Heavy metal trapping aid for catalytic cracking and its preparation method and application

Abstract

The application provides a heavy metal capturing aid for catalytic cracking and a preparation method and application thereof, and the preparation method comprises the following steps: uniformly mixing pseudo-boehmite, a binder, clay, acid and water, then adding a vanadium capturing component and mixing to obtain a vanadium capturing slurry; performing spray drying forming on the vanadium capturing slurry, then calcining to obtain solid microspheres; uniformly mixing the solid microspheres with melamine in an organic solvent and water, then adding a nickel passivation component and mixing to obtain a heavy metal capturing slurry; filtering, drying and calcining the heavy metal capturing slurry to obtain the heavy metal capturing aid for catalytic cracking. The heavy metal capturing aid can efficiently capture vanadium and passivate nickel in the catalytic cracking process, effectively slows down the damage of heavy metals to the catalyst and the influence of heavy metals on product yield, improves conversion rate and total liquid yield, and reduces coke and dry gas yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil refining and chemical industry, in particular to a heavy metal capturing additive for catalytic cracking, a preparation method and application thereof. BACKGROUND

[0002] With the heavy oil refining and the increase of heavy metal Ni and V content in raw oil, the performance of the catalytic cracking catalyst is damaged more and more. At present, the anti-heavy metal technology mainly adds rare earth metals in the main catalyst to achieve the purpose of resisting heavy metals, but too high content of rare earth metals will increase the amount of strong acid of the catalyst, which increases the coke and dry gas yield. Therefore, for the catalytic cracking raw material with high vanadium and nickel content, a heavy metal capturing additive should be added in the catalytic cracking catalyst, which can effectively reduce the coke and dry gas yield and improve the economic benefit of the catalytic cracking unit.

[0003] CN100450608C discloses a new type of solid anti-metal FCC additive and a preparation method thereof. The additive contains Na2O: 0.3-0.8%, Al2O3: 35-50%, MgO: 1-10%, RE2O3: 1-10%. The preparation method is as follows: taking kaolin as raw material, adding additives and magnesium oxide or its precursor in the kaolin slurry process, spraying into microspheres, the microspheres are mainly concentrated in 40-80μm, the microspheres are calcined at 900-1100℃, and after the calcined microspheres are extracted by an alkali solution and washed with water to reduce sodium, and then treated with a rare earth precursor, the anti-heavy metal FCC additive is prepared. The use of this additive can significantly improve the reaction activity of the FCC base agent. However, the utilization rate of the rare earth element of the additive is low, and the passivation ability of the additive to nickel in the raw oil is limited. SUMMARY

[0004] To solve the above technical problems, the present application aims to provide a heavy metal capturing additive for catalytic cracking, a preparation method and application thereof, so as to alleviate the damage of heavy metals such as vanadium and nickel to the catalyst.

[0005] To achieve the above-mentioned purpose, the present application provides a preparation method of a heavy metal capturing additive for catalytic cracking, which comprises the following steps:

[0006] S1: uniformly mixing pseudo-boehmite, a binder, clay, acid and water to obtain a first slurry, then adding a vanadium capturing component and mixing to obtain a vanadium capturing slurry; spray drying and forming the vanadium capturing slurry, and then calcining to obtain solid microspheres;

[0007] S2: uniformly mixing the solid microspheres and melamine in an organic solvent and water to obtain a second slurry, then adding a nickel passivation component and mixing to obtain a heavy metal capturing slurry; filtering, drying and calcining the heavy metal capturing slurry to obtain the heavy metal capturing additive for catalytic cracking.

[0008] The mass ratio of the solid microspheres, the melamine and the nickel passivation component in terms of oxide in the second slurry is 10-20:1:1-3.

