An adsorbent for aromatic hydrocarbon separation, its preparation method and application

Abstract

This invention discloses an adsorbent for aromatic hydrocarbon separation, its preparation method, and its application. The adsorbent comprises: 2.0 to 20.0 parts nickel; 0.3 to 2.0 parts rare earth metals; and 72.0 to 97.1 parts alumina support. The adsorbent exhibits a ternary distribution of weak acid, moderately strong acid, and strong acid; wherein the ratio of weak acid: moderately strong acid: strong acid is 100:5 to 20:15 to 35. This adsorbent is used for the separation of aromatic hydrocarbons from feedstock oils, effectively separating aromatic hydrocarbons and exhibiting significant advantages such as high adsorption rate and large adsorption capacity.

Description

Technical Field

[0001] This invention belongs to the field of adsorbents, specifically relating to an adsorbent for the separation of aromatic hydrocarbons, its preparation method, and its application. Background Technology

[0002] Diesel fuel has a distillation range of 180–350℃ and a carbon number distribution of 12–15. It mainly originates from ethylene cracking units, catalytic reforming units, and coal tar units. Its chemical composition is complex, including alkanes, cycloalkanes, aromatics, and organic sulfur and nitrogen compounds. The cetane number of diesel fuel is closely related to its chemical composition. n-alkanes have the highest cetane number, followed by isoalkanes, with monocyclic cycloalkanes and monocyclic aromatics in the middle, and fused-ring cycloalkanes and fused-ring aromatics having the lowest cetane numbers. Catalytic diesel fuel contains over 60 wt% aromatics, of which bicyclic and tricyclic aromatics account for approximately 75 wt%. The high content of fused-ring aromatics is the main reason for the low cetane number of catalytic diesel fuel, and the utilization of fused-ring aromatics is key to improving the quality of catalytic diesel fuel.

[0003] The separation of aromatics, especially polycyclic aromatic hydrocarbons (PAHs), from diesel fuel has always been a hot topic in petrochemical research. The separation of PAHs from diesel fuel can be viewed as the separation of aromatics from aliphatic hydrocarbons. Hydrorefining achieves high aromatic removal efficiency, but the reaction conditions are high temperature and pressure, the process is long, and equipment investment is large. Among separation technologies, adsorption separation has advantages such as high efficiency, reversibility, short process, and no hazardous waste generation, attracting the attention of researchers. Adsorption separation relies on the chemical complexation between the adsorbent and the adsorbed substance. The efficiency of adsorption separation is closely related to the structure of the adsorbent.

[0004] CN 105289466 B discloses an adsorbent for the adsorption and separation of polycyclic aromatic hydrocarbons (PAHs) in diesel fuel. This adsorbent uses sodium silicate and inorganic acids as raw materials to prepare a silicon-containing support, which is then modified with transition metals, alkaline earth metals, and other metal elements. Using simulated diesel fuel with a PAH content of 17.2 wt%, the PAH removal rate can reach 83.95%. CN109022020B discloses a method for the adsorption and separation of multiple components in diesel fuel. This method employs two interconnected 16-24 column simulated moving bed adsorption devices, using shape-selective adsorbents such as SAPO-11 and Na-ZSM-11 molecular sieves, and metal-modified MCM-41 molecular sieves as aromatic hydrocarbon adsorbents. This method can achieve the separation of alkanes, cycloalkanes, monocyclic aromatic hydrocarbons, and bicyclic aromatic hydrocarbons. CN106140078B discloses a method for preparing a bimetallic aromatic hydrocarbon adsorbent, using silica as a carrier, loading alkaline earth metals and transition metals as active components, and using high-boiling-point aromatic hydrocarbon solvent oil with a distillation range of 150-300℃ as raw material, achieving an aromatic hydrocarbon removal rate of up to 95%.

[0005] Existing adsorbents for aromatic hydrocarbon separation mainly consist of molecular sieves and active metal-supported silica supports. However, existing adsorbents suffer from varying degrees of problems, including slow adsorption rates, low aromatic hydrocarbon separation efficiency, poor adsorption performance, and complex preparation processes. Therefore, developing an adsorbent suitable for aromatic hydrocarbon separation is of great significance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an adsorbent for aromatic hydrocarbon separation, its preparation method, and its application. The adsorbent is used for the separation of aromatic hydrocarbons from feedstock oil, and can effectively separate aromatic hydrocarbons from feedstock oil, exhibiting significant advantages such as high adsorption rate and large adsorption capacity.

