A process for the production of lower alkanes from a petroleum naphtha fraction
By preparing metal-modified molecular sieves and amorphous aluminum-silicon compound catalysts, the selectivity and stability issues of naphtha conversion to low-carbon olefins were solved, achieving efficient preparation of low-carbon alkanes, which is suitable for industrial applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-09
AI Technical Summary
In the existing technology for converting naphtha into low-carbon olefins, the selectivity for ethylene and propylene is not high, and the catalyst stability is insufficient, resulting in low yields of ethylene and propylene from naphtha cracking.
A catalyst composed of metal-modified molecular sieves, amorphous aluminum-containing compounds, and amorphous silicon-containing compounds was prepared by mixing, extrusion molding, drying, and calcination. The catalyst was then used to react naphtha fractions under a hydrogen atmosphere to produce low-carbon alkanes.
It achieves efficient preparation of low-carbon alkanes, with a catalyst exhibiting high activity and selectivity, and a simple process suitable for large-scale industrial production.
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Abstract
Description
Technical Field
[0001] This application relates to a method for producing low-carbon alkanes from naphtha fractions, belonging to the field of chemical engineering. Background Technology
[0002] my country's refining capacity continues to grow, resulting in a crude oil overcapacity. Meanwhile, demand for chemicals such as low-carbon olefins, primarily ethylene, propylene, and butene, has maintained a high growth rate. Currently, ethylene and propylene are mainly obtained through fluidized bed catalytic cracking processes in refineries. The former provides the majority of ethylene consumed in the market, while propylene, a byproduct of naphtha steam cracking, and gaseous products from catalytic cracking provide the majority of propylene consumed in the market. Currently, the main feedstock for producing low-carbon olefins worldwide is petroleum hydrocarbons, with naphtha accounting for the majority. Therefore, using lower-value naphtha to produce higher-value ethylene and propylene is a common practice. However, the yield of ethylene from naphtha cracking is typically only around 30%, far lower than that of ethane (approximately 80%), propane (approximately 40%), and n-butane (approximately 40%). C4-C6 alkanes are important components of naphtha; converting them first into ethane, propane, and n-butane before feeding them into a steam cracking unit can significantly increase the ethylene yield.
[0003] Patents CN1504540 and USP6211104 use 10-70% clay, 5-85% pentoxides, and 1-50% zeolite to form a catalyst, which shows good activity in converting naphtha into light olefins, but the selectivity for ethylene and propylene is not high.
[0004] The literature Lu, JY, et al., CrHZSM-5 zeolites - Highly efficient catalysts for catalytic cracking of isobutane to produce light olefins. CATALYSISLETTERS, 2006, 109(1-2): p.65-70. Fe / HZSM5 and Cr / HZSM5 catalysts were prepared by impregnation method. When studying the cracking performance of isobutane, it was found that the introduction of Fe and Cr can achieve high olefin selectivity. However, in the research process, it was found that a small amount of Fe and Cr can increase the acidity of the catalyst, but increasing the loading may cover more acidic sites, resulting in a decrease in acidity and a reduction in catalytic cracking activity. Summary of the Invention
[0005] The purpose of this invention is to provide a method for producing low-carbon alkanes from naphtha fractions and a catalyst thereof, which has high catalytic performance, high selectivity for low-carbon alkanes in the product, and high stability.
[0006] According to one aspect of this application, a method for producing low-carbon alkanes from naphtha fractions is provided, comprising the following steps:
[0007] In a reactor under a hydrogen atmosphere, naphtha from the C4-C6 fraction is used as a raw material and reacted with a catalyst to obtain low-carbon alkanes.
[0008] The low-carbon alkane is selected from at least one of ethane, ethylene, and n-butane;
[0009] The catalyst is composed of metal-modified molecular sieves, amorphous aluminum-containing compounds, and amorphous silicon-containing compounds.
