Mesoporous silica adsorbent, its preparation method and application

Abstract

The present disclosure relates to a kind of mesoporous silica adsorbent and its preparation method and application, the method includes the following steps: S1: mesoporous silica particles are pre-acidification treatment, obtain the acidification after silica particles;S2: the acidification after silica particles are contacted with metal ion solution, obtain the adsorbent after reaming;Remove metal in the adsorbent after reaming and dry.The mesoporous silica adsorbent can be applied to simulated moving bed adsorption separation process, separate aromatic and alkane component in diesel, with the advantages of fast mass transfer rate, large raw material processing capacity.

Description

Technical Field

[0001] This disclosure relates to the field of silica gel technology, specifically to a mesoporous silica adsorbent, its preparation method, and its application. Background Technology

[0002] With the development of electric vehicles, hydrogen fuel cell vehicles, and biofuels, the consumption of bulk petroleum products such as gasoline and diesel is bound to decrease, making the adjustment of refinery product structure an urgent matter. Traditional oil conversion processes include diesel hydrotreating, catalytic cracking, and deep catalytic cracking, which convert oil products into low-carbon olefins or BTX. These methods involve high reaction temperatures, high hydrogen consumption, high operating pressures, and high operating costs. Diesel adsorption separation technology, based on the concept of molecular refining, separates diesel into aromatics and alkanes. The aromatic components are fed into a hydrocracking unit to produce BTX, while the alkane components are fed into a catalytic cracking unit to produce low-carbon olefins, achieving "olefins where suitable" and "aromatics where suitable" at the molecular level. Diesel fuel has a complex composition, containing monocyclic, bicyclic, and tricyclic aromatic hydrocarbons (AHs). For monocyclic AHs, the carbon number ranges from 7 to 30, and the molecular size varies depending on the carbon number. For adsorption separation, the pore size of the adsorbent is a crucial indicator. If the pore size is much smaller than the molecular size of the AHs, large AHs will be difficult to adsorb, leading to a decrease in AH yield. Therefore, it is necessary to adjust the adsorbent pore size according to the properties of the diesel feedstock and the molecular size of the diesel fuel to improve the AH yield.

[0003] CN1173465A discloses a method for preparing silica gel with adjustable pore structure. The method involves preparing hydrogel using conventional equipment, then using a surfactant as an aging medium, and obtaining silica gel with different pore sizes after aging, drying, and calcination.

[0004] Meng Qingtao (Meng Qingtao, Zhang Yong. Pore expansion of porous silica microspheres[J]. Applied Science and Technology, 2000, 27(3):2.) et al. used the calcination method to expand the pores of porous silica microspheres. They prepared a solution of deionized water, sodium chloride, lithium chloride and potassium nitrate in a specific ratio, immersed the porous silica in the salt solution, degassed it under vacuum, and then calcined it.

[0005] Wu Hongyu (Wu Hongyu, Zhang Youyu, Li Haitao. Pore expansion and amino functionalization of mesoporous silica [J]. Chemical Research and Application, 2011, 23(11):6.) et al. used mesitylene as a pore expander to prepare a series of large-pore mesoporous silica materials under strong acid conditions. Based on the compatibilizing effect of mesitylene, the pore structure parameters of the mesoporous materials can be effectively adjusted to expand the mesoporous pore size, which can be used for the immobilization or sieving of biomolecular enzymes.

[0006] Zhou Huangxin (Zhou Huangxin, Liang Zhenhua, Peng Guihua, et al. Study on particle size and pore size control in the preparation of mesoporous silica [J]. Journal of Guangxi Normal University: Natural Science Edition, 2014(3):5.) et al. used tetraethyl orthosilicate as silicon source and hexadecyltrimethylammonium bromide as surfactant to study the effects of sodium hydroxide concentration and reaction temperature on the particles and pore size of mesoporous silica. The experimental results showed that adding a certain amount of trimethylbenzene can effectively increase the pore size of mesoporous silica.

