A method for producing biodiesel by combining a tubular reactor and a fixed bed reactor

Abstract

The present invention relates to the field of biofuel production and discloses a method for producing biodiesel by combining a shell-and-tube reactor and a fixed-bed reactor, comprising: (1) introducing an oil-based raw material into a shell-and-tube reactor in the presence of hydrogen for a first hydrotreatment to obtain a hydrotreatment effluent I; (2) introducing the hydrotreatment effluent I into a fixed-bed reactor in the presence of hydrogen for a second hydrotreatment to obtain a hydrotreatment effluent II; (3) subjecting the hydrotreatment effluent II to separation I to obtain a liquid hydrocarbon stream, water, and a gas stream; (4) subjecting at least a portion of the liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent; and (5) subjecting the hydroisomerization reaction effluent to separation II to obtain biodiesel. The method provided by the present invention has a simple process, a complete reaction, low energy consumption, and good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the field of biofuel production, and in particular to a method for producing biodiesel by combining a tubular reactor and a fixed bed reactor. Background Art

[0002] As the supply of traditional fossil energy sources becomes increasingly tight, the pressure to reduce carbon dioxide emissions continues to grow. How to effectively reduce carbon dioxide emissions while increasing fuel supply is a critical issue facing the refining industry. However, biofuels are produced from renewable biomass such as animal and vegetable oils or agricultural and forestry waste, and their greenhouse gas emissions over their entire life cycle are significantly lower than those of fossil fuels.

[0003] Therefore, the development of biomass fuels is considered to be one of the effective means to solve this problem.

[0004] Vegetable oil is the most readily available biofuel, primarily composed of triglycerides and small amounts of free fatty acids. The use of vegetable oil in diesel engines dates back to 1900, when Rudolf Diesel demonstrated the ability of peanut oil to operate in a diesel engine. However, subsequent developments in fuel technology led to petroleum becoming the primary energy source, particularly with significant improvements in diesel engine injectors and control systems, resulting in a single source of diesel fuel. Furthermore, the high viscosity, poor stability, and high cost of pure vegetable oil also limited its use as a transportation fuel.

[0005] The traditional method of converting vegetable oils or other fatty acid derivatives into liquid fuels is transesterification. However, the fatty acid methyl esters formed by transesterification have poor low-temperature fluidity, making them difficult to use in low-temperature environments. The carbon-carbon double bond can improve the low-temperature fluidity of fatty acid methyl esters, but it reduces their stability. At the same time, the presence of oxygen in fatty acid methyl esters causes them to emit more NO than traditional diesel fuel. x .

[0006] like Figure 1 As shown in Figure 1, hydrogenation of vegetable oil (palm oil as an example) can effectively solve the above problems. The reaction process mainly includes double bond saturation, direct hydrogenation deoxygenation, hydrogenation decarboxylation and hydrogenation decarbonylation reactions.

[0007] This series of reactions is typically carried out in a fixed-bed reactor. However, because the reaction releases a significant amount of heat and the reaction rates vary widely, if the temperature rise is not controlled by product recirculation or large amounts of cold hydrogen, the total reactor temperature rise will exceed 200°C, resulting in an inability to continue the reaction for a long time and poor product quality. Therefore, existing technologies often use combined processing with mineral oil or large-scale product recirculation to control the temperature.

[0008] Furthermore, oils and fats have high molecular weights, high viscosities, and high boiling points. Under fixed-bed hydroprocessing conditions, these materials coat the catalyst surface in a liquid film, and hydrogen must dissolve within this film for the hydrogenation reaction to proceed. However, some reactions during hydroprocessing consume the dissolved hydrogen in a short period of time, resulting in a lack of hydrogen in the liquid film. Furthermore, oils and fats are prone to polymerization, which can cause blockage at the top of the reactor, increasing the bed pressure drop and preventing long-term operation.

[0009] CN111100703A discloses a method for hydrodeoxygenation of bio-oil. This method involves introducing bio-oil into a hot, high-pressure separator, where it contacts a catalyst contained within the separator to undergo olefin saturation and shallow hydrodeoxygenation. This method utilizes the reactor effluent as a diluent, avoiding catalyst deactivation caused by excessive heat release during the bio-oil reaction and ensuring long-term stable operation of the device. However, this method consumes a high amount of energy because a large amount of unreacted oil must be recycled back to the reactor inlet after fractionation in the distillation tower.

[0010] CN106281401A discloses a method for producing aviation biofuel from waste animal and plant oils. This method pre-treats the feedstock oil, then conducts a hydrogenation reaction in a hydroprocessing unit. The effluent is degassed and dehydrated, and then subjected to hydroconversion and rectification to produce high-quality aviation kerosene. However, this method requires recycling the generated liquid phase back to the hydroprocessing unit inlet to prevent excessive temperature rise in the hydroprocessing unit, which can lead to catalyst deactivation and reduced product quality. Therefore, this method is complex to operate and has high energy consumption.

[0011] CN109294746A discloses a method for producing a diesel fraction by hydrogenating oil and fat feedstock. This method sequentially reacts the oil and fat feedstock with two different types of hydrotreating catalysts to produce liquid hydrocarbons, which are then reacted with a hydroisomerization catalyst to produce biodiesel with a low pour point and a high cetane number. However, this method also requires large amounts of cold hydrogen and circulating oil in the hydrotreating unit to control temperature rise, resulting in excessively high energy consumption during the production process.

