Modified molecular sieve and its preparation method and application

Abstract

The present invention relates to the technical field of molecular sieves, and in particular to a method for preparing a modified molecular sieve, a modified molecular sieve obtained by the preparation method and its application. The preparation method comprises: (1) exchanging metal ions on a Na-type molecular sieve to obtain a metal ion slurry; (2) adding a first precipitant so that part of the metal ions in the metal ion exchange slurry undergo a first precipitation to obtain a first precipitation slurry; (3) the first precipitation slurry is filtered, subjected to a first ammonium sulfate exchange, a first water wash, and a first roasting in sequence to obtain a cross-baked molecular sieve dry powder; (4) adding a second precipitant so that part of the metal ions in the cross-baked molecular sieve dry powder undergo a second precipitation, and then a second ammonium sulfate exchange, a second water wash, and an optional second roasting are performed in sequence to obtain a modified molecular sieve. The modified molecular sieve obtained by the method has a lower sulfate content and also improves the crystallinity and stability of the modified molecular sieve.

Description

Technical Field

[0001] The invention relates to the technical field of molecular sieves, and in particular to a method for preparing a modified molecular sieve, a modified molecular sieve prepared by the preparation method and applications thereof. Background Art

[0002] Catalytic cracking reaction is a typical acid-catalyzed gas-solid heterogeneous reaction, following the positive carbon ion mechanism. However, NaY molecular sieve itself is not acidic and usually needs to be exchanged and modified to remove Na ions and adjust its acidity and pore structure. + Too strong acidity can easily destroy the Y-type molecular sieve framework structure, resulting in a decrease in crystallinity and selectivity. REY-type molecular sieves are prone to coking and deactivation during catalytic cracking reactions due to their strong acidity and acid density. Therefore, the commonly used modification method is to use ammonium salts and / or rare earths for exchange, and then prepare modified REHY or REUSY-type molecular sieves with different acidity and pore structures through thermal or hydrothermal calcination.

[0003] Ammonium chloride is easy to decompose at high temperature and crystallize at low temperature, so it is easy to clog the catalyst flue and bag filter, resulting in the inability to produce continuously. Ammonium nitrate will explode under high temperature, high pressure, oxidizable substances (reducing agents) and electric sparks, and it is a key raw material for making explosives and is expensive, so it is not used. Ammonium sulfate is stable and cheap, and is often used in industrial molecular sieve exchange modification. However, because it easily reacts with rare earths to form rare earth sulfate precipitation, on the one hand, rare earth ions cannot migrate into the cage of the molecular sieve, effectively stabilizing the molecular sieve framework structure. On the other hand, it is easy to cause sulfate to exceed the standard and destroy the molecular sieve framework structure. In addition, after being made into a catalyst, sulfate will be converted into sulfide during the refining process, corroding equipment.

[0004] In the prior art, the method of precipitating rare earths is often used to improve the utilization rate of rare earths, and at the same time, generate independent phase rare earths to improve the anti-V pollution performance of molecular sieves; rare earths and ammonium salts are exchanged at the same time, and the exchange efficiency is low due to the competitive exchange; ammonium salt exchange is carried out before rare earth exchange, and the use of ammonium chloride and ammonium nitrate will cause problems such as high cost and equipment corrosion, while the use of low-cost recyclable ammonium sulfate, in order to avoid the formation of sulfate precipitation, requires a large amount of water washing to remove sulfate, which will increase water consumption. After the rare earth modified molecular sieve is hydrothermally calcined, it is inevitable that some rare earths cannot be located in the sodalite cage, so that ammonium sulfate exchange is used in the subsequent exchange, resulting in the formation of rare earth sulfate precipitation, resulting in an increase in molecular sieve sulfate and a decrease in crystallinity. Although pre-exchange can reduce the sodium oxide and sulfate of the modified molecular sieve, it has the problems of long process, water consumption and high cost. REY molecular sieves prepared without ammonium salts have the problem of high coke generation.

[0005] CN200610087535.2 discloses a method for preparing a REY molecular sieve, which comprises: contacting a NaY molecular sieve 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, contacting with an additional precipitant to precipitate part of the rare earth on the molecular sieve, then performing a hydrothermal treatment, and finally contacting with an ammonium salt aqueous solution, and the prepared molecular sieve has a strong vanadium resistance. Although a cross-linked and baked rare earth modified Y-type molecular sieve is prepared by rare earth exchange, precipitation, filtration, and roasting, and then directly performing ammonium salt exchange to obtain the REY molecular sieve, although rare earth loss is avoided by precipitation during the cross-linking process, rare earth will inevitably exist on the outer surface of the molecular sieve or in the super cage space due to the cross-linked and baked rare earth modified Y-type molecular sieve, and if ammonium sulfate is used as an exchange agent later, this part of the rare earth is easy to generate rare earth sulfate precipitation with sulfate radical, resulting in a high molecular sieve sulfate radical, low crystallinity, and poor stability.

[0006] CN201511020519.7 discloses a method for preparing a modified Y-type molecular sieve, which comprises: exchanging the NaY molecular sieve with an ammonium salt first, mixing the compound containing the IIIB element of the periodic table after filtering, spray drying and hydrothermal roasting directly without washing, and then exchanging with an ammonium salt again, adding a precipitant or a precipitant and a filter aid, and performing or not performing hydrothermal roasting after filtering. Although the method mixes and roasts the molecular sieve filter cake exchanged with the ammonium salt with the compound of the IIIB element, and adds a precipitant after the diammonium salt exchange, thereby avoiding the loss of the IIIB element compound, it also directly exchanges with the ammonium salt after one exchange and one roasting. If ammonium sulfate is used as an exchange agent, this part of the IIIB element is easy to generate rare earth sulfate precipitation with sulfate, resulting in high sulfate, low crystallinity and poor stability of the molecular sieve.

