Low melting point wax and method for producing the same

Abstract

The present application relates to the chemical technology field, specifically to a kind of low melting point wax and preparation method thereof.The preparation method of the low melting point wax described in the present application, characterized in that, the method comprises the following steps: raw oil is mixed with first solvent, heated and dissolved, to obtain first solution;The first solution is cooled, crystallized, first residence, to obtain first crystallization liquid;The first crystallization liquid is cooled, crystallized, second residence, to obtain second crystallization liquid;The second crystallization liquid is first solid-liquid separation, to obtain dewaxed oil and wax cream;The wax cream is mixed with second solvent, and then deoiled, second solid-liquid separation, to obtain deoiled wax cream;The deoiled wax cream is removed solvent, to obtain finished wax;Raw oil is fischer-tropsch oil at 280 DEG C-450 DEG C fraction;Solvent is selected from ester solvent.Using this method, the yield of product wax is improved, the oil content in product wax is reduced, and the melting point range of product wax can be flexibly controlled.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically to a low-melting-point wax and its preparation method. Background Technology

[0002] Currently, countries in Europe and the United States are imposing increasingly stringent legislation on the safety of chemical use. It is reported that the European Union will implement extremely strict standards to control the content of benzene compounds in everyday consumer goods. This will not only require that food, cosmetics, and pharmaceutical products not contain benzene compounds, but also that the production process must not involve the use of carcinogens such as benzene compounds. At that time, domestically produced petroleum wax products using the ketone-benzene dewaxing and deoiling process will not be able to meet the relevant EU requirements. Fischer-Tropsch wax, however, does not use benzene compounds in its production process and is currently the only product that can replace petroleum wax in the production of daily chemical products such as candles.

[0003] Fischer-Tropsch wax is a wax produced through Fischer-Tropsch synthesis during the coal gasification process. It is mainly composed of straight-chain, saturated high-carbon alkanes with a relative molecular weight of 500-1000, of which n-alkanes account for more than 80%. It is free of sulfur and nitrogen and has the characteristics of high purity, good lubricity, and good gloss. Therefore, Fischer-Tropsch crude wax is an important raw material for the production of high-quality waxes and high-melting-point waxes.

[0004] Fischer-Tropsch waxes are mainly used in hot melt adhesives, inks and coatings, and plastics processing, such as PVC lubricants, polyolefin lubricants, and masterbatch dispersants. Low-melting-point Fischer-Tropsch waxes, in particular, possess excellent softening and moisturizing properties and are commonly used in the production of chlorinated paraffins, candles, medical waxes, and temperature-sensing elements. Therefore, it is necessary to develop non-benzene solvent-based low-melting-point wax production technologies.

[0005] In the production of petroleum wax, the most common grades are 54#, 56#, 58#, 60#, 62#, 64#, and 66#. However, in actual demand, there are also grades of paraffin wax with lower and higher melting points, such as 50#, 52#, 70#, 75#, and 80#. Although these grades of wax are more difficult to produce, they have higher added value and are an effective way for enterprises to make full use of resources, improve their strength and competitiveness, and increase profits.

[0006] Although Fischer-Tropsch synthetic waxes have a high degree of orthomorphism, they still contain a small amount of oil components. The cut Fischer-Tropsch fraction waxes have a high oil content, especially the medium and low melting point Fischer-Tropsch waxes, which have an oil content of 5%-10%. This is significantly different from the oil content of about 0.5% in foreign products, and cannot meet the needs of high-end customers.

[0007] CN102453548A discloses a solvent dewaxing method using a dewaxing aid. This method involves mixing molten dewaxing material and a dewaxing aid, then adding a dewaxing solvent and cooling to the dewaxing temperature. The solvent can be added using a multi-point dilution method or a single total dilution method. Dewaxing oil and dewaxing wax paste are obtained by filtration at the dewaxing temperature. The dewaxing aid is a high-melting-point Fischer-Tropsch synthetic wax. The advantages are improved filtration speed and dewaxing oil yield, while the aid used does not need to be separated from the wax and does not adversely affect the properties of the wax.

