A post-treatment method for regulating the specific surface area of ​​molecular sieves

Abstract

The present invention provides a post-processing method for regulating the specific surface area of ​​a molecular sieve, and belongs to the technical field of molecular sieves. The present invention first mixes a molecular sieve to be treated with a mixed alkali solution, stirs it, and uses the mixed alkali solution to construct a mesoporous structure of the molecular sieve to be treated, shortens the micropore channel, and increases the external specific surface area. The residual alkali is removed by washing to obtain an alkali-treated molecular sieve, and an ammonium salt aqueous solution is exchanged to remove the residual Na in the molecular sieve framework, and the residual ammonium radical is removed by roasting to achieve the regulation of the molecular sieve specific surface area, and obtains a hydrogen-type molecular sieve. The method provided by the present invention can increase the specific surface area of ​​the molecular sieve while maintaining the original skeleton structure and high crystallinity of the molecular sieve, and is simple to operate, low in cost, and suitable for large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieves, and in particular to a post-processing method for regulating the specific surface area of ​​molecular sieves. Background Art

[0002] The deactivation of molecular sieve catalysts is mainly due to the coverage of acid sites by carbon deposits on the surface and the blockage of pores. In addition, the generation of macromolecular compounds in the pores will also cause pore blockage. Improving its pore structure and acid property distribution has become an effective way to solve these problems. At present, the industry usually uses a certain concentration of alkali to treat molecular sieves, which can achieve the purpose of introducing mesopores and increasing the carbon content of the molecular sieve pores, thereby delaying the deactivation of the catalyst due to carbon deposition.

[0003] Patent CN109835914A discloses a method of first introducing aluminum elements into a molecular sieve by heat treatment, and then performing alkali treatment, thereby regulating the mesopore pore size of the synthesized molecular sieve. Patent CN115010143A discloses a method of preparing a directing agent by alkali treatment and roasting of a ZSM-5 molecular sieve, and then mixing it with an aluminum source, a silicon source, etc. to perform hydrothermal treatment to synthesize a precursor, and finally filtering, washing, and secondary roasting to obtain a high-performance molecular sieve. Patent CN104724722A discloses a method of introducing a fluorine-containing substance into an alkaline medium, thereby regulating the secondary pore structure of the molecular sieve. However, the above-mentioned methods for synthesizing mesoporous molecular sieves are relatively complicated. While using a high-concentration alkali solution to obtain a high-specific surface area molecular sieve, it also causes a large amount of dissolution of the molecular sieve and the collapse of the pore structure, which ultimately leads to a significant decrease in the crystallinity of the molecular sieve, so that the performance and application of the molecular sieve are limited. Therefore, providing a post-processing method for improving the specific surface area of ​​the molecular sieve while maintaining the original skeleton structure and high crystallinity of the molecular sieve is a problem that the prior art urgently needs to solve. Summary of the invention

[0004] The object of the present invention is to provide a post-treatment method for regulating the specific surface area of ​​a molecular sieve. The method provided by the present invention can increase the specific surface area of ​​the molecular sieve while maintaining the original skeleton structure and high crystallinity of the molecular sieve.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a post-treatment method for regulating the specific surface area of ​​a molecular sieve, comprising the following steps:

[0007] (1) mixing the molecular sieve to be treated and the mixed alkali solution, stirring, filtering and washing in sequence to obtain the alkali-treated molecular sieve;

[0008] (2) exchanging the molecular sieve treated with alkali obtained in step (1) with an ammonium salt aqueous solution and calcining the molecular sieve in turn to adjust the specific surface area of ​​the molecular sieve and obtain a hydrogen-type molecular sieve.

[0009] Preferably, the molecular sieve to be treated in step (1) is at least one of ZSM-1, ZSM-35 and ZSM-11.

[0010] Preferably, the silicon-aluminum ratio of the molecular sieve to be treated in step (1) is 15 to 100, and the Na 2 The content of O is 0 to 3.5 wt%.

[0011] Preferably, in step (1), the mass ratio of the mixed alkaline solution to the molecular sieve to be treated is (5-30):1.

[0012] Preferably, the mixed alkaline solution in step (1) is a mixed solution containing a strong base and a weak base, and the mass ratio of the strong base to the weak base in the mixed alkaline solution is (50-200):1.

