A method for producing a biodiesel fraction from oil and fat raw materials

Abstract

The present invention relates to the field of biofuel production, and discloses a method for producing a biodiesel fraction from an oil-based raw material. The method includes: performing a first hydrotreating and heat exchange treatment on the oil-based raw material in the presence of hydrogen to obtain a hydrotreating effluent I; performing a second hydrotreating on the hydrotreating effluent I to obtain a hydrotreating effluent II; performing a gas-liquid separation on the hydrotreating effluent II to obtain a liquid hydrocarbon, water, and a gas stream; performing a hydroisomerization reaction on at least a part of the liquid hydrocarbon in the presence of a hydroisomerization catalyst and hydrogen to obtain a hydroisomerization reaction effluent; and separating the hydroisomerization reaction effluent to obtain a diesel fraction. Without using a large amount of cold hydrogen and product recycling, this method can still control the total temperature rise of the reaction system, reduce the production energy consumption, and at the same time, the biodiesel fraction prepared by the present invention has qualified quality and high purity.

Description

Technical Field

[0001] The present invention relates to the field of biofuel production, and particularly to a method for producing biodiesel fractions from oil-based raw materials. Background Art

[0002] With the tightening of the supply of traditional fossil energy and the increasing pressure of carbon dioxide emission reduction, how to effectively reduce the carbon dioxide gas emissions while increasing the fuel supply is an important issue faced by the refining industry. Using renewable biomass such as animal and vegetable oils or agricultural and forestry wastes to prepare biodiesel fuel and developing biomass fuels are considered to be one of the effective means to solve this problem.

[0003] Biofuels have gradually attracted people's attention mainly for the following reasons: 1. Biofuels are renewable energy sources; 2. The carbon-containing characteristics of biofuels are close to those of existing fuels; 3. The carbon dioxide absorbed by the precursors of biofuels can reduce the net emissions of greenhouse gases; 4. The distribution of bioenergy is more uniform than that of fossil energy.

[0004] Vegetable oil is the most easily available biofuel, which is mainly composed of triglycerides and a small amount of free fatty acids. However, pure vegetable oil is limited in its direct application as a transportation fuel due to its high viscosity, poor stability and high cost. The traditional method for converting vegetable oil or other fatty acid derivatives into liquid fuel is transesterification. The transesterification method converts the triglycerides forming vegetable oil into the corresponding fatty acid alkyl esters, usually fatty acid methyl esters. However, the poor low-temperature fluidity of fatty acid methyl esters limits their use in low-temperature environments. The presence of carbon-carbon double bonds can improve the low-temperature fluidity of fatty acid methyl esters, but reduces their stability. At the same time, the presence of oxygen in fatty acid methyl esters will result in higher NOx emissions compared to traditional diesel fuels.

[0005] During the hydrotreating reaction process of vegetable oil (taking palm oil as an example), it mainly includes double bond saturation, hydrodirect deoxygenation, hydrodecarboxylation and hydrodecarbonylation reactions, as Figure 1 shown. In this series of reaction processes, the reaction rates are different and the reaction heat release is very large. If the product circulation or a large amount of cold hydrogen is not used to control the temperature rise in a fixed-bed reactor, the total temperature rise of the reactor will reach more than 200 °C, resulting in the reaction being unable to proceed for a long time and the product quality cannot be guaranteed. Therefore, in the existing technologies, combined processing with mineral oil or a large amount of product circulation is mostly used to control the temperature.

[0006] Oily raw materials have large molecular weights, high viscosities, and high boiling points. Under the conditions of fixed-bed hydrotreating reactions, the oily raw materials cover the catalyst surface in the form of a liquid film, and hydrogen needs to dissolve into the liquid film to carry out the hydrogenation reaction. However, some reactions in the oily raw materials consume a large amount of the dissolved hydrogen in a short time, resulting in a lack of hydrogen in the liquid film. At the same time, the oily raw materials are prone to polymerization with each other, blocking at the top of the reactor, causing an increase in the bed pressure drop and making it impossible to operate for a long time.

[0007] In addition, when hydrodecarbonylation and hydrodecarboxylation reactions occur, in addition to generating liquid hydrocarbons and propane, the carbon chains of vegetable oils will also generate CO and CO2. This not only reduces the yield of liquid hydrocarbons, but also causes the catalyst to be deactivated when the generated CO and CO2 are recycled back to the reactor for reuse with the unreacted hydrogen. Therefore, the gas must be treated to remove CO and CO2 therein, but this process will increase the energy consumption of the entire production process.

[0008] CN101768469A discloses a combined hydrogenation method for mineral oil and animal and vegetable oils. This method uses mineral diesel fractions and animal and vegetable oils as raw materials, and performs hydrotreating under different conditions in two hydrogenation reaction zones respectively, and mixes the obtained products to obtain diesel products. This method can obtain clean diesel products with low sulfur content, high polycyclic aromatic hydrocarbon content, and high cetane number under relatively mild operating conditions, omits the equipment and operating procedures for regularly supplementing sulfur in the hydrotreating of bio-oil, reduces the influence of the water generated by the hydrogenation reaction of animal and vegetable oils on the activity of the hydrogenation catalyst, and extends the operation cycle of the device.

[0009] CN102504866A discloses a method for preparing biodiesel by mixing and hydrogenating kitchen waste oil and mineral diesel. This method first pre-treats the kitchen waste oil to remove salt and water, and then sequentially enters the first-stage hydrogenation unit and the second-stage hydrogenation unit, and obtains biodiesel with a relatively high cetane number through fractionation.

[0010] However, both of the above two methods require mixing and processing mineral oil and bio-oil, and cannot produce pure biodiesel.

[0011] CN111100703A discloses a method for hydrodeoxygenation of biological oils. This method first feeds the biological oils into a thermal high-pressure separator, and the catalyst loaded in the thermal high-pressure separator contacts to carry out olefin saturation and shallow hydrodeoxygenation reactions. Using the reactor effluent as a dilution medium, it avoids the deactivation of the catalyst caused by excessive heat release during the reaction of biological oils, and can ensure the long-term stable operation of the device. However, a large amount of unreacted oils need to be fractionated in a fractionating tower and recycled back to the reactor inlet, resulting in high energy consumption.

[0012] CN106281401A discloses a method for producing aviation biofuel from waste animal and vegetable oils and fats. The raw material oil is pretreated and then undergoes a hydrogenation reaction in a hydrotreating unit. After the effluent is degassed and dehydrated, it is further subjected to hydroconversion and rectification to obtain high-quality aviation kerosene. However, this method requires recycling the generated liquid phase back to the inlet of the hydrotreating unit to avoid excessive temperature rise in the hydrotreating unit, which may cause catalyst deactivation and product quality degradation.

[0013] CN109294746A discloses a method for hydrogenating oil and fat raw materials to prepare diesel fractions. The oil and fat raw materials react with two different types of hydrotreating catalysts in sequence, and the obtained liquid hydrocarbons react with a hydroisomerization catalyst to obtain biodiesel with a low pour point and a high cetane number. However, this method also requires a large amount of cold hydrogen and recycle oil to control the temperature rise in the hydrotreating unit, resulting in high energy consumption. Summary of the Invention

[0014] The object of the present invention is to overcome the defects in the prior art in the process of producing biodiesel fractions, such as high production energy consumption, fast reaction rate at the front of the reactor, large heat release, reactor blockage caused by oil and fat condensation, and low liquid hydrocarbon yield.

