Method for preparing high-quality industrial-grade mixed oil for SAF by taking acid oil as raw material

Abstract

The invention discloses a method for preparing high-quality industrial-grade mixed oil for SAF by taking acid oil as a raw material. The high-quality industrial-grade mixed oil for the SAF is prepared by sequentially adopting liquid caustic soda for neutralizing and removing desulfurized acid, calcium oxide for completely removing residual sulfate radicals, kieselguhr for assisting in filtering and removing impurities, glycerol esterification reaction, oxalic acid acidification for removing metal ions and dehydration. The method is simple and low in energy consumption, the acid value of the prepared high-quality industrial-grade mixed oil for SAF is within 6 mg KOH / g, and the yield is 100% or above.

Description

Technical Field

[0001] The present application relates to the field of aviation fuel technology, and in particular to a method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as a raw material. Background Art

[0002] Sustainable aviation fuel (SAF), also known as biojet fuel, has only emerged in the past two years and is seen as the most promising measure to achieve the aviation industry's emission reduction goals. SAF is a new type of aviation fuel made from waste animal and plant oils (such as vegetable oil, animal and plant fats, waste cooking oil, etc.), but there is a serious shortage of raw materials for making SAF.

[0003] At present, there are more than 1 million tons of acidified oil as a byproduct of oil refining in my country. If it is not used, it will cause great waste. Acidified oil is essentially fatty acid, which contains pigments and unacidified triglycerides, diglycerides, monoglycerides (neutral oil) and other components. The fatty acids in acidified oil are long-chain fatty acids, and the carbon chain is generally 12~24, of which 16~18 are the main ones. Acidified oil has the potential to manufacture fatty acid methyl esters (biodiesel) and SAF. However, the acid value of these acidified oils as a byproduct of oil refining is high (generally around 120mg KOH / g), and there is a problem of residual sulfate, so it cannot be directly used in the production of SAF. In combination with the actual situation at home and abroad, it is of great significance to professionally process the acidified oil to meet the raw material index requirements for the production of SAF.

[0004] Therefore, there is an urgent need to provide a method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as a raw material, so as to improve the resource utilization rate of the acidified oil. Summary of the invention

[0005] The purpose of this application is to overcome the above-mentioned technical deficiencies and propose a method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material, so as to solve the technical problem in the prior art that acidified oil, a by-product of oil refining, cannot be directly used in the production of SAF due to its high acid value and the presence of residual sulfate.

[0006] The present application provides a method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material, comprising the following steps: Liquid alkali neutralization and desulfurization: Use liquid alkali to neutralize the acidified oil to obtain the first oil; Calcium oxide removes residual sulfate: Calcium oxide is used to remove sulfate from the first oil to obtain the second oil; Diatomaceous earth assists in filtering and removing impurities: diatomaceous earth is used to adsorb the second grease and assist in filtering and removing impurities, thereby obtaining the third grease; Glycerol esterification reaction: esterifying the third oil with glycerol to obtain the fourth oil; Oxalic acid acidification and metal ion removal: the fourth oil is acidified with oxalic acid to obtain the fifth oil; Dehydration: Dehydrate the fifth oil to obtain high-quality industrial-grade mixed oil for SAF.

[0007] Compared with the prior art, the beneficial effects of this application include: The present application prepares high-quality industrial-grade mixed oil for SAF by sequentially using liquid alkali for neutralization and desulfurization, calcium oxide for removing residual sulfate, diatomaceous earth for filtration and removal of impurities, glycerol esterification reaction, oxalic acid acidification for removing metal ions, and dehydration. The method of the present application is simple and has low energy consumption. The acid value of the prepared high-quality industrial-grade mixed oil for SAF is within 6 mg KOH / g and the yield is above 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 It is a process flow chart of an embodiment of a method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material provided in the present application. DETAILED DESCRIPTION

[0009] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0010] See also Figure 1 The present application provides a method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material, comprising the following steps: S1, liquid alkali neutralization and desulfurization: using liquid alkali to neutralize the acidified oil to obtain the first oil; S2, removing residual sulfate with calcium oxide: removing sulfate from the first oil with calcium oxide to obtain a second oil; S3, diatomaceous earth assisted filtration and impurity removal: diatomaceous earth is used to adsorb the second oil and fat to assist filtration and impurity removal, thereby obtaining a third oil and fat; S4, glycerol esterification reaction: esterifying the third oil with glycerol to obtain a fourth oil; S5, oxalic acid acidification and metal ion removal: acidifying the fourth oil with oxalic acid to obtain the fifth oil; S6. Dehydration: Dehydrate the fifth oil to obtain high-quality industrial-grade mixed oil for SAF.

