Preparation method of low-sodium hydrothermal ultra-stable molecular sieve

Abstract

The present application relates to the technical field of molecular sieve material and its preparation, in particular to a preparation method of low-sodium hydrothermal ultrastable molecular sieve, which comprises the following steps: step one: mixing a silicon source and a sodium metaaluminate aqueous solution and aging to obtain a directing agent; step two: adding the sodium metaaluminate aqueous solution, the directing agent and aluminum sulfate into the silicon source to obtain a silicoaluminate gel; step three: warming and crystallizing to obtain a NaY type molecular sieve; step four: adding the NaY type molecular sieve into a first cation exchanger to obtain a first-interchange molecular sieve slurry, filtering, carrying out belt exchange, and washing to obtain a first-interchange molecular sieve; step five: carrying out one-time flashing and one-time calcination to obtain a first-interchange one-calcination molecular sieve; and step six: mixing the first-interchange one-calcination molecular sieve with the first cation exchanger to obtain a second-interchange one-calcination molecular sieve slurry, filtering and washing to obtain a second-interchange one-calcination molecular sieve. The present application can reduce the sodium content of Y type molecular sieve and improve the preparation efficiency of Y type molecular sieve.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of molecular sieve materials and its preparation, in particular to a preparation method of low-sodium hydrothermal ultrastable molecular sieve. BACKGROUND

[0002] Molecular sieve is a kind of silicate-aluminate compound with cubic lattice. Molecular sieve has a uniform microporous structure, and its pore diameter is uniform. These pores can adsorb molecules smaller than its diameter to the inside of the pore cavity, and have preferential adsorption capacity for polar molecules and unsaturated molecules, so they can separate molecules with different polarities, different saturation levels, different molecular sizes and different boiling points, that is, they have the function of "sieve" molecules, so they are called molecular sieve. In recent years, molecular sieve has been widely used in organic chemical industry, petroleum chemical industry, coal gas dehydration and waste gas purification due to its strong selective adsorption capacity, high internal surface area and good thermal stability.

[0003] Molecular sieve can be divided into A-type molecular sieve, X-type molecular sieve, Y-type molecular sieve and mordenite according to different compositions and structures. The Y-type molecular sieve refers to an artificial synthesized zeolite molecular sieve with a silicon-aluminum ratio (SiO2 / Al2O3) greater than 3.0. The crystal structure of Y-type molecular sieve contains supercage cavities and a three-dimensional twelve-membered ring pore system, and can be used as an active component of acidic catalyst for catalytic cracking reaction. NaY-type molecular sieve is a precursor of acidic Y-type molecular sieve. This kind of molecular sieve itself has no acidity and cracking activity, and cannot be directly used as an acidic catalyst. The existing technology usually modifies NaY-type molecular sieve by removing sodium ions in it to prepare Y-type molecular sieve to improve the catalytic activity. Since the structure of NaY-type molecular sieve is complex, the sodium ions at different positions have different steric hindrance. The sodium ions in the small cage are difficult to be exchanged out. The catalyst prepared by taking NaY-type molecular sieve as a precursor has the problems of low catalytic activity, poor thermal stability and poor structural stability. SUMMARY

[0004] In view of the technical problems of low catalytic activity, poor thermal stability and poor structural stability of the catalyst prepared by taking NaY-type molecular sieve as a precursor, the present application provides a preparation method of low-sodium hydrothermal ultrastable molecular sieve. The NaY-type molecular sieve is prepared by using a directing agent method, and the NaY-type molecular sieve is sequentially subjected to one-tank exchange, one-flash evaporation and one calcination, and two-tank exchange treatment. The sodium content of Y-type molecular sieve is reduced, and the preparation efficiency of Y-type molecular sieve is improved.

[0005] The present application provides a preparation method of low-sodium hydrothermal ultrastable molecular sieve, which comprises the following steps:

[0006] Step one: uniformly mix a silicon source and a sodium metaaluminate aqueous solution, and age at room temperature to obtain a directing agent;

[0007] Step two: adding sodium metaaluminate aqueous solution, directing agent and aluminum sulfate into the silicon source, and uniformly mixing to obtain a silicoaluminate gel;

[0008] Step three: passing water vapor into the silicoaluminate gel to heat and crystallize, to obtain a NaY type molecular sieve;

[0009] Step four: adding the NaY type molecular sieve into the first cationic exchanger, uniformly mixing, and performing a tank type exchange, then adjusting the pH to 3.5-4.5, heating to 60-70℃, and keeping the temperature constant for 0.5-1.5h, to obtain a first exchange molecular sieve slurry, in the tank type exchange process, the amount of the first cationic exchanger is 0.08-0.15g / g NaY type molecular sieve; filtering the first exchange molecular sieve slurry to obtain a first exchange molecular sieve crude product, and adding the first cationic exchanger to the first exchange molecular sieve crude product to perform a belt type exchange, then washing with water to obtain a first exchange molecular sieve, in the belt type exchange process, the amount of the first cationic exchanger is 0-0.25g / g first exchange molecular sieve crude product, preferably 0.12-0.25g / g first exchange molecular sieve crude product; wherein the first cationic exchanger is an ammonium sulfate solution or a lanthanum chloride solution, and the molar concentration of the first cationic exchanger is 0.9-1.1mol / L;

