Low-melting-point low-aromatic-hydrocarbon environment-friendly deoiling wax and preparation method thereof

Abstract

The invention provides low-melting-point low-aromatic-hydrocarbon environment-friendly deoiled wax and a preparation method thereof. The preparation method comprises the following steps: carrying out wax crystallization on a mixture of deoiled wax raw material oil and a non-aromatic hydrocarbon environment-friendly deoiling solvent to obtain a crystallized mixed material, and then carrying out a solvent deoiling process to obtain the low-melting-point low-aromatic hydrocarbon environment-friendly deoiled wax, the non-aromatic environment-friendly deoiling solvent is a mixture containing C4 ketone and cyclohexane, and the content of the C4 ketone accounts for 45-95 wt%. The novel non-aromatic hydrocarbon environment-friendly deoiling solvent is provided, the light wax oil fraction is used as a raw material, and three-stage solvent deoiling is performed, so that low-melting-point (less than 52 DEG C) low-aromatic hydrocarbon environment-friendly deoiling wax can be produced, the subsequent solvent separation effect can be improved, and the low-carbon environmental protection property of the production process can be improved.

Description

Technical Field

[0001] The present invention relates to a low-melting-point and low-aromatic-hydrocarbon environmentally friendly deoiled wax and a preparation method thereof, belonging to the technical field of petroleum product processing. Background Art

[0002] Paraffin wax (also known as crystalline wax) generally refers to a hydrocarbon mixture with about 18 - 30 carbon atoms. It is usually a white, odorless waxy solid, soluble in non-polar solvents such as gasoline, carbon disulfide, xylene, ether, benzene, chloroform, carbon tetrachloride, and naphtha, and insoluble in polar solvents such as water and methanol. The main components of paraffin wax are straight-chain alkanes, with a small amount of alkanes with individual branched chains and monocyclic naphthenes with long side chains. Paraffin wax can be used to produce higher fatty acids, higher alcohols, matches, candles, waterproofing agents, ointments, electrical insulation materials, etc., and has a wide range of applications in industrial, agricultural and other fields.

[0003] Paraffin wax is generally divided into different varieties every 2°C according to its melting point, such as grades 52, 54, 56, 58, etc. The main performance indicators of paraffin wax are oil content, melting point and stability. Excessive oil content will affect the color and storage stability of paraffin wax, and also reduce its hardness. Therefore, the oil-containing wax paste obtained from the vacuum distillate still needs to be dewaxed by the solvent method or sweating method to reduce its oil content.

[0004] Paraffin wax is generally obtained by solvent refining, solvent dewaxing of the wax oil fraction obtained from the atmospheric and vacuum distillation of crude oil, or by wax freezing crystallization and pressing dewaxing to obtain a wax paste, and then by solvent deoiling and refining to obtain flaky or needle-like crystals. With the continuous development of refining and chemical process technologies, dewaxing and deoiling technologies and methods have also been improved and developed in different directions due to differences in raw material properties and product requirements. The dewaxing and deoiling methods currently used in industry are roughly as follows:

[0005] (1) Cold pressing dewaxing. Also known as crystallization dewaxing, this dewaxing method was only used in the early stage and is now rarely used. This method is simple to operate and is suitable for the dewaxing of diesel and light lubricating oils. Its principle is to directly cool the oil to the low temperature required for wax precipitation, and then separate the wax oil by pressure filtration to obtain dewaxed oil and crude wax respectively. For high-viscosity oils, due to their high viscosity itself and even higher viscosity at low temperatures, the formed wax crystals are smaller and not easy to filter, and the oil and wax cannot be completely separated, resulting in a poor dewaxing effect. It is difficult to ensure the dewaxing accuracy at low temperatures, the oil content in the crude wax is high, and the yield of dewaxed oil is not very high. At the same time, the efficiency of the freezing crystallization and pressure filtration equipment used in the process is not high, which cannot meet the requirements of continuous industrial production. Therefore, this type of dewaxing method has almost been phased out.

[0006] (2) Urea dewaxing. This method utilizes the ability of urea to form a complex with paraffin, and the complex is filtered out from the waxy feedstock oil to achieve the separation of paraffin and oil. This method is applicable to the case where the viscosity of the waxy feedstock oil is relatively low, such as light diesel fractions and light lubricating oil feeds.

[0007] (3) Molecular sieve dewaxing. This method selectively adsorbs oil and wax hydrocarbon components under the action of a molecular sieve to achieve the dewaxing effect. Generally, a molecular sieve with a pore size of is used for dewaxing through the adsorption of the molecular sieve. The molecular sieve has the function of adsorbing normal paraffins in petroleum products. At the same time, it does not adsorb isoparaffins and naphthenes, thereby achieving the separation of normal paraffins and non-normal paraffins in the waxy feedstock oil. Due to the relatively small pore size of this molecular sieve, it is applicable to waxy feedstock oils with relatively low viscosity. The equipment for adsorption dewaxing has a simple structure and low price, but the feedstock oil must be pre-treated by deep refining to remove gums because the molecular sieve cannot desorb after adsorbing such substances.

[0008] (4) Bacterial dewaxing. This method involves mixing Candida lipolytica with the waxy feedstock oil. Candida lipolytica will consume the paraffin in the waxy feedstock oil and then float on the surface, which is separated by centrifugation.

[0009] (5) Catalytic dewaxing. Also known as hydrodewaxing, this method is carried out at relatively high temperatures and pressures. Through the action of a catalyst, the waxy feedstock oil reacts with hydrogen to undergo hydroisomerization and selective hydrocracking reactions, converting normal paraffins with a relatively high freezing point into isoparaffins and small-molecule paraffins with a relatively low freezing point, thereby achieving the removal of paraffin and reducing the pour point of the waxy feedstock oil.

[0010] (6) Solvent dewaxing. The process principle of solvent dewaxing is basically the same as that of solvent deoiling. Generally, the waxy feedstock oil is mixed with a solvent. Mainly due to different solubilities, the oil in the feedstock oil dissolves in the solvent, while the wax either does not dissolve or dissolves very little in the solvent. At low temperatures, the solvent itself has a low viscosity and a large solubility for oil, but a small solubility for wax. Eventually, the viscosity of the oil product is reduced, and the wax grows into large crystals. Then, by lowering the temperature, the paraffin precipitates, and after filtration, the paraffin and oil can be separated. This method is widely used and applicable to various wax oil feedstocks with different viscosities. It is the mainstream process for producing paraffin at present.

