Method for separating and removing impurities through grease reaction

Abstract

The invention provides a method for separating and removing impurities through grease reaction, which comprises the following steps: heating a grease raw material in the presence of a polar medium, fully reacting the grease raw material under the action of a basic catalyst, and separating the polar medium in a mixture obtained after the reaction to obtain pretreated grease; wherein the polar medium comprises one or a combination of more of C1 to C6 monohydroxy alcohols and carbonates of the C1 to C6 monohydroxy alcohols. According to the method provided by the invention, the grease raw materials are high in adaptability, and various grease raw materials can be directly processed; the grease reaction separation process is short in flow and low in material consumption; the grease raw material recycling rate is high; and the obtained refined oil has low impurity content and high quality.

Description

Technical Field

[0001] This invention relates to a method for separating and removing impurities from oils and fats through reaction, belonging to the field of biomass energy technology, particularly the field of oil refining and separation technology. Background Technology

[0002] The long-term and extensive use of fossil resources to produce liquid fuels has had negative environmental impacts, such as the greenhouse effect. Moreover, the reserves of these non-renewable resources are decreasing year by year as they are continuously consumed. Biofuels are low-carbon, clean, green, and renewable fuels, and with increasing public awareness of environmental and health issues, they are gradually becoming an important supplement to petrochemical diesel.

[0003] Biofuels prepared by hydrodeoxygenation isomerization of oils and fats (such as hydrocarbon-based biodiesel and biojet fuel) have attracted widespread attention due to their superior characteristics, including high calorific value, good combustion performance, similar composition to petrochemical fuels, and good compatibility. Therefore, research on the technology of preparing liquid fuels through hydrodeoxygenation of oils and fats has become increasingly important in this field.

[0004] Oil and fat feedstocks contain various impurities, such as phospholipids, sulfur, chlorine, nitrogen, and metals. These impurities can accelerate the deactivation of hydrodeoxygenation catalysts and reactor corrosion, leading to unstable reactor operation and even increasing safety risks. Therefore, thorough refining and separation of oils and fats to obtain high-quality refined oil is crucial for ensuring the stable operation of oil-based biofuel production plants.

[0005] Currently, edible vegetable oil refining processes are widely used. Oil refining technologies targeting edible oils mainly include key units such as pressing, extraction, degumming, deacidification, dehydration, decolorization, deodorization, and dewaxing. For example, vegetable oil refining technologies can refine jatropha oil, palm oil, cottonseed oil, and castor oil to obtain high-quality refined oils. However, these oil refining technologies have high material consumption, large amounts of solid waste, and poor raw material adaptability. For oils recovered from the catering industry with high acid values, fatty acid loss is significant. In energy utilization, vegetable oil refining processes require crude oil to have a free fatty acid content of less than 15 wt%, a sulfur content of less than 30 mg / kg, and a chlorine content of less than 8 mg / kg; while edible oil refining processes typically require crude oil to have an acid value of less than 10 mg KOH / g.

[0006] More importantly, edible vegetable oil refining processes are extremely ineffective at separating impurities such as chlorine and sulfur from low-quality oil feedstocks, such as recycled cooking oil from the catering industry, and typically cannot yield refined oils that meet the requirements for hydrogenation reactions. Therefore, the oil feedstocks used to prepare hydrocarbon-based biodiesel and biojet fuel are mainly refined vegetable oils or some higher-quality recycled cooking oils. Large quantities of inexpensive recycled cooking oils are difficult to refine and remove impurities due to their complex and varied composition, and thus cannot be used for hydrogenation and deoxygenation for energy utilization.

[0007] Furthermore, there are significant differences in the refining requirements for oils used for energy purposes and those used for food. For food purposes, phospholipids, vitamin E, and sterols in oils are beneficial components, while free fatty acids and trans fatty acids need to be restricted. However, for energy applications, free fatty acids remain an important raw material, while other components need to be restricted. Inferior oil raw materials such as recycled oil from the catering industry often have high acid values, sometimes exceeding 120 mg KOH / g, requiring full utilization of free fatty acid raw materials.

[0008] Waste oils and other raw materials recycled from the catering industry are usually inexpensive, have high acid values, and contain a wide variety of impurities in varying amounts. In particular, impurities such as sulfur, chlorine, phosphorus, nitrogen, and metals (with contents reaching 500 mg / kg, 160 mg / kg, 1 wt%, 400 mg / kg, and 800 mg / kg, respectively) significantly increase the technical difficulty of refining waste oils.

