Preparation method of ethylene and propylene

Abstract

The invention provides a preparation method of ethylene and propylene, which comprises the following steps: under the action of a lanthanum-containing hydrogen type Beta molecular sieve catalyst, carrying out cracking treatment on normal hexane at 500-700 DEG C to obtain ethylene and propylene, in the lanthanum-containing hydrogen type Beta molecular sieve catalyst, the mass percentage content of lanthanum is 0.7%-1.2%. The method is helpful for improving the yield of ethylene and propylene.

Description

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on May 8, 2025, with application number 202510593058.X and application name “A method for preparing ethylene and propylene”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates to the technical field of hydrocarbon catalytic cracking, and in particular to a method for preparing ethylene and propylene. Background Art

[0003] As important chemical raw materials, olefins such as ethylene and propylene are widely used in modern industry. They are the basic raw materials for the synthesis of polymer materials such as plastics, rubber, and fibers, and play a vital role in the development of the national economy.

[0004] In traditional chemical production, ethylene is primarily produced through steam cracking of hydrocarbon feedstocks such as naphtha. While this method is widely used in industry, it has several limitations: steam cracking requires high temperatures (750-900°C) and consumes a lot of energy.

[0005] The existing methods for producing ethylene and propylene have the problems of low raw material conversion rate and high energy consumption. Summary of the Invention

[0006] The present invention provides a method for preparing ethylene and propylene, which is helpful to improve the raw material conversion rate and the yield of ethylene and propylene and reduce energy consumption.

[0007] The present invention provides a method for preparing ethylene and propylene, comprising: cracking n-hexane at 500-700° C. under the action of a hydrogen-type Beta molecular sieve catalyst containing lanthanum to obtain the ethylene and propylene; the mass percentage of lanthanum in the hydrogen-type Beta molecular sieve catalyst containing lanthanum is 0.7%-1.2%.

[0008] Optionally, it also includes: 1) dissolving a raw material system including an aluminum source and an alkali source in water to obtain a first mixed solution; 2) adding sodium dodecylbenzenesulfonate to the first mixed solution, and then adding white carbon black to obtain a second mixed solution; 3) adding Beta molecular sieve seed crystals to the second mixed solution, and performing a crystallization reaction at 100-200°C. After the crystallization reaction is completed, filtering, washing, and drying in sequence to obtain a Beta molecular sieve catalyst; 4) performing ammonium ion exchange on the Beta molecular sieve catalyst in an ammonium salt aqueous solution, washing, drying, and performing a first calcination to obtain a hydrogen-type Beta molecular sieve catalyst; 5) immersing the hydrogen-type Beta molecular sieve catalyst in a lanthanum salt aqueous solution, and then drying to obtain a solid powder; after the solid powder is subjected to a second calcination, it is placed in hydrogen for reduction to obtain the hydrogen-type Beta molecular sieve catalyst containing lanthanum.

[0009] Optionally, step 2) further comprises: adding the sodium dodecylbenzenesulfonate to the first mixed solution under the action of ultrasound, and then adding the white carbon black to obtain the second mixed solution.

[0010] Optionally, in step 4), the ammonium ion exchange is performed at least twice.

[0011] Optionally, the aluminum source includes one or more of sodium metaaluminate, aluminum sol, pseudo-boehmite, and aluminum sulfate.

[0012] Optionally, the alkali source includes one or more of sodium hydroxide, ammonia water, and potassium hydroxide.

[0013] Optionally, the ammonium salt in the ammonium salt aqueous solution includes one or more of ammonium nitrate, ammonium chloride, and ammonium sulfate.

[0014] Optionally, the lanthanum salt in the lanthanum salt aqueous solution includes one or more of lanthanum nitrate, lanthanum sulfate, lanthanum chloride, and lanthanum oxalate.

[0015] Optionally, the mass ratio of the white carbon black to the sodium dodecylbenzenesulfonate is 5:(0.1-0.3).

[0016] Optionally, in step 4), the temperature of the first calcination is 450-550°C.

[0017] The present invention provides a method for preparing ethylene and propylene, which utilizes a hydrogen-type Beta molecular sieve catalyst containing lanthanum to catalyze the cracking of n-hexane to produce ethylene and propylene. The raw material conversion rate and the yield of ethylene and propylene are both high, and the energy consumption is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 The type and mass percentage of the product of Example 1;

[0020] Figure 2 This is the X-ray diffraction (XRD) pattern of the lanthanum-containing hydrogen-type Beta molecular sieve catalyst (La-HBeta molecular sieve) of Example 1. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific embodiments listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present invention.

[0022] In the prior art, methods for producing ethylene and propylene have the problems of low raw material conversion rate and high energy consumption.

[0023] To overcome the deficiencies in the prior art, an embodiment of the present invention provides a method for preparing ethylene and propylene, comprising: cracking n-hexane at 500-700°C under the action of a hydrogenated Beta molecular sieve catalyst containing lanthanum to obtain ethylene and propylene; the mass percentage (loading amount) of lanthanum in the hydrogenated Beta molecular sieve catalyst containing lanthanum (La-HBeta catalyst) is 0.7%-1.2%.

