Iron-containing FER structure molecular sieve as well as synthesis method and application thereof

Abstract

The invention relates to a preparation method of an iron-containing FER structure molecular sieve, which comprises the following steps: mixing an aluminum source, a silicon source, an alkali source, an organic template agent, a first phosphorus source and optional water to obtain a first mixture; mixing an iron source, a second phosphorus source, the first mixture and optional water to obtain a second mixture; performing crystallization treatment on the second mixture to obtain a crystallized product; wherein the second mixture is composed of M, Al2O3, SiO2, P2O5, Fe2O3, R and H2O according to the ratio of M to Al2O3 to SiO2 to P2O5 to Fe2O3 to R to H2O being (0.01-1) to (0.01-0.1) to 1 to (0.001-1) to (0.001-1) to (0.01-1) to (5-300) in terms of oxide and mole, M represents an alkali metal oxide, and R represents an organic template agent. The iron-containing FER structure molecular sieve disclosed by the invention has the advantages of high silica-alumina ratio, simple preparation process and low production cost, and shows higher catalytic activity when being used for catalytic cracking to produce more low-carbon olefins.

Description

Technical Field

[0001] The present invention relates to an iron-containing FER structure molecular sieve and a synthesis method and application thereof. Background Art

[0002] The skeleton of FER structured molecular sieve contains 0.42nm×0.54nm ten-membered ring channels and 0.35nm×0.48nm eight-membered ring channels, which are cross-linked and layered; in addition, there are six-membered ring channels parallel to the ten-membered ring channels, and the six-membered ring and eight-membered ring channels intersect to form a small cage (diameter 0.6-0.7nm). FER structured molecular sieve has good selectivity due to its unique pore structure, so it has the potential to improve the selectivity of low-carbon olefins in catalytic cracking products. The existing FER structured molecular sieve has a relatively low silicon-aluminum ratio, and the preparation method has problems such as complex process and high cost. Summary of the invention

[0003] The purpose of the present disclosure is to provide an iron-containing FER structure molecular sieve and a synthesis method and application thereof, so as to simplify the preparation process, reduce the synthesis cost and improve the silicon-aluminum ratio of the molecular sieve.

[0004] The silicon-aluminum ratio of the FER structured molecular sieve synthesized by this method is significantly higher than that of the FER structured molecular sieve synthesized by traditional template agents.

[0005] In order to achieve the above-mentioned object, the present disclosure provides, in a first aspect, a method for preparing an iron-containing FER structured molecular sieve, the method comprising:

[0006] mixing an aluminum source, a silicon source, an alkali source, an organic template, a first phosphorus source, and optionally water to obtain a first mixture;

[0007] mixing an iron source, a second phosphorus source, the first mixture, and optionally water to obtain a second mixture;

[0008] performing a crystallization treatment on the second mixture to obtain a crystallized product;

[0009] Wherein, the composition of the second mixture, calculated in terms of oxides and in moles, is M:A12O3:SiO2:P2O5:Fe2O3:R:H2O=(0.01~1):(0.01~0.1):1:(0.001~1):(0.001~1):(0.01~1):(5~300), where M represents an alkali metal oxide and R represents an organic template.

[0010] Optionally, the composition of the mixture to be crystallized, calculated in terms of oxides and in moles, is M:A12O3:SiO2:P2O5:Fe2O3:R:H2O=(0.1~0.5):(0.02~0.1):1:(0.01~0.1):(0.01~0.5):(0.02~0.5):(6~100), where M represents an alkali metal oxide and R represents an organic template.

[0011] Optionally, calculated as oxide, the molar ratio of the first phosphorus source to the second phosphorus source is 1:(1-2).

[0012] Optionally, the organic template is at least one selected from n-butylamine, pyrrolidine, pyridine and piperidine.

[0013] Optionally, the aluminum source is at least one selected from metallic aluminum, boehmite, pseudo-boehmite, sodium aluminate, aluminum sol, aluminum sulfate, gibbsite, aluminum hydroxide, aluminum oxide and aluminum alcoholate.

[0014] Optionally, the silicon source is at least one selected from silicate, silicon dioxide, silicic acid, silica gel, clay and ethyl silicate.