[0013] Preferably, the strong base is at least one of NaOH and KOH, and the weak base is carbonate, sulfate, NH 3 ·H 2 At least one of O.

[0014] Preferably, the ammonium salt in the ammonium salt aqueous solution in step (2) is one of ammonium carbonate, ammonium chloride and ammonium sulfate; and the concentration of the ammonium salt in the ammonium salt aqueous solution is 3 to 0.1 mol / L.

[0015] Preferably, the mass ratio of the aqueous ammonium salt solution in step (2) to the molecular sieve to be treated in step (1) is (1-10):1.

[0016] Preferably, the temperature for exchanging the ammonium salt aqueous solution in step (2) is 30 to 60° C., and the time for exchanging the ammonium salt aqueous solution is 2 to 6 hours.

[0017] Preferably, the calcination temperature in step (2) is 500-600° C., and the calcination time is 2-6 hours.

[0018] The present invention provides a post-processing method for regulating the specific surface area of ​​a molecular sieve. First, after mixing a molecular sieve to be treated and a mixed alkali solution, stirring is performed, and the molecular sieve to be treated is mesoporously constructed using the mixed alkali solution, the micropore channel is shortened, and the external specific surface area is increased. The residual alkali is removed by washing to obtain an alkali-treated molecular sieve, and an ammonium salt aqueous solution is exchanged to remove the residual Na in the molecular sieve framework, and the residual ammonium radical is removed by roasting to achieve the regulation of the molecular sieve specific surface area, and a hydrogen-type molecular sieve is obtained. The method provided by the present invention can improve the specific surface area of ​​the molecular sieve while maintaining the original skeleton structure and higher crystallinity of the molecular sieve, and is simple to operate, low in cost, and suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a SEM image of the ZSM-5 molecular sieve to be treated in Example 1 of the present invention;

[0020] Figure 2 This is a SEM image of the alkali-treated molecular sieve obtained after mixed alkali treatment in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The present invention provides a post-treatment method for regulating the specific surface area of ​​a molecular sieve, comprising the following steps:

[0022] (1) mixing the molecular sieve to be treated and the mixed alkali solution, stirring, filtering and washing in sequence to obtain the alkali-treated molecular sieve;

[0023] (2) exchanging the molecular sieve treated with alkali obtained in step (1) with an ammonium salt aqueous solution and calcining the molecular sieve in turn to adjust the specific surface area of ​​the molecular sieve and obtain a hydrogen-type molecular sieve.

[0024] In the present invention, unless otherwise specified, the raw materials used are conventional commercial products in the art.

[0025] The present invention mixes the molecular sieve to be treated with the mixed alkali solution, and then stirs, filters and washes the mixture in sequence to obtain the alkali-treated molecular sieve.

[0026] In the present invention, the molecular sieve to be treated is preferably at least one of ZSM-1, ZSM-35, and ZSM-11. In the present invention, the silicon-aluminum ratio of the molecular sieve to be treated is preferably 15 to 100, and the Na 2 The content of O is preferably 0 to 3.5 wt%.

[0027] In the present invention, the mass ratio of the mixed alkali solution to the molecular sieve to be treated is preferably (5-30) g:1 g. The present invention controls the ratio of the mixed alkali solution to the molecular sieve to be treated within the above range to regulate the treatment capacity of the mixed alkali solution on the molecular sieve, thereby regulating the specific surface area of ​​the molecular sieve.

[0028] In the present invention, the mixed alkali solution is preferably a mixed solution containing a strong base and a weak base, and the mass ratio of the strong base to the weak base in the mixed alkali solution is preferably (50-200): 1. The present invention controls the ratio of the strong base to the weak base in the mixed alkali solution within the above range to regulate the processing capacity of the mixed alkali solution on the molecular sieve, thereby regulating the specific surface area and crystallinity of the molecular sieve.

[0029] In the present invention, the strong base is preferably at least one of NaOH and KOH, and the weak base is preferably carbonate, sulfate, NH 3 ·H 2 At least one of O. In the present invention, the concentration of the strong alkali solution in the mixed alkali solution is preferably 0.01 to 2 mol / L; the concentration of the weak alkali solution in the mixed alkali solution is preferably 0.05 to 2 mol / L.

