A coupling process for producing biodiesel from waste oil

Abstract

The invention discloses a coupling process for preparing biodiesel from waste oil and fat, comprising the following steps: 1) removing solid impurities from the waste oil and fat, mixing the waste oil and fat with alcohol and a liquid acid catalyst for pre-esterification reaction to generate a pre-esterified mixture; 2) mixing the pre-esterified mixture with water and passing it into a liquid-liquid separator, separating the water phase and removing metal ions to obtain an esterified product II; 3) mixing the esterified product II with a sulfiding agent and H 2 After mixing, a pre-hydrogenation reaction is carried out to generate product I; 4) product I is separated from the oil phase and then mixed with H 2 The mixture is introduced into a fixed bed reactor, and separated by a gas-liquid separator to obtain an oil phase product II; 5) the oil phase product II and hydrogen are introduced into a hydroisomerization reactor to react and generate product II; 6) product II is introduced into a gas-liquid separator, and the separated liquid phase product is introduced into a fractionation tower to separate the biodiesel product. The production process of the present invention is stable and reliable, and has strong raw material adaptability. In addition, the catalyst and excess hydrogen and other raw materials can be recycled during the production process to ensure the long-term operation of the system.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic conversion of bio-oil, and in particular to a coupling process for preparing biodiesel from waste oil. Background Art

[0002] The development and utilization of fossil resources have greatly promoted the progress of human civilization and the development of modern industry. However, it has also brought about a series of environmental problems such as climate warming, acid rain, and haze. Moreover, fossil resources are a non-renewable resource, and its reserves are becoming increasingly depleted with the rapid growth of the global population. Therefore, it is urgent to develop new, green, and renewable energy sources. Among them, biodiesel, a renewable liquid fuel obtained by transesterification or hydrodeoxygenation reaction using bio-oils such as animal and plant oils, microbial oils, and catering waste oils as raw materials, has received widespread attention and is one of the important development directions for reducing carbon emissions and responding to climate change. Bio-oils are composed of long-chain fatty acid glycerides, free fatty acids, etc., and have a carbon chain structure similar to that of petrochemical diesel. According to the International Energy Agency, by 2030, the global annual demand for biodiesel will exceed 50 million tons, and my country will reach 7.5 million tons. Compared with animal and plant oils, my country's waste oils come from a wide range of sources, and about 11 million tons of waste oils such as gutter oil, acidified oil, and slop oil are produced each year. Therefore, the development of biodiesel production technology using waste oil as raw material has important strategic significance and industrial application prospects.

[0003] Biodiesel is mainly the first generation of biodiesel - fatty acid methyl esters - produced by transesterification. However, this type of biodiesel has problems such as high oxygen content, poor stability and poor low-temperature fluidity. It cannot be used directly as a fuel and can only be used as an additive for petrochemical diesel. The addition amount generally does not exceed 5%, which greatly limits its application value. Therefore, the current research focus in this field is to obtain a hydrocarbon mixture similar to the composition of traditional petrochemical diesel by hydrodeoxygenation of oils and fats, namely the second generation of biodiesel. The second generation of biodiesel has the advantages of high cetane number, low oxygen content and high stability, and can be mixed with petrochemical diesel in any proportion. In the actual production process, it also undergoes a hydroisomerization process while hydrodeoxygenation to generate branched alkane products, which further reduces the low-temperature fluidity of biodiesel.

[0004] At present, there have been several commercial cases reported for the production of second-generation biodiesel, including the NExBTL technology developed by Finland's Neste, the Ecofining technology jointly developed by the UOP Company of the United States and the ENI Company of Italy, and the RN-OIL technology of Sinopec in my country. However, most of the existing technologies mainly use finished vegetable oils with relatively high prices as raw materials. For example, the RN-OIL process uses edible oils such as rapeseed oil and soybean oil as raw materials, which has the problem of competing with people for food. At the same time, when the existing process uses waste oil as raw material, due to the high content of impurities such as free fatty acids, phospholipids, metal ions, and water in the waste oil, it is easy to cause the catalyst to pulverize and deactivate, making it difficult to operate stably for a long period of time. Therefore, it is urgent to develop a second-generation biodiesel production process using waste oil as raw material to improve the production efficiency and economic benefits of the second-generation biodiesel. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a coupling process for producing biodiesel from waste oil and fat. The production process is stable and reliable, has strong adaptability to raw materials, and can recycle raw materials such as catalysts and excess hydrogen during the production process to ensure long-term operation of the system.

