A true moving bed diesel adsorptive separation system and method

Abstract

The application discloses a real moving bed diesel adsorption separation system and method. The application realizes the separation of alkanes and aromatics in diesel by a real moving bed process, in which the raw diesel is firstly introduced into an adsorption chamber to be in countercurrent contact with aromatic adsorbents, the aromatic adsorbents adsorb the aromatics in the diesel, and then the aromatic components adsorbed by the adsorbents are transported to a regeneration chamber, and the desorbents in the regeneration chamber replace the aromatics, so that the aromatic components are obtained, and finally the separation of the alkanes and the aromatics in the diesel is realized. The method can realize the efficient separation of diesel components at low cost and simple process, the content of the aromatics in the aromatic product is greater than or equal to 95 wt.%, and the content of the aromatics in the non-aromatic components is less than or equal to 5 wt.%.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of adsorption separation technology, and particularly relates to a system and method for separating diesel aromatic hydrocarbon and alkane components by using a real moving bed process. BACKGROUND

[0002] Diesel is a light petroleum product, a complex hydrocarbon mixture, and is a fuel for diesel engines. Diesel is mainly composed of diesel fractions produced by processes such as crude oil distillation, catalytic cracking, thermal cracking, hydrocracking, and petroleum coking.

[0003] With increasing emphasis on environmental protection, in order to reduce automobile exhaust pollution, as with the development trend of gasoline quality, it has become inevitable to improve diesel quality. The attitude of countries and regions is almost unanimous in substantially reducing the sulfur content of diesel for vehicles, and the main reason is that the sulfur contained in diesel directly affects the composition of particulate matter in the exhaust of diesel vehicles. This particulate matter is mainly carbon (smoke), soluble organic matter, and sulfate. The higher the sulfur content in diesel, the more sulfate is generated, which can easily cause respiratory diseases in humans and may cause cancer. If a high-efficiency exhaust converter is installed on a diesel vehicle, the sulfur in the diesel can easily poison the catalyst, greatly reducing its function and increasing exhaust emissions. In addition, the aromatic hydrocarbons in diesel are also one of the reasons for the high concentration of ammonia oxides and particulate matter in diesel exhaust emissions. Therefore, it is expected that the limit on the content of aromatic hydrocarbons and polycyclic aromatic hydrocarbons in diesel for vehicles will gradually become more stringent in the future. The polycyclic aromatic hydrocarbon content of diesel produced in catalytic cracking, coking, and catalytic cracking unit processes is much higher than 11%, which does not meet the requirement in the national standard GB19147-2016 that the polycyclic aromatic hydrocarbon content of diesel for vehicles should be no more than 11%. If the aromatic hydrocarbons and non-aromatic components in diesel are separated to obtain high-purity alkane and aromatic hydrocarbons, not only is the classification management of diesel components achieved, but also the raw materials for efficient conversion and accurate processing of diesel are provided, and the diesel-to-gasoline ratio of the refinery is reduced, improving the economic and social benefits of the enterprise.

[0004] CN1566284A discloses a method for diesel hydro-upgrading, which can improve the cetane number of diesel while reducing the aromatic hydrocarbon content. The diesel raw material and hydrogen enter a first reactor and are in contact with a non-noble metal hydro-upgrading catalyst, the reaction effluent of the first reactor is separated or not separated and enters a second reactor, and is in contact with a noble metal hydro-dearomatization catalyst, and the reaction effluent of the second reactor is separated to obtain diesel products. Although this method can achieve good de-aromatization effect, the process flow is relatively complex, and the investment and operating costs are high.

[0005] CN102465029A discloses a method for diesel hydrofining, under diesel hydrotreating conditions, the raw diesel and hydrogen are first introduced into a gas-liquid mixer through a heating furnace to make the hydrogen fully mixed with the raw oil, then into a first reactor to contact with a non-noble metal hydrofining catalyst under hydrofining conditions to carry out conventional hydrofining reaction, the reaction effluent is introduced into a gas stripping hydrogen mixing device to remove the dissolved hydrogen sulfide and ammonia in the oil and make the hydrogen reach a saturated state in the oil, then mixed with supplemental hydrogen to enter a second reactor to contact with a noble metal hydrofining catalyst to carry out deep de-aromatics reaction, and finally obtain clean diesel product. The two reactors of this method need to be operated at a high hydrogen to oil ratio and a low space velocity, and there are problems of high hydrogen consumption, low processing capacity of the device, etc.

