Preparation method of spherical alumina carrier

Abstract

The invention discloses a spherical alumina carrier preparation method, which comprises: adding hydrochloric acid to aluminum powder to prepare an alumina sol, adding urea, low carbon alcohol and an inorganic salt to the alumina sol, completely mixing, adding a hexamethylenetetramine solution to prepare a gel, dropwise adding the gel into a hot oil column, molding, and drying to obtain the spherical alumina carrier. And aging, washing, drying and roasting the gel balls to obtain the spherical alumina carrier. According to the method, the urea, the low-carbon alcohol and the inorganic salt are added into the alumina sol at the same time and act together, so that carrier burrs are reduced, and the circularity is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of alumina carriers, and particularly relates to a method for preparing a spherical alumina carrier. Background Art

[0002] At present, there are many studies at home and abroad on the preparation methods of millimeter-sized (1.6-2.0 mm) alumina ball carriers for moving beds. The main methods used are hot oil column method and oil-ammonia column method.

[0003] The hot oil column molding method has a history of more than 50 years and is currently the main method for preparing high-performance spherical alumina carriers. The spherical Al2O3 prepared by this method not only has the characteristics of high sphericity, tight packing, smooth surface, high yield and few impurities, but also has the advantages of large specific surface area, large pore volume, high mechanical strength, good stability and long life. This method prepares aqueous aluminum sols with different aluminum-chlorine ratios by reacting high-purity aluminum powder with hydrochloric acid, and drips the water-soluble sol into a hydrophobic oily medium at a certain preheating temperature in the form of small droplets through a dispersing dropper. The droplets naturally shrink into spheres in the oil phase due to the oil-water interface effect. During the sphering process, the aluminum sol reacts with a weak alkaline coagulant to form a gel pseudo-boehmite microsphere with a certain strength, and then the spherical alumina carrier of the desired crystal form is prepared through aging, washing and roasting.

[0004] Moser et al. investigated the effect of molding oils of different viscosities on the molding and morphology of spherical alumina. When the viscosity of the molding oil is low, the droplets fall faster in the oil column, making it difficult to mold. When the viscosity of the molding oil is high, the droplets fall slowly in the oil column, which easily causes adhesion between the droplets, and the morphology of the resulting spherical gel particles is poor. In addition, the spherical alumina carrier prepared by the oil column method has good uniformity in small tests, but after magnification, due to reasons such as needle clogging, it is easy to cause uneven particle size, and it needs to be screened before it can be used in the preparation of moving bed catalysts, resulting in a large amount of waste.

[0005] The oil-ammonia column molding method is a method developed from the oil-ammonia column molding device. The spherical alumina prepared by the oil-ammonia column method has low cost, short time and simple operation, but due to the fast coagulation speed of ammonia water, the sphericity is slightly poor, the wear rate is slightly high, and the oil-ammonia column process is prone to environmental pollution.

[0006] CN201911271664.0 introduces a method for preparing spherical alumina by an oil column molding process. By adding low-carbon alcohols (propanol, glycerol, etc.) to the aluminum sol, a small-particle spherical alumina carrier can be prepared without using a very fine dispersing dropper. The particle size is generally between 1.6 and 2.0 mm, but the sphericity of the obtained alumina is poor.

[0007] CN201110322480.X introduces a method for preparing spherical alumina, in which an aluminum source, polyethylene glycol and at least one selected from low-carbon alcohols and water are uniformly mixed, a low-carbon alkylene oxide is added to the mixture, and the mixture is formed into a sphere through an oil column, and then aged, dried and calcined to obtain macroporous alumina. The role of the low-carbon alcohol is to prepare macroporous alumina with strong three-dimensional permeability. The alumina obtained by this method has poor sphericity. Summary of the invention

[0008] The object of the present invention is to provide a method for preparing a spherical alumina carrier. The carrier prepared by the method has good sphericity and an average particle size of 0.1 to 4.0 mm.

[0009] To achieve the above-mentioned purpose, the present invention provides a method for preparing a spherical alumina carrier, which is characterized in that it includes the following steps: adding hydrochloric acid to aluminum powder to prepare aluminum sol, then adding urea, low-carbon alcohol and inorganic salt to the aluminum sol, adding hexamethylenetetramine solution after sufficient mixing to prepare a gel, dripping the gel into a hot oil column to form it, and aging, washing, drying and calcining the gel balls to obtain a spherical alumina carrier.

[0010] In the method for preparing the spherical alumina carrier of the present invention, the mass fraction of aluminum in the aluminum sol is 8% to 12%.

[0011] In the method for preparing the spherical alumina carrier of the present invention, the added amount of urea is 1% to 30% of the mass of the aluminum sol, preferably 8% to 15%.