[0006] The present invention adopts the following technical solution:

[0007] A waste oil-to-biodiesel coupling process comprises the following steps:

[0008] S1, preheating and dissolving the waste oil and fat, and then passing it through a filter to remove solid impurities, and then passing it through a pre-esterification reactor with a certain amount of short-chain alcohol and a liquid acid catalyst to perform a pre-esterification reaction to generate a pre-esterification mixture;

[0009] S2, passing the pre-esterification mixture into a liquid-liquid separator for liquid-liquid separation, separating an aqueous phase and an organic phase, wherein the organic phase is separated by a second flash separator to obtain a pre-esterification product I and an alcohol solvent, wherein the pre-esterification product I is passed through a water washing tower to remove metal ions to obtain an esterification product II;

[0010] S3, subjecting the esterification product II to a pre-hydrogenation reaction with an oil-soluble hydrogenation catalyst, a sulfiding agent and hydrogen in a suspended bed reactor to generate a product I;

[0011] S4, passing the product I into a gas-liquid-solid separator, and recycling the hydrogen and the hydrogenation catalyst through a desulfurization adsorption tower and a first pressure swing adsorption tower to obtain an oil phase product I;

[0012] S5, the oil phase product I is mixed with hydrogen and enters into a fixed bed reactor for deep deoxygenation reaction to obtain a mixed product I, and is separated by a first gas-liquid separator to obtain an oil phase product II;

[0013] S6, the oil phase product II is mixed with hydrogen and then introduced into a hydroisomerization reactor, and an isomerization reaction is carried out under the action of a catalyst to generate product II;

[0014] S7. The product II is passed into a second gas-liquid separator to separate the gas phase and the liquid phase, wherein the liquid phase product is passed into a fractionation tower to separate the isomerized biodiesel and aviation fuel products.

[0015] The aqueous phase separated in step S2 enters a first flash separator to separate liquid acid catalyst and water, wherein the liquid acid catalyst is recovered and returned to the pre-esterification reactor;

[0016] The alcohol solvent separated by the second flash separator in step S2 is recovered and returned to the pre-esterification reactor;

[0017] In the step S2, the pre-esterification product I passes through the first water washing tower and the second water washing tower to remove metal ions, thereby obtaining the esterification product II.

[0018] The gas phase product separated in step S5 is passed into a second pressure swing adsorption tower to separate CO, CO2, hydrogen and light hydrocarbons, wherein the hydrogen is circulated back to the fixed bed reactor;

[0019] The gas phase product separated in step S7 is passed into a third pressure swing adsorption tower to separate hydrogen and light hydrocarbons, wherein the hydrogen is circulated back to the hydroisomerization reactor.

[0020] In step S1, the waste oil added includes but is not limited to one or more of acidified oil, sewage oil, and waste cooking oil; the short-chain alcohol added includes but is not limited to any one of methanol, ethanol, propanol and butanol; the liquid acid catalyst added includes but is not limited to one or more of sulfuric acid, hydrochloric acid, and acidic ionic liquids.

[0021] The pre-esterification temperature in step S1 is 50-85° C.; the mass ratio of the added waste oil, liquid acid catalyst and short-chain alcohol is 1:(0.05-0.25):(0.80-1.50).

[0022] The vulcanizing agent added in step S3 includes but is not limited to one of sulfur powder, carbon disulfide, dimethyl disulfide, and H2S; the oil-soluble hydrogenation catalyst added includes but is not limited to one or more of molybdate imidazolium ion liquid, molybdate pyridinium ion liquid, molybdate quaternary ammonium ion liquid, and transition metal chloride ion liquid, wherein the transition metal chloride is one or more of NiCl2, CoCl2, CuCl2, and FeCl3.

[0023] The molar ratio of the esterification product II added in step S3 to the oil-soluble hydrogenation catalyst is (1000-5000):1, and the molar ratio of the esterification product II added to the sulfiding agent is (300-1000):1.

[0024] In step S4, product I passes through a gas-liquid-solid separator, and the gas phase product enters a desulfurization absorption tower to remove residual H2S gas, and then enters a pressure swing adsorption tower to separate CO, CO2, light hydrocarbons and recover H2;

[0025] The hydrogenation catalyst separated by the gas-liquid-solid separator in step S4 is filtered and then enters the suspended bed reactor for recycling, while the oil phase product I enters the fixed bed reactor for deep deoxygenation reaction.

[0026] The hydrogenation catalyst added in step S3 is one of NiMoS and CoMoS supported by graphitized mesoporous carbon; the operating pressure of the pre-hydrogenation reaction is 2-10 MPa, the reaction temperature is 280-400°C, and the liquid hourly space velocity is 0.2-8h -1 , the hydrogen-to-oil ratio is 500-1500.

[0027] In step S6, the catalyst used in the hydroisomerization reactor includes but is not limited to Pt / ZrO2, Pt / Al2O3, Pt / ZrPO x One of them.

