CN1325375C - Beta zeolite granule possessing multiple grade pore passage and its preparation method - Google Patents

Abstract

The invention relates to a beta zeolite particle with multi-level pores, the molar ratio of SiO ₂ /Al ₂ O ₃ is 80-120, the average particle size is 0.1-0.5 μm, the pore volume is 0.35-0.50ml/g, and the pore diameters are concentratedly distributed There are three sections of 0.1~1.7nm, 1.7~6.0nm, and 10.0~90.0nm. The preparation process of the beta zeolite of the present invention adopts the hydrothermal synthesis method with optimized conditions, and after the synthesis process, the ammonium salt treatment process is carried out first, and the obtained zeolite is subjected to acid treatment and hydrothermal treatment under suitable conditions to obtain the final beta zeolite product. The beta zeolite of the present invention has three kinds of pores with different pore diameters and suitable particle size. Compared with the prior art, it can greatly improve the utilization rate of the outer surface of the small-grained zeolite, reduce diffusion resistance, reduce secondary reactions, and improve reaction selectivity. . The preparation method of the invention is simple, low in cost and good in product repeatability. The beta zeolite of the present invention can be used in various catalysts such as hydrocracking.

Description

Beta zeolite particles with hierarchical pores and preparation method thereof

technical field

The invention relates to a beta zeolite and a preparation method thereof, in particular to a beta zeolite particle with a multi-level pore structure and a preparation method thereof.

Background technique

Beta zeolite is a high-silica zeolite (US3,308,069) with a three-dimensional pore structure successfully developed by Mobil Corporation of the United States in the 1960s. Catalytic performance, has broad application prospects in petroleum and chemical industry. Industrial application results show that β zeolite has high hydrocracking activity and hydroisomerization performance, and can be used for hydrocracking, hydroisomerization, hydrofinishing, hydrodewaxing, Diesel decondensation and other processes.

The narrow pores inside the zeolite grains increase the diffusion resistance and reduce the reaction performance. After the crystal grains become smaller, the outer surface expands and the internal diffusion rate increases, which has positive effects on improving catalyst utilization, enhancing macromolecular conversion capabilities, reducing deep reactions, and improving selectivity. For example, EP-02042362 has studied the small-grain NaY zeolite and the large-grain NaY zeolite in depth, and the comparison results show that the former has higher activity and better selectivity for catalytic cracking of heavy oil. Therefore, the preparation technology of small crystal zeolite has been paid more and more attention by people.

The prior art can synthesize beta zeolite with various grain sizes. The zeolite beta grain size synthesized by the method described in US3308069 is 0.3～0.5 μm; More than 0.1 μm, the crystal grains of zeolite beta synthesized in CN1268545A are 0.7-1.5 μm, and the crystal grains of zeolite beta synthesized in CN1324762A are 50-90 nm.

Generally speaking, the pore size in zeolite grains is single, and for zeolite with larger grains, its diffusion will be seriously affected, thereby affecting the selectivity of the reaction and the life of the catalyst. Reducing the crystal grains of zeolite can solve this problem to a certain extent, which is also the reason why small crystal grain zeolites (including nano zeolites) have been paid attention to in recent years. However, in many cases, the zeolite content in the catalyst is less, such as the zeolite content in the hydrocracking catalyst is generally only 1% to 30%, that is to say, a small amount of zeolite is "coated" in a large number of other materials . As in hydrocracking catalysts, a small amount of zeolite is mixed with a large amount of alumina which is not cracking active. As a result, a large amount of the outer surface of the zeolite is bound to alumina, which makes it difficult to fully exert the effect on the small-grain zeolite characterized by a large outer area and externalization of the active center. Therefore, the zeolites in the prior art, no matter whether they are large crystal grains or small crystal grains, have certain deficiencies when they are used as part of catalyst components. In addition, in the preparation method of zeolite beta in the prior art, the amount of template agent (tetraethylammonium hydroxide) is large, the solid-to-liquid ratio of the feed is low, the single-pot yield is low, the crystallization temperature is high, and the time is long, and miscellaneous crystals are prone to appear. The result was poor reproducibility, difficult filtration and low yield.

Contents of the invention

Aiming at the deficiencies of the prior art, the invention provides a small particle beta zeolite with a multi-level pore structure and a preparation method thereof.

