Light hydrocarbon dehydrogenation and cracking bifunctional catalyst and preparation method thereof

Abstract

The application discloses a light hydrocarbon dehydrogenation and cracking bifunctional catalyst and a preparation method thereof. The catalyst contains the following components in percentage by weight: 5-65% of molecular sieve in dry basis; 10-20% of binder in dry basis; 10-40% of clay in dry basis; 10-40% of powder in dry basis; and 0.05-10% of metal compound in dry basis. The preparation method comprises the following steps: a, preparing a catalytic cracking catalyst; b, preparing a catalytic dehydrogenation catalyst; c, placing the prepared catalytic cracking catalyst into a balling machine as a core; adding equal parts of deionized water into the prepared catalytic dehydrogenation catalyst to prepare wet powder, and then coating the wet powder on the core by using a rolling ball method to prepare a straight spherical light hydrocarbon dehydrogenation and cracking bifunctional catalyst. The application has the beneficial effect of having a core-shell structure, and the maximum synergistic catalytic effect of dehydrogenation and cracking can be realized, and the selectivity of ethylene and propylene is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petroleum chemical industry, in particular to a light hydrocarbon dehydrogenation and cracking bifunctional catalyst and a preparation method thereof. BACKGROUND

[0002] Ethylene, propylene and other low-carbon olefins are important petrochemical raw materials, and their production is an important indicator of the development level of a country's petrochemical industry. At present, the demand for basic chemical raw materials such as ethylene and propylene is growing, and high-end chemical products using them as raw materials are structurally short. In order to respond to changes in market demand, refining enterprises have begun to transform from producing a large amount of finished oil to producing more high-value-added chemical raw materials.

[0003] At present, 95% of the world's ethylene and 61% of the propylene are derived from steam cracking technology, which has high energy consumption per unit product. Compared with steam cracking technology, catalytic cracking technology can greatly reduce energy consumption, improve olefin yield, and the product distribution is flexible and adjustable. In addition, with the increase of China's oil refining capacity and the expansion of ethylene production capacity, the C4-C7 alkanes produced by refineries have increased significantly, and the added value is low, most of which are used as low-value fuels. Using dehydrogenation and cracking technology to convert this part of resources into ethylene, propylene and other low-carbon olefins can not only improve the utilization rate of light hydrocarbon chemicals, but also achieve the purpose of producing more low-carbon olefins.

[0004] The existing catalysts still have problems such as low selectivity of ethylene and propylene, low conversion rate of light hydrocarbon components, and high selectivity of methane during the reaction process, which affects the stability and technical economy of the device and limits the further promotion of the light hydrocarbon dehydrogenation and cracking technology. SUMMARY

[0005] The present application aims to provide a light hydrocarbon dehydrogenation and cracking bifunctional catalyst, which has a core-shell structure, and the light hydrocarbon raw material preferentially contacts the dehydrogenation active component of the catalyst shell, and the product after dehydrogenation further contacts the cracking active component of the catalyst core, which maximizes the synergistic catalytic effect of dehydrogenation and cracking and improves the selectivity of ethylene and propylene.

[0006] The present application aims to provide a preparation method of a light hydrocarbon dehydrogenation and cracking bifunctional catalyst, which has a core-shell structure, and the light hydrocarbon raw material preferentially contacts the dehydrogenation active component of the catalyst shell, and the product after dehydrogenation further contacts the cracking active component of the catalyst core, which maximizes the synergistic catalytic effect of dehydrogenation and cracking and improves the selectivity of ethylene and propylene.

[0007] To achieve the above-mentioned purposes, the present application adopts the following technical solutions, comprising:

[0008] The catalyst has a core-shell structure. The core has catalytic cracking function and includes molecular sieves, binders, and clay; the outer shell has catalytic dehydrogenation function and includes powders and metal compounds. The catalyst contains the following components by weight percentage:

[0009] Molecular sieves with a dry basis content of 5-65%;

[0010] 10-20% adhesive on a dry basis;

[0011] 10-40% clay on a dry basis;

[0012] Powders comprising 10–40% on a dry basis; and

[0013] Metal compounds, calculated as oxides, comprising 0.05–10%;

[0014] Wherein, the clay is one or two of kaolin, bentonite, and attapulgite; the powder is one or two of alumina, silicon dioxide, and titanium dioxide; the metal compound is one or two of the metal oxides corresponding to iron, chromium, zinc, and gallium; the molecular sieve is one or two of ZSM-5, Y, β, and MCM-22 zeolite; and the binder is one or two of boehmite, silica sol, and alumina sol.