[0006] CN1566284A discloses a method for diesel hydro-upgrading, which can increase the cetane number of diesel while reducing the aromatic content. The diesel raw material and hydrogen are introduced into a first reactor to contact with a non-noble metal hydro-upgrading catalyst, the reaction effluent of the first reactor is introduced into a second reactor with or without separation to contact with a noble metal hydro-dearomatization catalyst, and the reaction effluent of the second reactor is separated to obtain diesel product. This method can obtain good de-aromatic effect, but the process flow is relatively complex, and the investment and operating cost is high.

[0007] CN101328430A discloses a method for catalytic diesel hydro-upgrading. In the presence of hydrogen, the reaction temperature is 330-370℃, the hydrogen partial pressure is 6-9MPa, the hydrogen to oil volume ratio is 500:1-1000:1, and the liquid hourly space velocity is 1.0-2.0h-1; the diesel yield is above 97wt%, the aromatic removal rate of diesel is above 60%, the total sulfur and nitrogen removal rate is above 98.5%, and the density of the product is reduced by above 0.04g / cm3. The de-aromatic rate of this method is low, and the cetane number cannot directly meet the requirements of the national standard.

[0008] The above-mentioned diesel upgrading methods, whether hydrofining or hydro-upgrading technology, have problems of resource waste, low cetane number of product, high hydrogen consumption, high energy consumption, large equipment investment, etc. SUMMARY

[0009] In order to solve the above technical problems, the present application provides a real moving bed diesel adsorption separation system and method, which separates and processes diesel components through a real moving bed to obtain high-purity aromatic and non-aromatic components.

[0010] In a first aspect, the present application provides a real moving bed diesel adsorption separation system, which is realized by the following technical scheme.

[0011] A real moving bed diesel adsorption separation system, comprising a raw material tank, the raw material tank is connected with the feed inlet of the lower part of the moving bed adsorption chamber through a pipeline, the upper end of the moving bed adsorption chamber is connected with the adsorbent storage tank; the discharge port of the moving bed adsorption chamber is connected with the moving bed regeneration chamber through a slide valve, the upper end of the moving bed regeneration chamber is connected with the desorbent storage tank; the discharge port of the moving bed regeneration chamber is connected with the rectifying column.

[0012] Further, the moving bed adsorption chamber is also connected with a non-aromatic storage tank.

[0013] Further, the moving bed regeneration chamber is also connected with a regenerant storage tank, and the regenerant storage tank is connected with the adsorbent storage tank through a pipeline.

[0014] Further, the discharge port of the rectifying column is connected with the desorbent storage tank through a pipeline.

[0015] In a second aspect, the present application provides a real moving bed diesel adsorption separation method, which is realized by using the following technical scheme.

[0016] A real moving bed diesel adsorption separation method, comprising the following steps:

[0017] S1. The diesel raw material is sent into a pre-adsorption tower to remove sulfur-containing, nitrogen-containing compounds and impurities under the action of a pre-adsorbent;

[0018] S2. The diesel raw material after removing impurities is sent from the lower end to the moving bed adsorption chamber, and the aromatic adsorbent is sent from the upper end of the moving bed adsorption chamber, the aromatic adsorbent and the diesel raw material realize countercurrent contact, and the aromatic component and the non-aromatic component adsorbed by the adsorbent are obtained; the treatment temperature in the moving bed adsorption chamber is 50-100℃, and the adsorption pressure is 0.5-1.5MPa;

[0019] S3. The adsorbent adsorbed with aromatic hydrocarbons is intermittently discharged through a slide valve and enters the moving bed regeneration chamber, the desorbent is sent from the top of the moving bed regeneration chamber, the aromatic component on the adsorbent is washed and desorbed, and the desorbed aromatic component, the desorbent and the regenerated adsorbent are obtained; the treatment temperature of the moving bed regeneration chamber is 50-80℃, and the adsorption pressure is 0.5-1.5MPa;

[0020] S4. The desorbed aromatic component and the desorbent are used as an extract to realize the separation of aromatic hydrocarbons and non-aromatic components, and the aromatic product is obtained.