[0011] The world's first acetone-benzene dewaxing unit using the solvent dewaxing process was built in 1927 and has been continuously improved and developed since then. Currently, the commonly used dewaxing and deoiling solvents in industry are mainly the mixed solvent of methyl ethyl ketone and toluene. The processes of solvent dewaxing and solvent deoiling are generally the same. Taking ketone-benzene dewaxing and deoiling as an example, it generally includes parts such as crystallization, filtration, and solvent recovery. Industrially, generally, the raw material and the solvent first exchange heat with the filtrate in a double-pipe crystallizer with a scraper, and part of the solvent is added. Then, after ammonia cooling and solvent dilution, filtration is carried out. The filtrate and the wax liquid after filtration are respectively evaporated and stripped to recover the solvent. The composition of the added mixed solvent and the solvent ratio vary depending on the properties of the raw material (boiling range, wax content, etc.) and the dewaxing depth. Generally, the methyl ethyl ketone-toluene solvent contains 40%-60% methyl ethyl ketone. The dilution solvent is added in several times, which is beneficial to forming good wax crystals, reducing the dewaxing temperature difference (i.e., the difference between the freezing point of the dewaxed oil and the dewaxing temperature), and increasing the yield of the dewaxed oil. The cooling rate of the raw material in the double-pipe crystallizer should not be too fast to avoid generating too many fine wax crystals, which is not conducive to filtration. Filtration is generally carried out in a filter press. According to the wax content of the raw material, one-stage or two-stage filtration is respectively adopted to recover the solvent from the filtrate and the wax liquid.

[0012] The conventional solvent deoiling and dewaxing process generally aims to remove the high pour point paraffin components in the wax oil raw material and meet the low temperature fluidity requirements of the base oil. It can produce oil and wax jointly according to the demand. The solvent deoiling process generally aims to produce high-quality paraffin. Modern refining and chemical production enterprises generally adopt a two- or three-stage dewaxing and deoiling process to produce deoiled wax and dewaxed oil. If the wax oil content still does not meet the standard after two-stage deoiling, a three-stage deoiling process can be adopted to produce deoiled wax. The three-stage deoiling process is generally as follows: After the raw material and the solvent are mixed, the temperature is adjusted to the first-stage deoiling temperature, and the first-stage deoiled wax paste is obtained by filtration. The first-stage deoiled wax paste is mixed with the solvent, the temperature is adjusted to the second-stage deoiling temperature, and the second-stage deoiled wax paste is obtained by filtration. The second-stage deoiled wax paste is mixed with the solvent, the temperature is adjusted to the third-stage deoiling temperature, and the third-stage deoiled wax paste is obtained by filtration. After the third-stage deoiled wax paste removes the solvent, deoiled wax is obtained. Adopting three-stage deoiling can effectively reduce the oil content of the wax and meet the product quality requirements.

[0013] The industrial traditional process of solvent deoiling and dewaxing is ketone-benzene deoiling and dewaxing. The solvent is mainly the mixed solvent of methyl ethyl ketone and toluene. When producing conventional paraffin products (melting point ≥ 52°C), it has good oil-wax selectivity and raw material dilution performance. However, when producing low melting point (<52°C) paraffin products with the traditional ketone-benzene process, there are problems such as difficulties in separating subsequent wax agents and oil agents, and high aromatic hydrocarbon content in low melting point paraffin products. The preparation technology of high-quality low melting point paraffin needs to be further improved and enhanced.

[0014] CN104109559A discloses a preparation method of long-chain low-melting-point wax for producing non-short-chain chlorinated paraffin. Among them, the method includes: (1) taking raw material oil, heating and melting it, adding an ester solvent and a crystallization modifier to the melted raw material oil, and keeping the temperature at 45 - 65 °C to obtain a mixture; (2) cooling and crystallizing the mixture obtained in step (1) until the crystallization temperature drops to -15 to -20 °C to obtain a crystalline mixture; (3) filtering the crystalline mixture obtained in step (2) to obtain a filter cake and a filtrate, heating and distilling the filter cake to remove the ester solvent, and thus obtaining the long-chain low-melting-point wax.

[0015] CN110776955A discloses a production method of low-melting-point wax for soap. Among them, the method includes hydrocracking tail oil → furfural refining → ketone-benzene dewaxing and deoiling → selective deoiling wax → primary sweating → selective component mixing → secondary sweating → blending → cutting and deodorizing → clay refining → ammonia cooling and forming → product. The low-melting-point paraffin fraction enters a rectifying column for deodorization treatment, then undergoes clay refining to improve its color and stability, and then is subjected to freezing and forming for packaging.

[0016] CN107267213A discloses a production method of low-melting-point wax for soap. Among them, the method includes hydrocracking tail oil → furfural refining → ketone-benzene dewaxing and deoiling → selective deoiling wax → primary sweating → selective component mixing → secondary sweating → blending → cutting and deodorizing → clay refining → ammonia cooling and forming → product. The low-melting-point paraffin fraction enters a rectifying column for deodorization treatment, then undergoes clay refining to improve its color and stability, and then is subjected to freezing and forming for packaging.

[0017] CN105802669A discloses a production method of soap wax and low-melting-point paraffin. Among them, the method includes adding a low-boiling liquid to the raw material, and during the heating and sweating process, using an air flow to carry out the liquid oil through the wax layer to forcibly separate the wax and the oil, enhancing the separation effect and accelerating the separation speed, thereby increasing the yield of the target product and shortening the production cycle.

[0018] CN105754657A discloses a preparation method of low-melting-point paraffin. Among them, the method includes evenly spreading solid particles on the surface of the wax layer before the heating and sweating process, and during the heating and sweating process, forcing an air flow through the wax layer to carry out the liquid oil, accelerating the separation speed of the wax and the oil, and enhancing the separation effect of the wax and the oil.

[0019] CN107523344A discloses a method for sweating to produce soap wax and low-melting-point paraffin. Among them, the method includes, on the basis of the ordinary sweating and deoiling process, forming stable micro-bubbles in the wax layer under the action of a bubble stabilizer for the sweating raw material to facilitate the rapid discharge of oil, and at the same time, using an air flow to carry out the liquid oil through the wax layer during the sweating process to forcibly separate the wax and the oil, thereby increasing the yield of the target product and shortening the production cycle.

[0020] CN107513409B discloses a production method of soap wax and low melting point paraffin wax. Among them, the method includes, on the basis of the ordinary sweating and deoiling process, using air flow to carry out the liquid oil through the wax layer during the sweating process to forcibly separate the wax and the oil, and preferably emulsifying the raw material with water or salt solution, so as to shorten the production cycle while increasing the yield of the target product.