[0011] The present application prepares high-quality industrial-grade mixed oil for SAF by sequentially using liquid alkali for neutralization and desulfurization, calcium oxide to remove residual sulfate, diatomaceous earth to assist in filtering and removing impurities, glycerol esterification reaction, oxalic acid acidification to remove metal ions, and dehydration. The method of the present application is simple and has low energy consumption. The acid value of the prepared high-quality industrial-grade mixed oil for SAF is within 6 mg KOH / g, and the yield is above 100%. Specifically, the present application can neutralize free acid by alkali neutralization of the acidified oil; the present application can further deeply remove sulfate by adding calcium oxide to the first oil; the combination of the two can improve the sulfate removal effect while avoiding the problem of free fatty acid saponification, reduced yield, and increased difficulty in subsequent separation due to excessive addition of sodium hydroxide and calcium oxide. The present application adopts diatomaceous earth as a filter aid to remove impurities. Diatomaceous earth as a filter aid can remove calcium sulfate, calcium oxide, mechanical impurities, etc.; the present application can obtain a crude industrial-grade mixed oil with a low acid value (i.e., the fourth oil) through a glycerol esterification reaction; the present application can remove metal ion impurities through oxalic acid acidification; the present application can reduce the water content in the oil through dehydration.

[0012] In this embodiment, in step S1, the acid value of the acidified oil is ≤150 mg KOH / g, the sulfate content is ≤0.5%, the total metal ion content is ≤300 ppm, and the phosphorus content is ≤100 ppm. The present application does not limit the type of acidified oil, and those skilled in the art can select it according to actual conditions. In some specific embodiments of the present application, the acidified oil is soybean acidified oil.

[0013] In this embodiment, in step S1, the process of liquid alkali neutralization and desulfurization includes: using sodium hydroxide solution to neutralize the acidified oil, and then performing a first static sedimentation separation to obtain a first oil and a first wastewater. The reaction formula involved is as follows: 2NaOH+H2SO4=Na2SO4+2H2O The mass fraction of the sodium hydroxide solution is 2%-5%, including but not limited to 2%, 3%, 4%, 5%, etc.; the amount of the sodium hydroxide solution added is 5%-15% of the mass of the acidified oil, including but not limited to 5%, 7%, 9%, 11%, 13%, 15%, etc.

[0014] The temperature for alkali neutralization is 60-80°C, including but not limited to 60°C, 65°C, 70°C, 75°C, 80°C, etc.; the time for alkali neutralization is 15-30 minutes, including but not limited to 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.

[0015] Among them, the temperature of the first static sedimentation separation is 60-80°C, including but not limited to 60°C, 65°C, 70°C, 75°C, 80°C, etc.; the time of the first static sedimentation separation is 3-6 hours, including but not limited to 3 hours, 4 hours, 5 hours, 6 hours, etc.

[0016] The pH of the first wastewater is controlled to be ≥6. If the pH of the first wastewater is too low, the sulfuric acid in the oil cannot be completely neutralized, resulting in an increase in subsequent side reactions and corrosion of equipment. Therefore, if the pH of the first wastewater is less than 6, sodium hydroxide solution needs to be added to repeat the above liquid alkali neutralization and desulfurization process until the pH of the first wastewater is ≥6.

[0017] In this embodiment, the reaction formula involved in step S2 is as follows: CaO+H2SO4=CaSO4+H2O CaO+2RCOOH=(RCOO)2Ca+H2O (excess calcium oxide and fatty acids generate fatty acid calcium soap) Wherein, the particle size of calcium oxide is 200-2000 mesh, including but not limited to 200 mesh, 400 mesh, 800 mesh, 1200 mesh, 1600 mesh, 2000 mesh and the like.

