Method for improving ball-forming strength of drop balls

Abstract

The present invention relates to the technical field of the drop ball method and discloses a method for improving the strength of drop ball formation. The method comprises: 1) preparing a precursor slurry using the drop ball method to obtain small balls; 2) contacting the small balls with a mixture containing aluminum sol; and 3) calcining the small balls after contact with the mixture containing aluminum sol in step 2). The method can improve the strength of the formed balls, is simple to prepare, and can produce small balls with controllable strength.

Description

Technical Field

[0001] The present invention relates to the technical field of ball dropping method, and in particular to a method for improving the ball-forming strength of a ball dropped. Background Art

[0002] A large number of catalysts, adsorbents, etc. are spherical particles. In order to obtain spherical particles with good uniformity and excellent roundness, the drop ball method is often used for ball formation. During the drop ball method, an inorganic slurry precursor is dripped into a forming auxiliary liquid to obtain regular spherical particles. Generally speaking, hot oil column molding or oil-ammonia column molding is the most common. For example, CN107837797A discloses a hot oil column molding method, which requires dripping aluminum hydroxide sol and a gelling agent into a hot oil column to obtain multiplying small balls. For another example, CN109692703A discloses a hot oil column method for preparing molecular sieve small balls. This method mixes aluminum hydroxide sol, molecular sieve, acid solution mixed sol and hexamethylenetetramine, and drips it into the hot oil column to form. This method is a common industrial practice and can produce small balls with a strength of about 60N / particle. However, due to the large amount of amine / ammonia and oil used in this method, the working environment is harsh and a large amount of wastewater is generated, which has gradually failed to meet the increasingly prominent environmental protection requirements. The recently emerged sodium alginate-based drop-shaped ball production technology offers a more environmentally friendly and cleaner production route. For example, CN104477953A discloses a method for producing balls by dropping a mixed slurry of aluminum gel and sodium alginate into a metal salt solution. However, this method suffers from difficulties controlling the strength of the resulting balls, resulting in low strength. This limits the practical industrial application of this drop-shaped ball production method.

[0003] Therefore, it is necessary to propose a method for improving the strength of small balls prepared by the drop ball method, especially a strength improvement strategy suitable for the sodium alginate system, so as to improve the strength of the prepared small balls and meet the requirements of clean production. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art such as difficulty in strength control and low strength, and to provide a method for improving the strength of drop balls. The method of the present invention can improve the ball strength, the preparation method is simple, and small balls with controllable strength can be obtained.

[0005] In order to achieve the above object, the present invention provides a method for improving the ball-forming strength of a drop ball, wherein the method comprises the following steps:

[0006] 1) preparing small balls from the precursor slurry by a ball drop method;

[0007] 2) contacting the pellets with a mixture containing aluminum sol;

[0008] 3) calcining the pellets after contacting with the mixture containing aluminum sol in step 2).

[0009] Preferably, the mixture containing aluminum sol is a mixture of aluminum sol and water or a mixture of aluminum sol, pseudo-boehmite and water.

[0010] Preferably, the content of aluminum sol in the mixture of aluminum sol and water calculated as Al2O3 is 1-30% by weight, preferably 5-20% by weight.

[0011] Preferably, the total content of aluminum sol and pseudo-boehmite calculated as Al2O3 in the mixture of aluminum sol, pseudo-boehmite and water is 1-65% by weight, preferably 5-50% by weight;

[0012] Preferably, in the mixture of the aluminum sol, pseudo-boehmite and water, the weight ratio of the aluminum sol calculated as Al2O3 to the pseudo-boehmite calculated as Al2O3 is 1:0.01-5.

[0013] Preferably, the contacting is carried out under stirring and ultrasound.

[0014] Preferably, the contact temperature is 5-45° C., and the contact time is 10 min-4 h.

[0015] Preferably, the precursor slurry contains one or more of aluminum sol, pseudo-boehmite, kaolin, molecular sieve, metal oxide, metal hydroxide and metal inorganic salt.

[0016] Preferably, step 1) is hot oil column molding, and the small balls are prepared by dripping the precursor slurry and the first molding aid into the second molding aid; more preferably, the small balls are prepared by dripping the precursor slurry containing the first molding aid into the second molding aid.

[0017] Preferably, the first molding aid is one or more of urea and organic amine, and the second molding aid is one or more of kerosene, lubricating oil and paraffin oil.

[0018] Preferably, step 1) is oil-ammonia column molding, and the pellets are prepared by dripping the precursor slurry into a third molding aid.

[0019] Preferably, the third molding aid is one or more of ammonia water and organic amine.

