Preparation method of fatty acid type diesel antiwear agent

Abstract

The present invention relates to a method for preparing an acid-type diesel antiwear agent, belonging to the technical field of diesel antiwear agents. The present invention proposes an innovative preparation process. Suitable mixed fatty acids are selected and subjected to static freeze crystallization to produce a semi-finished acid-type diesel antiwear agent with a ΣSFA content of 3-4%. The ΣSFA content in the semi-finished product is further reduced to less than 2.5% using a urea encapsulation method. The present invention has the advantages of a short production cycle, high product yield, low investment cost, simple production process, low material and energy consumption, and excellent improvement in diesel lubrication performance.

Description

Technical Field

[0001] The invention relates to a preparation method of a fatty acid type diesel antiwear agent, belonging to the technical field of diesel antiwear agents. Background Art

[0002] The current status of the acid-type diesel anti-wear agent process: crude oleic acid is produced by hydrolyzing oils (generally vegetable oils) and acidifying them, and then the mixed unsaturated acid is purified by vacuum distillation and freezing to produce fatty acid-type diesel anti-wear agents.

[0003] The two processes each have their advantages and disadvantages. The vacuum distillation process can easily remove low-molecular saturated fatty acids, but components with larger molecular weights, such as palmitic acid (boiling point 340.6°C), stearic acid (boiling point 361.0°C), and oleic acid (boiling point 360.0°C), have similar boiling points and are difficult to separate by distillation. The freezing process requires little investment and is safe and environmentally friendly. However, due to the low crystallization point of low-molecular saturated acids, it is difficult to achieve ultra-low temperature crystallization in industry. There are also problems such as long production cycles and relatively low yields. Therefore, the industry currently uses vacuum distillation to treat crude oleic acid to remove low-molecular saturated fatty acids, and then uses a freezing process to remove larger molecular weight saturated fatty acids such as palmitic acid, stearic acid, and arachidic acid to meet the saturated acid content requirements of acid-type diesel anti-wear agents.

[0004] Acid-type diesel antiwear agents are composed of a mixture of saturated fatty acids (SFA) and unsaturated fatty acids (UFA).

[0005] The saturated acid content (ΣSFA) of the acid-type diesel antiwear agent is not more than 2.5%. The lower the ΣSFA content, the better the dispersibility in diesel and the better the low-temperature fluidity effect. Summary of the Invention

[0006] The present invention addresses the technical problem of providing a method for preparing a fatty acid-based diesel antiwear agent. This method utilizes a two-step process involving freezing pretreatment and urea inclusion to separate mixed oleic acid to produce the acid-based diesel antiwear agent. This method achieves a qualified ΣSFA content (less than 2.5%), excellent performance (lubricity of the additive-added diesel), and greater stability, along with advantages such as a short production cycle (the entire test process is less than 80 hours) and a high product yield (greater than 85%). The final product exhibits a lower difference between the saponification value and the acid value (i.e., the ester value), resulting in a higher purity of the oleic acid.

[0007] In order to solve the above technical problems, the technical solution proposed in the present invention includes the following steps:

[0008] (1) Selecting a suitable commercially available mixed fatty acid, and subjecting it to static rapid freezing and crystallization to prepare an acid-type diesel antiwear agent semi-finished product having a saturated fatty acid ΣSFA content of 3-4%;

[0009] (2) The semi-finished product of the acid-type diesel anti-wear agent is added to the urea alcohol solution and refluxed at 78-85°C for 30-60 minutes to uniformly mix the semi-finished product of the acid-type diesel anti-wear agent, urea, and 95% ethanol, thereby facilitating the inclusion of straight-chain fatty acids by urea. The product is then naturally cooled to 60°C and then placed in a circulating cold bath for programmed cooling. The product is filtered using a suction funnel. At the end of the filtration, the filter residue and filter paper are washed with isooctane or petroleum ether. The washed isooctane or petroleum ether is incorporated into the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase. The collected filtrate is treated in the same way to obtain an unsaturated acid-rich phase. The unsaturated acid-rich phase is the acid-type diesel anti-wear agent.

[0010] The ΣSFA in the semi-finished product is further reduced by using the urea adduct method, that is, the unsaturated fatty acid UFA is purified to obtain an acid-type diesel antiwear agent with a ΣSFA content of less than 2.5%.

[0011] The mixed fatty acids in step (1) are soybean oleic acid and rice bran oleic acid in a mass ratio of 6:4, and cottonseed oleic acid and rice bran oleic acid in a mass ratio of 1:1.

[0012] The lowest temperature of the static rapid freezing crystallization in step (1) is -3°C to 2.6°C, and the total freezing time is 49 to 55 hours.

[0013] In the urea inclusion method in step (2), the amount of urea used is 0.3 to 0.6 times the mass of the semi-finished anti-wear agent; 95% ethanol is selected as the solvent, and the amount of 95% ethanol used is 6 to 8 times the mass of the urea; after urea inclusion, the temperature is programmed to decrease (10°C / h to 40°C, 5°C / h from 40°C to 30°C, and 1°C / h from 30°C to 20°C), and the temperature is maintained at 20°C for 4h, which is conducive to the separation of crystals.

[0014] Preferably, the controlled cooling of the static rapid freezing crystallization in step (1) is as follows: when the sample is naturally cooled to a temperature of 40°C, it is placed in a circulating cold bath and cooled to 30°C at 2°C / h, and then cooled from 30°C to 0°C at 1°C / h, and then placed in a laboratory refrigerator and controlled to cool down to -2.9°C at 0.2°C / h, and then kept constant for a period of time, with the lowest temperature being -2.9°C.

[0015] Preferably, the acid-type diesel antiwear agent semi-finished product in step (2) is added to the urea-alcohol solution and refluxed at 83° C. for 30 minutes to uniformly mix the acid-type diesel antiwear agent semi-finished product, urea, and 95% ethanol.

[0016] Preferably, the mixed fatty acid comprises soybean oleic acid and rice bran oleic acid in a mass ratio of 6:4.

[0017] Preferably, in step (2), urea, 95% ethanol and the semi-finished antiwear agent are all placed in a three-necked flask, refluxed at 82-84°C for 30 minutes, and naturally cooled to 60°C. The three-necked flask is placed in a circulating cold bath filled with ethylene glycol and programmed to cool: 10°C / h to 40°C, 5°C / h to 30°C, 1°C / h to 20°C, and kept at a constant temperature for 4 hours, and then filtered for a total of 18 hours. The filter is filtered using a suction funnel, and after the filtration is completed, the filter residue and filter paper are washed with petroleum ether with a specification of 60-90°C. The washing liquid is incorporated into the filtrate, and the collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is treated in the same way to obtain an unsaturated acid-rich phase, and the unsaturated acid-rich phase is the acid-type diesel antiwear agent.

