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 biodiesel fractions from oil-based raw materials. The method includes: under the presence of hydrogen, subjecting the oil-based raw materials to a first hydrotreating and heat exchange treatment to obtain a hydrotreating effluent I; subjecting the hydrotreating effluent I to a second hydrotreating to obtain a hydrotreating effluent II; performing gas-liquid separation on the hydrotreating effluent II to obtain liquid hydrocarbons, water, and a gas stream; subjecting at least part of the liquid hydrocarbons to hydroisomerization reaction and then performing separation to obtain diesel fractions. The method provided by the present invention completes the reactions with fast reaction rates and large heat releases during the oil hydrogenation process in the reaction module, and at the same time, a plurality of heat exchange templates are added between the reaction modules. Without adopting a large amount of cold hydrogen and product circulation, the total temperature rise of the reaction system can still be controlled, resulting in low production energy consumption and qualified quality of the prepared biodiesel fractions.

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. Preparing biodiesel fuel from renewable biomass such as animal and vegetable oils or agricultural and forestry waste, and developing biomass fuels are considered to be one of the effective means to solve this problem.

[0003] Vegetable oil is the most easily available biofuel, 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.

[0004] During the hydrotreating reaction of vegetable oil (taking coconut oil as an example), it mainly includes double bond saturation, direct hydrodeoxygenation, hydrodecarboxylation and hydrodecarbonylation reactions, as Figure 1 shown. In this series of reaction processes, due to the different reaction rates and large heat release, 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 being unable to 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.

[0005] Oil-based raw materials have large molecular weights, high viscosities and high boiling points. Under the conditions of fixed-bed hydrotreating reactions, the oil-based raw materials cover the catalyst surface in the form of a liquid film, and hydrogen also needs to dissolve into the liquid film to carry out the hydrogenation reaction. However, some reactions in the oil-based raw materials consume the dissolved hydrogen in a short time, resulting in a lack of hydrogen in the liquid film. At the same time, the oil-based 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.

[0006] CN101768469A discloses a combined hydrogenation method of mineral oil and animal and vegetable oils. This method uses a mineral diesel fraction and animal and vegetable oils as raw materials, and performs hydrogenation treatment under different conditions in two hydrogenation reaction zones respectively. After mixing the obtained products, a diesel product is obtained. This method can obtain a clean diesel product 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 hydrogenation treatment 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 prolongs the operation cycle of the device.

[0007] 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 successively enters the first-stage hydrogenation unit and the second-stage hydrogenation unit, and obtains biodiesel with a relatively high cetane number through fractionation.

[0008] However, the above two methods both require mixing and processing mineral oil and bio-oil, and cannot produce pure biodiesel.

[0009] CN111100703A discloses a method for hydrodeoxygenation of bio-oils. This method first feeds the bio-oils into a hot high-pressure separator, and the catalyst loaded in the hot high-pressure separator contacts for 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 bio-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.

[0010] CN106281401A discloses a method for producing aviation biofuel from waste animal and vegetable oils. The raw material oil is pretreated and then undergoes a hydrogenation reaction in a hydrogenation treatment unit. After the effluent is degassed and dehydrated, it is further subjected to hydrogenation conversion and rectification to obtain high-quality aviation kerosene. However, this method needs to recycle the generated liquid phase part back to the inlet of the hydrogenation treatment unit to avoid excessive temperature rise in the hydrogenation treatment unit, which may cause catalyst deactivation and product quality degradation.

[0011] CN109294746A discloses a method for hydrogenating oil-based raw materials to prepare a diesel fraction. The oil-based raw materials react with two different types of hydrogenation treatment catalysts in sequence, and the obtained liquid hydrocarbons react with a hydroisomerization catalyst to obtain biodiesel with a low freezing point and a high cetane number. However, this method also needs to control the temperature rise through a large amount of cold hydrogen and recycle oil in the hydrogenation treatment unit, resulting in high energy consumption. Summary of the Invention

[0012] The purpose of the present invention is to overcome the defects of high production energy consumption and easy blockage of the reactor caused by oil condensation in the prior art during the production of biodiesel fractions.

[0013] To achieve the above object, the present invention provides a method for producing a biodiesel fraction from an oil-based raw material, the method comprising:

[0014] (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, such that the material can sequentially perform a hydrogenation reaction and heat exchange in each of the hydrotreating units; a monolithic hydrotreating catalyst is loaded in each of the reaction modules;

[0015] (2) Introducing the hydrotreating effluent I into a fixed-bed reactor loaded with a hydrotreating catalyst A for a second hydrotreating to obtain a hydrotreating effluent II;

[0016] (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;

[0017] (4) In the presence of a hydroisomerization catalyst and hydrogen, subjecting at least a portion of the liquid hydrocarbon to a hydroisomerization reaction to obtain a hydroisomerization reaction effluent;

[0018] (5) Separating the hydroisomerization reaction effluent to obtain a diesel fraction.

[0019] The method for producing a biodiesel fraction from an oil-based raw material provided by the present invention adopts a hydrotreating device containing one or at least two serially connected hydrotreating units. By utilizing the characteristics of the monolithic hydrotreating catalyst, the reactions with a fast reaction rate and large heat release during the oil hydrogenation process are completed in the reaction modules of the hydrotreating units. At the same time, multiple heat exchange templates are added between the reaction modules, effectively controlling the reaction temperature rise. Without adopting a large amount of cold hydrogen and product circulation, the total temperature rise of the reaction system can still be controlled, resulting in low production energy consumption. It effectively avoids the problem of reactor blockage caused by the fast reaction rate and large heat release of the first hydrotreating reaction, as well as the oil condensation reaction, etc. Description of the Drawings

[0020] Figure 1 is a schematic diagram of the hydrotreating reaction process of coconut oil;

[0021] Figure 2 is a schematic diagram of the structure of a monolithic honeycomb ceramic shown in a preferred specific embodiment provided by the present invention;

[0022] Figure 3 is a process flow diagram for producing a biodiesel fraction from an oil-based raw material in a preferred specific embodiment provided by the present invention.