[0010] Step five: sequentially performing a first flash and a first calcination on the first exchange molecular sieve mixed slurry to obtain a first exchange first calcination molecular sieve, wherein the temperature of the first flash is 110-150℃, and the temperature of the first calcination is 500-800℃;

[0011] Step six: adding the first exchange first calcination molecular sieve into the first cationic exchanger, uniformly mixing, and performing a second tank type exchange, then heating to 60-70℃, and keeping the temperature constant for 0.5-1.5h, to obtain a second exchange first calcination molecular sieve slurry, filtering and washing the second exchange first calcination molecular sieve slurry to obtain a second exchange first calcination molecular sieve, wherein the amount of the first cationic exchanger is 0.08-0.15g / g first exchange first calcination molecular sieve, the first cationic exchanger is an ammonium sulfate solution or a lanthanum chloride solution, and the molar concentration of the first cationic exchanger is 0.9-1.1mol / L.

[0012] In step four, filtering and washing the first exchange molecular sieve slurry can remove the chloride ions in the first exchange molecular sieve slurry with the sewage, to avoid the chloride ions entering the first flash and the first calcination.

[0013] Further, step four further comprises: adding a first ion exchange agent into the second cation exchange agent and mixing uniformly to obtain a first ion exchange agent mixed slurry, the second cation exchange agent is used in an amount of 0.01-0.09 g / g of the first ion exchange agent, the second cation exchange agent is a lanthanum nitrate solution or a yttrium nitrate solution, and a molar concentration of the second cation exchange agent is 1.1-1.3 mol / L. Nitrate ions in the second cation exchange agent can enter the primary flash and primary calcination links in the form of nitrogen oxides into the tail gas recovery device.

[0014] Further, step seven is further included: sequentially performing secondary flash and secondary calcination on the second ion exchange and calcined molecular sieve to obtain a second ion exchange and calcined molecular sieve, wherein the secondary flash temperature is 110-150℃, and the secondary calcination temperature is 500-800℃. The secondary flash and secondary calcination are beneficial to further improve the thermal stability and structural stability of the Y-type molecular sieve.

[0015] Further, the silicon source is a sodium silicate aqueous solution, in which the mass percentage of SiO2 is 20wt%, and the mass percentage of Na2O is 7wt%; the sodium aluminate aqueous solution is a high-alkali sodium aluminate aqueous solution or a low-alkali sodium aluminate aqueous solution, the caustic ratio of the high-alkali sodium aluminate aqueous solution is 10.5 mol / mol, and the caustic ratio of the low-alkali sodium aluminate aqueous solution is 2.4 mol / mol.

[0016] Further, in step one, the silicon source and the sodium aluminate aqueous solution are mixed according to a molar ratio of 10.67Na2O:1Al2O3:10SiO2:180H2O, and the aging time is 12-24 h, preferably 12-14 h.

[0017] Further, in step two, the silicon source, the sodium aluminate aqueous solution, the directing agent, and the aluminum sulfate are mixed according to a molar ratio of 8Na2O:1Al2O3:20SiO2:320H2O. The addition of the aluminum sulfate is beneficial to realize the recycling of silicon and improve the yield of the NaY-type molecular sieve.

[0018] Further, in step three, the crystallization temperature is 92-98℃, and the crystallization time is 20-30 h.

[0019] Further, in step four, the first ion exchange agent slurry is filtered and washed with water to obtain the first ion exchange agent, and the amount of water used is 3-5 g / g of the first ion exchange agent. The solid content of the filtered first ion exchange agent slurry is 440-460 g / L. Washing the first ion exchange agent slurry with water and filtering can remove the crystallization residue remaining in the first ion exchange agent slurry.

[0020] Further, in step six, the two-interaction one-calcined molecular sieve slurry is filtered and washed with water to obtain the two-interaction one-calcined molecular sieve, and the amount of water is 3-5 g / g of the two-interaction one-calcined molecular sieve. The solid content of the two-interaction one-calcined molecular sieve slurry after filtration is 460-480 g / L.

[0021] Further, in step four, sulfuric acid or hydrochloric acid is used to adjust the pH. The concentration of sulfuric acid is preferably 98 wt%, and the concentration of hydrochloric acid is preferably 31 wt%; in steps four and six, filtration is performed on a belt filter. The use of a belt filter to filter and wash the molecular sieve slurry can achieve flexible control of the filter cake thickness and water washing amount, and according to the need, fine crystal Y-type molecular sieve in the molecular sieve slurry is trapped to achieve reuse. The belt filter also has the characteristics of low failure rate, simple operation, and high filtration efficiency, which is conducive to improving the preparation efficiency of Y-type molecular sieve.