[0008] CN1978597A discloses a method for improving solvent dewaxing efficiency. This method involves a first-stage deoiling process using a contact line between the raw oil and solvent. After filtration at -5°C to 30°C, a wax paste and a first-stage deoiling solution are obtained. The wax paste is then slurried with solvent and subjected to one or two more stages of deoiling, followed by filtration at 0°C to 30°C to obtain a wax product meeting the requirements for petroleum wax products. The first-stage deoiling filtrate and filter aid are frozen to -15°C to 35°C and then subjected to low-temperature deep dewaxing. After filtration at -15°C to 35°C, low-melting-point waxes are removed to obtain dewaxed oil. The solvent used in this method is propane or a mixture of ketones and benzenes, wherein the ketones are acetone or butanone, and the benzenes are toluene and benzene.

[0009] CN106554822A discloses a method for degreasing Fischer-Tropsch synthetic wax. This method uses methyl isobutyl ketone as the sole solvent to dilute the oil-containing Fischer-Tropsch wax. After several dilutions and cooling crystallization, a solvent-containing crystalline liquid is obtained. The crystalline liquid is filtered to obtain a deoiled wax paste, which is then evaporated to recover the solvent, yielding the final product wax. This method for degreasing Fischer-Tropsch synthetic wax achieves high degreasing efficiency, relatively high wax yield, and fast filtration speed.

[0010] CN112574785A discloses a method for degreasing Fischer-Tropsch synthetic wax and its application. The method includes the following steps: mixing molten Fischer-Tropsch synthetic wax with a degreasing solvent under pressure to obtain a mixture, then diluting and cooling to crystallize, separating the solid and liquid to obtain a supernatant and wax paste, removing the wax paste and recovering the solvent to obtain degreased wax.

[0011] CN102311802A discloses a method for producing wax from synthetic oil. This method uses the wax-containing fraction of FT synthetic oil as a waxy feedstock, and performs solvent dewaxing and deoiling to produce wax. The light fraction (50-200℃) of Fischer-Tropsch synthetic oil is used alone or in mixture with ketones (methyl ethyl ketone and / or methyl isobutyl ketone) as the dewaxing and deoiling solvent. The advantage of this method is that it can directly produce refined wax with reduced oil content and free of aromatics, sulfur, and nitrogen. The methyl isobutyl ketone used in this method has a boiling point of 117℃, high heat capacity and latent heat of vaporization, and therefore high energy consumption for its recovery and recycling.

[0012] The purpose of this invention is to provide a method for preparing low-melting-point wax using low-toxicity solvents, based on existing solvent dewaxing and deoiling technologies. Summary of the Invention

[0013] The purpose of this invention is to overcome the problems of high solvent toxicity, low dewaxing efficiency, high oil content in the product wax, and difficulty in adjusting the melting point range of the product wax in existing technologies. This invention provides a method for preparing low-melting-point wax. By selecting specific raw materials and combining them with ester solvents, this method not only improves the yield of the product wax but also reduces its oil content and allows for flexible control of the melting point range of the product wax.

[0014] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a low-melting-point wax, characterized in that the method includes the following steps:

[0015] (1) Mix the raw oil with the first solvent and heat to dissolve to obtain the first solution;

[0016] (2) The first solution undergoes a first cooling, a first crystallization, and a first dwell time to obtain a first crystalline liquid;

[0017] (3) The first crystallizing liquid undergoes a second cooling, a second crystallization, and a second residence to obtain a second crystallizing liquid;

[0018] (4) The second crystallized liquid is subjected to a first solid-liquid separation to obtain dewaxed oil and wax paste;

[0019] (5) After the wax paste is mixed with the second solvent, it undergoes deoiling and second solid-liquid separation to obtain deoiled wax paste and dewaxing liquid;

[0020] (6) Remove the solvent from the deoiled wax paste to obtain the finished wax;

[0021] The feedstock oil is a fraction of Fischer-Tropsch oil at 280℃-450℃;

[0022] The first solvent and the second solvent are each independently an ester solvent.

