A method for producing olefins from naphtha via catalytic cracking and the olefins obtained

Abstract

This invention discloses a method for producing olefins from naphtha via catalytic cracking and the resulting olefins. The method includes: contacting a naphtha feedstock containing C4-C15 hydrocarbons with a carbon-containing EMT molecular sieve catalyst to obtain an olefin stream containing ethylene and propylene; the reaction temperature is 550℃-850℃, the pressure is 0.1-2.0 MPa, and the weight hourly space velocity is 0.2 h⁻¹. ‑1 -5.0h ‑1 The carbon-containing EMT molecular sieve catalyst has a carbon content of 0.02–0.5 wt% and a Na₂O content of less than 2.5 wt%. Based on NH₃-TPD results, the ratio of weak acid content to moderately strong acid content in the carbon-containing EMT molecular sieve catalyst is (1.05–1.5):1. The method described in this invention has the advantages of high reaction conversion rate and high ethylene + propylene yield.

Description

Technical Field

[0001] This invention relates to the field of naphtha catalytic cracking technology, specifically to a method for producing olefins from naphtha catalytic cracking and the resulting olefins. Background Technology

[0002] With the increasing trend of heavier and lower-quality crude oil globally, the increasingly stringent standards for gasoline and diesel fuels at home and abroad, and the continuous rise in global demand for ethylene and propylene, the requirements for catalytic cracking (FCC) technology in oil refining are becoming increasingly stringent.

[0003] FCC catalysts account for approximately one-third of the global refining catalyst market share. Their technological level not only affects plant operation but also directly impacts refinery profitability. Currently, a series of catalysts have been developed for heavy oil cracking, high-octane gasoline production, and increased low-carbon olefin production, and new products are constantly being introduced to meet the ever-changing demands of the oil and chemical feedstock markets. Because product market demands, plant structures, and crude oil types vary across different regions of the world, the demand for FCC catalysts also differs. However, increasing olefin production, raising octane numbers, and increasing gasoline production remain the primary production goals of refineries.

[0004] Grace Chemical Company in the United States has developed a new Achieve-400 catalyst that employs dual molecular sieve technology. Utilizing traditional Y-type and Pentasi-type molecular sieves, it preferentially cracks C7 and higher olefins in gasoline, promoting the formation of more butene. Rive and Grace have collaborated to apply ordered mesoporous molecular sieves to multiple grades of catalytic cracking catalysts.

[0005] CN 104549466A discloses a fluidized bed catalyst for naphtha catalytic cracking using ZSM-5 / Beta symbiotic molecular sieves as a support. CN 101190417B uses combinations of symbiotic molecular sieves such as ZSM-5 / mordenium, ZSM-5 / Beta, and ZSM-5 / Y as catalysts to catalytically crack naphtha to produce ethylene and propylene.

[0006] US6211104 uses clay, inorganic oxides, and molecular sieves as catalysts, wherein the molecular sieves are high Si / Al Y molecular sieves or ZSM-5 molecular sieves. CN1274342A discloses a high Si / Al molecular sieve with a pore size of 0.5-0.65 nm as a catalyst for preparing ethylene and propylene from light hydrocarbons containing olefins. CN1413244A discloses a method for preparing small-molecule hydrocarbon mixtures by combining modified mesoporous phosphate materials as catalysts with primary catalytic cracking materials.

[0007] EMT molecular sieves have a zeolite framework structure with a three-dimensional 12-membered ring cross-channel system. They are highly acidic and have a high acid content, making them excellent catalytic materials for isomerization and catalytic cracking.

[0008] Currently, there is no literature on the use of carbon-containing EMT molecular sieve catalysts for naphtha catalytic cracking. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a method for producing olefins by naphtha catalytic cracking and the resulting olefins, wherein naphtha is reacted with a carbon-containing EMT molecular sieve catalyst to generate a stream containing ethylene and propylene.