[0007] Existing silica adsorbents still need further improvement in terms of increasing the yield of aromatics in diesel adsorption and separation and increasing the space velocity of the adsorption unit. Summary of the Invention

[0008] The purpose of this disclosure is to provide a mesoporous silica adsorbent, its preparation method, and its application. The mesoporous silica adsorbent prepared by this method has the advantages of fast mass transfer rate and large raw material processing capacity.

[0009] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing a mesoporous silica adsorbent, the method comprising the following steps:

[0010] S1: Pre-acidification treatment is performed on mesoporous silica particles to obtain acidified silica particles;

[0011] S2: The acidified silica particles are contacted with a metal ion solution to obtain a pore-expanded adsorbent; the metal in the pore-expanded adsorbent is removed and then dried.

[0012] Optionally, the pre-acidification treatment includes mixing mesoporous silica particles with an inorganic acid solution, reacting at a first temperature for 6-12 hours, filtering and washing the resulting material until the pH of the filtrate is 6.5-7.0, and drying the resulting solid to obtain the acidified silica particles; the first temperature is 40-100°C.

[0013] Optionally, the volume ratio of the mesoporous silica particles to the inorganic acid solution is 0.2 to 1:1, the mass percentage concentration of the inorganic acid solution is 1% to 10%, and the inorganic acid is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

[0014] Optionally, the contact temperature in S2 is 60–100°C; the contact time is 6–12 hours.

[0015] Optionally, the metal ion is one or more of Group IA metals, Group IIA metals and transition metals, preferably one or more of sodium, cesium, calcium, copper and silver; the concentration of the metal ion solution is 0.05 to 0.4 mol / L.

[0016] Optionally, removing metal from the pore-expanding adsorbent includes rinsing the pore-expanding adsorbent with water until the aqueous solution is free of metal ions.

[0017] Optionally, the preparation method further includes: preparing the mesoporous silica particles using the following steps:

[0018] (1) The preheated water glass was mixed with sulfuric acid solution to obtain a mixed solution, and then reacted at a second temperature for 6-12 hours to obtain silica sol;

[0019] (2) The silica sol is rinsed, and the rinsed silica sol is mixed with water to obtain silica water slurry; the silica water slurry is formed into mesoporous silica particles.

[0020] The second temperature is 60-80℃; the mesoporous silica particles are spherical particles.

[0021] Optionally, the concentration of the sulfuric acid solution in (1) is 0.1 to 1 mol / L; the mass concentration of Na2O in the water glass is 0.01 to 0.10 g / g, and the mass concentration of SiO2 is 0.10 to 0.50 g / g.

[0022] Optionally, the rinsing in (2) includes rinsing with water to make the pH of the silica sol 6-7; the ratio of the rinsed silica sol to the water in the silica slurry is 1:0.5-2;

[0023] The process of molding silica slurry into mesoporous silica particles includes using spray drying or air granulation methods to mold silica slurry into spherical particles.

[0024] The mesoporous silica particles have a particle size of 200–900 μm, preferably 250–600 μm.

[0025] The second aspect of this disclosure provides a mesoporous silica adsorbent prepared using the method described in the first aspect of this disclosure, wherein the mass fraction of silica in the mesoporous silica adsorbent is 99% or more, and the mass fraction of metal elements is less than 1%.

[0026] The most probable pore size of the mesoporous silica adsorbent is 2–10 nm.

[0027] Optionally, the BET specific surface area of ​​the mesoporous silica adsorbent is 350–800 m². 2 / g, microporous specific surface area is 500m² 2 / g or less, with an external surface area of ​​260-750m² 2 / g, with an average pore size of 2–7 nm and a micropore volume of 1 cm³. 3The particle size is less than / g and the particle size is 250-600μm.

[0028] This disclosure provides a third aspect regarding the use of the mesoporous silica adsorbent described in the second aspect of this disclosure in the separation of aromatics and alkanes.

[0029] Optionally, the aromatic and alkane components in diesel fuel are separated by a simulated moving bed. The operating conditions of the simulated moving bed include: the desorbent used is one of benzene, toluene, or o-xylene; the mass ratio of the desorbent to the diesel feedstock is 1 to 3:1; and the adsorption-desorption temperature is 80 to 200°C.