[0007] A first aspect of the present invention provides an adsorbent for the separation of aromatic hydrocarbons. The adsorbent, by weight, comprises:

[0008] 2.0 to 20.0 parts of nickel, preferably 7.0 to 14.0 parts of nickel;

[0009] 0.3 to 2.0 parts rare earth metals;

[0010] 72.0 to 97.1 parts of carrier alumina, preferably 79.7 to 90.7 parts of carrier alumina.

[0011] According to the present invention, the acidity of the adsorbent exhibits a ternary distribution of weak acid, moderately strong acid, and strong acid. Further, the ratio of weak acid: moderately strong acid: strong acid is 100:5–20:15–35.

[0012] According to the present invention, the order of acidity of the adsorbent is: weak acid > strong acid > moderately strong acid.

[0013] According to the present invention, the rare earth metal includes at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, preferably at least one of lanthanum, cerium, europium, and praseodymium.

[0014] According to the present invention, the adsorbent is clover-shaped.

[0015] According to the present invention, the diameter of the adsorbent is 1 to 3 mm.

[0016] According to the present invention, the specific surface area of ​​the adsorbent is 270–350 m². 2 / g; the pore volume of the adsorbent is 0.6–0.9 cm³. 3 / g; the most probable pore size of the adsorbent is 8–13 nm.

[0017] A second aspect of the present invention provides a method for preparing the adsorbent. The preparation method includes the following steps:

[0018] (1) The alumina carrier is obtained by molding the alumina raw powder and first calcining it.

[0019] (2) The alumina carrier is impregnated with an impregnation solution containing a nickel source, a rare earth metal source, a first additive, and a second additive, and then dried and calcined to obtain the adsorbent.

[0020] According to the present invention, the most probable pore size of the alumina raw powder in step (1) is 10-13 nm; the specific surface area is 300-350 m². 2 / g; pore volume is 0.8~1.0cm³ 3 / g.

[0021] According to the present invention, the conditions for the first roasting in step (1) are: roasting temperature of 500-700°C and roasting time of 4-8h.

[0022] According to the present invention, in step (1), before molding the alumina raw powder, an auxiliary agent and / or an acidic solution may be added. The auxiliary agent includes at least one selected from guar gum powder, methylcellulose, polyethylene glycol, calcium nitrate, and potassium nitrate. The acidic solution includes at least one selected from nitric acid, phosphoric acid, acetic acid, hydrogen chloride, and tartaric acid. The mass ratio of the auxiliary agent to the alumina raw powder is 2:100 to 6:100; the mass ratio of the acidic solution to the alumina raw powder is 2:100 to 15:100. During the molding process, an appropriate amount of water may be added as needed. The mass ratio of water to alumina raw powder is 80:100 to 120:100.

[0023] According to the present invention, the molding process in step (1) is a kneading and extrusion process.

[0024] According to the present invention, drying can be performed before the first calcination in step (1). The drying conditions are: drying temperature of 105-120°C and drying time of 10-16 hours.

[0025] According to the present invention, the first auxiliary agent in step (2) includes at least one selected from citric acid, tartaric acid, dimethylglyoxime, ethylenediaminetetraacetic acid (EDTA), aminotriacetic acid (also known as NTA), diethylenetriaminepentaacetic acid (DTPA), and their salts. The mass ratio of the first auxiliary agent to the nickel source, calculated as nickel, is 0.05 to 0.4, preferably 0.1 to 0.4.

[0026] According to the present invention, the second auxiliary agent in step (2) includes at least one of dodecyl dimethyl benzyl ammonium chloride, sodium N-dodecyl ethylenediamine triacetate (NaLED3A), and sodium N-dodecyl ethylenediamine triacetate (LED3A). The amount of the second auxiliary agent added is 0.05 to 0.4 by mass ratio of nickel to the nickel source, preferably 0.1 to 0.4.