[0018] Preferably, the method comprises the following steps:

[0019] (1) 123.5 g of soybean oleic acid (ΣSFA content 8.0%) and 82.1 g of rice furan acid (ΣSFA content 8.21%) were mixed and heated to 60°C, stirred for 10 minutes, and placed in a 500 ml ground glass tube. The glass tube was fixed in a bracket and naturally cooled to 40°C. A glycerol-propylene glycol bath was used to cool from 40°C to 30°C at 2°C / h and then from 30°C to 0°C at 1°C / h. The mixture was then placed in a laboratory refrigerator and the temperature was controlled to drop to -2.9°C at 0.2°C / h. The temperature was then kept constant for a period of time, with the lowest temperature being -2.9°C, for a total of 53 hours. After freezing and constant temperature, the raw material mixed oleic acid was quickly filtered and the inner wall of the glass tube and filter paper were rinsed with the filtrate to obtain 12.8 g of filter residue and 192.5 g of filtrate. The filtrate was used as a semi-finished fatty acid type diesel anti-wear agent.

[0020] (2) 112.4g of urea, 902.5g of 95% ethanol and 192.5g of the semi-finished anti-wear agent are placed in a 2L three-necked flask, refluxed at 82-84℃ for 30min, cooled naturally to 60℃, and placed in a circulating cold bath filled with ethylene glycol for programmed cooling: 10℃ / h to 40℃, 5℃ / h to 30℃, 1℃ / h to 20℃, and kept at constant temperature for 4h, then filtered for a total of 18h, filtered with a suction funnel, and then washed with 140g of 60-90℃ petroleum ether. The washing liquid is added to the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is treated in the same way to obtain an unsaturated acid-rich phase, which is the acid-type diesel anti-wear agent.

[0021] 5.5 g of saturated acid-rich phase was obtained, with a ΣSFA content of 46.0%; 186.2 g of acid-type diesel antiwear agent product was obtained, with a ΣSFA content of 2.20%. The total yield of the acid-type diesel antiwear agent was 90.6%.

[0022] Beneficial effects of the present invention:

[0023] In order to ensure that the diesel anti-wear agent has a qualified ΣSFA content, good performance (lubricity of the additive diesel), and an optimized production process, the present invention selects a suitable mixed fatty acid (mainly adjusting the appropriate ratio of oleic acid and linoleic acid), and quickly freezes and crystallizes to obtain an acid-type diesel anti-wear agent semi-finished product with a ΣSFA content of 3-4%; then uses the urea complexation method (urea coating method) to further reduce the SFA in the semi-finished product, that is, to purify the UFA, so as to achieve the requirement of an acid-type diesel anti-wear agent with a ΣSFA content of less than 2.5%.

[0024] The optimal binary single-variety oleic acid ratio is selected by comprehensively considering factors such as supernatant yield, freezing time, supernatant wear scar diameter, and supernatant iodine value. The recommended binary single-variety oleic acid ratio is a 6:4 soybean oleic acid to rice bran oleic acid mass ratio, and a 1:1 cottonseed oleic acid to rice bran oleic acid mass ratio. High-efficiency freezing (reducing saturated acid content to approximately 3.5% in just one-third the time required for direct freezing of acid-based diesel antiwear agents) yields over 90% for the semi-finished acid-based diesel antiwear agent.

[0025] The present invention selects suitable urea coating (urea coating) process conditions for a semi-finished anti-wear agent with a lower ΣSFA content, suitable for raw material oleic acid (ΣSFA content 8-10%). The optimized process conditions are as follows: the amount of urea used in the urea coating method is 0.3-0.6 times the mass of the semi-finished anti-wear agent; the solvent is 95% ethanol, and the amount of 95% ethanol used is 6-8 times the mass of the urea; after urea coating, the temperature is programmed to decrease (10°C / hour to 40°C, 5°C / hour from 40°C to 30°C, and 1°C / hour from 30°C to 20°C), and then maintained at 20°C for 4 hours, which is conducive to the separation of crystals.

[0026] Compared with traditional direct freezing crystallization, the present invention has the advantages of short production cycle and high product yield.

[0027] Compared with the direct urea coating method for separating saturated acids, the direct urea coating method is used to treat the raw material oleic acid (ΣSFA content 8-10%), and the ΣSFA content is less than 2.5%. The yield of the unsaturated acid-rich phase is difficult to exceed 50%, which is not economical; and the amount of solvent and urea recovered by the urea coating is large, and the solvent is generally methanol and ethanol. The process is unsafe and not environmentally friendly. By urea coating the semi-finished acid-type diesel anti-wear agent, its ΣSFA content can be reduced from 3-4% to less than 2.5%, which basically does not change the ratio of oleic acid to linoleic acid, and at the same time consumes relatively less solvent and urea.

[0028] The characteristic peaks measured by gas chromatography show that the component types of the final product prepared in Example 5 of the present invention are greater than those of the diesel anti-wear agent prepared by soybean oil acid, which is the mainstream of the current freezing process. The difference between the saponification value and the acid value, that is, the ester value, is lower, and the purity of the oleic acid is higher.

[0029] After inspection and analysis:

[0030] Commercially available soybean oil acid type diesel antiwear agent: saponification value 202.9mgKOH / g, acid value 201.0mgKOH / g, iodine value 138gI2 / 100g, iron-cobalt colorimetric number: 5#.

[0031] The diesel antiwear agent prepared by the mixed acid two-step method of the present invention has the following characteristics: saponification value 200.1 mgKOH / g, acid value 199.9 mgKOH / g, iodine value 123 gI2 / 100g, and iron-cobalt colorimetric number: 2#.

[0032] Gas chromatography analysis shows that the main components of the commercial anti-wear agent (oleic acid, linoleic acid) account for 79%, while the main components of the anti-wear agent prepared by the present invention account for 82%; under the same conditions, the former has 29 identified peaks, while the latter has 24.

[0033] Taking all factors into consideration, Example 5 of the present invention is the best embodiment. It can be seen from Examples 4 to 6 that Example 5 has the highest yield, the total yield of the acid-type diesel antiwear agent is 90.6%; the ΣSFA value is the lowest, which is 2.20%; and the total preparation time is only 76 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] Figure 1 Flow chart of purification of semi-finished acid-type diesel antiwear agent by urea inclusion method

[0036] Figure 2 Effect of urea dosage on urea inclusion effect

[0037] Figure 3 Effect of the ratio of solvent to urea on urea inclusion effect

[0038] Figure 4 Effect of crystallization temperature on urea inclusion effect

[0039] Figure 5 Flow chart of mixed fatty acid acid-type diesel antiwear agent

[0040] Figure 6 Chromatogram of commercial soybean oil acid type diesel antiwear agent

[0041] Figure 7 Chromatogram of diesel antiwear agent prepared in Example 5 of the present invention DETAILED DESCRIPTION

[0042] Example 1

[0043] Preparation of semi-finished acid diesel antiwear agent:

[0044] The raw material oleic acid for acid-type diesel antiwear agents is mainly selected from one of the plant oleic acids such as soybean oleic acid, cottonseed oleic acid, and rice bran acid. These fatty acids are relatively easy to obtain, especially soybean oleic acid and cottonseed oleic acid, which have a large source. The ΣSFA content of these commercially available raw oleic acids is usually 6-10%. The production of industrial acid-type diesel antiwear agents mainly involves the fine processing of this type of oleic acid. This embodiment will explore the innovation of the freezing process after mixing various types of oleic acid. Taking into account various factors such as filtrate yield, filtrate ΣUFA content, and freezing efficiency, a suitable mixing scheme is determined. A relatively fast freezing scheme is used to produce a semi-finished acid-type diesel antiwear agent with a ΣSFA content of 3-4%, so that it can be used in the subsequent urea inclusion process.

