Method for ultrastably modifying Y-type molecular sieve in short process

Abstract

The invention discloses a method for ultrastably modifying a Y-type molecular sieve in a short process. Washing the NaY molecular sieve with water until the NaY molecular sieve is qualified, and preparing first slurry by using the working solution; adding a rare earth salt solution into the first slurry, adding inorganic acid to adjust the pH value, and carrying out ion exchange to obtain second slurry; washing and filtering the second slurry, performing flash evaporation drying, and roasting at 500 DEG C for 2.5 hours to prepare first powder; feeding the first powder and SiCl4 gas into a reactor, staying reaction materials for 10 minutes, feeding the reaction materials into a negative-pressure pulping tank, adding water, pulping, and controlling the pH value to be 2.5-3.5 to obtain third slurry; and washing and filtering the third slurry, adding water and pulping to obtain the ultra-stable molecular sieve slurry. According to the prepared ultra-stable molecular sieve, the content of rare earth oxide is 8%-15%, the cell constant is 24.25-24.60 angstroms, and the specific surface area is 600-650 m < 2 > / g; and flexible adjustment of the rare earth content is realized.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve preparation technology, and relates to the gas-phase ultrastable modification technology of Y-type molecular sieves, specifically to an industrial preparation method of ultrastable molecular sieves. Background Technology

[0002] The improvement of catalytic cracking catalyst performance mainly depends on the improvement of the performance of its active component, the ultrastable molecular sieve. In recent years, research on the ultrastabilization modification of Y-type molecular sieves has also attracted much attention. Currently, the main methods for ultrastabilization modification of Y-type molecular sieves used in industrial applications are hydrothermal methods, liquid-phase ammonium fluoride salt methods, and gas-phase chemical methods. Hydrothermal and liquid-phase ammonium fluoride salt methods have inherent shortcomings and drawbacks. Both of these methods face the problem of treating high ammonia nitrogen wastewater during production, resulting in long production processes and high energy consumption, severely restricting cost reduction and efficiency improvement for catalyst manufacturers, and placing a huge burden on clean and environmentally friendly production. The liquid-phase ammonium fluoride salt method also faces the problem of environmental pollution caused by the discharge of fluoride-containing production wastewater from the production unit, and the challenge of residual fluoride affecting the stability of the molecular sieve during the production process.

[0003] The entire production process of gas-phase ultrastabilization modification does not generate wastewater containing high levels of ammonia nitrogen and fluorides. While meeting clean and environmentally friendly production requirements, the resulting modified molecular sieve is an ideal active component for residue cracking catalysts and octane-enhancing catalysts. The gas-phase ultrastabilization modification of Y-type molecular sieves can utilize the principle of isomorphous substitution of NaReY molecular sieves to complete dealumination and silicon replenishment in a single reaction. Through the second-level reaction of the substitution process, it can effectively avoid the lattice collapse and framework structure damage that occurs during the dealumination of NaReY molecular sieves, thus preventing any impact on the molecular sieve's activity.

