Modified ZSM-5 molecular sieve and preparation method thereof

Abstract

The invention provides a modified ZSM-5 molecular sieve and a preparation method thereof. The preparation method comprises the following steps: step 1, mixing and stirring a ZSM-5 molecular sieve, an acidic solution and a zinc-containing compound; step 2, mixing the slurry obtained in the step 1 with a phosphorus-containing compound, and stirring; and step 3, filtering, drying and roasting the slurry obtained in the step 2 to obtain the modified ZSM-5 molecular sieve. The modified ZSM-5 molecular sieve disclosed by the invention is used for catalytic cracking reaction and has relatively high propylene yield.

Description

Technical Field

[0001] The invention belongs to the field of catalytic cracking, and specifically relates to a preparation method of a modified ZSM-5 molecular sieve and a modified ZSM-5 molecular sieve obtained by the preparation method. Background Art

[0002] Affected by the domestic refined oil supply-demand ratio and the rapid development of new energy vehicles, domestic oil refining enterprises have excess production capacity, and the transformation and upgrading of refining and chemical industry has become an important challenge for oil refining enterprises. As an important chemical raw material, about one-third of propylene comes from catalytic cracking units, and increasing propylene production has also become an important goal for adjusting the product distribution of catalytic cracking units. ZSM-5 molecular sieve has a good application in the field of catalytic cracking to increase propylene production due to its unique pore structure, rich acid centers, and good thermal and hydrothermal stability. With the increase in the demand for propylene by oil refining enterprises, the reaction performance of ZSM-5, the key active component for increasing propylene production, needs to be further improved.

[0003] Phosphorus modification is an important method for ZSM-5 modification. Phosphorus modification can effectively improve the stability of ZSM-5 molecular sieves, adjust their acidity, and thus improve their propylene yield. Metal ion modification is also an important way to improve the reaction performance of ZSM-5 molecular sieves, such as Zn modification of ZSM-5. Studies have shown that ZSM-5 molecular sieves modified with phosphorus and zinc can further optimize the reaction performance of ZSM-5 molecular sieves.

[0004] CN 1298425C reports an aromatization catalyst and its preparation method and application, which uses a modified ZSM-5 molecular sieve, and the modified elements used in the modified ZSM-5 molecular sieve are zinc, phosphorus and rare earth metals. The modification method is that the ZSM-5 molecular sieve is mixed and stirred with zinc and rare earth compounds, exchanged, filtered, dried and roasted, and the roasted product is then contacted with a phosphorus-containing solution, dried and roasted to obtain the modified ZSM-5 molecular sieve. The catalyst prepared by this method has high aromatization activity, strength, stability and fluidity.

[0005] CN101440302B introduces a method for reducing the benzene content in gasoline and a catalyst thereof, wherein the active component of the catalyst contains a modified ZSM-5 molecular sieve. The modifying elements of the ZSM-5 molecular sieve are phosphorus and one or more metals selected from zinc and rare earth metals. The modification method is to prepare a solution of phosphorus, zinc and / or rare earth compounds, then add the ZSM-5 molecular sieve for impregnation, and then dry and roast to obtain the modified ZSM-5 molecular sieve. The catalyst is applied to catalytic cracking to reduce the benzene content in gasoline and effectively increase the propylene yield.

[0006] CN103816936B reports a modified aluminum phosphate molecular sieve and its preparation method. The modification method is to mix ZSM-5 molecular sieve with water, then add phosphorus-containing compounds and zinc-containing compounds, stir evenly, heat to 120-150°C, stir for 120-150min under a certain pressure, then filter, dry and roast to obtain a modified aluminum phosphate molecular sieve. The molecular sieve has a strong B acid center, good thermal and hydrothermal stability, and excellent adsorption performance and cracking performance.

