A process for the polymerization of ethylene to aviation fuel

Abstract

This invention relates to the technical field of ethylene polymerization and discloses a method for producing aviation fuel by ethylene polymerization, comprising the following steps: in the presence of a catalyst, using a mixture of ethylene and an inert gas as the reaction gas, ethylene is subjected to a polymerization reaction to prepare C8-C2 fuel. 16 Aviation fuel; wherein the catalyst is prepared by: modifying a MOR molecular sieve with NiCu, calcining it in air containing water vapor to obtain a NiCu-modified MOR molecular sieve containing non-framework aluminum, i.e., the catalyst; the mass content of non-framework aluminum in the catalyst is 1-10%. This invention utilizes a NiCu-modified MOR molecular sieve containing non-framework aluminum to catalyze the polymerization of ethylene to prepare aviation fuel, which not only improves ethylene conversion and aviation fuel selectivity, but also exhibits high catalytic stability, with no significant deactivation observed within 50 hours of reaction.

Description

Technical Field

[0001] This invention relates to the technical field of ethylene polymerization, and in particular to a method for producing aviation fuel by ethylene polymerization. Background Technology

[0002] Among numerous alternative aviation fuel production technologies, ethylene polymerization for aviation fuel has attracted significant attention due to its unique advantages. Ethylene, as one of the most basic chemical raw materials, is widely available, obtained from petroleum cracking, biomass ethanol dehydration, or carbon dioxide hydrogenation, offering the possibility of reducing the carbon footprint of aviation fuels. Ethylene undergoes selective oligomerization under the action of appropriate catalysts, producing fuels with C8-C4 carbon atoms. 16 Linear or branched hydrocarbons within the range, these components have high energy density, low freezing point and good combustion characteristics, fully meeting the stringent standards for jet fuels.

[0003] Traditional ethylene polymerization catalysts are mainly classified into homogeneous catalysts and heterogeneous catalysts. Homogeneous catalysts, including Ziegler-Natta type catalysts and metallocene catalysts, have high activity but suffer from difficulties in separation and recovery, as well as ligand loss. Heterogeneous catalysts include solid phosphoric acid catalysts and supported metal catalysts. Solid phosphoric acid catalysts have high catalytic activity, good gasoline selectivity, and low production cost, but they are prone to sludge formation and deactivation and are non-renewable. Supported metal catalysts, while possessing advantages such as high activity and renewability, still require some time before industrial application. Among these, molecular sieve catalysts have lower cost, better hydrothermal stability, and are easy to regenerate. Furthermore, the degree of polymerization of the product can be controlled by adjusting the pore type, which has led to extensive research on molecular sieve catalysts in catalyzing olefin oligomerization reactions. For example, patent CN1261464C discloses a method for preparing a post-transition metal olefin polymerization catalyst supported on a mesoporous molecular sieve. The catalyst consists of two components, A and B. Component A is expressed as [JK-Cat(MLX2)-PC], where JK represents the mesoporous molecular sieve material SBA-15, PC represents the type of loading method (physical adsorption and chemisorption), Cat represents the post-transition metal olefin polymerization catalyst, M represents any one of iron, cobalt, nickel, and palladium, L represents any one of bidentate or tripentate organic ligands, X represents a halogen Cl or Br, and component B is methylaluminoxane (MAO). However, the severe carbon deposition in molecular sieve catalysts makes it difficult to meet the required activity and stability, which limits the industrial application of ethylene polymerization technology for producing aviation fuel. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for producing aviation fuel through ethylene polymerization. This method utilizes NiCu-modified MOR molecular sieves containing non-framework aluminum to catalyze the polymerization of ethylene to prepare C8-C... 16Aviation fuel not only improves ethylene conversion and selectivity, but also the catalyst has high catalytic stability, with no obvious deactivation observed within 50 hours of reaction.