[0027] According to the present invention, the nickel source in step (2) is a nickel salt; further, the nickel source includes at least one of basic nickel carbonate, nickel nitrate, and nickel acetate.

[0028] According to the present invention, the rare earth metal source in step (2) is a rare earth metal salt; further, the rare earth metal salt is at least one of a nitrate or a chloride containing rare earth metal.

[0029] According to the present invention, the impregnation in step (2) is an equal-volume impregnation. In the impregnation solution, the amount of water added is 2 to 10 times the mass of the nickel source added.

[0030] According to the present invention, the drying conditions in step (2) are: drying temperature 105-120°C; drying time 10-16h.

[0031] According to the present invention, the conditions for the second calcination in step (2) are: calcination temperature of 200-450°C, preferably 200-400°C; and calcination time of 4-8 hours. After this calcination, the first and second additives undergo complete thermal decomposition, and nickel and rare earth metals are uniformly dispersed.

[0032] A third aspect of this invention provides the application of the adsorbent in the separation of aromatics. This application can effectively separate aromatics from feedstock oils.

[0033] According to the present invention, in the aforementioned application, the feedstock is diesel oil. The feedstock has a distillation range of 170°C to 240°C. The aromatic hydrocarbon content is 10 wt% to 60 wt%; the non-aromatic hydrocarbon content is 40 wt% to 90 wt%. Further, the bicyclic aromatic hydrocarbon content is 8 wt% to 58 wt%.

[0034] According to the present invention, in the application described, the mass ratio of raw oil to adsorbent is 3:1 to 5:1.

[0035] Compared with the prior art, the present invention has significant advantages and outstanding effects, mainly as follows:

[0036] (1) The adsorbent of the present invention comprises 2.0 to 20.0 parts nickel; 0.3 to 2.0 parts rare earth metals; and 72.0 to 97.1 parts alumina support. The acidity of the adsorbent exhibits a ternary distribution of weak acid, moderately strong acid, and strong acid; wherein the ratio of strong acid: moderately strong acid: weak acid is 100:5 to 20:15 to 35. This adsorbent has a high specific surface area, suitable pore size distribution, and suitable acid distribution. The acidic centers of the support can accept electrons from aromatic hydrocarbons, and the empty d orbitals of the supported metal can coordinate with the π-bonded orbitals of the aromatic hydrocarbons, promoting the adsorption process of aromatic hydrocarbons and increasing the adsorption capacity.

[0037] The adsorbent of this invention has a suitable pore size distribution, which is conducive to the diffusion of aromatics in the pores of the adsorbent and accelerates the physical adsorption process.

[0038] (2) The adsorption of adsorbents is divided into physical adsorption and chemical adsorption. Chemical adsorption is generally stronger than physical adsorption. The alumina support of this invention provides certain Lewis acid centers, which act as electron acceptors, while the benzene ring in the aromatic hydrocarbon acts as an electron donor. The coordination complexation between the two is beneficial to the adsorption of aromatic hydrocarbons, and the greater the electron cloud density of the aromatic hydrocarbon, the easier it is to be adsorbed. This invention loads active metal ions Ni onto the alumina support. 2+ and rare earth metals such as La 3+ The loaded nickel and rare earth metal ions possess empty 3d orbitals, allowing them to accept electrons from the outside and coordinate with the π-bonded orbitals of aromatic hydrocarbons to form dp bonds, which also facilitates the adsorption of aromatic hydrocarbons. In contrast, non-aromatic hydrocarbons, especially aliphatic hydrocarbons, in the feedstock oil lack empty π orbitals. Furthermore, nickel and rare earth metals exhibit a synergistic effect, with the adsorption performance improved upon the addition of rare earth metals. The inventors discovered that the acidic centers of the support can accept electrons from aromatic hydrocarbons, and the empty d orbitals of the loaded metal can coordinate with the π-bonded orbitals of aromatic hydrocarbons, accelerating the adsorption process and increasing the adsorption capacity. Under the dual action of the alumina support and the active metal, there is a significant difference in the adsorption rates of aromatic hydrocarbons and non-aromatic hydrocarbons, especially aliphatic hydrocarbons, with the adsorbent. Therefore, the adsorbent of this invention can achieve the separation of aromatic hydrocarbons from diesel fuel.