[0018] Among them, the added amount of calcium oxide is 0.1%-0.3% of the mass of the first oil, including but not limited to 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0019] The temperature for desulfation of calcium oxide is 60-80°C, including but not limited to 60°C, 65°C, 70°C, 75°C, 80°C, etc.; the time for desulfation of calcium oxide is 45-60 minutes, including but not limited to 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc.

[0020] In this embodiment, in step S3, diatomaceous earth is used to adsorb the second oil to assist in filtering out impurities, and then the third oil is obtained by filtering.

[0021] The added amount of diatomaceous earth is 0.2%-0.5% of the mass of the second oil, including but not limited to 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0022] Among them, the temperature for adsorption-assisted filtration and impurity removal is 70-90°C, including but not limited to 70°C, 75°C, 80°C, 85°C, 90°C, etc.; the time for adsorption-assisted filtration and impurity removal is 45-60 minutes, including but not limited to 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc.

[0023] In this embodiment, in step S4, the amount of glycerol added is 6%-9% of the mass of the third oil, including but not limited to 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, etc.

[0024] In this embodiment, in step S4, a triglyceride esterification reaction is adopted.

[0025] Wherein, the temperature of the primary esterification reaction is 180-200°C, including but not limited to 180°C, 185°C, 190°C, 195°C, 200°C, etc.; the vacuum residual pressure of the primary esterification reaction is 8000-15000Pa, including but not limited to 8000Pa, 9000Pa, 10000Pa, 12000Pa, 13000Pa, 14000Pa, 15000Pa, etc.; the time of the primary esterification reaction is 1-4 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, etc. By adopting the above process parameters, the present application can control the acid value of the primary glycerol esterification product within 50 mg KOH / g.

[0026] Wherein, the temperature of the secondary esterification reaction is 200-220°C, including but not limited to 200°C, 205°C, 210°C, 215°C, 220°C, etc.; the vacuum residual pressure of the secondary esterification reaction is 5000-8000Pa, including but not limited to 5000Pa, 6000Pa, 7000Pa, 8000Pa, etc.; the time of the secondary esterification reaction is 1-4 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, etc. By adopting the above process parameters, the present application can control the acid value of the secondary glycerol esterification product within 20 mg KOH / g.

[0027] The temperature of the tertiary esterification reaction is 220-245°C, including but not limited to 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, etc.; the vacuum residual pressure of the tertiary esterification reaction is 500-1500Pa, including but not limited to 500Pa, 700Pa, 900Pa, 1100Pa, 1300Pa, 1500Pa, etc.; the time of the tertiary esterification reaction is 1-4 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, etc. By adopting the above process parameters, the present application can control the acid value of the tertiary glycerol esterification product within 6 mg KOH / g.

[0028] Wherein, glycerol is added in whole or in part during the primary esterification reaction.

[0029] In this embodiment, in step S4, the metal ion content of the fifth oil is ≤10 ppm, wherein the phosphorus content is ≤3 ppm.

[0030] In this embodiment, in step S5, the process of removing metal ions by oxalic acid acidification includes: acidifying the fourth oil with oxalic acid, and then performing a second static sedimentation separation to obtain the fifth oil and the second wastewater. The reaction formula involved is as follows: H2C2O4+(RCOO)2Ca=2RCOOH+CaC2O4 Among them, the added amount of oxalic acid is 0.5%-1.0% of the mass of the fourth oil, including but not limited to 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc.

[0031] Wherein, oxalic acid is added in the form of an aqueous solution, and the mass fraction of the oxalic acid solution is 20%-30%, including but not limited to 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0032] The acidification temperature is 80-100°C, including but not limited to 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the acidification time is 10-90 minutes, including but not limited to 10 minutes, 30 minutes, 50 minutes, 70 minutes, 90 minutes, etc.

[0033] Among them, the temperature of the second static sedimentation separation is 80-100°C, including but not limited to 80°C, 85°C, 90°C, 95°C, 100°C, etc.; the time of the second static sedimentation separation is 1-4 hours, including but not limited to 1 hour, 2 hours, 3 hours, 4 hours, etc.

[0034] The present application uses oxalic acid to remove metal ions from the fourth oil and fat, and in combination with the above-mentioned process parameters, it is possible to control the total metal ion content of the fifth oil and fat within 10 ppm and the phosphorus content within 3 ppm.

