A method for separating oleic acid from by-products of OPO grease and oleic acid

Abstract

The present disclosure provides a method for separating oleic acid from a byproduct of OPO oil and fat, and oleic acid. The method comprises: (1) in mass percentage, seed crystals comprising 70-100 wt% of stearic acid, 0-20 wt% of palmitic acid triglyceride, and 0-15 wt% of monostearate or mono- and distearate glycerol; (2) seed crystals are added to the OPO byproduct in an amount of 10-50 wt%, stirred at 70°C under nitrogen; (3) the slurry is pumped into a crystallization kettle, stirred under nitrogen, and the initial kettle temperature is set to 70°C, which is kept warm for 1 hour; the temperature is lowered from 70°C to 55°C at 3-5°C / h; the temperature is lowered from 55°C to 20°C at 2-3°C / h; the temperature is lowered from 20°C to 15-8°C at 1-2°C / h, and kept warm for at least 5 hours to obtain crystals; the crystals are filtered under 0.6 MPa and 8-15°C to obtain a filter cake and a filtrate. The method of the present application uses OPO byproduct as raw material to recover oleic acid, and the purity of oleic acid is greater than 80%.

Description

Technical Field

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

[0002] With regard to currently available separation technologies, for example, Chinese patent application (CN115960678A) discloses a method for separating fatty acids from animal fats using a temperature crystallization method, which includes: (1) freezing the animal fat at low temperatures to convert the liquid animal fat into a solid state; (2) heating the solid animal fat until it is completely melted, filtering it while hot, and collecting the liquid fat; (3) adding an aqueous solution containing ascorbyl glucoside and electrolytes to the liquid fat, stirring it evenly, cooling it, maintaining the temperature to allow crystallization, separating the solid from the liquid, and collecting the solid fat and liquid fat separately. This patent application uses a temperature crystallization method 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 applicable to systems with OPO byproducts.

[0003] For example, Chinese patent application (CN109832351B) provides a fat crystallization promoter and its composition. The stearic acid content in the promoter is ≥40%, and the triglyceride composition of the promoter includes palmitic acid stearyl (PPP) ≤20% and tristearin triglyceride (StStSt) ≥10%. CN 115053931B provides a fat crystallization promoter comprising 50-70% monooleyl dipalmitate, 10-20% distearic acid diglyceride, and 15-30% dioleic acid diglyceride, totaling 100%. These promoters can induce fat crystallization, accelerate fat crystal formation, improve crystal size, optimize the structure and texture of the crystal network, and suppress product grit and post-hardening. They are suitable for use in oil-containing foods such as margarine and shortening. However, they are not suitable for systems using OPO distillation byproducts. Furthermore, the promoter uses organic solvents such as acetone, petroleum ether, and ether in its preparation.

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

[0005] A Chinese patent application (CN110194716A) provides a method for preparing high-purity oleic acid. Mixed fatty acids are dissolved in an organic solvent to produce a mixed solution. The organic solvent is one or more of an alcohol, ketone, alkane, and ester. Oleic acid is obtained through a process of stirring, heat preservation, crystallization, and filter press separation. However, the purity of the prepared oleic acid is not specified.

[0006] The publicly reported literature materials mentioned above cannot meet the technical requirements for separating OPO distillation by-products and recovering 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 by-products as raw materials, specifically:

[0008] 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.

[0009] 2. The conventional crystallization process for treating OPO refining by-products fails to 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.

[0010] 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.

[0011] 4. The filter cake remaining after filtration cannot be reused multiple times.

[0012] 5. The raw materials used in the process should be available through commercial channels. Summary of the Invention

[0013] The present disclosure provides a method for separating oleic acid from a byproduct of OPO oil and fat and oleic acid, so as to at least solve one of the technical problems existing in the prior art.