[0012] In the preparation method of the spherical alumina carrier of the present invention, the low-carbon alcohol is one or more of ethanol, propanol, ethylene glycol, glycerol and n-butanol, and the addition amount of the low-carbon alcohol is 1% to 15% of the mass of the aluminum sol, preferably 4% to 8%.

[0013] In the method for preparing the spherical alumina carrier of the present invention, the inorganic salt is one or more of potassium salt, sodium salt and calcium salt, and the addition amount of the inorganic salt is 0.5% to 15% of the mass of the aluminum sol, preferably 2% to 8%.

[0014] In the preparation method of the spherical alumina carrier of the present invention, the mass concentration of the hexamethylenetetramine solution is 30% to 40%, and the added amount is 20% to 40% of the mass of the aluminum sol.

[0015] In the method for preparing the spherical alumina carrier of the present invention, the hot oil in the hot oil column is one or more of hydraulic oil, lubricating oil, white oil and kerosene, and the temperature is 80°C to 110°C.

[0016] The preparation method of the spherical alumina carrier of the present invention comprises the following aging conditions: temperature of 100° C. to 170° C. and aging time of 4 to 10 hours.

[0017] The preparation method of the spherical alumina carrier of the present invention comprises the following calcination conditions: calcination at 550°C to 980°C for 4 to 6 hours.

[0018] Beneficial effects of the present invention:

[0019] The method of the present invention adds urea, low-carbon alcohol and inorganic salt to the aluminum sol at the same time, and the three work together to reduce the burrs of the carrier and improve the circularity. The simultaneous addition of urea and low-carbon alcohol can improve the fluidity of the aluminum sol and reduce the clogging of the needle. At the same time, the oleophobicity of the wet ball surface after aging is improved, and the oil phase is easier to remove during washing, thereby reducing the mutual adhesion between the small balls, making the outer surface of the product smoother and less burred, but the circularity of the small balls is not good. By adding the method of inorganic salt, the interfacial tension between the aluminum sol and the oil phase is increased, so that the circularity of the gel balls dropped in is higher.

[0020] The roundness of the spherical carrier prepared by the method of the present invention can be improved from 0.899 to 0.932, and the burr rate can be reduced from 6.8% to 1.0% at the highest. DETAILED DESCRIPTION

[0021] The present invention is described in detail below by way of examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Those skilled in the art in this field can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0022] Example 1

[0023] Weigh 60g of aluminum powder and react it with 440g of 10% dilute hydrochloric acid to obtain an aluminum sol with an aluminum content of 12.0w%.

[0024] Weigh 200g of the aluminum sol, add 2g of urea, 30g of ethanol, and 30g of sodium chloride, mix thoroughly, mix with 54g of 35%w hexamethylenetetramine solution, drop into a hot oil column of 85°C hydraulic oil to form balls. The gel balls are aged at 0.2MPa and 100°C for 10h, washed, dried, and calcined at 550°C for 6h to obtain a spherical alumina carrier.

[0025] Example 2

[0026] Weigh 60g of aluminum powder and react it with 690g of 10% dilute hydrochloric acid to obtain an aluminum sol with an aluminum content of 8.0w%.

[0027] Weigh 200g of the aluminum sol, add 30g of urea, 8g of propanol, and 1g of sodium chloride, mix thoroughly, mix with 44g of 40w% hexamethylenetetramine solution, drop into a 100℃ hot oil column of lubricating oil to form balls. The gel balls are aged at 0.6MPa and 120℃ for 8h, washed, dried, and calcined at 800℃ for 4h to obtain a spherical alumina carrier.

[0028] Example 3

[0029] Weigh 60g of aluminum powder and react it with 506g of 8.6% dilute hydrochloric acid to produce an aluminum sol with an aluminum content of 10.6w%.

[0030] Weigh 200g of the aluminum sol, add 60g of urea, 2g of ethylene glycol, and 8g of calcium chloride, mix thoroughly, mix with 65g of 35%w hexamethylenetetramine solution, drop into a 110℃ white oil hot oil column to form balls. The gel balls are aged at 0.8MPa and 150℃ for 6h, washed, dried, and calcined at 940℃ for 4h to obtain a spherical alumina carrier.

[0031] Example 4

[0032] Weigh 60g of aluminum powder and react it with 506g of 8.6% dilute hydrochloric acid to produce an aluminum sol with an aluminum content of 10.6w%.

[0033] Weigh 200g of the aluminum sol, add 16g of urea, 16g of propylene glycol, and 16g of potassium chloride, mix thoroughly, mix with 80g of 30w% hexamethylenetetramine solution, drop into a 85°C kerosene hot oil column to form balls. The gel balls are aged at 0.8MPa and 170°C for 4h, washed, dried, and calcined at 980°C for 4h to obtain a spherical alumina carrier.