[0035] In this embodiment, in step S6, the fifth fat is vacuum-dehydrated.

[0036] Among them, the temperature of vacuum dehydration is 90-120℃, including but not limited to 90℃, 100℃, 110℃, 120℃, etc.; the residual pressure of vacuum dehydration is 3000-5000Pa, including but not limited to 3000Pa, 3500Pa, 4000Pa, 4500Pa, 5000Pa, etc.; the time of vacuum dehydration is 30-60 minutes, including but not limited to 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc.

[0037] The present application adopts vacuum dehydration of the fifth oil and fat and cooperates with the above-mentioned process parameters to control the water residue of high-quality industrial-grade mixed oil to less than 0.5%.

[0038] Example 1 (1) Liquid alkali neutralization and desulfurization Add 1000g of soybean acidified oil with an acid value of 120mg KOH / g, 0.32% sulfate ion, 124ppm metal ion content and 42ppm phosphorus content to a 2000ml three-necked flask. Install a stirrer and thermometer, and slowly heat the electric bowl under stirring. When the temperature reaches 70℃, add a sodium hydroxide aqueous solution (concentration of 3%) with a 10% oil weight, maintain stirring at 70℃ for 30 minutes, pour into a heat-insulating separatory funnel, keep warm at 70℃ for 6 hours, and remove the bottom aqueous solution. The pH value of the aqueous solution is required to be greater than 6. If it is lower than 6, sodium hydroxide aqueous solution needs to be added to continue the reaction until the pH value of the lower aqueous solution is greater than 6; after the pH value of the aqueous solution is qualified, the clear oil enters the next process.

[0039] (2) Calcium oxide removes residual sulfate Add alkali to a 2000ml three-necked flask to neutralize the reaction oil. Install a stirrer and thermometer, and slowly heat the electric bowl under stirring conditions. When the temperature reaches 70°C, add 0.2% of the oil weight of 400-mesh calcium oxide, maintain 70°C and stir for 60 minutes, and the reaction liquid enters the next process.

[0040] (3) Diatomaceous earth helps filter out impurities Add 0.3% diatomaceous earth by weight of oil to the above reaction solution, slowly raise the temperature to 90°C, maintain the temperature for 1 hour, and remove the waste diatomaceous earth residue by vacuum filtration with a Buchner funnel. The clear oil enters the next process.

[0041] (4) Glycerol esterification reaction Add filtered clean oil into a 2000ml three-necked flask, install a stirrer and a thermometer, heat the electric bowl slowly under stirring, turn on the water ring vacuum pump, control the vacuum residual pressure to 12000Pa, add glycerol that is 8% of the oil weight, start timing at 200℃, react for 2 hours, take samples to test the acid value according to GB / T5530, and the acid value test result is 38 mg KOH / g.

[0042] The mechanical vacuum pump was replaced, and the vacuum residual pressure was controlled to 6000Pa. The temperature was adjusted to 220°C and the temperature was maintained for 2 hours with stirring. The acid value was tested according to GB / T5530 and the acid value test result was 17 mg KOH / g.

[0043] Adjust the vacuum residual pressure to control the vacuum residual pressure to 600Pa, adjust the control temperature to 245°C, continue the reaction for 2 hours, and test the acid value according to GB / T5530. The acid value test result is 5.7 mg KOH / g.

[0044] (5) Oxalic acid acidification to remove metal ions The esterified oil was cooled to 90°C, and a 25% aqueous oxalic acid solution was slowly added under stirring. The amount of oxalic acid added was 0.5% of the weight of the oil. The temperature was maintained for 40 minutes, and the oil was poured into a heat-insulating separatory funnel for sedimentation and separation for 2 hours. The bottom water and interface layer were removed, and the clear oil was tested for metal ions and phosphorus according to ASTM D5185-18. The test results showed that the total metal ions were 9 ppm, of which the phosphorus was 2 ppm.

