Modified ZSM-5 molecular sieve and preparation method thereof

Abstract

The invention provides a modified ZSM-5 molecular sieve and a preparation method thereof, and the preparation method comprises the following steps: step 1, mixing a ZSM-5 molecular sieve, an alkaline compound and water, stirring, and filtering to obtain an alkali modified ZSM-5 molecular sieve; step 2, mixing the alkali modified ZSM-5 molecular sieve, an acidic solution and a zinc-containing compound, and stirring; step 3, mixing the slurry obtained in the step 2 with a phosphorus-containing compound, and stirring; and step 4, filtering, drying and roasting the slurry obtained in the step 3 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 molecular preparation steps 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. In the step-by-step impregnation scheme, the interaction between the two elements and ZSM-5 can be promoted to 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.

[0009] The unique pore structure of ZSM-5 molecular sieve is an important feature of its high selectivity in shape-selective catalysis. However, when ZSM-5 molecular sieve is modified with zinc or phosphorus, its pore structure is often partially blocked, and its pore structure needs to be further improved to further optimize the reaction performance. Summary of the invention

[0010] 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.

[0011] 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:

[0012] Step 1, mixing ZSM-5 molecular sieve, a basic compound and water, stirring and filtering to obtain a base-modified ZSM-5 molecular sieve;

[0013] Step 2, mixing the base-modified ZSM-5 molecular sieve, the acidic solution and the zinc-containing compound, and stirring;

[0014] Step 3, mixing the slurry obtained in step 2 with the phosphorus-containing compound and stirring;

[0015] Step 4, filtering, drying and calcining the slurry obtained in step 3 to obtain a modified ZSM-5 molecular sieve.

[0016] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein step 2 further comprises the step of exchanging the alkali-modified ZSM-5 molecular sieve with an ammonium salt, and then mixing and slurrying with an acidic solution.

[0017] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the alkaline compound is an inorganic base or an organic base, the alkaline compound is calculated as an oxide, and the weight ratio of the ZSM-5 molecular sieve to the alkaline compound is 1:0.08-0.5; the temperature for stirring the ZSM-5 molecular sieve and the alkaline compound is 40-100°C, and the stirring time is 0.5-5h.

[0018] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the ammonium salt is one or more of ammonium sulfate, ammonium chloride, ammonium nitrate and ammonium phosphate.

[0019] 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%.

[0020] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein, in step 2, the temperature for stirring the alkali-modified ZSM-5 molecular sieve and the zinc-containing compound is 40-100° C., and the stirring time is 0.3-3 h.

[0021] 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%.

[0022] In the method for preparing the modified ZSM-5 molecular sieve of the present invention, the slurry obtained in step 2 is stirred with the phosphorus-containing compound at a temperature of 120-180° C. and a stirring time of 0.2-3 h.

[0023] The preparation method of the modified ZSM-5 molecular sieve of the present invention, wherein the drying temperature in step 4 is 100-120° C., the calcination temperature is 400-700° C., and the calcination time is 0.5-4 h.

[0024] 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.

[0025] Beneficial effects of the present invention:

[0026] (1) The modified ZSM-5 molecular sieve of the present invention is used for catalytic cracking reaction and has a high propylene yield. Specifically, the modified ZSM-5 molecular sieve is first treated with alkali modification to form a rich medium- and macro-pore structure, which is conducive to the full dispersion of the subsequent modified medium in the pores and reduces the effect of the subsequent modification on the pore blockage of the ZSM-5 molecular sieve.

[0027] (2) More importantly, the zinc modification and phosphorus modification of the present invention are carried out in steps and are carried out under acidic conditions, so that there is no need for roasting after zinc modification and phosphorus modification can be carried out directly, thereby reducing the modification steps and simplifying the modification process.

[0028] (3) The present invention combines alkali treatment with zinc and phosphorus exchange of ZSM-5 molecular sieve under acidic medium conditions. Zinc exchange can remove part of the framework aluminum and fragment aluminum of ZSM-5 molecular sieve, further optimize the pore structure, acid distribution and the dispersion of zinc in the pores of 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

[0029] Figure 1 This is the XRD spectrum of the modified ZSM-5 prepared in Example 2. DETAILED DESCRIPTION

[0030] 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.