[0007] CN107737607A reports a SP-5 molecular sieve catalyst for increasing propylene production and its preparation method. The preparation steps of the molecular sieve are: soaking HZSM-5 in water, slowly spraying a solution containing diammonium hydrogen phosphate into HZSM-5 to obtain a PZSM-5 molecular sieve wet product, then drying and roasting the wet product; adding zinc nitrate and ferric chloride solution to the roasted PZSM-5 molecular sieve for impregnation, then drying and roasting to obtain the SP-5 molecular sieve product. The molecular sieve has good thermal and hydrothermal stability, and has excellent adsorption and cracking properties.

[0008] In the bifunctional molecular sieves modified by P and Zn, it is generally believed that phosphorus modification of ZSM-5 molecular sieves can improve the thermal and hydrothermal stability of ZSM-5, and optimize the acid distribution of ZSM-5 molecular sieves, thereby reducing secondary reactions in catalytic cracking and promoting the improvement of propylene selectivity. Zinc, as a modifying element, has a certain dehydrogenation effect and can promote the conversion of alkanes in catalytic cracking. In the bifunctional modification process, the dispersibility of zinc in ZSM-5 and the interaction between phosphorus and ZSM-5 are important factors for improving product performance. From the above prior art, in the bifunctional modification of P and Zn, phosphorus and zinc can be added simultaneously or in steps. In the step-by-step addition process, one element is impregnated first, and then another element is impregnated after drying and roasting, and then the product is obtained by drying and roasting. The step-by-step impregnation scheme can promote the interaction between the two elements and ZSM-5 and improve its reaction performance; but the disadvantages of this scheme are long steps and processes, secondary drying and roasting, and high energy consumption. In CN101440302B and CN103816936B, zinc and phosphorus are added in one step, and only one step of calcination is required. However, during the one-step addition process, the zinc-containing solution and the phosphorus-containing solution are prone to interact with each other, affecting the reaction performance of the modified molecular sieve. Summary of the invention

[0009] The main purpose of the present invention is to provide a modified ZSM-5 molecular sieve and a preparation method thereof, so as to further improve the catalytic performance of the ZSM-5 molecular sieve.

[0010] In order to achieve the above object, the present invention provides a method for preparing a modified ZSM-5 molecular sieve, comprising the following steps:

[0011] Step 1, mixing ZSM-5 molecular sieve, acidic solution and zinc-containing compound, and stirring;

[0012] Step 2, mixing the slurry obtained in step 1 with the phosphorus-containing compound and stirring;

[0013] Step 3, filtering, drying and calcining the slurry obtained in step 2 to obtain a modified ZSM-5 molecular sieve.

[0014] The method for preparing the modified ZSM-5 molecular sieve of the present invention, wherein the ZSM-5 molecular sieve in step 1 is a HZSM-5 molecular sieve.

[0015] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the acidic solution is an organic acid solution or an inorganic acid solution, the concentration of the acidic solution is 0.1-4 mol / L; the zinc-containing compound is a water-soluble zinc-containing salt, the zinc-containing compound is calculated as zinc oxide, and the mass ratio of the zinc-containing compound to the ZSM-5 molecular sieve is 0.1%-2%.

[0016] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the zinc-containing compound is one or more of zinc nitrate, zinc chloride and zinc acetate.

[0017] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein, in step 1, the temperature for stirring the ZSM-5 molecular sieve and the zinc-containing compound is 40-100°C, and the stirring time is 0.3-3h.

[0018] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the phosphorus-containing compound is phosphoric acid or phosphate, the phosphorus-containing compound is calculated as phosphorus pentoxide, and the mass ratio of the phosphorus-containing compound to the ZSM-5 molecular sieve is 2%-8%.

[0019] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the phosphorus-containing compound is one or more of phosphoric acid, ammonium phosphate, diammonium phosphate, and ammonium hydrogen phosphate.

[0020] In the method for preparing the modified ZSM-5 molecular sieve of the present invention, the slurry obtained in step 1 is stirred with the phosphorus-containing compound at a temperature of 120-180° C. and a stirring time of 0.2-3 h.

