CN116173895B - NMP adsorbent and preparation method thereof - Google Patents

Abstract

The invention provides an N-methylpyrrolidone (NMP) adsorbent and a preparation method thereof, wherein the NMP adsorbent comprises: a zeolite having a silicon-aluminum ratio of 3-45, and metal ions loaded on the zeolite; the loading amount of the metal ions is 0.5wt% to 16wt%. The NMP adsorbent of the invention has high adsorption efficiency and good adsorption effect for NMP, and reduces the desorption temperature of NMP, thereby reducing the influence of the high boiling point on the desorption performance, is conducive to the cyclic application of the adsorbent, and reduces the industrial cost.

Description

A kind of NMP adsorbent and preparation method thereof

Technical Field

The present invention relates to the technical field of adsorbents, and in particular to an NMP adsorbent and a preparation method thereof.

Background Art

N-methylpyrrolidone (NMP) is a large molecular substance (molecular formula is C ₅ H ₉ NO, molecular dynamics diameter 0.76nm, melting point -24.4℃, boiling point 202℃, flash point 95℃, dipole moment 4.09D, molecular weight 99, relative density 1.0260), with a slight ammonia smell, and can be miscible with water, alcohol, ether, ester, ketone, halogenated hydrocarbons, and aromatic hydrocarbons. It has the advantages of high flash point, low corrosiveness, high solubility, strong polarity, low viscosity, low volatility, high thermal stability and chemical stability.

NMP is expensive, but it is widely used in lithium battery production, medicine, pesticides, pigments, cleaning agents, insulation materials and other industries. At the same time, NMP can cause lesions in the central nervous system, vascular system, respiratory system and kidneys, posing a threat to people's health. The EU's NMP emission limit is 5mg/ ^m3 , and China's current NMP emission standard is 25mg/ ^m3 . As the country's requirements for volatile organic compounds (VOCs) emissions increase, the emission standards will continue to decrease in the future. Therefore, in recent years, NMP treatment technology has received widespread attention.

Adsorption is the most widely used VOCs capture technology at present. It has high maturity, simple operation process and relatively low economic cost. The technical core of the adsorption method lies in the development of high-performance adsorbents with high VOCs adsorption capacity, controllable desorption and easy regeneration. The quality of adsorption performance depends on the combined effect of adsorbent and adsorbate. Each VOCs has different physical and chemical properties, and the suitable adsorbent is also different. Therefore, for the purification of NMP, it is also necessary to develop high-performance NMP adsorbents.

There are three outstanding issues in the development of NMP adsorbents:

1) NMP has a large molecular size, with a kinetic diameter of 0.76nm. The pore size of commercial activated carbon is mainly distributed in the narrow micropore range of less than 0.7nm. The mismatch between NMP molecules and the pore configuration and pore size of the adsorbent will form a significant steric effect, affecting the adsorption performance;

2) The boiling point of NMP is 202°C, which is a high-boiling-point VOCs. When the regeneration temperature is lower than the boiling point of NMP, NMP is not easily desorbed, which affects the regeneration of the adsorbent, while the high desorption temperature is not suitable for industrial applications;

3) NMP has strong polarity, with a dipole moment of 4.09 D. In actual NMP waste gas, water vapor and NMP coexist, and water molecules, both polar molecules, can form competitive adsorption with NMP, reducing the adsorption capacity of the adsorbent for NMP.

In view of this, the present invention is proposed.

Summary of the invention

The first object of the present invention is to provide a NMP adsorbent, which improves the adsorption capacity of NMP, reduces the desorption temperature, and ensures a higher NMP adsorption amount by limiting the silicon-aluminum ratio of zeolite and modifying the zeolite with metal ions.

The second object of the present invention is to provide a method for preparing the above-mentioned NMP adsorbent, which is simple to operate and satisfies the loading amount of metal ions by controlling the ion exchange degree, thereby improving the competitive adsorption capacity of NMP and reducing the desorption energy consumption of NMP.