[0005] The objective of this invention is achieved through the following technical solutions:

[0006] This invention provides a method for producing aviation fuel by ethylene polymerization, comprising the following steps: in the presence of a catalyst, using a mixture of ethylene and an inert gas as the reactant gas, ethylene is subjected to a polymerization reaction to prepare C8-C2 fuel. 16 Aviation fuel; wherein the preparation of the catalyst includes: modifying MOR molecular sieve with NiCu, calcining it in air containing water vapor, wherein the volume content of water vapor in the air is 1-6%, the calcination temperature is 400-500℃, and the calcination time is 3-5 h, to obtain NiCu-modified MOR molecular sieve containing non-framework aluminum, i.e., catalyst; wherein the mass content of non-framework aluminum in the catalyst is 1-10%.

[0007] This invention introduces two non-noble metals, Ni and Cu, as active components. Ni's d-electron orbital characteristics provide excellent ethylene activation capabilities, while the addition of Cu promotes a synergistic effect between Ni and Cu, creating a suitable electronic and spatial environment that helps control chain growth within a certain range. Therefore, the synergistic effect of these two metal elements can significantly improve the conversion rate of ethylene and the C8-C chain length. 16 Selectivity of aviation fuel.

[0008] In addition, the pore structure of MOR molecular sieves is suitable for C8-C 16 The product is formed, but due to the diffusion restriction of its one-dimensional channels, it is easily deactivated by carbon deposition. By calcining the MOR molecular sieve in air containing water vapor, non-framework aluminum can be introduced into the molecular sieve. The presence of non-framework aluminum in the MOR molecular sieve significantly inhibits the formation of carbon deposits (such as aromatics) during the catalytic reaction, thereby significantly improving the stability of the catalytic reaction and the yield and selectivity of aviation fuel. However, excessively high non-framework aluminum content in the MOR molecular sieve can also lead to diffusion restriction, affecting conversion and selectivity. Therefore, the non-framework aluminum content needs to be controlled within a certain range to obtain optimal catalytic performance.

[0009] Preferably, the volume content of water vapor in the air is 1-5%, and more preferably, the volume content of water vapor in the air is 1-3%.

[0010] Preferably, the calcination temperature is 400-460℃ and the calcination time is 3-5 h.

[0011] Preferably, the mass content of non-framework aluminum in the catalyst is 1-6%.

[0012] The content of non-framework aluminum was quantified using in-situ infrared spectroscopy. After sample pretreatment and dehydration, spectra were acquired at room temperature and peak fitting analysis was performed. The wavenumber was 3660 cm⁻¹. -1 The peak corresponds to non-framework aluminum, with a wavenumber of 3610 cm⁻¹. -1 The peak corresponds to aluminum in a twelve-membered ring channel, with a wavenumber of 3590 cm⁻¹. -1 The peak corresponds to aluminum in the octagonal ring channel.

[0013] Preferably, the content of medium-strong acid sites in the catalyst is 0.5-1.5 mol / kg; more preferably, the content of medium-strong acid sites in the catalyst is 0.5-1.2 mol / kg; and even more preferably, the content of medium-strong acid sites in the catalyst is 0.5-0.9 mol / kg.

[0014] The acid strength is defined by the NH3-TPD peak, encompassing three acidities: weak acid, moderately strong acid, and strong acid. The NH3-TPD is based on the desorption peak position of NH3. This desorption peak position refers to the position of the desorption peak under standard test conditions: a sample mass w to carrier gas flow rate f ratio (w / f) = 100 g•h / L, and a heating rate of 10℃ / min. The TCD records the thermal conductivity signal of desorbed NH3, and a desorption curve is plotted. Based on the peak position of the curve, the inorganic solid is classified into three acid strengths: weak acid (NH3 desorption temperature below 245℃), moderately strong acid (NH3 desorption temperature between 245-500℃), and strong acid (NH3 desorption temperature above 500℃).

[0015] Preferably, the catalyst contains 1-10% Ni by mass.

[0016] Preferably, the catalyst contains 1-8% Cu by mass.

[0017] Preferably, the NiCu modification includes impregnating or ion-exchanging the MOR molecular sieve with a nickel precursor solution and a copper precursor solution, respectively.

[0018] Preferably, the nickel precursor includes one or more of nickel chloride, nickel nitrate, and nickel acetylacetonate.