[0020] Preferably, step 1) is polymer cross-linking molding, and the pellets are prepared by dripping the precursor slurry and the fourth molding aid into the fifth molding aid.

[0021] Preferably, the pellets are prepared by dropping a precursor slurry containing the fourth molding aid into the fifth molding aid.

[0022] Preferably, the fourth molding aid is one or more of sodium alginate polymers and chitosan polymers, and the fifth molding aid is one or more of divalent metal salts and trivalent metal salts, preferably one or more of calcium salts, aluminum salts and barium salts.

[0023] Preferably, the calcination temperature is 50-1200°C.

[0024] The method of the present invention can improve the strength of the pellets, has a simple preparation method, and can obtain pellets with controllable strength. DETAILED DESCRIPTION

[0025] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0026] The present invention provides a method for improving the ball-forming strength of a drop ball, wherein the method comprises the following steps:

[0027] 1) preparing small balls from the precursor slurry by a ball drop method;

[0028] 2) contacting the pellets with a mixture containing aluminum sol;

[0029] 3) calcining the pellets after contacting with the mixture containing aluminum sol in step 2).

[0030] According to the present invention, the ball dropping method can be various methods and conditions commonly used in the art, and the present invention is not limited thereto.

[0031] For example, step 1) can be hot oil column molding, and the pellets are prepared by dripping the precursor slurry and the first molding aid into the second molding aid; preferably, the pellets are prepared by dripping the precursor slurry containing the first molding aid into the second molding aid.

[0032] Preferably, the first molding aid is one or more of urea and organic amine, and the second molding aid is one or more of kerosene, lubricating oil and paraffin oil.

[0033] In addition, step 1) can also be oil-ammonia column molding, and the pellets are prepared by dripping the precursor slurry into a third molding aid. Preferably, the third molding aid is one or more of ammonia water and organic amine.

[0034] In addition, step 1) can also be polymer cross-linking molding, and the small balls are prepared by dripping the precursor slurry and the fourth molding aid into the fifth molding aid; preferably, the small balls are prepared by dripping the precursor slurry containing the fourth molding aid into the fifth molding aid.

[0035] Preferably, the fourth molding aid is one or more of sodium alginate polymers and chitosan polymers, and the fifth molding aid is one or more of divalent metal salts and trivalent metal salts.

[0036] The fifth molding aid is more preferably one or more of calcium salts, aluminum salts and barium salts.

[0037] The present invention is preferably polymer cross-linked molding.

[0038] In a preferred embodiment of the present invention, the fourth molding aid is sodium alginate, and the fifth molding aid is calcium chloride.

[0039] In another preferred embodiment of the present invention, the fourth molding aid is sodium alginate, and the fifth molding aid is BaAc2.

[0040] According to the present invention, the specific conditions of the hot oil column molding, oil-ammonia column molding and polymer cross-linking molding are not particularly limited and can be carried out using the common conditions in the art, which will not be described in detail here.

[0041] According to the present invention, preferably, the precursor slurry can be various slurries commonly used in the ball dropping method in the art. For example, the precursor slurry can contain one or more of aluminum sol, pseudo-boehmite, kaolin, molecular sieves, metal oxides, metal hydroxides and metal inorganic salts.

[0042] In a preferred embodiment of the present invention, the precursor slurry contains pseudo-boehmite, and the content of the pseudo-boehmite converted to Al2O3 is 10-50% by weight.

[0043] According to the present invention, preferably, the method further comprises the step of drying the pellets before contacting the pellets with the mixture containing aluminum sol.

[0044] The drying conditions include: a drying temperature of 20-100° C., preferably 40-60° C., a drying time of 2-96 hours, preferably 12-48 hours, and a drying humidity of preferably 40-60 RH%, more preferably 45-55 RH%.

[0045] According to the present invention, preferably, the mixture containing aluminum sol is a mixture of aluminum sol and water or a mixture of aluminum sol, pseudo-boehmite and water.

[0046] According to the present invention, preferably, the contacting is carried out by immersing the pellets in a mixture of the aluminum sol and water or a mixture of the aluminum sol, pseudo-boehmite and water. The immersion only requires immersing all the pellets in the mixture.

[0047] According to the present invention, preferably, the content of aluminum sol in the mixture of aluminum sol and water, calculated as Al2O3, is 1-30% by weight, preferably 5-20% by weight, and more preferably 10-20% by weight.

