperature containing ozone inert gas is further 105-115℃.

[0022] Based on the above technical solution, the treatment time for ozone-containing inert gas is further 6 to 24 hours.

[0023] Based on the above technical solution, the hydrogen treatment temperature is further set at 400–550°C.

[0024] Based on the above technical solution, the hydrogen treatment time is further 6 to 20 hours.

[0025] Based on the above technical solution, the heating rate is further 1 to 40℃ / min.

[0026] Based on the above technical solution, the regeneration pressure is further defined as atmospheric pressure.

[0027] Another aspect of the present invention provides a method for preparing methylamine by catalytic methanol amination, comprising the following steps: a catalyst is loaded into a fixed-bed reactor, hydrogen is first introduced for pretreatment for 0.5-1.0 h, then a mixture of methanol and liquid ammonia is introduced into a preheater for vaporization, and then introduced into the fixed-bed reactor to react and obtain a mixture of different methylamine products.

[0028] Based on the above technical solution, the vaporization temperature is further set to 200–300℃.

[0029] Based on the above technical solution, the reaction temperature is further set at 350–450°C.

[0030] Based on the above technical solution, the reaction pressure is further set to 1–3 MPa.

[0031] Based on the above technical solution, the molar ratio of liquid ammonia to methanol is further 1.2 to 2:1.

[0032] The regeneration method for the metal-modified mordenite zeolite catalyst of this invention can effectively remove carbon deposits on the catalyst surface and reduce the formation of non-framework aluminum at low temperatures. Furthermore, the regeneration process can be achieved at a low temperature of 105–115°C, effectively extending the catalyst's lifespan. The regenerated catalyst exhibits good stability in the methanol amination reaction, with its reactivity essentially restored to the level of a fresh catalyst, which is of great significance for the continuous industrial production of methylamine. Attached Figure Description

[0033] Figure 1 This is a stability test diagram of the regenerated catalyst in Example 6 of the present invention during the methanol amination reaction to prepare trimethylamine. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments and comparative examples. However, the implementation of the present invention is not limited thereto, and other similar embodiments are all within the protection scope of the present invention.

[0035] Example 1

[0036] The shaped Ba and Ni metal-modified mordenite zeolite catalyst was prepared by impregnation and extrusion molding using silica sol as a binder. Freshly shaped Ba and Ni metal-modified mordenite zeolite was loaded into a fixed-bed reactor for methanol amination to prepare methylamine. When the methanol conversion rate decreased to 80%, the feeding and heating were stopped, and N2 was continuously introduced for purging. When the temperature dropped to room temperature and the fixed-bed pressure dropped to atmospheric pressure, the deactivated trimethylamine catalyst was removed for later use.

[0037] Example 2

[0038] The deactivated trimethylamine catalyst from Example 1 was immersed in a 4-chloro-3-nitrobenzoic acid solution at 80°C and pH=5 for 5 h. After immersion, the catalyst was filtered out and dried at 110°C for 10 h. The acid-treated catalyst was then washed with ethanol, filtered, and dried at 110°C for 4 h. The dried and cooled catalyst was then packed into a fixed-bed reactor. Under a N2 atmosphere, the reactor temperature was raised to 90°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a 10% hydrogen peroxide solution was introduced at a rate of 0.50 mL / min for 10 h. Subsequently, an N2 purge was introduced, and the regeneration temperature was raised to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h. Finally, an N2 purge was introduced, and the regeneration temperature was raised to 450°C at a rate of 5°C / min. The regeneration temperature stabilized for 0.5 h. After h, H2 at a flow rate of 0.4 mL / min was introduced for another 10 h. The regeneration pressure was atmospheric pressure. After catalyst regeneration, methanol amination reaction was carried out. The molar ratio of the reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹. -1 After 2 hours of reaction, samples were taken every 1 hour for gas chromatography analysis. The average value of the analysis data of 6 parallel samples was taken, and the results are shown in Table 1.