[0019] Preferably, the copper precursor includes one or more of copper chloride and copper nitrate.

[0020] Preferably, the conditions for the polymerization reaction include: a mixed gas pressure of 0.5-5 MPa, a reaction temperature of 150-300°C, and a space velocity of 500-12000 mL / g / h; more preferably, a mixed gas pressure of 2-5 MPa, a reaction temperature of 150-250°C, and a space velocity of 500-7000 mL / g / h.

[0021] Preferably, the molar ratio of ethylene to inert gas in the mixed gas is 2.5-20:1, and more preferably, the molar ratio of ethylene to inert gas in the mixed gas is 4-20:1.

[0022] Preferably, the inert gas is argon or nitrogen.

[0023] Preferably, the polymerization reaction is carried out in a fixed bed or a moving bed.

[0024] When the reaction temperature is 150-250℃ and the space velocity is 500-7000 h⁻¹ -1 When the molar ratio of ethylene to inert gas is 4-20:1, the conversion rate of ethylene can reach 50-60%, and the selectivity of aviation fuel can reach 80-90%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The pore structure of MOR molecular sieve is suitable for C8-C 16 The product formation, through the synergistic modification of two non-noble metals, Ni and Cu, as active components, can significantly improve the conversion rate of ethylene and the C8-C ratio. 16 Selectivity of aviation fuel;

[0027] (2) By calcining the MOR molecular sieve in air containing water vapor, non-framework aluminum can be introduced into the molecular sieve. The presence of non-framework aluminum in the MOR molecular sieve will significantly inhibit the formation of carbon deposits during the catalytic reaction, thereby significantly improving the stability of the catalytic reaction and the yield and selectivity of aviation fuel. Attached Figure Description

[0028] Figure 1 The image shows the in-situ infrared spectrum of the catalyst prepared in Example 1.

[0029] Figure 2 The image shows the XRD pattern of the catalyst prepared in Example 1.

[0030] Figure 3 The attached figure shows the nitrogen adsorption-desorption process of the catalyst prepared in Example 1.

[0031] Figure 4 This is a scanning electron microscope image of the catalyst prepared in Example 1.

[0032] Figure 5 This is a distribution diagram of the products obtained after ethylene polymerization in Example 1. Detailed Implementation

[0033] The following specific embodiments illustrate the technical solution of the present invention, but the scope of protection of the present invention is not limited thereto. The MOR molecular sieve used in the present invention can be purchased or made in-house. Moderately strong acids can be tested by solid-state NMR spectroscopy, NH3-TPD, infrared spectroscopy, chemical titration, etc., but the methods for testing acidity are not limited to the above methods.

[0034] The preparation method of the catalyst (NiCu-modified MOR molecular sieve containing non-framework aluminum) in this invention includes the following steps:

[0035] (1) Preparation of MOR molecular sieve.

[0036] (2) Modify the MOR molecular sieve with NiCu by impregnating or ion exchanging the MOR molecular sieve with nickel precursor solution and copper precursor solution respectively. The nickel precursor includes one or more of nickel chloride, nickel nitrate, and nickel acetylacetonate, and the copper precursor includes one or more of copper chloride and copper nitrate.

[0037] Impregnation method: Weigh out nickel or copper precursor and dissolve it in water to obtain a nickel precursor solution or copper precursor solution with a mass content of 1-15%; then add molecular sieve to the above precursor solution, with a mass ratio of molecular sieve to precursor solution of 1:10-15, and stir continuously at 60-80℃ until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 100-150℃ for 8-15 h.

[0038] Ion exchange method: Weigh out nickel or copper precursor and dissolve it in water to obtain a nickel precursor solution or copper precursor solution with a mass content of 1-15%; then add molecular sieve to the above precursor solution, with a mass ratio of molecular sieve to precursor solution of 1:10-15, and stir in a water bath at 80-90℃ for 4 hours or more; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 100-150℃ for 8-15 hours.