[0021] CN107523348B discloses a method for producing soap wax and low melting point paraffin wax. Among them, the method includes, on the basis of the ordinary sweating and deoiling process, preferably emulsifying the raw material with the aqueous solutions of two or more substances that can react to generate gas respectively and then carrying out sweating, and using air flow to carry out the liquid oil through the wax layer during the sweating process to forcibly separate the wax and the oil, so as to increase the yield of the target product and shorten the production cycle at the same time.

[0022] CN107523346A discloses a method for sweating and preparing soap wax and low melting point paraffin wax. Among them, the method includes, on the basis of the ordinary sweating and deoiling process, dissolving an oil-soluble emulsifier and an oil-soluble acid in the sweating raw material as the oil-phase material, using an inorganic salt solution as the water-phase material, emulsifying and then carrying out sweating, using the bubbles generated by the reaction of the oil-soluble acid and the inorganic salt and the tiny space formed after the salt solution is discharged to form a channel for discharging the oil to promote the rapid discharge of the oil, and at the same time using air flow to carry out the liquid oil through the wax layer during the sweating process to forcibly separate the wax and the oil, so as to increase the yield of the target product and shorten the production cycle at the same time.

[0023] CN1472255A discloses a preparation method of a low melting point thermosensitive wax. Among them, the method is composed of 45-99% of basic soft wax, 0.2-10% of crystal improver, 0.5-30% of tackifier, and 0.3-15% of heat conductive agent. Mix 45-99% of basic soft wax, 0.2-10% of crystal improver, 0.5-3% of tackifier, and 0.3-15% of heat conductive agent at 100-150 °C, stir for 20-300 minutes and then cool to obtain the low melting point thermosensitive wax.

[0024] Liu Huizhen et al. (Liu Huizhen, Chen Wenyi, Liu Ying, Yao Erwei. Research and Development of Special Wax with Low Melting Point and High Hardness [J]. Petroleum Processing and Petrochemicals, 2016, (02): 79-83.) used polyethylene wax and lauric acid as paraffin modifiers, and investigated the effects of modification process conditions and modifier addition amounts on the properties of paraffin. The results showed that the optimal process conditions were: modification time 3 h, modification temperature 130 °C, stirring rate 600 r / min, the addition amount (w) of polyethylene wax was 5%, and the addition amount (w) of lauric acid was 8%; by blending the above two additives, a modified paraffin product with low dropping melting point and appropriate hardness was prepared; on this basis, adding a certain amount of stearic acid, that is, when the addition amount (w) of polyethylene wax was 5%, the addition amount (w) of lauric acid was 8%, and the stearic acid was 0-25%, a modified wax with lower dropping melting point and increased hardness could be obtained; and SPSS software was used for linear regression to obtain the relationship between the addition amounts of polyethylene wax, lauric acid and stearic acid and the dropping melting point and penetration (25 °C) of paraffin.

[0025] Zheng Lihui (Zheng Lihui. Research on Preparation of Paraffin with Low Melting Point by Urea Inclusion Method [J]. Fine Petrochemicals, 2002, (06): 11-13.) used commercially available paraffin as raw material and obtained paraffin with appropriate phase change temperature (melting range of 26-26.6 °C) by urea inclusion method. Experiments proved that the primary and secondary factors affecting the reaction were in turn inclusion temperature, mass ratio of urea to paraffin, reaction time, and mass ratio of ethanol to urea; when the reaction temperature was 70 °C, the mass ratio of urea to paraffin was 3:1, the reaction time was 2.5 h, and the mass ratio of ethanol to urea was 0.2, paraffin with initial melting point of 26 °C and final melting point of 26.6 °C was obtained.

[0026] Feng Tao (Feng Tao. Using Low Melting Point Oil-Containing Wax to Select Appropriate Production Process to Produce High-Quality Paraffin [J]. Guangdong Chemical Industry, 2012, (04): 265-266.) used the surplus low melting point wax from the ketone-benzene dewaxing unit as the main raw material, combined with the use of the fourth side-stream oil-containing wax, and adopted the sweating narrow fraction cutting and deoiling process and solvent deoiling process to pre-treat the raw material, and combined with the clay refining process to produce high-quality semi-refined wax.

[0027] Wang Shixin et al. (Wang Shixin, Liu Huiqing, Lin Zhenfa. Producing Lubricating Oil Base Oil and Low Melting Point Food Paraffin from MHUG Tail Oil [J]. Petroleum Processing and Petrochemicals, 1996, (01): 32-36.) used MHUG tail oil to produce lubricating oil base oil and low melting point food paraffin. By using the method of methyl ethyl ketone-toluene (MEK-TOL) dewaxing and deoiling and clay refining, high-quality lubricating oil base oil and high-yield food paraffin could be prepared from medium pressure hydro-upgrading (MHUG) tail oil, and the dewaxed oil could also be used as the raw material for high-quality white oil.

[0028] However, when producing paraffin wax with a low melting point (<52 °C) by the ketone-benzene process, problems such as a relatively high aromatic content in the low-melting-point paraffin wax product, difficulties in subsequent solvent separation, and an insufficiently low-carbon and environmentally friendly process have not been fundamentally solved, restricting the preparation of low-melting-point environmentally friendly paraffin wax. Therefore, there is a current need to provide a method for preparing low-melting-point and low-aromatic-content environmentally friendly dewaxed oil using a non-aromatic environmentally friendly mixed solvent. Summary of the Invention

[0029] To solve the above technical problems, the object of the present invention is to provide a low-melting-point and low-aromatic-content environmentally friendly dewaxed oil and a preparation method thereof. By using a non-aromatic environmentally friendly dewaxing solvent in the solvent dewaxing process, dewaxed oil with low aromatic content, low melting point, and low oil content is prepared.

[0030] To achieve the above object, the present invention provides a method for preparing a low-melting-point and low-aromatic-content environmentally friendly dewaxed oil, which includes: subjecting a mixture of a dewaxed oil feedstock and a non-aromatic environmentally friendly dewaxing solvent to wax crystallization to obtain a crystallized mixture, and then performing a solvent dewaxing process to obtain the low-melting-point and low-aromatic-content environmentally friendly dewaxed oil.

[0031] According to a specific embodiment of the present invention, preferably, the non-aromatic environmentally friendly dewaxing solvent is a mixture of C4 ketone and cyclohexane, wherein, based on the total mass of the mixture of C4 ketone and cyclohexane, the content of C4 ketone is 45-95 wt%, and the content of cyclohexane is 5-55 wt%.

[0032] According to a specific embodiment of the present invention, preferably, the dewaxed oil feedstock is a light wax oil fraction.

