CN1093086C - Process for synthesizing surfactant of EMT zeolite - Google Patents

Abstract

The invention is a new method for reducing the synthesis cost and crystallization time of EMT zeolite. The existing method to reduce the synthesis cost is the so-called dense system method of reducing the water content, but it has the disadvantage of difficult operation. The present invention reduces the relative dosage of the expensive 18-crown-6 template by 40-50% by adding a small amount of cheap and easy-to-obtain surfactants in the traditional synthesis system, and also shortens the crystallization time to 5 days. The temperature range is extended to 100-130°C. The present invention has the following characteristics: one, the use efficiency of the 18-crown-6 template is obviously improved, and the synthesis cost is lower; two, since the usage amount of water solvent is not reduced in the synthesis, the operation process is simple and easy; three, the used The synthetic steps have not been reported so far.

Description

Synthetic method of EMT zeolite with surfactant as auxiliary agent

The invention relates to a new method for efficiently synthesizing EMT zeolite by adding a surfactant.

In the 1960s, people speculated that in addition to FAU (the general name of X and Y zeolites) zeolite, there may also be a zeolite called EMT in faujasite. Both of these two zeolites are composed of sodalite cages (or beta cages) connected to each other through double six-membered rings, but due to the different connection methods, there are significant differences between the two, mainly as follows: EMT zeolites include Hypercage and Hypocage has two types of supercages and has a two-dimensional intersecting 12-member ring straight channel system, so the structure is very smooth; FAU has only one type of supercage without straight channels. Due to the superior structural characteristics of EMT, people have been trying to synthesize a pure EMT crystal phase. Until 1990, pure EMT zeolite was obtained for the first time by F.Delprato et al. using 18-crown-6 as a template, and found that EMT zeolite has a high silicon-aluminum ratio (Si/Al Between 3 and 5), later studies on this zeolite also found that the acid strength of hydrogen-type EMT is greater than that of hydrogen-type Y zeolite with the same silicon-aluminum ratio.

As we all know, in today's catalytic field, especially in the process of fluid catalytic cracking (FCC), Y zeolite plays a very important role, and EMT zeolite has many advantages over Y zeolite in terms of structure and physical and chemical properties, so this This zeolite has aroused the interest of the industry and has very attractive potential application prospects. However, until now, expensive 18-crown-6 templates must be used to synthesize pure EMT zeolites, which makes the synthesis cost of EMT zeolites too high. On the other hand, the crystallization time required for the synthesis of EMT zeolites is also longer (crystallization When the temperature is 110 ° C, it generally crystallizes for more than a week), which will severely limit its industrial application. Therefore, in the case that 18-crown-6 cannot be completely replaced at present, it is very meaningful to reduce the relative dosage and crystallization time of 18-crown-6 as much as possible, and there are few literature reports in this regard. T. Chatelain et al. used the so-called "dense system method" to reduce the relative amount of 18-crown-6 by about 40%, but this method increased the difficulty of operation because the amount of water solvent was greatly reduced.

The purpose of the present invention is to develop a simple and fast practical method for synthesizing pure EMT zeolite which can effectively reduce the relative dosage of 18-crown-6 template agent without increasing the difficulty of operation.

The present invention can add cationic surfactant (for example: hexadecyl trimethyl ammonium bromide, dodecyl benzyl dimethyl ammonium chloride etc.), anionic surfactant (for example: ten Dialkyl sodium sulfate, etc.) and non-ionic surfactants (such as alkyl glycosides, lauric acid monoethanolamide polyoxyethylene (15) ether, etc.), with 18-crown-6 as template agent, using cheap silica sol and sodium aluminate are used as silicon source and aluminum source respectively, and pure EMT zeolite is synthesized through crystallization steps.

