Preparation method of yield-increasing light olefin catalytic cracking aid with sulfur transfer function

Abstract

The invention relates to a preparation method of a yield-increasing light olefin catalytic cracking aid with a sulfur transfer function. The method comprises the following steps: 1) uniformly mixing components such as kaolin, and performing spray drying and roasting; 2) uniformly mixing kaolin, sepiolite or attapulgite and other components, and carrying out spray drying and roasting; (3) adding the roasted microspheres in the step (1) into water glass and alkali liquor, and synthesizing a composite material containing the MFI structure molecular sieve under a certain condition; (4) adding the roasted microspheres in the step (2) into the filtrate obtained in the step (3), adding a zinc salt solution at a constant speed, aging the system at a certain temperature for a certain time, filtering, drying and roasting; and 5) mixing the composite material obtained in the step 3) and the roasted product obtained in the step 4), carrying out ammonium exchange, mixed rare earth exchange and vanadium exchange, and roasting to obtain the additive product.The additive has high reaction activity and excellent wear resistance, can significantly improve the yield of light olefins, and has excellent sulfur transfer ability and tower bottom oil cracking ability.

Description

Technical Field

[0001] The invention relates to a method for preparing a light olefin production-increasing catalytic cracking aid with a sulfur transfer function, and belongs to the technical field of chemical catalysts. Background Art

[0002] As the basic material of chemical products, light olefins have become the cornerstone of the modern chemical industry, and their demand is increasing. China is the world's largest importer of light olefins, and it is predicted that domestic light olefin production will not be able to meet market demand within 20 years. For propylene, the contribution of cracking process is close to 50% of the market demand, and the contribution of catalytic cracking is about 40%. The cracking process faces problems such as shortage of high-quality raw materials, high prices, and harsh operating conditions. The catalytic cracking process is favored due to its advantages such as wide source of raw materials, low prices, mild reaction and separation conditions, and the production cost can be shared with the main products of gasoline, diesel, and liquefied gas. According to national conditions, the low-cost and quick-acting solution is to use catalytic cracking units and high-efficiency light olefin additives to reasonably adjust the output ratio of light olefins to gasoline, kerosene and diesel, which can produce 1-2 million tons of light olefins per year, realize the rational use of the unit and maximize the economic benefits, and quickly improve the market's urgent demand for light olefins. However, in recent years, with the increase in the proportion of residual oil blended in catalytic cracking units and the increase in the amount of imported sulfur-containing crude oil processed, the sulfur content in the raw materials has continued to increase, resulting in a significant increase in the concentration of SOx in the regeneration flue gas generated by the unit, aggravating environmental pollution and equipment corrosion. The use of sulfur transfer agents to control the emission of SOx in catalytic cracking flue gas has the advantages of low equipment investment costs, low operating costs, and fewer waste disposal problems. It is considered to be the most economical and reasonable method to reduce SOx emissions under existing conditions. Based on the above situation, the development of green, highly active, light olefin catalytic cracking additives with sulfur transfer function has become a core issue to be solved.

[0003] There are few documents on catalytic cracking aids that have both sulfur transfer function and increased light olefin yield. Patent CN101905168B discloses a catalytic cracking aid for increasing propylene production with the function of a sulfur transfer agent. The amount of the aid added is the same as that of a separate aid for increasing propylene production, which can reduce the dilution of the main catalyst. The design and preparation principle of the aid is that since magnesium aluminum spinel is chemically inert and has weak surface acidity, it is considered to partially introduce it into the matrix, and ZSM-5 is used as the active component, so that the prepared catalyst can be added as a catalytic cracking aid in small amounts to simultaneously have the functions of a sulfur transfer agent and increasing propylene production.

[0004] Patent CN106178924B discloses a method for preparing a sulfur transfer agent for catalytic cracking flue gas. The method comprises the following steps: preparing MgAl2O4 spinel oxide by sol-gel method, then using cerium nitrate and n-butyl titanate as cerium source and titanium source to synthesize CeO2-TiO2 composite oxide, and finally mixing spinel oxide, cerium titanium oxide and magnesium oxide in a specific ratio and calcining to obtain the product.

