Preparation method of super-macroporous residual oil hydrodemetallization tooth spherical alumina carrier

Abstract

The invention belongs to the technical field of catalyst carriers, and particularly relates to a preparation method of a super-macroporous residual oil hydrodemetallization tooth spherical alumina carrier. Aluminum hydroxide and deionized water are mixed and peptized, a modifier is added to regulate and control the pore structure of the aluminum hydroxide, a pore-enlarging agent and a sintering aid are added into a muddy material, and uniformly-distributed pore structures can be formed in an alumina carrier under the action of the pore-enlarging agent and the sintering agent in the roasting process, so that the pore-enlarging effect of the alumina carrier is improved; and the pore structure is further expanded through roasting, so that the pore volume and the macropore ratio in the alumina carrier are improved. In addition, hydroxyl groups on the surface of the alumina carrier are subjected to condensation reaction in the roasting process, so that the acidity of the carrier is effectively reduced, and the corresponding catalytic performance is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst carriers, and in particular relates to a method for preparing a super-large-pore residual oil hydrodemetallization toothed ball-type alumina carrier. Background Art

[0002] At present, most of the hydroprocessing catalysts used in oil refining and petrochemicals are supported solid catalysts. They are mainly composed of active components, co-catalysts and carriers. As an important component of supported catalysts, the carrier plays a role in dispersing the active components, improving the utilization rate of active metals and reducing the amount of active components. On the other hand, it can provide diffusion channels for reactant and product molecules, thereby improving mass transfer efficiency.

[0003] The shape of the carrier has gone through a development process from spherical, cylindrical, clover-shaped, four-leaf clover-shaped to toothed spherical. Compared with conventional shapes, the catalyst prepared by the toothed spherical carrier has the advantages of high pre-hydrogenation activity, large processing load, low initial reaction temperature, good mechanical properties of the catalyst and long service life. Therefore, the preparation and application technology of the toothed spherical carrier plays an important role in promoting the progress and development of residual oil pre-hydrogenation technology. Since most of the specific surface area of ​​the catalyst is the inner surface, and the active centers are also mostly distributed on the inner surface, the reactant molecules must diffuse through the pores of the catalyst to reach the active centers on the inner surface of the catalyst before being adsorbed. This diffusion process is closely related to the pore structure of the catalyst. Therefore, the catalytic performance of the catalyst, such as activity, selectivity and stability, depends not only on the intrinsic characteristics of the active components, but also on the pore structure of the carrier. In order to improve the comprehensive performance of the catalyst, it is urgent to develop an alumina toothed spherical carrier with a high packing density and a high proportion of mesopores on the basis of understanding the influence of the carrier pore size on the desulfurization activity and selectivity of the selective hydrodesulfurization catalyst.

[0004] A Chinese patent application document with publication number CN110860281A discloses a method for preparing a rod-shaped alumina carrier, comprising the following steps: (1) mixing rod-shaped alumina powder and an extrusion aid evenly; (2) mixing a peptizing agent and water evenly, and spraying them evenly onto the mixture obtained in step (1); (3) molding the material obtained in step (2), drying, and roasting to obtain the final alumina carrier. The alumina carrier prepared by this method has a relatively strong skeleton structure, and can evenly distribute active components in the pores, showing comprehensive properties such as high mechanical strength and suitable water absorption, and is particularly suitable for use as a carrier for alkane dehydrogenation catalysts. However, the pore size of the alumina carrier prepared by this method is 2.75-3.66nm, and the pore volume is 0.21-0.43cm 3 , which is a small-pore carrier and can only carry a limited amount of active substances. The catalytic performance of the catalyst prepared using this alumina carrier is poor, resulting in a large amount of catalyst used and a short service life. Summary of the invention

[0005] In order to solve the technical problems in the above-mentioned prior art that the pore size of the alumina carrier is small and the proportion of large pores is small, the present invention provides a method for preparing a super-large pore residue oil hydrodemetallization toothed ball alumina carrier.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A method for preparing a super-large pore residue oil hydrodemetallization toothed spherical alumina carrier comprises the following steps: S1: mixing aluminum hydroxide powder and deionized water evenly, adding a modifier, heating to react under stirring, filtering, and drying to obtain modified aluminum hydroxide powder; S2: dry-mix the modified aluminum hydroxide powder, pore-enlarging agent, sintering aid and extrusion aid obtained in step S1, add a peptizing agent and knead until the mixture is in a slurry state to obtain a slurry-like material; S3: The sludge obtained in step S2 is formed by a tooth-shaped mold, pelletized, dried, and calcined to obtain a super-large-pore residual oil hydrodemetallization toothed spherical alumina carrier.