[0039] (3) The NiCu-modified MOR molecular sieve is calcined in air containing water vapor. The volume content of water vapor in the air is 1-6%, and the water vapor content is controlled by the flow rate of the air flowing through it (taking a volume content of water vapor in the air of 3% as an example, the first pipeline is adjusted to make the dry air flow through the 70℃ constant temperature bubble generator at 3 mL / min, and the second pipeline is adjusted to fix the total flow rate through the tube furnace at 100 mL / min). Then, the flow rate is increased to 1-5℃•min. -1The temperature was increased at a rate of [unspecified rate], and calcined at 400-500℃ for 3-5 hours to obtain a catalyst (NiCu-modified MOR molecular sieve containing non-framework aluminum). The catalyst contained 1-10% by mass of non-framework aluminum, 1-10% by mass of Ni, 1-8% by mass of Cu, and 0.5-1.5 mol / kg of medium-strong acid sites.

[0040] The method for producing aviation fuel by ethylene polymerization in this invention includes the following steps:

[0041] Taking a fixed-bed reactor as an example, the catalyst is also suitable for moving-bed reactors. The device is equipped with a gas mass flow meter and an online product analysis chromatograph (the reactor exhaust gas is directly connected to the quantitative valve of the chromatograph for periodic real-time sampling and analysis).

[0042] The catalyst was placed in a fixed-bed reactor, and the air in the reactor was replaced with N2. The reactor was then heated to 400°C in an N2 atmosphere and held for 3 h. The temperature was then lowered to the reaction temperature of 150-300°C, and a mixture of ethylene and argon (C2H4 / Ar molar ratio of 2.5-20:1) was switched. The pressure of the mixture was 0.5-5 MPa, and the space velocity of the mixture was adjusted to 500-12000 mL / g / h. The product was analyzed by online chromatography.

[0043] The preparation methods of catalysts (parts 1-24) are shown below, and the detailed parameters of the preparation process are shown in Table 1.

[0044] The preparation of fraction 1 includes the following steps:

[0045] Weigh out the raw materials silica sol, aluminum nitrate, sodium hydroxide, and deionized water according to the molar ratio of SiO2:Al2O3:Na2O:H2O of 1:0.03:0.28:40. Mix at room temperature and age at 30°C for 2 h with stirring. Transfer to a stainless steel hydrothermal reactor and heat to 140°C at 2°C / min and maintain for 160 h for crystallization. After crystallization, cool to room temperature in a water bath and repeatedly centrifuge and wash until the pH of the supernatant is 7 at the end of washing. Dry the resulting precipitate at 120°C for 12 h. Perform an ion exchange process between the dried MOR solid and ammonium nitrate solution. Add 5 g of MOR powder to 100 mL of a 1 mol•L⁻¹ solution. -1 The solid was placed in an ammonium nitrate solution and kept at 80°C for 2 h. After repeating the ion exchange process three times, the solid product was centrifuged and washed three times with deionized water. Finally, the obtained solid was dried at 110°C overnight and then dried at 1°C·min. -1 The temperature was increased at a certain rate to 450℃ and calcined at this temperature for 4 h. The resulting MOR molecular sieve was labeled as 1.

[0046] The preparation of fractions 2 to 4 includes the following steps:

[0047] (1) Preparation of fraction 1.

[0048] (2) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir in a water bath at 80°C for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120°C for 12 h to obtain the Ni-modified MOR molecular sieve.

[0049] Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of Ni-modified MOR molecular sieve to the above precursor solution and stir continuously at 60℃ until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain NiCu-modified MOR molecular sieve.

[0050] (3) The NiCu-modified MOR molecular sieve was calcined in air containing water vapor. The flow rate of the first pipeline was adjusted to make the volume content of water vapor in the air 1-6%. The flow rate of the second pipeline was adjusted to fix the total flow rate through the tube furnace at 100 mL / min. Then, the flow rate was increased at 1℃•min. -1 The temperature was increased at a certain rate and calcined at 400-500℃ for 4 hours to obtain the catalyst.

[0051] The preparation of fractions 5-7 includes the following steps:

[0052] (1) Preparation of fraction 1.