[0023] Explanation of the reference numerals

[0024] 1. Oil-based raw materials, 2. Hydrogen, 3. Heating furnace, 4. Mixer, 5. Monolithic hydrotreating catalyst, 6. Heat exchanger, 7. Fixed-bed reactor, 8. Hot high-pressure separator, 9. Cold high-pressure separator, 10. Liquid hydrocarbons, 11. Liquid effluent I, 12. Water, 13. Gas-phase effluent I, 14. Gas treatment unit, 15. Hydrogen, 16. Hydroisomerization reactor, 17. Hot high-pressure separator, 18. Cold high-pressure separator, 19. Liquid-phase effluent II, 20. Hot low-pressure separator, 21. Cold low-pressure separator, 22. Fractionating column. Detailed implementation manners

[0025] The endpoints and any values disclosed in this text for a range are not limited to the exact range or value. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this text.

[0026] The present invention provides a method for producing a biodiesel fraction from oil-based raw materials, and the method includes:

[0027] (1) In the presence of hydrogen, introducing the oil-based raw materials into a hydrotreating device for the 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; a monolithic hydrotreating catalyst is filled in each of the reaction modules;

[0028] (2) Introducing the hydrotreating effluent I into a fixed-bed reactor filled with a hydrotreating catalyst A for the second hydrotreating to obtain a hydrotreating effluent II;

[0029] (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;

[0030] (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;

[0031] (5) Separating the hydroisomerization reaction effluent to obtain a diesel fraction.

[0032] According to a preferred specific embodiment, the method further includes: before the oil raw material and hydrogen are introduced into the hydrotreating equipment, they are first heated to 220-300 °C in a heating furnace, then mixed in a mixer, and then enter the hydrotreating equipment for the first hydrotreating and heat exchange treatment.

[0033] In the present invention, there is no particular limitation on the type of the mixer, which may be a static mixer, a microbubble generator, a vortex shear mixer, etc. Those skilled in the art should not understand it as a limitation to the present invention.

[0034] Preferably, in step (1), the active component in the monolithic hydrotreating catalyst contains a first metal element and a second metal element.

[0035] Preferably, the first metal element is cobalt element and / or nickel element, and the second metal element is molybdenum element and / or tungsten element.

[0036] Preferably, based on the total weight of the monolithic hydrotreating catalyst, the content of the first metal element in terms of oxide is 0.02-3% by weight, and the content of the second metal element in terms of oxide is 0.1-12% by weight.

[0037] It should be noted that in the present invention, the monolithic hydrotreating catalyst can be purchased or prepared by known technical means in the art.

[0038] In order to improve the conversion rate of the hydrogenation reaction and the purity of biodiesel, the present invention exemplarily provides a method for preparing a monolithic hydrotreating catalyst, which includes:

[0039] S1: Immerse the support in the carrier slurry to obtain Intermediate I; the carrier slurry contains the material for forming the carrier of the monolithic hydrotreating catalyst.

[0040] S2: Immerse Intermediate I in the solution containing the active component, and obtain the monolithic hydrotreating catalyst after drying.

[0041] Preferably, in the method for preparing the monolithic hydrotreating catalyst, the material for forming the active component of the monolithic hydrotreating catalyst is the same as the material for forming the active component in the RJW-3 catalyst; the material for forming the carrier of the monolithic hydrotreating catalyst is the same as the carrier material in the RJW-3 catalyst.

[0042] That is, preferably, the monolithic hydrotreating catalyst described in the present invention can have the catalytic function of the RJW-3 catalyst and is formed on the support described in the present invention.

[0043] Preferably, the support is a monolithic honeycomb ceramic made of cordierite. Among them, a preferred specific embodiment of the Figure 2 shows the structure of the monolithic honeycomb ceramic made of cordierite described in a preferred specific embodiment.

[0044] Preferably, the weight ratio of the active component to the carrier in the monolithic hydrotreating catalyst is the same as that in the RJW-3 catalyst.

[0045] According to a preferred specific embodiment, in step (1), the porosity of the monolithic hydrotreating catalyst in each of the reaction modules is greater than or equal to 65%, and along the flow direction of the liquid stream, from the upstream most hydrotreating unit to the downstream most hydrotreating unit, the porosity of the monolithic hydrotreating catalyst loaded in the reaction module decreases in sequence, and the number of pores per square centimeter increases in sequence. The inventors 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 blockage of the catalyst bed caused by local large heat release, local hydrogen deficiency, and oil condensation can be avoided.

[0046] In the present invention, the porosity of the monolithic hydrotreating catalyst = the sum of the pore areas through which the stream can flow / the cross-sectional area of the monolithic hydrotreating catalyst.

[0047] 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 loaded in the reaction module of the upstream hydrotreating unit is 1-5% higher than that of the monolithic hydrotreating catalyst loaded in the reaction module of the adjacent downstream hydrotreating unit.

[0048] 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 loaded in the reaction module of the upstream hydrotreating unit is 10-50 less than that of the monolithic hydrotreating catalyst loaded in the reaction module of the adjacent downstream hydrotreating unit.