[0009] The prepared auxiliary agent has the dual function of trapping heavy metals. Since the heavy metal vanadium has migration flowability under high temperature conditions of the reaction, and the heavy metal nickel does not have migration flowability, the vanadium trapping component is added inside the structure of the auxiliary agent, and the nickel passivation component is added to the surface of the auxiliary agent structure. The nickel passivation component on the surface preferentially passivates the heavy metal nickel, so that the heavy metal nickel loses the dehydrogenation performance, thereby giving consideration to the trapping and passivation effects of the auxiliary agent on the two kinds of metals, protecting the main catalyst from being damaged by vanadium, and also reducing the coke rate and dry gas yield caused by the heavy metal nickel.

[0010] When the nickel passivation component is added to the surface of the auxiliary agent, problems such as uneven distribution, low loss rate and low utilization rate of the nickel passivation component are prone to occur. To this end, when the nickel passivation component is loaded on the auxiliary agent, the auxiliary agent is treated with melamine in the present application. The nickel passivation component forms a complex in a flocculent precipitate with the melamine on the surface of the auxiliary agent before being deposited on the surface of the auxiliary agent. Compared with the ionic state in water, the nickel passivation component in the flocculent precipitate is more evenly dispersed on the surface of the auxiliary agent, has a low loss rate and a higher utilization rate. In the preparation of the first slurry, the solid microspheres are mixed with the melamine uniformly, and then the nickel passivation component is added. At this time, the melamine is in a sufficient amount, and when it contacts the nickel passivation component to form a precipitate, there are also enough solid microspheres to complete the deposition. This is more conducive to improving the utilization rate of the nickel passivation component and reducing the loss.

[0011] The current technology commonly used in catalytic cracking to resist heavy metal vanadium is to add rare earth metals to the main catalyst to improve the vanadium resistance of the catalyst. However, too high a content of rare earth metals will increase the strong acid amount of the catalyst, increasing the coke and dry gas yields. The vanadium trapping component, i.e. the rare earth metal, is added to the auxiliary agent in the present application, which does not affect the original activity of the main catalyst and does not cause side reactions such as an increase in coke yield. In addition, the vanadium trapping component can efficiently trap and passivate heavy metals during the catalytic cracking reaction. The content of the vanadium trapping component in the auxiliary agent can be flexibly adjusted according to the change in the content of heavy metal V in the raw oil, thereby reducing the damage of heavy metal vanadium to the main catalyst.

[0012] The auxiliary agent developed in the present application can preferentially trap and passivate heavy metals V and Ni during the catalytic cracking reaction, forming a high-temperature thermal stable compound, effectively slowing down the poisoning of V and Ni to the main catalyst, improving the conversion rate and total liquid yield, effectively reducing the coke and dry gas yields, reducing the regeneration temperature of the device, reducing the energy consumption of the device and improving the economic benefits.

[0013] According to the specific embodiments of the present application, preferably, the mass ratio of the melamine to the organic solvent and water is 1:0.4-1:10-30.

[0014] According to the embodiment of the present application, preferably, the organic solvent comprises acetic acid and / or ethylene glycol. The organic solvent of the present application can improve the dispersibility of melamine.

[0015] According to the embodiment of the present application, preferably, the vanadium capturing component comprises a water-soluble lanthanum salt; the mass percentage of the water-soluble lanthanum salt, calculated as lanthanum oxide, is 30-60% based on the total mass of the additive.

[0016] According to the embodiment of the present application, preferably, the water-soluble lanthanum salt comprises one or a combination of two or more of lanthanum carbonate, lanthanum chloride and lanthanum nitrate.

[0017] According to the embodiment of the present application, preferably, the mass percentage of the nickel passivating component, calculated as oxide, is 10-20% based on the total mass of the additive.

[0018] According to the embodiment of the present application, preferably, the nickel passivating component comprises one or a combination of two or more of boric acid, phosphoric acid, a water-soluble bismuth salt, a water-soluble manganese salt and a water-soluble zirconium salt.