[0010] The catalyst is obtained through the following steps:
[0011] The catalyst is obtained by mixing a metal-modified molecular sieve, an amorphous aluminum-containing compound precursor, and an amorphous silicon-containing compound precursor, extruding the mixture, drying it, and calcining it.
[0012] The amorphous aluminum-containing compound precursor is selected from at least one of alumina sol, kaolin, montmorillonite, sepiolite, and diatomaceous earth.
[0013] The amorphous silicon-containing compound precursor is selected from at least one of silica sol, silica fume and magnesium silicate;
[0014] The mass ratio of the metal-modified molecular sieve, the amorphous aluminum-containing compound precursor, and the amorphous silicon-containing compound precursor is 30:1 to 20:1 to 20.
[0015] The drying temperature is 30–120°C;
[0016] The drying time is 1 to 12 hours;
[0017] The roasting temperature is 400–600°C;
[0018] The roasting time is 1 to 10 hours.
[0019] The metal-modified molecular sieve is obtained through the following steps:
[0020] The molecular sieve is mixed with an aqueous solution of a metal salt, subjected to ion exchange, washing, centrifugation, separation, drying, and calcination to obtain the metal-modified molecular sieve.
[0021] The silica-to-alumina ratio of the molecular sieve is 10–200;
[0022] The molecular sieve is a hydrogen-type molecular sieve, selected from at least one of β molecular sieve, MCM-24 molecular sieve, Y molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, and ZSM-5 molecular sieve;
[0023] The metal salt is selected from at least one of ferric sulfate, nickel nitrate, copper sulfate, manganese nitrate, lanthanum nitrate, and cerium nitrate;
[0024] The solid-liquid ratio of the molecular sieve to the aqueous solution of the metal salt is 1:5-20 g / ml;
[0025] The temperature for ion exchange is 30–80°C;
[0026] The ion exchange time is 0.1–10 h;
[0027] The drying temperature is 30–120°C;
[0028] The drying time is 1 to 12 hours;
[0029] The roasting temperature is 400–600°C;
[0030] The roasting time is 1 to 10 hours.
[0031] The reaction temperature is 550–700°C;
[0032] The reaction pressure is 0.001–1 MPa;
[0033] The mass hourly space velocity (MSV) of the raw material is 0.1–4 h⁻¹. -1 .
[0034] The beneficial effects that this application can produce include:
[0035] This invention provides a one-step, highly efficient method for preparing low-carbon alkanes from naphtha fractions (C4-C6 range) via catalysis. This method offers advantages such as a short process flow, simple operation, and low energy consumption. The catalyst used in this method comprises metal-modified molecular sieves, amorphous aluminum-containing compounds, and amorphous silicon-containing compounds. This catalyst exhibits high catalytic activity and good selectivity in the naphtha fraction to low-carbon alkane production reaction. Furthermore, the preparation process is simple, easy to operate, and has good reproducibility, making it suitable for large-scale industrial production. Detailed Implementation
[0036] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.
[0037] Unless otherwise specified, all raw materials used in the examples are commercially available, and the instruments and equipment are configured with parameters recommended by the manufacturer.
[0038] Example 1
[0039] (1) The MCM-24 molecular sieve matrix was added to a 0.08 mol / L ferric sulfate aqueous solution and ion exchange modified under the conditions of magnetic stirring at 200 r / min, liquid-solid ratio of 15:1 mL / g, and 50℃. After 4 h of ion exchange modification, the sieve was washed with deionized water, centrifuged, dried at 120℃ for 12 h, and calcined at 500℃ to obtain the metal-modified molecular sieve.
[0040] (2) Mix 30 parts by weight of the modified molecular sieve obtained in step (1), 10 parts by weight of aluminum sol, and 5 parts by weight of silica sol evenly, knead, extrude into strips, dry at 120°C for 12 hours, and calcine at 500°C for 2 hours to obtain catalyst 1. # .