[0024] According to research analysis: n-hexane molecules diffuse rapidly in the pores of La-HBeta catalyst → adsorbed on Brønsted acid ( acid) and La 3 + Synergistic Site → Propylene (primary product) and ethylene are generated through β-bond cleavage → La species inhibit secondary cracking and aromatization side reactions → Hydrogen reduction removes carbon deposits and regenerates active sites. This mechanism reaches an optimal balance in the La loading range of 0.7% to 1.2%, achieving near-100% conversion and high olefin selectivity.

[0025] Illustratively, the temperature of the cracking treatment may be 500°C, 550°C, 560°C, 600°C, 650°C, 700°C, or a range consisting of any two thereof, preferably 550°C to 650°C, such as 600°C.

[0026] For example, the mass percentage content (loading amount) of lanthanum can be 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2% or a range consisting of any two thereof.

[0027] Specifically, in a cracking reactor, under an inert protective atmosphere, the lanthanum-containing hydrogen-type Beta molecular sieve catalyst with a mesh size of 20 to 40 mesh and a catalyst carrier are added to a reaction system containing n-hexane to catalytically crack the n-hexane to obtain ethylene and propylene.

[0028] It is understandable that the above-mentioned inert protective atmosphere includes nitrogen, and its flow rate can be 40 to 60 mL / min, such as 40, 50, 60 mL / min or a range consisting of any two thereof.

[0029] In specific implementation, the temperature in the cracking reactor can be equal to the temperature of the above cracking treatment.

[0030] It is understandable that the above-mentioned inert protective atmosphere includes nitrogen, and its flow rate can be 40 to 60 mL / min, such as 40, 50, 60 mL / min or a range consisting of any two thereof.

[0031] The flow rate of n-hexane can be 10 to 20 mL / h, for example, 10, 15, 20 mL / h or a range consisting of any two thereof.

[0032] The catalyst carrier includes quartz sand, and the mesh size thereof can be 20 to 40 meshes.

[0033] In addition, the usage ratio of the above-mentioned hydrogen-type Beta molecular sieve catalyst containing lanthanum to the catalyst carrier can be 1:(35-40), such as 1:35, 1:36, 1:40 or a range consisting of any two thereof.

[0034] In some embodiments, the above-mentioned hydrogen-type Beta molecular sieve catalyst containing lanthanum can be prepared by a method comprising at least the following processes: 1) dissolving a raw material system including an aluminum source and an alkali source in water to obtain a first mixed solution; 2) adding sodium dodecylbenzenesulfonate to the first mixed solution, and then adding white carbon black to obtain a second mixed solution; 3) adding Beta molecular sieve seed crystals to the second mixed solution, and performing a crystallization reaction at 100-200°C. After the crystallization reaction is completed, filtering, washing, and drying are performed in sequence to obtain a Beta molecular sieve catalyst; 4) exchanging ammonium ions on the Beta molecular sieve catalyst in an ammonium salt aqueous solution, washing, drying, and performing a first calcination to obtain a hydrogen-type Beta molecular sieve catalyst; 5) immersing the hydrogen-type Beta molecular sieve catalyst in a lanthanum salt aqueous solution, and then drying to obtain a solid powder; after the solid powder is subjected to a second calcination, it is placed in hydrogen for reduction to obtain a hydrogen-type Beta molecular sieve catalyst containing lanthanum.

[0035] In step 1), a raw material system including an aluminum source and an alkali source is dissolved in water (eg, deionized water) to obtain a first mixed solution.

[0036] In a specific implementation process, after the raw material system including the aluminum source and the alkali source is mixed with deionized water, the mixture may be stirred to make the mixed solution clear, that is, the raw material system is dissolved in the deionized water to obtain a first mixed solution.

[0037] The aluminum source may include one or more of sodium aluminate (NaAlO2), aluminum sol, pseudo-boehmite, and aluminum sulfate; the alkali source may include one or more of sodium hydroxide (NaOH), ammonia water, and potassium hydroxide.

[0038] The concentration of the aluminum source in the first mixed solution can be 0.03-0.05 g / mL, for example, 0.03, 0.04, 0.05 g / mL or a range consisting of any two thereof.

[0039] The concentration of the alkali source in the first mixed solution can be 0.05 to 0.10 g / mL, for example, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10 g / mL or a range consisting of any two thereof.

[0040] In a specific implementation, 0.7-0.9 g of an aluminum source and 1.3-1.5 g of an alkali source can be dissolved in 18-22 mL of deionized water to obtain a first mixed solution. For example, the mass of the aluminum source can be 0.7 g, 0.8 g, 0.9 g, or a range consisting of any two thereof; the mass of the alkali source can be 1.3 g, 1.4 g, 1.5 g, or a range consisting of any two thereof; and the volume of the deionized water can be 18 mL, 20 mL, 22 mL, or a range consisting of any two thereof.

[0041] Since silica is insoluble in water, the process of using silica to prepare molecular sieves is difficult to carry out industrial production. However, the study found that suitable methods can be used to hydrophilize silica, which helps to increase the solubility of silica in water, accelerate its dissolution process, and help realize the industrial production of molecular sieves using silica.

