Ag-zsm-5 molecular sieve adsorbent for separating fischer-tropsch synthesis oil into alkane and alkene, preparation method and application thereof

Abstract

The application discloses an Ag-ZSM-5 molecular sieve adsorbent for separating and adsorbing Fischer-Tropsch synthesis oil alkane and alkene, which comprises Ag, a binder and ZSM-5 molecular sieve, and the mass ratio of Ag, the binder and ZSM-5 molecular sieve is (1-10):(10-20):(70-89). The preparation method comprises the following steps: alkali treatment, agglomeration molding, drying and calcination, silver ion exchange, drying and calcination. In the application, Ag is impregnated and loaded on the ZSM-5 molecular sieve, the pi complexation of Ag to the double bond of alkene and the high silicon-aluminum ratio (Si / Al=44-46) of the ZSM-5 molecular sieve are fully utilized, the adsorption selectivity to alpha-alkene is improved, the isomerization and oligomerization reactivity of alpha-alkene in the adsorption separation process is reduced, the adsorbent for separating and adsorbing Fischer-Tropsch synthesis oil alkane and alkene to produce high-purity alpha-alkene is prepared, and the adsorbent has the characteristics of high adsorption capacity, high alpha-alkene selectivity, fast adsorption and desorption rate, small desorption agent consumption and low separation energy consumption.

Description

Technical Field

[0001] This invention relates to the field of adsorption separation technology, specifically to Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, its preparation method, and its application. Background Technology

[0002] Fischer-Tropsch synthetic oil products contain a large amount of valuable chemical raw materials—olefins. Olefins are key raw materials for the production of other fine chemical products and have a significant impact on their downstream industries. Currently, the subsequent processing methods for Fischer-Tropsch synthetic oil products, both domestically and internationally, mainly focus on distillation and rectification.

[0003] Currently, the industry mainly uses extractive distillation to separate long-chain α-olefins from n-alkanes. However, because α-olefins and their n-alkanes with the same number of carbon atoms have very similar structures, with a boiling point difference of only 1°C to 5°C, and they often exhibit azeotropic phenomena, this separation method suffers from drawbacks such as long process time and high energy consumption. In addition, a single type of extractant is difficult to meet the separation requirements of multi-carbon-number olefins and alkanes in Fischer-Tropsch synthesis oils.

[0004] Compared with separation technologies such as distillation, adsorption separation has advantages such as large processing capacity and low energy consumption. At the same time, a single adsorbent can often be used to separate α-olefins and n-alkanes with multiple carbon numbers. This feature greatly enhances the application range of adsorption technology, making it a promising industrial technology in the field of Fischer-Tropsch synthesis oil separation.

[0005] The UOP Olex process is a process for separating straight-chain olefins from petroleum-based olefins and n-alkanes. The range of feedstocks that can be separated can be up to C10. 18 This process involves the separation of n-alkanes and n-olefins using a continuous simulated moving bed operation. Currently, there are no industrial application examples of its use in the Fischer-Tropsch synthesis for the separation of alkane and olefin to produce high-purity α-olefins. The process is based on US Patent Publication No. 3510423, with C... 10 ~C 15Using a mixture of alkanes and alkenes as raw materials, olefins are separated through a simulated moving bed adsorption separation process. The adsorbent is an Ag-exchanged X- or Y-type molecular sieve, and the purity of the olefin product can reach 98%. US Patent No. 3718580 discloses a method for preparing copper-exchanged X-type zeolites and a separation method using this method. This method involves the selective separation of olefins from saturated hydrocarbons, using an X-type zeolite with copper cations at some of its cation exchange sites. Ag and Cu have a π-complexing effect on the olefin double bonds, which improves the adsorption selectivity for α-olefins. US 5276246 describes the separation of n-olefins from a mixture with branched olefins using a high-silica zeolite molecular sieve (e.g., silica zeolite, ZSM-5, etc.) with low acid catalytic reactivity. This molecular sieve selectively adsorbs n-olefins. Such high silica-to-alumina ratio molecular sieves essentially lack active acidic sites, i.e., they are not catalytically active for olefin isomerization and oligomerization reactions.