[0019] According to the embodiment of the present application, preferably, the mass percentage of the pseudo-boehmite, calculated as aluminum oxide, is 20-40%, the mass percentage of the binder is 10-30%, and the mass percentage of the clay is 5-20% based on the total mass of the additive.

[0020] According to the embodiment of the present application, preferably, the mass ratio of the acid to the dry-basis pseudo-boehmite in the first slurry, calculated as 37% hydrochloric acid, is 0.1-0.3:1.

[0021] According to the embodiment of the present application, preferably, the solid-liquid ratio of the first slurry is 1:10-15.

[0022] According to the embodiment of the present application, preferably, the binder comprises silica sol and / or alumina sol, and more preferably alumina sol.

[0023] According to the embodiment of the present application, preferably, the clay comprises one or a combination of two or more of kaolin, halloysite, montmorillonite and palygorskite, and more preferably kaolin.

[0024] According to the embodiment of the present application, preferably, the calcination condition in S1 is calcination at a temperature of 430-550℃ for 0.5-1h.

[0025] According to the embodiment of the present application, preferably, the calcination condition in S2 is calcination at a temperature of 480-580℃ for 1-4h.

[0026] According to the specific embodiment of the present application, preferably, the drying condition in S2 is drying at a temperature of 100-110℃ for 12-24h.

[0027] According to the specific embodiment of the present application, preferably, the preparation method of the heavy metal trapping aid for catalytic cracking comprises the following steps:

[0028] (1) mixing and stirring deionized water, pseudo-boehmite, a binder, clay and acid at room temperature for 10-30min to obtain a slurry a, and the solid-liquid ratio of the slurry a is 1:10-15;

[0029] (2) adding a vanadium trapping component into the slurry a and stirring for 1-1.5h to obtain a slurry b;

[0030] (3) spray drying the slurry b to form a solid microsphere c, and then calcining the solid microsphere c at 430-550℃ for 0.5-1h;

[0031] (4) mixing deionized water, an organic solvent, melamine and the above-mentioned solid microsphere c, and stirring uniformly to obtain a slurry d;

[0032] (5) adding a nickel passivation component into the solution d at room temperature, and stirring for 30-60min to obtain a slurry e;

[0033] (6) filtering, drying and calcining the slurry e to obtain the heavy metal trapping aid for catalytic cracking.

[0034] The present application also provides a heavy metal trapping aid for catalytic cracking, which is obtained by the above-mentioned preparation method of the heavy metal trapping aid for catalytic cracking.

[0035] The present application also provides an application of the above-mentioned heavy metal trapping aid for catalytic cracking in catalytic cracking of heavy catalytic raw materials, wherein the catalyst comprises a main catalyst and the heavy metal trapping aid for catalytic cracking, and the amount of the heavy metal trapping aid for catalytic cracking is 5-15wt% based on the total mass of the catalyst, and the amount of the main catalyst is 85-95wt%.

[0036] The technical solution provided by the present application has the following beneficial effects:

[0037] The heavy metal trapping agent of the present application can realize efficient vanadium trapping and nickel passivation in the catalytic cracking process, effectively slow down the damage of heavy metals to the catalyst and the influence of heavy metals on the product yield, improve the conversion rate and total liquid yield, reduce the coke and dry gas yield, reduce the regeneration temperature of the device, reduce the energy consumption of the device, and improve the economic benefit. Specific embodiment

[0038] In order to have a clearer understanding of the technical features, objectives and benefits of the present application, the technical solutions of the present application are described in detail as follows, but cannot be understood as limiting the implementable scope of the present application.