[0010] One of the objectives of this invention is to provide a method for producing olefins by catalytic cracking of naphtha, comprising: contacting naphtha feedstock containing C4-C15 hydrocarbons with a carbon-containing EMT molecular sieve catalyst to obtain an olefin stream containing ethylene and propylene.

[0011] In a preferred embodiment, the reaction temperature is 550°C-850°C; and / or the pressure is 0.1-2.0 MPa; and / or the weight hourly space velocity (WHSV) is 0.2 h⁻¹. -1 -5.0h -1 .

[0012] In a further preferred embodiment, the reaction temperature is 550°C-750°C; and / or the pressure is 0.2-1.0 MPa; and / or the weight hourly space velocity is 0.5 h⁻¹. -1 -1.5h -1 .

[0013] For example, the reaction temperature is 550°C, 600°C, 650°C, 700°C, or 750°C; and / or, the pressure is 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, or 1.0 MPa; and / or, the weight hourly space velocity is 0.5 h⁻¹. -1 0.6h -1 0.8h -1 1h -1 1.2h -1 1.4h -1 Or 1.5h -1 .

[0014] In a preferred embodiment, the EMT molecular sieve is a carbon-containing EMT molecular sieve, wherein the carbon content is 0.02-0.5 wt% and the Na2O content is less than 2.5 wt%.

[0015] In a preferred embodiment, the carbon-containing EMT molecular sieve catalyst has a carbon content of 0.02–0.2 wt% and a Na₂O content of less than 1 wt%.

[0016] For example, the carbon content in carbon-containing EMT molecular sieve catalysts is 0.02 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.12 wt%, 0.15 wt%, 0.18 wt%, or 0.2 wt%.

[0017] In a preferred embodiment, based on the NH3-TPD results, the ratio of the amount of weak acid to the amount of medium-strong acid in the carbon-containing EMT molecular sieve catalyst is (1.05-1.5):1, preferably (1.05-1.3):1.

[0018] For example, the ratio of weak acid content to medium-strong acid content in carbon-containing EMT molecular sieve catalysts is 1.05:1, 1.1:1, 1.15:1, 1.2:1, 1.25:1, or 1.3:1.

[0019] In a preferred embodiment, the carbon-containing EMT molecular sieve catalyst is obtained by a method comprising the following steps:

[0020] (1) Mix aluminum source, sodium hydroxide, silicon source, organic amine and solvent to obtain a mixture;

[0021] (2) The mixture is crystallized, and after crystallization, the solvent is removed, the mixture is washed with water, and dispersed in acid to obtain a dispersion.

[0022] (3) The dispersion is crystallized, and the solvent is removed and the mixture is washed with water after crystallization.

[0023] (4) Drying and calcining to obtain the EMT molecular sieve.

[0024] In this invention, the introduction of organic amines into the raw material solution serves several purposes: ① It replaces a portion of the sodium hydroxide, meaning the amount of sodium hydroxide used is less than in existing technologies, facilitating subsequent sodium exchange; ② The organic amines form residual carbon within the EMT molecular sieve after the subsequent crystallization process; ③ While adjusting the pH of the dispersion in step 3 using organic acids, they work together with the organic amine derivatives to control the carbon content of the molecular sieve. Furthermore, this invention adds organic amines and organic acids during the in-situ synthesis of the molecular sieve, ensuring a uniform distribution of these substances within the pores of the molecular sieve.

[0025] In a preferred embodiment, the aluminum source is selected from at least one of aluminum sol, sodium aluminate, aluminum sulfate, aluminum nitrate, and aluminum isopropoxide.

[0026] In a further preferred embodiment, the aluminum source is selected from at least one of aluminum sol and sodium aluminate.

[0027] In a preferred embodiment, the silicon source is selected from at least one of silica sol, water glass, tetraethyl orthosilicate, and sodium silicate.

[0028] In a further preferred embodiment, the silicon source is selected from at least one of silica sol and sodium silicate.

[0029] In a preferred embodiment, the organic amine is a small molecule organic amine.