[0009] CN117431087A discloses a method for removing organochlorine compounds from plastic pyrolysis oil, waste cooking oil, crude oil, and its distillates. This method involves mixing the oil, a nucleophile (such as potassium hydroxide, sodium hydroxide, and sodium ethoxide), and a solvent (such as ethylene glycol, glycerol, and ethanolamine) and reacting them. The oil and solvent phases are then separated to obtain dechlorinated oil. However, because organochlorine compounds in oil are weakly polar, they do not easily dissolve in polar solvents, making the reaction between the organochlorine compounds and the nucleophile relatively difficult. To enhance the removal effect, CN117887520A discloses a method for removing chlorinated compounds (mainly chlorinated fatty acid glycerides) from waste oils. This method involves reacting the waste oil with organochlorine removal agents (such as hexamethylenediamine, propylenediamine, and hydrophilic β-cyclodextrin and its derivatives) in the presence of water and nitrogen, followed by electro-desalting treatment to obtain dechlorinated oil. However, the poor mutual solubility of oil and water still presents the problem of difficult contact between the reaction reagents. CN105368580A discloses a method for removing organochlorine from recycled cooking oil in the catering industry. Based on electro-dechlorination, this method enhances the dechlorination effect by adding alkali metal hydroxides, phase transfer agents (quaternary ammonium salts, etc.), and solvents (glycerol, dimethyl sulfoxide, etc.). However, phase transfer agents are usually partially dissolved in the cooking oil, which complicates the composition of the reaction system.

[0010] Addressing the challenges of oil refining in biofuel production, particularly the efficient refining and removal of impurities such as chlorine from crude animal and vegetable oils and recycled cooking oils, a novel method for oil reaction separation and impurity removal has become a pressing technical issue in this field. This method simplifies the process, improves the adaptability of oil raw materials, and enhances their utilization rate. Summary of the Invention

[0011] In order to overcome the above-mentioned shortcomings and deficiencies, the purpose of this invention is to provide a method for removing impurities through reaction separation of oils.

[0012] To achieve the above objectives, on the one hand, the present invention provides a method for separating and removing impurities from oils and fats by reaction, wherein the method includes: heating the oil and fat raw materials in the presence of a polar medium, and allowing the oil and fat raw materials to react fully under the action of an alkaline catalyst, and then separating the polar medium in the mixture obtained after the reaction to obtain pretreated oils and fats;

[0013] The polar medium includes one or more of C1 to C6 monohydroxy alcohols and their carbonates. When using two or more of the substances such as C1 to C6 monohydroxy alcohols and their carbonates in the method described above, the specific ratio of each component is not required and can be adjusted as needed.

[0014] In one specific embodiment of the method described above, the polar medium includes one or a combination of several selected from methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, and hexanol and their carbonates. Generally, the reaction rate decreases as the molecular weight of the polar medium increases. Therefore, preferably, the polar medium includes one or a combination of several selected from methanol, ethanol, propanol, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0015] As a specific embodiment of the method described above in this invention, the method further includes mixing polyols and / or water into the polar medium.

[0016] As a specific embodiment of the method described above in this invention, the polyol includes one or a combination of several of the following: ethylene glycol, glycerol, polyglycerol with a molecular weight of less than 800, pentitol, and sorbitol.

[0017] As a specific embodiment of the method described above in this invention, the amount of polyol and / or water used does not exceed 100 wt%, based on the total weight of the oil raw materials as 100%.

[0018] As a specific embodiment of the method described above in this invention, the oil raw materials include one or a combination of several of the following: raw materials of animal and vegetable oils, oils or crude oils obtained through preliminary processing, such as animal fats obtained by heat treatment of fats, crude vegetable oils (vegetable oils) obtained by pressing or extraction, and waste oils.

[0019] As a specific embodiment of the method described above in this invention, the raw materials for the animal and vegetable oils include one or a combination of animal fat, cottonseed, and rapeseed.

[0020] The animal fats include one or a combination of several of the following: beef tallow, lard, chicken fat, duck fat, and fish oil.

[0021] The vegetable oils include one or a combination of several of the following: peanut oil, soybean oil, rapeseed oil, palm oil, cottonseed oil, corn oil, sunflower oil, rice bran oil, jatropha fruit oil, and microalgae oil.

