Castor oil and its refining method

Abstract

The invention discloses castor oil and a refining method thereof. The refining method comprises irradiating crude castor oil under the action of a composite photocatalyst; the composite photocatalyst is a catalyst of activated carbon loaded with transition metal oxides; and the irradiation is performed by ultraviolet light. The method has a simple process flow, low energy consumption, low production cost, is suitable for industrial production, and the prepared castor oil meets the requirements of injection-grade drugs.

Description

Technical Field

[0001] The present invention relates to castor oil and a refining method thereof Background Art

[0002] Castor oil is a fatty oil obtained by extracting the mature seeds of the Euphorbiaceae plant Ricinus communis L. from the shell, and then refining it through alkali refining, washing, drying, bleaching and other steps. Castor oil contains a large amount of ricinoleic acid (more than 80wt%). Among common vegetable oils, only olive oil (containing about 80wt% oleic acid), safflower oil (more than 70wt% linoleic acid) and tung oil (containing about 85wt% eleostearic acid) have this characteristic.

[0003] Castor oil is easily soluble in ethanol, which is a feature that general oils do not have: it has an advantage in dissolving certain specific substances. Castor oil has a higher viscosity, a lower freezing point than general vegetable oils, and good fluidity at low temperatures: refined castor oil can still flow at -22°C, and there is no turbidity after rapid cooling at -50°C. Castor oil has a low peroxide value and is stable and not prone to rancidity: it avoids affecting the stability of active drugs, is easy to store, and reduces the risk of deterioration.

[0004] Castor oil is widely used in cosmetics and medicines. It is used as an emollient in cosmetics; it can be used as a laxative for oral administration; it is used as an oily base in topical medicines; it can also be used as a solvent for oral tablets, capsules and intramuscular injections: in Fulvestrant injection, castor oil is used as a non-aqueous solvent. It has been listed as GRAS. It has been included in the FDA's "Marketed Drug Inactive Ingredient Database" (for intramuscular injections; oral capsules and tablets; topical creams, emulsions, ointments and solutions). The UK permits its use in non-injectable drug preparations. Canada has included it in the list of acceptable non-medicinal ingredients.

[0005] Usually, castor oil obtained by the pressing process can only be used in industry, because the ricin and ricin contained in castor beans will be brought into the oil during pressing. Medicinal castor oil must be made by water-cooled low-temperature pressing process. Pure castor oil is colorless, and domestic medicinal castor oil is yellowish in color. This is because it contains lutein, zeaxanthin, lycopene, a variety of natural carotene, etc., and the impurity content is high, which cannot meet the injection grade requirements. Domestic low-temperature cold-pressed castor oil needs to be further decolorized and refined to obtain castor oil that can be used for injection preparations.

[0006] In the prior art, the refining of castor oil adopts an adsorption method to remove the pigment in castor oil. The process is simple and the stability is high. The adsorbents used include activated clay, activated carbon, diatom aluminum, aluminum oxide and magnesium oxide, among which activated carbon and activated clay are the most commonly used. However, the use of the above-mentioned adsorbents has the problems of large dosage, long operation time, high energy consumption and high acid value of finished products. Chinese patent document CN104099172A discloses a refining process of castor oil, which adopts activated clay as an adsorbent, and the acid value of the castor oil finished product obtained is high and does not reflect the decolorization effect. Chinese patent document CN111234920 discloses a refining method of low acid value and low chromaticity castor oil, which adopts activated clay and activated carbon as adsorbents. Although the acid value and chromaticity of the prepared finished castor oil are low, it needs to use 1kg of adsorbent to process 10kg of castor oil, and the amount of adsorbent is large. When using adsorbent for decolorization, the adsorbent needs to be eluted with a solvent after recovery before it can be reused. This is costly, not environmentally friendly and has a poor decolorization effect. Summary of the invention

[0007] The invention mainly aims to solve the problem that the final product of castor oil in the prior art has high acid value, dark color and cannot meet the injection grade standard, and proposes a castor oil and a refining method thereof. The method has simple process flow, low energy consumption, low production cost, is suitable for industrial production, and the prepared castor oil meets the requirements of injection grade medicine.