[0015] Optionally, the alkali source is at least one selected from lithium hydroxide, sodium hydroxide and potassium hydroxide.

[0016] Optionally, the first phosphorus source and the second phosphorus source are each independently at least one selected from phosphoric acid, hypophosphorous acid, diammonium hydrogen phosphate, ammonium hypophosphite, sodium phosphate and sodium hypophosphite.

[0017] Optionally, the iron source is at least one selected from ferric nitrate, ferric chloride, ferric sulfate and ferric nitrate nonahydrate.

[0018] Optionally, the crystallization treatment conditions include: a temperature of 120 to 190° C. and a time of 2 to 72 hours.

[0019] Optionally, the method further comprises the steps of drying and calcining the crystallized product;

[0020] The drying conditions include: a temperature of 50 to 120°C and a time of 6 to 24 hours;

[0021] The calcination conditions include: a temperature of 400 to 700° C. and a time of 1 to 10 hours.

[0022] In a second aspect of the present disclosure, there is provided an iron-containing FER structure molecular sieve prepared by the method described in the first aspect of the present disclosure.

[0023] The third aspect of the present disclosure provides the use of the iron-containing FER structured molecular sieve described in the second aspect of the present disclosure in catalytic cracking to produce more light olefins.

[0024] Through the above technical scheme, the iron-containing FER structure molecular sieve disclosed in the present invention has a relatively high silicon-aluminum ratio, a simple preparation process, a low production cost, a high preparation yield, and shows a high catalytic activity for catalytic cracking to produce more low-carbon olefins.

[0025] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0027] Figure 1 is the XRD spectrum of the iron-containing FER structured molecular sieve prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0029] In a first aspect, the present disclosure provides a method for synthesizing an iron-containing FER structure molecular sieve, the method comprising:

[0030] mixing an aluminum source, a silicon source, an alkali source, an organic template, a first phosphorus source, and optionally water to obtain a first mixture;

[0031] mixing an iron source, a second phosphorus source, the first mixture, and optionally water to obtain a second mixture;

[0032] performing a crystallization treatment on the second mixture to obtain a crystallized product;

[0033] Wherein, the composition of the second mixture, calculated in terms of oxides and in moles, is M:A12O3:SiO2:P2O5:Fe2O3:R:H2O=(0.01~1):(0.01~0.1):1:(0.001~1):(0.001~1):(0.01~1):(5~300), where M represents an alkali metal oxide and R represents an organic template.

[0034] According to the present disclosure, the aluminum source, silicon source, and alkali source can be conventionally used in the art. Specifically, the aluminum source can be at least one selected from metallic aluminum, boehmite, pseudo-boehmite, sodium aluminate, aluminum sol, aluminum sulfate, gibbsite, aluminum hydroxide, aluminum oxide, and aluminum alcoholate, preferably at least one selected from sodium aluminate, aluminum sol, and aluminum sulfate. The silicon source can be at least one selected from silicate, silicon dioxide, silicic acid, silica gel, clay, and ethyl silicate, preferably at least one selected from silica gel, fumed silica, precipitated silica, and ethyl silicate. The alkali source can be at least one selected from lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0035] The organic template may be at least one selected from n-butylamine, pyrrolidine, cyclohexylamine, ethylenediamine, pyridine and piperidine. In particular, the organic template is preferably a single template, i.e., one of the above substances, and further, the organic template is preferably n-butylamine or pyrrolidine.

[0036] The first phosphorus source and the second phosphorus source can each be a common phosphorus-containing compound. Specifically, the first phosphorus source and the second phosphorus source can each independently be at least one selected from phosphoric acid, hypophosphorous acid, diammonium hydrogen phosphate, ammonium hypophosphite, sodium phosphate and sodium hypophosphite. Preferably, the first phosphorus source and the second phosphorus source can each independently be selected from phosphoric acid and / or sodium phosphate. Further, the molar ratio of the first phosphorus source to the second phosphorus source can be 1:(1-2) in terms of oxide.

[0037] The iron source may be a common iron-containing compound. Specifically, the iron source may be at least one selected from ferric nitrate, ferric sulfate, ferric chloride and ferric nitrate nonahydrate, preferably at least one selected from ferric nitrate nonahydrate, ferric sulfate and ferric chloride.