[0028] The operating pressure of the hydroisomerization reaction in step S6 is 2-10 MPa, the reaction temperature is 280-400° C., and the liquid hourly space velocity is 0.2-8 h -1 , the hydrogen-to-oil ratio is 500-1500.

[0029] In the step S7, the operating temperature of the second gas-liquid separator is 25-45°C; the distillation tower is a sieve plate type or a packing type, the bottom temperature is 200-360°C, and the operating pressure is 0.1-0.4MPa.

[0030] The technical solution of the present invention has the following advantages:

[0031] A. The waste oil and fat biodiesel coupling process provided by the present invention has a stable and reliable process flow, strong raw material adaptability, and the addition of a pre-esterification process can effectively reduce the fatty acid and metal content in the waste oil and fat, solving the problem of catalyst pulverization and deactivation caused by excessive acid value and metal deposition. At the same time, a suspended bed pre-hydrogenation reactor is set before the fixed bed reactor to remove impurities such as residual metals, phospholipids, and unsaponifiable matter in the waste oil and fat, forming further effective protection for the fixed bed deep deoxygenation reactor, and realizing long-term stable operation of the entire system.

[0032] B. The present invention has good catalytic conversion efficiency of oils and fats, and the alkane yield can reach more than 90%, among which the isoalkane yield reaches more than 40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention, the drawings required for use in the specific embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 This is a schematic diagram of the coupled process flow of producing biodiesel from waste oils and fats according to the present invention.

[0035] The following are marked in the figure:

[0036] 1-filter; 2-pre-esterification reactor; 3-liquid-liquid separator; 4-flash separator; 5-second flash separator; 6-water washing tower, 61-first water washing tower, 62-second water washing tower; 7-suspended bed reactor; 8-gas-liquid-solid separator; 9-desulfurization adsorption tower; 10-first pressure swing adsorption tower; 20-fixed bed reactor; 30-first gas-liquid separator; 40-second pressure swing adsorption tower; 50-hydroisomerization reactor; 60-second gas-liquid separator; 70-third pressure swing adsorption tower; 80-fractionation tower. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Embodiment 1:

[0039] like Figure 1 As shown, this embodiment provides a waste oil and fat biodiesel production coupling process, including the following steps:

[0040] S1. The waste grease is heated and dissolved at 100°C and then passed into a filter 1. The solid residue is filtered out at a temperature of 100°C and normal pressure. Then, the waste grease is mixed with methanol and concentrated sulfuric acid and subjected to a pre-esterification reaction in a pre-esterification reactor 2 at 80°C to obtain a pre-esterified mixture, wherein the mass ratio of methanol to grease is 1.2:1, and the mass ratio of concentrated sulfuric acid to grease is 0.1:1.

[0041] S2, the pre-esterification mixture and deionized water are mixed in a ratio of 1:2 and then separated into an aqueous phase and an organic phase by a liquid-liquid separator 3 (operating temperature is 60° C.), the aqueous phase is subjected to a first flash separator 4 at 100° C. to recover the liquid acid catalyst, and the organic phase is subjected to a second flash separator 5 at 80° C. to obtain a pre-esterification product I and an alcohol solvent, and the pre-esterification product I is subjected to a first water washing tower 61 and a second water washing tower 62 to further remove impurities such as metal ions to obtain an esterification product II;

[0042] S3, pre-hydrogenating the esterified product II with 1-octyl-3-methylimidazolium molybdate, sulfur powder and hydrogen in a suspended bed reactor 7 at 320° C. to obtain product I, wherein the ratio of the esterified product II to 1-octyl-3-methylimidazolium molybdate is 1000:1, the ratio to sulfur powder is 500:1, the hydrogen-to-oil ratio is 1000, and the operating pressure is 5 MPa;

[0043] S4, passing the product I into the gas-liquid-solid separator 8, and recycling the hydrogen and the hydrogenation catalyst through the desulfurization adsorption tower 9 and the first pressure swing adsorption tower 10 to obtain the oil phase product I;

[0044] S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor 20 for deep deoxygenation reaction at 320°C to obtain a mixed product I, wherein the catalyst is supported by graphitized mesoporous carbon (MC), CoMoS is a dispersed phase, the loading amount is 10%, the operating pressure is 5MPa, and the liquid hourly space velocity is 4h -1 , the hydrogen-to-oil ratio is 1000; the obtained mixed product I is used to obtain the oil phase product II by the first gas-liquid separator 30, and the gas phase product is passed through the first pressure swing adsorption tower 10 to recover hydrogen;

[0045] S6. The oil phase product II is mixed with hydrogen and passed through the hydroisomerization reactor 50 for isomerization reaction to generate product II. Product II is passed through the second gas-liquid separator 60 to obtain gas phase product and oil phase product. The third pressure swing adsorption tower 70 and the fractionation tower 80 are used to separate the products respectively to obtain the final product biodiesel, and other fractions of aviation fuel and gasoline products; the isomerization catalyst used is γ-Al2O3 as the carrier, Pt as the dispersed phase, the loading amount is 3%, the reaction temperature is 360°C, the operating pressure is 3MPa, and the liquid hourly space velocity is 4h -1 , the hydrogen-to-oil ratio is 1000.