[0006] Domestic researchers have also attempted to apply simulated moving bed adsorption separation technology to the separation of alkane and olefin in coal-based Fischer-Tropsch synthesis oil. Patent publication number CN111647423 provides a method for separating α-olefins using a simulated moving bed. This method includes using coal-based Fischer-Tropsch synthesis oil as raw material, targeting olefins with 9-18 carbon atoms (N), and undergoing pretreatment, fractionation, alkane and olefin separation, and isomer separation to obtain high-purity α-olefin products.

[0007] Patent CN115779492 discloses a method for determining process parameters of a simulated moving bed separation process and a method for separating long-chain α-olefins / alkanes. The method employs a fixed bed for the first separation treatment of the materials to be separated, determining the adsorption temperature, adsorption pressure, and the first feed flow rate, desorbent feed flow rate, and first discharge flow rate of the fixed bed. A simulated moving bed is then used for the second separation treatment, determining the adsorption temperature, adsorption pressure, and the second feed flow rate, desorbent feed flow rate, extract flow rate, and raffinate flow rate of the simulated moving bed based on the above results. A second component analysis is performed on the material in the raffinate discharge unit to determine the state maintenance time of the simulated moving bed's feed and discharge units. This allows for the determination of process parameters for separating different material systems using a simulated moving bed, thereby achieving effective material separation and improving the purity and yield of the separated materials.

[0008] Patent CN111001382 discloses a method for preparing a Fischer-Tropsch oil alkane-olefin separation adsorbent. The adsorbent includes a pre-adsorbent and a main adsorbent. The pre-adsorbent removes oxygen-containing organic matter from the Fischer-Tropsch synthetic oil. The resulting refined alkane-olefin mixture is then subjected to deep adsorption separation by the main adsorbent through a simulated moving bed process.

[0009] However, the aforementioned coal-based Fischer-Tropsch synthesis alkane-olefin separation adsorbents generally suffer from low adsorption selectivity and are prone to olefin isomerization and oligomerization reactions, thus failing to meet the requirements for producing high-purity α-olefins. Summary of the Invention

[0010] To overcome the shortcomings of the prior art, the present invention aims to provide an Ag-ZSM-5 molecular sieve oleanene separation adsorbent for Fischer-Tropsch synthesis, its preparation method, and its application. By impregnating and loading Ag onto ZSM-5 molecular sieves, the π-complexation effect of Ag on olefin double bonds and the high silica-to-alumina ratio (Si / Al = 44-46) of ZSM-5 molecular sieve are fully utilized to improve the adsorption selectivity for α-olefins and reduce the isomerization and oligomerization reactivity of α-olefins during the adsorption separation process. This adsorbent is used for the separation of oleanenes in Fischer-Tropsch synthesis to produce high-purity α-olefins. The adsorbent features high adsorption capacity, high α-olefin selectivity, fast adsorption-desorption rate, low desorbent dosage, and low separation energy consumption.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, wherein the adsorbent comprises Ag, binder, and ZSM-5 molecular sieve, and by mass ratio, Ag: binder: ZSM-5 molecular sieve = (1-10): (10-20): (70-89).

[0013] The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Al n Si 96-n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

[0014] The binder is one or more of kaolin, attapulgite, and silica sol in any proportion.

[0015] The preparation method of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent includes the following steps:

[0016] Step 1: Place the ZSM-5 molecular sieve raw powder in NaOH solution and let it stand and soak for 10-12 hours at 80-95℃. Then wash, dry and calcine in sequence to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution is (1-2):(5-10). The mass percentage concentration of the NaOH solution is 0.2-7.4 wt.%.

[0017] Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with binder and additives, and add deionized water to mix evenly and agglomerate into granules; by mass ratio, alkali-treated ZSM-5 molecular sieve: binder: additives: deionized water = (70-89): (10-20): (1-2): (10-20);

[0018] Step 3: Select particles with a diameter of 20-40 mesh from Step 2, and dry and calcine them sequentially to obtain the adsorbent precursor;

[0019] Step 4: Impregnate an equal volume of the adsorbent precursor obtained in Step 3 in AgNO3 solution for 4-10 hours to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution ratio is 1:(0.5-0.6) by mass; the mass percentage concentration of the AgNO3 solution is 1.7-14.5 wt.%.