[0021] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the drying temperature in step 3 is 100-120° C., the calcination temperature is 400-700° C., and the calcination time is 0.5-4 h.

[0022] In order to achieve the above object, the present invention also provides a modified ZSM-5 molecular sieve prepared by the above preparation method, wherein the zinc oxide content in the modified ZSM-5 molecular sieve is 0.1%-2%, and the phosphorus pentoxide content in the modified ZSM-5 molecular sieve is 2%-8% based on the total mass of the modified ZSM-5 molecular sieve.

[0023] Beneficial effects of the present invention:

[0024] (1) The modified ZSM-5 molecular sieve of the present invention is used for catalytic cracking reaction, and has a high propylene yield. The zinc modification and phosphorus modification of the present invention are carried out step by step, and by being carried out under acidic conditions, it is possible to directly carry out phosphorus modification without calcination after zinc modification, thereby reducing the modification steps and simplifying the modification process.

[0025] (2) The present invention performs zinc exchange on the ZSM-5 molecular sieve under acidic medium conditions, which can remove part of the framework aluminum and fragment aluminum of the ZSM-5 molecular sieve, further optimize the pore structure, acid distribution and the dispersion of zinc in the pores of the ZSM-5 molecular sieve. Then, the ZSM-5 molecular sieve is phosphorus modified. In this way, the modified ZSM-5 molecular sieve has a rich medium and large pore structure and good thermal and hydrothermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the XRD spectrum of the modified ZSM-5 prepared in Example 2. DETAILED DESCRIPTION

[0027] The technical scheme of the present invention is described in detail below. The following implementation modes are implemented on the premise of the technical scheme of the present invention, and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following implementation modes. The structures or experimental methods of specific conditions are not specified in the following implementation modes, and generally conventional conditions are followed.

[0028] The present invention provides a method for preparing a modified ZSM-5 molecular sieve. The modified ZSM-5 molecular sieve of the present invention is used for catalytic cracking reaction to improve the yield of propylene. The method for preparing the modified ZSM-5 molecular sieve of the present invention comprises:

[0029] Step 1, mixing ZSM-5 molecular sieve, acidic solution and zinc-containing compound, and stirring;

[0030] Step 2, mixing the slurry obtained in step 1 with the phosphorus-containing compound and stirring;

[0031] Step 3, filtering, drying and calcining the slurry obtained in step 2 to obtain a modified ZSM-5 molecular sieve.

[0032] The present invention performs zinc modification on the ZSM-5 molecular sieve under acidic medium conditions, which can remove part of the framework aluminum and fragment aluminum of the ZSM-5 molecular sieve, optimize the pore structure, acid distribution and the dispersion of zinc in the pores of the ZSM-5 molecular sieve. More importantly, zinc and phosphorus are added step by step during the modification process of the ZSM-5 molecular sieve of the present invention, which can promote the dispersion of zinc elements in the ZSM-5 molecular sieve and the interaction between phosphorus and the molecular sieve, and in the acidic medium, after zinc modification, drying, roasting and other operations can be omitted, and the ZSM-5 molecular sieve can be directly modified with phosphorus, which reduces the modification steps and simplifies the modification process.

[0033] In addition, the modified ZSM-5 molecular sieve wet product of the present invention is directly filtered, dried and roasted, avoiding the traditional impregnation method of drying the entire modified slurry and reducing the modification energy consumption.

[0034] The modified ZSM-5 molecular sieve prepared by the present invention has good thermal and hydrothermal stability. The modified ZSM-5 molecular sieve prepared by the present invention can effectively promote the shape-selective cracking reaction of gasoline components in the catalytic cracking process, increase the yield of liquefied gas and propylene, and increase the propylene content in the liquefied gas.