[0034] Comparative Example 1

[0035] Weigh 60g of aluminum powder and react it with 440g of 10% dilute hydrochloric acid to obtain an aluminum sol with an aluminum content of 12.0w%.

[0036] Weigh 200g of the aluminum sol, mix it with 60g of 35%w hexamethylenetetramine solution, and drop it into a hot oil column at 85℃ to form balls. The gel balls are aged at 0.2MPa and 100℃ for 10h, washed, dried, and calcined at 550℃ for 6h to obtain a spherical alumina carrier.

[0037] Comparative Example 2

[0038] 60 g of high-purity aluminum powder was weighed and reacted with 690 g of 10% dilute hydrochloric acid to obtain an aluminum sol with an aluminum content of 8.0 w%.

[0039] Weigh 200g of the above aluminum sol, add 16g of urea, mix thoroughly, mix with 50g of 40w% hexamethylenetetramine solution, drop into 85℃ hot oil column to form balls, and the gel balls are aged at 0.6MPa and 120℃ for 8h, washed, dried, and calcined at 800℃ for 4h to obtain spherical alumina carrier.

[0040] Comparative Example 3

[0041] Weigh 60g of aluminum powder and react it with 506g of 8.6% dilute hydrochloric acid to produce an aluminum sol with an aluminum content of 10.6w%.

[0042] Weigh 200g of the aluminum sol, add 18g of urea and 16g of propanol, mix thoroughly, mix with 56g of 35%w hexamethylenetetramine solution, drop into a hot oil column at 85°C to form balls. The gel balls are aged at 0.8MPa and 150°C for 6h, washed, dried, and calcined at 940°C for 4h to obtain a spherical alumina carrier.

[0043] Comparative Example 4

[0044] Weigh 60g of aluminum powder and react it with 440g of 10% dilute hydrochloric acid to obtain an aluminum sol with an aluminum content of 12.0w%.

[0045] Weigh 200g of the aluminum sol, add 10g of sodium chloride, mix thoroughly, mix with 60g of 35%w hexamethylenetetramine solution, drop into 85℃ hot oil column to form balls, and the gel balls are aged at 0.6MPa and 120℃ for 8h, washed, dried, and calcined at 800℃ for 4h to obtain spherical alumina carrier.

[0046] Analysis and testing: The BT-2900 dry and wet image particle size and shape analyzer produced by Liaoning Dandong Better Instrument Co., Ltd. was used to test 500 particles randomly, and the proportion of burrs was calculated. The roundness was directly calculated by the software. The test results are shown in Table 1 below.

[0047] Table 1 Carrier circularity and burr rate test results

[0048] serial number Roundness Burr rate / % Average particle size / mm Example 1 0.932 1.4 1.66 Example 2 0.931 1.0 1.76 Example 3 0.932 1.4 1.88 Example 4 0.931 1.2 2.12 Comparative Example 1 0.899 6.8 1.68 Comparative Example 2 0.900 5.4 1.78 Comparative Example 3 0.900 2.2 1.87 Comparative Example 4 0.906 6.2 2.14

[0049] 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 spherical alumina carrier, characterized in that: The following steps are involved: Aluminum powder is added with hydrochloric acid to prepare aluminum sol, and then urea, low-carbon alcohol and inorganic salt are added to the aluminum sol. After fully mixing, hexamethylenetetramine solution is added to prepare gel. The gel is dropped into a hot oil column to form the gel ball. The gel ball is aged, washed, dried and calcined to obtain a spherical alumina carrier.

2. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The mass fraction of aluminum in the aluminum sol is 8% to 12%.

3. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The added amount of urea is 1% to 30% of the mass of the aluminum sol, preferably 8% to 15%.

4. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The low-carbon alcohol is one or more of ethanol, propanol, ethylene glycol, glycerol and n-butanol. The addition amount of the low-carbon alcohol is 1% to 15% of the mass of the aluminum sol, preferably 4% to 8%.

5. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The inorganic salt is one or more of potassium salt, sodium salt and calcium salt. The addition amount of the inorganic salt is 0.5% to 15% of the mass of the aluminum sol, preferably 2% to 8%.

6. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The mass concentration of the hexamethylenetetramine solution is 30% to 40%, and the added amount is 20% to 40% of the mass of the aluminum sol.

7. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The hot oil in the hot oil column is one or more of hydraulic oil, lubricating oil, white oil and kerosene, and the temperature is 80°C to 110°C.

8. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The aging conditions are: temperature 80° C. to 170° C., pressure 0.2 to 0.8 MPa, and aging time 4 to 10 hours.

9. The method for preparing a spherical alumina carrier according to claim 1, characterized in that: The calcination conditions are: calcination at 550° C. to 980° C. for 4 to 8 hours.