[0015] To achieve the above object, the present invention provides a method for producing biodiesel fractions from oil and fat raw materials, which method comprises:

[0016] (1) In the presence of hydrogen, introducing the oil and fat raw materials into a hydrotreating device for first hydrotreating and heat exchange treatment to obtain a hydrotreating effluent I; the hydrotreating device contains one or at least two serially connected hydrotreating units, and each of the hydrotreating units contains a serially connected reaction module and heat exchange module, so that the material can sequentially undergo a hydrogenation reaction and heat exchange in each of the hydrotreating units; a monolithic hydrotreating catalyst I is loaded in each of the reaction modules;

[0017] (2) Introducing the hydrotreating effluent I into a fixed-bed reactor for second hydrotreating to obtain a hydrotreating effluent II; a hydrotreating catalyst II and a hydrotreating catalyst III are sequentially loaded in the fixed-bed reactor;

[0018] (3) Introducing the hydrotreating effluent II into a hot high-pressure separator for gas-liquid separation to obtain liquid hydrocarbons, water and a gas stream;

[0019] (4) In the presence of a hydroisomerization catalyst and hydrogen, subjecting at least part of the liquid hydrocarbons to a hydroisomerization reaction to obtain a hydroisomerization reaction effluent;

[0020] (5) Separating the hydroisomerization reaction effluent to obtain diesel fractions;

[0021] Among them, molybdenum element is contained in the active components of both the integral hydrotreating catalyst I and the hydrotreating catalyst II; at least two different metal elements are contained in the active component of the hydrotreating catalyst III.

[0022] The method for producing biodiesel fraction from oil and fat raw materials provided by the present invention can improve the liquid hydrocarbon yield, reduce the generation of CO and CO2, and the recycle gas does not need to be treated by adopting a hydrotreating unit with one or at least two hydrotreating units connected in series and a fixed-bed reactor containing the hydrotreating catalyst II and the hydrotreating catalyst III; meanwhile, by utilizing the characteristics of the integral hydrotreating catalyst I, the reactions with fast reaction rate and large heat release during the oil and fat hydrogenation process are completed in the reaction module, and multiple heat exchange templates are added between the reaction modules to effectively control the reaction temperature rise. Without using a large amount of cold hydrogen and product recycle, the total temperature rise of the reaction system can still be controlled, reducing the energy consumption during the production process, effectively avoiding the problems of fast reaction rate, large heat release in the first hydrotreating reaction, and blockage of the reactor caused by oil and fat condensation reaction. The obtained diesel product has a high yield, and the gas stream after the thermal high-pressure separator in step (3) does not need to be purified and can be directly recycled. Description of the Drawings

[0023] Figure 1 is a schematic diagram of the hydrotreating reaction process of vegetable oil;

[0024] Figure 2 is a schematic diagram of the structure of the integral honeycomb ceramic shown in a preferred specific embodiment provided by the present invention;

[0025] Figure 3 is a process flow diagram for producing biodiesel fraction from oil and fat raw materials in a preferred specific embodiment provided by the present invention.

[0026] Description of the Reference Numerals

[0027] 1. Oil and fat raw materials, 2. Hydrogen, 3. Heating furnace, 4. Mixer, 5. Integral hydrotreating catalyst I, 6. Heat exchanger, 7. Fixed-bed reactor, 8. Thermal high-pressure separator, 9. Cold high-pressure separator, 10. Liquid hydrocarbon, 11. Liquid effluent I, 12. Water, 13. Gas-phase effluent I, 14. Recycle compressor, 15. Hydrogen, 16. Hydroisomerization reactor, 17. Thermal high-pressure separator, 18. Cold high-pressure separator, 19. Liquid-phase effluent II, 20. Thermal low-pressure separator, 21. Cold low-pressure separator, 22. Fractionating tower. Specific Embodiments

[0028] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0029] The present invention provides a method for producing a biodiesel fraction from an oil-based raw material, the method comprising:

[0030] (1) In the presence of hydrogen, introducing the oil-based raw material into a hydrotreating device for a first hydrotreating and heat exchange treatment to obtain a hydrotreating effluent I; the hydrotreating device contains one or at least two serially connected hydrotreating units, and each of the hydrotreating units contains a serially connected reaction module and a heat exchange module, so that the material can sequentially perform a hydrogenation reaction and heat exchange in each of the hydrotreating units; an integral hydrotreating catalyst I is loaded in each of the reaction modules;

[0031] (2) Introducing the hydrotreating effluent I into a fixed-bed reactor for a second hydrotreating to obtain a hydrotreating effluent II; a hydrotreating catalyst II and a hydrotreating catalyst III are sequentially loaded in the fixed-bed reactor;

[0032] (3) Introducing the hydrotreating effluent II into a hot high-pressure separator for gas-liquid separation to obtain a liquid hydrocarbon, water, and a gas stream;

[0033] (4) In the presence of a hydroisomerization catalyst and hydrogen, subjecting at least part of the liquid hydrocarbon to a hydroisomerization reaction to obtain a hydroisomerization reaction effluent;

[0034] (5) Separating the hydroisomerization reaction effluent to obtain a diesel fraction;

[0035] Wherein, molybdenum elements are contained in the active components of both the integral hydrotreating catalyst I and the hydrotreating catalyst II; at least two different metal elements are contained in the active component of the hydrotreating catalyst III.

[0036] According to a preferred specific embodiment, the method further comprises: before the oil-based raw material and hydrogen are introduced into the hydrotreating device, they are first heated to 220 - 300 °C in a heating furnace, then mixed by a mixer, and then introduced into the hydrotreating device for the first hydrotreating and heat exchange treatment.

[0037] In the present invention, there is no particular limitation on the type of the mixer, and it can be a static mixer, a microbubble generator, a swirl shear mixer, etc.

[0038] Preferably, in step (1), the monolithic hydrotreating catalyst I contains a support, a carrier, and an active component. Based on the total weight of the monolithic hydrotreating catalyst I, the loading amount of the carrier and the active component is 1-40% by weight. More preferably, in step (1), based on the total weight of the monolithic hydrotreating catalyst I, the loading amount of the carrier and the active component is 2-32% by weight.

[0039] Preferably, based on the total weight of the monolithic hydrotreating catalyst I, the content of the molybdenum element in terms of oxide is 0.2-5.1% by weight.

[0040] Preferably, based on the total weight of the hydrotreating catalyst II, the content of the molybdenum element in terms of oxide is 10-17% by weight.

[0041] Preferably, the active component of the hydrotreating catalyst III contains a first metal element and a second metal element. More preferably, the first metal element is cobalt element and / or nickel element, and the second metal element is molybdenum element and / or tungsten element.

[0042] Preferably, based on the total weight of the hydrotreating catalyst III, the content of the first metal element in terms of oxide is 1-10% by weight, and the content of the second metal element in terms of oxide is 5-40% by weight.

[0043] Preferably, the weight ratio of the sum of the active components of the monolithic hydrotreating catalyst I and the hydrotreating catalyst II to the content of the active component in the hydrotreating catalyst III is 70:30 to 95:5, and the weight ratio of the content of the active components of the monolithic hydrotreating catalyst I and the hydrotreating catalyst II is 1:0.5 to 1.5.

[0044] Preferably, the carriers in the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, and the hydrotreating catalyst III are each independently selected from at least one of alumina and silica.

[0045] It should be noted that in the present invention, the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, and the hydrotreating catalyst III can be purchased or prepared by known technical means in the art.

[0046] Preferably, the hydrotreating catalyst III is RJW-3 catalyst.

[0047] Preferably, the carrier of the hydrotreating catalyst II is alumina and the active metal component is molybdenum element. Based on the total weight of the hydrotreating catalyst II, the content of the molybdenum element in terms of oxide is 10-20% by weight.

[0048] In order to improve the conversion rate of the hydrogenation reaction, the present invention preferably provides a method for preparing the monolithic hydrotreating catalyst I, which method comprises:

[0049] S1: Immersing the support in the carrier slurry to obtain Intermediate I; the carrier slurry contains the materials for forming the carrier of the monolithic hydrotreating catalyst I;

[0050] S2: Immersing Intermediate I in the solution containing the active component to obtain the monolithic hydrotreating catalyst I.

[0051] Preferably, in the method for preparing the monolithic hydrotreating catalyst I, the materials for forming the active component of the monolithic hydrotreating catalyst I are the same as the materials for forming the active component in the hydrotreating catalyst II; the materials for forming the carrier of the monolithic hydrotreating catalyst I are the same as the carrier materials in the hydrotreating catalyst II.

[0052] That is, preferably, the monolithic hydrotreating catalyst I of the present invention can have the catalytic function of the hydrotreating catalyst II and is formed on the support of the present invention.