[0004] In previous industrial applications, in order to ensure the effect of gas-phase ultra-stable modification, such as to ensure the high silicon content of molecular sieves, excessive use of silicon tetrachloride has been used, which has led to the need to adopt high-energy-consuming and environmentally friendly treatment to ensure the continuity of production. To address this, CN102451655A proposes a continuous industrial production equipment for molecular sieves based on gas-phase ultrastable modification. This equipment utilizes a riser reaction technology with inclined and straight tubes connected in series, improving production efficiency and reducing silicon tetrachloride usage. However, the ultrastable modified Y-type molecular sieve obtained has a lower rare earth oxide content (i.e., rare earth mass percentage calculated as RE2O3) compared to industrial REY, affecting the catalyst's performance. CN103769193A describes a reactor and gas-solid separator that can operate under slight negative pressure. By using a conveying device (e.g., a screw conveyor to move the molecular sieve within the tubular reactor), carrier gas is no longer required, increasing the reaction rate and reducing reaction time. Furthermore, obtaining a molecular sieve slurry through pulping reduces the amount of adhesive used in catalyst preparation. However, the rare earth oxide content of the ultrastable modified Y-type molecular sieve is reduced. CN114100531A discloses a vertical gas-phase ultrastable reactor for gas-phase ultrastable modification... In the process of producing Y-type molecular sieves, the dried molecular sieves are passed through a distributor and then mixed with countercurrent gaseous silicon tetrachloride (i.e., SiCl4 gas) to form a fully mixed and partially fully mixed state, which effectively ensures gas-solid contact and allows for instantaneous reaction within a very short contact time. This avoids excessive contact time and excessive SiCl4 molecules carried by the molecular sieves after the reaction. By slurrying under different pH conditions (pH: 3.5, 5.5, 8.0, etc.), a gas-phase ultrastable Y-type molecular sieve with relatively high crystallinity is obtained. However, for the reaction process using NaY and NaReY (i.e., NaY after rare earth ion exchange) as molecular sieve raw materials, the change in relative crystallinity before and after the reaction cannot accurately reflect the product quality. Furthermore, the reaction time in this patent is difficult to control, and the post-reaction material needs to be degassed. CN106517238A describes a parallel-flow continuous automated operation based on a vertical reactor, and produces a low-sodium, high-silicon-aluminum ratio Y-type molecular sieve using NaY molecular sieves as raw material. However, this also requires gas-solid separation of the post-reaction material, and the reaction time is long.CN113952969A absorbs the tail gas generated during the preparation of ultrastable molecular sieves and uses the resulting HCl-containing solution to prepare colloids and to mix with colloids, clay, ultrastable molecular sieves, and binders in the catalyst preparation process. This improves the catalyst's performance to some extent, such as improving its cracking performance and increasing conversion rate. However, by comparing the rare earth oxide content in the different REY molecular sieve raw materials and the rare earth oxide content in the prepared catalyst, it was found that the higher the rare earth content in the raw materials, the more significant the rare earth content loss may occur in the dealumination and silicon replenishment reaction. This objectively indicates that a shorter process flow and lower energy consumption were not used to obtain highly active ultrastable molecular sieves to better ensure the catalyst's performance.

[0005] Furthermore, the study "The Influence of Rare Earth Ion Exchange Process on the Performance of Gas-Phase Ultrastable Y Molecular Sieves" points out that "for ultrastable Y molecular sieves with a cell constant shrinking to 2.446 nm," it is difficult to obtain modified Y molecular sieves with high rare earth mass fractions through rare earth ion exchange after the reaction. CN113941359A not only points out the problems existing in the past industrial REY preparation technology (either the problem of ammonia nitrogen wastewater pollution caused by the use of ammonium salts, or the problem of the rare earth content of molecular sieve products not meeting the requirements for application in catalysts due to the simplification of the "two-exchange-two-calcination" preparation process), but also proposes an ammonium salt-free preparation process of "one-exchange-one-calcination" (high ion exchange temperature, low calcination temperature) to obtain high-activity REY (REY molecular sieve with rare earth oxide content of 16wt%-24.5wt%) by pre-impregnating rare earth solution (containing rare earth nitrate and / or rare earth chloride) in the calcination process for the "one-exchange material". However, these technologies and studies have not been able to optimize rare earth ion exchange and other related processes from the perspective of industrial continuous production and application to solve the problem of poor controllability of molecular sieves after ultrastabilization modification and its impact on catalyst performance. Summary of the Invention

[0006] The purpose of this invention is to provide a short-process method for modifying ultrastable Y-type molecular sieves. By developing an industrial technology for gas-phase ultrastabilization modification that generates no ammonia nitrogen wastewater and consumes little energy, the rare earth loss of molecular sieves during the preparation of ultrastable molecular sieves is significantly reduced, thereby achieving the flexible and controllable preparation of highly active ultrastable Y-type molecular sieves.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, a method for preparing gas-phase ultrastable molecular sieves is provided, the method comprising the following steps: The molecular sieve raw material is subjected to rare earth ion exchange, water washing and filtration (e.g., filtration, water washing and vacuum filtration on a filter press), high-temperature drying and then calcined to obtain powder. The calcined powder is reacted with a gas containing halogen silanes (the gas is mainly composed of gaseous halogen silanes or only gaseous halogen silanes; under non-vacuum reaction conditions, it may also contain a small amount of ambient air) as reactant to undergo a full and quantitative dealumination and silicon replenishment reaction to obtain a gas-phase ultrastable modified molecular sieve material. The molecular sieve material is then acidically slurried under negative pressure to produce an ultrastable molecular sieve product.

[0008] Preferably, the conditions that the molecular sieve raw material meets include: using NaY molecular sieve with a relative crystallinity of ≥83% and a silica-alumina ratio of ≥4.80, and pH ≤11 (e.g., the pH measured when the NaY molecular sieve is washed with water before use).