[0042] Specifically, it was found through research that sodium dodecylbenzene sulfonate is an anionic surfactant, and its molecular structure consists of a lipophilic alkyl chain (dodecyl) and a hydrophilic sulfonic acid group. When sodium dodecylbenzene sulfonate is added to water, under the hydrophilic effect of the sulfonic acid group, the sodium dodecylbenzene sulfonate molecules (surfactant molecules) will spontaneously form micelles in the water. The inside of the micelle is a hydrophobic core formed by the aggregation of lipophilic alkyl chains, while the outside of the micelle is composed of hydrophilic sulfonic acid groups and can be in contact with water. When white carbon black is added, the sodium dodecylbenzene sulfonate molecules will be adsorbed on the surface of the white carbon black particles through physical adsorption. Since the surface of the white carbon black particles usually has a certain lipophilicity, the sodium dodecylbenzene sulfonate molecules will be adsorbed on the surface of the white carbon black particles through physical adsorption. The lipophilic alkyl chains of sodium benzenesulfonate can interact with the surface of silica, while the hydrophilic sulfonic acid groups face the water phase, thus forming a hydrophilic layer on the surface of the silica particles. As a result, the silica particles that were originally highly lipophilic are modified into silica particles with a certain degree of hydrophilicity, thereby reducing the mutual attraction between the silica particles and reducing the occurrence of agglomeration. When stirred, the silica particles can be better dispersed in water to form a relatively stable dispersion system. That is, sodium dodecylbenzenesulfonate increases the surface hydrophilicity of the silica particles by adsorbing on the surface of the silica particles, making them easier to disperse in water, which is conducive to the preparation of Beta molecular sieve catalysts with low interfacial tension and good dispersibility.

[0043] Based on this, in step 2), sodium dodecylbenzenesulfonate is added to the first mixed solution, and then white carbon black is added to obtain a second mixed solution.

[0044] The mass ratio of the silica to sodium dodecylbenzenesulfonate can be 5:(0.1-0.3), such as 5:0.1, 5:0.2, 5:0.3, or any combination thereof. This can improve the dispersibility of the silica in the preparation system, thereby improving the interfacial tension and dispersibility of the Beta molecular sieve catalyst.

[0045] The above step 2) further includes: adding sodium dodecylbenzenesulfonate to the first mixed solution under the action of ultrasound, and then adding white carbon black to obtain a second mixed solution. The cavitation effect of the ultrasound can break up the agglomeration of the white carbon black, making it more dispersed in water.

[0046] In a specific implementation, the first mixed solution can be placed in an ultrasonic stirring device and stirred while being ultrasonically treated. At the same time, sodium dodecylbenzenesulfonate is added to the first mixed solution. After it is evenly dispersed in the first mixed solution, white carbon black is added and ultrasonic stirring is carried out at room temperature (e.g., 20-25°C) for 22-26 hours, for example, 22 hours, 24 hours, 26 hours or a range consisting of any two thereof, to obtain a second mixed solution.

[0047] The above-mentioned white carbon black includes fumed silica.

[0048] In step 3), Beta molecular sieve seed crystals are added to the second mixed solution, and a crystallization reaction is carried out at 100-200° C. After the crystallization reaction is completed, filtration, washing, and drying are carried out in sequence to obtain a Beta molecular sieve catalyst.

[0049] In a specific implementation, after adding the Beta molecular sieve seed crystals to the second mixed solution, the mixture can be stirred at room temperature for 3 to 8 minutes, for example, 3 minutes, 5 minutes, 8 minutes, or a range consisting of any two thereof. The mixed solution (mixture) is then transferred to a polytetrafluoroethylene-lined reactor and crystallized at 100 to 200° C. After the crystallization reaction is completed, the mixture is filtered, washed, and dried in sequence to obtain a Beta molecular sieve catalyst. The Beta molecular sieve catalyst can be used for oil cracking to prepare olefins with 2 to 4 carbon atoms, such as ethylene, propylene, and butene. It has the advantages of high raw material conversion rate and low energy consumption, as well as low production cost and simple process flow.

[0050] In some embodiments, the mass ratio of the aluminum source to the Beta molecular sieve seed crystals may be (2-4):1, such as 2:1, 3:1, 4:1, or a range consisting of any two thereof.

[0051] Illustratively, the temperature of the crystallization reaction may be 100° C., 120° C., 140° C., 160° C., 180° C., 200° C., or a range consisting of any two thereof.

[0052] In addition, the crystallization reaction time may be 2 to 90 hours.

[0053] The embodiments of the present invention do not particularly limit the operating conditions of the above-mentioned filtration, washing and drying, and conventional conditions in the art may be adopted.

[0054] The above-mentioned Beta molecular sieve seed crystals can be purchased.

[0055] In step 4), the Beta molecular sieve catalyst is subjected to ammonium ion exchange in an ammonium salt aqueous solution, followed by washing, drying, and a first calcination to obtain a hydrogen-type Beta molecular sieve catalyst having low interfacial tension and good dispersion performance.

[0056] Specifically, the ammonium salt in the above-mentioned ammonium salt aqueous solution includes one or more of ammonium nitrate, ammonium chloride, and ammonium sulfate.

