CN1073968C - Process for preparing fine-grain octahedra zeolite - Google Patents

Abstract

The invention provides a method for preparing fine-grain Y-type zeolite, which is to prepare a synthetic Y-type zeolite by a faujasite directing agent, silicon source, aluminum source, water and acid or alkali according to the prior art method The reaction mixture is hydrothermally crystallized according to conventional conditions, which is characterized in that the reaction mixture contains rare earth ions, and the amount of the rare earth ions is 0.005-0.5 times the mole number of Al ₂ O ₃ in the reaction mixture. The Y-type molecular sieve synthesized according to the method provided by the present invention generally has an average grain size less than 300 nanometers, and can have an average grain size less than 100 nanometers under preferred conditions. The skeleton silicon-aluminum ratio of the product is generally greater than 5.0, and the crystallization The degree is generally above 80%.

Description

A kind of preparation method of fine grain faujasite

The invention relates to a fine-grain faujasite, especially a synthesis method of Y-type faujasite.

As we all know, the main application of molecular sieves in industrial processes basically lies in two aspects: catalysis and selective adsorption. In these processes, the size of the diffusion properties of adsorbed molecules through the pores and cages of molecular sieve crystals plays an important and sometimes decisive role. For reactant shape-selective catalysis, only when the molecular size of the reactant is smaller than the pore size of the molecular sieve and overcomes the surface energy barrier of the molecular sieve crystal can it diffuse into the pores of the molecular sieve and a specific catalytic reaction occur. However, the conversion of reactant molecules whose size is larger than the molecular sieve aperture on the catalyst can only depend on the active sites on the outer surface of the molecular sieve crystal. At this time, the size of the outer surface of the molecular sieve and the diffusion of reactant molecules on the outer surface are more important Most importantly, the size of molecular sieve grains plays an important role. Compared with larger grains, small or even ultrafine molecular sieves have more external area and better diffusion properties, so they are more conducive to the occurrence of the above process. .

Due to its high activity, molecular sieves are generally dispersed in a relatively inert matrix, such as silica gel, alumina or silica-alumina gel, and used in a composite state. However, the molecular sieve prepared by the conventional method has a large grain size, which is not conducive to uniform dispersion in the matrix, resulting in the fluctuation of the concentration of the molecular sieve in various parts of the matrix, and there are only a few active centers in the catalyst, which reduces its use. Efficiency (molecular sieve and reactant molecules are not fully contacted and product molecules cannot leave quickly), and shorten the life of the catalyst (easy to coke and deactivate). However, if small or even ultrafine molecular sieves are used, the above disadvantages will be overcome. In addition, with the heavy and inferior quality of refining raw materials, catalysts are required to have higher resistance to sulfur, nitrogen and heavy metals. Compared with large-particle molecular sieves, more ultrafine molecular sieves can be dispersed in the catalyst. Therefore, for the pollution of sulfur, nitrogen and heavy metals, catalysts containing ultrafine molecular sieves will have more residual activity and thus have higher life.

There are some hydrocarbon processing processes using molecular sieves and supported metal catalysts, such as hydrocracking, hydroisomerization, reforming, etc. The effective loading and dispersion performance of metal components on the support are the main factors determining the catalytic performance of this type of catalyst. The higher the payload of the metal component, the better the dispersibility, and the higher the efficiency of the catalyst. Generally, on the large molecular sieve grains, there is a limit to the content of metal components, beyond this limit, the metal components exist in the form of agglomerates on the surface or accumulate in the pores, which reduces the activity and selectivity of the catalyst. . On the ultrafine molecular sieve, the dispersion and effective content of metal components are both improved, which can increase the activity and selectivity of the catalyst and maintain a longer catalyst life.

The effect of faujasite crystal size on the performance and selectivity of catalytic cracking reactions has been reported in the literature. K.Rajagopalan, A.W.Peters and G.C.Edwards et al. [Applied Catalysis, 23 (1986) pp. 69-80] reported that on the Y-type molecular sieve with a grain size of 50 nm, it has higher activity for the cracking of heavy gas oil and better selectivity.

Several patent documents have reported methods for reducing the grain size of molecular sieves. In US3864282 and US3528615, it is described that faujasite can be reduced to 100 nm in size after treatment with thermal pulverization techniques. US4587115 and EP0435625A2 report that before crystallization, the synthesis system is subjected to high-shear stirring at a rate higher than 3000 r/min, and the faujasite crystal size prepared is 100-50 nanometers. The preparation method reported in US3755538 is to add a small amount of B, V, P, Mo, W, Ge or Ga elements to silica-alumina gel, and the synthesized faujasite has a grain size of 200-600 nanometers.