In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

The present invention provides an NMP adsorbent, comprising: a zeolite with a silicon-aluminum ratio of 3-45, and metal ions loaded on the zeolite;

The metal ion loading is 0.5 wt % to 16 wt % of the zeolite.

Preferably, the type of the zeolite is one of FAU type, MFI type, MOR type, BEA* type and STI type, or a mixture of several of them.

Preferably, the zeolite is a mixture of FAU and MFI, and the mass ratio of FAU to MFI is 3:1.

Preferably, the silicon-aluminum ratio of the zeolite is 3 to 15. More preferably, the silicon-aluminum ratio of the zeolite is 5 to 10. Further, the silicon-aluminum ratio of the zeolite is 9.2.

Preferably, when the zeolite is FAU, the silicon-aluminum ratio is 6-45, when the zeolite is MFI, the silicon-aluminum ratio is 9-40, when the zeolite is MOR, the silicon-aluminum ratio is 5-30, when the zeolite is BEA*, the silicon-aluminum ratio is 8-24, and when the zeolite is STI, the silicon-aluminum ratio is 3-15.

Preferably, the metal ion is any one or a combination of Cu, Fe, Zn, Na, Ca, Ba, K, and Ce.

Preferably, the metal ions loaded are of two types; the exchange degree of the first type of ions is 80% to 100%, and the exchange degree of the second type of ions is 1% to 50%;

Preferably, the metal ions and the exchange order are Ca and Cu, the ion exchange degree of Ca is 100%, and the ion exchange degree of Cu is 33%.

Preferably, there are three types of metal ions loaded, the exchange degree of the first type of ions is 80% to 100%, the exchange degree of the second type of ions is 30% to 78%, and the exchange degree of the third type of ions is 1% to 50%;

Preferably, the metal ions and the exchange order are Fe, Ca and Cu, the ion exchange degree of Fe is 100%, the ion exchange degree of Ca is 66%, and the ion exchange degree of Cu is 33%;

Preferably, the type of zeolite is a mixture of FAU and MFI, and the mass ratio of FAU to MFI is 3:1. The metal ions and the exchange order are Fe, Ca and Cu, the ion exchange degree of Fe is 100%, the ion exchange degree of Ca is 66%, and the ion exchange degree of Cu is 33%;

The NMP adsorbent of the present invention is to load metal ions on zeolite, and optimize the silicon-aluminum ratio of the zeolite and the type and ratio of specific metal ions to improve the adsorption effect of NMP. Although it is a common technology to load zeolite molecular sieves with metal ions to improve the adsorption effect, there are not many studies specifically on the adsorption performance of NMP by zeolite molecular sieves. In addition, due to the special properties of NMP mentioned above, the adsorption effect of general zeolite molecular sieves on NMP is not significant. Therefore, in order to improve the adsorption effect of NMP, the present invention optimizes various parameters of the zeolite molecular sieve to achieve a good adsorption effect.

Preferably, the calculation method of the metal ion loading is as follows:

According to the mass M of the original molecular sieve powder, the molecular mass m of the molecular sieve, the valence state S ₂ of the cations in the original molecular sieve powder, the relative atomic mass m ₂ , and the molar amount of the cations contained when they are monovalent:

The exchange degree of metal ions is Q, the valence state of metal ions is S ₁ , the relative atomic mass is m ₁ , and the mass of the metal ions exchanged is:

The mass of the exchanged cation is:

The ion loading is:

In the prior art, since water vapor and NMP coexist in NMP waste gas, water molecules and NMP, both polar molecules, can form competitive adsorption, reducing the adsorption capacity of the adsorbent for NMP. In addition, the mismatch between the NMP molecule and the adsorbent pore configuration and pore size will form a significant steric effect, affecting the adsorption performance; in addition, NMP is a high-boiling point VOCs. When the regeneration temperature is lower than the boiling point of NMP, NMP is not easy to be desorbed, affecting the regeneration of the adsorbent, and the high desorption temperature is not suitable for industrial applications. These have restricted the application of NMP adsorbents.