[0007] Therefore, a new method for preparing modified molecular sieves is urgently needed. Summary of the invention

[0008] The purpose of the present invention is to overcome the problems of high sulfate content, low crystallinity, equipment corrosion, long production process, high cost, etc. in the existing preparation method of modified molecular sieves, and to provide a preparation method of modified molecular sieves, a modified molecular sieve prepared by the preparation method and its application. The modified molecular sieve prepared by the preparation method has the characteristics of low sulfate content, high crystallinity, good stability, etc. At the same time, the method simplifies the process flow and is convenient for industrial production.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a modified molecular sieve, the preparation method comprising the following steps:

[0010] (1) exchanging metal ions on a Na-type molecular sieve to obtain a metal ion slurry;

[0011] (2) adding a first precipitant to cause a portion of the metal ions in the metal ion exchange slurry to undergo a first precipitation to obtain a first precipitation slurry;

[0012] (3) the first precipitation slurry is filtered, subjected to a first ammonium sulfate exchange, subjected to a first water wash, and subjected to a first roasting in sequence to obtain a cross-exchanged and roasted molecular sieve dry powder;

[0013] (4) adding a second precipitant to cause a second precipitation of some metal ions in the cross-calcined molecular sieve dry powder, and then sequentially performing a second ammonium sulfate exchange, a second water washing, and an optional second calcination to obtain a modified molecular sieve.

[0014] The second aspect of the present invention provides a modified molecular sieve obtained by the preparation method provided in the first aspect.

[0015] The third aspect of the present invention provides an application of the modified molecular sieve provided in the second aspect in heavy oil conversion and resistance to heavy metal vanadium pollution.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The preparation method of the modified molecular sieve provided by the present invention is to add a precipitant (i.e., a first precipitant and a second precipitant) to the Na-type molecular sieve after metal ion exchange and before ammonium sulfate exchange to form a precipitate precursor of a metal oxide with the metal ions, thereby avoiding the formation of precipitation of free metal ions and sulfate in the exchange system solution, on the surface of the molecular sieve or in the super cage during the subsequent ammonium sulfate exchange and sodium reduction process, thereby achieving the purpose of reducing sulfate;

[0018] (2) The preparation method provided by the present invention also improves the crystallinity and stability of the modified molecular sieve, improves the metal utilization rate, generates independent phase multivalent metal oxides, improves the heavy oil conversion capacity and the ability to resist heavy metal vanadium pollution; at the same time, the preparation method is simple to operate, simplifies the process flow, and is convenient for industrial production. DETAILED DESCRIPTION

[0019] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0020] In the present invention, unless otherwise specified, "first" and "second" do not indicate a sequence, nor do they limit the materials or steps, but are only used to distinguish that they are not the same steps or materials. For example, "first" and "second" in "first ammonium sulfate exchange" and "second ammonium sulfate exchange" are only used to indicate that they are not the same ammonium sulfate exchange.

[0021] The first aspect of the present invention provides a method for preparing a modified molecular sieve, the preparation method comprising the following steps:

[0022] (1) exchanging metal ions on a Na-type molecular sieve to obtain a metal ion slurry;

[0023] (2) adding a first precipitant to cause a portion of the metal ions in the metal ion exchange slurry to undergo a first precipitation to obtain a first precipitation slurry;

[0024] (3) the first precipitation slurry is filtered, subjected to a first ammonium sulfate exchange, subjected to a first water wash, and subjected to a first roasting in sequence to obtain a cross-exchanged and roasted molecular sieve dry powder;

[0025] (4) adding a second precipitant to cause a second precipitation of some metal ions in the cross-calcined molecular sieve dry powder, and then sequentially performing a second ammonium sulfate exchange, a second water washing, and an optional second calcination to obtain a modified molecular sieve.

[0026] In some embodiments of the present invention, preferably, in step (1), the conditions for metal ion exchange include: temperature of 25-180°C, preferably 50-80°C; pH of 2.8-6.5, preferably 3.5-4.5; time of 0.3-3.5h, preferably 0.5-1.5h.

[0027] In some embodiments of the present invention, preferably, the process of metal ion exchange comprises: mixing the Na-type molecular sieve and water, and then adding a soluble metal salt to perform the metal ion exchange.

[0028] In some embodiments of the present invention, preferably, the weight ratio of the Na-type molecular sieve to water is 1:1.5-30, for example, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:10, 1:20, 1:30, and any value in the range of any two numerical values, preferably 1:2-5.

[0029] In some embodiments of the present invention, preferably, the content of the soluble metal salt in terms of oxide in the Na-type molecular sieve in terms of dry basis is 1-20wt%, for example, 1wt%, 4wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 16wt%, 20wt%, and any value in the range of any two values, preferably 6-16wt%. The preferred conditions are more conducive to reducing the sulfate content in the modified molecular sieve, thereby eliminating the influence of sulfate on the performance of the modified molecular sieve, and improving the crystallinity and catalytic performance of the modified molecular sieve.

[0030] In the present invention, during the metal ion exchange process, the metal ions in the soluble metal salt are completely attached to the surface and internal pores of the Na-type molecular sieve. Therefore, the weight ratio of the Na-type molecular sieve calculated on a dry basis to the soluble metal salt calculated on an oxide basis is 100:1-20, preferably 100:6-16.