[0021] Further, the distillation range of the diesel raw material is 150-400℃.

[0022] Further, in step S1, the adsorbent bed temperature of the pre-adsorption tower is 30-150℃, the mass space velocity is 0.1-3.0h -1 , and the adsorption pressure is 0.1-5.0MPa.

[0023] Furthermore, in step S1, silica gel or 13X molecular sieve are selected as the pre-adsorbent.

[0024] Furthermore, in step S2, the aromatic adsorbent is selected from one or more of the following: metal-modified MCM-41 molecular sieve, metal-modified silica gel, and metal-modified 13X molecular sieve. The modified metal is selected from one or more of the following: K, Cs, Mg, Ca, Ba, Mo, and Ni.

[0025] Furthermore, in step S3, the desorbent is selected from one or more of benzene, toluene, o-xylene, m-xylene, cyclohexane, and methylcyclohexane.

[0026] Furthermore, the volumetric flow rate ratio of the adsorbent to the diesel feedstock entering the moving bed adsorption chamber is 1:(0.5-2.5); the mass flow rate ratio of the adsorbent to the desorbent entering the moving bed regeneration chamber is 1:(0.5-5).

[0027] This application has the following beneficial effects.

[0028] (1) The real moving bed process used in this invention is a green and efficient separation technology that can achieve efficient conversion of diesel fuel;

[0029] (2) The adsorption separation method of the present invention can separate components in diesel fuel under low pressure and low temperature. The process is a single tower adsorption process, which has the characteristics of being environmentally friendly and pollution-free, having mild reaction conditions, low investment, low energy consumption, and easy control.

[0030] (3) The adsorption separation method of the present invention achieves efficient separation of diesel components with low cost and simple process. The aromatic content in the aromatic product is ≥95wt.%, and the aromatic content in the non-aromatic components is ≤5wt.%.

[0031] (4) The alkanes separated by the adsorption separation method of this invention can be used as high cetane number components or as high-quality feedstock for catalytic ethylene cracking, increasing the production of low-carbon olefins; the separated cycloalkanes can be blended into diesel fuel as clean diesel fuel components or sold directly as non-aromatic solvents; the separated aromatics can be further separated into monocyclic and polycyclic aromatics, among which monocyclic aromatics can be used as feedstock for the lightening of heavy aromatics, and hydrogenated under medium and low pressure to produce light aromatics such as BTX or high-octane gasoline; polycyclic aromatics can be blended into high-aromatic solvent oil, and the market prospects for aromatic solvent oil in my country are broad, especially in the paint industry where the usage is quite considerable. The classified management of diesel components not only achieves the goal of efficient diesel conversion and reduces the diesel-to-gasoline ratio, but also makes reasonable use of the resources of each component of diesel fuel, creating objective economic benefits. Attached Figure Description

[0032] Figure 1 This is a connection diagram of the separation system of the present invention;

[0033] The components include: 1. Raw material tank; 2. Pump; 3. Moving bed adsorption chamber; 4. Adsorbent storage tank; 5. Non-aromatic storage tank; 6. Buffer tank; 7. Moving bed regeneration chamber; 8. Desorbent storage tank; 9. Regenerator storage tank; 10. Extraction liquid storage tank; and 11. Distillation column. Detailed Implementation

[0034] The present patent application will be further described below with reference to the accompanying drawings and embodiments.

[0035] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following preparation examples and examples are commercially available unless otherwise specified.

[0036] like Figure 1 As shown, a real moving bed diesel adsorption separation system includes a feed tank 1, a pump 2, a moving bed adsorption chamber 3, an adsorbent storage tank 4, a non-aromatic storage tank 5, a buffer tank 6, a moving bed regeneration chamber 7, a desorbent storage tank 8, a regenerator storage tank 9, an extractant storage tank 10, and a distillation column 11.