[0014] 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:

[0015] (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;

[0016] Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate;

[0017] Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic glycerol;

[0018] Alternatively, the seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of glyceryl monostearate;

[0019] 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;

[0020] (2) Preparation of slurry:

[0021] The seed crystals were added to the OPO by-product in an amount of 10-50 wt %, and stirred at 70° C. under N2 protection to obtain a slurry;

[0022] (3) Crystallization and filtration of slurry:

[0023] The slurry was pumped into the crystallization kettle, stirred under N2 protection, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1 hour;

[0024] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 3-5°C / h;

[0025] Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h;

[0026] Finally, the temperature was lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h and kept warm for at least 5h to obtain crystals;

[0027] 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.

[0028] 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 glyceryl monostearate;

[0029] 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.

[0030] In one embodiment, in step (1), the seed crystals include 85 wt% of stearic acid, 10 wt% of palmitic acid triglyceride, and 5 wt% of glyceryl monostearate;

[0031] 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.

[0032] In one embodiment, in step (2), the prepared 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%.

[0033] In one embodiment, in step (2), the stirring rate is at least 200 r / min, and the stirring time is at least 30 min.

[0034] In one embodiment, in step (3), the stirring rate of the crystallization kettle is 10-50 r / min.

[0035] In one embodiment, in step (3), the temperature is first lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0036] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0037] Finally, the temperature was lowered 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.

[0038] In one embodiment, the method of the present application further comprises the steps of:

[0039] (4): The filter cake is melted at 70°C and stearic acid, palmitic acid triglyceride, monostearate, and mono- and distearate glycerides are selectively added according to the composition thereof to obtain secondary seed crystals, and then the secondary seed crystals are added to the OPO by-product in an amount of 10-50 wt%; under N2 protection, the temperature is 70°C, and stirring is performed to obtain a secondary slurry;

[0040] The secondary seed crystals include 80-100 wt% of stearic acid and 0-20 wt% of palmitic acid triglyceride;

[0041] Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate;

[0042] Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic acid glyceryl;

[0043] 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;

[0044] 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;

[0045] (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;

[0046] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 3-5°C / h;

[0047] Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h;

[0048] Finally, the temperature was lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h and kept warm for at least 5h to obtain crystals;

[0049] 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;

[0050] Repeat steps (4) to (5) multiple times.

[0051] 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%.

[0052] 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.

[0053] Compared with the existing technology, 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 intermediates contained in the system itself are used as crystal seeds. Therefore, no solvent residues in the oleic acid are detected (quantification 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, this can greatly ensure the freshness and safety of the oils and fats, avoid some of the problems caused by traditional high-temperature extraction, and make the product safer. 3) The method of this application is fully applicable to the OPO production system and can separate and recover high-quality oleic acid using OPO refining by-products as raw materials. The oleic acid purity is >80% and the recovery rate is >60%. 4) To improve the safety of oleic acid, this method does not add organic solvents, does not use high-temperature processes (process temperatures do not exceed 70°C), and does not introduce any substances other than the OPO production system. The resulting oleic acid contains no detectable residual solvents (limit of quantification: 10 mg / kg), an insoluble impurity content of ≤0.05%, and a peroxide value of ≤1.0 mmol / kg. 5) In this method, the filter cake remaining after filtration can be reused up to five times, maximizing the utilization of the OPO byproduct. In this application, the components of the seed crystals all meet food safety requirements and are commercially available, making them readily available and amenable to industrial application.

[0054] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present disclosure, nor are they intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] 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 which several embodiments of the present disclosure are shown by way of example and not limitation, wherein:

[0056] In the drawings, the same or corresponding reference numerals denote the same or corresponding parts.

[0057] Figure 1 shows a gas chromatogram of the untreated OPO by-product of the present disclosure;

[0058] Figure 2 shows a gas chromatogram of the filtrate obtained in Example 1 of the present disclosure;

[0059] Figure 3 shows a gas chromatogram of the filtrate obtained in Example 2 of the present disclosure;

[0060] Figure 4 shows a gas chromatogram of the filtrate obtained in Example 3 of the present disclosure;

[0061] Figure 5 shows a gas chromatogram of the filtrate obtained in Example 4 of the present disclosure;

[0062] Figure 6 shows a gas chromatogram of the filtrate obtained in Example 5 of the present disclosure;

[0063] Figure 7 shows a gas chromatogram of the filtrate obtained in Example 6 of the present disclosure;

[0064] Figure 8 shows a gas chromatogram of the filtrate obtained in Comparative Example 1 of the present disclosure;

[0065] Figure 9 The gas chromatogram of the filtrate obtained in Comparative Example 2 of the present disclosure is shown. DETAILED DESCRIPTION

[0066] To make the purposes, features, and advantages of the present disclosure more apparent and understandable, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative work shall fall within the scope of protection of the present disclosure.

