WO2016061727A1

WO2016061727A1 - Method for synthesizing slice-shaped nanometer sapo-34 molecular sieve

Info

Publication number: WO2016061727A1
Application number: PCT/CN2014/088921
Authority: WO
Inventors: 郜贝贝; 田鹏; 杨淼; 刘中民; 王德花; 刘琳
Original assignee: 中国科学院大连化学物理研究所
Priority date: 2014-10-20
Filing date: 2014-10-20
Publication date: 2016-04-28

Abstract

Provided are a method for preparing a slice-shaped nanometer SAPO-34 molecular sieve, and catalyst and adsorption separation materials prepared via the slice-shaped nanometer SAPO-34 molecular sieve. The method at least comprises the following steps: a) mixing an aluminum source, a phosphorus source, a silicon source, a template agent R, an alcohol compound A and water to obtain an initial gel mixture; b) adding a nanometer SAPO-34 molecular sieve seed crystal into the initial gel mixture obtained in step a), and aging and crystallizing the mixture, the amount of the added nanometer SAPO-34 molecular sieve seed crystal being 1-30% of the dry weight of the initial gel mixture; c) after completing the crystallization in step b), separating, washing and drying a solid product to obtain the slice-shaped nanometer SAPO-34 molecular sieve.

Description

Method for synthesizing flake nano SAPO-34 molecular sieve

Technical field

The present application relates to a method for preparing a SAPO-34 molecular sieve, and belongs to the field of molecular sieve synthesis.

Background technique

In 1984, U.S. Union Carbide developed a silica alumina molecular sieve. Among them, the silica-phosphorus aluminum molecular sieve SAPO-34 with CHA topology exhibits excellent catalytic performance in methanol to olefin (MTO) reaction due to its special pore structure and suitable acid properties, and the methanol conversion rate is 100% or Near 100%, the C2-C4 olefin selectivity is about 90%, and there is almost no C5 or higher product. However, the SAPO-34 molecular sieve catalyst prepared by the conventional method is easily deactivated and has a short single life. Studies have shown that reducing the grain size of SAPO-34 can effectively increase the specific surface area of the catalyst, reduce the diffusion limit, and prolong the life of the catalyst.

At present, it is common to reduce the grain size of SAPO-34 by adding fluoride into the system, using expensive tetraethylammonium hydroxide as a template, and using ultrasonics. However, the above methods are not suitable for large-scale industrial production: industrial application of ultrasonic technology is difficult; HF is prone to environmental pollution, equipment corrosion and safety problems; tetraethylammonium hydroxide is expensive and economic value is not high.

The present application provides a method for synthesizing a sheet-like nano-SAPO-34 molecular sieve, which is suitable for large-scale industrial production and production by using an inexpensive templating agent such as triethylamine, adding nano-seed crystals and multi-stage crystallization to synthesize nano-SAPO-34 molecular sieve. The rate is higher. The synthesized SAPO-34 molecular sieve has a lamellar morphology with a thickness of nanometer, and has a very short diffusion path in the direction of the sheet, the catalyst life The life is greatly extended and has important industrial application significance.

Summary of the invention

According to one aspect of the present application, there is provided a method of preparing a sheet-like nano-SAPO-34 molecular sieve which is suitable for large-scale industrial production and has a high yield. The synthesized SAPO-34 molecular sieve has a lamellar morphology with a thickness of nanometer, and exhibits a long life as a catalyst for the acid-catalyzed reaction and the MTO reaction.

The method for preparing a sheet-like nano SAPO-34 molecular sieve, characterized in that it comprises at least the following synthetic steps:

a) mixing an aluminum source, a phosphorus source, a silicon source, a templating agent R, an alcohol compound A, and water to obtain an initial gel mixture having the following ratio:

R: A: Al ₂ O ₃ : P ₂ O ₅ : SiO ₂ : H ₂ O = 1.5 to 6.0: 0.1 to 1: 1.0: 0.5 to 3.0: 0.05 to 2.0: 20 to 200;

b) adding nano-SAPO-34 molecular sieve seed crystal to the initial gel mixture obtained in the step a), aging for 1 to 12 hours before 100-120 ° C, and then crystallization for 3 to 48 hours at 180-220 ° C; The nano-SAPO-34 molecular sieve seed crystal is added in an amount of 1 to 30% by weight of the dry basis in the initial gel mixture;

c) After the step b) is completed, the solid product is separated, washed and dried to obtain the sheet-like nano SAPO-34 molecular sieve.