[0009] Preferably, the rare earth oxide content of the calcined powder (or NaY molecular sieve after rare earth ion exchange) is 8%-16% (e.g., 8%-13%). Preferably, the high-temperature drying conditions include: removing moisture at 100-180°C after decompression (e.g., reaching a negative pressure of 500-1500 Pa); and the moisture content of the molecular sieve material after drying (i.e., the moisture content of the NaY molecular sieve after rare earth ion exchange) is ≤3%.

[0010] Preferably, the halogenated silane is a silane in which some or all of the hydrogen atoms are replaced by halogens, such as SiCl4.

[0011] Preferably, the amount of the calcined powder used in the dealumination and silicon replenishment reaction is controlled at 200 kg / h-500 kg / h (i.e., the rate at which the calcined powder is discharged from the calcination furnace to the reactor is controlled at 200 kg / h-500 kg / h), for example, at 200 kg / h-450 kg / h; the gas does not contain carrier gas.

[0012] Preferably, the conditions for the dealumination and silicon replenishment reaction include: a reaction temperature controlled at 280-400℃ and a reaction time controlled at 5-15 minutes. Under these reaction conditions, the reactants can directly undergo a second-level dealumination and silicon replenishment gas-phase ultrastable modification reaction in the reactor.

[0013] Preferably, the conditions for the dealumination and silicon replenishment reaction further include: the calcined powder is subjected to full gas-solid contact with SiCl4 gas in a reactor at a dry basis mass ratio of 1:0.15-0.6.

[0014] Preferably, the dealumination and silicon replenishment reaction is carried out in a conveying device reactor (e.g., a double-helix tube reactor with the rotation speed controlled at 35 Hz-50 Hz). This reactor has good mass and heat transfer effects, uniform product properties, and SiCl4 utilization rate of 90%-100%. It is not only superior to riser reaction technology, but also eliminates the need for tail gas emissions, allowing the reacted material (including gas-phase ultra-stable modified molecular sieve material and gases such as HCl) to be directly discharged to the pulping tank.

[0015] Preferably, the acidic pulping specifically includes the following steps: pulping the gas-phase ultrastable modified molecular sieve material under a negative pressure of 0-200 Pa and controlling the pH to be 2-5.

[0016] Preferably, the finished ultrastable molecular sieve is an ultrastable molecular sieve slurry obtained by sequentially washing, filtering, and pulping after the acidic pulping is completed.

[0017] Preferably, the preparation method specifically includes the following steps: Step 1: Wash the NaY molecular sieve to a qualified standard (e.g., wash NaY molecular sieve with a relative crystallinity ≥83% and a silica-alumina ratio ≥4.80 until pH≤11). After washing, use water or working solution to prepare a first slurry with a solid content of 100 g / L-450 g / L (specifically, the total mass concentration of molecular sieve in the first slurry is 100 g / L-450 g / L). Step 2: Mix the first slurry with the prepared rare earth salt solution at a weight ratio of 1:0.01-0.2 for NaY (mainly referring to the NaY molecular sieve in the first slurry, the rest may be NaY molecular sieves from the recovered exchange liquid that have undergone rare earth ion exchange) dry basis to rare earth oxide (specifically referring to the rare earth salts in the prepared rare earth salt solution calculated as rare earth oxide), adjust the pH to 3.5-4.5, and then carry out ion exchange at a temperature of 10-75℃ (the lower the exchange temperature, the lower the energy consumption required) (exchange time 0.5-1h) to obtain the second slurry; Step 3: Filter the second slurry to obtain the first filter cake. Wash the first filter cake with water (using 3-5 times the amount of water to remove impurities and anions and cations), and then perform vacuum filtration, flash drying, and calcination at 450-600℃ for 2-3.5 hours to obtain the first powder with a moisture content (i.e., water content) of less than 3%. Step 4: In the reactor, the first powder, fed at a rate of 250 kg / h-400 kg / h, is reacted with SiCl4 gas (no carrier gas required) at a temperature controlled at 80-120℃ to carry out the second-level dealuminization and silicon replenishment gas-phase ultra-stable modification reaction. The reactant (e.g., the first powder undergoing this gas-phase ultra-stable modification reaction) remains in the reactor for 8-12 minutes (the residence time depends on the reactor speed) to form the post-reaction material. The post-reaction material is then transferred to a pulping tank, where water is added and pulped under micro-negative pressure control until the first powder is completely discharged from the calcination furnace (and has entered the pulping tank after the reactor reaction), resulting in a third slurry with a pH of 2.5-3.5. The micro-negative pressure control refers to maintaining the pressure inside the pulping tank at 10-100 Pa. Step 5: Filter the third slurry to obtain a second filter cake. Wash the second filter cake with water (using 3-5 times the amount of water) and then perform vacuum filtration and water addition and pulping (at normal pressure) to obtain an ultra-stable molecular sieve slurry.