[0067] 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:

[0068] (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;

[0069] Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate;

[0070] Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic glycerol;

[0071] Alternatively, the seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of glyceryl monostearate;

[0072] 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;

[0073] (2) Preparation of slurry:

[0074] Add seed crystals in an amount of 10-50 wt% to the OPO by-product, under N2 protection, at a temperature of 70°C, and stir to obtain a slurry;

[0075] (3) Crystallization and filtration of slurry:

[0076] The slurry was pumped into the crystallization kettle, stirred under N2 protection, and the initial temperature of the crystallization kettle was set to 70℃ and kept warm for 1 hour;

[0077] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 3-5°C / h;

[0078] Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h;

[0079] Finally, the temperature was lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h and kept warm for at least 5h to obtain crystals;

[0080] 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.

[0081] The method of the present application utilizes seed crystals and a high-precision gradient temperature control method to separate oleic acid from the by-products produced by synthesizing OPO oils, thereby obtaining high-content oleic acid, and the oleic acid is free of residual solvents and is safe and reliable.

[0082] 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, no solvent residues in oleic acid are detected (quantitative limit: 10mg / kg), and the insoluble impurity content is ≤0.05%. 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 the oils and fats, avoid some of the problems caused by traditional high-temperature extraction, and the product is safer.

[0083] The method described in this application is fully applicable to the OPO production system and can be used to separate and recover high-quality oleic acid using OPO refining byproducts as raw materials. The purity of the oleic acid is >80% and the recovery rate is >60%. To enhance the safety of oleic acid, this method does not add organic solvents, does not employ high-temperature processes (process temperatures do not exceed 70°C), and does not introduce any substances other than those in the OPO production system. The resulting oleic acid contains no detectable residual solvents (limit of quantification: 10 mg / kg), an insoluble impurity content of ≤0.05%, and a peroxide value of ≤1.0 mmol / kg. In this method, the filter cake remaining after filtration can be reused up to five times, maximizing the utilization of the OPO byproduct. The seed crystal components used in this application all meet food safety requirements and are commercially available, making them readily available and amenable to industrial application.

[0084] In this 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 more delicate oleic acid crystals, thereby improving the purity of oleic acid. Considering the food safety requirements of OPO, in principle, it is prioritized not to introduce other substances outside the OPO production system.

[0085] In this application, stearic acid, palmitic triglyceride, monostearic glyceride, and mono- and distearic glycerides are all commercially available. Stearic acid is stearic acid (also known as octadecanoic acid), a food additive, and complies with national standard GB 1886.101. Monostearic glyceride is distilled monostearic glyceride, a food additive, and complies with national standard GB 15612. Mono- and distearic glycerides are mono- and distearic glycerides, food additives, and complies with national standard GB 1986. Palmitic triglyceride is a synthetic raw material derived from OPO, processed from edible vegetable oil, with a melting point ≥52°C and an iodine value ≤34 g I² / 100 g.

[0086] 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, with a stirring rate of 10~50r / min and a temperature control accuracy of ±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 temperature is kept at this temperature for 1h to completely melt the slurry and destroy the original crystal form. When the cooling temperature range is between 70℃ and 55℃, the actual temperature is higher than the crystallization temperature, no crystals are produced, and the system is clear and transparent, and rapid cooling is adopted; when the cooling temperature range is between 55℃ and 20℃, the actual temperature gradually approaches the crystallization temperature, crystals begin to be produced, and the system is white and translucent, and slow cooling is adopted; when the cooling temperature range is between 20℃ and a temperature between 15~8℃, the crystal form is full and presents a milky white semi-solid state. To avoid oleic acid crystallization, slow cooling is required during the entire gradient cooling process.