[0041] Example 2
[0042] (1) The β-zeolite matrix was added to a 0.08 mol / L nickel nitrate aqueous solution and ion-exchange modified under the conditions of magnetic stirring at 200 r / min, liquid-to-solid ratio of 15:1, and 50 °C. After 4 h of ion-exchange modification, the matrix was washed with deionized water, centrifuged, dried at 120 °C for 12 h, and calcined at 500 °C to obtain the metal-modified zeolite.
[0043] (2) Mix 30 parts by weight of the modified molecular sieve obtained in step (1), 5 parts by weight of kaolin, and 15 parts by weight of silica sol evenly, knead, extrude into strips, dry at 120°C for 12 hours, and calcine at 500°C for 2 hours to obtain catalyst 2. # .
[0044] Example 3
[0045] (1) ZSM-22 molecular sieve matrix was added to a 0.08 mol / L copper sulfate aqueous solution and ion exchange modified under the conditions of magnetic stirring speed of 200 r / min, liquid-solid ratio of 15:1, and 50℃. After 4 h of ion exchange modification, the matrix was washed with deionized water, centrifuged, dried at 120℃ for 12 h, and calcined at 500℃ to obtain the metal-modified molecular sieve.
[0046] (2) Mix 30 parts by weight of the modified molecular sieve obtained in step (1), 6 parts by weight of aluminum sol, and 12 parts by weight of silica evenly, knead, extrude into strips, dry at 120°C for 12 hours, and calcine at 500°C for 2 hours to obtain catalyst 3. # .
[0047] Example 4
[0048] (1) The ZSM-23 molecular sieve matrix was added to a 0.08 mol / L lanthanum nitrate aqueous solution and ion exchange modified under the conditions of magnetic stirring at 200 r / min, liquid-solid ratio of 15:1, and 50℃. After 4 h of ion exchange modification, the sieve was washed with deionized water, centrifuged, dried at 120℃ for 12 h, and calcined at 500℃ to obtain the metal-modified molecular sieve.
[0049] (2) Mix 30 parts by weight of the modified molecular sieve obtained in step (1), 15 parts by weight of aluminum sol, and 12 parts by weight of magnesium silicate evenly, knead, extrude into strips, dry at 120°C for 12 hours, and calcine at 500°C for 2 hours to obtain catalyst 4. # .
[0050] Example 5
[0051] (1) ZSM-5 molecular sieve matrix was added to a 0.08 mol / L cerium nitrate aqueous solution and ion exchange modified under the conditions of magnetic stirring speed of 200 r / min, liquid-solid ratio of 15:1, and 50℃. After 4 h of ion exchange modification, the matrix was washed with deionized water, centrifuged, dried at 120℃ for 12 h, and calcined at 500℃ to obtain the metal-modified molecular sieve.
[0052] (2) Mix 30 parts by weight of the modified molecular sieve obtained in step (1), 10 parts by weight of diatomaceous earth, and 5 parts by weight of silica sol evenly, knead, extrude into strips, dry at 120°C for 12 hours, and calcine at 500°C for 2 hours to obtain catalyst 5. # .
[0053] Example 6 Comparative Example
[0054] (1) The ZSM-5 molecular sieve matrix was added to a 0.01 mol / L lanthanum nitrate aqueous solution and ion exchange modified under the conditions of magnetic stirring speed of 200 r / min, liquid-solid ratio of 20:1, and 50℃. After 4 h of ion exchange modification, the sieve was washed with deionized water, centrifuged, dried at 120℃ for 12 h, and calcined at 500℃ to obtain the metal-modified molecular sieve.
[0055] (2) Mix 30 parts by weight of the modified molecular sieve obtained in step (1), 5 parts by weight of diatomaceous earth, and 5 parts by weight of silica sol evenly, knead, extrude into strips, dry at 120°C for 12 hours, and calcine at 500°C for 2 hours to obtain the comparative catalyst.
[0056] Example 7: Evaluation of the catalyst's activity in converting naphtha fractions.