[0057] For example, the above-mentioned ammonium salt aqueous solution includes an ammonium nitrate aqueous solution, and its concentration can be in the range of 0.5, 1, 1.5 mol / L or any two thereof.

[0058] During the ammonium ion exchange process, the temperature can be maintained at 70-90° C., for example, 70, 80, 90° C. or any combination thereof, and the process can be carried out under stirring.

[0059] The embodiment of the present invention does not particularly limit the time of the above-mentioned ammonium ion exchange process. For example, it can be 1 hour, 2 hours, 3 hours, 4 hours or a range consisting of any two thereof.

[0060] The ammonium ion exchange may be performed at least twice, that is, the ammonium ion exchange process at the above temperature, stirring state, and time may be repeated at least twice.

[0061] The washing and drying after the ammonium ion exchange can be carried out according to conventional conditions in the art.

[0062] The first calcination temperature can be 450-550°C, such as 450, 500, 550°C or a range consisting of any two thereof, and the first calcination time can be 3-5h, such as 3, 4, 5h or a range consisting of any two thereof.

[0063] In step 5), the hydrogen-type Beta molecular sieve catalyst is immersed in a lanthanum salt aqueous solution and then dried to obtain a solid powder; the solid powder is subjected to a second calcination and then placed in hydrogen for reduction to obtain a hydrogen-type Beta molecular sieve catalyst containing lanthanum.

[0064] The lanthanum-containing hydrogen-type Beta molecular sieve catalyst has low interfacial tension, good dispersion performance, high raw material conversion rate, and high conversion rate of olefins with 2 to 4 carbon atoms (such as ethylene, propylene, and butene).

[0065] In some embodiments, the lanthanum salt in the lanthanum salt aqueous solution includes one or more of lanthanum nitrate (eg, lanthanum nitrate hexahydrate), lanthanum sulfate, lanthanum chloride, and lanthanum oxalate.

[0066] In a specific implementation, the lanthanum salt can be added into water, stirred and dissolved to obtain the above-mentioned lanthanum salt aqueous solution.

[0067] The process of immersing the hydrogen-type Beta molecular sieve catalyst in the lanthanum salt aqueous solution may include slowly pouring the lanthanum salt aqueous solution into a container (eg, a beaker) containing the hydrogen-type Beta molecular sieve catalyst at room temperature.

[0068] In some embodiments, the immersion time is 8 to 12 hours.

[0069] In a specific implementation, the drying process may include placing the impregnated hydrogen-type Beta molecular sieve catalyst in an oven, drying it at 110°C to 130°C, such as 110, 120, 130°C or any two thereof, for 6 to 8 hours, and stirring it 3-4 times during the drying process.

[0070] The process of performing a second calcination on the solid powder may include placing the solid powder into a crucible and then placing the crucible into a muffle furnace for the second calcination.

[0071] The second calcination temperature can be 450-600°C, such as 450, 500, 600°C or a range consisting of any two thereof, and the second calcination time can be 3-5h, such as 3, 4, 5h or a range consisting of any two thereof.

[0072] Next, the molecular sieve catalyst after the second calcination is placed in hydrogen for reduction, specifically including: placing it in a hydrogen flow and reducing it at 250°C to 350°C, such as 250, 300, 350°C or a range composed of any two thereof, for 2 to 4 hours, such as 2, 3, 4 hours or a range composed of any two thereof.

[0073] The present invention is further described below by way of specific examples and comparative examples. Unless otherwise specified, the reagents, materials, and instruments used below are all conventional reagents, materials, and instruments, all of which are commercially available, and the reagents and materials involved can also be synthesized by conventional synthesis methods.

[0074] Beta molecular sieve seed crystals were purchased from the Catalyst Factory of Nankai University.

[0075] Example 1

[0076] Preparation of hydrogen-type Beta molecular sieve catalyst containing lanthanum (La-HBeta molecular sieve):

[0077] Dissolve 0.8 g of NaAlO2 and 1.4 g of NaOH in 20 ml of deionized water and stir until clear to obtain a first mixed solution (Solution A);

[0078] Under ultrasonic treatment and stirring, 0.1 g of sodium dodecylbenzenesulfonate was added to the first mixed solution (Solution A), and after ultrasonic stirring, 5 g of fumed silica (white carbon black) was added, and ultrasonic stirring was carried out at room temperature for 24 h to obtain a second mixed solution;

[0079] 0.25 g of Beta molecular sieve seed crystals were added to the second mixed solution, stirred at room temperature for 5 minutes, and then transferred to a polytetrafluoroethylene-lined reactor for crystallization at 120° C. for 90 hours. The crystallization product was then filtered, washed with deionized water, and dried to obtain a Beta molecular sieve catalyst.

[0080] 1.0 g of the above-mentioned Beta molecular sieve catalyst was dissolved in 50 mL of a 1 mol / L NH4NO3 aqueous solution and stirred at 80°C for 2 h for ammonium ion exchange. The above-mentioned ammonium ion exchange operation was then repeated once. After filtering, washing, and drying, the catalyst was first calcined at 500°C for 4 h to obtain a hydrogen-type Beta molecular sieve catalyst (HBeta-SDBS molecular sieve).