In order to solve the above technical problems, the present invention provides an NMP adsorbent, which improves the adsorption effect of NMP by limiting the silicon-aluminum ratio; by combining and applying zeolites and utilizing the different pore sizes of molecular sieves of different zeolites, the steric effect is prevented and the adsorption performance is improved; the zeolite is modified by metal ions to reduce the desorption temperature of NMP, thereby reducing the influence of the high boiling point on the desorption performance, which is beneficial to the cyclic application of the adsorbent and reduces the industrial cost.

The present invention also provides a method for preparing the above-mentioned NMP adsorbent, comprising:

The zeolite is subjected to ion exchange with a metal salt solution containing the metal ions, and the ion exchange is performed under a certain degree of control to meet the loading amount.

Preferably, the method for the first ion exchange is: when the zeolite is H-type, the exchange is performed by a volume impregnation method; when the zeolite is non-H-type, the exchange is performed by a liquid phase ion exchange method.

Preferably, when the number of the metal ions is two, if the ion valence of the second exchange is not lower than the ion valence of the first exchange, the liquid phase ion exchange method is used for exchange, otherwise, the solid phase ion exchange method is used for exchange.

Preferably, when the number of metal ions is three, if the zeolite type is FAU or BEA*, after the first ion exchange, the remaining two metal ions are exchanged in sequence with the zeolite after the previous ion exchange; if the zeolite type is MFI, MOR or STI, after the first ion exchange, the remaining two metal ions are configured into a mixed solution and then exchanged with the zeolite after the first ion exchange by a liquid phase ion exchange method.

Preferably, the equal volume impregnation method comprises the following steps:

The zeolite raw powder and the metal ion solution are mixed, and then dried by microwave flash evaporation. After drying, the temperature is increased to 300-550° C. at a rate of 5-20° C./min in a muffle furnace and kept at a constant temperature for 3-5 hours.

Preferably, the mixing of zeolite raw powder and metal ion solution comprises:

Take a certain mass of zeolite powder, add deionized water or distilled water drop by drop into the powder until the powder forms a paste-like non-Newtonian fluid, record the mass of the added water, and calculate the saturated water absorption per unit mass of zeolite powder;

Calculate the mass of metal salt required to modify a unit mass of zeolite raw powder according to the target ion loading rate;

Take a predetermined mass of raw powder, measure the same volume of deionized water or distilled water as the total water absorption, weigh the metal salt required to modify the predetermined mass of raw powder and dissolve it in the deionized water or distilled water, add the metal ion solution to the zeolite raw powder one by one, and stir until the mixture becomes a paste-like non-Newtonian fluid;

The above-mentioned paste-like non-Newtonian fluid is kneaded into a uniform cake shape.

Furthermore, the microwave flash drying temperature is 500-900W, and the time is 30-240s.

Preferably, the liquid phase ion exchange method comprises the following steps:

The zeolite raw powder is mixed with the metal ion solution, and dynamic ion exchange is performed in a magnetic stirrer with an oil bath. After the exchange, the zeolite raw powder is centrifuged and washed, and then dried in an oven. After drying, the temperature is increased to 100-200°C at 2-10°C/min in a muffle furnace, and the temperature is kept constant for 1-2 hours, and then the temperature is increased to 300-500°C at 2-10°C/min, and the temperature is kept constant for 2-4 hours.

Furthermore, the exchange temperature is 10°C to 100°C, and the exchange time is 0.5 to 3 hours;

Furthermore, the drying temperature is 40 to 90° C., and the drying time is 12 to 36 hours.

Preferably, the solid phase ion exchange method comprises the following steps:

Mix the zeolite molecular sieve to be ion exchanged with the metal salt required for the exchange, grind manually for 1 to 6 minutes, then heat up to 120 to 200°C at 2 to 10°C/min, keep constant temperature for 1 to 2 hours, then heat up to 300 to 500°C at 2 to 10°C/min, keep constant temperature for 2 to 4 hours, take out after cooling, centrifuge and wash, and place in an oven to dry.