[0022] The beneficial effects of the present application are:

[0023] The preparation method of the low-sodium hydrothermal ultra-stable molecular sieve provided by the present application uses a silicon source and a sodium metaaluminate aqueous solution to prepare a directing agent under hydrothermal conditions, and introduces aluminum sulfate in the process of preparing a silico-aluminate gel, thereby improving the yield of NaY-type molecular sieve; the NaY-type molecular sieve is subjected to two times of cation exchange using a first cation exchanger and a second cation exchanger, respectively, and the reaction conditions of the two times of cation exchange are controlled, so that the cations in the first cation exchanger and the cations in the second cation exchanger replace the sodium ions in the NaY-type molecular sieve, thereby reducing the sodium content of the Y-type molecular sieve while improving the catalytic activity of the Y-type molecular sieve; the first cation exchanger combined with the cations is removed by flashing and calcining the one-interaction molecular sieve slurry, and the dehydrated cations can enter the small cage structure of the Y-type molecular sieve to replace the sodium ions, thereby further reducing the sodium content of the Y-type molecular sieve. DETAILED DESCRIPTION

[0024] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0025] Embodiment 1

[0026] A low-sodium hydrothermal ultra-stable molecular sieve, and a preparation method thereof, includes the following steps:

[0027] Step one: 9.6 g of sodium silicate aqueous solution and 13.8 g of high-alkali sodium metaaluminate aqueous solution were mixed and stirred uniformly, and then were aged at room temperature for 12 h to obtain a directing agent. In the sodium silicate aqueous solution, the mass percentage of SiO2 was 20 wt%, and the mass percentage of Na2O was 7 wt%; the caustic ratio of the high-alkali sodium metaaluminate aqueous solution was 10.5 mol / mol.

[0028] Step two: 41.3 g of sodium silicate aqueous solution was weighed, and then 10.3 g of low-alkali sodium metaaluminate aqueous solution, 6.9 g of the directing agent and 12.8 g of aluminum sulfate were sequentially added thereto to obtain a silicoaluminate gel after mixing uniformly.

[0029] Step three: water vapor was introduced into the silicoaluminate gel to heat it to 98℃, and then the temperature was kept constant for crystallization for 28 h. After the crystallization was completed, a crystallization slurry was obtained. The crystallinity of the crystallization slurry was tested. The crystallization slurry with a crystallinity of 90%-93% was NaY-type molecular sieve. The testing method of the crystallinity of the crystallization slurry was as follows:

[0030] Firstly, the crystallization slurry was introduced into a vacuum Buchner funnel for suction filtration to form a filter cake with a thickness of about 2 mm. Then, the filter cake was washed with water until the pH value was 9.0. After the filter cake was taken out of the Buchner funnel, it was dried in an oven at 140℃ for 1 h to obtain a sample to be tested. After the sample to be tested was prepared, the crystallinity of the sample to be tested was tested by using an X-ray diffractometer.

[0031] Step four: the filtration and water washing of the NaY-type molecular sieve were performed on a belt filter to obtain a filter cake, which was water-washed NaY-type molecular sieve. The water consumption during the water washing was 3-5 L / Kg of the NaY-type molecular sieve.

[0032] Step five: a sample of the water-washed NaY-type molecular sieve was taken for content analysis, so as to calculate the total weight of the water-washed NaY-type molecular sieve according to the volume of the water-washed NaY-type molecular sieve, and then the addition amount of the ammonium sulfate solution was calculated according to the total weight of the water-washed NaY-type molecular sieve. In this embodiment, the solid content of the sample of the water-washed NaY-type molecular sieve was 440 g / L. Then, 10 g of the water-washed NaY-type molecular sieve was added into 8 mL of the ammonium sulfate solution to mix uniformly, one-tank exchange was performed, a mixed solution was obtained, the pH of the mixed solution was adjusted to 3.5 by using concentrated sulfuric acid with a concentration of 98 wt%, and the temperature was raised to 60℃ and kept constant for 1 h to obtain a one-exchange molecular sieve slurry. The molar concentration of the ammonium sulfate solution was 0.9 mol / L.

[0033] Step six: the one-exchange molecular sieve slurry was filtered on a belt filter, 15.3 mL of the ammonium sulfate solution was added for belt exchange, and then 50 g of filtered water was added for washing to obtain a filter cake, which was the one-exchange molecular sieve and was ready for use.

[0034] Step seven: 3.5 g of lanthanum nitrate solution was added into the intermolecular sieve to obtain an intermolecular sieve mixed slurry, and the molar concentration of the lanthanum nitrate solution was 1.1 mol / L.