[0035] In one embodiment, the ZSM-5 molecular sieve of the present invention is a HZSM-5 molecular sieve. The present invention does not particularly limit the preparation method of the HZSM-5 molecular sieve. For example, NaZSM-5 molecular sieve is used as a raw material, and sodium reduction treatment is carried out with ammonium salt, that is, NaZSM-5 molecular sieve is mixed with water for pulping, and then ammonium salt is added, filtered, washed, and HZSM-5 molecular sieve is obtained. Of course, commercially available HZSM-5 molecular sieves can also be directly used.

[0036] The present invention does not specifically limit the ammonium salt. In one embodiment, the ammonium salt is one or more of ammonium sulfate, ammonium chloride, ammonium nitrate, and ammonium phosphate. The present invention does not specifically limit the method of ion exchange between the ZSM-5 molecular sieve and the ammonium salt. Conventional ion exchange methods in the art can be used.

[0037] The acidic solution of the present invention can be an inorganic acid solution or an organic acid solution, preferably a hydrochloric acid solution. The concentration of the acidic solution is 0.1-4 mol / L, preferably 0.2-2 mol / L, and the mass ratio of the acidic solution to the ZSM-5 molecular sieve is 2-10. The zinc-containing compound of the present invention refers to a water-soluble zinc-containing salt, which can be derived from one or more of zinc nitrate, zinc chloride, and zinc acetate. The zinc-containing compound is calculated as zinc oxide, and the mass ratio of the zinc-containing compound to the ZSM-5 molecular sieve is 0.1%-2%.

[0038] In one embodiment, the ZSM-5 molecular sieve of the present invention and the zinc-containing compound are stirred at a temperature of 40-100° C. and a stirring time of 0.3-3 h.

[0039] Step 2 is: mixing the slurry obtained in step 1 with the phosphorus-containing compound and stirring;

[0040] In one embodiment, the phosphorus-containing compound is a compound containing phosphate, such as phosphoric acid or phosphate, and further, phosphoric acid, ammonium phosphate, diammonium phosphate, ammonium hydrogen phosphate and other substances containing phosphate. The phosphorus-containing compound is calculated as phosphorus pentoxide, and the mass ratio of the phosphorus-containing compound to the molecular sieve is 2%-8%.

[0041] In another embodiment, the slurry obtained in step 1 of the present invention is stirred with the phosphorus-containing compound at a temperature of 120-180° C. and a stirring time of 0.2-3 h.

[0042] In step 3 of the present invention, the drying temperature in the preparation of the modified ZSM-5 molecular sieve is 100-120° C., the calcination temperature is 400-700° C., and the calcination time is 0.5-4 h.

[0043] In summary, the modified ZSM-5 molecular sieve of the present invention is a ZSM-5 molecular sieve modified with zinc and phosphorus. Based on the total mass of the modified ZSM-5 molecular sieve, the zinc oxide content is 0.1%-2%, and the phosphorus pentoxide content is 2-8%.

[0044] The modified ZSM-5 molecular sieve of the present invention includes phosphorus and zinc composite modification. The present invention first stirs and exchanges with zinc element for a certain period of time under acidic medium conditions, then introduces a phosphorus-containing solution, further reacts with the ZSM-5 molecular sieve at a certain temperature, and obtains a modified ZSM-5 molecular sieve with high propylene selectivity through one-step drying and roasting. In the present invention, zinc exchange under acidic medium can remove part of the skeleton aluminum and fragmented aluminum in the pores of the ZSM-5 molecular sieve, further optimize the pores and acid distribution, form more defect sites, and promote the dispersion of zinc element through the interaction between zinc element and defect sites. Exchange under acidic medium can also avoid the reaction between zinc and phosphorus elements to form zinc phosphate precipitation, and reduce the interaction between zinc phosphate and molecular sieve. During the modification process, zinc and phosphorus are added step by step. The zinc element is added first, which can promote the dispersion of the zinc element on the molecular sieve and strengthen the interaction between the zinc element and the molecular sieve. After the zinc exchange is completed, the high-temperature phosphorus modification is carried out, which reduces the interaction between phosphorus and zinc, and reduces the interference between the interaction between the two elements and the molecular sieve when phosphorus and zinc are added at the same time, so as to achieve the high dispersion of the zinc element and the effective effect of phosphorus, zinc and molecular sieve. At the same time, the zinc and phosphorus modification can be realized in a reaction system, which simplifies the modification process. The modified ZSM-5 molecular sieve of the present invention solves the problem of long process and high energy consumption caused by the separate impregnation and roasting of phosphorus and zinc during the composite modification of phosphorus and zinc on the one hand; on the other hand, it solves the problem that the reaction performance of the ZSM-5 molecular sieve needs to be further improved when phosphorus and zinc are added at the same time in the existing report. The modified ZSM-5 molecular sieve of the present invention is used as a catalytic cracking adjuvant, and then applied to the catalytic cracking process, which can effectively improve the yield of liquefied gas and increase the propylene concentration in the liquefied gas.

