Method for separating oleic acid from byproduct of OPO grease and oleic acid

Abstract

The invention provides a method for separating oleic acid from a byproduct of OPO grease and oleic acid. The method comprises the following steps: (1) a seed crystal comprises the following components in percentage by mass: 70-100 wt% of stearic acid, 0-20 wt% of palmitic acid triglyceride and 0-15 wt% of glyceryl monostearate or glyceryl monostearate and glyceryl distearate; (2) adding the seed crystal into the OPO by-product according to the addition amount of 10-50wt%, and stirring at the temperature of 70 DEG C under the protection of N2 to obtain crystal slurry; (3) pumping the crystal mush into a crystallization kettle, protecting by N2, stirring, setting the initial temperature of the crystallization kettle to be 70 DEG C, and preserving heat for 1 hour; reducing the temperature from 70 DEG C to 55 DEG C at 3-5 DEG C / h; the temperature is reduced from 55 DEG C to 20 DEG C at the speed of 2-3 DEG C / h; finally, the temperature is reduced to 15-8 DEG C from 20 DEG C at the speed of 1-2 DEG C / h, heat preservation is conducted for at least 5 h, and a crystal substance is obtained; carrying out filter pressing on the crystal substance at the pressure of 0.6 MPa and the temperature of 8-15 DEG C to obtain a filter cake and filtrate; according to the method, the OPO byproduct is used as a raw material to recover high-quality oleic acid, the purity of the oleic acid is more than 80%, and the recovery rate is more than 60%.

Description

Technical Field

[0001] The present disclosure relates to the technical field of separation of OPO byproducts, and in particular to a method for separating oleic acid from OPO oil byproducts and oleic acid. Background Art

[0002] According to the currently available separation technology, for example, Chinese patent application (CN115960678A) discloses a method for separating fatty acids from animal fats by temperature crystallization, which includes (1) freezing the animal fats at low temperature to convert all the liquid animal fats into solid state; (2) heating the solid animal fats until they are completely melted, filtering them while hot, and collecting the liquid fats; (3) adding an aqueous solution containing ascorbyl glucoside and electrolytes to the liquid fats, stirring them evenly, cooling them, keeping them warm for crystallization, separating the solid from the liquid, and collecting the solid fats and liquid fats respectively. This patent application uses temperature crystallization to separate fatty acids from fats, which can only be used in animal fats, and the preparation method is relatively simple, but it is not suitable for systems with OPO byproducts.

[0003] For example, the Chinese patent application (CN109832351B) provides a fat crystallization promoter and a fat composition thereof, wherein the stearic acid content in the promoter is ≥40%; and in the triglyceride composition of the promoter, palm stearyl (PPP) ≤20%, and tristearic acid triglyceride (StStSt) ≥10%. CN 115053931B provides a fat crystallization promoter, the components of which include 50-70% of oleyl glycerol dipalmitate, 10-20% of distearic acid diglyceride, and 15-30% of dioleic acid diglyceride, the total of which is 100%. The above promoters can induce fat crystallization, accelerate the formation of fat crystals, improve crystal size, optimize the structure and texture of the crystal network, inhibit the sanding and hardening of the product, and are applied to oil-containing foods such as margarine and shortening, but are not applicable to the system of OPO distillation byproducts, and acetone, petroleum ether, and ether organic solvents are used in the preparation of the promoter.

[0004] The Chinese patent application (CN102408324A) provides a high-purity oleic acid purification process, which uses hydrolyzed palm oil fatty acids as raw materials and prepares high-purity oleic acid through a dry fractionation process by first crystallizing and then filtering. The prepared oleic acid has a C18:1 content of 70%.

[0005] The Chinese patent application (CN110194716A) provides a method for preparing high-purity oleic acid, which uses mixed fatty acids as raw materials and dissolves them in an organic solvent to obtain a mixed solution, wherein the organic solvent is one or more of an alcohol solvent, a ketone solvent, an alkane solvent, and an ester solvent. Oleic acid is obtained by stirring, heat preservation, crystallization, and filter press separation, but the purity of the prepared oleic acid is not specifically stated.

[0006] The publicly reported literature materials mentioned above cannot meet the technical requirements for separation of OPO distillation by-products and recovery of high-quality oleic acid. Since OPO distillation by-products come from a specific process and have special components, there are currently no reports on their separation and recovery research.