[0035] Step eight: the intermolecular sieve mixed slurry was subjected to primary flashing and primary calcination in sequence to obtain the intermolecular sieve calcined once. The primary flashing was carried out in a flashing tower, the temperature of the primary flashing was 110 ℃, the tower pressure of the flashing tower was controlled at 1.2 KPa, the intermolecular sieve calcined once was instantaneously dried in the flashing tower, and then was subjected to primary calcination in a calcination furnace, the temperature of the primary calcination was 800 ℃, and the primary calcination time was 1.5 h.

[0036] Step nine: the intermolecular sieve calcined once was added into 8 mL of ammonium sulfate solution to mix uniformly, and was subjected to secondary tank exchange, and then was heated to 60 ℃ for 1 h to obtain a two-intermolecular sieve calcined once slurry. The two-intermolecular sieve calcined once slurry was filtered on a belt filter, and then 50 g of filtered water was added for washing to obtain a filter cake of the two-intermolecular sieve calcined once.

[0037] Step ten: the two-intermolecular sieve slurry was subjected to secondary flashing and secondary calcination in sequence to obtain the two-intermolecular sieve calcined twice, i.e. the ultrastable Y-type molecular sieve. The secondary flashing was carried out in a flashing tower, the temperature of the secondary flashing was 110 ℃, the tower pressure of the flashing tower was controlled at 1.2 KPa, the two-intermolecular sieve calcined twice was instantaneously dried in the flashing tower, and then was subjected to secondary calcination in a calcination furnace, the temperature of the secondary calcination was 800 ℃, and the secondary calcination time was 1 h.

[0038] Example 2

[0039] A low-sodium hydrothermal ultrastable molecular sieve, a preparation method comprising the following steps:

[0040] Step one: 9.6 g of sodium silicate aqueous solution and 13.8 g of high-alkali sodium metaaluminate aqueous solution were mixed and stirred uniformly, and were aged at room temperature for 12 h to obtain a directing agent. In the sodium silicate aqueous solution, the mass percentage of SiO2 was 20 wt%, and the mass percentage of Na2O was 7 wt%; the caustic ratio of the high-alkali sodium metaaluminate aqueous solution was 10.5 mol / mol.

[0041] Step two: 41.3 g of sodium silicate aqueous solution was weighed, and 10.3 g of low-alkali sodium metaaluminate aqueous solution, 6.9 g of the directing agent and 12.8 g of aluminum sulfate were sequentially added thereto to mix uniformly to obtain a silicoaluminate gel. The caustic ratio of the low-alkali sodium metaaluminate aqueous solution was 2.4 mol / mol.

[0042] Step three: water vapor was introduced into the silicoaluminate gel to heat it to 98 ℃, and then was crystallized at constant temperature for 28 h. After the crystallization was completed, a crystallization slurry was obtained, and the crystallinity of the crystallization slurry was tested. The crystallization slurry with a crystallinity of 90%-93% was a NaY-type molecular sieve. The crystallinity test method of the crystallization slurry was as follows:

[0043] Firstly, the crystallized slurry is introduced into a vacuum Buchner funnel for suction filtration to form a filter cake with a thickness of about 2 mm, and then the filter cake is washed with water until the pH value is 9.0. After the filter cake is taken out of the Buchner funnel, it is dried in an oven at 140℃ for 1 hour to obtain a sample to be tested. After the sample to be tested is prepared, the crystallinity of the sample to be tested is tested by using an X-ray diffractometer.

[0044] Step four: filtration and water washing of the NaY type molecular sieve on a belt filter to obtain a water-washed NaY type molecular sieve. The water consumption during the water washing process is 3-5 L / Kg of the NaY type molecular sieve.

[0045] Step five: sampling and content analysis of the water-washed NaY type molecular sieve. The mass of the water-washed NaY type molecular sieve and the amount of lanthanum chloride solution to be added are calculated according to the total volume of the water-washed NaY type molecular sieve. In this embodiment, the solid content of the water-washed NaY type molecular sieve sample is 442 g / L. Then 10 g of the water-washed NaY type molecular sieve is added into 1 mL of the lanthanum chloride solution and mixed uniformly to perform a first tank exchange to obtain a mixed solution. The pH of the mixed solution is adjusted to 4.5 by using concentrated hydrochloric acid with a concentration of 32 wt%, and the temperature is raised to 70℃ and kept constant for 1.5 h to obtain a first-exchange molecular sieve slurry. The molar concentration of the lanthanum chloride solution is 1.0 mol / L.

[0046] Step six: filtration of the first-exchange molecular sieve slurry on a belt filter, then 2 mL of the lanthanum chloride solution is added for belt exchange, and then 50 g of filtered water is added for washing to obtain a first-exchange molecular sieve, which is ready for use.