[0046] The isomerized biodiesel was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography-hydrogen flame ionization detector, and the obtained alkane yield was 94.6%, and the isoalkane ratio was 42.1%.

[0047] Embodiment 2:

[0048] This embodiment provides a coupled process for producing biodiesel from waste oil and fat, comprising the following steps:

[0049] S1. The waste grease is heated and dissolved at 100°C and then passed into filter 1. The solid residue is filtered out at 100°C and normal pressure. Then, the waste grease is mixed with methanol and concentrated sulfuric acid and pre-esterified in a pre-esterification reactor 2 at 85°C to obtain a pre-esterified mixture, wherein the mass ratio of methanol to grease is 1.3:1, and the mass ratio of concentrated sulfuric acid to grease is 0.15:1.

[0050] S2, the pre-esterification mixture is mixed with deionized water at a ratio of 1:2.5 and then separated into an aqueous phase and an organic phase by a liquid-liquid separator 3 (operating temperature is 60° C.), the aqueous phase is subjected to a first flash separator 4 at 100° C. to recover the liquid acid catalyst, the organic phase is subjected to a second flash separator 5 at 80° C. to obtain a pre-esterification product I and an alcohol solvent, the pre-esterification product I is subjected to a first water washing tower 61 and a second water washing tower 62 to further remove impurities such as metal ions to obtain an esterification product II;

[0051] S3, pre-hydrogenating the esterified product II with 1-octyl-3-methylimidazolium molybdate, sulfur powder and hydrogen in a suspended bed reactor 7 at 330° C. to obtain product I, wherein the ratio of the esterified product II to 1-octyl-3-methylimidazolium molybdate is 2000:1, the ratio to sulfur powder is 500:1, the hydrogen-to-oil ratio is 1000, and the operating pressure is 6 MPa;

[0052] S4, passing the product I into the gas-liquid-solid separator 8, and recycling the hydrogen and the hydrogenation catalyst through the desulfurization adsorption tower 9 and the first pressure swing adsorption tower 10 to obtain the oil phase product I;

[0053] S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor 20 for deep deoxygenation reaction at 320°C to obtain a mixed product I, wherein the catalyst is supported by graphitized mesoporous carbon (MC), CoMoS is a dispersed phase, the loading amount is 15%, the operating pressure is 5MPa, and the liquid hourly space velocity is 3h -1 , the hydrogen-to-oil ratio is 1500; the obtained mixed product I is used to obtain the oil phase product II by the first gas-liquid separator 30, and the gas phase product is passed through the first pressure swing adsorption tower 10 to recover hydrogen;

[0054] S6, the oil phase product II is mixed with hydrogen and passed through the hydroisomerization reactor 50 for isomerization reaction to generate product II, and product II is passed through the second gas-liquid separator 60 to obtain gas phase product and oil phase product, and the third pressure swing adsorption tower 70 and the fractionation tower 80 are used to separate the products respectively to obtain the final product biodiesel, and other fractions of aviation fuel and gasoline products; the isomerization catalyst used is γ-Al2O3 as the carrier, Pt as the dispersed phase, the loading amount is 2%, the reaction temperature is 360°C, the operating pressure is 3MPa, and the liquid hourly space velocity is 3h -1 , the hydrogen-to-oil ratio is 1000.

[0055] The isomerized biodiesel was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography-hydrogen flame ionization detector, and the obtained alkane yield was 91.9% and the isoalkane ratio was 46.3%.

[0056] Embodiment 3:

[0057] This embodiment provides a coupled process for producing biodiesel from waste oil and fat, comprising the following steps:

[0058] S1. The waste grease is heated and dissolved at 90°C and then passed into filter 1. The solid residue is filtered out at 90°C and normal pressure. Then, the waste grease is mixed with methanol and concentrated sulfuric acid and pre-esterified in pre-esterification reactor 2 at 70°C to obtain a pre-esterified mixture, wherein the mass ratio of methanol to grease is 1.5:1, and the mass ratio of concentrated sulfuric acid to grease is 0.2:1.