Changing the conditions of liquid phase synthesis is also one of the effective ways to reduce the grain size of molecular sieves. The synthesis conditions are generally high alkalinity, high silicon-aluminum ratio, dilute solution and lower temperature. The grain size of the synthesized faujasite can also be effectively reduced by introducing a water-miscible organic solvent into the synthesis system. US3516786 reports that a small amount of water-miscible organic solvents, such as methanol, ethanol, dimethyl sulfone, N,N-dimethylformamide, tetrahydrofuran, acetone, etc., are added to the synthesis system before the temperature rise crystallization step , the synthesized faujasite has a grain size of 10-100 nanometers. In US4372931, faujasite with a grain size of 40-60 nanometers was synthesized by adding monosaccharide or polysaccharide. However, the molecular sieves synthesized after adding organic solvents or sugars generally have a relatively low skeleton silicon-aluminum ratio, generally lower than 2.5, which means that no Y-type molecular sieves can be synthesized but only X-type molecular sieves can be synthesized, and organic solvents in water It is easy to volatilize under thermal crystallization conditions.

The purpose of this invention is to provide a kind of synthetic method of fine-grain Y-type zeolite, make the Y-type zeolite synthesized have the average grain size less than 300 nanometers, also have higher skeleton silicon-aluminum ratio and higher simultaneously crystallinity.

The synthesis method of Y-type zeolite provided by the present invention is to prepare a kind of faujasite directing agent, silicon source, aluminum source, water and acid or alkali according to the method of the prior art into a molar composition of SiO ₂ /Al ₂ O ₃ =8~30, Na ₂ O/SiO ₂ =0.2~0.6, H ₂ O/Na ₂ O=25~80, the preferred composition is SiO ₂ /Al ₂ O ₃ =8~15, Na ₂ O/SiO ₂ =0.3～0.5, H ₂ O/Na ₂ O=35～50 reaction mixture, then hydrothermal crystallization according to conventional conditions, characterized in that the reaction mixture contains rare earth ions, the amount of the rare earth ions (number of moles) It is 0.005 to 0.5 times, preferably 0.01 to 0.4 times, the number of moles of Al ₂ O ₃ in the reaction mixture. Among them, Na ₂ O represents the alkalinity of the mixture.

In the method provided by the present invention, the reaction mixture is preferably prepared by mixing various raw materials at a temperature of 0-10° C., so that the crystal size of the obtained molecular sieve can be further reduced.

Said faujasite directing agent in the method provided by the present invention is the existing faujasite directing agent in the prior art, _and its molar composition is generally (11～18) _Na2O : _Al2O3 :(10～18) 17) SiO ₂ : (100-350) H ₂ O, the directing agent can be prepared according to various methods for preparing faujasite directing agents in the prior art, for example according to USP3,639,099, USP3,671,191, USP4,166,099, CN85102733A and CN1081425A proposed method for preparing the directing agent to prepare. The molar amount of Al ₂ O ₃ contained in the directing agent should be 1-30%, preferably 5-20%, of the total molar amount of Al ₂ O ₃ in the reaction mixture.

In the method provided by the present invention, the silicon source is preferably water glass or silica sol, and the aluminum source is preferably aluminum sulfate.

In the method provided by the present invention, said rare earth element is at least one of elements such as La, Ce, Nb, Pr, Sm, Gd or a mixture of two or more of them, or is prepared from rare earth minerals Rare earth mixture.

The hydrothermal crystallization condition in the method provided by the present invention is generally crystallization at a temperature of 80-120°C for 6-60 hours, and preferably crystallization at a temperature of 90-110°C for 10-48 hours.

In the method provided by the present invention, since rare earth ions are added to the synthesis reaction mixture, the rare earth ions can promote the nucleation of molecular sieves and the growth of crystals, thereby significantly reducing the grain size of the obtained molecular sieves, while the skeleton of the product is silicon aluminum Ratio and crystallinity did not decrease. The Y-type molecular sieve synthesized according to the method provided by the present invention generally has an average grain size less than 300 nanometers, and can have an average grain size less than 100 nanometers under preferred conditions. The skeleton silicon-aluminum ratio of the product is generally greater than 5.0, and the crystallization The degree is generally above 80%.

Fig. 1 is the transmission electron microscope (TEM) photo of the product molecular sieve obtained in Example 3 (magnification is 27K).

The following examples will further illustrate the present invention. In each embodiment and comparative example, the average grain size of the obtained molecular sieve product is measured by transmission electron microscopy (TEM), the specific surface area is measured by the Chinese national standard GB/T5816-1995 method, and the relative crystallinity is measured according to the RIPP146-90 standard method (See "Petrochemical Analysis Methods", edited by Yang Cuiding, etc., Science Press, published in 1990) Determination, the measurement method of the skeleton silicon-aluminum ratio (SiO ₂ /Al ₂ O ₃ ) is first according to the RIPP145-90 standard method (same as above) The unit cell parameter a ₀ of the molecular sieve is determined, and then calculated according to the formula SiO ₂ /Al ₂ O ₃ =(25.248-a ₀ )×2÷0.245.