[0030] In a further preferred embodiment, the organic amine is selected from small molecule organic amines of C1 to C6, preferably from small molecule organic amines of C1 to C4.

[0031] Wherein, the small molecule refers to a molecular weight less than 200, preferably less than 100; for example, the organic amine is selected from at least one of methylamine, ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, and butyldiamine.

[0032] The reason why small molecule organic amines are preferred in this invention is that high carbon organic amines (such as organic amines with more than C7) have relatively weak alkalinity and cannot meet the alkalinity required for crystallization.

[0033] In a preferred embodiment, the solvent is water.

[0034] In a preferred embodiment, the molar ratio of aluminum source, silicon source, sodium oxide, organic amine, and solvent is 1:(1-20):(2-10):(0.5-20):(100-500), wherein the molar amount of aluminum source is calculated as the molar amount of Al2O3, the molar amount of silicon source is calculated as the molar amount of SiO2, the molar amount of sodium oxide is the total amount including the molar amounts of sodium oxide (Na2O) in the aluminum source and silicon source and the molar amounts of sodium hydroxide converted to sodium oxide (Na2O), and the molar amounts of organic amine and solvent are respectively calculated as the molar amounts of their molecules.

[0035] In a further preferred embodiment, the molar ratio of aluminum source, silicon source, sodium oxide, organic amine and solvent is 1:(3-10):(3-8):(1-10):(150-400), wherein the molar amount of aluminum source is calculated as the molar amount of Al2O3, the molar amount of silicon source is calculated as the molar amount of SiO2, the molar amount of sodium oxide is the total amount including the molar amount of sodium oxide (Na2O) in aluminum source and silicon source and the molar amount of sodium hydroxide converted to sodium oxide (Na2O), and the molar amounts of organic amine and solvent are respectively calculated as the molar amount of their molecules.

[0036] For example, the molar ratio of aluminum source to silicon source is 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10; the molar ratio of aluminum source to sodium oxide is 1:3, 1:4, 1:5, 1:6, 1:7 or 1:8; the molar ratio of aluminum source to organic amine is 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10; and the molar ratio of aluminum source to solvent is 1:150, 1:200, 1:250, 1:300, 1:350 or 1:400.

[0037] In a preferred embodiment, step (1) is performed as follows:

[0038] (1.1) Mix the aluminum source, sodium hydroxide and solvent to obtain solution A;

[0039] (1.2) Mix the silicon source, organic amine, and solvent to obtain solution B;

[0040] (1.3) Cool solutions A and B, then slowly add solution A to solution B to obtain the mixture.

[0041] In a preferred embodiment, the weight concentration of solution A is 3-35 wt%, preferably 4-30 wt%.

[0042] For example, the weight concentration of solution A is 3 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, or 35 wt%.

[0043] In a preferred embodiment, the weight concentration of solution B is 25-50 wt%, preferably 28-48 wt%.

[0044] For example, the weight concentration of solution B is 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%.

[0045] In a preferred embodiment, in step (1.3), the temperature is cooled to -10 to 10°C, preferably to 0 to 4°C.

[0046] In a preferred embodiment, the crystallization in step (2) is carried out at 5–60°C for 0.5–8 days.

[0047] In a further preferred embodiment, the crystallization in step (2) is carried out at 10–40°C for 1–5 days.

[0048] The crystallization described in step (2) is carried out at 10°C, 20°C, 30°C or 40°C for 1, 2, 3, 4 or 5 days.

[0049] In a preferred embodiment, in step (2), the solvent is removed by vacuum filtration.

[0050] In a preferred embodiment, in step (2), the filtrate is washed with water until the pH of the filtrate is 9-10.

[0051] For example, in step (2), the filtrate is washed with water until the pH of the filtrate is 9, 9.5 or 10.

[0052] In step (2), if the pH is controlled to be below 9, the amount of organic amine will be too low. For example, the organic amine may be washed away by water, resulting in insufficient organic amine in the molecular sieve system.