[0059] S2, the pre-esterification mixture and deionized water are mixed in a ratio of 1:2 and then separated into an aqueous phase and an organic phase by a liquid-liquid separator 3 (operating temperature is 60° C.), the aqueous phase is subjected to a first flash separator 4 at 100° C. to recover the liquid acid catalyst, and the organic phase is subjected to a second flash separator 5 at 80° C. to obtain a pre-esterification product I and an alcohol solvent, and the pre-esterification product I is subjected to a first water washing tower 61 and a second water washing tower 62 to further remove impurities such as metal ions to obtain an esterification product II;

[0060] S3, pre-hydrogenating the esterified product II with 1-octyl-3-methylimidazolium molybdate, sulfur powder and hydrogen in a suspended bed reactor 7 at 380° C. to obtain product I, wherein the ratio of the esterified product II to 1-octyl-3-methylimidazolium molybdate is 3000:1, the ratio to sulfur powder is 500:1, the hydrogen-to-oil ratio is 1500, and the operating pressure is 6 MPa;

[0061] S4, passing the product I into the gas-liquid-solid separator 8, and recycling the hydrogen and the hydrogenation catalyst through the desulfurization adsorption tower 9 and the first pressure swing adsorption tower 10 to obtain the oil phase product I;

[0062] S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor 20 for deep deoxygenation reaction at 320°C to obtain a mixed product I, wherein the catalyst is supported by graphitized mesoporous carbon (MC), CoMoS is a dispersed phase, the loading amount is 5%, the operating pressure is 5MPa, and the liquid hourly space velocity is 5h -1 , the hydrogen-to-oil ratio is 1000; the obtained mixed product I is used to obtain the oil phase product II by the first gas-liquid separator 30, and the gas phase product is passed through the first pressure swing adsorption tower 10 to recover hydrogen;

[0063] S6. The oil phase product II is mixed with hydrogen and passed through the hydroisomerization reactor 50 for isomerization reaction to generate product II. Product II is passed through the second gas-liquid separator 60 to obtain gas phase product and oil phase product. The products are separated by the third pressure swing adsorption tower 70 and the fractionation tower 80 respectively to obtain the final product biodiesel and other fractions of aviation fuel and gasoline products. The isomerization catalyst used is γ-Al2O3 as the carrier, Pt as the dispersed phase, the loading amount is 4%, the reaction temperature is 380°C, the operating pressure is 2MPa, and the liquid hourly space velocity is 8h -1 , the hydrogen-to-oil ratio is 1500.

[0064] The isomerized biodiesel was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography-hydrogen flame ionization detector, and the obtained alkane yield was 92.5%, and the isoalkane ratio was 48.4%.

[0065] Embodiment 4:

[0066] This embodiment provides a coupled process for producing biodiesel from waste oil and fat, comprising the following steps:

[0067] S1. The waste grease is heated and dissolved at 90°C and then passed into filter 1. The solid residue is filtered out at 90°C and normal pressure. Then, the waste grease is mixed with methanol and concentrated sulfuric acid and pre-esterified in pre-esterification reactor 2 at 50°C to obtain a pre-esterified mixture, wherein the mass ratio of methanol to grease is 1.5:1, and the mass ratio of concentrated sulfuric acid to grease is 0.25:1.

[0068] S2, the pre-esterification mixture is mixed with deionized water at a ratio of 1:2.5 and then separated into an aqueous phase and an organic phase by a liquid-liquid separator 3 (operating temperature is 60° C.), the aqueous phase is subjected to a first flash separator 4 at 100° C. to recover the liquid acid catalyst, the organic phase is subjected to a second flash separator 5 at 80° C. to obtain a pre-esterification product I and an alcohol solvent, the pre-esterification product I is subjected to a first water washing tower 61 and a second water washing tower 62 to further remove impurities such as metal ions to obtain an esterification product II;

[0069] S3, pre-hydrogenating the esterified product II with 1-octyl-3-methylimidazolium molybdate, sulfur powder and hydrogen in a suspended bed reactor 7 at 280° C. to obtain product I, wherein the ratio of the esterified product II to 1-octyl-3-methylimidazolium molybdate is 1000:1, the ratio to sulfur powder is 300:1, the hydrogen-to-oil ratio is 1000, and the operating pressure is 10 MPa;

[0070] S4, passing the product I into the gas-liquid-solid separator 8, and recycling the hydrogen and the hydrogenation catalyst through the desulfurization adsorption tower 9 and the first pressure swing adsorption tower 10 to obtain the oil phase product I;

[0071] S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor 20 for deep deoxygenation reaction at 340°C to obtain a mixed product I, wherein the catalyst is supported by graphitized mesoporous carbon (MC), CoMoS is a dispersed phase, the loading amount is 12%, the operating pressure is 5MPa, and the liquid hourly space velocity is 4h -1 , the hydrogen-to-oil ratio is 500; the obtained mixed product I is used to obtain the oil phase product II by the first gas-liquid separator 30, and the gas phase product is passed through the first pressure swing adsorption tower 10 to recover hydrogen;