Example 1

This example illustrates the preparation of faujasite directing agents useful in the present invention.

45.1 grams of aluminum sulfate (Al ₂ (SO ₄ ) ₃ 18H ₂ O, analytically pure commercial reagent, the same below), 235.2 grams of silica sol (produced by Beijing Changhong Chemical Plant, containing 25.9% by weight SiO ₂ and 0.2% by weight Na ₂ O, the same below), 105.9 grams of sodium hydroxide (analytical grade commercially available reagents, the same below) and 189.8 grams of deionized water were mixed uniformly at room temperature (25°C) under stirring conditions, and then left to stand at room temperature Aged for 24 hours, the resulting reaction mixture was used as a directing agent.

Comparative example 1

This comparative example illustrates the preparation of a conventional Y zeolite.

Under the conditions of room temperature and stirring, 26.65 grams of sodium hydroxide, 148.2 grams of silica sol, 45.1 grams of aluminum sulfate, 38.0 grams of deionized water, and 64.0 grams of the directing agent prepared in Example 1 were mixed, and continued to stir rapidly for 0.5 hours, and then put the resulting mixture into a sealed stainless steel reaction vessel, and conduct hydrothermal crystallization at 90° C. for 48 hours. The crystallized product was filtered and washed with water until the pH of the filtrate was <10, and the resulting filtrate was dried at 100°C. X-ray diffraction (XRD) analysis shows that the obtained product is Y-type molecular sieve, SiO ₂ /Al ₂ O ₃ =5.11, and the relative crystallinity is 90%. TEM analysis showed that the average grain size of the product molecular sieve was 850 nanometers. The specific surface area measured by BET method is 750m ² /g.

Example 2

At room temperature (25° C.) and stirring, 28.5 grams of sodium hydroxide, 148.1 grams of silica sol, 45.1 grams of aluminum sulfate, 37.1 grams of deionized water, and 64.0 grams of the directing agent prepared in Example 1 were mixed uniformly, Then add 3.8 grams of rare earth chloride mixture (Baotou Rare Earth Company product, wherein the percentage by weight in terms of oxides consists of: 46% Ce, 26% La, 17% Nb, 6% Pr, 3% Sm and 2% Gd, the following Same), continue to stir for 0.5 hours. Then the obtained mixture was put into a sealed stainless steel reaction kettle, and hydrothermally crystallized at 100° C. for 24 hours. The crystallized product was filtered and washed with water until the pH of the filtrate was <10, and the resulting filtrate was dried at 100°C. X-ray diffraction (XRD) analysis showed that the obtained product was a Y-type molecular sieve (see Table 1 for XRD diffraction peak positions and intensities), SiO ₂ /Al ₂ O ₃ =5.55, and a relative crystallinity of 85%. TEM analysis showed that the average grain size of the product molecular sieve was 110 nanometers. The specific surface area measured by BET method is 760m ² /g.

Table 1 2θ h ² +k ² +l ² d I/I ₀ 6.2210.1711.9415.7118.7520.4322.8723.7425.8727.1427.8729.7330.8531.5132.5733.1934.2134.838.03 3811192732404351565967727580838891108 14.198.6887.4075.6354.7294.3443.8853.7473.4413.2833.1993.0022.8962.8372.7472.6972.6192.5762.364 100152441233513479378142048217191113

Example 3

Under the condition of 0 ℃ and stirring, mix 30.5 grams of sodium hydroxide, 166.7 grams of silica sol, 50.7 grams of aluminum sulfate, 42.7 grams of deionized water, and 72.0 grams of the directing agent prepared in Example 1, and then add 1.1 gram of rare earth chloride and continued to stir for 0.5 hour. Then the resulting mixture was put into a sealed stainless steel reaction kettle, and hydrothermally crystallized at 90° C. for 24 hours. The crystallized product was filtered and washed with water until the pH of the filtrate was <10, and the resulting filtrate was dried at 100°C. X-ray diffraction (XRD) analysis shows that the obtained product is Y-type molecular sieve (XRD diffraction peak position and intensity are basically the same as those in Table 1), SiO ₂ /Al ₂ O ₃ =5.83, and relative crystallinity is 80%. TEM analysis showed that the average grain size of the product molecular sieve was 70 nanometers. The specific surface area measured by BET method is 755m ² /g.