[0081] 0.14 g of lanthanum nitrate hexahydrate was added to 3.5 mL of water and stirred to dissolve to obtain a lanthanum nitrate aqueous solution; 5 g of the above-mentioned hydrogenated Beta molecular sieve catalyst was immersed in the above-mentioned lanthanum nitrate aqueous solution at room temperature for 10 hours, and then the impregnated hydrogenated Beta molecular sieve catalyst was dried at 120° C. for 7 hours, stirring four times during the drying process, to obtain a solid powder; the solid powder was subjected to a second calcination at 500° C. for 4 hours, and then placed in a hydrogen flow at 300° C. for 3 hours to obtain a hydrogenated Beta molecular sieve catalyst containing lanthanum, with a lanthanum loading (or mass percentage) of 0.9%;

[0082] Preparation of ethylene, propylene and butene:

[0083] Take 0.1g of the above-mentioned hydrogen-type Beta molecular sieve catalyst containing lanthanum (20 mesh to 40 mesh) and 3.6g of quartz sand (20 mesh to 40 mesh) and add them to the cracking reactor. The temperature in the cracking reactor is maintained at 600°C, and the flow rate of nitrogen in the reactor is 50mL / min. Then, n-hexane is introduced (injected) at a flow rate of 15mL / h. After the reaction lasts for 10 minutes, samples are taken for analysis.

[0084] The conversion rate of n-hexane in Example 1 is 100%; and in the product, the mass percentage of ethylene is 50.5%, the mass percentage of propylene is 14%, the mass percentage of methane is 12%, the mass percentage of ethane is 2%, the mass percentage of propane is 0.5%, the mass percentage of aromatics is 9%, and the mass percentage of other products is 12%. Figure 1 shown.

[0085] The XRD pattern of the lanthanum-containing hydrogen-type Beta molecular sieve catalyst (La-HBeta molecular sieve) of Example 1 is shown in FIG. Figure 2 .

[0086] Example 2

[0087] This embodiment is basically the same as the first embodiment, except that:

[0088] The temperature in the cracking reactor was maintained at 500°C; other conditions remained unchanged.

[0089] The conversion rate of n-hexane in Example 2 was 94%; and in the product, the mass percentage of ethylene was 48.2%, the mass percentage of propylene was 13.5%, the mass percentage of methane was 8%, the mass percentage of ethane was 4.5%, the mass percentage of propane was 2.0%, the mass percentage of aromatics was 6%, and the mass percentage of other products was 17.8%.

[0090] Example 3

[0091] This embodiment is basically the same as the first embodiment, except that:

[0092] The temperature in the cracking reactor was maintained at 700°C; other conditions remained unchanged.

[0093] The conversion rate of n-hexane in Example 3 was 99%. The mass percentage of ethylene in the product was 47.5%, the mass percentage of propylene was 7.8%, the mass percentage of methane was 23%, the mass percentage of ethane was 2.2%, the mass percentage of propane was 0.3%, the mass percentage of aromatics was 9.5%, and the mass percentage of other products was 9.7%.

[0094] Example 4

[0095] This embodiment is basically the same as the first embodiment, except that:

[0096] In the hydrogen-type Beta molecular sieve catalyst containing lanthanum, the loading amount (or mass percentage) of lanthanum is 0.7%; other conditions remain unchanged.

[0097] The conversion rate of n-hexane in Example 4 is 98%; and in the product, the mass percentage of ethylene is 48.5%, the mass percentage of propylene is 13.5%, the mass percentage of methane is 12%, the mass percentage of ethane is 3%, the mass percentage of propane is 1%, the mass percentage of aromatics is 8%, and the mass percentage of other products is 14%.

[0098] Example 5

[0099] This embodiment is basically the same as the first embodiment, except that:

[0100] In the hydrogen-type Beta molecular sieve catalyst containing lanthanum, the loading amount (or mass percentage) of lanthanum is 1.2%; other conditions remain unchanged.

[0101] The conversion rate of n-hexane in Example 5 was 97%; and in the product, the mass percentage of ethylene was 49%, the mass percentage of propylene was 11%, the mass percentage of methane was 15%, the mass percentage of ethane was 3%, the mass percentage of propane was 1%, the mass percentage of aromatics was 9%, and the mass percentage of other products was 12%.

[0102] Comparative Example 1

[0103] Preparation of hydrogen-type Beta molecular sieve catalyst:

[0104] Dissolve 0.8 g of NaAlO2 and 1.4 g of NaOH in 20 ml of deionized water and stir until clear to obtain a first mixed solution (Solution A);

[0105] Under ultrasonic treatment and stirring, 0.1 g of sodium dodecylbenzenesulfonate was added to the first mixed solution (Solution A), and after ultrasonic stirring, 5 g of fumed silica (white carbon black) was added, and ultrasonic stirring was carried out at room temperature for 24 h to obtain a second mixed solution;

[0106] 0.25 g of Beta molecular sieve seed crystals were added to the second mixed solution, stirred at room temperature for 5 minutes, and then transferred to a polytetrafluoroethylene-lined reactor for crystallization at 120° C. for 90 hours. The crystallization product was then filtered, washed with deionized water, and dried to obtain a Beta molecular sieve catalyst.