[0012] Therefore, the defects of the existing technology, such as complex process, incomplete reaction, and high energy consumption in production, are urgently needed to be solved in the field of biofuels. Summary of the Invention

[0013] The purpose of the present invention is to overcome the defects of the prior art in that a large amount of product circulation is required to control the reaction temperature rise, resulting in complex process and high production energy consumption.

[0014] To achieve the above objectives, the present invention provides a method for producing biodiesel using a combination of a tubular reactor and a fixed bed reactor. The method comprises:

[0015] (1) In the presence of hydrogen, an oil and fat feedstock is introduced into a shell-and-tube reactor for a first hydrotreatment to obtain a hydrotreatment effluent I, wherein each tube of the shell-and-tube reactor is filled with a hydrotreatment catalyst I, wherein the hydrotreatment catalyst I is a monolithic hydrotreatment catalyst;

[0016] (2) In the presence of hydrogen, introducing the hydroprocessing effluent I into a fixed bed reactor filled with a hydroprocessing catalyst II for a second hydroprocessing to obtain a hydroprocessing effluent II;

[0017] (3) separating the hydroprocessing effluent II to obtain a liquid hydrocarbon stream, water, and a gas stream;

[0018] (4) subjecting at least a portion of the liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0019] (5) Separating the hydroisomerization reaction effluent II to obtain biodiesel.

[0020] The method for producing biodiesel by combining a tubular reactor and a fixed bed reactor provided by the present invention can control the total temperature rise of the reaction system without using a large amount of cold hydrogen and product circulation. The production process has low energy consumption, complete reaction, good product properties, and good industrial application prospects.

[0021] The solution of the present invention also has the following specific advantages:

[0022] (1) By using a shell-and-tube reactor, the large amount of heat released by the hydrogenation reaction of oil and fat raw materials can be removed from the reaction system through heat exchange, allowing the hydrogenation reaction to proceed within a suitable temperature range and avoiding the occurrence of side reactions. At the same time, effective heat exchange avoids the use of a product circulation method that is several times that of the oil and fat raw materials, significantly reducing energy consumption.

[0023] (2) An integral hydroprocessing catalyst is used in the shell-and-tube reactor. By adjusting the porosity and pore size of the catalyst, the rate of the hydrogenation reaction of the oil and fat raw materials is adjusted, thereby avoiding large-scale local heat release and local hydrogen deficiency, and avoiding oil condensation and catalyst bed blockage. In addition, the total temperature rise of the reaction system can be controlled without using a large amount of cold hydrogen and product circulation.

[0024] (3) A fixed-bed hydrotreating reactor is set up after the shell-and-tube reactor. The reactor is filled with a catalyst with a high active metal content and a lower bed porosity, which provides sufficient active sites and ensures the complete reaction of some difficult-to-react oxides and some nitrides, colloids and other substances in the oil raw materials.

[0025] (4) The hydroisomerization step uses a non-precious metal catalyst and has good isomerization selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic flow chart of a method for producing biodiesel by combining a tubular reactor and a fixed bed reactor, as shown in a preferred embodiment of the present invention;

[0027] Figure 2 It is a structural schematic diagram of a monolithic honeycomb ceramic shown in a preferred embodiment provided by the present invention.

[0028] Description of Reference Numerals

[0029] 1. Oil and fat raw materials 2. Hydrogen

[0030] 3 Heating furnace 4 Mixer

[0031] 5 Shell and Tube Reactor 6 Monolithic Hydroprocessing Catalyst

[0032] 7 Fixed bed hydroprocessing reactor 8 Hot high pressure separator I

[0033] 9 Cold high pressure separator I 10 Liquid hydrocarbon flow

[0034] 11 Liquid phase I 12 Sulfur-containing wastewater

[0035] 13 Gas Phase 14 Gas Handling System

[0036] 15 Hydrogen 16 Hydroisomerization Reactor

[0037] 17 Hot High Pressure Separator II 18 Cold High Pressure Separator II

[0038] 19 Liquid Phase II 20 Hot Low-Pressure Separator

[0039] 21 Cold low pressure separator 22 Fractionation tower DETAILED DESCRIPTION

[0040] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0041] As mentioned above, the first aspect of the present invention provides a method for producing biodiesel by combining a tubular reactor and a fixed bed reactor, the method comprising:

[0042] (1) In the presence of hydrogen, an oil and fat feedstock is introduced into a shell-and-tube reactor for a first hydrotreatment to obtain a hydrotreatment effluent I, wherein each tube of the shell-and-tube reactor is filled with a hydrotreatment catalyst I, wherein the hydrotreatment catalyst I is a monolithic hydrotreatment catalyst;

[0043] (2) In the presence of hydrogen, introducing the hydroprocessing effluent I into a fixed bed reactor filled with a hydroprocessing catalyst II for a second hydroprocessing to obtain a hydroprocessing effluent II;

[0044] (3) separating the hydroprocessing effluent II to obtain a liquid hydrocarbon stream, water, and a gas stream;

[0045] (4) subjecting at least a portion of the liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0046] (5) Separating the hydroisomerization reaction effluent II to obtain biodiesel.