[0053] Preferably, the support is a monolithic honeycomb ceramic made of cordierite. The Figure 2 shows the structure of a preferred specific embodiment of the monolithic honeycomb ceramic made of cordierite.

[0054] Preferably, the weight ratio of the active component to the carrier in the monolithic hydrotreating catalyst I is the same as the weight ratio of the active component to the carrier in the hydrotreating catalyst II.

[0055] According to a preferred specific embodiment, in step (1), the porosity of the monolithic hydrotreating catalyst I in each of the reaction modules is greater than or equal to 65%, and along the flow direction of the liquid stream, from the most upstream hydrotreating unit to the most downstream hydrotreating unit, the porosity of the monolithic hydrotreating catalyst I filled in the reaction module decreases in sequence, and the number of pores per square centimeter increases in sequence. The inventors of the present invention have found that in this preferred case, the rate of the first hydrotreating reaction of the oil-based raw material can be effectively adjusted, and the catalyst bed plugging caused by local large heat release, local hydrogen deficiency and oil condensation can be avoided.

[0056] In the present invention, the porosity of the monolithic hydrotreating catalyst I = the sum of the pore areas through which the fluid can flow / the cross-sectional area of the monolithic hydrotreating catalyst I.

[0057] Preferably, the hydrotreating equipment contains at least two serially connected hydrotreating units. Along the flow direction of the liquid-phase stream, the porosity of the monolithic hydrotreating catalyst I packed in the reaction module of the upstream hydrotreating unit is 1-5% higher than that of the monolithic hydrotreating catalyst I packed in the reaction module of the adjacent downstream hydrotreating unit.

[0058] Preferably, the hydrotreating equipment contains at least two serially connected hydrotreating units. Along the flow direction of the liquid-phase stream, the number of pores per square centimeter of the monolithic hydrotreating catalyst I packed in the reaction module of the upstream hydrotreating unit is 10-50 less than that of the monolithic hydrotreating catalyst I packed in the reaction module of the adjacent downstream hydrotreating unit.

[0059] According to a preferred specific embodiment, in the hydrotreating equipment, there are three serially connected hydrotreating units. Along the flow direction of the liquid-phase stream, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst I of the first hydrotreating unit is 8-12% by weight, and the number of pores per square centimeter is 22-27; the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst I of the second hydrotreating unit is 13-18% by weight, and the number of pores per square centimeter is 55-65; the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst I of the third hydrotreating unit is 22-28% by weight, and the number of pores per square centimeter is 80-100. In the present invention, the loading amount of the carrier and the active component = the sum of the weights of the carrier and the active component in the monolithic hydrotreating catalyst I / the total weight of the monolithic hydrotreating catalyst I * 100%.

[0060] According to another preferred specific embodiment, in step (1), the reaction module is an oil and gas transmission pipe filled with the monolithic hydrotreating catalyst I, and the heat exchange module is a heat exchanger.

[0061] Preferably, the outer diameter of each monolithic hydrotreating catalyst I is 3-5 mm smaller than the inner diameter of the oil and gas transmission pipe. It should be noted that the outer diameter of the monolithic hydrotreating catalyst I is the outer diameter of the support after loading the active component and the carrier.

[0062] Preferably, in step (1), in each reaction module, the inlet temperature is independently 220-300 °C, and the outlet temperature is independently 300-380 °C.

[0063] Preferably, in step (1), the inlet temperature of each reaction module is lower than the outlet temperature.

[0064] Preferably, in step (1), the sum of the temperature rises of each of the reaction modules is 80 - 220°C. It should be noted that in the present invention, "the sum of the temperature rises of each of the reaction modules" means the sum of the temperature differences between the outlet temperature and the inlet temperature of each of the reaction modules.

[0065] Preferably, in step (1), when the temperature difference between the outlet temperature and the inlet temperature of the reaction module in the lowermost hydrotreating unit ≤ 35°C or the sum of the temperature rises of each of the reaction modules in all hydrotreating units ≥ 220°C, heat exchange is terminated to obtain a gas-liquid mixed hydrotreating effluent I, and then the obtained hydrotreating effluent I is introduced into a fixed-bed reactor.

[0066] Preferably, the hydrotreating equipment contains at least two serially connected hydrotreating units. In the present invention, the material obtained from the reaction module in the upstream hydrotreating unit enters the heat exchange module for heat exchange and then enters the reaction module in the adjacent downstream hydrotreating unit for a hydrotreating reaction to obtain material I, and then material I enters the heat exchange module for heat exchange; when the number of hydrotreating units is greater than two, and so on. When the temperature difference between the outlet temperature and the inlet temperature of the reaction module in the lowermost hydrotreating unit ≤ 35°C, or the sum of the temperature rises of each of the reaction modules in all hydrotreating units ≥ 220°C, the material flows out to obtain a gas-liquid mixed hydrotreating effluent I; the hydrotreating effluent I is introduced into a fixed-bed reactor for reaction.

[0067] Preferably, in step (1), the hydrotreating effluent I contains unreacted oil, partially reacted oil, intermediate products of oil reaction, C8 - C24 alkanes, propane, water, carbon monoxide, carbon dioxide, hydrogen sulfide, and hydrogen.

[0068] Preferably, in step (1), the conditions for the first hydrotreating at least satisfy: the inlet reaction pressure of the uppermost hydrotreating unit is 0.5 - 10 MPa, the hydrogen-oil volume ratio of the uppermost hydrotreating unit is 600 - 2000 Nm 3 / m 3 , and the overall volume space velocity is 0.5 - 10 h -1 . It should be noted that the overall volume space velocity refers to the volume space velocity relative to the total volume of the monolithic hydrotreating catalyst I, hydrotreating catalyst II, and hydrotreating catalyst III.

[0069] Preferably, in step (2), in the fixed-bed reactor, the inlet temperature is 280 - 380°C and the outlet temperature is 320 - 400°C.

[0070] Preferably, in step (2), the inlet temperature of the fixed-bed reactor is lower than the outlet temperature.

[0071] Preferably, the hydrotreated effluent II contains alkanes with 8 - 24 carbon atoms, propane, water, carbon monoxide, carbon dioxide, hydrogen sulfide, and hydrogen.

[0072] In the present invention, during the first hydrotreating and second hydrotreating processes of the oil-based raw material, olefin saturation and hydrodeoxygenation reactions mainly occur; among them, the oxygen in the oil-based raw material is removed in the form of water, carbon monoxide, and carbon dioxide. Specifically, olefin saturation reaction and partial hydrodeoxygenation reaction mainly occur during the first hydrotreating process, and hydrodeoxygenation reaction mainly occurs during the second hydrotreating process to achieve deep deoxygenation, and sulfur, nitrogen, and gum substances in the oil-based raw material are removed, reducing the content of nitrogen compounds in the system.

[0073] Preferably, the final boiling point temperature of the liquid hydrocarbon obtained in step (3) is less than 380 °C.

[0074] Preferably, the sulfur content in the liquid hydrocarbon obtained in step (3) is less than 10.0 mg / kg, and the nitrogen content is less than 10.0 mg / kg.

[0075] Preferably, in step (3), the conditions of the gas-liquid separation are controlled such that the yield of the liquid hydrocarbon is greater than 83% by weight.

[0076] Preferably, in step (4), the conditions of the hydroisomerization reaction include: temperature is 280 - 450 °C, pressure is 1.0 - 10.0 MPa, volume space velocity is 0.1 - 10.0 h -1 , and the hydrogen-oil volume ratio is 200 - 1500 Nm 3 / m 3 . More preferably, in step (4), the conditions of the hydroisomerization reaction include: temperature is 320 - 400 °C, pressure is 2.0 - 7.0 MPa, volume space velocity is 0.5 - 5.0 h -1 , and the hydrogen-oil volume ratio is 500 - 1000 Nm 3 / m 3 .

[0077] Preferably, in step (4), the hydroisomerization catalyst contains a carrier and an active metal component.

[0078] Preferably, in the hydroisomerization catalyst, the carrier is alumina and / or silica-alumina.

