Aromatic hydrocarbon adsorbent as well as preparation method and application thereof

Abstract

The invention discloses an aromatic hydrocarbon adsorbent as well as a preparation method and application thereof. The adsorbent comprises silica gel and transition metal; the transition metal is nickel; the pore size distribution of the adsorbent is bimodal pore distribution, and bimodal pores are intensively distributed at 3-5nm and 6-16nm. The adsorbent is suitable for separating aromatic hydrocarbon and non-aromatic components in aromatic-rich distillate oil, and has the advantages of high adsorption rate, large adsorption capacity and high aromatic hydrocarbon removal rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of adsorbents, and particularly relates to an aromatic hydrocarbon adsorbent and a preparation method and application thereof. BACKGROUND

[0002] Heavy aromatic-rich distillate oil refers to a resource rich in C9 and above aromatic hydrocarbons, which is mainly derived from catalytic cracking, catalytic reforming, coal coking, ethylene cracking and the like; the heavy aromatic-rich distillate oil has a complex composition, a high content of condensed ring aromatic hydrocarbons, a high content of sulfur and nitrogen, and a large difficulty in secondary processing and utilization. The heavy aromatic-rich distillate oil is usually processed by a two-stage combined process of hydrofining and hydrocracking. The hydrofining unit selectively saturates the condensed ring aromatic hydrocarbons to convert naphthalene series aromatic hydrocarbons into tetrahydronaphthalene series aromatic hydrocarbons, and removes sulfur and nitrogen in the raw material; the hydrocracking unit mainly causes selective ring-opening and side-chain breaking reactions of tetrahydronaphthalene series aromatic hydrocarbons to generate BTX and the like light aromatic hydrocarbons and cracking gas. The product of the hydrofining unit contains a certain amount of paraffins and naphthenes in addition to aromatic hydrocarbons. These saturated hydrocarbons are the main source of the generation of cracking gas in the hydrocracking unit. If an adsorption separation unit is added before or after the hydrofining unit, and only aromatic hydrocarbons are allowed to enter the hydrocracking unit, the generation of cracking gas will be greatly reduced, the yield of BTX and the like light aromatic hydrocarbons will be improved, and the economic performance and market competitiveness of the technology will be improved.

[0003] The aromatic hydrocarbon adsorption separation technology is a non-hydrogen, low-temperature and low-pressure green and efficient separation technology, which can separate fuel oil into chemical raw materials with higher purity. For the adsorption of aromatic hydrocarbons, alumina, molecular sieve and silica gel adsorption systems have been developed in the prior art.

[0004] CN105289466B discloses a modified silica gel adsorbent, the pore channels of which are directionally adjusted by using an appropriate acid solution or alkali solution, and are modified by a metal, so that the removal rate of polycyclic aromatic hydrocarbons can reach 91.74% when diesel oil (non-aromatic content is 55.2wt%, single-ring aromatic hydrocarbon content is 27.6wt%, and polycyclic aromatic hydrocarbon content is 17.2wt%) is used as the adsorbate. The adsorbent is mainly suitable for the adsorption separation of distillate oil with a low aromatic hydrocarbon content (<50wt%), and is not suitable for the adsorption separation of heavier distillate oil.

[0005] The adsorbents in the prior art have a general adsorption effect when applied to the separation of aromatic hydrocarbons and non-aromatic components in aromatic-rich distillate oil (aromatic hydrocarbon content is more than 50wt%). Therefore, the adsorbents suitable for the separation of aromatic hydrocarbons and non-aromatic components in aromatic-rich distillate oil, especially the adsorbents suitable for the separation of aromatic hydrocarbons and non-aromatic components in aromatic-rich distillate oil with a high content of aromatic hydrocarbons, need to be further developed and researched. SUMMARY

[0006] In view of the problems in the prior art, the present application provides an aromatic hydrocarbon adsorbent, a preparation method and application thereof. The adsorbent is suitable for separation of aromatic hydrocarbons and non-aromatic components in aromatic-rich distillate oil, and has the advantages of fast adsorption rate, large adsorption capacity and high removal rate of aromatic hydrocarbons. In particular, the adsorbent is suitable for separation of aromatic hydrocarbons and non-aromatic components in aromatic-rich distillate oil with a high content of aromatic hydrocarbons (more than 50 wt%).