[0037] The raw material tank 1 is connected to the feed inlet at the bottom of the moving bed adsorption chamber 3 via a pipeline, and a pump 2 is installed on the pipeline. The upper end of the moving bed adsorption chamber 3 is connected to the adsorbent storage tank 4, and the upper part of the moving bed adsorption chamber 3 is also connected to the non-aromatic storage tank 5. The discharge port of the moving bed adsorption chamber 3 is connected to the moving bed regeneration chamber 7 via a slide valve. A buffer tank 6 may also be provided between the moving bed adsorption chamber 3 and the moving bed regeneration chamber 7. The upper end of the moving bed regeneration chamber 7 is connected to the desorbent storage tank 8. The moving bed regeneration chamber 7 is also connected to the regenerator storage tank 9, and the regenerator storage tank 9 is connected to the adsorbent storage tank 4 via a pipeline. The discharge port of the moving bed regeneration chamber 7 is connected to the distillation column 11, and an extractant storage tank 10 may also be provided between the moving bed regeneration chamber 7 and the distillation column 11. The discharge port of the distillation column 11 is connected to the desorbent storage tank 8 via a pipeline.

[0038] The actual moving bed of this invention consists of an adsorption chamber, a regeneration chamber, and a solid particle feeding and feed liquid delivery pipeline. The adsorption chamber and the regeneration chamber are connected in series via a slide valve. An adsorbent storage tank is located at the top of the adsorption chamber, connected via a delivery pipeline, and feed liquid delivery pipes are located at both ends of the bottom. The adsorbent enters the adsorption chamber from the storage tank downwards, while the feed liquid enters the adsorption chamber through the delivery pipeline, flowing upwards to the top. At this point, it forms a countercurrent contact with the falling adsorbent, allowing for adsorption, separation, regeneration, adsorption, and desorption processes to be performed at different temperatures according to process requirements. The relative movement direction between the liquid and particles in the reaction chamber is countercurrent, achieved using a special pressure control method.

[0039] Example 1

[0040] A real moving bed diesel adsorption separation method includes the following steps:

[0041] (1) The diesel feedstock first enters the pre-adsorption tower, and the sulfur-containing, nitrogen-containing compounds and gum impurities therein are removed under the action of the pre-adsorbent; the pre-adsorbent is selected from silica gel, the adsorbent bed temperature is 50°C, the mass space velocity is 0.1h -1 , and the adsorption pressure is 0.5MPa;

[0042] (2) The diesel feedstock after removal of impurities is sent to the moving bed adsorption chamber 3 by pump 2 and is fed from the lower end. At the same time, the aromatic adsorbent is fed from the upper end of the moving bed adsorption chamber 3 and moves downward under the action of gravity to realize countercurrent contact with the diesel feedstock. The aromatic components in the diesel are adsorbed by the adsorbent and move downward, and the remaining non-aromatic components are taken out as raffinate at the top of the adsorption chamber to obtain a non-aromatic product;

[0043] The aromatic adsorbent of this embodiment is a metal-modified MCM-41 molecular sieve, and the metal oxide is introduced by impregnation method; after the metal salt solution is prepared, it is placed in a beaker, the carrier is MCM-41 molecular sieve, the impregnation temperature is 80°C, the impregnation time is 6h, and finally the impregnated molecular sieve is washed, dried at 120°C for 4h, and calcined at 550°C for 6h; the modified metal is K, Cs and Mg, wherein the content of K2O is 0.5wt%, the content of Cs2O is 0.5wt%, and the content of MgO is 0.5wt%; the specific surface area is 920m 2 / g, the pore volume is 0.75cm 3 / g, and the average pore size is 4.8nm; the mass flow rate ratio of the adsorbent to the feedstock is 1:0.8; the reaction temperature and the adsorption pressure of the moving bed adsorption chamber 3 are shown in Table 2;

[0044] (3) The adsorbent adsorbed with aromatics is intermittently discharged from the bottom of the moving bed adsorption chamber 3 through a slide valve and enters the moving bed regeneration chamber 7. The desorbent is fed into the top of the moving bed regeneration chamber 7 to flush and desorb the aromatic components on the adsorbent, so that the adsorbent is regenerated. The desorbed aromatic components and the desorbent are taken out from the bottom of the moving bed regeneration chamber 7 as the extracted liquid. The regenerated adsorbent is then fed into the top of the moving bed adsorption chamber 3 again through the feeding hopper for recycling.