[0018] Preferably, in step 2, the rare earth salt content of the rare earth salt solution, calculated as rare earth oxide, is 290 g / L-300 g / L.

[0019] Preferably, in step 3, the filtrate obtained from the second slurry filtration contains 2.0 g / L to 3.0 g / L of rare earth salts calculated as rare earth oxides and contains molecular sieves with a concentration of 50 g / L to 60 g / L. This filtrate can be used as the working solution described above.

[0020] Secondly, an ultrastable molecular sieve (specifically, the finished product is the ultrastable molecular sieve slurry) prepared by the above-mentioned gas-phase ultrastable molecular sieve preparation method is provided.

[0021] Preferably, the ultrastable molecular sieve has a rare earth oxide content of 8%-15% (specifically, a rare earth mass percentage calculated as rare earth oxide of 8%-15%), a cell constant of 24.25-24.60 angstroms, and a specific surface area of ​​600 m. 2 / g-650 m 2 / g.

[0022] The beneficial effects of this invention are reflected in: The method for modifying ultrastable Y-type molecular sieves described in this invention mainly involves rare earth ion exchange, calcination, dealumination and silicon replenishment reaction, and slurry treatment of the reaction products under negative pressure. This method enables the preparation of highly active (i.e., high rare earth content) ultrastable molecular sieves with a simplified modification process. It can be applied in industrial continuous production, and the rare earth content of the ultrastable molecular sieves can be flexibly adjusted during the production process (due to less rare earth loss during the preparation process, the rare earth loss rate of the finished ultrastable molecular sieves is <5% compared to NaY molecular sieves that have undergone rare earth ion exchange).

[0023] Furthermore, in the preparation process of this invention, by adjusting the pH of the rare earth ion exchange system to a certain range using an acidic reagent (e.g., an inorganic acid), the alkaline cations in the NaY molecular sieve channels can be cleared, promoting RE exchange. 3+ Ions are effectively positioned within the β cage, thereby ensuring the rare earth ion exchange effect and reducing the loss of raw material rare earth salts.

[0024] Furthermore, the preparation process of this invention does not use an exchange solution containing ammonium salts for sodium reduction, does not introduce ammonia nitrogen components, and does not generate ammonia nitrogen wastewater. The resulting filtrate can be used as a working solution (this measure can enhance the effect of "reducing the loss of rare earth salts in raw materials") or directly discharged after sedimentation treatment, thereby achieving the goal of ammonia-free, environmentally friendly, and clean production in the Y-type molecular sieve modification process.

[0025] Furthermore, in the preparation process of this invention, the gas-phase ultrastable modified molecular sieve material does not undergo other transfer, separation, and cooling processes, but is directly pulped, making the modification preparation process shorter and reducing energy consumption. At the same time, by controlling the pulping tank to a slightly negative pressure state (for example, maintaining the pressure inside the pulping tank at 10-100 Pa), the gas space inside the tank is guaranteed, and the molecular sieve does not experience suspension at the top of the tank after the reaction. During the pulping process, the residual reaction gas is rapidly desorbed, avoiding the formation of colloidal substances such as aluminates in various forms, which could damage the molecular sieve skeleton structure or block the pores. This has a significant advantage in ensuring product quality. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the embodiments. These embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0027] This invention proposes and verifies a method for producing ultrastable molecular sieves through ammonium-free rare earth (generally lanthanum and cerium) ion exchange and short-process gas-phase ultrastable modification. In this method, the rare earth content of the modified ultrastable molecular sieves is controllable and high through processes such as dealumination and silica replenishment gas-phase ultrastable modification reaction and slurry preparation. For details, please refer to the process flow of the Y-type molecular sieve gas-phase ultrastable modification method in each embodiment. The specific detection methods for raw materials, rare earth ion exchange, and the modified finished product are as follows: The determination of relative crystallinity is based on "Q / SY LS1277-2021 Determination of Crystallinity of Dealaluminated Y-type Molecular Sieves by X-ray Diffraction". The determination of the silicon-to-aluminum ratio is based on the "Q / SY LS1227-2021 Method for Determination of Silicon-to-Aluminum Ratio of Na-Y Molecular Sieves"; pH determination should refer to "Q / SY LS1232-2021 pH value determination method"; The determination of rare earth salt concentration and RE2O3 content refers to "Q / SY LS1244-2021 Determination of Rare Earth Solutions - Azo Arsenic I Method" and "Q / SY LS1050-2014 X-ray Fluorescence Spectroscopy". The determination of the cell constant was based on the method described in "Q / SY LS1307-2021 Analytical Method for Cell Constant of Ultrastable Molecular Sieves". The determination of specific surface area is based on "NB_SH_T 0959-2017 Determination of specific surface area of ​​catalytic cracking catalyst by static nitrogen adsorption capacity method".