[0022] The waste oil includes one or a combination of several of the following: acidified oil, frying oil, swill oil, and recycled oil from the catering industry, all of which have undergone impurity removal treatment. The acidified oil is produced during the oil refining process, while the frying oil, swill oil, and recycled oil from the catering industry are waste oils whose main structure has not changed after being used for other purposes.

[0023] As a specific embodiment of the method described above in this invention, the method further includes pre-separating the oil raw material by filtering, distilling or adsorbing to reduce impurities and obtain oil with lower impurity content, and / or further includes processing the oil raw material by shearing, extruding, grinding or pulverizing to improve reaction efficiency.

[0024] As a specific embodiment of the method described above in this invention, the alkaline catalyst includes one or a combination of oxides, hydroxides, carbonates and bicarbonates of sodium, potassium, magnesium, calcium, zinc and aluminum.

[0025] In one specific embodiment of the method described above in this invention, the amount of alkaline catalyst used is less than 1 wt% of the oil mass.

[0026] In one specific embodiment of the method described above in this invention, the mass ratio of the grease to the polar medium is 1:0.2-1:2.

[0027] In one specific embodiment of the method described above in this invention, the reaction temperature is 120-360℃, the pressure is 0.5-25MPa, and the reaction time is 0.5-4h.

[0028] In the method described above in this invention, the reaction includes the hydrolysis, esterification, and transesterification of the effective components (fatty acids and fatty acid glycerides) in the oil raw materials. Specifically, it includes the hydrolysis reaction of fatty acid glycerides, the esterification reaction of fatty acids with alcohols, the transesterification reaction of fatty acid glycerides with alcohols, and the transesterification reaction of fatty acids and fatty acid glycerides with carbonates. The reaction also includes the reaction and transformation of impurities such as sulfur, chlorine, phosphorus, nitrogen, and metals in the oil raw materials.

[0029] Depending on the structure of compounds containing chlorine and other hetero-elements and the differences in reaction conditions, they can react and transform into inorganic substances, low-boiling-point organic substances, or high-boiling-point organic substances, and separate from the weakly polar phase rich in oils.

[0030] In the methods described above, when the reaction temperature is too low, the reaction rate may be slow, or even some reactions may not occur; while when the reaction temperature is high, the reaction conditions are usually harsh, increasing equipment investment. Excessive reaction time reduces equipment utilization, while insufficient reaction time may result in incomplete oil and fat reaction. Furthermore, increasing the mass ratio of polar medium to oil and fat is beneficial for the complete reaction and conversion of the oil and fat.

[0031] In one specific embodiment of the method described above, the reaction is either a continuous reaction or a batch reaction, and / or the reaction is a single reaction or a multiple reaction. Generally, continuous reactions can improve production efficiency and reduce labor intensity, while batch reactions reduce technical difficulty. By conducting multiple reactions and separating byproducts or renewing the polar medium in between, the reaction effect can be improved and the reaction conditions can be reduced.

[0032] As a specific embodiment of the method described above in this invention, the separation includes separation methods such as distillation, sedimentation, or centrifugation.

[0033] In the method described above in this invention, polar media are separated by methods such as distillation, sedimentation, or centrifugation, based on their physical properties, to obtain pretreated oils with reduced impurity content, such as chlorine. For example, atmospheric distillation is a suitable choice for low-boiling-point polar media such as water, methanol, and ethanol; while for high-boiling-point polar media such as ethylene glycol and glycerol, due to their low solubility and high density, sedimentation or centrifugation can be used for separation. The polar media recovered after separation can be purified for recycling.

[0034] As a specific embodiment of the method described above in this invention, the method further includes performing vacuum distillation and / or adsorption treatment on the pretreated oil to obtain high-quality refined oil.

[0035] The pretreated oils referred to in this invention are oils that have undergone processing to remove most impurities such as chlorine. If the chlorine content and other indicators meet the requirements for hydrogenation reactions, they can be directly used as refined oils for the hydrogenation and deoxygenation of oils to produce hydrocarbon-based biodiesel or bio-jet fuels. Depending on the quality requirements of the refined oils, this invention can further treat the pretreated oils with vacuum distillation and / or adsorption, which is equivalent to refining, to obtain high-quality refined oils with extremely low chlorine and other impurity content that meet the requirements for hydrogenation reactions.