[0045] 1. Fatty acid composition of various commercially available oleic acids

[0046] The oleic acid content varies from variety to variety. Even for the same variety, there will be slight differences due to factors such as the origin and planting climate environment. Table 1 below shows the approximate fatty acid content in oleic acid of each variety.

[0047] Table 1: Approximate fatty acid content of oleic acid in various varieties

[0048]

[0049] 2. Statistics of freezing tests of various types of oleic acid

[0050] The crystallization process consists of several stages: formation of a supercooled or supersaturated solution, generation of crystal nuclei, crystal growth, and recrystallization. Nucleation involves the formation of a certain number of nuclei in a supercooled or supersaturated solution; these nuclei gradually grow into crystals, which are then physically separated. The experimental data presented in this paper are based on a static freezing method that does not use solvents. This method has a simple process principle and is easy to operate. The static, undisturbed state at low temperatures prevents deterioration of polyunsaturated fatty acids.

[0051] Static Freeze Crystallization: Crude oleic acid is placed into colorimetric tubes and stacked regularly in a laboratory temperature-controlled freezer. The freezer gradually cools the saturated acid to form crystals that settle at the bottom of the tubes. Filter the saturated acid using a laboratory filtration device, and the filtrate can be used as an acid-based anti-wear agent. Advantages and Disadvantages: Large crystal nuclei are easy to filter, and oxidation and water absorption are less of a concern. However, the freezing and cooling time is relatively long.

[0052] Dynamic freezing crystallization: Oleic acid is placed in a jacketed glass stirred tank containing a coolant. The coolant circulates through the tank to remove heat from the oleic acid, achieving a cooling effect. After cooling, the saturated acid crystallized is suspended in the oleic acid. Unlike static freezing, this method requires the entire suspension in the tank to be filtered using a filter press. Advantages and Disadvantages: Rapid freezing, fine crystals, and difficulty in filtration make it suitable for filter presses, not for direct filtration with filter paper or suction filtration. The oleic acid is exposed to air for a long time during the filter press, making it susceptible to oxidation, discoloration, and water absorption. Table 2 below shows a comparison of static freezing data (testing 100g of crude oleic acid).

[0053] Table 2: Comparison of static freezing data (100g crude oleic acid test)

[0054]

[0055] According to the above experimental data, each type of oleic acid has its own advantages and disadvantages when subjected to freeze purification:

[0056] Rice bran oleic acid, an oleic acid with a relatively low iodine value, cannot be frozen to -1.5°C, while soybean oleic acid and cottonseed oleic acid with relatively high iodine values can be cooled to very low temperatures and can reach a saturated acid content of 2.0% at night. However, as the temperature decreases, the yield also decreases; the saturated acid content of high iodine value oleic acid decreases from about 3.5%, and it takes a long time to slowly freeze (static method).

[0057] At the same time, it can be seen that the wear scar diameter of soybean oil acid and cottonseed oil acid frozen clear solution with higher iodine value is better. The wear scar diameter of 3.5% and 2.0% saturated oleic acid of the same type is similar.

[0058] Iodine value is equivalent, the main component The higher the content, the lower the content of fatty acids with multiple double bonds and other impurities, and the better the oleic acid's antioxidant properties. Furthermore, the solubility of oleic acid in diesel is inversely proportional to the molecular chain length (molecular weight) and directly proportional to the number of unsaturated double bonds. Chromatographic analysis reveals that soybean oleic acid and cottonseed oleic acid have relatively complex compositions, while rice bran oleic acid has the simplest composition.

[0059] Therefore, we can consider various aspects such as composition, freezing time, clear liquid yield, wear scar diameter, etc., and mix various types of oleic acid to efficiently freeze out semi-finished oleic acid (ΣSFA content 3.0-4.0%) of acid-type diesel antiwear agent.

[0060] 3. Freezing test after compounding with each single type of oleic acid

[0061] Based on the above industrial experience data, a freezing test was conducted by mixing vegetable oleic acid with high iodine value and vegetable oleic acid with low iodine value. The same laboratory freezer and the same cooling process conditions were used (when the sample was naturally cooled to 40°C, it was placed in a circulating cold bath and cooled to 30°C at 2°C / h, then cooled from 30°C to 0°C at 1°C / h, and then placed in a laboratory refrigerator for controlled cooling, with the temperature dropped to the lowest constant temperature at 0.2°C / h, and then kept constant for a period of time). The results are as follows:

[0062] Table 3 Freezing test of each single oleic acid variety after compounding

[0063]

[0064]

[0065] 4. Summary:

[0066] The above experiments have verified that by using a suitable oleic acid mixing ratio and adopting efficient freezing (only 1 / 3 of the time of direct freezing to make acid-type diesel antiwear agent, reducing the saturated acid to about 3.5%), a semi-finished acid-type diesel antiwear agent can be obtained with a yield of more than 90%.

[0067] Recommended oleic acid main component content range ( The content is less than 5%; The content is less than 3%; The content is 34-39%; The content is 45-50%; The content is less than 3%; The content is less than 2%; The content of other components is less than 1%.

[0068] Taking comprehensive consideration of the clear liquid yield, freezing time, supernatant iodine value and other aspects, the optimal binary single variety oleic acid ratio is selected. The recommended binary single variety oleic acid ratio is: soybean oleic acid and rice bran oleic acid mass ratio of 6:4.

[0069] Further purification was performed on this basis, reducing the ΣSFA content to below 2.5%. Experiments were conducted using the urea inclusion method. This method for separating mixed fatty acids is simple, easy to operate, requires mild conditions, and both the urea and solvent can be recycled. It is low-cost and offers excellent separation results. Compared to direct urea inclusion of the raw oleic acid, it is more economical, environmentally friendly, and has considerable potential for industrialization.

[0070] Example 2

[0071] Further purification of unsaturated acid - urea inclusion method

[0072] Urea adsorption is a common and effective method for separating mixed fatty acids and is widely used for the separation and purification of polyunsaturated fatty acids. Numerous reports have been published on the separation of fatty acids using urea adsorption. However, due to the varying composition of mixed fatty acids and the varying experimental conditions, the separation results can be significantly affected, and no single optimal condition can be applied.

[0073] This example focuses on the effects of factors such as the selection and dosage of solvent, urea dosage, heating time, inclusion temperature, inclusion time, and number of inclusions on the fatty acid separation effect of the finished product of the acid-type diesel antiwear agent with a low ΣSFA content (3-4%) during the urea inclusion process, thereby obtaining the most suitable urea inclusion process conditions.