[0005] Patent CN101905118 discloses a method for preparing an active component of a catalytic cracking flue gas sulfur transfer agent: (1) preparing a mixed salt solution of a soluble magnesium salt, a soluble aluminum salt and a soluble cerous salt; (2) adding an alkaline solution and the mixed salt solution of step (1) to a fully backmixed liquid membrane reactor to mix and react to obtain a slurry, wherein the alkaline solution is used to adjust the pH value to 8.5-13; (3) heating the slurry under strong stirring to crystallize it to obtain a hydrotalcite precursor, filtering and washing it to neutrality; (4) roasting the product to obtain an active component with good sulfur transfer performance.

[0006] Existing patents basically disclose single agents of sulfur transfer agents or propylene-increasing agents. Flue gas sulfur transfer agents have small sulfur absorption capacity and poor reduction effect, and cannot deeply remove sulfur oxides in catalytic cracking units and have a great impact on catalytic reaction activity; while propylene-increasing catalytic cracking agents also have low activity. After being added to the system, the overall system catalytic activity is reduced, resulting in a decrease in total liquid recovery, affecting the normal operation of the unit and economic benefits, and other key common problems. Summary of the invention

[0007] The purpose of the present invention is to overcome the key common problems that the existing single sulfur transfer additives and light olefin production increasing additives have low activity, and after being added to the system, they cause the main catalyst activity to decrease, the product selectivity to deteriorate, the conversion rate to decrease, etc., and to provide a method for preparing a light olefin production increasing catalytic cracking additive with sulfur transfer function.

[0008] The present invention relates to a method for preparing a light olefin production-increasing catalytic cracking aid having a sulfur transfer function, the preparation method being characterized by the following steps:

[0009] 1) Mix kaolin, dispersant, seed crystal and water, stir evenly, spray dry to obtain spray microsphere A, calcine the spray microsphere A at 950-1000°C for 1-3 h to obtain calcined microsphere A;

[0010] 2) Mix kaolin, sepiolite or attapulgite, dispersant and water, stir evenly, spray dry to obtain spray microspheres B, and calcine the spray microspheres B at 750-770 °C for 1-3 h to obtain calcined microspheres B;

[0011] 3) Add the calcined microspheres A to water glass and alkali solution to form a reaction system, the composition of which is:n (SiO2) / n (Al2O3)=10~20, n(Na2O) / n(SiO2)=0.25~0.35, n (H2O) / n (Na2O)=50~150; pH value is 10.0~11.0; the reaction system is crystallized at 130~180°C for 35~75 h; after the crystallization is completed, filtrate C is obtained by filtration, and the filter cake is washed with water until it is neutral to obtain a composite material containing MFI structure molecular sieve.

[0012] 4) The calcined microspheres B are added to the filtrate C to form a slurry, and the zinc salt solution is added at a uniform rate and stirred evenly. The reaction system is aged at 50-90°C for 5-15 h. After filtering, the filter cake is calcined at 800-900°C for 2-5 h to obtain product D.

[0013] 5) The composite material and product D are mixed and added to an ammonium salt solution, exchanged at room temperature for 10-30 min, filtered and washed with water, filtered again and added to a lanthanum-cerium mixed rare earth solution, exchanged at 50-70°C for 0.5-1h, filtered and washed with water, filtered again and added to a vanadyl oxalate solution, exchanged at 50-70°C for 0.5-1h, filtered and washed with water, dried the reactants, and calcined at 500-600°C for 2-5h to obtain additive E.

[0014] The present invention provides a method for preparing a light olefin production-increasing catalytic cracking additive with a sulfur transfer function. In steps 1) and 2), the dispersant is one or more of water glass, sodium tripolyphosphate, tetrasodium pyrophosphate, sodium trimetaphosphate, sodium hexametaphosphate, sodium carbonate, carboxyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, sodium polyacrylate, and polyethylene oxide, and the amount of the dispersant added is 1-10% of the weight of the system.

