Gasoline pre-hydrogenation tooth spherical alumina carrier and preparation method thereof

Abstract

The invention belongs to the field of catalyst carriers, and particularly relates to a gasoline pre-hydrogenation tooth spherical alumina carrier and a preparation method thereof. The preparation method comprises the following steps: (1) performing primary mixing and kneading on pseudo-boehmite powder and an extrusion aid, then adding an acidic aqueous solution, and continuing secondary mixing and kneading to obtain a muddy material; (2) carrying out extrusion molding by adopting a five-tooth ball module, extruding the muddy material, and granulating to obtain a granular material; and (3) firstly drying the granular material, and then roasting to obtain the gasoline pre-hydrogenation tooth spherical alumina carrier. The bulk density of the carrier is 0.6-0.7 g / mL, pores with the particle size of 4-10 nm account for 65-75%, pores with the particle size larger than 15 nm account for 10-20%, industrial continuous production can be achieved, and the carrier is suitable for an efficient pre-hydrogenation catalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalyst carriers, and particularly relates to a spherical alumina carrier for gasoline pre-hydrogenation and a preparation method thereof. BACKGROUND

[0002] As a large consumer of refined oil, with the landing of the national VI and more stringent fuel emission standards, the limits of sulfur content and olefin content of motor gasoline continue to tighten. The national VIb standard requires that the sulfur content of gasoline is not higher than 10 mg / kg, and the olefin content is not more than 15%. In the structure of refined oil in China, fluid catalytic cracking (FCC) gasoline accounts for more than 80% of the blending components of commercial gasoline. It is not only the main source of olefins in motor gasoline, but also the source of more than 90% of sulfur. Therefore, deep desulfurization and olefin reduction of FCC gasoline is the core link of clean gasoline production.

[0003] The sulfur compounds in FCC gasoline are various, and most of the sulfur compounds in the light fraction below 100 DEG C are mercaptans and sulfides which are easy to remove. About 90% of the sulfur compounds in the heavy fraction above 100 DEG C are thiophene and benzothiophene which are difficult to remove. The efficient removal of these sulfur compounds directly determines the overall desulfurization effect of gasoline. Although conventional hydrodesulfurization technology can effectively reduce the sulfur content, it will be accompanied by a large amount of olefin and aromatic saturation reaction, which will cause a large decrease in the octane number of gasoline. The octane number is the core index to measure the anti-knock performance of gasoline, and its loss will directly affect the performance of gasoline. Therefore, "desulfurization and octane number preservation" has become the key technical bottleneck of gasoline hydrogenation technology.

[0004] Gasoline pre-hydrogenation technology can selectively remove sulfur compounds and part of olefins by virtue of its selective hydrogenation characteristics, which can reduce the sulfur and olefin content while maximizing the preservation of octane number, and can also improve the stability of gasoline and reduce the emission of harmful substances in exhaust gas. It has become the mainstream technology for clean gasoline production. The core of this technology is the high-efficiency supported catalyst, and the catalyst carrier is the carrier and dispersion medium of active components, whose performance directly determines the reaction activity, selectivity and service life of the catalyst.

[0005] From the development process of the carrier morphology, it has successively experienced the iteration of spherical, cylindrical, clover-shaped, four-leaf clover-shaped to tooth spherical. Compared with the traditional carrier, the tooth spherical carrier has the advantages of large specific surface area, excellent mass transfer channel and high mechanical strength. The pre-hydrogenation catalyst prepared based on the tooth spherical carrier can realize the reduction of reaction temperature by 10-20 DEG C, the increase of processing load by 15%-20%, and the prolongation of catalyst life by more than 30%. However, the preparation of the existing tooth spherical alumina carrier has two major problems: firstly, it is difficult to realize industrial continuous production, and the mismatch between the mold structure and the extrusion parameters easily leads to uneven carrier morphology and poor batch stability; secondly, the carrier pore structure and the bulk density are difficult to be considered, and most products either have insufficient 4-10nm effective mesopore ratio, affecting the dispersion of active components, or have too low >15nm pore ratio, restricting the mass transfer efficiency, and the bulk density deviates from the optimal interval of 0.6-0.7g / mL of industrial loading, resulting in low space utilization of the reactor. Therefore, it is of great significance to develop a tooth spherical alumina carrier which can be continuously produced, has reasonable pore structure and meets the standard of bulk density, for promoting the upgrading of gasoline pre-hydrogenation technology.

