Method for producing biological aviation kerosene by adopting ultra-low hydrogen-oil ratio

Abstract

The invention provides a continuous hydrogenation-isomerization method capable of meeting the treatment requirements of biological oil and fat, especially waste oil and fat, a homogeneous hydrogenation process with strong raw material adaptability is used as a raw material pretreatment process, and meanwhile, a high-activity nano transition metal sulfide catalyst is matched. On the basis, the long-chain alkane is selectively cracked by adopting a catalytic distillation process, so that the yield of the medium-chain and long-chain alkane is increased; an ultramicro-flow hydrogen mixer and a reduction-state non-noble metal hydroisomerization catalyst are adopted, so that the production cost of the catalyst is reduced while the hydrogen-oil ratio and the energy consumption of a circulating hydrogen system are reduced, and finally, high-efficiency and low-carbon conversion of waste grease and low-cost and high-selectivity preparation of biological aviation kerosene are realized.

Description

Technical Field

[0001] This invention relates to a method for producing bio-jet fuel, and more particularly to the production of ultra-low hydrogen-to-oil ratio fuel. Background Technology

[0002] With rapid socio-economic development and excessive consumption of fossil fuels, coupled with global climate change, the development of renewable energy sources, including biomass energy, is imperative to address these issues. Bio-jet fuel, as an important component of biomass energy, is considered an ideal alternative to traditional aviation fuel. Developing bio-jet fuel production technology is of great significance for achieving carbon emission reduction targets and promoting the green development of my country's aviation industry.

[0003] Bio-jet fuel is the most promising sustainable aviation fuel, primarily composed of a mixture of hydrocarbons with a carbon number distribution between C8 and C16, mainly alkanes. It boasts high calorific value, low pour point, and a carbon emission reduction of up to 80% over its entire life cycle. Since the American Society for Testing and Materials (ASTM) first certified bio-jet fuel in 2009, six technical routes have successively passed ASTM D7566 standard certification, including the Fischer-Tropsch synthesis route (FT-SPK), the oil / fatty acid hydrodeoxygenation route (HEFA), the sugar fermentation hydrogenation route (SIP), the light aromatic alkylation route (SPK / A), the low-carbon alcohol route (ATJ-SPK), and the catalytic hydrothermal cracking route (CHJ). Considering factors such as feedstock supply, operating costs, and technological maturity, the oil / fatty acid hydrodeoxygenation route remains the preferred choice for producing oil-based bio-jet fuel.

[0004] To increase the aviation fuel oil content in the product, selective hydrocracking and isomerization processes must be added after hydrotreating. Patent FI100248B describes a method for converting vegetable oil into intermediate base distillate oil through hydrodeoxygenation and isomerization. This method uses a hydrodesulfurization catalyst and a metal-containing molecular sieve as catalysts for hydrodeoxygenation and isomerization, respectively. Patent US2004 / 0230085 A1 also describes a method for treating biomass as feedstock to obtain alkane products via hydrodeoxygenation through an isomerization process. Patent CN200910188170.6 discloses a hydrodewaxing catalyst, its preparation method, and its application. This catalyst uses a molecular sieve support modified with metal additives and silicone oil. By sequentially depositing additives and silicone oil, the acidity and pore shape of the inner and outer surfaces of the molecular sieve support are adjusted, thereby improving the isomerization rate of the feedstock. However, the preparation process of this catalyst is complex, involving multiple impregnation and high-temperature calcination steps, resulting in a long preparation cycle. Patent CN201810935163.7 discloses a hydrocracking catalyst, its preparation method, and its application. The catalyst is prepared by impregnation and contains different types of phosphorus-containing molecular sieves and non-precious metal components. It exhibits excellent cracking performance in the hydrocracking reaction of Saudi vacuum residue. However, this catalyst cannot achieve the co-production of bio-jet fuel and low-pour-point biodiesel and is not suitable for the isomerization reaction of C15-C18 bio-based long-chain alkanes. Furthermore, this catalyst requires sulfidation during use and is unsuitable for processing almost sulfur-free bio-based feedstocks. Patent CN201610412721.2 discloses an isomerization dewaxing method for producing bio-jet fuel and a catalyst used in this method. The catalyst consists of one or more molecular sieves selected from silicon-modified ZSM-22, ZSM-23, ZSM-12, and SAPO-11, and the active metal component is selected from precious metals Pt and / or Pd with a content of 0.1-5 wt%. Similarly, patent CN202010497292.X discloses a hydroisomerization catalyst, its preparation method, and its application. This catalyst uses a ZSM-48 molecular sieve with a hollow spherical structure as a support, and the active metal component is selected from at least one of Group VIII noble metals, prepared by an impregnation method.

[0005] Most of the aforementioned patents use precious metals as active components. While these catalysts exhibit high activity at low temperatures, they are also expensive, sensitive to impurities, and highly susceptible to poisoning. To reduce operating costs and carbon emissions during biofuel production, in addition to avoiding the use of precious metal catalysts, the key operating parameter of the hydrogen-to-oil ratio (volume ratio of hydrogen to feedstock oil) can be lowered. In actual production, considering the low solubility of hydrogen in feedstock oil, hydrogen dissolution, diffusion, and mass transfer are typically enhanced by increasing hydrogen pressure or the hydrogen-to-oil ratio. Since the hydrogen consumption in the alkane isomerization process is much lower than in the preceding hydrodeoxygenation process, a higher hydrogen-to-oil ratio increases the amount of fresh hydrogen used and the load on the circulating hydrogen system, thereby increasing operating costs and energy consumption.