Furthermore, the drying temperature is 50-90° C. and the drying time is 10-36 hours.

The preparation method of the present invention selects different exchange methods according to different zeolite types and ion types during ion exchange, in order to improve the loading effect of metal ions through a suitable exchange method; at the same time, when performing ion exchange, the heating rate during calcination is also controlled, because during calcination, the heating rate will affect the volatilization rate of water, and the migration of metal cations in the pores is achieved by the flow of water. By adjusting the heating rate, the metal can be loaded to the specified adsorption position, thereby improving the adsorption performance.

Compared with the prior art, the present invention has the following beneficial effects:

The NMP adsorbent of the invention has high adsorption efficiency and good adsorption effect for NMP, and reduces the desorption temperature of NMP, thereby reducing the influence of the high boiling point on the desorption performance, is beneficial to the recycling application of the adsorbent, and reduces the industrial cost.

BRIEF DESCRIPTION OF THE DRAWINGS

Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

FIG1 is an adsorption breakthrough curve of the NMP adsorbent provided in Example 1 of the present invention;

FIG2 is an adsorption breakthrough curve of the NMP adsorbent provided in Example 2 of the present invention;

FIG3 is an adsorption breakthrough curve of the NMP adsorbent provided in Example 3 of the present invention;

FIG4 is an adsorption breakthrough curve of the NMP adsorbent provided in Example 4 of the present invention;

FIG5 is an adsorption breakthrough curve of the NMP adsorbent provided in Example 14 of the present invention.

DETAILED DESCRIPTION

The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

Example 1

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 26.8 and put it into a beaker. At the same time, weigh 0.7232g of copper nitrate and dissolve it in 8.9ml of deionized water to prepare a Cu(NO ₃ ) ₂ ·H ₂ O solution with a concentration of 0.34mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a culture dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 900W for 90s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4 hours. The Cu ²⁺ exchange-modified adsorbent can be obtained.

Example 2

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 1.5770g of copper nitrate and dissolve it in 10.6ml of deionized water to prepare a Cu(NO ₃ ) ₂ ·H ₂ O solution with a concentration of 0.62mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a culture dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 900W for 100s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4 hours. The Cu ²⁺ exchange-modified adsorbent can be obtained.

Example 3

Take 5g of H-FAU molecular sieve with a silicon-aluminum ratio of 26.8, weigh 0.1970g of calcium nitrate and dissolve it in 3.9ml of deionized water to prepare a Ca(NO ₃ ) ₂ solution with a concentration of 0.31mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Place the colloidal mixture in a culture dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 900W for 80s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4 hours. You can get a Ca ²⁺ exchange-modified adsorbent.

Example 4

Take 7g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 1.2510g of zinc acetate and dissolve it in 7.4ml of deionized water to prepare a C ₄ H ₆ O ₄ Zn·2H ₂ O solution with a concentration of 0.77mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a culture dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 900W for 120s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4 hours. You can get a Zn ²⁺ exchange-modified adsorbent.

Example 5

Take 10g of MFI molecular sieve with a silicon-aluminum ratio of 25 and put it into a beaker. Weigh 0.696g of copper nitrate and dissolve it in 7.4ml of deionized water to prepare a Cu(NO ₃ ) ₂ ·H ₂ O solution with a concentration of 0.39mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a culture dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 900W for 120s until it is completely dry. Take it out and bake it in a muffle furnace at 10℃/min to 550℃ for 4 hours. The Cu ²⁺ exchange-modified adsorbent can be obtained.

Example 6

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 1.339g of calcium nitrate and dissolve it in 10.6ml of deionized water to prepare a Ca(NO ₃ ) ₂ solution with a concentration of 0.77mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a petri dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 900W for 100s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4 hours.