[0074] 1. Principle description:

[0075] The principle of this method is to achieve separation based on the difference in the degree of unsaturation of each fatty acid. The urea inclusion complex is centered around a straight-chain aliphatic compound. Urea is a tetrahedral crystal. Urea molecules are strongly hydrogen-bonded to each other, spiraling upward in a right-handed manner around this axis, encapsulating the straight-chain fatty acid compound to form a hexagonal crystal. Six urea molecules are used as a unit to complete one circle of spiraling. When the molecular size of a substance is smaller than the inner diameter of the framework formed by urea, it can be encapsulated in the hexagonal crystal; otherwise, it cannot be encapsulated. The encapsulated substance and urea form a stable inclusion complex through van der Waals forces such as dispersion forces and electrostatic attraction. The more stable the inclusion complex, the more stable the inclusion complex. The characteristic of urea inclusion complexes is that urea can selectively encapsulate fatty acid molecules, so the ease with which different fatty acids are encapsulated varies greatly. Longer carbon chains are more easily included. Polyunsaturated fatty acids, due to their greater number of double bonds, possess a specific spatial structure. Monounsaturated fatty acids are more easily included than polyunsaturated fatty acids. Therefore, the order of inclusion is: saturated fatty acids take precedence over monounsaturated fatty acids, which in turn take precedence over polyunsaturated fatty acids (stearic acid > palmitic acid > oleic acid > linoleic acid > linolenic acid). After crystallization, urea inclusion complexes all appear as hexagonal prisms of varying shapes. Unsaturated fatty acids generally form short, thick crystals, while pure urea forms quadrangular prisms. The structure of urea inclusion complexes resembles a honeycomb, with the central cavity occupied by a straight-chain aliphatic compound. The cavity length of the urea inclusion complex formed by the aliphatic compound and urea is proportional to the aliphatic chain length. After the inclusion complex is formed, filtration is used to separate the high-purity polyunsaturated fatty acid filtrate and urea inclusion complex residue.

[0076] 2 Experimental Introduction

[0077] 2.1 Experimental materials and reagents

[0078] The acid-type diesel antiwear agent semi-finished product (ΣSFA content 3.8%) and the acid-type diesel antiwear agent semi-finished product in the following experiment were prepared by compounding soybean oil acid and rice bran oil acid in a mass ratio of 6:4 in Table 3 and then freezing them, urea, methanol, anhydrous ethanol, 95% ethanol, petroleum ether (60-90°C), ethylene glycol for cold bath; isooctane; anhydrous Na2SO4; N2.

[0079] 2.2 Experimental steps

[0080] (1) After urea and solvent are mixed in a certain ratio, stir at a certain temperature until the urea is completely dissolved, then add a certain amount of acid-type diesel anti-wear agent semi-finished product, mix thoroughly, reflux for a certain period of time, cool to 60 ° C, and place in an ethylene glycol cold bath.

[0081] (2) The temperature is then lowered, and after inclusion crystallization at a certain temperature for a period of time, the mixture is rapidly filtered, and the residue is washed and filtered with isooctane or petroleum ether. The washed solvent is incorporated into the filtrate. The residue is dissolved and emulsified with warm water, and then liquid-liquid extracted with petroleum ether. The lower layer of urea aqueous solution is removed, and the upper organic solution is washed with water until neutral. Anhydrous Na2SO4 is added for drying and filtration, and rotary evaporation is performed to obtain the saturated fatty acid enrichment in the residue. The filtrate is treated in the same way to obtain the unsaturated acid enrichment phase, which is used as an acid-type diesel anti-wear agent.

[0082] (3) Determine the fatty acid iodine value in the saturated fatty acid-rich phase and the unsaturated fatty acid-rich phase, and the fatty acid content by gas chromatography analysis.

[0083] 3 Experiments and Discussion

[0084] By adjusting process parameters such as reflux time, cooling rate, urea dosage, solvent type, solvent / urea dosage, and urea package crystallization temperature, mixed fatty acid samples with varying degrees of enrichment were obtained. Because urea more readily forms inclusion complexes with saturated or monounsaturated fatty acids and is removed by filtration, the ΣUFA content in the unsaturated acid-enriched phase increases. The ΣUFA enrichment effect can be assessed by measuring changes in the fatty acid composition.

[0085] The filter residue contains fatty acids that are not included and wrapped between crystals during crystallization, which cannot be easily extracted from the filter residue and need to be washed and filtered with isooctane or petroleum ether, which will increase the ΣSFA content in the non-urea inclusion phase, but will also increase the yield of the urea inclusion phase.

[0086] 3.1 Effect of reflux time on the purity of unsaturated acid-rich phase

[0087] The urea inclusion method can be categorized as either homogeneous or heterogeneous, with the homogeneous reaction being the more commonly used. A mixed fatty acid is added to a urea-alcohol solution (mixed fatty acid: urea: 95% ethanol = 1:0.5:4.0, w / w / w) in a three-necked flask equipped with a vertical condenser. The mixture is heated and refluxed to achieve uniform mixing, thereby facilitating the inclusion of the fatty acid by urea. Within a reflux time of 15 to 100 minutes, the purity and yield of unsaturated oleic acid in the urea-included liquid phase fluctuate within a narrow range. The reflux time before urea inclusion has little effect on the purity and yield of the unsaturated acid. Considering that longer reflux times waste energy and time while increasing the risk of deterioration of unsaturated fatty acids such as linoleic acid and linolenic acid through other reactions, a reflux time of 30 minutes was chosen.

[0088] 3.2 Effect of cooling rate on urea inclusion separation degree

[0089] The shapes of the fatty acid crystals obtained using direct cooling and programmed cooling are different. Direct freezing results in fine, fragmented fatty acid crystals that are difficult to separate. However, programmed cooling results in strips or granules that facilitate separation.

[0090] Because the slow cooling time is long and the crystallization process reaches equilibrium, the saturated fatty acids are all included into crystals, the generated grains are larger, and it is not easy to carry unincluded fatty acids during filtration; while the rapid cooling time is short, the crystallization process does not reach equilibrium, the saturated fatty acids are not completely included, and the grains are smaller (less than 10μm). Unsaturated fatty acids are wrapped between the grains during filtration.

[0091] Table 4: Effect of cooling rate on urea inclusion separation degree

[0092]

[0093] Based on the above analysis, the slow cooling crystallization process is beneficial to the removal of saturated fatty acids.

[0094] 3.3 Effect of solvent type on urea inclusion effect

[0095] Under the conditions selected above, methanol, ethanol, and 95% ethanol were used as solvents to compare their ability to enrich unsaturated fatty acids (compared by iodine value). The reaction conditions were: programmed cooling (number 6 in Table 4), a crystallization temperature of 20°C, and a constant temperature crystallization time of 4 hours. The results showed that under the same reaction conditions, there was no significant difference in the effectiveness of the three solvents used to dissolve urea in the urea inclusion reaction. However, considering the cost of inclusion, the toxicity of methanol, and the safety of the operation, ethanol is still the preferred solvent for the urea inclusion method. Urea inclusion was essentially equivalent using anhydrous ethanol and 95% ethanol as solvents. Considering the small amount of water in the solvent, which facilitates urea dissolution, and the lower price of 95% ethanol, 95% ethanol was selected as the solvent for urea inclusion.