[0006] Therefore, the technical scheme of the present application is proposed. SUMMARY

[0007] In order to solve the problems existing in the prior art, the present application provides a kind of gasoline pre-hydrogenation tooth spherical alumina carrier and its preparation method, to solve how to continuously produce tooth ball carrier on industrial device, meet the index of bulk density 0.6-0.7g / mL, 4-10nm pore ratio 65-75%, >15nm pore ratio 10-20%.

[0008] The purpose of the present application is to provide a preparation method of a gasoline pre-hydrogenation tooth spherical alumina carrier, which comprises the following steps:

[0009] (1) knead pseudo-boehmite powder and extrusion aid for the first time, then add acid aqueous solution to continue kneading for the second time to obtain mud material; wherein the peptization index of the pseudo-boehmite powder is >50%, and the pore volume is 0.6-0.7mL / g; (2) extruding and molding by using five-tooth ball module, and cutting the extruded mud material into granules to obtain granular material; (3) drying and calcining the granular material to obtain the gasoline pre-hydrogenation tooth spherical alumina carrier.

[0010] Preferably, in step (1), the extrusion aid comprises sesbania powder, cellulose and citric acid monohydrate; wherein: The mass ratio of the sesbania powder, cellulose and citric acid monohydrate is 30-50:10-30:10-20.

[0011] Preferably, in step (1), the aqueous acid solution is an aqueous nitric acid solution.

[0012] Preferably, in step (1), the first-time kneading time is 5-8 min, and the second-time kneading time is 20-40 min.

[0013] Preferably, in step (2), the five-toothed ball module is a rectangular tooth with a tooth width of 1.2 mm.

[0014] Preferably, in step (2), during the extrusion molding process, the feeding frequency is 10-15 Hz, and the extrusion frequency is 5-15 Hz; the pelletizing cutter is a circular arc blade, the cutter gap is 0.3 mm, the blade gap is 4.0 mm, and the depth is 2.1 mm.

[0015] Preferably, in step (3), the drying temperature is 100-120℃, and the drying time is 2-4 h. The calcination temperature is 750-800℃, and the calcination time is 3-4 h.

[0016] Based on the same technical concept, another aspect of the present application provides a gasoline pre-hydrogenation tooth-shaped alumina carrier prepared by the above preparation method.

[0017] Preferably, the gasoline pre-hydrogenation tooth-shaped alumina carrier has a bulk density of 0.6-0.7 g / mL, a 4-10 nm pore ratio of 65-75%, and a >15 nm pore ratio of 10-20%.

[0018] The present application has the following beneficial effects: The present application solves the technical problems that the existing gasoline pre-hydrogenation tooth-shaped alumina carrier is difficult to realize industrial continuous production and the pore structure and bulk density cannot be considered, and the prepared carrier can meet the performance requirements of high-efficiency pre-hydrogenation catalyst, providing a high-quality carrier solution for clean gasoline production, which has the following specific beneficial effects: 1. Realize industrial continuous and stable production By precisely matching the five-toothed ball module parameters (rectangular tooth, tooth width 1.2 mm), extrusion process parameters (feeding frequency 10-15 Hz, extrusion frequency 5-15 Hz), and pelletizing cutter specifications (circular arc blade, cutter gap 0.3 mm, etc.), the present application can realize the continuous formation of tooth-shaped carriers on an industrial device, solve the problems of uneven carrier morphology and large batch fluctuations in traditional processes, and ensure the consistency of carrier products.

[0019] 2. Consider both pore structure and bulk density indicators On the one hand, a special pseudo-boehmite powder with a peptization index > 50% and a pore volume of 0.6-0.7 mL / g is used in combination with a specific ratio of extrusion aid to lay the foundation for the pore structure of the carrier; on the other hand, through the 1.2 mm widened tooth ball mold and the 750-800℃ calcination process, the carrier bulk density is stabilized in the optimal loading interval of 0.6-0.7 g / mL, and the reasonable pore distribution of 65-75% of 4-10 nm pores and 10-20% of > 15 nm pores is realized, which takes into account the activity component dispersibility and the reactant mass transfer efficiency.