[0006] Furthermore, although existing series fixed-bed hydrogenation processes are relatively mature, supported catalysts are prone to coking and poisoning when processing waste oils with high gum and metal content and high acid values, such as swill oil and acidified oil, leading to a rapid decline in activity. Therefore, pretreatment of the feedstock to remove impurities such as ash, pigments, and colloids is essential. This process is not only complex and costly, but also generates large amounts of wastewater and waste residue after large-scale production, causing secondary pollution. In view of this, it is imperative to find a new, low-cost, and low-energy-consumption method for producing bio-jet fuel to overcome the shortcomings of existing processes. Summary of the Invention

[0007] To address the poor feedstock adaptability of existing hydrogenation units, this invention aims to provide a continuous hydrogenation-isomerization method that meets the requirements for treating bio-oils, especially waste oils. This method differs from existing fixed-bed hydrogenation processes by innovatively employing a homogeneous suspended-bed hydrogenation process with high feedstock adaptability. During suspended-bed hydrogenation, the catalyst is efficiently converted in situ into a highly active nano-transition metal sulfide catalyst, achieving deep depurification of waste oils. This eliminates the need for complex bio-oil feedstock pretreatment processes and completely solves the problem of existing units' inability to directly process waste oils. Furthermore, a catalytic distillation process is used for selective cracking pretreatment of long-chain alkanes, improving the yield of medium- and long-chain alkanes. An ultra-microfluidic hydrogen mixer and a reduced-state non-precious metal hydrogenation isomerization catalyst are used to reduce the hydrogen-to-oil ratio and the energy consumption of the circulating hydrogen system, while simultaneously lowering the catalyst production cost. Ultimately, this achieves efficient, low-carbon conversion of waste oils and low-cost, highly selective preparation of bio-jet fuel. The objective of this invention is achieved through the following technical solutions:

[0008] A method for producing bio-jet fuel using an ultra-low hydrogen-to-oil ratio according to the present invention includes the following steps:

[0009] (1) The heavy oil obtained from the bottom oil separation of the suspended bed prehydrogenation reactor is heated to 380~420℃ as circulating oil and mixed with biomass feed oil containing 1wt.% dimethyl sulfide and one stream of material from the gas stripping purification treatment in step (4) and the bottom oil of the product fractionation tower. After mixing with 500~5000ppm oil-soluble catalyst, it enters a suspended bed prehydrogenation reactor without solid catalyst packing for reaction, with a residence time of 1~2 hours;

[0010] (2) The top effluent from the suspended bed prehydrogenation reactor enters a fixed bed hydrodeoxygenation reactor packed with a solid catalyst and undergoes hydrodeoxygenation at 280~340℃; the bottom oil from the suspended bed prehydrogenation reactor is separated to obtain heavy oil and oil residue. The heavy oil is used as the circulating oil in step (1) above, and the oil residue is discharged by centrifugation.

[0011] (3) The top effluent from the fixed-bed hydrodeoxygenation reactor is heat exchanged and then enters the fixed-bed catalytic distillation reactor for selective cracking reaction at 240~320℃;

[0012] (4) The liquid phase material of the fixed bed catalytic distillation reactor is divided into two streams after gas stripping purification. One stream merges with the bottom oil of the product fractionation tower and becomes part of the feed of the suspended bed pre-hydrogenation reactor in step (2) above. The other stream is mixed with fresh hydrogen in the ultra-micro flow hydrogen mixer and then enters the fixed bed heterogeneous dewaxing reactor.

[0013] (5) The liquid phase product of the fixed bed heterogeneous dewaxing reactor enters the stripping tower to obtain bio-based liquefied petroleum gas (LPG) product, and the bottom oil enters the atmospheric distillation tower for fractionation to obtain bio-solvent oil, bio-jet fuel, low-pour-point biodiesel and bottom oil (high-pour-point biodiesel).

[0014] The mass ratio of the biomass feedstock oil to the circulating oil in step (1) is 1:(1~5).

[0015] Specifically, the hydrogen-to-oil ratio of the fixed-bed heterogeneous dewaxing reactor is (100~300):1, and the pressure is 4~6 MPa.

[0016] Specifically, the preparation method of the oil-soluble catalyst in the suspended bed pre-hydrogenation reactor includes the following steps: A bi / multi-metal composite oxide precursor containing two or more non-noble transition metals is first synthesized through an oxidation-precipitation process in a hydrogen peroxide-ethanol mixed solution; then, the precursor is modified with ion ligands in methanol to obtain the oil-soluble catalyst. The bi / multi-metal composite oxide precursor is one or more of the following: basic cobalt ammonium molybdate [(NH4)HCo2(OH)2Mo2O8], basic nickel ammonium molybdate [(NH4)HNi2(OH)2Mo2O8], basic cobalt ammonium tungstate [(NH4)HCo2(OH)2W2O8], and basic nickel ammonium tungstate [(NH4)HNi2(OH)2W2O8].