[0030] Through the above technical solution, this disclosure obtains a mesoporous silica adsorbent by pre-acidification treatment and metal ion pore-expansion treatment of mesoporous silica particles. This adsorbent can be applied to simulated moving bed adsorption separation process to separate aromatic and alkane components in diesel fuel, and has the advantages of fast mass transfer rate and large feed throughput.

[0031] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0032] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0033] Figure 1 This is the infrared spectrum of the mesoporous silica adsorbent in Example 1.

[0034] Figure 2 This is the XRD pattern of the mesoporous silica adsorbent in Example 1.

[0035] Figure 3 This is a schematic diagram of the simulated moving bed position and switching direction for material entry and exit in Example 5 and Comparative Example 1. Detailed Implementation

[0036] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0037] The first aspect of this disclosure provides a method for preparing a mesoporous silica adsorbent, the method comprising the following steps:

[0038] S1: Pre-acidification treatment is performed on mesoporous silica particles to obtain acidified silica particles;

[0039] S2: The acidified silica particles are contacted with a metal ion solution to obtain a pore-expanded adsorbent; the metal in the pore-expanded adsorbent is removed and then dried.

[0040] The adsorbent prepared by the method disclosed herein has the advantages of fast mass transfer rate and large raw material processing capacity.

[0041] According to one embodiment of this disclosure, the pre-acidification treatment includes mixing mesoporous silica particles with an inorganic acid solution, reacting at a first temperature for 6–12 hours, filtering and washing the resulting material until the pH of the filtrate is 6.5–7.0, and then drying the resulting solid to obtain the acidified silica particles; the first temperature is 40–100°C; the volume ratio of the mesoporous silica particles to the inorganic acid solution is 0.2–1:1, preferably 0.2–0.6:1; the mass percentage concentration of the inorganic acid solution is 1%–10%, preferably 1%–6%; the inorganic acid is one or more of hydrochloric acid, sulfuric acid, and nitric acid. The above embodiment is beneficial for removing impurity particles from the pores and avoiding pore blockage.

[0042] According to one embodiment of this disclosure, the contact temperature in step S2 is 60–100°C, preferably 75–95°C; the contact time is 6–12 h, preferably 7–11 h; the metal ion is one or more of Group IA metals, Group IIA metals, and transition metals, preferably one or more of sodium, cesium, calcium, copper, and silver; the concentration of the metal ion solution is 0.05–0.4 mol / L, preferably 0.2–0.4 mol / L; and the drying temperature is 100–200°C, preferably 120–200°C. The above embodiment is beneficial for obtaining mesoporous silica adsorbents with a large mesoporous external surface area, further improving the mass transfer rate and raw material throughput of the adsorbent.

[0043] In one embodiment, the metal ion solution includes adjusting the pH of the metal ion solution to 6-8 using a pH adjuster. The pH adjuster may be one of ammonia, ammonium chloride, hydrochloric acid, and nitric acid.

[0044] According to this disclosure, removing metals from the expanded-pore adsorbent includes rinsing the expanded-pore adsorbent with water until the aqueous solution is free of metal ions; the water is preferably deionized water. The presence of metal ions in the aqueous solution can be determined using conventional methods in the art, such as chemical precipitation to identify the presence of metal ions in the washing solution. Even if the rinsing water is free of metal ions, the mesoporous silica may still contain trace amounts of residual metal elements; for example, the mass fraction of metal elements in the mesoporous silica adsorbent may be less than 1%. The above-described embodiments are beneficial for improving the mass transfer rate and feedstock throughput of the mesoporous silica adsorbent.

[0045] According to this disclosure, the preparation method further includes: preparing the mesoporous silica particles using the following steps:

[0046] (1) Mix the preheated water glass with sulfuric acid solution to obtain a mixed solution, and then stir at a second temperature for 6-12 hours to obtain silica sol;

[0047] (2) The silica sol is rinsed, and the rinsed silica sol is mixed with water to obtain silica water slurry; the silica water slurry is formed into mesoporous silica particles.