[0033] In some specific embodiments, preferably, the light wax oil fraction is selected from the second reduced-line fraction of the first-stage processing of crude oil, or other waxy oil materials with similar distillation range components.

[0034] According to a specific embodiment of the present invention, preferably, the C4 ketone is methyl ethyl ketone; based on the total mass of the mixture of methyl ethyl ketone and cyclohexane, the content of methyl ethyl ketone is 45-95 wt%, and the content of cyclohexane is 5-55 wt%.

[0035] In some specific embodiments, preferably, the content of methyl ethyl ketone is 55-85 wt%, and the content of cyclohexane is 15-45 wt%.

[0036] According to a specific embodiment of the present invention, preferably, the wax crystallization is performed by multi-point dilution for wax crystallization.

[0037] In some specific embodiments, preferably, the multi-point dilution is two-point dilution, and the dilution conditions include: the temperature of the first-point dilution is 20 - 60 °C, and the temperature of the second-point dilution is 3 - 25 °C; more preferably, the temperature of the first-point dilution is 23 - 55 °C, and the temperature of the second-point dilution is 6 - 20 °C.

[0038] According to the specific embodiments of the present invention, preferably, the dilution conditions further include: when performing the first-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly deoiling solvent to the deoiling wax raw material oil is 0.2 - 7.5:1; when performing the second-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly deoiling solvent to the deoiling wax raw material oil is 0.5 - 7.5:1.

[0039] In some specific embodiments, preferably, when performing the first-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly deoiling solvent to the deoiling wax raw material oil is 0.5 - 4.5:1; when performing the second-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly deoiling solvent to the deoiling wax raw material oil is 0.8 - 4.5:1.

[0040] According to the specific embodiments of the present invention, preferably, the solvent deoiling process includes: under the first-stage deoiling conditions, performing the first-stage solvent deoiling on the mixture of the crystalline mixed material and the first-stage deoiling dilution solvent to obtain a first-stage deoiling wax paste and a first-stage deoiling filtrate; under the second-stage deoiling conditions, performing the second-stage solvent deoiling on the mixture of the first-stage deoiling wax paste and the second-stage deoiling dilution solvent to obtain a second-stage deoiling wax paste and a second-stage deoiling filtrate; under the third-stage deoiling conditions, performing the third-stage solvent deoiling on the mixture of the second-stage deoiling wax paste and the third-stage deoiling dilution solvent to obtain a third-stage deoiling wax paste and a third-stage deoiling filtrate; after the third-stage deoiling wax paste undergoes solvent separation, a low-melting-point and low-aromatic-hydrocarbon environmentally friendly deoiling wax is obtained.

[0041] According to the specific embodiments of the present invention, preferably, the process of the first-stage solvent deoiling is: filtering the mixture of the crystalline mixed material and the first-stage deoiling dilution solvent under the first-stage deoiling conditions to obtain a first-stage deoiling wax paste and a first-stage deoiling filtrate.

[0042] According to the specific embodiments of the present invention, preferably, the process of the first-stage solvent deoiling further includes washing the first-stage deoiling wax paste with a first-stage deoiling washing solvent under the first-stage deoiling conditions.

[0043] According to the specific embodiments of the present invention, preferably, the first-stage deoiling dilution solvent includes one or more combinations of a non-aromatic hydrocarbon environmentally friendly deoiling solvent, a second-stage deoiling filtrate, and a third-stage deoiling filtrate, and is preferably a non-aromatic hydrocarbon environmentally friendly deoiling solvent; wherein, the second-stage deoiling filtrate and the third-stage deoiling filtrate are respectively the reuse of the products of the second-stage solvent deoiling and the third-stage solvent deoiling.

[0044] According to a specific embodiment of the present invention, preferably, the first-stage deoiling washing solvent includes one or a combination of two or more of non-aromatic environmentally friendly deoiling solvents, second-stage deoiling filtrate, and third-stage deoiling filtrate.

[0045] According to a specific embodiment of the present invention, preferably, the first-stage solvent deoiling conditions include: the temperature T1 of the first-stage solvent deoiling is -25°C to 20°C, preferably -20°C to 15°C, and more preferably -15°C to 12°C. The temperature of the solvent deoiling includes the filtration temperature and the washing temperature during solvent deoiling.

[0046] According to a specific embodiment of the present invention, preferably, the first-stage solvent deoiling conditions further include: the mass ratio of the first-stage deoiling dilution solvent to the deoiled wax feedstock oil is 0.5 - 4.0:1, preferably 1.0 - 3.5:1.

[0047] According to a specific embodiment of the present invention, preferably, the mass ratio of the first-stage deoiling washing solvent to the deoiled wax feedstock oil is 0.1 - 3.0:1, preferably 0.3 - 1.0:1.

[0048] According to a specific embodiment of the present invention, preferably, the process of the second-stage solvent deoiling is: filtering the mixture of the first-stage deoiled wax paste and the second-stage deoiling dilution solvent under the second-stage deoiling conditions to obtain a second-stage deoiled wax paste and a second-stage deoiling filtrate.

[0049] According to a specific embodiment of the present invention, preferably, the process of the second-stage solvent deoiling further includes washing the second-stage deoiled wax paste with the second-stage deoiling washing solvent under the second-stage deoiling conditions.

[0050] According to a specific embodiment of the present invention, preferably, the second-stage deoiling conditions include: the temperature of the second-stage solvent deoiling is T2, and T2 - T1 = -6°C to 20°C, preferably -3°C to 15°C, and more preferably 0°C to 10°C. The temperature of the solvent deoiling includes the filtration temperature and the washing temperature during solvent deoiling.

[0051] According to a specific embodiment of the present invention, preferably, the second-stage deoiling conditions further include: the mass ratio of the second-stage deoiling dilution solvent to the deoiled wax feedstock oil is 0.5 - 4.0:1, preferably 1.0 - 3.5:1.

[0052] According to a specific embodiment of the present invention, preferably, the mass ratio of the second-stage deoiling washing solvent to the deoiled wax feedstock oil is 0.1 - 3.0:1, preferably 0.3 - 1.0:1.

[0053] According to a specific embodiment of the present invention, preferably, the process of the third-stage solvent dewaxing is as follows: filtering the mixture of the second-stage dewaxed wax paste and the third-stage dewaxing diluting solvent under the third-stage dewaxing conditions to obtain a third-stage dewaxed wax paste and a third-stage dewaxing filtrate.

[0054] According to a specific embodiment of the present invention, preferably, the process of the third-stage solvent dewaxing further includes washing the third-stage dewaxed wax paste with a third-stage dewaxing washing solvent under the third-stage dewaxing conditions.