[0045] The switching time of the slide valve of this embodiment is shown in Table 2; the desorbent is 70% methylcyclohexane and 30% toluene; the mass flow rate ratio of the adsorbent after adsorption to the desorbent is 1:1; the reaction temperature in the moving bed regeneration chamber 7 is 60°C, and the adsorption pressure is 0.8MPa.

[0046] (4) The extracted liquid is cut with the desorbent to obtain an aromatic product.

[0047] The diesel feedstock composition analysis is shown in Table 1 for No. 1 diesel, the actual moving bed adsorption separation process conditions are shown in Table 2, and the evaluation results are shown in Table 3.

[0048] Example 2

[0049] A true moving bed diesel adsorption separation method, the difference between this embodiment and example 1 is:

[0050] (1) the aromatic hydrocarbon adsorbent is metal modified silica gel, sodium silicate is dissolved in water, then NaOH is added to form a gel. After the gel is formed, a metal salt solution is prepared, and stirring is continuously added. After filtration, drying and calcination are carried out to remove water and organic matter, and finally metal modified silica gel is obtained; the reaction temperature is 80℃, the stirring time is 12h, and finally 120℃ drying for 4h and 550℃ calcination for 6h; the modified metal is K, Cs and Ba, wherein the content of K2O is 0.5wt%, the content of Cs2O is 0.5wt%, and the content of BaO is 0.5wt%; the desorbent is 50% methylcyclohexane and 50% o-xylene.

[0051] (2) the mass flow rate ratio of the adsorbent to the raw material is 1:1.2; the mass flow rate ratio of the adsorbent after adsorption to the desorbent is 1:1.3.

[0052] The diesel raw material composition analysis is shown in table 1 1# diesel, the true moving bed adsorption separation process conditions are shown in table 2, and the evaluation results are shown in table 3.

[0053] Example 3

[0054] A true moving bed diesel adsorption separation method, the difference between this embodiment and example 1 is:

[0055] (1) the aromatic hydrocarbon adsorbent is metal modified 13X molecular sieve, the modification method is the same as that of example 1, the carrier uses 13X molecular sieve, and the modified metal is K, Cs and Mo, wherein the content of K2O is 0.5wt%, the content of Cs2O is 0.5wt%, and the content of MoO3 is 0.5wt%; the desorbent is 50% cyclohexane and 50% toluene.

[0056] (2) the mass flow rate ratio of the adsorbent to the raw material is 1:1.5; the mass flow rate ratio of the adsorbent after adsorption to the desorbent is 1:1.8.

[0057] The diesel raw material composition analysis is shown in table 1 2# diesel, the true moving bed adsorption separation process conditions are shown in table 2, and the evaluation results are shown in table 3.

[0058] Example 4

[0059] A true moving bed diesel adsorption separation method, the difference between this embodiment and example 1 is:

[0060] (1) The aromatic adsorbent is metal modified MCM-41 molecular sieve, the modification method is the same as that in Example 1, the modified metal is Mg, Ca and Mo, wherein the MgO content is 0.5 wt%, the CaO content is 0.5 wt% and the MoO3 content is 1 wt%; the carrier is MCM-41 molecular sieve which is the same as that in Example 1; the desorbent is 50% cyclohexane-50% methylcyclohexane (70% alkanes) and benzene (30%).

[0061] (2) The mass flow rate ratio of the adsorbent to the raw material is 1:1.9; the mass flow rate ratio of the adsorbed adsorbent to the desorbent is 1:2.2.

[0062] The diesel raw material composition analysis is shown in Table 1 2# diesel, the real moving bed adsorption separation process conditions are shown in Table 2, and the evaluation results are shown in Table 3.

[0063] Example 5

[0064] A real moving bed diesel adsorption separation method, the difference between this embodiment and Example 1 is that:

[0065] (1) The aromatic adsorbent is metal modified MCM-41 molecular sieve, the modification method is the same as that in Example 1, the modified metal is Mg, Ca and Mo, wherein the MgO content is 0.5 wt%, the CaO content is 0.5 wt% and the MoO3 content is 1 wt%; the carrier is MCM-41 molecular sieve which is the same as that in Example 1; the desorbent is 50% cyclohexane-50% methylcyclohexane (70% alkanes) and benzene (30%).