[0049] According to a preferred specific embodiment, there are three hydrotreating units connected in series in the hydrotreating equipment. Along the flow direction of the liquid-phase stream, in the monolithic hydrotreating catalyst of the first hydrotreating unit, the loading amount of the carrier and the active component is 8-12% by weight, and the number of pores per square centimeter is 40-50; in the monolithic hydrotreating catalyst of the second hydrotreating unit, the loading amount of the carrier and the active component is 13-18% by weight, and the number of pores per square centimeter is 55-65; in the monolithic hydrotreating catalyst of the third hydrotreating unit, the loading amount of the carrier and the active component is 22-28% by weight, and the number of pores per square centimeter is 80-100.

[0050] According to a preferred specific embodiment, there are four hydrotreating units connected in series in the hydrotreating equipment. Along the flow direction of the liquid-phase stream, in the monolithic hydrotreating catalyst of the first hydrotreating unit, the loading amount of the carrier and the active component is 3-7% by weight, and the number of pores per square centimeter is 22-27; in the monolithic hydrotreating catalyst of the second hydrotreating unit, the loading amount of the carrier and the active component is 8-12% by weight, and the number of pores per square centimeter is 40-50; in the monolithic hydrotreating catalyst of the third hydrotreating unit, the loading of the carrier and the active component is 13-18% by weight, and the number of pores per square centimeter is 55-65; in the monolithic hydrotreating catalyst of the fourth hydrotreating unit, the loading amount of the carrier and the active component is 22-28% by weight, and the number of pores per square centimeter is 80-100.

[0051] 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) / (the total weight of the monolithic hydrotreating catalyst) * 100%.

[0052] Preferably, in step (1), the reaction module is an oil and gas delivery pipe filled with the monolithic hydrotreating catalyst, and the heat exchange module is a heat exchanger.

[0053] Preferably, the outer diameter of each of the monolithic hydrotreating catalysts is 3-5 mm smaller than the inner diameter of the oil and gas delivery pipe. It should be noted that the outer diameter of the monolithic hydrotreating catalyst is the outer diameter of the support after loading the active component and the carrier.

[0054] Preferably, in step (1), in each reaction module, the inlet temperature is independently 250-300 °C, and the outlet temperature is independently 300-380 °C.

[0055] Preferably, in step (1), the inlet temperature of each reaction module is lower than the outlet temperature.

[0056] Preferably, in step (1), the sum of the temperature rises of each of the reaction modules is 80 - 220°C. In the present invention, "the sum of the temperature rises of each of the reaction modules" in step (1) means the sum of the temperature differences between the outlet temperature and the inlet temperature of each reaction module.

[0057] 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, the heat exchange is ended to obtain a gas-liquid mixed hydrotreating effluent I, and then the hydrotreating effluent I is subjected to a second hydrotreating.

[0058] Preferably, the hydrotreating effluent I contains unreacted oil, partially reacted oil, intermediate products of oil reaction, alkanes with C8 - C24, propane, water, carbon monoxide, carbon dioxide, hydrogen sulfide, and hydrogen.

[0059] Preferably, in step (2), the active components in the hydrotreating catalyst A contain a third metal element and a fourth metal element.

[0060] More preferably, the third metal element is cobalt element and / or nickel element; the fourth metal element is molybdenum element and / or tungsten element.

[0061] Preferably, based on the total weight of the hydrotreating catalyst A, 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%.

[0062] Preferably, the weight ratio of the active component content of the monolithic hydrotreating catalyst to that of the hydrotreating catalyst A is 1:0.5 - 1.5.

[0063] It should be noted that in the present invention, the hydrotreating catalyst A can be purchased or prepared by known technical means in the art.

[0064] Preferably, the hydrotreating catalyst A is the RJW-3 catalyst produced by Changling Catalyst Branch of Sinopec Catalyst Company.

[0065] Preferably, in step (2), in the fixed-bed reactor, the inlet temperature is 280 - 380°C and the outlet temperature is 320 - 400°C.

[0066] Preferably, in step (2), the inlet temperature of the fixed-bed reactor is lower than the outlet temperature.

[0067] Preferably, the hydrotreated effluent II contains alkanes having 8 to 24 carbon atoms, propane, water, carbon monoxide, carbon dioxide, hydrogen sulfide, and hydrogen.

[0068] Preferably, in step (1), the first hydrotreating conditions include: the inlet reaction pressure of the uppermost hydrotreating unit is 0.5 - 10 MPa, the hydrogen-to-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 and hydrotreating catalyst A.

[0069] In the present invention, during the first hydrotreating and second hydrotreating 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-like substances in the oil-based raw material are removed, reducing the content of nitrogen compounds in the system.

[0070] 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.

[0071] Preferably, the final boiling point temperature of the liquid hydrocarbon obtained in step (3) is less than 380 °C.

[0072] According to a preferred specific embodiment, the method further includes:

[0073] 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;

[0074] S32: Introduce the liquid effluent I into step (4) to carry out the hydroisomerization reaction with at least part of the liquid hydrocarbon; remove CO and CO2 from the gas-phase effluent I through a gas treatment unit to obtain a recycle gas;

[0075] S33: Introduce the recycle gas into the hydrotreating equipment to carry out the first hydrotreating and heat exchange treatment with hydrogen and the oil-based raw material.

[0076] Preferably, the recycle gas first returns to the heating furnace and then is introduced into the hydrotreating equipment to carry out the first hydrotreating and heat exchange treatment with hydrogen and the oil-based raw material.

[0077] Preferably, the reaction conditions of the gas treatment unit are controlled such that the CO content in the recycled gas obtained in step S32 is less than or equal to 0.05% by volume, and the CO2 content is less than or equal to 0.1% by volume.

[0078] Preferably, the water in step S31 is sulfur-containing sewage.