[0015] Preferably, the binder is boehmite.

[0016] Preferably, the molecular sieve is composed of ZSM-5 molecular sieve and β molecular sieve.

[0017] Preferably, the clay is kaolin.

[0018] Preferably, the powder is silicon oxide.

[0019] Preferably, the metal compound is a zinc oxide.

[0020] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons, wherein the catalyst is any one of the catalysts described above, comprising the following steps:

[0021] a. Weigh 1-15 parts of molecular sieve, 2-4 parts of binder, and 2-8 parts of clay. Add 2-30 parts of deionized water to the weighed molecular sieve, binder, and clay and stir until homogeneous to obtain a slurry. Then, add an acidic solution to the slurry to adjust the pH to 2-6. Perform spray granulation, controlling the outlet temperature at 140-150℃ and the atomizer speed at 5000-10000 r / min. The solid content of the slurry is 10-30%. Then, dry at 100-200℃ for 2-6 hours. Finally, calcine at 550-650℃ for 2-6 hours to obtain a catalytic cracking catalyst with a diameter of 40-200 μm.

[0022] b. Weigh 0.01–2 parts of one or two of ferric nitrate, chromium nitrate, zinc nitrate, and gallium chloride, and weigh 2–8 parts of powder; add one or two of the weighed ferric nitrate, chromium nitrate, zinc nitrate, and gallium chloride to 4–10 parts of deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed powder; then dry at 100–200℃ for 2–6 hours; finally calcine at 550–650℃ for 2–6 hours to obtain the catalytic dehydrogenation catalyst;

[0023] c. The prepared catalytic cracking catalyst is placed in a pelletizer as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to form a wet powder, which is then coated onto the core using a rolling pellet method; then dried at 100-200℃ for 2-6 hours; finally calcined at 550-650℃ for 2-6 hours to obtain a spherical light hydrocarbon dehydrogenation cracking bifunctional catalyst with a diameter of 500-3000 μm.

[0024] Wherein, the clay is one or two of kaolin, bentonite, and attapulgite; the powder is one or two of alumina, silicon dioxide, and titanium dioxide; the molecular sieve is one or two of ZSM-5, Y, β, and MCM-22 zeolite; and the binder is one or two of boehmite, silica sol, and alumina sol.

[0025] Preferably, the acidic solution is one or two of formic acid solution, acetic acid solution, nitric acid solution, and hydrochloric acid solution, and its hydrogen ion concentration is 0.1 to 10 mol / L.

[0026] The beneficial effects of this invention are: It has a core-shell structure, where light hydrocarbon feedstock preferentially contacts the dehydrogenation active component in the catalyst shell, and the dehydrogenated products further contact the cracking active component in the catalyst core, thereby maximizing the synergistic catalytic effect of dehydrogenation and cracking, and improving the selectivity of ethylene and propylene. Detailed Implementation

[0027] The invention will now be described in further detail so that those skilled in the art can implement it based on the description.

[0028] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0029] Example 1

[0030] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons includes the following steps:

[0031] a. Weigh an estimated 8 parts of ZSM-5 molecular sieve and β molecular sieve, 3 parts of boehmite and 4 parts of kaolin. Add 15 parts of deionized water to the weighed ZSM-5 molecular sieve, β molecular sieve, boehmite and kaolin and stir evenly to obtain a slurry. Then add formic acid solution (with a hydrogen ion concentration of 5 mol / L) to the slurry to adjust the pH to 4. Then perform spray granulation, controlling the atomizer outlet temperature at 145℃ and the atomizer speed at 8000 r / min. The solid content of the slurry is 25%. Then dry at 150℃ for 4 h. Finally, calcine at 600℃ for 4 h to obtain a catalytic cracking catalyst with a diameter of 150 μm.

[0032] b. Weigh 1 part zinc nitrate and 4 parts silicon oxide; add the weighed zinc nitrate to 5 parts deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed silicon oxide; dry at 150℃ for 4 hours; finally calcine at 600℃ for 4 hours to obtain the catalytic dehydrogenation catalyst.

[0033] c. The prepared catalytic cracking catalyst is placed in a pelletizer as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to make a wet powder, and then the core is coated by the rolling ball method; then it is dried at 150℃ for 4h; finally, it is calcined at 600℃ for 4h to obtain a spherical light hydrocarbon dehydrogenation cracking bifunctional catalyst with a diameter of 1500um.