[0047] In order to improve the conversion rate of the reaction, the method also includes: before entering the shell and tube reactor, the oil and fat raw materials and hydrogen are first heated in a heating furnace, and then mixed in a mixer before entering the shell and tube reactor for a first hydrogenation reaction. The mixer can be exemplarily selected from at least one of a static mixer, a microbubble generator and a swirl shear mixer.

[0048] According to a preferred specific embodiment, the method further includes: passing the low-temperature oil and fat raw materials and / or hydrogen through the tubes of the shell-and-tube reactor for heat exchange before entering the heating furnace. The inventors have found that in this preferred case, the low-temperature oil and fat raw materials passing through the tubes are heat exchanged with the reactants in the tubes, which can further reduce the energy consumption of the reaction system.

[0049] Preferably, the hydrotreating catalyst I, the hydrotreating catalyst II and the hydroisomerization catalyst are each independently selected from a catalyst A having the following characteristics:

[0050] The catalyst A contains active components; the active metal elements in the active components include a first metal element and a second metal element; the first metal element is cobalt and / or nickel; and the second metal element is molybdenum and / or tungsten.

[0051] Preferably, in step (1), the monolithic hydroprocessing catalyst comprises a support, a carrier, and an active component, and the loading amount of the carrier and the active component is 1-40 wt % based on the total weight of the monolithic hydroprocessing catalyst. More preferably, in step (1), the loading amount of the carrier and the active component is 2-32 wt % based on the total weight of the monolithic hydroprocessing catalyst.

[0052] In order to improve the conversion rate of the hydrogenation reaction and the purity of biodiesel, the present invention preferably provides a method for preparing an integral hydroprocessing catalyst, the method comprising:

[0053] S1: impregnating the support into a carrier slurry to obtain an intermediate I; the carrier slurry contains a material forming a carrier of the monolithic hydroprocessing catalyst;

[0054] S2: The intermediate I is immersed in a solution containing active components, and the monolithic hydroprocessing catalyst is obtained after drying.

[0055] According to a preferred embodiment, in the present invention, the support body is a monolithic honeycomb ceramic made of cordierite. Figure 2 FIG. 3 shows a structure of a monolithic honeycomb ceramic made of cordierite material according to a preferred embodiment.

[0056] Preferably, in the method for preparing the integral hydroprocessing catalyst, the material forming the active component of the integral hydroprocessing catalyst is the material forming the active component in the RJW-3 catalyst; the material forming the carrier of the integral hydroprocessing catalyst is the material forming the carrier in the RJW-3 catalyst.

[0057] That is, preferably, the monolithic hydroprocessing catalyst of the present invention can have the catalytic function of the RJW-3 catalyst and is formed on the support of the present invention.

[0058] Preferably, the weight ratio of the active component to the support in the monolithic hydroprocessing catalyst is consistent with the weight ratio of the active component to the support in the RJW-3 catalyst.

[0059] Preferably, the outer diameter of the support body is 4-10 cm.

[0060] Preferably, in the shell-and-tube reactor, the porosity of the monolithic hydroprocessing catalyst is greater than or equal to 65%.

[0061] It should be noted that, in the present invention, the porosity of the monolithic hydroprocessing catalyst = the pore area through which the material can flow / the cross-sectional area of the monolithic hydroprocessing catalyst.

[0062] Preferably, in the shell-and-tube reactor, along the flow direction of the liquid phase flow, the porosity of the monolithic hydroprocessing catalyst decreases successively, and the number of pores per square centimeter increases successively.

[0063] Preferably, at least two reaction zones are provided in the shell-and-tube reactor, the porosity of the monolithic hydroprocessing catalyst in each of the reaction zones is the same, and along the flow direction of the liquid phase logistics, the porosity of the monolithic hydroprocessing catalyst in the upstream reaction zone is 1-5% higher than the porosity of the monolithic hydroprocessing catalyst in the adjacent downstream reaction zone.

[0064] Preferably, at least two reaction zones are provided in the shell-and-tube reactor, the number of pores per square centimeter of the monolithic hydroprocessing catalyst in each of the reaction zones is the same, and along the flow direction of the liquid phase stream, the number of pores per square centimeter of the monolithic hydroprocessing catalyst in the upstream reaction zone is 10-50 less than the number of pores per square centimeter of the monolithic hydroprocessing catalyst in the adjacent downstream reaction zone.

[0065] According to a particularly preferred embodiment, the shell-and-tube reactor is provided with four reaction zones, and the monolithic hydroprocessing catalyst is arranged such that, along the flow direction of the liquid phase stream, the carrier and active component loading in the first reaction zone is 4-6% by weight, and the number of pores per square centimeter is 22-27; the carrier and active component loading in the second reaction zone is 8-12% by weight, and the number of pores per square centimeter is 42-48; the carrier and active component loading in the third reaction zone is 13-18% by weight, and the number of pores per square centimeter is 55-65; and the carrier and active component loading in the fourth reaction zone is 22-28% by weight, and the number of pores per square centimeter is 80-100. In the present invention, the carrier and active component loading = the sum of the weight of the carrier and active component in the monolithic hydroprocessing catalyst / the total weight of the monolithic hydroprocessing catalyst * %.

[0066] According to a preferred embodiment, in step (1), based on the total weight of the integral hydroprocessing catalyst, the content of the first metal element calculated as oxide is 0.02-3 wt%, and the content of the second metal element calculated as oxide is 0.1-12 wt%.