In the present invention, the surfactant is first dissolved in water so that the concentration range is between 0.02 and 0.20 mol/L, and then silicon source, aluminum source and 18-crown-6 are mixed with the surfactant solution and heated at 20 to 35°C Stirring at low temperature for 0.5~1.5h, the molar ratio of the raw materials in the obtained mixture is: SiO ₂ /Al ₂ O ₃ =8~12, Na ₂ O/Al ₂ O ₃ =1.8~3.0, 18-crown-6/ Al ₂ O ₃ =0.2 to 1.0. Then the reaction mixture is aged at room temperature for 12-48 hours and then transferred into a stainless steel autoclave for crystallization at 80-160° C. for 3-30 days. The solid precipitate obtained after crystallization is filtered, washed and dried to obtain a synthetic EMT zeolite. The synthetic EMT was calcined in an air atmosphere to remove the 18-crown-6 template in the zeolite (program: 200°C/2h, 540°C/4h) to obtain a calcined EMT zeolite.

The preferred concentration range of the above-mentioned surfactant solution is 0.03-0.10 mol/L. For different surfactants, the concentration that the solution should achieve is also different, this is because the surfactant can significantly change the physical and chemical properties of the water solvent only after exceeding the critical micelle concentration (CMC), so as to play an important role. Some effect.

The suitable aging time of the above reaction mixture at room temperature is 20-24h. For the synthesis of EMT zeolites, the aging stage is beneficial to accelerate the crystallization of the zeolites.

The preferred ranges of molar ratios among the above raw materials are as follows: SiO ₂ /Al ₂ O ₃ =9-11, Na ₂ O/Al ₂ O ₃ =1.8-2.4, 18-crown-6/Al ₂ O ₃ =0.35 ~0.70.

The best ranges of molar ratios among the above raw materials are as follows: SiO ₂ /Al ₂ O ₃ =10-11, Na ₂ O/Al ₂ O ₃ =2.1-2.2, 18-crown-6/Al ₂ O ₃ =0.35 ~0.40.

The preferable range of the above-mentioned crystallization temperature is 100-130°C. A decrease in the crystallization temperature will prolong the crystallization time, and an increase in the crystallization temperature will cause a small amount of miscellaneous crystals to appear, reducing the purity of the EMT zeolite.

The preferable range of the above-mentioned crystallization time is 5-7 days. EMT zeolite can also be obtained by prolonging the crystallization time, but the synthesis efficiency is reduced.

The surfactant that the present invention uses obtains following effect as the synthetic method of auxiliary agent:

(1) In the hydrothermal synthesis system reported in the literature, only a small amount of cheap and easy-to-obtain surfactant is added as an auxiliary agent to reduce the relative dosage of 18-crown-6 by 40-50%;

(2) The crystallization time of synthetic EMT zeolite is shortened greatly;

(3) The crystallization temperature range of the synthesized EMT zeolite has been broadened.

Surfactant of the present invention is made the contrast of the productive rate of the EMT synthetic method of auxiliary agent and the synthetic method of traditional EMT zeolite and crystallization time two indexes: The method of surfactant as auxiliary agent traditional method Yield (gram EMT/gram 18-crown-6) Crystallization time (days) 4.0～4.55～7 6.5～7.0＞25

The EMT zeolite of the present invention has the typical characterization results shown in Figures 1-6.

Figure 1 is the powder X-ray diffraction spectrum (XRD) of the synthesized EMT zeolite. In the range of 2θ=5-7°, there are three diffraction peaks with decreasing intensities, corresponding to [100], [002] and [101] crystal planes of EMT zeolite, which are the characteristic diffraction peaks of EMT zeolite.

Fig. 2 is a powder X-ray diffraction spectrum (XRD) of calcined EMT zeolite. This figure shows that the framework structure of zeolite can be well maintained in the process of template release for synthetic EMT.

Figure 3 is a scanning electron microscope (SEM) image of a synthetic EMT zeolite. It can be clearly seen from the figure that the appearance of the synthesized EMT grains is hexagonal, and the size is generally less than 2 μm.

