阅读说明：本技术 测定小孔笼结构sapo分子筛酸性的方法 (Method for measuring acidity of SAPO molecular sieve with small-hole cage structure ) 是由 张雯娜 孙毯毯 徐舒涛 魏迎旭 刘中民 桑石云 于 2019-03-25 设计创作，主要内容包括：本申请公开了一种测定小孔笼结构SAPO分子筛酸性的方法,包括：将碱性探针分子与小孔笼结构SAPO分子筛的笼中酸性位接触,表征,得到所述小孔笼结构SAPO分子筛的酸性信息；其中,所述碱性探针分子的动力学直径大于所述小孔笼结构SAPO分子筛的孔口孔径。本申请中所述方法解决了以往大体积碱性探针分子无法进入小孔分子筛笼中与酸位接触这一难题。(The application discloses a method for measuring acidity of a SAPO molecular sieve with a small-pore cage structure, which comprises the following steps: contacting alkaline probe molecules with acid sites in cages of the SAPO molecular sieves with the small-hole cage structures, and representing to obtain acid information of the SAPO molecular sieves with the small-hole cage structures; wherein the kinetic diameter of the alkaline probe molecule is larger than the aperture of the pore opening of the SAPO molecular sieve with the small pore cage structure. The method solves the problem that the prior large-volume alkaline probe molecules cannot enter a small-hole molecular sieve cage to contact with acid sites.)

1. A method for measuring the acidity of a SAPO molecular sieve with a small-pore cage structure is characterized by comprising the following steps:

contacting alkaline probe molecules with acid sites in cages of the SAPO molecular sieves with the small-hole cage structures, and representing to obtain acid information of the SAPO molecular sieves with the small-hole cage structures;

wherein the kinetic diameter of the alkaline probe molecule is larger than the aperture of the pore opening of the SAPO molecular sieve with the small pore cage structure.

2. The method of claim 1, wherein the small pore cage structure SAPO molecular sieve is selected from at least one of SAPO-34 molecular sieve, SAPO-44 molecular sieve, SAPO-18 molecular sieve, DNL-6 molecular sieve, SAPO-35 molecular sieve, SAPO-56 molecular sieve, SAPO-17 molecular sieve;

the alkaline probe molecule is selected from at least one of phosphine-containing organic alkaline molecules;

preferably, the basic probe molecule is selected from at least one of trialkylphosphines;

preferably, the basic probe molecule is selected from at least one of trimethylphosphine, triethylphosphine, tripropylphosphine, tributylphosphine, and tripentylphosphine;

the characterization is a solid nuclear magnetic resonance characterization.

3. The method according to claim 1, characterized in that it comprises: contacting alkaline probe molecules with acid sites of the SAPO molecular sieves with the small-hole cage structures through an auxiliary agent, removing the auxiliary agent, and representing to obtain acid information of the SAPO molecular sieves with the small-hole cage structures;

preferably, the adjuvant is selected from at least one of carbon dioxide, water, hydrogen chloride, hydrogen fluoride, ammonium fluoride.

4. The method of claim 3, wherein the method comprises:

(1) heating SAPO molecular sieve with small-hole cage structure under vacuum condition¹Obtaining a precursor I;

(2) heating the mixture containing the alkaline probe molecules, the auxiliary agent and the precursor I under a sealed condition²And removing the auxiliary agent to obtain a precursor II, and characterizing to obtain the acidity information of the SAPO molecular sieve with the small-pore cage structure.

5. The method of claim 4, wherein the heating in step (1)¹The conditions of (a) are as follows: heating of¹The temperature of (A) is 300-600 ℃; heating of¹The time is 1-48 h;

preferably, the heating is¹The temperature of (a) is 400-550 ℃.

6. The method of claim 4, wherein the SAPO molecular sieve with the small pore cage structure in step (1) is treated to remove at least a portion of the template before use.

7. The method according to claim 4, wherein the molar ratio of the basic probe molecule to the adjuvant in step (2) is 0.01 to 100;

the molar weight of the alkaline probe molecules is 0.01-100 times of the Br phi nsted acid content in the precursor I;

the heating²The conditions of (a) are as follows: heating of²At a temperature of 30 to 600 ℃, and heating²The time is 0.1-100 h;

preferably, the heating is²At a temperature of 100 to 350 ℃, and heating²The time is 0.1-12 h.