[0039] Raw materials or equipment sources of the embodiment of the present application:

[0040] Kaolin, China Kaolin Co., Ltd., kaolinite content 86 / wt%, loss on ignition 27.59 / wt%, particle size D(V, 0.5), um = 2.131;

[0041] Pseudo-boehmite, loss on ignition 35.03 / wt%;

[0042] Aluminum sol, alumina content 20.15 / wt%;

[0043] Lanthanum carbonate, lanthanum nitrate hexahydrate, lanthanum chloride heptahydrate, melamine, acetic acid, ethylene glycol, phosphoric acid, boric acid, bismuth chloride dihydrate, manganese chloride tetrahydrate and zirconium chloride are all analytically pure, from National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0044] Example 1

[0045] The present embodiment provides a heavy metal trapping aid for catalytic cracking, and the preparation method is as follows:

[0046] (1) 247 g of deionized water, 31 g of pseudo-boehmite, 99 g of aluminum sol and 14 g of kaolin are uniformly mixed, and then 3.4 mL of hydrochloric acid is slowly added and stirred for 30 min to obtain slurry a;

[0047] (2) 144.6 g of lanthanum carbonate is added to slurry a and stirred for 1 h to obtain slurry b;

[0048] (3) After slurry b is spray-dried and shaped, it is calcined at 480℃ for 40 min to obtain solid microspheres c;

[0049] (4) 100 g of solid microspheres c, 4.69 g of ethylene glycol and 6.67 g of melamine are added to 134 g of water, and stirred uniformly to obtain slurry d;

[0050] (5) 114.5 g of boric acid is added to slurry d and stirred for 40 min to obtain slurry e;

[0051] (6) Slurry e is filtered, the obtained solid is dried at 110℃ for 24 h, and then calcined at 550℃ for 2 h to obtain the heavy metal trapping aid for catalytic cracking ZJ1.

[0052] Example 2

[0053] The present embodiment provides a heavy metal trapping aid for catalytic cracking, and the preparation method is as follows:

[0054] (1) 185 g of deionized water, 38 g of pseudoboehmite, 50 g of aluminum sol and 7 g of kaolin were mixed uniformly, and then 7.5 mL of hydrochloric acid was slowly added, stirred for 30 min to obtain slurry a;

[0055] (2) 159.4 g of lanthanum nitrate hexahydrate was added to slurry a, stirred for 1 h to obtain slurry b;

[0056] (3) After slurry b was spray-dried and formed, it was calcined at 430℃ for 1 h to obtain solid microspheres c;

[0057] (4) 100 g of solid microspheres c, 4 g of acetic acid and 10 g of melamine were added to 100 g of water, stirred uniformly to obtain slurry d;

[0058] (5) 31.6 g of phosphoric acid was added to slurry d, stirred for 30 min to obtain slurry e;

[0059] (6) Slurry e was filtered, and the obtained solid was dried at 100℃ for 15 h, and then calcined at 480℃ for 4 h to obtain a heavy metal trapping aid for catalytic cracking ZJ2.

[0060] Example 3

[0061] The present example provides a heavy metal trapping aid for catalytic cracking, and the preparation method is as follows:

[0062] (1) 195 g of deionized water, 31 g of pseudoboehmite, 149 g of aluminum sol and 14 g of kaolin were mixed uniformly, and then 5.0 mL of hydrochloric acid was slowly added, stirred for 30 min to obtain slurry a;

[0063] (2) 68.4 g of lanthanum nitrate hexahydrate was added to slurry a, stirred for 1.5 h to obtain slurry b;

[0064] (3) After slurry b was spray-dried and formed, it was calcined at 550℃ for 30 min to obtain solid microspheres c;

[0065] (4) 100 g of solid microspheres c, 5 g of ethylene glycol and 5.0 g of melamine were added to 150 g of water, stirred uniformly to obtain slurry d;

[0066] (5) 34.81 g of bismuth nitrate pentahydrate was added to slurry d, stirred for 30 min to obtain slurry e;

[0067] (6) Slurry e was filtered, and the obtained solid was dried at 105℃ for 12 h, and then calcined at 550℃ for 1 h to obtain a heavy metal trapping aid for catalytic cracking ZJ3.