[0067] Preferably, in step (2), in the hydroprocessing catalyst II in the fixed bed reactor, the content of the first metal element calculated as oxide is 1-10 wt%, and the content of the second metal element calculated as oxide is 5-40 wt%, based on the total weight of the hydroprocessing catalyst II.

[0068] Preferably, the outer diameter of the monolithic hydroprocessing catalyst is 3-5 mm smaller than the diameter of the tubes of the shell-and-tube reactor.

[0069] Preferably, the hydroprocessing catalyst II is RJW-3 catalyst.

[0070] Preferably, the weight ratio of the active component of the hydroprocessing catalyst I to the active component of the hydroprocessing catalyst II is 0.5-1.5:1, calculated as oxides.

[0071] Preferably, in step (4), the hydroisomerization catalyst further contains a carrier.

[0072] Preferably, in step (4), in the hydroisomerization catalyst, the carrier is alumina and / or silica-alumina.

[0073] Preferably, in step (4), the hydroisomerization catalyst further contains a carrier; the carrier is alumina and / or silica-alumina.

[0074] According to a preferred embodiment, the support comprises 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.

[0075] According to a preferred embodiment, the integral hydroprocessing catalyst and the hydroprocessing catalyst II further contain a carrier.

[0076] It should be noted that, in the present invention, when defining the composition and content of the catalyst, the total weight of the monolithic hydroprocessing catalyst includes the weight of the active component, the weight of the carrier and the weight of the support.

[0077] The total weight of the hydroprocessing catalyst II includes the weight of the active component and the weight of the support.

[0078] Preferably, in step (4), in the hydroisomerization catalyst, based on the total weight of the hydroisomerization catalyst, the content of the first metal element calculated as oxide is 1-10 weight%, and the content of the second metal element calculated as oxide is 5-40 weight%. More preferably, based on the total weight of the hydroisomerization catalyst, the content of the first metal element calculated as oxide is 2-8 weight%, and the content of the second metal element calculated as oxide is 10-35 weight%.

[0079] It should be noted that the hydroisomerization catalyst described in the present invention can be purchased or prepared by techniques known 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.

[0080] Preferably, in step (1), the inlet temperature of the shell-and-tube reactor is 250-340°C, the inlet pressure is 0.5-10 MPa, and the inlet hydrogen-to-oil volume ratio is 600-2000 Nm 3 / m 3 , the outlet temperature is 300-380°C, and the total temperature rise is 20-80°C; the total temperature rise represents the temperature difference between the inlet and outlet of the shell and tube reactor.

[0081] Preferably, in step (2), the inlet temperature of the fixed bed reactor is 280-360°C, the outlet temperature is 300-380°C, and the total temperature rise is 10-60°C; the total temperature rise represents the temperature difference between the inlet and outlet of the shell-and-tube reactor.

[0082] Preferably, the total volume space velocity of the first hydrotreatment and the second hydrotreatment is 0.5-10h -1 .

[0083] Preferably, in step (4), the conditions of the hydroisomerization reaction at least meet the following conditions: reaction temperature of 280-450°C, reaction pressure of 1.0-10.0 MPa, volume space velocity of 0.1-10.0 h -1 , hydrogen to oil volume ratio is 200-1500Nm 3 / m 3 More preferably, the conditions of the hydroisomerization reaction at least meet the following requirements: reaction temperature of 320-400°C, reaction pressure of 2.0-7.0 MPa, volume space velocity of 0.5-5.0 h -1 , hydrogen to oil volume ratio is 500-1000Nm 3 / m 3 .

[0084] Preferably, in the separation in step (3), the final boiling point temperature of the liquid hydrocarbon is 330-390°C.

[0085] Preferably, in step (3), the liquid hydrocarbon can be used as a diesel blending component with a high cetane number.

[0086] Preferably, in step (1), the oil raw material is selected from at least one of animal and plant oils, fatty acids, fatty acid methyl esters, fatty alcohols, slop oil, gutter oil, and algae oil.

[0087] Preferably, the oil raw material is coconut oil and / or waste cooking oil.

[0088] Preferably, the sulfur content in the oil and fat raw material is ≤0.05% by weight.

[0089] According to a preferred embodiment, the method further comprises: sulfiding the hydroprocessing catalyst I, the hydroprocessing catalyst II and the hydroisomerization catalyst, wherein the sulfiding operation comprises: subjecting the catalyst to be sulfided to a sulfiding reaction with a sulfiding agent in the presence of a medium and hydrogen to obtain a sulfided catalyst.

[0090] Preferably, the vulcanizing agent is selected from at least one of H2S, CS2, dimethyl disulfide (DMDS) or other sulfur-containing organic compounds.

[0091] Preferably, the medium is selected from at least one of biodiesel, biokerosene, petroleum-based diesel, and petroleum-based kerosene.

[0092] Preferably, the separation I and separation II are performed identically or independently using a hot high-pressure separator.

[0093] According to a preferred embodiment, the method further comprises, in step (3), introducing the gas stream obtained from the hot high-pressure separator into a cold high-pressure separator I for separation III, and then introducing the resulting liquid phase I together with the liquid hydrocarbon stream obtained from the hot high-pressure separator into a hydroisomerization reactor for hydroisomerization. The gas phase I obtained from the cold high-pressure separator I is post-treated to remove carbon monoxide and carbon dioxide, and then introduced into the system together with the oil and fat feedstock and hydrogen for recycling.