[0048] The second temperature is 60-80°C, preferably 65-75°C; the mesoporous silica particles are spherical particles.

[0049] According to one embodiment of this disclosure, the concentration of the sulfuric acid solution in (1) can be 0.1-1 mol / L, preferably 0.2-0.8 mol / L; the mass concentration of Na2O in the water glass can be 0.01-0.10 g / g, preferably 0.02-0.08 g / g, and the mass concentration of SiO2 can be 0.10-0.50 g / g, preferably 0.2-0.4 g / g. In a further embodiment, the water glass is first preheated to a constant temperature of 60-100°C, and then sulfuric acid is slowly added to the water glass. When the pH of the mixed solution is 2-6, it is stirred at a second temperature for 6-12 hours to age it. The above embodiments are beneficial for obtaining silica sol.

[0050] According to one embodiment of this disclosure, the rinsing in (2) includes rinsing with water to make the pH of the silica sol 6-7; the ratio of the rinsed silica sol to the water in the silica slurry is 1:0.5-2, preferably 1:0.5-1.5; the step of forming the silica slurry into mesoporous silica particles includes using spray drying or air granulation to form the silica slurry into spherical particles. The operating conditions of the spray drying or air granulation method can be conventional techniques in the art, and will not be described in detail here.

[0051] According to this disclosure, the size of the silica particles can be 200–900 μm, preferably 250–600 μm. The above-described embodiments are beneficial for improving the mass transfer rate and feed throughput of the mesoporous silica adsorbent.

[0052] The second aspect of this disclosure provides a mesoporous silica adsorbent prepared using the method described in the first aspect of this disclosure, wherein the mass fraction of silica in the mesoporous silica adsorbent is above 99%; the mass fraction of metal elements is below 1%; and the most probable pore size of the mesoporous silica adsorbent is 2 to 10 nm.

[0053] According to one embodiment of this disclosure, the XRD pattern of the mesoporous silica adsorbent has characteristic peaks between 2θ and 25°.

[0054] According to one embodiment of this disclosure, the infrared spectrum of the mesoporous silica adsorbent is in the range of 3400–3500 cm⁻¹. -1 1500~1700cm -1 1000~1100cm -1 and 700-850cm -1 Characteristic peaks exist, with the 3400–3500 cm⁻¹ range being particularly prominent. -1 and 1500~1700cm -1 The peak is attributed to the -OH stretching vibration in silica, 1000–1100 cm⁻¹ -1 and 700-850cm -1 The peaks are attributed to the stretching vibrations of the Si-O bond.

[0055] According to one embodiment of this disclosure, the BET specific surface area of ​​the mesoporous silica adsorbent can be 350–800 m². 2 / g, preferably 500-800m 2 / g; the specific surface area of ​​the micropores can be 550m² 2 / g or less, preferably 500m 2 / g or less; external surface area can be 260-750m² 2 / g, preferably 280-650m 2 / g; average pore size can be 2-10nm, preferably 2-7nm; micropore volume can be 1cm³ 3 / g or less, preferably 0.3cm 3 The particle size can be 250-600 μm, preferably 290-580 μm, and the particle size can be below / g.

[0056] This disclosure provides, in a third aspect, the use of the mesoporous silica adsorbent described in the second aspect of this disclosure in the separation of aromatics and alkanes. For example, it describes the separation of aromatics and alkanes by adsorption using a mesoporous silica adsorbent in a stream containing a mixture of aromatics and alkanes. In one embodiment, the mass content of aromatics in the analyte can be 18% to 30%.

[0057] According to one embodiment of this disclosure, aromatic and alkane components in diesel fuel are separated by a simulated moving bed. The operating conditions of the simulated moving bed include: the desorbent used can be one of benzene, toluene, or o-xylene, preferably toluene; the mass ratio of the desorbent to the diesel feedstock can be 1 to 3:1, preferably 1.2 to 2.5:1; and the adsorption-desorption temperature can be 80 to 200°C, preferably 80 to 150°C.