[0079] Preferably, the carrier is alumina and silica-alumina; based on the total weight of the carrier, the content of alumina is 5-95% by weight, and the content of silica-alumina is 5-95% by weight. More preferably, based on the total weight of the carrier, the content of alumina is 5-45% by weight, and the content of silica-alumina is 55-95% by weight.

[0080] Preferably, based on the total weight of the silica-alumina, the silica-alumina contains 5-60% by weight of silica and 40-95% by weight of alumina.

[0081] Preferably, the active metal component contains a third metal element and a fourth metal element. More preferably, the third metal element is cobalt element and / or nickel element, and the fourth metal element is molybdenum element and / or tungsten element.

[0082] Preferably, based on the total weight of the hydroisomerization catalyst, the content of the third metal element in terms of oxide is 1-10% by weight, and the content of the fourth metal element in terms of oxide is 5-40% by weight. More preferably, based on the total weight of the hydroisomerization catalyst, the content of the third metal element in terms of oxide is 2-8% by weight, and the content of the fourth metal element in terms of oxide is 10-35% by weight.

[0083] It should be noted that the hydroisomerization catalyst in the present invention can be purchased or prepared by known technical means in the art. In order to improve the catalytic activity of the catalyst, the hydroisomerization catalyst preferably used in the present invention is the hydroisomerization catalyst C in CN109294746A.

[0084] According to a preferred specific embodiment, the method further includes:

[0085] S31: Introduce the gas stream obtained in step (3) into a cold high-pressure separator for gas-liquid separation to obtain a liquid effluent I, water, and a gas-phase effluent I;

[0086] S32: Introduce the liquid effluent I into step (4) to carry out the hydroisomerization reaction with at least part of the liquid hydrocarbon.

[0087] Preferably, the gas-phase effluent I obtained in step S31 is passed through a recycle compressor to obtain a recycle gas; then the recycle gas is introduced into the hydrotreating equipment described in step (1) after passing through a heating furnace for the first hydrotreating and heat exchange treatment.

[0088] Preferably, the water in step S31 is sulfur-containing sewage.

[0089] Preferably, the liquid hydrocarbon in step (3) can be used as a blending component for diesel with a high cetane number. The remaining liquid hydrocarbon in the present invention can be directly fractionated to obtain diesel fraction I. The diesel fraction I has a relatively high cetane number and pour point and cannot be directly used as vehicle diesel, but can be blended with diesel components produced from mineral oil to increase the cetane number of the diesel components produced from mineral oil.

[0090] According to a preferred specific embodiment, the separation step in step (5) includes:

[0091] S51: Introduce the hydroisomerization reaction effluent into a hot high-pressure separator for gas-liquid separation to obtain gas-phase effluent II, water, and liquid-phase effluent II;

[0092] S52: Perform a first separation on the gas-phase effluent II to obtain gas-phase effluent III, water, and liquid-phase effluent III; perform a second separation on the liquid-phase effluent II to obtain gas-phase effluent IV, water, and liquid-phase effluent IV;

[0093] S53: Mix the gas-phase effluent IV and the liquid-phase effluent III for a third separation to obtain gas-phase effluent V, water, and liquid-phase effluent V;

[0094] S54: Fractionate the liquid-phase effluent V and the liquid-phase effluent IV to obtain a diesel fraction.

[0095] According to another preferred specific embodiment, introduce the gas-phase effluent III obtained in step S52 into step (4) to perform the hydroisomerization reaction with the liquid effluent I and at least part of the liquid hydrocarbon.

[0096] Preferably, the oil-based raw material contains 1.0 - 500.0 μg / g of sulfur element, 10 - 15 wt% of oxygen element, and 1.0 - 500 μg / g of nitrogen element.

[0097] Preferably, the oil-based raw material is selected from at least one of vegetable and animal oils, fatty acids, fatty acid methyl esters, fatty alcohols, waste cooking oil, and algal oil. Preferably, the vegetable and animal oil is palm oil.

[0098] According to a preferred specific embodiment, the method further includes: before introducing the oil-based raw material into the hydrotreating equipment for the first hydrotreating, first sulfide the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, the hydrotreating catalyst III, and the hydroisomerization catalyst. The sulfiding operation includes: in the presence of a medium and hydrogen, perform a sulfiding reaction on the catalyst to be sulfided with a sulfiding agent to obtain a sulfided catalyst.

[0099] Preferably, the medium is selected from at least one of biodiesel, bio-kerosene, petroleum-based diesel, and petroleum-based kerosene. In the present invention, there is no particular requirement for the dosage of the medium, and those skilled in the art can select according to needs.

[0100] Preferably, the sulfurizing agent is selected from at least one of H2S, CS2, dimethyldisulfide (DMDS), or other sulfur-containing organic compounds.

[0101] According to a preferred specific embodiment, the present invention combines Figure 3 to provide a process flow for producing biodiesel fractions from oil-based raw materials; specifically:

[0102] First, introduce hydrogen into the heating furnace to fill each reactor with hydrogen and circulate it, and then sulfide the monolithic hydrotreating catalyst I, hydrotreating catalyst II, hydrotreating catalyst III, and hydroisomerization catalyst. Then introduce the oil-based raw material 1 and hydrogen 2 into the heating furnace 3 and heat it to 220 - 300 °C. After mixing through the mixer 4, introduce it into the uppermost hydrotreating unit and carry out a hydrotreating reaction with the monolithic hydrotreating catalyst I 5 filled in the oil and gas pipeline. The material after the hydrotreating reaction is heat-exchanged with the raw material or other medium through the heat exchanger 6. Preferably, introduce the heat-exchanged material into the adjacent next hydrotreating unit in sequence to carry out hydrotreating reaction and heat-exchange treatment until the temperature difference between the outlet temperature and the inlet temperature of the reaction module in the lowermost hydrotreating unit ≤ 35 °C or the sum of the temperature rises of each reaction module ≥ 220 °C, then the material flows out to obtain the hydrotreating effluent I;

[0103] Introduce the hydrotreating effluent I into the fixed-bed reactor 7 and contact it with the hydrotreating catalyst II and hydrotreating catalyst III in sequence to carry out a second hydrotreating to obtain the hydrotreating effluent II. Then introduce the hydrotreating effluent II into the hot high-pressure separator 8 for gas-liquid separation to obtain liquid hydrocarbon 10, water, and gas stream; introduce the gas stream into the cold high-pressure separator 9 for gas-liquid separation to obtain liquid effluent I 11, water 12, and gas-phase effluent I 13; introduce the liquid effluent I 11, at least part of the liquid hydrocarbon 10, and hydrogen 15 into the hydroisomerization reactor 16 to carry out a hydroisomerization reaction with the hydroisomerization catalyst to obtain the hydroisomerization reaction effluent; pass the gas-phase effluent I 13 through the recycle compressor 14 to obtain recycle gas, and return the recycle gas to the heating furnace for recycling;

[0104] The hydroisomerization reaction effluent is subjected to gas-liquid separation in the hot high-pressure separator 17 to obtain a gas-phase effluent II, water, and a liquid-phase effluent II 19; the gas-phase effluent II is introduced into the cold high-pressure separator 18 for the first separation to obtain a gas-phase effluent III, water, and a liquid-phase effluent III, and the gas-phase effluent III is returned to the hydroisomerization reactor 16 to carry out a hydroisomerization reaction with the liquid effluent I 11, at least part of the liquid hydrocarbon 10, and hydrogen 15;

[0105] The liquid-phase effluent II 19 is introduced into the hot low-pressure separator 20 for the second separation to obtain a gas-phase effluent IV, water, and a liquid-phase effluent IV; then the gas-phase effluent IV and the liquid-phase effluent III are introduced into the cold low-pressure separator 21 for the third separation to obtain a gas-phase effluent V, water, and a liquid-phase effluent V, and then the liquid-phase effluent V and the liquid-phase effluent IV are introduced into the fractionating tower 22 for fractionation. Naphtha is obtained at the upper outlet of the fractionating tower 22, and diesel is obtained at the lower outlet. (Only the main equipment listed in the figure is shown, and other auxiliary equipment such as valves and pumps are ignored).