The molecular sieve obtained after the first exchange was subjected to dynamic ion exchange with 27 ml of 0.1 mol/L Cu(NO ₃ ) ₂ ·3H ₂ O in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 1 hour. The exchange was repeated until the exchange degree of Cu ²⁺ was 33%. After the exchange, the sieve was centrifuged, washed, and dried in an oven. The drying temperature was 90°C for 12 hours. Then the temperature was raised to 160°C in a muffle furnace at 5°C/min, kept constant for 1 hour, and then raised to 550°C at 5°C/min and calcined for 4 hours.

Example 7

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 1.18g of cerium nitrate and dissolve it in 10.6ml of deionized water to prepare a Ce(NO ₃ ) ₃ ·6H ₂ O solution with a concentration of 0.26mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a petri dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power for 100s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4 hours.

The molecular sieve obtained after the first exchange was subjected to dynamic ion exchange with 90 ml of Cu(NO ₃ ) ₂ ·3H ₂ O with a metal salt solubility of 0.05 mol/L in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 1 hour. After the exchange, the sieve was centrifuged, washed, and dried in an oven. The drying temperature was 80°C for 13 hours. Then, the temperature was raised to 160°C in a muffle furnace at 5°C/min, kept constant for 1 hour, and then raised to 550°C at 5°C/min for calcination for 4 hours.

Example 8

The specific operation method is the same as that of Example 6, except that the molecular sieve used is H-MFI type.

Example 9

The specific operation method is the same as that of Example 7, except that the molecular sieve used is H-MFI type.

Example 10

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 2.197g of ferric nitrate and dissolve it in 10.6ml of deionized water to prepare a Fe(NO ₃ ) ₃ ·9H ₂ O solution with a concentration of 0.51mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a petri dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a fixed power of 800W for 100s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4h.

Take 8.5g of the molecular sieve prepared above and 4g of Ca(NO ₃ ) ₂ , mix them manually for 5min, mix them evenly, place them in a muffle furnace, raise the temperature to 200℃ at 5℃/min, keep the temperature constant for 1h, and then raise the temperature to 500℃ at 5℃/min and calcine for 3h. After cooling, take out the reactant, wash it, and dry it in an oven. The drying temperature is 90℃ and the time is 20h.

The molecular sieves after the exchange were subjected to dynamic ion exchange with 40 ml of 0.1 mol/L Cu(NO ₃ ) ₂ ·3H ₂ O solution in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 2 h. The exchange was repeated twice. After the exchange, the zeolites were centrifuged, washed, and dried in an oven. The drying temperature was 90°C for 12 h. The temperature was then raised to 160°C at 5°C/min in a muffle furnace, kept constant for 1 h, and then raised to 500°C at 5°C/min and calcined for 3 h.

Embodiment 11

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 1.18g of cerium nitrate and dissolve it in 10.6ml of deionized water to prepare a Ce(NO ₃ ) ₃ ·6H ₂ O solution with a concentration of 0.26mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a petri dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a power of 800W for 100s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 3h.

Take 8g of the molecular sieve prepared above and 6g of Ca(NO ₃ ) ₂ , mix them manually for 4 minutes, mix them evenly, place them in a muffle furnace, raise the temperature to 200°C at 8°C/min, keep the temperature constant for 2 hours, and then raise the temperature to 500°C at 5°C/min and bake for 3 hours. After cooling, take out the reactants, wash them, and dry them in an oven. The drying temperature is 90°C and the time is 22 hours.

The molecular sieves after the exchange were subjected to dynamic ion exchange with 40 ml of 0.15 mol/L Cu(NO ₃ ) ₂ ·3H ₂ O solution in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 1.5 h. The exchange was repeated twice. After the exchange, the zeolites were centrifuged, washed, and dried in an oven. The drying temperature was 80°C for 12 h. The temperature was then raised to 160°C in a muffle furnace at 6°C/min, kept constant for 1 h, and then raised to 500°C at 6°C/min and calcined for 3 h.