[0087] Wherein, in step (1), the seed crystals include 85-100 wt% of stearic acid and 0-15 wt% of glyceryl monostearate;

[0088] Alternatively, the seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic acid glyceryl;

[0089] Alternatively, the seed crystals include 70-100 wt % of stearic acid, 0-20 wt % of palmitic acid triglyceride, and 0-15 wt % of glyceryl monostearate;

[0090] 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.

[0091] 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 glyceryl monostearate;

[0092] Or 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.

[0093] For example, the stearic acid content is 70wt%, 80wt%, 85wt%, 90wt%, 95wt%, and 100wt%. The monostearic acid glyceryl content is 0wt%, 5wt%, 10wt%, and 15wt%. The mono- and distearic acid glyceryl content is 0wt%, 5wt%, 10wt%, and 15wt%. The palmitic acid triglyceride content is 0wt%, 5wt%, 10wt%, 15wt%, and 20wt%.

[0094] More preferably, in step (1), the seed crystals include 85 wt% of stearic acid, 10 wt% of palmitic acid triglyceride, and 5 wt% of glyceryl monostearate;

[0095] 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.

[0096] Preferably, in step (2), the prepared 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%.

[0097] 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 olein, palmitin and stearin, and esters in the seed crystals, including monostearin, mono- and distearin and palmitic triglycerides.

[0098] 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 be ensured that after the subsequent crystallization and filtration of the slurry, the filtrate obtained, i.e., oleic acid, is maintained at the same standard level, thereby ensuring 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. Thus, after the subsequent crystallization and filtration, it can be ensured that each batch of products meets the production requirements and the product is stable.

[0099] Preferably, in step (2), the stirring rate is at least 200 r / min and the stirring time is at least 30 min.

[0100] Preferably, in step (3), the stirring rate of the crystallization kettle is 10-50 r / min.

[0101] Preferably, in step (3), the crystals obtained after 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.

[0102] Preferably, in step (3), the temperature is first cooled from 70°C to 55°C at a cooling rate of 5°C / h;

[0103] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0104] Finally, the temperature was lowered 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.

[0105] Furthermore, the application method further includes the steps of:

[0106] (4): Melt the filter cake at 70°C and selectively add stearic acid, palmitic acid triglyceride, monostearate, and mono- and distearate glycerides according to their composition to obtain secondary seed crystals, which are then added to the OPO by-product in an amount of 10-50 wt%; under N2 protection, at a temperature of 70°C, with stirring, to obtain a secondary slurry;

[0107] The secondary seed crystals include 80-100 wt% of stearic acid and 0-20 wt% of palmitic acid triglyceride;

[0108] Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate;

[0109] Alternatively, the secondary seed crystals include 85-100 wt % of stearic acid and 0-15 wt % of mono- and distearic acid glyceryl;

[0110] 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;

[0111] 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;

[0112] (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℃, and keep it warm for 1h;

[0113] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 3-5°C / h;

[0114] Then cool the temperature from 55°C to 20°C at a cooling rate of 2-3°C / h;

[0115] Finally, the temperature was lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h and kept warm for at least 5h to obtain crystals;

[0116] 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.

[0117] Repeat steps (4) to (5) multiple times.

[0118] Preferably, in step (3), the main components of the filter cake obtained are saturated fatty acids and esters, and then in step (4), the filter cake is melted at 70°C, the addition amount is calculated based on its fatty acid composition, secondary seed crystals are obtained, and the OPO by-product is re-added.

[0119] Preferably, 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%.

[0120] 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.

[0121] 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%).