[0058] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0059] In the following embodiments of this disclosure, the X-ray scanning diffractometer (XRD) used is the Empyrean X-ray Diffraction System instrument from Panaco, Netherlands.

[0060] The infrared spectrometer used was a Bruker EQUINOX 55 instrument;

[0061] The BET specific surface area was measured using an ASAP 2420 instrument from Micromertics.

[0062] The elemental content of the adsorbent was determined using X-ray fluorescence spectroscopy (XRF) analysis with an Axios PW4400 instrument. All chemical reagents used in the embodiments and comparative examples of this disclosure were of analytical grade purity.

[0063] Unless otherwise specified, the chemical reagents used in the following examples and comparative examples are commercially available products.

[0064] Example 1

[0065] Preparation of silica particles: Silica sol was synthesized using water glass and sulfuric acid as raw materials. The water glass contained 0.05 g / g of Na2O, 0.20 g / g of SiO2, and 0.2 mol / L of sulfuric acid. The amounts of water glass and sulfuric acid were adjusted to make the pH of the solution equal to 5. The reaction was carried out at 70°C for 10 h to obtain silica sol. The silica sol was washed five times with deionized water until the pH of the silica sol reached 7. Then, the silica sol and deionized water were mixed at a volume ratio of 1:1 and spray-dried and air-granulated at 180°C to obtain silica particles. Silica particles with a size of 250–600 μm were selected by sieving for further processing.

[0066] Pre-acidification treatment: Place silica particles in a stirred reactor, add dilute hydrochloric acid with a mass percentage concentration of 2%, and the volume ratio of silica particles to dilute hydrochloric acid is 0.2:1. Perform pre-acidification treatment at 90℃ for 10h. Wash silica particles with deionized water until the pH of the filtrate is 7. Dry the obtained solid to obtain acidified silica particles.

[0067] Metal ion pore-expanding treatment: Acidified silica particles are poured into a 0.4 mol / L sodium chloride solution and stirred for 8 hours at 90°C to obtain an expanded pore adsorbent. The expanded pore adsorbent is rinsed with deionized water to remove metal ions until the effluent no longer contains sodium ions. A precipitation reaction is carried out using silver nitrate solution. If no precipitate is formed, there are no chloride ions, i.e., no sodium ions. The adsorbent is then dried at 150°C.

[0068] Example 2

[0069] The preparation method in this embodiment is the same as in Example 1, except that a 0.4 mol / L silver nitrate solution is used in the metal ion pore-expanding treatment. Acidified silica particles are poured into the silver nitrate solution and stirred at 90°C for 8 hours. After the reaction, the adsorbent after pore expansion is rinsed with deionized water to remove metal ions until the effluent no longer contains silver ions. The adsorbent is then dried at 150°C.

[0070] Example 3

[0071] The preparation method in this embodiment is the same as in Example 1, except that a 0.4 mol / L copper chloride solution is used in the metal ion pore-expanding treatment, and an appropriate amount of ammonia is added to adjust the pH of the metal solution to 7. The acidified silica particles are poured into the copper chloride solution, and the reaction is carried out at 90°C with stirring for 8 hours. After the reaction, the adsorbent after pore expansion is rinsed with deionized water to remove metal ions until no copper ions are present in the effluent. The detection method is the same as in Example 1. The adsorbent is then dried at 150°C.

[0072] Example 4

[0073] The preparation method in this embodiment is the same as in Example 1, except that a 0.4 mol / L calcium chloride solution is used in the metal ion pore-expanding treatment. Acidified silica particles are poured into the calcium chloride solution and stirred at 90°C for 8 hours. After the reaction, the adsorbent after pore expansion is rinsed with deionized water to remove metal ions until the effluent no longer contains calcium ions. The detection method is the same as in Example 1. The adsorbent is then dried at 150°C.