[0007] The first aspect of the present application provides an aromatic hydrocarbon adsorbent. The adsorbent comprises silica gel and a transition metal; the transition metal is nickel; and the pore size distribution of the adsorbent is a bimodal pore distribution, with the bimodal pores being concentrated in the range of 3-5 nm and 6-16 nm.

[0008] According to the present application, the pores with a pore size of 3-5 nm account for 10.0%-16.5% of the total pore volume, and the pores with a pore size of 6-16 nm account for 80.0%-84.5% of the total pore volume.

[0009] According to the present application, the most probable pore diameters corresponding to the bimodal pores are 3-4 nm and 11-12 nm, respectively.

[0010] According to the present application, the adsorbent further comprises a rare earth metal, preferably, the rare earth metal is a lanthanide element; further, the rare earth metal comprises 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.

[0011] According to the present application, the specific surface area of the adsorbent is 400-800 m 2 / g, the mesopore specific surface area is 350-600 m 2 / g, and the mesopore volume is 0.2-0.4 cm 3 / g.

[0012] According to the present application, the mass content of the transition metal is 1 wt%-12 wt% based on the mass of the adsorbent, calculated as metal elements; and / or, the mass content of the silica gel is 88 wt%-99 wt% based on the mass of the adsorbent, calculated as Si elements.

[0013] According to the present application, preferably, the mass content of the transition metal is 1.5 wt%-10 wt% based on the mass of the adsorbent, calculated as metal elements; and / or, the mass content of the silica gel is 89 wt%-98 wt% based on the mass of the adsorbent, calculated as Si elements; and / or, the mass content of the rare earth metal is 0.2 wt%-1 wt% based on the mass of the adsorbent, calculated as metal elements.

[0014] The second aspect of the present application provides a preparation method of the adsorbent, comprising:

[0015] (1) A template agent, organosiloxane and acid are mixed to obtain a silica sol, which is then aged and first calcined to obtain a multi-level porous silica gel;

[0016] (2) Loading metal onto the multi-porous silica gel and then calcining it to obtain the adsorbent;

[0017] In step (1), the template agent has the structure shown in formula (I):

[0018]

[0019] Wherein, n is an integer from 2 to 10, preferably an integer from 2 to 6;

[0020] R1 and R2 are each independently selected from n-alkyl groups, preferably n-alkyl groups with 6 to 18 carbon atoms.

[0021] X - For Cl - and / or Br - .

[0022] According to the present invention, in formula (I) of step (1), R1 and R2 can be the same or different.

[0023] According to the present invention, in step (1), the template agent can be commercially available or homemade. The preparation method of the template agent is not particularly limited in the present invention; for example, it can be obtained by heating a dihalogen-substituted alkane with a long-chain alkyl-substituted dimethyl tertiary amine in anhydrous ethanol under reflux and recrystallization.

[0024] According to the present invention, in step (1), the mass ratio of organosiloxane to template agent is 1:(0.01-0.2), preferably 1:(0.03-0.18).

[0025] According to the present invention, in step (1), the organosiloxane is an orthosilicate, preferably at least one of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate, and butyl orthosilicate.

[0026] According to the present invention, the acid in step (1) includes organic acid and inorganic acid, and the amount of acid added makes the pH of the system 2 to 6, preferably 4 to 5. The acid is preferably one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.

[0027] According to the present invention, in step (1), the mixing is carried out under stirring until the mixture is clear and transparent. A drying step may be performed before the first calcination. The drying temperature is 105–120°C, and the time is 4–8 hours. Further, in step (1), the aging conditions are: temperature 60°C–80°C, time 2–6 hours. The first calcination temperature is 400–650°C, and the first calcination time is 4–10 hours.

[0028] According to the present application, in step (2), the loading method can be impregnation. The impregnation is preferably isovolumetric impregnation.

[0029] According to the present application, in step (2), the impregnation solution is an impregnation solution containing a transition metal salt and a complexing agent. Preferably, the impregnation solution is an impregnation solution containing a transition metal salt, a rare earth metal salt and a complexing agent.

[0030] According to the present application, in step (2), the transition metal salt is preferably at least one of a nitrate salt and a basic carbonate salt; the rare earth metal salt is preferably a nitrate salt. The complexing agent is at least one of citric acid and hydrogen peroxide.