[0015] The present invention provides a method for preparing a light olefin production increasing catalytic cracking aid having a sulfur transfer function. In step 1), the seed crystal is an MFI structure molecular sieve, and the added amount thereof is 0.1-1.0% of the weight of the system.

[0016] The present invention provides a method for preparing a light olefin production-increasing catalytic cracking additive with a sulfur transfer function. In step 2), the content of kaolin is not less than 50%.

[0017] The present invention provides a method for preparing a light olefin production-increasing catalytic cracking aid having a sulfur transfer function. In step 3), the content of the MFI structured molecular sieve in the obtained composite material is not less than 70%.

[0018] The present invention provides a method for preparing a light olefin production increasing catalytic cracking additive with a sulfur transfer function. In step 4), the zinc salt may be a chloride, a sulfate or a nitrate, and the amount of the zinc salt added is 1-5% of the weight of the calcined microspheres B.

[0019] The present invention provides a method for preparing a catalytic cracking aid for increasing the production of light olefins with a sulfur transfer function. In step 5), the ammonium salt may be a chloride, a sulfate or a nitrate, and the amount of the ammonium salt added is 10-100% of the weight of the solid in step 5); the concentration of the lanthanum-cerium mixed rare earth solution is 5-25 g / L, wherein the content of cerium is not less than 60%, and the amount of the mixed rare earth added is 1-10% of the weight of the system in step 5); the concentration of the vanadyl oxalate solution is 5-25 g / L, and the amount of the vanadyl oxalate solution added (in terms of vanadium) is 0.3-0.6% of the weight of the system in step 5).

[0020] Compared with the prior art, the present invention also has the following advantages:

[0021] (1) The additive prepared by the present invention is used in a catalytic cracking process. The additive has high catalytic activity and can efficiently realize the sulfur transfer function and increase the yield of light olefins while ensuring the bottom oil cracking capacity of the device and maintaining high activity and conversion rate of the system.

[0022] (2) The present invention uses kaolin as the main component to synthesize a molecular sieve containing an MFI structure, wherein the molecular sieve content is greater than 70% and the anti-wear index is less than 1%. This type of molecular sieve ensures the additive's ability to lighten olefins. The matrix part is silicon-aluminum spinel and mullite formed by clays such as kaolin after their characteristic heat release, which serves as one of the effective components for sulfur transfer.

[0023] (3) The present invention uses clay components as the matrix, utilizes its phase transformation to obtain active alumina and magnesium oxide, then adds zinc solution, reacts with the filtrate of the crystallization reaction to form a colloidal system, and after aging reaction and roasting, active substances with sulfur transfer function, such as magnesium aluminum spinel, zinc aluminum spinel, zinc magnesium spinel, and silicon aluminum spinel, can be obtained. The carrier has excellent fluidization performance and thermal stability. At the same time, the reuse of molecular sieve synthesis filtrate eliminates the treatment of waste liquid and realizes a green and environmentally friendly synthesis route.

[0024] (4) The present invention mixes the sulfur transfer active component with the light olefin production increasing active component and then performs functional modification. By exchanging the mixture with mixed lanthanum, cerium and rare earth and introducing vanadium species, the activity of the auxiliary agent is ensured and the auxiliary agent has excellent sulfur transfer ability.