[0023] A second aspect of the present invention provides a low-melting-point wax prepared by the above-described preparation method.

[0024] Through the above technical solutions, the low-melting-point wax and its preparation method provided by the present invention achieve the following beneficial effects:

[0025] The ester solvents used in this invention are not only low in toxicity but also have low boiling points. By selecting raw oils with specific fractionation points and employing a two-stage crystallization process, the wax products prepared have the advantages of low melting point, high yield, and low oil content while avoiding the use of highly toxic solvents such as benzene. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation method of low-melting-point wax. Detailed Implementation

[0027] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] The first aspect of this invention provides a method for preparing a low-melting-point wax, characterized in that the method includes the following steps:

[0029] (1) Mix the raw oil with the first solvent and heat to dissolve to obtain the first solution;

[0030] (2) The first solution undergoes a first cooling, a first crystallization, and a first dwell time to obtain a first crystalline liquid;

[0031] (3) The first crystallizing liquid undergoes a second cooling, a second crystallization, and a second residence to obtain a second crystallizing liquid;

[0032] (4) The second crystallized liquid is subjected to a first solid-liquid separation to obtain dewaxed oil and wax paste;

[0033] (5) After the wax paste is mixed with the second solvent, it undergoes deoiling and second solid-liquid separation to obtain deoiled wax paste and dewaxing liquid;

[0034] (6) Remove the solvent from the deoiled wax paste to obtain the finished wax;

[0035] The feedstock oil is a fraction of Fischer-Tropsch oil at 280℃-450℃;

[0036] The first solvent and the second solvent are each independently an ester solvent.

[0037] In this invention, a fraction with a temperature range of 280℃-450℃ is used as the feedstock oil. 5% of the Fischer-Tropsch synthetic oil has a distillation temperature not lower than 280℃, and 95% has a distillation temperature not higher than 450℃. By using ester solvents and combining them with the preparation process of this invention, the resulting wax product has the advantages of low melting point, high yield, and low oil content.

[0038] In this invention, the main components of the dewaxing oil are a mixture of alkane and ester solvents in Fischer-Tropsch oil that are not used to prepare low-melting-point waxes. The dewaxing solution is a mixture of ester solvents and a small amount of Fischer-Tropsch oil (oil washed from wax paste).

[0039] According to the present invention, the feedstock oil is a fraction of Fischer-Tropsch oil at 300°C-425°C.

[0040] According to the present invention, the heating and melting temperature is 40-80°C.

[0041] Furthermore, the heating and melting temperature is 50-60℃.

[0042] According to the present invention, the ester solvent is a C3-C6 ester solvent.

[0043] In this invention, C3-C6 ester solvents are used, which can both increase the yield of wax products and reduce the oil content of wax products.

[0044] Furthermore, the ester solvent is selected from at least one of methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, and ethyl butyrate.

[0045] According to the present invention, the mass ratio of the first solvent to the raw material oil is 1-8:1.

[0046] In this invention, the ratio of the first solvent to the raw material oil satisfies the above-mentioned ratio, which is conducive to the crystallization of the material and can effectively prevent the wax product from entering the solvent, thus reducing the product yield.

[0047] Furthermore, the mass ratio of the first solvent to the raw material oil is 1.5-3:1.

[0048] According to the present invention, the first cooling rate is 0.1-3℃ / min.

[0049] In this invention, under the premise of selecting specific raw material oil and specific solvent, the first cooling process adopts the above-mentioned cooling rate, which can effectively avoid the phenomenon of "wax encapsulating oil" during the crystallization process. "Wax encapsulating oil" makes it difficult to separate wax and oil, thereby improving the yield of wax products and reducing the oil content of wax products.

