Process for the preparation of molecular sieves containing rare earth elements

Abstract

This invention relates to the field of molecular sieve catalytic materials preparation, and discloses a method for preparing molecular sieves containing rare earth elements. The method includes: under hot-pressing conditions, subjecting a molecular sieve containing ammonium ions to an ion exchange reaction with rare earth element ions in an ion exchange reaction solution to obtain a molecular sieve containing rare earth elements; wherein the hot-pressing conditions include: a temperature of 160-190℃ and a pressure of (P+0.1)~(P+2) MPa, where P represents the saturated vapor pressure of water at the ion exchange temperature, in MPa. The method of this invention enables efficient and continuous exchange production, obtaining molecular sieves containing rare earth elements without the need for high-temperature calcination in a calcination converter.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve catalytic materials preparation, and specifically to a method for preparing a molecular sieve containing rare earth elements. Background Technology

[0002] In industry, sodium-type molecular sieves are generally prepared by hydrothermal synthesis. Typically, the cations in molecular sieves prepared by hydrothermal synthesis are sodium ions. However, in practical applications, it is necessary to replace the sodium ions with other cations, such as hydrogen ions, potassium ions, or rare earth metal ions, depending on the specific circumstances, in order to enable them to have specific catalytic functions.

[0003] Among them, Na in NaY type molecular sieves + RE 3+ Rare earth Y-type molecular sieves (REY, REHY, and REUSY) prepared by ion exchange (RE represents rare earth elements) are highly active components of catalytic cracking catalysts. In REY molecular sieves, rare earth ions migrate into the sodalite cages and form a polynuclear cation structure containing oxygen bridges, increasing the stability of the acid centers in the molecular sieve under high-temperature hydrothermal conditions, improving the cracking activity and activity stability of the molecular sieve catalyst, thereby improving the heavy oil conversion activity and selectivity of the catalyst and exhibiting excellent catalytic performance. Therefore, how to promote the migration of rare earth ions and increase the occupancy rate of rare earth ions at the locked cation sites (within the cages) is directly related to the activity stability of REY molecular sieves. However, when NaY molecular sieves undergo ion exchange with rare earth-containing aqueous solutions at room temperature and pressure, hydrated rare earth ions with a diameter of approximately 0.79 nm have difficulty passing through the 0.24 nm six-membered ring pore window of the Y-type molecular sieve to enter the sodalite cage (β cage) and interact with the Na... + The exchange process is completed. Therefore, in the preparation of REY molecular sieves, high-temperature calcination is usually required to remove the hydrated water layer surrounding the rare earth element ions, so that the dehydrated rare earth element ions can relatively easily enter the sodalite cages. At the same time, the rare earth element ions in these cages also transfer to the larger cages (supercages) through high-temperature calcination. This creates conditions for further ion exchange between the molecular sieve and the ion exchange process.

[0004] To promote the migration of rare earth element ions, increase the exchange rate of rare earth element ions, and reduce the residual sodium content in molecular sieves, industrial practice typically employs alternating processes of multiple exchange cycles and high-temperature calcination.

[0005] Existing rare earth Y molecular sieve preparation processes involve long rare earth ion exchange times and complex production processes. Furthermore, prolonged high-temperature calcination places extremely high demands on the materials of the industrial calcination furnace, resulting in high energy consumption and production costs. Moreover, reports indicate that rare earth ions that have migrated into the sodalite cages tend to return to the supercages during high-temperature calcination.

[0006] To further optimize the preparation method of rare earth Y molecular sieves, researchers have proposed many related modification methods. In order to achieve the required exchange degree of rare earth element ions in a single exchange, scholars have studied the use of hot-press exchange method. However, the long-term high temperature and high pressure exchange conditions not only increase production energy consumption, but may also affect the crystal structure of the molecular sieve.

[0007] In CN101518749A, a horizontal belt multi-stage vacuum filter is used for ion exchange of zeolite molecular sieves, integrating ion exchange, filtration, and washing into a single process. This facilitates continuous production, significantly improves the utilization rate of exchanged ions, and greatly reduces the content of exchanged ions in the discharged waste liquid. This method operates exchange, washing, and filtration within the same equipment, requiring fewer unit devices. Materials at each stage can be regulated via control valves, resulting in low labor intensity. However, the multi-stage continuous exchange and washing processes have poor classification effects, easily causing back-mixing between adjacent stages and affecting the exchange efficiency. The process equipment is complex, and operation is complicated. It is only suitable for ammonium salt solution exchange with a relatively wide range of Na2O quality indicators.