[0034] Example 2

[0035] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons includes the following steps:

[0036] a. Weigh 1 part ZSM-5 molecular sieve, 4 parts silica sol, and 2 parts bentonite. Add 2 parts deionized water to the weighed ZSM-5 molecular sieve, silica sol, and bentonite and stir until homogeneous to obtain a slurry. Then, add acetic acid solution (with a hydrogen ion concentration of 0.1 mol / L) to the slurry to adjust the pH to 2. Then, perform spray granulation, controlling the outlet temperature at 150℃ and the atomizer speed at 5000 r / min. The solid content of the slurry is 30%. Then, dry at 100℃ for 6 hours. Finally, calcine at 550℃ for 6 hours to obtain a catalytic cracking catalyst with a diameter of 40 μm.

[0037] b. Weigh 0.01 parts of ferric nitrate and 2 parts of alumina; add the weighed ferric nitrate to 4 parts of deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto 8 parts of weighed alumina; dry at 200℃ for 2 hours; finally calcine at 650℃ for 2 hours to obtain the catalytic dehydrogenation catalyst.

[0038] c. The prepared catalytic cracking catalyst is placed in a pelletizer as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to make a wet powder, and then the powder is coated on the core by a rolling ball method; then it is dried at 100℃ for 6h; finally, it is calcined at 650℃ for 2h to obtain a spherical light hydrocarbon dehydrogenation cracking bifunctional catalyst with a diameter of 500um.

[0039] Example 3

[0040] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons includes the following steps:

[0041] a. Weigh 15 parts of β-zeolite molecular sieve, 2 parts of alumina sol, and 8 parts of attapulgite. Add 30 parts of deionized water to the weighed β-zeolite molecular sieve, alumina sol, and attapulgite and stir until homogeneous to obtain a slurry. Then, add nitric acid and hydrochloric acid solutions (with a hydrogen ion concentration of 10 mol / L) to the slurry to adjust the pH to 6. Then, perform spray granulation, controlling the outlet temperature at 140℃ and the atomizer speed at 10000 r / min. The solid content of the slurry is 10%. Then, dry at 200℃ for 2 hours. Finally, calcine at 650℃ for 2 hours to obtain a catalytic cracking catalyst with a diameter of 200 μm.

[0042] b. Weigh out a total of 2 parts of chromium nitrate and gallium chloride, and 8 parts of titanium oxide; add the weighed chromium nitrate and gallium chloride to 10 parts of deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed titanium oxide; dry at 100℃ for 6 hours; finally calcine at 550℃ for 6 hours to obtain the catalytic dehydrogenation catalyst.

[0043] c. The prepared catalytic cracking catalyst is placed in a pelletizing machine as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to make a wet powder, and then the core is coated by the rolling ball method; then it is dried at 200℃ for 2h; finally, it is calcined at 550℃ for 6h to obtain a spherical light hydrocarbon dehydrogenation cracking bifunctional catalyst with a diameter of 3000um.

[0044] Example 4

[0045] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons includes the following steps:

[0046] a. Weigh out a total of 6 parts of Y molecular sieve and MCM-22 zeolite molecular sieve, a total of 3 parts of boehmite and alumina sol, and a total of 6 parts of kaolin. Add 20 parts of deionized water to the weighed Y molecular sieve, MCM-22 zeolite molecular sieve, boehmite and alumina sol, and kaolin and stir evenly to obtain a slurry. Then add formic acid solution (formic acid solution hydrogen ion concentration of 5 mol / L) to the slurry and adjust the pH to 3.5. Then perform spray granulation, controlling the atomizer outlet temperature at 148℃ and the atomizer speed at 6000 r / min. The solid content of the slurry is 15%. Then dry at 160℃ for 3 h. Finally, calcine at 580℃ for 5 h to obtain a catalytic cracking catalyst with a diameter of 180 μm.

[0047] b. Weigh a total of 1.5 parts of ferric nitrate and zinc nitrate, and weigh 1.5 parts of silicon oxide; add the weighed ferric nitrate and zinc nitrate to 6 parts of deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed silicon oxide; dry at 180℃ for 4.5 h; finally calcine at 565℃ for 2.8 h to obtain the catalytic dehydrogenation catalyst;

[0048] c. The prepared catalytic cracking catalyst is placed in a pelletizer as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to make a wet powder, and then the core is coated by the rolling ball method; then it is dried at 180℃ for 3.5h; finally, it is calcined at 620℃ for 4.8h to obtain a spherical light hydrocarbon dehydrogenation cracking bifunctional catalyst with a diameter of 2500um.