[0031] 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:

[0032] Step 1, mixing ZSM-5 molecular sieve, a basic compound and water, stirring and filtering to obtain a base-modified ZSM-5 molecular sieve;

[0033] Step 2, mixing the base-modified ZSM-5 molecular sieve, the acidic solution and the zinc-containing compound, and stirring;

[0034] Step 3, mixing the slurry obtained in step 2 with the phosphorus-containing compound and stirring;

[0035] Step 4, filtering, drying and calcining the slurry obtained in step 3 to obtain a modified ZSM-5 molecular sieve.

[0036] The present invention firstly performs alkali treatment on the ZSM-5 molecular sieve to remove part of silicon species, form a rich medium- and macro-pore structure, improve the pore structure, facilitate the full dispersion of the subsequent modified medium in the pores, and reduce the influence of the subsequent modification on the pore blockage of the ZSM-5 molecular sieve.

[0037] Subsequently, the ZSM-5 molecular sieve is zinc-modified under acidic medium conditions, which can remove part of the framework aluminum and fragment aluminum of the ZSM-5 molecular sieve, further optimizing 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 in the ZSM-5 molecular sieve and the interaction between phosphorus and the molecular sieve, and in an acidic medium, after zinc modification, drying, roasting and other operations can be omitted, and the ZSM-5 molecular sieve can be directly phosphorus-modified, which reduces the modification steps and simplifies the modification process.

[0038] 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.

[0039] The modified ZSM-5 molecular sieve prepared by the present invention has rich medium and large pore structures and 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 simultaneously increase the propylene content in the liquefied gas.

[0040] In one embodiment, in step 1, the ZSM-5 molecular sieve of the present invention is a NaZSM-5 molecular sieve, and the basic compound of the present invention is a conventional basic compound in the art, which can be an organic base or an inorganic base, preferably one or more of NaOH, Na2CO3, NaHCO3, and NaAlO2. The basic compound is calculated as an oxide, and the weight ratio of the ZSM-5 molecular sieve to the basic compound is 1:0.08-0.5. When one or more of the preferred NaOH, Na2CO3, NaHCO3, and NaAlO2 are used, the basic compound is calculated as Na2O, and the weight ratio of the ZSM-5 molecular sieve to the basic compound is 1:0.08-0.5.

[0041] In another embodiment, in step 1, the ZSM-5 molecular sieve, the alkaline compound and water are mixed and stirred at a temperature of 40-100° C. and a stirring time of 0.5-5 h.

[0042] In one embodiment, the alkali-modified ZSM-5 molecular sieve is subjected to a sodium reduction treatment by exchanging with an ammonium salt, that is, the alkali-modified ZSM-5 molecular sieve is mixed with water for pulping, and then the ammonium salt is added, filtered, and washed. The ZSM-5 molecular sieve after sodium reduction is then mixed with an acidic solution for pulping, and then mixed with a zinc-containing compound and stirred.

[0043] 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 ion exchange method between the alkali-modified ZSM-5 molecular sieve and the ammonium salt. Conventional ion exchange methods in the art can be used.

[0044] 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%.

[0045] In one embodiment, the temperature for stirring the ZSM-5 molecular sieve after sodium reduction and the zinc-containing compound is 40-100° C., and the stirring time is 0.3-3 h.

[0046] Step 3 is: mixing the slurry obtained in step 2 with the phosphorus-containing compound, stirring at a temperature of 120-180° C., and reacting for 0.2-3 hours.

[0047] 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%.

[0048] In step 4 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.

[0049] In summary, the modified ZSM-5 molecular sieve of the present invention is a ZSM-5 molecular sieve that has been treated with alkali, zinc-modified and phosphorus-modified. 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%.

[0050] The modified ZSM-5 molecular sieve of the present invention includes alkali treatment and phosphorus and zinc composite modification. The present invention first performs alkali treatment on the ZSM-5 molecular sieve to remove part of the silicon species and improve the pore structure. After the alkali-treated ZSM-5 molecular sieve is exchanged and sodium-reduced, it is first stirred and exchanged with zinc element for a certain time under acidic medium conditions, and then a phosphorus-containing solution is introduced to further act with the ZSM-5 molecular sieve at a certain temperature, and a modified ZSM-5 molecular sieve with high propylene selectivity is obtained through one-step drying and roasting. In the present invention, ZSM-5 is firstly subjected to alkali treatment to form a rich mesoporous structure, and zinc exchange under acidic medium can remove part of the skeleton aluminum in the ZSM-5 molecular sieve and the fragmented aluminum in the pores, 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 of 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.