[0038] In a preferred embodiment, the composition of the mixture to be crystallized, calculated in terms of oxides and in moles, is M:A12O3:SiO2:P2O5:Fe2O3:R:H2O=(0.1~0.5):(0.02~0.1):1:(0.01~0.1):(0.01~0.5):(0.02~0.5):(6~100), where M represents an alkali metal oxide and R represents an organic template.

[0039] The crystallization treatment conditions may include: a temperature of 120 to 190° C., preferably 160 to 180° C., and a time of 2 to 72 hours, preferably 12 to 60 hours. The crystallization treatment may be performed in a sealed state.

[0040] The method may further include the steps of drying and calcining the crystallized product; wherein the drying conditions may include: a temperature of 50 to 120° C. and a time of 6 to 24 hours; and the calcining conditions may include: a temperature of 400 to 700° C. and a time of 1 to 10 hours.

[0041] In one embodiment, the method comprises the following steps:

[0042] a. Add an aluminum source into deionized water and stir thoroughly to obtain an aluminum-containing solution;

[0043] b. adding an alkali source to the aluminum-containing solution obtained in step a;

[0044] c. adding an organic template to the mixture obtained in step b;

[0045] d. adding the first phosphorus source to the mixture obtained in step c and stirring thoroughly;

[0046] e. Add the silicon source to the mixture obtained in step d, and stir thoroughly until uniform;

[0047] f. adding the mixture containing the iron source and the second phosphorus source to the mixture obtained in step e, and stirring until uniform, to obtain a mixture to be crystallized;

[0048] g. subjecting the mixture to be crystallized obtained in step f to a crystallization treatment to obtain a crystallized product;

[0049] h. Wash and filter the crystallized product obtained in step g to obtain a filtrate and a filter cake;

[0050] i. Drying and calcining the filter cake obtained in step h to obtain an iron-containing FER structure molecular sieve.

[0051] In a second aspect of the present disclosure, there is provided an iron-containing FER structure molecular sieve prepared by the method described in the first aspect of the present disclosure. The iron-containing FER structure molecular sieve may have a SiO2 / Al2O3 molar ratio of 35 to 500 and a BET specific surface area of ​​190 to 330 m 2 / g, preferably 290 to 330 m 2 / g. Calculated as oxide and based on the dry weight of the iron-containing FER structure molecular sieve, the iron content of the iron-containing FER structure molecular sieve may be 1 to 10% by weight, preferably 4 to 5% by weight; the phosphorus content may be 0.001 to 2.5% by weight, preferably 0.08 to 2% by weight. The iron-containing FER structure molecular sieve may have an alkali metal content of 0.05 to 1.4% by weight, preferably 0.15 to 1.2% by weight, especially a sodium content.

[0052] The iron-containing FER structure molecular sieve disclosed in the present invention has a relatively high silicon-aluminum ratio, a simple preparation process, a low production cost, a high preparation yield, and shows a relatively high catalytic activity for catalytic cracking to produce more low-carbon olefins.

[0053] The third aspect of the present disclosure provides the use of the iron-containing FER structure molecular sieve described in the second aspect of the present disclosure in catalytic cracking to produce more light olefins. Using the iron-containing FER structure molecular sieve for catalytic cracking to produce more light olefins is conducive to obtaining a higher conversion rate and target product selectivity.

[0054] Specifically, the application may include: using 1-octene as a raw material to carry out a catalytic cracking reaction, and the reaction conditions include: a temperature of 500 to 600° C. and a catalyst-oil weight ratio of 0.6 to 1.2.

[0055] The present disclosure is further described below by way of examples, but the contents of the present disclosure are not limited thereby.

[0056] In the examples, the chemical composition of the molecular sieve is determined by X-ray fluorescence. For specific methods, see "Synthesis of ZSM11 molecular sieve using EU1 molecular sieve as seed and its characterization", Geng Chenchen et al., Petroleum Refining and Chemical Industry, 2011, 7. The alkali metal content (determination of sodium and potassium) in the mixture to be crystallized is determined by the national standard method GBT 15337-2008. The BET surface area of ​​the molecular sieve sample is determined by the GB / T5816-1995 standard method.