Example 12

The specific preparation method is the same as that of Example 11, except that the zeolite molecular sieve is H-MFI with a silicon-aluminum ratio of 9.2.

Example 13

The specific preparation method is the same as that of Example 10, except that the zeolite molecular sieve is H-MFI with a silicon-aluminum ratio of 9.2.

Embodiment 14

The specific preparation method is the same as that of Example 13, except that the zeolite molecular sieve is a composite of FAU type and MFI type in a mass ratio of 3:1, and both zeolites are H type.

Embodiment 15

The specific preparation method is the same as that of Example 12, except that the zeolite molecular sieve is a composite of FAU type and MFI type in a mass ratio of 3:1, and both zeolites are H type.

Example 16

The specific preparation method is the same as that of Example 14, except that the zeolite molecular sieve is a composite of FAU type and MOR type in a mass ratio of 1:1, and both zeolites are H type.

Embodiment 17

The molecular sieve prepared in Example 14 was subjected to dynamic ion exchange with 80 ml of potassium nitrate solution with a metal salt solubility of 0.05 mol/L in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 1 hour. After the exchange, the sieve was centrifuged, washed, and dried in an oven. The drying temperature was 90°C for 12 hours. The temperature was then raised to 160°C in a muffle furnace at 4°C/min, kept constant for 1.5 hours, and then raised to 500°C at 4°C/min and calcined for 2 hours.

Embodiment 18

The specific preparation method is the same as that of Example 14, except that the silicon-to-aluminum ratio is 3.

Embodiment 19

The specific preparation method is the same as that of Example 14, except that the silicon-to-aluminum ratio is 45.

Embodiment 20

The specific preparation method is the same as that of Example 14, except that 2.197 g of ferric nitrate is added, the concentration of Fe(NO ₃ ) ₃ ·9H ₂ O solution is 0.51 mol/L; 6 g of calcium nitrate is added; and 30 ml of 0.1 mol/L Cu(NO ₃ ) ₂ ·3H ₂ O solution is used for exchange once.

Embodiment 21

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and put it into a beaker. Weigh 1.7912g of copper nitrate and dissolve it in 10.6ml of deionized water to prepare a Cu(NO ₃ ) ₂ ·H ₂ O solution with a concentration of 0.70mol/L. Use a pipette to add the prepared solution to the original powder one by one, and stir it continuously with a glass rod until the mixture becomes a non-Newtonian fluid. Put the colloidal mixture in a petri dish, twist it into a uniform cake with a spoon, put it into a microwave heater, and flash it at a power of 900W for 80s until it is completely dry. Take it out and bake it in a muffle furnace at 5℃/min to 550℃ for 4h.

Take 8.5g of the molecular sieve prepared above and 5.5g of Ca(NO ₃ ) ₂ , mix them manually for 5 minutes, mix them evenly, place them in a muffle furnace, raise the temperature to 200°C at 5°C/min, keep the temperature constant for 1 hour, and then raise the temperature to 500°C at 5°C/min and calcine for 3 hours. After cooling, take out the reactants, wash them, and dry them in an oven. The drying temperature is 90°C and the time is 21 hours.

The molecular sieves after the exchange were subjected to dynamic ion exchange with 70 ml of 0.05 mol/L Fe(NO ₃ ) ₃ ·9H ₂ O solution in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 2 h. The exchange was repeated twice. After the exchange, the sieves were centrifuged, washed, and dried in an oven. The drying temperature was 90°C for 12 h. The temperature was then raised to 160°C in a muffle furnace at 5°C/min, kept constant for 1 h, and then raised to 500°C at 5°C/min and calcined for 3 h.

Embodiment 22

The specific preparation method is the same as that of Example 14, except that the added zeolites are all Na type.

