An efficient denitrification process for the production of sustainable aviation fuel feedstocks

Abstract

This invention discloses an effective method for reducing nitrogen content in the production of sustainable aviation fuel feedstock, belonging to the field of sustainable aviation fuel production technology. Through a tiered processing approach, high-nitrogen feedstock is first pretreated with microwave-assisted plasma to efficiently break the C-N bonds of macromolecular nitrogen heterocycles. Then, pre-denitrification is performed using an AI-intelligent optimized adsorption bed filled with amino-functionalized modified MOF adsorbent. Subsequently, in a multi-field coupled microchannel reactor, mild hydrogenation is carried out for deep denitrification under the synergistic effects of ultrasound, electric field, and near-infrared photothermal treatment. Finally, the fraction is separated and purified using a membrane separation-distillation coupled system to obtain aviation kerosene fraction with a nitrogen content of less than 1 ppm, achieving a total yield of up to 92%. This invention also converts the desorbed and enriched nitrogen resources into high-purity acetonitrile through electrochemical synthesis. This method overcomes the limitations of traditional high-temperature, high-pressure hydrogenation refining, achieving ultra-deep denitrification under mild conditions, significantly reducing energy consumption and catalyst coking rate, while simultaneously realizing high-value conversion of nitrogen resources.

Description

Technical Field

[0001] This invention relates to the field of sustainable aviation fuel production technology, specifically to an effective method for reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock. Background Technology

[0002] Sustainable aviation fuel, as a key pathway for the aviation industry to achieve carbon neutrality, has a wide range of feedstock sources, including waste oils and biomass liquefied oil (BTL). However, these feedstocks generally contain high concentrations of nitrogen compounds, such as quinoline, carbazole, pyridine, and other amine compounds. These nitrogenous impurities can seriously harm downstream processing and the quality of the final product: on the one hand, they can poison expensive precious metal or transition metal catalysts during hydrorefining, significantly shortening catalyst life; on the other hand, nitrogenous compounds are converted into nitrogen oxides during fuel combustion, causing environmental pollution. Therefore, deep removal of nitrogen compounds from feedstocks is an essential step in producing qualified aviation fuel.

[0003] Currently, the mainstream denitrification technology in industry is high-temperature and high-pressure hydrogenation refining. This method typically requires harsh reaction conditions to break the extremely stable CN bonds, especially those present in nitrogen heterocyclic structures. This traditional method has several technical drawbacks: First, extremely high energy consumption and equipment investment; the high temperature and pressure conditions significantly increase operating costs and safety risks. Second, rapid catalyst deactivation due to carbon buildup; excessively high reaction temperatures exacerbate the thermal cracking and condensation of hydrocarbons, leading to severe carbon buildup on the catalyst surface, a rapid increase in bed pressure drop, frequent shutdowns for regeneration, and poor operational stability. Third, poor selectivity and low product yield; under harsh conditions, excessive hydrogenation saturation of aromatics not only results in excessive hydrogen consumption but also a significant decrease in the yield of the target liquid product, damaging economic efficiency. Fourth, limited denitrification depth; even with such harsh conditions, the removal effect on large, stubborn nitrogen heterocyclic compounds in the feedstock is still unsatisfactory, and the residual nitrogen content in the product is difficult to consistently reach the ultra-low requirement of below 1 ppm. Furthermore, existing pretreatment methods, such as conventional adsorption or extraction, often suffer from poor selectivity, low adsorption capacity, and difficulty in regeneration, failing to effectively reduce nitrogen content in the raw materials to alleviate the pressure on subsequent refining processes. Meanwhile, the removed nitrogen resources are typically discharged or neutralized as waste ammonia, increasing the cost of waste treatment and resulting in a significant waste of nitrogen resources.

[0004] Therefore, there is an urgent need to develop a new method that can achieve highly selective and deep denitrification under mild conditions, while simultaneously improving product yield, reducing energy consumption and inhibiting coking, and effectively realizing the high-value conversion of nitrogen resources. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes an effective nitrogen reduction method for producing sustainable aviation fuel feedstock, comprising the following steps:

[0006] S1. Nitrogen-containing raw materials are formed into micro-droplets through an atomizing nozzle and sprayed into a microwave resonant cavity reactor, where microwaves and plasma are applied simultaneously for treatment;

[0007] S2. The pretreated raw material from step S1 is passed into an adsorption bed filled with a modified metal-organic framework adsorbent for adsorption and denitrification, and the adsorption operation parameters are optimized in real time using an AI model.

[0008] S3. The low-nitrogen raw material obtained in step S2 is mixed with hydrogen and introduced into a multi-field coupled microchannel reactor to carry out a hydrogenation and denitrification reaction under the synergistic effect of ultrasonic field, electric field and photothermal.

[0009] S4. The product after the reaction in step S3 is separated by membrane separation and distillation to obtain sustainable aviation fuel products.