[0020] Step 5: The adsorbent precursor impregnated with silver nitrate in Step 4 is dried and calcined sequentially to obtain Ag-ZSM-5 adsorbent.

[0021] The drying temperature in step 1 is 100-150℃, and the time is 10-15h; the calcination temperature is 200-400℃, and the time is 2-5h.

[0022] The binder in step 2 is one or more of kaolin, attapulgite, and silica sol in any proportion; the additive is one or more of guar gum powder, soluble starch, and carboxymethyl cellulose in any proportion.

[0023] The agglomeration method for forming particles in step 2 is extrusion molding or ball rolling molding.

[0024] The drying temperature in step 3 is 100-150℃, and the time is 2-5 hours; the calcination temperature is 400-600℃, and the time is 3-6 hours.

[0025] The drying temperature in step 5 is 100-150℃, and the time is 5-10h; the calcination temperature is 300-400℃, and the time is 2-4h.

[0026] The application of Ag-ZSM-5 molecular sieve adsorbent for the separation of alkane and alkene in Fischer-Tropsch synthesis oil is demonstrated in a simulated moving bed alkane and alkene separation process for Fischer-Tropsch synthesis oil.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The present invention further reduces the active acid sites on the surface of the high silica-alumina ratio ZSM-5 molecular sieve by alkali treatment in step 1. Compared with the prior art, this reduces the isomerization and oligomerization activity of α-olefins in the adsorption and separation process.

[0029] 2. In step 4, the present invention loads Ag onto the alkali-treated ZSM-5 molecular sieve, giving full play to the π-complexation effect of Ag on olefin double bonds, thereby improving the adsorption selectivity for α-olefins compared with the prior art.

[0030] In summary, this invention addresses the common problems of low adsorption selectivity and olefin isomerization and oligomerization reactions in existing coal-based Fischer-Tropsch synthesis olean-alkane separation adsorbents. It provides an Ag-exchange ZSM-5 molecular sieve adsorbent that can be used in a simulated moving bed process for Fischer-Tropsch synthesis olean-alkane separation. This significantly improves the purity of α-olefin products, reduces the isomerization and oligomerization activity of α-olefins during adsorption separation, and achieves efficient separation of α-olefins and alkanes. Compared with existing technologies, this adsorbent features high adsorption capacity, high α-olefin selectivity, fast adsorption-desorption rate, low desorbent dosage, and low separation energy consumption. Detailed Implementation

[0031] The present invention will now be described in detail with reference to embodiments and performance tests.

[0032] Example 1

[0033] Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, wherein the adsorbent comprises Ag, kaolin, and ZSM-5 molecular sieve, and the mass ratio of Ag:kaolin:ZSM-5 molecular sieve is 1:10:70.

[0034] The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Al n Si 96-n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

[0035] The preparation method of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent includes the following steps:

[0036] Step 1: Prepare ZSM-5 molecular sieve raw powder (Si / Al = 44-46, loss on ignition 0-5%, S...) BET ≥310m 2ZSM-5 molecular sieve powder (containing 0.53-0.58 nm pore size) was placed in NaOH solution and soaked at 80℃ for 10 h. Then, it was washed, dried, and calcined sequentially to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution was 1:5; the mass percentage concentration of the NaOH solution was 0.2 wt.%; the drying temperature was 100℃ for 10 h in air; and the calcination temperature was 200℃ for 2 h. The alkali treatment reduced the acidity of the zeolite molecular sieve, inhibiting its catalytic activity for isomerization and oligomerization of α-olefins.

[0037] Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with kaolin (moisture content 15%) and carboxymethyl cellulose, add deionized water and mix evenly, then extrude into strips (diameter 2mm); by mass ratio, alkali-treated ZSM-5 molecular sieve: kaolin: carboxymethyl cellulose: deionized water = 70:10:1:10;

[0038] Step 3: Select the 20-mesh particles from Step 2, and dry and calcine them sequentially to obtain the adsorbent precursor; the drying temperature is 100℃, and the drying time is 2 hours in air; the calcination temperature is 400℃, and the calcination time is 3 hours.