[0017] Specifically, the catalyst used in the fixed-bed hydrodeoxygenation reactor is an alumina-supported nickel-molybdenum bimetallic catalyst, which needs to be pre-sulfurized before use; the catalyst used in the fixed-bed catalytic distillation reactor is a nickel-based catalyst supported on a high silica-to-alumina ratio mesoporous-microporous composite molecular sieve; and the catalyst used in the fixed-bed isomerization dewaxing reactor is a reduced non-precious metal isomerization catalyst.

[0018] The catalyst pre-sulfurization treatment involved adding 1-2 wt% dimethyl sulfide as a sulfiding agent using light kerosene as a solvent. Sulfurization conditions were: temperature 350ºC, hydrogen pressure 6 MPa, and space velocity 2.0 h⁻¹. -1 The hydrogen-to-oil ratio is 600:1.

[0019] The positive effects of this invention:

[0020] 1. A four-stage reaction process (pre-hydrogenation in a suspended bed reactor + deep deoxygenation and upgrading in a fixed bed reactor + distillation cracking in a fixed bed reactor + isomerization and dewaxing in a fixed bed reactor, combined with a circulating hydrogen system), featuring a unique four-stage innovative catalyst system (dual / multiple non-precious transition metal liquid homogeneous catalysts + water-resistant and etching-resistant hydrogenation and deoxygenation catalysts + nickel-based distillation cracking catalysts + reduced non-precious metal isomerization catalysts), synergistically using an ultra-microfluidic hydrogen diffusion process, achieving high yield (5-10% higher total carbon lifecycle than traditional methods), high activity (reaction temperature lower than precious metals), high selectivity, low cost, high stability (ensuring long-term operation), and high feedstock adaptability (full hydrogenation process).

[0021] 2. The heterogeneous dewaxing process uses an ultra-microfluidic high-dispersion hydrogen mixer to achieve an ultra-low hydrogen-to-oil ratio (100~300, conventionally greater than 1000) for bio-jet fuel.

[0022] 3. A fixed-bed catalytic distillation reactor is used to improve reaction equilibrium and enhance gas-liquid mass transfer. At the same time, the gas rich in generated water vapor is separated and sent directly to the cold high-resolution analyzer shared by the two units.

[0023] 4. A unique one-stage gas stripping method is used to strip the liquid phase products of a one-stage fixed-bed catalytic distillation reactor using two-stage tail gas (mainly pure hydrogen), achieving ultra-low sulfur in the heterogeneous dewaxing feed. At the same time, the feed is fed directly without cooling or depressurization, reducing energy consumption and production costs.

[0024] 5. A unique in-situ nickel atom molecular sieve framework is used to prepare a reduced non-precious metal isomerization catalyst, which improves the catalyst activity by 200% compared with precious metals (adapting to match ultra-microfluidics and enhancing the synergy of the reaction).

[0025] 6. The liquid homogeneous hydrogenation suspension bed reaction uses oil-soluble dual / multi-non-noble transition metal catalysts. The catalysts are not mechanically mixed and have a molecular structure of dual / multi-metal compounds with specific molecular structures.

[0026] 7. Liquid homogeneous hydrogenation pretreatment is used to replace non-hydrogen-dependent pretreatment, and the liquid phase of the fixed-bed catalytic distillation reactor is used as the circulating oil. The feed heat exchanger and feed heater in the conventional process are eliminated, thus eliminating coking and corrosion of biomass feedstock and ensuring safe operation. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of an embodiment of the present invention.

[0028] In the diagram: 1. Raw material tank; 2. Centrifuge; 3. Dehydration tower; 4. Liquid catalyst injection pump; 5. Booster pump; 6. Suspended bed pre-hydrogenation reactor; 7. Fixed bed hydrodeoxygenation reactor; 8. High-pressure buffer tank; 9. Heat exchanger; 10. Fixed bed catalytic distillation reactor; 11. First-stage hot high-pressure stripping separator; 12. Assist pump; 13. Fresh hydrogen compressor; 14. Ultra-microfluidic hydrogen mixer; 15. Second-stage heater; 16. Fixed bed heterogeneous decondensation reactor; 17. Second-stage hot high-pressure separator; 18. Cold high-pressure separator; 19. Circulating hydrogen compressor; 20. Cold low-pressure separator; 21. Stripping tower; 22. Product fractionation heater; 23. Product fractionation tower; 24. Product fractionation tower bottom reflux booster pump; 25. First-stage heater. Detailed Implementation

[0029] Example 1

[0030] Reference Appendix Figure 1 This embodiment relates to an oil hydrogenation reaction system for producing bio-jet fuel using an ultra-low hydrogen-to-oil ratio. The system operates according to the following steps:

[0031] (1) Biomass raw materials are stored in raw material tank 1 as feed for the process system.