[0053] (2) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir in a water bath at 80°C for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120°C for 12 h to obtain the Ni-modified MOR molecular sieve.

[0054] Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of Ni-modified MOR molecular sieve to the above precursor solution and stir in a water bath at 80℃ for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain NiCu-modified MOR molecular sieve.

[0055] (3) The NiCu-modified MOR molecular sieve was calcined in air containing water vapor. The flow rate of the first pipeline was adjusted to make the volume content of water vapor in the air 1-6%. The flow rate of the second pipeline was adjusted to fix the total flow rate through the tube furnace at 100 mL / min. Then, the flow rate was increased at 1℃•min. -1 The temperature was increased at a certain rate and calcined at 400-500℃ for 4 hours to obtain the catalyst.

[0056] The preparation of fractions 8 to 10 includes the following steps:

[0057] (1) Preparation of fraction 1.

[0058] (2) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir continuously at 60 °C until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120 °C for 12 h to obtain the Ni-modified MOR molecular sieve.

[0059] Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of Ni-modified MOR molecular sieve to the above precursor solution and stir in a water bath at 80℃ for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain NiCu-modified MOR molecular sieve.

[0060] (3) The NiCu-modified MOR molecular sieve was calcined in air containing water vapor. The flow rate of the first pipeline was adjusted to make the volume content of water vapor in the air 1-6%. The flow rate of the second pipeline was adjusted to fix the total flow rate through the tube furnace at 100 mL / min. Then, the flow rate was increased at 1℃•min. -1 The temperature was increased at a certain rate and calcined at 400-500℃ for 4 hours to obtain the catalyst.

[0061] The preparation of fractions 11-13 includes the following steps:

[0062] (1) Preparation of fraction 1.

[0063] (2) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir continuously at 60 °C until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120 °C for 12 h to obtain the Ni-modified MOR molecular sieve.

[0064] Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of Ni-modified MOR molecular sieve to the above precursor solution and stir continuously at 60℃ until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain NiCu-modified MOR molecular sieve.

[0065] (3) The NiCu-modified MOR molecular sieve was calcined in air containing water vapor. The flow rate of the first pipeline was adjusted to make the volume content of water vapor in the air 1-6%. The flow rate of the second pipeline was adjusted to fix the total flow rate through the tube furnace at 100 mL / min. Then, the flow rate was increased at 1℃•min. -1 The temperature was increased at a certain rate and calcined at 400-500℃ for 4 hours to obtain the catalyst.

[0066] The preparation of fraction 14 includes the following steps:

[0067] (1) Preparation of fraction 1.

[0068] (2) Calcine fraction 1 in air containing water vapor. Adjust the flow rate of the first pipeline to 2 mL / min so that the volume content of water vapor in the air is 2%. Adjust the second pipeline to fix the total flow rate through the tube furnace at 100 mL / min. Then, at 1℃•min -1 The temperature was increased at a certain rate and calcined at 460℃ for 4 hours to obtain the catalyst.

[0069] The preparation of fraction 15 includes the following steps:

[0070] (1) Preparation of fraction 1.

[0071] (2) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir in a water bath at 80°C for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120°C for 12 h to obtain the catalyst.

[0072] The preparation of fraction 16 includes the following steps:

[0073] (1) Preparation of 15 portions.

[0074] (2) Calcine 15 parts in air containing water vapor. Adjust the flow rate of the first pipeline to 1 mL / min so that the volume content of water vapor in the air is 1%. Adjust the second pipeline to fix the total flow rate through the tube furnace at 100 mL / min. Then, at 1℃•min -1 The temperature was increased at a certain rate and calcined at 490℃ for 4 hours to obtain the catalyst.

[0075] The preparation of fraction 17 includes the following steps:

[0076] (1) Preparation of fraction 1.

[0077] (2) Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir continuously at 60℃ until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain catalyst.

[0078] The preparation of fraction 18 includes the following steps:

[0079] (1) Preparation of 17.