[0036] Therefore, the method provided by this invention enables the oil raw materials to undergo chemical reactions and physical separation to fully separate impurities such as sulfur, chlorine, phosphorus, nitrogen and metals, thereby obtaining high-quality refined oil to meet the requirements for the preparation of biofuels by hydrodeoxygenation of oils.

[0037] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0038] 1. It has strong adaptability to oil raw materials and can directly process a variety of oil raw materials, realizing the energy utilization of oil raw materials;

[0039] 2. The oil reaction separation process has a short flow rate and low material consumption;

[0040] 3. High recycling rate of oil raw materials;

[0041] 4. The method provided by this invention uses polar media such as C1 to C6 monohydroxy alcohols and their carbonates, which can promote the dispersion of alkaline catalysts into the oils and fats and fully convert impurities such as chlorine in the oils and fats. Therefore, the refined oil obtained by this invention has low impurity content and high quality, which is beneficial for ensuring the long-term stable operation of the hydrotreating unit. Detailed Implementation

[0042] It should be noted that the term "comprising" and any variations thereof in the specification and claims of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0043] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0044] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0045] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0046] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0047] In this invention, unless otherwise specified, all steps mentioned herein may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0049] Example 1

[0050] This embodiment provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0051] Methanol and propanol were mixed to obtain a first mixture, with propanol comprising 10 wt% and the remainder being methanol, based on the total weight of the first mixture being 100%. Sodium carbonate, at a mass of 0.3 wt% of rapeseed, was mixed with the first mixture to obtain a second mixture. Rapeseed (oil content 42.1 wt%, sulfur, chlorine, phosphorus, nitrogen, and metal contents 36 mg / kg, 16 mg / kg, 860 mg / kg, 420 mg / kg, and 340 mg / kg, respectively) was mixed with the first mixture at a mass ratio of 1:2 and then fed into a high-pressure reactor. The mixture was then heated, reacting the rapeseed at 360°C and 25 MPa for 4 hours under the influence of sodium carbonate. The reaction product was filtered to obtain a filter cake and a filtrate. The filter cake was reacted again under the same conditions, and the filter cake was separated to obtain the filtrate. The two filtrates were combined and distilled at 90°C to recover the polar medium. The resulting immiscible mixture was allowed to settle and separate into layers to obtain the upper pretreated oil. Finally, the pretreated oil was distilled under reduced pressure at 500 Pa and 260 °C to obtain refined oil. The contents of sulfur, chlorine, phosphorus, nitrogen and metals in the refined oil were only 3.5 mg / kg, 1.2 mg / kg, 0.5 mg / kg, 4.9 mg / kg and 3 mg / kg, respectively.

[0052] Example 2

[0053] This embodiment provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0054] Methanol and ethanol are mixed to obtain a first mixture, with ethanol comprising 30 wt% and the remainder being methanol, based on the total weight of the first mixture (100%). Calcium oxide is mixed with the first mixture at a mass ratio of 1 wt% of the crude oil obtained from cottonseed pressing to obtain a second mixture. The crude oil obtained from cottonseed pressing (acid value of 15 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen, and metal contents of 6.8 mg / kg, 4.2 mg / kg, 124 mg / kg, 81 mg / kg, and 395 mg / kg, respectively) is mixed with the first mixture at a mass ratio of 1:1 and then fed into a tubular reactor. Subsequently, it undergoes heat treatment, where the crude oil obtained from cottonseed pressing is heated at 290°C, 20 MPa, and an oil space velocity of 0.5 h⁻¹ under the action of calcium oxide. -1The reaction was carried out under specific conditions, and the polar medium was recovered by distillation at 90℃ and atmospheric pressure. The resulting immiscible mixture was allowed to settle and separate into layers to obtain the upper pretreated oil. Finally, the pretreated oil was fed into a fixed bed containing γ-alumina adsorbent for adsorption treatment (the mass ratio of pretreated oil to adsorbent was 1:1) to obtain refined oil. The content of sulfur, chlorine, phosphorus, nitrogen, and metals in the refined oil was only 1.5 mg / kg, 0.8 mg / kg, 1.5 mg / kg, 5.9 mg / kg, and 5 mg / kg, respectively.