[0039] Example 3

[0040] The deactivated trimethylamine catalyst from Example 1 was immersed in a p-nitrotoluene-o-sulfonic acid solution at 80°C and pH=5 for 5 h. After immersion, the catalyst was filtered out and dried at 110°C for 10 h. The acid-treated catalyst was then washed with diethyl ether, filtered, and dried at 110°C for 4 h. The dried and cooled catalyst was then loaded into a fixed-bed reactor. Under a N2 atmosphere, the reactor temperature was raised to 90°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a 10% hydrogen peroxide solution was introduced at a rate of 0.50 mL / min for 10 h. Subsequently, an N2 purge line was introduced, and the regeneration temperature was raised to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h. Finally, an N2 purge line was introduced, and the regeneration temperature was raised to 450°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a volumetric flow rate of 0.4 mL / min was introduced. The catalyst was treated with H2 at a rate of mL / min for 10 h. Regeneration was carried out at atmospheric pressure. After catalyst regeneration, methanol amination was performed. The molar ratio of reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹.-1 After 2 hours of reaction, samples were taken every 1 hour for gas chromatography analysis. The average value of the analysis data of 6 parallel samples was taken, and the results are shown in Table 1.

[0041] Example 4

[0042] The deactivated trimethylamine catalyst from Example 1 was immersed in a 4-bromophthalic acid solution at 80°C and pH=5 for 5 h. After immersion, the catalyst was filtered out and dried at 110°C for 10 h. The acid-treated catalyst was then washed with chloroform, filtered, and dried at 110°C for 4 h. The dried and cooled catalyst was then packed into a fixed-bed reactor. Under a N2 atmosphere, the reactor temperature was raised to 90°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a 10% hydrogen peroxide solution was introduced at a rate of 0.50 mL / min for 10 h. Subsequently, an N2 purge was introduced, and the regeneration temperature was raised to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h. Finally, an N2 purge was introduced, and the regeneration temperature was raised to 450°C at a rate of 5°C / min. The regeneration temperature stabilized for 0.5 h. After h, H2 at a flow rate of 0.4 mL / min was introduced for another 10 h. The regeneration pressure was atmospheric pressure. After catalyst regeneration, methanol amination reaction was carried out. The molar ratio of the reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹. -1 After 2 hours of reaction, samples were taken every 1 hour for gas chromatography analysis. The average value of the analysis data of 6 parallel samples was taken, and the results are shown in Table 1.

[0043] Example 5

[0044] The deactivated trimethylamine catalyst from Example 1 was immersed in a 2,2'-dithiodibenzoic acid solution at 80°C and pH=6 for 5 h. After immersion, the catalyst was filtered out and dried at 110°C for 10 h. The acid-treated catalyst was then washed with ethanol, filtered, and dried at 110°C for 4 h. The dried and cooled catalyst was then loaded into a fixed-bed reactor. Under a N2 atmosphere, the reactor temperature was increased to 90°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a 10% hydrogen peroxide solution was introduced at a rate of 0.50 mL / min for 10 h. Subsequently, an N2 purge was introduced, and the regeneration temperature was increased to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h. Finally, an N2 purge was introduced, and the regeneration temperature was increased to 450°C at a rate of 5°C / min. The regeneration temperature stabilized for 0.5 h. After h, H2 at a flow rate of 0.4 mL / min was introduced for another 10 h. The regeneration pressure was atmospheric pressure. After catalyst regeneration, methanol amination reaction was carried out. The molar ratio of the reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹. -1 After 2 hours of reaction, samples were taken every 1 hour for gas chromatography analysis. The average value of the analysis data of 6 parallel samples was taken, and the results are shown in Table 1.