[0080] (2) Calcine the fraction 17 in air containing water vapor. Adjust the flow rate of the first pipeline to 3 mL / min so that the volume content of water vapor in the air is 3%. Adjust the second pipeline to fix the total flow rate through the tube furnace at 100 mL / min. Then, at 1℃•min -1 The temperature was increased at a certain rate and calcined at 450℃ for 4 hours to obtain the catalyst.

[0081] The preparation of fractions 19-22 includes the following steps:

[0082] (1) Preparation of fraction 1.

[0083] (2) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of the precursor solution to the above precursor solution and stir in a water bath at 80°C for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120°C for 12 h to obtain the Ni-modified MOR molecular sieve.

[0084] Cu-modified, Ca-modified, or Ge-modified: Weigh out a copper precursor (or calcium precursor or germanium precursor) and dissolve it in 50 mL of deionized water to obtain a copper precursor solution (or calcium precursor solution or germanium precursor solution); then add 5 g of Ni-modified MOR molecular sieve to the above precursor solution and stir continuously at 60 °C until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing; dry the obtained precipitate at 120 °C for 12 h to obtain the catalyst.

[0085] The preparation of fraction 23 includes the following steps:

[0086] (1) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of ZSM-5 molecular sieve (purchased) to the above precursor solution and stir in a water bath at 80 °C for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120 °C for 12 h to obtain the Ni-modified ZSM-5 molecular sieve.

[0087] Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of Ni-modified ZSM-5 molecular sieve to the above precursor solution and stir continuously at 60℃ until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain NiCu-modified ZSM-5 molecular sieve.

[0088] (3) The NiCu-modified ZSM-5 molecular sieve was calcined in air containing water vapor. The flow rate of the first pipeline was adjusted to 3 mL / min so that the volume content of water vapor in the air was 3%. The flow rate of the second pipeline was adjusted to fix the total flow rate through the tube furnace at 100 mL / min. Then, the flow rate was increased to 1℃•min. -1 The temperature was increased at a certain rate and calcined at 450℃ for 4 hours to obtain the catalyst.

[0089] The preparation of fraction 24 includes the following steps:

[0090] (1) Ni modification: Weigh out the nickel precursor and dissolve it in 50 mL of deionized water to obtain a nickel precursor solution; then add 5 g of ZSM-12 molecular sieve (purchased) to the above precursor solution and stir in a water bath at 80°C for 4 h; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120°C for 12 h to obtain the Ni-modified ZSM-12 molecular sieve.

[0091] Cu modification: Weigh out copper precursor and dissolve it in 50 mL of deionized water to obtain copper precursor solution; then add 5 g of Ni-modified ZSM-12 molecular sieve to the above precursor solution and stir continuously at 60℃ until the solution evaporates to dryness; repeatedly centrifuge and wash the obtained product until the pH of the supernatant is 7 at the end of the washing, and dry the obtained precipitate at 120℃ for 12 h to obtain NiCu-modified ZSM-12 molecular sieve.

[0092] (3) The NiCu-modified ZSM-12 molecular sieve was calcined in air containing water vapor. The flow rate of the first pipeline was adjusted to 3 mL / min so that the volume content of water vapor in the air was 3%. The flow rate of the second pipeline was adjusted to fix the total flow rate through the tube furnace at 100 mL / min. Then, the flow rate was increased at 1℃•min. -1 The temperature was increased at a certain rate and calcined at 450℃ for 4 hours to obtain the catalyst.

[0093] Table 1. Preparation and performance parameters of catalysts

[0094]

[0095] Examples 1-12 and Comparative Examples 1-12

[0096] The catalyst was placed in a fixed-bed reactor, and the air in the reactor was replaced with N2. The reactor was then heated to 400°C in an N2 atmosphere and held for 3 h. The temperature was then lowered to the reaction temperature of 150-300°C, and a mixture of ethylene and argon (C2H4 / Ar molar ratio of 2.5-20:1) was switched. The pressure of the mixture was 0.5-5 MPa, and the space velocity of the mixture was adjusted to 500-12000 mL / g / h. The product was analyzed by online chromatography.