[0008] CN1053808A reports a method for preparing rare earth Y molecular sieves. The method involves exchanging NaY with a rare earth salt solution once, followed by calcination at 450-600℃ for 1-3 hours in a 100% steam environment. This method shortens the preparation process, reduces the amount of rare earth elements used, and lowers production costs. Furthermore, the prepared molecular sieve exhibits relatively high hydrothermal structural stability and cracking activity stability.

[0009] CN101088613A discloses a method for preparing REY molecular sieves. The method involves contacting NaY molecular sieves with an aqueous solution containing rare earth ions, or with an aqueous solution containing rare earth ions and a solution or colloid containing aluminum ions. A precipitant is then added to precipitate some of the rare earth ions onto the molecular sieve. Following this, the sieve is calcined, and finally contacted with an ammonium salt solution. This method is simple and easy to implement, shortens the preparation process of REY molecular sieves, and the prepared molecular sieve is suitable for processing heavy oil with high vanadium content, exhibiting good cracking reactivity.

[0010] CN108097288A discloses a method for preparing rare earth Y molecular sieves. First, NaY molecular sieves, a rare earth chloride solution, and deionized water are mixed and subjected to ion exchange. Oxalic acid solution is added to the exchange solution to completely precipitate the unexchanged rare earth elements. The filtered filter cake is then subjected to further ion exchange with rare earth chloride and deionized water. After filtration, a filter cake and a recycled filtrate are obtained. The filter cake is calcined in a muffle furnace to obtain the REY molecular sieve product. The recycled filtrate completely or partially replaces the aforementioned rare earth chloride solution and enters the ion exchange process for the next batch of NaY molecular sieves. The utilization rate of rare earth elements is almost 100%, reducing production costs. Simultaneously, it yields REY with high rare earth content, exhibiting advantages such as high activity and high thermal stability.

[0011] CN1493402A discloses a method for mixed exchange of ammonium and rare earth ions in molecular sieves. The molecular sieve filter cake is sequentially passed through an ion exchange zone on a horizontal belt filter to complete the exchange, washing, and filtration, followed by calcination. This method can simultaneously exchange ammonium salts and rare earth compounds in a Y-type molecular sieve with one-exchange-one-calcination process, resulting in low water consumption and high efficiency.

[0012] CN104275215A discloses a continuous microwave ion exchange method using molecular sieves. A sodium-type molecular sieve is introduced into the exchange vessel from the top, while the ion exchange solution is fed from the bottom, contacting the molecular sieve inside. Microwave radiation is used to exchange the molecular sieve and the ion exchange solution within the vessel. This method provides a reactor and exchange process with advantages such as high ion exchange efficiency and the ability to achieve continuous exchange production. However, the reactor is costly, has limited microwave radiation depth, cannot avoid the drawback of rapid microwave energy decay, and suffers from uneven heating of the solution within the vessel, making its industrial application and engineering transformation extremely difficult.

[0013] While the above solutions have optimized and improved the preparation process of rare earth Y molecular sieves to some extent, or simplified the production process or increased the utilization rate of rare earths, they still cannot achieve truly rapid and efficient continuous exchange production. Furthermore, existing industrial continuous exchange technologies cannot achieve high exchange rates and are prone to backmixing. The operation is complex, the residual Na2O content is still high, and high-temperature calcination is still required to promote rare earth ion migration. The production process is relatively long and the cost is relatively high. Summary of the Invention

[0014] The purpose of this invention is to overcome the problems of existing technologies, such as cumbersome production process of molecular sieves containing rare earth elements, inability to obtain high exchange degree through continuous exchange, need for long-term high-temperature calcination, high energy consumption, and high preparation cost. This invention provides a method for preparing molecular sieves containing rare earth elements, which can achieve efficient continuous exchange production and obtain molecular sieves containing rare earth elements without high-temperature calcination in a calcination converter.

[0015] To achieve the above objectives, the present invention provides a method for preparing a molecular sieve containing rare earth elements. The method includes: under hot-pressing conditions, subjecting a molecular sieve containing ammonium ions to an ion exchange reaction with rare earth element ions in an ion exchange reaction solution to obtain a molecular sieve containing rare earth elements; wherein the hot-pressing conditions include: a temperature of 160-190℃ and a pressure of (P+0.1)~(P+2)MPa, where P represents the saturated vapor pressure of water at the ion exchange temperature, in MPa.

[0016] Preferably, the hot pressing conditions include a temperature of 160-180°C.

[0017] Preferably, the hot pressing conditions include a pressure of (P+0.5) to (P+1.5) MPa.