[0007] Through comparison and analysis of existing public technologies, the following technical difficulties exist in separating and recovering high-quality oleic acid using OPO distillation byproducts as raw materials, specifically: 1. The by-product components of OPO oil are more complex. The main components include oleic acid, linoleic acid, linolenic acid, stearic acid, palmitic acid, myristic acid, lauric acid, and oleic acid glyceride, palmitic acid glyceride, stearic acid glyceride and their ester exchange products. The conventional oleic acid separation and recovery process is not suitable for the OPO production system. The oleic acid separation and recovery process for OPO refining by-products needs to be developed.

[0008] 2. The conventional crystallization process for treating OPO refining by-products cannot achieve the expected level in terms of the number of crystals formed, size, polymorphic type, and final distribution of crystals. The crystal morphology is poor and the purity of oleic acid is low.

[0009] 3. Adding organic solvents or high-temperature processes can easily lead to a decrease in the safety of oleic acid and fail to meet the production needs of OPO.

[0010] 4. The filter cake remaining after filtration cannot be reused many times.

[0011] 5. The raw materials used in the process should be available through commercial channels. Summary of the invention

[0012] The present disclosure provides a method for separating oleic acid from a byproduct of OPO oil and fat and oleic acid to at least solve one of the technical problems existing in the prior art.

[0013] According to a first aspect of the present disclosure, there is provided a method for separating oleic acid from a byproduct of OPO oil, comprising the following steps: (1) Configuration of seed crystals: In terms of mass percentage, the seed crystals include 80-100 wt % of stearic acid and 0-20 wt % of palmitic acid triglyceride; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of monostearate glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of mono- and distearic acid glyceryl; (2) Preparation of slurry: The seed crystals are added into the OPO byproduct in an amount of 10-50 wt %, and stirred at 70° C. under N2 protection to obtain a slurry; (3) Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle, and under N2 protection, the mixture was stirred, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 3-5°C / h; Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h; Finally, the temperature is lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h, and then kept warm for at least 5h to obtain a crystal; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8-15° C. to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use.

[0014] In one embodiment, in step (1), the seed crystals include 85-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of monostearate glyceryl; Alternatively, the seed crystals include 85-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of mono- and distearic acid glyceryl.

[0015] In one embodiment, in step (1), the seed crystals include 85 wt % stearic acid, 10 wt % palmitic acid triglyceride, and 5 wt % glyceryl monostearate; Or the seed crystals include 85 wt % of stearic acid, 10 wt % of palmitic acid triglyceride, and 5 wt % of mono- and distearic acid glyceryl.

[0016] In one embodiment, in step (2), the prepared slurry meets the following requirements: in terms of mass percentage, saturated fatty acids 25-50wt%, unsaturated fatty acids 50-75wt%, esters and impurities 0-5wt%.

[0017] In one embodiment, in step (2), the stirring rate is at least 200 r / min, and the stirring time is at least 30 min.

[0018] In one embodiment, in step (3), the stirring rate of the crystallization kettle is 10-50 r / min.

[0019] In one embodiment, in step (3), the temperature is firstly lowered from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was cooled from 20°C to 15-8°C at a cooling rate of 2°C / h and kept warm for at least 5h to obtain crystals.

[0020] In one embodiment, the method of the present application further comprises the steps of: (4): Melting the filter cake at 70°C and selectively adding stearic acid, palmitic acid triglyceride, monostearate glyceryl and mono- and distearate glyceryl according to its composition to obtain secondary seed crystals, and then adding the secondary seed crystals into the OPO byproduct in an amount of 10-50wt%; stirring at 70°C under N2 protection to obtain secondary slurry; The secondary seed crystals include 80-100wt% of stearic acid and 0-20wt% of palmitic acid triglyceride; Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic acid glyceryl; Alternatively, the secondary seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of monostearate glyceryl; Alternatively, the secondary seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of mono- and distearic acid glyceryl; (5): Pump the secondary slurry into the crystallization kettle, fill it with nitrogen for protection, stir it, set the initial temperature of the crystallization kettle to 70°C, and keep it warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 3-5°C / h; Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h; Finally, the temperature is lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h, and then kept warm for at least 5h to obtain a crystal; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8-15° C. to obtain a filter cake and a filtrate, wherein the filtrate is collected to obtain oleic acid, and the filter cake is collected for later use; Repeat steps (4) to (5) multiple times.