[0106] Compared with the prior art, the present solution has the following advantages:

[0107] (1) In the present invention, the monolithic hydrotreating catalyst I, hydrotreating catalyst II, and hydrotreating catalyst III are used, which can improve the liquid yield, reduce the generation of CO and CO2, and the recycle gas does not need to be treated.

[0108] (2) The monolithic hydrotreating catalyst I with different porosities and pore diameters is used, which can adjust the hydrotreating reaction rate of the oil raw materials, avoid the situation of local large heat release and local hydrogen deficiency, and thus avoid the catalyst bed plugging caused by oil condensation.

[0109] (3) In the present invention, the reaction module filled with the monolithic hydrotreating catalyst I is connected to the heat exchange module, which can remove the heat released by the first hydrotreating of the oil raw materials from the reaction system, make the hydrotreating reaction occur within a suitable temperature range, avoid the generation of side reactions, and improve the conversion rate of the oil raw materials. At the same time, without adopting a product recycle mode several times that of the oil raw materials, effective heat exchange can be achieved, and the energy consumption for production is greatly reduced.

[0110] (4) The hydrotreating catalyst III with a high active metal content is filled in the fixed-bed reactor, providing sufficient active sites to ensure that some difficult-to-react oxides, part of nitrides, resins, etc. in the oil are completely reacted, avoiding the influence on the subsequent hydroisomerization reaction.

[0111] (5) A non-noble metal catalyst is used in the hydroisomerization reaction process, which has good isomerization selectivity.

[0112] The present invention will be described in detail below with reference to examples.

[0113] In the following examples and comparative examples, a 3271E X-ray fluorescence spectrometer purchased from Rigaku Corporation, Japan was used to determine the content of each element in the catalyst.

[0114] The liquid hydrocarbon distillation range was determined according to the ASTM 2887 method.

[0115] The hydrotreating catalyst III used the RJW-3 catalyst. Based on the total weight of the hydrotreating catalyst III, the content of the first metal element (type: nickel) in terms of oxide was 3.2% by weight, and the content of the second metal elements (types: molybdenum and tungsten) in terms of oxide was 0.8% by weight (molybdenum) and 22.2% by weight (tungsten), which was produced by Changling Catalyst Branch of Sinopec Catalyst Company.

[0116] The hydrotreating catalyst II included a carrier (alumina) and an active component (molybdenum element). Based on the total weight of the hydrotreating catalyst II, the content of the molybdenum element in terms of oxide was 15% by weight.

[0117] The monolithic hydrotreating catalyst I was prepared by using the aforementioned method for preparing the monolithic hydrotreating catalyst I. In Examples 1, 2, and 5 below, the hydrotreating equipment contained three serially connected hydrotreating units. Along the flow direction of the liquid stream,

[0118] In the first (uppermost) hydrotreating unit, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst I was 10% by weight, the porosity of the monolithic hydrotreating catalyst I was 70%, and the number of pores per square centimeter was 25;

[0119] In the second hydrotreating unit, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst I was 15% by weight, the porosity of the monolithic hydrotreating catalyst I was 67%, and the number of pores per square centimeter was 60;

[0120] In the third (lowermost) hydrotreating unit, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst I was 25% by weight, the porosity of the monolithic hydrotreating catalyst I was 65%, and the number of pores per square centimeter was 100.

[0121] Among them, the weight ratio and types of the carrier and the active component of the monolithic hydrotreating catalyst I were respectively the same as those of the carrier and the active component of the hydrotreating catalyst II.

[0122] The yield of biodiesel = mass of diesel / mass of the hydroisomerization reaction effluent * 100%;

[0123] Yield of liquid hydrocarbons = mass of liquid hydrocarbons / mass of oil-based raw materials * 100%;

[0124] Yield of hydroisomerization reaction effluent = (mass of diesel + mass of naphtha) / mass of liquid hydrocarbons * 100%;

[0125] Conversion rate of oil-based raw materials = (oxygen content in oil-based raw materials - oxygen content in liquid hydrocarbon products) / oxygen content in oil-based raw materials * 100%.

[0126] The hydroisomerization catalyst used in the following applications is the same as that in Table 1 of CN109294746A.

[0127] Unless otherwise specified, the sulfiding method of the catalyst in the following examples specifically includes: after loading 100 g of the catalyst into the reactor, the sulfiding agent is formulated in a medium to form a 2 wt% solution and introduced into the reactor. At the same time, hydrogen is introduced into the reactor to form a pressure of 6.0 MPa, and after heating to 320 °C, the sulfiding reaction is carried out for 8 h to obtain the sulfided catalyst, where the sulfiding agent is DMDS and the medium is biodiesel.

[0128] Unless otherwise specified, the following examples all adopt Figure 3 the process flow shown in. In the following examples, before introducing the oil-based raw materials into the hydrotreating equipment for the first hydrotreating, the catalysts in the corresponding reactors loaded in each reactor are sulfided first.

[0129] Example 1

[0130] Using palm oil as the oil-based raw material, the main properties of palm oil are shown in Table 1, and the production of biodiesel fraction is carried out using Figure 3 the process flow shown in. Specifically as follows:

[0131] (1) Introduce the oil-based raw material 1 and hydrogen 2 into the heating furnace 3 and heat to 260 °C. After mixing through the mixer 4, introduce them into the upstreammost hydrotreating unit and carry out a hydrotreating reaction with the monolithic hydrotreating catalyst I 5 loaded in the oil and gas transmission pipe. The material after the hydrotreating reaction is heat-exchanged with the raw material or other media through the heat exchanger 6, and the heat-exchanged material is introduced into the adjacent next hydrotreating unit to carry out the hydrotreating reaction and heat exchange in turn until the obtained material is introduced into the third (downstreammost) hydrotreating unit to obtain the hydrotreating effluent I;

[0132] Conditions for the first hydrotreating: the inlet reaction pressure of the upstreammost hydrotreating unit is 6.4 MPa, the hydrogen-oil volume ratio of the upstreammost hydrotreating unit is 1500 Nm 3 / m 3 , the overall volume space velocity is 1.0 h -1 ,

[0133] Among them, the inlet temperature of the reaction module in the first hydrotreating unit is 260 °C, and the outlet temperature is 310 °C; the inlet temperature of the reaction module in the second hydrotreating unit is 270 °C, and the outlet temperature is 320 °C; the inlet temperature of the reaction module in the third hydrotreating unit is 290 °C, and the outlet temperature is 325 °C; the sum of the temperature rises of each of the said reaction modules is 135 °C;

[0134] (2) Introduce the hydrotreating effluent I into the fixed-bed reactor 7, and successively contact with the hydrotreating catalyst II and the hydrotreating catalyst III for the second hydrotreating to obtain the hydrotreating effluent II;

[0135] Among them, the inlet temperature of the fixed-bed reactor is 300 °C, and the outlet temperature is 340 °C;

[0136] The weight ratio of the active components in the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, and the hydrotreating catalyst III is 50:35:15;

[0137] (3) Introduce the hydrotreating effluent II into the hot high-pressure separator 8 for gas-liquid separation to obtain liquid hydrocarbons 10, water, and a gas stream; introduce the gas stream into the cold high-pressure separator 9 for gas-liquid separation to obtain a liquid effluent I11, water, and a gas-phase effluent I13; pass the gas-phase effluent I13 through a recycle compressor 14 to obtain recycle gas, and return the said recycle gas to the heating furnace for recycling;

[0138] Among them, the conversion rate of the oil and fat raw material is 100%, the final boiling point temperature of the liquid hydrocarbons is 350 °C, the sulfur content in the liquid hydrocarbons is 1.5 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbons is 85% by weight;

[0139] (4) Introduce the liquid effluent I11, at least part of the liquid hydrocarbons 10, and hydrogen 15 into the hydroisomerization reactor 16 to carry out a hydroisomerization reaction with a sulfided hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0140] Among them, the conditions of the hydroisomerization reaction are: temperature is 360 °C, pressure is 5.0 MPa, the volume hourly space velocity is 1.0 h -1 , and the hydrogen-oil volume ratio is 500 Nm 3 / m 3 ; the yield of the hydroisomerization reaction effluent is 96% by weight;

[0141] (5) Carry out gas-liquid separation on the hydroisomerization reaction effluent in the hot high-pressure separator 17 to obtain a gas-phase effluent II, water, and a liquid-phase effluent II 19;

[0142] The vapor effluent II is introduced into the cold high-pressure separator 18 for the first separation to obtain a vapor effluent III, water, and a liquid effluent III. The vapor effluent III is returned to the hydroisomerization reactor 16 and undergoes a hydroisomerization reaction with the liquid effluent I11, at least part of the liquid hydrocarbon 10, and hydrogen 15.