[0050] Furthermore, the first cooling rate is 0.5-1.5℃ / min.

[0051] According to the present invention, the temperature of the first crystallization is 5-40°C.

[0052] Furthermore, the temperature of the first crystallization is 15-25℃.

[0053] According to the present invention, the duration of the first dwell time is 5-30 minutes.

[0054] Furthermore, the duration of the first stay is 10-20 minutes.

[0055] According to the present invention, the method further includes the step of adding a first replenishing solvent to the product obtained after the first residence.

[0056] According to the present invention, the mass ratio of the first supplementary solvent to the raw material oil is 0.4-1.2:1.

[0057] Furthermore, the mass ratio of the first supplementary solvent to the raw material oil is 0.5-0.8:1.

[0058] According to the present invention, the first supplemental solvent is selected from ester solvents and / or dewaxing solutions.

[0059] According to the present invention, the second cooling rate is 0.5-5℃ / min.

[0060] In this invention, by employing a process that combines first and second cooling, the crystallization process can be effectively controlled, resulting in large and compact wax crystal particles. This not only increases the yield of wax products but also effectively reduces the oil content of the wax products.

[0061] Furthermore, the second cooling rate is 2-4 °C / min.

[0062] According to the present invention, the temperature of the second crystallization is 0-15°C.

[0063] In this invention, the temperature of the second crystallization works synergistically with other process parameters (e.g., the type of raw materials, solvent, and the temperature of the first crystallization) to achieve the desired effect. If the temperature of the second crystallization is too low, lower melting point waxes will precipitate, resulting in a lower melting point and affecting the quality of the wax product. If the temperature of the second crystallization is too high, less wax will precipitate, resulting in a low wax yield, an increased wax content in the deoiled wax, a higher melting point, and the wax product failing to meet requirements.

[0064] Furthermore, the temperature for the second crystallization is 5-10°C.

[0065] According to the present invention, the second dwell time is 5-60 minutes.

[0066] Furthermore, the second stay lasts for 20-40 minutes.

[0067] According to the present invention, the method further includes the step of adding a second supplementary solvent to the product obtained after the second residence.

[0068] According to the present invention, the mass ratio of the second supplementary solvent to the raw material oil is 0.2-0.8:1.

[0069] Furthermore, the mass ratio of the second supplementary solvent to the raw material oil is 0.3-0.6:1.

[0070] According to the present invention, the second supplementary solvent is selected from ester solvents and / or dewaxing solutions.

[0071] According to the present invention, the deoiling conditions include a residence time of 10-60 min under stirring conditions.

[0072] Furthermore, the deoiling conditions include a residence time of 30-40 minutes under stirring conditions.

[0073] According to the present invention, the oil removal temperature is 3-18°C.

[0074] In this invention, the deoiling temperature is within the above-mentioned range, which can effectively prevent the light components from precipitating out of the mixture of wax paste and the second solvent, the heavy components from melting, and other factors from damaging the crystal morphology of the wax crystals; at the same time, it can ensure that the second solid-liquid separation has high efficiency, which is beneficial to improving product purity and reducing product oil content.

[0075] Furthermore, the oil removal temperature is 5-13°C.

[0076] According to the present invention, the weight ratio of the second solvent to the wax paste is 1-4:1.

[0077] Furthermore, the weight ratio of the second solvent to the wax paste is 1.5-2.5:1.

[0078] One specific embodiment of the present invention, combined with Figure 1 :

[0079] Fischer-Tropsch oil is distilled, and the fraction at 280-450℃ is used as the feedstock. The feedstock is mixed with a first solvent and heated to dissolve, yielding a first solution. This first solution undergoes a first cooling and first crystallization process to obtain a first crystalline liquid. The first crystalline liquid then undergoes a second cooling and a second crystallization process to obtain a second crystalline liquid. The second crystalline liquid undergoes a first solid-liquid separation to obtain dewaxed oil and wax paste. The wax paste is mixed with a second solvent, then subjected to deoiling and a second solid-liquid separation to obtain deoiled wax paste and dewaxed liquid. The deoiled wax paste is then desolventized to obtain the finished wax.