[0057] Catalyst 1 prepared in Examples 1-5 # ~5 #The catalytic performance of the catalyst and a comparative catalyst in naphtha fraction conversion was evaluated using a fixed-bed reactor with an inner diameter of 9 mm and a catalyst loading of 2 mL. After reduction with hydrogen, the catalyst was reacted with naphtha fraction and hydrogen. The products were analyzed online using an Agilent 7890A chromatograph. The catalyst activity was evaluated based on indicators such as naphtha fraction conversion rate and selectivity for high-quality cracked feedstock. The calculation methods for each indicator are as follows:
[0058]
[0059] naphtha fraction 进 Mass flow rate (g / h) of naphtha fraction at reactor inlet; naphtha fraction 出 and (ethane + propane + n-butane) 出 The values represent the mass flow rates (g / h) of the naphtha fraction and the high-quality cracked feedstock at the reactor outlet, respectively. Table 1 shows the catalysts used in Examples 1–9, their pretreatment conditions, reaction conditions, and naphtha fraction conversion activities.
[0060] Table 1. Reaction conditions and catalyst activity of Examples 1-9
[0061]
[0062]
[0063] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for producing low-carbon alkanes from naphtha fractions, characterized in that, Includes the following steps: In a reactor under a hydrogen atmosphere, naphtha from the C4-C6 fraction is used as a raw material and reacted with a catalyst to obtain low-carbon alkanes. The low-carbon alkane is selected from at least one of ethane, ethylene, and n-butane; The catalyst is composed of metal-modified molecular sieves, amorphous aluminum-containing compounds, and amorphous silicon-containing compounds.
2. The method according to claim 1, characterized in that, The catalyst is obtained through the following steps: The catalyst is obtained by mixing a metal-modified molecular sieve, an amorphous aluminum-containing compound precursor, and an amorphous silicon-containing compound precursor, extruding the mixture, drying it, and calcining it.
3. The method according to claim 2, characterized in that, The amorphous aluminum-containing compound precursor is selected from at least one of alumina sol, kaolin, montmorillonite, sepiolite, and diatomaceous earth. The amorphous silicon-containing compound precursor is selected from at least one of silica sol, silica fume and magnesium silicate; The mass ratio of the metal-modified molecular sieve, the amorphous aluminum-containing compound precursor, and the amorphous silicon-containing compound precursor is 30:1 to 20:1 to 20. The drying temperature is 30–120°C; The drying time is 1 to 12 hours; The roasting temperature is 400–600°C; The roasting time is 1 to 10 hours.
4. The method according to claim 2, characterized in that, The metal-modified molecular sieve is obtained through the following steps: The molecular sieve is mixed with an aqueous solution of a metal salt, subjected to ion exchange, washing, centrifugation, separation, drying, and calcination to obtain the metal-modified molecular sieve.
5. The method according to claim 4, characterized in that, The silica-to-alumina ratio of the molecular sieve is 10–200; The molecular sieve is a hydrogen-type molecular sieve, selected from at least one of β molecular sieve, MCM-24 molecular sieve, Y molecular sieve, ZSM-22 molecular sieve, ZSM-23 molecular sieve, and ZSM-5 molecular sieve; The metal salt is selected from at least one of ferric sulfate, nickel nitrate, copper sulfate, manganese nitrate, lanthanum nitrate, and cerium nitrate; The solid-liquid ratio of the molecular sieve to the aqueous solution of the metal salt is 1:5-20 g / ml; The temperature for ion exchange is 30–80°C; The ion exchange time is 0.1–10 h; The drying temperature is 30–120°C; The drying time is 1 to 12 hours; The roasting temperature is 400–600°C; The roasting time is 1 to 10 hours.
6. The method according to claim 1, characterized in that, The reaction temperature is 550–700°C; The reaction pressure is 0.001–1 MPa; The mass space velocity of the raw material is 0.1-4 h -1 .