[0079] Preferably, the liquid hydrocarbon in step (3) can be used as a blending component for diesel with a high cetane number. The liquid hydrocarbon in step (3) of the present invention can directly enter the fractionation unit to obtain diesel fraction I. The cetane number and pour point of diesel fraction I are relatively high and it cannot be directly used as vehicle diesel, but it can be blended with diesel components produced from mineral oil to increase the cetane number of the diesel components produced from mineral oil.

[0080] Preferably, in step (4), the hydroisomerization catalyst contains a support and an active metal component.

[0081] Preferably, in the hydroisomerization catalyst, the support is alumina and / or silica-alumina. Preferably, in the hydroisomerization catalyst, the support is alumina and silica-alumina; and based on the total weight of the support, 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 support, the content of alumina is 5-45% by weight, and the content of silica-alumina is 55-95% by weight.

[0082] 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.

[0083] Preferably, the active metal component contains a fifth metal element and a sixth metal element, and the fifth metal element is cobalt element and / or nickel element, and the sixth metal element is molybdenum element and / or tungsten element.

[0084] Preferably, based on the total weight of the hydroisomerization catalyst, the content of the fifth metal element in terms of oxide is 1-10% by weight, and the content of the sixth 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 fifth metal element in terms of oxide is 2-8% by weight, and the content of the sixth metal element in terms of oxide is 10-35% by weight.

[0085] It should be noted that the hydroisomerization catalyst described in the present invention can be purchased or prepared by known technical means in the art. To improve the catalytic activity of the catalyst, the hydroisomerization catalyst preferably used in the present invention is the hydroisomerization catalyst C in CN109294746A.

[0086] Preferably, in step (4), the conditions of the hydroisomerization reaction include: the temperature is 280 - 450 °C, the pressure is 1.0 - 10.0 MPa, the volume hourly space velocity is 0.1 - 10.0 h -1 , and the hydrogen - to - oil volume ratio is 200 - 1500 Nm 3 / m 3 .

[0087] More preferably, in step (4), the conditions of the hydroisomerization reaction include: the temperature is 320 - 400 °C, the pressure is 2.0 - 7.0 MPa, the volume hourly space velocity is 0.5 - 5.0 h -1 , and the hydrogen - to - oil volume ratio is 500 - 1000 Nm 3 / m 3 .

[0088] According to a preferred specific embodiment, the separation step in step (5) includes:

[0089] S51: Introduce the hydroisomerization reaction effluent into a hot high - pressure separator for gas - liquid separation to obtain a gas - phase effluent II, water, and a liquid - phase effluent II;

[0090] S52: Perform a first separation on the gas - phase effluent II to obtain a gas - phase effluent III, water, and a liquid - phase effluent III; perform a second separation on the liquid - phase effluent II to obtain a gas - phase effluent IV, water, and a liquid - phase effluent IV;

[0091] S53: Mix the gas - phase effluent IV with the liquid - phase effluent III for a third separation to obtain a gas - phase effluent V, water, and a liquid - phase effluent V;

[0092] S54: Fractionate the liquid - phase effluent V and the liquid - phase effluent IV to obtain a diesel fraction.

[0093] Preferably, the method further includes: introducing the gas - phase effluent III into step (4) to perform the hydroisomerization reaction with the liquid effluent I and at least part of the liquid hydrocarbons.

[0094] Preferably, the oil and fat raw material contains 1.0 - 500 μg / g of sulfur element, 10 - 15 wt% of oxygen element, and 1.0 - 500 μg / g of nitrogen content. Preferably, the oil and fat raw material is selected from at least one of animal and vegetable oils, fatty acids, fatty acid methyl esters, fatty alcohols, waste cooking oil, and algal oil. The present invention does not have specific limitations on the specific types of the animal and vegetable oils, waste cooking oil, and algal oil. For example, the vegetable oil can be coconut oil, palm oil, etc., and the waste cooking oil can be gutter oil, etc.

[0095] Preferably, the method further includes: before introducing the oil and fat raw material into the hydrotreating equipment for the first hydrotreating, first sulfiding the monolithic hydrotreating catalyst, the hydrotreating catalyst A, and the hydroisomerization catalyst. The sulfiding operation includes: in the presence of a medium and hydrogen, carrying out a sulfiding reaction between the catalyst to be sulfided and a sulfiding agent to obtain a sulfided catalyst.

[0096] Preferably, the conditions of the sulfiding reaction at least satisfy: the reaction temperature is 310 - 330 °C, and the reaction time is 4 - 12 h.

[0097] 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.

[0098] In the present invention, the sulfiding agent can be at least one of H2S, CS2, dimethyl disulfide (DMDS), or other sulfur-containing organic compounds.

[0099] The present invention combines Figure 3 to provide a preferred process flow for producing a biodiesel fraction from an oil and fat raw material; specifically:

[0100] First, introduce hydrogen into the heating furnace to make each reactor filled with hydrogen and circulate, and then sulfide the monolithic hydrotreating catalyst, the hydrotreating catalyst A, and the hydroisomerization catalyst. Then introduce the oil and fat raw material 1 and hydrogen 2 into the heating furnace 3 and heat to 220 - 300 °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 5 filled in the oil and gas pipeline. The material after the hydrotreating reaction exchanges heat 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 for hydrotreating reaction and heat exchange 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, and then the material flows out to obtain the hydrotreating effluent I;