[0008] The present invention mainly adopts the following technical solutions to solve the above technical problems:

[0009] The present invention provides a method for refining castor oil, characterized in that it comprises the following steps:

[0010] Crude castor oil is irradiated with light under the action of composite photocatalyst;

[0011] The composite photocatalyst is a catalyst of activated carbon loaded with transition metal oxides;

[0012] The illumination is performed by ultraviolet light.

[0013] In the present invention, the crude castor oil is conventional in the art, and generally contains ricinoleic acid. The content of ricinoleic acid is preferably above 80 wt %, more preferably 85 wt % to 90 wt %, for example 88.6 wt %.

[0014] In the present invention, the crude castor oil preferably meets the following conditions: color value Y5.0, acid value 0.33, hydroxyl value 162.4, iodine value 84.5, water content 0.39wt%.

[0015] In the present invention, the types of pigments in the crude castor oil preferably include one or more of carotene, carotenoids, lutein, zeaxanthin, phytochrome and lycopene.

[0016] In the present invention, the composite photocatalyst is preferably an activated carbon-supported zinc oxide catalyst and / or an activated carbon-supported titanium dioxide catalyst, and more preferably an activated carbon-supported silicon dioxide and zinc oxide catalyst.

[0017] In the present invention, when the composite photocatalyst is a catalyst of activated carbon loaded with silicon dioxide and zinc oxide, its preparation method preferably includes: after solid-liquid separation of an alcohol solution of oxalic acid and zinc acetate, calcining the obtained solid to obtain zinc oxide; adding tetraethyl orthosilicate to the alcohol solution of zinc oxide, mixing to obtain a gel; mixing activated carbon with the gel, and then sequentially subjecting the mixture to solid-liquid separation and calcination to obtain the composite photocatalyst.

[0018] The weight ratio of the zinc oxide, the tetraethyl orthosilicate and the activated carbon is preferably 1:(1-3):(1-5), for example, 1:1:2.

[0019] The calcination temperature is preferably 100-300°C, for example 200°C.

[0020] In the present invention, when the composite photocatalyst is an activated carbon-loaded titanium dioxide catalyst, its preparation method preferably comprises: mixing the activated carbon with an alcohol solution of butyl titanate to obtain a gel, and drying and calcining the gel to obtain the composite photocatalyst.

[0021] The alcohol solution of butyl titanate is preferably prepared by the following method: adding butyl titanate to ethanol and mixing evenly, then adding acetic acid to obtain a yellow transparent solution; mixing anhydrous ethanol and distilled water evenly to obtain a white transparent solution; adding the white transparent solution to the yellow transparent solution and mixing to obtain the alcohol solution of butyl titanate.

[0022] The weight ratio of the butyl titanate to the activated carbon is preferably (8-10):1, for example, 9.66:1.

[0023] The calcination temperature is preferably 350°C to 450°C, such as 400°C.

[0024] Wherein, in the activated carbon-supported titanium dioxide catalyst, the loading amount of titanium dioxide is preferably 45wt% to 50wt%, for example 48.34wt%.

[0025] In the present invention, the weight percentage of the composite photocatalyst to the crude castor oil is preferably 0.1-0.5%, for example 0.3%.

[0026] In the present invention, the irradiation preferably comprises the following steps: irradiating a mixture of the crude castor oil and the composite photocatalyst in a transparent container.

[0027] The irradiation temperature is preferably 25-40°C, for example 30°C or 35°C.

[0028] Wherein, the transparent container is preferably quartz glass or high borosilicate glass.

[0029] In the present invention, the wavelength of the ultraviolet light is preferably 220-380 nm, more preferably 254 nm, 313 nm, 340 nm, 351 nm or 365 nm.

[0030] In the present invention, the power of the ultraviolet light is preferably 100W to 300W, for example, 100W or 300W.

[0031] In the present invention, when the power of the ultraviolet light is 100 W, the wavelength of the ultraviolet light is preferably greater than 254 nm, and more preferably 313 nm to 365 nm.

[0032] In the present invention, when the power of the ultraviolet light is 300W, the wavelength of the ultraviolet light is preferably less than 365nm, and more preferably 254nm to 340nm.

[0033] In the present invention, the distance between the ultraviolet light source and the transparent container is preferably 10 to 30 cm, for example, 20 cm.