[0096] Table 5: Effect of solvent type on urea inclusion effect

[0097]

[0098]

[0099] 3.4 Effect of urea dosage on urea inclusion effect

[0100] When the ratio of 95% ethanol to mixed fatty acids was 4.0:1 (w / w), after crystallization at 20°C for 4 hours, the effect of urea dosage on the enrichment effect was shown in Figure 2. Figure 2

[0101] When the amount of urea increases to a certain level, the saturated fatty acids that are easier to be included are included as much as possible, and some monounsaturated fatty acids gradually form inclusion complexes with urea (the order of easy inclusion: stearic acid>palmitic acid>oleic acid>linoleic acid>linolenic acid). Therefore, when the amount of urea exceeds the saturated amount of fatty acids to be included, further increasing the amount of urea will slightly increase the purity of the unsaturated acid in the unsaturated acid-rich phase (the unsaturated fatty acid content of the raw material mixed fatty acids has reached more than 96%, and there is not much room for improvement), but the yield will drop significantly. However, when the amount of urea is too little, there are fewer frameworks to form inclusion complexes in ethanol, and saturated fatty acids will not be completely included. From Figure 2 The results shown in the table show that when the urea / mixed fatty acid (w / w) ratio is between 0.3 and 0.6, the purity of linoleic acid is higher and the yield is also higher. Figure 2 Effect of urea dosage on urea inclusion effect.

[0102] 3.5 Effect of the ratio of solvent to urea on urea inclusion effect

[0103] Selecting a 95% ethanol / urea (w / w) ratio within the range of 2 to 10, the mixture was cooled to 20°C and allowed to stand for 4 hours. This allowed the urea to slowly crystallize at a lower temperature, resulting in the separation of urea number 6 in Table 4. The steric hindrance of the different fatty acids allowed for selective inclusion. During the experiment, it was found that when the ethanol:urea ratio was less than 2:1, ethanol had difficulty dissolving urea, requiring increased temperature for complete dissolution.

[0104] from Figure 3 It can be seen that with the increase of the amount of 95% ethanol / urea, the degree of enrichment of unsaturated acids by the urea package, that is, its concentration in the liquid phase, increases steadily, the concentration in the crystal phase decreases, and the yield of high-purity unsaturated acids gradually increases. This may be because as the amount of solvent increases, more unsaturated acids are redissolved in 95% ethanol, which avoids the inclusion of crystals during the filtration process, thereby increasing the yield in the liquid phase; the solvent is a place that provides mass transfer and molecular movement in the crystallization process. With the increase of the amount of solvent, the selectivity of the urea package for fatty acids increases, that is, the degree to which urea includes stearic acid, palmitic acid and oleic acid increases, and the inclusion degree of polyunsaturated acids decreases, resulting in a decrease in the relative concentration and absolute amount of unsaturated acids in the crystal phase. At the same time, increasing the amount of solvent will reduce the crystallization temperature, which is not conducive to laboratory filtration operations, and consuming a large amount of solvent is also uneconomical. The appropriate 95% ethanol / urea (w / w) is in the range of 6 to 8. Figure 3 Effect of the ratio of solvent to urea on the urea inclusion effect.

[0105] 3.6 Effect of crystallization temperature on urea inclusion effect

[0106] Under the conditions of urea to mixed fatty acid ratio of 0.6:1 (w / w), 95% ethanol to urea ratio of 8:1 (v / w), programmed cooling (Table 4) condition 6 and constant temperature crystallization time of 4h, the effect of final crystallization temperature on urea inclusion effect is as follows: Figure 4 shown.

[0107] At the same crystallization time, the yield of the unsaturated acid-rich phase increases with increasing temperature, while the ΣUFA content decreases. When the temperature reaches 30°C, the ΣSFA content requirement of the acid-type diesel antiwear agent is no longer met.

[0108] Looking at the urea-encapsulated phase, that is, the unsaturated acid content in the crystalline phase is basically stable at 10°C to 25°C, and decreases significantly above 25°C. This is because the formation of urea inclusion complexes is an exothermic process. As the temperature decreases, the reaction proceeds in the direction of forming inclusion complexes. At low temperatures, inclusion complex crystals form rapidly, and the resulting crystal nuclei are small and uniform. However, if the temperature is too low (below 10°C), the inclusion complex solidifies together with the solvent, increasing the viscosity of the mixture. It also causes some unsaturated acids to form inclusion complexes, making filtration difficult, increasing the loss of mixed fatty acids in the filtrate, and reducing the yield of the unsaturated acid-rich phase. In addition, the unsaturated acid content in the raw material before urea encapsulation is about 96%, so the curve has no obvious effect on the unsaturated acid-rich phase in the 0-30°C range. As the temperature rises, the solubility of urea in the solvent increases, the inclusion complex crystals form more slowly, the nucleus grows more slowly, the number of crystals generated is small, and the shape is coarse and long. At the same time, the movement between the urea inclusion complex molecules intensifies and moves in the direction of decomposition, making it difficult to form crystals, which increases the selectivity of the urea inclusion reaction for fatty acids, thereby allowing more unsaturated acids to remain in the liquid phase.

[0109] When the temperature is above 10℃, the ΣUFA content and yield in the unsaturated acid-rich phase are relatively high. However, if the temperature is raised to above 25℃, the ΣUFA content in the unsaturated acid-rich phase will be reduced, resulting in the product not meeting the requirements of acid-type diesel anti-wear agents. Maintaining a high temperature for a long time will lead to oxidation of the unsaturated acid in the liquid phase. In addition, considering the operating temperature that is conducive to filtration, an appropriate operating temperature can be selected according to the purity requirements, and it should not be too high or too low. It is recommended that 15-25℃ is appropriate. Figure 4 Effect of crystallization temperature on urea inclusion effect.

[0110] 3.7 Amount of washing solvent

[0111] After the experimental filtration is complete, the filter residue and filter paper are washed with isooctane or petroleum ether as the washing solvent. Since urea is insoluble in isooctane or petroleum ether, while fatty acids are readily soluble in these two solvents, the free fatty acids are washed into the filtrate during washing, significantly increasing the yield of the unsaturated acid-rich phase but increasing its ΣSFA content. Simultaneously, as the free fatty acids decrease, the relative content of encapsulated ΣSFA in the filter residue also increases.

[0112] Experiments show that when the filter residue is washed with a solvent, the washing solvent must permeate the filter residue, and the ratio of the amount of solvent to the filter residue is 0.5 to 1 (mass ratio). This can ensure a high yield of the unsaturated acid-rich phase while meeting the requirements for the saturated fatty acid content of the acid-type diesel anti-wear agent.

[0113] 4. Conclusion

[0114] The experiment mainly established the process route for preparing fatty acid-based diesel anti-wear agents by urea inclusion. After the acid-based diesel anti-wear agent semi-finished product (ΣSFA content 3-4%) was included in the urea, the yield of the unsaturated acid-rich phase and the purity of the unsaturated acid were used as evaluation indicators. The effects of reflux time, solvent type, different urea dosages, solvent volume, and crystallization temperature on the enrichment of unsaturated fatty acids in mixed fatty acids during the urea inclusion process were analyzed. Verification experiments were also conducted, resulting in the following conclusions:

[0115] The more suitable process conditions for preparing acid-type diesel anti-wear agent using a specific mixed fatty acid with a ΣSFA content of 3-4% were selected as follows: the reflux time was selected as 30 min, the urea dosage was 0.3-0.6 times that of the mixed fatty acid; 95% ethanol was selected as the solvent, and the solvent dosage was 6-8 times that of urea; after urea inclusion, the temperature was programmed to drop (10℃ / h to 40℃, 5℃ / h from 40℃ to 30℃, 1℃ / h from 30℃ to 20℃), and then kept constant at 20℃ for 4h, which is conducive to the separation of crystals.