[0053] In a preferred embodiment, in step (2), the acid is an organic acid.

[0054] In a further preferred embodiment, the organic acid is selected from at least one of formic acid, acetic acid, propionic acid, citric acid, oxalic acid, benzoic acid, and tartaric acid.

[0055] In the prior art, inorganic acids are mostly used, but the present invention uses organic acids because some organic acids will form residual carbon in the molecular sieve during the crystallization process in step 3.

[0056] In a further preferred embodiment, the pH of the dispersion is adjusted to 1-5, preferably 2-4, using the acid.

[0057] For example, the pH of the dispersion is adjusted to 2, 2.5, 3, 3.5 or 4 using the acid.

[0058] In a preferred embodiment, in step (3), the crystallization is carried out at 100-300°C for 1-30 hours.

[0059] In a further preferred embodiment, in step (3), the crystallization is carried out at 130–250°C for 4–24 hours.

[0060] For example, in step (3), the crystallization is carried out at 130°C, 150°C, 180°C, 200°C, 230°C or 250°C for 4h, 6h, 10h, 12h, 15h, 18h, 20h, 22h or 24h.

[0061] In a preferred embodiment, in step (3), the solvent is removed by vacuum filtration.

[0062] In a preferred embodiment, in step (3), the filtrate is washed with water until the pH of the filtrate is 6 to 8, for example, pH = 7.

[0063] In a preferred embodiment, in step (4), the drying temperature is 50-150°C, preferably 80-120°C.

[0064] For example, in step (4), the drying temperature is 50°C, 80°C, 100°C, 120°C or 150°C.

[0065] In a preferred embodiment, in step (4), the calcination temperature is 400-650°C, preferably 500-550°C.

[0066] For example, in step (4), the roasting temperature is 400°C, 450°C, 500°C, 550°C, 600°C or 650°C.

[0067] A second objective of this invention is to provide an olefin stream obtained using the method described in one objective of this invention.

[0068] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0069] Compared with the prior art, the present invention has the following beneficial effects:

[0070] (1) The carbon-containing EMT molecular sieve has a low silicon-to-aluminum ratio, abundant active sites, moderate acid distribution, and possesses weak acid and medium-strong acid centers.

[0071] (2) The carbon-containing EMT molecular sieve catalyst described in this invention has carbon residue on the EMT molecular sieve and the Na content in the molecular sieve (calculated as Na2O content characterized by XRF) is low.

[0072] (3) The carbon-containing EMT molecular sieve catalyst of the present invention has a high reaction conversion rate and a high yield of ethylene + propylene in the catalytic cracking of naphtha to olefins reaction. Detailed Implementation

[0073] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0074] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0075] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0076] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0077] [Example 1] Preparation of carbon-containing EMT molecular sieve catalyst

[0078] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A, with a mass concentration of 11.5 wt%. Silica sol (SiO2 weight percentage 40%), ethylenediamine, and water were mixed and stirred until homogeneous to obtain solution B, with a mass concentration of 29.1 wt%. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled at Al2O3:SiO2:Na2O:ethylenediamine:H2O = 1:5.3:3.7:3.3:180. The mixture was crystallized at 30°C for 3 days to obtain a suspension. This suspension was filtered under reduced pressure and washed with distilled water until the pH reached 10. The filter cake was dispersed in water, and oxalic acid was added to adjust the pH to 3. The dispersion was crystallized at 230℃ for 12 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve (named EMT-1). The Si / Al ratio was 1.5, the carbon content was 0.10 wt%, and the Na2O content was 0.83 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 1.08:1.