[0051] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0052] Analytical methods

[0053] 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). The pore structure was characterized by a Mack ASAP 2010 nitrogen adsorption instrument. The pores were degassed at 300°C for 12 hours before testing. The specific surface area was calculated by the BET method, and the pore volume, micropore volume and external specific surface area were calculated by the t-plot method. The pore distribution was the BJH pore distribution.

[0054] 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.

[0055] Table 1 Raw oil properties

[0056]

[0057] Source of raw materials

[0058] 1. NaZSM-5 molecular sieve, SiO2 / Al2O3=30, provided by the Catalyst Plant of PetroChina Lanzhou Petrochemical Company;

[0059] 2.NaOH, Na2CO3, NaAlO2, reagents from China National Pharmaceutical Group;

[0060] 3. Zinc chloride, zinc nitrate, zinc acetate, reagents from China National Pharmaceutical Group;

[0061] 4. Hydrochloric acid, Sinopharm reagent;

[0062] 5. Phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, China National Pharmaceutical Group reagents;

[0063] 6. Kaolin, produced by China Kaolin Corporation;

[0064] 7. Alumina sol, USY, provided by the Catalyst Plant of Lanzhou Petrochemical Company of PetroChina. Specific embodiment:

[0066] Example 1

[0067] Take 500g NaZSM-5 molecular sieve (dry basis, the same below), add 1500g water, add 250g NaCO3 under stirring, heat to 60°C, continue stirring for 1h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 5 times the weight of deionized water, then add NH4Cl according to 40% of the weight ratio of the alkali-modified sample, stir at 90°C for 0.5h, filter, wash and dry to obtain the alkali-modified HZSM-5 molecular sieve.

[0068] Take 250ml of 1.9mol / L hydrochloric acid solution, add 2.48g (CH3COO)2Zn, stir evenly, and after it is completely dissolved, add 100g alkali-modified HZSM-5 molecular sieve (dry basis, the same below), heat to 55℃, stir for 2.5h, then add 9.44g (NH4)3PO4, stir evenly, and after it is completely dissolved, heat to 155℃, stir for 1.5h, filter, dry at 105℃ for 30h, and then calcine at 460℃ for 1.8h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZP-1. XRF shows that AZP-1 contains 1.1wt% ZnO and 4.5wt% P2O5.

[0069] Example 2

[0070] Take 500g NaZSM-5 molecular sieve, add 2000g water, add 100g NaOH under stirring, heat to 80℃, continue stirring for 3h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 7 times the weight of deionized water, then add (NH4)2SO4 according to 50% of the weight ratio of the alkali-modified sample, stir at 80℃ for 1.0h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0071] Take 650ml of 0.5mol / L hydrochloric acid solution, add 2.20g Zn(NO3).6H2O, stir evenly, and after it is completely dissolved, add 100g alkali-modified HZSM-5 molecular sieve, heat to 95℃, stir for 3.0h, then add 6.51g (NH4)2HPO4, stir evenly, and after it is completely dissolved, heat to 165℃, stir for 2.8h, filter, dry at 115℃ for 20h, and then calcine at 620℃ for 3.5h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZP-2. XRF shows that AZP-2 contains 0.6wt% ZnO and 3.5wt% P2O5.

[0072] 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 ZSM-5.

[0073] Example 3

[0074] Take 500g NaZSM-5 molecular sieve, add 2500g water, add 350g NaCO3 under stirring, heat to 45℃, continue stirring for 2h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 6 times the weight of deionized water, then add NH4NO3 according to 80% of the weight ratio of the alkali-modified sample, stir at 70℃ for 1.5h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0075] Take 450ml of 1.4mol / L hydrochloric acid solution, add 1.33g ZnCl2, stir evenly, and after it is completely dissolved, add 100g alkali-modified HZSM-5 molecular sieve, heat to 65℃, stir for 1.8h, then add 10.55g H3PO4, stir evenly, and after it is completely dissolved, heat to 145℃, stir for 0.9h, filter, dry at 118℃ for 26h, and then calcine at 510℃ for 2.4h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZP-3. XRF shows that AZP-3 contains 0.8wt% ZnO and 6.5wt% P2O5.