[0018] Preferably, the ion exchange reaction is a continuous thermo-pressure exchange carried out in a continuous ion exchange reactor, which includes two or more reactor stages.

[0019] More preferably, the conditions for continuous heat-pressure exchange include: the temperature of the preheated material is 150-190°C, the heat-pressure exchange temperature of each stage reactor is 160-190°C, and the residence time of the molecular sieve slurry from the completion of preheating to the outlet of the last stage reactor is 0.1-40 min.

[0020] More preferably, the heat exchange temperature of the subsequent reactor is not lower than that of the preceding reactor, and more preferably, the heat exchange temperature of the subsequent reactor is 3-15°C higher than that of the preceding reactor.

[0021] Preferably, the ammonium ion-containing molecular sieve is one or more of the following: X-type molecular sieve, Y-type molecular sieve, ZSM-5 type molecular sieve, A-type molecular sieve, and β-type molecular sieve.

[0022] Preferably, the ammonium ion-containing molecular sieve is a Y-type molecular sieve.

[0023] Preferably, the rare earth element ions are derived from one or more of rare earth element hydrochlorides and rare earth element nitrates.

[0024] Preferably, the rare earth element is one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium.

[0025] More preferably, the rare earth element ions are derived from one or more of lanthanum chloride, cerium chloride, lanthanum nitrate, and cerium nitrate.

[0026] Preferably, the weight ratio of rare earth elements to the molecular sieve containing ammonium ions is 0.1-1:1, the weight ratio of water to the molecular sieve containing ammonium ions is 5-20:1, and the pH value of the ion exchange reaction solution is 2.5-5.

[0027] Preferably, the ammonium ion-containing molecular sieve is obtained by subjecting a sodium-type molecular sieve to an ammonium exchange reaction with ammonium ions.

[0028] Preferably, the ammonium ion is derived from one or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium oxalate, and ammonium carbonate; more preferably, the ammonium ion is derived from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate.

[0029] Preferably, the concentration of ammonium ions in the reaction solution of the ammonium exchange reaction is 0.01-30% by weight, preferably 5-25% by weight, and the pH value is 2-6, preferably 3-4.5.

[0030] Preferably, the ammonium ion concentration in the reaction solution for the ammonium exchange reaction is 0.01-3.5% by weight, more preferably 0.1-1.5% by weight, relative to the sodium molecular sieve.

[0031] Preferably, the conditions for the ammonium exchange reaction include: a temperature of 5-100℃ and a time of 5-60 min; more preferably, a temperature of 20-70℃ and a time of 10-40 min.

[0032] Preferably, the solid-liquid ratio of the ammonium exchange reaction is 1:1-100.

[0033] Preferably, the method further includes washing and drying the molecular sieve containing rare earth elements. Preferably, the drying temperature is 60-200℃;

[0034] Preferably, the sodium oxide content in the rare earth element-containing molecular sieve is less than 1.2% by weight, and the rare earth oxide content is 2-18.5% by weight.

[0035] The above technical solution enables continuous high-temperature hot-pressing high-efficiency ion exchange production, achieving high rare earth ion exchange degree. It eliminates the need for high-temperature calcination to obtain molecular sieves with low sodium oxide content and rare earth elements. The production process is simple, greatly shortens the molecular sieve preparation process, and significantly reduces production energy consumption and costs. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the continuous ion exchange reaction device provided by the method of the present invention.

[0037] Explanation of reference numerals in the attached figures

[0038] 1. Raw material tank 2. Electronic scale 3. Washing tank

[0039] 4. Raw material pump; 5. Preheater; 6. First ion exchange reactor

[0040] 7. Second ion exchange reactor; 8. Third ion exchange reactor

[0041] 9. Cooler; 10. First product tank; 11. Second product tank

[0042] 12. Exhaust gas washing tank 13. Gas source outlet Detailed Implementation

[0043] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0044] This invention relates to a method for preparing a molecular sieve containing rare earth elements. The method includes: under hot-pressing conditions, subjecting a molecular sieve containing ammonium ions to an ion exchange reaction with rare earth element ions in an ion exchange reaction solution to obtain a molecular sieve containing rare earth elements; wherein the hot-pressing conditions include: a temperature of 160-190℃ and a pressure of (P+0.1)~(P+2)MPa, where P represents the saturated vapor pressure of water at the ion exchange temperature, in MPa.

[0045] The inventors of this invention have discovered that by carrying out rare earth ion exchange reactions under the above-mentioned hot-pressing conditions, a high degree of ion exchange can be obtained. Molecular sieves containing rare earth elements with low sodium oxide content can be obtained without high-temperature calcination. The production process is simple, greatly shortens the molecular sieve preparation process, and significantly reduces production energy consumption and production costs.