[0031] In the present invention, unless otherwise specified, solubility means being easily soluble in water or being easily soluble in water with the help of an auxiliary agent.

[0032] In some embodiments of the present invention, preferably, the soluble metal salt is selected from chlorates and / or nitrates containing at least one of rare earth elements, alkaline earth metal elements, and transition metal elements, preferably selected from chlorates and / or nitrates containing rare earth elements, and more preferably selected from lanthanum chloride and / or lanthanum nitrate. In the present invention, the alkaline earth metal element is selected from calcium and / or barium; the transition metal element is selected from silver and / or lead.

[0033] In the present invention, the type of the Na-type molecular sieve has a wide selection range. Preferably, the silicon-aluminum ratio of the Na-type molecular sieve is 2-100, preferably 2-50; further preferably, the Na-type molecular sieve is selected from at least one of NaY molecular sieve, NaHY molecular sieve, NaUSY molecular sieve, NaREHY molecular sieve, NaREUSY molecular sieve, Naβ molecular sieve, NaHβ molecular sieve, NaREHβ molecular sieve, NaX molecular sieve, NaREX molecular sieve and NaHX molecular sieve, preferably selected from NaY molecular sieve and / or NaHY molecular sieve, more preferably NaY molecular sieve.

[0034] In some embodiments of the present invention, preferably, in step (2), the amount of the first precipitant is such that the molar ratio of the metal ions in the Na-type molecular sieve is 1-4wt% after the first precipitation; further preferably, the amount of the first precipitant is such that the molar ratio of the metal ions in the Na-type molecular sieve is 1.5-2.5wt% after the first precipitation. The preferred conditions are more conducive to reducing the sulfate content of the modified molecular sieve, thereby improving the crystallinity and catalytic performance of the modified molecular sieve.

[0035] In the present invention, the type of the first precipitant has a wide range of choices, as long as the metal ions are converted into metal oxides. Preferably, the first precipitant is selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate, ammonia water, urea and ammonium acetate, and is preferably selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate and ammonia water.

[0036] In some embodiments of the present invention, preferably, the conditions for the first precipitation include: a temperature of 25-180°C, preferably 50-80°C; and a time of 0.1-5h, preferably 0.1-2h.

[0037] In the present invention, the first ammonium sulfate exchange is intended to further exchange the Na + Preferably, in step (3), the first ammonium sulfate exchange process comprises: exchanging the filtered product with the first ammonium sulfate aqueous solution.

[0038] In some embodiments of the present invention, preferably, the weight ratio of the first ammonium sulfate aqueous solution and the Na-type molecular sieve calculated as ammonium sulfate is 5-50:100, for example, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 40:100, 50:100, and any value in the range composed of any two values, preferably 10-25:100.

[0039] In some embodiments of the present invention, preferably, the concentration of ammonium sulfate in the first aqueous ammonium sulfate solution is 20-400 g / L, for example, 20 g / L, 50 g / L, 80 g / L, 120 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, 400 g / L, and any value in the range consisting of any two values, preferably 120-250 g / L.

[0040] In some embodiments of the present invention, preferably, the conditions for the first ammonium sulfate exchange include: temperature of 15-150°C, preferably 50-80°C; time of 0.1-5h, preferably 0.5-2h.

[0041] In some embodiments of the present invention, preferably, the amount of water used in the first water wash is 1-8 times the weight of the Na-type molecular sieve, for example, 1 times, 2 times, 3 times, 4 times, 5 times, 8 times, and any value in the range of any two values, preferably 2-5 times.

[0042] In some embodiments of the present invention, preferably, the conditions for the first calcination include: 100% water vapor atmosphere; temperature of 400-700° C., preferably 500-650° C.; time of 0.1-5 h, preferably 0.5-3 h.

[0043] In some embodiments of the present invention, preferably, the amount of the second precipitant satisfies the molar ratio of the metal ions in the cross-roasted molecular sieve dry powder of 0.5-3wt% through the second precipitation; further preferably, the amount of the second precipitant satisfies the molar ratio of the metal ions in the cross-roasted molecular sieve dry powder of 1-2wt% through the second precipitation. The use of the preferred conditions is more conducive to reducing the sulfate content of the modified molecular sieve, thereby improving the crystallinity and catalytic performance of the modified molecular sieve.

[0044] In some embodiments of the present invention, preferably, the second precipitant is selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate, ammonia water, urea and ammonium acetate, preferably selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate and ammonia water.

[0045] In some embodiments of the present invention, preferably, the conditions for the second precipitation include: a temperature of 15-40°C, preferably 20-30°C; and a time of 0.1-5h, preferably 0.1-2h.

[0046] In some embodiments of the present invention, preferably, in step (4), the second ammonium sulfate exchange process comprises: exchanging the second precipitated product with the second ammonium sulfate aqueous solution.

[0047] In some embodiments of the present invention, preferably, the weight ratio of the second aqueous ammonium sulfate solution to the cross-baked molecular sieve dry powder, calculated as ammonium sulfate, is 5-50:100, for example, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 40:100, 50:100, and any value in the range consisting of any two values, preferably 10-25:100.

[0048] In some embodiments of the present invention, preferably, the concentration of ammonium sulfate in the second aqueous ammonium sulfate solution is 20-400 g / L, for example, 20 g / L, 50 g / L, 80 g / L, 120 g / L, 150 g / L, 200 g / L, 250 g / L, 300 g / L, 400 g / L, and any value in the range consisting of any two values, preferably 120-250 g / L.