[0072] S6, the oil phase product II is mixed with hydrogen and passed through the hydroisomerization reactor 50 for isomerization reaction to generate product II, and product II is passed through the second gas-liquid separator 60 to obtain gas phase product and oil phase product, and the third pressure swing adsorption tower 70 and the fractionation tower 80 are used for product separation respectively to obtain the final product biodiesel, and other fractions of aviation fuel and gasoline products; the isomerization catalyst used is γ-Al2O3 as the carrier, Pt as the dispersed phase, the loading amount is 3%, the reaction temperature is 400°C, the operating pressure is 10MPa, and the liquid hourly space velocity is 3h -1 , the hydrogen-to-oil ratio is 500.

[0073] The isomerized biodiesel was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography-hydrogen flame ionization detector, and the obtained alkane yield was 93.3%, and the isoalkane ratio was 47.1%.

[0074] Embodiment 5:

[0075] This embodiment provides a coupled process for producing biodiesel from waste oil and fat, comprising the following steps:

[0076] S1. The waste grease is heated and dissolved at 100°C and then passed into filter 1. The solid residue is filtered out at 100°C and normal pressure. Then, the waste grease is mixed with methanol and concentrated sulfuric acid and pre-esterified in a pre-esterification reactor 2 at 60°C to obtain a pre-esterified mixture, wherein the mass ratio of methanol to grease is 0.8:1, and the mass ratio of concentrated sulfuric acid to grease is 0.2:1.

[0077] S2, the pre-esterification mixture and deionized water are mixed in a ratio of 1:2 and then separated into an aqueous phase and an organic phase by a liquid-liquid separator 3 (operating temperature is 60° C.), the aqueous phase is subjected to a first flash separator 4 at 100° C. to recover the liquid acid catalyst, and the organic phase is subjected to a second flash separator 5 at 80° C. to obtain a pre-esterification product I and an alcohol solvent, and the pre-esterification product I is subjected to a first water washing tower 61 and a second water washing tower 62 to further remove impurities such as metal ions to obtain an esterification product II;

[0078] S3, pre-hydrogenating the esterified product II with 1-octyl-3-methylimidazolium molybdate, sulfur powder and hydrogen in a suspended bed reactor 7 at 400° C. to obtain product I, wherein the ratio of the esterified product II to 1-octyl-3-methylimidazolium molybdate is 3000:1, the ratio to sulfur powder is 500:1, the hydrogen-to-oil ratio is 500, and the operating pressure is 2 MPa;

[0079] S4, passing the product I into the gas-liquid-solid separator 8, and recycling the hydrogen and the hydrogenation catalyst through the desulfurization adsorption tower 9 and the first pressure swing adsorption tower 10 to obtain the oil phase product I;

[0080] S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor 20 for deep deoxygenation reaction at 300°C to obtain a mixed product I, wherein the catalyst is supported by graphitized mesoporous carbon (MC), CoMoS is a dispersed phase, the loading amount is 8%, the operating pressure is 2MPa, and the liquid hourly space velocity is 6h -1 , the hydrogen-to-oil ratio is 1000; the obtained mixed product I is used to obtain the oil phase product II by the first gas-liquid separator 30, and the gas phase product is passed through the first pressure swing adsorption tower 10 to recover hydrogen;

[0081] S6, the oil phase product II is mixed with hydrogen and passed through the hydroisomerization reactor 50 for isomerization reaction to generate product II, and product II is passed through the second gas-liquid separator 60 to obtain gas phase product and oil phase product, and the products are separated by the third pressure swing adsorption tower 70 and the fractionation tower 80 respectively, so as to obtain the final product biodiesel, and other fractions of aviation fuel and gasoline products; the isomerization catalyst used is γ-Al2O3 as the carrier, Pt as the dispersed phase, the loading amount is 3%, the reaction temperature is 280°C, the operating pressure is 3MPa, and the liquid hourly space velocity is 0.2h -1 , the hydrogen-to-oil ratio is 1000.

[0082] The isomerized biodiesel was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography-hydrogen flame ionization detector, and the obtained alkane yield was 93.7%, and the isoalkane ratio was 45.9%.

[0083] Embodiment 6:

[0084] S1. The waste grease is heated and dissolved at 100°C and then passed into filter 1. The solid residue is filtered out at 100°C and normal pressure. Then, the waste grease is mixed with methanol and concentrated sulfuric acid and pre-esterified in a pre-esterification reactor 2 at 50°C to obtain a pre-esterified mixture, wherein the mass ratio of methanol to grease is 1.1:1, and the mass ratio of concentrated sulfuric acid to grease is 0.05:1.