[0143] The liquid effluent II 19 is introduced into the hot low-pressure separator 20 for the second separation to obtain a vapor effluent IV, water, and a liquid effluent IV. The vapor effluent IV and the liquid effluent III are introduced into the cold low-pressure separator 21 for the third separation to obtain a vapor effluent V, water, and a liquid effluent V. The liquid effluent V and the liquid effluent IV are introduced into the fractionating tower 22 for fractionation. Naphtha is obtained at the upper outlet of the fractionating tower 22, and diesel is obtained at the lower outlet.

[0144] Among them, the yield of the diesel fraction is 90% by weight, and the pour point and cold filter plugging point are -11°C and -6°C respectively, which can meet the requirements of No. -10 diesel.

[0145] Example 2

[0146] In this example, used cooking oil is used as the oil raw material. The main properties of the used cooking oil are shown in Table 1. The following Figure 3 shown process flow is adopted to produce the biodiesel fraction. Specifically as follows:

[0147] (1) The oil raw material 1 and hydrogen 2 are introduced into the heating furnace 3 and heated to 250°C. After being mixed by the mixer 4, they are then introduced into the uppermost hydrotreating unit and react with the monolithic hydrotreating catalyst I 5 filled in the oil and gas transmission pipe. The material after the hydrotreating reaction is heat-exchanged with the raw material or other media through the heat exchanger 6, and the heat-exchanged material is introduced into the adjacent next hydrotreating unit for hydrotreating reaction and heat exchange in sequence. The obtained material is introduced into the third (lowermost) hydrotreating unit to obtain the hydrotreating effluent I.

[0148] The conditions for the first hydrotreating: the inlet reaction pressure of the uppermost hydrotreating unit is 6.4 MPa, the hydrogen-oil volume ratio of the uppermost hydrotreating unit is 1800 Nm 3 / m 3 , and the total volume space velocity is 1.0 h -1 ;

[0149] Among them, the inlet temperature of the reaction module in the first hydrotreating unit is 250°C, and the outlet temperature is 300°C; the inlet temperature of the reaction module in the second hydrotreating unit is 270°C, and the outlet temperature is 320°C; the inlet temperature of the reaction module in the third hydrotreating unit is 290°C, and the outlet temperature is 325°C; the sum of the temperature rises of each of the said reaction modules is 135°C;

[0150] (2) Introduce the hydrotreating effluent I into the fixed-bed reactor 7, and contact it successively with the hydrotreating catalyst II and the hydrotreating catalyst II to carry out the second hydrotreating to obtain the hydrotreating effluent II;

[0151] Among them, the inlet temperature of the fixed-bed reactor is 300 °C; the outlet temperature is 340 °C;

[0152] The weight ratio of the active components in the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, and the hydrotreating catalyst III is 40:45:15;

[0153] (3) Introduce the hydrotreating effluent II into the hot high-pressure separator 8 for gas-liquid separation to obtain liquid hydrocarbons 10, water, and a gas stream; introduce the gas stream into the cold high-pressure separator 9 for gas-liquid separation to obtain a liquid effluent I11, water, and a gas-phase effluent I13; pass the gas-phase effluent I13 through a recycle compressor 14 to obtain a recycle gas, and return the recycle gas to the heating furnace for recycling;

[0154] Among them, the conversion rate of the oil and fat raw materials is 100%, the final boiling point temperature of the liquid hydrocarbons is 370 °C, the sulfur content in the liquid hydrocarbons is 2 mg / kg, and the nitrogen content is 2 mg / kg; the yield of the liquid hydrocarbons is 84.5% by weight;

[0155] (4) Introduce the liquid effluent I11, at least part of the liquid hydrocarbons 10, and hydrogen 15 into the hydroisomerization reactor 16 to carry out a hydroisomerization reaction with the sulfided hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0156] Among them, the conditions of the hydroisomerization reaction: the temperature is 360 °C, the pressure is 5.0 MPa, the volume space velocity is 1.0 h -1 , and the hydrogen-oil volume ratio is 500 Nm 3 / m 3 ; the yield of the hydroisomerization reaction effluent is 96% by weight;

[0157] (5) Carry out gas-liquid separation of the hydroisomerization reaction effluent in the hot high-pressure separator 17 to obtain a gas-phase effluent II, water, and a liquid-phase effluent II 19;

[0158] Introduce the gas-phase effluent II into the cold high-pressure separator 18 for the first separation to obtain a gas-phase effluent III, water, and a liquid-phase effluent III, and return the gas-phase effluent III to the hydroisomerization reactor 16 to carry out a hydroisomerization reaction with the liquid effluent I11, at least part of the liquid hydrocarbons 10, and hydrogen 15;

[0159] The liquid-phase effluent II 19 is introduced into a thermal low-pressure separator 20 for a second separation to obtain a gas-phase effluent IV, water, and a liquid-phase effluent IV; the gas-phase effluent IV and the liquid-phase effluent III are introduced into a cold low-pressure separator 21 for a third separation to obtain a gas-phase effluent V, water, and a liquid-phase effluent V, and the liquid-phase effluent V and the liquid-phase effluent IV are introduced into a fractionating tower 22 for fractionation. Naphtha is obtained at the upper outlet of the fractionating tower 22, and diesel is obtained at the lower outlet;

[0160] Among them, the yield of the diesel fraction is 90% by weight, and the freezing point and cold filter plugging point are -12°C and -7°C respectively, which can meet the requirements of No. -10 diesel.

[0161] Example 3

[0162] Palm oil is used as the oil raw material. The main properties of palm oil are shown in Table 1. In this example, a method similar to that in Example 1 is used to prepare biodiesel. The differences are as follows:

[0163] In step (1), there is only one hydrotreating unit in the hydrotreating equipment. The loading amounts of the active component and the carrier in the monolithic hydrotreating catalyst I in the hydrotreating unit are 10% by weight, the porosity is 70%, and the number of pores per square centimeter is 25;

[0164] The conditions for the first hydrotreating: the inlet reaction pressure of the uppermost hydrotreating unit is 6.4 MPa, and the hydrogen-oil volume ratio in the uppermost hydrotreating unit is 1500 Nm 3 / m 3 , and the overall volume space velocity is 1.0 h -1 ;

[0165] Among them, the inlet temperature of the reaction module in the first hydrotreating unit is 250°C, and the outlet temperature is 385°C; the sum of the temperature rises of the reaction module is 135°C;

[0166] (2) The hydrotreating effluent I is introduced into a fixed-bed reactor 7 and contacted with a hydrotreating catalyst II and a hydrotreating catalyst III in sequence to perform a second hydrotreating to obtain a hydrotreating effluent II;

[0167] Among them, the inlet temperature of the fixed-bed reactor is 300°C, and the outlet temperature is 340°C;

[0168] The weight ratio of the content of the active component in the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, and the hydrotreating catalyst III is 50:35:15;

[0169] The remaining steps are the same as those in Example 1;

[0170] In step (3), the conversion rate of the oil and fat raw material is 100%, the final boiling point temperature of the obtained liquid hydrocarbon is 350 °C, the sulfur content in the liquid hydrocarbon is 1.5 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbon is 83.9% by weight;

[0171] In step (4), the yield of the hydroisomerization reaction effluent obtained is 96% by weight;

[0172] In step (5), the yield of the diesel fraction obtained is 90% by weight, the pour point and cold filter plugging point are -11 °C and -6 °C respectively, which can meet the requirements of No. -10 diesel.