[0021] In one embodiment, in step (4), the secondary slurry meets the following requirements: in terms of mass percentage, saturated fatty acids 25-50 wt%, unsaturated fatty acids 50-75 wt%, esters and impurities 0-5 wt%.

[0022] According to a second aspect of the present disclosure, there is provided oleic acid, which is prepared by any one of the methods described above.

[0023] Compared with the prior art, the advantages of this application are: 1) In the method of this application, no additional substances outside the OPO system are added, and the raw materials or intermediate products contained in the system itself are used as crystal seeds. Therefore, the solvent residue in the oleic acid is not detected (quantitative limit: 10 mg / kg), and the insoluble impurity content is ≤0.05%. 2) In the method of this application, low temperature control is used during crystallization, coupled with high-precision gradient temperature control. For oils and fats, it can greatly ensure the freshness and safety of oils and fats, avoid some problems caused by traditional high-temperature extraction, and the product is safer. 3) The method of this application is fully applicable to the OPO production system, and can use OPO refining by-products as raw materials to separate and recover high-quality oleic acid, with oleic acid purity >80% and recovery rate >60%. 4) In order to improve the safety of oleic acid, the method of this application does not add organic solvents, does not use high-temperature processes (process temperature does not exceed 70°C), and does not introduce other substances outside the OPO production system. The solvent residue in the prepared oleic acid is not detected (quantitative limit: 10 mg / kg), the insoluble impurity content is ≤0.05%, and the peroxide value is ≤1.0 mmol / kg. 5) In the method of this application, the filter cake remaining from the filter press can be reused up to 5 times, maximizing the utilization of OPO by-products. In this application, the components of the seed crystals all meet food safety requirements and are commercially available, with convenient access channels and easy industrial application.

[0024] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, in which: In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0026] Figure 1 shows a gas chromatogram of an untreated OPO byproduct of the present disclosure; Figure 2 shows the gas chromatogram of the filtrate obtained in Example 1 of the present disclosure; Figure 3 shows the gas chromatogram of the filtrate obtained in Example 2 of the present disclosure; Figure 4shows the gas chromatogram of the filtrate obtained in Example 3 of the present disclosure; Figure 5 shows the gas chromatogram of the filtrate obtained in Example 4 of the present disclosure; Figure 6 shows the gas chromatogram of the filtrate obtained in Example 5 of the present disclosure; Figure 7 shows the gas chromatogram of the filtrate obtained in Example 6 of the present disclosure; Figure 8 The gas chromatogram of the filtrate obtained in Comparative Example 1 of the present disclosure is shown; Fig. 9 The gas chromatogram of the filtrate obtained in Comparative Example 2 of the present disclosure is shown. DETAILED DESCRIPTION

[0027] In order to make the purpose, features, and advantages of the present disclosure more obvious and easy to understand, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0028] According to one embodiment of the present disclosure, the present invention provides a method for separating oleic acid from a byproduct of OPO oil (hereinafter referred to as OPO byproduct), comprising the following steps: (1) Configuration of seed crystals: In terms of mass percentage, the seed crystals include 80-100wt% of stearic acid and 0-20wt% of palmitic acid triglyceride; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of monostearate glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of mono- and distearic acid glyceryl; (2) Preparation of slurry: Add seed crystals in an amount of 10-50wt% to the OPO byproduct, under N2 protection, at a temperature of 70°C, and stir to obtain a slurry; (3) Crystallization and filtration of slurry: The slurry was pumped into the crystallization kettle, and under N2 protection, the mixture was stirred and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1 hour. Then the temperature was cooled from 70°C to 55°C at a cooling rate of 3-5°C / h; Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h; Finally, the temperature is lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h, and then kept warm for at least 5h to obtain a crystal; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8-15°C to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use.

[0029] The method of the present application utilizes seed crystals and a high-precision gradient temperature control method to separate oleic acid from byproducts produced by synthesizing OPO oils, thereby obtaining high-content oleic acid, and the oleic acid has no residual solvent and is safe and reliable.

[0030] In the method of this application, no additional substances outside the OPO system are added, and the raw materials or intermediates contained in the system itself are used as crystal seeds. Therefore, the solvent residue in oleic acid is not detected (quantitative limit: 10 mg / kg), and the insoluble impurity content is ≤0.05%. In the method of this application, low temperature control is used during crystallization, and high-precision gradient temperature control is used. For oils and fats, the freshness and safety of the oils and fats can be greatly guaranteed, and some problems caused by traditional high-temperature extraction can be avoided, making the product safer.