[0034] In the present invention, the irradiation time is preferably 60 to 120 minutes, for example 90 minutes.

[0035] It is known to those skilled in the art that in order to remove the composite photocatalyst, a filtering step is usually included after the illumination; in order to remove small molecules generated by the degradation of the pigment molecules after the illumination, a heating step is usually included after the illumination. The heating is preferably heating the liquid after the filtration. It can be seen that the present invention can recover the composite photocatalyst by a simple filtration operation, and no organic solvent is used for elution in the filtration. The filtered catalyst can be directly reused, which is green and environmentally friendly. The refining method can not only effectively remove the pigment molecules, but also remove organic impurities and small molecules with special odors at the same time.

[0036] Wherein, the filtration is preferably carried out using a precision microporous filter.

[0037] Wherein, the precision microporous filter may be conventional in the art, and the pore size of the filter membrane in the precision microporous filter is generally 0.2 to 1 μm.

[0038] The heating is preferably performed by placing the filtered mixture in a heater.

[0039] The vacuum degree of the heating is preferably -0.090 to -0.095 MPa.

[0040] Wherein, the heating temperature is preferably 105-115°C.

[0041] The heating time is preferably 60 to 120 minutes, for example 90 minutes.

[0042] The invention also provides castor oil, which is prepared by adopting the above refining method.

[0043] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0044] The reagents and raw materials used in the present invention are commercially available.

[0045] The positive and progressive effects of the present invention are:

[0046] The present invention provides a method for refining castor oil. The method does not use a traditional adsorbent to remove the pigment in castor oil, but uses a specific composite catalyst to irradiate the crude castor oil with ultraviolet light to achieve degradation and removal of the pigment. Compared with the traditional adsorbent, the catalyst used in the present invention is neutral and will not affect the acid value of the finished castor oil product. In the prior art, an adsorption process is used for decolorization, and the adsorption is greatly affected by the concentration of the pigment in the crude castor oil. The greater the concentration of the pigment, the faster the adsorption. After a certain period of time, the concentration of the pigment in the castor oil decreases, the adsorption slows down, and gradually reaches adsorption saturation. The present invention uses a catalyst for degradation, the reaction is not affected by the concentration of the pigment molecules, there is no problem of adsorption saturation, and the decolorization time is shorter.

[0047] The color value of injection-grade castor oil specified in the general rules of the Chinese Pharmacopoeia is converted to the European Pharmacopoeia standard, which needs to reach Y5.0. The European Pharmacopoeia stipulates that the acid value of injection-grade castor oil must be below 0.8. The finished castor oil prepared by the present invention has low color value, acid value, hydroxyl value, iodine value and moisture content, high ricinoleic acid and finished product yield, and the refractive index, saponification value, acid value and color value all meet the requirements for injection-grade drugs in the general rules of the Chinese Pharmacopoeia and the European Pharmacopoeia. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 The figure is a comparison chart of the color value of commercially available medicinal castor oil Y6.0 and the color value of the medicinal castor oil Y6.5 after decolorization of the present invention, wherein Figure 1 a and Figure 1 b is a comparison chart at different angles. DETAILED DESCRIPTION

[0049] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0050] The preparation method of the catalyst of activated carbon loaded with silicon dioxide and zinc oxide used in Examples 1 to 6 and 9 to 11 of the present invention is as follows: 2 parts of oxalic acid and 3 parts of zinc acetate are dissolved in anhydrous ethanol to form a white mixed solution, and the obtained solid is dried at 80°C for 8 hours after centrifugal separation, and then calcined at 200°C for 2 hours to obtain nano ZnO particles. The obtained ZnO particles are dissolved in anhydrous ethanol, and then tetraethyl orthosilicate is added dropwise and stirred in a water bath at 80°C for 6 hours to form a gel. Activated carbon is added to the gel, stirred at room temperature for 60 minutes, and then the obtained solid is dried at 80°C for 8 hours after centrifugal separation, and then calcined at 200°C for 2 hours to obtain an activated carbon loaded with silicon dioxide and zinc oxide catalyst, which is recorded as composite photocatalyst 1. Among them, the weight ratio of nano ZnO particles, tetraethyl orthosilicate and activated carbon is 1:1:2.