[0173] Compared with Example 1, there is only one hydrotreating unit in the hydrotreating equipment of this example, and the heat released by the reaction cannot be removed. Although products with similar quality to those in Example 1 can also be obtained, at high temperatures, the oil and fat is prone to condensation, causing reactor blockage and shortening the operation cycle. At the same time, more CO and CO2 will be generated at high temperatures, resulting in a decrease in the yield of liquid hydrocarbons.

[0174] Example 4

[0175] Using palm oil as the oil and fat raw material, the main properties of the palm oil are shown in Table 1, and the following Figure 3 shown process flow is used to produce the biodiesel fraction. Specifically as follows:

[0176] (1) Introduce the oil and fat raw material 1 and hydrogen 2 into the heating furnace 3 and heat to 260 °C. After mixing through the mixer 4, introduce them into the uppermost hydrotreating unit, and carry out a hydrotreating reaction with the monolithic hydrotreating catalyst I 5 filled in the oil and gas transmission pipe. The material after the hydrotreating reaction is heat-exchanged with the raw material or other medium through the heat exchanger 6, and the heat-exchanged material is introduced into the adjacent next hydrotreating unit in sequence for hydrotreating reaction and heat exchange until the obtained material is introduced into the third (lowermost) hydrotreating unit to obtain the hydrotreating effluent I;

[0177] The conditions for the first hydrotreating: the inlet reaction pressure of the uppermost hydrotreating unit is 6.4 MPa, the hydrogen-oil volume ratio of the uppermost hydrotreating unit is 1500 Nm 3 / m 3 , the total volume space velocity is 1.0 h -1 ,

[0178] Among them, the inlet temperature of the reaction module in the first hydrotreating unit is 260 °C, and the outlet temperature is 300 °C; the inlet temperature of the reaction module in the second hydrotreating unit is 280 °C, and the outlet temperature is 320 °C; the inlet temperature of the reaction module in the third hydrotreating unit is 300 °C, and the outlet temperature is 330 °C; the sum of the temperature rises of each of the said reaction modules is 110 °C;

[0179] (2) Introduce the hydrotreated effluent I into the fixed-bed reactor 7, and successively contact with the hydrotreating catalyst II and the hydrotreating catalyst III for the second hydrotreating to obtain the hydrotreated effluent II;

[0180] Among them, the inlet temperature of the fixed-bed reactor is 300 °C, and the outlet temperature is 365 °C;

[0181] The weight ratio of the active components in the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, and the hydrotreating catalyst III is 25:25:50;

[0182] (3) Introduce the hydrotreated effluent II into the hot high-pressure separator 8 for gas-liquid separation to obtain the liquid hydrocarbon 10, water, and gas stream; introduce the gas stream into the cold high-pressure separator 9 for gas-liquid separation to obtain the liquid effluent I11, water, and the gas-phase effluent I13; the volume of CO and CO2 in the gas-phase effluent I13 is greater than 1.0%. After removing CO and CO2 through the gas treatment unit, the recycled gas is returned to the heating furnace for recycling;

[0183] Among them, the conversion rate of the oil and fat raw materials is 100%, the final boiling point temperature of the liquid hydrocarbon is 350 °C, the sulfur content in the liquid hydrocarbon is 1.5 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbon is 83.5% by weight;

[0184] (4) Introduce the liquid effluent I11, at least part of the liquid hydrocarbon 10, and hydrogen 15 into the hydroisomerization reactor 16 to carry out hydroisomerization reaction with the sulfided hydroisomerization catalyst to obtain the hydroisomerization reaction effluent;

[0185] Among them, the conditions of the hydroisomerization reaction: the temperature is 360 °C, the pressure is 5.0 MPa, the volume space velocity is 1.0 h -1 , and the hydrogen-oil volume ratio is 500 Nm 3 / m 3 ; the yield of the hydroisomerization reaction effluent is 96% by weight;

[0186] (5) Carry out gas-liquid separation of the hydroisomerization reaction effluent in the hot high-pressure separator 17 to obtain the gas-phase effluent II, water, and the liquid-phase effluent II 19;

[0187] Introduce the gas-phase effluent II into the cold high-pressure separator 18 for the first separation to obtain the gas-phase effluent III, water, and the liquid-phase effluent III, and return the gas-phase effluent III to the hydroisomerization reactor 16 to carry out the hydroisomerization reaction with the liquid effluent I11, at least part of the liquid hydrocarbon 10, and hydrogen 15;

[0188] The liquid-phase effluent II 19 is introduced into a thermal low-pressure separator 20 for a second separation to obtain a gas-phase effluent IV, water, and a liquid-phase effluent IV; the gas-phase effluent IV and the liquid-phase effluent III are introduced into a cold low-pressure separator 21 for a third separation to obtain a gas-phase effluent V, water, and a liquid-phase effluent V, and the liquid-phase effluent V and the liquid-phase effluent IV are introduced into a fractionating tower 22 for fractionation. Naphtha is obtained at the upper outlet of the fractionating tower 22, and diesel is obtained at the lower outlet;

[0189] Among them, the yield of the diesel fraction is 90% by weight, the freezing point and cold filter plugging point are -11°C and -6°C respectively, which can meet the requirements of No. -10 diesel.

[0190] Comparative Example 1

[0191] Using palm oil as the oil raw material, the main properties of palm oil are shown in Table 1. This comparative example uses a method similar to that of Example 1 to prepare biodiesel, and the differences are as follows:

[0192] In this comparative example, the first hydrotreatment and heat exchange treatment in step (1) are not carried out, and hydrogen and the oil raw material are directly introduced into a fixed-bed reactor filled with hydrotreating catalyst III for a second hydrotreatment; specifically, in this comparative example:

[0193] SS1: In the presence of hydrogen, the oil raw material (the same type as the palm oil raw material in Example 1) and the liquid hydrocarbon obtained in SS2 are introduced into a fixed-bed reactor filled with hydrotreating catalyst III for a second hydrotreatment reaction to obtain a hydrotreated effluent II;

[0194] The weight ratio of the liquid hydrocarbon to the palm oil is 3.5:1;

[0195] Among them, before the second hydrogenation reaction, the hydrotreating catalyst III and the hydroisomerization catalyst are sulfided;

[0196] The conditions for the second hydrogenation reaction are: the inlet pressure of the fixed-bed reactor is 6.4 MPa, the hydrogen-oil volume ratio is 1500 Nm 3 / m 3 , the relative total catalyst space velocity is 1.0 h -1 , the inlet temperature is 290°C, and the outlet temperature is 340°C;

[0197] SS2: The hydrotreated effluent II is introduced into a thermal high-pressure separator 8 for gas-liquid separation to obtain a liquid hydrocarbon 10, water, and a gas stream; the gas stream enters a cold high-pressure separator 9 for gas-liquid separation to obtain a liquid effluent I11, water, and a gas-phase effluent I13; the gas-phase effluent I13 passes through a recycle compressor 14 to obtain a recycle gas, and the recycle gas is returned to the most upstream hydrotreating unit for recycling;

[0198] Among them, the conversion rate of the oil-based raw material is 100%, the final boiling point temperature of the liquid hydrocarbon is 350 °C, the sulfur content in the liquid hydrocarbon is 1.5 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbon is 82% by weight; the volume of CO and CO2 in the gas-phase effluent I13 is greater than 3%. After removing CO and CO2 through the gas treatment unit, the recycled gas is obtained through the recycle compressor 14, and the recycled gas is returned to the heating furnace for recycling.

[0199] The remaining steps are the same as those in Example 1;

[0200] The yield of the hydroisomerization reaction liquid hydrocarbon obtained is 96% by weight;

[0201] The yield of the finally obtained diesel fraction is 90% by weight, and the pour point and cold filter plugging point are -11 °C and -6 °C respectively, which can meet the requirements of -10 diesel.