[0010] Furthermore, in step S1, the nitrogen-containing raw material is a biomass liquefaction oil raw material containing nitrogen-containing heterocyclic compounds, including quinoline, carbazole, and pyridine.

[0011] Furthermore, in step S1, the microwave power is 600W and the frequency is 2.45GHz; the plasma uses a hydrogen / argon mixture with a volume ratio of 1:9 as the working gas, the plasma high-voltage power supply voltage is 1.2kV; the pressure inside the reactor is 0.12MPa, and the processing time is 3s.

[0012] Further, in step S2, the modified metal-organic framework adsorbent is a modified ZIF-8 adsorbent with amino functional groups grafted onto its surface, obtained by synthesizing a ZIF-8 matrix, calcining and activating it under an inert atmosphere, and performing surface functionalization treatment using 3-aminopropyltriethoxysilane.

[0013] Furthermore, in step S2, the AI ​​model optimizes the adsorption operation parameters in real time by using neural network forward inference to dynamically adjust the adsorption temperature and feed flow rate based on the fluctuation of the feed concentration, wherein the adsorption temperature is adjusted within the range of 65℃±5℃.

[0014] Further, in step S3, the inner wall of the multi-field coupled microchannel reactor is coated with a Ni-Mo-P / Al2O3 hydrogenation catalyst coating; in the catalyst coating, the final mass percentage of the active catalyst components is: NiO 4.8%, MoO3 24.2%, P2O5 2.9%, with the balance being Al2O3.

[0015] Furthermore, in step S3, the conditions for applying the three physical fields are as follows:

[0016] (a) Ultrasonic field: frequency 40kHz, power density 25W / L;

[0017] (b) Electric field: A micro electric field of approximately 500V / m is formed by applying a 2.5V DC voltage through the interdigitated electrodes;

[0018] (c) Photothermal synergy: Irradiation with a near-infrared laser with a wavelength of 808 nm, with gold nanorods doped in the catalyst serving as the photothermal conversion medium, and a laser power density of 2.5 W / cm². 2 This maintains the catalyst surface temperature at 260±5℃.

[0019] Furthermore, in step S3, the reaction conditions within the multi-field coupled microchannel reactor are: a global temperature of 240°C and a pressure of 12 MPa.

[0020] Furthermore, in step S4, the membrane separation uses a polyimide hollow fiber membrane, and the hydrogen recovered on the permeate side is recycled back to the reactor inlet of step S3; the distillation is carried out under the conditions of an absolute pressure of 10 kPa, a column top temperature of 165°C, and a reflux ratio of 5:1, and the C8-C16 fraction is collected to obtain a sustainable aviation fuel product with a nitrogen content of <1 ppm, with a total yield of 92%.

[0021] Furthermore, it also includes a nitrogen resource-oriented conversion step, in which the condensate rich in ammonia / methylamine produced by adsorption-desorption regeneration in step S2 is passed into an electrochemical reactor, operating at ambient temperature and pressure, with a working voltage of 1.8V and a current density of 20mA / cm³. 2 Electrochemical synthesis was carried out under specific conditions to obtain a chemical product with acetonitrile as the main product.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] By combining microwave-assisted plasma pretreatment, AI-powered intelligent optimized adsorption pre-denitrification, and multi-field coupled catalytic deep denitrification, this invention significantly improves denitrification efficiency and drastically reduces reaction severity. This invention can reduce the total nitrogen content in the raw materials to extremely low levels. Particularly in the multi-field coupled catalytic stage, the synergistic effect of ultrasound, electric field, and photothermal action effectively lowers the apparent activation energy of the denitrification reaction, enabling deep denitrification to be completed under mild conditions. In contrast, traditional methods require more stringent high-temperature and high-pressure environments, and the products often have higher nitrogen residues.

[0024] This invention utilizes microwave volumetric heating, local plasma activation, and precise photothermal temperature control to efficiently concentrate energy on carbon-nitrogen bond weakening and catalyst active sites, avoiding overall overheating. Compared to traditional external heating methods, photothermal synergy significantly reduces system energy consumption, thus reducing energy consumption and carbon emissions while maintaining the same catalyst surface temperature. Simultaneously, the combination of microwave pretreatment and AI adsorption preferentially removes the most difficult-to-crack large-molecule nitrogen heterocycles and small-molecule nitrides, mitigating the risk of nitrogen poisoning in the hydrogenation catalyst from the source. Furthermore, the electric field in the multi-field coupling enhances the surface concentration and overflow of active hydrogen species, while local photothermal heating avoids overall high temperatures in the fluid and catalyst bed. These mechanisms work synergistically to effectively reduce the coking rate on the catalyst surface, extending the regeneration cycle and service life.