[0055] Example 3

[0056] This embodiment provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0057] Methanol and dimethyl carbonate were mixed to obtain a first mixture, with dimethyl carbonate comprising 10 wt% and methanol as the remainder, based on the total weight of the first mixture (100%). Potassium hydroxide was mixed with the first mixture at a mass ratio of 0.2 wt% of the recycled cooking oil to obtain a second mixture. The recycled cooking oil (acid value 58 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen, and metal contents 380 mg / kg, 68 mg / kg, 1.6 mg / kg, 96 mg / kg, and 295 mg / kg, respectively) was mixed with the second mixture at a mass ratio of 1:0.8 and then fed into a tubular reactor. Subsequently, the recycled cooking oil was heated under the influence of potassium hydroxide at 260°C, 10 MPa, and an oil space velocity of 1 h⁻¹. -1 The reaction was carried out under certain conditions, and the reaction product was distilled at 95℃ and atmospheric pressure to recover the polar medium. The resulting immiscible mixture was allowed to stand and separate into layers to obtain the upper pretreated oil, in which the contents of sulfur, chlorine, phosphorus, nitrogen and metal were 58.6 mg / kg, 5.3 mg / kg, 0.6 mg / kg, 36.1 mg / kg and 26 mg / kg, respectively.

[0058] The pretreated oil was reacted again under the same conditions, and the polar solvent was recovered by distillation. The resulting immiscible mixture was centrifuged to obtain the upper layer of pretreated oil again. Finally, this portion of pretreated oil was distilled under reduced pressure at 500 Pa and 260 °C to obtain refined oil. The contents of sulfur, chlorine, phosphorus, nitrogen, and metals in the refined oil were 18.6 mg / kg, 1.3 mg / kg, 0.1 mg / kg, 16.1 mg / kg, and 3 mg / kg, respectively.

[0059] Example 4

[0060] This embodiment provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0061] Acidified soybean oil (acid value 168 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen and metal contents 1510 mg / kg, 6.8 mg / kg, 185 mg / kg, 126 mg / kg and 395 mg / kg respectively) was mixed with water and isopropanol at a mass ratio of 1:0.5:1. Magnesium oxide (1 wt% of the weight of the acidified soybean oil) was then added, and the resulting mixture was fed into a reaction vessel. The mixture was then heated to 180°C and 4 MPa for 1 hour under the action of magnesium oxide. The reaction product... The polar medium was recovered by distillation at atmospheric pressure and 160℃. Then, an equal amount of methanol was added (i.e., the mass ratio of distillate to methanol was 1:1), and the mixture was reacted again for 1 hour at 180℃ and 4 MPa using magnesium oxide (1 wt% of the mass of the distillate) as a catalyst. The reaction product was then distilled at atmospheric pressure to recover the polar medium, yielding a pretreated oil with sulfur, chlorine, phosphorus, nitrogen, and metal contents of 87.6 mg / kg, 2.7 mg / kg, 23.9 mg / kg, 56.1 mg / kg, and 109 mg / kg, respectively. Finally, the pretreated oil was subjected to vacuum distillation at 500 Pa and 280℃ to obtain refined oil. The refined oil contained sulfur, chlorine, phosphorus, nitrogen, and metal contents of 17.6 mg / kg, 0.7 mg / kg, 0.9 mg / kg, 16.1 mg / kg, and 4 mg / kg, respectively.

[0062] Example 5

[0063] This embodiment provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0064] Lard (acid value 18 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen, and metal content 16.8 mg / kg, 7.2 mg / kg, 84 mg / kg, 181 mg / kg, and 295 mg / kg, respectively) was mixed with glycerol (pre-dissolved with 0.1 wt% potassium hydroxide, the amount of potassium hydroxide calculated based on 100% of the total weight of lard) and tert-butanol at a mass ratio of 1:1:2. The mixture was then fed into a tubular reactor and subsequently heated under the influence of potassium hydroxide at 240°C, 6 MPa, and a fat hourly space velocity (FHSV) of 0.5 h⁻¹. -1The reaction was carried out under specific conditions, and the reaction product was centrifuged to obtain the upper pretreated oil, in which the contents of sulfur, chlorine, phosphorus, nitrogen, and metal were 8.6 mg / kg, 2.7 mg / kg, 1.9 mg / kg, 26.1 mg / kg, and 16 mg / kg, respectively. Finally, the pretreated oil was fed into a fixed bed containing SiO2 adsorbent for adsorption treatment (the mass ratio of pretreated oil to adsorbent was 1:1) to obtain refined oil. The contents of sulfur, chlorine, phosphorus, nitrogen, and metal in the refined oil were 5.6 mg / kg, 0.7 mg / kg, 0.9 mg / kg, 16.1 mg / kg, and 3 mg / kg, respectively.