[0116] Experiments have shown that the ΣUFA content in the unsaturated acid-rich phase (urine-in-liquid phase) can be increased from about 96% to about 98%, with a yield of more than 85%; the filter residue is washed with a solvent, and the washing solvent must be diffused throughout the filter residue. The ratio of the washing solvent to the filter residue is 0.5 to 1 (mass ratio), which can further improve the yield.

[0117] The results also show that under certain conditions, increasing the purity of the unsaturated acid in the unsaturated acid-rich phase will sacrifice the yield. However, since the content of unsaturated fatty acids in the raw mixed fatty acids is already relatively high, the unsaturated acid content does not change much after increasing the yield.

[0118] Example 3

[0119] Based on the above experimental conclusions, fatty acid-type diesel antiwear agents can be efficiently obtained by selecting fatty acids with a special ratio and using appropriate urea inclusion conditions.

[0120] The recommended ratio of binary single-variety oleic acid is 6:4 by mass of soybean oleic acid and rice bran oleic acid. Rapid freezing (50-60 hours) and filtration can be performed to produce a semi-finished acid-type diesel antiwear agent with a saturated acid content of 3-4%.

[0121] The unsaturated acid is further purified from the semi-finished product using urea adducts. The optimal process conditions are: urea dosage is 0.3-0.6 times that of the mixed fatty acids; 95% ethanol is used as the solvent, at a dosage of 6-8 times that of urea; after urea adducts, the temperature is programmed to decrease (10°C / hour to 40°C, 5°C / hour from 40°C to 30°C, and 1°C / hour from 30°C to 20°C), followed by a constant temperature of 20°C for 4 hours, which facilitates the separation of crystals. The entire urea adduct process takes approximately 20 hours.

[0122] The total yield of acid-type diesel antiwear agent by this method can reach more than 85%, and the overall test time is shortened by half compared with direct freezing.

[0123] Table 6 Comparison results of three methods

[0124]

[0125]

[0126] The present invention selects a suitable mixed fatty acid (mainly adjusting the appropriate ratio of oleic acid and linoleic acid), and rapidly freezes and crystallizes to obtain an acid-type diesel antiwear agent semi-finished product with a ΣSFA content of 3-4%. The urea encapsulation method (urea coating method) is then used to further reduce the SFA in the semi-finished product, that is, to purify the UFA, to achieve the requirement of an acid-type diesel antiwear agent with a ΣSFA content of less than 2.5%. Figure 5 Schematic diagram of the process for producing acid-type diesel antiwear agent from mixed fatty acids.

[0127] Compared with traditional direct freezing crystallization, it has the advantages of short production cycle, high product yield and good anti-wear effect.

[0128] Compared with the direct urea coating method for separating saturated acids, the direct urea coating method is used to treat the raw oleic acid (ΣSFA content 8-10%) to a ΣSFA content of less than 2.5%. The yield of the unsaturated acid-rich phase is difficult to exceed 50%, which is not economical. In addition, the amount of solvent and urea recovered by urea coating is large, and the solvent is generally methanol and ethanol. The process is unsafe and not environmentally friendly. By urea coating the semi-finished acid-type diesel anti-wear agent, its ΣSFA content can be reduced from 3-4% to less than 2.5%, which basically does not change the ratio of oleic acid to linoleic acid, and the consumption of solvent and urea is relatively small.

[0129] Example 4

[0130] (1) 150.2 g of soybean oleic acid (ΣSFA content 8.50%) and 100.2 g of rice bran oleic acid (ΣSFA content 8.21%) were mixed and heated to 60°C, stirred for 10 minutes, and placed in a 500 ml ground glass tube. The glass tube was fixed in a bracket. When the sample was naturally cooled to 40°C, it was placed in an ethylene glycol cold bath and cooled from 40°C to 30°C at 2°C / h, and then from 30°C to 0°C at 1°C / h. It was then placed in a laboratory refrigerator. The temperature was controlled to drop to -2.9°C at 0.2°C / h, and then kept constant for a period of time, with the lowest temperature being -2.9°C, for a total of 53 hours. After freezing and constant temperature, the raw material mixed oleic acid was quickly filtered (the filtrate was used to rinse the inner wall of the glass tube and the filter paper), and finally 18.1 g of filter residue and 231.7 g of filtrate were obtained. The filtrate was used as a semi-finished fatty acid type diesel anti-wear agent.

[0131] (2) 140g of urea, 840g of 95% ethanol and 231.7g of the semi-finished anti-wear agent are placed in a 2L three-necked flask, refluxed at 83℃ for 30 minutes, and cooled naturally to 60℃. The three-necked flask is placed in a circulating cold bath filled with ethylene glycol and the temperature is programmed to decrease: 10℃ / h to 40℃, 5℃ / h to 30℃, and 1℃ / h to 20℃ and kept constant for 4 hours, for a total of 18 hours. Then, a suction funnel is used for suction filtration. After the filtration is completed, the filter residue and filter paper are washed with 80g of isooctane, and the washing liquid is added to the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is treated in the same way to obtain an unsaturated acid-rich phase, which is the acid-type diesel anti-wear agent.

[0132] 13.6 g of saturated acid-rich phase was obtained, with a ΣSFA content of 26.33%; 217.7 g of acid-type diesel antiwear agent was obtained, with a ΣSFA content of 2.4%.

[0133] Yield calculation:

[0134] Yield of step (1): 92.53%, yield of step (2): 93.96%; total yield of acid diesel antiwear agent: 86.9%

[0135] Table 7 Summary of analysis data of each stage of two-step diesel antiwear agent (Example 4)

[0136]

[0137]

[0138] Example 5

[0139] (1) 123.5 g of soybean oleic acid (ΣSFA content 8.0%) and 82.1 g of rice bran oleic acid (ΣSFA content 8.21%) were mixed and heated to 60°C, stirred for 10 minutes, and placed in a 500 ml ground glass tube. The glass tube was fixed in a bracket. When the sample was naturally cooled to 40°C, it was placed in an ethylene glycol cold bath and cooled from 40°C to 30°C at 2°C / h, and then from 30°C to 0°C at 1°C / h. It was then placed in a laboratory refrigerator. The temperature was controlled to drop from 0°C to -2.9°C at 0.2°C / h, and then kept constant for a period of time, with the lowest temperature being -2.9°C, for a total of 53 hours. After freezing and constant temperature, the raw material mixed oleic acid was quickly filtered (the filtrate was used to rinse the inner wall of the glass tube and the filter paper), and finally 12.8 g of filter residue and 192.5 g of filtrate were obtained. The filtrate was used as a semi-finished fatty acid type diesel anti-wear agent.

[0140] (2) Place 112.4g of urea, 902.5g of 95% ethanol, and 192.5g of the semi-finished anti-wear agent in a 2L three-necked flask and reflux at 82-84°C for 30 minutes. Cool naturally to 60°C, place the three-necked flask in a circulating cold bath filled with ethylene glycol, and program the temperature to drop: 10°C / h to 40°C, 5°C / h to 30°C, 1°C / h to 20°C, and keep constant at this temperature for 4 hours, for a total of 18 hours. Then filter. Use a suction funnel to filter. After the filtration is completed, wash the filter residue and filter paper with 140g of 60-90°C petroleum ether, and add the washing liquid to the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is treated in the same way to obtain an unsaturated acid-rich phase, which is the acid-type diesel anti-wear agent.