[0101] The hydrotreated effluent I is introduced into a fixed-bed reactor 7 filled with a hydrotreating catalyst A for a second hydrotreating to obtain a hydrotreated effluent II, and the hydrotreated effluent II is introduced into a hot 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 I 11, water 12, and a gas-phase effluent I 13; the liquid effluent I 11, at least a part of the liquid hydrocarbon 10, and hydrogen 15 are introduced into a hydroisomerization reactor 16 to carry out a hydroisomerization reaction with a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent; the gas-phase effluent I 13 is passed through a gas treatment unit 14 to remove CO and CO2 to obtain a recycled gas, and the recycled gas is returned to a heating furnace and then enters the hydrotreating equipment for recycling;

[0102] The hydroisomerization reaction effluent is subjected to gas-liquid separation in a 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 a cold high-pressure separator 18 for a 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 a part of the liquid hydrocarbon 10, and hydrogen 15;

[0103] The liquid-phase effluent II 19 is introduced into a hot 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 from the upper outlet of the fractionating tower 22, and diesel is obtained from the lower outlet (only the main equipment listed in the figure is shown, and other auxiliary equipment such as valves and pumps are ignored).

[0104] Compared with the prior art, the present solution has the following advantages:

[0105] (1) In the present invention, the reaction module filled with the monolithic hydrotreating catalyst is connected to the heat exchange module, which can remove the heat released by the first hydrotreating of the oil-based raw material from the reaction system, enabling the hydrotreating reaction to occur within an appropriate temperature range, avoiding the generation of side reactions, and improving the conversion rate of the oil-based raw material. At the same time, effective heat exchange can be achieved without adopting a product circulation method several times that of the oil-based raw material, significantly reducing the production energy consumption.

[0106] (2) A hydrotreating catalyst A 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, some nitrides, resins, and other substances in the oil are completely reacted, avoiding affecting the subsequent hydroisomerization reaction.

[0107] (3) A non-noble metal hydroisomerization catalyst is used in the hydroisomerization reaction process, which has good isomerization selectivity.

[0108] The present invention will be described in detail below through examples.

[0109] In the following examples and comparative examples, a 3271E type X-ray fluorescence spectrometer purchased from Rigaku Corporation of Japan was used to determine the content of each element in the catalyst.

[0110] The liquid hydrocarbon distillation range was determined with reference to the ASTM 2887 method.

[0111] The hydrotreating catalyst A is the RJW-3 catalyst. Based on the total weight of the hydrotreating catalyst A, the content of the first metal element (type: nickel) in terms of oxide is 3.2% by weight, and the content of the second metal elements (types: molybdenum and tungsten) in terms of oxide is 0.8% by weight (molybdenum) and 22.2% by weight (tungsten), and it is produced by Changling Catalyst Branch of Sinopec Catalyst Company.

[0112] In the examples, the monolithic hydrotreating catalyst was prepared by using the aforementioned method for preparing the monolithic hydrotreating catalyst.

[0113] The following In Example 1 There are four serially connected hydrotreating units in the hydrotreating equipment. Along the flow direction of the liquid phase stream,

[0114] In the first (uppermost stream) hydrotreating unit, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst is 5% by weight, the porosity is 70%, and the number of pores per square centimeter is 25;

[0115] In the second hydrotreating unit, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst is 10% by weight, the porosity is 68%, and the number of pores per square centimeter is 45;

[0116] In the third hydrotreating unit, the loading of the carrier and the active component in the monolithic hydrotreating catalyst is 15% by weight, the porosity is 67%, and the number of pores per square centimeter is 60;

[0117] In the fourth (lowermost stream) hydrotreating unit, the loading amount of the carrier and the active component in the monolithic hydrotreating catalyst is 25% by weight, the porosity is 65%, and the number of pores per square centimeter is 100.

[0118] In Example 2 There are three serially connected hydrotreating units in the hydrotreating equipment. Along the flow direction of the liquid phase stream,

[0119] In the monolithic hydrotreating catalyst in the first hydrotreating unit, the loading amount of the carrier and the active component is 10% by weight, the porosity is 68%, and the number of pores per square centimeter is 45;

[0120] In the monolithic hydrotreating catalyst in the second hydrotreating unit, the loading amount of the carrier and the active component is 15% by weight, the porosity is 67%, and the number of pores per square centimeter is 60;

[0121] In the monolithic hydrotreating catalyst in the third (the most downstream) hydrotreating unit, the loading amount of the carrier and the active component is 25% by weight, the porosity is 65%, and the number of pores per square centimeter is 100.

[0122] Yield of biodiesel = mass of diesel / mass of 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 = (sum of the mass of diesel and 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 catalyst as 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% by weight 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 each reactor are sulfided first.

[0129] Example 1

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

[0131] (1) Introduce the oil and fat raw materials 1 and hydrogen 2 into the heating furnace 3 and heat them to 250 °C. After mixing in the mixer 4, introduce them into the upstream hydrotreating unit and carry out a hydrotreating reaction with the monolithic hydrotreating catalyst 5 filled in the oil and gas transmission pipe. The material after the hydrotreating reaction exchanges heat with the raw material or other medium through the heat exchanger 6. Then introduce the heat-exchanged material into the adjacent next (second) hydrotreating unit to successively carry out the hydrotreating reaction and heat exchange. Introduce the material heat-exchanged in the second hydrotreating unit into the third hydrotreating unit to successively carry out the hydrotreating reaction and heat exchange. Then introduce the material heat-exchanged in the third hydrotreating unit into the fourth (downstream) hydrotreating unit to successively carry out the hydrotreating reaction and heat exchange to obtain the hydrotreating effluent I;

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

[0133] 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 260 °C, and the outlet temperature is 310 °C; the inlet temperature of the reaction module in the third hydrotreating unit is 270 °C, and the outlet temperature is 315 °C; the inlet temperature of the reaction module in the fourth hydrotreating unit is 285 °C, and the outlet temperature is 320 °C; the sum of the temperature rises of each reaction module is 180 °C;