[0055] According to a specific embodiment of the present invention, preferably, the second-stage dewaxing diluting solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the third-stage dewaxing filtrate, preferably a non-aromatic hydrocarbon environmentally friendly dewaxing solvent; wherein, the third-stage dewaxing filtrate is equivalent to the reuse of the product of the third-stage solvent dewaxing.

[0056] According to a specific embodiment of the present invention, preferably, the third-stage dewaxing diluting solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the third-stage dewaxing filtrate, preferably a non-aromatic hydrocarbon environmentally friendly dewaxing solvent.

[0057] According to a specific embodiment of the present invention, preferably, the second-stage dewaxing washing solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the third-stage dewaxing filtrate.

[0058] According to a specific embodiment of the present invention, preferably, the third-stage dewaxing washing solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the third-stage dewaxing filtrate.

[0059] According to a specific embodiment of the present invention, preferably, the third-stage dewaxing conditions include: the temperature of the third-stage solvent dewaxing is T3, T3 - T2 = -6°C to 20°C, preferably -3°C to 15°C, more preferably 0°C to 10°C. The temperature of the solvent dewaxing includes the filtration temperature and the washing temperature during the solvent dewaxing.

[0060] According to a specific embodiment of the present invention, preferably, the third-stage dewaxing conditions further include: the mass ratio of the third-stage dewaxing solvent to the dewaxed wax raw material oil is 0.5 - 4.0:1, preferably 1.0 - 3.5:1.

[0061] According to a specific embodiment of the present invention, preferably, the mass ratio of the third-stage dewaxing washing solvent to the dewaxed wax raw material oil is 0.1 - 3.0:1, preferably 0.3 - 1.0:1.

[0062] The present invention also provides a low-melting-point and low-aromatic-hydrocarbon environmentally friendly dewaxed wax, which is obtained by the above preparation method.

[0063] According to a specific embodiment of the present invention, preferably, the melting point of the dewaxed wax is less than 52°C, preferably 40°C - 50°C.

[0064] According to a specific embodiment of the present invention, preferably, the benzene content of the dewaxed oil is 0 - 0.49 μg·g -1 , preferably 0.1614 - 0.2091 μg·g -1 , the toluene content is 0 - 4.9 μg·g -1 , preferably 0 μg·g -1 .

[0065] According to a specific embodiment of the present invention, preferably, the oil content of the dewaxed oil is 0.3% - 2.0%, preferably 0.51% - 0.8%.

[0066] The inventors of the present invention found that when using light wax oil fraction as raw material and adopting conventional ketone-benzene solvent for dewaxing process to produce paraffin wax with low melting point (<52°C), in the subsequent wax-solvent separation process of the methyl ethyl ketone - toluene mixed solvent, the solvent separation effect is not good, making it easy for toluene to be carried into the wax, which easily leads to a high aromatic hydrocarbon content in the dewaxed oil and poor environmental protection performance of the paraffin wax product. Due to the presence of toluene, the process is also not low-carbon and environmentally friendly enough.

[0067] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0068] (1) The present invention provides a new type of non-aromatic hydrocarbon environmentally friendly dewaxing solvent. Since the entire process does not involve aromatic hydrocarbon solvents, it not only improves the low-carbon level of the production process, but also enables the production of low-aromatic hydrocarbon environmentally friendly dewaxed oil with low melting point (<52°C).

[0069] (2) The present invention uses a new type of non-aromatic hydrocarbon environmentally friendly dewaxing solvent for solvent dewaxing. When the dewaxed oil is subjected to solvent distillation separation subsequently, due to the significantly lower normal boiling point of the new non-aromatic hydrocarbon solvent compared to the normal boiling point of the industrial conventional methyl ethyl ketone - toluene solvent, the solvent separation effect can be significantly improved. Therefore, this preparation method can not only improve the solvent recovery efficiency, but also improve the product quality of low-aromatic hydrocarbon environmentally friendly paraffin wax with low melting point (<52°C).

[0070] (3) The present invention uses a new type of non-aromatic hydrocarbon environmentally friendly dewaxing solvent for three-stage solvent dewaxing, which can achieve the full separation of low-melting-point paraffin wax and oil. On the premise of achieving a low aromatic hydrocarbon content in the low-melting-point environmentally friendly paraffin wax, the oil content of the low-melting-point paraffin wax is further reduced to meet the low oil content standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Figure 1 It is a flow diagram of the preparation process of low-melting-point dewaxed oil according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0072] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the following detailed description of the technical solution of the present invention is provided, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0073] According to the present invention, the method includes: subjecting a mixture of light wax oil fraction and a non-aromatic hydrocarbon environmentally friendly dewaxing solvent to wax crystallization to obtain a crystallized mixed material, and then performing a solvent dewaxing process; the solvent dewaxing process includes: under the first-stage dewaxing conditions, subjecting the crystallized mixed material and a first-stage dewaxing diluent solvent mixture to first-stage solvent dewaxing to obtain a first-stage dewaxed wax paste and a first-stage dewaxed filtrate; under the second-stage dewaxing conditions, subjecting the first-stage dewaxed wax paste and a second-stage dewaxing diluent solvent mixture to second-stage solvent dewaxing to obtain a second-stage dewaxed wax paste and a second-stage dewaxed filtrate, and the temperature of the second-stage dewaxing is generally not lower than the dewaxing temperature of the first stage; under the third-stage dewaxing conditions, subjecting the second-stage dewaxed wax paste and a third-stage dewaxing diluent solvent mixture to third-stage solvent dewaxing to obtain a third-stage dewaxed wax paste and a third-stage dewaxed filtrate, and the temperature of the third-stage dewaxing is generally not lower than the dewaxing temperature of the second stage; after the third-stage dewaxed wax paste undergoes solvent separation, a low-melting-point and low-aromatic hydrocarbon environmentally friendly dewaxed wax is obtained.

[0074] The present invention will be described in detail below through specific examples:

[0075] Example 1

[0076] This example provides a method for preparing a low-melting-point and low-aromatic hydrocarbon environmentally friendly dewaxed oil, which includes the following steps:

[0077] The feedstock oil is the 1# second reduced-line fraction oil, and its specific properties are shown in Table 1. The three-stage dewaxing method is adopted, and the diluent solvent and washing solvent used in the wax crystallization and three-stage solvent dewaxing processes are both a mixture of methyl ethyl ketone and cyclohexane, wherein the mass content of methyl ethyl ketone is 85%, and the mass content of cyclohexane is 15%. The dilution ratio of the diluent solvent (the mass ratio of the diluent solvent to the feedstock oil) and the cold washing ratio of the washing solvent (the mass ratio of the washing solvent to the feedstock oil) are both relative to the feedstock oil.