[0057] Example 1

[0058] Sodium aluminate (Beijing Inokai Technology Co., Ltd., content ≥99 weight %) was mixed with deionized water; after stirring until the sodium aluminate was dissolved, NaOH (Beijing Inokai Technology Co., Ltd., content ≥96 weight %) was added; after stirring until the NaOH was dissolved, n-butylamine (Aladdin Biochemical Technology Co., Ltd., content ≥98 weight %) was added; after stirring for half an hour, diammonium hydrogen phosphate (Aladdin Biochemical Technology Co., Ltd., content ≥99 weight %) was added; after stirring for another half an hour, silica sol (Shanghai McLean Biochemical Technology Co., Ltd., silicon dioxide content 29-31 weight %) was added, and stirred evenly to obtain a gel-like first mixture A. Deionized water was taken separately and added with ferric nitrate nonahydrate (Beijing Inokai Technology Co., Ltd., content 98.0-101.0 weight %), and then phosphoric acid (Tianjin Fuyu Fine Chemical Co., Ltd., content 85 weight %) was added to the iron-containing solution to obtain a mixed solution B, and the molar ratio of diammonium hydrogen phosphate to phosphoric acid was 1:1.35. Pour the mixed solution B into the first mixture A, and continue stirring until it is completely uniform to obtain a second mixture, whose composition is Na2O:A12O3:SiO2:P2O5:Fe2O3:R:H2O=0.135:0.025:1:0.02:0.02:0.17:15, where R represents n-butylamine. The uniformly stirred mixture is placed in a high-pressure reactor containing a polytetrafluoroethylene lining, and crystallized at 180°C for 60 hours, and then cooled to room temperature. The crystallized molecular sieve is filtered, washed, dried at 120°C for 4 hours, and calcined at 550°C for 3 hours to obtain the iron-containing FER structure molecular sieve prepared in this embodiment.

[0059] The XRD spectrum of the molecular sieve is as follows Figure 1 As shown, the spectrum peak has the characteristic peak of FER molecular sieve and no impurity peak, the silicon-aluminum molar ratio is 44, the Fe2O3 content is 4.26% by weight, the P2O5 content is 0.1% by weight, the Na2O content is 0.183% by weight, and the BET specific surface area is 326m 2 / g.

[0060] Example 2

[0061] Sodium aluminate (Beijing Inokai Technology Co., Ltd., content ≥99 weight %) was mixed with deionized water; after stirring until the sodium aluminate was dissolved, NaOH (Beijing Inokai Technology Co., Ltd., content ≥96 weight %) was added; after stirring until the NaOH was dissolved, n-butylamine (Aladdin Biochemical Technology Co., Ltd., content ≥98 weight %) was added; after stirring for half an hour, diammonium hydrogen phosphate (Aladdin Biochemical Technology Co., Ltd., content ≥99 weight %) was added; after stirring for another half an hour, silica sol (Shanghai McLean Biochemical Technology Co., Ltd., silicon dioxide content 29-31 weight %) was added, and stirred evenly to obtain a gel-like first mixture A. Deionized water was taken separately and added with ferric nitrate nonahydrate (Beijing Inokai Technology Co., Ltd., content 98.0-101.0 weight %), and then phosphoric acid (Tianjin Fuyu Fine Chemical Co., Ltd., content 85%) was added to the iron-containing solution to obtain a mixed solution B, and the molar ratio of diammonium hydrogen phosphate to phosphoric acid was 1:1.35. Pour the mixed solution B into the first mixture A, and continue stirring until it is completely uniform to obtain a second mixture, whose composition is Na2O:A12O3:SiO2:P2O5:Fe2O3:R:H2O=0.165:0.025:1:0.096:0.02:0.02:15, where R represents n-butylamine. The uniformly stirred mixture is placed in a high-pressure reactor containing a polytetrafluoroethylene lining, and crystallized at 180°C for 60 hours, and then cooled to room temperature. The crystallized molecular sieve is filtered, washed, dried at 120°C for 4 hours, and calcined at 550°C for 3 hours to obtain the iron-containing FER structure molecular sieve prepared in this embodiment.

[0062] The XRD spectrum of the molecular sieve is Figure 1 Similarly, its silicon-aluminum molar ratio is 42, the Fe2O3 content is 4.35% by weight, the P2O5 content is 2% by weight, the Na2O content is 0.64% by weight, and the BET specific surface area is 319m 2 / g.