[0122] The present application is described in detail below with reference to specific embodiments:

[0123] Example 1

[0124] A method for separating oleic acid from a byproduct of OPO oil comprises the following steps:

[0125] Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 100 wt% of stearic acid;

[0126] Step (2): Preparation of slurry:

[0127] Add 10 wt% of seed crystals to the OPO byproduct, and stir at 70°C and 200 rpm for 30 min under N2 protection to obtain a slurry. The composition of the slurry is as follows: 25-50 wt% of saturated fatty acids; 50-75 wt% of unsaturated fatty acids; esters and other impurities ≤ 5 wt%;

[0128] Step (3): Crystallization and filtration of slurry:

[0129] The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirring 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;

[0130] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0131] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0132] 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 5 h to obtain crystals;

[0133] The crystals were filtered under 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.

[0134] Example 2

[0135] A method for separating oleic acid from a byproduct of OPO oil comprises the following steps:

[0136] Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 95 wt% of stearic acid and 5 wt% of glyceryl monostearate;

[0137] Step (2): Preparation of slurry:

[0138] The seed crystals were added to the OPO by-product in an amount of 50 wt%, and stirred at 70 ° C and 200 r / min for 30 minutes under N2 protection to obtain a slurry; the components of the slurry met the following requirements: saturated fatty acids 25-50 wt%; unsaturated fatty acids 50-75 wt%; esters and other impurities ≤ 5 wt%.

[0139] Step (3): Crystallization and filtration of slurry:

[0140] The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 50 r / min, and the initial temperature of the crystallization kettle was set to 70 ° C and kept warm for 1 hour;

[0141] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0142] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0143] 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 5 h to obtain crystals;

[0144] The crystals were filtered under a pressure of 0.6 MPa and a temperature of 8°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.

[0145] Example 3

[0146] A method for separating oleic acid from a byproduct of OPO oil comprises the following steps:

[0147] Step (1): Preparation of seed crystals: In terms of mass percentage, the seed crystals include 85 wt% of stearic acid and 15 wt% of palmitic acid triglyceride;

[0148] Step (2): Preparation of slurry:

[0149] The seed crystals were added to the OPO byproduct at a rate of 20 wt%, and stirred at 70°C and 200 r / min for 30 min under N2 protection to obtain a slurry. The composition of the slurry was as follows: 25-50 wt% saturated fatty acids;

[0150] Unsaturated fatty acids 50-75wt%;

[0151] Esters and other impurities ≤5wt%.

[0152] Step (3): Crystallization and filtration of slurry:

[0153] The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 30 r / min, and the initial temperature of the crystallization kettle was set to 70 ° C and kept warm for 1 hour;

[0154] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0155] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0156] 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 5 h to obtain crystals;

[0157] The crystals were filtered under a pressure of 0.6 MPa and a temperature of 8°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.

[0158] Example 4

[0159] A method for separating oleic acid from a byproduct of OPO oil comprises the following steps:

[0160] 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;

[0161] Step (2): Preparation of slurry:

[0162] The seed crystals were added to the OPO by-product in an amount of 30 wt%, and stirred at 70 ° C and a stirring rate of 200 r / min for 30 minutes under N2 protection to obtain a slurry; the components of the slurry met the following requirements: saturated fatty acids 25-50 wt%; unsaturated fatty acids 50-75 wt%; esters and other impurities ≤ 5 wt%.

[0163] Step (3): Crystallization and filtration of slurry:

[0164] The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 50 r / min, and the initial temperature of the crystallization kettle was set to 70 ° C and kept warm for 1 hour;

[0165] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0166] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0167] 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 5 h to obtain crystals;

[0168] The crystals were filtered under a pressure of 0.6 MPa and a temperature of 8°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.

[0169] Example 5

[0170] A method for separating oleic acid from a byproduct of OPO oil comprises the following steps:

[0171] 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;

[0172] Step (2): Preparation of slurry:

[0173] The seed crystals were added to the OPO by-product in an amount of 40 wt%, and stirred at 70 ° C and 200 r / min for 30 minutes under N2 protection to obtain a slurry; the components of the slurry met the following requirements: saturated fatty acids 25-50 wt%; unsaturated fatty acids 50-75 wt%; esters and other impurities ≤ 5 wt%.