[0025] This invention avoids damage to the carbon skeleton of hydrocarbons and achieves a significantly higher overall yield of the target fraction than traditional methods through a mild and highly selective denitrification reaction. Combined with a membrane separation and distillation coupling system, the product has extremely low nitrogen content and high hydrogen recycling purity. The nitrogen-containing waste liquid obtained from adsorption enrichment is passed into an electrochemical reactor and directly converted into high-purity acetonitrile through electrochemical synthesis. This avoids the drawbacks of traditional methods where nitrogen is discharged as worthless waste ammonia and incurs costly treatment, transforming pollutants into high-value chemicals. Attached Figure Description

[0026] Figure 1 A flowchart of the efficient nitrogen reduction method for producing sustainable aviation fuel feedstock according to the present invention;

[0027] Figure 2 Characterized by optical emission spectroscopy Spectral line intensity;

[0028] Figure 3 Image of ZIF-8 raw powder;

[0029] Figure 4 This is a curve showing the adsorption capacity as a function of temperature.

[0030] Figure 5 Transmission electron microscopy characterization of the coating cross section. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0032] Example 1

[0033] like Figure 1As shown, the effective nitrogen reduction method for producing sustainable aviation fuel feedstock in this embodiment includes the following steps:

[0034] S1: Microwave-assisted plasma pretreatment and activation of raw materials

[0035] The BTL feedstock with a nitrogen content of 850 ppm is mainly composed of C12-C22 normal and isoalkanes, including nitrogen-containing compounds such as quinoline (about 300 ppm), carbazole (about 200 ppm), pyridine (about 150 ppm), and other amines (about 200 ppm). The BTL feedstock with a nitrogen content of 850 ppm is passed through an atomizing nozzle preheated to 120°C at a flow rate of 500 g / h to form microdroplets with an average particle size of 50 μm, which are then injected into a microwave resonant cavity reactor pre-filled with argon gas.

[0036] The key method parameters for this step were determined through the following preliminary experiments. With other conditions kept constant, the treatment effects were investigated at microwave powers of 200W, 400W, 600W, 800W, and 1000W, and plasma high-voltage power supply voltages of 0.5kV, 0.8kV, 1.2kV, 1.6kV, and 2.0kV. The total residual amount of quinoline and carbazole in the treated raw material was used as the evaluation index. The total residual amount of quinoline and carbazole (initial 510ppm) under different microwave powers and plasma voltages is shown in Table 1.

[0037] Table 1

[0038] Microwave power (W) Plasma voltage 0.5kV Plasma voltage 1.2kV Plasma voltage 2.0kV 200 378 ppm 310 ppm 265 ppm 400 295 ppm 178 ppm 142 ppm 600 213 ppm 46 ppm 55 ppm 800 185 ppm 52 ppm 68 ppm 1000 168 ppm 88 ppm 104 ppm

[0039] Table 1 shows that when the microwave power is 600W and the plasma voltage is 1.2kV, the total residue of quinoline and carbazole is the lowest, reaching 46ppm, corresponding to a removal rate as high as 91%. When the power is further increased, although the thermal effect is enhanced, the excessively high temperature causes localized cracking of the raw materials, generating hydrocarbon free radicals. These free radicals compete with active hydrogen free radicals, weakening the selectivity of CN bond breaking and causing a rebound in residue. However, when the microwave power is 600W, further increasing the voltage from 1.2kV to 2.0kV only slightly improves the denitrification effect, reducing the residue from 46ppm to 44ppm. Therefore, the optimal combination is determined to be a microwave power of 600W and a plasma voltage of 1.2kV.

[0040] It should be noted that 2.45 GHz was chosen as the microwave operating frequency based on the following comprehensive considerations: This frequency falls within the Industrial, Scientific, and Medical (ISM) open band designated by the International Telecommunication Union (ITU), ensuring mature and reliable equipment; at this frequency, the microwave penetration depth into the raw material matches the reactor size, enabling effective volumetric heating of microdroplets; simultaneously, the polar functional groups of nitrogen-containing heterocyclic compounds in the raw material generate dielectric loss and molecular rotational responses in the alternating electromagnetic field, which is beneficial for selectively coupling microwave energy and weakening the reactive inertia of CN bonds. Density functional theory calculations show that the applied alternating electric field can reduce the apparent activation energy required for CN bond breakage in heterocyclic molecules such as quinoline from 375.3 kJ / mol to approximately 352.1 kJ / mol, thereby kinetically accelerating their decomposition. The plasma working gas uses a hydrogen / argon volume ratio of 1:9, which was experimentally determined. This ratio, while maintaining stable plasma discharge, generates a sufficient concentration of hydrogen free radicals, as characterized by optical emission spectroscopy. Spectral line intensity as Figure 2 As shown, the black curve represents experimental measurement data, and the red curve represents theoretical fitting results. If the hydrogen ratio is too high, it will cause the plasma to shrink or even extinguish; if the ratio is too low, there will be insufficient activation of hydrogen free radicals.