[0049] In some embodiments of the present invention, preferably, the conditions for the second ammonium sulfate exchange include: temperature of 20-85°C, preferably 50-80°C; time of 0.1-5h, preferably 0.1-2h.

[0050] In some embodiments of the present invention, preferably, the amount of water used in the second water washing is 1-8 times the weight of the cross-baked molecular sieve dry powder, for example, 1 time, 2 times, 3 times, 4 times, 5 times, 8 times, and any value in the range consisting of any two values, preferably 2-5 times.

[0051] In some embodiments of the present invention, preferably, the conditions for the second calcination include: 20-100% water vapor atmosphere; temperature of 400-700° C., preferably 450-650° C.; time of 0.1-10 h, preferably 0.5-5 h.

[0052] In some embodiments of the present invention, preferably, before the second precipitation, the cross-calcined molecular sieve dry powder is mixed with water.

[0053] In some embodiments of the present invention, preferably, in step (4), the weight ratio of the cross-baked molecular sieve dry powder to water is 1:1.5-30, for example, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:10, 1:20, 1:30, and any value in the range consisting of any two values, preferably 1:2-5.

[0054] The second aspect of the present invention provides a modified molecular sieve obtained by the preparation method provided in the first aspect.

[0055] The modified molecular sieve prepared by the preparation method provided by the invention has low sulfate content, high crystallinity, good stability, etc., and has high activity in heavy oil conversion and resistance to medium metal vanadium pollution.

[0056] In some embodiments of the present invention, preferably, the modified molecular sieve satisfies: SO 4 2- The content is ≤0.5wt%, preferably 0.01-0.45wt%.

[0057] In the present invention, unless otherwise specified, SO 4 2- The content parameters were measured by XRF fluorescence method; the crystallinity parameters were measured by X-ray diffraction method; the micro-reaction activity parameters were tested as follows: the samples were pre-treated at 800°C and 100% water vapor for different times; the reaction raw material was Dagang light diesel, the reaction temperature was 460°C, the reaction time was 70s, the catalyst loading was 5g, the catalyst-oil weight ratio was 3.2, and the total conversion rate was taken as the micro-reaction activity.

[0058] The third aspect of the present invention provides an application of the modified molecular sieve provided in the second aspect in heavy oil conversion and resistance to heavy metal vanadium pollution.

[0059] According to a particularly preferred embodiment of the present invention, a method for preparing a modified molecular sieve comprises the following steps:

[0060] (1) exchanging metal ions on a Na-type molecular sieve to obtain a metal ion slurry;

[0061] (2) adding a first precipitant to cause a portion of the metal ions in the metal ion exchange slurry to undergo a first precipitation to obtain a first precipitation slurry;

[0062] (3) the first precipitation slurry is filtered, subjected to a first ammonium sulfate exchange, subjected to a first water wash, and subjected to a first roasting in sequence to obtain a cross-exchanged and roasted molecular sieve dry powder;

[0063] (4) adding a second precipitant to cause a second precipitation of some metal ions in the cross-baked molecular sieve dry powder, and then sequentially performing a second ammonium sulfate exchange, a second water washing, and an optional second calcination to obtain a modified molecular sieve;

[0064] Wherein, in step (2), the amount of the first precipitant used satisfies the molar ratio of the metal ions in the Na-type molecular sieve with a content of 1.5-2.5wt% through the first precipitation;

[0065] Wherein, in step (3), the first calcination conditions include: 100% water vapor atmosphere; temperature of 500-650° C.; time of 0.5-3 h;

[0066] Wherein, in step (4), the amount of the second precipitant is such that the molar ratio of the metal ions in the cross-calcined molecular sieve dry powder is 1-2wt% after the second precipitation; the conditions of the second calcination include: 20-100% water vapor atmosphere; temperature of 450-650°C; time of 0.5-5h.

[0067] The present invention will be described in detail below through examples.

[0068] NaY molecular sieve was purchased from a commercial product produced by Lanzhou Catalyst Factory;

[0069] SO 4 2- The content parameters were measured by XRF fluorescence method;

[0070] The crystallinity parameters were measured by X-ray diffraction;

[0071] The micro-reactor activity parameter test is as follows: the samples are pre-treated at 800°C and 100% water vapor for different times; the reaction raw material is Dagang light diesel, the reaction temperature is 460°C, the reaction time is 70s, the catalyst loading is 5g, the catalyst-oil weight ratio is 3.2, and the total conversion rate is taken as the micro-reactor activity.

[0072] The physical properties of the modified molecular sieves (Z1-Z7 and DZ1-DZ4) prepared in Examples 1-7 and Comparative Examples 1-4 are listed in Table 1.