[0030] In the present invention, the stirring temperature is preferably 50-90°C, more preferably 55-85°C; the stirring time is preferably 0.5-3h. The present invention controls the stirring temperature and time within the above range to regulate the processing capacity of the mixed alkaline solution on the molecular sieve, thereby regulating the specific surface area of ​​the molecular sieve.

[0031] The present invention has no particular limitation on the filtering method, as long as solid-liquid separation is achieved. In the present invention, the washing is preferably performed by washing with deionized water until neutral.

[0032] After obtaining the alkali-treated molecular sieve, the present invention sequentially performs ammonium salt aqueous solution exchange and calcination on the alkali-treated molecular sieve to achieve regulation of the specific surface area of ​​the molecular sieve and obtain a hydrogen-type molecular sieve.

[0033] In the present invention, the ammonium salt in the ammonium salt aqueous solution is preferably one of ammonium carbonate, ammonium chloride and ammonium sulfate; the concentration of the ammonium salt in the ammonium salt aqueous solution is preferably 3-0.1 mol / L. In the present invention, the mass ratio of the ammonium salt aqueous solution to the molecular sieve to be treated is (1-10):1. The present invention controls the concentration of the strong base and the weak base within the above range to regulate the treatment capacity of the mixed alkaline solution on the molecular sieve, thereby regulating the specific surface area of ​​the molecular sieve.

[0034] In the present invention, the ammonium salt aqueous solution exchange is preferably carried out under stirring. In the present invention, the temperature of the ammonium salt aqueous solution exchange is preferably 30 to 60° C., and the time of the ammonium salt aqueous solution exchange is preferably 2 to 6 hours. The present invention controls the temperature and time of the ammonium salt aqueous solution exchange within the above range to ensure the exchange efficiency and optimize the exchange product quality.

[0035] After the exchange of the ammonium salt aqueous solution is completed, the present invention sequentially filters, washes and dries the product of the exchange of the ammonium salt aqueous solution to obtain a dry product.

[0036] The present invention has no special restrictions on the filtering and washing methods, and the technical solutions known in the art can be used. In the present invention, the drying temperature is preferably 100 to 140° C., and the drying time is preferably 10 to 14 hours. The present invention removes residual reagents by drying.

[0037] After obtaining the dried product, the present invention calcines the dried product to obtain a hydrogen-type molecular sieve. In the present invention, the calcination temperature is preferably 500-600°C, more preferably 550°C; the calcination time is preferably 2-6h, more preferably 3-5h. The present invention controls the calcination temperature and time within the above range to remove residues and improve the uniformity and stability of the molecular sieve.

[0038] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0041] (1) Take 15 g ZSM-5 molecular sieve (Si / Al=35, Na 2 O content <3wt%) was added to 150g of 0.8mol / LNaOH and 0.1mol / LK 2 CO 3 The mixture was placed in a mixed alkali solution and magnetically stirred at 65°C for 1 hour, and then filtered and washed with deionized water until neutral to obtain an alkali-treated molecular sieve;

[0042] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 10g:1g;

[0043] The mass ratio of the strong base to the weak base in the mixed alkaline solution is 200g:1g;

[0044] (2) The alkali-treated molecular sieve obtained in step (1) is added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1g:4g, and magnetically stirred at 45°C for 3h, and then filtered and washed in sequence, dried at 120°C for 12h, and then calcined in a muffle furnace at 550°C for 4h to achieve the regulation of the specific surface area of ​​the molecular sieve, thereby obtaining a hydrogen-type molecular sieve, which is recorded as sample A.

[0045] Figure 1 is a SEM image of the ZSM-5 molecular sieve to be treated in Example 1, Figure 2 This is a SEM image of the alkali-treated molecular sieve obtained after mixed alkali treatment in Example 1. Figure 1 and Figure 2 By comparison, compared with the ZSM-5 molecular sieve to be treated, the surface of the ZSM-5 molecular sieve particles after the mixed alkali treatment began to become blurred and uneven, and the particles began to adhere and agglomerate.