[0051] The preparation method of the activated carbon-supported titanium dioxide catalyst used in Examples 7 and 8 of the present invention is as follows: 10 ml of butyl titanate is added dropwise to 25 ml of anhydrous ethanol and mixed evenly to obtain a mixed solution A, and then 2 ml of glacial acetic acid is added to the mixed solution A to obtain a yellow transparent solution A. 12.5 ml of anhydrous ethanol and 2 ml of distilled water are mixed evenly to obtain a mixed solution B, and the pH of the mixed solution B is adjusted to 2-3 with concentrated hydrochloric acid to obtain a white transparent solution B. The white transparent solution B is slowly added to the yellow transparent solution A and stirred for 0.5 h to obtain a yellow transparent solution C. After adding 1 g of activated carbon powder to the yellow transparent solution C and stirring for 0.5 h, it is allowed to stand at 70 ° C for 3 h to form a gel, and then placed in an oven for drying. The dried sample is placed in a resistance box and calcined at 400 ° C for 1 h, and the calcined sample is washed and dried in sequence to obtain a gray activated carbon-supported titanium dioxide catalyst, which is recorded as composite photocatalyst 2, wherein the loading amount of titanium dioxide is about 48.34 wt%.

[0052] In the following Examples 1 to 11, the heating temperature in the round-bottom flask after filtration is set to 115° C. and 105° C. only to volatilize the small molecules obtained by degradation as much as possible. Within the range of above 100° C., the small molecules obtained by degradation can be completely volatilized, and there is no significant effect on the final castor oil obtained. This is a reasonable fluctuation of the temperature setting within the error range.

[0053] The parameters of crude castor oil in the following Examples 1 to 11 are shown in Table 1 below.

[0054] Example 1

[0055] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 1 g of composite photocatalyst 1 was added, the mixture was kept at 25 °C and stirred, a 100 W ultraviolet light source (365 nm) was placed 10 cm from the bottom of the round-bottom flask (quartz material), and the mixture was irradiated at a constant temperature and stirred for 60 min to obtain a mixture.

[0056] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa. The mixture was heated to 115°C and stirred at a constant temperature for 60 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0057] Example 2

[0058] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 3 g of composite photocatalyst 1 was added, and the mixture was stirred at 30 °C. A 200 W ultraviolet light source (351 nm) was placed 20 cm from the bottom of the round-bottom flask (made of borosilicate), and the mixture was irradiated at a constant temperature for 90 min with stirring.

[0059] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.090 MPa, heated to 105°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0060] Example 3

[0061] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 5 g of composite photocatalyst 1 was added, and the mixture was kept at 35 °C with stirring. A 300 W ultraviolet light source (340 nm) was placed 30 cm from the bottom of the round-bottom flask (quartz material), and the mixture was irradiated with constant temperature stirring for 120 min to obtain a mixture.

[0062] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa. The mixture was heated to 105°C and stirred at a constant temperature for 120min, and finally cooled to room temperature to obtain the finished castor oil.

[0063] Example 4

[0064] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 1 g of composite photocatalyst 1 was added, the mixture was kept at 40 °C and stirred, a 100 W ultraviolet light source (313 nm) was placed 20 cm from the bottom of the round-bottom flask (made of borosilicate), and the mixture was irradiated at a constant temperature and stirred for 60 min to obtain a mixture.

[0065] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.090 MPa, heated to 115°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0066] Example 5

[0067] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 3 g of composite photocatalyst 1 was added, the mixture was kept at 25 °C and stirred, a 300 W ultraviolet light source (254 nm) was placed 20 cm from the bottom of the round-bottom flask (quartz material), and the mixture was stirred and irradiated at a constant temperature for 90 min to obtain a mixture.

[0068] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa, heated to 105°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0069] Example 6

[0070] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 1 g of composite photocatalyst 1 was added, the mixture was kept at 30 °C and stirred, a 300 W ultraviolet light source (313 nm) was placed 10 cm from the bottom of the round-bottom flask (quartz material), and the mixture was stirred and irradiated at a constant temperature for 90 min to obtain a mixture.

[0071] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa, heated to 105°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0072] Example 7

[0073] The composite photocatalyst in Example 4 was replaced by composite photocatalyst 2, and the other conditions were the same as those in Example 4.