[0068] Example 4

[0069] The present example provides a heavy metal trapping aid for catalytic cracking, and the preparation method is as follows:

[0070] (1) 225 g of deionized water, 62 g of pseudoboehmite, 74 g of aluminum sol and 7 g of kaolin were mixed uniformly, 6.7 mL of hydrochloric acid was slowly added and stirred for 30 min to obtain slurry a;

[0071] (2) 126.4 g of lanthanum carbonate was added to slurry a and stirred for 1 h to obtain slurry b;

[0072] (3) After slurry b was spray dried and formed, it was calcined at 500 ℃ for 40 min to obtain solid microspheres c;

[0073] (4) 100 g of solid microspheres c, 4.67 g of acetic acid and 6.67 g of melamine were added to 127.4 g of water and stirred uniformly to obtain slurry d;

[0074] (5) 46.8 g of manganese chloride tetrahydrate was added to slurry d and stirred for 30 min to obtain slurry e;

[0075] (6) Slurry e was filtered, the obtained solid was dried at 105 ℃ for 20 h, and then calcined at 550 ℃ for 2 h to obtain a heavy metal trapping aid for catalytic cracking ZJ4.

[0076] Example 5

[0077] The present example provides a heavy metal trapping aid for catalytic cracking, and the preparation method is as follows:

[0078] (1) 281 g of deionized water, 31 g of pseudoboehmite, 50 g of aluminum sol and 28 g of kaolin were mixed uniformly, 3 mL of hydrochloric acid was slowly added and stirred for 30 min to obtain slurry a;

[0079] (2) 108 g of lanthanum carbonate was added to slurry a and stirred for 1 h to obtain slurry b;

[0080] (3) After slurry b was spray dried and formed, it was calcined at 500 ℃ for 40 min to obtain solid microspheres c;

[0081] (4) 100 g of solid microspheres c, 4.44 g of ethylene glycol and 6.56 g of melamine were added to 140 g of water and stirred uniformly to obtain slurry d;

[0082] (5) 46.2 g of zirconium chloride was added to slurry d and stirred for 30 min to obtain slurry e;

[0083] (6) Slurry e was filtered, the obtained solid was dried at 110 ℃ for 18 h, and then calcined at 550 ℃ for 2 h to obtain a heavy metal trapping aid for catalytic cracking ZJ5.

[0084] Comparative Example 1

[0085] The comparative example provides a preparation method of a heavy metal trapping aid for catalytic cracking, which is the same as that of Example 1, and the only difference is that no melamine is added.

[0086] The preparation method of the comparative example is as follows:

[0087] (1) 247 g of deionized water, 31 g of pseudoboehmite, 99 g of aluminum sol and 14 g of kaolin were uniformly mixed, and then 3.4 mL of hydrochloric acid was slowly added and stirred for 30 min to obtain slurry a;

[0088] (2) 144.6 g of lanthanum carbonate was added to slurry a and stirred for 1 h to obtain slurry b;

[0089] (3) After slurry b was spray-dried and shaped, it was calcined at 480°C for 40 min to obtain solid microspheres c;

[0090] (4) 100 g of solid microspheres c and 4.69 g of ethylene glycol were added to 134 g of water and stirred uniformly to obtain slurry d;

[0091] (5) 114.5 g of boric acid was added to slurry d and stirred for 40 min to obtain slurry e;

[0092] (6) Slurry e was filtered, the obtained solid was dried at 110°C for 24 h, and then calcined at 550°C for 2 h to obtain a heavy metal trapping aid for catalytic cracking DB1.

[0093] Comparative Example 2

[0094] The comparative example provides a preparation method of a heavy metal trapping aid for catalytic cracking, which is the same as that of Example 1, and the only difference is that the vanadium trapping component and the nickel passivating component are added at the same time.