[0028] Example 1 (1) At room temperature, the NaY molecular sieve with a relative crystallinity of 86% and a silicon-to-aluminum ratio of 5.12 was washed with water, and the NaY molecular sieve slurry (which was washed to a pH of 10.7 as a qualified molecular sieve raw material) was prepared into a first slurry with a solid content of 180 g / L using a working solution (i.e. the filtrate obtained in step 3) with a rare earth salt content of 2.4 g / L calculated by RE2O3 (specifically referring to lanthanum oxide) and a molecular sieve concentration of 58 g / L. (2) At room temperature, a rare earth salt solution with a rare earth salt content of 292 g / L (specifically referring to lanthanum oxide) was added to the first slurry at a weight ratio of NaY dry basis:RE2O3 of 1:0.08. Then, 15% inorganic acid (specifically, industrial hydrochloric acid solution with a mass percentage concentration of 15%) was added to adjust the pH to 4.0. Then, ion exchange was carried out at 60℃ for 1 h to obtain the second slurry. (3) The obtained second slurry is sent to a filter press (room temperature) for filtration to obtain the first filter cake. The first filter cake is washed with 5 times (mass ratio) of water and then filtered. The filter cake is then flash-dried under 122℃ and 700 Pa negative pressure conditions, and then calcined at 500℃ for 2.5 hours to obtain the first powder with a moisture content of less than 3% and a RE2O3 content of 8.1%. (4) The first powder obtained is fed into the reactor at a rate of 350 kg / h, and gaseous SiCl4 at 90°C is introduced into the reactor at a dry basis mass ratio of 1:0.15. The two reactants are subjected to gas-phase ultra-stable modification reaction at 320°C (using the heat of the materials themselves). The reactants stay in the reactor for 10 minutes. The reactants are then conveyed by an auger into a negative pressure pulping tank of 18 Pa (room temperature; that is, using the heat of the reactants after the reaction, without heating the tank separately). Water is added and pulping is performed to obtain the third slurry. The pH of the third slurry is controlled at 2.5. (5) The obtained third slurry is sent to a filter press (at room temperature) for filtration to obtain a second filter cake. The second filter cake is washed with 5 times (by mass) water and then filtered. The filter cake is then mixed with water and slurryed under normal pressure to obtain the finished modified molecular sieve slurry. The modified molecular sieve contained in this slurry has a RE2O3 content of 8% (i.e., a rare earth loss rate of about 1.2%), a cell constant of 24.60 Å, and a specific surface area of ​​620 m. 2 / g of ultrastable molecular sieve.