[0085] S2, the pre-esterification mixture and deionized water are mixed in a ratio of 1:2 and then separated into an aqueous phase and an organic phase by a liquid-liquid separator 3 (operating temperature is 60° C.), the aqueous phase is subjected to a first flash separator 4 at 100° C. to recover the liquid acid catalyst, and the organic phase is subjected to a second flash separator 5 at 80° C. to obtain a pre-esterification product I and an alcohol solvent, and the pre-esterification product I is subjected to a first water washing tower 61 and a second water washing tower 62 to further remove impurities such as metal ions to obtain an esterification product II;

[0086] S3, pre-hydrogenating the esterified product II with 1-octyl-3-methylimidazolium molybdate, sulfur powder and hydrogen in a suspended bed reactor 7 at 300° C. to obtain product I, wherein the ratio of the esterified product II to 1-octyl-3-methylimidazolium molybdate is 5000:1, the ratio to sulfur powder is 1000:1, the hydrogen-to-oil ratio is 1500, and the operating pressure is 3 MPa;

[0087] S4, passing the product I into the gas-liquid-solid separator 8, and recycling the hydrogen and the hydrogenation catalyst through the desulfurization adsorption tower 9 and the first pressure swing adsorption tower 10 to obtain the oil phase product I;

[0088] S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor 20 for deep deoxygenation reaction at 300°C to obtain a mixed product I, wherein the catalyst is supported by graphitized mesoporous carbon (MC), CoMoS is a dispersed phase, the loading amount is 5%, the operating pressure is 4MPa, and the liquid hourly space velocity is 8h -1 , the hydrogen-to-oil ratio is 1500; the obtained mixed product I is used to obtain the oil phase product II by the first gas-liquid separator 30, and the gas phase product is passed through the first pressure swing adsorption tower 10 to recover hydrogen;

[0089] S6, the oil phase product II is mixed with hydrogen and passed through the hydroisomerization reactor 50 for isomerization reaction to generate product II, and product II is passed through the second gas-liquid separator 60 to obtain gas phase product and oil phase product, and the third pressure swing adsorption tower 70 and the fractionation tower 80 are used to separate the products respectively to obtain the final product biodiesel, and other fractions of aviation fuel and gasoline products; the isomerization catalyst used is γ-Al2O3 as the carrier, Pt as the dispersed phase, the loading amount is 3%, the reaction temperature is 360°C, the operating pressure is 3MPa, and the liquid hourly space velocity is 2h -1 , the hydrogen-to-oil ratio is 1000.

[0090] The isomerized biodiesel was qualitatively and quantitatively analyzed by gas chromatography-mass spectrometry and gas chromatography-hydrogen flame ionization detector, and the obtained alkane yield was 90.4%, and the isoalkane ratio was 40.6%.

[0091] The waste oil and fat biodiesel coupling process provided by the present invention has a stable and reliable process flow, strong raw material adaptability, and the addition of a pre-esterification process can effectively reduce the fatty acid and metal content in the waste oil and fat, solving the problem of catalyst pulverization and deactivation caused by excessively high acid value and metal deposition. At the same time, a suspended bed pre-hydrogenation reactor is arranged before the fixed bed reactor to remove impurities such as residual metals, phospholipids, and unsaponifiable matter in the waste oil and fat, thereby forming further effective protection for the fixed bed deep deoxygenation reactor and realizing long-term stable operation of the entire system. The present invention has a good catalytic conversion efficiency of oil and fat, and the alkane yield can reach more than 90%, wherein the isoparaffin yield reaches more than 40%.

[0092] Any matters not described in the present invention are applicable to the prior art.