[0031] According to the present application, in step (2), the mass ratio of transition metal to complexing agent in the impregnation solution is 1-12:1 by weight, preferably 1.5-10:1, wherein the transition metal is calculated as the metal element.

[0032] According to the present application, in step (2), a drying step can be performed before the second calcination. The drying temperature is 105-120℃, and the drying time is 4-8h. The second calcination temperature is 250-360℃, and the second calcination time is 4-8h.

[0033] The third aspect of the present application provides an adsorbent prepared by the above method.

[0034] The fourth aspect of the present application provides the use of the adsorbent in the separation of aromatic hydrocarbons from non-aromatic components in an aromatic-rich fraction.

[0035] According to the present application, the saturated adsorption capacity of the adsorbent for aromatic hydrocarbons can reach 0.13g / g or more, preferably 0.14g / g or more, and the single-pass aromatic hydrocarbon removal rate can reach 43% or more, preferably 45% or more.

[0036] According to the present application, the aromatic hydrocarbon content of the aromatic-rich fraction is 50wt% or more, preferably 50wt%-80wt%. The non-aromatic components are preferably saturated hydrocarbons.

[0037] According to the present application, the aromatic-rich fraction oil refers to a fraction oil rich in C9 and above aromatic hydrocarbons, which is mainly derived from at least one of catalytic cracking, catalytic reforming, coal coking and ethylene cracking device.

[0038] According to the present application, the adsorption conditions are that the mass ratio of the aromatic-rich fraction oil to the adsorbent is 1-10:1, and the adsorption time is 50-70min.

[0039] Compared with the prior art, the present application has significant advantages and outstanding effects, mainly as follows:

[0040] (1) The adsorbent of the present application comprises silica gel and transition metal; the transition metal is nickel; the pore size distribution of the adsorbent is bimodal pore distribution, and the bimodal pores are concentrated in 3-5 nm and 6-16 nm. The adsorbent has large specific surface area, suitable pore size distribution, and both microporous and mesoporous structures. The adsorbent is suitable for separating aromatic hydrocarbons and non-aromatic components in aromatic-rich distillate oil, and has the advantages of large adsorption capacity and high aromatic hydrocarbon removal rate.

[0041] The transition metal nickel (and preferably rare earth metal) supported on the hierarchical porous silica gel enhances the adsorption effect between aromatic hydrocarbons and the adsorbent by d-π complexation between the metal and the aromatic hydrocarbons, and further improves the saturated adsorption capacity of the aromatic hydrocarbons.

[0042] By introducing the hierarchical porous structure into the adsorbent, on the one hand, the large amount of microporous structure can increase the surface area of the silica gel, increase the number of adsorption sites (-Si-OH), and thus improve the saturated adsorption capacity of the aromatic hydrocarbons; on the other hand, the hierarchical porous channel structure with micropores and mesopores penetrating each other in the silica gel can improve the faster transport and diffusion rate of the macromolecular aromatic hydrocarbon compounds in the silica gel, and thus effectively shorten the adsorption equilibrium time.

[0043] (2) In the preparation method of the adsorbent of the present application, a specific template agent is used to make the silica gel have both microporous and mesoporous structures, and the pore size distribution of the adsorbent is bimodal pore distribution, with the bimodal pores concentrated in 3-5 nm and 6-16 nm. The adsorbent increases the number of adsorption sites (-Si-OH) and improves the saturated adsorption capacity of the aromatic hydrocarbons; and improves the transport and diffusion rate, and thus effectively shortens the adsorption equilibrium time.

[0044] (3) In the application of the adsorbent of the present application, the adsorbent can effectively adsorb the aromatic hydrocarbons in the aromatic-rich distillate, and is particularly suitable for the aromatic hydrocarbons with an aromatic content of more than 50%. The adsorbent has the advantages of high adsorption rate, large adsorption capacity, and high aromatic hydrocarbon removal rate. The saturated adsorption capacity of the adsorbent for aromatic hydrocarbons can be more than 0.13 g / g of adsorbent, preferably more than 0.14 g / g of adsorbent, and the single-pass aromatic hydrocarbon removal rate can be more than 43%, preferably more than 45%. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 XRD spectra of the adsorbents described in Example 1 and Example 6;

[0046] Figure 2 Pore size distribution graphs of the adsorbents described in Example 1 and Example 6;

[0047] Figure 3 Static adsorption curves of the adsorbents described in Example 1 and Example 6;

[0048] Figure 4The pore size distribution of the adsorbent described in Comparative Example 1 is shown in Figure 1.