Take 10g of H-FAU molecular sieve with a silicon-aluminum ratio of 9.2 and 80ml of 0.05mol/L Fe(NO ₃ ) ₃ ·9H ₂ O solution in a magnetic stirrer with an oil bath for dynamic ion exchange. The exchange temperature is 50℃ and the exchange time is 2h. Repeat the exchange 4 times. After the exchange, centrifuge, wash and dry in an oven. The drying temperature is 90℃ for 12h. Then raise the temperature to 160℃ in a muffle furnace at 5℃/min, keep the temperature constant for 1h, and then raise the temperature to 500℃ at 5℃/min and roast for 3h.

Take 8.5g of the molecular sieve prepared above and 5.5g of Ca(NO ₃ ) ₂ , mix them manually for 5 minutes, mix them evenly, place them in a muffle furnace, raise the temperature to 200°C at 5°C/min, keep the temperature constant for 1 hour, and then raise the temperature to 450°C at 5°C/min for 3 hours. After cooling, take out the reactants, wash them, and dry them in an oven. The drying temperature is 90°C and the time is 21 hours.

The molecular sieves after the exchange were subjected to dynamic ion exchange with 40 ml of 0.1 mol/L Cu(NO ₃ ) ₂ ·3H ₂ O solution in a magnetic stirrer with an oil bath. The exchange temperature was 50°C and the exchange time was 2 h. The exchange was repeated twice. After the exchange, the zeolites were centrifuged, washed, and dried in an oven. The drying temperature was 90°C for 12 h. The temperature was then raised to 160°C at 5°C/min in a muffle furnace, kept constant for 1 h, and then raised to 500°C at 5°C/min and calcined for 3 h.

Experimental Example 1

The adsorbents of Examples 1-22 were subjected to NMP penetration experiments, and the adsorbents were evaluated by the penetration time and adsorption amount. Experimental conditions: NMP was generated at 20°C, the gas flow rate was 15mL/min, the heating temperature and adsorption temperature were both 30°C, the adsorbent particle size was 60-40 mesh, the adsorption column was a quartz tube with an outer diameter of 6mm and an inner diameter of 4mm, 40mg of adsorbent was loaded each time, and the penetration adsorption amount was counted. Among them, the adsorption penetration curves of Examples 1-5 are shown in Figures 1-5. The specific results are shown in Table 1 below:

Table 1 Experimental results

Experimental Example 2

Some of the adsorbents in the above-mentioned embodiments were subjected to NMP penetration experiments, and the competitive adsorption between the adsorbent and water was evaluated by the penetration time and adsorption amount. Experimental conditions: NMP was generated at 20°C, the gas flow rate was 15mL/min, the relative humidity of the gas flow was RH=50%, the heating temperature and the adsorption temperature were both 30°C, the adsorbent particle size was 60-40 mesh, the adsorption column was a quartz tube with an outer diameter of 6mm and an inner diameter of 4mm, 40mg of adsorbent was loaded each time, and the adsorption amount was counted. Among them, the adsorption curves of Examples 1-5 are shown in Figures 1-5. The specific results are shown in Table 2 below:

Table 2 Experimental results

It can be seen from Table 1 and Table 2 that the NMP adsorbents of the embodiments of the present invention are excellent in all indicators. Among them, the adsorption effect of embodiment 14 is the best.

By comparing Example 14 and Example 17, it can be seen that when four metal ions are exchanged, the adsorbent obtained has a worse adsorption effect on NMP than the adsorbent obtained by exchanging three metal ions. This is because the added fourth metal ion is not well adsorbed on the zeolite molecular sieve due to the limitation of the number of adsorption sites of the zeolite molecular sieve itself, and it also affects the loading amount of the three metal ions that have been exchanged. It can be seen that only when three metal ions are exchanged can the best adsorption effect be achieved.

By comparing Example 14, Example 13 and Example 10, it can be seen that the adsorption capacity of Example 14 is significantly better than that of the two single-component zeolites of Example 10 and Example 13, indicating that the zeolite combination of FAU and MFI can significantly improve the adsorption capacity for NMP.

By comparing Example 14 and Example 15, it can be seen that the adsorption effect of Example 14 is significantly better than that of Example 15, indicating that the optimal adsorption effect can be achieved only when the zeolite combination of FAU and MFI is used.