[0063] Example 3

[0064] Sodium aluminate (Beijing Inokai Technology Co., Ltd., content ≥99 weight %) was mixed with deionized water; after stirring until the sodium aluminate was dissolved, NaOH (Beijing Inokai Technology Co., Ltd., content ≥96 weight %) was added; after stirring until the NaOH was dissolved, n-butylamine (Aladdin Biochemical Technology Co., Ltd., content ≥98 weight %) was added; after stirring for half an hour, diammonium hydrogen phosphate (Aladdin Biochemical Technology Co., Ltd., content ≥99 weight %) was added; after stirring for another half an hour, silica sol (Shanghai McLean Biochemical Technology Co., Ltd., silicon dioxide content 29-31 weight %) was added, and stirred evenly to obtain a gel-like first mixture A. Deionized water was taken separately and added with ferric nitrate nonahydrate (Beijing Inokai Technology Co., Ltd., content 98.0-101.0 weight %), and then phosphoric acid (Tianjin Fuyu Fine Chemical Co., Ltd., content 85 weight %) was added to the iron-containing solution to obtain a mixed solution B, and the molar ratio of diammonium hydrogen phosphate to phosphoric acid was 1:1.01. The mixed solution B is poured into the first mixture A, and the stirring is continued until it is completely uniform to obtain a second mixture, whose composition is Na2O: A12O3: SiO2: P2O5: Fe2O3: R: H2O = 0.08: 0.017: 1: 0.005: 0.005: 0.015: 15, where R represents n-butylamine. The stirred mixture is placed in a high-pressure reactor containing a polytetrafluoroethylene lining, and crystallized at 180°C for 60 hours, and then cooled to room temperature. The crystallized molecular sieve is filtered, washed, dried at 120°C for 4 hours, and calcined at 550°C for 3 hours to obtain the iron-containing FER structure molecular sieve prepared in this embodiment.

[0065] The XRD spectrum of the molecular sieve is Figure 1 Similarly, its silicon-aluminum molar ratio is 38, the Fe2O3 content is 2.23% by weight, the P2O5 content is 0.8% by weight, the Na2O content is 0.35% by weight, and the BET specific surface area is 229m 2 / g.

[0066] Example 4

[0067] Sodium aluminate (Beijing Inokai Technology Co., Ltd., NaAlO2 content ≥ 99 wt%) was mixed with deionized water; after stirring until the sodium aluminate was dissolved, NaOH (Beijing Inokai Technology Co., Ltd., content ≥ 96 wt%) was added; after stirring until the NaOH was dissolved, n-butylamine (Aladdin Biochemical Technology Co., Ltd., content ≥ 98 wt%) was added; after stirring for half an hour, diammonium hydrogen phosphate (Aladdin Biochemical Technology Co., Ltd., content ≥ 99 wt%) was added; after stirring for another half an hour, silica sol (Shanghai McLean Biochemical Technology Co., Ltd., silicon dioxide content 29-31 wt%) was added, and stirred evenly to obtain a gel-like first mixture A. Deionized water was taken separately and added with ferric nitrate nonahydrate (Beijing Inokai Technology Co., Ltd., content 98.0-101.0 wt%), and then phosphoric acid (Tianjin Fuyu Fine Chemical Co., Ltd., content 85 wt%) was added to the iron-containing solution to obtain a mixed solution B, and the molar ratio of diammonium hydrogen phosphate to phosphoric acid was 1:1.01. The mixed solution B is poured into the first mixture A, and the stirring is continued until it is completely uniform to obtain a second mixture, whose composition is Na2O: A12O3: SiO2: P2O5: Fe2O3: R: H2O = 0.6: 0.014: 1: 0.05: 0.05: 0.6: 15, where R represents n-butylamine. The stirred mixture is placed in a high-pressure reactor containing a polytetrafluoroethylene lining, and crystallized at 180°C for 60 hours, and then cooled to room temperature. The crystallized molecular sieve is filtered, washed, dried at 120°C for 4 hours, and calcined at 550°C for 3 hours to obtain the iron-containing FER structure molecular sieve prepared in this embodiment.