[0079] [Example 2] Carbon-containing EMT molecular sieve catalyst

[0080] Aluminum sulfate and sodium hydroxide were dissolved in distilled water to obtain solution A, with a mass concentration of 24.8 wt%. Sodium silicate, propylenediamine, and water were mixed and stirred until homogeneous to obtain solution B, with a mass concentration of 45.9 wt%. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled to be Al₂O₃:SiO₂:Na₂O:propylenediamine:H₂O = 1:5.0:6.9:3.7:240. The mixture was crystallized at 30°C for 3 days to obtain a suspension. The suspension was filtered under reduced pressure and washed with distilled water until the pH reached 9.5. The filter cake was dispersed in water, and citric acid was added to adjust the pH to 4. The dispersion was crystallized at 200℃ for 24 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve (named EMT-2). The Si / Al ratio was 1.2, the carbon content was 0.07wt%, and the Na2O content was 0.95wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 1.05:1.

[0081] [Example 3] Carbon-containing EMT molecular sieve catalyst

[0082] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A, with a mass concentration of 10.7 wt%. Sodium silicate, ethylenediamine, and water were mixed and stirred until homogeneous to obtain solution B, with a mass concentration of 34.1 wt%. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled to be Al₂O₃:SiO₂:Na₂O:ethylenediamine:H₂O = 1:5.2:7.2:4.8:300. The mixture was crystallized at 30°C for 3 days to obtain a suspension. The suspension was filtered under reduced pressure and washed with distilled water until the pH reached 10. The filter cake was dispersed in water, and oxalic acid was added to adjust the pH to 2. The dispersion was crystallized at 230℃ for 24 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve (named EMT-3). The Si / Al ratio was 1.3, the carbon content was 0.16 wt%, and the Na2O content was 0.79 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 1.22:1.

[0083] [Example 4] Carbon-containing EMT molecular sieve catalyst

[0084] Aluminum sol (Al₂O₃ weight percentage 24%) and sodium hydroxide were dissolved in distilled water to obtain solution A, with a mass concentration of 4.1 wt%. Sodium silicate, butanediamine, and water were mixed and stirred until homogeneous to obtain solution B, with a mass concentration of 42.8 wt%. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled to be Al₂O₃:SiO₂:Na₂O:butanediamine:H₂O = 1:5.1:6.6:5:270. The mixture was crystallized at 30°C for 3 days to obtain a suspension. The suspension was filtered under reduced pressure and washed with distilled water until the pH reached 9. The filter cake was dispersed in water, and acetic acid was added to adjust the pH to 3. The dispersion was crystallized at 250℃ for 12 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve (named EMT-4). The Si / Al ratio was 1.7, the carbon content was 0.12 wt%, and the Na2O content was 0.74 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 1.15:1.

[0085] [Example 5] Carbon-containing EMT molecular sieve catalyst

[0086] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A, with a mass concentration of 10.7 wt%. Sodium silicate, an aqueous solution of ethylamine (ethylamine content 65-70%), and water were mixed and stirred until homogeneous to obtain solution B, with a mass concentration of 34.8 wt%. Solutions A and B were cooled separately in an ice bath at 4°C. Then, under magnetic stirring, solution A was slowly added to solution B to form a mixture. The molar ratio of the mixture was controlled to be Al₂O₃:SiO₂:Na₂O:ethylamine:H₂O = 1:5.2:7.2:10:300. The mixture was crystallized at 30°C for 3 days to obtain a suspension. The suspension was filtered under reduced pressure and washed with distilled water until the pH reached 10. The filter cake was dispersed in water, and oxalic acid was added to adjust the pH to 2. The dispersion was crystallized at 230℃ for 24 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve (named EMT-5). The Si / Al ratio was 1.8, the carbon content was 0.19 wt%, and the Na2O content was 0.66 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 1.11:1.

[0087] [Example 6] Method for Catalytic Cracking of Naphtha

[0088] The molecular sieve prepared in Example 1 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor. C4-C15 hydrocarbon naphtha was used as the raw material. The reaction temperature was 700℃, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 66.2%, and the ethylene-propylene yield was 48.2%.

[0089] [Example 7] Method for Catalytic Cracking of Naphtha

[0090] The molecular sieve prepared in Example 2 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as feedstock. The reaction temperature was 700°C, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 63.3%, and the ethylene-propylene yield was 45.0%.