The SiO ₂ /Al ₂ O ₃ of the β zeolite of the present invention is 80-120 (molar ratio), the average particle size is 0.1-0.5 μ m, the pore volume is 0.35-0.50 ml/g, and the pores with a pore diameter of 0.1-1.7 nm account for the total 20% to 50% of the pore volume, pores with a pore diameter greater than 1.7nm to 6.0nm account for 5% to 20% of the total pore volume, and pores with a pore diameter of 10.0 to 90.0nm account for 30% to 60% of the total pore volume.

The preparation process of the beta zeolite of the present invention includes: the silicon source and the aluminum source are crystallized in two stages by a hydrothermal method in the presence of a tetraethylammonium hydroxide template agent, first low-temperature nucleation, and then high-temperature crystallization, and one-step crystallization can also be used. Ammonium salt is added to treat for a certain period of time, the above crystallization and treatment are carried out under continuous stirring, and then filtered, dried, and roasted in three stages to remove organic ammonium, acid treatment and high temperature and high pressure hydrothermal treatment under mild conditions, to produce more Beta zeolite products with grade pores.

The specific process is as follows: the silicon source uses porous solid silica gel particles, the aluminum source uses sodium aluminate, and the template agent uses tetraethylammonium hydroxide. A two-stage crystallization method is adopted, first low-temperature nucleation, and then high-temperature crystallization, that is, crystallization in a crystallization kettle at 90-130°C for 10-40 hours, and crystallization at 110-170°C for 20-50 hours. When using one-step crystallization, crystallize at 100°C-170°C for 10-60 hours. Then directly add ammonium salt and treat at 80-120° C. for 0.2-3.0 hours. Ammonium salt treatment can be carried out 1-3 times, and the concentration of ammonium salt in the mixture is 0.5-3 mol/L. After ammonium salt treatment, filter, wash, and dry, remove organic ammonium by three-stage temperature-controlled roasting, dehydrate at low temperature (150-250°C) for 1.0-6.0 hours, and decompose organic ammonium at medium temperature (250-450°C) for 1.0-4.0 hours. High temperature (450-650°C) to remove free carbon for 6.0-20.0 hours. Acid treatment of inorganic acid at 0.1-5.0mol/L (preferably 0.5-1.5mol/L), treatment temperature 20-100°C, treatment time 1.0-3.0 hours, high temperature and high pressure hydrothermal treatment at temperature 500-700°C, pressure 0.05 -0.5MPa, treatment for 0.5-5.0 hours, to obtain multi-stage zeolite beta granular products. Ratio (mole) of each raw material: Na ₂ O/Al ₂ O ₃ is 0.5-5.0, preferably 1.0-2.0; (TEA) ₂ O/Al ₂ O ₃ is 0.5-5.0, preferably 1.0-3.0 ; SiO ₂ /Al ₂ O ₃ is 10-100, preferably 10-50; H ₂ O/Al ₂ O ₃ is 100-500; best is 100-300.

Said porous solid silica gel in the method of the present invention can be coarse-pored, medium-pored, fine-pored silica gel, said aluminum source can be solid sodium aluminate or liquid sodium aluminate, and sodium source can be sodium aluminate or aluminate A mixture of sodium and sodium hydroxide. Ammonium salt can be ammonium chloride, ammonium nitrate or ammonium sulfate, also can be mixed ammonium salt. The inorganic acid used in acid treatment is generally hydrochloric acid, nitric acid or sulfuric acid.

The beta zeolite of the present invention can be used as a catalyst for hydrocarbon conversion processes such as hydrocracking, hydroprocessing, isomerization, disproportionation, olefin hydration, alcohol dehydration, dehydrogenation, oxidation, condensation, and polymerization.

The beta zeolite of the present invention has a suitable particle size and a multi-level pore structure. Among them, the micropores are the pores of zeolite beta itself, which is the main reaction site of substances. Mesopores may be secondary pores generated during acid treatment and hydrothermal treatment, reducing diffusion resistance, reducing secondary reactions, and improving selectivity. The macropores may be the pores formed between the primary particles after the zeolite primary particles are aggregated into the final zeolite particles. On the one hand, its main function can reduce the diffusion resistance and reduce the secondary reaction. More importantly, this zeolite particle structure protects the primary particles. The outer surface of the zeolite is fully exposed and is not affected by other catalyst components, which overcomes the problem that the outer surface of the small grain or nano-sized zeolite cannot be fully utilized when used as a catalyst component. Aggregation of primary particles into final suitable particles may be accomplished during the ammonium salt treatment.