[0074] Example 5

[0075] The preparation method in this embodiment is the same as in Example 1, except that a 0.4 mol / L cesium chloride solution is used in the metal ion pore-expanding treatment. Acidified silica particles are poured into the cesium chloride solution and stirred at 90°C for 8 hours. After the reaction, the adsorbent after pore expansion is rinsed with deionized water to remove metal ions until the effluent no longer contains cesium ions. The detection method is the same as in Example 1. The adsorbent is then dried at 150°C.

[0076] Example 6

[0077] The preparation method in this embodiment is the same as in Embodiment 1, except that the contact temperature in the metal ion pore-expanding treatment is 40°C and the contact time is 5 hours.

[0078] Example 7

[0079] The preparation method of this embodiment is the same as that of Example 1, except that the metal ion pore-expanding treatment is carried out in 0.2 mol / L sodium chloride solution at 70°C for 10 h of stirring to obtain the expanded pore adsorbent. The expanded pore adsorbent is then rinsed with deionized water to remove metal ions until the effluent no longer contains sodium ions. The detection method is the same as that of Example 1. The adsorbent is then dried at 150°C.

[0080] Comparative Example 1

[0081] The preparation method of this comparative example is the same as that of Example 1, except that only the preparation of silica particles in Example 1 is performed, and the silica particles are dried at 150°C.

[0082] Comparative Example 2

[0083] The preparation method of this comparative example is the same as that of Example 1, except that only the steps of preparing silica particles and pre-acidification treatment in Example 1 are performed, and the acidified silica particles are dried at 150°C.

[0084] Test Example 1

[0085] The results of the metal element mass content of the adsorbents in Examples 1 to 7 are shown in Table 1.

[0086] Example 1 0.0841 Example 2 0.206 Example 3 0.127 Example 4 0.137 Example 5 0.956 Example 6 0.0769 Example 7 0.0837

[0087] According to the data in Table 1, the mass content of metal elements in the mesoporous silica particle adsorbent disclosed herein is all below 1%.

[0088] Test Example 2

[0089] The adsorbents in Examples 1-7 and Comparative Examples 1-2 were subjected to BET tests, and the test results are shown in Table 2.

[0090] Table 2

[0091]

[0092]

[0093] According to the data in Table 2, after the mesoporous silica particles are expanded by metal ions, the average pore size of the mesoporous silica increases. As the average pore size of silica increases, the microporous specific surface area gradually decreases until there is no microporous specific surface area in the silica. The most probable pore size distribution also varies when different metal ions are used for pore expansion.

[0094] Test Example 3

[0095] Dynamic pulse experiments were conducted on the adsorbents in Examples 1-7 and Comparative Examples 1-2 to determine the adsorption strength and adsorption-desorption rate of the adsorbents. The test results are shown in Tables 3 and 4.

[0096] The specific testing method is as follows: The pulse device mainly consists of a feeding system, a nitrogen system, and a heating furnace. The adsorption column is placed in an automatically temperature-controlled heating furnace. The adsorption column is a stainless steel straight tube with an inner diameter of 8mm and a length of 1000mm. The adsorbent content is 45g. The lower end of the adsorption column is connected to the feeding system and the nitrogen system. The outlet is connected to a pressure valve and an effluent collection port.