[0074] Example 8

[0075] The composite photocatalyst in Example 5 was replaced by composite photocatalyst 2, and the other conditions were the same as those in Example 5.

[0076] Example 9

[0077] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 3 g of composite photocatalyst 1 was added, the mixture was kept at 25 °C and stirred, a 100 W ultraviolet light source (254 nm) was placed 20 cm from the bottom of the round-bottom flask (quartz material), and the mixture was stirred and irradiated at a constant temperature for 90 min to obtain a mixture.

[0078] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa, heated to 105°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0079] Example 10

[0080] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 3 g of composite photocatalyst 1 was added, the mixture was kept at 25 °C and stirred, a 300 W ultraviolet light source (365 nm) was placed 20 cm from the bottom of the round-bottom flask (quartz material), and the mixture was irradiated at a constant temperature and stirred for 90 min to obtain a mixture.

[0081] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa, heated to 105°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0082] Embodiment 11

[0083] 1 kg of crude castor oil was placed in a 2 L round-bottom flask, 3 g of composite photocatalyst 1 was added, the mixture was kept at 25 °C and stirred, a 300 W ultraviolet light source (254 nm) was placed 20 cm from the bottom of the round-bottom flask (quartz material), and the mixture was irradiated at a constant temperature and stirred for 120 min to obtain a mixture.

[0084] The mixture was filtered through a precision microporous filter, and the filtrate was then transferred to a 2L round-bottom flask and evacuated to -0.095MPa, heated to 105°C and stirred at a constant temperature for 90 minutes, and finally cooled to room temperature to obtain the finished castor oil.

[0085] Effect Example 1

[0086] In the present invention, the detection methods for the acid value, hydroxyl value, iodine value, moisture, ricinoleic acid content, refractive index and saponification value of the crude castor oil and the finished castor oil of Examples 1 to 11 are based on the relevant entries for determining the acid value, hydroxyl value, iodine value and fatty acid composition in General Chapter 0713 (Determination of Fats and Fatty Oils) of the "Chinese Pharmacopoeia 2022 Edition", and the color value is tested according to the test method for liquid coloration in Section 2.2.2 of the "European Pharmacopoeia 10.0". Figure 1 The figure is a comparison chart of the color value of commercially available medicinal castor oil Y6.0 and the color value of the medicinal castor oil Y6.5 after decolorization of the present invention, wherein Figure 1 a and Figure 1 b is a comparison chart at different angles.

[0087] The test results of crude castor oil and Examples 1 to 6 are shown in Table 1, and the test results of Examples 7 to 11 are shown in Table 2.

[0088] Table 1

[0089]

[0090]

[0091] Note: The color value adopts the EP (European Pharmacopoeia) standard. The larger the value, the lighter the color. Y5.0 refers to yellow 5.0, and Y7.0 refers to colorless.

[0092] Table 2

[0093]

[0094] The present invention adopts a composite photocatalyst in combination with a certain ultraviolet light power and wavelength, and can ensure the content of nutrients (ricinoleic acid) in castor oil while keeping the acid value, hydroxyl value and water content of the finished castor oil basically unchanged compared with the crude castor oil. At the same time, the color value of the finished castor oil can be increased and the color can be lighter, thereby meeting the requirements of injection-grade castor oil.

[0095] Compared with zinc oxide, the present invention uses titanium dioxide as a catalyst. Although the color value, acid value and hydroxyl value of the finished castor oil remain basically unchanged, the ricinoleic acid content is greatly reduced, which is not conducive to the efficacy of the finished castor oil.

Claims

1. A method for refining castor oil, characterized in that, It includes the following steps: Crude castor oil is irradiated with light under the action of composite photocatalyst; The composite photocatalyst is a catalyst of activated carbon loaded with silicon dioxide and zinc oxide; The preparation method of the activated carbon-loaded silica and zinc oxide catalyst comprises: dissolving oxalic acid and zinc acetate in anhydrous ethanol to form a white mixed liquid, performing solid-liquid separation, drying and calcining the obtained solid to obtain nano zinc oxide particles; dissolving the nano zinc oxide particles in anhydrous ethanol, then dropping ethyl orthosilicate, and mixing to obtain a gel; mixing the activated carbon with the gel, performing solid-liquid separation, and drying and calcining the obtained solid to obtain the composite photocatalyst; The illumination is performed by ultraviolet light.