[0049] Comparative Example 1

[0050] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons includes the following steps:

[0051] a. Weigh a total of 20 parts of ZSM-5 molecular sieve and β molecular sieve, 1 part of boehmite and 10 parts of kaolin. Add 40 parts of deionized water to the weighed ZSM-5 molecular sieve, β molecular sieve, boehmite and kaolin and stir evenly to obtain a slurry. Then add formic acid solution (with a hydrogen ion concentration of 5 mol / L) to the slurry and adjust the pH to 7. Then perform spray granulation, controlling the atomizer outlet temperature at 160℃ and the atomizer speed at 12000 r / min. The solid content of the slurry is 5%. Then dry at 80℃ for 12 h. Finally, calcine at 800℃ for 1.5 h to obtain a catalytic cracking catalyst with a diameter of 30 μm.

[0052] b. Weigh 3 parts zinc nitrate and 1 part silicon oxide; add the weighed zinc nitrate to 15 parts deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed silicon oxide; dry at 85℃ for 14 hours; finally calcine at 700℃ for 1 hour to obtain the catalytic dehydrogenation catalyst.

[0053] c. The prepared catalytic cracking catalyst is placed in a pelletizing machine as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to make a wet powder, and then the powder is coated on the core by a rolling ball method; then it is dried at 250°C for 1 hour; finally, it is calcined at 400°C for 8 hours to obtain a catalyst with a diameter of 400 μm.

[0054] Comparative Example 2

[0055] A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons includes the following steps:

[0056] a. Weigh out a total of 0.5 parts of ZSM-5 molecular sieve and β molecular sieve, 6 parts of boehmite and 1 part of kaolin. Add 10 parts of deionized water to the weighed ZSM-5 molecular sieve, β molecular sieve, boehmite and kaolin and stir evenly to obtain a slurry. Then add formic acid solution (with a hydrogen ion concentration of 5 mol / L) to the slurry and adjust the pH to 1.5. Then perform spray granulation, controlling the atomizer outlet temperature at 130℃ and the atomizer speed at 4000 r / min. The solid content of the slurry is 35%. Then dry at 210℃ for 1 h. Finally, calcine at 450℃ for 8 h to obtain a catalytic cracking catalyst with a diameter of 250 μm.

[0057] b. Weigh 0.005 parts of zinc nitrate and 10 parts of silicon oxide; add the weighed zinc nitrate to 15 parts of deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed silicon oxide; dry at 250℃ for 1 hour; finally calcine at 500℃ for 12 hours to obtain the catalytic dehydrogenation catalyst.

[0058] c. The prepared catalytic cracking catalyst is placed in a pelletizing machine as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to make a wet powder, and then the powder is coated on the core by a rolling ball method; then it is dried at 80°C for 11 h; finally, it is calcined at 800°C for 1.5 h to obtain a catalyst with a diameter of 4000 μm.

[0059] Data Analysis

[0060] The composition of the light hydrocarbons to be processed is shown in Table 1.

[0061] Table 1

[0062] Component n-alkanes / wt.% iso-alkanes / wt.% cycloalkanes / wt.% aromatics / wt.% C4 8.5 6.6 0 0 C5 12.8 50.1 0.9 0 C6 1.2 15.5 1.8 0.1 C7 0 2.4 0.1 0 total 22.5 74.6 2.8 0.1

[0063] Using the aforementioned light hydrocarbons as raw materials, the reaction was carried out at a temperature of 650℃, a pressure of 0.1 MPa, and a mass hourly space velocity of 1.0 h⁻¹. -1 The reaction performance of the catalysts prepared in Examples 1-4 and Comparative Examples 1-2 was evaluated using fixed-bed reactors, and the results are shown in Table 2.

[0064] Table 2

[0065] Item conversion / % methane selectivity / wt% ethylene selectivity / wt% propylene selectivity / wt% di-olefins selectivity / wt% Example 1 63.5 0.99 32.4 35.3 67.9 Example 2 56.3 1.82 25.5 31.3 56.8 Example 3 52.2 1.71 27.2 28.6 55.8 Example 4 50.2 1.54 25.3 27.2 52.5 Comparative Example 1 46.2 1.98 21.5 22.2 43.7 Comparative Example 2 42.3 1.31 20.1 21.3 41.4

[0066] As shown in Table 2, the bifunctional catalyst for light hydrocarbon dehydrogenation and cracking prepared according to this invention exhibits relatively high conversion rate and selectivity for diolefins, but relatively low selectivity for methane. Under the action of the core-shell bifunctional catalyst, the light hydrocarbon feedstock preferentially contacts the dehydrogenation active component in the catalyst shell, and the dehydrogenated product further contacts the cracking active component in the catalyst core. This maximizes the synergistic catalytic effect of dehydrogenation and cracking, thereby maximizing the single-pass conversion rate, suppressing hydrogen transfer and aromatization reactions, and ultimately improving the selectivity for ethylene and propylene.