8. The method of claim 4, wherein the method of removing the auxiliary agent comprises: heating under vacuum³；

Preferably, the heating is under vacuum conditions³The conditions of (a) are as follows: 20 to 300 ℃.

9. The method of claim 4, wherein the method comprises:

1) roasting the SAPO molecular sieve with the small-hole cage structure, and heating to 300-600 ℃ under a vacuum-pumping condition to obtain a precursor I; the SAPO molecular sieve with the small-hole cage structure is a molecular sieve for removing part of the template agent and/or a molecular sieve for removing all the template agent;

2) introducing alkaline probe molecules and an auxiliary agent into the device filled with the precursor I in the step 1), sealing, and heating to obtain a precursor II;

3) and (3) heating the precursor II prepared in the step 2) under a vacuum condition to remove the auxiliary agent and the physically adsorbed alkaline probe molecules, obtaining a sample enriched with the alkaline probe molecules in the molecular sieve cage, and performing solid nuclear magnetic characterization to obtain the acidity information of the molecular sieve.

10. The method of any one of claims 1 to 9 applied to at least one of characterization of molecular sieve acid strength, characterization of molecular sieve acidic species, and characterization of molecular sieve acidic site distribution.

Technical Field

The application relates to a method for measuring acidity of a SAPO molecular sieve with a small-pore cage structure, belonging to the field of solid acid characterization.

Background

At present, various methods for characterizing the acidity of solid acid exist, and the method is mainly a Hammett indicator method in the early stage and is widely applied. However, with the progress and development of analytical instruments, the solid acid characterization method has made a long-term progress, and the indicator method is gradually replaced by the 20 th century and the 70 th late, and at present, the solid acid characterization method mainly comprises: adsorption microcalorimetry, probe molecule adsorption-temperature programmed thermal desorption (TPD) method, probe molecule adsorption infrared spectroscopy (IR) method, etc. These methods all have significant disadvantages, such as: the adsorption microcalorimetry procedure and the temperature rising desorption (TPD) method cannot distinguish the type of acid (B acid or L acid) and only can give the related information of the acid amount and the acid strength; while the probe molecular adsorption infrared spectroscopy (IR) method can distinguish the types of acids well, the method is difficult to be used for quantifying the amount of molecular acids due to the difference of extinction coefficients between hydroxyl groups, so the methods cannot completely characterize the acidic properties of solid acids. In recent years, the technology of solid nuclear magnetic resonance combined with alkaline probe molecules for characterizing the acidity of solid acid is rapidly developed. The method is a relatively fine means for characterizing the acidity of the solid acid, and the technology can give a comprehensive characterization to information such as the acidity type, the acidity strength, the acidity position, the acidity amount, the acidity position correlation and the like of the solid acid catalyst.

SAPO molecular sieves with small pore cage structures have wide application in industry. For example, SAPO-34 as a catalyst shows excellent catalytic performance when being used in an industrial methanol-to-olefin (MTO) reaction process. The acid center of the molecular sieve is an active site in the catalytic process, and the acid type, the acid strength, the acid distribution and the like can directly influence the catalytic activity of the molecular sieve, so that the representation of the acid property of the solid acid has very important significance for researching the catalytic activity of the catalyst. Due to the limitation of the orifice of the molecular sieve with the small-pore cage structure, molecules with kinetic diameters larger than the orifice diameter can not diffuse into the molecular sieve cage, so that the acidic characterization of the molecules by utilizing the solid nuclear magnetic resonance combined with the alkaline probe is limited. At present, the characterization of the acidity of the small pore molecular sieve mainly utilizes the alkaline probe molecules with small volume and no diffusion resistance, such as: acetone, acetonitrile, and the like. When the probe molecules are adsorbed on acid sites, atoms contacted with the acid sites are mostly atoms with low nuclear magnetic signal abundance, such as C atoms and N atoms, and therefore the probe molecules are often used only by isotopic enrichment. Thus, the use of such alkaline probe molecules to characterize the acidic properties of small pore molecular sieves is limited.