2. The method for refining castor oil as claimed in claim 1, characterized in that In the preparation method of the activated carbon-supported silica and zinc oxide catalyst, the weight ratio of the nano zinc oxide particles, the tetraethyl orthosilicate and the activated carbon is 1:1:2; And / or, in the preparation method of the activated carbon-supported silica and zinc oxide catalyst, the calcination temperature is 100-300°C.

3. The method for refining castor oil as claimed in claim 2, characterized in that: In the preparation method of the activated carbon-supported silica and zinc oxide catalyst, the calcination temperature is 200°C.

4. The method for refining castor oil as claimed in claim 1, characterized in that The preparation method of the activated carbon-supported silica and zinc oxide catalyst is as follows: 2 parts of oxalic acid and 3 parts of zinc acetate are dissolved in anhydrous ethanol to form a white mixed liquid, the obtained solid is dried at 80°C for 8 hours after centrifugal separation, and then calcined at 200°C for 2 hours to obtain nano ZnO particles, the obtained ZnO particles are dissolved in anhydrous ethanol, ethyl orthosilicate is added dropwise, and the mixture is stirred in a water bath at 80°C for 6 hours to form a gel, activated carbon is added to the gel, and the mixture is stirred at room temperature for 60 minutes, and then the obtained solid is dried at 80°C for 8 hours after centrifugal separation, and then calcined at 200°C for 2 hours to obtain the activated carbon-supported silica and zinc oxide catalyst.

5. The method for refining castor oil as claimed in claim 1, characterized in that The weight percentage of the composite photocatalyst to the weight of the crude castor oil is 0.1-0.5%; And / or, the irradiation comprises the following steps: irradiating a mixture of the crude castor oil and the composite photocatalyst in a transparent container; And / or, the irradiation time is 60 to 120 minutes.

6. The method for refining castor oil as claimed in claim 5, characterized in that: The weight percentage of the composite photocatalyst to the weight of the crude castor oil is 0.3%; And / or, the irradiation time is 90 minutes.

7. The method for refining castor oil as claimed in claim 5, characterized in that: The irradiation temperature is 25-40°C; And / or, the transparent container is quartz glass or high borosilicate glass; And / or, the distance between the ultraviolet light source and the transparent container is 10-30 cm.

8. The method for refining castor oil as claimed in claim 7, characterized in that: The irradiation temperature is 30°C or 35°C; And / or, the distance between the ultraviolet light source and the transparent container is 20 cm.

9. The method for refining castor oil according to any one of claims 1 to 8, characterized in that The wavelength of the ultraviolet light is 220-380nm; And / or, the power of the ultraviolet light is 100W~300W; Alternatively, when the power of the ultraviolet light is 100 W, the wavelength of the ultraviolet light is 254-380 nm; Alternatively, when the power of the ultraviolet light is 300 W, the wavelength of the ultraviolet light is 220-365 nm.

10. The method for refining castor oil according to claim 9, characterized in that: The wavelength of the ultraviolet light is 254nm, 313nm, 340nm, 351nm or 365nm; And / or, the power of the ultraviolet light is 100W or 300W.

11. The method for refining castor oil according to claim 9, characterized in that: When the power of the ultraviolet light is 100W, the wavelength of the ultraviolet light is 313nm~365nm; Alternatively, when the power of the ultraviolet light is 300 W, the wavelength of the ultraviolet light is 254 nm to 340 nm.

12. The method for refining castor oil according to claim 1, characterized in that: The method further comprises a filtering step after the illumination; And / or, a heating step is also included after the irradiation.

13. The method for refining castor oil according to claim 12, characterized in that: The filtration adopts a precision microporous filter; And / or, the heating time is 60 to 120 minutes; And / or, the heating vacuum degree is -0.090~-0.095MPa; And / or, the heating temperature is 105-115°C; And / or, the heating is heating the liquid after the filtration.

14. The method for refining castor oil according to claim 13, characterized in that: The heating time is 90 min.

15. A castor oil, characterized in that The castor oil is prepared by the refining method of castor oil as described in any one of claims 1 to 14.

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