[0091] [Example 8] Method for catalytic cracking of naphtha

[0092] The molecular sieve prepared in Example 3 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as raw material. The reaction temperature was 700℃, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 71.3%, and the ethylene-propylene yield was 50.2%.

[0093] [Example 9] Method for catalytic cracking of naphtha

[0094] The molecular sieve prepared in Example 4 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as raw material. The reaction temperature was 700℃, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 71.8%, and the ethylene-propylene yield was 48.8%.

[0095] [Example 10] Method for catalytic cracking of naphtha

[0096] The molecular sieve prepared in Example 5 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as feedstock. The reaction temperature was 700℃, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 60.8%, and the ethylene-propylene yield was 42.5%.

[0097] [Example 11] Method for catalytic cracking of naphtha

[0098] The molecular sieve prepared in Example 1 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor. C4-C15 hydrocarbon naphtha was used as raw material. The reaction temperature was 650°C, the pressure was 0.5 MPa, and the weight hourly space velocity was 0.5 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 67.5%, and the ethylene-propylene yield was 51.1%.

[0099] [Example 12] Method for catalytic cracking of naphtha

[0100] The molecular sieve prepared in Example 1 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor. C4-C15 hydrocarbon naphtha was used as raw material. The reaction temperature was 550°C, the pressure was 0.2 MPa, and the weight hourly space velocity was 0.5 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 58.8%, and the ethylene-propylene yield was 43.8%.

[0101] [Example 13] Method for catalytic cracking of naphtha

[0102] The molecular sieve prepared in Example 1 was compressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as raw material. The reaction temperature was 750°C, the pressure was 0.8 MPa, and the weight hourly space velocity was 1.5 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 61.3%, and the ethylene-propylene yield was 45.5%.

[0103] Comparative Example 1

[0104] The process of Example 1 was repeated, except that in the preparation of EMT molecular sieves, organic amines were not used, and only sodium hydroxide was used to adjust the alkalinity.

[0105] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A. Silica sol (40% SiO2 by weight), sodium hydroxide, and water were mixed and stirred until homogeneous to obtain solution B. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled at Al₂O₃:SiO₂:Na₂O:H₂O = 1:5.3:17.8:180. The mixture was crystallized at 30°C for 3 days to obtain a suspension. This suspension was filtered under reduced pressure and washed with distilled water until the pH reached 10. The filter cake was dispersed in water, and oxalic acid was added to adjust the pH to 3. The dispersion was crystallized at 230℃ for 12 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve with a Si / Al ratio of 1.2 and a carbon content of 0.04 wt%. The Na2O content was 6.55 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 0.84:1.

[0106] The naphtha catalytic cracking method in Example 5 was repeated. The molecular sieve prepared in Comparative Example 1 was pressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as feedstock. The reaction temperature was 700°C, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 11.3%, and the ethylene-propylene yield was 15.2%.

[0107] Comparative Example 2

[0108] Repeat the process of Example 1, except that the C1-C4 organic amines are replaced with an equal amount of octanediamine.

[0109] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A; silica sol (SiO2 weight percentage 40%), octanediamine, and water were mixed and stirred until homogeneous to obtain solution B; solutions A and B were cooled separately in an ice bath at 4°C, and then A was slowly added to B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled at Al2O3:SiO2:Na2O:octanediamine:H2O = 1:5.3:3.7:3.3:180. The mixture was crystallized at 30°C for 3 days to obtain a suspension, which was then filtered under reduced pressure and washed with distilled water until the pH reached 10. XRD characterization of the dried sample showed that the product was amorphous and lacked the characteristic diffraction peaks of EMT molecular sieves.

[0110] Comparative Example 3

[0111] Repeat the process of Example 1, except that the pH is adjusted to 8 in step (2).