[0047] Step seven: the first-exchange molecular sieve is sequentially subjected to a first flash evaporation and a first calcination to obtain a first-exchange first-calcination molecular sieve. The first flash evaporation is performed in a flash evaporation tower. The temperature of the first flash evaporation is 150℃, and the tower pressure of the flash evaporation tower is controlled at 1.2 KPa. The first-exchange first-calcination molecular sieve is instantaneously dried in the flash evaporation tower, and then enters a calcination furnace for a first calcination. The temperature of the first calcination is 500℃, and the first calcination time is 1 h.

[0048] Step eight: the first-exchange first-calcination molecular sieve is added into 8 mL of an ammonium sulfate solution and mixed uniformly to perform a second tank exchange, and then the temperature is raised to 70℃ and kept constant for 0.5 h to obtain a second-exchange first-calcination molecular sieve slurry. The molar concentration of the ammonium sulfate solution is 0.9 mol / L. The second-exchange first-calcination molecular sieve slurry is filtered on a belt filter, and then 50 g of filtered water is added for washing to obtain a second-exchange first-calcination molecular sieve.

[0049] Step nine: the two-interchange two-calcination molecular sieve slurry is subjected to secondary flash and secondary calcination in sequence to obtain a two-interchange two-calcination molecular sieve, i.e. an ultrastable Y-type molecular sieve. The secondary flash is performed in a flash tower, the temperature of the secondary flash is 150℃, the tower pressure of the flash tower is controlled to be 1.2KPa, the two-interchange two-calcination molecular sieve is instantaneously dried in the flash tower, and then enters a calcination furnace to perform secondary calcination, the temperature of the secondary calcination is 500℃, and the secondary calcination time is 1.5h.

[0050] Example 3

[0051] A low-sodium hydrothermal ultrastable molecular sieve, a preparation method comprising the following steps:

[0052] Step one: 9.6g of a sodium silicate aqueous solution and 13.8g of a high-alkali sodium metaaluminate aqueous solution are mixed and stirred uniformly, and then are aged at room temperature for 12h to obtain a directing agent. In the sodium silicate aqueous solution, the mass percentage of SiO2 is 20wt%, and the mass percentage of Na2O is 7wt%; the caustic ratio of the high-alkali sodium metaaluminate aqueous solution is 10.5mol / mol.

[0053] Step two: 41.3g of a sodium silicate aqueous solution is weighed, and then 10.3g of a low-alkali sodium metaaluminate aqueous solution, 6.9g of the directing agent and 12.8g of aluminum sulfate are sequentially added thereto, and the mixture is uniformly mixed to obtain a silicoaluminate gel. The caustic ratio of the low-alkali sodium metaaluminate aqueous solution is 2.4mol / mol.

[0054] Step three: water vapor is introduced into the silicoaluminate gel to heat it to 98℃, and then the temperature is kept constant for crystallization for 28h. After the crystallization is completed, a crystallization slurry is obtained. The crystallinity of the crystallization slurry is tested, and the crystallization slurry with a crystallinity of 90%-93% is a NaY-type molecular sieve. The crystallinity test method of the crystallization slurry is as follows:

[0055] Firstly, the crystallization slurry is introduced into a vacuum Buchner funnel for suction filtration to form a filter cake with a thickness of about 2mm. Then, the filter cake is washed with water until the pH value is 9.0. The filter cake is taken out of the Buchner funnel and dried in an oven at 140℃ for 1h to obtain a sample to be tested. The sample to be tested is prepared and then the crystallinity of the sample to be tested is tested by using an X-ray diffractometer.

[0056] Step four: the filtration and water washing of the NaY-type molecular sieve are performed on a belt filter, and the obtained filter cake is a water-washed NaY-type molecular sieve. The water consumption during the water washing is 3-5L / Kg of the NaY-type molecular sieve.

[0057] Step five: the sample of the water-washed NaY molecular sieve is subjected to content analysis, so as to calculate the mass of the water-washed NaY molecular sieve and the amount of the first cationic exchanger to be added according to the total volume of the water-washed NaY molecular sieve, and in this embodiment, the solid content of the sample of the water-washed NaY molecular sieve is 445 g / L. Then, 10 g of the water-washed NaY molecular sieve is added into 3 mL of the lanthanum chloride solution and mixed uniformly, one-tank exchange is performed to obtain a mixed solution, the pH of the mixed solution is adjusted to 3.0-4.0 by using concentrated hydrochloric acid with a concentration of 32 wt%, and the temperature is increased to 60-70℃ and kept constant for 1 h to obtain a first-exchange molecular sieve slurry, wherein the molar concentration of the lanthanum chloride solution is 1.0 mol / L.