[0067] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A bifunctional catalyst for the dehydrogenation and cracking of light hydrocarbons, characterized in that, The catalyst has a core-shell structure. The core has catalytic cracking function and includes molecular sieves, binders, and clay; the outer shell has catalytic dehydrogenation function and includes powders and metal compounds. The catalyst contains the following components by weight percentage: Molecular sieves with a dry basis content of 5-65%; 10-20% adhesive on a dry basis; 10-40% clay on a dry basis; Powder with a dry basis content of 10-40%; as well as Metal compounds, on a dry basis, comprising 0.05–10%; Wherein, the clay is one or two of kaolin, bentonite, and attapulgite; the powder is one or two of alumina, silicon dioxide, and titanium dioxide; the metal compound is one or two of the metal oxides corresponding to iron, chromium, zinc, and gallium; the molecular sieve is one or two of ZSM-5, Y, β, and MCM-22 zeolite; and the binder is one or two of boehmite, silica sol, and alumina sol.

2. The bifunctional catalyst for light hydrocarbon dehydrogenation cracking according to claim 1, characterized in that: The binder is boehmite.

3. The bifunctional catalyst for light hydrocarbon dehydrogenation cracking according to claim 1, characterized in that: The molecular sieve is composed of ZSM-5 molecular sieve and β molecular sieve.

4. The bifunctional catalyst for light hydrocarbon dehydrogenation cracking according to claim 1, characterized in that: The clay is kaolin.

5. The bifunctional catalyst for light hydrocarbon dehydrogenation cracking according to claim 1, characterized in that: The powder is silicon dioxide.

6. The bifunctional catalyst for light hydrocarbon dehydrogenation cracking according to claim 1, characterized in that: The metal compound is a zinc oxide.

7. A method for preparing a bifunctional catalyst for the dehydrogenation cracking of light hydrocarbons, wherein the catalyst is the catalyst according to any one of claims 1-6, characterized in that, Includes the following steps: a. Weigh 1-15 parts of molecular sieve, 2-4 parts of binder, and 2-8 parts of clay. Add 2-30 parts of deionized water to the weighed molecular sieve, binder, and clay and stir until homogeneous to obtain a slurry. Then, add an acidic solution to the slurry to adjust the pH to 2-6. Perform spray granulation, controlling the outlet temperature at 140-150℃ and the atomizer speed at 5000-10000 r / min. The solid content of the slurry is 10-30%. Then, dry at 100-200℃ for 2-6 hours. Finally, calcine at 550-650℃ for 2-6 hours to obtain a catalytic cracking catalyst with a diameter of 40-200 μm. b. Weigh 0.01–2 parts of one or two of ferric nitrate, chromium nitrate, zinc nitrate, and gallium chloride, and weigh 2–8 parts of powder; add one or two of the weighed ferric nitrate, chromium nitrate, zinc nitrate, and gallium chloride to 4–10 parts of deionized water and stir evenly to prepare an impregnation solution; then spray the impregnation solution onto the weighed powder; then dry at 100–200℃ for 2–6 hours; finally calcine at 550–650℃ for 2–6 hours to obtain the catalytic dehydrogenation catalyst; c. The prepared catalytic cracking catalyst is placed in a pelletizer as the core; then an equal amount of deionized water is added to the prepared catalytic dehydrogenation catalyst to form a wet powder, which is then coated onto the core using a rolling pellet method; then dried at 100-200℃ for 2-6 hours; finally calcined at 550-650℃ for 2-6 hours to obtain a spherical light hydrocarbon dehydrogenation cracking bifunctional catalyst with a diameter of 500-3000 μm. Wherein, the clay is one or two of kaolin, bentonite, and attapulgite; the powder is one or two of alumina, silicon dioxide, and titanium dioxide; the molecular sieve is one or two of ZSM-5, Y, β, and MCM-22 zeolite; and the binder is one or two of boehmite, silica sol, and alumina sol.

8. The method for preparing the bifunctional catalyst for light hydrocarbon dehydrogenation cracking according to claim 7, characterized in that: The acidic solution is one or two of formic acid solution, acetic acid solution, nitric acid solution, and hydrochloric acid solution, and its hydrogen ion concentration is 0.1 to 10 mol / L.