[0039] In the preparation method of the adsorbent of the present invention, the acidity of the alumina support is adjusted by controlling the calcination temperature in step (1) of the preparation of the alumina support. In step (2), by adding a first auxiliary agent and a second auxiliary agent to the impregnation solution, the auxiliary agents can weaken the competitive interaction of hydroxyl groups on the alumina surface, and complex with metal ions through chelation. During the subsequent calcination process, they thermally decompose, which can uniformly disperse the nickel and rare earth metal components, achieving the purpose of atomic-level dispersion. This is beneficial for forming an active phase at a lower temperature, and can further adjust the acidity distribution of the adsorbent to obtain an adsorbent with a suitable acidity distribution.

[0040] In the preparation method of the adsorbent of the present invention, alumina powder with large pores and high specific surface area is used as raw material, and the resulting alumina carrier has a high specific surface area, which is conducive to the adsorption of aromatics on the inner and outer surfaces of the adsorbent.

[0041] (3) In the application of the adsorbent of the present invention, the adsorbent can effectively adsorb aromatics, especially bicyclic aromatics, in diesel fractions, and has the advantages of high adsorption rate and large adsorption capacity. The static saturated adsorption capacity of the adsorbent of the present invention is greater than 0.10 g / g adsorbent, and the initial adsorption rate is greater than 0.014 g / (min / g adsorbent). Attached Figure Description

[0042] Figure 1The XRD patterns are of the alumina raw powder, alumina support (Comparative Example 1), and adsorbent in Example 1.

[0043] Figure 2 The image shows the pore size distribution of the alumina raw powder, alumina carrier (Comparative Example 1), and adsorbent in Example 1.

[0044] Figure 3 The NH3-TPD spectra are for Examples 1, 3, and 4. Detailed Implementation

[0045] The present invention will now be described in detail with reference to specific embodiments. The specific embodiments described herein are used to illustrate and explain the present invention, but are not intended to limit the present invention.

[0046] In this invention, model diesel oil was used as the raw material for adsorption evaluation in each example. The model diesel oil had a distillation range of 185℃ to 220℃, an aromatic hydrocarbon content of 57.38 wt%, and a non-aromatic hydrocarbon content of 42.62 wt%.

[0047] In this invention, the performance evaluation method for each adsorbent is as follows: Adsorption experiments are conducted at 20°C and normal pressure, with a raw material to adsorbent mass ratio of 5:1. The adsorbent is immersed in the raw material and continuously stirred to ensure full contact. The stirring speed is selected as 300 r / min. Samples are continuously taken over the reaction time, and the content of each component in the raw material and product is determined by gas chromatography. The adsorption capacity and adsorption rate are then calculated.

[0048]

[0049] M1, M2: Mass of diesel fuel in the model before and after the adsorption experiment.

[0050] c1, c2: Mass fraction of aromatics in the model diesel fuel before and after the adsorption experiment.

[0051] M0: Mass of the adsorbent.

[0052] In this invention, chromatographic analysis was performed using a Shimadzu GC-2010plus gas chromatograph with a DM-WAX column (60m × 0.25mm × 0.5μm) and a flame ionization detector. N2 was used as the carrier gas, with an injection volume of 0.6μL. The column was programmed for temperature increase: the temperature was raised from room temperature to 50℃ and held for 3 minutes, then increased to 240℃ at a rate of 10℃ / min and held for 5 minutes.

[0053] In this invention, the acidity of the adsorbent was tested using a programmed temperature rise ammonia adsorption instrument manufactured by Tianjin Pengxiang Technology Co., Ltd. The test method and conditions were as follows: the sample was pretreated with N2 at 550℃ for 60 min, cooled to room temperature, and then adsorbed ammonia for 30 min before desorption in an N2 atmosphere. According to the NH3-TPD spectrum, the spectrum showed a low-temperature desorption region (100–400℃ excluding 400℃), a medium-temperature desorption region (400–530℃), and a high-temperature desorption region (>530℃), each with desorption peaks. The desorption peaks in the low-temperature region represent the desorption of NH3 from weak acid sites on the adsorbent surface, corresponding to the weak acid centers of the adsorbent. The desorption peaks in the medium-temperature region represent the desorption of NH3 from medium-strong acid sites on the adsorbent surface, corresponding to the medium-strong acid centers of the adsorbent. The desorption peaks in the high-temperature region represent the desorption of NH3 from strong acid sites on the adsorbent surface, corresponding to the strong acid centers of the adsorbent. Gaussian curve fitting was performed on the NH3-TPD spectrum, and the ratios of the strong acid content, medium strong acid content, and weak acid content of the adsorbent were calculated based on the peak areas of the weak acid peak, medium strong acid peak, and strong acid peak.