[0093] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. However, the obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A waste oil and fat biodiesel coupling process, characterized in that: The steps include: S1, preheating and dissolving the waste oil and fat, and then passing it into a filter (1) to filter out solid impurities, and then passing it into a pre-esterification reactor (2) with a certain amount of short-chain alcohol and a liquid acid catalyst to carry out a pre-esterification reaction to generate a pre-esterification mixture; S2, passing the pre-esterification mixture into a liquid-liquid separator (3) for liquid-liquid separation, separating an aqueous phase and an organic phase, wherein the organic phase is separated by a second flash separator (5) to obtain a pre-esterification product I and an alcohol solvent, wherein the pre-esterification product I is passed through a water washing tower (6) to remove metal ions to obtain an esterification product II; S3, subjecting the esterification product II to a pre-hydrogenation reaction with an oil-soluble hydrogenation catalyst, a sulfiding agent and hydrogen in a suspended bed reactor (7) to generate a product I; S4, passing the product I into a gas-liquid-solid separator (8), and after the hydrogen and the hydrogenation catalyst are recycled through a desulfurization adsorption tower (9) and a first pressure swing adsorption tower (10), an oil phase product I is obtained; S5, the oil phase product I is mixed with hydrogen and enters the fixed bed reactor (20) for deep deoxygenation reaction to obtain a mixed product I, and is separated by a first gas-liquid separator (30) to obtain an oil phase product II; S6, the oil phase product II is mixed with hydrogen and then introduced into a hydroisomerization reactor (50), where an isomerization reaction is carried out under the action of a catalyst to generate product II; S7, passing product II into a second gas-liquid separator (60) to separate a gas phase and a liquid phase, wherein the liquid phase product is passed into a fractionation tower (80) to separate isomerized biodiesel and aviation fuel products; The added oil-soluble hydrogenation catalyst is one or more of molybdate imidazolium ionic liquid, molybdate pyridinium ionic liquid, molybdate quaternary ammonium ionic liquid, and transition metal chloride ionic liquid, wherein the transition metal chloride is one or more of NiCl2, CoCl2, CuCl2, and FeCl3; In the step S6, the catalyst used in the hydroisomerization reactor (50) is one of Pt / ZrO2, Pt / Al2O3, and Pt / ZrPOx.

2. The waste oil to biodiesel coupling process according to claim 1, characterized in that: The aqueous phase separated in step S2 enters the first flash separator (4) to separate the liquid acid catalyst and water, wherein the liquid acid catalyst is recovered and returned to the pre-esterification reactor (2); The alcohol solvent separated by the second flash separator (5) in step S2 is recovered and returned to the pre-esterification reactor (2); The gaseous product separated in step S5 is passed into a second pressure swing adsorption tower (40) to separate CO, CO2, hydrogen and light hydrocarbons, wherein the hydrogen is circulated back to the fixed bed reactor (20); The gas phase product separated in step S7 is introduced into a third pressure swing adsorption tower (70) to separate hydrogen and light hydrocarbons, wherein the hydrogen is circulated back to the hydroisomerization reactor (50).

3. The waste oil to biodiesel coupling process according to claim 1, characterized in that: In step S1, the waste oil added is one or more of acidified oil, sewage oil, and waste cooking oil; the short-chain alcohol added is one of methanol, ethanol, normal alcohol or normal alcohol; and the liquid acid catalyst added is one or more of sulfuric acid, hydrochloric acid, and acidic ionic liquid.

4. The waste oil to biodiesel coupling process according to claim 1, characterized in that: The pre-esterification temperature in step S1 is 50-85°C; the mass ratio of the added waste oil, liquid acid catalyst and short-chain alcohol is 1:(0.05-0.25):(0.80-1.50).

5. The waste oil to biodiesel coupling process according to claim 1, characterized in that: The vulcanizing agent added in step S3 is one of sulfur powder, carbon disulfide, dimethyl disulfide and H2S.

6. The waste oil to biodiesel coupling process according to claim 1, characterized in that: The molar ratio of the esterification product II added in step S3 to the oil-soluble hydrogenation catalyst is (1000-5000):1, and the molar ratio of the esterification product II added to the sulfiding agent is (300-1000):

1.

7. The waste oil to biodiesel coupling process according to claim 1, characterized in that: In step S4, product I passes through a gas-liquid-solid separator (8), and the gaseous product enters a desulfurization adsorption tower (9) to remove residual H2S gas, and then enters a first pressure swing adsorption tower (10) to separate CO, CO2, and low-carbon hydrocarbons and recover H2; The hydrogenation catalyst separated by the gas-liquid-solid separator (8) in step S4 is filtered and then enters the suspended bed reactor (7) for recycling, while the oil phase product I enters the fixed bed reactor (20) for deep deoxygenation reaction.

8. The waste oil to biodiesel coupling process according to claim 1, characterized in that: The hydrogenation catalyst added in step S3 is one of NiMoS and CoMoS supported by graphitized mesoporous carbon; the operating pressure of the pre-hydrogenation reaction is 2-10 MPa, the reaction temperature is 280-400 °C, the liquid hourly space velocity is 0.2-8 h-1, and the hydrogen-to-oil ratio is 500-1500.

9. The waste oil to biodiesel coupling process according to claim 1, characterized in that: The operating pressure of the hydroisomerization reaction in step S6 is 2-10 MPa, the reaction temperature is 280-400°C, the liquid hourly space velocity is 0.2-8 h-1, and the hydrogen-to-oil ratio is 500-1500.

10. The waste oil to biodiesel coupling process according to claim 1, characterized in that: In step S7, the operating temperature of the second gas-liquid separator (60) is 25-45°C; the fractionation tower (80) is a sieve plate type or a packing type, the tower bottom temperature is 200-360°C, and the operating pressure is 0.1-0.4 MPa.

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