[0049] Figure 5 The pore size distribution of the adsorbent described in Comparative Example 3 is shown in Figure 3. DETAILED DESCRIPTION

[0050] The present application will be described in detail below with reference to specific examples, which are described herein to illustrate and explain the present application, but not as a limitation thereof.

[0051] In the present application, each example is carried out with a rich aromatic diesel fraction as a raw material for adsorption evaluation, and the distillation range of the fraction oil is 190-340℃, and the basic composition is shown in Table 1.

[0052] In the present application, the performance evaluation method of each example adsorbent is as follows: static adsorption experiments are carried out at 20℃ and normal pressure, and the mass ratio of the raw material rich aromatic fraction oil to the adsorbent is 3:1. The adsorbent is immersed in the raw material and continuously stirred to make full contact, and the stirring speed is selected as 300r / min. Continuous periodic sampling analysis is carried out, and the content of aromatics and non-aromatics in the sample is determined by gas chromatography. With the extension of sampling time, the content of aromatics in the sample gradually decreases, and when the adsorbent reaches saturated adsorption, the saturated adsorption amount of aromatics and the single-pass aromatics removal rate % are calculated.

[0053] The saturated adsorption amount of aromatics = (the mass of the raw material oil before adsorption x the mass percentage of aromatics in the raw material oil before adsorption - the mass of the raw material oil after saturated adsorption x the mass percentage of aromatics in the raw material oil after saturated adsorption) / the mass of the adsorbent;

[0054] The single-pass aromatics removal rate % = (the mass percentage of aromatics in the raw material oil before adsorption - the mass percentage of aromatics in the raw material oil after saturated adsorption) / the mass percentage of aromatics in the raw material oil before adsorption x 100%.

[0055] In the present application, gas chromatography analysis is carried out by using a GC-2010plus gas chromatograph of Shimadzu Corporation of Japan, a DM-WAX chromatographic column with a size of 60m x 0.25mm x 0.5μm, and a hydrogen flame detector. N2 is used as the carrier gas, and the injection amount is 0.6μL. The chromatographic column is subjected to programmed temperature rising, and the temperature is raised from room temperature to 50℃ for 3min, and then raised to 240℃ at a rate of 10℃ / min, and kept for 5min.

[0056] In the present application, XRD is determined by using a D8 Advance X-ray powder diffractometer of Bruker Corporation of Germany, the working current is 30mA, and the working voltage is 30kV. The experimental conditions are as follows: scanning is carried out by using Cu Kα(λ=1.54nm) ray, and the scanning range is 5-50°.

[0057] 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, and the results were calculated using the BET and BJH methods.

[0058] In this invention, the template agent in each example is obtained by heating and refluxing a dihalogenated alkane and a long-chain alkyl-substituted dimethyl tertiary amine in anhydrous ethanol and then recrystallizing.

[0059]

Example 1

[0060] (1) Weigh 18g of template agent C 12 H 25 - N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ·2Cl - Under continuous stirring, 100 g of methyl orthosilicate was added to the template agent. The pH of the system was adjusted to approximately 5 with 1 mol / L HCl solution, and the mixture was vigorously stirred at 70 °C until the solution became clear and transparent. Aging was continued at 70 °C for 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110 °C for 4 hours and calcined in a muffle furnace at 550 °C for 4 hours to obtain hierarchical porous silica gel.

[0061] (2) Metal modification: Weigh 7.43 g of nickel nitrate hexahydrate, 0.45 g of lanthanum chloride (anhydrous), and 0.5 g of citric acid, and dissolve them in 20 g of water to prepare an impregnation solution. Impregnate the hierarchical porous silica gel with the impregnation solution. After impregnation by equal volume, let it stand in a fume hood for 12 h, then dry it at 110 °C for 4 h, and calcine it at 280 °C for 4 h to obtain the adsorbent.

[0062] The XRD pattern of the adsorbent is shown in the figure. Figure 1 The pore size distribution diagram of the adsorbent is shown in [reference needed]. Figure 2 The adsorption evaluation results of the adsorbent are shown in [the table below]. Figure 3 And Table 2.