Although the present invention has been illustrated and described with specific embodiments, it will be appreciated that many other changes and modifications may be made without departing from the spirit and scope of the present invention. Therefore, it is intended to include all such changes and modifications within the scope of the present invention in the appended claims.

Claims (14)

1. An N-methylpyrrolidone adsorbent, characterized in that it comprises: a zeolite with a silicon-aluminum ratio of 3-45, and metal ions supported on the zeolite; The metal ion loading is 0.5wt% to 16wt% of the zeolite; The zeolite is a mixture of FAU and MFI, and the mass ratio of FAU to MFI is 3:1; The metal ion is any one or a combination of Cu, Fe, Zn, Na, Ca, Ba, K, and Ce. 2. The adsorbent according to claim 1, characterized in that the silicon-aluminum ratio of the zeolite is 3-15. 3. The adsorbent according to claim 2, characterized in that the silicon-aluminum ratio of the zeolite is 5-10. The adsorbent according to claim 3 , characterized in that the silicon-aluminum ratio is 9.2. 5. The adsorbent according to claim 1 is characterized in that there are two types of metal ions loaded; the exchange degree of the first ion is 80% to 100%, and the exchange degree of the second ion is 1% to 50%. 6. The adsorbent according to claim 5, characterized in that the metal ions are exchanged in the order of Ca and Cu, the ion exchange degree of Ca is 100%, and the ion exchange degree of Cu is 33%. 7. The adsorbent according to claim 1 is characterized in that there are three types of metal ions loaded, the exchange degree of the first ion is 80%~100%, the exchange degree of the second ion is 30%~78%, and the exchange degree of the third ion is 1%~50%. 8. The adsorbent according to claim 7, characterized in that the metal ions are exchanged in the order of Fe, Ca, and Cu, the ion exchange degree of Fe is 100%, the ion exchange degree of Ca is 66%, and the ion exchange degree of Cu is 33%. 9. A method for preparing the adsorbent according to any one of claims 1 to 8, characterized in that it comprises: The zeolite is subjected to ion exchange with a metal salt solution containing the metal ions, and the ion exchange is performed under a certain degree of control to meet the loading amount. 10. The preparation method according to claim 9, characterized in that the method of the first ion exchange is: when the zeolite is H-type, the exchange is carried out by an equal volume impregnation method; when the zeolite is not H-type, the exchange is carried out by a liquid phase ion exchange method. 11. The preparation method according to claim 9 is characterized in that when there are two types of metal ions, if the ion valence of the second exchange is not lower than the ion valence of the first exchange, the liquid phase ion exchange method is used for exchange, otherwise, the solid phase ion exchange method is used for exchange. 12. The preparation method according to claim 10, characterized in that the equal volume impregnation method comprises the following steps: The zeolite raw powder and the metal ion solution are mixed, and then dried by microwave flash evaporation. After drying, the temperature is increased to 300-550°C at a rate of 5-20°C/min in a muffle furnace and kept constant for 3-5 hours. 13. The preparation method according to claim 10, characterized in that the liquid phase ion exchange method comprises the following steps: The zeolite raw powder is mixed with the metal ion solution, centrifugally cleaned and dried, and then heated to 100-200°C at 2-10°C/min in a muffle furnace, kept at the constant temperature for 1-2 hours, and then heated to 300-500°C at 2-10°C/min, and kept at the constant temperature for 2-4 hours. 14. The preparation method according to claim 11, characterized in that the solid phase ion exchange method comprises the following steps: Mix the zeolite molecular sieve that needs to be ion exchanged with the metal salt required for the exchange. After mixing, heat it to 120-200°C at 2-10°C/min and keep it at a constant temperature for 1-2 hours. Then heat it to 300-500°C at 2-10°C/min and keep it at a constant temperature for 2-4 hours. After cooling, take it out for centrifugal cleaning and place it in an oven to dry.