[0041] Based on the optimization results above, the microwave power was set to 600W to volumetrically heat the raw material microdroplets, rapidly raising their temperature to 180°C within 0.5 seconds. Simultaneously, a stable plasma jet was generated using a hydrogen-argon mixture (volume ratio 1:9) at 1.2kV, and vertically injected into the region through which the raw material droplets flowed. The reactor pressure was maintained at 0.12MPa, and the processing time was 3 seconds.

[0042] Testing revealed that the content of macromolecular nitrogen heterocyclic compounds such as quinoline and carbazole in the treated raw material decreased by 91%, mainly converted into smaller molecular weight pyridine, fatty amines, and ammonia. The total nitrogen content decreased to 800 ppm, and no nitrogen oxides were generated. The viscosity of the raw material decreased from 23 mm. 2 / s decreased to 8mm 2 / s.

[0043] S2: AI Intelligent Optimized Adsorption Pre-Denitrification

[0044] The pretreated raw material from step S1 was fed into the AI ​​real-time optimized adsorption bed at an initial flow rate of 1000 g / h. The adsorption bed was packed with 800 g of modified ZIF-8 MOF adsorbent, prepared as follows:

[0045] Preparation of modified ZIF-8 MOF adsorbent:

[0046] The first step was the synthesis of the ZIF-8 matrix. 2.94 g of Zn(NO3)2·6H2O and 6.49 g of 2-methylimidazole were dissolved separately in 100 mL of methanol. The two solutions were mixed and vigorously stirred for 1 hour at 25 °C, allowed to stand and age for 24 hours, and then centrifuged to obtain a white solid. This solid was washed three times with methanol and dried under vacuum at 120 °C for 12 hours to obtain ZIF-8 raw powder. Figure 3 As shown.

[0047] The second step is calcination activation. The ZIF-8 raw powder is placed in a tube furnace and heated to 450°C at a heating rate of 5°C / min under a nitrogen atmosphere. It is then calcined at this temperature for 2 hours and allowed to cool naturally to room temperature. This step aims to remove residual solvents and activate the metal sites.

[0048] The third step is surface functionalization. The calcined ZIF-8 powder was dispersed in anhydrous toluene (solid-liquid ratio 1 g:50 mL), and 3-aminopropyltriethoxysilane (APTES) was added as a functionalizing agent at a concentration of 0.05 mol / L. The reaction was carried out under reflux at 110 °C for 12 hours under nitrogen protection. After the reaction, the solid product was washed three times each with toluene and ethanol, and then vacuum dried at 80 °C for 8 hours to obtain the modified ZIF-8 MOF adsorbent.

[0049] Characterization showed that the specific surface area of ​​the modified ZIF-8 MOF adsorbent was 1850 m². 2 The sample has an average pore size of 0.8 nm and has been successfully grafted with amino functional groups (XPS analysis shows that the N 1s peak area is approximately 2.8 times larger than that of the original powder). Its selectivity for pyridine and amine nitrogen compounds is significantly higher than that for alkanes. Static adsorption tests showed that the saturated adsorption capacity for pyridine at 40 °C reached 52 mg N / g.

[0050] The optimal range of adsorption temperature was investigated through preliminary experiments. Breakthrough curves were measured at different constant temperatures (50℃, 55℃, 60℃, 65℃, 70℃, 75℃, and 80℃) with the same feed composition (pyridine content 120ppm). The breakthrough point was defined as the outlet nitrogen concentration reaching 5ppm, and the breakthrough adsorption capacity was recorded. The breakthrough adsorption capacity at different adsorption temperatures (with a fixed feed pyridine concentration of 120ppm) is shown in Table 2.

[0051] Table 2

[0052] Adsorption temperature (°C) Breakthrough adsorption capacity (mgN / g) 50 32.1 55 36.5 60 41.2 65 44.7 70 42.8 75 37.3 80 31.9

[0053] Experiments show that the adsorption capacity reaches its maximum of 44.7 mg N / g at 65℃. At excessively low temperatures, the diffusion rate of pyridine molecules is slow, mass transfer resistance is high, and the utilization rate of adsorption sites is low; at excessively high temperatures, the adsorption equilibrium shifts towards desorption, thus reducing the effective adsorption capacity. Therefore, 65℃ is used as the baseline temperature for the adsorption step, allowing the AI ​​model to be dynamically adjusted within ±5℃ of this value.