[0078] Press Figure 1 The dewaxed wax is prepared according to the shown process flow. The specific process is as follows: multi-point dilution is adopted (first, the feedstock oil is melted at 60 °C, and then multi-point dilution is carried out during the solvent dewaxing process by adding the diluent solvent multiple times), and the melted feedstock oil is sequentially mixed with the diluent solvent, and the temperature is decreased step by step for paraffin wax crystallization; when performing the first-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly dewaxing solvent to the dewaxed wax feedstock oil is 0.5:1, and the first-point dilution temperature is 33 °C. When performing the second-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly dewaxing solvent to the dewaxed wax feedstock oil is 1.2:1, and the second-point dilution temperature is 10 °C.

[0079] The total dilution ratio of the diluting solvent for the first-stage dewaxing is 0.8:1. The filtration temperature for the first-stage solvent dewaxing is -5°C. The wax cake is cold-washed with the first-stage dewaxing washing solvent at -5°C, and the cold-washing ratio is 0.5:1. After filtration, the first-stage dewaxed wax paste and the first-stage dewaxed filtrate are obtained.

[0080] The total dilution ratio of the diluting solvent for the second-stage dewaxing is 1.5:1. The second-stage dewaxing diluting solvent is added to the first-stage dewaxed wax paste and mixed evenly. The temperature is adjusted. The filtration temperature for the second-stage solvent dewaxing is 0°C. The wax cake is cold-washed with the second-stage dewaxing washing solvent at 0°C, and the cold-washing ratio is 0.5:1. After filtration, the second-stage dewaxed wax paste and the second-stage dewaxed filtrate are obtained.

[0081] The total dilution ratio of the diluting solvent for the third-stage dewaxing is 1.5:1. The third-stage dewaxing diluting solvent is added to the second-stage dewaxed wax paste and mixed evenly. The temperature is adjusted. The filtration temperature for the third-stage dewaxing is 3°C. The wax cake is cold-washed with the third-stage dewaxing washing solvent at 3°C, and the cold-washing ratio is 0.5:1. After filtration, the third-stage dewaxed wax paste and the third-stage dewaxed filtrate are obtained.

[0082] After the third-stage dewaxed wax paste is separated by distillation, a low-melting-point and low-aromatic hydrocarbon environmentally friendly dewaxed wax is obtained. The oil content of the dewaxed wax is 0.66%, the yield is 27.3%, the melting point is 43°C, and the benzene content is 0.1785 μg·g -1 and the toluene content is 0 μg·g -1 .

[0083] Example 2

[0084] This example provides a preparation method of a low-melting-point and low-aromatic hydrocarbon environmentally friendly dewaxed wax, which includes the following steps:

[0085] The feedstock oil is the 2# reduced second-line fraction oil, and its specific properties are shown in Table 1. The three-stage dewaxing method is adopted. The diluting solvent and the washing solvent used in the wax crystallization and the three-stage solvent dewaxing process are both mixtures of methyl ethyl ketone and cyclohexane. Among them, the mass content of methyl ethyl ketone is 80%, and the mass content of cyclohexane is 20%. The dilution ratio of the diluting solvent (the mass ratio of the diluting solvent to the feedstock oil) and the cold-washing ratio of the washing solvent (the mass ratio of the washing solvent to the feedstock oil) are both relative to the feedstock oil.

[0086] According to Figure 1 the shown technological process, the dewaxed wax is prepared. The specific process is as follows: Multi-point dilution is adopted (first, the feedstock oil is melted at 60°C, and then multi-point dilution is carried out during the solvent dewaxing process by adding the diluting solvent multiple times). The melted feedstock oil is sequentially mixed with the diluting solvent, and the temperature is decreased step by step for paraffin crystallization. When performing the first-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly dewaxing solvent to the dewaxed wax feedstock oil is 0.4:1, and the first-point dilution temperature is 30°C. When performing the second-point dilution, the mass ratio of the non-aromatic hydrocarbon environmentally friendly dewaxing solvent to the dewaxed wax feedstock oil is 1.1:1, and the second-point dilution temperature is 8°C.

[0087] The total dilution ratio of the solvent for the first-stage deoiling is 0.8:1. The filtration temperature for the first-stage solvent deoiling is -9°C. The wax cake is cold-washed with the first-stage deoiling washing solvent at -9°C, and the cold-washing ratio is 0.5:1. After filtration, the first-stage deoiled wax paste and the first-stage deoiled filtrate are obtained.

[0088] The total dilution ratio of the solvent for the second-stage deoiling is 1:1. The second-stage deoiling dilution solvent is added to the first-stage deoiled wax paste and mixed evenly. The temperature is adjusted. The filtration temperature for the second-stage solvent deoiling is 0°C. The wax cake is cold-washed with the second-stage deoiling washing solvent at 0°C, and the cold-washing ratio is 0.5:1. After filtration, the second-stage deoiled wax paste and the second-stage deoiled filtrate are obtained.

[0089] The total dilution ratio of the solvent for the third-stage deoiling is 1:1. The third-stage deoiling dilution solvent is added to the second-stage deoiled wax paste and mixed evenly. The temperature is adjusted. The filtration temperature for the third-stage solvent deoiling is 3°C. The wax cake is cold-washed with the third-stage deoiling washing solvent at 3°C, and the cold-washing ratio is 0.5:1. After filtration, the third-stage deoiled wax paste and the third-stage deoiled filtrate are obtained.

[0090] After the third-stage deoiled wax paste is separated by distillation, a low-melting-point and low-aromatic-hydrocarbon environmentally friendly deoiled wax is obtained. The oil content of the deoiled wax is 0.75%, the yield is 21.4%, the melting point is 41°C, and the benzene content is 0.1801 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0091] Example 3

[0092] Except as otherwise specified, the feedstock oil, process, and other process conditions in this example are all referred to Example 1. The difference is that the filtration temperature for the first-stage solvent deoiling is -1°C, and the temperature for cold-washing with the first-stage deoiling washing solvent is -1°C. The oil content of the prepared deoiled wax is 0.51%, the yield is 25.6%, the melting point is 44°C, and the benzene content is 0.1633 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0093] Example 4

[0094] Except as otherwise specified, the feedstock oil, process, and other process conditions in this example are all referred to Example 1. The difference is that the filtration temperature for the first-stage solvent deoiling is -9°C, and the temperature for cold-washing with the first-stage deoiling washing solvent is -9°C. The oil content of the prepared deoiled wax is 0.78%, the yield is 29.1%, the melting point is 42°C, and the benzene content is 0.1791 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0095] Example 5