[0045] Table 1. Effects of different organic acid solutions on the reactivity of the metal-modified mordenite catalyst after regeneration

[0046]

[0047] Example 6

[0048] The deactivated trimethylamine catalyst from Example 1 was immersed in a 4-bromophthalic acid solution at 80°C and pH=5 for 5 h. After immersion, the catalyst was filtered out and dried at 110°C for 10 h. The acid-treated catalyst was then washed with chloroform, filtered, and dried at 110°C for 4 h. The dried and cooled catalyst was then packed into a fixed-bed reactor. Under a N2 atmosphere, the reactor temperature was raised to 90°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a 10% hydrogen peroxide solution was introduced at a rate of 0.50 mL / min for 10 h. Subsequently, an N2 purge was introduced, and the regeneration temperature was raised to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h. Finally, an N2 purge was introduced, and the regeneration temperature was raised to 450°C at a rate of 5°C / min. The regeneration temperature stabilized for 0.5 h. After h, H2 at a flow rate of 0.4 mL / min was introduced for another 10 h. The regeneration pressure was atmospheric pressure. After catalyst regeneration, methanol amination reaction was carried out. The molar ratio of the reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹. -1 After 2 hours of reaction feed, samples were taken every 1 hour for gas chromatography analysis. Stability testing was performed after 300 hours of continuous operation. The results are as follows: Figure 1 As shown.

[0049] Comparative Example 1

[0050] The deactivated trimethylamine catalyst from Example 1 was loaded into a fixed-bed reactor. Under a N2 atmosphere, the reactor temperature was raised to 90°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, a 10% hydrogen peroxide solution was introduced at a rate of 0.50 mL / min for 10 h. Subsequently, an N2 purge line was introduced, and the regeneration temperature was raised to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h. Afterward, an N2 purge line was introduced, and the regeneration temperature was raised to 450°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, H2 was introduced at a flow rate of 0.4 mL / min for 10 h. The regeneration pressure was atmospheric pressure. After catalyst regeneration, a methanol amination reaction was carried out. The molar ratio of the reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹. -1 After 2 hours of reaction, samples were taken every 1 hour for gas chromatography analysis. The average value of the analysis data of 6 parallel samples was taken, and the results are shown in Table 2.

[0051] Comparative Example 2

[0052] The deactivated trimethylamine catalyst from Example 1 was immersed in a 2,2'-dithiodibenzoic acid solution at 80°C and pH=6 for 5 h. After immersion, the catalyst was filtered out and dried at 110°C for 10 h. The acid-treated catalyst was then washed with ethanol, filtered, and dried at 110°C for 4 h. The dried and cooled catalyst was then packed into a fixed-bed reactor. An N2 purge line was introduced, and the regeneration temperature was increased to 110°C at a rate of 5°C / min. After the regeneration temperature stabilized for 2 h, a 20% O3-N2 mixed gas was introduced at a rate of 0.6 mL / min for 20 h of regeneration. Then, an N2 purge line was introduced, and the regeneration temperature was increased to 450°C at a rate of 5°C / min. After the regeneration temperature stabilized for 0.5 h, H2 was introduced at a flow rate of 0.4 mL / min for 10 h. The regeneration pressure was atmospheric pressure. After catalyst regeneration, a methanol amination reaction was carried out. The molar ratio of the reactants was liquid ammonia:methanol = 2:1, the reaction pressure was 2 MPa, the vaporization temperature was 280℃, the reaction temperature was 400℃, and the liquid hourly space velocity was 1.3 h⁻¹. -1 After 2 hours of reaction, samples were taken every 1 hour for gas chromatography analysis. The average value of the analysis data of 6 parallel samples was taken, and the results are shown in Table 2.

[0053] Table 2. Effects of different regeneration methods on the reaction performance of metal-modified mordenite catalyst after regeneration

[0054]

[0055] In summary, this invention first uses organic acids to remove non-framework aluminum from the catalyst, then uses organic solvents to wash away residual organic acids and some carbon deposits, and finally uses a combination of low-temperature oxidation with a mixture of hydrogen peroxide and ozone-containing inert gas and hydrogen reduction to regenerate the metal-modified mordenite in situ. The catalyst regeneration method is simple and efficient, and the regenerated catalyst still maintains good reaction performance in the methanol amination reaction.