[0025] (5) The preparation method of the additive is simple, low-cost, and has better social and economic benefits. DETAILED DESCRIPTION

[0026] The specific embodiments of the present invention are described in detail below. The specific embodiments described here are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0027] Example 1

[0028] 1) 1000 g of kaolin, 23.3 g of sodium hexametaphosphate, 9.9 g of seed crystals, and 1376 g of water were mixed and stirred to obtain a slurry with a solid content of 38%, and spray-dried to obtain spray microspheres A. Spray microspheres A were calcined at 950 °C for 3 h to obtain calcined microspheres A;

[0029] 2) 550 g of kaolin, 280 g of sepiolite, 19.6 g of tetrasodium pyrophosphate and 1163 g of water were mixed and stirred to obtain a slurry with a solid content of 36%, and spray dried to obtain spray microspheres B. Spray microspheres B were calcined at 770 °C for 1 h to obtain calcined microspheres B;

[0030] 3) Add 100 g of calcined microspheres A to 75.0 ml of water glass, 15 ml of alkali solution, and 60 ml of water to form a reaction system. The composition of the system is: n (SiO2) / n (Al2O3)=17, n(Na2O) / n(SiO2)=0.26, n (H2O) / n (Na2O)=135; pH value is 10.5; the reaction system is crystallized at 170°C for 45 h; after the crystallization, filtrate C is obtained by filtration, and the filter cake is washed with water until neutral to obtain a composite material, in which the crystallinity of the MFI structure molecular sieve is 77%.

[0031] 4) 100 g of calcined microspheres B were added to the filtrate C obtained in step 3) to form a slurry, 33 ml of zinc chloride solution was added at a uniform rate, and the mixture was stirred evenly. The reaction system was aged at 90 °C for 15 h, filtered, and the filter cake was calcined at 900 °C for 2 h to obtain product D.

[0032] 5) Add 80 g of the composite material and 80 g of product D into 800 ml of ammonium chloride solution, exchange at room temperature for 30 min, filter and wash with water, then add into 320 ml of lanthanum-cerium mixed rare earth solution (with a concentration of 25 g / L), exchange at 50 °C for 1 h, filter and wash with water, and then add into 144 ml of vanadium oxalate solution (with a concentration of 5 g / L), exchange at 70 °C for 0.5 h, filter, wash with water, and dry the product, and calcine at 500 °C for 5 h to obtain additive E1.

[0033] Example 2

[0034] 1) 500 g of kaolin, 25.1 g of sodium carbonate, 17.6 g of sodium trimetaphosphate, 7.5 g of sodium polyacrylate, 2.6 g of seed crystals, and 850 g of water were mixed and stirred evenly to prepare a slurry with a solid content of 35%, and spray dried to obtain spray microspheres A. Spray microspheres A were calcined at 960 °C for 2 h to obtain calcined microspheres A;

[0035] 2) 700 g of kaolin, 715 g of attapulgite, 32.3 g of sodium tripolyphosphate, 21.6 g of polyvinyl alcohol, and 1446 g of water were mixed and stirred to obtain a slurry with a solid content of 37%, and spray-dried to obtain spray microspheres B. Spray microspheres B were calcined at 750°C for 3 h to obtain calcined microspheres B;

[0036] 3) Add 50 g of calcined microspheres A to 43.0 ml of water glass, 10 ml of alkali solution, and 33 ml of water to form a reaction system. The composition of the system is: n (SiO2) / n (Al2O3)=15, n(Na2O) / n(SiO2)=0.29, n (H2O) / n (Na2O)=122; pH value is 11.0; the reaction system is crystallized at 150°C for 60 h; after the crystallization, filtrate C is obtained by filtration, and the filter cake is washed with water until neutral to obtain a composite material, in which the crystallinity of the MFI structure molecular sieve is 80%.

[0037] 4) Add 50 g of calcined microspheres B to the filtrate C obtained in step 3) to form a slurry, add 25 ml of zinc sulfate solution at a uniform rate, stir evenly, age the reaction system at 70 °C for 5 h, filter and calcine the filter cake at 800 °C for 5 h to obtain product D.

[0038] 5) Add 60 g of the composite material and 60 g of product D into 600 ml of ammonium sulfate solution, exchange at room temperature for 10 min, filter and wash with water, then add into 480 ml of lanthanum-cerium mixed rare earth solution (with a concentration of 10 g / L), exchange at 70 °C for 0.5 h, filter and wash with water, and then filter again, add into 15 ml of vanadium oxalate solution (with a concentration of 25 g / L), exchange at 50 °C for 1 h, filter, wash with water, and dry the product, and calcine at 600 °C for 2 h to obtain additive E2.