[0046] Comparative Example 1

[0047] A method for treating molecular sieves, comprising the steps of:

[0048] Take 10g ZSM-5 molecular sieve (Si / Al=30, Na 2 O content <3wt%) was added to 100mL of 0.8mol / LNaOH solution, magnetically stirred at 60°C for 30min, filtered and washed with deionized water to neutrality, and then the alkali-treated molecular sieve was added to 6% ammonium nitrate solution with a solid-liquid ratio of 1g:4g, magnetically stirred at 45°C for 3h, then filtered and washed, dried at 120°C for 12h, and then calcined in a muffle furnace at 550°C for 4h to obtain the treated molecular sieve, which was recorded as Comparative A.

[0049] Example 2

[0050] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0051] (1) Take 10 g ZSM-5 molecular sieve (Si / Al=30, Na 2 O content <3wt%) was added to 100mL containing 0.8mol / LNaOH and 0.1mol / LNa 2 CO 3 The mixture was placed in a mixed alkali solution and magnetically stirred at 60°C for 30 minutes, and then filtered and washed with deionized water until neutral to obtain an alkali-treated molecular sieve;

[0052] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 10g:1g;

[0053] The mass ratio of the strong base to the weak base in the mixed alkaline solution is 175g:1g;

[0054] (2) The alkali-treated molecular sieve obtained in step (1) was added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1 g:4 g, and magnetically stirred at 45°C for 3 h, and then filtered and washed in sequence, dried at 120°C for 12 h, and then calcined in a muffle furnace at 550°C for 4 h to achieve the regulation of the specific surface area of ​​the molecular sieve, thereby obtaining a hydrogen-type molecular sieve, which was recorded as sample B.

[0055] Example 3

[0056] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0057] (1) Take 10 g ZSM-5 molecular sieve (Si / Al=50, Na 2 O content <3wt%) was added to a solution containing 240mL of a mixed alkali solution of 0.5mol / LNaOH and 10mol / L ammonia water, and magnetically stirred at 70°C for 1.5h, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0058] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 24g:1g;

[0059] The mass ratio of the strong base to the weak base in the mixed alkaline solution is 150g:1g;

[0060] (2) The alkali-treated molecular sieve obtained in step (1) is added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1 g:4 g, and magnetically stirred at 45°C for 3 h, and then filtered and washed in sequence, dried at 120°C for 12 h, and then calcined in a muffle furnace at 550°C for 4 h to achieve the regulation of the molecular sieve specific surface area, thereby obtaining a hydrogen-type molecular sieve, which is recorded as sample C.

[0061] Example 4

[0062] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0063] (1) Take 32g ZSM-5 molecular sieve (Si / Al=25, Na 2 O content <3wt%) was added to a solution containing 450mL of a mixed alkali solution of 0.2mol / LNaOH and 16mol / L ammonia water, and magnetically stirred at 80°C for 1h, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0064] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 14g:1g;

[0065] The mass ratio of the strong base to the weak base in the mixed alkaline solution is 150g:1g;

[0066] (2) The alkali-treated molecular sieve obtained in step (1) was added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1:4, and magnetically stirred at 45°C for 3 hours, and then filtered and washed in sequence, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours to achieve the regulation of the specific surface area of ​​the molecular sieve, thereby obtaining a hydrogen-type molecular sieve, which was recorded as sample D.

[0067] Example 5

[0068] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0069] (1) Take 20 g ZSM-5 molecular sieve (Si / Al=35, Na 2 O content <3wt%) was added to a solution containing 240mL of a mixed alkali solution of 0.5mol / LNaOH and 17.1mol / L ammonia water, and magnetically stirred at 60°C for 60min, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0070] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 12g:1g;

[0071] The ratio of strong base to weak base in the mixed alkaline solution is 130g:1g;

[0072] (2) The alkali-treated molecular sieve obtained in step (1) was added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1 g:4 g, and magnetically stirred at 45°C for 3 h, and then filtered and washed in sequence, dried at 120°C for 12 h, and then calcined in a muffle furnace at 550°C for 4 h to achieve the regulation of the specific surface area of ​​the molecular sieve, thereby obtaining a hydrogen-type molecular sieve, which was recorded as sample E.