[0073] Example 1

[0074] (1) 1000 g NaY molecular sieve (dry basis) was slurried with 5 L deionized water and 0.537 L (La 2 O 3 The concentration of LaCl is 298 g / L 3 Solution (La 3+ 0.98 mol) was used for metal ion exchange (temperature was 80°C, time was 0.5 h) to obtain a metal ion exchange slurry; wherein La 2 O 3 LaCl 3 The content of NaY molecular sieve on a dry basis is 16 wt%;

[0075] (2) Add (32 g, 0.225 mol) ammonium oxalate monohydrate to make 2.4 wt% of La in the above metal ion exchange slurry 3+ Performing a first precipitation (temperature of 80° C., time of 0.5 h) to obtain a first precipitation slurry;

[0076] (3) The first precipitate slurry was filtered and drained, 0.833 L of 180 g / L ammonium sulfate aqueous solution was added, exchanged at 60° C. for 1 h, drained, rinsed with 3 L of water, and then calcined at 500° C. for 2 h in a 100% water vapor atmosphere to obtain a cross-calcined molecular sieve dry powder;

[0077] (4) After slurrying the above 1000 g (dry basis) cross-linked roasted molecular sieve powder with 5 L of deionized water, 25.6 g (0.18 mol) of ammonium oxalate monohydrate was added to make 2 wt% of La in the above cross-linked roasted molecular sieve powder. 3+ After the second precipitation (temperature is 25°C, time is 0.5h), add 0.6L of 250g / L ammonium sulfate aqueous solution, exchange at 80°C for 1.5h, filter, drain, add 5L of water for rinsing, and calcine at 450°C for 2h in a 100% water vapor atmosphere to obtain modified molecular sieve Z1.

[0078] Example 2

[0079] (1) 1000 g NaY molecular sieve (dry basis) was slurried with 5 L deionized water and 0.358 L of 280 g / L (La 2 O 3 La(NO 3 ) 3 Solution (La 3+ 0.615 mol) was used for metal ion exchange (temperature was 50°C, time was 1.5 h) to obtain a metal ion exchange slurry; wherein La 2 O 3 The La(NO 3 ) 3 The content of NaY molecular sieve on a dry basis is 10wt%;

[0080] (2) Add (25.6 g, 0.18 mol) of ammonium oxalate monohydrate to make 2 wt% of La in the above metal ion exchange slurry. 3+ Performing a first precipitation (temperature of 50° C., time of 0.5 h) to obtain a first precipitation slurry;

[0081] (3) The first precipitate slurry was filtered and drained, 1.111 L of 180 g / L ammonium sulfate aqueous solution was added, exchanged at 80° C. for 1 h, drained, rinsed with 3 L of water, and then calcined at 600° C. for 2 h in a 100% water vapor atmosphere to obtain a cross-linked and roasted molecular sieve dry powder;

[0082] (4) After slurrying the above 1000 g (dry basis) cross-roasted molecular sieve powder with 5 L of deionized water, 13 g (0.135 mol) of ammonium carbonate was added to make the La content in the cross-roasted molecular sieve powder 1.5 wt%. 3+ After the second precipitation (temperature is 25°C, time is 0.5h), add 1.666L of 120g / L ammonium sulfate aqueous solution, exchange at 50°C for 1h, filter, drain, add 2L of water for rinsing, and calcine at 500°C for 2.5h in 80% water vapor atmosphere to obtain modified molecular sieve Z2.

[0083] Example 3

[0084] (1) 1000 g NaY molecular sieve (dry basis) was slurried with 5 L deionized water and 0.336 L of 298 g / L (La 2 O 3 LaCl 3 Solution (La 3+ 0.615 mol) for metal ion exchange (temperature 50°C, time 1 h) to obtain metal ion exchange slurry; wherein La 2 O 3 LaCl 3The content of NaY molecular sieve on a dry basis is 10wt%;

[0085] (2) Add 16 mL of 28% industrial ammonia water to make 1.5 wt% of La in the above metal ion exchange slurry. 3+ Performing a first precipitation (temperature of 50° C., time of 0.5 h) to obtain a first precipitation slurry;

[0086] (3) The first precipitate slurry was filtered and drained, and 1.389 L of 180 g / L ammonium sulfate aqueous solution was added, exchanged at 50° C. for 1.5 h, drained, rinsed with 3 L of water, and then calcined at 650° C. for 2 h in a 100% water vapor atmosphere to obtain a cross-calcined molecular sieve dry powder;

[0087] (4) After slurrying the above 1000 g (dry basis) cross-linked roasted molecular sieve powder with 5 L of deionized water, 12.8 g (0.09 mol) of ammonium oxalate monohydrate was added to make 1 wt% of La in the above cross-linked roasted molecular sieve powder. 3+ After the second precipitation (temperature is 25°C, time is 0.5h), add 1.389L of 180g / L ammonium sulfate aqueous solution, exchange at 50°C for 1h, filter, drain, add 3L of water for rinsing, and calcine at 650°C for 2h in a 60% water vapor atmosphere to obtain modified molecular sieve Z3.

[0088] Example 4

[0089] (1) 1000 g NaY molecular sieve (dry basis) was slurried with 5 L deionized water and 0.43 L of 326 g / L (RE 2 O 3 Mixed RECl 3 Solution (Ce 2 O 3 and La 2 O 3 The weight ratio is 6:4; (RE 3+ 0.9287 mol) for metal ion exchange (temperature 60°C, time 1 h) to obtain metal ion exchange slurry; wherein RE 2 O 3 RECl 3 The content of NaY molecular sieve on a dry basis is 14 wt%;

[0090] (2) Add (25.6 g, 0.18 mol) of ammonium oxalate monohydrate and then add 5 mL of 28% industrial ammonia water to make 2.4 wt% of RE in the above metal ion exchange slurry. 3+ Performing a first precipitation (temperature of 60° C., time of 0.5 h) to obtain a first precipitation slurry;

[0091] (3) The first precipitate slurry was filtered and drained, and 1.222 L of 180 g / L ammonium sulfate aqueous solution was added, exchanged at 100° C. for 0.5 h, drained, rinsed with 5 L of water, and then calcined at 600° C. for 2 h in a 100% water vapor atmosphere to obtain a cross-calcined molecular sieve dry powder;

[0092] (4) After slurrying the above 1000 g (dry basis) cross-linked roasted molecular sieve powder with 5 L of deionized water, 18 g (0.187 mol) of ammonium carbonate was added to make 1.8 wt% of RE in the above cross-linked roasted molecular sieve powder. 3+ After the second precipitation (temperature is 25°C, time is 0.5h), add 1L of 120g / L ammonium sulfate aqueous solution, exchange at 25°C for 1h, filter, drain, add 4L of water for rinsing, and calcine at 550°C for 2h in a 20% water vapor atmosphere to obtain modified molecular sieve Z4.