[0054] In actual operation, the adsorption system uses 55℃ as the initial operating temperature. When the AI ​​model runs for the first hour, it monitors a fluctuation in the feed pyridine concentration, which rises from the baseline level to 120 ppm. Through neural network forward inference (inference time approximately 3 ms), based on optimized data of adsorption capacity changes with temperature, such as... Figure 4 As shown, the adsorption capacity is highest at 65℃, reaching 44.7 mgN / g. The automatic decision-making process optimized the adsorption tower temperature from the initial 55℃ to 65℃ and fine-tuned the feed flow rate from 1000 g / h to 950 g / h. The optimization rationale is that while increasing the feed pyridine concentration increases the adsorption driving force, it also exacerbates concentration polarization within the diffusion layer. Moderate heating can reduce liquid viscosity and enhance the molecular diffusion coefficient (the diffusion coefficient of pyridine at 65℃ is approximately 35% higher than at 55℃), thereby overcoming mass transfer resistance and maintaining a high adsorption rate. The model also predicts that the adsorbent will reach its breakthrough point after 3.8 hours of operation.

[0055] S3: Multi-field coupled catalytic deep denitrification

[0056] The low-NOx feedstock obtained in step S2 is mixed with circulating hydrogen (hydrogen / feedstock volume ratio of 500:1), preheated to 220°C, and then introduced into a multi-field coupled microchannel reactor. The reactor contains 1000 rectangular microchannels with dimensions of 0.5 mm × 1.0 mm (depth × width).

[0057] Specific preparation method of Ni-Mo-P / Al2O3 hydrogenation catalyst:

[0058] The first step is carrier pretreatment. γ-Al₂O₃ powder (specific surface area 220 m²) is used as the carrier pretreatment. 2 / g (average particle size 20μm) was calcined at 500℃ in air for 4 hours to remove moisture and impurities, and then cooled for later use.

[0059] The second step is to prepare the impregnation solution. (NH4)6Mo7O 24 ·4H2O and Ni(NO3)2·6H2O were dissolved in deionized water to prepare an aqueous solution with a MoO3 concentration of 25wt% and a NiO concentration of 5wt%. H3PO4 was then added as a co-catalyst precursor, so that P2O5 accounted for 3wt% of the total oxide mass. After stirring evenly, an appropriate amount of citric acid was added, with a molar ratio of citric acid to total metal ions of 1:1, to improve the dispersion of the active components.

[0060] The third step is equal-volume impregnation. The pretreated γ-Al2O3 powder is placed in a rotary evaporation flask, and the impregnation solution prepared in the first step is slowly added dropwise. The volume of the impregnation solution is equal to the volume of the carrier pores, about 0.48 mL / g. The mixture is impregnated by rotation at 25°C for 2 hours, and then allowed to stand at room temperature for 12 hours.

[0061] The fourth step is drying and calcination. The impregnated powder is dried at 110°C for 6 hours, then placed in a tube furnace and calcined at 500°C at a rate of 3°C / min in air atmosphere for 4 hours to obtain the oxide precursor.

[0062] Step 5: Pre-sulfurization. The oxide precursor is loaded into a fixed-bed reactor, and a H2S / H2 mixture containing 3 vol% H2S is used as the sulfiding agent. Sulfurization is carried out at 300℃ and 0.1 MPa for 4 hours to obtain the sulfidated Ni-Mo-P / Al2O3 hydrogenation catalyst. Inductively coupled plasma atomic emission spectrometry analysis shows that the final mass percentage of each component in the catalyst is: NiO 4.8 wt%, MoO3 24.2 wt%, P2O5 2.9 wt%, with the balance being Al2O3.

[0063] Step 6: Introduction of gold nanorods. A gold nanorod sol with an aspect ratio of approximately 4:1 (the longitudinal plasmon resonance absorption peak is located near 808 nm) was synthesized using a seed-mediated method. The synthesized gold nanorod sol was slowly added dropwise to the prepared Ni-Mo-P / Al2O3 catalyst powder under stirring, so that the gold nanorod loading was 0.1% of the total catalyst mass. After stirring for 1 hour, the mixture was vacuum dried overnight at 60°C to obtain a catalyst composite powder containing gold nanorods.

[0064] Step 7: Coating Preparation. Low-temperature plasma spraying was employed, controlling the powder residence time to less than 2 ms to maintain the rod-like morphology of the gold nanorods and their 808 nm plasmon resonance absorption characteristics. The prepared Ni-Mo-P / Al2O3 catalyst powder was sprayed onto the inner wall of the microchannel at a distance of 80 mm, a current of 600 A, a main gas (Ar) flow rate of 40 L / min, and a powder feed rate of 15 g / min. The coating thickness was controlled at 20 μm, with a loading of 15 wt%.

[0065] Determination and mechanism of multi-field parameters:

[0066] The reactor is subjected to three physical fields simultaneously during the reaction process, and the parameters are determined based on the following mechanism and experimental verification:

[0067] (1) Ultrasonic Field: Ultrasonic waves with a frequency of 40 kHz and a power density of 25 W / L were continuously applied through a piezoelectric ceramic transducer integrated on the side wall of the reactor. The mechanism for choosing the 40 kHz frequency is that the cavitation effect at this frequency can generate transient cavitation bubbles with a diameter of about 5 μm in the liquid. The microjets generated when the bubbles collapse can reach a velocity of more than 100 m / s, which can effectively remove the laminar boundary layer on the catalyst surface and enhance the mass transfer of reactants to active sites. Experimentally, at a power density of 25 W / L, the volumetric mass transfer coefficient kLa value increased from 0.015 s⁻¹ without ultrasound. -1 Improved to 0.057s -1 The increase is approximately 3.8 times. When the power density is too low (<15W / L), the cavitation effect is insufficient to overcome the inherent boundary layer resistance of the microchannel, while when it is too high (>35W / L), it causes physical erosion of the catalyst coating.