[0076] Example 4

[0077] Take 500g NaZSM-5 molecular sieve, add 1000g water, add 50g NaOH and 25g NaAlO2 under stirring, heat to 90℃, continue stirring for 4.5h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 8 times the weight of deionized water, then add NH4NO3 according to 70% of the weight ratio of the alkali-modified sample, stir at 60℃ for 2h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0078] Take 190ml of 1.7mol / L hydrochloric acid solution, add 1.46g Zn(NO3)·6H2O, stir evenly, and after complete dissolution, add 100g alkali-modified HZSM-5 molecular sieve, heat to 75℃, stir for 0.7h, then add 13.95g (NH4)2HPO4, stir evenly, and after complete dissolution, heat to 175℃, stir for 0.6h, filter, dry at 120℃ for 32h, and then calcine at 570℃ for 1.6h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZP-4. XRF shows that AZP-4 contains 0.4wt% ZnO and 7.5wt% P2O5.

[0079] Example 5

[0080] Take 500g NaZSM-5 molecular sieve, add 3000g water, add 170g NaCO3 and 60g NaAlO2 under stirring, heat to 70℃, continue stirring for 1.5h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 10 times the weight of deionized water, then add NH4Cl according to 60% of the weight ratio of the alkali-modified sample, stir at 50℃ for 3h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0081] Take 350ml of 0.9mol / L hydrochloric acid solution, add 5.84g Zn(NO3)·6H2O, stir evenly, and after complete dissolution, add 100g alkali-modified HZSM-5 molecular sieve, heat to 85℃, stir for 1.2h, then add 8.91g NH4H2PO4, stir evenly, and after complete dissolution, heat to 135℃, stir for 2.2h, filter, dry at 109℃ for 30h, and then calcine at 690℃ for 0.8h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZP-5. XRF shows that AZP-5 contains 1.6wt% ZnO and 5.5wt% P2O5.

[0082] Example 6

[0083] Take the AZP-2 molecular sieve prepared in Example 2, as well as kaolin, aluminum sol, and USY, and mix them in a mass ratio of AZP-2: kaolin: aluminum sol: USY = 2:48:15:35 to prepare a slurry, and then prepare model catalyst microspheres by spray drying. The catalyst microspheres are calcined at 480°C for 1.5h, and then deionized water and ammonium chloride are added at 7 times and 0.28 times the mass of the catalyst microspheres, respectively. The temperature is raised to 92°C, stirred at a constant temperature for 60 minutes, filtered, and washed to obtain catalyst CAT-1.

[0084] Comparative Example 1

[0085] NaZSM-5 molecular sieve was added to the exchange container, and 7 times of deionized water was added, and then (NH4)2SO4 was added according to 50% of the weight ratio of NaZSM-5 molecular sieve, and stirred at 80°C for 1.0h, filtered, washed, and dried to obtain HZSM-5 molecular sieve. Unmodified HZSM-5 molecular sieve and kaolin, aluminum sol, and USY were mixed in a mass ratio of unmodified ZSM-5: kaolin: aluminum sol: USY = 2:48:15:35 to prepare a slurry, and then spray-dried to prepare a model catalyst microsphere. The catalyst microsphere was calcined at 480°C for 1.5h, and then deionized water and ammonium chloride were added according to 7 times and 0.28 times of the mass of the catalyst microsphere, respectively, and the temperature was raised to 92°C, stirred at a constant temperature for 60 minutes, filtered, washed, and the catalyst CATD-1 was obtained.

[0086] Comparative Example 2

[0087] Modified ZSM-5 molecular sieve was prepared according to CN103816936B. NaZSM-5 molecular sieve was added to an exchange container, 7 times the weight of deionized water was added, and then (NH4)2SO4 was added according to 50% of the weight ratio of NaZSM-5 molecular sieve, stirred at 80°C for 1.0h, filtered, washed, and dried to obtain HZSM-5 molecular sieve.

[0088] Take 650ml of deionized water, add 2.20g Zn(NO3)·6H2O, 6.51g (NH4)2HPO4, stir evenly, and after complete dissolution, add 100g unmodified HZSM-5 molecular sieve, heat to 165℃, stir for 2.8h, filter, dry at 115℃ for 20h, and then calcine at 620℃ for 3.5h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZPD-1. XRF shows that AZPD-1 contains 0.6wt% ZnO and 3.5wt% P2O5.