[0107] 1.0 g of the above-mentioned Beta molecular sieve catalyst was dissolved in 50 mL of a 1 mol / L NH4NO3 aqueous solution and stirred at 80°C for 2 h for ammonium ion exchange. The above-mentioned ammonium ion exchange operation was then repeated once. After filtering, washing, and drying, the catalyst was first calcined at 500°C for 4 h to obtain a hydrogen-type Beta molecular sieve catalyst.

[0108] Preparation of ethylene, propylene and butene:

[0109] 0.1 g of hydrogen-type Beta molecular sieve catalyst (20-40 mesh) and 3.6 g of quartz sand (20-40 mesh) were added to a cracking reactor. The temperature in the cracking reactor was maintained at 400°C, and the flow rate of nitrogen in the reactor was 50 mL / min. Then, n-hexane was introduced (injected) at a flow rate of 15 mL / h. After the reaction lasted for 10 minutes, samples were taken for analysis.

[0110] The conversion rate of n-hexane in Comparative Example 1 was 10%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) was 24%, and the mass percentage of other products was 76%.

[0111] Comparative Example 2

[0112] This comparative example is basically the same as comparative example 1, except that:

[0113] The temperature in the cracking reactor was maintained at 500°C; other conditions remained unchanged.

[0114] The conversion rate of n-hexane in Comparative Example 2 is 30%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) is 50%, the mass percentage of aromatic hydrocarbons is 5%, and the mass percentage of other products is 45%.

[0115] Comparative Example 3

[0116] This comparative example is basically the same as Example 1, except that:

[0117] In the hydrogen-type Beta molecular sieve catalyst containing lanthanum, the loading amount (or mass percentage) of lanthanum is 0.6%; other conditions remain unchanged.

[0118] The conversion rate of n-hexane in Comparative Example 3 was 95%; and in the product, the mass percentage of ethylene was 41%, the mass percentage of propylene was 10%, the mass percentage of methane was 15%, the mass percentage of ethane was 5%, the mass percentage of propane was 3%, the mass percentage of aromatics was 10%, and the mass percentage of other products was 16%.

[0119] Comparative Example 4

[0120] This comparative example is basically the same as comparative example 1, except that:

[0121] The temperature in the cracking reactor was maintained at 600°C; other conditions remained unchanged.

[0122] The conversion rate of n-hexane in Comparative Example 4 was 100%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) was 39.6%, the mass percentage of aromatic hydrocarbons was 25%, and the mass percentage of other products was 35.4%.

[0123] Comparative Example 5

[0124] This comparative example is basically the same as comparative example 1, except that:

[0125] The ultrasonic treatment process was not added, and other conditions remained unchanged.

[0126] The conversion rate of n-hexane in Comparative Example 5 was 9%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) was 20%, and the mass percentage of other products was 80%.

[0127] Comparative Example 6

[0128] Preparation of H-Beta-TEA molecular sieve:

[0129] First, 1.5 g of NaAlO2 and 0.80 g of NaOH were dissolved in 63 mL of deionized water and stirred until clear. Then, 97 mL of TEAOH (tetraethylammonium hydroxide) solution was added and stirred at room temperature for 30 min. Then, 24 g of hydrophobic silica was added in batches to promote the dissolution of silica. After stirring at room temperature overnight, the mixture was transferred to a polytetrafluoroethylene reactor and crystallized at 140 ° C for 96 h.

[0130] After the crystallization is completed, the obtained Beta-TEA molecular sieve is centrifuged, washed with deionized water, dried, and finally calcined at 550° C. for 5 h in an oxygen atmosphere to eliminate the organic template (tetraethylammonium hydroxide) to obtain the Beta-TEA molecular sieve catalyst;

[0131] 1.0 g of the above-mentioned Beta molecular sieve was added to 50 mL of 1 mol / L NH4NO3 aqueous solution and stirred at 80°C for 2 h. The above ion exchange process was then repeated once. The product was then filtered, washed, dried, and calcined at 450°C for 5 h to obtain H-Beta-TEA molecular sieve.

[0132] Preparation of ethylene, propylene and butene:

[0133] The H-Beta-TEA molecular sieve was used as a catalyst, and the ethylene, propylene and butene of this comparative example were prepared according to the method for preparing ethylene, propylene and butene in comparative example 1.

[0134] The conversion rate of n-hexane in Comparative Example 6 was 5%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) was 26%, and the mass percentage of other products was 74%.

[0135] Comparative Example 7

[0136] This comparative example is basically the same as comparative example 2, except that:

[0137] The hydrogen-type Beta molecular sieve catalyst of Comparative Example 2 was replaced by the H-Beta-TEA molecular sieve of Comparative Example 6; other conditions remained unchanged.

[0138] The conversion rate of n-hexane in Comparative Example 7 is 20%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) is 35%, the mass percentage of aromatic hydrocarbons is 2.2%, and the mass percentage of other products is 62.8%.

[0139] Comparative Example 8

[0140] This comparative example is basically the same as comparative example 3, except that:

[0141] The hydrogen-type Beta molecular sieve catalyst in Comparative Example 3 was replaced by the H-Beta-TEA molecular sieve in Comparative Example 6; other conditions remained unchanged.