[0141] 5.5 g of a saturated acid-rich phase was obtained, with a ΣSFA content of 46.0%; and 186.2 g of an acid-type diesel antiwear agent was obtained, with a ΣSFA content of 2.20%.

[0142] Yield calculation:

[0143] Yield of step (1): 93.60%, yield of step (2): 96.73%; total yield of acid diesel antiwear agent: 90.6%

[0144] Table 8 Summary of analysis data at each stage of the two-step method for preparing diesel antiwear agent (Example 5)

[0145]

[0146] Example 6

[0147] (1) Mix 108.5g of cottonseed oleic acid (ΣSFA content 8.4%) and 108.9g of rice bran oleic acid (ΣSFA content 8.21%) and heat to 60℃, stir for 10 minutes, and place in a 500ml ground glass tube. Fix the glass tube in a holder. When the sample is naturally cooled to 40℃, place it in an ethylene glycol cold bath and cool it from 40℃ to 30℃ at 2℃ / h, and then from 30℃ to 0℃ at 1℃ / h. Then place it in a laboratory refrigerator. Control the cooling, 0.2℃ / h from 0℃ to -2.9℃, and then keep the temperature constant for a period of time, with the lowest temperature at -2.9℃, for a total of 49 hours. After freezing and keeping the temperature constant, quickly filter the raw material mixed oleic acid (use the filtrate to rinse the inner wall of the glass tube and the filter paper), and finally obtain 12.8g of filter residue and 204.3g of filtrate. The filtrate is used as a semi-finished fatty acid type diesel anti-wear agent.

[0148] (2) Place 143.5g of urea, 998.83g of 95% ethanol, and 204.3g of the semi-finished anti-wear agent in a 2L three-necked flask and reflux at 81-85°C for 30 minutes. Cool naturally to 60°C, place the three-necked flask in a circulating cold bath filled with ethylene glycol, and program the temperature to drop: 10°C / h to 40°C, 5°C / h to 30°C, 1°C / h to 20°C, and keep constant at this temperature for 4 hours, for a total of 18 hours. Then filter. Use a suction funnel to filter. After the filtration is completed, wash the filter residue and filter paper with 140g of 60-90°C petroleum ether, and add the washing liquid to the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is treated in the same way to obtain an unsaturated acid-rich phase, which is the acid-type diesel anti-wear agent.

[0149] 10.1 g of saturated acid-rich phase was obtained, with a ΣSFA content of 28.4%; 191.9 g of acid-type diesel antiwear agent was obtained, with a ΣSFA content of 2.35%.

[0150] Yield calculation:

[0151] Yield of step (1): 94.0%, yield of step (2): 93.9%; total yield of acid diesel antiwear agent: 88.3%

[0152] Table 9 Summary of analysis data of each stage of two-step diesel antiwear agent (Example 5)

[0153]

[0154] Taking all factors into consideration, Example 5 of the present invention is the best embodiment. From Examples 4, 5, and 6, it can be seen that Example 5 has the highest yield, the total yield of the acid-type diesel antiwear agent is 90.6%, the ΣSFA value is the lowest, which is 2.20%, and the total preparation time is only 76 hours.

[0155] Example 7

[0156] As can be seen from Examples 4-6 above, the two-step method can achieve a comprehensive yield of over 85%, and the total time does not exceed 80 hours, which is highly efficient. The urea coating conditions tested are suitable for the separation of ΣSFA from 3-4% acid-type anti-wear agent semi-finished products. The solvent used to wash the urea-coated phase (the filtered crystallized residue) is controlled within an appropriate dosage range to ensure that the product ΣSFA content is qualified while increasing the yield of the final product, making it more economical. The washing amount is 0.5-1 times (by mass) the amount of the urea-coated phase. After urea complexation, the temperature is programmed to decrease (10°C / h to 40°C, 5°C / h from 40°C to 30°C, and 1°C / h from 30°C to 20°C), followed by a constant temperature of 20°C for 4 hours, which is beneficial for the separation of crystals.

[0157] After the diesel anti-wear agent prepared in a small trial was added to blank automotive diesel, the wear scar diameter index could meet the requirements of the national standard for automotive diesel GB19147-2016.

[0158] Others: The characteristic peaks measured by gas chromatography show that the types of components of the final product obtained in the experiment account for more characteristic peaks than those of diesel anti-wear agents made from soybean oil acid, which is the mainstream now (due to the simple composition of rice bran oil). The difference between the saponification value and the acid value (that is, the ester value) is lower, and the purity of oleic acid is higher. Figure 6 Chromatogram of commercial soybean oil type diesel antiwear agent, such as Figure 7 Chromatogram of the diesel antiwear agent prepared in Example 5 of the present invention.

[0159] Table 10 Chromatography of commercial soybean oil type diesel antiwear agent

[0160] Peak Component name Retention time Peak shape Half-peak width area high concentration min min μVs μV ％ 1 Palmitic acid 13.887 BB 0.087 10937 1976 1.6824 2 15.741 BB 0.08B 310 65 0.0477 3 17.028 BB 0.076 216 47 0.0332 4 stearic acid 17.829 BB 0.130 6593 784 1.0142 5 18.755 BB 0.203 13997 1127 2.1531 6 Oleic acid 19.273 BB 0.123 158939 21813 24.4495 7 19.382 BB 0.058 7896 2093 1.2146 8 20.171 VV 0.155 2759 273 0.4244 9 20.373 VB 0.132 2419 302 0.3721 10 20.735 BV 0.135 12475 1507 1.9190 11 20.960 VB 0.129 5068 595 0.7796 12 Linoleic acid 21.407 BB 0.145 354993 40183 54.6083 13 22.403 BB 0.089 321 63 0.0494 14 Arachidic acid 22.553 BV 0.052 290 108 0.0446 15 22.560 VB 0.046 381 112 0.0586 16 22.B33 BB 0.113 5032 697 0.7741 17 23.352 BV 0.171 6990 659 1.0753 18 Linolenic acid 23.677 VV 0.113 45644 5955 7.0214 19 24.096 VV 0.163 2511 256 0.3863 20 24.450 VB 0.305 3524 216 0.5421 21 25.227 BB 0.129 6534 780 1.0051 22 27.320 BB 0.133 466 60 0.0717 23 28.613 BB 0.083 142 30 0.0218 24 29.142 BB 0.079 120 27 0.0185 25 31.695 BB 0.048 84 27 0.0129 26 31.882 BB 0.077 175 42 0.0269 27 32.481 BB 0.200 596 61 0.0917 28 32.912 BB 0.089 317 58 0.0488 29 33.087 BB 0.096 342 61 0.0526