Disclosure of Invention

According to one aspect of the application, a method for determining the acidity of a SAPO molecular sieve with a small pore cage structure is provided, and alkaline probe molecules are loaded into the molecular sieve cages by means of an auxiliary agent, so that the aim of characterizing the acidity property of the small pore molecular sieve is fulfilled. The method comprises the step of adsorbing alkaline probe molecules with molecular kinetic diameters larger than the aperture diameter of an orifice of a small-pore SAPO molecular sieve to acid sites on the inner surface of a cage of the SAPO molecular sieve. The acidic properties of the molecular sieve were characterized by solid nuclear magnetic resonance. Solves the problem that the prior large-volume alkaline probe molecules cannot enter a small-hole molecular sieve cage to contact with acid sites.

The method for determining the acidity of the SAPO molecular sieve with the small-pore cage structure is characterized by comprising the following steps of:

contacting alkaline probe molecules with acid sites in cages of the SAPO molecular sieves with the small-hole cage structures, and representing to obtain acid information of the SAPO molecular sieves with the small-hole cage structures;

wherein the kinetic diameter of the alkaline probe molecule is larger than the aperture of the pore opening of the SAPO molecular sieve with the small pore cage structure.

Optionally, the SAPO molecular sieve with the small-pore cage structure is selected from at least one of SAPO-34 molecular sieve, SAPO-44 molecular sieve, SAPO-18 molecular sieve, DNL-6 molecular sieve, SAPO-35 molecular sieve, SAPO-56 molecular sieve and SAPO-17 molecular sieve;

the alkaline probe molecule is selected from at least one of phosphine-containing organic alkaline molecules.

Optionally, the SAPO molecular sieve with the small-pore cage structure is a SAPO-34 molecular sieve.

Optionally, the alkaline probe molecule is selected from at least one of trialkylphosphines.

Optionally, the basic probe molecule is selected from the group consisting of trimethylphosphine (P- (CH)₃)₃) Triethylphosphine (P- (CH)₂CH₃)₃) Tripropyl phosphine (P- (CH)₂CH₂CH₃)₃) Tributylphosphine (P- (CH)₂CH₂CH₂CH₃)₃) Tripentylphosphine (P- (CH)₂CH₂CH₂CH₂CH₃)₃) At least one of (1).

Optionally, the characterization is a solid nuclear magnetic resonance characterization.

Alternatively, the solid nuclear magnetic model used in the method for determining the acidity of the SAPO molecular sieve with the small-pore cage structure is 600M.

Optionally, the method comprises: and (3) contacting alkaline probe molecules with the acid sites of the SAPO molecular sieves with the small-hole cage structures through the auxiliary agent, removing the auxiliary agent, and representing to obtain the acid information of the SAPO molecular sieves with the small-hole cage structures.

As a specific embodiment, the method comprises: the method comprises the steps of taking a small molecule as an auxiliary agent, filling the basic probe molecule with the aid of the small molecule, wherein the kinetic diameter of the basic probe molecule is larger than the aperture of an orifice of a small-pore molecular sieve, using the auxiliary agent to fill the basic probe molecule into an SAPO molecular sieve cage, then removing the auxiliary agent in vacuum, and using solid nuclear magnetic resonance to characterize the acidity of the molecular sieve.

Optionally, the adjuvant is selected from carbon dioxide (CO)₂) Water (H)₂O), hydrogen chloride (HCl), Hydrogen Fluoride (HF), ammonium fluoride (NH)₄F) At least one of (1).

Optionally, the adjuvant is selected from at least one of water and carbon dioxide.

Optionally, the method comprises:

(1) heating SAPO molecular sieve with small-hole cage structure under vacuum condition¹Obtaining a precursor I;

(2) heating the mixture containing the alkaline probe molecules, the auxiliary agent and the precursor I under a sealed condition²And removing the auxiliary agent to obtain a precursor II, and characterizing to obtain the acidity information of the SAPO molecular sieve with the small-pore cage structure.

Optionally, the heating in step (1)¹The conditions of (a) are as follows: heating of¹The temperature of (A) is 300-600 ℃; heating of¹The time is 1-48 h.

Optionally, the vacuum condition in step (1) is 10^-3～10^-5Pa。

Optionally, the heating¹The temperature of (a) is 400-550 ℃.

Optionally, the heating¹The temperature of (A) is 400-420 ℃.

Optionally, in the step (1), adsorbates such as water adsorbed on the surface layer of the molecular sieve are removed by heating under vacuum condition.