[0032] (2) The feed is dehydrated in the dehydration tower 3, then mixed with oil-soluble catalyst injected by the liquid catalyst injection pump 4. After being pressurized by the booster pump 5, it is mixed with a mixture of the material after being purified by gas stripping with hydrogen from the first-stage heating furnace 25 and the bottom reflux liquid of the product fractionation tower. Together, they enter the suspended bed pre-hydrogenation reactor 6 for pretreatment under hydrogenation conditions. The sulfur, nitrogen, oxygen, heavy metal elements, and non-ideal components such as gums and asphaltene in the feed are hydrogenated and converted to facilitate subsequent separation and removal. Specifically, the pretreatment process reduces the content of sulfur, nitrogen, chlorine, oxygen, and metal or non-metal impurities (calcium, sodium, silicon, potassium, iron) and gums in the raw material. Sulfur is converted into hydrogen sulfide, nitrogen into ammonia, chlorine into hydrogen chloride, and oxygen into water. Metal or non-metal atoms will be deposited on the catalyst surface and discharged with the catalyst. Gum is mainly composed of phospholipids and other substances, which will be converted into intermediate products of fatty acids and fatty alcohols. Since the pre-hydrogenation reaction occurs in the suspended bed pre-hydrogenation reactor, and different impurities have different reactivity and content, the process can achieve almost complete removal of metals, non-precious metals, and colloids, while removing 60-80% of other heteroatoms.

[0033] (3) The material after hydrogenation pretreatment enters the fixed bed hydrogenation deoxygenation reactor 7 for further deoxygenation treatment to prevent the oxygen generated water from having an adverse effect on the hydrophobic catalyst in the subsequent reactor. At the bottom of the suspended bed pre-hydrogenation reactor 6, the used oil-soluble catalyst components and other heavy mechanical impurities such as precipitates generated during the hydrogenation conversion process will settle and be enriched. After these components are discharged, they are first depressurized by the high-pressure buffer tank 8 and then returned to the raw material tank 1 as circulating oil to mix with the raw material. Then, through the supergravity action of the external centrifuge 2, they are separated and removed together with the mechanical impurities in the raw material.

[0034] (4) After deoxygenation, the material is cooled appropriately by heat exchanger 9 and enters fixed-bed catalytic distillation reactor 10 with two bed layers. In the lower bed, excessively long-chain hydrocarbons in the material are hydrocracking. At the same time, with the help of circulating hydrogen from circulating hydrogen compressor 19 blown in from the lower part of the bed, the dissolved hydrogen sulfide and dehydration of harmful gaseous components such as deoxygenation-generated water in the product are purified to meet the low sulfur and low water requirements of subsequent sulfur-sensitive and water-sensitive catalysts. The gas components generated by this gas stripping process are discharged from the top of the reactor and combined with other materials in the subsequent process. After cooling, they enter cold high-pressure separator 18 for further gas-liquid separation.

[0035] (5) The liquid material purified by the fixed-bed catalytic distillation reactor 10 enters the first-stage hot high-pressure gas stripping separator 11 for further gas stripping purification using fresh hydrogen. After being pressurized by the booster pump 12, the purified material is divided into two paths. One path merges with the material fed into the bottom reflux booster pump 24 of the product fractionation tower and is then injected with circulating hydrogen from the circulating hydrogen compressor 19, becoming part of the feed of the suspended bed pre-hydrogenation reactor 6 in the aforementioned step (2). The other path goes to the ultra-microflow hydrogen mixer 14 for mixing with the fresh hydrogen from the fresh hydrogen compressor 13. The gaseous material separated in the separator 11 is combined with the gaseous material discharged from the fixed-bed catalytic distillation reactor 10 and the liquid output from the second-stage hot high-pressure separator 17. After cooling, it becomes the feed of the cold high-pressure separator 18.

[0036] (6) The ultra-microfluidic hydrogen mixer 14 can achieve highly dispersed mixing of gas and liquid materials, which can effectively improve mass transfer efficiency and significantly reduce the amount of fresh hydrogen used in the system. The ultra-microfluidic high-dispersion hydrogen mixer is used for heterogeneous decondensation to achieve an ultra-low hydrogen-to-oil ratio (100~300) bio-jet fuel process. After the action of the ultra-microfluidic hydrogen mixer 14, a portion of the liquid phase material from the first-stage hot high-pressure gas stripping separator 11 is mixed with fresh hydrogen, and then heated by the second-stage heater 15 to become the feed of the fixed-bed heterogeneous decondensation reactor 16. After hydrogenation catalytic isomerization treatment in the reactor, the ideal discharge composition that meets the pour point requirements is obtained, and then the gas-liquid phase is separated in the second-stage hot high-pressure separator 17.

[0037] (7) After the gas-liquid separation process of separator 17, the separated liquid material, together with the gas material mentioned in steps (4) and (5) above, enters the cold high-pressure separator 18 for further gas-liquid separation.

[0038] (8) After the separation process of the cold high-pressure separator 18, the imported material is divided into two parts: gas phase and liquid phase. The liquid phase material needs to enter the cold low-pressure separator 20 for further low-pressure separation. The gas phase material is mainly residual hydrogen containing compounds such as hydrogen sulfide and ammonia. After desulfurization and ammonia removal purification treatment, it is pressurized by the circulating hydrogen compressor 19 and returned to the system as circulating hydrogen for recycling.

[0039] (9) After separation by the cold low-pressure separator 20, the moisture and a small amount of cracked gas in the material are removed, and the remaining material is a mixed oil containing dissolved light hydrocarbons. The mixed oil is then sent to the stripping tower 21 for stripping with steam, and biomass LPG can be obtained in the overhead gas. The material discharged from the bottom of the tower is heated by the product fractionation heater 22 and then sent to the product fractionation tower 23 for fractionation and cutting. Biosolvent oil, bio-aviation kerosene and low-pour-point biodiesel are collected on the corresponding side line of the tower. The components collected from the bottom of the tower are high-pour-point biodiesel components and other heavy oil components. They are pressurized by the product fractionation tower bottom reflux booster pump 24 and heated by the first-stage heater 25. They are then combined with the materials mentioned in steps (2) and (5) above and sent to the suspended bed pre-hydrogenation reactor 6 as return material.