[0056] It should be noted that all modifications or substitutions made directly or indirectly by those skilled in the art based on the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A method for regenerating a metal-modified mordenite zeolite catalyst used in a methanol amination reaction, characterized in that, Includes the following steps: 1) The metal-modified mordenite catalyst with reduced activity was sequentially immersed in an organic acid solution, then filtered and dried. The organic acid solution was selected from one or more of 4-chloro-3-nitrobenzoic acid, p-nitrotoluene-o-sulfonic acid, 4-bromophthalic acid, and 2,2'-dithiodibenzoic acid. 2) The dried catalyst was washed with an organic solvent, then filtered and dried. 3) The dried and cooled catalyst is loaded into a fixed-bed reactor. The reactor temperature is first raised to 70–90°C under an inert atmosphere. After the temperature stabilizes, hydrogen peroxide solution is introduced for treatment for 10–16 h. The concentration of the hydrogen peroxide solution is 5%–20%. 4) Purge the pipeline with inert gas and raise the reactor temperature to 105-115°C. After the temperature stabilizes for 2 hours, continuously introduce an inert gas mixture containing ozone for 6-24 hours. 5) Purge the pipeline with inert gas and raise the reactor temperature to 400-550℃. After the temperature stabilizes for 0.5-1h, continuously introduce hydrogen gas for 6-20h to obtain the regenerated catalyst.

2. The method for regenerating the metal-modified mordenite zeolite catalyst used in the methanol amination reaction according to claim 1, characterized in that, The metal-modified mordenite catalyst is mordenite modified with alkaline earth metals and transition metals, wherein the mass of the alkaline earth metal element accounts for 20% to 60% of the mass of the mordenite; the mass of the transition metal element accounts for 1% to 5% of the mass of the mordenite; the silicon-to-aluminum ratio of the mordenite is 5 to 60; the alkaline earth metal element is selected from one or more of barium and calcium, and the transition metal element is selected from one or more of nickel, cobalt, copper, and zinc.

3. The method for regenerating the metal-modified mordenite zeolite catalyst used in the methanol amination reaction according to claim 1, characterized in that, The pH range of organic acid solutions is 4 to 6.

4. The method for regenerating the metal-modified mordenite zeolite catalyst used in the methanol amination reaction according to claim 1, characterized in that, The organic solvent is selected from one or more of ethanol, diethyl ether, and chloroform.

5. The method for regenerating the metal-modified mordenite zeolite catalyst used in the methanol amination reaction according to claim 1, characterized in that, The heating rate is 1–40 °C / min.

6. The method for regenerating the metal-modified mordenite zeolite catalyst used in the methanol amination reaction according to claim 5, characterized in that, The heating rate is 5–8 °C / min.

7. The method for regenerating the metal-modified mordenite zeolite catalyst used in the methanol amination reaction according to claim 1, characterized in that, The ozone concentration in the ozone-containing inert atmosphere is 3-50%; the inert atmosphere is one or a combination of two or more of argon, nitrogen, and helium.

8. A method for preparing methylamine by catalytic amination of methanol, characterized in that, Includes the following steps: S1. The metal-modified mordenite catalyst with reduced activity is regenerated according to the regeneration method described in any one of claims 1 to 7 to obtain the metal-modified mordenite catalyst. S2. A mixture of methanol and liquid ammonia is passed into a preheater for vaporization, and then into a fixed-bed reactor containing the metal-modified mordenite catalyst obtained in step S1, to react and obtain a mixture of different methylamines.

9. The method according to claim 8, characterized in that, The vaporization temperature is 200–300℃.

10. The method according to claim 8, characterized in that, The reaction temperature is 350–450℃, and the reaction pressure is 1–3 MPa.

11. The method according to claim 8, characterized in that, The molar ratio of liquid ammonia to methanol is 1.2 to 2:1.

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