[0031] The method of this application is fully applicable to the OPO production system, and can separate and recover high-quality oleic acid with OPO refining by-products as raw materials, with oleic acid purity > 80% and recovery rate > 60%. In order to improve the safety of oleic acid, the method of this application does not add organic solvents, does not use high-temperature processes (process temperature does not exceed 70°C), and does not introduce other substances outside the OPO production system. The solvent residue in the prepared oleic acid is not detected (quantitative limit: 10 mg / kg), the insoluble impurity content is ≤0.05%, and the peroxide value is ≤1.0 mmol / kg. In the method of this application, the filter cake remaining from the filter press can be reused up to 5 times, maximizing the use of OPO by-products. In this application, the components of the seed crystals all meet food safety requirements and are commercially available, with convenient access channels and easy industrial applications.

[0032] In the present application, the seed crystal provides a rigid crystal nucleus, and the attachment of oleic acid to the rigid crystal nucleus is conducive to the formation of fuller and finer oleic acid crystals, thereby improving the purity of oleic acid. Considering the requirements of OPO for food safety, in principle, it is preferred not to introduce other substances outside the OPO production system.

[0033] In this application, stearic acid, palmitic triglyceride, monostearic glyceride, mono- and distearic glyceride are all commercially available, wherein stearic acid is stearic acid (also known as octadecanoic acid) which is a food additive, and complies with the national standard GB 1886.101; monostearic glyceride is distilled monostearic glyceride which is a food additive, and complies with the national standard GB 15612; mono- and distearic glyceride is mono- and distearic glyceride which is a food additive, and complies with the national standard GB 1986. Palmitic triglyceride is a synthetic raw material derived from OPO, and is processed from edible vegetable oil, with a melting point ≥52°C and an iodine value ≤34 g I2 / 100 g.

[0034] In the present application, in step (3), the slurry prepared in step (2) is pumped into a crystallization kettle with stirring, and nitrogen is filled for protection. The crystallization kettle adopts high-precision gradient temperature control, the stirring rate is 10~50r / min, and the temperature control accuracy is ±0.1℃. After the slurry is pumped into the crystallization kettle, the initial temperature of the crystallization kettle is set to 70℃, stirring is turned on, and the residence time at this temperature is 1h, so that the slurry is completely melted and the original crystal form is destroyed. When the cooling temperature range is in the range of 70℃ to 55℃, the actual temperature is higher than the crystallization temperature, no crystals are produced, the system is clear and transparent, and rapid cooling is adopted; when the cooling temperature range is in the range of 55℃ to 20℃, the actual temperature gradually approaches the crystallization temperature, crystals begin to be produced, the system is white and translucent, and slow cooling is adopted; when the cooling temperature range is in the range of 20℃ to 15~8℃, the crystal form is full and presents a milky white semi-solid state. In order to avoid oleic acid crystallization, slow cooling is required during the entire gradient cooling process.

[0035] Wherein, in step (1), the seed crystals include 85-100wt% of stearic acid and 0-15wt% of glyceryl monostearate; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of monostearate glyceryl; Alternatively, the seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of mono- and distearic acid glyceryl.

[0036] Preferably, in step (1), the seed crystals include 85-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of monostearate glyceryl; Or the seed crystals include 85-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of mono- and distearic acid glyceryl.

[0037] For example, the stearic acid content is 70wt%, 80wt%, 85wt%, 90wt%, 95wt%, 100wt%. The monostearate content is 0wt%, 5wt%, 10wt%, 15wt%. The mono- and distearate content is 0wt%, 5wt%, 10wt%, 15wt%. The palmitic acid triglyceride content is 0wt%, 5wt%, 10wt%, 15wt%, 20wt%.

[0038] More preferably, in step (1), the seed crystals include 85 wt % stearic acid, 10 wt % palmitic acid triglyceride, and 5 wt % glyceryl monostearate; Or the seed crystals include 85wt% of stearic acid, 10wt% of palmitic acid triglyceride, and 5wt% of mono- and distearic acid glyceryl. Preferably, in step (2), the prepared slurry meets the following requirements: in terms of mass percentage, saturated fatty acids 25-50wt%, unsaturated fatty acids 50-75wt%, esters and impurities 0-5wt%.