[0046] To further improve the exchange rate and efficiency of the ion exchange reaction, preferably, the hot-pressing conditions include a temperature of 160-185℃, more preferably 160-180℃. Specifically, the temperatures that can be used are 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, or 190℃. In the case of segmented continuous hot-pressing exchange, the temperature in the hot-pressing conditions refers to the average temperature relative to the residence time in each reactor. When all reactors are identical, it can be calculated by the arithmetic mean of the reaction temperatures in each reactor.

[0047] To further improve the exchange rate and efficiency of the ion exchange reaction, preferably, the hot-pressing conditions include a pressure of (P+0.5) to (P+1.5) MPa. Specifically, the pressures that can be used are (P+0.1) MPa, (P+0.2) MPa, (P+0.3) MPa, (P+0.4) MPa, (P+0.5) MPa, (P+0.6) MPa, (P+0.7) MPa, (P+0.8) MPa, (P+0.9) MPa, (P+1) MPa, (P+1.1) MPa, (P+1.2) MPa, (P+1.3) MPa, (P+1.4) MPa, (P+1.5) MPa, (P+1.6) MPa, (P+1.7) MPa, (P+1.8) MPa, (P+1.9) MPa, and (P+2) MPa, etc. Specifically, for example, if the saturated vapor pressure of water at 180°C is 1.0 MPa, then when a hot-pressing reaction is carried out at this temperature, the pressure is 1.1-3 MPa, preferably 1.5-2.5 MPa. Specifically, the pressure can be 0.8-3 MPa, preferably 1-2.5 MPa, and more preferably 1.5-2.5 MPa.

[0048] The thermo-pressure conditions referred to in this invention can be controlled by pre-pressurizing the reaction apparatus and using pressure valves (e.g., back pressure valves) in the pipelines. For example, pre-pressurization can be performed by introducing pressure into a continuous ion exchange reaction apparatus (e.g., preheater, ion exchange reactor, cooler, product tank, and connecting pipelines) through a gas source outlet to ensure that the internal thermo-pressure conditions of each stage of the ion exchange reactor reach the required levels. The gas introduced is preferably air or an inert gas, such as nitrogen, argon, helium, or a mixture thereof.

[0049] According to the present invention, the apparatus used for the ion exchange is not particularly limited, and can be carried out on any ion exchange apparatus capable of providing the aforementioned thermo-pressurization conditions. Preferably, the ion exchange is a continuous thermo-pressurization exchange carried out on a continuous ion exchange reactor, which includes two or more reactor stages, preferably 3-5 stages, and more preferably each stage uses the same reactor. More preferably, the conditions for the continuous thermo-pressurization exchange include: the temperature of the preheated material is 150-190°C, the thermo-pressurization exchange temperature of each reactor is 160-190°C, and the residence time of the molecular sieve slurry from the completion of preheating to the outlet of the last reactor is 0.1-40 min, preferably 10-30 min. In addition, the material temperature at the outlet of the cooler is below 80°C.

[0050] According to a preferred embodiment of the present invention, in a continuous ion exchange reactor, the thermo-pressure exchange temperature of the subsequent reactor is not lower than that of the preceding reactor; for example, the thermo-pressure exchange temperature of each reactor can be increased sequentially. More preferably, the thermo-pressure exchange temperature of the subsequent reactor is 3-15°C higher than that of the preceding reactor, preferably 5-10°C. By ensuring that the thermo-pressure exchange temperature of the subsequent reactor is not lower than that of the preceding reactor, the degree of exchange of the reaction can be further improved.

[0051] The hot-pressure exchange method can be carried out as follows: Sodium molecular sieve and rare earth solution to be exchanged are added to the raw material tank in advance, and the reaction device is pre-pressurized through the gas source outlet. Then, the continuous ion exchange reaction device is started, so that the sodium molecular sieve comes into contact with the solution to be exchanged and high-temperature continuous hot-pressure exchange is carried out in the reactor pipeline. After being cooled by the cooler, it flows out of the product tank. After the product tank is depressurized, the material flows out from the discharge port. After filtration, solid-liquid separation and water washing, the exchanged molecular sieve containing rare earth elements is obtained.