[0080] To further enhance the separation effect, the method further includes the step of adding a first replenishing solvent to the product obtained after the first residence. The method also includes the step of adding a second replenishing solvent to the product obtained after the second residence.

[0081] The first and second replenishing solvents are selected from the dewaxing solution obtained from the second solid-liquid separation and / or the solvent in the solvent storage tank.

[0082] The dewaxed oil obtained from the first solid-liquid separation and the partial or complete dewaxed liquid obtained from the second solid-liquid separation are processed by solvent recovery. The recovered solvent is then stored in a solvent storage tank for reuse. The solvent stored in the storage tank is used as a first solvent, a second solvent, or other solvents, and fresh solvent is replenished to the storage tank as needed.

[0083] A portion of the dewaxing solution is used directly as the first and / or second replenishing solvent; the other portion undergoes impurity removal treatment to obtain recovered solvent, which is stored in a solvent storage tank.

[0084] In this invention, the first solid-liquid separation and the second solid-liquid separation can be carried out by centrifugal separation, filtration separation, etc.; preferably, filtration separation is used, wherein the filtration separation includes filtration, filter cake washing and filter cake drying.

[0085] One specific embodiment of the present invention is as follows:

[0086] (1) Take the fraction of Fischer-Tropsch oil at 300-450℃, the mass ratio of the first solvent to the raw oil is 1.5-7:1, and heat it at 40-80℃ to dissolve it to obtain the first solution;

[0087] (2) The first solution is cooled to 15-25℃ at a cooling rate of 0.5-1.5℃ / min to carry out the first crystallization, and the solution is held for 10-30 min. The first supplementary solvent is added, and the mass ratio of the first supplementary solvent to the raw material oil is 0.6-1:1 to obtain the first crystallization solution.

[0088] (3) The first crystallization solution is cooled to 5-10℃ at a cooling rate of 2-4℃ / min to carry out the second crystallization, and the solution is held for 20-40min. A second supplementary solvent is added, and the mass ratio of the second supplementary solvent to the raw material oil is 0.3-0.6:1 to obtain the second crystallization solution.

[0089] (4) The second crystallization liquid was filtered under reduced pressure at 5-10℃ to obtain dewaxed oil and wax paste;

[0090] (5) Mix the wax paste with an ester solvent (mass ratio of ester solvent to wax paste = 1.5-2.5:1), heat and stir at 5-13℃ for 30-40 min to remove oil, and then filter to separate to obtain deoiled wax paste and dewaxing liquid;

[0091] (6) Remove the solvent from the deoiled wax paste to obtain the finished wax;

[0092] The ester solvent described in this embodiment is a C3-C6 ester solvent.

[0093] According to the present invention, the yield of the low melting point wax is ≥20wt%, the melting point is 40-50℃, and the oil content is ≤0.4wt%.

[0094] A second aspect of the present invention provides a low-melting-point wax prepared by the above-described preparation method.

[0095] According to the present invention, the low melting point wax has a melting point of 40-50°C and an oil content of ≤0.5wt%.

[0096] In the following embodiments, unless otherwise specified, all raw materials used are commercially available.

[0097] The following are the test methods for performance parameters involved in this invention:

[0098] (1) Yield of low melting point wax:

[0099] Yield (wt%) = Product wax mass × 100% / Raw material oil mass.

[0100] (2) Melting point (°C) of low melting point wax:

[0101] In this invention, the method for testing the melting point of the low-melting-point wax is based on the national standard GB / T2539-2008.

[0102] (3) Oil content (wt%) of low melting point wax:

[0103] In this invention, the method for testing the oil content of the low melting point wax is based on the national standard GB / T3554-2008.