[0134] (2) Introduce the hydrotreating effluent I into the fixed-bed reactor 7 filled with the hydrotreating catalyst A for the second hydrotreating to obtain the hydrotreating effluent II;

[0135] Among them, the inlet temperature of the fixed-bed reactor is 290 °C, and the outlet temperature is 330 °C;

[0136] The weight ratio of the active component content of the monolithic hydrotreating catalyst to the hydrotreating catalyst A is 1:1.5;

[0137] (3) Introduce the hydrotreating effluent II into the hot high-pressure separator 8 for gas-liquid separation to obtain the liquid hydrocarbon 10, water, and gas stream. Let the gas stream enter the cold high-pressure separator 9 for gas-liquid separation to obtain the liquid effluent I11, water 12, and gas-phase effluent I13. After the gas-phase effluent I13 removes CO and CO2 through the gas treatment unit 14, the recycled gas is obtained for recycling;

[0138] Among them, the conversion rate of the oil-based raw material is 100%, the final boiling point temperature of the liquid hydrocarbon is 330 °C, the sulfur content in the liquid hydrocarbon is 1 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbon is 77% by weight;

[0139] The content of CO in the recycle gas obtained after the gas treatment unit removes CO and CO2 is 0.03% by volume, and the content of CO2 is 0.07% by volume;

[0140] (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 a hydroisomerization reaction with the sulfided hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0141] Among them, the conditions of the hydroisomerization reaction are: 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 98% by weight;

[0142] (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;

[0143] 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 hydrocarbon 10, and hydrogen 15;

[0144] Introduce the liquid-phase effluent II 19 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; introduce the gas-phase effluent IV and the liquid-phase effluent III 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 introduce the liquid-phase effluent V and the liquid-phase effluent IV 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;

[0145] Among them, the diesel fraction yield is 91% by weight, the pour point and cold filter plugging point are -14 °C and -8 °C respectively, which can meet the requirements of No. -10 diesel.

[0146] Example 2

[0147] In this example, waste cooking oil is used as the oil-based raw material. The main properties of the waste cooking oil are shown in Table 1. The following is the production of the biodiesel fraction using the Figure 3 shown process flow. Specifically as follows:

[0148] (1) Introduce the oil and fat raw material 1 and hydrogen 2 into the heating furnace 3 and heat to 270 °C. After mixing in the mixer 4, introduce them into the uppermost hydrotreating unit, and carry out a hydrotreating reaction with the monolithic hydrotreating catalyst 5 filled in the oil and gas pipeline. The material after the hydrotreating reaction is heat-exchanged with the raw material or other media in 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. The obtained material is introduced into the third (lowermost) hydrotreating unit to obtain the hydrotreating effluent I;

[0149] 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 ,

[0150] Among them, the inlet temperature of the reaction module in the first (uppermost) hydrotreating unit is 270 °C, and the outlet temperature is 320 °C; the inlet temperature of the reaction module in the second hydrotreating unit is 280 °C, and the outlet temperature is 330 °C; the inlet temperature of the reaction module in the third (lowermost) hydrotreating unit is 295 °C, and the outlet temperature is 330 °C; the sum of the temperature rises of each reaction module is 135 °C;

[0151] (2) Introduce the hydrotreating effluent I into the fixed-bed reactor 7 filled with the hydrotreating catalyst A to carry out the second hydrotreating to obtain the hydrotreating effluent II;

[0152] Among them, the inlet temperature of the fixed-bed reactor is 300 °C, and the outlet temperature is 340 °C;

[0153] The weight ratio of the content of the active components of the monolithic hydrotreating catalyst to the hydrotreating catalyst A is 1:1.5;

[0154] (3) Introduce the hydrotreating 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 12, and gas-phase effluent I13; after removing CO and CO2 from the gas-phase effluent I13 through the gas treatment unit 14, obtain the recycle gas for recycling;

[0155] Among them, the conversion rate of the oil and fat raw material is 100%, the final boiling point temperature of the liquid hydrocarbon is 375 °C, the sulfur content in the liquid hydrocarbon is 5 mg / kg, and the nitrogen content is 5 mg / kg; the yield of the liquid hydrocarbon is 82% by weight;

[0156] After the gas treatment unit 14 removes CO and CO2, the CO content in the recycled gas is 0.05% by volume, and the CO2 content is 0.09% by volume;

[0157] (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 a hydroisomerization reaction with the sulfided hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0158] Among them, the conditions of the hydroisomerization reaction are: 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;

[0159] (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;

[0160] 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 hydrocarbon 10, and hydrogen 15;

[0161] Introduce the liquid-phase effluent II 19 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; introduce the gas-phase effluent IV and the liquid-phase effluent III 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 introduce the liquid-phase effluent V and the liquid-phase effluent IV 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;

[0162] Among them, the diesel fraction yield is 90% by weight, the freezing point and cold filter plugging point are -11 °C and -6 °C respectively, and it can meet the requirements of -10 diesel.