[0097] The experimental materials used were a self-made pulse liquid and desorbent. The pulse liquid consisted of n-butadiene, tetrahydronaphthalene, n-hexadecane, benzothiophene, methylnaphthalene, and n-nonane. The desorbent was composed of a desorbent and n-heptane; the desorbent was toluene, and n-heptane was used as a diluent. The mesoporous silica adsorbent, after pore expansion, was vacuum dried and activated before being packed into the adsorption column. Nitrogen gas was first introduced to replace the air in the adsorbent, followed by the introduction of desorbent to purge the system. After purging, the pressure valve was adjusted to 0.8 MPa, and the electric furnace was turned on to heat to the target temperature. Once the target temperature was reached, the introduction of desorbent was stopped, and a certain volume of pulse liquid was injected. Desorbent was then introduced again for elution. Desorbed samples were taken every 2 mL at the adsorption column outlet until all components in the pulse liquid were completely desorbed. The composition of the samples was analyzed by gas chromatography. A mass fraction curve of each component was plotted with the amount of desorbent used as the x-axis and the peak area of ​​each component in the elution as the y-axis. In the pulsed solution, the non-adsorbed component elutes first, and the midpoint of its half-peak width is taken as the zero point. The volume difference between the midpoint of the peak width of each adsorbed component and the zero point is the net retention volume ΔM of that component. R The rate of mutual displacement between the desorbent and the adsorbed components in the feed can be determined by the half-maximum width W of the mass fraction curves of each adsorbed component. 1 / 2 To characterize the separation, the resolution R of the sample is twice the ratio of the difference in net retention volume of the two components to the sum of their half-peak widths (HWHM). A higher resolution R indicates a stronger separation ability of the adsorbent for the two components. The adsorption rate Sa of a component is defined as the ratio of the ordinate on the left side of the envelope curve from 0.1 wt% to... max Rising to 0.9w max The required volume of desorbent for desorption, Sa, indicates that the smaller the volume of the adsorption curve and the faster the adsorption rate; the desorption rate Sd is defined as the ordinate on the right side of the envelope curve from 0.9w... max It dropped to 0.1w max The required volume of desorbent for desorption, of which w maxThe vertical axis represents the peak value of the envelope curve of the component. The smaller the value of Sd, the smaller the volume of the desorption curve and the faster the desorption rate. Sd / Sa characterizes whether the adsorption and desorption rates are consistent and whether the pulse peak shape is symmetrical. The closer Sd / Sa is to 1, the more symmetrical the peak shape. In the simulated moving bed industrial device, the adsorbed component can be desorbed more easily in the desorption zone of the simulated moving bed device, which is beneficial to improving the product yield.

[0098] Table 3 Pulse Data Results

[0099]

[0100] As shown in Table 3, the mesoporous silica adsorbent of this disclosure exhibits increased separation degree R after pore expansion by metal ions, enhanced selectivity for aromatic components, improved adsorption and desorption capabilities, and increased mass transfer rate. A comparison of Examples 1-5 and Examples 7 with Example 6 reveals that the mesoporous silica adsorbent achieves better separation of aromatic and alkane components at the preferred contact temperature and contact time specified in this disclosure.

[0101] Table 4 Adsorption-Desorption Rates

[0102]

[0103] According to the data in Table 4, after the mesoporous silica adsorbent of this disclosure is expanded by metal ions, the aromatic hydrocarbons Sa and Sd both decrease, the adsorption rate and desorption rate of the aromatic hydrocarbon components both increase, the Sd / Sa ratio decreases, and the adsorption rate and desorption rate are close to the same.

[0104] Test Example 4

[0105] The adsorbents of Example 5 and Comparative Example 1 were applied to a simulated moving bed, and the process route is as follows: Figure 3 As shown, diesel feedstock enters a four-zone simulated moving bed and is introduced with a desorbent, toluene. The four-zone simulated moving bed contains 12 beds, divided into desorption, purification, adsorption, and buffer zones. Each zone has a 3-4-3-2 bed configuration. Each bed is uniformly filled with the adsorbent from Example 5 or Comparative Example 1. The adsorption / desorption temperature is 100°C, the desorbent to feedstock mass ratio is 2:1, and the step time is 160 s. The experimental results of the simulated moving bed are shown in Table 5.

[0106] Aromatic purity = (Mass of aromatics in the extract / Total mass of the extract) × 100%

[0107] Aromatics yield = (Mass of aromatics in the extract / Mass of aromatics in the feed) × 100%

[0108] Table 5 Results of the simulated moving bed test

[0109]

[0110] According to the data in Table 5, when the aromatic content of the diesel feedstock is similar, compared with the adsorbent in Comparative Example 1, the adsorbent in Example 5 has a smaller loading amount, a larger feedstock throughput, a higher space velocity, a higher aromatic content in the extract E, a lower aromatic content in the raffinate R, and a higher aromatic yield. After metal ion pore expansion, the pore size of the mesoporous silica adsorbent disclosed in this invention becomes larger, the mass transfer rate of aromatic components within the adsorbent channels is accelerated, and a larger feedstock can be processed per unit volume of adsorbent.