[0039] Step 4: The adsorbent precursor (water absorption rate 0.5 ml / g) obtained in Step 3 is immersed in AgNO3 solution for 4 hours to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution = 1:0.5 by mass ratio; the mass percentage concentration of the AgNO3 solution is 1.7 wt.%.

[0040] Step 5: Wash the adsorbent precursor impregnated with silver nitrate in Step 4 with deionized water until pH=7, and then dry and calcine it sequentially to obtain Ag-ZSM-5 adsorbent A-1; the drying temperature is 100℃ and the drying time is 5h in air; the calcination temperature is 300℃ and the time is 2h.

[0041] The application of Ag-ZSM-5 molecular sieve adsorbent for the separation of alkane and alkene in Fischer-Tropsch synthesis oil is demonstrated in a simulated moving bed alkane and alkene separation process for Fischer-Tropsch synthesis oil.

[0042] Example 2

[0043] Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, wherein the adsorbent comprises Ag, attapulgite, and ZSM-5 molecular sieve, and the mass ratio of Ag:attapulgite:ZSM-5 molecular sieve is 3.25:12.5:74.75.

[0044] The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Aln Si 96-n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

[0045] The preparation method of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent includes the following steps:

[0046] Step 1: Prepare ZSM-5 molecular sieve raw powder (Si / Al = 44-46, loss on ignition 0-5%, S...) BET ≥310m 2 ZSM-5 molecular sieve powder (containing 0.53-0.58 nm pore size) was placed in NaOH solution and soaked at 83.75℃ for 10.5 h. Then, it was washed, dried, and calcined sequentially to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution was 1.25:6.25; the mass percentage concentration of the NaOH solution was 2 wt.%; the drying temperature was 112.5℃ for 11.25 h in air; and the calcination temperature was 250℃ for 2.75 h. This process reduced the acidity of the zeolite molecular sieve and inhibited its catalytic activity for isomerization and oligomerization of α-olefins.

[0047] Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with attapulgite clay (moisture content 15%) and carboxymethyl cellulose, add deionized water and mix evenly, then roll into balls; by mass ratio, alkali-treated ZSM-5 molecular sieve:attapulgite clay:carboxymethyl cellulose:deionized water = 74.75:12.5:1.25:12.5;

[0048] Step 3: Select the 25-mesh particles from Step 2, and sequentially dry and calcine them to obtain the adsorbent precursor; the drying temperature is 112.5℃, and the drying time in air is 2.75h; the calcination temperature is 450℃, and the time is 3.75h.

[0049] Step 4: The adsorbent precursor (water absorption rate 0.5 ml / g) obtained in Step 3 is immersed in AgNO3 solution for 5.5 h to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution = 1:0.53 by mass ratio; the mass percentage concentration of the AgNO3 solution is 4.9 wt.%.

[0050] Step 5: Wash the adsorbent precursor impregnated with silver nitrate in Step 4 with deionized water until pH=7, and then dry and calcine it sequentially to obtain Ag-ZSM-5 adsorbent A-2; the drying temperature is 112.5℃ and the drying time in air is 6.25h; the calcination temperature is 325℃ and the time is 2.5h.

[0051] The application of Ag-ZSM-5 molecular sieve adsorbent for the separation of alkane and alkene in Fischer-Tropsch synthesis oil is demonstrated in a simulated moving bed alkane and alkene separation process for Fischer-Tropsch synthesis oil.

[0052] Example 3

[0053] Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, wherein the adsorbent comprises Ag, silica sol, and ZSM-5 molecular sieve, and the mass ratio of Ag:silica sol:ZSM-5 molecular sieve is 5.5:15:79.5.

[0054] The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Al n Si 96-n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

[0055] The preparation method of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent includes the following steps:

[0056] Step 1: Prepare ZSM-5 molecular sieve raw powder (Si / Al = 44-46, loss on ignition 0-5%, S...) BET ≥310m 2 ZSM-5 molecular sieve powder (containing 0.53-0.58 nm pore size) was placed in NaOH solution and soaked at 87.5℃ for 11 h. Then, it was washed, dried, and calcined sequentially to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution was 1.5:7.5; the mass percentage concentration of the NaOH solution was 3.8 wt.%; the drying temperature was 125℃, and the drying time in air was 12.5 h; the calcination temperature was 300℃, and the time was 3.5 h. This process reduced the acidity of the zeolite molecular sieve and inhibited its catalytic activity for the isomerization and oligomerization of α-olefins.