Example 4

Under the condition of stirring at 10°C, mix 27.6 grams of sodium hydroxide, 148.1 grams of silica sol, 45.1 grams of aluminum sulfate, 37.1 grams of deionized water, and 64.0 grams of the directing agent prepared in Example 1, and then add 1.9 gram of rare earth chloride and continued to stir for 0.5 hour. Then the resulting mixture was put into a sealed stainless steel reaction kettle, and hydrothermally crystallized at 90° C. for 24 hours. The crystallized product was filtered and washed with water until the pH of the filtrate was <10, and the resulting filtrate was dried at 100°C. X-ray diffraction (XRD) analysis showed that the obtained product was Y-type molecular sieve (XRD diffraction peak position and intensity were basically the same as those in Table 1), SiO ₂ /Al ₂ O ₃ =5.76, and relative crystallinity was 85%. TEM analysis showed that the average grain size of the product molecular sieve was 90 nanometers. The specific surface area measured by BET method is 762m ² /g.

Example 5

Under the conditions of 0°C and stirring, mix 26.8 grams of sodium hydroxide, 148.1 grams of silica sol, 45.1 grams of aluminum sulfate, 37.8 grams of deionized water, and 64.0 grams of the directing agent prepared in Example 1, and then add 0.3 gram of rare earth chloride and continued to stir for 0.5 hour. Then the obtained mixture was put into a sealed stainless steel reaction kettle, and hydrothermally crystallized at 90° C. for 20 hours. The crystallized product was filtered and washed with water until the pH of the filtrate was <10, and the resulting filtrate was dried at 100°C. X-ray diffraction (XRD) analysis showed that the obtained product was Y-type molecular sieve (XRD diffraction peak position and intensity were basically the same as those in Table 1), SiO ₂ /Al ₂ O ₃ =5.69, and relative crystallinity was 86%. TEM analysis showed that the average grain size of the product molecular sieve was 80 nanometers. The specific surface area measured by BET method is 770m ² /g.

Example 6

At room temperature (25°C) and stirring, 32.8 grams of sodium hydroxide, 205.9 grams of silica sol, 50.7 grams of aluminum sulfate, 38.3 grams of deionized water, and 72.0 grams of the directing agent prepared in Example 1 were mixed uniformly, Then add 4.3 g of rare earth chloride and continue stirring for 0.5 hour. Then the obtained mixture was put into a sealed stainless steel reaction kettle, and hydrothermally crystallized at 100° C. for 20 hours. The crystallized product was filtered and washed with water until the pH of the filtrate was <10, and the resulting filtrate was dried at 100°C. X-ray diffraction (XRD) analysis showed that the obtained product was Y-type molecular sieve (XRD diffraction peak position and intensity were basically the same as those in Table 1), SiO ₂ /Al ₂ O ₃ =5.75, and relative crystallinity was 90%. TEM analysis showed that the average grain size of the product molecular sieve was 100 nanometers. The specific surface area measured by BET method is 770m ² /g.

Claims (9)

1. the synthetic method of a y-type zeolite comprises that a kind of faujusite directed agents, silicon source, aluminium source, water and acid or alkali are prepared into a kind of mole consists of SiO ₂/ Al ₂O ₃=8～30, Na ₂O/SiO ₂=0.2～0.6, H ₂O/Na ₂The reaction mixture of O=25～80, condition hydrothermal crystallizing routinely is characterized in that containing rare earth ion in the said reaction mixture then, and the consumption of this rare earth ion is Al in the said reaction mixture ₂O ₃0.005～0.5 times of mole number.

2. according to the method for claim 1, it is characterized in that said reaction mixture is that said various raw materials are mixed and prepare under 0～10 ℃ temperature.

3. according to the process of claim 1 wherein that said faujusite directed agents consists of (11～18) Na for its mole ₂O: Al ₂O ₃: (10～17) SiO ₂: (100～350) H ₂O, contained Al in this directed agents ₂O ₃Mole number be Al in the said reaction mixture ₂O ₃Total mole number 5～20%.

4. according to the process of claim 1 wherein that said silicon source is water glass or silicon sol, said aluminium source is a Tai-Ace S 150.

5. according to the process of claim 1 wherein that said rare earth metal is to be selected from least a among La, Ce, Nb, Pr, Sm, the Gd or the two or more mixture in them, or from the prepared lucium of rare-earth mineral.

6. according to the method for claim 5, wherein said rare earth metal is from the prepared lucium of rare-earth mineral.

7. according to the process of claim 1 wherein that the mole of said reaction mixture consists of: SiO ₂/ Al ₂O ₃=8～15, Na ₂O/SiO ₂=0.3～0.5, H ₂O/Na ₂O=35～50, rare earth ion/Al ₂O ₃=0.01～0.4.

8. according to the process of claim 1 wherein that said hydrothermal crystallizing condition is a crystallization 6～60 hours under 80～120 ℃ temperature.

9. according to the method for claim 8, wherein said hydrothermal crystallizing condition is a crystallization 10～48 hours under 90～110 ℃ temperature.