[0029] Example 2 (1) At room temperature, the NaY molecular sieve with a relative crystallinity of 85% and a silicon-to-aluminum ratio of 5.12 was washed with water, and the NaY molecular sieve slurry (which was washed to pH 10.8 as the qualified molecular sieve raw material) was prepared into a first slurry with a solid content of 180 g / L using a working solution (i.e. the filtrate obtained in step 3) with a rare earth salt content of 2.1 g / L calculated by RE2O3 (specifically referring to lanthanum oxide) and a molecular sieve concentration of 52 g / L. (2) At room temperature, a rare earth salt solution with a rare earth salt content of 295 g / L (specifically referring to lanthanum oxide) was added to the first slurry at a weight ratio of NaY dry basis:RE2O3 of 1:0.10. Then, 15% inorganic acid (specifically, industrial hydrochloric acid solution with a mass percentage concentration of 15%) was added to adjust the pH to 3.5. Then, ion exchange was carried out at 10℃ for 1 h to obtain the second slurry. (3) The obtained second slurry is sent to a filter press (room temperature) for filtration to obtain the first filter cake. The first filter cake is washed with 5 times (mass ratio) of water and then filtered. The filter cake is then flash-dried under 140°C and 1000 Pa negative pressure conditions, and then calcined at 500°C for 2.5 hours to obtain the first powder with a moisture content of less than 3% and a RE2O3 content of 10.2%. (4) The first powder obtained is fed into the reactor at a rate of 400 kg / h, and gaseous SiCl4 at 100°C is introduced into the reactor at a dry basis mass ratio of 1:0.16. The two reactants are subjected to gas-phase ultra-stable modification reaction at 280°C (using the heat of the materials themselves). The reactants stay in the reactor for 10 minutes. The reactants are then conveyed by an auger into a negative pressure pulping tank of 65 Pa (room temperature; that is, using the heat of the reactants after the reaction, without heating the tank separately). Water is added and pulping is performed to obtain the third slurry. The pH of the third slurry is controlled at 2.8. (5) The obtained third slurry is sent to a filter press (at room temperature) for filtration to obtain a second filter cake. The second filter cake is washed with 5 times (by mass) water and then filtered. The filter cake is then mixed with water and slurryed under normal pressure to obtain the finished modified molecular sieve slurry. The modified molecular sieve contained in this slurry has a RE2O3 content of 9.9% (i.e., a rare earth loss rate of about 2.9%), a cell constant of 24.59 Å, and a specific surface area of ​​600 m.2 / g of ultrastable molecular sieve.

[0030] Example 3 (1) At room temperature, the NaY molecular sieve with a relative crystallinity of 86% and a silicon-to-aluminum ratio of 5.12 was washed with water, and the NaY molecular sieve slurry (which was washed to pH 10.5 as the qualified molecular sieve raw material) was prepared into a first slurry with a solid content of 180 g / L using a working solution (i.e. the filtrate obtained in step 3) with a rare earth salt content of 2.6 g / L calculated by RE2O3 (specifically referring to lanthanum oxide) and a molecular sieve concentration of 60 g / L. (2) At room temperature, a rare earth salt solution with a rare earth salt content of 299 g / L (specifically referring to lanthanum oxide) was added to the first slurry at a weight ratio of NaY dry basis:RE2O3 of 1:0.12. Then, 15% inorganic acid (specifically, industrial hydrochloric acid solution with a mass percentage concentration of 15%) was added to adjust the pH to 3.6. Then, ion exchange was carried out at 40°C for 0.8 h to obtain the second slurry. (3) The obtained second slurry is sent to a filter press (room temperature) for filtration to obtain the first filter cake. The first filter cake is washed with 5 times (mass ratio) of water and then filtered. The filter cake is then flash-dried under 150°C and 960 Pa negative pressure conditions, and then calcined at 500°C for 2.5 hours to obtain the first powder with a moisture content of less than 3% and a RE2O3 content of 12.2%. (4) The first powder obtained is fed into the reactor at a rate of 300 kg / h, and gaseous SiCl4 at 118°C is introduced into the reactor at a dry basis mass ratio of 1:0.18. The two reactants are subjected to gas-phase ultra-stable modification reaction at 350°C (using the heat of the materials themselves). The reactants stay in the reactor for 10 minutes. The reactants are then conveyed by an auger into a negative pressure pulping tank of 95 Pa (room temperature: that is, using the heat of the reactants, without heating the tank separately). Water is added and pulping is performed to obtain the third slurry. The pH of the third slurry is controlled at 2.8. (5) The obtained third slurry is sent to a filter press (at room temperature) for filtration to obtain a second filter cake. The second filter cake is washed with 5 times (by mass) water and then filtered. The filter cake is then mixed with water and slurryed under normal pressure to obtain the finished modified molecular sieve slurry. The modified molecular sieve in the slurry has a RE2O3 content of 12% (i.e., a rare earth loss rate of about 1.6%), a cell constant of 24.57 Å, and a specific surface area of ​​628 m. 2 / g of ultrastable molecular sieve.