[0058] Step six: the first-exchange molecular sieve slurry is filtered on a belt filter, 2.3 mL of the lanthanum chloride solution is then added for belt exchange, and 50 g of filtered water is added for washing to obtain a filter cake, which is the first-exchange molecular sieve and is ready for use.

[0059] Step seven: the first-exchange molecular sieve is sequentially subjected to one-time flashing and one-time calcination to obtain a first-exchange and first-calcination molecular sieve. The one-time flashing is performed in a flashing tower, the temperature of the one-time flashing is 123℃, and the tower pressure of the flashing tower is controlled to be 1.2 KPa. The first-exchange and first-calcination molecular sieve is instantaneously dried in the flashing tower, and then enters a calcination furnace for one-time calcination, the temperature of the one-time calcination is 700℃, and the one-time calcination time is 1 h.

[0060] Step eight: the first-exchange and first-calcination molecular sieve is added into 0.3 mL of the lanthanum chloride solution and mixed uniformly, second-tank exchange is performed to obtain a mixed solution, the pH of the mixed solution is adjusted to 4.0 by using concentrated hydrochloric acid with a concentration of 32 wt%, and then the temperature is increased to 66℃ and kept constant for 1 h to obtain a second-exchange and first-calcination molecular sieve slurry. The second-exchange and first-calcination molecular sieve slurry is filtered on a belt filter, 2.3 mL of the lanthanum chloride solution is then added for belt exchange, and 50 g of filtered water is added for washing to obtain a filter cake, which is the second-exchange and first-calcination molecular sieve, i.e., the ultrastable Y-type molecular sieve. The molar concentration of the lanthanum chloride solution is 1.0 mol / L.

[0061] Comparative Example 1

[0062] A hydrothermal ultrastable molecular sieve, a preparation method comprising the following steps:

[0063] Step one: 9.6 g of a sodium silicate aqueous solution and 13.8 g of a high-alkali sodium metaaluminate aqueous solution are mixed and stirred uniformly, and then are aged at room temperature for 12 h to obtain a directing agent. In the sodium silicate aqueous solution, the mass percentage of SiO2 is 20 wt%, and the mass percentage of Na2O is 7 wt%; the caustic ratio of the high-alkali sodium metaaluminate aqueous solution is 10.5 mol / mol.

[0064] Step two: 41.3g of sodium silicate aqueous solution was weighed, and 10.3g of low-alkali sodium metaaluminate aqueous solution, 6.9g of directing agent and 12.8g of aluminum sulfate were sequentially added thereto, and the mixture was uniformly mixed to obtain a silico-aluminate gel. The caustic ratio of the low-alkali sodium metaaluminate aqueous solution was 2.4 mol / mol.

[0065] Step three: water vapor was introduced into the silico-aluminate gel to heat it to 98℃, and then the temperature was kept constant for crystallization for 28h. After the crystallization was completed, a crystallized slurry was obtained. The crystallinity of the crystallized slurry was tested. The crystallized slurry with a crystallinity of 90%-93% was NaY-type molecular sieve. The crystallinity test method of the crystallized slurry was as follows:

[0066] Firstly, the crystallized slurry was introduced into a vacuum Buchner funnel for suction filtration to form a filter cake with a thickness of about 2mm. Then, the filter cake was washed with water until the pH value was 9.0. After the filter cake was taken out of the Buchner funnel, it was dried in an oven at 140℃ for 1h to obtain a sample to be tested. After the sample to be tested was prepared, the crystallinity of the sample to be tested was tested by using an X-ray diffractometer.

[0067] Step four: the NaY-type molecular sieve was filtered on a belt filter, and then washed with water to obtain a filter cake, which was a water-washed NaY-type molecular sieve. During the washing process, the amount of water used was 3-5L / Kg of the NaY-type molecular sieve.

[0068] Step five: a sample of the water-washed NaY-type molecular sieve was taken for content analysis, so as to calculate the mass of the water-washed NaY-type molecular sieve and the amount of the first cationic exchange agent to be added according to the total volume of the water-washed NaY-type molecular sieve. In this example, the solid content of the water-washed NaY-type molecular sieve sample was 440g / L. 10g of the water-washed NaY-type molecular sieve was added into 2mL of lanthanum chloride solution and mixed uniformly to obtain a mixed solution. The pH of the mixed solution was adjusted to 3.0-4.0 by using concentrated hydrochloric acid with a concentration of 32wt%, and then the temperature was raised to 60-70℃ for constant temperature for 1h for primary tank exchange to obtain a first-exchange molecular sieve slurry. The molar concentration of the lanthanum chloride solution was 1.0mol / L.

[0069] Step six: the first-exchange molecular sieve slurry was filtered on a belt filter, and then 50g of filtered water was added for washing to obtain a filter cake, which was a first-exchange molecular sieve, ready for use.