[0057] Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with silica sol (solid content 25%) and carboxymethyl cellulose, add deionized water and mix evenly, then extrude into strips (diameter 2mm); by mass ratio, alkali-treated ZSM-5 molecular sieve: silica sol: carboxymethyl cellulose: deionized water = 79.5:15:1.5:15;

[0058] Step 3: Select the 30-mesh particles from Step 2, and dry and calcine them sequentially to obtain the adsorbent precursor; the drying temperature is 125℃, and the drying time in air is 3.5h; the calcination temperature is 500℃, and the calcination time is 4.5h.

[0059] Step 4: The adsorbent precursor (water absorption rate 0.5 ml / g) obtained in Step 3 is immersed in AgNO3 solution for 7 h to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution = 1:0.55 by mass ratio; the mass percentage concentration of the AgNO3 solution is 8.1 wt.%.

[0060] Step 5: Wash the adsorbent precursor impregnated with silver nitrate in Step 4 with deionized water until pH=7, and then dry and calcine it sequentially to obtain Ag-ZSM-5 adsorbent A-3; the drying temperature is 125℃ and the drying time is 7.5h in air; the calcination temperature is 350℃ and the time is 3h.

[0061] The application of Ag-ZSM-5 molecular sieve adsorbent for the separation of alkane and alkene in Fischer-Tropsch synthesis oil is demonstrated in a simulated moving bed alkane and alkene separation process for Fischer-Tropsch synthesis oil.

[0062] Example 4

[0063] Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, wherein the adsorbent comprises Ag, kaolin, and ZSM-5 molecular sieve, and the mass ratio of Ag:kaolin:ZSM-5 molecular sieve is 7.75:17.5:84.25.

[0064] The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Al n Si 96-n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

[0065] The preparation method of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent includes the following steps:

[0066] Step 1: Prepare ZSM-5 molecular sieve raw powder (Si / Al = 44-46, loss on ignition 0-5%, S...) BET ≥310m 2 ZSM-5 molecular sieve powder (containing 0.53-0.58 nm pore size) was placed in NaOH solution and soaked at 91.25℃ for 11.5 h. Then, it was washed, dried, and calcined sequentially to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution was 1.75:8.75; the mass percentage concentration of the NaOH solution was 5.6 wt.%; the drying temperature was 137.5℃ for 13.75 h in air; and the calcination temperature was 350℃ for 4.25 h. This process reduced the acidity of the zeolite molecular sieve and inhibited its catalytic activity for isomerization and oligomerization of α-olefins.

[0067] Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with kaolin (moisture content 15%) and carboxymethyl cellulose, add deionized water and mix evenly, then roll into balls; by mass ratio, alkali-treated ZSM-5 molecular sieve: kaolin: carboxymethyl cellulose: deionized water = 84.25: 17.5: 1.75: 17.5;

[0068] Step 3: Select the 35-mesh particles from Step 2, and sequentially dry and calcine them to obtain the adsorbent precursor; the drying temperature is 137.5℃, and the drying time in air is 4.25h; the calcination temperature is 550℃, and the time is 5.25h.

[0069] Step 4: The adsorbent precursor (water absorption rate 0.5 ml / g) obtained in Step 3 is immersed in AgNO3 solution for 8.5 h to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution = 1:0.58 by mass ratio; the mass percentage concentration of the AgNO3 solution is 11.3 wt.%.

[0070] Step 5: Wash the adsorbent precursor impregnated with silver nitrate in Step 4 with deionized water until pH=7, and then dry and calcine it sequentially to obtain Ag-ZSM-5 adsorbent A-4; the drying temperature is 137.5℃ and the drying time in air is 8.75h; the calcination temperature is 375℃ and the time is 3.5h.

[0071] The application of Ag-ZSM-5 molecular sieve adsorbent for the separation of alkane and alkene in Fischer-Tropsch synthesis oil is demonstrated in a simulated moving bed alkane and alkene separation process for Fischer-Tropsch synthesis oil.