[0093] Example 5

[0094] The method of Example 1 is followed, except that in step (1), 0.537 L (in terms of La 2 O 3 The concentration of LaCl is 298 g / L 3 The solution was replaced with 0.67 L (in La 2 O 3 The concentration of LaCl is 298 g / L 3 solution, so that La 2 O 3 LaCl 3 The content of NaY molecular sieve on a dry basis is 20wt%;

[0095] The other conditions were the same to obtain modified molecular sieve Z5.

[0096] Example 6

[0097] The method of Example 1 was followed, except that in step (2), (32 g, 0.225 mol) of ammonium oxalate monohydrate was replaced with (12.8 g, 0.09 mol) of ammonium oxalate monohydrate, so that 1 wt% of La in the metal ion exchange slurry 3+ Carry out the first precipitation (temperature is 80°C, time is 0.5h);

[0098] The other conditions were the same to obtain modified molecular sieve Z6.

[0099] Example 7

[0100] The method of Example 1 was followed, except that in step (4), (25.6 g, 0.18 mol) of ammonium oxalate monohydrate was replaced with (6.4 g, 0.045 mol) of ammonium oxalate monohydrate, so that 0.5 wt% of La in the above cross-baked molecular sieve dry powder was 3+ Carry out the second precipitation (temperature is 25°C, time is 0.5h)

[0101] The other conditions were the same to obtain modified molecular sieve Z7.

[0102] Comparative Example 1

[0103] According to the method disclosed in CN200610087535.2, the modified molecular sieve DZ1 was prepared, namely,

[0104] Take 1000g NaY molecular sieve (dry basis), slurry it with 8L deionized water, and add 0.385L of 312g / L (La 2 O 3 RECl 3 solution, add 240g of aluminum sulfate, exchange at 90℃ for 1h, add 75g of ammonium bicarbonate, stir at constant temperature for 0.25h, filter, rinse with 5L of water, and then roast the filter cake at 600℃ and 100% water vapor atmosphere for 2h to obtain a cross-baked molecular sieve dry powder;

[0105] Take 1000 g (dry basis weight) of the cross-baked molecular sieve powder, slurry it with 6 L of deionized water, add 300 g of ammonium sulfate, exchange it at 75° C. for 1 h, filter it, rinse it with 6 L of water, and dry the filter cake to obtain the modified molecular sieve DZ1.

[0106] Comparative Example 2

[0107] The modified molecular sieve DZ2 was obtained by following the method of Example 1, except that in step (2), no (32 g, 0.225 mol) ammonium oxalate monohydrate was added, and the other conditions were the same.

[0108] Comparative Example 3

[0109] The modified molecular sieve DZ3 was obtained by following the method of Example 2, except that in step (4), no (25.6 g, 0.18 mol) ammonium oxalate monohydrate was added, and the other conditions were the same.

[0110] Comparative Example 4

[0111] The modified molecular sieve DZ4 was obtained by following the method of Example 3, except that in step (2), 8 mL of 28% industrial ammonia water was not added, and in step (4), (12.8 g, 0.09 mol) of ammonium oxalate monohydrate was not added. Other conditions were the same.

[0112] Table 1

[0113]

[0114]

[0115] It can be seen from the results in Table 1 that the modified molecular sieve prepared by the method provided by the present invention has a higher rare earth utilization rate, a lower sulfate content and a higher crystallinity.

[0116] Compared with Example 5, the modified molecular sieve obtained in Example 1 has a lower sulfate content and a higher crystallinity by regulating the content of the soluble metal salt calculated as oxide in the Na-type molecular sieve calculated on a dry basis within the preferred protection range.

[0117] Compared with Example 6, Example 1 adjusts the dosage of the first precipitant so that the content of the metal ions in the first precipitate is within the preferred protection range, and the modified molecular sieve obtained has a lower sulfate content and a higher crystallinity.

[0118] Compared with Example 7, Example 1 adjusts the dosage of the second precipitant so that the content of the precipitated metal ions is within the preferred protection range, and the modified molecular sieve obtained has a lower sulfate content and a higher crystallinity.

[0119] Test Example 1

[0120] The modified molecular sieves (Z1-Z7 and DZ1-DZ4) prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to a hydrothermal stability test.

[0121] The test conditions include: 100g (dry basis) of modified molecular sieves (Z1-Z7 and DZ1-DZ4) are respectively tableted and crushed into 20-40 mesh particles, and aged for 10 hours under 100% water vapor and 800°C in a fixed bed hydrothermal treatment device, and then the micro-activity index (MA1) is measured on a catalytic cracking automatic micro-reaction activity assessor. The test results are listed in Table 2.

[0122] Test Example 2

[0123] The modified molecular sieves (Z1-Z7 and DZ1-DZ4) prepared in Examples 1-7 and Comparative Examples 1-4 were tested for their resistance to heavy metal vanadium pollution.