[0054] In this invention, XRD was performed using a Bruker D8 Advance X-ray powder diffractometer (Germany), with an operating current of 30 mA and an operating voltage of 30 kV. Experimental conditions: scanning was performed using Cu Kα (λ = 1.54 nm) rays, with a scanning range of 5–50°.

[0055] In this invention, specific surface area, pore volume, most probable pore size, and pore size distribution were measured using a Tristar-3000 fully automated specific surface area and porosity analyzer from Micron Instruments, Inc. Pretreatment conditions: After vacuum degassing at 300℃ for 4 hours, N2 was introduced for physical isothermal adsorption measurement. Specific surface area and pore size distribution were calculated using the BET and BJH methods.

[0056] In this invention, Table 1 shows the pore structure properties of the adsorbent. Table 2 shows the acidity distribution of the adsorbent and the evaluation results of the adsorbent.

[0057]

Example 1

[0058] (1) Carrier preparation: 200g of alumina raw powder, 5.6g of guar gum powder, 4.8g of nitric acid, and 200g of deionized water were weighed, kneaded and extruded into strips, dried at 110℃ for 12h, and calcined at 550℃ for 4h to obtain the alumina carrier. The alumina raw powder had the following properties: specific surface area of ​​318.47m². 2 / g, pore volume is 0.84cm 3 / g, with a most probable pore size of 10.61m.

[0059] (2) Loading with active metal: 12.9g nickel nitrate, 1.32g cerium chloride, 1g citric acid, 1g dodecyl dimethyl benzyl ammonium chloride, and 100g deionized water were used to form an impregnation solution; 100g of the above alumina carrier was weighed and the impregnation solution was evenly sprayed onto the carrier. After impregnation, the carrier was dried at 110℃ for 12h and calcined at 280℃ for 4h to obtain the adsorbent.

[0060] The adsorbent is clover-shaped with a diameter of 2 mm. The adsorbent composition is: 2.5 parts Ni, 0.5 parts Ce, and 96.2 parts Al₂O₃.

[0061] The XRD pattern of the adsorbent is shown below. Figure 1 Specific surface area, pore volume, and pore size distribution are shown in [reference needed]. Figure 2 See Table 2; NH3-TPD spectrum is shown in Table 2. Figure 3 .

[0062] Depend on Figure 1 As can be seen, the XRD patterns of the adsorbent and the alumina support are similar, and no new diffraction peaks appeared after loading nickel and rare earth metals, indicating that the metals are uniformly dispersed on the support surface. Figure 2 As shown in Table 2, the specific surface area of ​​the adsorbent is 312.45 m². 2 / g, pore size 0.89cm 3 / g, the pore size distribution is monopore, with the most probable pore size being 9.95nm. (From...) Figure 3 It can be seen that the acidity of the adsorbent exhibits a ternary distribution of weak acid, medium-strong acid, and strong acid, and the ratio of weak acid: medium-strong acid: strong acid is 100:12:27.

[0063] (3) Adsorption evaluation: Weigh 100g of model diesel and 20g of dehydrated and activated adsorbent. The aromatic hydrocarbon adsorption experiment was carried out in a constant temperature continuous stirring device at 20℃ and atmospheric pressure. The stirring rate was 300r / min. Samples were continuously taken during the adsorption process. The adsorption evaluation results are shown in Table 2.

[0064]

Example 2

[0065] (1) Carrier preparation: Same as in Example 1.