In the initial gel mixture of step a), the phosphorus source is added in an amount of P ₂ O ₅ , the aluminum source is added in a molar amount of Al ₂ O ₃ , and the silicon source is added in an amount of SiO ₂ . Molar count.

Preferably, the aluminum source in step a) is selected from at least one of an aluminum salt, activated alumina, alkoxy aluminum, and metakaolin.

Preferably, the phosphorus source in step a) is selected from at least one of orthophosphoric acid, metaphosphoric acid, phosphate, and phosphite.

Preferably, the silicon source in step a) is selected from at least one of silica sol, active silica, orthosilicate, metakaolin.

Preferably, the templating agent R in step a) is selected from the group consisting of diethylamine, triethylamine, tetraethylammonium hydroxide, morpholine, diisopropylamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine And at least one of N,N-diethylethanolamine.

Preferably, the alcohol compound A in the step a) is at least one selected from the group consisting of ethanol, ethylene glycol, n-propanol, n-butanol, glycerol, and 1,3-butylene glycol.

Preferably, in the initial gel mixture of step a), the aluminum source is added in an amount of moles of Al ₂ O ₃ , and the molar ratio of the template R to the aluminum source is R: the upper limit of the range of Al ₂ O ₃ is selected from 6 4, 3, the lower limit is selected from 1.5, 2, 2.5.

Preferably, in the initial gel mixture of step a), the aluminum source is added in an amount of Al ₂ O ₃ , and the molar ratio of the alcohol compound A to the aluminum source A: the upper limit of the range of Al ₂ O ₃ is selected from 1, 0.8, 0.5, 0.3, the lower limit is selected from 0.1, 0.2. Further preferably, the molar ratio of the alcohol compound A to the aluminum source is A: Al ₂ O ₃ = 0.1 to 0.3.

Preferably, the particle size of the nano-SAPO-34 seed crystal in step b) does not exceed 800 nm. Further preferably, the nano SAPO-34 seed crystal in step b) has an average particle diameter of 100 to 800 nm. Still more preferably, the nano SAPO-34 seed crystals in step b) have an average particle diameter of from 100 to 500 nm. Still more preferably, the nano SAPO-34 seed crystal in step b) has an average particle diameter of 200 to 400 nm. The nano-SAPO-34 molecular sieve seed crystal can be obtained by direct synthesis, or can be obtained by post-processing a large particle size SAPO-34 molecular sieve such as a ball milling method.

Preferably, the nano-SAPO-34 molecular sieve seed in step b) is added in an amount of from 11 to 30% by weight of the dry basis in the initial gel mixture.

Preferably, the morphology of the sheet-like nano-SAPO-34 molecular sieve obtained in the step c) is lamellar, and the thickness of the single sheet is 50 to 200 nm. The surface of the sheet is not smooth, has a flower-like structure, and the size of the sheet layer is 0.4 to 1 μm at the maximum.

According to a preferred embodiment of the present application, the method for preparing a sheet-like nano SAPO-34 molecular sieve comprises at least the following steps:

1) Mixing aluminum source, phosphorus source, silicon source, templating agent R and water to obtain initial gel of synthetic SAPO-34 molecular sieve, stirring uniformly, adding alcohol compound A, stirring at room temperature for 1-24 hours, each group in gel The molar ratio of the fraction is as follows: (1.5 to 6.0) R: (0.1 to 1) A: 1.0 Al ₂ O ₃ : (0.5 to 3.0) P ₂ O ₅ : (0.05 to 2.0) SiO ₂ : (20 to 200) H ₂ O;

2) Adding SAPO-34 molecular sieve equivalent to 1 to 30% of the dry weight of the gel oxide to the gel obtained in the step 1) as a seed crystal, stirring uniformly, and then immersing in the reaction vessel at 100 to 120 ° C for aging 1 After ~12h, the temperature is raised to 180 ~ 220 ° C hydrothermal crystallization for 3 ~ 48h;

3) After the step 2) crystallization is completed, the solid product is centrifuged, washed with deionized water to neutrality, and dried in air at 120 ° C to obtain the sheet-like nano SAPO-34 molecular sieve.