[0052] According to a preferred embodiment of the present invention, the following can be employed: Figure 1 The continuous ion exchange apparatus shown performs ion exchange reactions. The apparatus includes a feed unit, a reaction unit, and a tail gas treatment unit. In this apparatus, the reaction unit includes a preheater 5, two or more stages of ion exchange reactors (e.g., a first ion exchange reactor 6, a second ion exchange reactor 7, and a third ion exchange reactor 8), a cooler 9, and product tanks (e.g., a first product tank 10 and a second product tank 11) connected in series. The ion exchange reactors provide the thermo-pressure conditions for ion exchange, allowing the reactants to be preheated in the preheater 5 and then undergo ion exchange reactions under the thermo-pressure conditions in each ion exchange reactor, followed by cooling in the cooler 9. The two or more stages of ion exchange reactors are connected in series to achieve continuous ion exchange. The tail gas treatment unit includes a tail gas scrubbing tank 12, and preferably, a back pressure valve is installed on the material pipeline between the product tank and the tail gas scrubbing tank 12. The back pressure valve controls the internal pressure of the preheater 5, the two or more stages of ion exchange reactors, the cooler 9, and the product tank to provide the thermo-pressure conditions for ion exchange. The feeding unit includes a raw material tank 1, an electronic scale 2, a washing tank 3, a raw material pump 4, and an air source outlet 13. The feeding unit can control the supply of material from the raw material tank 1.

[0053] Using the aforementioned continuous ion exchange reactor, the ion exchange reaction of this invention can be carried out, for example, in the following manner: A mixed molecular sieve slurry containing ammonium ions and a rare earth solution flows out from the raw material tank 1, is pressurized by the raw material pump 4, and then enters the preheater 5 for heating. The preheated molecular sieve slurry sequentially enters each stage of the ion exchange reactor (first ion exchange reactor 6, second ion exchange reactor 7, and third ion exchange reactor 8) for thermo-pressure ion exchange reaction. The reaction product is cooled by the cooler 9 and then enters the product tank. The gas phase in the product tank is vented after alkaline washing under the control of the system back pressure valve. After sampling is completed, the product tank is discharged from the bottom, and after filtration, solid-liquid separation, and water washing, the exchanged molecular sieve is obtained. The first product tank 10 and the second product tank 11 are switched for use by valve control. Before use, the product tank is pressurized by pressurizing gas, and after sampling is completed, the process is switched to the other product tank. Considering that the reactants may settle, pressure measuring elements are installed at the inlet and outlet of the raw material pump, reactor, and cooler. If settling or blockage occurs, the location of the blockage can be determined based on the pressure measuring element values.

[0054] According to the present invention, the ammonium ion-containing molecular sieve is not particularly limited and can be one or more of X-type molecular sieves, Y-type molecular sieves, ZSM-5 type molecular sieves, A-type molecular sieves, and β-type molecular sieves, preferably Y-type molecular sieves. To ensure the effectiveness of the ion exchange reaction and thus obtain the desired rare earth element-containing molecular sieve without calcination, preferably, the sodium ion content (calculated as sodium oxide) in the ammonium ion-containing molecular sieve is 5.0% by weight or less.

[0055] According to the present invention, preferably, the rare earth element ions are derived from one or more of rare earth element hydrochlorides and rare earth element nitrates; preferably, the rare earth element is one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium; more preferably, the rare earth element ions are derived from one or more of lanthanum chloride, cerium chloride, lanthanum nitrate, and cerium nitrate.

[0056] According to the present invention, preferably, the weight ratio of rare earth elements to the molecular sieve containing ammonium ions is 0.1-1:1, more preferably 0.4-0.8:1, the weight ratio of water to the molecular sieve containing ammonium ions is 5-20:1, more preferably 7-15:1, and the pH value of the ion exchange reaction solution is 2.5-5, more preferably 3-4.5.

[0057] In this invention, the preparation method of the ammonium ion-containing molecular sieve is not particularly limited. For example, it can be obtained by carrying out an ammonium exchange reaction between a sodium-type molecular sieve and ammonium ions. The sodium-type molecular sieve can be one or more of X-type molecular sieves, Y-type molecular sieves, ZSM-5 type molecular sieves, A-type molecular sieves, and β-type molecular sieves, preferably Y-type molecular sieves.

[0058] According to the present invention, preferably, the ammonium ion is derived from one or more of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium oxalate, and ammonium carbonate; more preferably, the ammonium ion is derived from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate.

[0059] According to the present invention, preferably, the concentration of ammonium ions in the reaction solution of the ammonium exchange reaction is 0.01-30% by weight, preferably 5-25% by weight, and the pH value is 2-6, preferably 3-4.5.

[0060] According to the present invention, preferably, the ammonium ion concentration in the reaction solution of the ammonium exchange reaction is 0.01-3.5 wt%, more preferably 0.1-1.5 wt%, relative to the sodium molecular sieve.