[0097] Table 2. Reaction conditions and catalytic effect data of Examples 1-12 and Comparative Examples 1-12

[0098]

[0099] like Figure 1 The image shown is the in-situ infrared spectrum of the catalyst in Example 1, with a wavenumber of 3660 cm⁻¹. -1 The peak corresponds to non-framework aluminum, with a wavenumber of 3610 cm⁻¹. -1 The peak corresponds to aluminum in a twelve-membered ring channel, with a wavenumber of 3590 cm⁻¹. -1 The peak corresponds to aluminum in the octagonal ring channel. For example... Figure 2 The X-ray diffraction pattern of the catalyst in Example 1 is shown, exhibiting diffraction peaks typical of the MOR topology, demonstrating that partial dealumination did not damage the structure of the molecular sieve itself. Figure 3 The attached diagram shows the nitrogen adsorption-desorption of the catalyst in Example 1, which is a typical type IV isotherm. Figure 4 The image shown is a scanning electron microscope (SEM) image of the catalyst in Example 1, combined with... Figure 1-4This indicates that the present invention has successfully prepared NiCu-modified MOR molecular sieves containing non-framework aluminum. The preparation process did not damage the topology and mesoporous structure of the MOR molecular sieve itself, but the resulting catalyst exhibits higher catalytic activity and stability. As shown in Table 2, the ethylene polymerization reaction was carried out using the NiCu-modified MOR molecular sieve containing non-framework aluminum prepared in this invention, and the resulting catalyst was composed of C8-C... 16 The selectivity of the aviation fuel composition can reach 75-90%, and the ethylene conversion rate can reach 45-60%, such as... Figure 5 The figure shows the product distribution obtained after ethylene polymerization using the catalyst in Example 1.

[0100] In Comparative Example 1, the catalyst was an unmodified MOR molecular sieve, lacking non-framework aluminum. This catalyst initially achieved a conversion of 18.4%, but exhibited significant deactivation after 50 h, with an ethylene conversion of only 2.1% and a selectivity of 70% for aviation fuel. This indicates that the pore structure of the MOR molecular sieve is suitable for C8-C... 16 The product is generated, but due to the fact that its one-dimensional channels are easily restricted by diffusion, it is prone to carbon deposition and deactivation.

[0101] Compared to Comparative Example 1, the molecular sieve in Comparative Example 2 contained a small amount of non-framework aluminum, which significantly improved the catalyst's stability. After 50 h, the ethylene conversion rate was 17.1%, and the selectivity for aviation fuel was 72%. This indicates that the presence of non-framework aluminum can significantly promote the formation of carbon deposits and ensure the long-term stability of the catalyst reaction. However, due to the lack of NiCu modification on the molecular sieve, the initial ethylene conversion rate was low.

[0102] Compared to Comparative Example 1, the molecular sieve in Comparative Example 3 underwent only Ni modification, and the catalyst achieved an initial conversion rate of 37.2%, indicating that the presence of Ni significantly improves ethylene conversion. However, it exhibited significant deactivation, with an ethylene conversion rate of only 3.5% after 50 h. In Comparative Example 5, the molecular sieve was modified only by Cu, and the catalyst achieved an initial conversion rate of 21.3%, indicating that the presence of Cu can improve ethylene conversion to some extent, while also promoting C8-C... 16 The formation of ethylene was observed, but significant deactivation was also observed, with an ethylene conversion rate of only 2.5% after 50 hours and a selectivity of 77% for aviation fuel.

[0103] Comparative Example 4 was calcined in air containing water vapor based on Comparative Example 3, and Comparative Example 6 was calcined in air containing water vapor based on Comparative Example 5. Thus, Comparative Examples 4 and 6 were able to obtain Ni-modified or Cu-modified molecular sieves containing non-framework aluminum. The catalysts exhibited higher catalytic stability, and the ethylene conversion rate was higher than that of Comparative Examples 3 and 5 after 50 h.

[0104] Compared to Comparative Example 1, the molecular sieve in Comparative Example 7 was modified with NiCu. This catalyst initially achieved a conversion rate of 57.1%, but also exhibited significant deactivation, with an ethylene conversion rate of only 5.2% after 50 h and a selectivity of 80% for aviation fuel. This indicates that the presence of the NiCu bimetallic compound can significantly improve ethylene conversion, while simultaneously enhancing the C8-C... 16 The generation of [something] has also been promoted to a certain extent.