[0068] The XRD spectrum of the molecular sieve is Figure 1 Similarly, its silicon-aluminum molar ratio is 36, the Fe2O3 content is 1.97% by weight, the P2O5 content is 0.6% by weight, the Na2O content is 0.31% by weight, and the BET specific surface area is 212m 2 / g.

[0069] Comparative Example 1

[0070] 544 grams of water were combined with 69.4 grams of sodium aluminate solution (23.5 wt. % Al2O3, 19.6 wt. % Na2O) and 42.6 grams of pyrrolidine. 600 grams of silica sol (40 wt. % SiO2, Nyacol (and 2.6 grams of CP914C seed crystals (Zeolyst International) were added and the resulting gel was stirred until homogeneous. The molar composition of the gel was 25SiO2:1.0Al2O3:3.35Na2O:3.75pyrrolidine:325H2O. The gel was heated at 170°C for 36 hours.

[0071] The molecular sieve has a silicon-aluminum molar ratio of 18.2, a Na2O content of 1.25% by weight, and a BET specific surface area of ​​317 m2 / g.

[0072] Comparative Example 2

[0073] 485 grams of water were combined with 28.9 grams of sodium hydroxide (50% w / w) solution, 74.1 grams of sodium aluminate solution (23.5 wt% Al2O3, 19.6 wt% Na2O) to form an aqueous solution. 65.6 grams of tetramethylammonium chloride solution (50% w / w, Sachem) and 44.8 grams of 1,3-diaminopropane (1,3-DAP, Sigma Aldrich) were mixed into the aqueous solution. 600 grams of silica sol (40 wt% SiO2, Nyacol) and 2.7 grams of CP 914C seed crystals (Zeolyst International) were added and the resulting gel was stirred until homogeneous. The molar composition of the gel was 23.4SiO2:1.0Al2O3:2.71Na2O:1.8TMA:3.51,3-DAP:304H2O. The gel was heated at 180°C for 36 hours. The resulting crystalline product was filtered, washed with deionized water and dried at 105°C in air and calcined at 550°C for 6 hours.

[0074] The molecular sieve has a silicon-aluminum molar ratio of 17.4, a Na2O content of 0.86% by weight, and a BET specific surface area of ​​298 m 2 / g.

[0075] Comparative Example 3

[0076] 4.6g of sodium aluminate and 13.6g of sodium hydroxide were dissolved in 720g of deionized water, and the mixture was stirred continuously to completely dissolve the mixture, which was marked as solution A. 208g of tetraethyl orthosilicate was gradually added to solution A and stirred thoroughly, which was marked as solution B. 28.4g of pyrrolidine and 7.3g of n-butylamine were added to solution B, and the mixture was mixed thoroughly and uniformly for 40 minutes to obtain the desired gel. The molar composition of the gel was SiO2:Al2O3:R1:R2:Na2O:H2O was 35:1:14.2:3.6:6.1:1430; R1 was pyrrolidine and R2 was n-butylamine. The obtained gel was aged at 70℃ for 12h, and then statically crystallized at 150℃ for 4 days. After the crystallization, the gel was filtered, dried at 120℃ for 4h, and calcined at 550℃ for 4h.

[0077] The molecular sieve has a silicon-aluminum molar ratio of 28.2, a Na2O content of 0.4% by weight, and a BET specific surface area of ​​313 m 2 / g.

[0078] Comparative Example 4

[0079] At 40°C, 600 g of silica sol (SiO2 content is 25%) and 0.28 g of sodium hydroxide are added to 1440 g of distilled water, stirred evenly, and then 31.9 g of aluminum sulfate (Al2O3 content is 16%) is added. Stirring is continued for a period of time until the solution is uniform, 114.7 g of pyridine is slowly added, and then 21 g of ethylenediamine is added. The molar ratio of the molecular sieve mixture is Al2O3: 50 SiO2: 1600 H2O: 7 I organic template + 29 II organic template: 0.14 - ; The molecular sieve mixture was heated to 180°C at a stirring speed of 300 rpm and crystallized at a constant temperature for 20 hours to obtain a crystallized mixture; the crystallized mixture was filtered, washed and dried at 120°C, and transferred to a muffle furnace and calcined at 400°C.