[0104] Example 1

[0105] (1) Take 100 kg of the Fischer-Tropsch oil fraction at 300-450℃ as the raw oil, mix it with 150 kg of ethyl acetate, and heat it at 60℃ to dissolve it to obtain the first solution; the mass ratio of the first solvent to the raw oil is 1.5:1.

[0106] (2) The first solution is cooled to 20°C at a cooling rate of 0.5°C / min to carry out the first crystallization, and the solution is held for 10 min. Then, 80 kg of the first supplementary solvent is added to obtain the first crystallized liquid. The mass ratio of the first supplementary solvent to the raw material oil is 0.8:1.

[0107] (3) The first crystallization liquid is cooled to 5°C at a cooling rate of 2°C / min to carry out the second crystallization, and the mixture is held for 30 min. Then, 6 kg of the second supplementary solvent is added to obtain the second crystallization liquid. The mass ratio of the second supplementary solvent to the raw material oil is 0.6:1.

[0108] (4) The second crystallization liquid was filtered under reduced pressure at 5°C to obtain dewaxed oil and wax paste;

[0109] (5) Mix 30 kg of the wax paste with 60 kg of ethyl acetate (mass ratio of ethyl acetate to wax paste = 2:1), heat and stir at 5°C for 30 min to remove oil, and then filter to separate to obtain deoiled wax paste and dewaxing liquid;

[0110] (6) Remove the solvent from the deoiled wax paste to obtain the finished wax.

[0111] Examples 1-15 and Comparative Examples 1-3

[0112] The examples and comparative examples all used the same preparation method as in Example 1. The types, amounts, and specific conditions of each material used in the examples and comparative examples are shown in Table 1.

[0113] Examples 1-15 are abbreviated as A1-A15, and Comparative Examples 1-3 are abbreviated as D1-D3.

[0114] Table 1

[0115]

[0116]

[0117] Example 6

[0118] The ester solvent is hexyl butyrate, and other conditions are the same as in Example 1.

[0119] Example 7

[0120] The mass ratio of the first solvent to the raw oil is 7:1, and other conditions are the same as in Example 1.

[0121] Example 8

[0122] The first cooling rate was 5°C / min, and other conditions were the same as in Example 1.

[0123] Example 9

[0124] The temperature of the first crystallization was 10°C, and other conditions were the same as in Example 1.

[0125] Example 10

[0126] The temperature for the second crystallization was 15°C, and other conditions were the same as in Example 1.

[0127] Example 11

[0128] The oil removal temperature was 20°C, and other conditions were the same as in Example 1.

[0129] Example 12

[0130] The ester solvent is butyl acetate solvent, and other conditions are the same as in Example 1.

[0131] Example 13

[0132] Without adding the first supplementary solvent, all other conditions were the same as in Example 1.

[0133] Example 14

[0134] Without adding the second supplementary solvent, all other conditions were the same as in Example 1.

[0135] Example 15

[0136] The second cooling rate was 6°C / min, and other conditions were the same as in Example 1.

[0137] Comparative Example 1

[0138] The raw material oil is in the range of 460-490℃, and other conditions are the same as in Example 1.

[0139] Comparative Example 2

[0140] Both the first solvent and the second solvent are phenyl ketone, and other conditions are the same as in Example 1.

[0141] Comparative Example 3

[0142] The two cooling crystallization processes were combined into one crystallization process, with the total time remaining the same as in Example 1, and other conditions remaining the same as in Example 1.

[0143] Table 2

[0144]

[0145]

[0146] As seen from the results of the embodiments of the present invention, the wax product prepared using the technical solution of the present invention not only has a low melting point, but also possesses the advantages of high yield and low oil content, and the melting point of the product wax can be adjusted according to actual needs. Using ester solvents, the ester solvents obtained from the first solid-liquid separation, the second solid-liquid separation, and the solvent removal separation of the deoiled wax paste can be recycled, significantly reducing production costs. While avoiding the use of highly toxic solvents such as benzene, the energy consumption of the subsequent solvent recovery unit is also significantly reduced.