[0161] Table 11 Chromatography of diesel antiwear agent obtained in Example 5

[0162] Peak Component name Retention time Peak shape Half-peak width area high concentration min min μVs μV ％ 1 Palmitic acid 13.977 BB 0.086 16617 3022 1.4905 2 stearic acid 17.928 BB 0.149 6581 723 0.5903 3 18.842 BB 0.212 25833 2007 2.3172 4 Oleic acid 19.407 BV 0.163 398622 39416 35.7554 5 19.500 VB 0.065 19225 5130 1.7244 6 20.261 BV 0.143 4575 497 0.4104 7 20.462 VB 0.131 4203 529 0.3770 8 20.739 BV 0.029 2980 1491 0.2673 9 20.794 VV 0.055 7438 2930 0.6672 10 Linoleic acid 21.488 VB 0.164 522498 45535 46.8668 11 22.474 BV 0.100 1040 158 0.0933 12 Arachidic acid 22.628 VV 0.095 1297 288 0.1163 13 22.642 VV 0.069 1316 295 0.1180 14 22.918 VB 0.116 7497 996 0.6725 15 23.417 BV 0.175 10888 1008 0.9766 16 Linolenic acid 23.758 VV 0.113 45172 6144 4.0518 17 23.916 VV 0.093 5817 998 0.5218 18 24.206 VV 0.293 5357 384 0.4805 19 24.508 VB 0.188 2531 238 0.2270 20 25.312 BB 0.125 7584 942 0.6803 21 27.368 BB 0.168 1960 143 0.1758 22 28.889 BB 0.117 3727 484 0.3343 23 33.159 VB 0.172 1241 117 0.1113 24 44.377 BB 0.803 10858 199 0.9739

[0163] The present invention is not limited to the specific technical solutions described in the above embodiments, and all technical solutions formed by equivalent replacement are within the protection scope required by the present invention.

Claims

1. A method for preparing a fatty acid type diesel antiwear agent, characterized in that : Includes the following steps: (1) Selecting a suitable mixed fatty acid, performing static rapid freezing crystallization and separation to obtain an acid-type diesel antiwear agent semi-finished product with a saturated fatty acid ΣSFA content of 3-4%; (2) The semi-finished product of the acid-type diesel anti-wear agent is added to the urea alcohol solution, and refluxed in a three-necked flask equipped with a condenser for 30-60 minutes at a material temperature of 78-85°C to uniformly mix the semi-finished product of the acid-type diesel anti-wear agent, urea, and 95% ethanol, thereby facilitating the inclusion of fatty acids by urea. The product is naturally cooled to 60°C and then placed in a circulating cold bath for program cooling. The product is filtered using a suction funnel, and the filter residue and filter paper are washed with isooctane or petroleum ether after filtration. The washed isooctane or petroleum ether is incorporated into the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase. The collected filtrate is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain an unsaturated acid-rich phase. The unsaturated acid-rich phase is the acid-type diesel anti-wear agent, and its ΣSFA content is less than 2.5%. Wherein step (1) the mixed fatty acid is soybean oleic acid and rice bran oleic acid mass ratio of 6:4, cottonseed oleic acid and rice bran oleic acid mass ratio of 1:1; The minimum temperature of the static rapid freezing crystallization in step (1) is -3°C to 2.6°C, and the total freezing time is 49-55 hours; In step (2), the amount of urea used is 0.3 to 0.6 times the mass of the semi-finished anti-wear agent; the solvent is 95% ethanol, and the amount of 95% ethanol used is 6 to 8 times the mass of the urea; the program cooling is 10°C / h to 40°C, 5°C / h from 40°C to 30°C, and 1°C / h from 30°C to 20°C, and the temperature is kept constant at 20°C for 4 hours, which is conducive to the separation of crystals.

2. The preparation method of the fatty acid type diesel antiwear agent according to claim 1, characterized in that The controlled cooling of the static rapid freezing crystallization in step (1) is as follows: when the mixed fatty acid is naturally cooled to a temperature of 40°C, it is placed in a circulating cold bath and cooled to 30°C at 2°C / h, and then cooled from 30°C to 0°C at 1°C / h, and then placed in a laboratory refrigerator and controlled to cool to -2.9°C at 0.2°C / h, and then kept at a constant temperature for a period of time.

3. The preparation method of the fatty acid type diesel antiwear agent according to claim 1, characterized in that In step (2), the semi-finished product of the medium-acid diesel anti-wear agent is added to the urea-alcohol solution and refluxed at 83° C. for 30 minutes to uniformly mix the semi-finished product of the medium-acid diesel anti-wear agent, urea, and 95% ethanol.

4. The preparation method of the fatty acid type diesel antiwear agent according to claim 1, characterized in that : The mixed fatty acids are soybean oil acid and rice bran oil acid in a mass ratio of 6:

4.

5. The preparation method of the fatty acid type diesel antiwear agent according to claim 1, characterized in that : In step (2), urea, 95% ethanol and the semi-finished anti-wear agent are all placed in a three-necked flask, refluxed at 82-84°C for 30 minutes, and naturally cooled to 60°C. The three-necked flask is placed in a circulating cold bath filled with ethylene glycol and programmed to cool: 10°C / h to 40°C, 5°C / h to 30°C, 1°C / h to 20°C, and kept at a constant temperature for 4 hours, and then filtered for a total of 18 hours. The filtration is performed using a suction funnel. After the filtration is completed, the filter residue and filter paper are washed with petroleum ether with a specification of 60-90°C. The washing liquid is added to the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain an unsaturated acid-rich phase. The unsaturated acid-rich phase is the acid-type diesel anti-wear agent.

6. A method for preparing a fatty acid type diesel antiwear agent, characterized in that : Includes the following steps: (1) 123.5 g of soybean oleic acid with a ΣSFA content of 8.0% and 82.1 g of rice bran oleic acid with a ΣSFA content of 8.21% were mixed and heated to 60°C, stirred for 10 minutes, and placed in a 500 ml ground glass tube. The glass tube was fixed in a bracket and cooled naturally to 40°C. The mixture was placed in a circulating cold bath filled with ethylene glycol and programmed to cool down to 30°C at 2°C / h and then to 0°C at 1°C / h. The mixture was then placed in a laboratory refrigerator and cooled to -2.9°C at -0.2°C / h. The mixture was then kept at a constant temperature for a total of 53 hours. After freezing and constant temperature, the raw material mixed oleic acid was quickly filtered and the inner wall of the glass tube and filter paper were rinsed with the filtrate. Finally, 12.8 g of filter residue and 192.5 g of filtrate were obtained. The filtrate was used as a semi-finished fatty acid type diesel anti-wear agent. (2) 112.4 g of urea, 902.5 g of 95% ethanol and 192.5 g of the semi-finished anti-wear agent are all placed in a 2L three-necked flask, refluxed at 82-84 ° C for 30 min, and cooled naturally to 60 ° C. The three-necked flask is placed in a circulating cold bath filled with ethylene glycol and programmed to cool: 10 ° C / h to 40 ° C, 5 ° C / h to 30 ° C, 1 ° C / h to 20 ° C, and kept at a constant temperature for 4 h, and then filtered for a total of 18 h. Filter with a suction funnel. After the filtration is completed, 140 g of petroleum ether with a specification of 60-90 ° C is used to wash the filter residue and filter paper. The washing liquid is added to the filtrate. The collected filter residue is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain a saturated acid-rich phase; the collected filtrate is washed with water, extracted with petroleum ether, dried and filtered with sodium sulfate, and distilled to obtain an unsaturated acid-rich phase. The unsaturated acid-rich phase is the fatty acid type diesel anti-wear agent; 5.5 g of saturated acid-rich phase was obtained, with a ΣSFA mass content of 46.0%; 186.2 g of fatty acid-type diesel antiwear agent was obtained, with a ΣSFA mass content of 2.20%.

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