[0007] In the present invention, aluminum hydroxide is mixed with deionized water for peptization. This process allows aluminum hydroxide to physically adsorb deionized water, remove interlayer structural water, achieve crystal phase transformation, and improve the peptization performance and crystallization performance of aluminum hydroxide. A modifier is added during the peptization process to regulate the pore structure of aluminum hydroxide, which is beneficial to increase the proportion of macropores in aluminum oxide. In addition, in the present invention, a pore expander is added to the mud-like material, and a uniformly distributed pore structure can be formed in the alumina carrier through the volatilization of the pore expander during the roasting process, and the pore structure is further expanded by roasting, thereby increasing the proportion of macropores in the alumina carrier; and the addition of a sintering aid can cause the alumina carrier to undergo a low-temperature sintering reaction during the roasting process, thereby effectively regulating the pore volume and pore size of the alumina carrier.

[0008] Furthermore, the modifier in step S1 is one of tert-butyl alcohol, 2-methyl-2-butanol and 2,2-dimethyl-1-propanol.

[0009] In the present invention, tert-butyl alcohol, 2-methyl-2-butanol or 2,2-dimethyl-1-propanol is selected as the modifier, and the hydroxyl groups in the molecular structure can react with the hydroxyl groups on the surface of aluminum hydroxide and occupy a larger space on the surface of aluminum hydroxide, so that the modifier on the surface of aluminum hydroxide is adsorbed outwardly through the functional groups. During the drying process, the modifier volatilizes to form pores between the aluminum hydroxide particles, and larger mesopores are formed in the alumina carrier after calcination.

[0010] Furthermore, the temperature of the heating reaction in step S1 is 110-120° C., and the heating reaction time is 3-4 hours.

[0011] Furthermore, the pore expanding agent in step S2 is composed of hexamethylenetetramine and ammonium bicarbonate in a mass ratio of 9-13:2-5.

[0012] In the present invention, hexamethylenetetramine and ammonium bicarbonate are selected to form a pore expanding agent. During the drying process, the ammonium bicarbonate is decomposed to form a pore structure inside the alumina carrier. During the roasting process, the hexamethylenetetramine is decomposed to continue to expand the pores inside the alumina carrier. The simultaneous use of hexamethylenetetramine and ammonium bicarbonate can effectively reduce the amount of the pore expanding agent, and avoid the problem of uneven pore distribution and uneven pore size in the alumina carrier caused by the simultaneous decomposition of a large amount of pore expanding agents.

[0013] Furthermore, the sintering aid in step S2 is sodium borate or lithium carbonate.

[0014] In the present invention, sodium borate or lithium carbonate is selected as a sintering aid. During the roasting process, the sodium atoms or lithium atoms in the sintering aid will be inserted into the network formed by the Al-O bonds, interrupting the interconnected Al-O bonds to form a broken network, thereby reducing the surface tension of the alumina carrier. During roasting, the pore wall of the alumina collapses, resulting in an increase in the pore size. At the same time, during the roasting process, the partial sublimation and decomposition of the sintering aid will also increase the pore volume.

[0015] Furthermore, the extrusion aid in step S2 is one or more of sesbania powder, fiber, carboxymethyl cellulose, hydroxypropyl methyl cellulose, and citric acid monohydrate.

[0016] Furthermore, the peptizing agent in step S2 is an aqueous solution of an acid with a mass percentage of 5%, and the acid is one of nitric acid, sulfuric acid, hydrochloric acid, citric acid, acetic acid, oxalic acid, and phosphoric acid.

[0017] Furthermore, the mass fractions of each component in step S1 are 200-250 parts of aluminum hydroxide powder, 500-600 parts of deionized water, and 20-30 parts of modifier; the mass fractions of each component in step S2 are: 100-120 parts of modified aluminum hydroxide powder, 10-15 parts of pore expander, 5-10 parts of sintering aid, 13-17 parts of extrusion aid, and 25-30 parts of peptizer.

[0018] Furthermore, in step S3, the drying temperature is 200-250° C., and the drying time is 2.4-2.6 h.

[0019] In the present invention, the alumina carrier is dried at 200-250° C. for 2.4-2.6 hours before being calcined. Within this temperature range, part of the pore-enlarging agent volatilizes, and a small amount of pore structure can be formed in the alumina carrier.

[0020] Furthermore, in step S3, the calcination temperature is 800-850° C., the calcination time is 3-3.5 h, and the heating rate is 3-5° C. / min.