[0072] Example 5

[0073] Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, wherein the adsorbent comprises Ag, kaolin, and ZSM-5 molecular sieve, and the mass ratio of Ag:kaolin:ZSM-5 molecular sieve is 10:20:89.

[0074] The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Al n Si 96-n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

[0075] The preparation method of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent includes the following steps:

[0076] Step 1: Prepare ZSM-5 molecular sieve raw powder (Si / Al = 44-46, loss on ignition 0-5%, S...) BET ≥310m 2 ZSM-5 molecular sieve powder (containing 0.53-0.58 nm pore size) was placed in NaOH solution and soaked at 95℃ for 12 h. Then, it was washed, dried, and calcined sequentially to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution was 2:10; the mass percentage concentration of the NaOH solution was 7.4 wt.%; the drying temperature was 150℃ for 15 h in air; and the calcination temperature was 400℃ for 5 h. This process reduced the acidity of the zeolite molecular sieve and inhibited its catalytic activity for the isomerization and oligomerization of α-olefins.

[0077] Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with kaolin (moisture content 15%) and guar gum powder, add deionized water and mix evenly, then extrude into strips (diameter 2mm); by mass ratio, alkali-treated ZSM-5 molecular sieve: kaolin: guar gum powder: deionized water = 89:20:2:20;

[0078] Step 3: Select the 40-mesh particles from Step 2, and dry and calcine them sequentially to obtain the adsorbent precursor; the drying temperature is 150℃, and the drying time is 5 hours in air; the calcination temperature is 600℃, and the calcination time is 6 hours.

[0079] Step 4: The adsorbent precursor (water absorption rate 0.5 ml / g) obtained in Step 3 is immersed in AgNO3 solution for 10 h to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution = 1:0.6 by mass ratio; the mass percentage concentration of the AgNO3 solution is 14.5 wt.%.

[0080] Step 5: Wash the adsorbent precursor impregnated with silver nitrate in Step 4 with deionized water until pH=7, and then dry and calcine it sequentially to obtain Ag-ZSM-5 adsorbent A-5; the drying temperature is 150℃ and the drying time is 10h in air; the calcination temperature is 400℃ and the time is 4h.

[0081] The application of Ag-ZSM-5 molecular sieve adsorbent for the separation of alkane and alkene in Fischer-Tropsch synthesis oil is demonstrated in a simulated moving bed alkane and alkene separation process for Fischer-Tropsch synthesis oil.

[0082] The performance of the Ag-ZSM-5 adsorbents prepared in the five examples is measured below.

[0083] The determination method is as follows:

[0084] The separation performance of the adsorbent was evaluated using a fixed-bed adsorption-desorption apparatus with a length of 200 mm and an inner diameter of 10 mm. After drying and dehydration, 5 g of the adsorbent was loaded into the adsorption-desorption apparatus for evaluation. Alkane / olefin separation experiments were conducted at a temperature of 50 °C, a pressure of 0.8 MPa, and methylcyclohexane as the desorbent. Adsorption was performed with continuous feed at a flow rate of 0.5 ml / min. Desorption was initiated when the composition of the effluent no longer changed, indicating adsorption saturation. The desorbent was continuously fed at a flow rate of 0.01 ml / min. The content of each component was determined using an Agilent 7890 gas chromatograph.

[0085] The simulated oil composition was: 1-hexene, 50% by mass, analytical grade; n-hexane, 50% by mass, analytical grade. The eluent, methylcyclohexane, was analytical grade.

[0086] The desorbent in a simulated moving bed is the same as the mobile phase in fixed-bed single-column chromatography. Screening for suitable desorbents through fixed-bed single-column chromatography is crucial for the design of the simulated moving bed. In fixed-bed single-column chromatography, the resolution R is a comprehensive indicator reflecting column efficiency and selectivity, and is also an important parameter for evaluating desorbents. It can be calculated using the following formula:

[0087]

[0088] Where t1 and t2 are the retention times of the corresponding substances in the chromatographic column, and w1 and w2 are the peak widths of the components, with 2 for 1-hexene and 1 for n-hexane. When R = 1, the two peaks are basically separated, with a bare peak area of ​​95.4% and an inner peak overlap of about 2%. When R = 1.5, the bare peak area is 99.7%. R ≥ 1.5 is considered complete separation.