[0020] 3. Improve the comprehensive performance of the carrier and the adaptability of the catalyst The calcination temperature of 750-800℃ realizes the complete sintering of the aluminum oxide carrier, which not only improves the mechanical strength of the carrier, but also forms a hierarchical pore structure through moderate pore collapse. The pre-hydrogenation catalyst prepared based on the carrier can effectively reduce the initial reaction temperature, improve the desulfurization selectivity, and prolong the service life of the catalyst, which is suitable for the harsh process requirements of clean gasoline production. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0022] Figure 1 is the pore size distribution graph of the gasoline pre-hydrogenation tooth ball-shaped aluminum oxide carrier obtained in Example 1. DETAILED DESCRIPTION

[0023] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of the present application.

[0024] Example 1 The present embodiment provides a preparation method of a gasoline pre-hydrogenation tooth ball-shaped aluminum oxide carrier, which comprises the following steps (detailed description): (1) Material pretreatment and weighing Accurately weigh 1428 g of pseudo-boehmite powder (peptization index 55%, pore volume 0.65 mL / g), 40 g of sesbania powder, 20 g of cellulose, 15 g of citric acid monohydrate, 83 g of 60% nitric acid, and 1043 g of deionized water; at the same time, clean and dry the inner wall of the kneading machine to remove residual impurities. Ensure the purity and accuracy of the raw materials, avoid impurities affecting the performance of the carrier, and dry the kneading machine to prevent premature clumping of the material.

[0025] (2) First dry kneading Put the weighed pseudo-boehmite powder and composite extrusion aid (sesbania powder, cellulose, citric acid monohydrate) into the kneading machine, set the kneading machine speed to 30 r / min, and dry knead for 5 min. The extrusion aid is uniformly dispersed in the pseudo-boehmite powder, the sesbania powder can improve the plasticity of the material, the cellulose enhances the strength of the formed body, and the citric acid monohydrate assists the subsequent peptization reaction. Dry kneading lays a foundation for uniform material for subsequent wet kneading.

[0026] (3) Preparation of acidic aqueous solution and second wet kneading Mix 83 g of 60% nitric acid and 1043 g of deionized water in a special container to prepare a uniform nitric acid aqueous solution; slowly and uniformly add the aqueous solution to the dry kneaded material in the kneading machine, adjust the kneading machine speed to 45 r / min, and continue kneading for 30 min until the material forms a uniform, non-granular, and highly tough mud-like material. The nitric acid aqueous solution can cause the pseudo-boehmite powder to undergo peptization reaction, forming a colloidal system with appropriate viscosity. Wet kneading ensures the smoothness and integrity of the subsequent extrusion molding.

[0027] (4) Extrusion molding parameter adjustment Install a five-tooth ball module (rectangular teeth, tooth width 1.2 mm) with an outer diameter of Ф4.0 mm in advance, and check that the module tooth shape is not worn or blocked; start the extrusion equipment, set the feeding frequency to 12 Hz and the extrusion frequency to 10 Hz, and test run the equipment to ensure that the extrusion pressure is stable in the range of 0.8-1.0 MPa. Adjusting the parameters can avoid material blockage and uneven extrusion during extrusion. The 1.2 mm wide module provides a specific tooth structure for the carrier, ensuring the subsequent bulk density and pore structure indicators.

[0028] (5) Pellet molding The wet-mixed mud material is put into the hopper of the extrusion equipment, and the material is extruded into continuous rack-shaped blank by a five-tooth ball module; a circular arc cutter (cutter gap 0.3 mm, blade gap 4.0 mm, blade depth 2.1 mm) is used to cut the extruded blank to obtain granular material with uniform particle size, and the material conveying speed and the cutter rotating speed are matched during the cutting process to avoid blank fracture or adhesion. The arc blade can ensure the integrity of the tooth ball morphology of the granular material, and the precise cutter gap parameter can control the consistency of the particle size, thereby providing uniform blank for subsequent drying and calcination.

[0029] (6) Drying treatment The granular material obtained by cutting is evenly laid on a tray (material thickness ≤2 cm), and is placed in a forced air drying oven. The drying temperature is set to 120°C, and the drying time is 3h. During the drying process, the air volume in the drying oven is kept at 2m 3 / h to ensure uniform heating of the material. Slow drying at 120°C can slowly remove free water from the material, avoiding rapid drying at high temperature which may cause cracking and deformation of the blank, thereby ensuring the integrity of the morphology of the carrier.