Optionally, the heating in step (1)¹The upper temperature limit is selected from 330 ℃, 360 ℃, 390 ℃, 410 ℃, 430 ℃, 450 ℃, 480 ℃, 500 ℃, 550 ℃ or 600 ℃; the lower limit is selected from 300 deg.C, 310 deg.C, 340 deg.C, 370 deg.C, 410 deg.C, 420 deg.C, 460 deg.C, 480 deg.C, 520 deg.C or 570 deg.C.

Optionally, the SAPO molecular sieve with the small-pore cage structure in the step (1) is subjected to a treatment for removing at least part of the template before use.

Optionally, the template in the molecular sieve is removed by calcination.

Optionally, the SAPO molecular sieve with the small pore cage structure in the step (1) is a molecular sieve with template agent removed.

Optionally, the molar ratio of the alkaline probe molecules to the auxiliary in the step (2) is 0.01-100.

Optionally, the molar ratio of the alkaline probe molecules to the auxiliary agent in the step (2) is 1-5.

Alternatively, the upper limit of the molar ratio of the basic probe molecule and the adjuvant is selected from 0.1, 0.4, 0.6, 0.9, 0.96, 0.98, 1, 1.2, 1.4, 1.8, 2, 5, 10, 20, 30, 50, 80, or 100; the lower limit is selected from 0.01, 0.05, 0.1, 0.5, 0.8, 0.9, 0.95, 0.98, 1, 1.1, 1.4, 1.8, 2, 10, 20, 30, 60, or 90.

Optionally, the molar weight of the alkaline probe molecules is 0.01-100 times of the amount of Br phi nsted acid contained in the precursor I.

Optionally, the molar weight of the alkaline probe molecules is 1-5 times of the amount of Br phi nsted acid contained in the precursor I.

Optionally, the upper limit of the molar amount of the alkaline probe molecules in step b) to the multiple of the amount of the Br phi nsted acid contained in the precursor I is selected from 0.1, 0.4, 0.6, 0.9, 0.96, 0.98, 1, 1.2, 1.4, 1.8, 2, 5, 10, 20, 30, 50, 80 or 100; the lower limit is selected from 0.01, 0.05, 0.1, 0.5, 0.8, 0.9, 0.95, 0.98, 1, 1.1, 1.4, 1.8, 2, 10, 20, 30, 60, or 90.

Optionally, the heating²The conditions of (a) are as follows: heating of²At a temperature of 30 to 600 ℃, and heating²The time is 0.1-100 h.

Optionally, the heating²The pressure of (a) is 0.5 to 20 bar.

Optionally, the heating²At a temperature of 100 to 350 ℃, and heating²The time is 0.1-12 h.

Optionally, the heating²At a temperature of not less than 100 deg.C, heating²The time is less than or equal to 12h

Optionally, the heating²The upper temperature limit is selected from 50 deg.C, 80 deg.C, 100 deg.C, 120 deg.C, 150 deg.C, 180 deg.C, 200 deg.C, 220 deg.C, 250 deg.C, 380 deg.C, 300 deg.C, 320 deg.C, 350 deg.C, 380 deg.C, 400 deg.C, 420 deg.C, 450 deg.C, 480 deg.C, 500 deg.C; the lower limit is selected from 30 deg.C, 50 deg.C, 80 deg.C, 100 deg.C, 120 deg.C, 150 deg.C, 180 deg.C, 200 deg.C, 220 deg.C, 250 deg.C, 380 deg.C, 300 deg.C, 320 deg.C, 350 deg.C, 380 deg.C, 400 deg.C, 420 deg.C, 450 deg.C, 480 deg.C, 500.

Optionally, the heating²The upper limit of time of (a) is selected from 0.5h, 1h, 1.5h, 2.0h, 2.5h, 3.0h, 4.0h, 5.0h, 6.0h, 8.0h, 10h, 20h, 30h, 40h, 50h, 60h, 70h, 80h or 90 h; the lower limit is selected from 0.1h, 0.5h, 1h, 1.5h, 2.0h, 2.5h, 3.0h, 4.0h, 5.0h, 6.0h, 8.0h, 10h, 20h, 30h, 40h, 50h, 60h, 70h, 80h or 90 h.