[0039] Among them, saturated fatty acids include stearic acid, palmitic acid, myristic acid and lauric acid. Unsaturated fatty acids include oleic acid, linoleic acid and linolenic acid. Esters include esters in OPO by-products and esters in seed crystals. Specifically, the esters in the slurry include esters in the original OPO by-products, such as oleic acid glyceride, palmitic acid glyceride, stearic acid glyceride, and the esters in the seed crystals include monostearic acid glyceride, mono- and distearic acid glyceride and palmitic acid triglyceride.

[0040] In this application, the mass ratio of seed crystals to OPO by-products is 10~50%:1. And among the components of the configured slurry, the saturated fatty acids composed of the sum of the percentages of stearic acid, palmitic acid, myristic acid, and lauric acid are limited to 25-50wt%; the unsaturated fatty acids composed of the sum of the percentages of oleic acid, linoleic acid, and linolenic acid are limited to 50-75wt%; and the esters and other impurities are limited to 0~5wt%; it can ensure that after the subsequent crystallization and filter pressing of the slurry, the filtrate obtained, i.e., oleic acid, remains at the same standard level to ensure the stability of the product. Among them, before the crystal slurry is crystallized and filtered, the composition of the slurry needs to be measured. If the content of a certain component in the slurry is not within the required range, the corresponding substances need to be adaptively added to ensure that the composition of the slurry meets the above requirements. Therefore, after the subsequent crystallization and filter pressing, it can be ensured that each batch of products meets the production requirements and the product is stable.

[0041] Preferably, in step (2), the stirring rate is at least 200 r / min and the stirring time is at least 30 min.

[0042] Preferably, in step (3), the stirring rate of the crystallization kettle is 10-50 r / min.

[0043] Preferably, in step (3), the crystals obtained after the crystallization are pumped into a membrane filter press, and filtered at a pressure of 0.6 MPa and a temperature of 8-15° C. The filtrate obtained is oleic acid, which is filled with nitrogen for storage, and the filter cake enriched in the filter bag is collected for later use.

[0044] Preferably, in step (3), the temperature is first cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was cooled from 20°C to 15-8°C at a cooling rate of 2°C / h and kept warm for at least 5h to obtain crystals.

[0045] Furthermore, the application method also includes the steps of: (4): Melting the filter cake at 70°C and selectively adding stearic acid, palmitic acid triglyceride, monostearate glyceryl and mono- and distearate glyceryl according to its composition to obtain secondary seed crystals, and then adding the secondary seed crystals into the OPO byproduct in an amount of 10-50wt%; stirring at 70°C under N2 protection to obtain secondary slurry; The secondary seed crystals include 80-100wt% of stearic acid and 0-20wt% of palmitic acid triglyceride; Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic acid glyceryl; Alternatively, the secondary seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of monostearate glyceryl; Alternatively, the secondary seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of mono- and distearic acid glyceryl; (5): Pump the secondary slurry into the crystallization kettle, fill it with nitrogen for protection, stir it, set the initial temperature of the crystallization kettle to 70°C, and keep it warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 3-5°C / h; Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h; Finally, the temperature is lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h, and then kept warm for at least 5h to obtain a crystal; The crystals are filtered under the conditions of a pressure of 0.6 MPa and a temperature of 8-15°C to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use; Repeat steps (4) to (5) multiple times.

[0046] Preferably, in step (3), the filter cake obtained has saturated fatty acids and esters as main components, and then in step (4), the filter cake is melted at 70°C, the amount of addition is calculated based on its fatty acid composition, secondary seed crystals are obtained, and the OPO by-product is re-added.

[0047] Preferably, in step (4), the secondary slurry meets the following requirements: in terms of mass percentage, saturated fatty acids 25-50wt%, unsaturated fatty acids 50-75wt%, esters and impurities 0-5wt%.

[0048] According to the second aspect of the present disclosure, the present application also provides oleic acid, which is prepared by any one of the methods described above.

[0049] In this application, the gas chromatogram of the by-products produced by the synthesis of OPO oil before treatment is as follows: Figure 1 As shown in Table 4, the main components are oleic acid (57.3640%), palmitic acid (26.0434%), stearic acid (6.992%), and linoleic acid (9.0856%).