[0096] Unless otherwise specified, the feedstock oil, process and other process conditions in this example are all referred to Example 1. The difference is that the filtration temperature of the second-stage solvent dewaxing is -5°C, and the cold washing temperature of the second-stage dewaxing washing solvent is -5°C. The oil content of the prepared dewaxed wax is 0.79%, the yield is 30.7%, the melting point is 42°C, and the benzene content is 0.1899 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0097] Example 6

[0098] Unless otherwise specified, the feedstock oil, process and other process conditions in this example are all referred to Example 1. The difference is that the filtration temperature of the second-stage solvent dewaxing is 5°C, and the cold washing temperature of the second-stage dewaxing washing solvent is 5°C. The oil content of the prepared dewaxed wax is 0.51%, the yield is 25.3%, the melting point is 44°C, and the benzene content is 0.1614 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0099] Example 7

[0100] Unless otherwise specified, the feedstock oil, process and other process conditions in this example are all referred to Example 1. The difference is that the filtration temperature of the third-stage solvent dewaxing is -1°C, and the cold washing temperature of the third-stage dewaxing washing solvent is -1°C. The oil content of the prepared dewaxed wax is 0.76%, the yield is 28.4%, the melting point is 43°C, and the benzene content is 0.1766 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0101] Example 8

[0102] Unless otherwise specified, the feedstock oil, process and other process conditions in this example are all referred to Example 1. The difference is that the filtration temperature of the third-stage solvent dewaxing is 7°C, and the cold washing temperature of the third-stage dewaxing washing solvent is 7°C. The oil content of the prepared dewaxed wax is 0.62%, the yield is 23.6%, the melting point is 44°C, and the benzene content is 0.1998 μg·g -1 , and the toluene content is 0 μg·g -1 .

[0103] Example 9

[0104] Unless otherwise specified, the feedstock oil, process and other process conditions in this example are all referred to Example 2. The difference is that the filtration temperature of the second-stage solvent dewaxing is 5°C, and the cold washing temperature of the second-stage dewaxing washing solvent is 5°C. The oil content of the prepared dewaxed wax is 0.70%, the yield is 16.77%, the melting point is 44°C, and the benzene content is 0.1694 μg·g -1, toluene content 0 μg·g -1 .

[0105] Example 10

[0106] Except as otherwise specified, the feedstock oil, process and other process conditions in this example are all referred to Example 2. The difference is that the mass content of methyl ethyl ketone is 85%, the mass content of cyclohexane is 15%, the filtration temperature of the first-stage solvent dewaxing is -5°C, and the cold washing temperature of the first-stage dewaxing washing solvent is -5°C. The oil content of the prepared dewaxed wax is 0.89%, the yield is 19.6%, the melting point is 42°C, benzene content 0.2091 μg·g -1 , toluene content 0 μg·g -1 .

[0107] Example 11

[0108] Except as otherwise specified, the feedstock oil, process and other process conditions in this comparative example are all referred to Example 2. The difference is that the mass content of methyl ethyl ketone is 85%, the mass content of cyclohexane is 15%, the filtration temperature of the first-stage solvent dewaxing is -5°C, and the cold washing temperature of the first-stage dewaxing washing solvent is -5°C. The total dilution ratio of the second-stage dewaxing dilution solvent is 1.5:1. The oil content of the prepared dewaxed wax is 0.80%, the yield is 18.8%, the melting point is 44°C, benzene content 0.1623 μg·g -1 , toluene content 0 μg·g -1 .

[0109] Table 1 Properties of the Feedstock Oil for Dewaxed Wax

[0110]

[0111]

[0112] It can be seen from the above Examples 1 - 11 that: the technical solution of the present invention is applicable to producing low-melting-point and low-aromatic environmental protection type dewaxed wax from vacuum light wax oil as the raw material through the solvent dewaxing process. By using a new type of low-boiling-point non-aromatic environmental protection type dewaxing solvent obtained by mixing methyl ethyl ketone and cyclohexane, efficient separation of the subsequent solvent can be achieved; the dewaxed wax obtained by means of the three-stage solvent dewaxing process has the characteristics of low aromatics, low oil content, and low melting point (<52°C).

Claims

1. A preparation method of a low-melting-point and low-aromatic-hydrocarbon environmentally friendly dewaxing wax, wherein, the preparation method includes: performing wax crystallization on a mixture of a dewaxing wax raw material oil and a non-aromatic-hydrocarbon environmentally friendly dewaxing solvent to obtain a crystallized mixture, and then performing a solvent dewaxing process to obtain the low-melting-point and low-aromatic-hydrocarbon environmentally friendly dewaxing wax; the non-aromatic-hydrocarbon environmentally friendly dewaxing solvent is a mixture of C4 ketone and cyclohexane, wherein, based on the total mass of the mixture of C4 ketone and cyclohexane, the content of C4 ketone is 45-95 wt%, and the content of cyclohexane is 5-55 wt%.

2. The preparation method according to claim 1, wherein, the dewaxing wax raw material oil is a light wax oil fraction; preferably, the light wax oil fraction is selected from the reduced second-line fraction of the primary processing of crude oil.

3. The preparation method according to claim 1, wherein, the C4 ketone is methyl ethyl ketone; based on the total mass of the mixture of methyl ethyl ketone and cyclohexane, the content of methyl ethyl ketone is 45-95 wt%, and the content of cyclohexane is 5-55 wt%; preferably, the content of methyl ethyl ketone is 55-85 wt%, and the content of cyclohexane is 15-45 wt%.

4. The preparation method according to claim 1, wherein, the wax crystallization is performed by multi-point dilution for wax crystallization; preferably, the multi-point dilution is two-point dilution, and the dilution conditions include: the first-point dilution temperature is 20-60 °C, and the second-point dilution temperature is 3-25 °C; more preferably, the first-point dilution temperature is 23-55 °C, and the second-point dilution temperature is 6-20 °C.

5. The preparation method according to claim 4, wherein, the dilution conditions further include: when performing the first-point dilution, the mass ratio of the non-aromatic-hydrocarbon environmentally friendly dewaxing solvent to the dewaxing wax raw material oil is 0.2-7.5:1, and when performing the second-point dilution, the mass ratio of the non-aromatic-hydrocarbon environmentally friendly dewaxing solvent to the dewaxing wax raw material oil is 0.5-7.5:1; preferably, when performing the first-point dilution, the mass ratio of the non-aromatic-hydrocarbon environmentally friendly dewaxing solvent to the dewaxing wax raw material oil is 0.5-4.5:1, and when performing the second-point dilution, the mass ratio of the non-aromatic-hydrocarbon environmentally friendly dewaxing solvent to the dewaxing wax raw material oil is 0.8-4.5:

1.