[0070] Step seven: 1.7g of lanthanum nitrate solution was added to the first-exchange molecular sieve for tank exchange, and then primary flashing and primary calcination were performed to obtain a first-exchange and first-calcination molecular sieve. The primary flashing was performed in a flashing tower. The temperature of the primary flashing was 130℃, and the tower pressure of the flashing tower was controlled at 1.2Kpa. The first-exchange and first-calcination molecular sieve was instantaneously dried in the flashing tower, and then entered a calcination furnace for primary calcination. The temperature of the primary calcination was 500℃, and the primary calcination time was 1h.

[0071] Step eight: water is added to the one-interaction-one-calcined molecular sieve to obtain a one-interaction-one-calcined molecular sieve slurry, and the amount of water added is determined according to the conveying condition of the centrifugal pump. The one-interaction-one-calcined molecular sieve slurry is sampled for content analysis, and the amount of ammonium oxalate added is calculated according to the total volume of the one-interaction-one-calcined molecular sieve slurry, and then solid ammonium oxalate is added to the one-interaction-one-calcined molecular sieve slurry and stirred for 40 min to obtain a mixed slurry, wherein the amount of solid ammonium oxalate added is 5wt% of the dry weight of the one-interaction-one-calcined molecular sieve. The pH of the mixed slurry is adjusted to 5.5 using ammonia water with a concentration of 15wt%, and then the temperature is raised to 60℃ and kept constant for 1h, and then the second belt exchange washing and filtration are carried out on the belt filter, and 15.3mL of ammonium sulfate is used as the cation exchange solution for the second belt exchange to obtain a two-interaction-one-calcined molecular sieve. Then the two-interaction-one-calcined molecular sieve is washed with water, and during the washing process, the two-interaction-one-calcined molecular sieve is washed with 50g of filtered water, and the obtained filter cake is the two-interaction-one-calcined molecular sieve. The mass fraction of solid ammonium oxalate is ≥99.0wt%, and the molar concentration of the ammonium sulfate solution is 0.9mol / L.

[0072] The Na2O content in the molecular sieves obtained in Examples 1-3 and Comparative Example 1 was tested by X-ray fluorescence intensity analysis method, and the test results are shown in Table 1.

[0073] Table 1 Na2O content in the molecular sieves obtained in Examples 1-3 and Comparative Example 1

[0074]

[0075] As shown in Table 1, the Na2O content in the molecular sieves obtained in Examples 1-3 is lower than that in the molecular sieve obtained in Comparative Example 1, and it can be seen that the preparation method provided by the application can effectively reduce the Na2O content in the molecular sieve.

[0076] Although the application has been described in detail by preferred embodiments, the application is not limited thereto. Various equivalent modifications and replacements can be made to the embodiments of the application by those skilled in the art without departing from the spirit and essence of the application, and these modifications and replacements shall be within the scope of the application. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, and these changes or replacements shall be within the protection scope of the application.

Claims

1. A method for preparing a low-sodium hydrothermally super-stable zeolite, characterized in that, The method comprises the following steps: Step 1: mixing a silicon source and a sodium metaaluminate aqueous solution, stirring uniformly, and aging at room temperature to obtain a directing agent; Step 2: adding the sodium metaaluminate aqueous solution, the directing agent and aluminum sulfate into the silicon source, mixing uniformly to obtain a silicoaluminate gel; Step 3: introducing water vapor into the silicoaluminate gel to heat and crystallize, and obtaining a NaY type molecular sieve; Step 4: adding the NaY type molecular sieve into a first cation exchanger, mixing uniformly, and performing a first tank type exchange, then adjusting the pH to 3.5-4.5, heating to 60-70 DEG C, and keeping the temperature constant for 0.5-1.5 h to obtain a first exchange molecular sieve slurry, in the first tank type exchange process, the amount of the first cation exchanger is 0.08-0.15 g / g NaY type molecular sieve; filtering the first exchange molecular sieve slurry to obtain a first exchange molecular sieve crude product, adding the first cation exchanger into the first exchange molecular sieve crude product to perform a belt type exchange, and then washing with water to obtain a first exchange molecular sieve, in the belt type exchange process, the amount of the first cation exchanger is 0-0.25 g / g first exchange molecular sieve crude product; wherein the first cation exchanger is an ammonium sulfate solution or a lanthanum chloride solution, and the molar concentration of the first cation exchanger is 0.9-1.1 mol / L; Step 5: sequentially performing a first flash evaporation and a first calcination on the first exchange molecular sieve to obtain a first exchange and first calcination molecular sieve, wherein the temperature of the first flash evaporation is 110-150 DEG C, and the temperature of the first calcination is 500-800 DEG C; Step 6: adding the first exchange and first calcination molecular sieve into a first cation exchanger, mixing uniformly, performing a second tank type exchange, then heating to 60-70 DEG C, and keeping the temperature constant for 0.5-1.5 h to obtain a second exchange and first calcination molecular sieve slurry, filtering and washing the second exchange and first calcination molecular sieve slurry to obtain a second exchange and first calcination molecular sieve, wherein the amount of the first cation exchanger is 0.08-0.15 g / g first exchange and first calcination molecular sieve, the first cation exchanger is an ammonium sulfate solution or a lanthanum chloride solution, and the molar concentration of the first cation exchanger is 0.9-1.1 mol / L.