[0094] It should be noted that this application does not specify the post-treatment method. It is sufficient that the treated gas stream meets the following requirements: a carbon monoxide content of less than 0.05% by volume and a carbon dioxide content of less than 0.1% by volume. The treatment method may illustratively be at least one of pressure swing adsorption, membrane separation, methanation, water-gas shift, and CO2 absorption.

[0095] According to a preferred embodiment, the method further comprises: in step (5), after separation II, introducing the obtained gas phase II into a cold high-pressure separator II, and the obtained liquid phase I into a hot low-pressure separator. Recycle gas for the hydroisomerization reaction is obtained in the cold high-pressure separator II, and the liquid phase II obtained in the cold high-pressure separator II enters a cold low-pressure separator. The liquid phase effluents of the hot low-pressure separator and the cold low-pressure separator are jointly introduced into a fractionation tower for fractionation to obtain a naphtha fraction and biodiesel. The recycle gas for the hydroisomerization reaction is introduced into the hydroisomerization reactor.

[0096] The following combination Figure 1 The preferred specific implementation of the method provided by the present invention is described, specifically:

[0097] Oil and fat feedstock 1, hydrogen 2, and treated recycle gas are introduced into a heating furnace 3 for heating. After mixing in a mixer 4, they enter a shell-and-tube reactor 5 for a first hydrogenation reaction. Each tube of the shell-and-tube reactor 5 is equipped with a monolithic hydroprocessing catalyst 6, which is arranged in descending pore size. The low-temperature oil and fat feedstock is located outside each tube of the shell-and-tube reactor 5, exchanging heat with the reactants within the tubes.

[0098] The hydroprocessing effluent I obtained from the shell-and-tube reactor enters the fixed-bed hydroprocessing reactor 7 for a second hydrogenation reaction. The resulting hydroprocessing effluent II is separated I in a hot high-pressure separator I 8 to obtain a liquid hydrocarbon stream 10 and a gas stream. The gas stream enters a cold high-pressure separator I 9 for separation III. The liquid phase I11 flowing out of the cold high-pressure separator I 9 is passed together with the liquid hydrocarbon stream 10, hydrogen 15, and the recycled gas from the hydroisomerization reaction into a hydroisomerization reactor 16 for a hydroisomerization reaction to obtain a hydroisomerization reaction effluent. Sulfur-containing wastewater 12 can also be obtained in the cold high-pressure separator I 9.

[0099] The gas phase I13 obtained in the cold high-pressure separator I9 is processed by the gas treatment system 14 to remove carbon monoxide and carbon dioxide and then returned to the system for recycling.

[0100] The effluent from the hydroisomerization reaction is separated II in a hot high-pressure separator II 17, the gas phase II obtained from the hot high-pressure separator II 17 enters a cold high-pressure separator II 18, the liquid phase II 19 obtained from the hot high-pressure separator II 17 enters a hot low-pressure separator 20, the gas phase I obtained in the cold high-pressure separator II 18 is introduced into the hydroisomerization reactor 16 as a circulating gas for the hydroisomerization reaction, the liquid phase III obtained from the cold high-pressure separator II 18 enters a cold low-pressure separator 21, the gas phase IV obtained from the hot low-pressure separator 20 is introduced into the cold low-pressure separator 21, and the liquid phase effluent from the hot low-pressure separator 20 and the liquid phase effluent from the cold low-pressure separator 21 enter a fractionation tower 22 together for fractionation to obtain a naphtha fraction and biodiesel.

[0101] The present invention will be described in detail below by way of examples, but the present invention is not limited thereto.

[0102] The content of each element in the catalyst was determined using a 3271E X-ray fluorescence spectrometer purchased from Rigaku Corporation of Japan.

[0103] The distillation range of liquid hydrocarbon streams is determined using ASTM 2887.

[0104] Yield of biodiesel = weight of biodiesel / weight of hydroisomerization reaction effluent * %;

[0105] Yield of liquid hydrocarbon stream = weight of liquid hydrocarbon stream / weight of oil and fat raw material * %;

[0106] Conversion rate of oil and fat feedstock = (oxygen content in oil and fat feedstock - oxygen content in liquid hydrocarbon stream product) / oxygen content of feedstock * %;

[0107] Yield of hydroisomerization reaction effluent = weight sum of naphtha fraction and biodiesel / weight sum of liquid hydrocarbon stream *%.

[0108] RJW-3 catalyst, the content of the first metal element (nickel) calculated as oxide is 3.2 weight%, and the content of the second metal element (molybdenum and tungsten) calculated as oxide is 0.8 weight% (molybdenum) and 22.2 weight% (tungsten), is produced by Changling Catalyst Branch of Sinopec Catalyst Company.

[0109] The hydroprocessing catalyst II used in the following examples is RJW-3 catalyst; the monolithic hydroprocessing catalyst is prepared by the aforementioned method for preparing the monolithic hydroprocessing catalyst, wherein the outer diameter of the support is 8 cm.