[0063] like Figure 2 As shown, the pore size distribution of the adsorbent exhibits a bimodal distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 16.3% of the total pore volume, while pores of 6–16 nm account for 82.9% of the total pore volume.

[0064]

Example 2

[0065] (1) Weigh 16g of template agent C 12 H 25 -N+ (CH3)2-C6H 12 -N + (CH3)2-C 12 H 25 ·2Br - Under continuous stirring, 100 g of tetrabutyl orthosilicate was added to the template agent. The pH of the system was adjusted to approximately 4 with 1 mol / L H₂SO₄ solution, and the mixture was vigorously stirred at 70 °C until the solution became clear and transparent. Aging was continued at 70 °C for 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110 °C for 4 hours and calcined in a muffle furnace at 550 °C for 4 hours to obtain hierarchical porous silica gel.

[0066] (2) Metal modification: Weigh 7.43 g of nickel nitrate hexahydrate, 0.45 g of lanthanum chloride (anhydrous), and 0.5 g of citric acid, and dissolve them in 20 g of water to prepare an impregnation solution. Impregnate the hierarchical porous silica gel with the impregnation solution. After impregnation by equal volume, let it stand in a fume hood for 12 h, then dry it at 110 °C for 4 h, and calcine it at 280 °C for 4 h to obtain the adsorbent.

[0067] The adsorbent exhibits a bimodal pore size distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 15.4% of the total pore volume, and pores of 6–16 nm account for 81.3% of the total pore volume.

[0068]

Example 3

[0069] (1) Weigh 3g of template agent C 18 H 37 - N + (CH3)2-C3H6-N + (CH3)2-C 18 H 37 ·2Cl - Under continuous stirring, 100 g of methyl orthosilicate was added to the template agent. The pH of the system was adjusted to approximately 5 with 1 mol / L HCl solution, and the mixture was vigorously stirred at 70 °C until the solution became clear and transparent. Aging was then continued at 65 °C for 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110 °C for 4 hours and calcined in a muffle furnace at 550 °C for 4 hours to obtain hierarchical porous silica gel.

[0070] (2) Metal modification: Weigh 18.58 g of nickel nitrate hexahydrate, 0.72 g of lanthanum chloride (anhydrous), and 0.5 g of citric acid, and dissolve them in 20 g of water to prepare an impregnation solution. Impregnate the hierarchical porous silica gel with the impregnation solution. After impregnation by equal volume, let it stand in a fume hood for 12 h, then dry it at 110 °C for 4 h, and calcine it at 280 °C for 4 h to obtain the adsorbent.

[0071] The adsorbent exhibits a bimodal pore size distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 13.4% of the total pore volume, while pores of 6–16 nm account for 84.1% of the total pore volume.

[0072]

Example 4

[0073] (1) Weigh 18g of template agent C 12 H 25 - N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ·2Cl - Under continuous stirring, 100 g of methyl orthosilicate was added to the template agent. The pH of the system was adjusted to approximately 5 with 1 mol / L HCl solution, and the mixture was vigorously stirred at 70 °C until the solution became clear and transparent. Aging was continued at 70 °C for 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110 °C for 4 hours and calcined in a muffle furnace at 500 °C for 4 hours to obtain hierarchical porous silica gel.

[0074] (2) Metal modification: Weigh 7.93g of nickel nitrate hexahydrate, 0.26g of cerium chloride (anhydrous), and 0.5g of citric acid, and dissolve them in 20g of water to prepare an impregnation solution. Impregnate the hierarchical porous silica gel with the impregnation solution. After impregnation by equal volume, let it stand in a fume hood for 12h, then dry it at 110℃ for 4h and calcine it at 280℃ for 4h to obtain the adsorbent.

[0075] The adsorbent exhibits a bimodal pore size distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 14.5% of the total pore volume, while pores of 6–16 nm account for 81.4% of the total pore volume.