[0163] Example 3

[0164] Coconut oil is used as the oil raw material. The main properties of coconut oil are shown in Table 1. This example uses a method similar to that of Example 1 to prepare biodiesel, and the differences are as follows:

[0165] In step (1), there is only one hydrotreating unit in the hydrotreating equipment. The loading amount of the active component and the carrier of the monolithic hydrotreating catalyst in the hydrotreating unit is 10% by weight, the porosity is 70, and the number of pores per square centimeter is 25;

[0166] Conditions for the first hydrotreating: The inlet reaction pressure of the uppermost hydrotreating unit is 6.4 MPa, and the hydrogen-to-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 ;

[0167] Among them, the inlet temperature of the reaction module in the first hydrotreating unit is 250 °C, and the outlet temperature is 450 °C; the sum of the temperature rises of each reaction module is 200 °C;

[0168] (2) Introduce the hydrotreating effluent I into the fixed-bed reactor 7 filled with the hydrotreating catalyst A for the second hydrotreating to obtain the hydrotreating effluent II;

[0169] Among them, the inlet temperature of the fixed-bed reactor is 290 °C, and the outlet temperature is 320 °C;

[0170] The weight ratio of the content of the active components of the monolithic hydrotreating catalyst to the hydrotreating catalyst A is 1:1.5;

[0171] The remaining steps are the same as those in Example 1;

[0172] 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 330 °C, the sulfur content in the liquid hydrocarbon is 1 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbon is 73% by weight;

[0173] The CO content in the recycled gas obtained after the gas treatment unit removes CO and CO2 is 0.03% by volume, and the CO2 content is 0.07% by volume;

[0174] In step (4), the yield of the hydroisomerization reaction effluent is 98% by weight;

[0175] In step (5), the diesel fraction yield is 91% by weight, and the pour point and cold filter plugging point are -14 °C and -8 °C respectively, which can meet the requirements of -10 diesel.

[0176] Compared with Example 1, in the first hydrotreating process of this example, due to the lack of continuous heat exchange, the reaction temperature continuously rises, resulting in a relatively high reaction temperature, the reactor is blocked by oil and fat condensation in a short time, the catalyst is also rapidly deactivated, and at the same time, the yield of liquid hydrocarbon decreases.

[0177] Comparative Example 1

[0178] Using coconut oil as the oil and fat raw material, the main properties of coconut oil are shown in Table 1. This comparative example uses a method similar to that in Example 1 to prepare biodiesel, and the differences are as follows:

[0179] In this comparative example, the first hydrotreating and heat exchange treatments in step (1) are not carried out, and hydrogen and an oil raw material are directly introduced into a fixed-bed reactor filled with hydrotreating catalyst A for the second hydrotreating; specifically, in this comparative example:

[0180] SS1: In the presence of hydrogen, an oil raw material (the same type as the coconut oil raw material in Example 1) and the liquid hydrocarbon obtained in SS2 are introduced into a fixed-bed reactor filled with hydrotreating catalyst A for the second hydrotreating reaction to obtain a hydrotreating effluent II;

[0181] The weight ratio of the liquid hydrocarbon to the coconut oil is 3.5:1;

[0182] Among them, before the second hydrogenation reaction, hydrotreating catalyst A and hydroisomerization catalyst are sulfided;

[0183] 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 355 °C.

[0184] SS2: The hydrotreating effluent I is introduced into a hot 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 12, and a gas-phase effluent I13; the gas-phase effluent I13 is passed through a gas treatment unit 14 to remove CO and CO2 to obtain a recycled gas, and this recycled gas is recycled;

[0185] Among them, the conversion rate of the oil raw material is 100%, the final boiling point temperature of the liquid hydrocarbon is 330 °C, the sulfur content in the liquid hydrocarbon is 1 mg / kg, and the nitrogen content is 1 mg / kg; the yield of the liquid hydrocarbon is 76.8 wt%; the CO content in the recycled gas is 0.03 vol%, and the CO2 content is 0.07 vol%;

[0186] The remaining steps are the same as those in Example 1;

[0187] The final diesel fraction yield is 91 wt%, and the freezing point and cold filter plugging point are -14 °C and -8 °C respectively, which can meet the requirements of -10 diesel.

[0188] As can be seen from the above results, although Comparative Example 1 can obtain No. -10 diesel that meets the requirements, in order to control the reaction temperature rise, avoid carbon deposition blockage at the reactor inlet, and prevent more decarbonylation, decarboxylation reactions, and thermal cracking reactions from occurring at high temperatures, resulting in a lower liquid hydrocarbon yield, 3.5 times the liquid hydrocarbon needs to be recycled at the reactor inlet, leading to high production energy consumption and poor economy.

[0189] Comparative Example 2

[0190] Using waste cooking oil as the oil raw material, the main properties of the waste cooking oil are shown in Table 1. This comparative example uses a method similar to that of Example 2 to prepare biodiesel. The differences are as follows:

[0191] In this comparative example, the second hydrogenation treatment in step (2) is not carried out, and the hydrogenation treatment effluent I obtained in step (1) is directly introduced into the hot high-pressure separator for gas-liquid separation;

[0192] The remaining steps are the same as those in Example 2;

[0193] In step (3), the conversion rate of the oil raw material is 99.9%, the final boiling point temperature of the liquid hydrocarbon is 380°C, the sulfur content in the liquid hydrocarbon is 8 mg / kg, and the nitrogen content is 18 mg / kg;

[0194] The yield of the liquid hydrocarbon is 82% by weight; the CO content in the recycle gas is 0.05% by volume, and the CO2 content is 0.09% by volume;

[0195] In step (4), the yield of the hydroisomerization reaction effluent is 97% by weight;

[0196] In step (5), the diesel fraction yield is 90% by weight, and the freezing point and cold filter plugging point are -6°C and 1°C respectively, which cannot meet the requirements of No. -10 diesel.

[0197] In this comparative example, due to the absence of the second hydrogenation treatment unit, the reaction activity is insufficient, and a small amount of oxygen-containing compounds and nitrogen compounds do not react and enter the isomerization unit, resulting in a decrease in the activity of the isomerization catalyst. Under the same reaction conditions, the freezing point and cold filter plugging point of the diesel product do not meet the requirements of No. -10 diesel.