[0061] According to the present invention, preferably, the conditions for the ammonium exchange reaction include: a temperature of 5-100°C and a time of 5-60 min, more preferably, a temperature of 20-70°C and a time of 10-40 min. Furthermore, preferably, the solid-liquid ratio for the ammonium exchange reaction is 1:1-100, more preferably 1:2-50.

[0062] In this invention, the apparatus used for carrying out the ammonium exchange reaction is not particularly limited and can be carried out on any apparatus commonly used in the art for ion exchange, and can be either continuous ammonium exchange or intermittent ammonium exchange. Preferably, the ammonium exchange reaction is carried out on a continuous ion exchange reactor.

[0063] According to a preferred embodiment of the present invention, the method for preparing the rare earth element-containing molecular sieve includes the following steps:

[0064] (1) The ammonium ions in the first ion exchange reaction solution containing sodium molecular sieve and ammonium ions are subjected to a first ion exchange reaction with the sodium ions in the sodium molecular sieve to obtain a molecular sieve containing ammonium ions.

[0065] (2) Under hot-press conditions, the rare earth element ions in the second ion exchange reaction solution containing the molecular sieve containing ammonium ions and rare earth element ions undergo a second ion exchange reaction with the molecular sieve containing ammonium ions to obtain a molecular sieve containing rare earth elements.

[0066] According to the present invention, the method preferably further includes washing and drying the molecular sieve containing rare earth elements. The washing and drying conditions and equipment are not particularly limited, and any washing and drying conditions or equipment suitable for molecular sieve preparation can be used. Preferably, the drying temperature is 60-200°C, more preferably 80-120°C.

[0067] According to the present invention, the rare earth element-containing molecular sieve obtained by the above preparation method is a Y-type rare earth element-containing molecular sieve. The rare earth element-containing molecular sieve obtained by the above preparation method has a sodium oxide content of less than 1.2% by weight and a rare earth oxide content of 2-18.5% by weight.

[0068] In this invention, unless otherwise specified, "%" means "weight %".

[0069] The present invention will be described in detail below through embodiments.

[0070] Example 1

[0071] 1) Ammonium exchange reaction: NaY molecular sieve and ammonium sulfate aqueous solution were mixed and slurried. The weight ratio of ammonium sulfate to NaY molecular sieve was 0.5, and the concentration of ammonium sulfate aqueous solution was 12% by weight. The pH of the exchange mixture was controlled at 3.8, the temperature at 60℃, and the time was 40 min. After the exchange was completed, the solid and liquid were separated by filtration, and the mixture was washed with 3 times the amount of washing water (the weight ratio of washing water to NaY molecular sieve was 3:1) to obtain the ammonium ion exchanged molecular sieve (NaNH4Y), in which the Na2O content was 5.0% by weight.

[0072] 2) Thermo-pressure ion exchange reaction of rare earth ions: using methods such as... Figure 1 The continuous ion exchange reaction is carried out in the apparatus shown. The ammonium-exchanged molecular sieve (NaNH4Y) and the aqueous solution containing chlorinated mixed rare earth (lanthanum chloride and cerium chloride in a molar ratio of 1:1) are added to the raw material tank to contact and form a uniformly mixed slurry. The weight ratio of water to NaNH4Y molecular sieve in the mixed slurry is 10:1, the weight ratio of chlorinated mixed rare earth to NaNH4Y molecular sieve is 0.5:1, and the pH value is 4.0. Nitrogen gas is introduced into the preheater, reactor, product tank, and connecting pipelines of the continuous ion exchange reactor through the gas source outlet equipment to pre-charge the pressure to 2.5 MPa. Then, the continuous ion exchange reactor is started. The molecular sieve mixed slurry flows out from the raw material tank (feed flow rate is 0.6 L / min), and after being pressurized by the raw material pump, it enters the preheater for heating (the temperature of the continuous flow molecular sieve slurry at the preheater outlet is set to 160℃). The preheated molecular sieve slurry enters the continuous three-stage reactor for thermo-pressure ion exchange reaction (the reaction temperature of the first, second, and third reactors is 160℃, the pressure is 2.5 MPa, and the residence time of the molecular sieve slurry from the preheater outlet to the outlet of the final reactor is controlled to be 20 min). The product after thermo-pressure exchange is cooled by the cooler and enters the product tank (the temperature of the molecular sieve slurry at the cooler outlet is controlled to be 60℃). The product tank filling volume is not higher than 70%, and the two product tanks are used alternately. After the product tank is depressurized, the molecular sieve after continuous hot-pressing and exchange flows out from the outlet. After filtration, solid-liquid separation and water washing, the exchanged rare earth Y molecular sieve (REY) is obtained, denoted as S-1.