[0040] This system can process all kinds of animal and vegetable oil raw materials, including waste oil, to produce high-quality reproducible fuels such as bio-LPG, bio-solvent oil, bio-jet fuel, low-pour-point biodiesel, and high-pour-point biodiesel, which has good environmental and economic benefits.

[0041] Example 2

[0042] This embodiment relates to a process for producing bio-jet fuel using an ultra-low hydrogen-to-oil ratio. The process adopts the system and system operation mode of Example 1. The ultra-low hydrogen-to-oil ratio process includes the following steps:

[0043] (1) The circulating oil is heated to 380~420℃ and mixed with biomass feedstock oil containing 1wt.% dimethyl sulfide, a mixture of one-way material and product fractionation bottom reflux liquid after gas stripping purification treatment, and 500~5000ppm oil-soluble catalyst. The mixture is then introduced into a suspended bed pre-hydrogenation reactor 6 without solid catalyst packing and reacted for 1-2 hours. The preparation method of the oil-soluble catalyst includes the following steps: a bimetallic composite oxide precursor containing two or more non-noble transition metals is first synthesized by oxidation-precipitation process in a hydrogen peroxide-ethanol mixed solution, and then the oil-soluble catalyst is obtained by ion ligand modification in methanol.

[0044] The bimetallic composite oxide precursor is one or more of the following: basic cobalt ammonium molybdate [(NH4)HCo2(OH)2Mo2O8], basic nickel ammonium molybdate [(NH4)HNi2(OH)2Mo2O8], basic cobalt ammonium tungstate [(NH4)HCo2(OH)2W2O8], and basic nickel ammonium tungstate [(NH4)HNi2(OH)2W2O8].

[0045] (2) The top effluent from the suspended bed prehydrogenation reactor enters the fixed bed hydrodeoxygenation reactor 7, which is packed with a solid catalyst, and undergoes hydrodeoxygenation at 280~340℃; the bottom oil from the suspended bed prehydrogenation reactor 6 is separated to obtain heavy oil and oil residue. The heavy oil is used as the circulating oil in the aforementioned step (1), and the oil residue is discharged by centrifugation.

[0046] (3) The top effluent from the fixed-bed hydrodeoxygenation reactor 7 is heat exchanged and then enters the fixed-bed catalytic distillation reactor for selective cracking reaction at 240~320℃;

[0047] (4) The liquid material in the fixed bed catalytic distillation reactor 10 is divided into two streams after gas stripping purification. One stream merges with the bottom oil of the product fractionation tower and becomes part of the feed of the suspended bed pre-hydrogenation reactor 6 in the aforementioned step (2). The other stream is mixed with fresh hydrogen in the ultra-microflow hydrogen mixer 14 and then enters the isomerization reactor.

[0048] (5) The liquid phase product of the isomerization reactor enters the stripping tower to obtain biomass LPG product, and the bottom oil enters the atmospheric distillation tower for fractionation to obtain biosolvent oil, biojet fuel, low pour point biodiesel and bottom oil.

[0049] This system can process all kinds of animal and vegetable oil raw materials, including waste oil, to produce high-quality reproducible fuels such as bio-LPG, bio-solvent oil, bio-jet fuel, and low-pour-point biodiesel, which has good environmental and economic benefits.

[0050] Example 3

[0051] This embodiment relates to a process for producing bio-jet fuel using an ultra-low hydrogen-to-oil ratio. The process adopts the system and system operation mode of Example 1. The ultra-low hydrogen-to-oil ratio process includes the following steps:

[0052] (1) The circulating oil is heated to 400℃ and mixed with waste oil with an acid value of 120mgKOH / g, a total content of inorganic elements such as calcium, silicon and sodium of 260ppm, a chlorine content of 37ppm and a sulfur content of 220ppm. After mixing with 1000ppm of (NH4)HCo2(OH)2Mo2O8 catalyst, it enters a suspended bed pre-hydrogenation reactor 6 without solid catalyst packing and reacts for 1.5 hours.

[0053] (2) The top effluent from the suspended bed prehydrogenation reactor 6 enters the fixed bed hydrodeoxygenation reactor 7, which is filled with a solid catalyst, and undergoes hydrodeoxygenation at 320°C; the bottom oil from the suspended bed prehydrogenation reactor 6 is separated to obtain heavy oil and oil residue. The heavy oil is mixed with waste oil, and the oil residue is discharged by centrifugation.

[0054] (3) The top effluent from the fixed-bed hydrodeoxygenation reactor 7 is heat exchanged and then enters the fixed-bed catalytic distillation reactor for selective cracking reaction at 260°C;

[0055] (4) The liquid material in the fixed bed catalytic distillation reactor 10 is divided into two streams after gas stripping purification. One stream merges with the bottom oil of the product fractionation tower and becomes part of the feed of the suspended bed pre-hydrogenation reactor 6 in the aforementioned step (2). The other stream is mixed with fresh hydrogen in the ultra-microflow hydrogen mixer 14 and then enters the fixed bed isomerization dewaxing reactor 16. The hydrogen-to-oil ratio of the isomerization reaction is 200:1 and the pressure is 4MPa.