[0095] The preparation method of the comparative example is as follows:

[0096] (1) 185 g of deionized water, 38 g of pseudoboehmite, 50 g of aluminum sol and 7 g of kaolin were uniformly mixed, and then 7.5 mL of hydrochloric acid was slowly added and stirred for 30 min to obtain slurry a;

[0097] (2) 159.4 g of lanthanum nitrate hexahydrate, 4 g of acetic acid, 10 g of melamine and 31.6 g of phosphoric acid were added to slurry a and stirred for 1 h to obtain a heavy metal trapping aid for catalytic cracking DB2.

[0098] Comparative Example 3

[0099] The example provides a preparation method of a heavy metal trapping aid for catalytic cracking, which is the same as that of Example 1, and the only difference is that the order of adding the vanadium trapping component and the nickel passivating component is reversed.

[0100] The preparation method of the comparative example is as follows:

[0101] (1) 195 g of deionized water, 31 g of pseudoboehmite, 149 g of aluminum sol and 14 g of kaolin were mixed uniformly, 5.0 mL of hydrochloric acid was slowly added, stirred for 30 min, to obtain slurry a;

[0102] (2) 5 g of ethylene glycol, 5.0 g of melamine and 34.81 g of bismuth nitrate pentahydrate were added to 150 g of water in slurry a, stirred for 1.5 h, to obtain slurry b;

[0103] (3) After slurry b was spray dried and formed, it was calcined at 550°C for 30 min to obtain solid microspheres c;

[0104] (4) 100 g of solid microspheres c and 68.4 g of lanthanum nitrate hexahydrate were added to 500 g of water, stirred for 30 min, to obtain slurry d;

[0105] (5) The slurry d was filtered, the obtained solid was dried at 105°C for 12 h, and then calcined at 550°C for 1 h, to obtain a heavy metal trapping aid DB3 for catalytic cracking.

[0106] Experimental Example

[0107] This experimental example is used to evaluate the performance of the heavy metal trapping aids of the above examples and comparative examples.

[0108] Evaluation and analysis method:

[0109] Lanzhou Petrochemical catalytic cracking industrial agent LDC-200 was selected as the main catalyst (blank agent), the aid and the main catalyst were mixed in a ratio of heavy metal trapping aid: main catalyst = 1:5.7-19, and the two were co-contaminated with vanadium content of 6000 ppm and nickel content of 3000 ppm.

[0110] The above aid and main catalyst were pretreated at 800°C, 100% steam for 4 hours. The catalytic cracking evaluation conditions of the advanced catalytic cracking evaluation device (ACE) were that the pretreated catalyst and heavy metal trapping aid were placed in the ACE experimental reactor, the reaction temperature was 530°C, the total amount of the main catalyst and the aid was 9 g, and the reaction raw material was the 3 million tons / year heavy catalyst raw material of Lanzhou Petrochemical Company, the agent to oil ratio (the mass ratio of the aid + main catalyst to the raw material oil) was 5.0.

[0111] Then the catalytic cracking performance evaluation was carried out on the above advanced catalytic cracking evaluation device (ACE) evaluation device, and the evaluation results are listed in Table 1.

[0112] In the evaluation of the present application:

[0113] Conversion rate = gasoline yield + liquefied gas yield + dry gas yield + coke yield;

[0114] Light oil yield = gasoline yield + diesel yield;

[0115] Total liquid yield = gasoline yield + diesel yield + liquefied gas yield;

[0116] Coke selectivity = ((100 - conversion rate) x coke yield) / conversion rate.

[0117] Table 1 Evaluation results of heavy metal trapping aids

[0118]

[0119] Note: 100B means using only the main catalyst without adding the heavy metal trapping aid; 90B + 10ZJ1 means that the catalyst of the reaction system is composed of 90wt% main catalyst and 10wt% heavy metal trapping aid ZJ1; the same applies to others.

[0120] As can be seen from the data in Table 1, the heavy metal trapping aid developed by compounding can effectively slow down the influence of heavy metals Ni and V on the performance of the system catalyst, significantly reduce the dehydrogenation performance of heavy metal Ni in the conversion process, and reduce the yield of coke and dry gas while improving the conversion rate and total liquid yield.