[0147] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a low-melting-point wax, characterized in that, The method includes the following steps: (1) Mix the raw oil with the first solvent and heat to dissolve, to obtain the first solution; (2) The first solution undergoes a first cooling, a first crystallization, and a first dwell time. Then, a first supplementary solvent is added to the product obtained after the first dwell time to obtain a first crystallized liquid. (3) The first crystallizing liquid undergoes a second cooling, a second crystallization, and a second residence. Then, a second supplementary solvent is added to the product obtained after the second residence to obtain a second crystallizing liquid. (4) The second crystallized liquid is subjected to a first solid-liquid separation to obtain dewaxed oil and wax paste; (5) After the wax paste is mixed with the second solvent, it is subjected to deoiling and second solid-liquid separation to obtain deoiled wax paste and dewaxing liquid; (6) Remove the solvent from the deoiled wax paste to obtain the finished wax; The feedstock oil is a fraction of Fischer-Tropsch oil at 280℃-450℃; The first solvent and the second solvent are each independently an ester solvent; The ester solvent is a C3-C6 ester solvent; The first cooling rate is 0.1-3℃ / min; The temperature at which the first crystallization occurs is 15-25℃; The temperature for the second crystallization is 5-10℃; The oil removal temperature is 3-18℃; The mass ratio of the first solvent to the raw oil is 1-8:1; The mass ratio of the first supplementary solvent to the raw material oil is 0.4-1.2:1; The second cooling rate is 0.5-5℃ / min; The mass ratio of the second supplementary solvent to the raw material oil is 0.2-0.8:1; The weight ratio of the second solvent to the wax paste is 1-4:1; The first replenishing solvent and the second replenishing solvent are selected from the dewaxing solution obtained from the second solid-liquid separation and / or the solvent in the solvent storage tank.

2. The preparation method according to claim 1, characterized in that, The feedstock oil is a fraction of Fischer-Tropsch oil at 300℃-425℃.

3. The preparation method according to claim 1, characterized in that, The heating and melting temperature is 40-80℃.

4. The preparation method according to claim 3, characterized in that, The heating and melting temperature is 50-60℃.

5. The preparation method according to claim 1, characterized in that, The ester solvent is selected from at least one of methyl acetate, ethyl acetate, ethyl propionate, butyl acetate, and ethyl butyrate.

6. The preparation method according to claim 1, characterized in that, The mass ratio of the first solvent to the raw material oil is 1.5-3:

1.

7. The preparation method according to claim 1, characterized in that, The first cooling rate is 0.5-1.5℃ / min.

8. The preparation method according to claim 1, characterized in that, The first dwell time is 5-30 minutes.

9. The preparation method according to claim 8, characterized in that, The first dwell time is 10-20 minutes.

10. The preparation method according to claim 1, characterized in that, The mass ratio of the first supplementary solvent to the raw material oil is 0.5-0.8:

1.

11. The preparation method according to claim 1, characterized in that, The second cooling rate is 2-4℃ / min.

12. The preparation method according to claim 1, characterized in that, The second stay lasts for 5-60 minutes.

13. The preparation method according to claim 12, characterized in that, The second stay lasts for 20-40 minutes.

14. The preparation method according to claim 1, characterized in that, The mass ratio of the second supplementary solvent to the raw material oil is 0.3-0.6:

1.

15. The preparation method according to claim 1, characterized in that, The conditions for oil removal include a residence time of 10-60 minutes under stirring conditions.

16. The preparation method according to claim 15, characterized in that, The deoiling conditions include a residence time of 30-40 minutes.

17. The preparation method according to claim 1, characterized in that, The oil removal temperature is 5-13℃.

18. The preparation method according to claim 1, characterized in that, The weight ratio of the second solvent to the wax paste is 1.5-2.5:

1.

19. The preparation method according to claim 1, characterized in that, The low-melting-point wax has a melting point of 40-50℃ and an oil content of ≤0.5 wt%.

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