[0142] The conversion rate of n-hexane in Comparative Example 8 is 90%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) is 46%, the mass percentage of aromatic hydrocarbons is 21%, and the mass percentage of other products is 33%.

[0143] Comparative Example 9

[0144] This comparative example is basically the same as comparative example 4, except that:

[0145] The hydrogen-type Beta molecular sieve catalyst in Comparative Example 4 was replaced by the H-Beta-TEA molecular sieve in Comparative Example 6; other conditions remained unchanged.

[0146] The conversion rate of n-hexane in Comparative Example 9 is 100%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) is 37.5%, the mass percentage of aromatic hydrocarbons is 34%, and the mass percentage of other products is 28.5%.

[0147] Comparative Example 10

[0148] This comparative example is basically the same as comparative example 1, except that:

[0149] Sodium dodecylbenzenesulfonate was not added and other conditions remained unchanged.

[0150] The conversion rate of n-hexane in Comparative Example 10 was 8%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) was 18%, and the mass percentage of other products was 82%.

[0151] Comparative Example 11

[0152] Preparation of Beta molecular sieve catalyst containing lanthanum:

[0153] Dissolve 0.8 g of NaAlO2 and 1.4 g of NaOH in 20 ml of deionized water and stir until clear to obtain a first mixed solution (Solution A);

[0154] Under ultrasonic treatment and stirring, 0.1 g of sodium dodecylbenzenesulfonate was added to the first mixed solution (Solution A), and after ultrasonic stirring, 5 g of fumed silica (white carbon black) was added, and ultrasonic stirring was carried out at room temperature for 24 h to obtain a second mixed solution;

[0155] 0.25 g of Beta molecular sieve seed crystals were added to the second mixed solution, stirred at room temperature for 5 minutes, and then transferred to a polytetrafluoroethylene-lined reactor for crystallization at 120° C. for 90 hours. The crystallization product was then filtered, washed with deionized water, and dried to obtain a Beta molecular sieve catalyst.

[0156] 0.14 g of lanthanum nitrate hexahydrate was added to 3.5 mL of water and stirred to dissolve to obtain a lanthanum nitrate aqueous solution; 5 g of the above-mentioned Beta molecular sieve catalyst was impregnated in the above-mentioned lanthanum nitrate aqueous solution at room temperature for 10 hours, and then the impregnated Beta molecular sieve catalyst was dried at 120° C. for 7 hours, stirring four times during the drying process, to obtain a solid powder; the solid powder was subjected to a second calcination at 500° C. for 4 hours, and then placed in a hydrogen flow at 300° C. for 3 hours to obtain a lanthanum-containing Beta molecular sieve catalyst (0.9% La-Beta molecular sieve) with a lanthanum loading (or mass percentage) of 0.9%;

[0157] Preparation of ethylene, propylene and butene:

[0158] 0.1 g of lanthanum-containing Beta molecular sieve catalyst (0.9% La-Beta molecular sieve) (20 mesh to 40 mesh) and 3.6 g of quartz sand (20 mesh to 40 mesh) were added to a cracking reactor. The temperature in the cracking reactor was maintained at 400°C, and the flow rate of nitrogen in the reactor was 50 mL / min. Then, n-hexane was introduced (injected) at a flow rate of 15 mL / h. After the reaction lasted for 10 minutes, samples were taken for analysis.

[0159] The conversion rate of n-hexane in Comparative Example 11 is 53%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) is 31%, the mass percentage of aromatic hydrocarbons is 10%, and the mass percentage of other products is 59%.

[0160] Comparative Example 12

[0161] Preparation of Beta molecular sieve catalyst containing lanthanum (La-Beta molecular sieve):

[0162] This comparative example is basically the same as comparative example 11, except that:

[0163] Sodium dodecylbenzenesulfonate was not added and other conditions remained unchanged.

[0164] The conversion rate of n-hexane in Comparative Example 12 is 32%; and in the product, the mass percentage of olefins with 2-4 carbon atoms (ethylene, propylene, butene) is 18%, the mass percentage of aromatic hydrocarbons is 8%, and the mass percentage of other products is 74%.

[0165] Comparative Example 13

[0166] This comparative example is basically the same as Example 1, except that:

[0167] In the hydrogen-type Beta molecular sieve catalyst containing lanthanum, the loading amount (or mass percentage) of lanthanum is 1.3%; other conditions remain unchanged.

[0168] The conversion rate of n-hexane in Comparative Example 13 was 92%; and in the product, the mass percentage of ethylene was 40%, the mass percentage of propylene was 9%, the mass percentage of methane was 18%, the mass percentage of ethane was 6%, the mass percentage of propane was 4%, the mass percentage of aromatics was 12%, and the mass percentage of other products was 11%.