[0031] Example 4 (1) At room temperature, the NaY molecular sieve with a relative crystallinity of 87% and a silicon-aluminum ratio of 5.0 was washed with water, and the NaY molecular sieve slurry washed to pH 11 (as the qualified molecular sieve raw material) was prepared into a first slurry with a solid content of 180 g / L using a working solution (i.e. the filtrate obtained in step 3) with a rare earth salt content of 2.8 g / L calculated by RE2O3 (specifically referring to lanthanum oxide) and a molecular sieve concentration of 58 g / L. (2) At room temperature, a rare earth salt solution with a rare earth salt content of 292 g / L (specifically referring to lanthanum oxide) was added to the first slurry at a weight ratio of NaY dry basis:RE2O3 of 1:0.11. Then, 15% inorganic acid (specifically, industrial hydrochloric acid solution with a mass percentage concentration of 15%) was added to adjust the pH to 3.8. Then, ion exchange was carried out at 60℃ for 1 h to obtain the second slurry. (3) The obtained second slurry is sent to a filter press (room temperature) for filtration to obtain the first filter cake. The first filter cake is washed with 5 times (mass ratio) of water and then filtered. The filter cake is then flash-dried under negative pressure conditions of 112℃ and 1200 Pa. After that, it is calcined at 500℃ for 2.5 hours to obtain the first powder with a moisture content of less than 3% and a RE2O3 content of 10.8%. (4) The first powder obtained is fed into the reactor at a rate of 400 kg / h, and gaseous SiCl4 at 97°C is introduced into the reactor at a dry basis mass ratio of 1:0.6. The two reactants are subjected to gas-phase ultra-stable modification reaction at a temperature of 372°C (using the heat of the materials themselves). The reactants stay in the reactor for 10 minutes. The reactants are then conveyed by an auger into a negative pressure pulping tank of 100 Pa (room temperature; that is, using the heat of the reactants after the reaction, without heating the tank separately). Water is added and pulping is performed to obtain the third slurry. The pH of the third slurry is controlled at 3.0. (5) The obtained third slurry is sent to a filter press (at room temperature) for filtration to obtain a second filter cake. The second filter cake is washed with 5 times (by mass) water and then filtered. The filter cake is then mixed with water and slurryed under normal pressure to obtain the finished modified molecular sieve slurry. The modified molecular sieve contained in this slurry has a RE2O3 content of 10.3% (i.e., a rare earth loss rate of about 4.6%), a cell constant of 24.30 Å, and a specific surface area of ​​650 m. 2 / g of ultrastable molecular sieve.

[0032] Example 5 (1) Wash the NaY molecular sieve with relative crystallinity ≥83% and silicon-aluminum ratio ≥4.80 with water until pH≤11. After washing, add water to the NaY molecular sieve to prepare a first slurry with a solid content of 100 g / L-450 g / L (specifically, the total mass concentration of molecular sieve in the first slurry is 100 g / L-450 g / L). (2) The first slurry is mixed with a prepared rare earth salt solution of 290 g / L-300 g / L (the rare earth salt content in the solution is calculated as RE2O3, which specifically refers to lanthanum oxide) at a weight ratio of NaY dry basis to RE2O3 (specifically referring to lanthanum oxide) of 1:0.01-0.2, and the pH is adjusted to 3.5-4.5. Then, ion exchange is carried out at a temperature of 10-75℃ for 0.5-1h to obtain the second slurry. (3) The second slurry is filtered on a filter press, and the resulting first filter cake is washed with water (using 3-5 times the amount of water), filtered by suction, and then flash-dried. It is then calcined at 500°C for 2.5 hours to obtain the first powder with a moisture content of less than 3% and a rare earth oxide content of 8%-13%. (4) In the reactor, the first powder is transferred at a rate of 250 kg / h-400 kg / h and reacted with SiCl4 gas (no carrier gas required) with a temperature controlled at 80-120℃. The reaction temperature is 280-400℃. The reactants stay in the reactor for 8-12 minutes to form the reaction material. The reaction material is transferred to a pulping tank and water is added and pulped in the pulping tank with a micro negative pressure of 10-100 Pa until the first powder is discharged, and a third slurry with a pH of 2.5-3.5 is obtained. (5) Filter the third slurry on a filter press, and wash the resulting second filter cake with water (using 3-5 times the amount of water), filter it by suction, and then add water to make slurry (at normal pressure) to obtain the finished modified molecular sieve slurry.