[0045] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0046] Analytical methods

[0047] The modified ZSM-5 molecular sieve was characterized by Rigaku D / Max-3C XRD diffractometer. The contents of zinc oxide and phosphorus pentoxide in the modified ZSM-5 molecular sieve were determined by X-ray fluorescence spectrometry (XRF).

[0048] The reaction performance of the modified ZSM-5 molecular sieve was evaluated using the ACE evaluation device of Kayser Company, USA. The reaction temperature was 530°C and the catalyst-oil mass ratio was 5.0. Before the evaluation, a model catalyst containing ZSM-5 molecular sieve was prepared, and the catalyst was aged at 800°C with 100% steam for 17 hours. The properties of the raw oil are shown in Table 1.

[0049] Table 1 Raw oil properties

[0050]

[0051] Source of raw materials

[0052] 1.HZSM-5 molecular sieve, SiO 2 / Al 2 O 3 =32, provided by the Catalyst Plant of PetroChina Lanzhou Petrochemical Company;

[0053] 2. Zinc chloride, zinc nitrate, zinc acetate, reagents from China National Pharmaceutical Group;

[0054] 3. Hydrochloric acid, Sinopharm reagent;

[0055] 4. Phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, China National Pharmaceutical Group reagents;

[0056] 5. Kaolin, produced by China Kaolin Corporation;

[0057] 6. Alumina sol, USY, provided by the Catalyst Plant of Lanzhou Petrochemical Company of PetroChina.

[0058] Example 1

[0059] Take 500ml of 1.0mol / L hydrochloric acid solution and add 1.83g Zn(NO 3 ) 2 6H 2 O, stir evenly, and after it is completely dissolved, add 100g ZSM-5 molecular sieve (dry basis, the same below), heat to 60℃, stir for 1h, and then add (NH 4 ) 2 HPO 4 9.30g, stirred evenly, and after it was completely dissolved, heated to 140℃, stirred for 1h, filtered, dried at 100℃ for 20h, and then calcined at 500℃ for 2.5h to obtain the modified ZSM-5 molecular sieve sample ZP-1. XRF showed that ZP-1 contained 0.5wt% ZnO and 5.1wt% P 2 O 5 .

[0060] Example 2

[0061] Take 400ml of 2mol / L hydrochloric acid solution and add 0.5g ZnCl 2 , stir evenly, and after it is completely dissolved, add 100g ZSM-5 molecular sieve, heat to 85℃, stir for 0.5h, and then add (NH 4 ) 3 PO 48.39g, stirred evenly, and after it was completely dissolved, the temperature was raised to 130℃, stirred for 1.5h, filtered, dried at 110℃ for 24h, and then calcined at 450℃ for 2h to obtain the modified ZSM-5 molecular sieve sample ZP-2. XRF showed that ZP-2 contained 0.3wt% ZnO and 3.9wt% P 2 O 5 .