[0039] Example 3

[0040] 1) 800 g of kaolin, 29.8 g of water glass, 17.2 g of carboxycellulose, 0.95 g of seed crystals, and 1044 g of water were mixed and stirred to obtain a slurry with a solid content of 40%, and spray-dried to obtain spray microspheres A. Spray microspheres A were calcined at 1000 °C for 1 h to obtain calcined microspheres A;

[0041] 2) 900 g of kaolin, 252 g of sepiolite, 45.5 g of sodium tripolyphosphate, 36.5 g of polyvinyl pyrrolidone, and 1183 g of water were mixed and stirred to obtain a slurry with a solid content of 39%, and spray-dried to obtain spray microspheres B. Spray microspheres B were calcined at 760 °C for 2 h to obtain calcined microspheres B;

[0042] 3) Add 80 g of calcined microspheres A to 62.0 ml of water glass, 12 ml of alkali solution, and 50 ml of water to form a reaction system. The composition of the system is: n (SiO2) / n (Al2O3)=11, n(Na2O) / n(SiO2)=0.32, n (H2O) / n (Na2O)=97; pH value is 10.0; the reaction system is crystallized at 130°C for 75 h; after the crystallization, the filtrate is filtered, and the filter cake is washed with water until neutral to obtain a composite material, wherein the crystallinity of the MFI structured molecular sieve in the composite material is 72%.

[0043] 4) 80 g of calcined microspheres B were added to the filtrate C obtained in step 3) to form a slurry, 16 ml of zinc nitrate solution was added at a uniform rate, and the mixture was stirred evenly. The reaction system was aged at 60 °C for 10 h, filtered, and the filter cake was calcined at 800 °C for 3 h to obtain product D.

[0044] 5) Add 40 g of the composite material and 40 g of product D into 320 ml of ammonium chloride solution, exchange at room temperature for 20 min, filter and wash with water, then add into 160 ml of lanthanum-cerium mixed rare earth solution (with a concentration of 5 g / L), exchange at 60 °C for 40 min, filter and wash with water, and then add into 48 ml of vanadium oxalate solution (with a concentration of 10 g / L), exchange at 60 °C for 40 min, filter and wash with water, and then filter again, and add into 48 ml of vanadium oxalate solution (with a concentration of 10 g / L), exchange at 60 °C for 40 min, filter and wash with water, and dry the product, and calcine at 550 °C for 3 h to obtain additive E3.

[0045] Table 1 shows the properties of the additives.

[0046]

[0047] Testing method for specific surface area and pore volume: measured on an American Micromeritics ASAP 2020 automatic adsorption instrument.

[0048] Evaluation of the performance of the additives: The reactivity and selectivity of the samples were evaluated on the ACE device. The main agent, the additives of Example E1 to E3, and the agent C (commercial propylene additive) were aged at 800 °C, 17 h, and 100% steam. After aging, 5% of the E1 to E3 additives and the agent C were mixed with 95% of the main agent to form test samples for evaluation. The specific evaluation results are shown in Table 2.

[0049] 0.5 g of the test sample was weighed and loaded into a fixed bed reactor with an inner diameter of 8 mm. The reactor was heated to 700 °C and a mixture of SO2 and air was introduced at a volume flow rate of 200 ml / min. The volume concentration of SO2 in the mixed gas was 2000 ppm. After the gas was introduced, the gas was taken every 10 min to measure the concentration of SO2 in the gas. The measuring instrument was the M650 enhanced flue gas online analyzer. The test results are shown in Table 3.

[0050]

[0051]

[0052] It can be seen from the data in Table 2 that the addition of the additive of the present invention can significantly increase the yield of liquefied gas and the yield of light olefins. When the addition amount accounts for 5% of the total amount of the catalyst, the liquefied gas increases by more than 2 percentage points, and the yields of propylene and butene increase by more than 1.5 percentage points.