The method of the invention optimizes the conditions of the crystallization process of the beta zeolite, adds a step of ammonium salt treatment process after the crystallization, and obtains the beta zeolite product with unique properties after proper post-treatment. The method of the invention carries out crystallization under the conditions of higher basicity, lower temperature, shorter crystallization time, high-speed stirring, etc., and then undergoes post-treatment processes such as ammonium salt treatment to obtain the final zeolite product. The method of the invention has high utilization rate of silicon source and aluminum source, high single-pot yield, short crystallization time, low temperature, reduced energy consumption, low production cost and good product repeatability.

Description of drawings

Fig. 1 is a transmission electron micrograph with a magnification of 20,000 times of zeolite beta obtained in Example 1 of the present invention.

Fig. 2 is the X-ray diffraction spectrogram of the beta zeolite obtained in Example 1 of the present invention.

Detailed ways

The following examples will give further description to the preparation method provided by the present invention.

Example 1

Mix 78g of sodium aluminate (contains 19.9m% of Al ₂ O ₃ and 21.44m% of Na ₂ O in laboratory preparation), 435g of tetraethylammonium hydroxide aqueous solution (industrial production, concentration 1.4N), coarse-pored silica gel particles 288g (manufactured by Qingdao Haiyang Chemical Factory, containing 95% SiO ₂ ) and 120g of purified water are mixed evenly, and reacted in a 2-liter stainless steel reactor at 100°C for 20 hours under sufficient and continuous stirring conditions, and then raised to 150°C for crystallization for 40 hours After the crystallization is completed, the pressure is relieved, the temperature is lowered, ammonium nitrate solution is added, and the concentration of ammonium nitrate in the system is 2mol/L, and the mixture is stirred at a constant temperature of 95°C for 1 hour, then filtered, and ammonium salt treatment is carried out again according to the above conditions. Then filter, wash with water, dry, remove organic ammonium by three-stage temperature-controlled roasting, dehydrate at a constant temperature of 200°C for 2 hours, decompose organic ammonium at 400°C for 3 hours, decompose free carbon at 550°C for 12 hours, and the concentration of hydrochloric acid for acid treatment is 0.5mol/L , treated at 80°C for 1 hour under fully stirred conditions, then filtered, washed with water, dried, and subjected to high-temperature and high-pressure hydrothermal treatment at a temperature of 650°C and a pressure of 0.1 MPa for 2 hours to obtain zeolite beta B-1 of the present invention.

Example 2

80g of sodium aluminate (prepared in the laboratory containing Al ₂ O ₃ 18.90m%, containing Na ₂ O 24.11m%), 382g of tetraethylammonium hydroxide aqueous solution (industrial product, concentration 1.55N), 280g of coarse-pore silica gel particles ( The product produced by Qingdao Ocean Chemical Factory contains SiO ₂ (95.2m%) and 158g of purified water, mixed evenly. Other conditions were the same as in Example 1 to obtain zeolite beta B-2.

Example 3

80kg sodium aluminate (industrial preparation, containing Al ₂ O _19.55m %, containing Na ₂ O 1.17m%), 459kg tetraethylammonium hydroxide (industrial product, concentration 1.35N) coarse-pore silica gel particles 288kg (Qingdao ocean Produced in a chemical factory, containing SiO ₂ (97m%) and 140kg of purified water, after fully mixing, under continuous stirring conditions in a 1000-liter stainless steel crystallization tank, the following is the same as in Example 1 to obtain zeolite beta, B-3.

Example 4

According to the method of Example 1, during crystallization, crystallize at 95° C. for 12 hours, and then crystallize at 155° C. for 25 hours. During ammonium salt treatment, the concentration of ammonium salt was adjusted to 1.0mol/L, the treatment temperature was 85°C, the time was 1.5 hours, and the number of treatments was 3 times. Acid treatment is at 1.5 hydrochloric acid, and treatment temperature is 90 ℃, and treatment time is 2.0 hours, and other is the same as embodiment 1, and product is B-4.

Example 5

According to the method of Example 2, ammonium chloride is used for ammonium salt treatment, the concentration in the system is 0.8mol/L, the temperature is 105°C, the time is 2 hours, and the number of times is 3 times. The acid treatment uses nitric acid, the concentration is at 1.2mol/L, the treatment temperature is 50°C, and the treatment time is 1.5 hours. The high-temperature and high-pressure hydrothermal treatment is at a temperature of 550°C, and a pressure of 0.2MPa, and is processed for 3.0 hours. Others are the same as in Example 1, and the product obtained is B-5.