[0073] The sodium oxide and rare earth oxide contents of the rare earth Y molecular sieve S-1 are shown in Table 1.

[0074] Example 2-13

[0075] Rare earth Y molecular sieves were prepared according to the method in Example 1, with the only difference being that the reaction conditions are shown in Table 1. The sodium oxide and rare earth oxide contents of the obtained rare earth Y molecular sieves are shown in Table 1.

[0076] Table 1

[0077]

[0078] Comparative Example 1

[0079] 1) Step 1) is performed according to the method of Example 1;

[0080] 2) Step 1) is carried out according to the method of Example 1, except that no pressure is pre-charged into the device, that is, the pressure under hot pressing conditions is the saturated vapor pressure of water at the reaction temperature of 160°C, to obtain a molecular sieve containing rare earth elements, denoted as D-1.

[0081] The molecular sieve D-1 of this rare earth element contains 1.86% sodium oxide and 15.6% rare earth oxide.

[0082] Comparative Example 2

[0083] 1) Step 1) is performed according to the method of Example 1;

[0084] 2) Step 1) is carried out according to the method of Example 3, except that no pressure is pre-charged into the device, that is, the pressure of the hot pressing condition is the saturated vapor pressure of water at the corresponding reaction temperature, and a molecular sieve containing rare earth elements is obtained, denoted as D-2.

[0085] The molecular sieve D-2 of this rare earth element contains 1.58% sodium oxide and 16.2% rare earth oxide.

[0086] Comparative Example 3

[0087] 1) Step 1) is performed according to the method of Example 1;

[0088] 2) The NaNH4Y obtained from the ammonium ion exchange in step 1) was subjected to intermittent thermo-pressure exchange with a mixed rare earth chloride aqueous solution in a high-pressure reactor. The reaction temperature, feed ratio, pH value, and other conditions were controlled in the same manner as in Example 1, and the pressure was the saturated vapor pressure of water at the corresponding reaction temperature. The mixed slurry was heated from room temperature to 160°C for 100 min, and then exchanged at a constant temperature of 160°C for 20 min. After cooling to room temperature, the reaction material was removed, filtered for solid-liquid separation, and washed with washing water (under the same post-processing conditions as in Example 1) to obtain a molecular sieve containing rare earth elements, denoted as D-3.

[0089] The molecular sieve D-3 for this rare earth element contains 2.7% sodium oxide and 14.9% rare earth oxide.

[0090] Comparative Example 4

[0091] 1) Step 1) is performed according to the method of Example 1;

[0092] 2) The NaNH4Y obtained from the ammonium ion exchange in step 1) was subjected to intermittent thermo-pressure exchange with a mixed rare earth chloride aqueous solution in a high-pressure reactor. The reaction temperature, feed ratio, pH value, and other conditions were controlled in the same manner as in Example 1, and the pressure was the saturated vapor pressure of water at the corresponding reaction temperature. The mixed slurry was heated from room temperature to 160°C for 100 min, and then exchanged at a constant temperature of 160°C for 120 min. After cooling to room temperature, the reaction material was removed, filtered for solid-liquid separation, and washed with washing water (under the same post-processing conditions as in Example 1) to obtain a molecular sieve containing rare earth elements, denoted as D-4.

[0093] The molecular sieve D-4 of this rare earth element has sodium oxide and rare earth oxide contents of 1.98% and 15.2%, respectively.

[0094] The sodium oxide and rare earth oxide contents in the rare earth-containing molecular sieves prepared by the above examples and comparative examples demonstrate that the high-temperature continuous hot-press exchange method of the present invention can greatly shorten the exchange time, obtain a higher degree of exchange, and result in a lower sodium oxide content in the molecular sieve after continuous hot-press exchange. Without the need for high-temperature calcination, the sodium oxide content in the rare earth Y-type molecular sieve prepared by the method of the present invention can be reduced to below 1.25%.

[0095] A comparison of Examples 1-5 shows that the rare earth element exchange rate decreases when the temperature reaches 185-190℃. Therefore, the preferred hot-press exchange temperature is 160-180℃.

[0096] A comparison of Examples 3 and 6-9 shows that the rare earth element exchange rate can be further improved by setting the hot-press exchange pressure to 1.5-2.5 MPa or (P+0.5~P+2) MPa.

[0097] A comparison of Examples 3 and 10 shows that by ensuring that the hot-press exchange temperature of the subsequent reactor is not lower than that of the preceding reactor, the rare earth element exchange rate can be further improved.