[0089] The prepared AZPD-1 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of AZPD-1: kaolin: aluminum sol: USY = 2:48:15:35 to prepare a slurry, which was then prepared into model catalyst microspheres by spray drying. The catalyst microspheres were calcined at 480°C for 1.5h, and then deionized water and ammonium chloride were added at 7 times and 0.28 times the mass of the catalyst microspheres, respectively. The temperature was raised to 92°C, stirred at a constant temperature for 60 minutes, filtered and washed to obtain catalyst CATD-2.

[0090] Comparative Example 3

[0091] Modified ZSM-5 molecular sieve was prepared according to CN101440302B. NaZSM-5 molecular sieve was added to an exchange container, 7 times the weight of deionized water was added, and then (NH4)2SO4 was added according to 50% of the weight ratio of NaZSM-5 molecular sieve, stirred at 80°C for 1.0h, filtered, washed, and dried to obtain HZSM-5 molecular sieve.

[0092] Take 650ml of deionized water, add 2.20g Zn(NO3)·6H2O, 6.51g (NH4)2HPO4, stir evenly, and after complete dissolution, add 100g unmodified HZSM-5 molecular sieve, dry at 115℃ for 20h, and then calcine at 620℃ for 3.5h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZPD-2. XRF shows that AZPD-2 contains 0.6wt% ZnO and 3.5wt% P2O5.

[0093] The prepared AZPD-2 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in the ratio of AZPD-2: kaolin: aluminum sol: USY = 2:48:15:35 to prepare a slurry, which was then prepared into model catalyst microspheres by spray drying. The catalyst microspheres were calcined at 480°C for 1.5h, and then deionized water and ammonium chloride were added at 7 times and 0.28 times the mass of the catalyst microspheres, respectively. The temperature was raised to 92°C, stirred at a constant temperature for 60 minutes, filtered and washed to obtain catalyst CATD-3.

[0094] Comparative Example 4

[0095] Take 500g NaZSM-5 molecular sieve, add 2000g water, add 100g NaOH under stirring, heat to 80℃, continue stirring for 3h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 7 times the weight of deionized water, then add (NH4)2SO4 according to 50% of the weight ratio of the alkali-modified sample, stir at 80℃ for 1.0h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0096] The modified ZSM-5 molecular sieve was prepared according to CN101440302B. Take 650ml of deionized water, add 2.20g Zn(NO3)·6H2O, (NH4)2HPO4 6.51g, stir evenly, and after complete dissolution, add 100g of the above alkali-modified HZSM-5 molecular sieve, dry at 115°C for 20h, and then calcine at 620°C for 3.5h to obtain a zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZPD-3. XRF shows that AZPD-3 contains 0.6wt% ZnO and 3.5wt% P2O5.

[0097] The prepared AZPD-3 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of AZPD-3: kaolin: aluminum sol: USY = 2:48:15:35 to prepare a slurry, which was then prepared by spray drying to form model catalyst microspheres. The catalyst microspheres were calcined at 480°C for 1.5h, and then deionized water and ammonium chloride were added at 7 times and 0.28 times the mass of the catalyst microspheres, respectively. The temperature was raised to 92°C, stirred at a constant temperature for 60 minutes, filtered and washed to obtain catalyst CATD-4.

[0098] Comparative Example 5

[0099] Take 500g NaZSM-5 molecular sieve, add 2000g water, add 100g NaOH under stirring, heat to 80℃, continue stirring for 3h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 7 times the weight of deionized water, then add (NH4)2SO4 according to 50% of the weight ratio of the alkali-modified sample, stir at 80℃ for 1.0h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0100] Take 650ml of 0.5mol / L hydrochloric acid solution, add 2.20g Zn(NO3).6H2O, stir evenly, and after it is completely dissolved, add 6.51g (NH4)2HPO4, stir evenly, and after it is completely dissolved, add 100g alkali-modified HZSM-5 molecular sieve, heat to 165℃, stir for 2.8h, filter, dry at 115℃ for 20h, and then calcine at 620℃ for 3.5h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZPD-4. XRF shows that AZPD-4 contains 0.6wt% ZnO and 3.5wt% P2O5. The prepared AZPD-4 molecular sieve, kaolin, aluminum sol and USY were taken and mixed in a mass ratio of AZPD-4: kaolin: aluminum sol: USY = 2:48:15:35 to prepare a slurry, which was then prepared into model catalyst microspheres by spray drying. The catalyst microspheres were calcined at 480°C for 1.5h, and then deionized water and ammonium chloride were added at 7 times and 0.28 times the mass of the catalyst microspheres, respectively. The temperature was raised to 92°C, stirred at a constant temperature for 60 minutes, filtered and washed to obtain catalyst CATD-5.