[0050] The present application is described in detail below with reference to specific embodiments: Example 1 A method for separating oleic acid from a byproduct of OPO oil comprises the following steps: Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 100 wt % of stearic acid; Step (2): Preparation of slurry: The seed crystals were added into the OPO byproduct in an amount of 10wt%, and stirred at 70°C and 200r / min for 30min under N2 protection to obtain a slurry; the components of the slurry were as follows: saturated fatty acids 25-50wt%; unsaturated fatty acids 50-75wt%; esters and other impurities ≤5wt%; Step (3): Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 10 r / min, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was lowered from 20°C to 15°C at a cooling rate of 2°C / h and kept at 15°C for 5h to obtain crystals; The crystals were filtered under the conditions of a pressure of 0.6 MPa and a temperature of 15°C to obtain a filter cake and a filtrate. The filtrate was collected to obtain oleic acid, and the filter cake was collected for later use.

[0051] Example 2 A method for separating oleic acid from a byproduct of OPO oil comprises the following steps: Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 95wt% stearic acid and 5wt% glyceryl monostearate; Step (2): Preparation of slurry: The seed crystals were added into the OPO by-product in an amount of 50wt%, and stirred at 70°C and 200r / min for 30min under N2 protection to obtain a slurry; the components of the slurry were as follows: saturated fatty acids 25-50wt%; unsaturated fatty acids 50-75wt%; esters and other impurities ≤5wt%.

[0052] Step (3): Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 50r / min, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1h; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was lowered from 20°C to 8°C at a cooling rate of 2°C / h and kept at 8°C for 5h to obtain crystals; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8°C to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use.

[0053] Example 3 A method for separating oleic acid from a byproduct of OPO oil comprises the following steps: Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 85wt% stearic acid and 15wt% palmitic acid triglyceride; Step (2): Preparation of slurry: The seed crystals were added into the OPO byproduct in an amount of 20 wt%, and stirred at 70 °C and 200 r / min for 30 min under N2 protection to obtain a slurry; wherein the components of the slurry satisfy the following requirements: 25-50 wt% saturated fatty acid; Unsaturated fatty acids 50-75wt%; Esters and other impurities ≤5wt%.

[0054] Step (3): Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 30r / min, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1h; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was lowered from 20°C to 10°C at a cooling rate of 2°C / h and kept at 10°C for 5h to obtain crystals; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8°C to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use.

[0055] Example 4 A method for separating oleic acid from a byproduct of OPO oil comprises the following steps: Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 85 wt % of stearic acid, 10 wt % of palmitic acid triglyceride, and 5 wt % of monostearate glyceryl; Step (2): Preparation of slurry: The seed crystals were added into the OPO by-product in an amount of 30wt%, and stirred at 70°C and 200r / min for 30min under N2 protection to obtain a slurry; the components of the slurry met the following requirements: saturated fatty acids 25-50wt%; unsaturated fatty acids 50-75wt%; esters and other impurities ≤5wt%.

[0056] Step (3): Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 50r / min, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1h; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was lowered from 20°C to 8°C at a cooling rate of 2°C / h and kept at 8°C for 5h to obtain crystals; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8°C to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use.

[0057] Example 5 A method for separating oleic acid from a byproduct of OPO oil comprises the following steps: Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 85 wt % of stearic acid, 10 wt % of palmitic acid triglyceride, and 5 wt % of mono- and distearic acid glyceryl; Step (2): Preparation of slurry: The seed crystals were added into the OPO by-product in an amount of 40wt%, and stirred at 70°C and 200r / min for 30min under N2 protection to obtain a slurry; the components of the slurry were as follows: saturated fatty acids 25-50wt%; unsaturated fatty acids 50-75wt%; esters and other impurities ≤5wt%.

[0058] Step (3): Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 50r / min, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1h; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was lowered from 20°C to 12°C at a cooling rate of 2°C / h and kept at 12°C for 5h to obtain crystals; The crystals were filtered under the conditions of a pressure of 0.6 MPa and a temperature of 10°C to obtain a filter cake and a filtrate. The filtrate was collected to obtain oleic acid, and the filter cake was collected for later use.

[0059] Example 6 This Example 6 is substantially the same as Example 4, except that: in step (3), the temperature is cooled from 70°C to 55°C at a cooling rate of 3°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 2°C / h; Finally, the temperature was cooled from 20°C to 8°C at a cooling rate of 2°C / h and kept at 8°C for 5 h to obtain crystals.

[0060] Comparative Example 1 This comparative example 1 is substantially the same as the example 1, except that the seed crystal of step (1) is not configured.

[0061] Comparative Example 2 This comparative example 2 is substantially the same as Example 4, except that: in step (3), the temperature is cooled from 70°C to 40°C at a cooling rate of 5°C / h; The temperature was then lowered from 40°C to 8°C at a cooling rate of 3°C / h; and kept at 8°C for 5 hours to obtain crystals.