[0110] The shell-and-tube reactor is provided with four reaction zones, and in step S2, along the flow direction of the liquid phase stream, the loading amount of the carrier and the active component in the first reaction zone is 5% by weight, the number of pores per square centimeter is 25, and the porosity is 70%;

[0111] The second reaction zone had a support and active component loading of 10% by weight, 45 pores per square centimeter, and a porosity of 68%;

[0112] The third reaction zone had a carrier and active component loading of 15% by weight, 60 pores per square centimeter, and a porosity of 67%;

[0113] The loading amount of the support and active components in the fourth reaction zone was 25% by weight, the number of pores per square centimeter was 100, and the porosity was 65%.

[0114] The hydroisomerization catalyst used below is the hydroisomerization catalyst C in CN109294746A.

[0115] Unless otherwise specified, the sulfidation method of the catalyst in the following examples specifically includes:

[0116] After loading 100 g of the catalyst into the reactor, the sulfiding agent was mixed with the medium to form a 2 wt% solution which was introduced into the reactor. At the same time, hydrogen was introduced into the reactor to form a pressure of 6.0 MPa. After the temperature was raised to 320°C, the sulfidation reaction was carried out for 8 hours to obtain a sulfided catalyst, wherein the sulfiding agent was DMDS and the medium was biodiesel.

[0117] Unless otherwise specified, the following examples all use Figure 1 The process is carried out as shown in .

[0118] Example 1

[0119] This example is used to illustrate the method for producing biodiesel by combining a tubular reactor and a fixed bed reactor provided by the present invention. The method comprises:

[0120] (1) In the presence of hydrogen, an oil and fat feedstock is introduced into a shell-and-tube reactor for a first hydrotreatment to obtain a hydrotreatment effluent I, wherein the shell-and-tube reactor is provided with four shells and tubes arranged in series to form four reaction zones, and the shells and tubes are filled with a hydrotreatment catalyst I, wherein the hydrotreatment catalyst I is a monolithic hydrotreatment catalyst;

[0121] The oil raw material is coconut oil, and its main properties are shown in Table 2. The outer diameter of the monolithic hydroprocessing catalyst is 3 mm smaller than the diameter of the tubes of the shell-and-tube reactor. According to the flow direction of the liquid phase material, the length of the monolithic hydroprocessing catalyst is set so that the weight ratio of the active components in the four reaction zones is 2:1:1:1.

[0122] The conditions for the first hydrotreatment were: the inlet of the tubular reactor, the reaction pressure was 6.4 MPa, the hydrogen-to-oil volume ratio was 1500 Nm 3 / m 3 , the inlet temperature of the shell and tube reactor is 280℃; the outlet temperature of the shell and tube reactor is 320℃, and the total temperature rise is 40℃;

[0123] (2) In the presence of hydrogen, introducing the hydroprocessing effluent I into a fixed bed reactor filled with a hydroprocessing catalyst II for a second hydroprocessing to obtain a hydroprocessing effluent II;

[0124] Wherein, before the hydroprocessing reaction, the hydroprocessing catalyst I and the hydroprocessing catalyst II are sulfurized;

[0125] The second hydrotreatment conditions were: fixed bed reactor, inlet temperature 290°C, outlet temperature 330°C, total temperature rise 40°C;

[0126] The total volumetric space velocity of the first hydrotreatment and the second hydrotreatment was 1.0 h -1 ;

[0127] The weight ratio of the active component of the hydroprocessing catalyst I to the active component of the hydroprocessing catalyst II is 1.5:1, calculated as oxides;

[0128] (3) separating the hydroprocessing effluent II by separation I to obtain a liquid hydrocarbon stream, water, and a gas stream; the conversion rate of the oil and fat feedstock is 100%, the terminal boiling point temperature of the liquid hydrocarbon stream is 330° C., the sulfur content of the liquid hydrocarbon stream is 1 mg / kg, and the nitrogen content of the liquid hydrocarbon stream is 1 mg / kg; and the yield of the liquid hydrocarbon stream is 77% by weight;

[0129] (4) subjecting the entire liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0130] Before the hydroisomerization reaction, the hydroisomerization catalyst was sulfurized. The conditions of the hydroisomerization reaction were as follows: reaction temperature of 360°C, reaction pressure of 5.0 MPa, volume space velocity of 1.0 h -1 , hydrogen to oil volume ratio is 500Nm 3 / m 3 ;

[0131] (5) Separating the hydroisomerization reaction effluent II to obtain biodiesel; based on the total weight of the effluent entering the hydroisomerization reactor, the yield of the hydroisomerization reaction effluent is 98% by weight, the yield of biodiesel is 91% by weight, and the pour point and cold filter plugging point meet the requirements of -10 diesel.

[0132] Example 2

[0133] This example is used to illustrate the method for producing biodiesel by combining a tubular reactor and a fixed bed reactor provided by the present invention. The method comprises:

[0134] (1) The steps are the same as those in step (1) of Example 1;

[0135] The oil and fat raw material is waste cooking oil, and its main properties are shown in Table 2. The weight ratios of the active components in the four reaction zones of the monolithic hydroprocessing catalyst are 1:1:1:1;

[0136] The conditions for the first hydrotreatment were: the inlet of the tubular reactor, the reaction pressure was 6.4 MPa, the hydrogen-to-oil volume ratio was 1500 Nm 3 / m 3 The inlet temperature of the shell and tube reactor is 300°C, the outlet temperature is 335°C, and the total temperature rise is 35°C.