[0124] The test conditions include: impregnating 2000ppm ammonium metavanadate (in terms of V) in equal volumes of the modified molecular sieves (Z1-Z7 and DZ1-DZ4), mixing them thoroughly, leaving them in a closed state for 12 hours, drying them in a forced air drying oven at 120°C for 16 hours, pressing them into tablets, crushing them into 20-40 mesh particles, aging them in a fixed bed hydrothermal treatment device under 100% water vapor and 800°C for 2 hours, and then measuring the micro-activity index (MA2) on a catalytic cracking automatic micro-reaction activity assessor. The test results are listed in Table 2.

[0125] Table 2

[0126] MA1, wt% MA2, wt% Example 1 72 59 Example 2 65 55 Example 3 62 54 Example 4 70 58 Example 5 71 58 Example 6 68 56 Example 7 66 55 Comparative Example 1 60 51 Comparative Example 2 61 53 Comparative Example 3 58 50 Comparative Example 4 52 46

[0127] It can be seen from the data in Table 2 that, compared with Comparative Examples 1-4, the modified molecular sieves prepared in Examples 1-7 have significantly higher microreaction activity (i.e., higher MA1 values) after aging for 10 hours under 100% water vapor and 800°C. Therefore, the modified molecular sieves provided by the present invention have better hydrothermal stability and cracking activity.

[0128] Similarly, it can be seen from the data in Table 2 that, compared with Comparative Examples 1-4, the modified molecular sieves prepared in Examples 1-7 were contaminated with 2000 ppm vanadium, and after aging for 2 hours under 100% water vapor and 800° C., the micro-reaction activity was significantly higher (i.e., had a higher MA2 value). Therefore, the modified molecular sieve provided by the present invention has a better ability to resist heavy metal vanadium pollution.

[0129] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a modified molecular sieve, characterized in that: The preparation method comprises the following steps: (1) exchanging metal ions on a Na-type molecular sieve to obtain a metal ion slurry; the metal ions in the metal ion slurry are selected from at least one of rare earth ions, alkaline earth metal ions, and transition metal ions; (2) adding a first precipitant to cause a portion of the metal ions in the metal ion exchange slurry to undergo a first precipitation to obtain a first precipitation slurry; the first precipitant is selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate, ammonia water, urea and ammonium acetate; (3) The first precipitation slurry is filtered, subjected to a first ammonium sulfate exchange, subjected to a first water wash, and subjected to a first roasting in sequence to obtain a cross-exchanged and roasted molecular sieve dry powder; (4) adding a second precipitant to cause a second precipitation of some metal ions in the cross-calcined molecular sieve dry powder, and then sequentially performing a second ammonium sulfate exchange, a second water washing, and a second calcination to obtain a modified molecular sieve; the second precipitant is selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate, ammonia water, urea, and ammonium acetate.

2. The preparation method according to claim 1, wherein In step (1), the conditions for the metal ion exchange are: temperature of 25-180°C; pH of 2.8-6.5; and time of 0.3-3.5h.

3. The preparation method according to claim 2, wherein The conditions for the metal ion exchange are: temperature of 50-80°C; pH of 3.5-4.5; and time of 0.5-1.5h.

4. The preparation method according to claim 2, wherein The process of metal ion exchange includes: mixing the Na-type molecular sieve and water, and then adding a soluble metal salt to perform the metal ion exchange.

5. The preparation method according to claim 4, wherein: The weight ratio of the Na-type molecular sieve to water is 1:1.5-30.

6. The preparation method according to claim 5, wherein: The weight ratio of the Na-type molecular sieve to water is 1:2-5.

7. The preparation method according to claim 4, wherein The content of the soluble metal salt calculated as oxide in the Na-type molecular sieve calculated on a dry basis is 1-20wt%.

8. The preparation method according to claim 7, wherein: The content of the soluble metal salt calculated as oxide in the Na-type molecular sieve calculated on a dry basis is 6-16wt%.

9. The preparation method according to claim 4, wherein: The soluble metal salt is selected from chlorates and / or nitrates containing at least one of rare earth elements, alkaline earth metal elements and transition metal elements.

10. The preparation method according to claim 2, wherein: The silicon-aluminum ratio of the Na-type molecular sieve is 2-100.

11. The preparation method according to claim 10, wherein: The silicon-aluminum ratio of the Na-type molecular sieve is 2-50.

12. The preparation method according to claim 2, wherein: The Na-type molecular sieve is at least one selected from NaY molecular sieve, NaHY molecular sieve, NaUSY molecular sieve, NaREHY molecular sieve, NaREUSY molecular sieve, Naβ molecular sieve, NaHβ molecular sieve, NaREHβ molecular sieve, NaX molecular sieve, NaREX molecular sieve and NaHX molecular sieve.

13. The preparation method according to claim 12, wherein: The Na-type molecular sieve is selected from NaY molecular sieve and / or NaHY molecular sieve.

14. The preparation method according to claim 1, wherein: In step (2), the amount of the first precipitant used satisfies the molar ratio of the metal ions in the Na-type molecular sieve with a content of 1-4 wt% after the first precipitation.

15. The preparation method according to claim 14, wherein: The amount of the first precipitant used satisfies the molar ratio of 1.5-2.5wt% of metal ions in the Na-type molecular sieve after the first precipitation.

16. The preparation method according to claim 14, wherein: The first precipitant is selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate and ammonia water.