[0080] The molecular sieve has a silicon-aluminum molar ratio of 32.3, a Na2O content of 0.67% by weight, and a BET specific surface area of ​​289 m 2 / g.

[0081] Test Case

[0082] The molecular sieves prepared in the examples and comparative examples were subjected to catalytic cracking to evaluate the production of light olefins. The operation steps are as follows: 1-octene was catalytically cracked using the above product in a microreactor, and the reaction conditions included: 550°C, catalyst-oil weight ratio of 0.83. The conversion rate and propylene selectivity were calculated according to the following formula, and the evaluation data are shown in Table 1.

[0083] Conversion rate = (1- reactant content in liquid product / reactant feed amount) × 100%

[0084] Propylene selectivity = molar amount of propylene produced / total molar amount of all products × 100%

[0085] Table 1

[0086] Example Conversion rate, % Propylene selectivity, weight % Example 1 78 39 Example 2 75 32 Example 3 74 29 Example 4 72 26 Comparative Example 1 69 23 Comparative Example 2 64 24 Comparative Example 3 63 19 Comparative Example 4 58 15

[0087] As can be seen from Table 1, the iron-containing FER structure molecular sieve disclosed in the present invention is used for catalytic cracking to produce more light olefins and shows higher catalytic activity.

[0088] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0089] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0090] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing an iron-containing FER structure molecular sieve, characterized in that: The method includes: mixing an aluminum source, a silicon source, an alkali source, an organic template, a first phosphorus source, and optionally water to obtain a first mixture; mixing an iron source, a second phosphorus source, the first mixture, and optionally water to obtain a second mixture; performing a crystallization treatment on the second mixture to obtain a crystallized product; Wherein, the composition of the second mixture, calculated in terms of oxides and in moles, is M:A12O3:SiO2:P2O5:Fe2O3:R:H2O=(0.01~1):(0.01~0.1):1:(0.001~1):(0.001~1):(0.01~1):(5~300), where M represents an alkali metal oxide and R represents an organic template.

2. The method according to claim 1, wherein: Calculated in terms of oxides and in terms of moles, the composition of the mixture to be crystallized is M:A12O3:SiO2:P2O5:Fe2O3:R:H2O=(0.1~0.5):(0.02~0.1):1:(0.01~0.1):(0.01~0.5):(0.02~0.5):(6~100), where M represents an alkali metal oxide and R represents an organic template.

3. The method according to claim 1, wherein: Calculated as oxides, the molar ratio of the first phosphorus source to the second phosphorus source is 1:(1-2).

4. The method according to claim 1, wherein: The organic template is at least one selected from n-butylamine, pyrrolidine, pyridine and piperidine.

5. The method according to claim 1, wherein: The aluminum source is at least one selected from metallic aluminum, boehmite, pseudo-boehmite, sodium aluminate, aluminum sol, aluminum sulfate, gibbsite, aluminum hydroxide, aluminum oxide and aluminum alcoholate.

6. The method according to claim 1, wherein: The silicon source is at least one selected from silicate, silicon dioxide, silicic acid, silica gel, clay and ethyl silicate.

7. The method according to claim 1, wherein: The alkali source is at least one selected from lithium hydroxide, sodium hydroxide and potassium hydroxide.

8. The method according to claim 1, wherein: The first phosphorus source and the second phosphorus source are each independently at least one selected from phosphoric acid, hypophosphorous acid, diammonium hydrogen phosphate, ammonium hypophosphite, sodium phosphate and sodium hypophosphite.

9. The method according to claim 1, wherein: The iron source is at least one selected from ferric nitrate, ferric chloride, ferric sulfate and ferric nitrate nonahydrate.

10. The method according to claim 1, wherein: The conditions of the crystallization treatment include: a temperature of 120 to 190° C. and a time of 2 to 72 hours.

11. The method according to claim 1, wherein: The method further comprises the steps of drying and calcining the crystallized product; The drying conditions include: a temperature of 50 to 120°C and a time of 6 to 24 hours; The calcination conditions include: a temperature of 400 to 700° C. and a time of 1 to 10 hours.

12. An iron-containing FER structure molecular sieve prepared by the method according to any one of claims 1 to 11.

13. Use of the iron-containing FER structure molecular sieve as claimed in claim 12 in catalytic cracking to produce more light olefins.

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