[0068] (2) Electric field assistance: A DC voltage of 2.5V was applied through interdigitated electrode pairs embedded under the catalyst coating to form a micro-electric field with an intensity of approximately 500V / m. Hydrogen dissociation efficiency was tested in the range of 0-800V / m, showing that the surface concentration of active hydrogen species on the catalyst surface was 4.6 times higher at 500V / m than without an electric field. This was quantified by the integrated peak area ratio in in-situ infrared spectroscopy, with the peak located at 2040 cm⁻¹. -1 The voltage at this point is attributed to the Ni-H stretching vibration. Further increasing the voltage is limited by the electrolytic side reactions of water, leading to a decrease in Faraday efficiency. The mechanism is as follows: After applying a DC voltage between the interdigitated electrodes beneath the catalyst coating, a localized electrostatic field is formed along the catalyst surface within the microchannel. This electric field alters the electronic density state of the active sites on the catalyst surface through polarization, which is beneficial for the polarization and heterolytic adsorption of hydrogen molecules at Ni sites. Simultaneously, the electric field gradient drives the directional migration of surface-adsorbed hydrogen species along the catalyst surface, enhancing the hydrogen spillover effect and allowing more active hydrogen species to reach the adjacent sites of the adsorbed nitrogen-containing heterocyclic molecules, thereby increasing the hydrodenitrification reaction rate. Quantitative analysis by in-situ infrared spectroscopy showed that at an applied electric field of 500 V / m, the voltage at 2040 cm⁻¹... -1 The peak area attributable to the Ni-H stretching vibration is approximately 4.6 times larger than that without an electric field.

[0069] (3) Photothermal Synergy: The reactor was uniformly irradiated with a near-infrared laser with a wavelength of 808 nm through an optical fiber. Gold nanorods (4:1 aspect ratio, prepared by seed-mediated method, doped with 0.1 wt%) loaded in the catalyst exhibited strong plasmon resonance absorption at this wavelength, achieving a photothermal conversion efficiency of 92%. The laser power was adjusted to 2.5 W / cm². 2This allows the catalyst surface temperature to be precisely maintained at 260±5℃, while the bulk fluid temperature is only 240℃. This temperature difference avoids the risk of overall high-temperature coking of the reactants, and simultaneously reduces the apparent activation energy of the denitrification reaction from 98 kJ / mol in conventional thermocatalysis to 63 kJ / mol (calculated from the slope of the Arrhenius curve) through a localized high-temperature effect, significantly accelerating CN bond breaking. Figure 5 Transmission electron microscopy characterization of the coating cross-section shows that the gold nanorods maintain their original morphology in the coating, and the longitudinal absorption peak position does not show a significant blue shift, indicating that the plasma spraying process did not significantly affect the photothermal properties of the gold nanorods.

[0070] Under the synergistic effect of the above-mentioned multiple factors, the hydrodenitrification reaction proceeds efficiently under mild global temperature of 240℃ and pressure of 12MPa. At the reactor outlet, the cracking rate of residual pyridine and trace amounts of recalcitrant nitrogen heterocycles in the feedstock reaches over 99.5%, and the total nitrogen content of the liquid phase product is reduced to 0.5ppm.

[0071] S4: High-efficiency separation and targeted conversion of nitrogen resources

[0072] The liquid product from the gas-liquid separation in step S3 is fed into a membrane separation-distillation coupled system. The product enters a membrane module made of polyimide hollow fiber membrane, where separation is performed at 100°C and 3.0 MPa. Hydrogen with a purity of 99.2% is obtained on the permeate side and recycled back to the reactor inlet of step S3. The residual liquid enters a vacuum distillation column, where precision fractionation is performed under conditions of 10 kPa absolute pressure, 165°C top temperature, and a reflux ratio of 5:1. The C8-C16 aviation kerosene fraction is collected, ultimately yielding a sustainable aviation fuel product with a nitrogen content of <1 ppm, with a total yield of 92% (based on the mass of the raw material).