17. The preparation method according to claim 14, wherein: The conditions of the first precipitation are: temperature of 25-180° C. and time of 0.1-5 h.

18. The preparation method according to claim 17, wherein: The conditions of the first precipitation are: temperature of 50-80°C; time of 0.1-2h.

19. The preparation method according to claim 1, wherein: In step (3), the first ammonium sulfate exchange process includes: exchanging the filtered product with the first ammonium sulfate aqueous solution.

20. The preparation method according to claim 19, wherein: The weight ratio of the first aqueous ammonium sulfate solution to the Na-type molecular sieve is 5-50:100, calculated as ammonium sulfate.

21. The preparation method according to claim 20, wherein: The weight ratio of the first ammonium sulfate aqueous solution to the Na-type molecular sieve is 10-25:100, calculated as ammonium sulfate.

22. The preparation method according to claim 19, wherein The concentration of ammonium sulfate in the first aqueous ammonium sulfate solution is 20-400 g / L.

23. The preparation method according to claim 22, wherein: The concentration of ammonium sulfate in the first ammonium sulfate aqueous solution is 120-250 g / L.

24. The preparation method according to claim 19, wherein The conditions of the first ammonium sulfate exchange are: temperature of 15-150° C.; time of 0.1-5 h.

25. The preparation method according to claim 24, wherein: The conditions of the first ammonium sulfate exchange are: temperature of 50-80° C.; time of 0.5-2 h.

26. The preparation method according to claim 1, wherein In step (3), the amount of water used in the first water washing is 1-8 times the weight of the Na-type molecular sieve.

27. The preparation method according to claim 26, wherein: In step (3), the amount of water used in the first water washing is 2-5 times the weight of the Na-type molecular sieve.

28. The preparation method according to claim 26, wherein The first calcination conditions are: 100% water vapor atmosphere; temperature of 400-700° C.; time of 0.1-5 h.

29. The preparation method according to claim 28, wherein: The first calcination conditions are: temperature of 500-650° C.; time of 0.5-3 h.

30. The preparation method according to claim 1, wherein: In step (4), the amount of the second precipitant is such that the molar ratio of the metal ions in the cross-calcined molecular sieve dry powder is 0.5-3wt% after the second precipitate.

31. The preparation method according to claim 30, wherein: The amount of the second precipitant is such that the molar ratio of the metal ions in the cross-calcined molecular sieve dry powder with a content of 1-2 wt % is satisfied by the second precipitate.

32. The preparation method according to claim 30, wherein: The second precipitant is selected from at least one of ammonium oxalate, ammonium carbonate, ammonium bicarbonate and ammonia water.

33. The preparation method according to claim 30, wherein: The conditions of the second precipitation are: temperature of 15-40°C; time of 0.1-5h.

34. The preparation method according to claim 33, wherein: The conditions of the second precipitation are: temperature of 20-30°C; time of 0.1-2h.

35. The preparation method according to claim 1, wherein: In step (4), the second ammonium sulfate exchange process includes: exchanging the second precipitated product and the second ammonium sulfate aqueous solution.

36. The preparation method according to claim 35, wherein The weight ratio of the second aqueous ammonium sulfate solution to the cross-calcined molecular sieve dry powder is 5-50:100, calculated as ammonium sulfate.

37. The preparation method according to claim 36, wherein The weight ratio of the second aqueous ammonium sulfate solution to the cross-calcined molecular sieve dry powder is 10-25:100, calculated as ammonium sulfate.

38. The preparation method according to claim 35, wherein: The concentration of ammonium sulfate in the second aqueous ammonium sulfate solution is 20-400 g / L.

39. The preparation method according to claim 38, wherein The concentration of ammonium sulfate in the second aqueous ammonium sulfate solution is 120-250 g / L.

40. The preparation method according to claim 35, wherein: The conditions for the second ammonium sulfate exchange are: temperature of 20-85° C.; time of 0.1-5 h.

41. The preparation method according to claim 40, wherein The conditions for the second ammonium sulfate exchange are: temperature of 50-80° C.; time of 0.1-2 h.

42. The preparation method according to claim 35, wherein The amount of water used in the second water washing is 1-8 times the weight of the cross-calcined molecular sieve dry powder.

43. The preparation method according to claim 42, wherein The amount of water used in the second water washing is 2-5 times the weight of the cross-calcined molecular sieve dry powder.

44. The preparation method according to claim 35, wherein The conditions for the second calcination are: 20-100% water vapor atmosphere; temperature of 400-700° C.; time of 0.1-10 h.

45. The preparation method according to claim 44, wherein The second calcination conditions are: temperature of 450-650° C. and time of 0.5-5 h.

46. ​​The preparation method according to any one of claims 1 to 45, wherein: Before the second precipitation, the cross-baked molecular sieve dry powder and water are mixed; Wherein, the weight ratio of the cross-baked molecular sieve dry powder to water is 1:1.5-30.

47. The preparation method according to claim 46, wherein The weight ratio of the cross-baked molecular sieve dry powder to water is 1:2-5.

48. The modified molecular sieve obtained by the preparation method described in any one of claims 1 to 47.

49. The modified molecular sieve according to claim 48, wherein The modified molecular sieve SO4 2- Content ≤0.5wt%.

50. The modified molecular sieve according to claim 49, wherein The modified molecular sieve SO4 2- Content 0.01-0.45wt%.

51. Use of the modified molecular sieve according to any one of claims 48 to 50 in heavy oil conversion and resistance to heavy metal vanadium pollution.

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