[0111] The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0112] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0113] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. The use of mesoporous silica adsorbent in separating aromatics and alkanes from diesel fuel, characterized in that, The method for preparing mesoporous silica adsorbents includes the following steps: S1: Pre-acidification treatment is performed on mesoporous silica particles to obtain acidified silica particles; S2: The acidified silica particles are contacted with a metal ion solution to obtain a pore-expanded adsorbent; the metal in the pore-expanded adsorbent is removed and then dried; The removal of metals from the pore-expanding adsorbent includes rinsing the pore-expanding adsorbent with water until the aqueous solution is free of metal ions; The contact temperature in S2 is 70~100℃; the contact time is 6~12h.

2. The use according to claim 1, wherein, The pre-acidification treatment includes mixing mesoporous silica particles with an inorganic acid solution, reacting at a first temperature for 6-12 hours, filtering and washing the resulting material until the pH of the filtrate is 6.5-7.0, and drying the resulting solid to obtain the acidified silica particles. The first temperature is 40~100℃.

3. The use according to claim 2, wherein, The volume ratio of the mesoporous silica particles to the inorganic acid solution is 0.2 to 1:1, the mass percentage concentration of the inorganic acid solution is 1% to 10%, and the inorganic acid is one or more of hydrochloric acid, sulfuric acid, and nitric acid.

4. The use according to claim 1, wherein, The metal ion is one or more of Group IA metals, Group IIA metals and transition metals, and the concentration of the metal ion solution is 0.05~0.4 mol / L.

5. The use according to claim 1, wherein, The metal ion is one or more of sodium, cesium, calcium, copper, and silver.

6. The use according to claim 1, wherein, The preparation method further includes preparing the mesoporous silica particles using the following steps: (1) Mix the preheated water glass with sulfuric acid solution to obtain a mixed solution, and then stir at a second temperature for 6-12 hours to obtain silica sol; (2) The silica sol is rinsed and the rinsed silica sol is mixed with water to obtain silica water slurry; the silica water slurry is formed into mesoporous silica particles. The second temperature is 60~80℃; the mesoporous silica particles are spherical particles.

7. The use according to claim 6, wherein, (1) The concentration of the sulfuric acid solution is 0.1~1 mol / L; the mass concentration of Na2O in the water glass is 0.01~0.10 g / g, and the mass concentration of SiO2 is 0.10~0.50 g / g.

8. The use according to claim 6, wherein, (2) The rinsing includes rinsing with water to make the pH of the silica sol 6~7; the ratio of the rinsed silica sol to the water in the silica slurry is 1:0.5~2; The process of molding silica slurry into mesoporous silica particles includes using spray drying or air granulation methods to mold silica slurry into spherical particles. The size of the mesoporous silica particles is 200~900μm.

9. The use according to claim 6, wherein, The size of the mesoporous silica particles is 250~600μm.

10. The use according to claim 1, wherein, The mesoporous silica adsorbent contains more than 99% silica by mass and less than 1% metal elements by mass. The most probable pore size of the mesoporous silica adsorbent is 2~10 nm.

11. The use according to claim 10, wherein, The mesoporous silica adsorbent has a BET specific surface area of ​​350~800 m². 2 / g, microporous specific surface area is 500m² 2 / g or less, with an external surface area of ​​260~750m² 2 / g, with an average pore size of 2~7nm and a micropore volume of 1cm³. 3 The particle size is below / g and the particle size is 250~600μm.

12. The use according to claim 1, wherein, The aromatic and alkane components in diesel fuel are separated by a simulated moving bed. The operating conditions of the simulated moving bed include: the desorbent used is one of benzene, toluene, or o-xylene; the mass ratio of the desorbent to the diesel feedstock is 1~3:1; and the adsorption-desorption temperature is 80~200℃.

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