The heating²The pressure of (a) is autogenous pressure.

Optionally, the heating²The upper limit of the pressure of (a) is selected from 1bar, 1.5bar, 2.0bar, 2.5bar, 2.8bar, 3.0bar, 5.0bar, 8.0bar, 10.0bar, 12.0bar, 14.0bar, 16.0bar, 18.0bar, 20.0 bar; the lower limit is selected from 0.5bar, 0.8bar, 1.0bar, 1.5bar, 2.0bar, 2.5bar, 3.0bar, 4.0bar, 6.0bar, 8.0bar, 10.0bar, 12.0bar, 14.0bar, or 16.0 bar.

Optionally, the method of removing the auxiliary agent comprises: heating under vacuum³。

Optionally, the heating under vacuum condition³The conditions of (a) are as follows: 20 to 300 ℃.

Optionally, the heating under vacuum condition³The conditions of (a) are as follows: 150 to 300 ℃.

Optionally, the heating under vacuum condition³Vacuum condition of (2) is 10^-3～10^-5Pa。

Optionally, the removal aid simultaneously removes the physisorbed alkaline probe molecules.

Optionally, the method comprises:

1) roasting the SAPO molecular sieve with the small-hole cage structure, and heating to 300-600 ℃ under a vacuum-pumping condition to obtain a precursor I; the SAPO molecular sieve with the small-hole cage structure is a molecular sieve for removing part of the template agent and/or a molecular sieve for removing all the template agent;

2) introducing alkaline probe molecules and an auxiliary agent into the device filled with the precursor I in the step 1), sealing, and heating to obtain a precursor II;

3) and (3) heating the precursor II prepared in the step 2) under a vacuum condition to remove the auxiliary agent and the physically adsorbed alkaline probe molecules, obtaining a sample enriched with the alkaline probe molecules in the molecular sieve cage, and performing solid nuclear magnetic characterization to obtain the acidity information of the molecular sieve.

As a specific embodiment, the method comprises:

a) heating the molecular sieve at 300-600 ℃ under a vacuum condition to obtain a sample I;

b) heating a mixture containing the sample I, the alkaline probe molecules and the auxiliary agent under a certain pressure under a sealed condition to obtain a sample II;

c) heating the sample II under a vacuum condition to obtain a sample enriched with alkaline probe molecules in the molecular sieve cage;

d) and (3) putting the sample II into a solid nuclear magnetic rotor in a glove box for solid nuclear magnetic characterization to obtain the acidity information of the molecular sieve.

As a specific embodiment, the method comprises:

a1) roasting the molecular sieve, then loading the molecular sieve into a dehydration tube, and heating the molecular sieve to 300-500 ℃ under a vacuum-pumping condition to remove adsorbates such as water adsorbed by the molecular sieve, thereby obtaining a sample I; the molecular sieve is a molecular sieve for removing part of the template agent and/or a molecular sieve for removing all the template agent;

b1) introducing a certain amount of alkaline probe molecules and an auxiliary agent into the dehydration tube loaded with the sample I in the step a1), and sealing the dehydration tube;

c1) heating the sealed dehydration tube obtained in the step b1) in a muffle furnace to obtain a sample enriched with alkaline probe molecules in the molecular sieve cage;

d1) heat treating the sample enriched with basic probe molecules in the molecular sieve cage prepared in step c1) under vacuum to remove the auxiliary agent and the physically adsorbed basic probe molecules.

e1) Loading the sample treated in the step d1) into a solid nuclear magnetic rotor in a glove box for solid nuclear magnetic characterization to obtain the acidity information of the molecular sieve.

Optionally, the dehydration tube is made of glass, quartz or steel material.

In another aspect of the present application, the method of any one of the above is applied to at least one of characterization of molecular sieve acid strength, characterization of molecular sieve acidic species, and characterization of molecular sieve acidic site distribution.

The invention provides an application of a method for measuring the acidity of a SAPO molecular sieve with a small-pore cage structure in the characterization of the acidity of the molecular sieve.

Optionally, the method for determining the acidity of the SAPO molecular sieve with the small-pore cage structure is applied to characterization of the acid strength of the molecular sieve.

Optionally, the method for determining the acidity of the SAPO molecular sieve with the small-pore cage structure is applied to the characterization of acidic species of the molecular sieve.