According to still another aspect of the present application, there is provided an acid catalyst characterized in that the sheet-like nano SAPO-34 molecular sieve synthesized according to any of the above methods is obtained by calcination in air at 400 to 700 °C.

According to still another aspect of the present application, there is provided a catalyst for the conversion of an oxygen-containing compound to an olefin, characterized in that the sheet-like nano-SAPO-34 molecular sieve synthesized according to any of the above methods is obtained by calcination in air at 400 to 700 °C.

According to still another aspect of the present application, there is provided an adsorption separation material of methane and/or nitrogen and carbon dioxide, It is characterized in that the sheet-like nano SAPO-34 molecular sieve synthesized according to any of the above methods is obtained by calcination in air at 400 to 700 °C.

The beneficial effects that can be produced by this application include:

(1) Using a temperature-changing crystallization mechanism and an organic additive, in addition to the more expensive tetraethylammonium hydroxide, a flaky nano-molecular sieve can be obtained by using an inexpensive templating agent such as triethylamine, without adding HF or the like, Conducive to its industrial applications.

(2) By changing the particle size, addition amount or aging temperature of the seed crystal, the particle size of the SAPO-34 molecular sieve can be effectively controlled to have a grain size of 0.4 to 1 μm and a thickness of 50 to 200 nm. .

(3) The solid product of the synthetic product has a high yield, usually higher than 80% by weight, and is economically high in mass production.

(4) Compared with the conventional SAPO-34, the prepared SAPO-34 molecular sieve has a significantly increased lifetime in the conversion of methanol or dimethyl ether to a lower olefin, and the total selectivity of ethylene and propylene can be as high as 85% or more.

(5) The prepared SAPO-34 molecular sieve showed good selectivity in CO ₂ /CH ₄ and CO ₂ /N ₂ adsorption separation.

DRAWINGS

Figure 1 is a scanning electron micrograph of sample 1#.

Figure 2 is a scanning electron micrograph of Comparative Sample 1#.

Figure 3 is a scanning electron micrograph of Comparative Sample 2#.

Figure 4 is a scanning electron micrograph of Comparative Sample 3#.

detailed description

The present application is described in detail below by way of examples, but the application is not limited thereto.

Unless otherwise specified, the test conditions of this application are as follows:

X-ray powder diffraction phase analysis (XRD) was carried out using an X'Pert PRO X-ray diffractometer from the PANalytical Company of the Netherlands, a Cu target, a Kα radiation source (λ = 0.15418 nm), a voltage of 40 kV, and a current of 40 mA.

The SEM morphology analysis was performed using the SU8020 and TM3000 scanning electron microscopes of the Scientific Instrument Factory of the Chinese Academy of Sciences.

Example 1 Preparation of Sample 1# to Sample 10#

Preparation of nano-SAPO-34 seed crystal: It was synthesized by the method of WO2003/048042 and tetraethylammonium hydroxide TEAOH as a template. The crystal product was nearly cubic and the average particle size was 300 nm.

9.1 g of pseudoboehmite (Al ₂ O ₃ content 67.5 wt%) and 52.3 g of deionized water were mixed, and after stirring uniformly, 13.8 g of phosphoric acid (85 wt%) was added dropwise to the mixture, and stirring was continued until uniformity was formed. The white gel was added with 4.0 g of an alkaline silica sol (31 wt%), stirred well, and finally 12.1 g of triethylamine was added, and 0.45 g of ethylene glycol was sufficiently stirred to obtain an initial gel of a synthetic SAPO-34 molecular sieve. To the initial gel, a seed crystal corresponding to 12% of the dry weight of the gel was added, stirred uniformly, transferred to a stainless steel autoclave, aged at 100 ° C for 6 h, and heated to 200 ° C for 24 h. After the crystallization was completed, the solid product was centrifuged, washed, and dried in air at 100 ° C to obtain the sheet-like nano SAPO-34 molecular sieve, which was designated as sample ##.