2. The method for preparing a low-sodium hydrothermally super-stable zeolite according to claim 1, characterized in that, Step 4 further comprises: adding the first exchange molecular sieve into a second cation exchanger, mixing uniformly to obtain a first exchange molecular sieve mixed slurry, the amount of the second cation exchanger is 0.01-0.09 g / g first exchange molecular sieve, the second cation exchanger is a lanthanum nitrate solution or a yttrium nitrate solution, and the molar concentration of the second cation exchanger is 1.1-1.3 mol / L.

3. The method for preparing a low-sodium hydrothermally stable molecular sieve according to claim 1, wherein the sodium ion is replaced with a potassium ion. Step 7: sequentially performing a second flash evaporation and a second calcination on the second exchange and first calcination molecular sieve to obtain a second exchange and second calcination molecular sieve, wherein the temperature of the second flash evaporation is 110-150 DEG C, and the temperature of the second calcination is 500-800 DEG C.

4. The method for preparing a low-sodium hydrothermally stable molecular sieve according to claim 1, wherein the sodium ion is replaced with a potassium ion. 5 The silicon source is a sodium silicate aqueous solution, in the sodium silicate aqueous solution, the mass percentage of SiO2 is 20 wt%, and the mass percentage of Na2O is 7 wt%; the sodium metaaluminate aqueous solution is a high-alkali sodium metaaluminate aqueous solution or a low-alkali sodium metaaluminate aqueous solution, the caustic ratio of the high-alkali sodium metaaluminate aqueous solution is 10.5 mol / mol, and the caustic ratio of the low-alkali sodium metaaluminate aqueous solution is 2.4 mol / mol.

5. The method for preparing a low-sodium hydrothermally stable molecular sieve as described in claim 1, characterized in that, In step one, the silicon source and the sodium aluminate aqueous solution are mixed in a molar ratio of 10.67 Na2O: 1 Al2O3: 10 SiO2: 180 H2O, and the aging time is 12-24 h.

6. The method for preparing a low-sodium hydrothermally stable molecular sieve as described in claim 1, characterized in that, In step two, the silicon source, the sodium aluminate aqueous solution, the directing agent and the aluminum sulfate are mixed in a molar ratio of 8 Na2O: 1 Al2O3: 20 SiO2: 320 H2O.

7. The method for preparing a low-sodium hydrothermally stable molecular sieve as described in claim 1, characterized in that, In step three, the crystallization temperature is 92-98°C, and the crystallization time is 20-30 h.

8. The method for preparing a low-sodium hydrothermally stable molecular sieve as described in claim 1, characterized in that, In step four, the one-exchange molecular sieve slurry is filtered and washed with water to obtain the one-exchange molecular sieve, and the amount of water used is 3-5 g / g of the one-exchange molecular sieve.

9. The method for preparing a low-sodium hydrothermally stable molecular sieve as described in claim 1, characterized in that, In step six, the two-exchange one-calcined molecular sieve slurry is filtered and washed with water to obtain the two-exchange one-calcined molecular sieve, and the amount of water used is 3-5 g / g of the two-exchange one-calcined molecular sieve.

10. The method for preparing a low-sodium hydrothermally stable molecular sieve as described in claim 1, characterized in that, In step four, sulfuric acid or hydrochloric acid is used to adjust the pH; in step four and step six, the filtration is performed on a belt filter. In step one, the silicon source and the sodium aluminate aqueous solution are mixed in a molar ratio of 10.67 Na2O: 1 Al2O3: 10 SiO2: 180 H2O, and the aging time is 12-24 h. In step two, the silicon source, the sodium aluminate aqueous solution, the directing agent and the aluminum sulfate are mixed in a molar ratio of 8 Na2O: 1 Al2O3: 20 SiO2: 320 H2O. In step three, the crystallization temperature is 92-98°C, and the crystallization time is 20-30 h. In step four, the one-exchange molecular sieve slurry is filtered and washed with water to obtain the one-exchange molecular sieve, and the amount of water used is 3-5 g / g of the one-exchange molecular sieve. In step six, the two-exchange one-calcined molecular sieve slurry is filtered and washed with water to obtain the two-exchange one-calcined molecular sieve, and the amount of water used is 3-5 g / g of the two-exchange one-calcined molecular sieve. In step four, sulfuric acid or hydrochloric acid is used to adjust the pH; in step four and step six, the filtration is performed on a belt filter.

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