[0053] It can be seen from the data in Table 3 that the additive of the present invention has a strong sulfide adsorption capacity, can significantly reduce the SO2 concentration in the mixed gas, and shows a strong sulfur transfer ability.

[0054] The above data show that the additive of the present invention has the advantages of significantly increasing the yield of light olefins and having a strong sulfur transfer ability while ensuring a good bottom oil cracking ability.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that for ordinary technicians in this technical field, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a light olefin catalytic cracking additive with sulfur transfer function, It is characterized by the following steps: 1) Mix kaolin, dispersant, seed crystal and water, stir evenly, spray dry to obtain spray microsphere A, calcine the spray microsphere A at 950-1000°C for 1-3 h to obtain calcined microsphere A; 2) Mix kaolin, sepiolite or attapulgite, dispersant and water, stir evenly, spray dry to obtain spray microspheres B, and calcine the spray microspheres B at 750-770 °C for 1-3 h to obtain calcined microspheres B; 3) Add the calcined microspheres A to water glass and alkali solution to form a reaction system, the composition of which is: n (SiO2) / n (Al2O3)=10~20, n(Na2O) / n(SiO2)=0.25~0.35, n (H2O) / n (Na2O)=50~150; pH value is 10.0~11.0; the reaction system is crystallized at 130~180°C for 35~75 h; after the crystallization, the filtrate C is obtained after filtration, and the filter cake is washed with water until neutral to obtain a composite material containing an MFI structure molecular sieve; 4) Add the calcined microspheres B to the filtrate C to form a slurry, add the zinc salt solution at a uniform rate, stir evenly, age the reaction system at 50-90°C for 5-15 h, filter the filter cake and calcine it at 800-900°C for 2-5 h to obtain product D; 5) The composite material and product D are mixed and added to an ammonium salt solution, exchanged at room temperature for 10-30 min, filtered and washed with water, filtered again and added to a lanthanum-cerium mixed rare earth solution, exchanged at 50-70°C for 0.5-1h, filtered and washed with water, filtered again and added to a vanadyl oxalate solution, exchanged at 50-70°C for 0.5-1h, filtered and washed with water, dried the reactants, and calcined at 500-600°C for 2-5h to obtain additive E.

2. The method according to claim 1, characterized in that In the steps 1) and 2), the dispersant is one or more of water glass, sodium tripolyphosphate, tetrasodium pyrophosphate, sodium trimetaphosphate, sodium hexametaphosphate, sodium carbonate, carboxyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, sodium polyacrylate, and polyethylene oxide, and the amount added is 1-10% of the weight of the system.

3. The method according to claim 1, characterized in that In the step 1), the seed crystal is an MFI structured molecular sieve, and the amount added is 0.1-1.0% of the weight of the system.

4. The method according to claim 1, characterized in that In the step 2), the content of kaolin is not less than 50%.

5. The method according to claim 1, characterized in that In the step 3), the content of MFI structured molecular sieve in the obtained composite material is not less than 70%.

6. The method according to claim 1, characterized in that In the step 4), the zinc salt may be chloride, sulfate or nitrate, and the amount added is 1-5% of the weight of the calcined microspheres B.

7. The method according to claim 1, characterized in that In the step 5), the ammonium salt may be chloride, sulfate or nitrate, and the amount added is 10-100% of the weight of the solid in step 5).

8. The method according to claim 1, characterized in that In the step 5), the concentration of the lanthanum-cerium mixed rare earth solution is 5-25 g / L, wherein the cerium content is not less than 60%, and the amount of the mixed rare earth added is 1-10% of the weight of the system in step 5).

9. The method according to claim 1, characterized in that In the step 5), the concentration of the vanadyl oxalate solution is 5-25 g / L, and the amount thereof added (in terms of vanadium) is 0.3-0.6% of the weight of the system in step 5).

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