The operation steps of sample 2# to sample 10# are the same, and the specific proportion of ingredients and aging and crystallization conditions are shown in Table 1.

The obtained samples 1# to 10# were calcined at 500 ° C and weighed, and the yields were all above 80%. The yield was calculated as follows: the quality of the product after calcination (inorganic dry basis mass + input seed crystal in the initial gel) Quality) × 100%.

Table 1

^a seed quality 干 dry basis mass in the initial gel × 100%.

Comparative Example 1 Preparation of Comparative Sample 1# to Comparative Sample 3#

The proportion of the ingredients and the crystallization process were the same as those of the sample 1# in Example 1, except that no ethylene glycol was added, and the obtained sample was recorded as Comparative Sample 1#.

The proportion of the ingredients and the crystallization process were the same as those of the sample 1# in Example 1, except that no seed crystals and ethylene glycol were added, and the obtained sample was recorded as Comparative Sample 2#.

The proportion of the ingredients was the same as that of the sample 1# in Example 1, except that there was no low temperature aging process, and the initial gel was directly heated to 200 ° C for 24 hours under dynamic conditions, and the obtained sample was recorded as Comparative Sample 3#.

Example 2 XRD and SEM characterization results

XRD analysis was performed on Sample 1# to Sample 10# in Example 1, and sample 1# was typically represented, and the XRD data results are shown in Table 2. The XRD data results of sample 2# to sample 10# are close to those of Table 2, that is, the peak position and shape are the same, and the peak relative peak intensity fluctuates within ±10% depending on the synthesis conditions, indicating that the synthesized product has the characteristics of SAPO-34 structure. .

Table 2 XRD results of sample 1#

The morphology of Sample 1# to Sample 10# and Comparative Sample 1# to Comparative Sample 3# in Example 1 was analyzed by scanning electron microscopy. The results show that each of the samples 1# to 10# has a lamellar morphology, the thickness of the individual sheets is 50-200 nm, and the surface of the sheet layer is not smooth and has a flower-like structure, and the size of the sheet layer is the largest , is 0.4 to 1 μm. Sample 1# is typical, and its scanning electron microscope photograph is shown in Fig. 1. As can be seen from the figure, the size of the sheet layer is the largest, the average size is about 700 nm, and the thickness of the sheet is 50 to 100 nm.

The average slice size and slice thickness of sample 2# to sample 10# are shown in the last column of Table 1.

The scanning electron micrograph of Comparative Sample 1# is shown in Fig. 2. As can be seen from the figure, Comparative Sample 1# is a cubic crystal grain having an average particle diameter of about 900 nm, and the crystal surface has no flower-like morphology. The scanning electron micrograph of Comparative Sample 2# is shown in Fig. 3. As can be seen from the figure, Comparative Sample 2# is a cubic crystal grain having an average particle diameter of about 4 μmm, and the crystal surface is smooth. The scanning electron micrograph of Comparative Sample 3# is shown in Fig. 4. As can be seen from the figure, Comparative Sample 3# is a cubic crystal grain having an average particle diameter of about 1.4 μm, and the crystal surface is smooth.

Example 3: Methanol conversion to olefin reaction performance test

Reactivity of methanol to olefins of sample 1#, comparative sample 1# and comparative sample 2# carry out testing.

Sample 1#, Comparative Sample 1# and Comparative Sample 2# were respectively subjected to air baking at 550 ° C for 4 hours, and then tableted and crushed to 20 to 40 mesh. 1.0 g of the sample was weighed into a fixed bed reactor, and MTO reaction evaluation was performed. It was activated by nitrogen at 550 ° C for 1 hour and then cooled to a reaction temperature of 450 ° C. Nitrogen gas was turned off, and a 40 wt% aqueous methanol solution was fed by a plunger pump at a methanol weight space velocity of 4.0 h ^-1 . The reaction product was analyzed by on-line gas chromatography (Varian 3800, FID detector, capillary column PoraPLOT Q-HT), and the results are shown in Table 3. It can be seen that the sample prepared according to the method of the present application is used as a catalyst for the methanol conversion to olefin reaction, and the life is greatly improved as compared with the sample synthesized by the conventional method.

Table 3 Results of methanol conversion to olefins*

*Lifetime refers to the time when the methanol conversion rate remains above 99%.