[0062] The oleic acid prepared in the above examples and comparative examples was tested as follows: 1: The oleic acid content and recovery rate prepared in the above Examples 1-6 and Comparative Examples 1-2 are shown in Table 1: Table 1 Oleic acid content and recovery rate of Examples 1-6 and Comparative Examples 1-2 As can be seen from Table 1 above, when seed is not introduced, even with high-precision gradient cooling, the oleic acid content and recovery obtained are also much smaller than the oleic acid content and recovery obtained by the application method introducing seed and high-precision gradient cooling for co-processing, and the oleic acid purity obtained by the application method is high, oleic acid content is more than 80%, and oleic acid recovery rate is more than 60%. This shows that in the present application, by introducing seed, seed provides rigid nucleus, so that oleic acid can be attached to rigid nucleus during crystallization, increasing oleic acid recovery rate and oleic acid content. It is further shown that seed and high-precision gradient cooling process are indispensable, and the two play a synergistic effect.

[0063] In addition, the oleic acid recovery rate and oleic acid content of Comparative Example 2 are lower than those of Example 4, especially the oleic acid recovery rate, which is much lower than that of Example 4. This shows that the use of three cooling gradients in the present application can provide favorable conditions for the crystallization of the slurry, and the use of the gradient cooling of the present application can improve the recovery rate of the slurry.

[0064] 2: Detection of solvent in oleic acid: Since the method of the present application does not add any additional substances outside the OPO system, and uses the raw materials or intermediate products contained in the system itself as crystal seeds, in the above Examples 1-6, the solvent residue in the oleic acid is not detected (quantitative limit: 10 mg / kg), and the insoluble impurity content is ≤0.05%, and the results are listed in Table 2. In addition, in the present application, the low temperature control of crystallization, coupled with high-precision gradient temperature control, can greatly ensure the freshness and safety of the oil, avoid some problems caused by traditional high-temperature extraction, and the product is safer.

[0065] Table 2 Detection results of solvent residues in oleic acid of Examples 1-6 3: Filter cake repeatability verification: Taking the filter cake prepared in Example 3 as an example, the following repeated cycles were performed: Specifically comprising: step (4) melting the filter cake at 70°C, and adding stearic acid and palmitic acid triglyceride according to the components in the filter cake to obtain secondary seed crystals, and then adding the secondary seed crystals in an amount of 10-50wt% to the OPO by-product; under N2 protection, at a temperature of 70°C, stirring, to obtain secondary slurry; The secondary seed crystals include 85wt% stearic acid and 15wt% palmitic acid triglyceride; The components of the secondary slurry meet the following requirements: saturated fatty acid 25-50wt%; Unsaturated fatty acids 50-75wt%; Esters and impurities ≤5wt%.

[0066] Step (5): pump the secondary slurry into the crystallization kettle, fill it with nitrogen for protection, stir it, set the initial temperature of the crystallization kettle to 70°C, and keep it warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was lowered from 20°C to 10°C at a cooling rate of 2°C / h and kept at 10°C for 5h to obtain crystals; The crystals were filtered under the conditions of pressure of 0.6 MPa and temperature of 8°C to obtain filter cake and filtrate. The filtrate was collected to obtain oleic acid, and the filter cake was collected for later use. Repeat steps (4) to (5).

[0067] According to the above method, step (4) to step (5) were cycled for 7 times, and the obtained oleic acid content and oleic acid peroxide value results are shown in Table 3: Table 3 Oleic acid content and oleic acid peroxide value after each filter cake reuse It can be seen from Table 3 above that the oleic acid content obtained in the seven reuses was >80%, but the peroxide value of oleic acid began to increase, indicating that the freshness of the oil began to decrease during the repeated processing. In order to ensure the safety of oleic acid, the filter cake was no longer reused after the fifth reuse.

[0068] 4: Gas chromatograms of OPO byproducts before and after treatment, such as Figure 1-Figure 9 As shown in Table 4. Table 4 is the main composition analysis of the untreated OPO byproduct, the filtrate obtained from Examples 1-6 and Comparative Examples 1-2.