[0174] Step (3): Crystallization and filtration of slurry:

[0175] The slurry was pumped into a crystallization kettle with stirring, filled with N2 protection, stirred at a rate of 50 r / min, and the initial temperature of the crystallization kettle was set to 70 ° C and kept warm for 1 hour;

[0176] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0177] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0178] 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 5 h to obtain crystals;

[0179] The crystals were filtered under 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.

[0180] Example 6

[0181] This Example 6 is substantially the same as Example 4, except that: in step (3), the temperature is lowered from 70°C to 55°C at a cooling rate of 3°C / h;

[0182] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 2°C / h;

[0183] 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 5 h to obtain crystals.

[0184] Comparative Example 1

[0185] This comparative example 1 is substantially the same as Example 1, except that the seed crystals of step (1) are not provided.

[0186] Comparative Example 2

[0187] 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;

[0188] 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 h to obtain crystals.

[0189] The oleic acid prepared in the above examples and comparative examples was subjected to the following tests:

[0190] 1: The oleic acid content and recovery rate prepared in Examples 1-6 and Comparative Examples 1-2 are shown in Table 1:

[0191] Table 1 Oleic acid content and recovery rate of Examples 1-6 and Comparative Examples 1-2

[0192]

[0193] As can be seen from Table 1 above, when not introducing crystal seed, even if high-precision gradient cooling is adopted, the oleic acid content and the rate of recovery obtained are also much smaller than the oleic acid content and the rate of recovery obtained by introducing crystal seed and high-precision gradient cooling for co-processing of the application method, and the oleic acid purity obtained using the application method is high, oleic acid content is more than 80%, and oleic acid rate of recovery is more than 60%. This shows that in the present application, by introducing crystal seed, crystal seed provides rigid nucleus, so that oleic acid can be attached to rigid nucleus during crystallization, increases oleic acid rate of recovery and oleic acid content. Thus further show that crystal seed and high-precision gradient cooling process are indispensable, and the two play the effect of synergistic effect.

[0194] 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 method of the present application can improve the recovery rate of the slurry.

[0195] 2: Detection of solvent in oleic acid:

[0196] Since the present method does not add any additional substances outside the OPO system, and uses the raw materials or intermediates contained in the system itself as seed crystals, in Examples 1-6 above, no residual solvent was detected in the oleic acid (limit of quantification: 10 mg / kg), and the insoluble impurity content was ≤0.05%. The results are listed in Table 2. In addition, in the present application, low-temperature control of crystallization, combined with high-precision gradient temperature control, can greatly ensure the freshness and safety of oils and fats, avoiding some of the problems caused by traditional high-temperature extraction, and making the product safer.

[0197] Table 2 Results of residual solvent test in oleic acid of Examples 1-6

[0198]

[0199] 3: Filter cake repeatability verification:

[0200] Taking the filter cake prepared in Example 3 as an example, the following repetitive cycles were performed:

[0201] 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 a secondary slurry;

[0202] The secondary seed crystals include 85 wt% of stearic acid and 15 wt% of palmitic acid triglyceride;

[0203] The components of the secondary slurry meet the following requirements: saturated fatty acid 25-50wt%;

[0204] Unsaturated fatty acids 50-75wt%;

[0205] Esters and impurities ≤5wt%.

[0206] 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;

[0207] Then the temperature was lowered from 70°C to 55°C at a cooling rate of 5°C / h;

[0208] Then, the temperature was lowered from 55°C to 20°C at a cooling rate of 3°C / h;

[0209] 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 5 h to obtain crystals;

[0210] The crystals were filtered under a pressure of 0.6 MPa and a temperature of 8°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.

[0211] Repeat steps (4) to (5).

[0212] According to the above method, step (4) to step (5) were cycled for 7 times. The results of oleic acid content and oleic acid peroxide value were shown in Table 3:

[0213] Table 3 Oleic acid content and oleic acid peroxide value after each filter cake reuse

[0214]

[0215] As can be seen from Table 3 above, the oleic acid content obtained after seven reuses was greater than 80%, but the peroxide value of oleic acid began to increase, indicating that the freshness of the oil began to decrease during repeated processing. To ensure the safety of oleic acid, the filter cake was no longer reused after the fifth reuse.