[0033] From the above embodiments, it can be concluded that the gas-phase ultrastable modification method for Y-type molecular sieves of the present invention has a simple process flow. Furthermore, considering the effectiveness of industrial continuous production applications, the process characteristics of preparing ultrastable molecular sieves using the present invention include: 1. The preparation process of ultrastable molecular sieves has a high utilization rate of SiCl4 (silicon will exist in the product in the form of silicon dioxide), and there is no need to increase the utility costs of the equipment for multiple treatments of acid-containing (such as HCl) waste gas; 2. The preparation process of ultra-stable molecular sieves does not use ammonium salts or ammonia water for sodium reduction, does not introduce ammonia nitrogen components, and does not generate ammonia nitrogen wastewater, thus achieving the goal of ammonia-free and clean production in the Y-type molecular sieve modification process; 3. The filtrate generated during the preparation of ultrastable molecular sieves can be directly discharged after natural sedimentation treatment because it does not contain ammonia nitrogen. This process is highly environmentally friendly and the preparation process is clean and efficient, completely eliminating the problems of high energy consumption and long process in the traditional hydrothermal ultrastable sieve preparation process.

[0034] 4. The preparation of ultrastable molecular sieves results in minimal loss of rare earth salts; it allows for flexible adjustment of rare earth content and ensures a high rare earth content in the finished product, effectively solving the problem of the impact of ultrastable modified Y-type molecular sieves on catalyst performance.

Claims

1. A method for preparing an ultrastable molecular sieve, characterized in that: The preparation method includes the following steps: The molecular sieve raw material is subjected to rare earth ion exchange, water washing and filtration, drying and then calcined. It is then reacted with a gas containing halogen silane as a reactant and subjected to gas-phase ultra-stable modification through a dealumination and silicon replenishment reaction. The resulting molecular sieve material is then acid-slurried under negative pressure to produce the finished ultra-stable molecular sieve.

2. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The molecular sieve raw material is a NaY molecular sieve with a relative crystallinity of ≥83% and a silica-alumina ratio of ≥4.80, and the pH of the NaY molecular sieve is ≤11.

3. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The rare earth oxide content of NaY molecular sieves after rare earth ion exchange is 8%-16%.

4. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The drying conditions include: removing moisture by vacuum evaporation at 100-180°C.

5. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The gas does not contain carrier gas; the amount of the calcined powder used in the dealumination and silicon replenishment reaction is controlled at 200-500 kg / h.

6. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The conditions for the dealumination and silicon replenishment reaction include: reaction temperature 280-400℃, reaction time 5-15 minutes; the calcined powder is brought into gas-solid contact with SiCl4 gas at a dry basis mass ratio of 1:0.15-0.

6.

7. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The acidic pulping process specifically includes the following steps: pulping the molecular sieve material at 0-200 Pa and controlling the pH to 2-5.

8. The method for preparing an ultrastable molecular sieve according to claim 1, characterized in that: The preparation method specifically includes the following steps: Step 1: Wash the NaY molecular sieve with water. After washing, adjust the NaY molecular sieve or NaY molecular sieve slurry with water or recycled rare earth ion exchange working solution to form a first slurry with a solid content of 100-450 g / L. Step 2: Mix the first slurry with the rare earth salt solution at a NaY dry basis to rare earth oxide weight ratio of 1:0.01-0.2, adjust the pH to 3.5-4.5, and then carry out ion exchange at 10-75℃ to obtain the second slurry; Step 3: Filter the second slurry to obtain a filter cake. Wash the filter cake with water, then filter it by suction filtration, flash dry it, and then calcine it at 450-600℃ for 2-3.5 hours to obtain powder. Step 4: The powder obtained in Step 3 is transferred into the reactor at a rate of 250 kg / h-400 kg / h and reacts with the SiCl4 gas introduced into the reactor to form the reacted material. The powder stays in the reactor for 8-12 minutes. The reacted material is then transferred into a pulping tank, where water is added and pulped under micro-negative pressure control to obtain a third slurry with a pH of 2.5-3.

5. The micro-negative pressure control refers to maintaining the pressure inside the pulping tank at 10-100 Pa. Step 5: Filter the third slurry to obtain a filter cake. Wash the filter cake with water, then filter it again, add water and beat it to obtain an ultra-stable molecular sieve slurry.

9. An ultrastable molecular sieve prepared by the method of any one of claims 1-8.

10. The ultrastable molecular sieve according to claim 9, wherein the rare earth oxide content of the ultrastable molecular sieve is 8%-15%, the cell constant is 24.25-24.60 Å, and the specific surface area is 600-650 μm. 2 / g.