6. The preparation method according to any one of claims 1-3, wherein, the solvent dewaxing process includes: under the first-stage dewaxing conditions, performing the first-stage solvent dewaxing on a mixture of the crystallized mixture and a first-stage dewaxing dilution solvent to obtain a first-stage dewaxed wax paste and a first-stage dewaxed filtrate; under the second-stage dewaxing conditions, performing the second-stage solvent dewaxing on a mixture of the first-stage dewaxed wax paste and a second-stage dewaxing dilution solvent to obtain a second-stage dewaxed wax paste and a second-stage dewaxed filtrate; under the third-stage dewaxing conditions, performing the third-stage solvent dewaxing on a mixture of the second-stage dewaxed wax paste and a third-stage dewaxing dilution solvent to obtain a third-stage dewaxed wax paste and a third-stage dewaxed filtrate; the third-stage dewaxed wax paste is separated by solvent to obtain the low-melting-point and low-aromatic-hydrocarbon environmentally friendly dewaxing wax.

7. The preparation method according to claim 6, wherein, The process of the first-stage solvent dewaxing is as follows: filtering a mixture of the crystalline mixed material and the first-stage dewaxing dilution solvent under the first-stage dewaxing conditions to obtain a first-stage dewaxed paste and a first-stage dewaxed filtrate; Preferably, the process of the first-stage solvent dewaxing further includes washing the first-stage dewaxed paste with a first-stage dewaxing washing solvent under the first-stage dewaxing conditions.

8. The preparation method according to claim 6, wherein, The first-stage dewaxing dilution solvent includes one or more combinations of a non-aromatic hydrocarbon environmentally friendly dewaxing solvent, a second-stage dewaxed filtrate, and a third-stage dewaxed filtrate, preferably a non-aromatic hydrocarbon environmentally friendly dewaxing solvent; Preferably, the first-stage dewaxing washing solvent includes one or more combinations of a non-aromatic hydrocarbon environmentally friendly dewaxing solvent, a second-stage dewaxed filtrate, and a third-stage dewaxed filtrate.

9. The preparation method according to claim 6, wherein, The first-stage solvent dewaxing conditions include: the temperature T1 of the first-stage solvent dewaxing is -25°C to 20°C, preferably -20°C to 15°C, and more preferably -15°C to 12°C.

10. The preparation method according to claim 6 or 9, wherein, The first-stage solvent dewaxing conditions further include: the mass ratio of the first-stage dewaxing dilution solvent to the dewaxed wax raw material oil is 0.5 - 4.0:1, preferably 1.0 - 3.5:1; Preferably, the mass ratio of the first-stage dewaxing washing solvent to the dewaxed wax raw material oil is 0.1 - 3.0:1, preferably 0.3 - 1.0:

1.

11. The preparation method according to claim 6, wherein, The process of the second-stage solvent dewaxing is as follows: filtering a mixture of the first-stage dewaxed paste and the second-stage dewaxing dilution solvent under the second-stage dewaxing conditions to obtain a second-stage dewaxed paste and a second-stage dewaxed filtrate; Preferably, the process of the second-stage solvent dewaxing further includes washing the second-stage dewaxed paste with a second-stage dewaxing washing solvent under the second-stage dewaxing conditions.

12. The preparation method according to claim 6, wherein, The second-stage dewaxing conditions include: the temperature of the second-stage solvent dewaxing is T2, and T2 - T1 = -6°C to 20°C, preferably -3°C to 15°C, and more preferably 0°C to 10°C.

13. The preparation method according to claim 11 or 12, wherein, The second-stage dewaxing conditions further include: the mass ratio of the second-stage dewaxing dilution solvent to the dewaxed wax raw material oil is 0.5 - 4.0:1, preferably 1.0 - 3.5:1; Preferably, the mass ratio of the second-stage dewaxing washing solvent to the dewaxed wax raw material oil is 0.1 - 3.0:1, preferably 0.3 - 1.0:

1.

14. The preparation method according to claim 6, wherein, The process of the third-stage solvent dewaxing is as follows: filtering a mixture of the second-stage dewaxed paste and the third-stage dewaxing dilution solvent under the third-stage dewaxing conditions to obtain a third-stage dewaxed paste and a third-stage dewaxed filtrate; Preferably, the process of the third-stage solvent dewaxing further includes washing the third-stage dewaxed paste with a third-stage dewaxing washing solvent under the third-stage dewaxing conditions.

15. The preparation method according to claim 11 or 14, wherein, The two-stage dewaxing diluent solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the filtrate of the three-stage dewaxing, preferably a non-aromatic hydrocarbon environmentally friendly dewaxing solvent; Preferably, the three-stage dewaxing diluent solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the filtrate of the three-stage dewaxing, preferably a non-aromatic hydrocarbon environmentally friendly dewaxing solvent; More preferably, the two-stage dewaxing washing solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the filtrate of the three-stage dewaxing; Further preferably, the three-stage dewaxing washing solvent is a non-aromatic hydrocarbon environmentally friendly dewaxing solvent and / or the filtrate of the three-stage dewaxing.

16. According to the preparation method described in claim 14, wherein, The conditions for the third-stage dewaxing include: the temperature of the third-stage solvent dewaxing is T3, T3 - T2 = -6°C to 20°C, preferably -3°C to 15°C, more preferably 0°C to 10°C.

17. According to the preparation method described in claim 14 or 16, wherein, The conditions for the third-stage dewaxing further include: the mass ratio of the three-stage dewaxing diluent solvent to the feedstock oil is 0.5 - 4.0:1, preferably 1.0 - 3.5:1; Preferably, the mass ratio of the three-stage dewaxing washing solvent to the dewaxed wax feedstock oil is 0.1 - 3.0:1, preferably 0.3 - 1.0:

1.

18. A low-melting-point and low-aromatic-hydrocarbon environmentally friendly dewaxed wax, which is obtained by the preparation method described in any one of claims 1 - 17; Preferably, the melting point of the dewaxed wax is less than 52°C, preferably 40°C - 50°C; Preferably, the benzene content of the dewaxed oil is 0 - 0.49 μg·g -1 , preferably 0.1614 - 0.2091 μg·g -1 , the toluene content is 0 - 4.9 μg·g -1 , preferably 0 μg·g -1 ; Preferably, the oil content of the dewaxed wax is 0.3% - 2.0%, preferably 0.51% - 0.8%.

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