[0073] Simultaneously, the ammonia / methylamine-rich condensate (ammonia concentration approximately 1.2 mol / L) generated from the desorption and regeneration in step S2 is pumped into the electrochemical reactor of the nitrogen resource directional conversion unit. The reactor uses a nickel-based alloy anode and a graphite cathode, operating at ambient temperature and pressure, with a working voltage of 1.8V and a current density of 20 mA / cm². 2 Electrochemical synthesis was carried out under specific conditions. The main component of the anolyte was acetonitrile (selectivity up to 85%), with a yield of 0.32 g / h. Subsequent extraction and distillation yielded acetonitrile with a purity of 99.5%.

[0074] Comparative Example 1

[0075] It only uses traditional high-temperature and high-pressure hydrogenation refining, without pretreatment or multi-field coupling steps.

[0076] This comparative example uses the same BTL feedstock as Example 1 (nitrogen content 850 ppm, total quinoline and carbazole content 510 ppm), with a processing rate of 500 g / h. This comparative example completely omits steps S1 (microwave-assisted plasma pretreatment) and S2 (AI intelligent optimized adsorption) from Example 1, directly performing a conventional hydrogenation treatment similar to step S3, without applying any multiphysics fields. The specific steps are as follows:

[0077] The feedstock was mixed with recycled hydrogen (hydrogen / feedstock volume ratio 500:1), preheated to 220°C, and then introduced into a tubular reactor (without microchannel structure, and without ultrasonic, electric field, or photothermal treatment) of similar size to a conventional fixed-bed reactor. The reactor was loaded with 100g of a commercial Ni-Mo-P / Al2O3 hydrogenation catalyst (composition similar to the S3 catalyst in Example 1, but without microchannel coating, and in conventionally extruded granules). The reaction was carried out under harsh conditions of 340°C and 18MPa, with the liquid hourly space velocity consistent with the S3 step of Example 1.

[0078] Testing revealed that the total nitrogen content of the liquid product at the reactor outlet was 12.3 ppm. To achieve fuel specifications comparable to Example 1 (total nitrogen 0.5 ppm), the product needed to be passed through the same membrane separation-distillation coupling system as S4 in Example 1 for deep separation. Ultimately, the nitrogen content in the C8-C16 aviation kerosene fraction collected in the distillation column decreased to 5.8 ppm, with a total yield of only 82% (based on the mass of the original feedstock). Furthermore, due to the high reaction temperature, thermogravimetric analysis revealed that the surface carbon content of the catalyst reached 8.5 wt% after 200 hours of operation, and the bed pressure drop increased by 35%, requiring frequent regeneration.

[0079] By omitting the pretreatment and multi-field coupling enhancement steps of this invention, the conventional method, even under more demanding temperature (340℃ vs 240℃) and pressure (18MPa vs 12MPa), still resulted in a significantly higher nitrogen content in the final product (5.8ppm) compared to this invention (<1ppm), and a 10 percentage point decrease in overall yield. This fully demonstrates the decisive role of steps S1 and S2 (pretreatment) and the S3 (multi-field coupling technology) of this invention in significantly improving denitrification depth and product yield.

[0080] Comparative Example 2

[0081] In step S3, the photothermal synergy function is turned off, relying solely on external heating.

[0082] The operating procedures of this comparative example are basically the same as those in Example 1, including the exact same S1 (microwave-assisted plasma pretreatment) and S2 (AI intelligent optimization adsorption pre-denitrification) steps, to obtain a low-NOx feedstock. The only difference is in step S3 (multi-field coupled catalytic deep denitrification):

[0083] The aforementioned low-nitrogen feedstock was mixed with circulating hydrogen and preheated to 220°C. The mixture was then introduced into a multi-field coupled microchannel reactor (containing 1000 microchannels coated with the same Ni-Mo-P / Al2O3 hydrogenation catalyst) identical to that in Example 1. The only difference between this comparative example and Example 1 was that the 808nm near-infrared laser irradiation system was shut off, and an external electric heating jacket was used entirely. The reactor wall temperature was set to 290°C, and external forced convection and conduction were used to maintain the overall temperature of the fluid and catalyst at 260±3°C. Simultaneously, the ultrasonic field (40kHz, 25W / L) and electric field assistance (2.5V) were kept on, while other conditions (pressure 12MPa, space velocity, etc.) remained completely identical.

[0084] Four hours into the experiment, the reactor outlet material was analyzed, and the total nitrogen content of the liquid product was 3.1 ppm. To maintain the reaction temperature of 260°C, the average power consumption of the external heating unit in this comparative example was 430 W. Through online visualization via a quartz window, and by performing cross-sectional and Raman spectroscopy analysis on a section of the microchannel reactor after 100 hours of operation, the small amount of carbonaceous species deposited on the catalyst surface in Example 1 showed a high Ig. D / I G The ratio (3.8) exhibits typical characteristics of amorphous carbon with a relatively loose structure; while the coke I deposited in Comparative Example 2... D / I G The ratio decreased to 2.1, indicating a relatively higher degree of graphitization and a denser structure. Typically, carbon deposits with a higher degree of graphitization are more difficult to oxidize and remove during catalyst regeneration. Furthermore, gravimetric analysis showed that the carbon deposit amount in Comparative Example 2 was approximately 2.9 times that of Example 1. Combined with its denser carbon deposits, this further explains its adverse effects on catalyst activity and the difficulty in regeneration.