[0089] The time required for the concentration of all analytes in the effluent to drop to 0 is the desorption time.

[0090] The results of the adsorbent performance test are shown in Table 1.

[0091] Table 1. Adsorbent performance test results

[0092]

[0093]

[0094] In summary, after alkali treatment and Ag loading, the separation degree R of the adsorbent... 烷 / 烯 Both olefin desorption time and desorption time were improved, especially for adsorbent A-4 (R 烷 / 烯=1.54) reached the standard of complete separation, indicating that the present invention significantly improves the purity of α-olefin products, reduces the isomerization and oligomerization reactivity of α-olefins in the adsorption separation process, and realizes the efficient separation of α-olefins and alkanes. Compared with the prior art, the adsorbent has the characteristics of high adsorption capacity, high α-olefin selectivity, fast adsorption and desorption rate, low desorbent dosage, and low separation energy consumption.

Claims

1. A method for preparing an Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, characterized in that, Includes the following steps: Step 1: Place the ZSM-5 molecular sieve raw powder in NaOH solution and let it stand and soak for 10-12 hours at 80-95℃. Then wash, dry and calcine in sequence to obtain alkali-treated ZSM-5 molecular sieve raw powder. The mass ratio of ZSM-5 molecular sieve to NaOH solution is (1-2):(5-10). The mass percentage concentration of the NaOH solution is 0.2-7.4 wt.%. Step 2: Mix the alkali-treated ZSM-5 molecular sieve raw powder obtained in Step 1 with binder and additives, and add deionized water to mix evenly and agglomerate into granules; by mass ratio, alkali-treated ZSM-5 molecular sieve: binder: additives: deionized water = (70-89): (10-20): (1-2): (10-20); Step 3: Select particles with a diameter of 20-40 mesh from Step 2, and dry and calcine them sequentially to obtain the adsorbent precursor; Step 4: Impregnate an equal volume of the adsorbent precursor obtained in Step 3 in AgNO3 solution for 4-10 hours to obtain the impregnated adsorbent precursor; the adsorbent precursor: AgNO3 solution ratio is 1:(0.5-0.6) by mass; the mass percentage concentration of the AgNO3 solution is 1.7-14.5 wt.%. Step 5: The adsorbent precursor impregnated with silver nitrate in step 4 is dried and calcined sequentially to obtain Ag-ZSM-5 adsorbent. The adsorbent includes Ag, binder, and ZSM-5 molecular sieve, with the mass ratio of Ag: binder: ZSM-5 molecular sieve being (1-10): (10-20): (70-89).

2. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 1, characterized in that, The ZSM-5 molecular sieve serves as the carrier for the adsorbent, and its cell composition is: Na n Al n Si 96- n O 192 ·16H2O, where n is the number of Al atoms in the unit cell, n=2.04-2.13, that is, Si / Al=44-46.

3. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 1, characterized in that, The binder is one or more of kaolin, attapulgite, and silica sol in any proportion.

4. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 1, characterized in that, The drying temperature in step 1 is 100-150℃, and the time is 10-15h; the calcination temperature is 200-400℃, and the time is 2-5h.

5. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 4, characterized in that, The additive is one or more of guar gum powder, soluble starch and carboxymethyl cellulose in any proportion.

6. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 4, characterized in that, The agglomeration method for forming particles in step 2 is extrusion molding or ball rolling molding.

7. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 4, characterized in that, The drying temperature in step 3 is 100-150℃, and the time is 2-5 hours; the calcination temperature is 400-600℃, and the time is 3-6 hours.

8. The preparation method of the Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent according to claim 4, characterized in that, The drying temperature in step 5 is 100-150℃, and the time is 5-10h; the calcination temperature is 300-400℃, and the time is 2-4h.

9. The application of Ag-ZSM-5 molecular sieve Fischer-Tropsch synthesis oleanene separation adsorbent, characterized in that, It is applied to the simulated moving bed alkane-alkene separation process in Fischer-Tropsch synthesis oil.

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