[0069] It can be seen from Table 4 above that in the untreated OPO by-product, the oleic acid content is only about 57%, which is relatively low. After being treated by the method of the present application, the main component of the collected filtrate is oleic acid, and the oleic acid content is above 80%, which is relatively high. The other components are mainly palmitic acid, stearic acid, linoleic acid, etc., which belong to the OPO system. Therefore, the oleic acid prepared by the method of the present application is safer and more reliable.

[0070] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps recorded in this disclosure can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved, and this document does not limit this.

[0071] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0072] The above is only a specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for separating oleic acid from a byproduct of OPO grease, characterized in that: The steps include: (1) Configuration of seed crystals: In terms of mass percentage, the seed crystals include 80-100 wt % of stearic acid and 0-20 wt % of palmitic acid triglyceride; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of monostearate glyceryl; Alternatively, the seed crystals include 70-100wt% of stearic acid, 0-20wt% of palmitic acid triglyceride, and 0-15wt% of mono- and distearic acid glyceryl; (2) Preparation of slurry: The seed crystals are added into the OPO byproduct in an amount of 10-50 wt %, and stirred at 70° C. under N2 protection to obtain a slurry; (3) Crystallization and filtration of slurry: The slurry was pumped into a crystallization kettle, and under N2 protection, the mixture was stirred, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 3-5°C / h; Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h; Finally, the temperature is lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h, and then kept warm for at least 5h to obtain a crystal; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8-15° C. to obtain a filter cake and a filtrate. The filtrate is collected to obtain oleic acid, and the filter cake is collected for later use.

2. The method according to claim 1, characterized in that: In the step (1), the seed crystals include 85-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of monostearate glyceryl; Alternatively, the seed crystals include 85-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of mono- and distearic acid glyceryl.

3. The method according to claim 2, characterized in that: In step (1), the seed crystals include 85 wt % stearic acid, 10 wt % palmitic acid triglyceride, and 5 wt % glyceryl monostearate; Or the seed crystals include 85 wt % of stearic acid, 10 wt % of palmitic acid triglyceride, and 5 wt % of mono- and distearic acid glyceryl.

4. The method according to claim 1, characterized in that: In step (2), the prepared slurry meets the following requirements: in terms of mass percentage, saturated fatty acids are 25-50wt%, unsaturated fatty acids are 50-75wt%, and esters and impurities are 0-5wt%.

5. The method according to claim 1, characterized in that: In the step (2), the stirring rate is at least 200 r / min and the stirring time is at least 30 min.

6. The method according to claim 1, characterized in that: In the step (3), the stirring rate of the crystallization kettle is 10-50 r / min.

7. The method according to claim 1, characterized in that: In the step (3), the temperature is firstly lowered from 70°C to 55°C at a cooling rate of 5°C / h; Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h; Finally, the temperature was cooled from 20°C to 15-8°C at a cooling rate of 2°C / h and kept warm for at least 5h to obtain crystals.

8. The method according to any one of claims 1 to 7, characterized in that: Also includes the steps: (4): Melting the filter cake at 70°C and selectively adding stearic acid, palmitic acid triglyceride, monostearate glyceryl and mono- and distearate glyceryl according to its composition to obtain secondary seed crystals, and then adding the secondary seed crystals into the OPO byproduct in an amount of 10-50wt%; stirring at 70°C under N2 protection to obtain secondary slurry; The secondary seed crystals include 80-100wt% of stearic acid and 0-20wt% of palmitic acid triglyceride; Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic acid glyceryl; Alternatively, the secondary seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of monostearate; Alternatively, the secondary seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of mono- and distearic acid glyceryl; (5): Pump the secondary slurry into the crystallization kettle, fill it with nitrogen for protection, stir it, set the initial temperature of the crystallization kettle to 70°C, and keep it warm for 1 hour; Then the temperature was cooled from 70°C to 55°C at a cooling rate of 3-5°C / h; Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h; Finally, the temperature is lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h, and then kept warm for at least 5h to obtain a crystal; The crystals are filtered under a pressure of 0.6 MPa and a temperature of 8-15° C. to obtain a filter cake and a filtrate, wherein the filtrate is collected to obtain oleic acid, and the filter cake is collected for later use; Repeat steps (4) to (5) multiple times.

9. The method according to claim 8, characterized in that: In step (4), the secondary slurry meets the following requirements: in terms of mass percentage, saturated fatty acids 25-50wt%, unsaturated fatty acids 50-75wt%, esters and impurities 0-5wt%.

10. Oleic acid, characterized in that: It is prepared by the method described in any one of claims 1 to 9.

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