[0045] (6) Vacuum dehydration The demetallized oil was poured into a 2000 ml three-necked flask, equipped with a stirrer and a thermometer. Under stirring conditions, the electric heating bowl was heated slowly, the water ring vacuum pump was turned on, the vacuum residual pressure was controlled to 5000Pa, the solution temperature was 120℃, and dehydration was performed for 40 minutes to obtain 1050 grams of high-quality industrial-grade mixed oil. The water content of the solution was tested according to ISO662, and the water content was 0.1%. (Due to the weight gain of glycerol esterification, the yield exceeded 100%) Example 2 (1) Liquid alkali neutralization and desulfurization Add 1000g of soybean acidified oil with an acid value of 112mg KOH / g, 0.41% sulfate ion, 67ppm metal ion content and 29ppm phosphorus content to a 2000ml three-necked flask. Install a stirrer and thermometer, and slowly heat the electric bowl under stirring. When the temperature reaches 60℃, add a sodium hydroxide aqueous solution (concentration of 2%) with a 15% oil weight, maintain 60℃ stirring reaction for 30 minutes, pour into a heat-insulating separatory funnel, keep 60℃ and separate by sedimentation for 5 hours, and remove the bottom aqueous solution. The pH value of the aqueous solution is required to be greater than 6. If it is lower than 6, sodium hydroxide aqueous solution needs to be added to continue the reaction until the pH value of the lower aqueous solution is greater than 6; after the pH value of the aqueous solution is qualified, the clear oil enters the next process.

[0046] (2) Calcium oxide removes residual sulfate Add alkali to a 2000ml three-necked flask to neutralize the reaction oil. Install a stirrer and thermometer, and slowly heat the electric bowl under stirring conditions. When the temperature reaches 60°C, add 0.3% of the oil weight of 200-mesh calcium oxide, maintain 60°C and stir for 60 minutes, and the reaction liquid enters the next process.

[0047] (3) Diatomaceous earth helps filter out impurities Add 0.2% diatomaceous earth by weight of oil to the above reaction solution, slowly raise the temperature to 70°C, maintain the temperature for 1 hour, and remove the waste diatomaceous earth residue by vacuum filtration with a Buchner funnel. The clear oil enters the next process.

[0048] (4) Glycerol esterification reaction Add filtered clean oil into a 2000ml three-necked flask, install a stirrer and a thermometer, heat the electric bowl slowly under stirring, turn on the water ring vacuum pump, control the vacuum residual pressure to 15000Pa, add glycerol that is 7% of the oil weight, start timing at 180℃, react for 4 hours, take samples to test the acid value according to GB / T5530, and the acid value test result is 31 mg KOH / g.

[0049] The mechanical vacuum pump was replaced, and the vacuum residual pressure was controlled to 8000Pa. The temperature was adjusted to 200°C and the temperature was maintained for 4 hours with stirring. The acid value was tested according to GB / T5530 and the acid value test result was 15 mg KOH / g.

[0050] Adjust the vacuum residual pressure to control the vacuum residual pressure to 1500Pa, adjust the control temperature to 220°C, continue the reaction for 4 hours, and test the acid value according to GB / T5530. The acid value test result is 5.2mg KOH / g.

[0051] (5) Oxalic acid acidification to remove metal ions The esterified oil was cooled to 95°C, and a 30% aqueous oxalic acid solution was slowly added under stirring, and the amount of oxalic acid added was 0.8% of the weight of the oil. The temperature was maintained for 10 minutes, and the oil was poured into a heat-insulating separatory funnel for sedimentation and separation for 4 hours. The bottom water and interface layer were removed, and the clear oil was tested for metal ions and phosphorus according to ASTM D5185-18. The test results showed that the total metal ions were 8 ppm, of which the phosphorus was 2 ppm.

[0052] (6) Vacuum dehydration The demetallized oil was poured into a 2000 ml three-necked flask, equipped with a stirrer and a thermometer. Under stirring conditions, the electric heating bowl was heated slowly, the water ring vacuum pump was turned on, the vacuum residual pressure was controlled to 4000Pa, the solution temperature was 90°C, and dehydration was performed for 30 minutes to obtain 1041 grams of high-quality industrial-grade mixed oil. The water content of the solution was tested according to ISO662, and the water content was 0.18%. (Due to the weight gain of glycerol esterification, the yield exceeded 100%) Example 3 (1) Liquid alkali neutralization and desulfurization Add 1000g of soybean acidified oil with an acid value of 134mg KOH / g, 0.37% sulfate ion, 66ppm metal ion content and 21ppm phosphorus content to a 2000ml three-necked flask. Install a stirrer and thermometer, and slowly heat the electric bowl under stirring. When the temperature reaches 80℃, add a 5% sodium hydroxide aqueous solution (concentration is 5%) of the oil weight, maintain 80℃ stirring reaction for 15 minutes, pour into a heat-insulating separatory funnel, keep 80℃ and separate by sedimentation for 3 hours, and remove the bottom aqueous solution. The pH value of the aqueous solution is required to be greater than 6. If it is lower than 6, sodium hydroxide aqueous solution needs to be added to continue the reaction until the pH value of the lower aqueous solution is greater than 6; after the pH value of the aqueous solution is qualified, the clear oil enters the next process.