[0066] (2) The mass flow rate ratio of the adsorbent to the raw material is 1:2.2; the mass flow rate ratio of the adsorbed adsorbent to the desorbent is 1:3.2.

[0067] The diesel raw material composition analysis is shown in Table 1 2# diesel, the real moving bed adsorption separation process conditions are shown in Table 2, and the evaluation results are shown in Table 3.

[0068] Table 1 Diesel raw material composition

[0069]

[0070]

[0071] Table 2 Real moving bed adsorption separation process conditions

[0072]

[0073] Table 3 Real moving bed evaluation results

[0074] Examples 1 2 3 4 5 % alkane yield 98.45 98.64 99.12 98.32 98.61 non-aromatic components - alkane content, % 97.25 97.68 96.25 95.41 96.31 % aromatic yield 97.56 98.46 98.75 98.64 99.12 aromatic components - aromatic content, % 95.43 96.47 98.26 98.54 97.67

[0075] Note:

[0076] Alkane yield = product alkane mass / alkane mass in feed diesel x 100%;

[0077] Aromatic yield = product aromatic mass / alkane-aromatic mass of feed x 100%;

[0078] Alkane content = alkane component alkane mass / total alkane component mass x 100%;

[0079] Aromatic content = aromatic component aromatic mass / total aromatic component mass x 100%.

[0080] The embodiments of the present specific implementation are the preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, and therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A real moving bed diesel adsorption separation method, characterized in that: Includes the following steps: S1. The diesel feedstock is fed into the pre-adsorption tower, where sulfur-containing and nitrogen-containing compounds and impurities are removed under the action of the pre-adsorbent; S2. The diesel feedstock after impurity removal is sent from the bottom to the moving bed adsorption chamber (3), and the aromatic adsorbent is sent from the top of the moving bed adsorption chamber (3). The aromatic adsorbent and the diesel feedstock are in countercurrent contact to obtain the aromatic and non-aromatic components adsorbed by the adsorbent. The processing temperature in the moving bed adsorption chamber (3) is 50-100℃ and the adsorption pressure is 0.5-1.5MPa. S3. The adsorbent that adsorbs aromatics is intermittently discharged through a slide valve and enters the moving bed regeneration chamber (7). The desorbent is fed from the top of the moving bed regeneration chamber (7) to rinse and desorb the aromatic components on the adsorbent, so as to obtain the desorbed aromatic components, the desorbent, and the regenerated adsorbent. The processing temperature of the moving bed regeneration chamber (7) is 50-80℃ and the adsorption pressure is 0.5-1.5MPa. S4. The desorbed aromatic components and the desorbent are used as extractant to separate the aromatics from the non-aromatic components, thus obtaining the aromatic product.

2. The method for diesel adsorption and separation in a real moving bed according to claim 1, characterized in that: The distillation range of diesel feedstock is 150–400℃.

3. The method for diesel adsorption and separation in a real moving bed according to claim 1, characterized in that: In step S1, the temperature of the adsorbent bed in the pre-adsorption tower is 30–150℃, and the mass hourly space velocity is 0.1–3.0 h⁻¹. -1 The adsorption pressure is 0.1–5.0 MPa.

4. The method for diesel adsorption and separation in a real moving bed according to claim 1, characterized in that: In step S2, the aromatic adsorbent is selected from one or more of the following: metal-modified MCM-41 molecular sieve, metal-modified silica gel, and metal-modified 13X molecular sieve.

5. The method for diesel adsorption and separation in a real moving bed according to claim 1, characterized in that: In step S3, the desorbent is selected from one or more of benzene, toluene, o-xylene, m-xylene, cyclohexane, and methylcyclohexane.

6. The method for diesel adsorption and separation in a real moving bed according to claim 1, characterized in that: The volume flow rate ratio of the adsorbent to the diesel feedstock entering the moving bed adsorption chamber (3) is 1:(0.5~2.5); the mass flow rate ratio of the adsorbent to the desorbent entering the moving bed regeneration chamber (7) is 1:(0.5~5).

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