[0076]

Example 5

[0077] (1) Weigh 16g of template agent C 12 H 25 -N + (CH3)2-C6H 12 -N + (CH3)2-C 12 H 25 ·2Br -Under continuous stirring, 100 g of tetrabutyl orthosilicate was added to the template agent. The pH of the system was adjusted to approximately 4 with 1 mol / L H₂SO₄ solution, and the mixture was vigorously stirred at 70 °C until the solution became clear and transparent. Aging was continued at 70 °C for 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110 °C for 4 hours and calcined in a muffle furnace at 550 °C for 4 hours to obtain hierarchical porous silica gel.

[0078] (2) Metal modification: Weigh 7.93g of nickel nitrate hexahydrate, 0.26g of cerium chloride (anhydrous), and 0.5g of citric acid, and dissolve them in 20g of water to prepare an impregnation solution. Impregnate the hierarchical porous silica gel with the impregnation solution. After impregnation by equal volume, let it stand in a fume hood for 12h, then dry it at 110℃ for 4h and calcine it at 280℃ for 4h to obtain the adsorbent.

[0079] The adsorbent exhibits a bimodal pore size distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 15.2% of the total pore volume, and pores of 6–16 nm account for 80.4% of the total pore volume.

[0080]

Example 6

[0081] (1) Weigh 18g of template agent C 12 H 25 - N + (CH3)2-C6H 12 -N + (CH3)2-C6H 13 ·2Cl - Under continuous stirring, 100 g of methyl orthosilicate was added to the template agent. The pH of the system was adjusted to approximately 5 with 1 mol / L HCl solution, and the mixture was vigorously stirred at 70 °C until the solution became clear and transparent. Aging was continued at 70 °C for 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110 °C for 4 hours and calcined in a muffle furnace at 550 °C for 4 hours to obtain hierarchical porous silica gel.

[0082] (2) Metal modification: Weigh 7.43g of nickel nitrate hexahydrate and 0.5g of citric acid, add 20g of water to dissolve and prepare an impregnation solution. Impregnate the hierarchical porous silica gel with the impregnation solution. After impregnation by equal volume, let it stand in a fume hood for 12h, then dry it at 110℃ for 4h and calcine it at 280℃ for 4h to obtain the adsorbent.

[0083] The XRD pattern of the adsorbent is shown in the figure. Figure 1 The pore size distribution diagram of the adsorbent is shown in [reference needed]. Figure 2 The adsorption evaluation results of the adsorbent are shown in [the table below]. Figure 3 And Table 2.

[0084] like Figure 2As shown, the pore size distribution of the adsorbent exhibits a bimodal distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 15.7% of the total pore volume, while pores of 6–16 nm account for 83.2% of the total pore volume.

[0085] Comparative Example 1

[0086] 100g of methyl orthosilicate was weighed, and the pH of the system was adjusted to approximately 5 with 1mol / L HCl solution. The mixture was vigorously stirred at 70℃ until the solution became clear and transparent, and then aged at 70℃ for another 4 hours. The resulting solid product was filtered and washed three times with water. The solid product was then dried at 110℃ for 4 hours and calcined in a muffle furnace at 550℃ for 4 hours to obtain silica gel. The prepared silica gel was used directly as an adsorbent. Figure 4 It is known that the silica gel prepared by conventional methods has a single-pore distribution with a most probable pore size of 3-4 nm.

[0087] Comparative Example 2

[0088] (1) Step (1) is the same as in Example 1.

[0089] (2) The difference between this example and Example 1 is that cobalt nitrate hexahydrate is used instead of nickel nitrate hexahydrate in Example 1. The rest is the same as in Example 1.

[0090] The adsorbent exhibits a bimodal pore size distribution, with the most probable pore sizes being 3–4 nm and 11–12 nm. Pores of 3–5 nm account for 14.7% of the total pore volume, while pores of 6–16 nm account for 80.7% of the total pore volume.

[0091] Comparative Example 3

[0092] This example uses triblock copolymer P123 (molecular formula PEO). 20 -PPO 70 -PEO 20 (Ma = 5800) was used as the template agent, and the rest was the same as in Example 1.

[0093] The adsorbent exhibits a bimodal pore size distribution, with the most probable pore sizes being 3–4 nm and 15–16 nm. Pores of 3–5 nm account for 33.2% of the total pore volume, while pores of 6–18 nm account for 65.8% of the total pore volume.

[0094] The pore size distribution of the adsorbent in this example is shown in the figure. Figure 5 .