[0101] Comparative Example 6

[0102] Take 500g NaZSM-5 molecular sieve, add 2000g water, add 100g NaOH under stirring, heat to 80℃, continue stirring for 3h, filter, wash and dry the sample after the reaction. Then add the alkali-modified sample to the exchange container, add 7 times the weight of deionized water, then add (NH4)2SO4 according to 50% of the weight ratio of the alkali-modified sample, stir at 80℃ for 1.0h, filter, wash and dry to obtain alkali-modified HZSM-5 molecular sieve.

[0103] Take 650ml of 0.5mol / L hydrochloric acid solution, add 6.51g of (NH4)2HPO4, stir evenly, and after it is completely dissolved, add 100g of alkali-modified HZSM-5 molecular sieve, heat to 165℃, stir for 2.8h, release the pressure and cool, add 2.20g of Zn(NO3).6H2O, stir evenly, after it is completely dissolved, heat to 165℃, stir for 2.8h, filter, dry at 115℃ for 20h, and then calcine at 620℃ for 3.5h to obtain zinc and phosphorus composite modified ZSM-5 molecular sieve sample AZPD-5. XRF shows that AZPD-5 contains 0.04wt% ZnO and 3.5wt% P2O5.

[0104] The ZnO content on the AZPD-5 molecular sieve is very low, indicating that a large amount of ZnO is lost when this solution is adopted.

[0105] 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.

[0106] Table 2 Pore structure data of modified ZSM-5 molecular sieve

[0107]

[0108] As shown in Table 2, the modified ZSM-5 molecular sieve prepared in the embodiment of the present invention has the characteristics of large pore volume, high mesopore volume and high surface area compared with the ZSM-5 molecular sieve prepared in the comparative example.

[0109] The reaction performance evaluation of the catalyst prepared by 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 is shown in Table 3.

[0110] Table 3 Reaction performance of catalysts prepared by modified ZSM-5 molecular sieve

[0111]

[0112]

[0113] As shown in the ACE evaluation data in Table 3, when used in catalytic cracking reactions, the catalyst containing 2 wt% of modified ZSM-5 molecular sieve prepared by the present invention is introduced, and the liquefied gas yield and propylene yield are significantly improved compared with the catalyst prepared by the modified ZSM-5 molecular sieve prepared in the comparative example, showing excellent propylene production performance.

[0114] 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, a basic compound and water, stirring and filtering to obtain a base-modified ZSM-5 molecular sieve; Step 2, mixing the base-modified ZSM-5 molecular sieve, the acidic solution and the zinc-containing compound, and stirring; Step 3, mixing the slurry obtained in step 2 with the phosphorus-containing compound and stirring; Step 4, filtering, drying and calcining the slurry obtained in step 3 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: Step 2 also includes the step of exchanging the alkali-modified ZSM-5 molecular sieve with an ammonium salt, and then mixing and slurrying with an acidic solution.

3. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: The alkaline compound is an inorganic base or an organic base, the alkaline compound is calculated as an oxide, and the weight ratio of the ZSM-5 molecular sieve to the alkaline compound is 1:0.08-0.5; the ZSM-5 molecular sieve and the alkaline compound are stirred at a temperature of 40-100° C. and a stirring time of 0.5-5 h.

4. The method for preparing the modified ZSM-5 molecular sieve according to claim 2, characterized in that: The ammonium salt is one or more of ammonium sulfate, ammonium chloride, ammonium nitrate and ammonium phosphate.

5. 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%.

6. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: Step 2: The temperature for stirring the alkali-modified ZSM-5 molecular sieve and the zinc-containing compound is 40-100° C. and the stirring time is 0.3-3 h.

7. 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%.

8. The method for preparing the modified ZSM-5 molecular sieve according to claim 1, characterized in that: The slurry obtained in step 2 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 4, the drying temperature is 100-120° C., the roasting temperature is 400-700° C., and the roasting time is 0.5-4 h.

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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