[0098] A comparison of Examples 9 and 11-13 shows that by making the weight ratio of rare earth to molecular sieve 0.45-0.8, more preferably 0.45-0.55, the rare earth element exchange rate can be further improved.

[0099] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a molecular sieve containing rare earth elements, characterized in that, The preparation method includes: under hot-pressing conditions, a molecular sieve containing ammonium ions is subjected to an ion exchange reaction with rare earth element ions in an ion exchange reaction solution to obtain a molecular sieve containing rare earth elements. The hot-pressing conditions include: a temperature of 160-190℃ and a pressure of (P+0.1)~(P+2)MPa, where P represents the saturated vapor pressure of water at the ion exchange temperature, in MPa. The ion exchange reaction is a continuous thermo-pressure exchange carried out in a continuous ion exchange reactor, which includes two or more reactor stages. The ammonium ion-containing molecular sieve is obtained by subjecting a sodium-type molecular sieve to an ammonium exchange reaction with ammonium ions. The heat exchange temperature of the subsequent reactor is 3-15℃ higher than that of the previous reactor.

2. The preparation method according to claim 1, wherein, The hot pressing conditions include: a temperature of 160-180℃; and / or, the hot pressing conditions include: a pressure of (P+0.5) to (P+1.5) MPa.

3. The preparation method according to claim 1, wherein, The conditions for continuous thermo-pressure exchange include: the temperature of the preheated material is 150-190℃, the thermo-pressure exchange temperature of each stage reactor is 160-190℃, and the residence time of the molecular sieve slurry from the completion of preheating to the outlet of the last stage reactor is 0.1-40 min.

4. The preparation method according to claim 1, wherein, The ammonium ion-containing molecular sieve is one or more of the following: X-type molecular sieve, Y-type molecular sieve, ZSM-5 type molecular sieve, A-type molecular sieve, and β-type molecular sieve.

5. The preparation method according to claim 4, wherein, The ammonium ion-containing molecular sieve is a Y-type molecular sieve.

6. The preparation method according to claim 1, wherein, The rare earth element ions are derived from one or more of rare earth element hydrochlorides and rare earth element nitrates.

7. The preparation method according to claim 6, wherein, The rare earth elements are one or more of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, yttrium, and scandium.

8. The preparation method according to claim 6, wherein, The rare earth element ions are derived from one or more of lanthanum chloride, cerium chloride, lanthanum nitrate, and cerium nitrate.

9. The preparation method according to any one of claims 1-8, wherein, The weight ratio of rare earth elements to molecular sieves containing ammonium ions is 0.1-1:1, the weight ratio of water to molecular sieves containing ammonium ions is 5-20:1, and the pH value of the ion exchange reaction solution is 2.5-5.

10. The preparation method according to claim 1, wherein, The ammonium ions are derived from one or more of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium oxalate, and ammonium carbonate.

11. The preparation method according to claim 1, wherein, The concentration of ammonium ions in the reaction solution of the ammonium exchange reaction is 0.01-30% by weight, and the pH value is 2-6.

12. The preparation method according to claim 10, wherein, The ammonium ions are derived from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate.

13. The preparation method according to claim 11, wherein, The concentration of ammonium ions in the reaction solution of the ammonium exchange reaction is 5-25% by weight, and the pH value is 3-4.

5.

14. The preparation method according to claim 11, wherein, Compared to sodium molecular sieves, the ammonium ion content in the reaction solution of ammonium exchange reaction is 0.01-3.5% by weight.

15. The preparation method according to claim 14, wherein, Compared to sodium-type molecular sieves, the ammonium ion content in the reaction solution of ammonium exchange reaction is 0.1-1.5% by weight.

16. The preparation method according to claim 10, wherein, The conditions for the ammonium exchange reaction include: a temperature of 5-100℃ and a time of 5-60 min.

17. The preparation method according to claim 16, wherein, The solid-liquid ratio of the ammonium exchange reaction is 1:1-100.

18. The preparation method according to claim 16, wherein, The conditions for the ammonium exchange reaction include: a temperature of 20-70℃ and a time of 10-40 min.

19. The preparation method according to any one of claims 1-8, wherein, The method further includes washing and drying the molecular sieve containing rare earth elements.

20. The preparation method according to claim 19, wherein, The drying temperature is 60-200℃.

21. The preparation method according to any one of claims 1-8, wherein, The sodium oxide content in the rare earth element-containing molecular sieve is less than 1.2% by weight, and the rare earth oxide content is 2-18.5% by weight.

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