[0030] (7) Calcination and shaping The dried granular material is transferred to a muffle furnace, and is first heated at a rate of 5°C / min to 790°C. After reaching the target temperature, it is kept at a constant temperature for 3h. After calcination, the power of the muffle furnace is turned off, and the furnace is cooled to room temperature. A gasoline pre-hydrogenation tooth-shaped alumina carrier is obtained. Calcination at 790°C can complete the crystal transformation of the pseudoboehmite powder, form γ-Al2O3 crystal phase, and realize complete sintering of the carrier, thereby improving the mechanical strength. Moderate high temperature can promote the collapse of part of the small pores to form >15nm pores, thereby optimizing the pore structure distribution.

[0031] Example 2 The present embodiment provides a preparation method of a gasoline pre-hydrogenation tooth-shaped alumina carrier, which comprises the following steps (brief description): (1) 1428g of pseudoboehmite powder with a peptization index of 51% and a pore volume of 0.6mL / g, and 30g of sesbania powder, 10g of cellulose and 10g of citric acid monohydrate are put into a kneader and dry-mixed for 8min. Then, 66g of an acid aqueous solution mixed with 60% nitric acid and 1000g of water is added, and the kneading is continued for 20min to obtain a mud material.

[0032] (2) A five-tooth ball module (rectangular teeth, tooth width 1.2mm) with an outer circle diameter of Ф4.0mm is used, and the feeding frequency is set to 10Hz and the extrusion frequency is set to 5Hz. A circular arc cutter with a cutter gap of 0.3mm, a blade gap of 4.0mm and a blade depth of 2.1mm is used to cut the granular material. (3) The granular material is dried at 100℃ for 4h, and then calcined at 750℃ for 4h to obtain the gasoline pre-hydrogenation denticulate spherical alumina carrier.

[0033] Example 3 The present example provides a preparation method of a gasoline pre-hydrogenation denticulate spherical alumina carrier, which comprises the following steps (briefly described): (1) 1428g of pseudo-boehmite powder with a peptization index of 57% and a pore volume of 0.7mL / g, and a dewatering aid composed of 50g of sesbania powder, 30g of cellulose and 20g of citric acid monohydrate, are put into a kneader for dry mixing for 8min; 100g of an acidic aqueous solution mixed from 60% nitric acid and 1087g of water is added, and the kneading is continued for 40min to obtain a mud-like material.

[0034] (2) A five-denticulate spherical module (rectangular teeth, tooth width 1.2mm) with an outer circle diameter of Ф4.0mm is used, and the feeding frequency is set to 15Hz and the extrusion frequency is set to 15Hz; a circular arc-shaped cutter with a cutter gap of 0.3mm, a blade gap of 4.0mm and a blade depth of 2.1mm is used to cut the particles to obtain a granular material; (3) The granular material is dried at 120℃ for 2h, and then calcined at 800℃ for 3h to obtain the gasoline pre-hydrogenation denticulate spherical alumina carrier.

[0035] Comparative Example 1 The difference between the present comparative example and Example 1 is that the peptization index of the pseudo-boehmite powder is 45%, and the other operations are the same as those of Example 1.

[0036] Comparative Example 2 The difference between the present comparative example and Example 1 is that the tooth width of the five-denticulate spherical module is the normal value, i.e. 1.0mm, and the other operations are the same as those of Example 1.

[0037] Comparative Example 3 The difference between the present comparative example and Example 1 is that the calcination temperature is 700℃, and the other operations are the same as those of Example 1.

[0038] Comparative Example 4 The difference between the present comparative example and Example 1 is that the calcination temperature is 850℃, and the other operations are the same as those of Example 1.

[0039] Verification Characterization Example 1 The gasoline pre-hydrogenation denticulate spherical alumina carriers obtained in Examples 1-3 and Comparative Examples 1-4 are tested, and the results are shown in Table 1.

[0040] Table 1

[0041] Table 1 (continued)

[0042] As shown in Table 1, Examples 1, 2, and 3 can all prepare a gasoline prehydrogenated toothed spherical alumina support with a bulk density of 0.6-0.7 g / mL, a pore size of 4-10 nm of 65-75%, and a pore size of >15 nm of 10-20%.