[0053] (2) Calcium oxide removes residual sulfate Add alkali to a 2000ml three-necked flask to neutralize the reaction oil. Install a stirrer and thermometer, and slowly heat the electric bowl under stirring conditions. When the temperature reaches 80°C, add 0.1% of the oil weight of 200-mesh calcium oxide, maintain 80°C and stir for 45 minutes, and the reaction liquid enters the next process.

[0054] (3) Diatomaceous earth helps filter out impurities Add 0.5% diatomaceous earth by weight of oil to the above reaction solution, slowly raise the temperature to 80°C, maintain the temperature for 45 minutes, and remove the waste diatomaceous earth residue by vacuum filtration with a Buchner funnel. The clear oil enters the next process.

[0055] (4) Glycerol esterification reaction Add filtered clean oil into a 2000ml three-necked flask, install a stirrer and a thermometer, heat the electric bowl slowly under stirring, turn on the water ring vacuum pump, control the vacuum residual pressure to 8000Pa, add glycerol with a weight of 8.5% of the oil, start timing at 190℃, react for 1 hour, take samples for acid value testing according to GB / T5530, and the acid value test result is 35 mg KOH / g.

[0056] Replace the mechanical vacuum pump, control the vacuum residual pressure to 5000Pa, adjust the temperature control to 210℃, maintain the temperature for 1 hour, take samples and test the acid value according to GB / T5530, and the acid value test result is 18 mg KOH / g.

[0057] Adjust the vacuum residual pressure to control the vacuum residual pressure to 500Pa, adjust the control temperature to 240°C, continue the reaction for 1 hour, and test the acid value according to GB / T5530. The acid value test result is 5.9 mg KOH / g.

[0058] (5) Oxalic acid acidification to remove metal ions The esterified oil was cooled to 80°C, and a 20% aqueous oxalic acid solution was slowly added under stirring, and the amount of oxalic acid added was 1% of the oil weight. The temperature was maintained for 90 minutes, and the oil was poured into a heat-insulating separatory funnel for sedimentation and separation for 1 hour. The bottom water impurities and the interface layer were removed, and the clear oil was tested for metal ions and phosphorus according to ASTM D5185-18. The test results showed that the total metal ions were 6ppm, of which the phosphorus element was 1ppm.

[0059] (6) Vacuum dehydration The demetallized oil was poured into a 2000 ml three-necked flask, equipped with a stirrer and a thermometer. Under stirring conditions, the electric heating bowl was heated slowly, the water ring vacuum pump was turned on, the vacuum residual pressure was controlled to 3000Pa, the solution temperature was 110℃, and dehydration was performed for 60 minutes to obtain 1064 grams of high-quality industrial-grade mixed oil. The water content of the solution was tested according to ISO662, and the water content was 0.07%. (Due to the weight gain of glycerol esterification, the yield exceeded 100%) Comparative Example 1 Compared with Example 1, the only difference is that there is no liquid alkali neutralization and desulfurization step, and calcium oxide is directly used to neutralize the acidified oil to remove residual sulfate, and the steps are as follows: 1000 g of soybean acidified oil with an acid value of 120 mg KOH / g, 0.32% sulfate ion, 124 ppm metal ion content and 42 ppm phosphorus content was added to a 2000 ml three-necked flask. Stirring and thermometer were installed, and the electric heating bowl was heated slowly under stirring conditions. When the temperature reached 70°C, 0.2% of the oil weight of 400 mesh calcium oxide was added, and the reaction was stirred at 70°C for 60 minutes. The reaction solution entered the subsequent diatomaceous earth assisted filtration to remove impurities, glycerol esterification reaction, oxalic acid acidification to remove metal ions, and vacuum dehydration steps. The specific process parameters were all consistent with those in Example 1.