[0048] Specific examples of the content of the aluminum sol in the mixture of the aluminum sol and water, calculated as Al2O3, include 1 weight%, 2 weight%, 3 weight%, 4 weight%, 5 weight%, 6 weight%, 7 weight%, 8 weight%, 9 weight%, 10 weight%, 11 weight%, 12 weight%, 13 weight%, 14 weight%, 15 weight%, 16 weight%, 17 weight%, 18 weight%, 19 weight%, 20 weight%, 21 weight%, 22 weight%, 23 weight%, 24 weight%, 25 weight%, 26 weight%, 27 weight%, 28 weight%, 29 weight%, 30 weight%, and the like.

[0049] According to the present invention, preferably, the total content of aluminum sol and pseudo-boehmite converted to Al2O3 in the mixture of aluminum sol, pseudo-boehmite and water is 1-65% by weight, preferably 5-50% by weight; more preferably 15-30% by weight.

[0050] Specific examples of the total content of the aluminum sol and the pseudo-boehmite calculated as Al2O3 in the mixture of the aluminum sol, pseudo-boehmite and water include: 1 weight %, 2 weight %, 3 weight %, 4 weight %, 5 weight %, 6 weight %, 7 weight %, 8 weight %, 9 weight %, 10 weight %, 11 weight %, 12 weight %, 13 weight %, 14 weight %, 15 weight %, 16 weight %, 17 weight %, 18 weight %, 19 weight %, 20 weight %, 21 weight %, 22 weight %, 23 weight %, 24 weight %, 25 weight %, 26 weight %, 27 weight %, 28 weight %, 29 weight %, 30 weight %, 31 weight %, 32 weight %, 33 weight %, 34 weight %, 35 weight %, 36 weight %, 37 weight %, 38 weight %, 39 weight %, 40 weight %, 41 weight %, 42 weight %, 43 weight %, 44 weight %, 45 weight %, 46 weight %, 47 weight %, 48 weight %, 49 weight %, 50 weight %, 51 weight %, 52 weight %, 53 weight %, 54 weight %, 55 weight %, 56 weight %, 57 weight %, 58 weight %, 59 weight %, 60 weight %, 61 weight %, 62 weight %, 63 weight %, 64 weight %, 65 weight %, etc.

[0051] According to the present invention, preferably, in the mixture of the aluminum sol, pseudo-boehmite and water, the weight ratio of the aluminum sol calculated as Al2O3 to the pseudo-boehmite calculated as Al2O3 is 1:0.01-5.

[0052] Examples of the weight ratio of the aluminum sol calculated as Al2O3 to the pseudo-boehmite calculated as Al2O3 include 1:0.01, 1:0.1, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:0.5, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, and 1:2.2 , 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4, 1:4.1, 1:4.2, 1:4.3, 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, etc.

[0053] According to the present invention, preferably, the contacting can be static mixing, or can be carried out under stirring or ultrasound, preferably under ultrasound.

[0054] According to the present invention, preferably, the contact temperature is 5-45°C, and the contact time is 10 min-4 h; more preferably, the contact temperature is 10-35°C, and the contact time is 20 min-1 h.

[0055] According to the present invention, preferably, the method further comprises: before calcining the pellets after contacting with the mixture containing aluminum sol in step 2), drying the pellets after contacting with the mixture.

[0056] The drying conditions include: a drying temperature of 20-100° C., preferably 40-60° C., a drying time of 2-96 hours, preferably 12-48 hours, and a drying humidity of preferably 40-60 RH%, more preferably 45-55 RH%.

[0057] According to the present invention, preferably, the calcination temperature is 50-1200° C., more preferably, the calcination temperature is 400-700° C. In addition, the calcination time can be 30-600 minutes, preferably 60-240 minutes.

[0058] The method of the present invention can improve the strength of the pellets, has a simple preparation method, and can obtain pellets with controllable strength.

[0059] The present invention will be described in detail below through examples, but the present invention is not limited to the following examples.

[0060] In the following examples and comparative examples, the strength was measured with reference to the Standard Test Method for Single PelletCrush Strength of Formed Catalysts and Catalyst Carriers (ASTM D4179-11(2017)) using an intelligent particle strength tester (ZQJ-III model from Dalian Intelligent Testing Machine Factory), and the average value of 10 pellets was taken.

[0061] Example 1

[0062] Mix 7.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. Prepare a mixture of 1g of pseudo-boehmite, 5mL of aluminum sol, and 5mL of water (the combined content of aluminum sol (converted as Al2O3) and pseudo-boehmite (converted as Al2O3) is 16wt%). Soak the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, rinse, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets are placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good molding quality and an average strength of 57N / pellet.

[0063] Example 2

[0064] Mix 7.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. Prepare a mixture of 2g of pseudo-boehmite, 5mL of aluminum sol, and 5mL of water (the combined content of aluminum sol (converted as Al2O3) and pseudo-boehmite (converted as Al2O3) is 22% by weight). Soak the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, rinse, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets are placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good molding quality and an average strength of 67N / pellet.