[0062] Figure 1 This is the XRD spectrum of the modified ZSM-5 prepared in Example 2. Figure 1 As shown, the modified ZSM-5 molecular sieve still has a high diffraction peak intensity, indicating that the modification has no significant effect on the crystal structure of the ZSM-5 molecular sieve.

[0063] Example 3

[0064] Take 600ml of 0.6mol / L hydrochloric acid solution, add 3.66g Zn(NO 3 ) 2 6H 2 O, stir evenly, and after it is completely dissolved, add 100g ZSM-5 molecular sieve, heat to 70℃, stir for 2.5h, and then add NH 4 H 2 PO 4 11.34 g, stirred evenly, and after it was completely dissolved, the temperature was raised to 120 ° C, stirred for 0.5 h, filtered, dried at 120 ° C for 18 h, and then calcined at 550 ° C for 3.0 h to obtain a modified ZSM-5 molecular sieve sample ZP-3. XRF showed that ZP-3 contained 1.0 wt% ZnO and 7.2 wt% P 2 O 5 .

[0065] Example 4

[0066] Take 200ml of 1.5mol / L hydrochloric acid solution and add 2.5g ZnCl 2 , stir evenly, and after it is completely dissolved, add 100g ZSM-5 molecular sieve, heat to 50℃, stir for 2.0h, (NH 4 ) 2 HPO 4 5.58g, stirred evenly, and after it was completely dissolved, the temperature was raised to 150℃, stirred for 2.5h, filtered, dried at 115℃ for 30h, and then calcined at 650℃ for 2.0h to obtain the modified ZSM-5 molecular sieve sample ZP-4. XRF showed that ZP-4 contained 1.5wt% ZnO and 3.0wt% P 2 O 5 .

[0067] Example 5

[0068] Take 700ml of 1.8mol / L hydrochloric acid solution, add 2.7g (CH 3 COO 2 Zn, stir evenly, and after it is completely dissolved, add 100g ZSM-5 molecular sieve, raise the temperature to 90℃, stir for 2.8h, and then add H 3 PO 4 9.74 g, stirred evenly, and after it was completely dissolved, the temperature was raised to 170 ° C, stirred for 2.0 h, filtered, dried at 105 ° C for 36 h, and then calcined at 600 ° C for 3.5 h to obtain a modified ZSM-5 molecular sieve sample ZP-5. XRF showed that ZP-5 contained (1.2 wt% ZnO and 5.9 wt% P 2 O 5 .

[0069] Example 6

[0070] Take the ZP-2 molecular sieve prepared in Example 2, as well as kaolin, aluminum sol, and USY, and mix them in a mass ratio of ZP-2: kaolin: aluminum sol: USY = 2:43:15:40 to prepare a slurry, and then prepare model catalyst microspheres by spray drying. The catalyst microspheres are calcined at 500°C for 1 h, and then deionized water and ammonium chloride are added at 5 times and 0.2 times the mass of the catalyst microspheres, respectively. The temperature is raised to 80°C, stirred at a constant temperature for 30 minutes, filtered, and washed to obtain catalyst CAT-1.

[0071] Comparative Example 1

[0072] Unmodified HZSM-5 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of unmodified ZSM-5: kaolin: aluminum sol: USY = 2:43:15:40 to prepare a slurry, which was then prepared into model catalyst microspheres by spray drying. The catalyst microspheres were calcined at 500°C for 1h, and then deionized water and ammonium chloride were added at 5 times and 0.2 times the mass of the catalyst microspheres, respectively. The temperature was raised to 80°C, stirred at a constant temperature for 30 minutes, filtered and washed to obtain catalyst CATD-1.

[0073] Comparative Example 2

[0074] Prepare modified ZSM-5 molecular sieve according to CN103816936B. Take 400 ml of water and add 0.5 g ZnCl 2 , (NH 4 ) 3 PO 48.39g, stirred evenly, and after it was completely dissolved, 100g of ZSM-5 molecular sieve was added, then the temperature was raised to 130℃, stirred for 1.5h, filtered, dried at 110℃ for 24h, and then calcined at 450℃ for 2h to obtain a modified ZSM-5 molecular sieve sample ZPD-1. XRF showed that ZPD-1 contained 0.3wt% ZnO and 3.9wt% P 2 O 5 .