[0060] In this comparative example, 1013 g of industrial-grade mixed oil was obtained, and its quality indicators were as follows: acid value 9.2 mg KOH / g, water content 0.09%, total metal ions 19 ppm, including phosphorus 5 ppm.

[0061] Comparative Example 2 Compared with Example 1, the only difference is that there is no step of removing residual sulfate with calcium oxide, and the acidified oil is directly neutralized and desulfurized with sodium hydroxide, and the steps are as follows: Add 1000 grams of soybean acidified oil with an acid value of 120 mg KOH / g, 0.32% sulfate ion, 124 ppm metal ion content, and 42 ppm phosphorus content to a 2000 ml three-necked flask. Install a stirrer and a thermometer, and slowly heat the electric bowl under stirring. When the temperature reaches 70°C, add a sodium hydroxide aqueous solution (concentration of 3%) with a weight of 10% of the oil, maintain 70°C stirring reaction for 30 minutes, pour into a heat-insulating separatory funnel, keep 70°C for sedimentation separation for 6 hours, and remove the bottom aqueous solution. The pH value of the aqueous solution is required to be greater than 6. If it is lower than 6, sodium hydroxide aqueous solution needs to be added to continue the reaction until the pH value of the lower aqueous solution is greater than 6; after the pH value of the aqueous solution is qualified, the clear oil enters the subsequent diatomaceous earth assisted filtration to remove impurities, glycerol esterification reaction, oxalic acid acidification to remove metal ions, and vacuum dehydration steps, and the specific process parameters are consistent with Example 1.

[0062] In this comparative example, 1018 g of industrial-grade mixed oil was obtained, and its quality indicators were as follows: acid value 7.9 mg KOH / g, water content 0.1%, total metal ions 32 ppm, including phosphorus 3 ppm.

[0063] Comparative Example 3 Compared with Example 1, the only difference is that liquid alkali is used for neutralization and desulfurization, calcium oxide is used to remove residual sulfate, diatomaceous earth is used to assist in filtering and removing impurities, oxalic acid is used for acidification and removal of metal ions, vacuum dehydration, and glycerol esterification are used to prepare high-quality industrial-grade mixed oil for SAF, and the specific process parameters are consistent with those in Example 1.

[0064] In this comparative example, 1027 g of industrial-grade mixed oil was obtained, and its quality indicators were as follows: acid value 8.3 mg KOH / g, water content 0.15%, total metal ions 17 ppm, including 5 ppm phosphorus.

[0065] The quality standards of industrial-grade mixed oil used for SAF are shown in Table 1.

[0066] Table 1

[0067] It can be seen from Table 1 that the SAF industrial-grade mixed oil produced in the examples of the present application can meet the standard requirements.

[0068] In summary, the present application prepares a high-quality industrial-grade mixed oil for SAF by sequentially neutralizing the acidified oil with liquid alkali for desulfurization, removing residual sulfate with calcium oxide, removing impurities with diatomaceous earth, esterifying with glycerol, removing metal ions with oxalic acid, and dehydrating under vacuum. The method is simple and has low energy consumption. The acid value of the high-quality industrial-grade mixed oil for SAF produced by the present application is controlled within 6 mg KOH / g, the total metal ion content is controlled within 10 ppm, the phosphorus content is controlled within 3 ppm, the residual water is controlled within 0.5%, and the yield is above 100%.

[0069] The specific implementation methods of the present application described above do not constitute a limitation on the protection scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the protection scope of the claims of the present application.

Claims

1. A method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material, characterized in that: The following steps are involved: Liquid alkali neutralization and desulfurization: Use liquid alkali to neutralize the acidified oil to obtain the first oil; Calcium oxide removes residual sulfate: calcium oxide is used to remove sulfate from the first oil to obtain a second oil; Diatomaceous earth assists in filtering and removing impurities: using diatomaceous earth to adsorb the second grease and assist in filtering and removing impurities, thereby obtaining a third grease; Glycerol esterification reaction: esterifying the third oil with glycerol to obtain a fourth oil; Oxalic acid acidification and metal ion removal: acidifying the fourth oil with oxalic acid to obtain a fifth oil; Dehydration: Dehydrate the fifth oil to obtain high-quality industrial-grade mixed oil for SAF.

2. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: The acid value of the acidified oil is ≤150 mg KOH / g, the sulfate content is ≤0.5%, the total metal ion content is ≤300 ppm, and the phosphorus content is ≤100 ppm.

3. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: The acid value of the fourth oil is ≤6 mg KOH / g; and / or, The metal ion content of the fifth oil is ≤10 ppm, wherein the phosphorus content is ≤3 ppm; and / or, The water residue of the high-quality industrial grade and mixed oil is ≤0.5%.

4. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: The process of neutralizing and desulfurizing with liquid caustic soda comprises: The acidified oil is alkali-neutralized with a sodium hydroxide solution, and then subjected to a first static sedimentation separation to obtain a first oil and a first wastewater; Detecting the pH of the first wastewater, if the pH of the first wastewater is less than 6, adding sodium hydroxide solution to repeat the liquid alkali neutralization and desulfurization process until the pH of the first wastewater is ≥ 6; wherein, The mass fraction of the sodium hydroxide solution is 2%-5%; and / or, The amount of sodium hydroxide solution added is 5%-15% of the mass of the acidified oil; and / or, The alkali neutralization temperature is 60-80°C, and the alkali neutralization time is 15-30 minutes; and / or, The temperature of the first static sedimentation separation is 60-80° C., and the time of the first static sedimentation separation is 3-6 hours.

5. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: In the process of removing residual sulfate radicals with calcium oxide, the particle size of calcium oxide is 200-2000 mesh; and / or, The amount of calcium oxide added is 0.1%-0.3% of the mass of the first oil; and / or, The temperature for desulfation of calcium oxide is 60-80°C, and the time for desulfation of calcium oxide is 45-60 minutes.

6. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: The process of diatomaceous earth-assisted filtration and impurity removal includes: The second oil is adsorbed and filtered with diatomaceous earth to remove impurities, and then filtered to obtain the third oil; wherein, The amount of diatomaceous earth added is 0.2%-0.5% of the mass of the second oil; and / or, The temperature of the adsorption-assisted filtration and impurity removal is 70-90° C., and the time of the adsorption-assisted filtration and impurity removal is 45-60 minutes.

7. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: During the glycerol esterification reaction, the amount of glycerol added is 6%-9% of the mass of the third oil.

8. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: A three-stage glycerol esterification reaction is used; wherein, The temperature of the primary esterification reaction is 180-200° C., the vacuum residual pressure of the primary esterification reaction is 8000-15000 Pa, and the time of the primary esterification reaction is 1-4 hours; and / or, The temperature of the secondary esterification reaction is 200-220° C., the vacuum residual pressure of the secondary esterification reaction is 5000-8000 Pa, and the time of the secondary esterification reaction is 1-4 hours; and / or, The temperature of the tertiary esterification reaction is 220-245° C., the vacuum residual pressure of the tertiary esterification reaction is 500-1500 Pa, and the time of the tertiary esterification reaction is 1-4 hours.

9. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: The process of oxalic acid acidification and metal ion removal comprises: The fourth oil is acidified with oxalic acid, and then subjected to a second static sedimentation separation to obtain a fifth oil and a second wastewater; wherein, The amount of oxalic acid added is 0.5%-1.0% of the mass of the fourth oil; and / or, The oxalic acid is added in the form of an aqueous solution, the mass fraction of the oxalic acid solution is 20%-30%; and / or, The acidification temperature is 80-100° C., and the acidification time is 10-90 minutes; and / or, The temperature of the second static sedimentation separation is 80-100° C., and the time of the second static sedimentation separation is 1-4 hours.

10. The method for preparing high-quality industrial-grade mixed oil for SAF using acidified oil as raw material according to claim 1, characterized in that: The fifth oil is subjected to vacuum dehydration; wherein, The temperature of the vacuum dehydration is 90-120° C., the residual pressure of the vacuum dehydration is 3000-5000 Pa, and the time of the vacuum dehydration is 30-60 minutes.

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