[0065] Example 3

[0066] Mix 7.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. Prepare a mixture of 3g of pseudo-boehmite, 5mL of aluminum sol, and 5mL of water (the combined content of aluminum sol (converted as Al2O3) and pseudo-boehmite (converted as Al2O3) is 26% by weight). Dried pellets are immersed in the mixture and ultrasonically treated for 0.5h. Remove, rinse, and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets are placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good formation and an average strength of 107N / pellet.

[0067] Example 4

[0068] Mix 7.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. Prepare a mixture of 4g of pseudo-boehmite, 5mL of aluminum sol, and 5mL of water (the combined content of aluminum sol (converted as Al2O3) and pseudo-boehmite (converted as Al2O3) is 30% by weight). Soak the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, rinse, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets are placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good molding quality and an average strength of 82N / pellet.

[0069] Example 5

[0070] Mix 5.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Prepare a 5mL aluminum sol and 5mL water mixture (the aluminum sol content, calculated as Al2O3, is 10wt%). Immerse the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, wash, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Place the dried pellets in a muffle furnace, heat to 550°C, and calcine for 4 hours. Analysis of the product revealed good molding and an average strength of 57N / pellet.

[0071] Example 6

[0072] Mix 6.0g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Prepare a 5mL aluminum sol and 5mL water mixture (the aluminum sol content, calculated as Al2O3, is 10wt%). Immerse the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, clean, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Place the dried pellets in a muffle furnace, heat to 550°C, and calcine for 4 hours. Analysis of the product revealed good molding and an average strength of 68N / pellet.

[0073] Example 7

[0074] Mix 6.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Prepare a 5mL aluminum sol and 5mL water mixture (the aluminum sol content, calculated as Al2O3, is 10wt%). Immerse the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, clean, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Place the dried pellets in a muffle furnace, heat to 550°C, and calcine for 4 hours. Analysis of the product revealed good molding and an average strength of 57N / pellet.

[0075] Example 8

[0076] Mix 7.0g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to make a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it stand for 0.5h, then remove and dry it in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Prepare a 5mL aluminum sol and 5mL water mixture (the aluminum sol content, calculated as Al2O3, is 10wt%). Immerse the dried pellets in the mixture and ultrasonically treat them for 0.5h. Remove, clean, and dry them in a low-temperature, wet-drying oven (drying temperature: 50°C, relative humidity: 50RH%, time: 24h). Place the dried pellets in a muffle furnace, heat to 550°C, and calcine for 4 hours. Analysis of the product revealed good molding and an average strength of 52N / pellet.

[0077] Example 9

[0078] 3.6g molecular sieve, 0.4g kaolin, 0.1g sodium alginate, and 10mL water were mixed to prepare a uniform slurry. The slurry was then added dropwise to a 5wt% BaAc2 aqueous solution, allowed to stand for 0.5h, removed, and then dried under low-temperature, wet-drying conditions (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. A 5mL aluminum sol and 5mL water mixture (containing 10% aluminum sol by weight, calculated as Al2O3) was prepared. The dried pellets were immersed in the mixture and ultrasonically treated for 0.5h. The pellets were then removed, cleaned, and dried under low-temperature, wet-drying conditions (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets were placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good formation and an average strength of 21N / pellet.

[0079] Example 10

[0080] 3.6g molecular sieve, 0.4g kaolin, 0.1g sodium alginate, and 10mL water were mixed to prepare a uniform slurry. The mixture was then added dropwise to a 5wt% BaAc2 aqueous solution, allowed to stand for 0.5h, removed, and then dried under low-temperature, wet drying (drying temperature: 50°C, relative humidity: 50RH%) for 24 hours. A mixture of 6.5mL aluminum sol and 3.5mL water (containing 13% aluminum sol by weight, calculated as Al2O3) was prepared. The dried pellets were immersed in the mixture and ultrasonically treated for 0.5h. The pellets were then removed, cleaned, and dried under low-temperature, wet drying (drying temperature: 50°C, relative humidity: 50RH%) for 24 hours. The dried pellets were placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good formation and an average strength of 23N / pellet.

[0081] Example 11

[0082] 3.6g molecular sieve, 0.4g kaolin, 0.1g sodium alginate, and 10mL water were mixed to prepare a uniform slurry. The slurry was then added dropwise to a 5wt% BaAc2 aqueous solution, allowed to stand for 0.5h, removed, and then dried under low-temperature, wet-drying conditions (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. A mixture of 8mL aluminum sol and 2mL water (containing 16% aluminum sol by weight, calculated as Al2O3) was prepared. The dried pellets were immersed in the mixture and ultrasonically treated for 0.5h. The pellets were then removed, cleaned, and dried under low-temperature, wet-drying conditions (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets were placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good formation and an average strength of 23N / pellet.