[0075] The prepared ZPD-1 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of ZPD-1: kaolin: aluminum sol: USY = 2:43:15:40 to prepare a slurry, which was then prepared by spray drying to form model catalyst microspheres. The catalyst microspheres were calcined at 500°C for 1h, and then deionized water and ammonium chloride were added at 5 times and 0.2 times the mass of the catalyst microspheres, respectively. The temperature was raised to 80°C, stirred at a constant temperature for 30 minutes, filtered and washed to obtain catalyst CATD-2.

[0076] Comparative Example 3

[0077] Prepare modified ZSM-5 molecular sieve according to CN101440302B. Take 400ml water and add 0.5g ZnCl 2 , (NH 4 ) 3 PO 4 8.39g, stirred evenly, and after it was completely dissolved, 100g of ZSM-5 molecular sieve was added, and then dried at 110℃ for 24h. After drying, the sample was calcined at 450℃ for 2h to obtain a modified ZSM-5 molecular sieve sample ZPD-2. XRF showed that ZPD-2 contained 0.3wt% ZnO and 3.9wt% P 2 O 5 .

[0078] The prepared ZPD-2 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of ZPD-2: kaolin: aluminum sol: USY = 2:43:15:40 to prepare a slurry, which was then prepared by spray drying to form model catalyst microspheres. The catalyst microspheres were calcined at 500°C for 1h, and then deionized water and ammonium chloride were added at 5 times and 0.2 times the mass of the catalyst microspheres, respectively. The temperature was raised to 80°C, stirred at a constant temperature for 30 minutes, filtered and washed to obtain catalyst CATD-3.

[0079] Comparative Example 4

[0080] Take 400ml of 2mol / L hydrochloric acid solution and add 0.5g ZnCl 2 , stir evenly, and after it is completely dissolved, add (NH 4 ) 3 PO4 8.39g, stirred evenly, and after it was completely dissolved, 100g of ZSM-5 molecular sieve was added, then the temperature was raised to 130℃, stirred for 1.5h, filtered, dried at 110℃ for 24h, and then calcined at 450℃ for 2h to obtain a modified ZSM-5 molecular sieve sample ZPD-3. XRF showed that ZPD-3 contained 0.3wt% ZnO and 3.9wt% P 2 O 5 .

[0081] The prepared ZPD-3 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of ZPD-3: kaolin: aluminum sol: USY = 2:43:15:40 to prepare a slurry, which was then prepared by spray drying to form model catalyst microspheres. The catalyst microspheres were calcined at 500°C for 1h, and then deionized water and ammonium chloride were added at 5 times and 0.2 times the mass of the catalyst microspheres, respectively. The temperature was raised to 80°C, stirred at a constant temperature for 30 minutes, filtered and washed to obtain catalyst CATD-4.

[0082] Comparative Example 5

[0083] Take 400ml of 2mol / L hydrochloric acid solution and add (NH 4 ) 3 PO 4 8.39g, stir evenly, and after it is completely dissolved, add 100g ZSM-5 molecular sieve, then heat to 130℃, stir for 1.5h, release the pressure and cool, then add 0.5g ZnCl 2 , stir evenly, and after it is completely dissolved, heat it up to 130℃ again, stir for 1.5h, filter it, dry it at 110℃ for 24h, and then calcine it at 450℃ for 2h to obtain the modified ZSM-5 molecular sieve sample ZPD-4. XRF shows that ZPD-4 contains 0.02wt% ZnO and 3.9wt% P 2 O 5 .

[0084] The ZnO content on the ZPD-4 molecular sieve is very low, indicating that a large amount of ZnO is lost when this solution is adopted.