[0198] Table 1

[0199] Item Coconut oil Waste oil <![CDATA[Density (20 °C), g / cm 3 > 922.5 904.9 Sulfur content, μg / g 2.2 162 Nitrogen content, μg / g 2.0 250 Oxygen content, % 14.0 10.9 Total acid value, mgKOH / g 0.12 89

[0200] As can be seen from the examples, by using the method of the present invention, the temperature rise of the reactor can be effectively controlled, and biodiesel can be produced using coconut oil or waste cooking oil as the raw material, which can meet the requirements of No. -10 diesel, effectively solving the problems of large heat release during the biodiesel hydrogenation treatment process, easy blockage at the top, and the need for a large amount of product recycling, and realizing the long-term operation of the device.

[0201] 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 biodiesel fractions from oil-based 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, so that the material can sequentially undergo a hydrogenation reaction and heat exchange in each of the hydrotreating units; an integral hydrotreating catalyst is loaded in each of the reaction modules; the porosity of the integral hydrotreating catalyst 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 loaded with a hydrotreating catalyst A for a second hydrotreating to obtain a hydrotreating effluent II; (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.

2. The method according to claim 1, wherein, In step (1), the active components in the integral hydrotreating catalyst contain a first metal element and a second metal element.

3. The method according to claim 2, wherein In step (1), the first metal element is cobalt and / or nickel, and the second metal element is molybdenum and / or tungsten.

4. The method according to claim 2, wherein, Based on the total weight of the integral hydrotreating catalyst, the content of the first metal element in terms of oxide is 0.02 - 3 wt%, and the content of the second metal element in terms of oxide is 0.1 - 12 wt%.

5. The method according to any one of claims 1-4, wherein, In step (1), the reaction module is an oil and gas delivery pipe loaded with the integral hydrotreating catalyst, and the heat exchange module is a heat exchanger.

6. The method according to any one of claims 1-4, wherein In step (1), in each reaction module, the inlet temperature is independently 250 - 300 °C, and the outlet temperature is independently 300 - 380 °C, and / or In step (1), the sum of the temperature rises of each of the reaction modules is 80 - 220 °C.

7. The method according to any one of claims 1-4, wherein, In step (2), the active components in the hydrotreating catalyst A contain a third metal element and a fourth metal element; the third metal element is cobalt and / or nickel; the fourth metal element is molybdenum and / or tungsten.

8. The method according to claim 7, wherein Based on the total weight of the hydrotreating catalyst A, 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%.

9. The method according to claim 8, wherein, The weight ratio of the active component content of the integral hydrotreating catalyst to the hydrotreating catalyst A is 1:0.5 - 1.

5.

10. The method according to any one of claims 1-4, 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 1-4, wherein, In step (1), the first hydrotreating conditions include: 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 total volume space velocity is 0.5 - 10 h -1 .

12. The method according to any one of claims 1-4, wherein, The 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 hydrocarbons; Remove CO and CO2 from the gas-phase effluent I through a gas treatment unit to obtain a recycle gas; S33: Introduce the recycle gas into the hydrotreating equipment to carry out the first hydrotreating and heat exchange treatment with hydrogen and an oil-based raw material.

13. The method according to claim 12, wherein, Control the reaction conditions of the gas treatment unit such that the CO content in the recycle gas obtained in step S32 is less than or equal to 0.05% by volume, and the CO2 content is less than or equal to 0.1% by volume.

14. The method according to any one of claims 1 to 4, wherein, The liquid hydrocarbons in step (3) can be used as a diesel blending component with a high cetane number.

15. The method according to any one of claims 1 to 4, wherein In step (4), the hydroisomerization catalyst contains a support and an active metal component.

16. The method according to claim 15, wherein, In the hydroisomerization catalyst, the support is alumina and / or silica-alumina.

17. The method according to claim 15, wherein, In the hydroisomerization catalyst, the support is alumina and silica-alumina; and based on the total weight of the support, the content of alumina is 5-95% by weight, and the content of silica-alumina is 5-95% by weight.

18. The method according to claim 16 or 17, wherein, 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.

19. The method according to claim 15, wherein The active metal component contains a fifth metal element and a sixth metal element, and the fifth metal element is cobalt and / or nickel, and the sixth metal element is molybdenum and / or tungsten.

20. The method according to claim 19, wherein, Based on the total weight of the hydroisomerization catalyst, the content of the fifth metal element in terms of oxide is 1-10% by weight, and the content of the sixth metal element in terms of oxide is 5-40% by weight.

21. The method according to claim 20, wherein Based on the total weight of the hydroisomerization catalyst, the content of the fifth metal element in terms of oxide is 2-8% by weight, and the content of the sixth metal element in terms of oxide is 10-35% by weight.

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

23. The method according to claim 22, wherein, In step (4), the conditions of 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-to-oil volume ratio is 500 - 1000 Nm 3 / m 3 .

24. The method according to any one of claims 1-4, wherein The oil-based raw material contains 1.0-500 μg / g of sulfur element, 10-15 wt% of oxygen element, and 1.0-500 μg / g of nitrogen content.

25. The method according to claim 24, wherein, The oil-based raw material is selected from at least one of vegetable and animal oils, fatty acids, fatty acid methyl esters, waste cooking oil, and algal oil.

26. The method according to any one of claims 1-4, wherein, The method further includes: Before introducing the oil-based raw material into the hydrotreating equipment to carry out the first hydrotreating, first sulfide the monolithic hydrotreating catalyst, the hydrotreating catalyst A, 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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