[0112] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A. Silica sol (SiO2 weight percentage 40%), ethylenediamine, and water were mixed and stirred until homogeneous to obtain solution B. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled to be Al2O3:SiO2:Na2O:ethylenediamine:H2O = 1:5.3:3.7:3.3:180. The mixture was crystallized at 30°C for 3 days to obtain a suspension. This suspension was filtered under reduced pressure and washed with distilled water until the pH reached 8. The filter cake was dispersed in water, and oxalic acid was added to adjust the pH to 3. The dispersion was crystallized at 230℃ for 12 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve with a Si / Al ratio of 1.5, a carbon content of 0.01 wt%, and a Na2O content of 0.80 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 1.02:1.

[0113] The naphtha catalytic cracking method in Example 5 was repeated. The molecular sieve prepared in Comparative Example 3 was pressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as feedstock. The reaction temperature was 700°C, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the yield of ethylene and propylene was 39.6%.

[0114] Comparative Example 4

[0115] Repeat the process of Example 1, except that an equal amount of hydrochloric acid is used to replace the organic acid.

[0116] Sodium aluminate and sodium hydroxide were dissolved in distilled water to obtain solution A. Silica sol (SiO2 weight percentage 40%), ethylenediamine, and water were mixed and stirred until homogeneous to obtain solution B. Solutions A and B were cooled separately in an ice bath at 4°C. Then, solution A was slowly added to solution B under magnetic stirring to form a mixture. The molar ratio of the mixture was controlled to be Al2O3:SiO2:Na2O:ethylenediamine:H2O = 1:5.3:3.7:3.3:180. The mixture was crystallized at 30°C for 3 days to obtain a suspension. This suspension was filtered under reduced pressure and washed with distilled water until the pH reached 10. The filter cake was dispersed in water, and hydrochloric acid was added to adjust the pH to 3. The dispersion was crystallized at 230℃ for 12 hours. After crystallization, it was filtered under reduced pressure and washed with distilled water until the pH reached 7. The filter cake was dried at 120℃ and calcined at 550℃ for 3 hours to obtain a carbon-containing EMT molecular sieve with a Si / Al ratio of 1.3, a carbon content of 0.03 wt%, and a Na2O content of 3.17 wt%. Based on the NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst was 0.83:1.

[0117] The naphtha catalytic cracking method in Example 5 was repeated. The molecular sieve prepared in Comparative Example 3 was pressed, crushed, and sieved. Two grams of 20-40 mesh particles were placed in a fixed-bed reactor using C4-C15 hydrocarbon naphtha as feedstock. The reaction temperature was 700°C, the pressure was 0.2 MPa, and the weight hourly space velocity was 1.0 h⁻¹. -1 Under these conditions, the naphtha conversion rate was 18.7%, and the ethylene-propylene yield was 24.4%.

[0118] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for producing olefins from naphtha via catalytic cracking, comprising: The reaction of C4-C15 hydrocarbon naphtha feedstock with a carbon-containing EMT molecular sieve catalyst yields an olefin stream containing ethylene and propylene. The carbon-containing EMT molecular sieve catalyst has a carbon content of 0.02-0.5 wt% and a Na2O content of less than 2.5 wt%. Based on NH3-TPD results, the ratio of weak acid content to medium-strong acid content in the carbon-containing EMT molecular sieve catalyst is (1.05-1.5):

1.

2. The method according to claim 1, characterized in that, The reaction temperature is 550℃-850℃; and / or, The reaction pressure is 0.1-2.0 MPa; and / or, The weight hourly space velocity (WHSV) of the reaction is 0.2 h⁻¹. -1 -5.0h -1 .

3. The method according to claim 1, characterized in that, The reaction temperature is 550℃-750℃; and / or, The reaction pressure is 0.2-1.0 MPa; and / or, The weight hourly space velocity (WHSV) of the reaction is 0.5 h⁻¹. -1 -1.5h -1 .