[0085] The pore structures of the zinc and phosphorus composite modified ZSM-5 molecular sieve of the embodiment of the present invention and the modified ZSM-5 molecular sieve of the comparative example are shown in Table 2.

[0086] Table 2 Pore structure data of modified ZSM-5 molecular sieve

[0087]

[0088] As shown in Table 2, compared with the HZSM-5 molecular sieve, the pore volume and specific surface area of ​​the molecular sieve after phosphorus and zinc composite modification are reduced to a certain extent. However, since the zinc and phosphorus are modified in an acidic solution in the present invention, and the phosphorus and zinc can be better dispersed in the molecular sieve by adopting the technical scheme of the present invention, the pore volume and specific surface area of ​​the molecular sieve prepared in the embodiment of the present invention decrease less. Compared with ZPD-1, ZPD-2, ZPD-3 and ZPD-4, the molecular sieve of the embodiment has a higher pore volume and specific surface area.

[0089] The reaction evaluation data of the catalysts prepared by the zinc and phosphorus composite modified ZSM-5 molecular sieves of the examples of the present invention and the modified ZSM-5 molecular sieves of the comparative examples are shown in Table 3.

[0090] Table 3 Reaction performance of catalysts prepared by modified ZSM-5 molecular sieve

[0091]

[0092] As shown in the ACE evaluation data in Table 3, when used in catalytic cracking reactions, the catalyst containing 2 wt% of the modified ZSM-5 molecular sieve material prepared by the present invention is introduced, compared with the catalyst of the comparative example ZSM-5 molecular sieve material, the liquefied gas yield and the propylene yield are significantly improved, showing excellent propylene production performance.

[0093] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a modified ZSM-5 molecular sieve, characterized in that: The steps include: Step 1, mixing ZSM-5 molecular sieve, acidic solution and zinc-containing compound, and stirring; Step 2, mixing the slurry obtained in step 1 with the phosphorus-containing compound and stirring; Step 3, filtering, drying and calcining the slurry obtained in step 2 to obtain a modified ZSM-5 molecular sieve.

2. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: In step 1, the ZSM-5 molecular sieve is HZSM-5 molecular sieve.

3. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: The acidic solution is an organic acid solution or an inorganic acid solution, and the concentration of the acidic solution is 0.1-4 mol / L; the zinc-containing compound is a water-soluble zinc-containing salt, and the zinc-containing compound is calculated as zinc oxide, and the mass ratio of the zinc-containing compound to the ZSM-5 molecular sieve is 0.1%-2%.

4. The method for preparing the modified ZSM-5 molecular sieve according to claim 3, characterized in that: The zinc-containing compound is one or more of zinc nitrate, zinc chloride and zinc acetate.

5. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: Step 1: The temperature for stirring the ZSM-5 molecular sieve and the zinc-containing compound is 40-100° C. and the stirring time is 0.3-3 h.

6. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: The phosphorus-containing compound is phosphoric acid or phosphate, the phosphorus-containing compound is calculated as phosphorus pentoxide, and the mass ratio of the phosphorus-containing compound to the ZSM-5 molecular sieve is 2%-8%.

7. The method for preparing the modified ZSM-5 molecular sieve according to claim 6, characterized in that: The phosphorus-containing compound is one or more of phosphoric acid, ammonium phosphate, diammonium phosphate, and ammonium hydrogen phosphate.

8. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: The slurry obtained in step 1 is stirred with the phosphorus-containing compound at a temperature of 120-180° C. and a stirring time of 0.2-3 h.

9. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: In step 3, the drying temperature is 100-120°C, the roasting temperature is 400-700°C, and the roasting time is 0.5-4h.

10. The modified ZSM-5 molecular sieve prepared by the preparation method according to any one of claims 1 to 9, characterized in that: Based on the total mass of the modified ZSM-5 molecular sieve, the content of zinc oxide in the modified ZSM-5 molecular sieve is 0.1%-2%, and the content of phosphorus pentoxide is 2%-8%.

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