[0021] The calcination temperature of the alumina carrier in the present invention is 800-850°C. Within this temperature range, the bound water and hydroxyl groups on the surface of the alumina carrier are gradually lost, the sintering degree of the alumina carrier particles increases, and the volatilization of the internal pore expander and sintering aid causes the rich inner wall of the pores provided by the alumina carrier to collapse, forming a macroporous structure, which effectively increases the macropore ratio inside the alumina carrier. In addition, the higher the sintering temperature, the greater the collapse of the inner wall of the pores of the alumina carrier, the higher the macropore ratio, but the alumina particles are denser, resulting in a decrease in the specific surface area of ​​the alumina carrier. The calcination temperature of 800-850°C selected in the present invention can increase the macropore ratio in the alumina carrier on the basis of ensuring the specific surface area of ​​the alumina carrier.

[0022] Compared with the prior art, the method for preparing the ultra-large pore residue oil hydrodemetallization toothed spherical alumina carrier provided by the present invention has the following technical advantages: (1) The bulk density of the alumina carrier provided by the present invention is 0.7-0.9 g / mL, the proportion of pore structures with diameters of 20-40 nm is 65%-75%, and the proportion of pore structures with diameters greater than 40 nm is 10%-15%; (2) The present invention uses a modifier to modify aluminum hydroxide powder, adds a pore expanding agent and a sintering aid, forms it through a toothed ball-shaped mold, and accurately controls the roasting temperature to obtain a toothed ball-shaped alumina carrier with a high proportion of macropores, which is applied to the residual oil hydrodemetallization catalyst and has a good catalytic effect and service life; (3) The alumina carrier provided by the present invention is of toothed ball type, with a small equivalent diameter and high mass transfer efficiency, which can improve the catalytic reaction efficiency factor and solve the shortcomings of spherical and strip catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The pore size distribution diagram of the toothed ball-shaped alumina carrier prepared in Example 1 to Example 3; Figure 2 The pore size distribution diagram of the toothed ball-shaped alumina carrier prepared in Example 3 and Comparative Example 1-Comparative Example 2; Figure 3 The pore size distribution diagram of the toothed ball-shaped alumina carrier prepared in Example 3 and Comparative Example 3-Comparative Example 4; Figure 4 The pore size distribution diagram of the toothed ball-shaped alumina carrier prepared in Example 3 and Comparative Example 5; Figure 5 This is the pore size distribution diagram of the toothed ball-shaped alumina carrier prepared in Example 3 and Comparative Example 6-Comparative Example 7. DETAILED DESCRIPTION

[0024] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art can make various modifications based on the basic idea of ​​the present invention, but as long as they do not deviate from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0025] In the preparation method of the super-large pore residue oil hydrodemetallization toothed ball alumina carrier in step S3 of this specific embodiment, the hole diameter of the toothed ball grinding tool used is 4.0 mm, the tooth width is 1.2 mm, and the pelletizing roller is 4.0 mm; the feeding frequency during molding is 15 Hz, and the extrusion frequency is 15 Hz.

[0026] Example 1 A method for preparing a super-large pore residue oil hydrodemetallization toothed spherical alumina carrier comprises the following steps: S1: 200 g aluminum hydroxide powder and 600 g deionized water were mixed evenly, 20 g tert-butyl alcohol was added, and the mixture was heated to 110° C. under stirring for 4 h, filtered, and dried to obtain modified aluminum hydroxide powder; S2: Take 100g of the modified aluminum hydroxide powder obtained in step S1, 10g of the pore expander, 5g of sodium borate and 13g of sesbania powder, dry mix them for 5min, add 25g of 5% by mass citric acid aqueous solution and knead for 20min, knead until it is in a muddy state that is conducive to extrusion molding and has strong toughness, and obtain a muddy material; the pore expander is composed of hexamethylenetetramine and ammonium bicarbonate in a mass ratio of 9:2; S3: The sludge obtained in step S2 is formed and pelletized through a tooth-shaped mold, dried at 200°C for 2.4 hours, heated to 800°C at a rate of 3°C / min, and calcined for 3 hours to obtain an ultra-large pore residue oil hydrodemetallization toothed spherical alumina carrier.