[0216] 4: Gas chromatograms of OPO byproducts before and after treatment, such as Figures 1-9 As shown in Table 4.

[0217] Table 4 is the main component analysis of the untreated OPO by-product, the filtrates obtained in Examples 1-6 and Comparative Examples 1-2.

[0218]

[0219] As can be seen from Table 4 above, 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 collected filtrate is mainly composed of oleic acid, with an oleic acid content of more than 80%, which is relatively high. The other components are mainly palmitic acid, stearic acid, linoleic acid, etc. These components belong to the OPO system. Therefore, the oleic acid prepared by the method of the present application is safer and more reliable.

[0220] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in this disclosure can be achieved. This is not a limitation herein.

[0221] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. Throughout the present disclosure, "plurality" means two or more, unless otherwise specifically defined.

[0222] The above description is merely a specific embodiment of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this disclosure should be included in the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1. A method for separating oleic acid from a by-product of OPO grease, characterized in that: The steps include: (1) Configuration of seed crystals: In terms of mass percentage, the seed crystals are composed of 80-100 wt% of stearic acid and 0-20 wt% of palmitic acid triglyceride; Alternatively, the seed crystals are composed of 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the seed crystals are composed of 70-100 wt% of stearic acid, 0-20 wt% of palmitic acid triglyceride, and 0-15 wt% of glyceryl monostearate; Alternatively, the seed crystals are composed of 70-100 wt% of stearic acid, 0-20 wt% of palmitic acid triglyceride, and 0-15 wt% of mono- and distearic acid glyceryl; (2) Preparation of slurry: The seed crystals are added to the OPO by-product in an amount of 10-50 wt %, and stirred at 70° C. under N2 protection to obtain a slurry; the stirring rate is at least 200 r / min, and the stirring time is at least 30 min; (3) Crystallization and filtration of slurry: The slurry was pumped into the crystallization kettle, stirred under N2 protection, and the initial temperature of the crystallization kettle was set to 70°C and kept warm for 1 hour; Then the temperature was lowered 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 was lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h and kept warm for at least 5h to obtain crystals; 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; Wherein, in said step (2), the prepared 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%.

2. The method according to claim 1, wherein: In the step (1), the seed crystals are composed of 85-100 wt% of stearic acid, 0-20 wt% of palmitic acid triglyceride, and 0-15 wt% of monostearate; Alternatively, the seed crystals are composed of 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, wherein: In the step (1), the seed crystals are composed of 85 wt% of stearic acid, 10 wt% of palmitic triglyceride, and 5 wt% of glyceryl monostearate; Or the seed crystals are composed of 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, wherein: In the step (3), the stirring rate of the crystallization kettle is 10-50 r / min.

5. The method according to claim 1, wherein: 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 lowered 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.

6. The method according to any one of claims 1 to 5, characterized in that: Also includes the steps: (4): The filter cake is melted at 70°C and stearic acid, palmitic acid triglyceride, monostearate, and mono- and distearate glycerides are selectively added according to the composition thereof to obtain secondary seed crystals, and then the secondary seed crystals are added to the OPO by-product in an amount of 10-50 wt%; under N2 protection, the temperature is 70°C, and stirring is performed to obtain a secondary slurry; The secondary seed crystals are composed of 80-100 wt% of stearic acid and 0-20 wt% of palmitic acid triglyceride; Alternatively, the secondary seed crystals are composed of 85-100 wt % of stearic acid and 0-15 wt % of glyceryl monostearate; Alternatively, the secondary seed crystals are composed of 70-100 wt% of stearic acid, 0-20 wt% of palmitic acid triglyceride, and 0-15 wt% of monostearate; Alternatively, the secondary seed crystals are composed of 70-100 wt% of stearic acid, 0-20 wt% of palmitic triglyceride, and 0-15 wt% of mono- and distearic glycerol; (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 lowered 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 was lowered from 20°C to 15-8°C at a cooling rate of 1-2°C / h and kept warm for at least 5h to obtain crystals; 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; Wherein, 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%.

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