[0085] Under identical feed conditions, simply replacing the precise localized photothermal synergy heating with traditional external overall heating, even while maintaining the same bulk fluid temperature, resulted in a denitrification depth that deteriorated from <0.5 ppm to 3.1 ppm due to the lack of kinetic enhancement effects in the high-temperature micro-regions on the catalyst surface. Simultaneously, the overall temperature increase not only increased system energy consumption by approximately 27% but also significantly exacerbated thermal coking throughout the fluid and catalyst bed, severely impacting the long-term operational stability of the method. This strongly demonstrates the unique advantages of the photothermal synergy field in this invention in reducing reaction activation energy, improving selectivity, and suppressing coking.

[0086] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. An effective method for reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock, characterized in that, Includes the following steps: S1. Nitrogen-containing raw materials are formed into micro-droplets through an atomizing nozzle and sprayed into a microwave resonant cavity reactor, where microwaves and plasma are applied simultaneously for treatment; S2. The pretreated raw material from step S1 is passed into an adsorption bed filled with a modified metal-organic framework adsorbent for adsorption and denitrification, and the adsorption operation parameters are optimized in real time using an AI model. S3. The low-nitrogen raw material obtained in step S2 is mixed with hydrogen and introduced into a multi-field coupled microchannel reactor to carry out a hydrogenation and denitrification reaction under the synergistic effect of ultrasonic field, electric field and photothermal. S4. The product after the reaction in step S3 is separated by membrane separation and distillation to obtain sustainable aviation fuel products.

2. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, In step S1, the nitrogen-containing raw material is a biomass liquefaction oil raw material containing nitrogen-containing heterocyclic compounds, including quinoline, carbazole, and pyridine.

3. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, In step S1, the microwave power is 600W and the frequency is 2.45GHz; the plasma uses a hydrogen / argon mixture with a volume ratio of 1:9 as the working gas, the plasma high-voltage power supply voltage is 1.2kV, the pressure inside the reactor is 0.12MPa, and the processing time is 3s.

4. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, In step S2, the modified metal-organic framework adsorbent is a modified ZIF-8 adsorbent with amino functional groups grafted onto its surface. It is obtained by synthesizing a ZIF-8 matrix, calcining and activating it under an inert atmosphere, and performing surface functionalization treatment using 3-aminopropyltriethoxysilane.

5. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, In step S2, the AI ​​model optimizes the adsorption operation parameters in real time by using neural network forward inference to dynamically adjust the adsorption temperature and feed flow rate based on the fluctuation of the feed concentration. The adsorption temperature is adjusted within the range of 65℃±5℃.

6. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, In step S3, the inner wall of the multi-field coupled microchannel reactor is coated with a Ni-Mo-P / Al2O3 hydrogenation catalyst coating; the final mass percentage of the active catalyst components in the catalyst coating is: NiO 4.8%, MoO3 24.2%, P2O5 2.9%, with the balance being Al2O3.

7. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 6, characterized in that, In step S3, the conditions for applying the three physical fields are as follows: (a) Ultrasonic field: frequency 40kHz, power density 25W / L; (b) Electric field: A micro electric field of approximately 500V / m is formed by applying a 2.5V DC voltage through the interdigitated electrodes; (c) Photothermal synergy: Irradiation with a near-infrared laser with a wavelength of 808 nm, with gold nanorods doped in the catalyst serving as the photothermal conversion medium, and a laser power density of 2.5 W / cm². 2 This maintains the catalyst surface temperature at 260±5℃.

8. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 6, characterized in that, In step S3, the reaction conditions inside the multi-field coupled microchannel reactor are: global temperature 240℃ and pressure 12MPa.

9. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, In step S4, the membrane separation uses a polyimide hollow fiber membrane, and the hydrogen recovered on the permeate side is recycled back to the reactor inlet of step S3; the distillation is carried out under the conditions of absolute pressure of 10 kPa, column top temperature of 165°C, and reflux ratio of 5:1, and the C8-C16 fraction is collected to obtain a sustainable aviation fuel product with a nitrogen content of <1 ppm, with a total yield of 92%.

10. The method for effectively reducing nitrogen oxide emissions in the production of sustainable aviation fuel feedstock according to claim 1, characterized in that, It also includes a nitrogen resource-oriented conversion step, in which the condensate rich in ammonia / methylamine produced by adsorption-desorption regeneration in step S2 is passed into an electrochemical reactor, operating at ambient temperature and pressure, with a working voltage of 1.8V and a current density of 20mA / cm³. 2 Electrochemical synthesis was carried out under specific conditions to obtain a chemical product with acetonitrile as the main product.

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