[0121] Comparing Example 1 and Comparative Example 1, it can be found that when the nickel passivation component is introduced, the addition of melamine can significantly improve the utilization rate of the nickel passivation component and reduce the coke selectivity.

[0122] Comparing Example 2 and Comparative Example 2, it is shown that the aid preparation process uses the sequential staged introduction of the vanadium trapping functional component and the nickel passivation component, which makes the introduced functional component more effective in improving the heavy metal resistance of the catalyst and reducing coke formation.

[0123] Comparing Example 3 and Comparative Example 3, it can be known that the method of first preparing vanadium trapping microspheres and then using melamine to complex the nickel passivation component to deposit the nickel passivation component on the surface of the aid microspheres can significantly improve the utilization rate of the nickel passivation component while reducing the coke selectivity.

Claims

1. A method for preparing a heavy metal capture aid for catalytic cracking, comprising the following steps: S1: Boehmite, binder, clay, acid, and water are mixed evenly to obtain a first slurry. Then, vanadium-capturing components are added and mixed to obtain a vanadium-capturing slurry. The vanadium-capturing slurry is spray-dried and shaped, then calcined to obtain solid microspheres. The vanadium-capturing component includes water-soluble lanthanum salt or lanthanum carbonate; based on the total mass of the additives, the mass percentage of water-soluble lanthanum salt or lanthanum carbonate, calculated as lanthanum oxide, is 30-60%. S2: Mix the solid microspheres with melamine in an organic solvent and water to obtain a second slurry. Then add the passivated nickel component and mix to obtain a heavy metal capturing slurry. The heavy metal capturing slurry is filtered, dried, and calcined to obtain the heavy metal capturing aid for catalytic cracking. In the second slurry, the mass ratio of solid microspheres, melamine, and passivated nickel component (calculated as oxide) is 10-20:1:1-3; based on the total mass of the additives, the mass percentage of passivated nickel component (calculated as oxide) is 10-20%, and the passivated nickel component includes one or more of boric acid, phosphoric acid, water-soluble bismuth salt, water-soluble manganese salt, and aqueous zirconium salt.

2. The method for preparing the heavy metal capture aid for catalytic cracking according to claim 1, wherein, The mass ratio of melamine to organic solvent and water is 1:0.4-1:10-30.

3. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The organic solvents include acetic acid and / or ethylene glycol.

4. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The water-soluble lanthanum salts include lanthanum chloride and / or lanthanum nitrate.

5. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, Based on the total mass of the additives, the mass percentage of boehmite (calculated as alumina) is 20-40%, the mass percentage of the binder is 10-30%, and the mass percentage of the clay is 5-20%.

6. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, In the first slurry, the mass ratio of acid (measured as 37% concentrated hydrochloric acid) to dry-basis boehmite is 0.1-0.3:

1.

7. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The solid-liquid ratio of the first slurry is 1:10-15.

8. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The binder includes silica sol and / or aluminum sol.

9. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The clay includes one or more of the following: kaolin, halloysite, montmorillonite, and attapulgite.

10. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The calcination conditions in S1 are: calcination at 430-550℃ for 0.5-1h.

11. The method for preparing the heavy metal capturing aid for catalytic cracking according to claim 1, wherein, The calcination conditions in S2 are: calcination at 480-580℃ for 1-4 hours.

12. A heavy metal capture aid for catalytic cracking, which is obtained by the preparation method of the heavy metal capture aid for catalytic cracking according to any one of claims 1-11.

13. The application of the heavy metal capture aid for catalytic cracking according to claim 12 in the feedstock of catalytic cracking heavy catalytic cracking, wherein, The catalyst includes a main catalyst and a heavy metal capture aid for catalytic cracking. Based on the total mass of the catalyst, the amount of heavy metal capture aid for catalytic cracking is 5-15 wt%, and the amount of the main catalyst is 85-95 wt%.

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