[0137] The rest are the same as step (1) in Example 1;

[0138] (2) In the presence of hydrogen, introducing the hydroprocessing effluent I into a fixed bed reactor filled with a hydroprocessing catalyst II for a second hydroprocessing to obtain a hydroprocessing effluent II;

[0139] Wherein, before carrying out the hydrotreating reaction, the hydrotreating catalyst I, the hydrotreating catalyst II and the hydroisomerization catalyst are sulfurized;

[0140] The conditions for the second hydrotreatment were: fixed bed reactor, inlet temperature 300°C, outlet temperature 340°C, and total temperature rise 40°C;

[0141] The total volumetric space velocity of the first hydrotreatment and the second hydrotreatment was 1.0 h -1 ;

[0142] The weight ratio of the active component of the hydroprocessing catalyst I to the active component of the hydroprocessing catalyst II is 0.67:1, calculated as oxides;

[0143] (3) Separating the hydroprocessing effluent II by separation I to obtain a liquid hydrocarbon stream, water, and a gas stream; the conversion rate of the oil and fat feedstock is 100%, the terminal boiling point temperature of the liquid hydrocarbon stream is 375° C., the sulfur content of the liquid hydrocarbon stream is 5 mg / kg, and the nitrogen content is 4 mg / kg; the yield of the liquid hydrocarbon stream is 82% by weight;

[0144] (4) subjecting the entire liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0145] Before the hydroisomerization reaction, the hydroisomerization catalyst was sulfurized. The conditions of the hydroisomerization reaction were as follows: reaction temperature of 365°C, reaction pressure of 6.0 MPa, volume space velocity of 1.2 h -1 , hydrogen to oil volume ratio is 600Nm 3 / m 3 ;

[0146] (5) Separating the hydroisomerization reaction effluent II to obtain biodiesel; based on the total weight of liquid hydrocarbons entering the hydroisomerization reactor, the yield of the hydroisomerization reaction effluent is 96% by weight, the yield of biodiesel is 90% by weight, and the pour point and cold filter plugging point meet the requirements of -10 diesel.

[0147] Comparative Example 1

[0148] This comparative example was carried out in the same manner as in Example 1, except that the operation of step (1) in Example 1 was not performed in this comparative example. Specifically, in this comparative example:

[0149] SS1: In the presence of hydrogen, an oil feedstock (same type as the coconut oil feedstock in Example 1), the liquid hydrocarbon stream obtained in SS2, and hydrogen are introduced into a fixed bed reactor filled with a hydrotreating catalyst II for a second hydrotreating reaction to obtain a hydrotreating effluent II;

[0150] The weight ratio of liquid hydrocarbon stream to coconut oil is 3.5:1;

[0151] Wherein, before the second hydrogenation reaction, the hydrotreating catalyst II and the hydroisomerization catalyst are sulfurized;

[0152] The conditions for the second hydrogenation reaction were: fixed bed reactor, inlet pressure 6.4 MPa, hydrogen to oil volume ratio 1500 Nm 3 / m 3 , relative catalyst total space velocity 1.0h -1 , the inlet temperature is 290℃ and the outlet temperature is 355℃.

[0153] SS2: Separating the hydroprocessing effluent II by separation I to obtain a liquid hydrocarbon stream, water, and a gas stream; the conversion rate of the oil feedstock is 100%, the terminal boiling point temperature of the liquid hydrocarbon is 330° C., the sulfur content of 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 %;

[0154] SS3: subjecting the remaining liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent;

[0155] Before the hydroisomerization reaction, the hydroisomerization catalyst was sulfurized. The conditions of the hydroisomerization reaction were as follows: reaction temperature of 360°C, reaction pressure of 5.0 MPa, volume space velocity of 1.0 h -1 , hydrogen to oil volume ratio is 500Nm 3 / m 3 ;

[0156] SS4: Separating the hydroisomerization reaction effluent II to obtain biodiesel; based on the total weight entering the hydroisomerization reactor, the biodiesel yield is 91% by weight, with a pour point and cold filter point of -14°C and -8°C, respectively, which can meet the needs of -10 diesel.

[0157] From the above results, it can be seen that although Comparative Example 1 can obtain -10 diesel that meets the requirements, in order to control the reaction temperature rise, avoid carbon deposit blockage at the reactor inlet and more decarbonylation, decarboxylation reactions and thermal cracking reactions at excessively high temperatures, resulting in a lower liquid hydrocarbon yield, 3.5 times the liquid hydrocarbon needs to be circulated at the reactor inlet, resulting in high production energy consumption and poor economic efficiency.

[0158] Table 2

[0159] project coconut oil gutter 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, weight % 14.0 10.9 Total acid value, mgKOH / g 0.12 89

[0160] As can be seen from the above examples, the method described in the present invention can effectively control the temperature rise of the reactor without the need for large-scale product circulation, successfully produce biodiesel products that meet the requirements of -10 diesel using low-cost oil and fat raw materials, reduce energy consumption, and achieve long-term operation of the device.