[0095] Table 1. Basic Properties of Aromatic Diesel Fraction

[0096]

[0097] Table 2 Properties and evaluation results of different adsorbents

[0098]

[0099]

Claims

1. An aromatic adsorbent, comprising silica gel and transition metal; the transition metal is nickel; the pore size distribution of the adsorbent is bimodal pore distribution, and the bimodal pores are concentrated in 3-5 nm and 6-16 nm.

2. The adsorbent of claim 1, wherein, The pore volume of the pores with a pore size of 3-5 nm accounts for 10.0-16.5% of the total pore volume, and the pore volume of the pores with a pore size of 6-16 nm accounts for 80.0-84.5% of the total pore volume; And / or, the most probable pore diameters corresponding to the bimodal pores are 3-4 nm and 11-12 nm, respectively.

3. The adsorbent of claim 1, wherein, The adsorbent further comprises rare earth metal, preferably, the rare earth metal is a lanthanide element; Further, the rare earth metal comprises 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; and / or the specific surface area of the adsorbent is 400 to 800 m 2 / g, and / or a mesopore specific surface area of 350 to 600 m 2 / g, and / or a mesopore volume of 0.2 to 0.4 cm3 / g 3 / g.

4. The adsorbent according to claim 1 or 2, wherein Based on the mass of the adsorbent, The mass content of the transition metal is 1-12 wt%, calculated as metal element; And / or, the mass content of the silica gel is 88-99 wt%, calculated as Si element.

5. The adsorbent of claim 1, 2, or 3, wherein, Based on the mass of the adsorbent, The mass content of the transition metal is 1.5-10 wt%, preferably 3-10 wt%, calculated as metal element; And / or, the mass content of the silica gel is 89-98 wt%, preferably 89-96 wt%, calculated as Si element; And / or, the mass content of the rare earth metal is 0.2-1 wt%, preferably 0.3-1 wt%, calculated as metal element. 6.A method for preparing the adsorbent according to any one of claims 1-5, comprising: (1) mixing a template agent, organosiloxane and acid to obtain silica sol, then aging and first calcining to obtain hierarchical porous silica gel; (2) loading metal on the hierarchical porous silica gel and second calcining to obtain the adsorbent; In step (1), the template agent has the structure shown in formula (I): In which, n is an integer of 2-10, preferably n is an integer of 2-6; R1 and R2 are each independently selected from n-alkyl, preferably n-alkyl with a carbon atom number of 6-18, X - is CI - and / or Br - .

7. The method of claim 6, wherein, In step (1), the mass ratio of organosiloxane to template agent is 1: (0.01-0.2), preferably 1: (0.03-0.18).

8. The method of claim 6, wherein, In step (1), the organosiloxane is at least one of orthosilicate, orthosilicate methyl ester, orthosilicate ethyl ester, orthosilicate propyl ester and orthosilicate butyl ester.

9. The method of claim 6, wherein, In step (1), the aging condition is: temperature of 60-80℃, time of 2-6h; And / or, in step (1), the first calcining temperature is 400-650℃, and the calcining time is 4-10h.

10. The method of claim 6, wherein, In step (2), the loading method is impregnation method; the impregnation solution is an impregnation solution containing transition metal salt and complexing agent; Preferably, the impregnation solution is an impregnation solution containing transition metal salt, rare earth metal salt and complexing agent; Further, in the impregnation solution, the mass ratio of transition metal to complexing agent is 1-12: 1, preferably 1.5-10: 1, by weight, wherein the transition metal is calculated as metal element.

11. The method of claim 6, wherein, In step (2), the second calcining temperature is 250-360℃, and the second calcining time is 4-8h.

12. The adsorbent of any one of claims 1 to 5 or the adsorbent produced by the method of any one of claims 6 to 11.

13. Use of the adsorbent of any one of claims 1 to 5 or the adsorbent produced by the method of any one of claims 6 to 11 in the separation of aromatic hydrocarbons from non-aromatic components in a rich aromatic fraction.

14. Use according to claim 13, characterized in that, The aromatic content of the rich aromatic fraction is 50 wt% or more, preferably 50 wt% to 80 wt%; and / or, the rich aromatic fraction oil refers to a fraction oil rich in C9 and above aromatic hydrocarbons, preferably derived from at least one of catalytic cracking, catalytic reforming, coal coking, ethylene cracking unit.

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