Optionally, the method for determining the acidity of the SAPO molecular sieve with the small pore cage structure is applied to characterization of acidic sites of the molecular sieve.

In the application, "small hole" in the SAPO molecular sieve with a small-hole cage structure means that the pore diameter is less than 0.40 × 0.40 nm.

In the present application, the "vacuum condition" is 10^-3～10^-5Pa。

The beneficial effects that this application can produce include:

1) the method for determining the acidity of the SAPO molecular sieve with the small-hole cage structure can enable alkaline probe molecules with the kinetic diameter larger than the orifice of the small-hole molecular sieve to enter the molecular sieve cage, and can be used for solving the problem that the prior large-volume alkaline probe molecules cannot enter the small-hole molecular sieve cage to be contacted with an acid site;

2) the method for determining the acidity of the SAPO molecular sieve with the small-pore cage structure is simple and reliable, and is easy to widely popularize and apply;

3) the method for determining the acidity of the SAPO molecular sieve with the small-pore cage structure can represent the acidity type, the acidity strength and the acidity site of the small-pore molecular sieve, can represent the acidity property of the molecular sieve more comprehensively, and has very important significance for researching the catalytic activity of a molecular sieve catalyst.

Drawings

FIG. 1 is a sample of SAPO-34 with Trimethylphosphine (TMP) in one embodiment of the present application¹H-³¹Heteronuclear correlation spectrum of P; wherein the content of the first and second substances,

A₁，A₂represents: the signals associated with P on the methyl group of TMP and H on the methyl group;

B₁，B₂，B₃，B₄represents: signals related to bridge type hydroxyl H on four oxygen positions of P on TMP and SAPO-34;

e: the correlation signal of P on the framework of the SAPO-34 molecular sieve and H on the methyl group of TMP;

d: a signal related to terminal phosphine hydroxyl P and a small amount of H in water;

g: the correlation signal of P on the framework of the SAPO-34 molecular sieve and bridge hydroxyl H on the acid position B on the SAPO-34.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

Unless otherwise specified, the starting materials in the examples of the present application were all purchased commercially, wherein the SAPO-18 molecular sieves used in the examples were prepared according to the methods in the cat.letters, 1994,241 literature; SAPO-34 molecular sieves were purchased from Nankai catalyst works; the DNL-6 molecular sieve was prepared according to the method described in chem.mater.2011,23,1406; the molecular sieves are not directly used after special treatment; the SAPO-35 molecular sieve is prepared according to a method in Chin.J.Catal,2013,34,798 literature; SAPO-44 molecular sieves were prepared according to the methods described in the Natural Gas Chemical Industry,2015,40,6 literature; SAPO-56 molecular sieves were prepared according to the methods described in CrystEngComm,2016,18,1000 literature.

The analysis method in the examples of the present application is as follows:

the NMR was measured by using an Infinity plus 600MB solid-state NMR spectrometer from Bruker, Germany, using a 4mm HXY MAS probe at a magnetic field intensity of 14.1T.

In the present application, the acidic nature of the molecular sieve is based on solid NMR¹H and³¹and (4) obtaining a P spectrum.

According to one embodiment of the present application, the method for determining the acidity of the SAPO molecular sieve with a small pore cage structure comprises:

1) after roasting the molecular sieve, putting the molecular sieve into a dehydration tube, and heating the molecular sieve to 300-600 ℃ under a vacuum-pumping condition to obtain a sample I; the molecular sieve is a molecular sieve for removing part of the template agent and/or a molecular sieve for removing all the template agent;

2) introducing alkaline molecules and an auxiliary agent into the dehydration tube filled with the sample I in the step 1), and sealing the dehydration tube;

3) heating the sealed dehydration tube obtained in the step 2) to obtain a sample II;

4) heating the sample II prepared in the step 3) under a vacuum condition to remove the auxiliary agent and the physically adsorbed alkaline probe molecules, so as to obtain a sample enriched with the alkaline probe molecules in the molecular sieve cage;

5) and (3) putting the sample obtained in the step 4) into a solid nuclear magnetic rotor in a glove box for solid nuclear magnetic characterization to obtain the acidity information of the molecular sieve.

The material of the dehydration tube that adopts in this application embodiment is glass material and makes.