Fig. 4 is ^{the 29} Si magic angle spinning nuclear magnetic resonance spectrum (MAS NMR) of the synthesized EMT zeolite. The three peaks in the chemical shift range of -90 to 110ppm correspond to Si(2Al), Si(1Al) and Si(0Al) in the EMT zeolite in turn, thus the framework silicon-aluminum ratio of the synthesized EMT zeolite can be calculated as 3.6.

Fig. 5 is the ²⁷ Al magic angle spinning nuclear magnetic resonance spectrum (MAS NMR) of the synthetic EMT zeolite. The chemical shift is that the peak at 60.6ppm corresponds to the four-coordinated framework aluminum, and there is no six-coordinated non-framework aluminum signal near 0ppm, which indicates that all aluminum species enter the zeolite framework.

Fig. 6 is a differential thermal analysis curve (DTA) of EMT. The removal of the 18-crown-6 templating agent contained in the EMT supercage occurred in two stages, corresponding to 218.1°C and 264.8°C, respectively.

Embodiment 1: be made into the hexadecyltrimethylammonium bromide surfactant solution that molar concentration is 0.04mol/L, then a certain amount of silicon source (SiO ₂ , 25～30%), aluminum source (Al ₂ O ₃ , 43%) and 18-crown-6 templating agent were mixed with surfactant solution, and the molar ratio of the resulting mixture was 9 SiO ₂ : 1 Al ₂ O ₃ : 2.1 Na _{2 O} : 0.4[18-crown-6 ]. Stir the mixture at room temperature (25°C) for 1 hour, then transfer it to a stainless steel reactor, firstly age it statically at room temperature for 24 hours, and then heat it to 100°C for crystallization for 6 days, and the resulting solid precipitate is filtered, washed and dried to obtain Synthetic EMT was calcined under air atmosphere (program: 250°C/2h, 500°C/4h) to obtain calcined EMT.

Embodiment 2: be made into the dodecylbenzyl dimethyl ammonium chloride surfactant solution that molar concentration is 0.09mol/L, then a certain amount of silicon source (SiO ₂ , 25～30%), aluminum source (Al ₂ O ₃ , 43%) and 18-crown-6 template were mixed with the surfactant solution, and the molar ratio of the resulting mixture was 10 SiO ₂ : 1 Al ₂ O ₃ : 2.2 Na _{2 O} : 0.4 [18-crown -6]. Stir the mixture at room temperature (30°C) for 0.5h, then transfer it to a stainless steel reactor, first statically age it at room temperature for 15h, then heat it to 100°C to crystallize for 7 days, and the resulting solid precipitate is filtered, washed and dried A synthetic EMT was obtained, which was calcined in an air atmosphere (program: 250°C/2h, 500°C/4h) to obtain a calcined EMT.

Embodiment 3: be made into the sodium lauryl sulfate surfactant solution that molar concentration is 0.05mol/L, then a certain amount of silicon source (SiO ₂ , 25～30%), aluminum source (Al ₂ O ₃ , 43%) and 18-crown-6 templating agent were mixed with surfactant solution, and the molar ratio of the obtained mixture was 11 SiO ₂ : 1 Al ₂ O ₃ : 2.4 Na _{2 O} : 0.4 [18-crown-6]. Stir the mixture at room temperature (20°C) for 1.5h, then transfer it to a stainless steel reactor, first statically age at room temperature for 20h, and then heat it to 120°C for 5 days of crystallization, and the resulting solid precipitate is filtered, washed and dried A synthetic EMT was obtained, which was calcined in an air atmosphere (program: 250°C/2h, 500°C/4h) to obtain a calcined EMT.