Selectivity refers to the highest selectivity when methanol conversion is maintained above 99%.

Example ₄ CO ₂ /CH ₄ /N ₂ adsorption separation performance test

Sample 1# was calcined in air at 550 ° C for 4 hours. The adsorption isotherms of CO ₂ and CH ₄ N ₂ were measured by a Micrometrics Gemini II apparatus. Before the measurement, the sample was degassed and pretreated at 350 ° C for 4 hours under vacuum, and the adsorption test temperature was 25 ° C. The adsorption results are shown in Table 4. As can be seen from the data in the table, the sample prepared according to the method of the present application can be used as an adsorption separation material for methane and/or nitrogen and carbon dioxide.

Table 4 Sample 1# CO ₂ /CH ₄ /N ₂ static adsorption results (25 ° C, 101 kPa)

The present application is disclosed in the above preferred embodiments, but is not intended to limit the scope of the claims. Any one of ordinary skill in the art can make various possible changes and modifications without departing from the spirit of the present application. The scope should be determined by the scope defined by the claims of the present application.

Claims

A method for preparing a sheet-like nano-SAPO-34 molecular sieve, characterized in that it comprises at least the following synthetic steps:

a) mixing an aluminum source, a phosphorus source, a silicon source, a templating agent R, an alcohol compound A, and water to obtain an initial gel mixture having the following ratio:

R: A: Al 2 O 3 : P 2 O 5 : SiO 2 : H 2 O = 1.5 to 6.0: 0.1 to 1: 1.0: 0.5 to 3.0: 0.05 to 2.0: 20 to 200;

b) adding nano-SAPO-34 molecular sieve seed crystal to the initial gel mixture obtained in the step a), aging for 1 to 12 hours before 100-120 ° C, and then crystallization for 3 to 48 hours at 180-220 ° C; The nano-SAPO-34 molecular sieve seed crystal is added in an amount of 1 to 30% by weight of the dry basis in the initial gel mixture;

c) After the step b) is completed, the solid product is separated, washed and dried to obtain the sheet-like nano SAPO-34 molecular sieve.
The method according to claim 1, wherein the source of aluminum in step a) is at least one selected from the group consisting of aluminum salts, activated alumina, aluminum alkoxides, and metakaolin; and the phosphorus source is selected from the group consisting of At least one of phosphoric acid, metaphosphoric acid, phosphate, phosphite; the silicon source is selected from at least one of silica sol, active silica, orthosilicate, metakaolin; At least one of diethylamine, triethylamine, tetraethylammonium hydroxide, morpholine, diisopropylamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine Kind.
The method according to claim 1, wherein the alcohol compound A in the step a) is selected from the group consisting of ethanol, ethylene glycol, n-propanol, n-butanol, glycerol, and 1,3-butanediol. At least one of them.
The method according to claim 1, wherein in the initial gel mixture of step a), the molar ratio of the alcohol compound A to the aluminum source is A: Al 2 O 3 = 0.1 to 0.3: 1.0.
The method according to claim 1, wherein the particle size of the nano-SAPO-34 seed crystal in step b) does not exceed 800 nm.
The method of claim 1 wherein said nano-SAPO-34 molecular sieve seed is added in step b) in an amount from 11 to 30% by weight of the dry basis of the initial gel mixture.
The method according to claim 1, wherein the sheet-like nano-SAPO-34 molecular sieve obtained in the step c) has a morphology of a sheet layer having a thickness of 50 to 200 nm.
An acid catalyst characterized in that the sheet-like nano SAPO-34 molecular sieve synthesized by the method according to any one of claims 1 to 7 is obtained by calcination in air at 400 to 700 °C.
A catalyst for the conversion of an oxygen-containing compound to an olefin, characterized in that the sheet-like nano-SAPO-34 molecular sieve synthesized by the method according to any one of claims 1 to 7 is obtained by calcination in air at 400 to 700 °C.
An adsorption separation material of methane and/or nitrogen and carbon dioxide, characterized in that the sheet-like nano SAPO-34 molecular sieve synthesized by the method according to any one of claims 1 to 7 is obtained by calcination in air at 400 to 700 °C.