[0065] Example 6

[0066] This embodiment provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0067] Refined cottonseed oil (acid value of 0.5 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen, and metal content of 11.6 mg / kg, 6.4 mg / kg, 18 mg / kg, 36 mg / kg, and 9 mg / kg, respectively) and dimethyl carbonate (with 0.3 wt% sodium hydroxide pre-dissolved, the amount of sodium hydroxide calculated based on 100% of the total weight of refined cottonseed oil) were mixed at a mass ratio of refined cottonseed oil to dimethyl carbonate of 1:1 and fed into a tubular reactor. Subsequently, the mixture underwent heat treatment, with the refined cottonseed oil heated at 260°C, 10 MPa, and an oil space velocity of 0.5 h⁻¹ under the influence of sodium hydroxide. -1 The reaction was carried out under specific conditions, and the reaction product was separated by sedimentation at room temperature to obtain the upper pretreated oil, in which the contents of sulfur, chlorine, phosphorus, nitrogen, and metal were 5.6 mg / kg, 2.7 mg / kg, 2.6 mg / kg, 9.1 mg / kg, and 16 mg / kg, respectively. Finally, the pretreated oil was fed into a fixed bed containing sulfonic acid resin adsorbent for adsorption treatment (the mass ratio of pretreated oil to adsorbent was 1:1) to obtain refined oil. The contents of sulfur, chlorine, phosphorus, nitrogen, and metal in the refined oil were 4.6 mg / kg, 1.7 mg / kg, 1.2 mg / kg, 6.1 mg / kg, and 3 mg / kg, respectively.

[0068] Comparative Example 1

[0069] This comparative example provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0070] Lard (acid value 18 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen, and metal content 16.8 mg / kg, 7.2 mg / kg, 84 mg / kg, 181 mg / kg, and 295 mg / kg, respectively) and glycerol (pre-dissolved with 0.1 wt% potassium hydroxide, the amount of potassium hydroxide calculated based on 100% of the total weight of lard) were mixed at a 1:1 mass ratio and fed into a tubular reactor. The mixture was then heated under the influence of potassium hydroxide at 240°C, 6 MPa, and a fat hourly space velocity (FHSV) of 0.5 h⁻¹. -1 The reaction was carried out under specific conditions, and the reaction product was centrifuged to obtain the upper pretreated oil, in which the contents of sulfur, chlorine, phosphorus, nitrogen, and metal were 12.8 mg / kg, 5.7 mg / kg, 79 mg / kg, 161 mg / kg, and 261 mg / kg, respectively. Finally, the pretreated oil was fed into a fixed bed containing SiO2 adsorbent for adsorption treatment (the mass ratio of pretreated oil to adsorbent was 1:1) to obtain refined oil. The contents of sulfur, chlorine, phosphorus, nitrogen, and metal in the refined oil were 11.5 mg / kg, 5.0 mg / kg, 54 mg / kg, 146 mg / kg, and 234 mg / kg, respectively.

[0071] Comparative Example 2

[0072] This comparative example provides a method for the reaction separation, refining, and removal of impurities such as chlorine from oils and fats, wherein the method includes the following specific steps:

[0073] Refined cottonseed oil (acid value of 0.5 mg KOH / g, sulfur, chlorine, phosphorus, nitrogen, and metal content of 11.6 mg / kg, 6.4 mg / kg, 18 mg / kg, 36 mg / kg, and 9 mg / kg, respectively) was mixed with glycerol (pre-dissolved with 0.3 wt% sodium hydroxide, the amount of sodium hydroxide being calculated based on 100% of the total weight of refined cottonseed oil) at a mass ratio of 1:1. The mixture was then fed into a tubular reactor and subjected to heat treatment at 260°C, 10 MPa, and an oil space velocity of 0.5 h⁻¹ under the influence of sodium hydroxide. -1 The reaction was carried out under specific conditions, and the reaction product was separated by sedimentation at room temperature to obtain the upper pretreated oil, in which the contents of sulfur, chlorine, phosphorus, nitrogen, and metal were 9.6 mg / kg, 5.2 mg / kg, 12 mg / kg, 24 mg / kg, and 12 mg / kg, respectively. Finally, the pretreated oil was fed into a fixed bed containing sulfonic acid resin adsorbent for adsorption treatment (the mass ratio of pretreated oil to adsorbent was 1:1) to obtain refined oil. The contents of sulfur, chlorine, phosphorus, nitrogen, and metal in the refined oil were 6.6 mg / kg, 4.7 mg / kg, 11 mg / kg, 19 mg / kg, and 6 mg / kg, respectively.