[0202] Table 1

[0203] Item Palm oil Waste cooking oil <![CDATA[Density (20 °C), g / cm 3 > 915.1 910.6 Sulfur content, μg / g 2.0 5.5 Nitrogen content, μg / g 2.0 59 Oxygen content, % 11.4 12.0 Total acid value, mgKOH / g 0.2 34.0

[0204] It can be seen from the examples that by using the method provided by the present invention to prepare the biodiesel fraction, the temperature rise of the reactor can be effectively controlled without product recycling. The biodiesel product produced from palm oil or waste cooking oil can meet the requirements of -10 diesel, effectively solving the problems of large heat release during the hydrotreating process of biodiesel, easy blockage at the top, and the need for a large amount of product recycling, and realizing the long-term operation of the device.

[0205] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for producing a biodiesel fraction from oil and fat raw materials, characterized in that, The method includes: (1) In the presence of hydrogen, introducing an oil raw material into a hydrotreating device for a first hydrotreating and heat exchange treatment to obtain a hydrotreating effluent I; the hydrotreating device contains at least two serially connected hydrotreating units, and each of the hydrotreating units contains a serially connected reaction module and a heat exchange module, such that the material can sequentially perform a hydrogenation reaction and heat exchange in each of the hydrotreating units; an integral hydrotreating catalyst I is loaded in each of the reaction modules; the porosity of the integral hydrotreating catalyst I in each of the reaction modules is greater than or equal to 65%, and along the flow direction of the liquid stream, from the most upstream hydrotreating unit to the most downstream hydrotreating unit, the porosity of the integral hydrotreating catalyst loaded in the reaction module decreases sequentially, and the number of pores per square centimeter increases sequentially; (2) Introducing the hydrotreating effluent I into a fixed-bed reactor for a second hydrotreating to obtain a hydrotreating effluent II; the fixed-bed reactor is sequentially loaded with a hydrotreating catalyst II and a hydrotreating catalyst III; (3) Introducing the hydrotreating effluent II into a hot high-pressure separator for gas-liquid separation to obtain a liquid hydrocarbon, water, and a gas stream; (4) In the presence of a hydroisomerization catalyst and hydrogen, subjecting at least part of the liquid hydrocarbon to a hydroisomerization reaction to obtain a hydroisomerization reaction effluent; (5) Separating the hydroisomerization reaction effluent to obtain a diesel fraction; wherein, the active components of the integral hydrotreating catalyst I and the hydrotreating catalyst II both contain molybdenum element; the active component of the hydrotreating catalyst III contains at least two different metal elements.

2. The method according to claim 1, wherein In step (1), the integral hydrotreating catalyst I contains a support, a carrier, and an active component. Based on the total weight of the integral hydrotreating catalyst I, the loading amounts of the carrier and the active component are 1-40% by weight.

3. The method according to claim 2, wherein, Based on the total weight of the integral hydrotreating catalyst I, the content of the molybdenum element in terms of oxide is 0.2-5.1% by weight; Based on the total weight of the hydrotreating catalyst II, the content of the molybdenum element in terms of oxide is 10-17% by weight.

4. The method according to claim 1, wherein The active component of the hydrotreating catalyst III contains a first metal element and a second metal element; the first metal element is cobalt element and / or nickel element, and the second metal element is molybdenum element and / or tungsten element.

5. The method according to claim 4, wherein Based on the total weight of the hydrotreating catalyst III, the content of the first metal element in terms of oxide is 1-10% by weight, and the content of the second metal element in terms of oxide is 5-40% by weight.

6. The method according to any one of claims 1-5, wherein The weight ratio of the sum of the active components of the integral hydrotreating catalyst I and the hydrotreating catalyst II to the content of the active component in the hydrotreating catalyst III is 70:30 to 95:5, and the weight ratio of the content of the active components of the integral hydrotreating catalyst I and the hydrotreating catalyst II is 1:0.5 to 1.

5.

7. The method according to any one of claims 1-5, wherein In step (1), the reaction module is an oil-gas transmission pipe filled with the monolithic hydrotreating catalyst I, and the heat exchange module is a heat exchanger.

8. The method according to any one of claims 1-5, wherein In step (1), in each reaction module, the inlet temperature is independently 220 - 300 °C, and the outlet temperature is independently 300 - 380 °C; and / or In step (1), the sum of the temperature rises of each reaction module is 80 - 220 °C.

9. The method according to any one of claims 1-5, wherein In step (1), the conditions of the first hydrotreating at least satisfy that the inlet reaction pressure of the uppermost hydrotreating unit is 0.5 - 10 MPa, the hydrogen-oil volume ratio of the uppermost hydrotreating unit is 600 - 2000 Nm 3 / m 3 , and the overall volumetric space velocity is 0.5 - 10 h -1 .

10. The method according to any one of claims 1-5, wherein, In step (2), in the fixed-bed reactor, the inlet temperature is 280 - 380 °C, and the outlet temperature is 320 - 400 °C.

11. The method according to any one of claims 1-5, wherein, In step (3), control the conditions of the gas-liquid separation such that the yield of the liquid hydrocarbon is greater than 83 wt%.

12. The method according to any one of claims 1-5, wherein, In step (4), the conditions for the hydroisomerization reaction include: temperature is 280 - 450 °C, pressure is 1.0 - 10.0 MPa, volume hourly space velocity is 0.1 - 10.0 h -1 , and the hydrogen-oil volume ratio is 200 - 1500 Nm 3 / m 3 .

13. The method according to claim 12, wherein, In step (4), the conditions for the hydroisomerization reaction include: temperature is 320 - 400 °C, pressure is 2.0 - 7.0 MPa, volumetric space velocity is 0.5 - 5.0 h -1 , and the hydrogen-oil volume ratio is 500 - 1000 Nm 3 / m 3 .

14. The method according to any one of claims 1-5, wherein, In step (4), the hydroisomerization catalyst contains a carrier and an active metal component; the carrier is alumina and / or silica-alumina.

15. The method according to claim 14, wherein, The carrier is alumina and silica-alumina; based on the total weight of the carrier, the content of alumina is 5 - 95 wt%, and the content of silica-alumina is 5 - 95 wt%.

16. The method according to claim 15, wherein, Based on the total weight of the silica-alumina, the silica-alumina contains 5 - 60 wt% of silica and 40 - 95 wt% of alumina.

17. The method according to claim 14, wherein, The active metal component contains a third metal element and a fourth metal element; the third metal element is cobalt element and / or nickel element, and the fourth metal element is molybdenum element and / or tungsten element.

18. The method according to claim 17, wherein Based on the total weight of the hydroisomerization catalyst, the content of the third metal element in terms of oxide is 1 - 10 wt%, and the content of the fourth metal element in terms of oxide is 5 - 40 wt%.

19. The method according to claim 18, wherein, Based on the total weight of the hydroisomerization catalyst, the content of the third metal element in terms of oxide is 2 - 8 wt%, and the content of the fourth metal element in terms of oxide is 10 - 35 wt%.

20. The method according to any one of claims 1-5, wherein, This method further includes: S31: Introduce the gas stream obtained in step (3) into a cold high-pressure separator for gas-liquid separation to obtain a liquid effluent I, water, and a gas-phase effluent I; S32: Introduce the liquid effluent I into step (4) to carry out the hydroisomerization reaction with at least part of the liquid hydrocarbon.

21. The method according to any one of claims 1-5, wherein The liquid hydrocarbon in step (3) can be used as a diesel blending component with a high cetane number.

22. The method according to any one of claims 1-5, wherein, The oil and fat raw material contains 1.0 - 200.0 μg / g of sulfur element, 10 - 15 wt% of oxygen element, and 1.0 - 100 μg / g of nitrogen element.

23. The method according to claim 22, wherein, The oil and fat raw material is selected from at least one of vegetable and animal oils and fats, fatty acids, fatty acid methyl esters, fatty alcohols, waste cooking oil, and algal oil.

24. The method according to any one of claims 1-5, wherein, This method further includes: Before introducing the oil and fat raw material into the hydrotreating equipment for the first hydrotreating, first sulfide the monolithic hydrotreating catalyst I, the hydrotreating catalyst II, the hydrotreating catalyst III, and the hydroisomerization catalyst. The sulfiding operation includes: In the presence of a medium and hydrogen, carry out a sulfiding reaction between the catalyst to be sulfided and a sulfiding agent to obtain a sulfided catalyst.

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