[0056] (5) The liquid phase product of the fixed bed heterogeneous dewaxing reactor 16 enters the stripping tower to obtain biomass LPG product, and the bottom oil enters the atmospheric distillation tower for fractionation to obtain biosolvent oil, biojet fuel, low-pour-point biodiesel and bottom oil.

[0057] Comparative Example 1

[0058] The process of Example 3 was modified so that the raw materials were directly fed into the fixed-bed reactor for hydrodeoxygenation. The specific steps are as follows:

[0059] (1) The circulating oil is heated to 400°C and mixed with waste oil with an acid value of 120 mg KOH / g, a total content of inorganic elements such as calcium, silicon and sodium of 260 ppm, a chlorine content of 37 ppm and a sulfur content of 220 ppm. The mixture is then fed into a fixed-bed reactor filled with a solid catalyst and hydrodeoxygenated at 320°C.

[0060] (2) The top effluent from the fixed-bed reactor is heat exchanged and then enters the fixed-bed catalytic distillation reactor for selective cracking at 260°C;

[0061] (3) The liquid phase material of the fixed bed catalytic distillation reactor is divided into two streams after gas stripping purification. One stream is combined with the bottom oil of the product fractionation tower and becomes part of the feed of the suspended bed pre-hydrogenation reactor in step (2) above. The other stream is mixed with fresh hydrogen in the ultra-microflow hydrogen mixer and then enters the fixed bed isomerization decondensation reactor. The hydrogen-to-oil ratio of the isomerization reactor is 200:1 and the pressure is 4MPa.

[0062] (4) The liquid phase product of the fixed bed heterogeneous dewaxing reactor enters the stripping tower to obtain biomass LPG product, and the bottom oil enters the atmospheric distillation tower for fractionation to obtain biosolvent oil, biojet fuel, low-pour-point biodiesel and bottom oil.

[0063] Comparative Example 2

[0064] The process of Example 3 was modified by not using the ultra-microflow hydrogen mixer. Part of the liquid phase material from the fixed-bed catalytic distillation reactor was mixed with fresh hydrogen in the pipeline before entering the fixed-bed isomer dewaxing reactor. The specific steps are as follows:

[0065] (1) The circulating oil is heated to 400℃ and mixed with waste oil with an acid value of 120mgKOH / g, a total content of inorganic elements such as calcium, silicon and sodium of 260ppm, a chlorine content of 37ppm and a sulfur content of 220ppm. After mixing with 1000ppm of (NH4)HCo2(OH)2Mo2O8 catalyst, it enters a suspended bed pre-hydrogenation reactor without solid catalyst packing for reaction, with a residence time of 1.5 hours.

[0066] (2) The top effluent from the suspended bed prehydrogenation reactor enters a fixed bed reactor packed with a solid catalyst for hydrodeoxygenation at 320°C; the bottom oil from the suspended bed prehydrogenation reactor is separated to obtain heavy oil and oil residue. The heavy oil is mixed with waste oil, and the oil residue is discharged by centrifugation.

[0067] (3) The top effluent from the fixed-bed reactor is heat exchanged and then enters the fixed-bed catalytic distillation reactor for selective cracking at 260°C;

[0068] (4) The liquid phase material of the fixed bed catalytic distillation reactor is divided into two streams after gas stripping purification. One stream is combined with the bottom oil of the product fractionation tower and becomes part of the feed of the suspended bed pre-hydrogenation reactor in step (2) above. The other stream is mixed with fresh hydrogen and enters the fixed bed isomerization decondensation reactor. The hydrogen-to-oil ratio of the isomerization reactor is 1000:1 and the pressure is 4MPa.

[0069] (5) The liquid phase product from the isomerization reactor enters the stripping tower to obtain bio-based LPG products, and the bottom oil enters the atmospheric distillation tower for fractionation to obtain bio-solvent oil, bio-jet fuel, low-pour-point biodiesel and bottom oil.

[0070] Table 1. Properties of the products at the reactor outlet

[0071]

[0072] Because the waste oil in Comparative Example 1 was not pre-hydrogenated in the suspended bed pre-hydrogenation reactor 6, but instead directly entered the fixed bed hydrodeoxygenation reactor 7 for hydrodeoxygenation, impurities in the feedstock, especially inorganic elements such as calcium, silicon, and sodium, were all deposited in the fixed bed hydrodeoxygenation catalyst, severely affecting the catalyst's activity and stability. Furthermore, the feedstock could not undergo deep deoxygenation in the fixed bed reactor (as shown in Table 1), causing some oxygen-containing compounds, such as free fatty acids and fatty alcohols, to enter the subsequent fixed bed catalytic distillation reactor 10. There, they competed for adsorption with long-chain alkanes on the acidic catalyst surface, affecting the long-chain alkane cracking reaction and thus reducing the yield of the bio-jet fuel component in the product. The results showed that in Example 3, the jet fuel fraction in the bottom outlet product of reactor 10 accounted for approximately 60 wt.%, while in Comparative Example 1 it was only approximately 19 wt.