Embodiment 4: be made into the alkyl glycoside surfactant solution that molar concentration is 0.04mol/L, then a certain amount of silicon source (SiO ₂ , 25～30%), aluminum source (Al ₂ O ₃ , 43%) and 18-crown-6 templating agent and surfactant solution, the molar ratio of the obtained mixture is 10 SiO ₂ : 1 Al ₂ O ₃ : 2.2 Na _{2 O} : 0.4 [18-crown-6]. Stir the mixture at room temperature (35°C) for 1.5h, then transfer it to a stainless steel reactor, first statically age at room temperature for 24h, and then heat it to 110°C for 5 days of crystallization, and the resulting solid precipitate is filtered, washed and dried A synthetic EMT was obtained, which was calcined in an air atmosphere (program: 250°C/2h, 500°C/4h) to obtain a calcined EMT.

Embodiment 5: be made into molar concentration and be the lauric acid monoethanolamide polyoxyethylene (15) ether surfactant solution of 0.04mol/L, then a certain amount of silicon source (SiO ₂ , 25～30%), aluminum source (Al ₂ O ₃ , 43%) and 18-crown-6 template were mixed with the surfactant solution, and the molar ratio of the resulting mixture was 11 SiO ₂ : 1 Al ₂ O ₃ : 2.3 Na ₂ O : 0.4 [18-crown -6]. Stir the mixture at room temperature (25°C) for 1.0h, then transfer it to a stainless steel reactor, firstly age it statically at room temperature for 20h, then heat it to 110°C to crystallize for 7 days, and the resulting solid precipitate is filtered, washed and dried A synthetic EMT was obtained, which was calcined in an air atmosphere (program: 250°C/2h, 500°C/4h) to obtain a calcined EMT.

Claims (7)

1. a tensio-active agent is made the method for the synthetic EMT zeolite of auxiliary, and respectively as silicon source and aluminium source, as template, the tensio-active agent of interpolation is cationic, anionic or non-ionic type with 18-hat-6 with silicon sol, sodium aluminate, and synthesis step is as follows:

(1) with surfactant dissolves in water, making its concentration range is 0.02～0.20mol/L;

(2) silicon source, aluminium source and 18-hat-6 are mixed with surfactant soln,, follow the 12～48h that at room temperature wears out, then mixture is changed in the reactor at 20～35 ℃ of following stir about 0.5～1.5h;

(3) molar ratio range between above-mentioned each raw material is as follows: SiO ₂/ Al ₂O ₃=8～12, Na ₂O/Al ₂O ₃=1.8～3.0,18-hat-6/Al ₂O ₃=0.2～1.0;

(4) crystallization 3～30 days under 80-160 ℃ condition;

(5) solid precipitation after the crystallization, after filtration, washing, oven dry, roasting get final product.

2. tensio-active agent according to claim 1 is made the synthetic method of the EMT zeolite of auxiliary, and the concentration range that it is characterized in that surfactant soln is 0.03～0.10mol/L.

3. tensio-active agent according to claim 1 is made the synthetic method of the EMT zeolite of auxiliary, it is characterized in that the aged at room temperature time is 20-24h.

4. tensio-active agent according to claim 1 is made the synthetic method of the EMT zeolite of auxiliary, it is characterized in that the molar ratio range between each raw material is SiO ₂/ Al ₂O ₃=9～11, Na ₂O/Al ₂O ₃=1.8～2.4,18-hat-6/Al ₂O ₃=0.35～0.70.

5. tensio-active agent according to claim 1 is made the synthetic method of the EMT zeolite of auxiliary, it is characterized in that the molar ratio range between each raw material is SiO ₂/ Al ₂O ₃=10-11, Na ₂O/Al ₂O ₃=2.1～2.2,18-hat-6/Al ₂O ₃=0.35～0.40.

6. tensio-active agent according to claim 1 is made the synthetic method of the EMT zeolite of auxiliary, it is characterized in that the crystallization temperature scope is 100～130 ℃.

7. tensio-active agent according to claim 1 is made the synthetic method of the EMT zeolite of auxiliary, it is characterized in that crystallization time is 5～7 days.

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