[0027] Example 2 A method for preparing a super-large pore residue oil hydrodemetallization toothed spherical alumina carrier comprises the following steps: S1: 250g aluminum hydroxide powder and 500g deionized water were mixed evenly, 30g 2-methyl-2-butanol was added, and the mixture was heated to 120°C for reaction for 3h under stirring, and then filtered and dried to obtain modified aluminum hydroxide powder; S2: Take 120g of the modified aluminum hydroxide powder obtained in step S1, 15g of a pore-enlarging agent, 10g of lithium carbonate and 17g of carboxymethyl cellulose, dry-mix for 5 minutes, add 30g of a 5% by mass sulfuric acid aqueous solution and knead for 40 minutes, knead until it is in a muddy state that is conducive to extrusion molding and has strong toughness, and obtain a muddy material; the pore-enlarging agent is composed of hexamethylenetetramine and ammonium bicarbonate in a mass ratio of 13:5; S3: The sludge obtained in step S2 is formed and pelletized through a tooth-shaped mold, dried at 250°C for 2.6 hours, heated to 850°C at a rate of 5°C / min, and calcined for 3.5 hours to obtain an ultra-large pore residue oil hydrodemetallization toothed spherical alumina carrier.

[0028] Example 3 A method for preparing a super-large pore residue oil hydrodemetallization toothed spherical alumina carrier comprises the following steps: S1: 230 g aluminum hydroxide powder and 550 g deionized water were mixed evenly, 24 g 2,2-dimethyl-1-propanol was added, and the mixture was heated to 115° C. under stirring for 3.3 h, and then filtered and dried to obtain modified aluminum hydroxide powder; S2: Take 110g of the modified aluminum hydroxide powder obtained in step S1, 13g of a pore expander, 8g of a sintering aid and 15g of hydroxypropyl methylcellulose, dry-mix them for 5 minutes, add 28g of a 5% by mass nitric acid aqueous solution and knead for 25 minutes, knead until it is in a muddy state that is conducive to extrusion molding and has strong toughness, and obtain a muddy material; the pore expander is composed of hexamethylenetetramine and ammonium bicarbonate in a mass ratio of 11:4; S3: The sludge obtained in step S2 is formed and pelletized through a tooth-shaped mold, dried at 235°C for 2.5 hours, heated to 835°C at a rate of 4°C / min and calcined for 3.2 hours to obtain an ultra-large pore residue oil hydrodemetallization toothed spherical alumina carrier.

[0029] Comparative Example 1 The preparation method of the toothed ball type alumina carrier in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of deionized water is used instead of the modifier in step S1 of this comparative example.

[0030] Comparative Example 2 The preparation method of the toothed ball type alumina carrier in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the modifier described in step S1 of this comparative example is isopropanol.

[0031] Comparative Example 3 The preparation method of the toothed ball type alumina carrier in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the pore expanding agent in step S2 of this comparative example is hexamethylenetetramine.

[0032] Comparative Example 4 The preparation method of the toothed ball type alumina carrier in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that the pore expanding agent in step S2 of this comparative example is ammonium bicarbonate.

[0033] Comparative Example 5 The preparation method of the toothed ball type alumina carrier in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that no sintering aid is added in step S2 of this comparative example.

[0034] Comparative Example 6 The preparation method of the toothed ball type alumina carrier described in this comparative example is similar to that of Example 3. The difference between this comparative example and Example 3 is that the calcination temperature described in step S3 of this comparative example is 500°C.

[0035] Comparative Example 7 The preparation method of the toothed ball type alumina carrier described in this comparative example is similar to that of Example 3. The difference between this comparative example and Example 3 is that the calcination temperature described in step S3 of this comparative example is 1100°C.

[0036] Test example The instrument used to characterize the pore structure characteristics of the material is a multifunctional physical adsorption instrument produced by Austrian company Quantachrome. The pore structure and specific surface area of ​​the alumina carriers obtained in Example 1 to Example 3 and Comparative Example 1 to Comparative Example 7 were measured at liquid nitrogen temperature. Before the test, the sample was first degassed at 300°C. This process removes impurities on the surface (carbon dioxide, water, and other impurities). The sample was tested at liquid nitrogen temperature (77K) using high-purity nitrogen as the adsorbent, and the adsorption amount changed with increasing relative pressure. The specific surface area of ​​the sample was calculated using the BET (Brunauer-Emmett-Teller) method; the pore size distribution and pore volume were calculated using the BJH method using the desorption curve. The test results are shown in Table 1 and Attached. Figure 1 -Attached Figure 5 .

[0037] Table 1

[0038] From Table 1 and Figure 1 It can be seen that the packing density of the toothed ball-shaped alumina carrier provided by the present invention is 0.72-0.90 g / mL and the specific surface area is 43-50 m 2 / g, the pore volume is 0.42-0.51mL / g, the pores of 20-40nm account for 65%-75%, and the pores larger than 40nm account for 10%-15%, which indicates that the toothed ball alumina carrier provided by the present invention has a larger pore structure and the proportion of large pores is relatively high.