[0073] In terms of energy consumption, compared with Example 3, Comparative Example 2 did not use an ultra-microfluidic hydrogen mixer. In order to achieve the same isomerization reaction conversion rate and selectivity, the hydrogen-to-oil ratio was increased from 200:1 in Example 3 to 1000:1, which directly resulted in a 4-fold increase in the circulating hydrogen flow rate and an increase in the energy consumption cost of the fresh hydrogen and circulating hydrogen compressors.

[0074] Example 4:

[0075] The synthesis of oil-soluble catalysts includes the following steps:

[0076] (1) Dissolve 0.1 mol of cobalt nitrate or nickel nitrate in 50 mL of ethanol to obtain solution A, and dissolve 0.1 mol of ammonium molybdate and / or ammonium metatungstate in 50 mL of deionized water to obtain solution B;

[0077] (2) Take 10 mL of hydrogen peroxide and add it to solution A to obtain solution C. Then add solution B dropwise to solution C to obtain mixture D.

[0078] (3) Add mixture D to a 200 mL hydrothermal crystallization vessel with a polytetrafluoroethylene liner, seal it, and place it in a 120°C oven for 6 hours.

[0079] (4) After the crystallization vessel is removed and cooled naturally, the obtained product is filtered, washed and dried to obtain a bimetallic composite oxide precursor; the bimetallic composite oxide precursor is one or more of the following: basic cobalt ammonium molybdate [(NH4)HCo2(OH)2Mo2O8], basic nickel ammonium molybdate [(NH4)HNi2(OH)2Mo2O8], basic cobalt ammonium tungstate [(NH4)HCo2(OH)2W2O8], and basic nickel ammonium tungstate [(NH4)HNi2(OH)2W2O8].

[0080] (5) Dissolve 0.4 mol of organic ionic ligand in methanol, then add 0.1 mol of bimetallic composite oxide precursor, add 0.4 mol of ionic ligand, reflux at 60°C for 6 hours, and then centrifuge to obtain oil-soluble catalyst.

[0081] The organic ion ligand in step (5) is one or more of the following: dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, 1-butyl-3-methylimidazolium chloride, and 1-alkyl-2,3-dimethylimidazolium bromide.

[0082] Example 5:

[0083] A method for preparing a reduced non-noble metal isomerization catalyst includes the following steps:

[0084] (1) A viscous liquid is obtained by dissolving a silicon source, an aluminum source, and sodium hydroxide in deionized water and then hydrothermally treating it at 30-80℃ to obtain Y molecular sieve seed crystals; wherein, based on the mass of oxides, the chemical composition of the viscous liquid is SiO2:Al2O3:Na2O:H2O=(20-40):(0.5-2):(20-40):(600-1000). The silicon source is one or two of silica sol, sodium silicate, and kaolin; and / or the aluminum source is one or two of aluminum sulfate, aluminum nitrate, aluminum chloride, and sodium aluminate.

[0085] (2) Disperse Y molecular sieve seeds in deionized water, add a template agent, and after dissolution, add a silicon source, an aluminum source, a nickel salt, and sodium hydroxide. React at 80℃-120℃, and after filtration, washing, and drying, obtain a metal-Y molecular sieve composite in which nickel metal nanoparticles are embedded in situ into Y molecular sieve seeds. The feed ratio of Y molecular sieve seeds, silicon source, aluminum source, nickel salt, sodium hydroxide, and water, calculated by the mass of oxides, is (0.5~1.5):(1.5~2.5):(0.3~0.8):(4~6):(3.5~5):(300~400). The nickel salt is one or more of nitrates, sulfates, chlorides, basic carbonates, and acetates.

[0086] (3) Add ZSM-5 molecular sieve, aluminum hydroxide dry adhesive powder, dilute nitric acid solution and guar gum powder to the metal-Y molecular sieve catalyst obtained in step (1), then mix, shape, dry, calcine and reduce to obtain a reduced non-precious metal isomerization catalyst.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, should fall within the protection scope of the present invention.

Claims

1. A method for producing bio-jet fuel using an ultra-low hydrogen-to-oil ratio, characterized in that... Includes the following steps: (1) The heavy oil obtained from the bottom oil separation of the suspended bed prehydrogenation reactor is heated to 380~420℃ as circulating oil and mixed with biomass feed oil containing 1wt.% dimethyl sulfide and a material from the gas stripping purification process. After mixing with 500~5000ppm oil-soluble catalyst, it enters a suspended bed prehydrogenation reactor without solid catalyst packing for reaction, with a residence time of 1~2 hours. (2) The top effluent from the suspended bed prehydrogenation reactor enters the fixed bed hydrodeoxygenation reactor packed with solid catalyst and is hydrodeoxygenated at 280~340℃; the bottom oil of the suspended bed prehydrogenation reactor is separated to obtain heavy oil and oil residue; the heavy oil is used as the circulating oil in the aforementioned step (1), and the oil residue is discharged by centrifugal separation. (3) The top effluent from the fixed-bed hydrodeoxygenation reactor is heat exchanged and then enters the fixed-bed catalytic distillation reactor for selective cracking reaction at 240~320℃; (4) The liquid phase material of the fixed bed catalytic distillation reactor is divided into two streams after gas stripping purification. One stream merges with the bottom oil of the product fractionation tower and becomes part of the feed of the suspended bed pre-hydrogenation reactor in step (2) above. The other stream is mixed with fresh hydrogen in the ultra-micro flow hydrogen mixer and then enters the fixed bed heterogeneous dewaxing reactor. (5) The liquid phase product of the fixed bed heterogeneous dewaxing reactor enters the stripping tower to obtain bio-based liquefied petroleum gas (LPG) product, and the bottom oil enters the atmospheric distillation tower for fractionation to obtain bio-solvent oil, bio-jet fuel, low-pour-point biodiesel and bottom oil (high-pour-point biodiesel).

2. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 1, characterized in that: In step (1), the mass ratio of the inferior biomass oil to the recycled oil is 1:(1~5).

3. The method for ultra-low hydrogen-to-oil ratio according to claim 1, characterized in that: The hydrogen-to-oil ratio of the isomerization reactor is (100~300):1, and the pressure is 4~6 MPa.

4. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 1, characterized in that: The preparation method of the oil-soluble catalyst includes the following steps: first, a bimetallic composite oxide precursor containing two or more non-noble transition metals is synthesized through an oxidation-precipitation process in a hydrogen peroxide-ethanol mixed solution, and then the oil-soluble catalyst is obtained by ion ligand modification in methanol.

5. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 4, characterized in that: The non-noble transition metal is a combination of two or more of cobalt, nickel, molybdenum, and tungsten; The oil-soluble catalyst synthesis steps include: (1) Dissolve 0.1 mol of cobalt nitrate or nickel nitrate in 50 mL of ethanol to obtain solution A, and dissolve 0.1 mol of ammonium molybdate and / or ammonium metatungstate in 50 mL of deionized water to obtain solution B; (2) Take 10 mL of hydrogen peroxide and add it to solution A to obtain solution C. Then add solution B dropwise to solution C to obtain mixture D. (3) Add mixture D to a 200 mL hydrothermal crystallization vessel with a polytetrafluoroethylene liner, seal it, and place it in a 120°C oven for 6 hours. (4) After the crystallization vessel is removed and allowed to cool naturally, the resulting product is filtered, washed and dried to obtain a bimetallic composite oxide precursor; (5) Dissolve 0.4 mol of organic ionic ligand in methanol, then add 0.1 mol of bimetallic composite oxide precursor, add 0.4 mol of ionic ligand, reflux at 60°C for 6 hours, and then centrifuge to obtain oil-soluble catalyst.

6. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 5, characterized in that: The bimetallic composite oxide precursor is one or more of the following: basic cobalt ammonium molybdate [(NH4)HCo2(OH)2Mo2O8], basic nickel ammonium molybdate [(NH4)HNi2(OH)2Mo2O8], basic cobalt ammonium tungstate [(NH4)HCo2(OH)2W2O8], and basic nickel ammonium tungstate [(NH4)HNi2(OH)2W2O8].

7. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 5, characterized in that: The organic ionic ligand is one or more of the following: dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, octadecyltrimethylammonium bromide, 1-butyl-3-methylimidazolium chloride, and 1-alkyl-2,3-dimethylimidazolium bromide.

8. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 1, characterized in that... The catalyst used in the fixed-bed hydrodeoxygenation reactor is an alumina-supported nickel-molybdenum bimetallic catalyst, which needs to be pre-sulfurized before use; the catalyst used in the fixed-bed catalytic distillation reactor is a nickel-based catalyst supported on a high silica-to-alumina ratio mesoporous-microporous composite molecular sieve; and the catalyst used in the fixed-bed isomerization dewaxing reactor is a reduced non-precious metal isomerization catalyst.

9. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 1, characterized in that, The preparation method of the reduced non-noble metal isomerization catalyst includes the following steps: (1) A viscous liquid is obtained by dissolving silicon source, aluminum source and sodium hydroxide in deionized water and then hydrothermally treating it at 30~80℃ to obtain Y molecular sieve seed crystals; wherein, the chemical composition of the viscous liquid, calculated by the mass of oxides, is SiO2:Al2O3:Na2O:H2O=(20~40):(0.5~2):(20~40):(600~1000); (2) Disperse Y molecular sieve seed crystals in deionized water, add template agent, and after dissolution, add silicon source, aluminum source, nickel salt and sodium hydroxide. React at 80~120℃, and after filtration, washing and drying, obtain metal-Y molecular sieve composite in which nickel metal nanoparticles are embedded in situ into Y molecular sieve seed crystals; wherein, calculated by the mass of oxides, the feeding ratio of Y molecular sieve seed crystals, silicon source, aluminum source, nickel salt, sodium hydroxide and water is (0.5~1.5):(1.5~2.5):(0.3~0.8):(4~6):(3.5~5):(300~400); (3) Add ZSM-5 molecular sieve, aluminum hydroxide dry adhesive powder, dilute nitric acid solution and guar gum powder to the metal-Y molecular sieve catalyst obtained in step (1), then mix, shape, dry, calcine and reduce to obtain a reduced non-precious metal isomerization catalyst.

10. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 9, characterized in that, The silicon source is one or two of silica sol, sodium silicate, and kaolin; the aluminum source is one or two of aluminum sulfate, aluminum nitrate, aluminum chloride, and sodium aluminate.

11. The method for producing bio-jet kerosene with an ultra-low hydrogen-to-oil ratio according to claim 9, characterized in that, The nickel salt is one or more of the following: nitrate, sulfate, chloride, basic carbonate, and acetate.

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