[0161] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for producing biodiesel using a combination of a tubular reactor and a fixed bed reactor, characterized in that: The method includes: (1) In the presence of hydrogen, an oil and fat feedstock is introduced into a shell-and-tube reactor for a first hydrotreatment to obtain a hydrotreatment effluent I, wherein each tube of the shell-and-tube reactor is filled with a hydrotreatment catalyst I, and the hydrotreatment catalyst I is a monolithic hydrotreatment catalyst; the porosity of the monolithic hydrotreatment catalyst is greater than or equal to 65%, and along the flow direction of the liquid phase stream, the porosity of the monolithic hydrotreatment catalyst decreases successively, and the number of pores per square centimeter increases successively; (2) In the presence of hydrogen, introducing the hydroprocessing effluent I into a fixed bed reactor filled with a hydroprocessing catalyst II for a second hydroprocessing to obtain a hydroprocessing effluent II; (3) separating the hydroprocessing effluent II by I to obtain a liquid hydrocarbon stream, water, and a gas stream; (4) subjecting at least a portion of the liquid hydrocarbon stream to a hydroisomerization reaction in the presence of hydrogen and a hydroisomerization catalyst to obtain a hydroisomerization reaction effluent; (5) Separating the hydroisomerization reaction effluent II to obtain biodiesel.

2. The method according to claim 1, wherein The hydrotreating catalyst I, the hydrotreating catalyst II and the hydroisomerization catalyst are each independently selected from a catalyst A having the following characteristics: The catalyst A contains active components; the active metal elements in the active components include a first metal element and a second metal element; the first metal element is cobalt and / or nickel; and the second metal element is molybdenum and / or tungsten.

3. The method according to claim 2, wherein: In step (1), the monolithic hydroprocessing catalyst contains a support, a carrier and an active component. Based on the total weight of the monolithic hydroprocessing catalyst, the loading amount of the carrier and the active component is 1-40 wt%.

4. The method according to claim 3, wherein: In step (1), based on the total weight of the integral hydroprocessing catalyst, the loading amount of the carrier and the active component is 2-32 wt%.

5. The method according to any one of claims 2 to 4, wherein: In step (2), based on the total weight of the hydroprocessing catalyst II, the content of the first metal element calculated as oxide is 1-10 wt %, and the content of the second metal element calculated as oxide is 5-40 wt %.

6. The method according to any one of claims 1 to 4, wherein: Calculated as oxides, the weight ratio of the active component of the hydroprocessing catalyst I to the active component of the hydroprocessing catalyst II is 0.5-1.5:

1.

7. The method according to any one of claims 1 to 4, wherein: In step (4), the hydroisomerization catalyst further contains a carrier; the carrier is alumina and / or silica-alumina.

8. The method according to claim 7, wherein: The carrier is alumina and silica-alumina; and based on the total weight of the carrier, the content of the alumina is 5-95% by weight, and the content of the silica-alumina is 5-95% by weight.

9. The method according to claim 8, wherein Based on the total weight of the carrier, the content of the aluminum oxide is 5-45% by weight, and the content of the silicon oxide-alumina is 55-95% by weight.

10. The method according to any one of claims 2 to 4, wherein: In step (4), in the hydroisomerization catalyst, based on the total weight of the hydroisomerization catalyst, the content of the first metal element calculated as oxide is 1-10 wt %, and the content of the second metal element calculated as oxide is 5-40 wt %.

11. The method according to claim 10, wherein: Based on the total weight of the hydroisomerization catalyst, the content of the first metal element calculated as oxide is 2-8 wt %, and the content of the second metal element calculated as oxide is 10-35 wt %.

12. The method according to any one of claims 1 to 4, wherein: In step (1), the inlet temperature of the shell-and-tube reactor is 250-340°C, the inlet pressure is 0.5-10 MPa, and the inlet hydrogen-to-oil volume ratio is 600-2000 Nm 3 / m 3 , the outlet temperature is 300-380℃, and the total temperature rise is 20-80℃.

13. The method according to any one of claims 1 to 4, wherein: In step (2), the inlet temperature of the fixed bed reactor is 280-360°C, the outlet temperature is 300-380°C, and the total temperature rise is 10-60°C.

14. The method according to any one of claims 1 to 4, wherein: The total volume space velocity of the first hydrotreatment and the second hydrotreatment is 0.5-10h -1 .

15. The method according to any one of claims 1 to 4, wherein: In step (4), the conditions of the hydroisomerization reaction at least meet the following requirements: reaction temperature of 280-450°C, reaction pressure of 1.0-10.0 MPa, volume space velocity of 0.1-10.0 h -1 , hydrogen to oil volume ratio is 200-1500Nm 3 / m 3 .

16. The method according to claim 15, wherein In step (4), the conditions of the hydroisomerization reaction at least meet the following requirements: reaction temperature of 320-400°C, reaction pressure of 2.0-7.0 MPa, volume space velocity of 0.5-5.0 h -1 , hydrogen to oil volume ratio is 500-1000Nm 3 / m 3 .

17. The method according to any one of claims 1 to 4, wherein: In step (1), the oil and fat raw material is selected from at least one of animal and plant oils and fats, fatty acids, fatty acid methyl esters, sewage oil, and algae oil.

18. The method according to any one of claims 1 to 4, wherein: The method further includes: before introducing the oil and fat raw material into the shell-and-tube reactor for the first hydrotreatment, first sulfiding the hydrotreatment catalyst I, the hydrotreatment catalyst II and the hydroisomerization catalyst, and the sulfiding operation includes: in the presence of a medium and hydrogen, subjecting the catalyst to be sulfided to a sulfiding reaction with a sulfiding agent to obtain a sulfided catalyst.

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