[0039] From Table 1 and Figure 2It can be seen that compared with Example 3, the aluminum hydroxide powder was not modified in Comparative Example 1, and the modifier used in step S1 of Comparative Example 2 was isopropanol, but the macropore ratio of the obtained alumina carrier was reduced, which means that the use of tert-butanol, 2-methyl-2-butanol or 2,2-dimethyl-1-propanol to modify the aluminum hydroxide powder in the present invention can effectively increase the macropore ratio in the alumina carrier, and although isopropanol can also react with the hydroxyl groups on the surface of aluminum hydroxide, its modification effect is poor.

[0040] From Table 1 and Figure 3 It can be seen that compared with Example 3, the pore expanding agent in step S2 of comparative example 3 is hexamethylenetetramine, and the pore expanding agent in step S2 of comparative example 4 is ammonium bicarbonate, but the bulk density of the obtained alumina carrier is increased, the specific surface area and pore volume are reduced to varying degrees, and the proportion of macropores is significantly reduced. This is due to the concentrated decomposition of the pore expanding agent, which leads to uneven distribution of the pore structure inside the alumina carrier; From Table 1 and Figure 4 It can be seen that compared with Example 3, no sintering aid was added in step S2 of Comparative Example 5, but the specific surface area, pore volume and macropore ratio of the prepared alumina support were reduced, which shows that the sintering aid can improve the pore structure and macropore ratio in the alumina support; From Table 1 and Figure 5 It can be seen that compared with Example 3, the calcination temperature in step S3 of comparative example 6 is lowered, but the packing density of the obtained alumina carrier is increased, and the specific surface area, pore volume and proportion of macropores are reduced, which shows that increasing the calcination temperature can expand the pore structure; the calcination temperature in step S3 of comparative example 7 is increased, but the specific surface area of ​​the obtained alumina carrier is reduced, and the pore volume and proportion of macropores are increased. This is because the excessively high calcination temperature causes the volume of alumina to shrink, resulting in a decrease in the specific surface area, and the excessively high calcination temperature causes the internal pore walls of the alumina carrier to collapse, and the proportion of macropores to increase.

[0041] The above embodiments are merely illustrative of the present invention, and are not intended to limit the present invention. Those skilled in the art should not modify the above embodiments without violating the spirit and scope of the present invention. All equivalent modifications or changes made by those with ordinary knowledge in the relevant technical field without departing from the technical concept of the present invention still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a super-large pore residue oil hydrodemetallization toothed spherical alumina carrier, characterized in that: The following steps are involved: S1: mixing aluminum hydroxide powder and deionized water evenly, adding a modifier, heating and reacting under stirring, filtering, and drying to obtain modified aluminum hydroxide powder; S2: dry-mix the modified aluminum hydroxide powder, pore-enlarging agent, sintering aid and extrusion aid obtained in step S1, add a peptizing agent and knead until the mixture is in a slurry state to obtain a slurry-like material; S3: forming the sludge obtained in step S2 through a tooth-shaped mold, pelletizing, drying, and calcining to obtain a super-large-pore residual oil hydrodemetallization toothed spherical alumina carrier; The modifier in step S1 is one of tert-butyl alcohol, 2-methyl-2-butyl alcohol and 2,2-dimethyl-1-propyl alcohol.

2. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The temperature of the heating reaction in step S1 is 110-120° C., and the heating reaction time is 3-4 hours.

3. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The pore expanding agent in step S2 is composed of hexamethylenetetramine and ammonium bicarbonate in a mass ratio of 9-13:2-5.

4. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The sintering aid in step S2 is sodium borate or lithium carbonate.

5. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The extrusion aid in step S2 is one or more of sesbania powder, fiber, carboxymethyl cellulose, hydroxypropyl methyl cellulose, and citric acid monohydrate.

6. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The peptizing agent in step S2 is an aqueous solution of an acid with a mass percentage of 5%, and the acid is one of nitric acid, sulfuric acid, hydrochloric acid, citric acid, acetic acid, oxalic acid, and phosphoric acid.

7. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The mass fractions of each component in step S1 are 200-250 parts of aluminum hydroxide powder, 500-600 parts of deionized water, and 20-30 parts of modifier; the mass fractions of each component in step S2 are: 100-120 parts of modified aluminum hydroxide powder, 10-15 parts of pore expander, 5-10 parts of sintering aid, 13-17 parts of extrusion aid, and 25-30 parts of peptizer.

8. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The drying temperature in step S3 is 200-250° C., and the drying time is 2.4-2.6 h.

9. The method for preparing the super-large pore residue oil hydrodemetallization toothed spherical alumina carrier according to claim 1, characterized in that: The calcination temperature in step S3 is 800-850°C, the calcination time is 3-3.5h, and the heating rate is 3-5°C / min.

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