[0105] Compared to Comparative Example 7, the Cu loading in the molecular sieve of Comparative Example 8 was increased to 13.1 wt%. The initial conversion rate of ethylene was only 38.6%, which is close to that of Comparative Example 3. This may be because the excess Cu cannot interact effectively with Ni.

[0106] Compared to Comparative Example 1, the molecular sieves in Comparative Examples 9 and 10 were modified with NiCa and NiGe, respectively. The reaction results showed that the conversion rates of ethylene were 33.9% and 34.4%, respectively, which were close to those of Comparative Example 3. This may be because the electronic effect between Ca and Ge and Ni is weak, and they cannot interact effectively with Ni. The synergistic catalytic effect with the MOR molecular sieve is also poor, resulting in low catalytic activity.

[0107] The results of Comparative Examples 1-10 above indicate that the NiCu bimetallic composition and the Cu-Ni ratio are crucial for improving the conversion capacity of ethylene. Meanwhile, non-framework aluminum also plays an important role in inhibiting carbon deposition and improving the stability of the catalytic reaction. Both of these are indispensable for achieving high-stability catalysis and obtaining high-yield aviation fuel.

[0108] In Comparative Example 11, the molecular sieve was ZSM-5. The reaction results showed that the initial ethylene conversion rate was only 35.5%, and the selectivity for aviation fuel after 50 hours was only 61%. This may be because ZSM-5 has a three-dimensional ten-membered ring porous structure, which cannot effectively generate C8-C... 16 Products within the specified range.

[0109] The molecular sieve in Comparative Example 12 was ZSM-12, which has a one-dimensional twelve-membered ring pore structure. The reaction results showed that the initial ethylene conversion rate was 52.3%, decreasing to only 6.9% after 50 h, and the selectivity for aviation fuel was 73% after 50 h. This may be because ZSM-12 has high hydrothermal stability, cannot effectively generate non-framework aluminum species, and therefore cannot effectively inhibit carbon deposition, resulting in poor catalytic stability.

[0110] The results of Comparative Examples 11-12 indicate that the structure of the molecular sieve itself is crucial for the high stability and high yield of aviation fuel.

[0111] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for producing aviation fuel by ethylene polymerization, characterized in that, The process includes the following steps: In the presence of a catalyst, using a mixture of ethylene and an inert gas as the reactant, ethylene undergoes a polymerization reaction to prepare C8-C. 16 The conditions for the polymerization reaction of aviation fuel include: a mixed gas pressure of 0.5-5 MPa, a reaction temperature of 150-300℃, and a space velocity of 500-12000 mL / g / h. The catalyst preparation includes: modifying MOR molecular sieves with NiCu; impregnating or ion-exchanging MOR molecular sieves with nickel precursor solutions and copper precursor solutions, respectively; then calcining in air containing water vapor, with a water vapor volume content of 1-6%, a calcination temperature of 400-500℃, and a calcination time of 3-5h, to obtain NiCu-modified MOR molecular sieves containing non-framework aluminum, i.e., the catalyst; the mass content of non-framework aluminum in the catalyst is 1-10%, the mass content of Ni is 1-10%, and the mass content of Cu is 1-8%.

2. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The catalyst contains 0.5-1.5 mol / kg of medium-strong acid sites.

3. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The nickel precursor includes one or more of nickel chloride, nickel nitrate, and nickel acetylacetonate.

4. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The copper precursor includes one or more of copper chloride and copper nitrate.

5. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The pressure of the mixed gas is 2-5 MPa.

6. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The reaction temperature is 150-250℃.

7. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The space velocity is 500-7000 mL / g / h.

8. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The molar ratio of ethylene to inert gas in the mixture is 2.5-20:

1.

9. The method for producing aviation fuel by ethylene polymerization according to claim 1, characterized in that, The polymerization reaction is carried out in a fixed bed or a moving bed.

Images