[0083] Example 12

[0084] 3.6g molecular sieve, 0.4g kaolin, 0.1g sodium alginate, and 10mL water were mixed to prepare a uniform slurry. The slurry was then added dropwise to a 5wt% BaAc2 aqueous solution, allowed to stand for 0.5h, removed, and then dried under low-temperature, wet-drying conditions (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. 10mL of aluminum sol solution (containing 20% ​​aluminum sol by weight, calculated as Al2O3) was prepared. The dried pellets were immersed in a sufficient amount of the solution and ultrasonically treated for 0.5h. The pellets were then removed, cleaned, and dried under low-temperature, wet-drying conditions (drying temperature: 50°C, relative humidity: 50%RH), for 24 hours. The dried pellets were placed in a muffle furnace, heated to 550°C, and calcined for 4 hours. Analysis of the product revealed good forming properties and an average strength of 35N / pellet.

[0085] Comparative Example 1

[0086] Mix 7.5g of pseudo-boehmite, 0.1g of sodium alginate, and 10mL of water to prepare a uniform slurry. Add the mixture dropwise into a 10wt% aqueous solution of CaCl2, let it sit for 0.5h, then remove it and dry it under low-temperature conditions (50°C, 50% relative humidity, for 24 hours). The dried particles are placed in a muffle furnace and calcined at 550°C for 4 hours. Analysis of the product revealed good formation and an average strength of less than 5N / particle, below the detection limit.

[0087] Comparative Example 2

[0088] Mix 3.9g of molecular sieve, 0.3g of kaolin, 0.1g of sodium alginate, and 10mL of water to prepare a uniform slurry. Add the mixture dropwise into a 10wt% CaCl2 aqueous solution, let it sit for 0.5h, then remove and dry at low temperature with moisture. The dried pellets are placed in a muffle furnace and calcined at 550°C for 4 hours. Analysis of the product revealed good formation and an average strength of less than 5N / pellet, below the detection limit.

[0089] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for improving the ball-forming strength of a drop ball, characterized in that: The method The following steps are included: 1) preparing small balls from the precursor slurry by a ball drop method; 2) contacting the pellets with a mixture containing aluminum sol; 3) calcining the pellets after contacting with the mixture containing aluminum sol in step 2), Wherein, the mixture containing aluminum sol is a mixture of aluminum sol, pseudo-boehmite and water, The method further comprises the step of drying the pellets before contacting the pellets with the mixture containing the aluminum sol. The drying conditions include: drying temperature of 20-100°C, drying time of 2-96 hours, drying humidity of 40-60RH%, Step 1) is polymer cross-linking molding, and the pellets are prepared by dripping the precursor slurry and the fourth molding aid into the fifth molding aid. The fourth molding aid is one or more of sodium alginate polymers and chitosan polymers, and the fifth molding aid is one or more of divalent metal salts and trivalent metal salts.

2. The method according to claim 1, wherein The total content of the aluminum sol and pseudo-boehmite in the mixture of the aluminum sol, pseudo-boehmite and water, calculated as Al2O3, is 1-65% by weight.

3. The method according to claim 2, wherein: The total content of the aluminum sol and pseudo-boehmite in the mixture of the aluminum sol, pseudo-boehmite and water, calculated as Al2O3, is 5-50% by weight.

4. The method according to claim 1, wherein In the mixture of the aluminum sol, pseudo-boehmite and water, the weight ratio of the aluminum sol converted to Al2O3 to the pseudo-boehmite converted to Al2O3 is 1:0.01-5.

5. The method according to claim 1, wherein The contact is carried out under stirring and ultrasound.

6. The method according to any one of claims 1 to 5, wherein: The contact temperature is 5-45° C., and the contact time is 10 min-4 h.

7. The method according to any one of claims 1 to 5, wherein: The precursor slurry contains one or more of aluminum sol, pseudo-boehmite, kaolin, molecular sieve, metal oxide, metal hydroxide and metal inorganic salt.

8. The method according to claim 1, wherein The pellets are prepared by dropping a precursor slurry containing the fourth molding aid into a fifth molding aid.

9. The method according to claim 1, wherein The fifth molding aid is one or more of calcium salt, aluminum salt and barium salt.

10. The method according to any one of claims 1 to 5, wherein: The calcination temperature is 50-1200°C.