4. The method according to claim 1, characterized in that, The carbon-containing EMT molecular sieve catalyst is obtained by a method comprising the following steps: (1) An aluminum source, sodium hydroxide, silicon source, organic amine, and solvent are mixed to obtain a mixture; the organic amine is selected from small molecule organic amines of C1 to C6. (2) The mixture is crystallized, and after crystallization, the solvent is removed, the mixture is washed with water until the pH of the filtrate is 9-10, and then dispersed in an acid, wherein the acid is an organic acid, to obtain a dispersion. (3) The dispersion is crystallized, and the solvent is removed and the mixture is washed with water after crystallization. (4) Drying and calcining to obtain the EMT molecular sieve.

5. The method according to claim 4, characterized in that, The aluminum source is selected from at least one of aluminum sol, sodium aluminate, aluminum sulfate, aluminum nitrate, and aluminum isopropoxide; and / or, The silicon source is selected from at least one of silica sol, water glass, tetraethyl orthosilicate, and sodium silicate; and / or, The organic amine is selected from small molecule organic amines of C1 to C4.

6. The method according to claim 4, characterized in that, The aluminum source is selected from at least one of aluminum sol and sodium aluminate; and / or, The silicon source is selected from at least one of silica sol and sodium silicate; and / or, The organic amine is selected from at least one of methylamine, ethylamine, propylamine, butylamine, ethylenediamine, propylenediamine, and butylenediamine.

7. The method according to claim 4, characterized in that, The molar ratio of aluminum source, silicon source, sodium oxide, organic amine and solvent is 1:(1~20):(2~10):(0.5~20):(100~500); wherein, the molar amount of aluminum source is calculated as the molar amount of Al2O3, the molar amount of silicon source is calculated as the molar amount of SiO2, the molar amount of sodium oxide is the total amount including the molar amount of sodium oxide in aluminum source and silicon source and the molar amount of sodium hydroxide converted to sodium oxide, and the molar amounts of organic amine and solvent are calculated as the molar amount of their molecules.

8. The method according to claim 4, characterized in that, The molar ratio of aluminum source, silicon source, sodium oxide, organic amine and solvent is 1:(3~10):(3~8):(1~10):(150~400); wherein, the molar amount of aluminum source is calculated as the molar amount of Al2O3, the molar amount of silicon source is calculated as the molar amount of SiO2, the molar amount of sodium oxide is the total amount including the molar amount of sodium oxide in aluminum source and silicon source and the molar amount of sodium hydroxide converted to sodium oxide, and the molar amounts of organic amine and solvent are calculated as the molar amount of their molecules.

9. The method according to claim 4, characterized in that, Step (1) is performed as follows: (1.1) Mix the aluminum source, sodium hydroxide and solvent to obtain solution A; (1.2) Mix the silicon source, organic amine, and solvent to obtain solution B; (1.3) Cool solutions A and B, then add solution A to solution B to obtain the mixture.

10. The method according to claim 9, characterized in that, The weight concentration of solution A is 3–35 wt%; and / or, The weight concentration of solution B is 25–50 wt%; and / or, In step (1.3), the temperature is cooled to -10 to 10°C.

11. The method according to claim 9, characterized in that, The weight concentration of solution A is 4–30 wt%; and / or, The weight concentration of solution B is 28–48 wt%; and / or, In step (1.3), the temperature is cooled to 0–4°C.

12. The method according to claim 4, characterized in that, The crystallization described in step (2) is carried out at 5–60°C for 0.5–8 days; and / or, In step (2), the solvent is removed by vacuum filtration; and / or, In step (2), the organic acid is selected from at least one of formic acid, acetic acid, propionic acid, citric acid, oxalic acid, benzoic acid, and tartaric acid.

13. The method according to claim 4, characterized in that, In step (3), the crystallization is carried out at 100–300°C for 1–30 hours; and / or, In step (3), the solvent is removed by vacuum filtration; and / or, In step (3), the filtrate is washed with water until the pH of the filtrate reaches 6-8.

14. The method according to any one of claims 4 to 13, characterized in that, In step (4), the drying temperature is 50–150°C; and / or, In step (4), the roasting temperature is 400-650°C.