[0169] Comparative Example 14:

[0170] Preparation of lanthanum-containing H-ZSM-5 molecular sieve catalyst (La-HZSM-5):

[0171] Step 1: 1.0 g of commercial ZSM-5 molecular sieve (SiO2 / Al2O3 molar ratio = 80) was stirred in 50 mL of 1 mol / L NH4NO3 aqueous solution at 80°C for 2 h for ammonium ion exchange, and then the above ammonium ion exchange operation was repeated once. After filtering, washing, and drying, the catalyst was first calcined at 500°C for 4 h to obtain a hydrogenated ZSM-5 molecular sieve catalyst;

[0172] Step 2: 0.14 g of lanthanum nitrate hexahydrate was added to 3.5 mL of water and stirred to dissolve to obtain a lanthanum nitrate aqueous solution; 5 g of the above-mentioned hydrogenated ZSM-5 molecular sieve catalyst was immersed in the above-mentioned lanthanum nitrate aqueous solution at room temperature for 10 hours, and then the impregnated hydrogenated ZSM-5 molecular sieve catalyst was dried at 120° C. for 7 hours, stirred 4 times during the period, to obtain a solid powder; the solid powder was subjected to a second calcination at 500° C. for 4 hours, and then placed in a hydrogen flow at 300° C. for reduction for 3 hours to obtain a hydrogenated ZSM-5 molecular sieve catalyst containing lanthanum, and the lanthanum loading (or mass percentage) was 0.9%;

[0173] The reaction conditions for preparing ethylene, propylene and butene were the same as those in Example 1 (temperature was 600°C).

[0174] The conversion rate of n-hexane in Comparative Example 14 was 85%; in the product, the mass percentage of ethylene was 38%, the mass percentage of propylene was 9%, the mass percentage of methane was 16%, the mass percentage of ethane was 4%, the mass percentage of propane was 2%, the mass percentage of aromatics was 13%, and the mass percentage of other products was 18%.

[0175] Comparative Example 15:

[0176] Preparation of lanthanum-containing HY molecular sieve catalyst (La-HY):

[0177] Take 1.0g of commercial ultra-stable Y-type molecular sieve with a sodium content of less than 0.1% and + Exchange (same as step 1 of Comparative Example 14) and convert to HY;

[0178] La loading and reduction were carried out in the same manner as in step 2 of Comparative Example 14 to obtain a lanthanum-containing HY molecular sieve catalyst (La-HY), in which the lanthanum loading amount (or mass percentage) was 0.9%.

[0179] The reaction conditions for preparing ethylene, propylene and butene were the same as those in Example 1 (temperature was 600°C).

[0180] The conversion rate of n-hexane in Comparative Example 15 was 78%; in the product, the mass percentage of ethylene was 32%, the mass percentage of propylene was 7%, the mass percentage of methane was 14%, the mass percentage of ethane was 5%, the mass percentage of propane was 3%, the mass percentage of aromatics was 15%, and the mass percentage of other products was 24%.

[0181] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing ethylene and propylene, characterized in that: include: Under the action of a hydrogen-type Beta molecular sieve catalyst containing lanthanum, n-hexane is cracked at 500-700° C. to obtain the ethylene and propylene; the mass percentage of lanthanum in the hydrogen-type Beta molecular sieve catalyst containing lanthanum is 0.7%-1.2%.

2. The preparation method according to claim 1, characterized in that Also includes: 1) dissolving a raw material system including an aluminum source and an alkali source in water to obtain a first mixed solution; 2) adding sodium dodecylbenzenesulfonate to the first mixed solution, and then adding white carbon black to obtain a second mixed solution; 3) adding Beta molecular sieve seed crystals to the second mixed solution, performing a crystallization reaction at 100-200° C., and after the crystallization reaction is completed, filtering, washing, and drying in sequence to obtain a Beta molecular sieve catalyst; 4) exchanging ammonium ions in an aqueous ammonium salt solution of the Beta molecular sieve catalyst, washing, drying, and performing a first calcination to obtain a hydrogen-type Beta molecular sieve catalyst; 5) immersing the hydrogenated Beta molecular sieve catalyst in a lanthanum salt aqueous solution and then drying the mixture to obtain a solid powder; calcining the solid powder for a second time and then reducing the solid powder in hydrogen to obtain the hydrogenated Beta molecular sieve catalyst containing lanthanum.

3. The preparation method according to claim 2, characterized in that Step 2) also includes: Under the action of ultrasound, the sodium dodecylbenzenesulfonate is added to the first mixed solution, and then the white carbon black is added to obtain the second mixed solution.

4. The preparation method according to claim 2, characterized in that In step 4), the ammonium ion exchange is performed at least twice.

5. The preparation method according to claim 2, characterized in that The aluminum source includes one or more of sodium metaaluminate, aluminum sol, pseudo-boehmite, and aluminum sulfate.

6. The preparation method according to claim 2, characterized in that The alkali source includes one or more of sodium hydroxide, ammonia water, and potassium hydroxide.

7. The preparation method according to claim 2, characterized in that The ammonium salt in the ammonium salt aqueous solution includes one or more of ammonium nitrate, ammonium chloride, and ammonium sulfate.

8. The preparation method according to claim 2, characterized in that The lanthanum salt in the lanthanum salt aqueous solution includes one or more of lanthanum nitrate, lanthanum sulfate, lanthanum chloride, and lanthanum oxalate.

9. The preparation method according to claim 2, characterized in that The mass ratio of the white carbon black to the sodium dodecylbenzenesulfonate is 5:(0.1-0.3).

10. The preparation method according to claim 2, characterized in that In step 4), the temperature of the first calcination is 450-550°C.

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