Table 1 The embodiment of the present invention makes the beta zeolite product property

Product number B-1 B-2 B-3 B-4 B-5 Scale L 2 2 1000 2 2 SiO ₂ /Al ₂ O ₃ 102 98 112 115 104   Average particle size μm 0.25 0.20 0.30 0.15 0.35 V _{total pores} ml/g 0.407 0.412 0.422 0.425 0.409  Product Yield% 85 87 84 88 89 Pore Distribution% ＜1.7nm 32.2 28.9 31.8 26.2 28.4 ＞1.7nm 67.8 71.1 68.8 67.8 71.6 1.7-6.0nm 8.2 12.3 10.5 15.8 14.3 10.0-90.0nm 54.5 54.4 53.2 46.3 43.4

Claims (9)

1. A beta zeolite with multi-level channels, the SiO ₂ /Al ₂ O ₃ molar ratio is 80-120, the average particle size is 0.1-0.5 μm, the pore volume is 0.35-0.50ml/g, and the pore diameter is 0.1-1.7 The pores with a diameter of 10.0 nm to 6.0 nm account for 5% to 20% of the total pore volume, and the pores with a diameter of 10.0 to 90.0 nm account for the total pore volume. 30% to 60% of that. 2. A method for preparing zeolite beta according to claim 1, characterized in that it comprises the following process: the silicon source and the aluminum source are crystallized in two stages by a hydrothermal method in the presence of a template agent, first low-temperature nucleation, and then high-temperature crystallization or adopt one-step crystallization; adding ammonium salts for treatment for a certain period of time, the above-mentioned crystallization and treatment are carried out under continuous stirring, then filtering, drying, roasting to remove organic ammonium, acid treatment and high temperature and high pressure hydrothermal treatment under mild conditions, to prepare Beta zeolite products with multi-order channels; The two-stage crystallization conditions described therein are: low-temperature nucleation first, followed by high-temperature crystallization, that is, crystallization in a crystallization kettle at 90-130°C for 10-40 hours, crystallization at 110-170°C for 20- 50 hours; the one-step crystallization at 100°C-170°C for 10-60 hours; The treatment condition of adding ammonium salt is: treatment at 80-120°C for 0.2-3.0 hours; The conditions of the high temperature and high pressure hydrothermal treatment are: treatment at a temperature of 500-700°C and a pressure of 0.05-0.5MPa for 0.5-5.0 hours; The template agent is tetraethylammonium hydroxide, and the acid treatment uses mineral acid. 3. The method according to claim 2, wherein the silicon source is porous solid silica gel particles, the aluminum source is sodium aluminate, and the ammonium salt treatment is ammonium nitrate, ammonium chloride or ammonium sulfate. 4. The method according to claim 3, characterized in that the aluminum source is solid sodium aluminate or liquid sodium aluminate, and the sodium source is sodium aluminate or a mixture of sodium aluminate and sodium hydroxide, which is used for acid treatment The preferred inorganic acid is hydrochloric acid, nitric acid or sulfuric acid. 5. The method according to claim 2, characterized in that the ammonium salt treatment is carried out 1-3 times, and the concentration of the ammonium salt in the mixture is 0.5-3 mol/L. 6. The method according to claim 2, characterized in that the roasting to remove organic ammonium adopts a three-stage temperature-controlled roasting process, roasting at 150-250°C for 1.0-6.0 hours, and roasting at 250-450°C for 1.0-4.0 hours, Roast at 450-650°C for 6.0-20.0 hours. 7. The method according to claim 2, characterized in that the acid treatment is 0.1-5.0 mol/L of inorganic acid, the treatment temperature is 20-100°C, and the treatment time is 1.0-3.0 hours. 8. The method according to claim 2, characterized in that the molar ratio of each raw material is: Na ₂ O/Al ₂ O ₃ is 0.5-5.0, (TEA) ₂ O/Al ₂ O ₃ is 0.5- 5.0, SiO ₂ /Al ₂ O ₃ is 10-100, H ₂ O/Al ₂ O ₃ is 100-500. 9. The method according to claim 2, characterized in that the molar ratio of each raw material is: Na ₂ O/Al ₂ O ₃ is 1.0-2.0, (TEA) ₂ O/Al ₂ O ₃ is 1.0- 3.0, SiO ₂ /Al ₂ O ₃ is 10-50, H ₂ O/Al ₂ O ₃ is 100-300.

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