[0074] As can be seen from Examples 1-6 of this invention, the method for removing impurities such as chlorine from oils through reaction separation and refining provided by this invention has strong adaptability to oil raw materials, can directly process various oil raw materials, and realize the energy utilization of oil raw materials; moreover, the oil reaction separation process has a short flow rate, low material consumption, and high oil raw material recovery rate; most importantly, the pretreated oil and refined oil obtained by this invention have low impurity content and high quality. This shows that the method of this invention can achieve the purpose of removing impurities such as chlorine from oil raw materials through reaction separation, thereby improving the quality of the obtained oil products.

[0075] The only difference between Comparative Example 1 and Example 5 of the present invention is the absence of tert-butanol. Similarly, the only difference between Comparative Example 2 and Example 6 of the present invention is the replacement of dimethyl carbonate with glycerol. In other words, neither Comparative Example 1 nor Comparative Example 2 uses C1 to C6 monohydroxy alcohols and their carbonates. Comparing the impurity content data in the pretreated oils and refined oils obtained from Example 5 and Comparative Example 1, and Example 6 and Comparative Example 2, it can be seen that the impurity content in the pretreated oils and refined oils obtained from Example 5 and Example 6 is significantly lower than that in Comparative Example 1 and Comparative Example 2, respectively. This indicates that the use of C1 to C6 monohydroxy alcohols and their carbonates in the embodiments of the present invention can promote the dispersion of the alkaline catalyst in the oil and fully convert impurities such as chlorine in the oil, thereby significantly reducing the impurity content in the obtained pretreated oils and refined oils and improving their quality.

[0076] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A method for separating and removing impurities from oils and fats, characterized in that, The method includes: heating the oil raw material in the presence of a polar medium, allowing the oil raw material to react fully under the action of an alkaline catalyst, and then separating the polar medium from the mixture obtained after the reaction to obtain pretreated oil; The polar medium includes one or more of C1 to C6 monohydroxy alcohols and their carbonates.

2. The method according to claim 1, characterized in that, The polar medium includes one or a combination of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, and hexanol and their carbonates.

3. The method according to claim 1 or 2, characterized in that, The method further includes mixing polyols and / or water into the polar medium.

4. The method according to claim 3, characterized in that, The polyols include one or a combination of several of the following: ethylene glycol, glycerol, polyglycerol with a molecular weight of less than 800, pentitol, and sorbitol.

5. The method according to claim 3, characterized in that, The amount of polyols and / or water shall not exceed 100 wt% based on the total weight of the oil raw materials (100%).

6. The method according to claim 1 or 2, characterized in that, The oil raw materials include one or a combination of animal and vegetable oil raw materials, animal fats, vegetable oils and waste oils.

7. The method according to claim 1, characterized in that, The alkaline catalyst comprises one or a combination of oxides, hydroxides, carbonates, and bicarbonates of sodium, potassium, magnesium, calcium, zinc, and aluminum.

8. The method according to claim 1 or 7, characterized in that, The amount of alkaline catalyst used is less than 1 wt% of the oil mass.

9. The method according to claim 1, characterized in that, The mass ratio of the grease to the polar medium is 1:0.2-1:

2.

10. The method according to claim 1 or 9, characterized in that, The reaction temperature is 120-360℃, the pressure is 0.5-25MPa, and the reaction time is 0.5-4h.

11. The method according to claim 1 or 9, characterized in that, The reaction is a continuous reaction or an intermittent reaction, and / or the reaction is a single reaction or a multiple reaction.

12. The method according to claim 1 or 2, characterized in that, The separation includes distillation, sedimentation, or centrifugation.

13. The method according to claim 1 or 2, characterized in that, The method further includes vacuum distillation and / or adsorption treatment of the pretreated oil to obtain high-quality refined oil.