[0066] (2) Loaded active metal: 51.6g nickel nitrate, 1.32g cerium chloride, 1g citric acid, 1g sodium N-dodecylethylenediaminetriacetate (NaLED3A), the rest are the same as in Example 1. The composition of the adsorbent is: 9.4 parts Ni, 0.4 parts Ce, 87.5 parts Al2O3.

[0067] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0068]

Example 3

[0069] (1) Carrier preparation: Calcination at 680℃ for 4 hours, the rest is the same as in Example 1.

[0070] (2) Loaded active metal: Same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts Ce, and 96.2 parts Al2O3.

[0071] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0072]

Example 4

[0073] (1) Carrier preparation: Same as in Example 1.

[0074] (2) Loading with active metal: calcined at 360℃ for 4 hours, the rest is the same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts Ce, and 96.2 parts Al2O3.

[0075] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0076]

Example 5

[0077] (1) Carrier preparation: Same as in Example 1.

[0078] (2) Loaded active metal: 12.9g nickel nitrate, 0.92g lanthanum chloride, 1g citric acid, 1g sodium N-dodecylethylenediaminetriacetate (NaLED3A), the rest are the same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts La, and 96.2 parts Al2O3.

[0079] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0080]

Example 6

[0081] (1) Carrier preparation: Same as in Example 1.

[0082] (2) Loaded active metal: 12.9g nickel nitrate, 1.54g praseodymium nitrate, 1g citric acid, 1g sodium N-dodecylethylenediaminetriacetate (NaLED3A), the rest are the same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts Pr, 96.2 parts Al2O3.

[0083] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0084]

Example 7

[0085] (1) Carrier preparation: Same as in Example 1.

[0086] (2) Loaded active metal: 12.9g nickel nitrate, 0.87g neodymium chloride, 1g citric acid, 1g sodium N-dodecylethylenediaminetriacetate (NaLED3A), the rest are the same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts Nd, and 96.2 parts Al2O3.

[0087] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0088] Comparative Example 1

[0089] Carrier preparation: 200g of alumina raw powder, 5.6g of guar gum powder, 4.8g of nitric acid, and 200g of deionized water were weighed, kneaded, and extruded into strips. The strips were dried at 110℃ for 12 hours and calcined at 550℃ for 4 hours to obtain the alumina carrier. The alumina raw powder had the following properties: specific surface area of ​​318.47 m². 2 / g, pore volume is 0.84cm 3 / g, with a most probable pore size of 10.61m.

[0090] The adsorption evaluation conditions were the same as in Example 1. The adsorption evaluation results of the alumina support in this example are shown in Table 2.

[0091] Comparative Example 2

[0092] (1) Carrier preparation: Same as in Example 1.

[0093] (2) Loading active metal: Except for the absence of cerium chloride, the other conditions were the same as in Example 1. The composition of the adsorbent was: 2.5 parts Ni and 96.2 parts Al2O3.

[0094] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0095] Comparative Example 3

[0096] (1) Carrier preparation: Same as in Example 1.

[0097] (2) Loading active metal: 5.8g nickel nitrate, 0.5g cerium chloride, other conditions are the same as in Example 1. The composition of the adsorbent is: 1.2 parts Ni, 0.2 parts Ce, 96.2 parts Al2O3.

[0098] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0099] Comparative Example 4

[0100] (1) Carrier preparation: calcined at 750℃ for 4h, with other conditions the same as in Example 1.

[0101] (2) Loaded active metal: Same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts Ce, and 96.2 parts Al2O3.

[0102] (3) Adsorption evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0103] Comparative Example 5

[0104] (1) Carrier preparation: Same as in Example 1.

[0105] (2) Loading active metal: Except for the absence of citric acid and dodecyl dimethyl benzyl ammonium chloride, the other conditions were the same as in Example 1. The composition of the adsorbent was: 2.5 parts Ni, 0.5 parts Ce, and 96.2 parts Al2O3.

[0106] (3) Adsorbent evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0107] Comparative Example 6

[0108] (1) Carrier preparation: Same as in Example 1.

[0109] (2) Loading active metal: The first auxiliary agent is citric acid, with an addition amount of 1g; the second auxiliary agent is 1-hydroxyethylidene-1,1-diphosphonic acid (HEDPA), with an addition amount of 1g; the remaining conditions are the same as in Example 1. The composition of the adsorbent is: 2.5 parts Ni, 0.5 parts Ce, and 96.2 parts Al2O3.