[0073] Example 6

[0074] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0075] (1) Take 17 g ZSM-5 molecular sieve (Si / Al=30, Na 2 O content <3wt%) was added to a solution containing 170mL of a mixed alkali solution of 0.5mol / LNaOH and 24mol / L ammonia water, and magnetically stirred at 55°C for 1h, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0076] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 10g:1g;

[0077] The ratio of strong base to weak base in the mixed alkaline solution is 130g:1g;

[0078] (2) The alkali-treated molecular sieve obtained in step (1) is added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1 g:4 g, and magnetically stirred at 45°C for 3 h, and then filtered and washed in sequence, dried at 120°C for 12 h, and then calcined in a muffle furnace at 550°C for 4 h to achieve the regulation of the molecular sieve specific surface area, thereby obtaining a hydrogen-type molecular sieve, which is recorded as sample F.

[0079] Example 7

[0080] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0081] (1) Take 10 g ZSM-5 molecular sieve (Si / Al=40, Na 2 O content <3wt%) was added to 200mL containing 0.2mol / L NaOH and 0.15mol / L K 2 CO 3 The solution was stirred magnetically at 75°C for 2 hours in a mixed alkali solution. Then, the solution was filtered and washed with deionized water until neutral to obtain an alkali-treated molecular sieve.

[0082] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 20g:1g;

[0083] The ratio of strong base to weak base in the mixed alkaline solution is 100g:1g;

[0084] (2) The alkali-treated molecular sieve obtained in step (1) is added to a 6% ammonium nitrate solution with a solid-liquid ratio of 1 g:4 g, and magnetically stirred at 45°C for 3 h, and then filtered and washed in sequence, dried at 120°C for 12 h, and then calcined in a muffle furnace at 550°C for 4 h to achieve the regulation of the specific surface area of ​​the molecular sieve, thereby obtaining a hydrogen-type molecular sieve, which is recorded as sample G.

[0085] Example 8

[0086] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0087] (1) Take 13 g ZSM-5 molecular sieve (Si / Al=20, Na 2 O content <3wt%) was added to a solution containing 400mL of a mixed alkali solution of 0.3mol / LNaOH and 23mol / L ammonia water, and magnetically stirred at 75°C for 1h, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0088] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 30g:1g;

[0089] The ratio of strong base to weak base in the mixed alkaline solution is 50g:1g;

[0090] (2) adding the alkali-treated molecular sieve obtained in step (1) to a 6% ammonium nitrate solution at a solid-liquid ratio of 1 g:4 g, magnetically stirring at 45° C. for 3 h, filtering and washing in sequence, drying at 120° C. for 12 h, and then calcining in a muffle furnace at 550° C. for 4 h to achieve the control of the molecular sieve specific surface area and obtain a hydrogen-type molecular sieve.

[0091] Example 9

[0092] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0093] (1) Take 15 g ZSM-5 molecular sieve (Si / Al=20, Na 2 O content <3wt%) was added to a solution containing 150mL of a mixed alkali solution of 0.4mol / LNaOH and 24mol / L ammonia water, and magnetically stirred at 70°C for 1.5h, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0094] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 10g:1g;

[0095] The ratio of strong base to weak base in the mixed alkaline solution is 100g:1g;

[0096] (2) adding the alkali-treated molecular sieve obtained in step (1) to a 6% ammonium nitrate solution at a solid-liquid ratio of 1 g:4 g, magnetically stirring at 45° C. for 3 h, filtering and washing in sequence, drying at 120° C. for 12 h, and then calcining in a muffle furnace at 550° C. for 4 h to achieve the control of the molecular sieve specific surface area and obtain a hydrogen-type molecular sieve.

[0097] Example 10

[0098] A post-treatment method for regulating the specific surface area of ​​a molecular sieve comprises the following steps:

[0099] (1) Take 30 g ZSM-5 molecular sieve (Si / Al=50, Na 2 O content <3wt%) was added to a solution containing 200mL of a mixed alkali solution of 0.2mol / LNaOH and 15.7mol / L ammonia water, and magnetically stirred at 65°C for 0.5h, and then filtered and washed with deionized water to neutrality to obtain an alkali-treated molecular sieve;

[0100] The mass ratio of the mixed alkali solution to the ZSM-5 molecular sieve to be treated is 6g:1g;

[0101] The ratio of strong base to weak base in the mixed alkaline solution is 50g:1g;

[0102] (2) adding the alkali-treated molecular sieve obtained in step (1) to a 6% ammonium nitrate solution at a solid-liquid ratio of 1 g:4 g, magnetically stirring at 45° C. for 3 h, filtering and washing in sequence, drying at 120° C. for 12 h, and then calcining in a muffle furnace at 550° C. for 4 h to achieve the control of the molecular sieve specific surface area and obtain a hydrogen-type molecular sieve.