[0043] Furthermore: (i) Compared with Example 1, the colloidal index of the pseudoboehmite powder in Comparative Example 1 is 45%, which is lower than 55% in Example 1. As a result, the two key indicators of "bulk density" and "4-10nm pore volume ratio" cannot meet the requirements. The reason may be that: a low colloidal index means poor dispersibility of the colloid, which leads to the particles not being packed tightly enough when the carrier is prepared, thereby reducing the bulk density of the carrier. The reduction in the bulk density of the carrier will lead to an increase in the proportion of >15nm pores, and thus a decrease in the proportion of 4-10nm pores.

[0044] (ii) Compared with Example 1, the tooth width of the five-tooth ball module in Comparative Example 2 is the normal value of 1.0 mm, which is smaller than 1.2 mm in Example 1. As a result, the two key indicators of "packing density" and "4-10 nm pore volume ratio" cannot meet the requirements. The reason may be that: reducing the tooth width reduces the mass of a single toothed spherical carrier of the same size, thereby reducing the packing density of the carrier. The reduction in the packing density of the carrier will lead to an increase in the proportion of >15 nm pores and a decrease in the proportion of 4-10 nm pores.

[0045] (iii) The difference between Comparative Example 3 and Example 1 is that the calcination temperature is 700°C, which is lower than 790°C in Example 1. As a result, the key indicator of ">15nm pore volume ratio" cannot meet the requirements. The reason may be that the lower the calcination temperature, the smaller the pore size is usually, which leads to an increase in the proportion of 4-10nm pores and a decrease in the proportion of >15nm pores.

[0046] (iv) The difference between Comparative Example 4 and Example 1 is that the calcination temperature is 850°C, which is higher than 790°C in Example 1. As a result, the key indicator of "4-10nm pore volume ratio" cannot meet the requirements. The reason may be that the higher the calcination temperature, the more grains grow and the more lightly sinter between particles, and the smaller pores merge into larger pores, resulting in a decrease in the proportion of 4-10nm pores.

[0047] Verification Characterization Example 2 The pore size of the gasoline pre-hydrogenated toothed spherical alumina support obtained in Example 1 was characterized, and the results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the carrier obtained in Example 1 has a pore size distribution that fully meets the requirements of 65-75% of pores in the 4-10nm range and 10-20% of pores in the >15nm range.

[0048] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a gasoline pre-hydrogenated toothed spherical alumina carrier, characterized in that, The preparation method includes the following steps: (1) The pseudoboehmite powder and extrusion aid are mixed for the first time, and then an acidic aqueous solution is added for the second mixing to obtain a mud-like material; wherein: the pseudoboehmite powder has a colloidal index > 50% and a pore volume of 0.6-0.7 mL / g; (2) The mud-like material is extruded and then granulated using a five-toothed ball module to obtain granular material; (3) The particulate material is dried and then roasted to obtain the gasoline pre-hydrogenated toothed spherical alumina carrier.

2. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (1), the extrusion aid includes guar gum powder, cellulose, and citric acid monohydrate; wherein: The mass ratio of guar gum powder, cellulose and citric acid monohydrate is 30-50:10-30:10-20.

3. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (1), the acidic aqueous solution is an aqueous solution of nitric acid.

4. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (1), the first kneading time is 5-8 minutes, and the second kneading time is 20-40 minutes.

5. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (2), the five-tooth ball module has rectangular teeth with a tooth width of 1.2 mm.

6. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (2), during the extrusion molding process, the feeding frequency is 10-15Hz and the extrusion frequency is 5-15Hz; the pelletizing cutter has an arc-shaped blade, a cutter gap of 0.3mm, a blade gap of 4.0mm, and a depth of 2.1mm.

7. The method for preparing the gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 1, characterized in that, In step (3), the drying temperature is 100-120℃ and the drying time is 2-4 hours; The roasting temperature is 750-800℃, and the roasting time is 3-4 hours.

8. The gasoline pre-hydrogenated toothed spherical alumina support obtained by the preparation method according to any one of claims 1-7.

9. The gasoline pre-hydrogenated toothed spherical alumina carrier according to claim 8, characterized in that, The gasoline pre-hydrogenated toothed spherical alumina support has a bulk density of 0.6-0.7 g / mL, a pore size of 4-10 nm of 65-75%, and a pore size of >15 nm of 10-20%.

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