[0110] (3) Adsorbent evaluation: Same as in Example 1, the adsorption evaluation results are shown in Table 2.

[0111] Table 1. Pore structure properties of the adsorbent

[0112]

[0113]

[0114] Table 2. Acidity distribution of the adsorbent and adsorption evaluation results

[0115]

[0116] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An adsorbent for the separation of aromatics, comprising, by weight: 2.0 to 20.0 parts nickel; 0.3 to 2.0 parts rare earth metals; 72.0 to 97.1 parts of alumina carrier; The acid content of the adsorbent exhibits a ternary distribution of weak acid, medium-strong acid, and strong acid; wherein, the ratio of weak acid content: medium-strong acid content: strong acid content = 100: 5~20: 15~35. The acidity was determined by the NH3-TPD method. The weak acid center corresponds to the desorption peak in the low temperature desorption region of 100~400℃ and does not include the 400℃ desorption peak. The medium strong acid center corresponds to the desorption peak in the medium temperature desorption region of 400~530℃. The strong acid center corresponds to the desorption peak in the high temperature desorption region of >530℃. The specific surface area of ​​the adsorbent is 270~350m². 2 / g; the pore volume of the adsorbent is 0.6~0.9cm³. 3 / g; the most probable pore size of the adsorbent is 8~13nm.

2. The adsorbent according to claim 1, characterized in that, The order of acid strength is: weak acid > strong acid > moderately strong acid.

3. The adsorbent according to claim 1, characterized in that, The rare earth metals include at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

4. The adsorbent according to claim 3, characterized in that, The rare earth metals include at least one of lanthanum, cerium, europium, and praseodymium.

5. A method for preparing the adsorbent according to any one of claims 1 to 4, comprising the following steps: (1) The alumina carrier is obtained by molding the alumina raw powder and first calcining it; (2) The alumina carrier is impregnated with an impregnation solution containing a nickel source, a rare earth metal source, a first additive and a second additive, and then dried and calcined to obtain the adsorbent.

6. The preparation method according to claim 5, characterized in that, In step (2), the first auxiliary agent includes at least one of citric acid, tartaric acid, dimethylglyoxime, ethylenediaminetetraacetic acid, aminotriacetic acid, diethylenetriaminepentaacetic acid and their salts; and / or, in step (2), the amount of the first auxiliary agent added is 0.05 to 0.4 times the mass ratio of the nickel source (calculated as nickel).

7. The preparation method according to claim 6, characterized in that, In step (2), the amount of the first additive added is 0.1 to 0.4 times the mass ratio of the nickel source (calculated as nickel).

8. The preparation method according to claim 5 or 6, characterized in that, In step (2), the second auxiliary agent includes at least one of dodecyl dimethyl benzyl ammonium chloride, sodium N-dodecyl ethylenediamine triacetate, and sodium N-dodecyl ethylenediamine triacetate; and / or, in step (2), the amount of the second auxiliary agent added is 0.05 to 0.4 times the mass ratio of the nickel source (calculated as nickel).

9. The preparation method according to claim 8, characterized in that, In step (2), the amount of the second additive added is 0.1 to 0.4 times the mass ratio of the nickel source (calculated as nickel).

10. The preparation method according to claim 5, characterized in that, The conditions for the second roasting in step (2) are: roasting temperature of 200~450℃ and roasting time of 4~8h; and / or the conditions for the first roasting in step (1) are: roasting temperature of 500~700℃ and roasting time of 4~8h.

11. The preparation method according to claim 10, characterized in that, The temperature of the second roasting in step (2) is 200~400℃.

12. The preparation method according to claim 5, characterized in that, The most probable pore size of the alumina raw powder in step (1) is 10~13 nm; and / or, the specific surface area is 300~350 m². 2 / g; and / or, pore volume of 0.8~1.0cm³ 3 / g.

13. The application of an adsorbent according to any one of claims 1 to 4 or an adsorbent prepared by any one of claims 5 to 12 in the separation of aromatic hydrocarbons.

Images