[0103] The structures and performance data of the molecular sieves to be treated and the corresponding molecular sieves prepared in Examples 1 to 7 and Comparative Example 1 are shown in Tables 1 and 2.

[0104] In Tables 1 and 2, the initial Si / Al, initial specific surface area and initial crystallinity are the data of the molecular sieve to be treated;

[0105] Table 1 Structure and properties of the molecular sieves to be treated and the corresponding molecular sieves prepared in Examples 1 to 3 and Comparative Example 1

[0106]

[0107]

[0108] Table 2 Structure and properties of the molecular sieves to be treated and the corresponding molecular sieves prepared in Examples 4 to 7

[0109]

[0110]

[0111] In summary, (1) the data of sample A and comparison A show that the molecular sieve treated with the mixed alkali solution has a higher crystallinity, proving that the weak alkali solution in the mixed alkali can protect the molecular sieve framework, thereby maintaining a high crystallinity of the molecular sieve; (2) changing the mass ratio and concentration of the strong and weak alkali in the mixed alkali solution can regulate the specific surface area and crystallinity of the molecular sieve. Increasing the mass of the strong alkali is conducive to increasing the specific surface area, and increasing the mass of the weak alkali is conducive to improving the crystallinity.

[0112] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A post-treatment method for regulating the specific surface area of ​​a molecular sieve, characterized in that: The following steps are involved: (1) mixing the molecular sieve to be treated and the mixed alkali solution, stirring, filtering and washing in sequence to obtain the alkali-treated molecular sieve; (2) exchanging the molecular sieve treated with alkali obtained in step (1) with an ammonium salt aqueous solution and calcining the molecular sieve in turn to adjust the specific surface area of ​​the molecular sieve and obtain a hydrogen-type molecular sieve.

2. The post-processing method according to claim 1, characterized in that: In the step (1), the molecular sieve to be treated is at least one of ZSM-1, ZSM-35 and ZSM-11.

3. The post-processing method according to claim 1 or 2, characterized in that: In the step (1), the silicon-aluminum ratio of the molecular sieve to be treated is 15-100, and the content of Na2O in the molecular sieve to be treated is 0-3.5wt%.

4. The post-processing method according to claim 1, characterized in that: In the step (1), the mass ratio of the mixed alkaline solution to the molecular sieve to be treated is (5-30):

1.

5. The post-processing method according to claim 1, characterized in that: The mixed alkali solution in step (1) is a mixed solution containing a strong alkali and a weak alkali, and the mass ratio of the strong alkali to the weak alkali in the mixed alkali solution is (50-200):

1.

6. The post-processing method according to claim 5, characterized in that: The strong base is at least one of NaOH and KOH, and the weak base is at least one of carbonate, sulfate, and NH3·H2O.

7. The post-processing method according to claim 1, characterized in that: The ammonium salt in the ammonium salt aqueous solution in step (2) is one of ammonium carbonate, ammonium chloride and ammonium sulfate; and the concentration of the ammonium salt in the ammonium salt aqueous solution is 3 to 0.1 mol / L.

8. The post-processing method according to claim 1 or 7, characterized in that: The mass ratio of the aqueous ammonium salt solution in step (2) to the molecular sieve to be treated in step (1) is (1-10):

1.

9. The post-processing method according to claim 1, characterized in that: The temperature for exchanging the aqueous ammonium salt solution in step (2) is 30 to 60° C., and the time for exchanging the aqueous ammonium salt solution is 2 to 6 hours.

10. The post-processing method according to claim 1, characterized in that: The calcination temperature in step (2) is 500-600° C., and the calcination time is 2-6 hours.

Images